Photo-induced radical trifluoromethylation/dearomatization of 3-substituted indoles

Abstract

A visible-light-induced cascade radical trifluoromethylation/cyclization/dearomatization reaction between 3-substituted indoles and CF₃Br in the presence of 4CzIPN and K₂CO₃ has been developed. This protocol provided a facile, efficient and cost-effective approach for the construction of 3,3-spirocyclic 2-trifluoromethylindolines in moderate to high yields under mild conditions. This process can be scaled up. A radical relay mechanism was proposed based on the control experiments. This protocol provides an efficient route for the synthesis of 3,3-spirocyclic 2-trifluoromethylindolines with the advantages of a broad substrate scope, a cheap trifluoromethyl source and a green source of energy.