Vinyl benzotriazole to indole: an iodine-mediated denitrogenative transannulation approach for the synthesis of indoles

Abstract

A novel, convenient, and molecular iodine-mediated approach for the synthesis of 3-sulfonylated indoles from vinyl benzotriazoles is described. The reaction proceeds via tosylation, denitrogenative ring opening, and cyclization, featuring the cleavage of C–N and N–N bonds and the concomitant formation of C–S, N–H, and C–C bonds. This operationally simple protocol utilizes environmentally benign iodine for ring-opening reaction and circumvents the need for the protection of benzotriazoles with strong electron-withdrawing groups, metal catalysts, elevated temperatures, and extended reaction times. The mechanism is well supported by online real-time mass monitoring analysis and control experiments.