Enantioselective N-Heterocyclic Carbene Catalysis that Exploits Imine Umpolung

Abstract

The catalytic umpolung of imines remains an underdeveloped approach to reaction discovery. Herein we report an enantioselective aza-Stetter reaction that proceeds via imine umpolung using N-heterocyclic carbene catalysis. The reaction proceeds with high levels of enantioselectivity (all ≥96:4 er) and good generality (21 examples). Mechanistic studies are reported and are consistent with turnover-limiting addition of the NHC to the imine.

Keywords: N-heterocyclic carbenes; Stetter reaction; enantioselective catalysis; imine umpolung.