Accounting for Different Reactivities of Sulfinate and Thiosulfate Salts in Regioselective Azetidine Coupling via C–H Sulfenylation of Indoles

The regioselective incorporation of azetidines into heteroaromatic compounds is reported via a formal C–H sulfenylation reaction. While sodium sulfinate salts undergo C3 sulfenylation of electron-rich indoles only, the corresponding thiosulfate salts have proved to be more generally useful. A mechanistic hypothesis for the different reactivities of sulfinate and thiosulfate salts is provided.