Sc³⁺-Catalyzed Aldol-Type Additions of N-Benzoylcyclopropanecarboxamides via Iodide-Mediated Ring-Opening:  Stereoselective Synthesis of γ-Lactams

A new catalytic aldol-type addition of cyclopropanecarboximides to aldehydes via iodide-mediated ring-opening is presented. The reaction was found to be catalyzed at 0 °C using either a Sc(OTf)₃/NaI system or ScI₃. Stereoselective formation of α,α-disubstituted enolates occurred in situ. γ-Lactams bearing α-carbonyl quaternary stereocenters were obtained in 97−57% yield and dr = 90:10−80:20 after ring closure.