Diversity‐Oriented Synthesis of β‐Lactams and γ‐Lactams by Post‐Ugi Nucleophilic Cyclization: Lewis Acids as Regioselective Switch

Abstract Heterocyclic fused α‐methylene β‐lactams were successfully synthesized by a post‐Ugi In III ‐catalyzed intramolecular addition reaction. Switching from InCl 3 to AlCl 3 led to the regioselective synthesis of α,β‐unsaturated γ‐lactams. Moreover, replacing terminal alkynes by substituted alkynes in the Ugi adducts resulted in the exclusive formation of γ‐lactams with both catalytic systems.