Direct Photoassisted α-Trifluoromethylation of Aromatic Ketones with Trifluoroacetic Anhydride (TFAA)

Direct alpha-Trifluoromethylation of acetophenone derivatives was achieved by using trifluoroacetic anhydride (TFAA) as the trifluoromethyl source and pyridine-N-oxide (Py-O) as activator and oxidant under visible light irradiation and tris-(2,2'-bipyridine)ruthenium(II) hexafluorophosphate (Ru(bpy)(3)(PF6)(2)) as the photocatalyst. Different acetophenone derivatives could be converted to the corresponding alpha-CF3 derivatives with high selectivity. Extensive mechanistic investigation revealed the formation of vinyl trifluoroacetate as the key intermediate for this transformation.