Synthesis, Structure, and Reactivity of Anionic sp2–sp3 Diboron Compounds: Readily Accessible Boryl Nucleophiles

英文原文与中文译文逐段对照 · English original with Chinese translation

Boron |Hot Paper

硼 |热点论文

Synthesis, Structure, and Reactivity of Anionic ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ Diboron Compounds: Readily Accessible Boryl Nucleophiles

阴离子型${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物的合成、结构及反应活性:易于获得的硼基亲核试剂

Sabrina Pietsch, ${}^{\left\lbrack \mathrm{a}\right\rbrack }$ Emily C. Neeve, ${}^{\left\lbrack \mathrm{a}\right\rbrack }$ David C. Apperley, ${}^{\left\lbrack \mathrm{b}\right\rbrack }$ Rüdiger Bertermann, ${}^{\left\lbrack \mathrm{a}\right\rbrack }$ Fanyang Mo, ${}^{\left\lbrack \mathrm{e}\right\rbrack }$ Di Qiu, ${}^{\left\lbrack \mathrm{e}\right\rbrack }$ Man Sing Cheung, ${}^{\left\lbrack \mathrm{c}\right\rbrack }$ Li Dang, ${}^{\left\lbrack \mathrm{c}\right\rbrack }$ Jianbo Wang, ${}^{\left\lbrack \mathrm{e}\right\rbrack }$ Udo Radius, ${}^{\left\lbrack \mathrm{a}\right\rbrack }$ Zhenyang Lin, ${}^{*\left\lbrack \mathrm{c}\right\rbrack }$ Christian Kleeberg, ${}^{*\left\lbrack {\mathrm{b},\mathrm{d}}\right\rbrack }$ and Todd B. Marder ${}^{*\left\lbrack {\mathrm{a},\mathrm{b}}\right\rbrack }$

萨布丽娜·皮茨，${}^{\left\lbrack \mathrm{a}\right\rbrack }$ 艾米丽·C·尼夫，${}^{\left\lbrack \mathrm{a}\right\rbrack }$ 大卫·C·阿珀利，${}^{\left\lbrack \mathrm{b}\right\rbrack }$ 吕迪格·贝特曼，${}^{\left\lbrack \mathrm{a}\right\rbrack }$ 莫凡洋，${}^{\left\lbrack \mathrm{e}\right\rbrack }$ 邱迪，${}^{\left\lbrack \mathrm{e}\right\rbrack }$ 张敏成，${}^{\left\lbrack \mathrm{c}\right\rbrack }$ 李党，${}^{\left\lbrack \mathrm{c}\right\rbrack }$ 王建波，${}^{\left\lbrack \mathrm{e}\right\rbrack }$ 乌多·拉迪乌斯，${}^{\left\lbrack \mathrm{a}\right\rbrack }$ 林振阳，${}^{*\left\lbrack \mathrm{c}\right\rbrack }$ 克里斯蒂安·克莱伯格，${}^{*\left\lbrack {\mathrm{b},\mathrm{d}}\right\rbrack }$ 以及托德·B·马德 ${}^{*\left\lbrack {\mathrm{a},\mathrm{b}}\right\rbrack }$

Abstract: Lewis base adducts of tetra-alkoxy diboron compounds, in particular bis(pinacolato)diboron $\left( {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}}\right)$ , have been proposed as the active source of nucleophilic boryl species in metal-free borylation reactions. We report the isolation and detailed structural characterization (by solid-state and solution NMR spectroscopy and X-ray crystallography) of a series of anionic adducts of ${B}_{2}{\text{ pin }}_{2}$ with hard Lewis bases, such as alkoxides and fluoride. The study was extended to alternative Lewis bases, such as acetate, and other di-boron reagents. The $B\left( {\mathrm{{sp}}}^{2}\right) - B\left( {\mathrm{{sp}}}^{3}\right)$ adducts exhibit two dis-

摘要:四烷氧基二硼化合物的路易斯碱加合物，特别是双(频哪醇)二硼$\left( {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}}\right)$，已被认为是无金属硼化反应中亲核硼基物种的活性来源。我们报道了一系列${B}_{2}{\text{ pin }}_{2}$与硬路易斯碱(如醇盐和氟化物)形成的阴离子加合物的分离及详细结构表征(通过固态和溶液核磁共振光谱以及X射线晶体学)。该研究扩展到了其他路易斯碱，如乙酸盐，以及其他二硼试剂。$B\left( {\mathrm{{sp}}}^{2}\right) - B\left( {\mathrm{{sp}}}^{3}\right)$加合物在固态和溶液核磁共振光谱中表现出两种不同的硼环境，除了$\left( {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}}\right)$，它在溶液中显示出快速的位点交换。进行了密度泛函理论计算以分析加合物相对于解离的稳定性。分离出的加合物与两个代表性的有机亲电试剂系列——即芳基卤化物和重氮盐——的化学计量反应证明了阴离子二硼化合物作为亲核硼基阴离子源的相对反应活性。

tinct boron environments in the solid-state and solution NMR spectra, except for ${\left\lbrack \left( 4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}\mathrm{O}\right) {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\right\rbrack }^{ - }$ , which shows rapid site exchange in solution. DFT calculations were performed to analyze the stability of the adducts with respect to dissociation. Stoichiometric reaction of the isolated adducts with two representative series of organic electro-philes-namely, aryl halides and diazonium salts-demonstrate the relative reactivities of the anionic diboron compounds as nucleophilic boryl anion sources.

固态和溶液核磁共振谱中的不同硼环境，除了${\left\lbrack \left( 4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}\mathrm{O}\right) {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\right\rbrack }^{ - }$，它在溶液中显示出快速的位点交换。进行了密度泛函理论计算以分析加合物相对于解离的稳定性。分离出的加合物与两个代表性的有机亲电试剂系列(即芳基卤化物和重氮盐)的化学计量反应证明了阴离子二硼化合物作为亲核硼基阴离子源的相对反应活性。

Introduction

引言

Boronic acids and boronate esters have become exceptionally valuable reagents for organic synthesis. ${}^{\left\lbrack 1\right\rbrack }$ However, the potential of boron-based nucleophiles was not realized until 2006, when Yamashita and Nozaki published their seminal work with regards to a stable boryl anion. ${}^{\left\lbrack 2\right\rbrack }$ Their isolated lithium boryl species had a highly polarized B-Li bond, which provided an anionic boron moiety with nucleophilic characteristics that displayed good reactivity with a range of organic electrophiles and could be used to prepare novel metal-boryl species. ${}^{\left\lbrack 2,3\right\rbrack }$ However, use of the lithium boryl species is still relatively limited due its sensitivity to moisture and oxygen and its difficult synthesis. ${}^{\left\lbrack 3,4\right\rbrack }$

硼酸和硼酸酯已成为有机合成中极为重要的试剂。${}^{\left\lbrack 1\right\rbrack }$ 然而，基于硼的亲核试剂的潜力直到200年才得以实现，当时山下和野崎发表了他们关于稳定硼负离子的开创性工作。${}^{\left\lbrack 2\right\rbrack }$ 他们分离出的锂硼物种具有高度极化的B-Li键，这为阴离子硼部分提供了亲核特性，使其与一系列有机亲电试剂表现出良好的反应性，并可用于制备新型金属硼物种。${}^{\left\lbrack 2,3\right\rbrack }$ 然而，由于锂硼物种对水分和氧气敏感且合成困难，其应用仍然相对有限。${}^{\left\lbrack 3,4\right\rbrack }$

${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ Tetra-alkoxy diboron compounds have attracted considerable attention over the past few years as an apparent source of nucleophilic boryl moieties due to the readily available and easy-to-handle diboron reagents from which they can be prepared. Thus, relatively mild bases can be utilized to prepare proposed synthetically useful borylborates from ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ (1; pin $= {\mathrm{{OCMe}}}_{2}{\mathrm{{CMe}}}_{2}\mathrm{O}$ ). Such compounds are involved in enhancing transmetalation in transition-metal-catalyzed borylation reactions, such as diboration of or conjugate addition to unsaturated organic reagents, or are proposed as reactive nucleo-philes themselves in metal-free borylation processes (Scheme 1). ${}^{\left\lbrack 5 - {10}\right\rbrack }$

${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 在过去几年中，四烷氧基二硼化合物作为亲核硼部分的明显来源受到了相当大的关注，因为可以从中制备它们的二硼试剂易于获得且易于处理。因此，相对温和的碱可用于从 ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ (1; pin $= {\mathrm{{OCMe}}}_{2}{\mathrm{{CMe}}}_{2}\mathrm{O}$ )制备提议的具有合成用途的硼硼酸酯。此类化合物参与增强过渡金属催化的硼化反应中的金属转移，例如不饱和有机试剂的双硼化或共轭加成，或者在无金属硼化过程中本身被提议作为活性亲核试剂(方案1)。${}^{\left\lbrack 5 - {10}\right\rbrack }$

Scheme 1. Generic reactions of the organoborates with an organic electro-phile or with a metal complex.

方案1. 有机硼酸酯与有机亲电试剂或金属配合物的一般反应。

In the copper-catalyzed $\beta$ -borylation of $\alpha ,\beta$ -unsaturated compounds, Miyaura et al. postulated that a copper-boryl complex, formed in situ by reaction of ${1}^{\left\lbrack {11}\right\rbrack }$ and a copper salt under basic conditions, transferred a boryl moiety to the elec-trophile. ${}^{\left\lbrack 5\right\rbrack }$ More recently, Santos et al. demonstrated that a neutral, preactivated ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron adduct, in the absence of a base, enhances the rate of transmetalation of an ${\mathrm{{sp}}}^{2}$ boryl moiety to the copper salt in the Cu-catalyzed $\beta$ -borylation of $\alpha ,\beta$ -unsaturated carbonyl compounds (Scheme 2). ${}^{\left\lbrack 9b\right\rbrack }$

在铜催化的 $\beta$ -不饱和化合物的 $\alpha ,\beta$ -硼化反应中，宫浦等人推测，在碱性条件下 ${1}^{\left\lbrack {11}\right\rbrack }$ 与铜盐反应原位形成的铜硼配合物将硼部分转移到亲电试剂上。${}^{\left\lbrack 5\right\rbrack }$ 最近，桑托斯等人证明，在没有碱的情况下，一种中性的、预活化的 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼加合物可提高在铜催化的 $\beta$ -不饱和羰基化合物的 $\alpha ,\beta$ -硼化反应中 ${\mathrm{{sp}}}^{2}$ 硼部分向铜盐的金属转移速率(方案2)。${}^{\left\lbrack 9b\right\rbrack }$

DFT investigations of the mechanism of copper-catalyzed borylation of unsaturated carbonyl compounds and alkenes using diboron(4) reagents were conducted by Lin, Marder and co-workers. ${}^{\left\lbrack {12}\right\rbrack }$ It was discovered that during the catalytic cycle the hybridization of one of the two boron moieties changes from ${\mathrm{{sp}}}^{2}$ to ${\mathrm{{sp}}}^{3}$ in a short-lived intermediate when the diboron compound associates to the model copper-alkoxide complex [Cu(NHC)OMe] (NHC=N-heterocyclic carbene). ${}^{\left\lbrack {12}\right\rbrack }$ Subsequent metathesis affords a copper-boryl complex, which facilitates transfer of the boryl group to the organic electrophile giving the desired organoboronate ester. ${}^{\left\lbrack 7\right\rbrack }$ An analogous ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ di-boron intermediate, in which the diboron reagent is bound to a nickel alkoxide, was observed in NMR studies by Mindiola et al. in the reaction of ${\mathrm{B}}_{2}{\mathrm{{cat}}}_{2}{\left( \mathrm{{cat}} = {\mathrm{O}}_{2}{\mathrm{C}}_{6}{\mathrm{H}}_{4}\right) }^{\left\lbrack {13}\right\rbrack }$ with $\left\lbrack {\mathrm{{Ni}}\left( {\mathrm{O}t\mathrm{{Bu}}}\right) }\right.$ - (PNP)] (PNP $= \mathrm{N}\left\lbrack {2 - \mathrm{P}{\left\{ {\mathrm{{CHMe}}}_{2}\right\} }_{2} - 4\text{ -methylphenyl] }{}_{2}{}^{ - }}\right\rbrack$ . ${}^{\left\lbrack {14}\right\rbrack }$

林、马德和他们的同事对使用二硼(4)试剂进行铜催化的不饱和羰基化合物和烯烃硼化反应的机理进行了密度泛函理论研究。${}^{\left\lbrack {12}\right\rbrack }$ 研究发现，在催化循环中，当二硼化合物与模型铜醇盐配合物[Cu(NHC)OMe](NHC = N-杂环卡宾)结合时，两个硼部分之一的杂化状态在一个短寿命中间体中从${\mathrm{{sp}}}^{2}$变为${\mathrm{{sp}}}^{3}$。${}^{\left\lbrack {12}\right\rbrack }$ 随后的复分解反应生成一个铜硼基配合物，该配合物促进硼基向有机亲电试剂的转移，生成所需的有机硼酸酯。${}^{\left\lbrack 7\right\rbrack }$ 明迪奥拉等人在${\mathrm{B}}_{2}{\mathrm{{cat}}}_{2}{\left( \mathrm{{cat}} = {\mathrm{O}}_{2}{\mathrm{C}}_{6}{\mathrm{H}}_{4}\right) }^{\left\lbrack {13}\right\rbrack }$与$\left\lbrack {\mathrm{{Ni}}\left( {\mathrm{O}t\mathrm{{Bu}}}\right) }\right.$-(PNP)](PNP $= \mathrm{N}\left\lbrack {2 - \mathrm{P}{\left\{ {\mathrm{{CHMe}}}_{2}\right\} }_{2} - 4\text{ -methylphenyl] }{}_{2}{}^{ - }}\right\rbrack$)的反应的核磁共振研究中观察到了一种类似的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼中间体，其中二硼试剂与镍醇盐结合。${}^{\left\lbrack {14}\right\rbrack }$

[a] S. Pietsch, ${}^{ + }$ Dr. E. C. Neeve, ${}^{ + }$ Dr. R. Bertermann, Prof. Dr. U. Radius, Prof. Dr. T. B. Marder

[a] S. 皮茨，${}^{ + }$ E. C. 尼夫博士，{{F}} R. 贝特曼博士，U. 拉迪乌斯教授，T. B. 马德教授

Institut für Anorganische Chemie

无机化学研究所

Julius-Maximilians-Universität Würzburg

维尔茨堡大学

Am Hubland, 97074 Würzburg (Germany)

德国维尔茨堡胡布兰德97074

[b] Dr. D. C. Apperley, Dr. C. Kleeberg, Prof. Dr. T. B. Marder

[b] D. C. 阿珀利博士，C. 克莱伯格博士，T. B. 马德教授

Department of Chemistry

化学系

Durham University

杜伦大学

South Road, Durham, DH1 3LE (UK)

英国杜伦南路DH1 3LE

[c] Dr. M. S. Cheung, Dr. L. Dang, Prof. Dr. Z. Lin

[c] M. S. 张博士，L. 当博士，Z. 林教授

Department of Chemistry

化学系

The Hong Kong University of Science and Technology

香港科技大学

Clear Water Bay, Kowloon, Hong Kong (P. R. China)

中国香港九龙清水湾

[d] Dr. C. Kleeberg

[d] C. 克莱伯格博士

Institut für Anorganische und Analytische Chemie

无机与分析化学研究所

Technische Universität Carolo-Wilhelmina zu Braunschweig

布伦瑞克工业大学卡罗洛 - 威廉米娜学院

Hagenring 30, 38106 Braunschweig (Germany)

哈根林30号，38106布伦瑞克(德国)

ch.kleeberg@tu - braunschweig.de

[e] Dr. F. Mo, D. Qiu, Prof. Dr. J. Wang

[e] 莫博士、邱博士、王教授

Beijing National Laboratory of Molecular Sciences (BNLMS)

北京分子科学国家实验室(BNLMS)

and Key Laboratory of Bioorganic Chemistry

以及生物有机化学重点实验室

and Molecular Engineering of Ministry of Education

和教育部分子工程重点实验室

College of Chemistry, Peking University

北京大学化学与分子工程学院

Beijing 100871 (P. R. China)

北京100871(中华人民共和国)

[†] These authors contributed equally to this work.

[†] 这些作者对本工作贡献相同。

Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201500235.

本文的支持信息可在网站http://dx.doi.org/10.1002/chem.201500235上获取。

Scheme 2. Examples of reported reactions of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ or ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$ diboron compounds. ${}^{\left\lbrack 5 - {10}\right\rbrack }$ EWG = electron-withdrawing group, NHC = N-heterocyclic carbene.

方案2. 报道的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$或${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$二硼化合物反应示例。${}^{\left\lbrack 5 - {10}\right\rbrack }$ EWG = 吸电子基团，NHC = N - 杂环卡宾。

The in situ quaternization of one of the boron atoms to form a borylborate was also proposed to enhance direct transfer of the boryl moiety to an organic electrophile. Fernández and co-workers proposed that an ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adduct of 1, formed when 1 reacts with base in the presence of methanol, was generated in situ and facilitated the transition-metal-free boryl-ation of unsaturated compounds (Scheme 2). ${}^{\left\lbrack {10}\right\rbrack }$ A similar situation applies to B-heteroatom systems, such as $B - {\mathrm{{Si}}}^{\left\lbrack {15}\right\rbrack }$ B-N, ${}^{\left\lbrack {10}\mathrm{\;m},{16}\right\rbrack }$ and B-Se, ${}^{\left\lbrack {17}\right\rbrack }$ for which the nucleophilicity of the heteroatom is enhanced by complexation of a Lewis base to the B atom. Furthermore, related base adducts of organo-boronate esters are frequently discussed as intermediates in the Suzuki-Miyaura cross-coupling reaction, and intramolecular Lewis base adducts of organoboronate esters have been explored as the active boryl species by Miyaura and others. ${}^{\left\lbrack {18}\right\rbrack }$

还提出通过硼原子之一的原位季铵化形成硼硼酸酯来增强硼基部分向有机亲电试剂的直接转移。费尔南德斯及其同事提出，当1在甲醇存在下与碱反应时原位生成的1的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$加合物促进了不饱和化合物的无过渡金属硼基化反应(方案2)。${}^{\left\lbrack {10}\right\rbrack }$ 类似的情况也适用于B - 杂原子体系，如$B - {\mathrm{{Si}}}^{\left\lbrack {15}\right\rbrack }$ B - N，${}^{\left\lbrack {10}\mathrm{\;m},{16}\right\rbrack }$ 和B - Se，${}^{\left\lbrack {17}\right\rbrack }$ 其中杂原子的亲核性通过路易斯碱与B原子的络合而增强。此外，有机硼酸酯的相关碱加合物经常被讨论为铃木 - 宫浦交叉偶联反应中的中间体，并且宫浦等人已经探索了有机硼酸酯的分子内路易斯碱加合物作为活性硼基物种。${}^{\left\lbrack {18}\right\rbrack }$

Literature reports of the structure and reactivity of isolated examples of Lewis base adducts of 1 are relatively limited, and the isolation and full characterization of only one neutral ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ (NHC) adduct are reported. ${}^{\left\lbrack 8a, b,{19}\right\rbrack }$ This was originally proposed by Hoveyda ${}^{\left\lbrack 8a, b\right\rbrack }$ to be the intermediate responsible for promotion of metal-free $\beta$ borylation of $\alpha ,\beta$ -unsaturated carbonyl compounds; the exact nature of the adduct was reported based on detailed experimental and theoretical studies by Marder and co-workers. ${}^{\left\lbrack {19}\right\rbrack }$ However, there have been previous reports about the isolation and characterization of several related adducts of more Lewis acidic diboron compounds. ${}^{\left\lbrack {20}\right\rbrack }$ Marder, Norman et al. studied ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ Lewis base adducts of bis(catecholato)diboron (Figure 1) and bis(thio-catecholato)di-boron in considerable detail, ${}^{\left\lbrack {20}\mathrm{\;b},\mathrm{\;d} - \mathrm{f}\right\rbrack }$ and Braunschweig and coworkers recently isolated and characterized various Lewis base adducts of 1,2-dihalodiboranes. ${}^{\left\lbrack {20}\mathrm{\;g} - \mathrm{j}\right\rbrack }$ Furthermore, an alkoxide adduct of an unsymmetrical ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$ diboron compound has recently been reported. ${}^{\left\lbrack {21}\right\rbrack }$

关于1的路易斯碱加合物的分离实例的结构和反应性的文献报道相对有限，并且仅报道了一种中性${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$(NHC)加合物的分离和完整表征。${}^{\left\lbrack 8a, b,{19}\right\rbrack }$ 这最初是由霍维达${}^{\left\lbrack 8a, b\right\rbrack }$提出的，是促进$\alpha ,\beta$-不饱和羰基化合物无金属$\beta$硼化的中间体；加合物的确切性质是根据马德及其同事的详细实验和理论研究报告的。${}^{\left\lbrack {19}\right\rbrack }$ 然而，以前有关于几种更具路易斯酸性的二硼化合物的相关加合物的分离和表征的报道。${}^{\left\lbrack {20}\right\rbrack }$ 马德、诺曼等人相当详细地研究了双(邻苯二酚)二硼(图1)和双(硫代邻苯二酚)二硼的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$路易斯碱加合物，${}^{\left\lbrack {20}\mathrm{\;b},\mathrm{\;d} - \mathrm{f}\right\rbrack }$ 布伦瑞克及其同事最近分离并表征了1,2-二卤代二硼烷的各种路易斯碱加合物。${}^{\left\lbrack {20}\mathrm{\;g} - \mathrm{j}\right\rbrack }$ 此外，最近报道了一种不对称${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$二硼化合物的醇盐加合物。${}^{\left\lbrack {21}\right\rbrack }$

Figure 1. Examples of isolated Lewis base adducts of diboron compounds. ${}^{\left\lbrack {19},{20}\mathrm{\;b},\mathrm{\;d} - \mathrm{j}\right\rbrack }$ Mes = mesityl, $\mathrm{{Cy}} =$ cyclohexyl, $\mathrm{X} =$ halide.

图1. 二硼化合物分离出的路易斯碱加合物实例。${}^{\left\lbrack {19},{20}\mathrm{\;b},\mathrm{\;d} - \mathrm{j}\right\rbrack }$ 甲基 = 均三甲苯基，$\mathrm{{Cy}} =$ 环己基，$\mathrm{X} =$ 卤化物。

Our attention was again drawn to ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adducts of di-boron compounds during our study of the copper-catalyzed borylation of aryl halides. ${}^{\left\lbrack {22}\right\rbrack }$ We found that an ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adduct of 1 with KOtBu was formed under the reaction conditions. The adduct was proposed to be responsible for the uncata-lyzed background reaction, which give arylboronate esters in trace quantities. ${}^{\left\lbrack {22}\right\rbrack }$ One of our groups has reported several protocols for the transition-metal-free borylation of aryl amines by the in situ formation of aryl diazonium salts and their reaction with ${1}^{\left\lbrack {23}\mathrm{a} - \mathrm{e}\right\rbrack }$ Similar systems were recently studied by Blanchet et al. ${}^{\left\lbrack {23}\mathrm{f},\mathrm{g}\right\rbrack }$ and Xue et al. ${}^{\left\lbrack {23}\mathrm{h}\right\rbrack }$ Because this reaction takes place in the presence of an alkoxide formed in situ from the reaction of tBuONO with the aryl amine, the reaction of an activated ${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$ derivative of 1 with the very electrophilic diazonium salt has to be considered as a possible reaction pathway (see below) for the synthesis of useful aryl boronates. ${}^{\left\lbrack {22} - {24}\right\rbrack }$

在我们对芳基卤化物的铜催化硼化反应的研究过程中，我们的注意力再次被吸引到二硼化合物的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 加合物上。${}^{\left\lbrack {22}\right\rbrack }$ 我们发现，在反应条件下会形成1与叔丁醇钾的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 加合物。该加合物被认为是未催化的背景反应的原因，该反应会产生痕量的芳基硼酸酯。${}^{\left\lbrack {22}\right\rbrack }$ 我们小组之一报道了几种通过原位形成芳基重氮盐并使其与${1}^{\left\lbrack {23}\mathrm{a} - \mathrm{e}\right\rbrack }$ 反应来实现芳基胺无过渡金属硼化的方法。最近，布兰切特等人${}^{\left\lbrack {23}\mathrm{f},\mathrm{g}\right\rbrack }$ 和薛等人${}^{\left\lbrack {23}\mathrm{h}\right\rbrack }$ 研究了类似的体系。${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$ 由于该反应是在叔丁基亚硝酸酯与芳基胺反应原位形成的醇盐存在下进行的，因此必须考虑1的活化${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$ 衍生物与非常亲电的重氮盐的反应是合成有用芳基硼酸酯的一种可能反应途径(见下文)。${}^{\left\lbrack {22} - {24}\right\rbrack }$

To improve our understanding of the role of these postulated adducts in borylation reactions and to promote development of the chemistry of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds, we set out to synthesize and fully characterize a series of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adducts of diboron compounds such as 1 with different anionic Lewis bases and to study the reactivity of the isolated adducts in stoichiometric borylation reactions with aryl electrophiles. ${}^{\left\lbrack {25}\right\rbrack }$

为了增进我们对这些假定加合物在硼化反应中作用的理解，并推动${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物化学的发展，我们着手合成并全面表征了一系列二硼化合物(如1)与不同阴离子路易斯碱形成的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$加合物，并研究了分离出的加合物在与芳基亲电试剂的化学计量硼化反应中的反应活性。${}^{\left\lbrack {25}\right\rbrack }$

Results and Discussion

结果与讨论

Synthesis

合成

As previously mentioned, 1 reacts with KOtBu in THF to form a colorless, microcrystalline precipitate. ${}^{\left\lbrack {22}\right\rbrack }$ The composition of this precipitate was determined by elemental analysis and is in agreement with the formula $\mathrm{K}\left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}}\right\rbrack$ (2). Further characterization of this adduct by solid-state and solution ( $\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF) NMR spectroscopy and single-crystal X-ray diffraction confirmed an ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compound that consisted of infinite chains of 2 in the solid state. Following this initial finding, 1 was allowed to react with other anionic Lewis bases $\left( {{\mathrm{{MeO}}}^{ - }\text{ , }}\right. \; \left. {t{\mathrm{{BuO}}}^{ - },\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) {\mathrm{O}}^{ - },{\mathrm{F}}^{ - }}\right)$ to synthesize a series of related ${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$ diboron compounds (Scheme 3).

