Electrochemical Switching between C–H Mono/Difunctionalization via Iodine Speciation and Tuning of Electrochemical Variables

Herein, we report a current-controlled electrochemical strategy that enables tunable access to either mono- or difunctionalized indole derivatives using indole and sulfonyl hydrazide precursors. By modulating key electrochemical variables, particularly current density, switchable access to C3-sulfonylated or 2-iodo-3-sulfonyl indoles is achieved. Mechanistic studies reveal that iodine speciation governs selectivity and confirm sulfonyl radical intermediates. The protocol is free of metal catalysts and stoichiometric oxidants, scalable to gram quantities, and compatible with downstream derivatization, thus providing a robust and sustainable platform for precise indole functionalization.