Modular Access to Chiral α-(Hetero)aryl Amines via Ni/Photoredox-Catalyzed Enantioselective Cross-Coupling.

Abstract

Chiral α-aryl N-heterocycles are commonly found in natural products, pharmaceutical agents, and chiral catalysts but remain challenging to access via asymmetric catalysis. Herein, we report a general and modular approach for the direct enantioselective α-arylation of saturated azacycles and acyclic N-alkyl benzamides via nickel/photoredox dual catalysis. This process exploits the hydrogen atom transfer ability of photoeliminated chlorine radicals to convert azacycles to the corresponding α-amino alkyl radicals that then are coupled with ubiquitous and inexpensive (hetero)aryl chlorides. These coupling reactions require no oxidants or organometallic reagents, feature feedstock starting materials, a broad substrate scope, and high enantioselectivities, and are applicable to late-stage diversification of medicinally relevant complex molecules. Mechanistic studies suggest that the nickel catalyst uncommonly plays multiple roles, accomplishing chlorine radical generation, α-amino radical capture, cross-coupling, and asymmetric induction.