Photocatalytic intramolecular radical cyclization involved synergistic SET and HAT: synthesis of 3,3-difluoro-γ-lactams

Abstract

A mild and metal-free protocol for visible-light induced intramolecular radical cyclization of N-allyl(propargyl)-2-bromo-2,2-difluoro-N-arylacetamide has been developed. This strategy showed excellent regioselectivity and simple operation to synthesize 4-substituted 3,3-difluoro-γ-lactams with a broad substrate scope. Moreover, mechanistic studies revealed that this transformation proceeded through a cascade radical-type cyclization and hydrogen atom transfer process with PMDETA as a hydrogen-atom donor.