Organocatalytic Iminium Ion/Carbene Reaction Cascade for the Formation of Optically Active 2,4-Disubstituted Cyclopentenones

An organocatalytic iminium ion/N-heterocyclic carbene (NHC) cascade reaction between beta-keto phenyltetrazolesulfones and alpha,beta-unsaturated aldehydes, providing direct access to optically active 2,4-disubstituted cyclopent-2-enones, has been developed. The products are isolated in good yields with high enantioselectivities.