Mechanoredox Enables Sulfonylation of Alkenes in a Heterogeneous System

The sulfur dioxide insertion strategy serves as a significant approach for the construction of C-S bonds. Nevertheless, current liquid-phase reaction systems utilizing inorganic SO₂ sources frequently suffer from poor solubility, necessitating an excess of reagents and resulting in low atom economy. Furthermore, these systems frequently rely on additional bases or transition metal additives, which may inadvertently trigger side reactions. To address these limitations, we have reported a novel method for sulfonylation of alkenes that employs ball milling in conjunction with a piezoelectric material. This approach leverages the transient electrochemical potential generated by BaTiO₃ under mechanical stress to reduce aryl diazonium salts to aryl radicals via a single-electron transfer (SET) process. Aryl radicals are then captured in situ by K₂S₂O₅ to generate aryl sulfonyl radicals, which subsequently add to alkenes to accomplish sulfonylation. The essential function in ball milling-induced mechanoredox processes was confirmed by high-resolution X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal imaging, isothermal experiments, and comparative studies employing different mechanical sources. This method features simple operation, mild condition, and recyclability of the catalyst. It eliminates the need for preactivation steps, metal catalysts, and external heating, providing a unique platform for the development of green and efficient solid-phase organic synthesis.