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 β-keto phenyltetrazolesulfones and α,β-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.