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

Abstract

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.