Copper-Catalyzed Visible-Light-Induced Allylic Difluoromethylation of Unactivated Alkenes Using Difluoroacetic Acid.

We herein describe a straightforward allylic difluoromethylation reaction of unactivated alkenes. Compared to cross-couplings of prefunctionalized allylic substrates for the construction of allylic CF 2 H bonds, this reaction employs readily available alkenes as substrates under mild conditions. Difluoroacetic acid is used as an inexpensive and easy-to-handle source of CF 2 H radical under visible light irradiation with PIDA. The copper catalyst plays an important role of diverting the reaction pathway toward allylic difluoromethylation as opposed to previously found hydrodifluoromethylation.