Cobalt-catalyzed enantioselective C–H/N–H annulation of aryl sulfonamides with allenes or alkynes: facile access to C–N axially chiral sultams
Xiao‐Ju Si, Xiaofang Zhao, Jianli Wang, Xinhai Wang, Yuanshuo Zhang, Dandan Yang, Mao‐Ping Song, Jun‐Long Niu
Abstract
as the oxidant, the annulation with allenes proceeds efficiently with a low catalyst/ligand loading of 5 mol% and tolerates a wide range of allenes, including 2,3-butadienoate, allenylphosphonate, and phenylallene, resulting in C-N axially chiral sultams with high enantio-, regio-, and position selectivities. The annulation with alkynes also exhibits excellent enantiocontrol (up to >99% ee) with a variety of functional aryl sulfonamides, and internal and terminal alkynes. Furthermore, electrochemical oxidative C-H/N-H annulation with alkynes is achieved in a simple undivided cell, demonstrating the versatility and robustness of the cobalt/Salox system. The gram-scale synthesis and asymmetric catalysis further highlight the practical utility of this method.