如前所述，1在四氢呋喃中与叔丁醇钾反应，形成无色微晶沉淀。${}^{\left\lbrack {22}\right\rbrack }$ 通过元素分析确定了该沉淀的组成，其与式$\mathrm{K}\left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}}\right\rbrack$ (2)一致。通过固态和溶液($\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ 二甲基甲酰胺)核磁共振光谱以及单晶X射线衍射对该加合物进行的进一步表征证实了一种${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼化合物，其在固态下由2的无限链组成。基于这一初步发现，使1与其他阴离子路易斯碱$\left( {{\mathrm{{MeO}}}^{ - }\text{ , }}\right. \; \left. {t{\mathrm{{BuO}}}^{ - },\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) {\mathrm{O}}^{ - },{\mathrm{F}}^{ - }}\right)$ 反应，以合成一系列相关的${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$ 二硼化合物(方案3)。

The solubility of these adducts was improved by the addition of a stoichiometric amount of 18-crown-6 (18-C-6) to the reaction of equimolar amounts of 1 and KOtBu to obtain a monomeric adduct. Instead,[K(18-crown-6)(thf) ${}_{2}$ ] $\left\lbrack {\mathrm{K}{\left( {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right) }_{2}}\right\rbrack$ (3), which consisted of a potassium-bridged dimer of two ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right\rbrack }^{ - }$ moieties with ${\left\lbrack \mathrm{K}\left( {18}\text{ -crown-6 }\right) {\left( \mathrm{{thf}}\right) }_{2}\right\rbrack }^{ + }$ as the counterion, was isolated as the sole product. Thus, only half of the potassium cations were complexed by the crown ether. Increasing the amount of 18-crown-6 led to isolation of the mononuclear adduct [K(18-crown-6)][B ${}_{2}$ pin ${}_{2}$ OtBu] (4) in low yield. However, obtaining material of this specific composition was not readily reproducible. In contrast, substitution of KOtBu with KOMe led to reproducible isolation of the analogous salt [K(18-crown-6)][B ${}_{2}{\text{ pin }}_{2}$ OMe] (5) in good yield. The reaction of the phenolate $\mathrm{{KO}}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right)$ with 1 led to isolation of $\mathrm{K}\left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) }\right\rbrack$ (6), whereas no adduct was isolated or observed by ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ and ${}^{1}\mathrm{H}$ NMR spectroscopy for the sterically more-demanding phenolate $\mathrm{{KO}}\left( {4 - \mathrm{{Me}} - 2,6 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right)$ . ${}^{\left\lbrack {26}\right\rbrack }$ Similarly, the reaction with less Lewis basic carboxylates ${\mathrm{{KO}}}_{2}\mathrm{{CPh}}$ and $\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{P}}\right\rbrack \left\lbrack \mathrm{{OAc}}\right\rbrack {\left( \mathrm{{TBPE}}\right) }^{\left\lbrack {27}\right\rbrack }$ did not lead to the isolation of any adducts, nor were any detected by ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ and ${}^{1}\mathrm{H}$ NMR spectroscopy. ${}^{\left\lbrack {26}\right\rbrack }$ In contrast, the analogous reactions of $\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{\;N}}\right\rbrack \mathrm{F} \cdot 3{\mathrm{H}}_{2}\mathrm{O}$ or ${\mathrm{{Me}}}_{4}\mathrm{\;N}\mathrm{\;F}$ with 1 furnished the adducts $\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack$ (7) and $\left\lbrack {{\mathrm{{Me}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack \left( \mathbf{8}\right)$ , respectively, in good yields. For 7 and 8 only monoadduct was isolated despite the presence of excess Lewis base, indicating that there was limited, if any, binding of a second equivalent of the base to obtain a di-anionic ${\mathrm{{sp}}}^{3} - {\mathrm{{sp}}}^{3}$ adduct. This may be rationalized by the unfavorable accumulation of negative charge in a potential bis-adduct and the reduced Lewis acidity of 1 compared with that of the catechol or thiocatechol analogues, which have been shown to form bis-adducts with neutral Lewis bases. ${}^{\left\lbrack {20}\mathrm{\;b},\mathrm{\;d} - \mathrm{f}\right\rbrack }$ However, the reaction of 1 with neutral Lewis bases, such as ${\mathrm{{PMe}}}_{3}$ , pyridine,4-dimethylaminopyridine (DMAP), or pyrrolidine, gave no adduct formation (analyzed by ${}^{1}\mathrm{H}$ and ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectroscopy), even in the presence of excess base.

通过向等摩尔量的1与叔丁醇钾的反应中加入化学计量的18-冠-6(18-C-6)来提高这些加合物的溶解度，以获得单体加合物。相反，分离得到了[K(18-冠-6)(thf) ${}_{2}$ ] $\left\lbrack {\mathrm{K}{\left( {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right) }_{2}}\right\rbrack$ (3)，它是由两个${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right\rbrack }^{ - }$部分通过钾桥连的二聚体，以${\left\lbrack \mathrm{K}\left( {18}\text{ -crown-6 }\right) {\left( \mathrm{{thf}}\right) }_{2}\right\rbrack }^{ + }$作为抗衡离子，是唯一的产物。因此，只有一半的钾阳离子被冠醚络合。增加18-冠-6的量会以低产率分离得到单核加合物[K(18-冠-6)][B ${}_{2}$ pin ${}_{2}$ OtBu] (4)。然而，获得具有这种特定组成的物质不容易重复。相反，用甲氧基钾代替叔丁醇钾可高产率地重复分离得到类似的盐[K(18-冠-6)][B ${}_{2}{\text{ pin }}_{2}$ OMe] (5)。酚盐$\mathrm{{KO}}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right)$与1的反应导致分离得到$\mathrm{K}\left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) }\right\rbrack$ (6)，而对于空间位阻更大的酚盐$\mathrm{{KO}}\left( {4 - \mathrm{{Me}} - 2,6 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right)$，通过${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$和${}^{1}\mathrm{H}$ NMR光谱未分离或观察到加合物。${}^{\left\lbrack {26}\right\rbrack }$同样，与路易斯碱性较弱的羧酸盐${\mathrm{{KO}}}_{2}\mathrm{{CPh}}$和$\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{P}}\right\rbrack \left\lbrack \mathrm{{OAc}}\right\rbrack {\left( \mathrm{{TBPE}}\right) }^{\left\lbrack {27}\right\rbrack }$的反应没有导致任何加合物的分离，通过${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$和${}^{1}\mathrm{H}$ NMR光谱也未检测到任何加合物。${}^{\left\lbrack {26}\right\rbrack }$相反，$\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{\;N}}\right\rbrack \mathrm{F} \cdot 3{\mathrm{H}}_{2}\mathrm{O}$或${\mathrm{{Me}}}_{4}\mathrm{\;N}\mathrm{\;F}$与1的类似反应分别以高产率得到加合物$\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack$ (7)和$\left\lbrack {{\mathrm{{Me}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack \left( \mathbf{8}\right)$。对于7和8，尽管存在过量的路易斯碱，但只分离得到了单加合物，这表明第二个当量的碱与形成双阴离子${\mathrm{{sp}}}^{3} - {\mathrm{{sp}}}^{3}$加合物的结合有限(如果有的话)。这可以通过潜在的双加合物中负电荷的不利积累以及与儿茶酚或硫代儿茶酚类似物相比1的路易斯酸性降低来解释，已表明后者能与中性路易斯碱形成双加合物。${}^{\left\lbrack {20}\mathrm{\;b},\mathrm{\;d} - \mathrm{f}\right\rbrack }$然而，1与中性路易斯碱如${\mathrm{{PMe}}}_{3}$、吡啶、4-二甲基氨基吡啶(DMAP)或吡咯烷的反应即使在存在过量碱的情况下也没有形成加合物(通过${}^{1}\mathrm{H}$和${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱分析)。

Scheme 3. Formation of intermolecular adducts of 1.

方案3. 1的分子间加合物的形成。

The investigations were also extended to incorporate other related diboron compounds. Attempts to synthesize and isolate anionic adducts of ${\mathrm{B}}_{2}{\mathrm{{neop}}}_{2}{}^{\left\lbrack {28}\right\rbrack }$ (neop $= {\mathrm{{OCH}}}_{2}{\mathrm{{CMe}}}_{2}{\mathrm{{CH}}}_{2}\mathrm{O}$ ) and ${\mathrm{B}}_{2}{\mathrm{{cat}}}_{2}$ with bases such as ${\mathrm{{RO}}}^{ - }$ and ${\mathrm{F}}^{ - }$ have been unsuccessful and are subject to ongoing research. However, when ${\mathrm{B}}_{2}{\mathrm{{dmeda}}}_{2}{}^{\left\lbrack {29}\right\rbrack }$ (dmeda=MeNCH ${}_{2}{\mathrm{{CH}}}_{2}\mathrm{{NMe}}$ ) was treated with KOMe (1 equiv) in the presence of 18-crown-6 the only product isolated was [K(18-crown-6)][dmedaB-B(OMe) ${}_{3}$ ] (9; Scheme 4), which was obtained in 62% yield with respect to the limiting reagent, KOMe. The formation of this mononuclear product implies that as the Lewis base binds to one of the [B(dmeda)] moieties, the B-N π-bonding system is disrupted, promoting the addition of further ${\mathrm{{MeO}}}^{ - }$ and the removal of the dmeda to form 9.

研究还扩展到纳入其他相关的二硼化合物。尝试用诸如${\mathrm{{RO}}}^{ - }$和${\mathrm{F}}^{ - }$等碱合成并分离${\mathrm{B}}_{2}{\mathrm{{neop}}}_{2}{}^{\left\lbrack {28}\right\rbrack }$(新戊基$= {\mathrm{{OCH}}}_{2}{\mathrm{{CMe}}}_{2}{\mathrm{{CH}}}_{2}\mathrm{O}$)和${\mathrm{B}}_{2}{\mathrm{{cat}}}_{2}$的阴离子加合物，但未成功，目前仍在研究中。然而，当${\mathrm{B}}_{2}{\mathrm{{dmeda}}}_{2}{}^{\left\lbrack {29}\right\rbrack }$(dmeda = MeNCH${}_{2}{\mathrm{{CH}}}_{2}\mathrm{{NMe}}$)在18-冠-6存在下用KOMe(1当量)处理时，分离出的唯一产物是[K(18-冠-6)]dmedaB - B(OMe)${}_{3}$，相对于限量试剂KOMe，产率为62%。这种单核产物的形成意味着，当路易斯碱与其中一个[B(dmeda)]部分结合时，B - N π键系统被破坏，促进了进一步的${\mathrm{{MeO}}}^{ - }$加成并去除dmeda以形成9。

Scheme 4. Formation of the Lewis base adduct 9.

方案4. 路易斯碱加合物9的形成。

NMR spectroscopy

核磁共振光谱法

For the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adducts, there should be two distinct signals in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra, which is comparable to the ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ (NHC) adduct isolated previously by the Marder group (Figure 1): ${}^{\left\lbrack {19}\right\rbrack }$ one with $\delta < {20}\mathrm{{ppm}}$ , which arises from the tetrahedral boron site, and one with $\delta > {20}\mathrm{{ppm}}$ , which represents the trigonal boron site. The line shapes of these signals should also differ significantly. In solution, the lower-symmetry trigonal site should show a larger peak width than the higher-symmetry tetrahedral site. However, in the solid state we expect a more complex line shape for the signal resulting from the trigonal site. A comparison of the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra in solution and the solid state allows further conclusions to be drawn about the molecular structures of the adducts in solution in relation to their solid-state structures. This is especially the case for 6 because the typical ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectral pattern for ${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$ diboron compounds was not detected in the solution NMR spectrum (Figure 2). ${}^{\left\lbrack {30}\right\rbrack }$

对于${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$加合物，在${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱中应该有两个不同的信号，这与Marder小组之前分离出的${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$(NHC)加合物相当(图1):${}^{\left\lbrack {19}\right\rbrack }$一个信号出现在$\delta < {20}\mathrm{{ppm}}$处，它来自四面体硼位点，另一个信号出现在$\delta > {20}\mathrm{{ppm}}$处，它代表三角硼位点。这些信号的线形也应该有显著差异。在溶液中，对称性较低的三角位点的峰宽应该比对称性较高的四面体位点的峰宽大。然而，在固态下，我们预计三角位点产生的信号的线形会更复杂。比较溶液和固态下的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱，可以进一步得出关于加合物在溶液中的分子结构与其固态结构之间关系的结论。对于6来说尤其如此，因为在溶液NMR光谱中未检测到${\mathrm{{sp}}}^{2} - \; {\mathrm{{sp}}}^{3}$二硼化合物的典型${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱模式(图2)。${}^{\left\lbrack {30}\right\rbrack }$

Only one signal at $\delta = {22.1}\mathrm{{ppm}}$ was observed in the solution-state ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectrum of 6 at ${20}^{ \circ }\mathrm{C}$ , whereas in the solid-state spectrum two separate signals are clearly visible. The line shape and chemical shift of these signals in the solid-state NMR spectrum are indicative of a lower-symmetry trigonal boron site and a higher-symmetry tetrahedral boron site. The isotropic chemical shift $\left( {\delta }_{\text{ iso }}\right)$ values of these signals were estimated by simulation of the spectrum to ${36.5}\left( {\pm {1.5}}\right)$ and ${4.7}\left( {\pm {1.7}}\right) \mathrm{{ppm}}$ (Figure 2). The ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra in solution and the solid state are explained by the presence of a dynamic mutual exchange of the boron sites in solution, leading to an averaged signal and chemical shift. This is in good agreement with the observation of a low barrier for the exchange of the pinacol methyl groups observed by ${}^{1}\mathrm{H}$ NMR spectroscopy. When the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectrum was obtained at lower temperatures two signals were not observed; instead, one signal disappeared altogether at $- {10}^{ \circ }\mathrm{C}$ and below $- {30}^{ \circ }\mathrm{C}$ a single broad signal appeared at $\delta = {6.6}\mathrm{{ppm}}\left( {-{55}^{ \circ }\mathrm{C}}\right)$ , which correlates to the assigned ${\mathrm{{sp}}}^{3}$ boron site. This suggests an ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboronic structure for 6 in solution similar to that detected in the solid state, rather than a possible alternative bridging coordination of the phenolate ligand in solution. The missing signal of the ${\mathrm{{sp}}}^{2}$ boron site at $- {55}^{ \circ }\mathrm{C}$ may be explained by the line width of the signal being similar to the line width of the background signal, thus the signal is removed as an effect of the backward linear prediction. ${}^{\left\lbrack {30}\right\rbrack }$

在 6 的溶液态 ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR 谱中，于 ${20}^{ \circ }\mathrm{C}$ 处仅观察到一个位于 $\delta = {22.1}\mathrm{{ppm}}$ 的信号，而在固态谱中，两个分离的信号清晰可见。固态 NMR 谱中这些信号的线形和化学位移表明存在一个低对称性的三角硼位点和一个高对称性的四面体硼位点。通过对谱图进行模拟，估计这些信号的各向同性化学位移 $\left( {\delta }_{\text{ iso }}\right)$ 值分别为 ${36.5}\left( {\pm {1.5}}\right)$ 和 ${4.7}\left( {\pm {1.7}}\right) \mathrm{{ppm}}$(图 2)。溶液态和固态的 ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR 谱可通过溶液中硼位点的动态相互交换来解释，这导致了平均信号和化学位移。这与通过 ${}^{1}\mathrm{H}$ NMR 光谱观察到的频哪醇甲基交换势垒较低的现象相符。当在较低温度下获得 ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR 谱时，未观察到两个信号；相反，在 $- {10}^{ \circ }\mathrm{C}$ 时一个信号完全消失，在 $- {30}^{ \circ }\mathrm{C}$ 以下，在 $\delta = {6.6}\mathrm{{ppm}}\left( {-{55}^{ \circ }\mathrm{C}}\right)$ 处出现一个单宽信号，这与所指定的 ${\mathrm{{sp}}}^{3}$ 硼位点相关。这表明 6 在溶液中的结构为 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼结构，与在固态中检测到的结构相似，而非溶液中酚盐配体可能的替代桥连配位结构。在 $- {55}^{ \circ }\mathrm{C}$ 处 ${\mathrm{{sp}}}^{2}$ 硼位点信号的缺失可能是由于该信号的线宽与背景信号的线宽相似，因此该信号作为反向线性预测的结果被去除。${}^{\left\lbrack {30}\right\rbrack }$

Figure 2. ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ VT-NMR spectra of 6(thf) in $\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF and ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ solid-state NMR spectrum (black) and simulation (gray) of 6.

图2. 6(thf)在$\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF中的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$变温NMR谱以及6的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$固态NMR谱(黑色)和模拟谱(灰色)。

In addition to the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR signals of 6 already discussed, three extremely sharp signals $\left( {\delta = {8.9},{6.4}\text{ , and }{5.2}\mathrm{{ppm}}}\right)$ of low intensity $\left( { < 3\% \text{ relative to the signal at }\delta = {22.1}\mathrm{{ppm}}\text{ at }{20}^{ \circ }\mathrm{C}}\right)$ were observed due to impurities (Figure 2). Moreover, a signal at a similar chemical shift was observed frequently in solutions of 5 and 7, indicating a common decomposition pathway for these adducts. ${}^{\left\lbrack {26}\right\rbrack }$ The narrow line shape and the chemical shift value suggest the presence of a highly symmetric borate, such as ${\left\lbrack {\text{ Bpin }}_{2}\right\rbrack }^{ - }$ . This is in agreement with a signal observed at $\delta = \; {8.9}\mathrm{{ppm}}$ in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectrum of tetra- $n$ -butyl-phosphonium dipinacolatoborate in $\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF, suggesting that this borate is indeed the major impurity. ${}^{\left\lbrack {19},{26},{27}\right\rbrack }$ Furthermore, we found crystallographic evidence that the decomposition of 5 and 7 leads to products containing the borate ion [Bpin2] ${}^{ - }$ . ${}^{\left\lbrack {26}\right\rbrack }$ Therefore, it can be concluded that the formation of [Bpin2] presents a common decomposition pathway for a number of Lewis base adducts of 1.

除了前面已讨论过的 6 的 ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR 信号外，由于杂质的存在，还观察到三个强度低、极其尖锐的信号 $\left( {\delta = {8.9},{6.4}\text{ , and }{5.2}\mathrm{{ppm}}}\right)$ $\left( { < 3\% \text{ relative to the signal at }\delta = {22.1}\mathrm{{ppm}}\text{ at }{20}^{ \circ }\mathrm{C}}\right)$(图 2)。此外，在 5 和 7 的溶液中经常观察到化学位移相似的信号，这表明这些加合物存在共同的分解途径。${}^{\left\lbrack {26}\right\rbrack }$ 窄的谱线形状和化学位移值表明存在高度对称的硼酸盐，如 ${\left\lbrack {\text{ Bpin }}_{2}\right\rbrack }^{ - }$ 。这与四 - $n$ - 丁基 - 鏻二频哪醇硼酸酯在 $\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF 中的 ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR 光谱中在 $\delta = \; {8.9}\mathrm{{ppm}}$ 处观察到的信号一致，表明这种硼酸盐确实是主要杂质。${}^{\left\lbrack {19},{26},{27}\right\rbrack }$ 此外，我们从晶体学上找到了证据，证明 5 和 7 的分解会产生含有硼酸根离子 [Bpin2] ${}^{ - }$ 的产物。${}^{\left\lbrack {26}\right\rbrack }$ 因此，可以得出结论，[Bpin2] 的形成是 1 的许多路易斯碱加合物的共同分解途径。

The simulations to determine ${\delta }_{\text{ iso }}$ were complicated, not only in the case of 6 , but also in the case of the adducts 2, 5, 7, and 8, due to the presence of magnetically inequivalent, but chemically equivalent, boron sites. Therefore, up to three boron sites per chemically equivalent site (trigonal or tetrahedral) had to be considered in the simulation. To ensure that these sites originated from a single (chemical) species and were not caused by the presence of impurities, only high-purity (determined by elemental analysis) samples were used. Additionally, ${}^{13}\mathrm{C}\left\{ {{}^{1}\mathrm{H}}\right\}$ magic angle spinning (MAS) NMR spectra were obtained for 5, 6(thf), 6(dmf), 7, and 8 to prove their purity and exact identity; these spectra only feature additional signals, relative to the spectra obtained in solution, that are in agreement with the reduced symmetry in the solid state. This indicates both the purity of the samples used and the similarity of the structures of the species present in solution and the solid state.

确定${\delta }_{\text{ iso }}$的模拟很复杂，不仅对于6是这样，对于加合物2、5、7和8也是如此，因为存在磁不等价但化学等价的硼位点。因此，在模拟中每个化学等价位点(三角形或四面体)最多要考虑三个硼位点。为确保这些位点来自单一(化学)物种而不是由杂质的存在引起，仅使用高纯度(通过元素分析确定)的样品。此外，还获得了5、6(thf)、6(dmf)、7和8的${}^{13}\mathrm{C}\left\{ {{}^{1}\mathrm{H}}\right\}$ 魔角旋转(MAS)NMR光谱以证明它们的纯度和确切身份；相对于在溶液中获得的光谱，这些光谱仅具有额外的信号，这与固态中降低后的对称性一致。这既表明了所用样品的纯度，也表明了溶液和固态中存在的物种结构的相似性。

Table 1. ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectroscopic data for complexes 1-9.

表1. 配合物1 - 9的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱数据。

[a] The given data were determined by simulation and are weighted and averaged values from up to three different ${}^{11}\mathrm{\;B}$ sites. All spectra were obtained at ambient temperature. Complex 2, 6(dmf), and 6(thf) show a similar ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ solid-state NMR spectrum and were simulated with the same set of parameters. For all solid-state NMR and simulated spectra, see section 2 of the Supporting Information. ${}^{\left\lbrack {26}\right\rbrack }$

[a] 给定数据通过模拟确定，是来自最多三个不同${}^{11}\mathrm{\;B}$ 位点的加权平均值。所有光谱均在室温下获得。配合物2、6(dmf)和6(thf)显示出相似的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ 固态NMR光谱，并使用同一组参数进行模拟。有关所有固态NMR和模拟光谱，请参阅支持信息的第2节。${}^{\left\lbrack {26}\right\rbrack }$

A comparison of the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{\;H}}\right\}$ NMR spectroscopic data for adducts (2, 3, and 5-9; Table 1) shows that the general expectation to find two signals for two distinctly different boron sites-trigonal and tetrahedral-is confirmed for all diboron adducts, apart from 6 (see above). The signal of the trigonal boron site typically has a significantly higher chemical shift than in 1 and is in agreement with similar ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR shifts observed for metal-boryl complexes that contain the Bpin fragment. ${}^{\left\lbrack {19},{31}\right\rbrack }$ Furthermore, in general, the chemical shift of the tetrahedral boron atom is similar to the value found for aryl-trialkoxyboronate anions. ${}^{\left\lbrack {18}a,{32}\right\rbrack }$ This indicates polarization of the B-B bond and could be described, as a limiting case, as a trigonal boryl anion coordinated to a trialkoxyborane.

对加合物(2、3和5 - 9；表1)的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{\;H}}\right\}$核磁共振光谱数据进行比较后发现，除了6(见上文)之外，对于所有二硼加合物而言，在两个明显不同的硼位点——三角型和四面体型——找到两个信号的一般预期得到了证实。三角型硼位点的信号通常具有比1中显著更高的化学位移，并且与含有Bpin片段的金属硼基配合物所观察到的类似${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振位移一致。${}^{\left\lbrack {19},{31}\right\rbrack }$此外，一般来说，四面体硼原子的化学位移与芳基 - 三烷氧基硼酸根阴离子的值相似。${}^{\left\lbrack {18}a,{32}\right\rbrack }$这表明B - B键的极化，并且作为一种极限情况，可以描述为一个三角型硼基阴离子与一个三烷氧基硼烷配位。

The solid-state ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR data are essentially comparable to the solution NMR data, indicating similar ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron (sub)structures in solution and the solid state. Dissolving adducts 2 and 6 induces a significant structural change (i.e. degree of aggregation), but this does not lead to a significant change in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR data (solid state versus in solution). The chemical shifts in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra appear to be rather insensitive to changes to the overall structure of the adducts. This can also be concluded from small variances of the signals in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra, especially for the solid-state data (Table 1). Hence, no information can be obtained from this data regarding the degree of association of the cation and anion in solution.

固态${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振数据与溶液核磁共振数据基本可比，表明溶液和固态中存在相似的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼(亚)结构。溶解加合物2和6会引起显著的结构变化(即聚集程度)，但这不会导致${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振数据(固态与溶液)的显著变化。${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振光谱中的化学位移似乎对加合物整体结构的变化相当不敏感。这也可以从${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振光谱中信号变化很小得出结论，特别是对于固态数据(表1)。因此，从这些数据中无法获得关于溶液中阳离子和阴离子缔合程度的信息。

A ${}^{1}$ H NMR spectroscopic study was also undertaken to analyze adducts 2,3, and 5-8. In solution, the ${}^{1}\mathrm{H}$ NMR spectra displayed similar splitting patterns for the pinacol methyl groups, even if the temperature dependence and, therefore, the dynamics in solution were different (Table 2).

