Metal‐Free Visible‐Light Synthesis of Arylsulfonyl Fluorides: Scope and Mechanism

The first metal‐free procedure for the synthesis of arylsulfonyl fluorides is reported. Under organo‐photoredox conditions, aryl diazonium salts react with a readily available SO2 source (DABSO) to afford the desired product through simple nucleophilic fluorination. The reaction tolerates the presence of both electron‐rich and ‐poor aryls and demonstrated a broad functional group tolerance. To shed the light on the reaction mechanism, several experimental techniques were combined, including fluorescence, NMR, and EPR spectroscopy as well as DFT calculations. The key to success in the new metal‐free visible‐light‐mediated synthesis of arylsulfonyl fluorides was using cyanoarene PC3 as organo‐photocatalyst. A variety of arene diazonium slats were smoothly converted to the corresponding product. Mechanistic investigations including luminescence, EPR spectroscopy as well as DFT calculation allowed us to identify several key intermediates and propose a plausible mechanism.