Carbene‐Catalyzed Activation of Remote Nitrogen Atoms of (Benz)imidazole‐Derived Aldimines for Enantioselective Synthesis of Heterocycles
Xing Yang, Yongtao Xie, Jun Xu, Shi‐Chao Ren, Bivas Mondal, Liejin Zhou, Weiyi Tian, Xinglong Zhang, Hao Lin, Zhichao Jin, Yonggui Robin
Abstract
A new mode of carbene-catalyzed heteroatom activation and asymmetric reactions is disclosed. The reaction starts with addition of a carbene catalyst to a (benz)imidazole-derived aldimine substrate. Subsequent oxidation and proton transfer lead to the formation of a catalyst-bound triaza-diene as the key intermediate, in which the nitrogen atom at a site remote to the catalyst-substrate bond is activated. This unusual triaza-diene intermediate then undergoes highly enantioselective reactions with activated ketones through a concerted asynchronous pathway, as supported by mechanistic studies and preliminary density function theory calculation.