还进行了${}^{1}$氢核磁共振光谱研究以分析加合物2、3和5 - 8。在溶液中，即使温度依赖性以及因此溶液中的动力学不同(表2)，${}^{1}\mathrm{H}$核磁共振光谱对频哪醇甲基显示出相似的分裂模式。

The splitting of the pinacol methyl groups into three signals with an intensity ratio of 12:6:6 is in agreement with structures of these compounds in solution that resemble the monomeric solid-state structures. The ${\mathrm{{sp}}}^{3}$ -Bpin moiety gives rise to two signals because, on the NMR timescale, its five-membered ring is perpendicular to the mirror plane parallel to the B-B bond. Therefore, two signals of equal intensity, each arising from two methyl groups either syn or anti to the coordinated Lewis base, are observed. The ${\mathrm{{sp}}}^{2}$ -Bpin moiety gives rise to only one signal, which integrates to 12, due to rapid interconversion of different conformers of this moiety. In contrast, for 6 no splitting of the pinacol methyl signals was detected; only a broadened singlet was observed, indicating rapid exchange even at $- {55}^{ \circ }\mathrm{C}$ (Table 2). ${}^{\left\lbrack {26}\right\rbrack }$

频哪醇甲基分裂为强度比为12:6:6的三个信号，这与这些化合物在溶液中的结构类似于单体固态结构一致。${\mathrm{{sp}}}^{3}$ - Bpin部分产生两个信号，因为在核磁共振时间尺度上，其五元环垂直于平行于B - B键的镜面。因此，观察到两个强度相等的信号，每个信号由与配位路易斯碱顺式或反式的两个甲基产生。由于该部分不同构象的快速相互转化，${\mathrm{{sp}}}^{2}$ - Bpin部分仅产生一个积分值为12的信号。相比之下，对于6，未检测到频哪醇甲基信号的分裂；仅观察到一个变宽的单峰，表明即使在$- {55}^{ \circ }\mathrm{C}$时也有快速交换(表2)。${}^{\left\lbrack {26}\right\rbrack }$

Table 2. ${}^{1}\mathrm{H}$ NMR shifts of the pinacol groups in 2,3, and 5-8.

表2. 2、3和5 - 8中频哪醇基团的${}^{1}\mathrm{H}$核磁共振位移。

DFT calculations

密度泛函理论计算

To gain information regarding the stability of these isolated adducts, we performed DFT calculations using both the B3LYP and MPW1K functionals to obtain thermochemical data for several cases of the Lewis acid/base reactions (Table 3).

为了获取有关这些孤立加合物稳定性的信息，我们使用B3LYP和MPW1K泛函进行了DFT计算，以获得几种Lewis酸/碱反应情况下的热化学数据(表3)。

The Lewis acid/base reactions involve two-to-one transformations; therefore, entropy is expected to be important. Consistent with this, the ${\Delta H}$ values are always much more negative than the Gibbs free energy $\left( {\Delta G}\right)$ values. Consequently, it is more appropriate to use ${\Delta G}$ values for the reactions to discuss the adduct stabilities. Interestingly, the $\Delta {G}_{\text{ gas }}$ values calculated by using the B3LYP functional are, in general, smaller than those calculated by using the tighter-binding MPW1K functional. However, after solvation energy corrections, the $\Delta {G}_{\text{ sol }}$ values calculated with both functionals do not differ significantly. Table 3 shows that the solvation-corrected ${\Delta G}$ values of the reactions were calculated to be in the range of -2 to $- {10}\mathrm{{kcal}} \; {\mathrm{{mol}}}^{-1}$ , with adduct 5 having the most negative calculated $\Delta {G}_{\text{ sol }}$ values (-9 to $- {10}\mathrm{{kcal}}{\mathrm{{mol}}}^{-1}$ ).

路易斯酸/碱反应涉及二比一的转化；因此，熵预计很重要。与此一致的是，${\Delta H}$值总是比吉布斯自由能$\left( {\Delta G}\right)$值更负得多。因此，使用${\Delta G}$值来讨论加合物稳定性对于这些反应更为合适。有趣的是，使用B3LYP泛函计算的$\Delta {G}_{\text{ gas }}$值通常比使用结合更紧密的MPW1K泛函计算的值小。然而，在进行溶剂化能校正后，用这两种泛函计算的$\Delta {G}_{\text{ sol }}$值没有显著差异。表3显示，反应的溶剂化校正后的${\Delta G}$值计算结果在-2到$- {10}\mathrm{{kcal}} \; {\mathrm{{mol}}}^{-1}$范围内，加合物5的计算出的$\Delta {G}_{\text{ sol }}$值最负(-9到$- {10}\mathrm{{kcal}}{\mathrm{{mol}}}^{-1}$)。

Table 3. Thermochemical data [electronic energies $\left( {\Delta E}\right)$ , enthalpies $\left( {\Delta H}\right)$ , and Gibbs free energies $\left( {\Delta G}\right)$ ] calculated for the formation of 4,5, and 7 (all values in $\mathrm{{kcal}}{\mathrm{{mol}}}^{-1}$ ).

表3. 为形成4、5和7计算得到的热化学数据电子能量$\left( {\Delta E}\right)$、焓$\left( {\Delta H}\right)$和吉布斯自由能$\left( {\Delta G}\right)$。

[a] $\Delta {H}_{\text{ solv }} = \Delta {H}_{\text{ gas }} + \left( {\Delta {E}_{\text{ solv }} - \Delta {E}_{\text{ gas }}}\right)$ . [b] $\Delta {G}_{\text{ solv }} = \Delta {G}_{\text{ gas }} + \left( {\Delta {E}_{\text{ solv }} - \Delta {E}_{\text{ gas }}}\right)$ .

[a] $\Delta {H}_{\text{ solv }} = \Delta {H}_{\text{ gas }} + \left( {\Delta {E}_{\text{ solv }} - \Delta {E}_{\text{ gas }}}\right)$ 。[b] $\Delta {G}_{\text{ solv }} = \Delta {G}_{\text{ gas }} + \left( {\Delta {E}_{\text{ solv }} - \Delta {E}_{\text{ gas }}}\right)$ 。

The $\Delta {G}_{\text{ sol }}$ values calculated for the adduct 4 are less negative by $2 - 4\mathrm{{kcal}}{\mathrm{{mol}}}^{-1}$ than those for 5, a result of steric effects of the bulkier $t{\mathrm{{BuO}}}^{ - }$ group. For the fluoride adduct 7, the $\Delta {G}_{\text{ gas }}$ values are also appreciably negative, and are comparable to those calculated for 5. However, the large solvation energies for both ${\mathrm{F}}^{ - }$ and $n{\mathrm{{Bu}}}_{4}{\mathrm{\;N}}^{ + }$ make the $\Delta {G}_{\text{ sol }}$ values (about -5 kcal ${\mathrm{{mol}}}^{-1}$ ) less negative than expected, based on the known affinity of boron for fluorine.

加合物4计算得到的$\Delta {G}_{\text{ sol }}$值比5的$\Delta {G}_{\text{ sol }}$值负性小$2 - 4\mathrm{{kcal}}{\mathrm{{mol}}}^{-1}$，这是由于体积更大的$t{\mathrm{{BuO}}}^{ - }$基团的空间效应所致。对于氟化物加合物7，$\Delta {G}_{\text{ gas }}$值也明显为负，且与5计算得到的$\Delta {G}_{\text{ gas }}$值相当。然而，${\mathrm{F}}^{ - }$和$n{\mathrm{{Bu}}}_{4}{\mathrm{\;N}}^{ + }$两者的大溶剂化能使得$\Delta {G}_{\text{ sol }}$值(约-5千卡${\mathrm{{mol}}}^{-1}$)比基于已知硼对氟的亲和力所预期的负性要小。

Crystal structure

晶体结构

To explore the exact structure of the Lewis base adducts, single-crystal structure analysis was performed for complexes 2-9. ${}^{\left\lbrack {26}\right\rbrack }$ Single crystals of 2 were obtained by diffusion of solutions of 1 and KOtBu in THF at ${0}^{ \circ }\mathrm{C}$ . This reactive crystallization approach only gave crystals of poor quality, despite several attempts at improvement (variation of the temperature, concentrations, and the geometry of the vessels employed).

为探究路易斯碱加合物的确切结构，对配合物2 - 9进行了单晶结构分析。${}^{\left\lbrack {26}\right\rbrack }$ 通过在${0}^{ \circ }\mathrm{C}$ 下使1和叔丁醇钾在四氢呋喃中的溶液扩散，得到了2的单晶。尽管多次尝试改进(改变温度、浓度以及所用容器的几何形状)，这种反应性结晶方法仅得到了质量较差的晶体。

Due to the poor quality of the diffraction data, a detailed discussion of the molecular structure of 2 is not feasible (Table 4; Tables S3-S5 in the Supporting Information). However, some principle features can be stated. Compound 2 exists as infinite chains parallel to the $c$ axis formed by connecting ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$ units with potassium atoms. ${}^{\left\lbrack {26}\right\rbrack }$ The potassium atoms are coordinated by five oxygen atoms of the ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$ moieties (Figure 3). A possible sixth interaction, O(5)–K(1), is very long (4.460(4) Å) and is not significant. The $t{\mathrm{{BuO}}}^{ - }$ group coordinates via the oxygen atom to one boron atom, leading to an ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compound. The geometry of the ${\mathrm{{sp}}}^{2}$ boron atom B(1) remains essentially unchanged compared to that in 1, whereas B(2) is now ${\mathrm{{sp}}}^{3}$ -hybridized.

由于衍射数据质量较差，对2的分子结构进行详细讨论是不可行的(表4；支持信息中的表S3 - S5)。然而，可以说明一些主要特征。化合物2以平行于$c$ 轴的无限链形式存在，由${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$ 单元与钾原子相连形成。${}^{\left\lbrack {26}\right\rbrack }$ 钾原子由${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$ 部分的五个氧原子配位(图3)。一种可能的第六种相互作用，O(5)–K(1)，非常长(4.460(4) Å)，并不显著。$t{\mathrm{{BuO}}}^{ - }$ 基团通过氧原子与一个硼原子配位，形成一个${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼化合物。与1相比，${\mathrm{{sp}}}^{2}$ 硼原子B(1)的几何形状基本保持不变，而B(2)现在是${\mathrm{{sp}}}^{3}$ 杂化的。

Crystallization of 2 from DMF/Et ${}_{2}\mathrm{O}$ led to the isolation of the adduct ${\left( \mathbf{2}\right) }_{2}\left( \mathrm{{dmf}}\right)$ , containing half a molecule of DMF per molecule of 2 (Figure 4). The structure of ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ is derived from the structure of 2, being assembled from infinite chains of alternating ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right\rbrack }^{ - }$ moieties and potassium atoms. However, in this compound, every second potassium atom is additionally coordinated by a molecule of DMF and this results in two different environments for the potassium atoms. ${}^{\left\lbrack {26}\right\rbrack }$ One of them, K(1), situated on a center of inversion, is sixfold coordinated by the oxygen atoms of the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron moiety, forming a distorted octahedron. The other potassium atom, K(2), is fivefold coordinated by four pinacolate oxygen atoms and one oxygen atom of a (disordered) DMF molecule (O(6)…K(2) 2.664(6) Å; Figure 4). ${}^{\left\lbrack {26}\right\rbrack }$ Compared with 2, the K(1) atoms are situated in a more saturated coordination environment, whereas the K(2) atoms remain coordinatively unsaturated. Any comparison with 2 must be done with considerable care because the errors in the determined structure of 2 are especially large. However, the geometry of the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron unit in ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ (Table 4) is similar to that in 2; the changes can be attributed to a twist around the B(1)-B(2) bond to maximize the oxygen-potassium interactions.

从DMF/Et ${}_{2}\mathrm{O}$ 中结晶2导致分离出加合物${\left( \mathbf{2}\right) }_{2}\left( \mathrm{{dmf}}\right)$ ，每个2分子含有半个DMF分子(图4)。${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ 的结构源自2的结构，由交替的${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right\rbrack }^{ - }$ 部分和钾原子的无限链组装而成。然而，在这种化合物中，每隔一个钾原子还额外与一个DMF分子配位，这导致钾原子有两种不同的环境。${}^{\left\lbrack {26}\right\rbrack }$ 其中之一，位于对称中心的K(1)，由${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼部分的氧原子六配位，形成一个扭曲的八面体。另一个钾原子K(2)由四个频哪醇氧原子和一个(无序的)DMF分子的氧原子五配位(O(6)…K(2) 2.664(6) Å；图4)。${}^{\left\lbrack {26}\right\rbrack }$ 与2相比，K(1)原子处于更饱和的配位环境，而K(2)原子仍处于配位不饱和状态。与2进行任何比较都必须非常小心，因为2的确定结构中的误差特别大。然而，${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ 中${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼单元的几何形状(表4)与2中的相似；这些变化可归因于围绕B(1)-B(2)键的扭转，以最大化氧 - 钾相互作用。

Figure 3. Perspective view of a section of the structure of 2. The bonds between the anionic and cationic part of the structure are drawn in dashed gray lines; thermal ellipsoids are drawn at the 30% probability level; disorder and hydrogen atoms are omitted for clarity.

图3. 2的结构的一部分的透视图。结构中阴离子部分和阳离子部分之间的键用灰色虚线表示；热椭球绘制在30%概率水平；为清晰起见，省略了无序部分和氢原子。

Table 4. Comparison of selected distances [Å] and angles [°] for 2, (2)(dmf), 3, 4, 5 , and 6(dmf).

表4. 2、(2)(dmf)、3、4、5和6(dmf)的选定距离[Å]和角度[°]的比较。

[a] Unified labelling scheme. [b] ${\Delta }_{\mathrm{{AB}},\mathrm{C},\mathrm{D}}$ is the maximum deviation of one of the atoms A, B, C, or D from the mean plane defined by A, B, C, and D. [c] The respective potassium atom is given in parentheses.

[a]统一标记方案。[b] ${\Delta }_{\mathrm{{AB}},\mathrm{C},\mathrm{D}}$是原子A、B、C或D之一与由A、B、C和D定义的平均平面的最大偏差。[c]相应的钾原子在括号中给出。

Figure 4. Perspective view of the asymmetric unit of the structure of ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ . The bonds between the anion and cation are drawn in dashed gray lines; thermal ellipsoids are drawn at the 50% probability level; disorder and hydrogen atoms are omitted for clarity.

图4. ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$结构的不对称单元的透视图。阴离子和阳离子之间的键用灰色虚线表示；热椭球绘制在50%概率水平；为清晰起见，省略了无序部分和氢原子。

The structure of the dimeric compound 3 can be easily derived from the polymeric structure of ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ . The infinite chains of ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ are broken apart into ion pairs by coordination of K(2) by one molecule of 18-crown-6 and two molecules of THF, leaving K(1) six-coordinated by two ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$ moieties (Figure 5). Remarkably, 3 is formed despite the presence of excess 18-crown-6 and THF as solvent, indicating the coordination capabilities of the anionic ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}{\mathrm{{OtBu}}}^{ - }\right\rbrack }^{ - }$ fragment. The binding of the potassium atom to this fragment benefits from the chelating, tridentate binding mode, the facial geometry, and coulombic interactions. The close structural relationship between ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ and 3 is also apparent in the similar local symmetry (in both cases, K(1) is situated on a center of inversion), bond lengths, and angles within these structures (Table 4).

二聚体化合物3的结构可以很容易地从${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$的聚合物结构推导出来。${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$的无限链通过18-冠-6的一个分子和四氢呋喃的两个分子与K(2)配位而断裂成离子对，使K(1)由两个${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$部分六配位(图5)。值得注意的是，尽管存在过量的18-冠-6和作为溶剂的四氢呋喃，仍形成了3，这表明阴离子${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}{\mathrm{{OtBu}}}^{ - }\right\rbrack }^{ - }$片段的配位能力。钾原子与该片段的结合得益于螯合、三齿结合模式、面式几何结构和库仑相互作用。${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$和3之间密切的结构关系在这些结构中相似的局部对称性(在两种情况下，K(1)位于对称中心)、键长和角度中也很明显(表4)。

Figure 5. Perspective view of the ${\left\lbrack \mathrm{K}{\left( {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right) }_{2}\right\rbrack }^{ - }$ subunit of 3. Thermal ellipsoids are drawn at the ${50}\%$ probability level; the disorder, the counterion ${\left\lbrack \mathrm{K}\left( {18}\text{ -crown-6 }\right) {\left( \mathrm{{thf}}\right) }_{2}\right\rbrack }^{ + }$ , and hydrogen atoms are omitted for clarity. The bonds between the anionic and cationic part of the structure are drawn in dashed gray lines.

图5. 3的${\left\lbrack \mathrm{K}{\left( {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right) }_{2}\right\rbrack }^{ - }$亚基的透视图。热椭球绘制在${50}\%$概率水平；为清晰起见，省略了无序部分、抗衡离子${\left\lbrack \mathrm{K}\left( {18}\text{ -crown-6 }\right) {\left( \mathrm{{thf}}\right) }_{2}\right\rbrack }^{ + }$和氢原子。结构中阴离子部分和阳离子部分之间的键用灰色虚线表示。

The monomeric compounds 4 and 5 are discussed together because their molecular structures are very similar, apart from the significant difference in packing observed between the two adducts.

单体化合物4和5一起讨论，因为它们的分子结构非常相似，只是在两种加合物之间观察到的堆积有显著差异。

In the crystal structure of 4, the atoms $\mathrm{K}\left( 1\right) ,\mathrm{B}\left( 1\right) ,\mathrm{C}\left( 1\right)$ , and C(2) are situated on a mirror plane (Figure 6), which accounts for extensive disorder within the molecular structure. ${}^{\left\lbrack {26}\right\rbrack }$ It appears that the similar steric properties of the $t{\mathrm{{BuO}}}^{ - }$ group and the $\mathrm{C} - {\mathrm{{CMe}}}_{2}$ substructure of the pinacol moiety are responsible for this disorder, a problem which was not encountered with the methoxy derivative 5 (Figure 7). It was possible to refine a reasonable split-atom model for the ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$ substructure of 4; however, it was not possible to refine an adequate model of the 18-crown-6 part of the structure. Hence, the electron density attributed to the 18-crown-6 moiety was partially removed from the data set by using the SQUEEZE function provided by the PLATON ${}^{\left\lbrack {33}\right\rbrack }$ program. The remaining electron-density maxima were interpreted, due to their geometry, as a set of partially occupied oxygen atoms of the 18-crown-6 substructure and were refined isotropically. This inadequate modeling of the disorder is, together with the disorder in the crystal itself, responsible for the low quality of the X-ray structure determination of 4. Refinement of this structure as pseudo-merohedrically twinned in the monoclinic crystal system did not lead to an increase in the quality of the refinement, nor did it resolve the disorder.

在4的晶体结构中，原子$\mathrm{K}\left( 1\right) ,\mathrm{B}\left( 1\right) ,\mathrm{C}\left( 1\right)$和C(2)位于一个镜面上(图6)，这导致了分子结构内的广泛无序。${}^{\left\lbrack {26}\right\rbrack }$似乎是$t{\mathrm{{BuO}}}^{ - }$基团与频哪醇部分的$\mathrm{C} - {\mathrm{{CMe}}}_{2}$子结构具有相似的空间性质导致了这种无序，甲氧基衍生物5(图7)没有遇到这个问题。对于4的${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{\;{Bu}}\right\rbrack }^{ - }$子结构，可以优化一个合理的分裂原子模型；然而，无法优化该结构中18-冠-6部分的合适模型。因此，通过使用PLATON${}^{\left\lbrack {33}\right\rbrack }$程序提供的SQUEEZE函数，从数据集中部分移除了归因于18-冠-6部分的电子密度。由于其几何形状，其余的电子密度最大值被解释为18-冠-6子结构的一组部分占据的氧原子，并进行了各向同性优化。这种对无序的不充分建模，连同晶体本身的无序，导致了4的X射线结构测定质量较低。在单斜晶体系统中将该结构作为假孪生体进行优化，并没有提高优化质量，也没有解决无序问题。

Figure 6. Perspective view of 4. Thermal ellipsoids are drawn at the 30% probability level; hydrogen atoms are omitted for clarity; the ${\mathrm{{CH}}}_{2}$ groups of 18-crown-6 could not be refined due to extensive disorder (see text); a unified labeling scheme is used. The bonds between the anionic and cationic parts of the structure are drawn in dashed gray lines.

图6. 4的透视图。热椭球体以30%的概率水平绘制；为清晰起见，省略了氢原子；由于广泛的无序，18-冠-6的${\mathrm{{CH}}}_{2}$基团无法优化(见正文)；使用统一的标记方案。结构中阴离子和阳离子部分之间的键用灰色虚线绘制。

Figure 7. Perspective view of 5. Thermal ellipsoids are drawn at the 50% probability level; disorder and hydrogen atoms are omitted for clarity. The bonds between the anionic and cationic part of the structure are drawn in dashed gray lines.

图7. 5的透视图。热椭球体以50%的概率水平绘制；为清晰起见，省略了无序和氢原子。结构中阴离子和阳离子部分之间的键用灰色虚线绘制。

Because the quality of the structure determination of the methoxy adduct 5 is much higher it is discussed representatively in detail. However, a brief discussion of 4 is essential to reveal the structural development from an infinite chain in 2 to a monomeric structure in 4. ${}^{\left\lbrack {26}\right\rbrack }$

由于甲氧基加合物5的结构测定质量高得多，因此将对其进行详细的代表性讨论。然而，对4进行简要讨论对于揭示从2中的无限链到4中的单体结构的结构发展至关重要。${}^{\left\lbrack {26}\right\rbrack }$

Interestingly, despite the use of THF as the solvent, no THF ligands are present in the crystals of 4 or 5 and the potassium atom is coordinated by the boron-bound oxygen atoms O(4) and O(5) as well as the crown ether moiety. This indicates the effective chelation of these oxygen atoms and is attributed, at least partially, to the attractive coulombic interaction between the ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}}\right\rbrack }^{ - }$ and the [(18-crown-6)K] ${}^{ + }$ fragments. This feature is also observed for the related 1,1-diamino-2,2,2-trialkoxy adduct, 9 (Figure S25 in the Supporting Information). ${}^{\left\lbrack {26}\right\rbrack }$ The fact that the ${\mathrm{{sp}}}^{3}$ and not the ${\mathrm{{sp}}}^{2}$ boron-bound oxygen atoms are coordinated to $\mathrm{K}\left( 1\right)$ may indicate the smaller donor capabilities of the latter oxygen atoms (they are involved in $\pi$ donation to a boron atom) and the increased donor capabilities of the formally, partially charged oxygen atoms bound to the ${\mathrm{{sp}}}^{3}$ boron atom. The geometries at the boron atoms in the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron substructures of 5 (and also 4, within error) are basically similar to those in the other adducts; however, the B-B bond length in both 4 and 5 are at the long end of the range (Table 4). This may be attributed to the lack of bridging coordination by the potassium atom between both boron sites, which may be favored by slightly shorter B-B bond lengths in the other adducts.

有趣的是，尽管使用四氢呋喃(THF)作为溶剂，但在化合物 4 或 5 的晶体中不存在 THF 配体，钾原子由与硼相连的氧原子 O(4) 和 O(5) 以及冠醚部分配位。这表明这些氧原子发生了有效螯合，并且这至少部分归因于 ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}}\right\rbrack }^{ - }$ 与 [(18-冠 - 6)K] ${}^{ + }$ 片段之间有吸引力的库仑相互作用。在相关的 1,1 - 二氨基 - 2,2,2 - 三烷氧基加合物 9 中也观察到了这一特征(支持信息中的图 S25)。${}^{\left\lbrack {26}\right\rbrack }$ ${\mathrm{{sp}}}^{3}$ 上与硼相连的氧原子而非 ${\mathrm{{sp}}}^{2}$ 上的氧原子与 $\mathrm{K}\left( 1\right)$ 配位，这一事实可能表明后者氧原子的给电子能力较弱(它们参与了向硼原子的 $\pi$ 给电子作用)，而与 ${\mathrm{{sp}}}^{3}$ 硼原子相连、形式上带有部分电荷的氧原子的给电子能力增强。化合物 5(在误差范围内，化合物 4 也是如此)的 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼亚结构中硼原子的几何结构与其他加合物中的基本相似；然而，化合物 4 和 5 中的 B - B 键长处于该范围的上限(表 4)。这可能归因于钾原子未在两个硼位点之间形成桥连配位，而在其他加合物中稍短的 B - B 键长可能有利于这种桥连配位。

The phenoxy derivative 6, isolated as (6)thf after reaction in THF, crystallizes from a solution in DMF/Et ${}_{2}$ O as solvated complex 6(dmf). The asymmetric unit contains three independent units of 6(dmf), but as the difference in the geometry between the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron substructures is negligible, one formula unit is discussed representatively (Table 4, Figure 8). ${}^{\left\lbrack {26}\right\rbrack }$ The individual formula units of ${\mathrm{K\lbrack B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}\rbrack \left( {dmf}\right) }$ form infinite chains parallel to the $b$ axis of alternating $\mathrm{K}\left( \mathrm{{dmf}}\right)$ and ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}}\right\rbrack }^{ - }$ units, similar to those in 2 or ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ . However, in 6(dmf), all the potassium atoms exhibit a heavily distorted octahedral coordination environment and the exact geometries differ significantly, causing the reduced symmetry of this crystal structure. The differences between the geometry of the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron substructure relative to the other ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}}\right\rbrack }^{ - }$ compounds, especially ${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$ , are only small, except for the longer B(2)- O(5) bond length (Table 4). This is an indication of the weaker donor capabilities of the phenoxy group relative to an alkoxy group. The O-B-O and O-B-B angles and the B-O bond lengths (Table 4) appear to be susceptible to small, but significant, variations throughout the series of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds. These variations do not appear to be caused by changes in the B-O interactions, but instead optimize the interactions with the coordinated potassium atom (e.g. O(3), O(4), and O(5) in (2), (dmf), 3, and 5).

