C–H bond sulfonylation of anilines with the insertion of sulfur dioxide under metal-free conditions

Abstract

C-H bond sulfonylation of anilines with the insertion of sulfur dioxide under metal-free conditions is described. 2-Sulfonylanilines are generated in moderate to good yields through a three-component reaction of anilines, DABCO·(SO₂)₂, and aryldiazonium tetrafluoroborates under mild conditions. No metal catalysts or additives are needed for this transformation. This direct C-H functionalization is highly efficient, and broad functional group tolerance is observed. A radical process is believed to be involved. In the reaction process, the arylsulfonyl radical and the tertiary amine radical cation generated in situ from DABCO·(SO₂)₂, and aryldiazonium tetrafluoroborate are the key intermediates. Additionally, the tertiary amine radical cation acts as the electron carrier through a single electron transfer process.