Synthesis of difluoromethylated 2-oxindoles and quinoline-2,4-diones via visible light-induced tandem radical cyclization of N-arylacrylamides.

Visible light-induced difluoromethylation of N-arylacrylamides to afford difluoromethylated 2-oxindoles and quinoline-2,4-diones with difluoromethyl 2-pyridyl sulfones as radical precursors has been disclosed. This method provides convenient access to a variety of 2-oxindoles and quinoline-2,4-diones under mild conditions via a proposed tandem radical addition/cyclization process along with good tolerance to various functional groups. In addition, preliminary experimental studies have revealed that water is a key factor in difluoromethylation and the reaction involves an oxidative quenching cycle of the photocatalyst.