Stereoselective Synthesis of trans β-Lactams through Iridium-Catalyzed Reductive Coupling of Imines and Acrylates

Iridium-catalyzed reductive coupling of acrylates and imines provides trans β-lactams with high diastereoselection. The optimal catalyst allows for the synthesis of trans β-lactams bearing aromatic, alkenyl, and alkynyl side chains. This reaction appears to proceed through a reductive Mannich addition−cyclization mechanism. Examination of substituent effects reveals a linear Hammett correlation for both the N-aryl group on the imine and the aryloxy group on the acrylate, thereby pointing to rate-determining cyclization in the reaction mechanism.