Straightforward Sulfonamidation via Metabisulfite-Mediated Cross Coupling of Nitroarenes and Boronic Acids under Transition-Metal-Free Conditions^†

A straightforward multicomponent sulfonamidation of nitroarenes, sodium metabisulfite and boronic acids was established under transition-metal-free conditions to access diverse sulfonamides from readily available and low-cost materials modularly. Inorganic salt sodium metabisulfite not only served as a sulfur dioxide source, but also played a key role for both activator and reductant during sulfonamidation. Notably, naturally occurring biomolecules and pharmaceuticals with multiple heteroatoms and sensitive functional groups were intensively investigated in this transformtion providing versatile sulfonamides collectively. Further mechanistic studies demonstrated that nitrosoarene is the key intermediate, and the activation of boronic acid is the rate-determining step in the transformation.