Metal-Free Synthesis of Sulfones and Sulfoxides through Aldehyde-Promoted Aerobic Oxidation of Sulfides

Metal-free aerobic oxidation of aryl sulfides to sulfoxides and sulfones has been developed in the presence of aliphatic aldehydes with excellent selectivity and yields. The reaction proceeded under mild conditions with the catalysis of N -hydroxyphthalimide (NHPI). Control experiments indicated that the reaction underwent a free radical pathway with the acylperoxyl radicals generated from aldehydes in situ as the key intermediates. The aromatic aldehydes were less efficient in the sulfide oxidation, which might be explained by the fact that the aromatic ring dispersed the electrons of free radicals and thus weakened the attacking ability of peroxy free radicals. Graphic Abstract