Potassium tert‐Butoxide‐Catalyzed Synthesis of α‐Methylene‐β‐Lactams from Propiolamides

Abstract We reported herein the regio‐ and stereoselective synthesis of α ‐methylene‐ β ‐lactams via a 4‐ exo ‐dig‐cyclization of N ‐benzyl‐ N ‐methyl‐propiolamides catalyzed by a base. The experimental evidence suggests that this transformation proceeds via a concerted ionic cyclization with a carbon nucleophilic addition to the carbon‐carbon triple bond, followed by protonation of the vinyl species promoted by tert ‐butanol. The obtained α ‐methylene‐ β ‐lactams were suitable substrates for the Heck coupling conditions affording the corresponding products via carbon‐carbon bond formation.