Electrochemical Radical–Radical Cross-Coupling Approach between Sodium Sulfinates and 2<i>H</i>-Indazoles to 3-Sulfonylated 2<i>H</i>-Indazoles

Abstract

A direct cross-coupling between sodium sulfinates and 2<i>H</i>-indazoles has been developed under electrochemical conditions. The utilization of a graphite anode and platinum cathode in an undivided cell with a constant current of 7 mA allowed the concurrent oxidations of sulfinates and 2<i>H</i>-indazoles to sulfonyl radical and radical cationic 2<i>H</i>-indazoles, facilitating the direct radical-radical coupling strategy to 3-sulfonylated 2<i>H</i>-indazole derivatives. The transition-metal- and redox-reagent-free synthetic approach should serve as a valuable synthetic tool to achieve heteroaromatic compounds.