Visible-light-initiated difluoromethylation of arene diazonium tetrafluoroborates

A mild and efficient method for the radical addition of alpha-aryl-beta,beta-difluoroenol silyl with arene diazonium tetrafluoroborates at room temperature has been disclosed, which involves an innate radical long chain cycle, so only a small amount ( 0.05 mol%) of photocatalyst and a short light exposure time are required as radical initiators. A proposed mechanism for the transformation is also illustrated based on the results of control experiments and quantum calculations. A variety of alpha-aryl-alpha, alpha-difluoroketones were formed in moderate to high yields, and can be easily further transformed into various difluoromethylarenes under basic conditions.