Aromatic Chlorosulfonylation by Photoredox Catalysis.

Visible-light photoredox catalysis enables the efficient synthesis of arenesulfonyl chlorides from anilines. The new protocol involves the convenient in situ preparation of arenediazonium salts (from anilines) and the reactive gases SO2 and HCl (from aqueous SOCl2 ). The photocatalytic chlorosulfonylation operates at mild conditions (room temperature, acetonitrile/water) with low catalyst loading. Various functional groups are tolerated (e.g., halides, azides, nitro groups, CF3 , SF5 , esters, heteroarenes). Theoretical and experimental studies support a photoredox-catalysis mechanism.