Liu Ke, Lei Mengna, Li Xin, Zhang Xuemei, Zhang Ying, Fan Weigang, Li Man-Bo, Zhang Sheng
Institutes of Physical Science and Information Technology, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Anhui University, Hefei, 230601, Anhui, China.
Nat Commun. 2024 Apr 4;15(1):2897. doi: 10.1038/s41467-024-47220-9.
Cross-dehydrogenative coupling of C(sp)-H bonds is an ideal approach for C(sp)-C(sp) bond construction. However, conventional approaches mainly rely on a single activation mode by either stoichiometric oxidants or electrochemical oxidation, which would lead to inferior selectivity in the reaction between similar C(sp)-H bonds. Herein we describe our development of a paired electrocatalysis strategy to access an unconventional selectivity in the cross-dehydrogenative coupling of alcoholic α C(sp)-H with allylic (or benzylic) C-H bonds, which combines hydrogen evolution reaction catalysis with hydride transfer catalysis. To maximize the synergistic effect of the catalyst combinations, a HER catalyst pentacoordinated Co-salen is disclosed. The catalyst displays a large redox-potential gap (1.98 V) and suitable redox potential. With the optimized catalyst combination, an electrochemical cross-dehydrogenative coupling protocol features unconventional chemoselectivity (C-C vs. C-O coupling), excellent functional group tolerance (84 examples), valuable byproduct (hydrogen), and high regio- and site-selectivity. A plausible reaction mechanism is also proposed to rationalize the experimental observations.
C(sp)−H键的交叉脱氢偶联是构建C(sp)−C(sp)键的理想方法。然而，传统方法主要依赖化学计量氧化剂或电化学氧化的单一活化模式，这会导致在相似的C(sp)−H键之间的反应中选择性较差。在此，我们描述了一种成对电催化策略的开发，该策略在醇类α C(sp)−H与烯丙基（或苄基）C−H键的交叉脱氢偶联中实现了非常规选择性，该策略将析氢反应催化与氢化物转移催化相结合。为了最大化催化剂组合的协同效应，公开了一种析氢反应催化剂五配位钴-双水杨醛缩乙二胺。该催化剂显示出较大的氧化还原电位差（1.98 V）和合适的氧化还原电位。通过优化的催化剂组合，一种电化学交叉脱氢偶联方法具有非常规的化学选择性（C−C与C−O偶联）、优异的官能团耐受性（84个实例）、有价值的副产物（氢气）以及高区域和位点选择性。还提出了一个合理的反应机理来解释实验现象。
