DIH-Catalyzed Vinylsulfonation via Halogen Bonding Activation of Sulfonyl Iodides for Late-Stage Functionalization

We report the development of a mild and efficient 1,3-diiodo-5,5-dimethylhydantoin (DIH)-catalyzed vinylsulfonation protocol that enables the selective coupling of sulfonyl radicals with a diverse array of alkenes. The transformation proceeds via an <i>N</i>-iodo imide intermediate and utilizes phenyliodine(III) diacetate (PIDA) as the terminal oxidant. Crucially, halogen bonding (XB) is harnessed to activate sulfonyl iodides, facilitating radical generation and alkene functionalization under metal-free conditions. Mechanistic studies─including NMR spectroscopy and radical inhibition experiments─revealed a previously unrecognized halogen bonding transposition from the <i>N</i>-iodo imide to the sulfonyl iodide that significantly enhances both sulfonyl radical formation and catalytic efficiency. This method demonstrates broad substrate scope and excellent functional group tolerance that enables late-stage vinylsulfonation of structurally complex molecules such as carbamates, amino acids, carbohydrates, heterocycles, and pharmaceutical agents. These findings establish a new paradigm for catalyst activation via noncovalent halogen bonding that expands the synthetic utility of sulfonyl radical chemistry in advanced molecular construction.