Benzylic C(sp)-H bond sulfonylation of 4-methylphenols with the insertion of sulfur dioxide under photocatalysis.

Sulfonylation of the benzylic C-H bond is developed through a three-component reaction of aryldiazonium tetrafluoroborates, 4-methylphenols and sodium metabisulfite (Na2S2O5). The inorganic sulfite of sodium metabisulfite is used as the SO2 surrogate. In this transformation, benzylic C(sp3)-H bond sulfonylation is achieved in the presence of a photocatalyst under visible light. A radical pathway involving the arylsulfonyl radical and intermolecular hydrogen atom abstraction is proposed.