Generation of sulfamoyl radicals via visible-light mediated fixation of sulfur dioxide as novel approach for the synthesis of sulfonamides

Herein, we report a so far unprecedented approach for the light-mediated generation of sulfamoyl radicals using sulfur dioxide a key building block and the direct application of these radicals in the synthesis of sulfonamides. In the presence of different photoredox catalysts, sulfamoyl radicals can be generated directly from SO2 or the SO2 surrogate DABSO (1,4-diazabicyclo[2.2.2]octane·bis (sulfur dioxide) adduct) and N-aminopyridinium salts as nitrogen radical precursors. Trapping of the in situ generated sulfamoyl radicals with selected electron-rich olefins affords different sulfonamides in moderate to good yields in a three-component procedure. This transformation provides an attractive and conceptually novel approach for the in situ generation of sulfamoyl radicals as synthetic intermediates for the assembly of the sulfonamide functionality, a privileged motif in active pharmaceutical ingredients.