Photocatalytic Three-Component Radical Sulfonarylation of Alkenes: Preparation of γ-Keto-Sulfone-Substituted Oxindoles.

A photocatalytic radical sulfonarylation of N-arylacrylamides via a three-component cascade cyclopropyl alcohol ring opening/sulfur dioxide insertion/sulfonyl radical addition/cyclization sequence has been developed. This method employs cyclopropyl alcohols as the precursors of β-carbonyl alkyl radicals and Na2S2O5 as a cheap source of sulfur dioxide. By using this cascade procedure, a wide variety of γ-keto-sulfone-substituted oxindoles were facilely synthesized.