Construction of Sulfonyl Oxindoles via a Radical-Mediated Relay Strategy of Sulfur Dioxide Insertion/Cyano Migration/Cyclization.

A simple and efficient methodology has been established for the three-component sulfonylation/cyanation of unactivated alkenes to construct β-cyanosulfone-containing oxindoles. This method through a sulfur dioxide insertion/remote cyano migration relay strategy enables the difunctionalization of the unactivated alkene, and the resulting in situ-formed radical intermediate is trapped by an aromatic ring to deliver valuable oxindoles. The reaction proceeds under mild conditions without the need for metal, photocatalysts, or oxidants, employing in situ sulfur dioxide insertion of an aryl radical to form an aromatic sulfone radical intermediate instead of unstable sulfonyl chlorides.