A simple and cost-effective metal-free method for vicinal Csp2−H difunctionalization of indole was reported. The common solvents dimethyl sulfoxide (DMSO) and dichloroethane (DCE) were used as precursor to generate chlorodimethylsulfonium ion for electrophilic methylthiolation followed by chlorination by enabling 2-chloro-3-methylthioindoles.

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.