Transition Metal-Free Synthesis of Sulfonyl- and Bromo-Substituted Indolo[2,1-α]isoquinoline Derivatives through Electrochemical Radical Cascade Cyclization

A tunable electrosynthesis of sulfonyl- and bromo-substituted indolo[2,1-α]isoquinoline derivatives has been disclosed. In this reaction, a variety of easily available 2-aryl-N-acryloyl indoles can readily react with sulfonyl and/or bromine radicals, which are generated from arylsulfonyl hydrazides and potassium bromide respectively, to furnish the valuable sulfonyl- and bromo-substituted benzindolo-fused polycyclic compounds in moderate to good yields. Control experiment indicated that the reaction proceeds via a radical cascade cyclization pathway. This protocol features broad substrate scope and good functional group tolerance under transition metal-free and oxidant-free conditions. (Figure presented.).