Photoredox 1,4-Hydroxysulfonylation of Methylenecyclobutane via Carbon-Radical-Mediated β-Scission of Cyclobutane

) bond cleavage is a central challenge in organic synthesis. While radical-mediated β-scission of strained cyclobutanes offers a valuable route to complex molecules, carbon-radical-based ring-opening remains underdeveloped due to the regioselective formation of the cyclobutylcarbinyl radical and high activation barrier issues. Herein, we report a photocatalytic strategy for the 1,4-functionalization of methylenecyclobutanes (MCBs) via a tosyl-radical-initiated cascade. This process involves regioselective addition to the exocyclic double bond, followed by β-scission and a radical-polar crossover, enabling efficient 1,4-hydroxysulfonylation. Mechanistic studies provided evidence of a radical chain process. Key features include a broad substrate scope, a removable tosyl group, controllable three-component reactivity, and the expansion of synthetic methodologies for carbon-radical-mediated cyclobutane ring-opening.