Copper-Catalyzed Radical Cascade Difluoromethylation/Cyclization of 2-(3-Arylpropioloyl)benzaldehydes: A Route to Difluoromethylated Naphthoquinones.

A novel copper-catalyzed cascade difluoromethylation/cyclization of 2-(3-arylpropioloyl)benzaldehydes has been developed. This method affords an efficient and straightforward access to structurally diverse difluoromethylated naphthoquinones in one pot, starting from readily available starting materials. The reaction represents the first trans-acyldifluoromethylation of internal alkynes, which features aldehydes as acceptors for the addition of alkenyl radicals. Furthermore, this protocol can also access to monofluoromethylated naphthoquinone and difluoromethylated indanones in the same reaction condition.