苯氧基衍生物6在四氢呋喃中反应后以(6)thf形式分离出来，它从N, N - 二甲基甲酰胺/乙醚(Et ${}_{2}$ O)的溶液中结晶为溶剂化配合物6(dmf)。不对称单元包含三个独立的6(dmf)单元，但由于二硼子结构之间的几何差异可忽略不计，因此代表性地讨论一个化学式单元(表4，图8)。${}^{\left\lbrack {26}\right\rbrack }$ ${\mathrm{K\lbrack B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}\rbrack \left( {dmf}\right) }$的各个化学式单元形成与$b$轴平行的无限链，由$\mathrm{K}\left( \mathrm{{dmf}}\right)$和${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}}\right\rbrack }^{ - }$单元交替组成，类似于2或${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$中的情况。然而，在6(dmf)中，所有钾原子都呈现出严重扭曲的八面体配位环境，并且确切的几何形状差异显著，导致该晶体结构的对称性降低。相对于其他${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OR}}\right\rbrack }^{ - }$化合物，特别是${\left( 2\right) }_{2}\left( \mathrm{{dmf}}\right)$，二硼子结构的几何形状差异很小，除了B(2)-O(5)键长较长(表4)。这表明苯氧基相对于烷氧基的给体能力较弱。在一系列${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物中，O - B - O和O - B - B角度以及B - O键长(表4)似乎容易受到微小但显著的变化影响。这些变化似乎不是由B - O相互作用的变化引起的，而是为了优化与配位钾原子的相互作用(例如(2)、(dmf)、3和5中的O(3)、O(4)和O(5))。

Figure 8. Perspective view of a section of the structure of 6(dmf). The bonds between the anionic and cationic part of the structure are drawn in dashed gray lines; thermal ellipsoids are drawn at the 50% probability level; disorder and hydrogen atoms are omitted for clarity; a unified labeling scheme is used.

图8. 6(dmf)结构的一部分的透视图。结构的阴离子部分和阳离子部分之间的键用灰色虚线表示；热椭球以50%概率水平绘制；为清晰起见，省略了无序和氢原子；使用统一的标记方案。

The fluoride adducts [nBu ${}_{4}$ N][B ${}_{2}$ pin ${}_{2}$ F] 7 and [Me ${}_{4}$ N][B ${}_{2}$ pin ${}_{2}$ F] 8 are substantially different from the adducts discussed so far; they are not derived from an alkoxide base and contain a non-Lewis acidic cation ${\mathrm{R}}_{4}{\mathrm{\;N}}^{ + }$ as the counterion. Compound 7 crystallizes with an ionic structure in an orthorhombic lattice. For 7, columns of alternating units of $n{\mathrm{{Bu}}}_{4}{\mathrm{\;N}}^{ + }$ and ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}\right\rbrack }^{ - }$ extend along the $b$ axis (Figure S24 in the Supporting Information). ${}^{\left\lbrack {26}\right\rbrack }$ For comparison to 7, adduct 8 was synthesized from 1 and ${\mathrm{{Me}}}_{4}\mathrm{{NF}}$ to exchange the counterion and use the anhydrous fluorinated base ${\mathrm{{Me}}}_{4}\mathrm{\;N}\mathrm{F}$ , instead of $n{\mathrm{{Bu}}}_{4}\mathrm{{NF}} - 3{\mathrm{H}}_{2}\mathrm{O}$ . Initial attempts to refine a crystal structure of 8 were unsuccessful due to the extreme disorder in the system. However, crystallization by slow cooling of a solution in THF gave well-developed needles of 8(thf) suitable for XRD analysis (Figure 9).

氟化物加合物[nBu ${}_{4}$ N][B ${}_{2}$ pin ${}_{2}$ F] 7和[Me ${}_{4}$ N][B ${}_{2}$ pin ${}_{2}$ F] 8与迄今为止讨论的加合物有很大不同；它们不是由醇盐碱衍生而来，并且含有一个非路易斯酸性阳离子${\mathrm{R}}_{4}{\mathrm{\;N}}^{ + }$作为抗衡离子。化合物7以离子结构结晶在正交晶格中。对于7，$n{\mathrm{{Bu}}}_{4}{\mathrm{\;N}}^{ + }$和${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}\right\rbrack }^{ - }$的交替单元列沿$b$轴延伸(支持信息中的图S24)。${}^{\left\lbrack {26}\right\rbrack }$为了与7进行比较，加合物8由1和${\mathrm{{Me}}}_{4}\mathrm{{NF}}$合成，以交换抗衡离子并使用无水氟化碱${\mathrm{{Me}}}_{4}\mathrm{\;N}\mathrm{F}$，而不是$n{\mathrm{{Bu}}}_{4}\mathrm{{NF}} - 3{\mathrm{H}}_{2}\mathrm{O}$。由于系统中的极端无序，最初对8的晶体结构进行精修的尝试未成功。然而，通过缓慢冷却THF溶液进行结晶得到了适合XRD分析的8(thf)的发育良好的针状晶体(图9)。

The structure of the anion in 8 is similar to those of the alkoxy adducts. Boron atom B(1) is essentially planar, whereas B(2) is tetrahedral (Figure 9). The B-B bond length is slightly shorter than those found in the molecular alkoxy adducts, such as 5. The longer B-F bond of 1.478(3) Å compared to those in simple ${\mathrm{{BF}}}_{4}{}^{ - }$ salts (1.369(5) Å on average) ${}^{\left\lbrack {34}\right\rbrack }$ suggests weaker bonding of the fluoride ion due to the increased donor capability of the alkoxy group relative to fluoride. The B-O bond lengths are essentially comparable to those discussed earlier for the alkoxy adducts. The angles F(1)-B(2)-O(3) and F(1)-B(2)-O(4) are more similar than the respective O(5)-B(2)- O(3) and O(5)-B(2)-O(4) angles in the alkoxy adducts because they are not influenced by coordination to a potassium cation. However, the O-B-O angle at the tetrahedral boron atom is again influenced by the bidentate binding mode of the pinacolate group. All bond lengths and angles are comparable with those of adduct 7 (for more details see the Supporting Information). ${}^{\left\lbrack {26}\right\rbrack }$

8中阴离子的结构与烷氧基加合物的结构相似。硼原子B(1)基本呈平面状，而B(2)呈四面体状(图9)。B-B键长略短于分子烷氧基加合物中的键长，例如5。与简单${\mathrm{{BF}}}_{4}{}^{ - }$盐中的B-F键长(平均1.369(5) Å)相比，1.478(3) Å的较长B-F键${}^{\left\lbrack {34}\right\rbrack }$表明由于醇氧基相对于氟的供体能力增加，氟离子的键合较弱。B-O键长与前面讨论的烷氧基加合物的键长基本相当。角度F(1)-B(2)-O(3)和F(1)-B(2)-O(4)比烷氧基加合物中相应的O(5)-B(2)-O(3)和O(5)-B(2)-O(4)角度更相似，因为它们不受与钾阳离子配位的影响。然而，四面体硼原子处的O-B-O角度再次受到频哪醇基团的双齿结合模式的影响。所有键长和角度与加合物7的键长和角度相当(更多细节见支持信息)。${}^{\left\lbrack {26}\right\rbrack }$

Figure 9. Perspective view of the anionic part of 8 in from 8(thf). Thermal ellipsoids are drawn at the 50% probability level; hydrogen atoms and the counterion are omitted for clarity. Selected bond lengths [Å] and angles [°]: $B\left( 1\right) - B\left( 2\right) {1.736}\left( 8\right) , O\left( 1\right) - B\left( 1\right) {1.389}\left( 2\right) , O\left( 2\right) - B\left( 1\right) {1.394}\left( 2\right) , O\left( 3\right) - B\left( 2\right) {1.472}\left( 2\right)$ , $O\left( 4\right) - B\left( 2\right) {1.468}\left( 2\right) , F\left( 1\right) - B\left( 2\right) {1.478}\left( 2\right) ;O\left( 3\right) - B\left( 2\right) - O\left( 4\right) {105.55}\left( {13}\right) , O\left( 3\right) - B\left( 2\right) - F\left( 1\right)$ 108.99(13), O(4)-B(2)-F(1) 106.79(13), O(3)-B(2)-B(1) 112.33(14), O(4)-B(2)-B(1) 115.50(14), F(1)-B(2)-B(1) 107.42(13).

图9. 8(thf)中8的阴离子部分的透视图。热椭球绘制在50%概率水平；为清晰起见，省略了氢原子和抗衡离子。选定的键长[Å]和角度[°]:$B\left( 1\right) - B\left( 2\right) {1.736}\left( 8\right) , O\left( 1\right) - B\left( 1\right) {1.389}\left( 2\right) , O\left( 2\right) - B\left( 1\right) {1.394}\left( 2\right) , O\left( 3\right) - B\left( 2\right) {1.472}\left( 2\right)$ ，$O\left( 4\right) - B\left( 2\right) {1.468}\left( 2\right) , F\left( 1\right) - B\left( 2\right) {1.478}\left( 2\right) ;O\left( 3\right) - B\left( 2\right) - O\left( 4\right) {105.55}\left( {13}\right) , O\left( 3\right) - B\left( 2\right) - F\left( 1\right)$ 108.99(13)，O(4)-B(2)-F(1) 106.79(13)，O(3)-B(2)-B(1) 112.33(14)，O(4)-B(2)-B(1) 115.50(14)，F(1)-B(2)-B(1) 107.42(13)。

The increase in the B-B bond length in the anionic intermolecular adducts 2-9 of typically 0.024-0.049 Å is attributed to the change of hybridization of one of the boron atoms. The B-B bond lengths and elongations relative to the parent ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$ diboron compounds are in the typical range found for related neutral adducts of tetra-alkoxy diboron, bis(catecholato)dibor-on, or bis(thio-catecholato)diboron compounds. ${}^{\left\lbrack {35}\right\rbrack }$ Generally, the Bpin moiety tends to provide disorder. For 2-5 and 8, this disorder, essentially represented by two envelope conformations of the five-membered ring, was refined successfully by employing a split-atom model and, if necessary, appropriate restraints and constraints. ${}^{\left\lbrack {26}\right\rbrack }$

阴离子分子间加合物2 - 9中B - B键长通常增加0.024 - 0.049 Å，这归因于其中一个硼原子杂化的变化。相对于母体${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$二硼化合物的B - B键长和伸长率处于发现的四烷氧基二硼、双(儿茶酚)二硼或双(硫代儿茶酚)二硼化合物相关中性加合物的典型范围内。${}^{\left\lbrack {35}\right\rbrack }$一般来说，Bpin部分往往会产生无序。对于2 - 5和8，这种无序基本上由五元环的两种信封构象表示，通过采用分裂原子模型并在必要时施加适当的限制和约束，成功地进行了精修。${}^{\left\lbrack {26}\right\rbrack }$

Reactivity of the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adducts toward aryl electrophiles

${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$加合物对芳基亲电试剂的反应活性

The reactions of selected isolated ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds with electrophiles were studied by in situ NMR spectroscopy to observe the ability of the compounds to act as sources of nucleophilic boryl anions. Additionally, a potential acetate adduct of 1 was tested, however, it could not be isolated, therefore an equimolar mixture of 1 and TBPE ([nBu ${}_{4}$ P][OAc]) or KOAc was employed in the reactions. ${}^{\left\lbrack {27},{36}\right\rbrack }$ Both electrophilic aryl iodides and aryl diazonium salts were investigated as reaction partners due to their relevance in synthetically useful reactions (Scheme 5). ${}^{\left\lbrack {22},{23}\mathrm{a} - \mathrm{e}\right\rbrack }$

通过原位核磁共振光谱研究了选定的分离出的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物与亲电试剂的反应，以观察这些化合物作为亲核硼基阴离子来源的能力。此外，对1的一种潜在乙酸酯加合物进行了测试，然而，它无法被分离出来，因此在反应中使用了1与TBPE([nBu${}_{4}$P][OAc])或KOAc的等摩尔混合物。${}^{\left\lbrack {27},{36}\right\rbrack }$由于亲电芳基碘化物和芳基重氮盐在合成有用反应中的相关性(方案5)，它们都被作为反应伙伴进行了研究。${}^{\left\lbrack {22},{23}\mathrm{a} - \mathrm{e}\right\rbrack }$

Scheme 5. Reaction of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds with the aryl electro-philes 4-methylphenyl diazonium tetrafluoroborate and 4-methylphenyl iodide.

方案5. ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物与芳基亲电试剂四氟硼酸4-甲基苯基重氮盐和4-甲基苯基碘的反应。

Reactivity of aryl iodides

芳基碘化物的反应活性

During our studies of the copper-catalyzed borylation of aryl halides, we observed a background reaction that gave the desired aryl-boronate ester in low yield. An ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ anionic dibor-on species, formed in situ, was detected. This species could be the active nucleophile source and facilitate transfer of a boron moiety to the aryl iodide without the necessity for a metal complex. ${}^{\left\lbrack {22}\right\rbrack }$ Furthermore, Wu and Zhang recently reported the transition-metal-free borylation of aryl iodides with ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ (1) or ${\mathrm{B}}_{2}{\mathrm{{neop}}}_{2}$ in pure methanol, with ${\mathrm{{Cs}}}_{2}{\mathrm{{CO}}}_{3}$ as the base, albeit with a limited substrate scope. ${}^{\left\lbrack {37}\right\rbrack }$ This reaction was tested and verified by our group and we proposed that a similar anionic adduct was likely to form in situ, which could facilitate the synthesis of the aryl-boronate esters. Initial studies $\left( {{}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\} }\right.$ or ${}^{1}\mathrm{H}$ NMR spectroscopy) by our group did not detect the formation of an adduct of 1 with ${\mathrm{{Cs}}}_{2}{\mathrm{{CO}}}_{3}$ . However, the presence of $\mathrm{{MeOH}}$ in the reaction could promote formation of a similar adduct to 5, as proposed previously by Fernández et al. ${}^{\left\lbrack {10}\mathrm{a} - \mathrm{c},\mathrm{e},\mathrm{j},\mathrm{l}\right\rbrack }$ Using DFT calculations, they suggested that ${\mathrm{{Cs}}}_{2}{\mathrm{{CO}}}_{3}$ deproto-nates MeOH present in the reaction mixture to afford a methoxy species, which then generates the adduct ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OMe}}\right\rbrack }^{ - }$ in situ.

在我们对芳基卤化物的铜催化硼化反应的研究过程中，我们观察到一个背景反应，该反应以低产率生成了所需的芳基硼酸酯。检测到原位形成的一种${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$阴离子二硼物种。该物种可能是活性亲核试剂来源，并有助于在无需金属配合物的情况下将硼部分转移至芳基碘化物上。${}^{\left\lbrack {22}\right\rbrack }$此外，Wu和Zhang最近报道了芳基碘化物与${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ (1) 或${\mathrm{B}}_{2}{\mathrm{{neop}}}_{2}$在纯甲醇中，以${\mathrm{{Cs}}}_{2}{\mathrm{{CO}}}_{3}$作为碱进行的无过渡金属硼化反应，尽管底物范围有限。${}^{\left\lbrack {37}\right\rbrack }$我们小组对该反应进行了测试和验证，我们提出可能原位形成了类似的阴离子加合物，这有助于芳基硼酸酯的合成。我们小组最初的研究$\left( {{}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\} }\right.$或${}^{1}\mathrm{H}$(核磁共振光谱法)未检测到1与${\mathrm{{Cs}}}_{2}{\mathrm{{CO}}}_{3}$形成加合物。然而，反应中$\mathrm{{MeOH}}$的存在可能促进形成与5类似的加合物，正如Fernández等人之前所提出的。${}^{\left\lbrack {10}\mathrm{a} - \mathrm{c},\mathrm{e},\mathrm{j},\mathrm{l}\right\rbrack }$通过密度泛函理论计算，他们表明${\mathrm{{Cs}}}_{2}{\mathrm{{CO}}}_{3}$使反应混合物中存在的甲醇去质子化，得到一种甲氧基物种，然后该物种原位生成加合物${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{{OMe}}\right\rbrack }^{ - }$。

To investigate the stoichiometric reaction of the adducts with aryl iodides, the isolated ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds (2, 5, and 7) were treated with 4-methylphenyl iodide in deuterat-ed THF at ${60}^{ \circ }\mathrm{C}$ . These reactions could be conveniently monitored by in situ NMR spectroscopy (Figure 10). ${}^{\left\lbrack {38}\right\rbrack }$

为了研究加合物与芳基碘化物的化学计量反应，将分离得到的${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物(2、5和7)在${60}^{ \circ }\mathrm{C}$下于氘代四氢呋喃中用4-甲基苯基碘处理。这些反应可以通过原位核磁共振光谱法方便地监测(图10)。${}^{\left\lbrack {38}\right\rbrack }$

It is evident from the data shown that the borylation of aryl iodides proceeds very slowly (if at all) and only under increased reaction temperatures in this solvent $\left( {{60}^{ \circ }\mathrm{C}}\right)$ . The most efficient source of a boryl nucleophile appears to be the methoxy adduct 5 (Figure 10). In the case of 7, only traces of 4-Me- ${\mathrm{C}}_{6}{\mathrm{H}}_{4}\mathrm{\;B}$ pin were observed by ${}^{1}\mathrm{H}$ NMR spectroscopy after 5 days at ${60}^{ \circ }\mathrm{C}$ . However, extending the reaction time did not lead to further formation of the aryl-boronate ester because, at this point, adduct 7 had decomposed (determined by ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\} ,{}^{19}\mathrm{\;F}$ , and ${}^{1}\mathrm{H}$ NMR spectroscopy). In the spectrum of the reaction mixture, all characteristic signals of 7 had disappeared, with concomitant detection of 1. ${}^{\left\lbrack {26}\right\rbrack }$

从所示数据可以明显看出，芳基碘化物的硼化反应进行得非常缓慢(如果有反应的话)，并且仅在该溶剂$\left( {{60}^{ \circ }\mathrm{C}}\right)$中升高反应温度时才会发生。最有效的硼基亲核试剂来源似乎是甲氧基加合物5(图10)。就7而言，在${60}^{ \circ }\mathrm{C}$下反应5天后，通过${}^{1}\mathrm{H}$核磁共振光谱法仅观察到痕量的4-Me-${\mathrm{C}}_{6}{\mathrm{H}}_{4}\mathrm{\;B}$频哪醇。然而，延长反应时间并没有导致芳基硼酸酯的进一步形成，因为此时加合物7已经分解(通过${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\} ,{}^{19}\mathrm{\;F}$和${}^{1}\mathrm{H}$核磁共振光谱法确定)。在反应混合物的光谱中，7的所有特征信号都消失了，同时检测到了1。${}^{\left\lbrack {26}\right\rbrack }$

Figure 10. In situ ${}^{1}\mathrm{H}$ NMR (400 MHz,[D8]THF) spectra (benzylic region) of the reaction of $4 - \mathrm{{Me}} - {\mathrm{C}}_{6}{\mathrm{H}}_{4}\mathrm{I}$ with ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds (percentage with respect to all signals in the region shown. All signals are assumed to be methyl groups; signals with less than 3% intensity are not given.

图10. $4 - \mathrm{{Me}} - {\mathrm{C}}_{6}{\mathrm{H}}_{4}\mathrm{I}$ 与 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼化合物反应的原位${}^{1}\mathrm{H}$核磁共振(400兆赫，[D8]四氢呋喃)光谱(苄基区域)(相对于所示区域内所有信号的百分比。所有信号均假定为甲基；强度低于3%的信号未给出。

In comparison to 7, 8 was also treated with 4-methylphenyl iodide (in $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ ), but no product was observed at room temperature. When the reaction mixture was heated to ${70}^{ \circ }\mathrm{C}$ , adduct 8 decomposed after several hours to give what we believe to be ${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$ , observed by NMR spectroscopy (Figures S32 and S33 in the Supporting Information). ${}^{\left\lbrack {26}\right\rbrack }$

与7相比，8也用对甲苯碘(在$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ 中)处理，但在室温下未观察到产物。当反应混合物加热到${70}^{ \circ }\mathrm{C}$ 时，加合物8在数小时后分解，得到我们认为是${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$ 的产物，通过NMR光谱观察到(支持信息中的图S32和S33)。${}^{\left\lbrack {26}\right\rbrack }$

In the cases of the potential acetate adduct (1+TBPE) and adduct 2, no reaction was observed after two weeks at ${60}^{ \circ }\mathrm{C}$ . Adduct 2 was far-less effective than the closely related complex 5, which could be explained by the very low solubility of 2 under the reaction conditions. However, when the reaction of 2 was repeated in the presence of methanol (either as the pure solvent or by addition of a drop of methanol to the reaction in $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ ), the solubility of the adducts increased and a small amount of product was observed by GC-MS. This slight improvement in reactivity and the results from many reported transition-metal-free borylation reactions indicate that methanol is required to facilitate the formation of organoboronate esters and further research is ongoing into the dependence of transition-metal-free borylation systems on methanol. ${}^{\left\lbrack {23},{37},{39}\right\rbrack }$

在潜在的乙酸酯加合物(1 + TBPE)和加合物2的情况下，在${60}^{ \circ }\mathrm{C}$ 下两周后未观察到反应。加合物2的效果远不如密切相关的配合物5，这可以通过2在反应条件下的极低溶解度来解释。然而，当在甲醇存在下(作为纯溶剂或向$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ 中的反应中加入一滴甲醇)重复2的反应时，加合物的溶解度增加，并且通过GC-MS观察到少量产物。反应性的这种轻微改善以及许多报道的无过渡金属硼化反应的结果表明，需要甲醇来促进有机硼酸酯的形成，并且正在对无过渡金属硼化体系对甲醇的依赖性进行进一步研究。${}^{\left\lbrack {23},{37},{39}\right\rbrack }$

In all cases, toluene was formed as the major byproduct and the GC-MS data suggests that, additionally, a biphenyl derivative ${\left( {\mathrm{C}}_{7}{\mathrm{H}}_{7}\right) }_{2}$ is formed. The synthesis of the byproducts may be rationalized by the production of an aryl radical and subsequent hydrogen-atom abstraction or dimerization. ${}^{\left\lbrack {40}\right\rbrack }$

在所有情况下，甲苯都是主要副产物，GC-MS数据表明，此外，还形成了一种联苯衍生物${\left( {\mathrm{C}}_{7}{\mathrm{H}}_{7}\right) }_{2}$ 。副产物的合成可以通过芳基自由基的产生以及随后的氢原子夺取或二聚来合理化。${}^{\left\lbrack {40}\right\rbrack }$

The fate of the second Bpin moiety was analyzed for the reaction of 5 and all data ( ${}^{1}\mathrm{H}$ and ${}^{11}\mathrm{B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR, GC-MS) supported the formation of MeOBpin. ${}^{\left\lbrack {26}\right\rbrack }$ Additionally, in the cases of 5 and 7 a singlet resonance was observed in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectrum at $\delta = {8.6}\mathrm{{ppm}}$ , which may indicate the formation of a small amount of the dipinacolatoborate ion ( ${\left\lbrack {\mathrm{{Bpin}}}_{2}\right\rbrack }^{ - }$ or a mixed methoxypinacolatoboron anion). ${}^{\left\lbrack {19}\right\rbrack }$

对5的反应分析了第二个Bpin部分的去向，所有数据(${}^{1}\mathrm{H}$ 和${}^{11}\mathrm{B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR、GC-MS)都支持形成MeOBpin。${}^{\left\lbrack {26}\right\rbrack }$ 此外，在5和7的情况下，在${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱中在$\delta = {8.6}\mathrm{{ppm}}$ 处观察到一个单重态共振，这可能表明形成了少量的双频哪醇硼酸根离子(${\left\lbrack {\mathrm{{Bpin}}}_{2}\right\rbrack }^{ - }$ 或混合的甲氧基频哪醇硼阴离子)。${}^{\left\lbrack {19}\right\rbrack }$

Reactivity of aryl diazonium salts

芳基重氮盐的反应活性

Previously, we reported a versatile method for the synthesis of aryl-boronate esters from aryl amines, in the presence of benzoyl peroxide (BPO). ${}^{\left\lbrack {23}\mathrm{a} - \mathrm{e}\right\rbrack }$ It was proposed that the reaction may proceed via a diazonium salt, formed in situ, as well as a postulated ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compound. To verify this hypothesis, the relatively stable diazonium salt $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ was prepared and its reaction with 1 was examined (Table 5).

此前，我们报道了一种在过氧化苯甲酰(BPO)存在下由芳基胺合成芳基硼酸酯的通用方法。${}^{\left\lbrack {23}\mathrm{a} - \mathrm{e}\right\rbrack }$ 有人提出该反应可能通过原位形成的重氮盐以及假定的 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼化合物进行。为了验证这一假设，制备了相对稳定的重氮盐 $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ 并研究了其与1的反应(表5)。

The diazonium salt $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ did not react with 1 at room temperature in the presence or absence of BPO (Table 5, entries 1 and 3). When the reaction temperature was increased to ${70}^{ \circ }\mathrm{C}$ for ${10}\mathrm{\;h}$ , the formation of PhBpin was observed by GC-MS, but in a very low yield (Table 5, entry 2). Several metal alkoxides, as well as potassium acetate, were introduced into the reaction system and, in all cases, PhBpin was formed after 10 min at room temperature (Table 5, entries 5-9). Addition of KOtBu resulted in the highest yield of 40% (see below), which is comparable to our earlier report for in situ formation of the diazonium salt from tert-butyl nitrite and aniline. ${}^{\left\lbrack {23}\mathrm{a} - \mathrm{e}\right\rbrack }$

重氮盐 $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ 在有或没有BPO的情况下于室温下不与1反应(表5，条目1和3)。当反应温度升至 ${70}^{ \circ }\mathrm{C}$ 用于 ${10}\mathrm{\;h}$ 时，通过GC-MS观察到PhBpin的形成，但产率非常低(表5，条目2)。将几种金属醇盐以及醋酸钾引入反应体系，在所有情况下，室温下10分钟后形成了PhBpin(表5，条目5 - 9)。加入叔丁醇钾导致产率最高达到40%(见下文)，这与我们早期关于由亚硝酸叔丁酯和苯胺原位形成重氮盐的报道相当。${}^{\left\lbrack {23}\mathrm{a} - \mathrm{e}\right\rbrack }$

Table 5. Reaction of1with $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ in the presence of different bases. ${}^{\left\lbrack a\right\rbrack }$

表5. 1在不同碱存在下与 $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ 的反应。${}^{\left\lbrack a\right\rbrack }$

[a] Reaction conditions: 1:1 $1/\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ . [b] GC-MS yield with mesitylene as an internal standard. [c] BPO = benzoyl peroxide.

