Photoinduced catalyst-free difluoromethylation-cyclization of indole derivatives via electron donor-acceptor complexes under visible light

Polycyclic indoles are prevalent in natural products, pharmaceuticals and biologically active compounds. Herein, photoinduced catalyst-free difluoromethylation-cyclization of indole derivatives via electron donor-acceptor (EDA) activation with difluoromethyl tetrazole sulfone as a CF2H radical source is described. This photochemical reaction tolerates an array of functional groups like ester, cyano, ketone, halide, ether and aldehyde. Mechanistic experiments indicated that the difluoromethyl radical and single-electron transfer were involved. The EDA complex between indole derivatives and difluoromethyl tetrazole sulfone is crucial for the success of this reaction.