Catalytic Synthesis of gamma-Lactams via direct annulations of enals and N-sulfonylimines.

[reaction: see text] Cinnamaldehydes and N-sulfonylimines undergo direct annulations to cis-disubstituted gamma-lactams via the intermediacy of catalytically generated homoenolates. Critical to the success of this process was overcoming inhibition of the N-heterocyclic carbene catalyst by the electrophilic imines. The overall process proceeds with good yields and diastereoselectivites and requires no stoichiometric reagents or additives.