[a] 反应条件:1:1 $1/\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ 。[b] 以均三甲苯为内标物的GC-MS产率。[c] BPO = 过氧化苯甲酰。

To further analyze the reactivity of the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adducts, several aryl diazonium salts were synthesized and their reactions with2,5,7, and the potential acetate adduct of1were studied by in situ NMR spectroscopy in $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ at room temperature (Figure 11; Figure S45 in the Supporting Information). In all reactions, equimolar amounts of the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compound and the electrophile were employed. Immediately upon mixing solutions of the starting materials, vigorous evolution of gas was observed, which lasted a few seconds and indicated an almost instantaneous reaction. This very fast reaction justifies the use of MeCN as the solvent because initial decomposition studies indicated a limited lifetime of a few hours for 5 and a few days for the diazonium salt in MeCN. ${}^{\left\lbrack {26}\right\rbrack }$ This difference in reactivity may reflect the increased electrophilicity of diazonium salts relative to aryl iodides.

为了进一步分析 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 加合物的反应活性，合成了几种芳基重氮盐，并通过室温下在 $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ 中的原位NMR光谱研究了它们与2、5、7以及1的潜在醋酸盐加合物的反应(图11；支持信息中的图S45)。在所有反应中，使用等摩尔量的 ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ 二硼化合物和亲电试剂。将起始原料溶液混合后立即观察到剧烈的气体逸出，持续了几秒钟，表明反应几乎是瞬间发生的。这种非常快速的反应证明使用乙腈作为溶剂是合理的，因为初步分解研究表明5在乙腈中的寿命有限，为几个小时，而重氮盐的寿命为几天。${}^{\left\lbrack {26}\right\rbrack }$ 这种反应活性的差异可能反映了重氮盐相对于芳基碘的亲电性增加。

Figure 11. In situ ${}^{1}\mathrm{H}$ NMR (400 MHz, $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ ) spectra (benzylic region) of the reaction of $\left\lbrack {4 - {\mathrm{{Me}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ with ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compounds and KOMe after ${30}\mathrm{\;{min}}$ at ambient temperature (percentage with respect to all signals in the region shown; all signals are assumed to be methyl groups; signals with less than $3\%$ intensity are not given).

图11. 在室温下于${30}\mathrm{\;{min}}$后，$\left\lbrack {4 - {\mathrm{{Me}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$与${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物及KOMe反应的原位${}^{1}\mathrm{H}$ NMR(400 MHz，$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$)光谱(苄基区域)(相对于所示区域中的所有信号的百分比；所有信号假定为甲基；强度小于$3\%$的信号未给出)。

The spectra clearly show that the main reaction, in each case, was the conversion of the diazonium salt [4-Me- ${\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}$ ] $\left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ to the aryl-boronate ester (Figure 11). Complete consumption of $\left\lbrack {4 - {\mathrm{{Me}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ was only observed in the case of the potential acetate adduct of 1 , whereas in all other cases a considerable amount of unreacted starting material was detected. Similar reactivity of 1 with an acetoxy moiety had been observed in the reaction of 1 with $\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ in the presence of KOAc (Table 5, entry 9). This may indicate the presence of a small amount of an acetate adduct formed in equilibrium, despite the fact that no evidence for such an adduct was observed spectroscopically. The formation of an acetate adduct of 1 in the reaction would provide further evidence to support the adduct originally proposed by Miyaura et al. ${}^{\left\lbrack 5\right\rbrack }$

光谱清楚地表明，在每种情况下，主要反应是重氮盐[4-Me - ${\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}$]$\left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$转化为芳基硼酸酯(图11)。仅在1的潜在乙酸酯加合物的情况下观察到$\left\lbrack {4 - {\mathrm{{Me}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$完全消耗，而在所有其他情况下，检测到大量未反应的起始原料。在KOAc存在下1与$\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$的反应中观察到1与乙酰氧基部分具有相似的反应性(表5，条目9)。这可能表明存在少量以平衡形式形成的乙酸酯加合物，尽管从光谱上没有观察到这种加合物的证据。反应中1的乙酸酯加合物的形成将提供进一步的证据来支持Miyaura等人最初提出的加合物${}^{\left\lbrack 5\right\rbrack }$。

As was the case in the reaction of 4-methylphenyl iodide with adducts 2, 5, 7, and 8, during the course of the reaction variable amounts of byproducts were formed; however, the only byproduct identified by ${}^{1}\mathrm{H}$ NMR spectroscopy was toluene. GC-MS analysis of the reaction mixtures suggested that azobenzene and biphenyl derivative ${\left( {\mathrm{C}}_{7}{\mathrm{H}}_{7}\right) }_{2}$ were among the minor byproducts. Remarkably, in all four reactions, essentially the same byproducts were formed in a similar distribution, which indicated the close mechanistic relationship of the reactions. ${}^{\left\lbrack {26}\right\rbrack }$

与4-甲基苯基碘与加合物2, 5, 7和8的反应情况一样，在反应过程中形成了不同量的副产物；然而，通过${}^{1}\mathrm{H}$ NMR光谱鉴定出的唯一副产物是甲苯。反应混合物的GC-MS分析表明，偶氮苯和联苯衍生物${\left( {\mathrm{C}}_{7}{\mathrm{H}}_{7}\right) }_{2}$是次要副产物。值得注意的是，在所有四个反应中，基本上形成了相同的副产物，且分布相似，这表明反应之间存在密切的机理关系。${}^{\left\lbrack {26}\right\rbrack }$

In the control reaction of the diazonium salt with either KOMe, KOtBu or NMe ${}_{4}$ F, byproducts, in particular toluene, were formed, which indicates that their formation does not involve either the diboron compounds or the aryl-boronate ester (Figure 11). Furthermore, reactions performed between an aryl-boronate ester and KOMe or an aryl-boronate ester and the diazonium salt (in the absence and presence of KOMe) gave neither product nor byproduct.

在重氮盐与KOMe、KOtBu或NMe${}_{4}$F的对照反应中，形成了副产物，特别是甲苯，这表明它们的形成既不涉及二硼化合物也不涉及芳基硼酸酯(图11)。此外，在芳基硼酸酯与KOMe之间或芳基硼酸酯与重氮盐之间(在不存在和存在KOMe的情况下)进行的反应既没有产生产物也没有产生副产物。

Yamane and Zhu’s study of the transition-metal-free boryla-tion of aryl triazenes showed that an aryl diazonium salt could be borylated by 1 at room temperature in methanol. ${}^{\left\lbrack {39}\right\rbrack }$ We verified Yamane and Zhu’s yield of about ${40}\%$ for the reaction of $\left\lbrack {4 - {\mathrm{{MeO}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ and1in MeOH. However, only a trace of aryl-boronate ester was formed after four days from the reaction between 1 and the diazonium salt in $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ or $\left\lbrack {\mathrm{D}}_{6}\right\rbrack$ acetone at ambient temperature. ${}^{\left\lbrack {26}\right\rbrack }$ When a drop of methanol was introduced to the system, the respective product was observed to form more rapidly, albeit still at a reduced rate relative to the reaction in pure methanol. ${}^{\left\lbrack {26},{39}\right\rbrack }$ Thus, it is possible that ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}\right\rbrack }^{ - }$ is formed from 1 and ${\mathrm{{BF}}}_{4}{}^{ - }$ in $\mathrm{{MeOH}}$ , as suggested by Yamane and Zhu. Reaction of8with $\left\lbrack {4 - {\mathrm{{MeO}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \; \left\lbrack {\mathrm{{BPh}}}_{4}\right\rbrack$ in $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ was also examined, and a similar product ratio was obtained to that found when the diazonium salt with a ${\left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack }^{ - }$ cation was used. Therefore, in the absence of methanol, it is necessary to preform the adduct in the reaction with diazonium salts to facilitate the reaction and, in this case, ${\mathrm{{BF}}}_{4}$ does not act as a source of ${\mathrm{F}}^{ - }$ to form the adduct in situ.

山根和朱对芳基三氮烯的无过渡金属硼化反应的研究表明，芳基重氮盐在室温下于甲醇中可被1硼化。${}^{\left\lbrack {39}\right\rbrack }$ 我们验证了山根和朱报道的$\left\lbrack {4 - {\mathrm{{MeO}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ 与1在甲醇中反应的产率约为${40}\%$ 。然而，在室温下，1与重氮盐在$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ 或$\left\lbrack {\mathrm{D}}_{6}\right\rbrack$ 丙酮中反应四天后，仅形成了痕量的芳基硼酸酯。${}^{\left\lbrack {26}\right\rbrack }$ 当向体系中加入一滴甲醇时，观察到相应产物形成得更快，尽管相对于在纯甲醇中的反应速率仍然降低。${}^{\left\lbrack {26},{39}\right\rbrack }$ 因此，正如山根和朱所指出的，${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}\right\rbrack }^{ - }$ 有可能在$\mathrm{{MeOH}}$ 中由1和${\mathrm{{BF}}}_{4}{}^{ - }$ 形成。还研究了8与$\left\lbrack {4 - {\mathrm{{MeO}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \; \left\lbrack {\mathrm{{BPh}}}_{4}\right\rbrack$ 在$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ 中的反应，得到了与使用具有${\left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack }^{ - }$ 阳离子的重氮盐时相似的产物比例。因此，在没有甲醇的情况下，在与重氮盐的反应中预先形成加合物以促进反应是必要的，在这种情况下，${\mathrm{{BF}}}_{4}$ 不作为原位形成加合物的${\mathrm{F}}^{ - }$ 来源。

As with the aryl iodides, we were interested in the fate of the other Bpin moiety after the reaction of the isolated adducts and aryl diazonium salts. According to all the available data ( ${}^{1}\mathrm{H}$ and ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectroscopy, GC-MS), the moiety was converted to a single product of the type X-Bpin (X=OMe or OtBu). These experimental observations are in agreement with the relevant literature data and authentic samples. ${}^{\left\lbrack {26},{31}\mathrm{c},{41}\right\rbrack }$

与芳基碘化物的情况一样，我们对分离出的加合物与芳基重氮盐反应后另一个Bpin部分的去向感兴趣。根据所有可用数据(${}^{1}\mathrm{H}$ 和${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR光谱、GC-MS)，该部分转化为单一产物X-Bpin(X = OMe或OtBu)。这些实验观察结果与相关文献数据和真实样品一致。${}^{\left\lbrack {26},{31}\mathrm{c},{41}\right\rbrack }$

Scheme 6. A postulated equilibrium involved in the reaction between 8 and FBpin.

方案6. 8与FBpin反应中涉及的假定平衡。

Further reactivity studies were conducted for the reactions of different para-substituted aryl diazonium salts with the ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ adducts. Adduct 2 reacted with 4-me-thoxyphenyl diazonium tetrafluoroborate and gave full conversion of the starting material, but consistent data could not be obtained due to the low solubility of the adduct. ${}^{\left\lbrack {26}\right\rbrack }$ Therefore, the fluoride adduct 8 was used because it was easier to handle on a larger scale and was more soluble in the relevant solvents relative to many of the alkoxide adducts. The previously used adduct 7 was ruled out on the grounds of a possible negative influence of water on the reaction due to water present in $n{\mathrm{{Bu}}}_{4}\mathrm{{NF}} \cdot 3{\mathrm{H}}_{2}\mathrm{O}$ . Initially,8 was treated with stoichiometric amounts of $\left\lbrack {4 - \mathrm{R} - {\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack \left( {\mathrm{R} = \mathrm{H},\mathrm{{Me}},\mathrm{{OMe}},{\mathrm{{NO}}}_{2},\mathrm{{Br}}}\right)$ in a 1:1 electrophile/adduct ratio, but only approximately 70% of the starting material was converted, however, if the ratio was increased to 1:1.4 the conversion of starting material increased to 100%.

针对不同对位取代的芳基重氮盐与${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$加合物的反应，开展了进一步的反应活性研究。加合物2与4-甲氧基苯基重氮四氟硼酸盐反应，起始原料完全转化，但由于加合物溶解度低，未能获得一致的数据。${}^{\left\lbrack {26}\right\rbrack }$因此，选用氟化物加合物8，因为它更易于大规模操作，且相对于许多醇盐加合物，在相关溶剂中的溶解度更高。之前使用的加合物7被排除，因为$n{\mathrm{{Bu}}}_{4}\mathrm{{NF}} \cdot 3{\mathrm{H}}_{2}\mathrm{O}$中存在的水可能会对反应产生负面影响。最初，以化学计量的量将8与$\left\lbrack {4 - \mathrm{R} - {\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack \left( {\mathrm{R} = \mathrm{H},\mathrm{{Me}},\mathrm{{OMe}},{\mathrm{{NO}}}_{2},\mathrm{{Br}}}\right)$按亲电试剂/加合物1:1的比例进行处理，但起始原料仅约70%发生转化，然而，如果将比例提高到1:1.4，起始原料的转化率则提高到100%。

All the aryl-boronate esters were isolated in good yields (Table 6). Interestingly, in all cases, FBpin was not observed as the major byproduct for the second Bpin moiety. Instead, the corresponding signals in the ${}^{1}\mathrm{H},{}^{11}\mathrm{B}\left\{ {{}^{1}\mathrm{H}}\right\}$ , and ${}^{19}\mathrm{\;F}$ NMR spectroscopic data are consistent with the formation of $\left\lbrack {\mathrm{{NMe}}}_{4}\right\rbrack \; \left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack \cdot {}^{\left\lbrack {26}\right\rbrack }$ The ${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$ anion was also observed in nonstoi-chiometric reactions of8with diazonium salts; in these cases only one sharp signal at $\delta \approx 5\mathrm{{ppm}}$ was observed in the ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra. ${}^{\left\lbrack {26}\right\rbrack }$ The abstraction of ${\mathrm{F}}^{ - }$ from 8 by FBpin to give ${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$ may explain that an excess of the adduct was required to convert the starting material into the product because ${\mathrm{F}}^{ - }$ abstraction may be faster than formation of the aryl-boronate ester. Formation of ${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$ could also account for the presence of 1 at the end of the reaction (Scheme 6). It appears that FBpin-a better fluoride acceptor than 1-depletes 8 competitively by its reaction with the diazonium salt, thus inhibiting the borylation reaction as the concentration of FBpin increases.

所有芳基硼酸酯均以良好的产率分离得到(表6)。有趣的是，在所有情况下，均未观察到FBpin是第二个Bpin部分的主要副产物。相反，${}^{1}\mathrm{H},{}^{11}\mathrm{B}\left\{ {{}^{1}\mathrm{H}}\right\}$和${}^{19}\mathrm{\;F}$核磁共振光谱数据中的相应信号与$\left\lbrack {\mathrm{{NMe}}}_{4}\right\rbrack \; \left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack \cdot {}^{\left\lbrack {26}\right\rbrack }$的形成一致。在8与重氮盐的非化学计量反应中也观察到了${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$阴离子；在这些情况下，在${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振光谱中仅在$\delta \approx 5\mathrm{{ppm}}$处观察到一个尖锐信号。${}^{\left\lbrack {26}\right\rbrack }$FBpin从8中夺取${\mathrm{F}}^{ - }$生成${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$，这可以解释为什么需要过量的加合物才能将起始原料转化为产物，因为夺取${\mathrm{F}}^{ - }$的速度可能比重氮硼酸酯的形成速度更快。${\left\lbrack {\mathrm{{BpinF}}}_{2}\right\rbrack }^{ - }$的形成也可以解释反应结束时1的存在(方案6)。似乎FBpin(一种比1更好的氟化物受体)通过与重氮盐反应竞争性地消耗8，因此随着FBpin浓度的增加抑制了硼化反应。

Table 6. Reaction of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$ diboron compound 8 with aryl diazonium

表6. ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{3}$二硼化合物8与芳基重氮盐的反应

tetrafluoroborates.
8 (1.4 equiv)	MeCN RT $- {\mathrm{N}}_{2}$ $+ \left\lbrack {\mathrm{{NMe}}}_{4}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack + \left\lbrack {\mathrm{{NMe}}}_{4}\right\rbrack \left\lbrack {\mathrm{{pinBF}}}_{2}\right\rbrack$
Product (R)	Conversion of ${\mathrm{{SM}}}^{\left\lbrack \mathrm{a}\right\rbrack }\left\lbrack \% \right\rbrack$ Isolated yield [%] ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ [ppm]
H	100 42 29.9
Me	100 66 30.7
OMe	100 40 29.7
${\mathrm{{NO}}}_{2}$	100 59 29.7
Br	100 72 29.7
[a] SM = starting material.

Conclusion

结论

We have investigated anionic adducts of ${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$ diboron species with different Lewis bases, such as ${\mathrm{{RO}}}^{ - }$ and ${\mathrm{F}}^{ - }$ . The main focus of our study was the isolation, characterization, and reactivity of the adducts formed from the reaction of 1 with $t{\mathrm{{BuO}}}^{ - },{\mathrm{{MeO}}}^{ - },\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) {\mathrm{O}}^{ - }$ , and ${\mathrm{F}}^{ - }$ to afford the adducts 2-8. These compounds have been characterized by NMR spectroscopy and X-ray crystallography. A structure with repeating units of ${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right\rbrack }^{ - }$ connected by potassium ions was observed for adduct 2. In an attempt to form the mononuclear species, one equivalent of 18-crown-6 was added to the reaction of KOtBu and 1. Under these conditions, adduct 3 was synthesized, which had a similar supramolecular structure to 2. However, the mononuclear adduct 4 was eventually formed in the presence of an excess of 18-crown-6. An extended-chain structure, with the repeating unit $\left\lbrack {\mathrm{K}\left( \mathrm{{dmf}}\right) }\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) }\right\rbrack$ was observed for adduct 6; however, adducts 5, 7, and 8 were found to be monomeric in the solid state. When bulky bases, such as $\mathrm{{KO}}\left( {4 - {\mathrm{{Me}}}^{ - }2,6 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right)$ , or neutral Lewis bases, such as ${\mathrm{{PMe}}}_{3}$ , were used no adducts were isolated or observed spectroscopically. The reaction of ${\mathrm{B}}_{2}{\mathrm{{dmeda}}}_{2}$ with KOMe in the presence of 18-crown-6 led to the isolation of adduct 9.

我们研究了${\mathrm{{sp}}}^{2} - {\mathrm{{sp}}}^{2}$二硼物种与不同路易斯碱(如${\mathrm{{RO}}}^{ - }$和${\mathrm{F}}^{ - }$)形成的阴离子加合物。我们研究的主要重点是由1与$t{\mathrm{{BuO}}}^{ - },{\mathrm{{MeO}}}^{ - },\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) {\mathrm{O}}^{ - }$和${\mathrm{F}}^{ - }$反应形成加合物2 - 8的分离、表征及反应活性。这些化合物已通过核磁共振光谱和X射线晶体学进行了表征。加合物2观察到由钾离子连接的具有${\left\lbrack {\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}t\mathrm{{Bu}}\right\rbrack }^{ - }$重复单元的结构。为了尝试形成单核物种，在叔丁醇钾与1的反应中加入了一当量的18 - 冠 - 6。在这些条件下，合成了加合物3，其具有与2相似的超分子结构。然而，在过量的18 - 冠 - 6存在下最终形成了单核加合物4。加合物6观察到具有重复单元$\left\lbrack {\mathrm{K}\left( \mathrm{{dmf}}\right) }\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) }\right\rbrack$的延伸链结构；然而，发现加合物5、7和8在固态下是单体。当使用大体积碱(如$\mathrm{{KO}}\left( {4 - {\mathrm{{Me}}}^{ - }2,6 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right)$)或中性路易斯碱(如${\mathrm{{PMe}}}_{3}$)时，未分离到加合物或通过光谱观察到加合物。${\mathrm{B}}_{2}{\mathrm{{dmeda}}}_{2}$与甲氧基钾在18 - 冠 - 6存在下的反应导致分离出加合物9。

Solution and solid-state NMR spectroscopy showed similarities between the structures of the complexes regardless of the nature of the Lewis base or degree of aggregation found in the crystal structures. The ${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$ NMR spectra of each the different adducts displayed a broad resonance between $\delta = {37.5}$ and ${35}\mathrm{{ppm}}$ for the ${\mathrm{{sp}}}^{2}$ trigonal boron site and a sharper resonance between $\delta = {5.5}$ and ${4.7}\mathrm{{ppm}}$ for the ${\mathrm{{sp}}}^{3}$ tetrahedral site. In contrast to the alkoxide and fluoride adducts, the phenoxide adduct 6 showed dynamic behavior in solution.

溶液和固态核磁共振光谱表明，无论路易斯碱的性质或晶体结构中发现的聚集程度如何，配合物的结构之间都存在相似性。不同加合物的${}^{11}\mathrm{\;B}\left\{ {{}^{1}\mathrm{H}}\right\}$核磁共振光谱在$\delta = {37.5}$和${35}\mathrm{{ppm}}$之间显示出${\mathrm{{sp}}}^{2}$三角硼位点的宽共振，在$\delta = {5.5}$和${4.7}\mathrm{{ppm}}$之间显示出${\mathrm{{sp}}}^{3}$四面体位点的更尖锐共振。与醇盐和氟化物加合物不同，酚盐加合物6在溶液中表现出动态行为。

The importance of these adducts in the formation of aryl-boronate esters from the reactions with both aryl diazonium salts and an aryl iodide was investigated. The increase in reactivity of the aryl diazonium salts relative to 4-methylphenyl iodide is likely due to the increased electrophilicity of the former. Although no spectroscopic evidence for adduct formation between 1 and an acetoxy moiety was observed, the combination reacted cleanly with aryl diazonium salts to give the respective aryl-boronate esters. The isolated adducts were shown to serve as effective sources of nucleophilic boryl moieties in reactions with aryl electrophiles.

