碳硼烷选择性硼-氢键活化及官能团化研究

Carboranes are a class of boron hydride clusters in which one or more of the BH vertices are replaced by CH unit, which can be viewed as three-dimensional relatives of benzene. They are finding many applications in medicine and materials, however, their unique structures make derivatization very difficult. To address the challenge of realizing selectivity among 10 similar B vertexes, we plan to use the organometallic methods to directly active and functionalize the B-H bonds in o-carboranes. Electron-rich transition-metal can catalyze the 3,6- and 4,5-B-H bond activation, respectively, controlled by electronic and steric effect in the non-directing group reaction system. Electron-deficient transition-metal can catalyze the B-I bond activation, 8,9-B-H bond activation and cross-coupling cascade reaction to assemble complex multi-functionalized carboranes in a single operation. It is anticipated that this research will result in a new toolbox for the preparation of a new class of B-substituted carborane derivatives, which will have potential application in medicine and materials. The developed methodology will also enhance our basic understanding of elemento organic and organometallic chemistry.

碳硼烷是两个CH和十个BH顶点组成的笼状分子，被视为苯的三维类似物，具有超芳香性及很好的化学和热稳定性。目前碳硼烷化学领域的重大挑战在于如何高效、高选择性官能团化以扩展其在医药、材料等领域的重要应用。本项目针对如何在碳硼烷十个化学环境非常类似的硼顶点间控制选择性这一重大挑战，采用金属有机化学方法直接活化硼-氢键实现官能团化。利用无导向基团策略，通过电性和位阻控制，用富电子金属催化剂分别活化碳硼烷近端3,6-和4,5-位硼氢，直接构建硼-碳键和硼-杂原子键；利用贫电子金属催化硼-碘键、硼-氢键活化串联交叉偶联反应，活化远端8,9-位硼氢，一步简单高效构筑多官能团化的复杂碳硼烷衍生物。本项目所发展的官能团化碳硼烷化合物将有望在医药、材料领域取得潜在的应用，所发展的合成方法学也可以为金属催化有机合成方法学提供有利的借鉴，对主族元素化学、金属有机化学等学科的发展具有重要的意义。

项目执行四年来，开展了邻-碳硼烷的选择性硼-氢键活化及官能团化研究。针对碳硼烷十个化学环境非常类似的硼顶点间的选择性控制，发展了过渡金属催化剂直接活化硼-氢键实现系列碳硼烷官能团化；钯迁移反应实现碘代-邻-碳硼烷选择性多官能团化；对映选择性B–H键活化反应实现不对称合成笼手性碳硼烷。本项目提供了碳硼烷官能团化路线设计的新思路，发展了多项硼顶点高效、高选择性的衍生化方法，合成一系列新颖结构的碳硼烷衍生物。主要成果如下：.1. 共发表学术论文14篇。其中含J. Am. Chem. Soc. 1篇，Angew. Chem. Int. Ed. 1篇，Nat. Commun. 1篇，以及Chin. J. Chem.、Chem. Commun.、Eur. J. Chem.等期刊8 篇，并在Acc. Chem. Res.、ACS Catal.、Chin. J. Org. Chem.撰写过渡金属促进碳硼烷官能团化研究进展综述共3篇;.2. 3人取得博士学位，1人取得硕士学位;.3. 本项目相关研究工作在国际学术会议做邀请、口头报告7次。