Aldehyde–Olefin Couplings via Sulfoxylate-Mediated Oxidative Generation of Ketyl Radical Anions

Ketyl radicals are valuable reactive intermediates because\nthey\nallow carbonyl chemistry to be extended beyond traditional electrophilic\nreactivity through simple single-electron reduction to a nucleophilic\nradical. However, this pathway is challenging due to the large negative\nreduction potentials of carbonyls, thus requiring highly reducing\nconditions. Herein, we describe the development of an alternative\nstrategy to access ketyl radicals from aldehydes, which avoids the\nreduction pathway by instead proceeding via single-electron oxidation\nand desulfination of α-hydroxy sulfinates. These redox-active\naldehyde adducts are generated <i>in situ</i> through the\naddition of sulfoxylate (SO<sub>2</sub><sup>2–</sup>) to aldehydes\nand possess low oxidation potentials, thereby facilitating ketyl radical\nformation and circumventing the need for strongly reducing conditions.\nWe demonstrate the application of this sulfoxylate-mediated ketyl\nradical formation in ketyl–olefin coupling reactions.