Copper-Mediated Direct Functionalization of Unsaturated C–C Bonds with Ethyl Bromo(difluoro)acetate: A Straightforward Access to Highly Valuable Difluoromethylated Alkenes

A copper-mediated fluorofunctionalization of alkenes and alkynes has been developed. This method provides ready access to trisubstituted difluoromethylated olefins (from dihydropyrans, glycal derivatives, or terminal alkynes) or to tetrasubstituted olefins (from disubstituted alkynes). The products were obtained in good to high yields with acceptable E / Z selectivities. Finally, a first direct route to difluoromethylated alkynes is reported, albeit with low yields.