过渡金属催化的芳基羧酸脱羧硼化反应研究

Arylboron reagents have important application value in organic synthesis; therefore, research on the methods to prepare such compounds has gained wide attention. Many kinds of chemical bonds, such as C–X and C–H bonds, can be transformed to C–B bonds directly, but there is still no precedent that may realize the direct transformations from carboxylic acids to boronyl groups. The carboxyl group is one of the most common functional groups in organic chemistry, and carboxylic acids are usually stable, cheap and readily-available. So this project intends to obtain an efficient reaction pathway to achieve the direct conversions from aryl carboxylic acids to arylboron reagents through reasonable experimental design and intensive condition screening. When screening conditions and exploring the best combination of catalyst, ligand, solvent and other experimental variables, the detailed reaction mechanism will also be confirmed by means of Density Functional Theory calculations. The theoretical simulation will focus on the effects of some variables on potential energy surface and rate-determining step, providing theoretical explanation for the experimental observation and theoretical guidance for the improvement and modification of experimental design. The research work can not only provide a new synthetic pathway for the preparation of arylboron reagents, but also verify the function of synergistic interplay between experimental exploration and theoretical calculation in the study of synthetical methodology, providing new research ideas for the development and optimization of catalytic reactions.

芳基硼试剂在有机合成中具有重要的应用价值，因此，其制备方法研究一直受到广泛关注。过渡金属催化下，多种化学键（如碳卤键、碳氢键等）可直接转化为碳硼键，而羧酸基团向硼基团的直接转化，则至今仍未见报道。羧基为有机化学中最常见的官能团之一，且羧酸类化合物大多性质稳定、廉价易得。鉴于此，本项目拟通过合理的实验设计和细致的条件筛选，获得一条高效的反应路径，实现芳基羧酸到芳基硼试剂直接转化。在开展实验条件筛选，探索催化剂、配体、反应溶剂等实验变量最佳组合的同时，通过密度泛函理论计算，确定反应的详细机理。另外，理论模拟工作将重点关注一些实验变量对反应势能面和决速步的影响，为实验现象提供理论解释，为实验方案的改进和修正提供理论指导。这些研究工作，不仅可以为合成芳基硼试剂提供新路径，而且可以验证实验探索与理论计算相互结合在有机合成方法学研究中的作用，为开发和优化催化反应提供新的研究思路。

有机硼化合物的制备和应用是有机化学中最常用的转化之一。在本项目的支持下，我们开展了芳基硼试剂的利用研究，旨在开发一些有效构建碳氮键的方法。总的来说，我们实现了几种铜催化的芳基硼酸和双/多亲核试剂之间Chan-Evans-Lam（CEL）C-N交叉偶联反应。氨基苯甲酰胺和氨基苯磺酰胺与芳基硼酸可在敞口瓶中发生反应，室温下搅拌即可发生化学选择性的碳氮偶联反应。双/多亲核试剂中的不同亲核位点可以在不同的反应条件下得到有效区分。在进行这一研究的过程中，我们发现，羰基可作为定位基团诱导CEL反应的发生。在羰基诱导下，芳基频哪醇硼酸酯也可在温和条件下发生C-N偶联反应。同时，利用密度泛函理论，我们计算了无金属条件下环化硼化反应的反应机理，详细阐述了该反应的中间体、过渡态及反应机理。