研究了这些加合物在与芳基重氮盐和芳基碘反应形成芳基硼酸酯中的重要性。芳基重氮盐相对于4 - 甲基苯基碘反应活性的增加可能是由于前者亲电性的增加。尽管未观察到1与乙酰氧基部分之间形成加合物的光谱证据，但该组合与芳基重氮盐干净地反应生成相应的芳基硼酸酯。已表明分离出的加合物在与芳基亲电试剂的反应中作为亲核硼基部分的有效来源。

Experimental Section

实验部分

General

总则

Unless otherwise noted, all manipulations were performed by using standard Schlenk or glovebox (Innovative Technology Inc.) techniques under an atmosphere of dry nitrogen or argon. Reagent grade solvents (Fisher Scientific and J. T. Baker) were saturated with nitrogen gas, then dried and deoxygenated with an Innovative Technology Inc. Pure-Solv 400 Solvent Purification System, and further deoxygenated by the freeze-pump-thaw method. $\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},\left\lbrack {\mathrm{D}}_{4}\right\rbrack \mathrm{{MeOH}}$ , and $\left\lbrack {\mathrm{D}}_{1}\right\rbrack \mathrm{{MeOH}}$ were obtained from Cambridge Isotope Laboratories or EURISOTOP and dried over potassium/benzophenone, ${\mathrm{{CaH}}}_{2}$ , or thoroughly dried 4 Å molecular sieves, then deoxygenated by the freeze-pump-thaw method. ${\mathrm{B}}_{2}{\mathrm{{dmeda}}}_{2},\left\lbrack {4 - {\mathrm{{MeO}}}_{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack ,\left\lbrack {4 - {\mathrm{{NO}}}_{2} - {\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ , $\left\lbrack {4 - {\mathrm{{Me}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack ,\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$ , and $\left\lbrack {4 - {\mathrm{{MeO}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BPh}}}_{4}\right\rbrack$ were prepared according to literature procedures. ${}^{\left\lbrack {29},{42}\right\rbrack }{\mathrm{{KO}}}_{2}\mathrm{{CPh}},\mathrm{{KO}}(4 - \; t{\mathrm{{Bu}}}_{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}$ ), and $\mathrm{{KO}}\left( {2,6 - t{\mathrm{{Bu}}}_{2} - 4 - \left( {\mathrm{{CH}}}_{3}\right) {\mathrm{C}}_{6}{\mathrm{H}}_{4}}\right)$ were prepared from $\mathrm{{KO}}t{\mathrm{{Bu}}}_{ - }$ and the respective acid or phenol in dry ${\mathrm{{Et}}}_{2}\mathrm{O}$ under nitrogen and were checked for purity by elemental analysis. All other reagents were purchased from commercial sources, checked for purity by GC-MS, elemental analysis, and/or NMR spectroscopy, then used as received (if appropriate, the reagents were stored over thoroughly dried ${4\text{ Å }}$ molecular sieves). ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ was kindly provided by Ally-Chem Co. Ltd. (Dalian, China). NMR spectra in solution were recorded with a Bruker Avance ${200}\left( {{}^{1}\mathrm{H} : {200}\mathrm{{MHz}},{}^{13}\mathrm{C} : {50}\mathrm{{MHz}},{}^{19}\mathrm{F} : }\right. \; {188}\mathrm{{MHz}},{}^{11}\mathrm{\;B}$ : ${64}\mathrm{{MHz}}$ ), Avance III HD ${300}\left( {{}^{1}\mathrm{H} : {300}\mathrm{{MHz}},{}^{13}\mathrm{C} : }\right. \; {75}\mathrm{{MHz}},{}^{11}\mathrm{\;B}$ : ${96}\mathrm{{MHz}}$ ), Varian Mercury-400 (1H: 400 MHz, ${}^{13}\mathrm{C}$ : ${100}\mathrm{{MHz}},{}^{19}\mathrm{\;F} : {376}\mathrm{{MHz}},{}^{31}\mathrm{P} : {162}\mathrm{{MHz}}$ ), Bruker Avance ${400}\left( {{}^{1}\mathrm{H} : }\right. \; {400}\mathrm{{MHz}},{}^{13}\mathrm{C} : {100}\mathrm{{MHz}},{}^{11}\mathrm{\;B} : {128}\mathrm{{MHz}}$ ), Varian Inova- ${500}\left( {{}^{1}\mathrm{H} : }\right)$ 500 MHz, ${}^{13}\mathrm{C}$ : 125 MHz, ${}^{19}\mathrm{F}$ : 470 MHz, ${}^{11}\mathrm{B}$ : 160 MHz), Bruker Avance 500 ( ${}^{1}\mathrm{H}$ : 500 MHz, ${}^{13}\mathrm{C}$ : 125 MHz, ${}^{19}\mathrm{F}$ : 470 MHz, ${}^{11}\mathrm{B}$ : 160 MHz), or Varian VNMR 700 ( ${}^{1}\mathrm{H}$ : 700 MHz, ${}^{13}\mathrm{C}$ : 175 MHz, ${}^{19}\mathrm{\;F}$ : 658 MHz, ${}^{11}\mathrm{\;B}$ : 224 MHz) spectrometer. ${}^{1}\mathrm{H}$ NMR chemical shifts are reported relative to TMS and referenced to residual proton resonances of the deuterated solvent $\left( {\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}} : \delta = {1.73}}\right.$ ,3.58 ppm, $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}} : \delta = {1.94}\mathrm{{ppm}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}} : \delta = {8.03}\mathrm{{ppm}},\left\lbrack {\mathrm{D}}_{4}\right\rbrack \mathrm{{MeOH}} : \delta =$ 3.31 ppm, $\left\lbrack {\mathrm{D}}_{1}\right\rbrack \mathrm{{MeOH}} : \delta = {3.08}\mathrm{{ppm}}$ ); ${}^{13}\mathrm{C}$ NMR spectra are reported relative to TMS and referenced to the carbon signals of the deuter-ated solvent ( $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF: $\delta = {67.5},{25.3}\mathrm{{ppm}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF: $\delta = {34.8}\mathrm{{ppm}}$ ). ${}^{11}\mathrm{\;B},{}^{31}\mathrm{P}$ , and ${}^{19}\mathrm{\;F}$ NMR chemical shifts are reported relative to external ${\mathrm{{BF}}}_{3} \cdot {\mathrm{{Et}}}_{2}\mathrm{O},{\mathrm{H}}_{3}{\mathrm{{PO}}}_{4}$ , and ${\mathrm{{CFCl}}}_{3}$ , respectively. All ${}^{13}\mathrm{C},{}^{31}\mathrm{P}$ , and ${}^{11}\mathrm{B}$ NMR spectra were recorded with ${}^{1}\mathrm{H}$ decoupling. Air-sensitive NMR samples were handled under nitrogen or argon in WILMAD NMR tubes equipped with J. Young valves. Solid-state MAS NMR (SS-NMR) spectra (2-7, and 9) were recorded with a Varian VNMRS spectrometer $\left( {{}^{11}\mathrm{\;B} : {128}\mathrm{{MHz}},{}^{1}\mathrm{H} : {400}\mathrm{{MHz}},{}^{13}\mathrm{C} : {100}\mathrm{{MHz}}}\right.$ equipped with a MAS probe [4 mm rotor outside diameter (o.d.)]. The spectra were referenced to external ${\mathrm{{BF}}}_{3} \cdot {\mathrm{{Et}}}_{2}\mathrm{O}$ . Isotropic chemical shifts $\left( {\delta }_{\text{ iso }}\right)$ were estimated by simulation of the observed spectrum by using the Varian STARS program. The SS-NMR spectrum of 8 was recorded with a Bruker DSX-400 spectrometer $\left( {{}^{11}\mathrm{\;B} : {128}\mathrm{{MHz}},{}^{1}\mathrm{H} : }\right. \; {400}\mathrm{{MHz}},{}^{13}\mathrm{C}$ : 100 MHz) equipped with a MAS probe ( $4\mathrm{\;{mm}}$ rotor o.d.). Chemical shifts were calibrated by using adamantane as an external standard $\left( {\delta = {38.48}\mathrm{{ppm}}}\right) {.}^{\left\lbrack {26}\right\rbrack }$ Isotropic chemical shifts were estimated by simulation of the observed spectrum by using the Solid Line-Shape Analysis 2.2.4 (SOLA) programme. Elemental analysis was performed with an Exeter Analytical Inc. CE 440 elemental analyzer or ELEMENTAR Vario Micro Cube (Elementar Analysensys-teme GmbH). Melting points were determined with a Sanyo Gallen-kamp apparatus in flame-sealed capillary tubes filled with nitrogen. Automated flash chromatography was performed on silica gel with a Biotage Isolera Four system (Biotage SNAP cartridge KP-Sil 10 g and KP-Sil 25 g) obtained from Biotage. Precoated TLC plates (Polygram Sil G/UV254) were purchased from Machery-Nagel.

除非另有说明，所有操作均在干燥氮气或氩气气氛下，使用标准的Schlenk技术或手套箱(Innovative Technology Inc.)技术进行。试剂级溶剂(Fisher Scientific和J. T. Baker)用氮气饱和，然后用Innovative Technology Inc. Pure-Solv 400溶剂纯化系统干燥并脱氧，并通过冷冻-抽气-解冻方法进一步脱氧。$\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},\left\lbrack {\mathrm{D}}_{4}\right\rbrack \mathrm{{MeOH}}$和$\left\lbrack {\mathrm{D}}_{1}\right\rbrack \mathrm{{MeOH}}$购自Cambridge Isotope Laboratories或EURISOTOP，并在钾/二苯甲酮、${\mathrm{{CaH}}}_{2}$或充分干燥的4 Å分子筛上干燥，然后通过冷冻-抽气-解冻方法脱氧。${\mathrm{B}}_{2}{\mathrm{{dmeda}}}_{2},\left\lbrack {4 - {\mathrm{{MeO}}}_{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack ,\left\lbrack {4 - {\mathrm{{NO}}}_{2} - {\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$、$\left\lbrack {4 - {\mathrm{{Me}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack ,\left\lbrack {{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BF}}}_{4}\right\rbrack$和$\left\lbrack {4 - {\mathrm{{MeO}}}^{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{\;N}}_{2}}\right\rbrack \left\lbrack {\mathrm{{BPh}}}_{4}\right\rbrack$按照文献方法制备。${}^{\left\lbrack {29},{42}\right\rbrack }{\mathrm{{KO}}}_{2}\mathrm{{CPh}},\mathrm{{KO}}(4 - \; t{\mathrm{{Bu}}}_{ - }{\mathrm{C}}_{6}{\mathrm{H}}_{4}$和$\mathrm{{KO}}\left( {2,6 - t{\mathrm{{Bu}}}_{2} - 4 - \left( {\mathrm{{CH}}}_{3}\right) {\mathrm{C}}_{6}{\mathrm{H}}_{4}}\right)$由$\mathrm{{KO}}t{\mathrm{{Bu}}}_{ - }$与相应的酸或酚在干燥的${\mathrm{{Et}}}_{2}\mathrm{O}$中于氮气下制备，并通过元素分析检查纯度。所有其他试剂均从商业来源购买，通过GC-MS、元素分析和/或NMR光谱检查纯度，然后按收到的状态使用(如果合适，试剂储存在充分干燥的${4\text{ Å }}$分子筛上)。${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$由Ally-Chem Co. Ltd.(中国大连)慷慨提供。溶液中的NMR光谱用Bruker Avance ${200}\left( {{}^{1}\mathrm{H} : {200}\mathrm{{MHz}},{}^{13}\mathrm{C} : {50}\mathrm{{MHz}},{}^{19}\mathrm{F} : }\right. \; {188}\mathrm{{MHz}},{}^{11}\mathrm{\;B}$记录:${64}\mathrm{{MHz}}$)，Avance III HD ${300}\left( {{}^{1}\mathrm{H} : {300}\mathrm{{MHz}},{}^{13}\mathrm{C} : }\right. \; {75}\mathrm{{MHz}},{}^{11}\mathrm{\;B}$:${96}\mathrm{{MHz}}$)，Varian Mercury-400(1H:400 MHz，${}^{13}\mathrm{C}$:${100}\mathrm{{MHz}},{}^{19}\mathrm{\;F} : {376}\mathrm{{MHz}},{}^{31}\mathrm{P} : {162}\mathrm{{MHz}}$)，Bruker Avance ${400}\left( {{}^{1}\mathrm{H} : }\right. \; {400}\mathrm{{MHz}},{}^{13}\mathrm{C} : {100}\mathrm{{MHz}},{}^{11}\mathrm{\;B} : {128}\mathrm{{MHz}}$)，Varian Inova-${500}\left( {{}^{1}\mathrm{H} : }\right)$ 500 MHz，${}^{13}\mathrm{C}$:125 MHz，${}^{19}\mathrm{F}$:470 MHz，${}^{11}\mathrm{B}$:160 MHz)，Bruker Avance 500(${}^{1}\mathrm{H}$:500 MHz，${}^{13}\mathrm{C}$:125 MHz，${}^{19}\mathrm{F}$:470 MHz，${}^{11}\mathrm{B}$:160 MHz)或Varian VNMR 700(${}^{1}\mathrm{H}$:700 MHz，${}^{13}\mathrm{C}$:175 MHz，${}^{19}\mathrm{\;F}$:658 MHz，${}^{11}\mathrm{\;B}$:224 MHz)光谱仪记录。${}^{1}\mathrm{H}$ NMR化学位移相对于TMS报告，并参考氘代溶剂$\left( {\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}} : \delta = {1.73}}\right.$的残余质子共振，3.58 ppm，$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}} : \delta = {1.94}\mathrm{{ppm}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}} : \delta = {8.03}\mathrm{{ppm}},\left\lbrack {\mathrm{D}}_{4}\right\rbrack \mathrm{{MeOH}} : \delta =$ 3.31 ppm，$\left\lbrack {\mathrm{D}}_{1}\right\rbrack \mathrm{{MeOH}} : \delta = {3.08}\mathrm{{ppm}}$)；${}^{13}\mathrm{C}$ NMR光谱相对于TMS报告，并参考氘代溶剂的碳信号($\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF:$\delta = {67.5},{25.3}\mathrm{{ppm}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack$ DMF:$\delta = {34.8}\mathrm{{ppm}}$)。${}^{11}\mathrm{\;B},{}^{31}\mathrm{P}$和${}^{19}\mathrm{\;F}$ NMR化学位移分别相对于外部${\mathrm{{BF}}}_{3} \cdot {\mathrm{{Et}}}_{2}\mathrm{O},{\mathrm{H}}_{3}{\mathrm{{PO}}}_{4}$和${\mathrm{{CFCl}}}_{3}$报告。所有${}^{13}\mathrm{C},{}^{31}\mathrm{P}$和${}^{11}\mathrm{B}$ NMR光谱均在${}^{1}\mathrm{H}$去耦下记录。对空气敏感的NMR样品在氮气或氩气下于配备J. Young阀的WILMAD NMR管中处理。固态MAS NMR(SS-NMR)光谱(2 - 7和9)用配备MAS探头[外径(o.d.)4 mm转子]的Varian VNMRS光谱仪$\left( {{}^{11}\mathrm{\;B} : {128}\mathrm{{MHz}},{}^{1}\mathrm{H} : {400}\mathrm{{MHz}},{}^{13}\mathrm{C} : {100}\mathrm{{MHz}}}\right.$记录。光谱参考外部${\mathrm{{BF}}}_{3} \cdot {\mathrm{{Et}}}_{2}\mathrm{O}$。通过使用Varian STARS程序模拟观察到的光谱来估计各向同性化学位移$\left( {\delta }_{\text{ iso }}\right)$。8的SS-NMR光谱用配备MAS探头($4\mathrm{\;{mm}}$转子o.d.)的Bruker DSX-400光谱仪$\left( {{}^{11}\mathrm{\;B} : {128}\mathrm{{MHz}},{}^{1}\mathrm{H} : }\right. \; {400}\mathrm{{MHz}},{}^{13}\mathrm{C}$:100 MHz)记录。化学位移通过使用金刚烷作为外标$\left( {\delta = {38.48}\mathrm{{ppm}}}\right) {.}^{\left\lbrack {26}\right\rbrack }$进行校准。通过使用Solid Line-Shape Analysis 2.2.4(SOLA)程序模拟观察到的光谱来估计各向同性化学位移。元素分析用Exeter Analytical Inc. CE 440元素分析仪或ELEMENTAR Vario Micro Cube(Elementar Analysensysteme GmbH)进行。熔点用Sanyo Gallen-kamp仪器在填充氮气的火焰密封毛细管中测定。自动快速柱色谱在硅胶上用从Biotage获得的Biotage Isolera Four系统(Biotage SNAP柱KP-Sil 10 g和KP-Sil 25 g)进行。预涂TLC板(Polygram Sil G/UV254)购自Machery-Nagel。

Synthesis

合成

K[(B2pin2)OtBu] (2): Bulk material: Under a nitrogen atmosphere, KOtBu (77 mg, 686 μmol) and 1 (175 mg, 689 μmol) were separately dissolved in dry THF (3 mL each). The two solutions were combined and a colorless precipitate separated immediately. After stirring at rt (2.5 h), the precipitate was collected by centrifugation or filtration, washed with dry THF (2×3 mL), and dried under vacuum to give 2 (191 mg, 521 μmol, 76%) as a colorless solid. Crystals for XRD: A tube [3.5 mm internal diameter (i.d.)] was placed in a vial (1 cm i.d.). The outer vial was filled with a solution of KOtBu (20 mg) in dry THF (3 mL), the inner tube was filled with a solution of 1 $\left( {{45}\mathrm{{mg}}}\right)$ in dry THF $\left( {{0.5}\mathrm{\;{mL}}}\right)$ . Both vessels were carefully filled with THF until the inner tube was submerged. After several days at ${0}^{ \circ }\mathrm{C}$ , crystals of 2 suitable for XRD analysis were deposited on the inner wall of the inner tube. In addition, crystals of (2),(dmf) suitable for XRD analysis were obtained by diffusion of diethyl ether into a solution of 2 in DMF at ${0}^{ \circ }\mathrm{C}$ . M.p. $> {300}^{ \circ }\mathrm{C};{}^{1}\mathrm{H}$ NMR $\left( {{700}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {1.17}\left( {\mathrm{\;s},9\mathrm{H};t\mathrm{{Bu}}}\right) ,{1.13}$ (brs,12H; $\left. {\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{1.06}$ (brs, $6\mathrm{H},\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) ),{0.94}\mathrm{{ppm}}$ (brs, $6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) );{}^{13}\mathrm{C}$ NMR (175 MHz, [D ${}_{7}$ ]DMF, 25°C): $\delta = {80.9},{77.5},{67.4},{33.6},{27.6},{27.2}$ , 25.9 ppm; ${}^{11}$ B NMR (224 MHz,[D7]DMF, rt): $\delta = {37.7}$ (vbrs),4.8 ppm (brs); elemental analysis calcd (%) for ${\mathrm{C}}_{16}{\mathrm{H}}_{33}{\mathrm{O}}_{5}{\mathrm{\;B}}_{2}\mathrm{\;K}$ : C 52.48, H 9.08, N 0.00; found: C 52.54, H 9.10, N 0.00.

K[(B2pin2)OtBu] (2):大块材料:在氮气气氛下，将叔丁醇钾(77 mg，686 μmol)和1(175 mg，689 μmol)分别溶于干燥的四氢呋喃(各3 mL)。将两种溶液混合，立即析出无色沉淀。在室温搅拌(2.5小时)后，通过离心或过滤收集沉淀，用干燥的四氢呋喃(2×3 mL)洗涤，并在真空下干燥，得到2(191 mg，521 μmol，76%)，为无色固体。用于X射线衍射的晶体:将一根管[内径3.5 mm]置于一个小瓶[内径1 cm]中。将外小瓶中装入叔丁醇钾(20 mg)在干燥四氢呋喃(3 mL)中的溶液，内管中装入1 $\left( {{45}\mathrm{{mg}}}\right)$ 在干燥四氢呋喃 $\left( {{0.5}\mathrm{\;{mL}}}\right)$ 中的溶液。小心地向两个容器中加入四氢呋喃，直到内管被淹没。在 ${0}^{ \circ }\mathrm{C}$ 放置几天后，适合X射线衍射分析的2的晶体沉积在内管内壁上。此外，通过在 ${0}^{ \circ }\mathrm{C}$ 将乙醚扩散到2在N, N - 二甲基甲酰胺中的溶液中，得到适合X射线衍射分析的(2),(dmf)晶体。熔点 $> {300}^{ \circ }\mathrm{C};{}^{1}\mathrm{H}$ 核磁共振 $\left( {{700}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {1.17}\left( {\mathrm{\;s},9\mathrm{H};t\mathrm{{Bu}}}\right) ,{1.13}$ (宽单峰，12H； $\left. {\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{1.06}$ (宽单峰， $6\mathrm{H},\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) ),{0.94}\mathrm{{ppm}}$ (宽单峰， $6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) );{}^{13}\mathrm{C}$ 核磁共振(175 MHz，[D ${}_{7}$ ]N, N - 二甲基甲酰胺，25°C): $\delta = {80.9},{77.5},{67.4},{33.6},{27.6},{27.2}$ ，25.9 ppm； ${}^{11}$ 硼核磁共振(224 MHz，[D7]N, N - 二甲基甲酰胺，室温): $\delta = {37.7}$ (非常宽的单峰)，4.8 ppm(宽单峰)； ${\mathrm{C}}_{16}{\mathrm{H}}_{33}{\mathrm{O}}_{5}{\mathrm{\;B}}_{2}\mathrm{\;K}$ 的元素分析计算值(%):C 52.48，H 9.08，N 0.00；实测值:C 52.54，H 9.10，N 0.00。

[K(18-crown-6)thf ${}_{2}$ ][K((B ${}_{2}$ pin ${}_{2}$ )OtBu) ${}_{2}$ ] (3): Bulk material: Under a nitrogen atmosphere, KOtBu (38 mg, 344 μmol) and 18-crown-6 (91mg, 344 μmol) were dissolved in dry THF (2mL), then 1 (87 mg, 344 μmol) was added. After a few seconds, a colorless precipitate started to separate, which was isolated after $2\mathrm{\;h}$ , washed with THF/n-hexane (1:2, $2 \times 2\mathrm{\;{mL}}$ ), and dried under vacuum to give analytically pure 3 (71 mg, 62 μmol, 36%). Crystals for XRD analysis: A solution of KOtBu ( ${19}\mathrm{{mg}},{172\mu }\mathrm{{mol}}$ ) and 18- crown-6 (45 mg, 172 μmol) in THF (4 mL) was placed in a vial (23 mm i.d.). A second, smaller vial (10 mm o.d.) that contained 1 (44 mg, 172 μmol) in THF (4 mL) was immersed in this solution. The solvent level was carefully adjusted to be slightly higher than the height of the inner vial. After 3 d, well-developed crystals of 3 formed. M.p. ${65}^{ \circ }\mathrm{C}$ (decomp.); ${}^{1}\mathrm{H}$ NMR (700 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {3.64}\left( {\mathrm{\;s},{24}\mathrm{H};{\mathrm{{OCH}}}_{2}}\right) ,{3.62}\left( {\mathrm{\;s},8\mathrm{H};\mathrm{{THF}}}\right) ,{1.78}\left( {\mathrm{\;s},8\mathrm{H};\mathrm{{THF}}}\right) ,{1.17}(\mathrm{\;s}$ , ${18}\mathrm{H}$ ; tBu), ${1.15}\left( {\mathrm{\;s},{24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{1.07}\left( {\mathrm{\;s},{12}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{0.96}\mathrm{{ppm}}(\mathrm{s}$ , 12H; $\mathrm{C}{\left( {\mathrm{{CH}}}_{3}\right) }_{3}{\mathrm{\;K}}_{3}\mathrm{{CNMR}}\left( {{175}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {80.9},{77.6}$ , 71.0,33.6,27.6,27.2 ppm, four signals (THF, $\mathrm{C}{\left( {\mathrm{{CH}}}_{3}\right) }_{3}$ ), and $\mathrm{C}{\left( {\mathrm{{CH}}}_{3}\right) }_{3}$ ) could not be separated from the solvent signals; ${}^{11}\mathrm{\;B}$ NMR (224 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {41.1}$ (vbrs),8.1 ppm (brs); elemental analysis calcd (%) for ${\mathrm{C}}_{52}{\mathrm{H}}_{106}{\mathrm{O}}_{18}{\mathrm{\;B}}_{4}{\mathrm{\;K}}_{2}$ : C 54.75, H 9.37, N 0.00; found: C 54.71, H 9.42, N 0.00.

[K(18-冠-6)四氢呋喃${}_{2}$]K((B${}_{2}$频哪醇${}_{2}$)OtBu)${}_{2}$:大块材料:在氮气气氛下，将叔丁醇钾(38毫克，344微摩尔)和18-冠-6(91毫克，344微摩尔)溶解于干燥的四氢呋喃(2毫升)中，然后加入1(87毫克，344微摩尔)。几秒钟后，开始析出无色沉淀，$2\mathrm{\;h}$后分离出来，用四氢呋喃/正己烷(1:2，$2 \times 2\mathrm{\;{mL}}$)洗涤，并在真空下干燥，得到分析纯的3(71毫克，62微摩尔，产率36%)。用于X射线衍射分析的晶体:将叔丁醇钾(${19}\mathrm{{mg}},{172\mu }\mathrm{{mol}}$)和18-冠-6(45毫克，172微摩尔)在四氢呋喃(4毫升)中的溶液置于一个小瓶(内径23毫米)中。将另一个装有四氢呋喃(4毫升)中的1(44毫克，172微摩尔)的较小的小瓶(外径10毫米)浸入该溶液中。小心地将溶剂液面调节至略高于内小瓶的高度。3天后，形成了发育良好的3的晶体。熔点${65}^{ \circ }\mathrm{C}$(分解)；${}^{1}\mathrm{H}$核磁共振(700兆赫，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$四氢呋喃，${25}^{ \circ }\mathrm{C}$):$\delta = {3.64}\left( {\mathrm{\;s},{24}\mathrm{H};{\mathrm{{OCH}}}_{2}}\right) ,{3.62}\left( {\mathrm{\;s},8\mathrm{H};\mathrm{{THF}}}\right) ,{1.78}\left( {\mathrm{\;s},8\mathrm{H};\mathrm{{THF}}}\right) ,{1.17}(\mathrm{\;s}$，${18}\mathrm{H}$；叔丁基)，${1.15}\left( {\mathrm{\;s},{24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{1.07}\left( {\mathrm{\;s},{12}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{0.96}\mathrm{{ppm}}(\mathrm{s}$，12个氢；$\mathrm{C}{\left( {\mathrm{{CH}}}_{3}\right) }_{3}{\mathrm{\;K}}_{3}\mathrm{{CNMR}}\left( {{175}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {80.9},{77.6}$，71.0、33.6、27.6,27.2 ppm，四个信号(四氢呋喃，$\mathrm{C}{\left( {\mathrm{{CH}}}_{3}\right) }_{3}$)，并且$\mathrm{C}{\left( {\mathrm{{CH}}}_{3}\right) }_{3}$)无法与溶剂信号分离；${}^{11}\mathrm{\;B}$核磁共振(224兆赫，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$四氢呋喃，${25}^{ \circ }\mathrm{C}$):$\delta = {41.1}$(宽峰)，8.1 ppm(宽峰)；${\mathrm{C}}_{52}{\mathrm{H}}_{106}{\mathrm{O}}_{18}{\mathrm{\;B}}_{4}{\mathrm{\;K}}_{2}$的元素分析计算值(%):碳54.75，氢9.37，氮0.00；实测值:碳54.71，氢9.42，氮0.00。

[K(18-crown-6)][(B2pin2)OtBu] (4): Under a nitrogen atmosphere, KOtBu (38 mg, 339 μmol, 1 equiv), 18-crown-6 (272 mg, 1.03 mmol, 3 equiv), and 1 (86 mg, 339 μmol, 1 equiv) were dissolved in dry THF (3 mL), assisted by stirring. After 2 h, n-hexane (10 mL) was added to the clear solution and the precipitate formed was crystallized by diffusion of $n$ -hexane into a solution of the precipitate in THF at rt. After several days, some irregular crystals were deposited, along with microcrystalline powder. The crystals were collected (8 mg, 13 μmol, 4%) under an optical microscope and subjected to single-crystal X-ray diffraction. The crystals were washed with $n$ - hexane and dried under vacuum, then subjected to elemental analysis. Several attempts to reproduce the isolation of 4 were unsuccessful. Attempts to obtain 4 under somewhat altered reaction conditions (reactive crystallization, different solvents, different concentrations, and different stoichiometries) were unsuccessful and only 3 was isolated after crystallization. Elemental analysis calcd (%) for ${\mathrm{C}}_{28}{\mathrm{H}}_{57}{\mathrm{O}}_{11}{\mathrm{\;B}}_{2}\mathrm{\;K}$ : C 53.34, $\mathrm{H}{9.11},\mathrm{\;N}{0.00}$ ; found: C 53.48, $\mathrm{H}{9.01}$ , N 0.00.

