Photocatalytic Three-ComponentRadical Sulfonarylationof Alkenes: Preparation of γ‑Keto-Sulfone-SubstitutedOxindoles

A photocatalytic radical sulfonarylation of <i>N</i>-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.