A Dual Lewis Base Activation Strategy for Enantioselective Carbene-Catalyzed Annulations

A dual activation strategy integrating
N-heterocyclic carbene (NHC)
catalysis and a second Lewis base has been developed. NHC-bound homoenolate
equivalents derived from α,β-unsaturated aldehydes combine
with transient reactive o-quinone methides in an
enantioselective formal [4 + 3] fashion to access 2-benzoxopinones.
The overall approach provides a general blueprint for the integration
of carbene catalysis with additional Lewis base activation modes.