[K(18-冠醚-6)][(B2pin2)OtBu] (4):在氮气气氛下，将叔丁醇钾(38毫克，339微摩尔，1当量)、18-冠醚-6(272毫克，1.03毫摩尔，3当量)和1(86毫克，339微摩尔，1当量)在搅拌辅助下溶解于干燥的四氢呋喃(3毫升)中。2小时后，向澄清溶液中加入正己烷(10毫升)，通过将$n$ -己烷扩散到室温下沉淀在四氢呋喃中的溶液中使形成的沉淀结晶。几天后，沉积出一些不规则晶体以及微晶粉末。在光学显微镜下收集晶体(8毫克，13微摩尔，4%)并进行单晶X射线衍射。晶体用$n$ -己烷洗涤并在真空下干燥，然后进行元素分析。多次尝试重现4的分离均未成功。尝试在稍微改变的反应条件下(反应结晶、不同溶剂、不同浓度和不同化学计量比)获得4均未成功，结晶后仅分离出3。${\mathrm{C}}_{28}{\mathrm{H}}_{57}{\mathrm{O}}_{11}{\mathrm{\;B}}_{2}\mathrm{\;K}$的元素分析计算值(%):C 53.34，$\mathrm{H}{9.11},\mathrm{\;N}{0.00}$；实测值:C 53.48，$\mathrm{H}{9.01}$，N 0.00。

[K(18-crown-6)][(B ${}_{2}$ pine ${}_{2}$ )OMe] (5): Under a nitrogen atmosphere, KOMe $({33}\mathrm{{mg}},{470\mu }\mathrm{{mol}}$ ,2 equiv) and 18-crown-6 $({125}\mathrm{{mg}}$ , 473 μmol, 2 equiv) were dissolved in dry THF (3 mL), aided by stirring. After about ${10}\mathrm{\;{min}}$ of stirring,1 (60 mg, ${236\mu }\mathrm{{mol}}$ ,1 equiv) was added and the resulting clear solution was stirred overnight at rt. After concentration under reduced pressure to a volume of approximately $1\mathrm{\;{mL}}$ , the residue was layered with $n$ -hexane and crystallized at $- {20}^{ \circ }\mathrm{C}$ to give $5\left( {{129}\mathrm{{mg}},{220\mu }\mathrm{{mol}},{93}\% }\right)$ as colorless crystals, suitable for X-ray crystallography. M.p. ${84} - {87}{}^{ \circ }\mathrm{C}$ ; ${}^{1}\mathrm{H}$ NMR $\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {3.62}\left( {\mathrm{\;s},{24}\mathrm{H};{\mathrm{{OCH}}}_{2}}\right) ,{3.11}(\mathrm{\;s},3\mathrm{H}$ ; ${\mathrm{{OCH}}}_{3}),{1.06}\mathrm{{ppm}}$ (brs, ${24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) );{}^{1}\mathrm{H}$ NMR $\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}}}\right)$ , $- {55}^{ \circ }\mathrm{C}) : \delta = {3.64}\left( {\mathrm{\;s},{24}\mathrm{H};{\mathrm{{OCH}}}_{2}}\right) ,{3.16}\left( {\mathrm{\;s},3\mathrm{H};{\mathrm{{OCH}}}_{3}}\right) ,{1.08}(\mathrm{\;s},{12}\mathrm{H}; \; \left. {\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{1.03}\left( {\mathrm{\;s},6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{0.98}\mathrm{{ppm}}\left( {\mathrm{s},6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ;{}^{13}\mathrm{C}$ NMR $\left( {{125}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {80.1},{77.3},{71.0},{50.6},{27.4},{27.0},$ 25.9 ppm; ${}^{11}\mathrm{B}$ NMR (160 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {37.5}$ (vbrs), 5.8 ppm (brs); ${}^{11}\mathrm{\;B}$ NMR (160 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, $- {55}^{ \circ }\mathrm{C}$ ): $\delta = {6.4}\mathrm{{ppm}}$ (brs); ${}^{13}\mathrm{C}$ SS-NMR (100 MHz, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {80.1},{77.8},{77.6},{70.9}$ (br), 51.5, 29.9, 27.7, 27.0, 26.8, 26.1, 25.6 ppm; elemental analysis calcd (%) for ${\mathrm{C}}_{25}{\mathrm{H}}_{51}{\mathrm{O}}_{11}{\mathrm{\;B}}_{2}\mathrm{\;K} : \mathrm{C}{51.03},\mathrm{H}{8.74},\mathrm{\;N}{0.00}$ ; found: $\mathrm{C}{51.24},\mathrm{H}$ 8.76, N 0.00.

[K(18-冠-6)][(B${}_{2}$pin${}_{2}$)OMe] (5):在氮气气氛下，将KOMe$({33}\mathrm{{mg}},{470\mu }\mathrm{{mol}}$(2当量)和18-冠-6$({125}\mathrm{{mg}}$(473 μmol，2当量)在搅拌辅助下溶解于干燥的THF(3 mL)中。搅拌约${10}\mathrm{\;{min}}$后，加入1(60 mg，${236\mu }\mathrm{{mol}}$，1当量)，所得澄清溶液在室温下搅拌过夜。在减压下浓缩至约$1\mathrm{\;{mL}}$体积后，残余物用$n$-己烷分层，并在$- {20}^{ \circ }\mathrm{C}$结晶，得到$5\left( {{129}\mathrm{{mg}},{220\mu }\mathrm{{mol}},{93}\% }\right)$，为适合X射线晶体学的无色晶体。熔点${84} - {87}{}^{ \circ }\mathrm{C}$；${}^{1}\mathrm{H}$核磁共振$\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {3.62}\left( {\mathrm{\;s},{24}\mathrm{H};{\mathrm{{OCH}}}_{2}}\right) ,{3.11}(\mathrm{\;s},3\mathrm{H}$；${\mathrm{{OCH}}}_{3}),{1.06}\mathrm{{ppm}}$(宽峰单峰，${24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) );{}^{1}\mathrm{H}$核磁共振$\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}}}\right)$，$- {55}^{ \circ }\mathrm{C}) : \delta = {3.64}\left( {\mathrm{\;s},{24}\mathrm{H};{\mathrm{{OCH}}}_{2}}\right) ,{3.16}\left( {\mathrm{\;s},3\mathrm{H};{\mathrm{{OCH}}}_{3}}\right) ,{1.08}(\mathrm{\;s},{12}\mathrm{H}; \; \left. {\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{1.03}\left( {\mathrm{\;s},6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{0.98}\mathrm{{ppm}}\left( {\mathrm{s},6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ;{}^{13}\mathrm{C}$核磁共振$\left( {{125}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {80.1},{77.3},{71.0},{50.6},{27.4},{27.0},$ 25.9 ppm；${}^{11}\mathrm{B}$核磁共振(160 MHz，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF，${25}^{ \circ }\mathrm{C}$):$\delta = {37.5}$(非常宽的峰单峰)，5.8 ppm(宽峰单峰)；${}^{11}\mathrm{\;B}$核磁共振(160 MHz，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF，$- {55}^{ \circ }\mathrm{C}$):$\delta = {6.4}\mathrm{{ppm}}$(宽峰单峰)；${}^{13}\mathrm{C}$固体核磁共振(100 MHz，${25}^{ \circ }\mathrm{C}$):$\delta = {80.1},{77.8},{77.6},{70.9}$(宽峰)，51.5、29.9、27.7、27.0、26.8、26.1、25.6 ppm；${\mathrm{C}}_{25}{\mathrm{H}}_{51}{\mathrm{O}}_{11}{\mathrm{\;B}}_{2}\mathrm{\;K} : \mathrm{C}{51.03},\mathrm{H}{8.74},\mathrm{\;N}{0.00}$的元素分析计算值(%)；实测值:$\mathrm{C}{51.24},\mathrm{H}$ 8.76，N 0.00。

$\mathrm{K}\left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) }\right\rbrack$ (6): Under a nitrogen atmosphere, KO- $\left( {t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) \left( {{148}\mathrm{{mg}},{790\mu }\mathrm{{mol}}}\right)$ and $\mathbf{1}\left( {{200}\mathrm{{mg}},{790\mu }\mathrm{{mol}}}\right)$ were combined in dry THF (6 mL). After ${16}\mathrm{\;h}$ of stirring at rt, the precipitate was collected by centrifugation, washed with dry THF $\left( {2 \times 3\mathrm{\;{mL}}}\right)$ , and dried under vacuum to give (6)thf (302 mg, 586 μmol, 74%) as a colorless solid. M.p. >240°C (decomp.); ${}^{1}\mathrm{H}$ NMR (700 MHz, $\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},{25}^{ \circ }\mathrm{C}) : \delta = {6.97}\;\left( {\mathrm{\;d},{}^{3}\mathrm{\;J}\left( {\mathrm{H},\mathrm{H}}\right) = 9\mathrm{\;{Hz}},2\mathrm{H};\mathrm{{CH}}}\right) ,{6.74}(\mathrm{\;d}$ , ${}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 9\mathrm{\;{Hz}},2\mathrm{H};\mathrm{{CH}}),{3.65} - {3.62}\left( {\mathrm{\;m},4\mathrm{\;H};\mathrm{{THF}}}\right) ,{1.80} - {1.78}(\mathrm{\;m},4\mathrm{H}$ ; THF), 1.21 (s, 9 H; tBu), 1.05 ppm (s, 24 H; C(CH ${}_{3}$ )); ${}^{1}\mathrm{H}$ NMR $\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}}, - {55}^{ \circ }\mathrm{C}}\right) : \delta = {7.01}\left( {\mathrm{{brd}},{}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = {10}\mathrm{\;{Hz}},2\mathrm{\;H};\mathrm{{CH}}}\right)$ , 6.80 (brs, 2H; CH), 3.67-3.63 (m, 4H; THF), 1.82-1.76 (m, 4H; THF), ${1.21}\left( {\mathrm{\;s},9\mathrm{H};t\mathrm{{Bu}}}\right) ,{1.04}\mathrm{{ppm}}\left( {\mathrm{{brs}},{24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ;{}^{13}\mathrm{C}\mathrm{{NMR}}({125}\mathrm{{MHz}}$ , $\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},{25}^{ \circ }\mathrm{C}) : \delta = {161.9},{137.2},{125.7},{118.8},{80.4},{68.4},{34.4},{32.6}$ (br), 26.4, 26.2 ppm; ${}^{11}\mathrm{\;B}$ NMR (224 MHz, [D7]DMF, 25°C): $\delta =$ 22.1 ppm (brs); ${}^{11}\mathrm{\;B}$ NMR (224 MHz, [D ${}_{7}$ ]DMF, -55°C): $\delta = {5.7}\mathrm{{ppm}}$ (brs); ${}^{13}\mathrm{C}$ SS-NMR (100 MHz, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {159.9},{139.4},{125.1}$ (br), 118.5 (br), 81.9, 79.1, 77.7, 68.5, 34.2, 32.5, 27.5, 27.0, 26.4, 25.7, 25.4 ppm; elemental analysis calcd (%) for ${\mathrm{C}}_{22}{\mathrm{H}}_{37}{\mathrm{O}}_{5}{\mathrm{\;B}}_{2}\mathrm{\;K} \cdot {\mathrm{C}}_{4}{\mathrm{H}}_{5}\mathrm{O}$ : $\mathrm{C}$ 60.71, H 8.82, N 0.00; found: C 60.75, H 8.90, N 0.00. Crystals of 6(dmf) suitable for XRD analysis were obtained by diffusion of diethyl ether into a solution of (6)thf in DMF at ${0}^{ \circ }\mathrm{C}$ . M.p. $> {240}^{ \circ }\mathrm{C}$ (decomp.); ${}^{13}\mathrm{C}$ SS-NMR (100 MHz, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {161.8},{160.3},{139.4}$ , 125.2 (br), 119.6 (br), 81.6, 78.4, 77.4, 36.7, 34.1, 32.1, 30.6, 27.2, 26.7, 26.1, 25.3 ppm; elemental analysis calcd (%) for ${\mathrm{C}}_{22}{\mathrm{H}}_{37}{\mathrm{O}}_{5}{\mathrm{\;B}}_{2}\mathrm{\;K} \cdot {\mathrm{C}}_{3}{\mathrm{H}}_{7}\mathrm{{ON}} : \mathrm{C}{58.27},\mathrm{H}{8.61},\mathrm{\;N}{2.72}$ ; found: $\mathrm{C}{58.37},\mathrm{H}$ 8.60, N 2.77.

$\mathrm{K}\left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{O}\left( {4 - t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) }\right\rbrack$ (6):在氮气氛围下，将KO - $\left( {t{\mathrm{{BuC}}}_{6}{\mathrm{H}}_{4}}\right) \left( {{148}\mathrm{{mg}},{790\mu }\mathrm{{mol}}}\right)$ 与 $\mathbf{1}\left( {{200}\mathrm{{mg}},{790\mu }\mathrm{{mol}}}\right)$ 在干燥的四氢呋喃(6毫升)中混合。室温搅拌 ${16}\mathrm{\;h}$ 后，通过离心收集沉淀，用干燥的四氢呋喃 $\left( {2 \times 3\mathrm{\;{mL}}}\right)$ 洗涤，并在真空下干燥，得到 (6)thf(302毫克，586微摩尔，产率74%)，为无色固体。熔点>240°C(分解)；${}^{1}\mathrm{H}$ 核磁共振(700兆赫兹，$\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},{25}^{ \circ }\mathrm{C}) : \delta = {6.97}\;\left( {\mathrm{\;d},{}^{3}\mathrm{\;J}\left( {\mathrm{H},\mathrm{H}}\right) = 9\mathrm{\;{Hz}},2\mathrm{H};\mathrm{{CH}}}\right) ,{6.74}(\mathrm{\;d}$ ，${}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 9\mathrm{\;{Hz}},2\mathrm{H};\mathrm{{CH}}),{3.65} - {3.62}\left( {\mathrm{\;m},4\mathrm{\;H};\mathrm{{THF}}}\right) ,{1.80} - {1.78}(\mathrm{\;m},4\mathrm{H}$ ；四氢呋喃)，1.21(单峰，9个氢；叔丁基)，1.05 ppm(单峰，24个氢；C(CH ${}_{3}$ ))；${}^{1}\mathrm{H}$ 核磁共振 $\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}}, - {55}^{ \circ }\mathrm{C}}\right) : \delta = {7.01}\left( {\mathrm{{brd}},{}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = {10}\mathrm{\;{Hz}},2\mathrm{\;H};\mathrm{{CH}}}\right)$ ，6.80(宽单峰，2个氢；CH)，3.67 - 3.63(多重峰，4个氢；四氢呋喃)，1.82 - 1.76(多重峰，4个氢；四氢呋喃)，${1.21}\left( {\mathrm{\;s},9\mathrm{H};t\mathrm{{Bu}}}\right) ,{1.04}\mathrm{{ppm}}\left( {\mathrm{{brs}},{24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ;{}^{13}\mathrm{C}\mathrm{{NMR}}({125}\mathrm{{MHz}}$ ，$\left\lbrack {\mathrm{D}}_{7}\right\rbrack \mathrm{{DMF}},{25}^{ \circ }\mathrm{C}) : \delta = {161.9},{137.2},{125.7},{118.8},{80.4},{68.4},{34.4},{32.6}$ (宽峰)，26.4，26.2 ppm；${}^{11}\mathrm{\;B}$ 核磁共振(2,24兆赫兹，[D7]二甲基甲酰胺，25°C):$\delta =$ 22.1 ppm(宽单峰)；${}^{11}\mathrm{\;B}$ 核磁共振(2,24兆赫兹，[D ${}_{7}$ ]二甲基甲酰胺，-55°C):$\delta = {5.7}\mathrm{{ppm}}$ (宽单峰)；${}^{13}\mathrm{C}$ 固态核磁共振(100兆赫兹，${25}^{ \circ }\mathrm{C}$ ):$\delta = {159.9},{139.4},{125.1}$ (宽峰)，118.5(宽峰)，81.9，79.1，77.7，68.5，34.2，32.5，27.5，27.0，26.4，25.7，25.4 ppm；${\mathrm{C}}_{22}{\mathrm{H}}_{37}{\mathrm{O}}_{5}{\mathrm{\;B}}_{2}\mathrm{\;K} \cdot {\mathrm{C}}_{4}{\mathrm{H}}_{5}\mathrm{O}$ 的元素分析计算值(%)为:$\mathrm{C}$ 60.71，氢8.82，氮0.00；实测值:碳60.75，氢8.90，氮0.00。适合X射线衍射分析的6(二甲基甲酰胺)晶体通过在 ${0}^{ \circ }\mathrm{C}$ 将乙醚扩散到 (6)thf在二甲基甲酰胺中的溶液中获得。熔点 $> {240}^{ \circ }\mathrm{C}$ (分解)；${}^{13}\mathrm{C}$ 固态核磁共振(100兆赫兹，${25}^{ \circ }\mathrm{C}$ ):$\delta = {161.8},{160.3},{139.4}$ ，125.2(宽峰)，119.6(宽峰)，81.6，78.4，77.4，36.7，34.1，32.1，30.6，27.2，26.7，26.1，25.3 ppm；${\mathrm{C}}_{22}{\mathrm{H}}_{37}{\mathrm{O}}_{5}{\mathrm{\;B}}_{2}\mathrm{\;K} \cdot {\mathrm{C}}_{3}{\mathrm{H}}_{7}\mathrm{{ON}} : \mathrm{C}{58.27},\mathrm{H}{8.61},\mathrm{\;N}{2.72}$ 的元素分析计算值(%)为；实测值:$\mathrm{C}{58.37},\mathrm{H}$ 8.60，氮2.77。

$\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack$ (7): Under a nitrogen atmosphere, $n{\mathrm{{Bu}}}_{4}\mathrm{\;N} \cdot 3{\mathrm{H}}_{2}\mathrm{O}$ (429 mg, 1.35 mmol, 2 equiv) and 1 (180 mg, 702 μmol, 1 equiv) were combined in dry THF (5 mL). After ${16}\mathrm{\;h}$ stirring at rt, the mixture was concentrated under vacuum until turbid, then crystallized at $- {20}^{ \circ }\mathrm{C}$ to give crystals suitable for XRD analysis. The solvent was decanted and the crystals were washed with $n$ -hexane (3 $\times$ 2 mL) and dried under vacuum to give 7 (239 mg, 463 μmol, 66%) as a colorless solid. M.p. 125-128°C; ${}^{1}\mathrm{H}$ NMR (700 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}) : \delta = {3.53}\left( {\mathrm{\;m},{}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 8\mathrm{\;{Hz}},8\mathrm{H};\mathrm{{NC}}{\mathrm{H}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}}\right) ,{1.76} - {1.67}$ (overlapping with THF, 8H; NCH ${}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$ ), 1.47 (apparent sextet, ${}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 7\mathrm{{Hz}},8\mathrm{H};{\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}),{1.08}$ (brs, ${24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right)$ ), ${1.00}\mathrm{{ppm}}\;\left( {\mathrm{t},{}^{3}\mathrm{\;J}\left( {\mathrm{H},\mathrm{H}}\right) = 7\mathrm{{Hz}},\;{12}\mathrm{H};\;{\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}}\right) ;{}^{1}\mathrm{H}$ NMR $\left( {{700}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}}, - {40}^{ \circ }\mathrm{C}}\right) : \delta = {3.55}$ (brs,8 H; ${\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$ ), 1.70 (brs,8 H; ${\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{N}}_{3}$ ),1.48-1.41 (brm,8 H; ${\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$ ),1.11 (s,12 H; C(C ${\mathrm{H}}_{3}$ )),1.04 (s,6 H; C(C ${\mathrm{H}}_{3}$ )),1.00 (t, ${}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 7\mathrm{{Hz}},{12}\mathrm{H};{\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$ ),0.94 ppm (s,6H; $\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right)$ ); ${}^{13}\mathrm{C}$ NMR (175 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {80.4}$ (br),77.9 (br),58.9,26.5 (br), 25.3 (overlapping with THF signal), 20.8, 14.6 ppm; ${}^{11}$ B NMR (224 MHz, [D8]THF, 25°C): δ =31.4 (vbrs), 5.1 ppm (brs); ${}^{19}$ F NMR (658 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}$ ): $\delta = - {129.5}\mathrm{{ppm}}$ (s); ${}^{13}\mathrm{C}$ SS-NMR (100 MHz, 25°C): δ =80.4, 77.9, 76.9, 58.4, 58.9, 27.9, 27.5, 26.1, 25.6, 25.2, 24.4, 24.0, 21.2, 19.9, 19.7, 15.0, 14.4, 13.5 ppm; ${}^{19}$ F SS-NMR (658 MHz, ${25}^{ \circ }\mathrm{C}$ ): $\delta = - {127.3}\mathrm{{ppm}}$ ; elemental analysis calcd (%) for ${\mathrm{C}}_{28}{\mathrm{H}}_{60}{\mathrm{O}}_{4}{\mathrm{{NB}}}_{2}\mathrm{\;F}$ : $\mathrm{C}{65.25},\mathrm{H}{11.73},\mathrm{\;N}{2.72}$ ; found: $\mathrm{C}{65.10},\mathrm{H}$ 11.55, N 2.92.

$\left\lbrack {n{\mathrm{{Bu}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack$ (7):在氮气氛围下，将$n{\mathrm{{Bu}}}_{4}\mathrm{\;N} \cdot 3{\mathrm{H}}_{2}\mathrm{O}$(429毫克，1.35毫摩尔，2当量)和1(180毫克，702微摩尔，1当量)在干燥的四氢呋喃(5毫升)中混合。在室温下搅拌${16}\mathrm{\;h}$后，将混合物在真空下浓缩直至浑浊，然后在$- {20}^{ \circ }\mathrm{C}$结晶，得到适合进行X射线衍射分析的晶体。倒出溶剂，并用$n$ -己烷(3 $\times$ 2毫升)洗涤晶体，并在真空下干燥，得到7(239毫克，463微摩尔，66%)，为无色固体。熔点125 - 128°C；${}^{1}\mathrm{H}$核磁共振(700兆赫，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$四氢呋喃，${25}^{ \circ }\mathrm{C}) : \delta = {3.53}\left( {\mathrm{\;m},{}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 8\mathrm{\;{Hz}},8\mathrm{H};\mathrm{{NC}}{\mathrm{H}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}}\right) ,{1.76} - {1.67}$(与四氢呋喃重叠，8H；NCH ${}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$)，1.47(表观六重峰，${}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 7\mathrm{{Hz}},8\mathrm{H};{\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}),{1.08}$(宽单峰，${24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right)$)，${1.00}\mathrm{{ppm}}\;\left( {\mathrm{t},{}^{3}\mathrm{\;J}\left( {\mathrm{H},\mathrm{H}}\right) = 7\mathrm{{Hz}},\;{12}\mathrm{H};\;{\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}}\right) ;{}^{1}\mathrm{H}$核磁共振$\left( {{700}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}}, - {40}^{ \circ }\mathrm{C}}\right) : \delta = {3.55}$(宽单峰，8H；${\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$)，1.70(宽单峰，8H；${\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{N}}_{3}$)，1.48 - 1.41(宽多重峰，8H；${\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$)，1.11(单峰，12H；C(C ${\mathrm{H}}_{3}$))，1.04(单峰，6H；C(C ${\mathrm{H}}_{3}$))，1.00(三重峰，${}^{3}J\left( {\mathrm{H},\mathrm{H}}\right) = 7\mathrm{{Hz}},{12}\mathrm{H};{\mathrm{{NCH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{2}{\mathrm{{CH}}}_{3}$)，0.94 ppm(单峰，6H；$\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right)$)；${}^{13}\mathrm{C}$核磁共振(175兆赫，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$四氢呋喃，${25}^{ \circ }\mathrm{C}$):$\delta = {80.4}$(宽峰)，77.9(宽峰)，58.9，26.5(宽峰)，25.3(与四氢呋喃信号重叠)，20.8，14.6 ppm；${}^{11}$硼核磁共振(224兆赫，[D8]四氢呋喃，25°C):δ = 31.4(非常宽的单峰)，5.1 ppm(宽单峰)；${}^{19}$氟核磁共振(658兆赫，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$四氢呋喃，${25}^{ \circ }\mathrm{C}$):$\delta = - {129.5}\mathrm{{ppm}}$(单峰)；${}^{13}\mathrm{C}$固态核磁共振(100兆赫，25°C):δ = 80.4，77.9，76.9，58.4，58.9，27.9，27.5，26.1，25.6，25.2，24.4，24.0，21.2，19.9，19.7，15.0，14.4，13.5 ppm；${}^{19}$氟固态核磁共振(658兆赫，${25}^{ \circ }\mathrm{C}$):$\delta = - {127.3}\mathrm{{ppm}}$；${\mathrm{C}}_{28}{\mathrm{H}}_{60}{\mathrm{O}}_{4}{\mathrm{{NB}}}_{2}\mathrm{\;F}$的元素分析计算值(%):$\mathrm{C}{65.25},\mathrm{H}{11.73},\mathrm{\;N}{2.72}$；实测值:$\mathrm{C}{65.10},\mathrm{H}$ 11.55，N 2.92。

$\left\lbrack {{\mathrm{{Me}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack$ (8): Under a nitrogen atmosphere, $\left\lbrack {{\mathrm{{Me}}}_{4}\mathrm{\;N}}\right\rbrack \mathrm{F}$ (257 mg, 2.76 mmol) and 1 (700 mg, 2.76 μmol) were combined in dry THF (60 mL). After ${16}\mathrm{\;h}$ stirring at ${70}^{ \circ }\mathrm{C}$ , the precipitate was collected by filtration and washed with dry THF $\left( {2 \times 5\mathrm{\;{mL}}}\right)$ . The residue was crystallized from acetonitrile to give 8 (565 mg, 163 μmol, 60%) as a colorless crystalline solid. Recrystallization from THF by somewhat elaborate conditions [flame-sealed ampoule, heating to ${100}^{ \circ }\mathrm{C}$ over $2\mathrm{\;h}$ , holding at ${100}^{ \circ }\mathrm{C}$ for $4\mathrm{\;h}$ , and finally slow cooling to rt (150 h)] gave well-developed needles of 8(thf). ${}^{1}\mathrm{H}$ NMR $\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {1.03}\left( {\mathrm{\;s},{24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{3.14}\mathrm{{ppm}}(\mathrm{t}$ , ${}^{3}J\left( {\mathrm{\;N},\mathrm{H}}\right) = {0.6}\mathrm{\;{Hz}},\;{12}\mathrm{H};{\mathrm{N({CH}}}_{3}{)}_{4});{}^{1}\mathrm{H}\mathrm{{NMR}}\;({200}\mathrm{{MHz}},\;\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$ , $- {30}^{ \circ }\mathrm{C}) : \delta = {3.10}$ (s, ${12}\mathrm{\;H};\mathrm{N}{\left( {\mathrm{{CH}}}_{3}\right) }_{4}),{1.04}$ (s, ${12}\mathrm{\;H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) ),{0.96}$ (s, $6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) ),{0.88}\mathrm{{ppm}}$ (s, $6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) );{56.1}$ (t, ${}^{1}\mathrm{J}\left( {\mathrm{N},\mathrm{C}}\right) = 4\mathrm{{Hz}}$ , $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}) : \delta = {78.9}$ (br, $C\left( {\mathrm{{CH}}}_{3}\right)$ ),56.1(t, ${}^{1}\mathrm{J}\left( {\mathrm{N},\mathrm{C}}\right) = 4\mathrm{{Hz}}$ , $\mathrm{N}{\left( {\mathrm{{CH}}}_{3}\right) }_{4}),{26.2}\mathrm{{ppm}}\left( {\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ;{}^{11}\mathrm{B}\mathrm{{NMR}}\left( {{160}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}}\right)$ : $\delta = {33.9}$ ,(vbrs),5.7 ppm (brs); ${}^{19}\mathrm{\;F}$ NMR (188 MHz, $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}$ ): $\delta = - {125.6}\mathrm{{ppm}}\left( \mathrm{s}\right) ;{}^{13}\mathrm{C}$ SS-NMR $\left( {{100}\mathrm{{MHz}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {80.2}$ (br, $\left. {C\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{77.0}\left( {\mathrm{{lbr}};C\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{54.9}\left( {\mathrm{\;N}{\left( {\mathrm{{CH}}}_{3}\right) }_{4}}\right) ,{25.9}\mathrm{{ppm}}\left( {\mathrm{{lbr}};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right)$ ; ${}^{19}\mathrm{F}$ SS-NMR (376 MHz, ${25}^{ \circ }\mathrm{C}$ ): $\delta = - {130.6}\mathrm{{ppm}}$ ; elemental analysis calcd (%) for ${\mathrm{C}}_{16}{\mathrm{H}}_{36}{\mathrm{O}}_{4}{\mathrm{{NB}}}_{2}\mathrm{\;F}$ : C 55.37, $\mathrm{H}{10.45},\mathrm{\;N}{4.04}$ ; found: $\mathrm{C}$ 55.24, H 10.67, N 4.35.

