tert-Butyl Hydroperoxide (TBHP)-Initiated Vicinal Sulfonamination of Alkynes: A Radical Annulation toward 3-Sulfonylindoles

A novel, efficient, and facile vicinal sulfonamination of alkynes by the reaction of accessible 2-alkynyl arylazides with sulfinic acids in the presence of tert-butyl hydroperoxide (TBHP) has been developed. This protocol utilizes sulfinic acids as the sulfonating reagent, azidos as the aminating reagent, and TBHP as the sulfonyl radical initiator. By using this protocol, a variety of potentially bioactive 3-sulfonylindoles were facilely synthesized via direct annulation.