Metal‐Free Regioselective Chlorosulfenylation of Indoles by Dimethylsulfoxide and 1,2‐Dichloroethane

Abstract Direct chloromethylthiolation of the C(sp2)−H bonds of indole was achieved with the commonly used solvents dimethyl sulfoxide (DMSO) and dichloroethane (DCE). Initially, chlorodimethylsulfonium ion is generated in situ from the reaction of DMSO and DCE on simple heating at 120 °C and is used for electrophilic methylthiolation followed by chlorination, enabling the synthesis of 2‐chloro‐3‐methylthioindoles.