$\left\lbrack {{\mathrm{{Me}}}_{4}\mathrm{\;N}}\right\rbrack \left\lbrack {{\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}\mathrm{\;F}}\right\rbrack$ (8):在氮气气氛下，将$\left\lbrack {{\mathrm{{Me}}}_{4}\mathrm{\;N}}\right\rbrack \mathrm{F}$(257毫克，2.76毫摩尔)和1(700毫克，2.76微摩尔)在干燥的四氢呋喃(60毫升)中混合。在${70}^{ \circ }\mathrm{C}$搅拌${16}\mathrm{\;h}$后，通过过滤收集沉淀并用干燥的四氢呋喃$\left( {2 \times 5\mathrm{\;{mL}}}\right)$洗涤。残余物从乙腈中结晶，得到8(565毫克，163微摩尔，60%)，为无色结晶固体。通过稍微精细的条件[火焰密封安瓿，在$2\mathrm{\;h}$上加热至${100}^{ \circ }\mathrm{C}$，在${100}^{ \circ }\mathrm{C}$保持$4\mathrm{\;h}$，最后缓慢冷却至室温(150小时)]从四氢呋喃中重结晶，得到发育良好 的8(thf)针状晶体。${}^{1}\mathrm{H}$核磁共振$\left( {{500}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {1.03}\left( {\mathrm{\;s},{24}\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{3.14}\mathrm{{ppm}}(\mathrm{t}$，${}^{3}J\left( {\mathrm{\;N},\mathrm{H}}\right) = {0.6}\mathrm{\;{Hz}},\;{12}\mathrm{H};{\mathrm{N({CH}}}_{3}{)}_{4});{}^{1}\mathrm{H}\mathrm{{NMR}}\;({200}\mathrm{{MHz}},\;\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}$，$- {30}^{ \circ }\mathrm{C}) : \delta = {3.10}$(单峰，${12}\mathrm{\;H};\mathrm{N}{\left( {\mathrm{{CH}}}_{3}\right) }_{4}),{1.04}$(单峰，${12}\mathrm{\;H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) ),{0.96}$(单峰，$6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) ),{0.88}\mathrm{{ppm}}$(单峰，$6\mathrm{H};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) );{56.1}$(三重峰，${}^{1}\mathrm{J}\left( {\mathrm{N},\mathrm{C}}\right) = 4\mathrm{{Hz}}$，$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}) : \delta = {78.9}$(宽峰，$C\left( {\mathrm{{CH}}}_{3}\right)$)，56.1(三重峰，${}^{1}\mathrm{J}\left( {\mathrm{N},\mathrm{C}}\right) = 4\mathrm{{Hz}}$，$\mathrm{N}{\left( {\mathrm{{CH}}}_{3}\right) }_{4}),{26.2}\mathrm{{ppm}}\left( {\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right) ;{}^{11}\mathrm{B}\mathrm{{NMR}}\left( {{160}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}}\right)$:$\delta = {33.9}$，(非常宽的单峰)，5.7 ppm(宽单峰)；${}^{19}\mathrm{\;F}$核磁共振(188兆赫，$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}},{25}^{ \circ }\mathrm{C}$):$\delta = - {125.6}\mathrm{{ppm}}\left( \mathrm{s}\right) ;{}^{13}\mathrm{C}$固态核磁共振$\left( {{100}\mathrm{{MHz}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {80.2}$(宽峰，$\left. {C\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{77.0}\left( {\mathrm{{lbr}};C\left( {\mathrm{{CH}}}_{3}\right) }\right) ,{54.9}\left( {\mathrm{\;N}{\left( {\mathrm{{CH}}}_{3}\right) }_{4}}\right) ,{25.9}\mathrm{{ppm}}\left( {\mathrm{{lbr}};\mathrm{C}\left( {\mathrm{{CH}}}_{3}\right) }\right)$；${}^{19}\mathrm{F}$固态核磁共振(376兆赫，${25}^{ \circ }\mathrm{C}$):$\delta = - {130.6}\mathrm{{ppm}}$；${\mathrm{C}}_{16}{\mathrm{H}}_{36}{\mathrm{O}}_{4}{\mathrm{{NB}}}_{2}\mathrm{\;F}$的元素分析计算值(%):碳55.37，$\mathrm{H}{10.45},\mathrm{\;N}{4.04}$；实测值:$\mathrm{C}$ 55.24，氢10.67，氮4.35。

[K(18-crown-6)][dmedaB-B(OMe) ${}_{3}$ ] (9): Under a nitrogen atmosphere, KOMe (35 mg, 499 μmol, 1 equiv), 18-crown-6 (140 mg, ${530\mu }\mathrm{{mol}}$ ,1.1 equiv), and ${\mathrm{B}}_{2}{\text{ dmeda }}_{2}$ (51 mg, ${490\mu }\mathrm{{mol}}$ ,1 equiv) were dissolved in dry THF (4 mL), aided by stirring. After 16 h, the cloudy solution was filtered through a pad of Celite, concentrated under vacuum to a volume of approximately 2 mL, and layered with $n$ -hexane ( $7\mathrm{\;{mL}}$ ). After crystallization at $- {20}^{ \circ }\mathrm{C}$ , colorless crystals suitable for XRD analysis were obtained and dried under vacuum to give 9(thf) (52mg, 103 μmol, 62% with KOMe as the stoichiometrically limiting starting material). M.p. 68-72°C; ${}^{1}\mathrm{H}$ NMR (500 MHz; $\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ THF, ${25}^{ \circ }\mathrm{C}$ ): $\delta = {3.60}$ (s,26H; ${\mathrm{{CH}}}_{2}\mathrm{O}$ (18-crown-6, THF)), 3.03 (s, 9H; 3×OMe), 2.98 (s, 4H; NCH2), 2.88 (s, 6H; NMe), ${1.78}\mathrm{{ppm}}\left( {\mathrm{s},2\mathrm{H};\mathrm{{THF}}}\right) ;{}^{13}\mathrm{C}\mathrm{{NMR}}\left( {{125}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {71.4}$ , 67.5,54.2,48.9,36.6,26.6 ppm; ${}^{11}\mathrm{B}$ NMR (160 MHz, $\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}$ ): $\delta = {35.9}$ (vbrs), ${4.3}\mathrm{{ppm}}$ (brs); elemental analysis calcd (%) for ${\mathrm{C}}_{19}{\mathrm{H}}_{43}{\mathrm{O}}_{9}{\mathrm{\;N}}_{2}{\mathrm{\;B}}_{2}{\mathrm{\;K}}^{\cdot 1}/{}_{2}{\mathrm{C}}_{4}{\mathrm{H}}_{8}\mathrm{O} : \mathrm{C}{46.68},\mathrm{H}{8.77},\mathrm{\;N}{5.18}$ ; found: $\mathrm{C}{46.61},\mathrm{H}$ 8.71, N 4.92.

[K(18-冠醚-6)][dmedaB-B(OMe) ${}_{3}$ ] (9):在氮气气氛下，将甲醇钾(35毫克，499微摩尔，1当量)、18-冠醚-6(140毫克，${530\mu }\mathrm{{mol}}$ ，1.1当量)和${\mathrm{B}}_{2}{\text{ dmeda }}_{2}$ (51毫克，${490\mu }\mathrm{{mol}}$ ，1当量)溶解于干燥的四氢呋喃(4毫升)中，并搅拌。16小时后，将浑浊溶液通过硅藻土垫过滤，在真空下浓缩至约2毫升体积，并用$n$ -己烷($7\mathrm{\;{mL}}$ )进行分层。在$- {20}^{ \circ }\mathrm{C}$ 结晶后，获得适合X射线衍射分析的无色晶体，并在真空下干燥，得到9(thf)(52毫克，103微摩尔，以甲醇钾作为化学计量限制起始原料时产率为62%)。熔点68 - 72°C；${}^{1}\mathrm{H}$ 核磁共振(500兆赫；$\left\lbrack {\mathrm{D}}_{8}\right\rbrack$ 四氢呋喃，${25}^{ \circ }\mathrm{C}$ ):$\delta = {3.60}$ (单峰，26H；${\mathrm{{CH}}}_{2}\mathrm{O}$ (18-冠醚-6，四氢呋喃))，3.03(单峰，9H；3×OMe)，2.98(单峰，4H；NCH2)，2.88(单峰，6H；NMe)，${1.78}\mathrm{{ppm}}\left( {\mathrm{s},2\mathrm{H};\mathrm{{THF}}}\right) ;{}^{13}\mathrm{C}\mathrm{{NMR}}\left( {{125}\mathrm{{MHz}},\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}}\right) : \delta = {71.4}$ ，67.5、54.2、48.9、36.6、26.6 ppm；${}^{11}\mathrm{B}$ 核磁共振(160兆赫，$\left\lbrack {\mathrm{D}}_{8}\right\rbrack \mathrm{{THF}},{25}^{ \circ }\mathrm{C}$ ):$\delta = {35.9}$ (宽峰单峰)，${4.3}\mathrm{{ppm}}$ (宽峰)；元素分析计算值(%)为${\mathrm{C}}_{19}{\mathrm{H}}_{43}{\mathrm{O}}_{9}{\mathrm{\;N}}_{2}{\mathrm{\;B}}_{2}{\mathrm{\;K}}^{\cdot 1}/{}_{2}{\mathrm{C}}_{4}{\mathrm{H}}_{8}\mathrm{O} : \mathrm{C}{46.68},\mathrm{H}{8.77},\mathrm{\;N}{5.18}$ ；实测值:$\mathrm{C}{46.61},\mathrm{H}$ 8.71，N 4.92。

Procedure for the reaction of $4 - {\mathrm{{MeC}}}_{6}{\mathrm{H}}_{4}\mathrm{I}$ with Lewis base adducts: The reactions were performed by mixing freshly prepared solutions $\left( {{0.15}\mathrm{\;{mL}}}\right.$ each) of $4 - {\mathrm{{MeC}}}_{6}{\mathrm{H}}_{4}\mathrm{I}\;\left( {{46\mu }\mathrm{{mol}}}\right)$ and adduct (46 μmol) in the required solvent in a J. Young NMR tube and addition of more solvent to give a total volume of 0.6 mL). Only analytically pure compounds (determined by CHN analysis) were used and the preparation took place in a nitrogen-filled glovebox with appropriately dried and degassed NMR solvents. The progress of the reaction was monitored by in situ NMR spectroscopy and GC-MS analysis.

$4 - {\mathrm{{MeC}}}_{6}{\mathrm{H}}_{4}\mathrm{I}$ 与路易斯碱加合物的反应步骤:反应通过在J. Young核磁共振管中，将$4 - {\mathrm{{MeC}}}_{6}{\mathrm{H}}_{4}\mathrm{I}\;\left( {{46\mu }\mathrm{{mol}}}\right)$ 和加合物(46微摩尔)在所需溶剂中的新鲜制备溶液(各$\left( {{0.15}\mathrm{\;{mL}}}\right.$ )混合，并加入更多溶剂使总体积达到0.6毫升来进行。仅使用分析纯化合物(通过CHN分析确定)，且制备在充满氮气的手套箱中进行，使用适当干燥和脱气的核磁共振溶剂。反应进程通过原位核磁共振光谱和气相色谱 - 质谱分析进行监测。

Procedure for the reaction of diazonium salts with Lewis base adducts: The reactions were performed by mixing freshly prepared diazonium salt with the respective adduct or 1 (1 equiv) and base (1 equiv) in $\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}\left( {{0.6}\mathrm{\;{mL}}}\right)$ . Only analytically pure compounds (determined by CHN analysis) were used and the preparation took place under inert conditions in a glovebox. All NMR solvents were dried and degassed. The progress of the reaction was monitored by in situ NMR spectroscopy and GC-MS analysis.

重氮盐与路易斯碱加合物反应的步骤:反应通过将新制备的重氮盐与相应的加合物或1(1当量)和碱(1当量)在$\left\lbrack {\mathrm{D}}_{3}\right\rbrack \mathrm{{MeCN}}\left( {{0.6}\mathrm{\;{mL}}}\right)$中混合进行。仅使用分析纯化合物(通过CHN分析确定)，并且制备在手套箱中的惰性条件下进行。所有NMR溶剂均经过干燥和脱气处理。反应进程通过原位NMR光谱和GC-MS分析进行监测。

Procedure for the reaction of 8 with diazonium salts: Under an atmosphere of argon, 8 (0.865 mmol, 300 mg, 1.4 equiv) and freshly prepared diazonium salt (0.618 mmol, 1 equiv) were combined in dry acetonitrile $\left( {{20}\mathrm{\;{mL}}}\right)$ to give a dark-red solution. Afterwards, the reaction mixture was quenched with ${\mathrm{{Et}}}_{2}\mathrm{O}\left( {{10}\mathrm{\;{mL}}}\right)$ and the solution was filtered to remove the precipitate. The solvent was evaporated under vacuum and the residue was re-dissolved in $n$ - hexane (20 mL). The solution was filtered to remove any insoluble material and the product was purified by automated flash chromatography (n-hexane $/{\mathrm{{Et}}}_{2}\mathrm{O}$ ).

8与重氮盐反应的步骤:在氩气气氛下，将8(0.865 mmol，300 mg，1.4当量)和新制备的重氮盐(0.618 mmol，1当量)在干燥的乙腈$\left( {{20}\mathrm{\;{mL}}}\right)$中混合，得到深红色溶液。之后，用${\mathrm{{Et}}}_{2}\mathrm{O}\left( {{10}\mathrm{\;{mL}}}\right)$淬灭反应混合物，然后过滤溶液以除去沉淀。在真空下蒸发溶剂，残余物重新溶解于$n$ - 己烷(20 mL)中。过滤溶液以除去任何不溶物，产物通过自动快速柱色谱法(正己烷$/{\mathrm{{Et}}}_{2}\mathrm{O}$)纯化。

X-ray crystallography

X射线晶体学

The crystals were obtained as specified for the individual compounds (see above). The single crystals were coated with per-fluoropolyether oil, mounted on a human hair at ambient temperature (or, in the cases for which the crystals were obtained at $- {20}^{ \circ }\mathrm{C}$ , under cooling with dry ice), and frozen in the cold nitrogen gas stream on the goniometer. More than a hemisphere of data were collected with a Bruker SMART 1000 or SMART 6000 diffractometer $\left( \omega \right.$ scans, ${0.3}^{ \circ }$ width) by using ${\mathrm{{Mo}}}_{\mathrm{K}\alpha }$ radiation $(\lambda =$ 0.71073Å). In the case of 7 and 8(thf), ${\mathrm{{Cu}}}_{\mathrm{K}\alpha }$ radiation $(\lambda =$ 1.54184 Å) was used and an Oxford Diffraction Gemini Ultra or Oxford Diffraction Nova A instrument was employed, respectively ( $\omega$ scans). The data were reduced (SAINT, ${}^{\left\lbrack {43}\mathrm{a}\right\rbrack }$ CrysAlisPro) ${}^{\left\lbrack {43}\mathrm{\;b}\right\rbrack }$ and, in the case of 1, (2), (dmf), 4, 5, 6(dmf), 7, and 9, corrected for absorption (SADABS, ${}^{\left\lbrack {43}\mathrm{c}\right\rbrack }$ SCALE3 ABSPACK). ${}^{\left\lbrack {43}\mathrm{\;d}\right\rbrack }$ The structures were solved by direct methods and refined by the full-matrix least-squares method on all ${F}^{2}$ data (SHELX). ${}^{\left\lbrack {43}\mathrm{e}\right\rbrack }$ Unless specified, ${}^{\left\lbrack {26}\right\rbrack }$ all non-hydrogen atoms were refined with anisotropic displacement parameters and hydrogen atoms were included in the calculated positions and refined by using a riding model. Refinement, analysis of the structures, and the preparation of graphics were performed by using the SHELX, ${}^{\left\lbrack {43}\mathrm{e}\right\rbrack }$ ORTEP 3, ${}^{\left\lbrack {43}\mathrm{f}\right\rbrack }$ MERCURY, ${}^{\left\lbrack {43}\mathrm{g}\right\rbrack }$ DIAMOND, ${}^{\left\lbrack {43}\mathrm{h}\right\rbrack }$ WinGX, ${}^{\left\lbrack {43}\mathrm{i}\right\rbrack }$ or PLATON ${}^{\left\lbrack {33}\right\rbrack }$ programmes.

晶体按照各化合物的特定要求获得(见上文)。将单晶用全氟聚醚油包裹，在室温下安装在一根头发上(或者，对于在$- {20}^{ \circ }\mathrm{C}$获得晶体的情况，在干冰冷却下)，并在测角仪上的冷氮气流中冷冻。使用布鲁克SMART 1000或SMART 6000衍射仪通过$\left( \omega \right.$扫描、${0.3}^{ \circ }$宽度)收集超过半球的数据，使用${\mathrm{{Mo}}}_{\mathrm{K}\alpha }$辐射$(\lambda =$0.71073Å)。对于7和8(thf)的情况，分别使用${\mathrm{{Cu}}}_{\mathrm{K}\alpha }$辐射$(\lambda =$1.54184 Å)并使用牛津衍射双子座超型或牛津衍射新星A仪器($\omega$扫描)。数据进行了还原(SAINT，${}^{\left\lbrack {43}\mathrm{a}\right\rbrack }$CrysAlisPro)${}^{\left\lbrack {43}\mathrm{\;b}\right\rbrack }$，并且对于1、(2)、(dmf)、4、5、6(dmf)、7和9，进行了吸收校正(SADABS，${}^{\left\lbrack {43}\mathrm{c}\right\rbrack }$SCALE3 ABSPACK)。${}^{\left\lbrack {43}\mathrm{\;d}\right\rbrack }$结构通过直接法求解，并在所有${F}^{2}$数据上通过全矩阵最小二乘法进行精修(SHELX)。${}^{\left\lbrack {43}\mathrm{e}\right\rbrack }$除非另有说明，${}^{\left\lbrack {26}\right\rbrack }$所有非氢原子用各向异性位移参数进行精修，氢原子包含在计算位置中并使用骑乘模型进行精修。精修、结构分析以及图形制备使用SHELX、${}^{\left\lbrack {43}\mathrm{e}\right\rbrack }$ORTEP 3、${}^{\left\lbrack {43}\mathrm{f}\right\rbrack }$MERCURY、${}^{\left\lbrack {43}\mathrm{g}\right\rbrack }$DIAMOND、${}^{\left\lbrack {43}\mathrm{h}\right\rbrack }$WinGX、${}^{\left\lbrack {43}\mathrm{i}\right\rbrack }$或PLATON${}^{\left\lbrack {33}\right\rbrack }$程序进行。

Computational details

计算细节

The structures of all the species were optimized by DFT calculations without constraints at the B3LYP level of theory, ${}^{\left\lbrack {44}\right\rbrack }$ by using the related X-ray crystal structures as the starting geometries, including the relevant cations. Frequency calculations at the same level of theory were also performed to identify all stationary points as minima and to obtain enthalpies and free energies at ${298.15}\mathrm{\;K}$ . The 6-311G* Pople basis ${\text{ set }}^{\left\lbrack {45}\right\rbrack }$ was used for boron, oxygen, and fluorine atoms involved in the dative bonds of the acid/base adducts. The standard 6-31G basis set was used for all other atoms. We also estimated the solvation energies by performing single-point self-consistent reaction field (SCRF) calculations based on the polarizable continuum model (PCM) ${}^{\left\lbrack {46}\right\rbrack }$ with “scfvac” as the keyword and THF as the solvent. The estimated solvation energies were used to correct the thermochemical data obtained from the gas-phase calculations. We also employed DFT functional MPW1K ${}^{\left\lbrack {47}\right\rbrack }$ for the geometry optimization calculations to examine whether a different DFT functional would produce significantly different results. All of the DFT calculations were performed with the Gaussian 03 package. ${}^{\left\lbrack {48}\right\rbrack }$

所有物种的结构均通过在B3LYP理论水平下无约束的DFT计算进行优化，${}^{\left\lbrack {44}\right\rbrack }$通过使用相关的X射线晶体结构作为起始几何结构，包括相关阳离子。还在相同理论水平下进行了频率计算，以将所有驻点识别为极小值，并在${298.15}\mathrm{\;K}$处获得焓和自由能。6-311G* Pople基组${\text{ set }}^{\left\lbrack {45}\right\rbrack }$用于酸碱加合物配位键中涉及的硼、氧和氟原子。所有其他原子使用标准的6-31G基组。我们还通过基于极化连续介质模型(PCM)${}^{\left\lbrack {46}\right\rbrack }$进行单点自洽反应场(SCRF)计算来估计溶剂化能，关键词为“scfvac”，溶剂为THF。估计的溶剂化能用于校正从气相计算获得的热化学数据。我们还使用DFT泛函MPW1K ${}^{\left\lbrack {47}\right\rbrack }$进行几何优化计算，以检查不同的DFT泛函是否会产生显著不同的结果。所有DFT计算均使用Gaussian 03软件包进行。${}^{\left\lbrack {48}\right\rbrack }$

Acknowledgements

致谢

C.K. thanks the Deutsche Forschungsgemeinschaft (DFG) for a postdoctoral fellowship. T.B.M. thanks AllyChem Co. Ltd. for the generous gift of ${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$ , Lei Liu for the TBPE, Maik Finze for the ${\mathrm{{Me}}}_{4}\mathrm{{NF}}$ salt, the Royal Society for a Wolfson Research Merit Award, the Alexander von Humboldt Foundation for a Research Award, the EPSRC for an Overseas Research Travel Grant, the Royal Society of Chemistry for a Journals Grant for International Authors and the DFG (Ma4471/1-1) for financial support. Z.L. thanks the Research Grants Council of Hong Kong for support (HKUST 603313). We thank the EPSRC National Solid-State NMR Research Service (Durham) for recording the solid-state NMR spectra and for valuable discussions and J. Magee (Durham) for performing elemental analyses.

C.K. 感谢德国研究基金会(DFG)授予博士后奖学金。T.B.M. 感谢AllyChem有限公司慷慨提供的${\mathrm{B}}_{2}{\mathrm{{pin}}}_{2}$，感谢刘雷提供的TBPE，感谢Maik Finze提供的${\mathrm{{Me}}}_{4}\mathrm{{NF}}$盐，感谢英国皇家学会授予沃尔夫森研究优秀奖，感谢亚历山大·冯·洪堡基金会授予研究奖，感谢英国工程和物理科学研究委员会(EPSRC)授予海外研究旅行补助金，感谢英国皇家化学学会授予国际作者期刊补助金，以及感谢德国研究基金会(Ma4471/1 - 1)提供资金支持。Z.L. 感谢香港研究资助局的支持(香港科技大学603313)。我们感谢英国工程和物理科学研究委员会国家固态核磁共振研究服务中心(达勒姆)记录固态核磁共振谱并进行有价值的讨论，以及感谢J. Magee(达勒姆)进行元素分析。

Keywords: boron - boronic acids - cross-coupling - Lewis bases $\cdot$ metal-free borylation

关键词:硼 - 硼酸 - 交叉偶联 - 路易斯碱$\cdot$无金属硼化

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Received: January 19, 2015

收到日期:2015年1月19日

Published online on April 15, 2015

于2015年4月15日在线发表