Fe-Catalyzed\nFluorosulfonylation of Alkenes via Sulfur\nDioxide Insertion: Synthesis of Lactam-Functionalized Alkyl Sulfonyl\nFluorides

A novel Fe-catalyzed fluorosulfonylation of alkenes with\nNa<sub>2</sub>S<sub>2</sub>O<sub>4</sub> and <i>N</i>-fluorobenzenesulfonimide\n(NFSI) for assembling various lactam-functionalized alkyl sulfonyl\nfluorides is disclosed. In this reaction, Na<sub>2</sub>S<sub>2</sub>O<sub>4</sub> acts as both an SO<sub>2</sub> source and a reductant.\nFurthermore, the resulting products can be efficiently transformed\ninto valuable chemicals, including sulfonyl esters and sulfonamides,\nvia the sulfur(VI) fluoride exchange (SuFEx) click reaction. Preliminary\nmechanistic studies suggest that the transformation proceeds through\nintramolecular radical cyclization, SO<sub>2</sub> insertion, sulfite\nanion formation, and fluorination.