Journal of the American Chemical Society, Vol.133, No.32, 12466-12469, 2011
N-Heterocyclic Carbene and Bronsted Acid Cooperative Catalysis: Asymmetric Synthesis of trans-gamma-Lactams
An efficient enantioselective approach to form trans-gamma-lactams in up to 99% yield, 93% ee, and >20/1 dr using unactivated imines has been developed. The cyclohexyl-substituted azolium and the weak base sodium o-chlorobenzoate are most suitable for this transformation. Notably, the process involves cooperative catalysis by an N-heterocyclic carbene and a Bronsted acid.