Two-in-One Role of Benzophenone in Photoinduced C(sp 3 )-H Monofluoralkenylation: Hydrogen-Atom Transfer and Single-Electron Transfer.

A new protocol for monofluoralkenylation of C(sp 3 )-H bonds with gem -difluoroalkenes was reported. In this protocol, benzophenone serves as a photocatalyst with dual roles of hydrogen-atom transfer and single-electron transfer. The excited state of benzophenone abstracts a hydrogen atom from a C(sp 3 )-H bond to generate a corresponding carbon radical, which subsequently undergoes a radical addition/SET/β-F elimination process rather than radical-radical cross-coupling of previous work. This reaction shows high regioselectivity for the α-carbon atoms of ethers, thioethers, and amines, enabling the preparation of monofluoroalkenes.