化学学报 ›› 2017, Vol. 75 ›› Issue (8): 824-830.DOI: 10.6023/A17040141 上一篇    

研究论文

有机胺盐/硼烷体系与炔烃的硼氢化加成反应机理研究

孙国峰, 苏敏, 方洁, Borzov Maxim, 聂万丽   

  1. 乐山师范学院化学学院 天然产物化学与小分子催化四川省高校重点实验室 乐山 614000
  • 收稿日期:2017-04-06 出版日期:2017-08-15 发布日期:2017-05-24
  • 通讯作者: 聂万丽,E-mail:niewl126@126.com E-mail:niewl126@126.com
  • 基金资助:

    项目受国家自然科学基金(No.21542011)和四川省教育厅及乐山市科技局(Nos.15ZB0256,Z14GZ010)资助.

Research of the Stereoselectivity and Mechanism of the Hydroboration Reaction Between B(C6F5)3/Ammonium Chloride Systems with Terminal Alkyne

Sun Guofeng, Su Min, Fang Jie, Borzov Maxim, Nie Wanli   

  1. Sichuan Province Key Laboratory of Natural Products and Small Molecule Synthesis, Chemical Department of Leshan Normal University, Leshan 614000, China
  • Received:2017-04-06 Online:2017-08-15 Published:2017-05-24
  • Contact: 10.6023/A17040141 E-mail:niewl126@126.com
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No.21542011),Scientific Research Fund of Sichuan Educational Department and Leshan Technology Division (Nos.15ZB0256,Z14GZ010).

炔烃的立体选择性硼氢化加成反应是有机合成中重要的反应之一.在硅烷的存在下,有机胺盐酸盐/硼烷体系可与炔烃在温和的反应条件下发生计量的加成反应.该反应不仅可高立体选择性地得到Z-式构型的1,2-硼氢化胺盐加成产物,而且反应产率高,产物易于分离提纯.对有机胺盐酸盐/硼烷体系与炔烃的加成反应机理进行的研究表明,胺盐与B(C6F53及硅烷反应所生成的硼氢化胺盐"[R2NH2]+[H-B(C6F53]-",虽然被认为是受限路易斯酸碱对化学的活性中间体,但其本身并不能直接还原炔烃;炔烃必须首先被催化量的路易斯酸B(C6F53活化后才可与[H-B(C6F53]-加成.同时,胺盐氯阴离子Cl-与路易斯酸B(C6F53之间的弱的相互作用直接决定着产物的立体选择性,[H-B(C6F53]-以反式加成的方式进攻活化后的炔烃最终得到Z-式构型的硼氢化加成产物.

关键词: 有机胺盐酸盐, 三(五氟苯基)硼, 硅烷, 炔烃, 硼氢化反应

Stereoselective hydroboration reaction of alkynes has been considered as one of the most important organic reaction. To date a handful of metal-catalyzed systems have been demonstrated to achieve trans-hydroboration of alkynes. This paper describes the first non-metal-catalyzed systems which could stereoselectively hydroborate the terminal alkynes in a trans-configuration. The Lewis acid B(C6F5)3 and ammonium chloride have been used as the reaction substrates, and phenylsilane as the hydride source. The hydroboration reaction could be performed in a one-pot procedure by mixing of B(C6F5)3, ammonium chloride and silane together in an equivalent amount. But this one-pot reaction is not so nice since there is always mixed with the ammonium hydroborate[R2NH2]+[H-B(C6F5)3]- intermediates products. A series of ammonium hydroborates prepared from the corresponding primary, secondary, tertiary and quaternary amine hydrochlorides have been isolated, and used in the directly hydroboration with terminal alkynes. To our surprise the ammonium hydroborate[R2NH2]+[H-B(C6F5)3]- could not react with the alkynes alone. When using[R2NH2]+[H-B(C6F5)3]- to react with alkynes, trace amount of catalytic Lewis acid B(C6F5)3 is necessary to firstly activate the carbon-carbon triple bonds and form the crucial zwitterionic σ-complexes. The mechanism study has shown that different from the typical Lewis acid/Lewis base FLPs system reacted with alkynes, in this B(C6F5)3/ammonium chloride system the ammonium chloride plays an important role on the stereoselective control of the reaction. The week interaction between the Cl ion and B(C6F5)3 in the σ-complexes has not only slowed down the unfavorite 1,1-carboboration reaction, but also stabilized the σ-complexes which has offer the chance for the nucleophilic reagent to attack the reaction center in a cis-or trans-mode. In our experiment the bulky ion[H-B(C6F5)3]-could only attach the active alkynes from the trans-side and form the Z-hydroboration product. This work demonstrates that the combination of the ammonium halides with the Lewis acid B(C6F5)3 could act as a novel "frustrated Lewis pair" to activate alkynes, and will enable the development of even more sophisticated FLP and related catalyzed reactions.

Key words: ammonium chloride, B(C6F5)3, silane, alkyne, hydroboration