Asymmetric Counteranion-Directed Electrocatalysis for Enantioselective Control of Radical Cation.

Abstract

The control of enantioselectivity in radical cation reactions presents long-standing challenges, despite a few successful examples. We introduce a novel strategy of asymmetric counteranion-directed electrocatalysis to address enantioselectivity in radical cation chemistry. This concept has been successfully demonstrated in two reactions: an asymmetric dehydrogenative indole-phenol [3 + 2] coupling and an atroposelective C-H/N-H dehydrogenative coupling. These reactions have enabled the synthesis of benzofuroindolines and C-N axially chiral indoles with high yields and excellent enantiomeric excesses. Detailed mechanistic studies confirmed a radical-radical coupling mechanism. Moreover, density functional theory (DFT) calculations supported the indole radical cation as the pivotal intermediate, rather than a neutral indolyl radical, shedding new light on the underlying processes driving these reactions.