A mild and metal-free method for the direct C3-sulfenylation of indoles using a KI/K₂S₂O₈ oxidative system has been developed. The reaction proceeds efficiently in MeCN/H₂O at 60 °C, affording 3-sulfenylindoles in up to 93% yield without the need for transition metals or bases. A wide range of indole derivatives and aromatic sulfenylating agents bearing electron-donating or electron-withdrawing substituents are well tolerated. This protocol provides an efficient, scalable, and environmentally benign approach to the synthesis of 3-sulfenylindoles under simple operational conditions.
Benchawan et al. (2026) studied this question.