Salen Promoted Enantioselective Nazarov Cyclizations of Activated and Unactivated Dienones

A novel class of chiral 5,5'-di(2,4,6-trialkyl)-aryl salen-metal complexes have been developed and shown to catalyze highly enantioselective Nazarov cyclization reactions, giving rise to cyclopentenoids in 90:10-98:2 er. Significantly, the catalysts also promote, for the first time, highly enantioselective Nazarov reactions of unactivated dienones, producing hydrindenone products having in place three contiguous chiral centers.