Enantioselective N-Heterocyclic Carbene Catalysis via Acyl Azolium without Exogenous Oxidants

An approach to the alpha,beta-unsaturated acyl azolium has been developed that exploits N-heterocyclic carbenes (NHCs) and acyl fluorides, without additional oxidants, bases, or preactivated pro-nucleophiles. These conditions have been applied in four classes of NHC-catalyzed reaction. In all cases, the expected products were produced with high yield and enantioselectivity, using two sets of closely related reaction conditions, without additional optimization.