Intramolecular nucleophilic carbonyl trapping of α-ketenyl radicals by an amino group

Abstract

Free-radical carbonylation of ω-alkynylamines with tributyltin hydride gives a mixture of α-methylene lactams and α-stannylmethylene lactams. Nucleophilic addition of an internal amino group to the carbonyl group of α-ketenyl radicals is proposed as the cyclization step. The subsequent unusual 1,4-H shift from the resulting 1-hydroxyallyl radical, followed by elimination of the β-tributyltin radical leads to the formation of α-methylene lactams.