Metal-free phosphine-catalyzed visible-light-induced radical cyclization of alkenes: access to cyclic gem-difluoroacyl scaffolds†

In this study, we developed the first visible-light-induced phosphine-catalyzed radical cyclization of bromodifluoroacyl arenes with diverse alkenes, affording a variety of cyclic gem-difluoroacyl scaffolds in good to excellent yields. The strategy is highlighted by metal photocatalyst-free nature, mild reaction conditions and excellent functional group tolerance, and it is amenable to late-stage modification of complex molecules and gram-scale synthesis, and expands the reaction profiles of phosphine catalysis. Preliminary experimental and computational studies indicate that this reaction involves a radical process that is triggered by the photochemical activity of an electron donor–acceptor complex formed from bromodifluoroacyl and phosphine.