Diastereoselective Base-Catalyzed Formal [4 + 2] Cycloadditions of N‑Sulfonyl Imines and Cyclic Anhydrides

A diastereoselective base-catalyzed Mannich reaction of cyclic, enolizable anhydrides and N-sulfonyl imines for the synthesis of δ-lactams is reported. This anhydride Mannich reaction tolerates imines derived from aryl and enolizable aldehydes. A base-catalyzed product epimerization pathway ensures high anti diastereoselectivity in aryl and achiral enolizable imines.