Enantioselective Aerobic Oxidation of Sulfides Catalyzed by Optically Active β-Oxo Aldiminatomanganese(III) Complexes

Enantioselective aerobic oxidation of sulfides into optically active sulfoxides was achieved by using pivalaldehyde in the presence of a catalytic amount of optically active β-oxo aldiminatomanganese(III) complexes. An acylperoxomanganese complex, formed from the original manganese complex, molecular oxygen, and pivalaldehyde, was supposed to be a key intermediate in the present oxidation. The crystal structure of chloro-{N,N′-bis[3-oxo-2-(2,4,6-trimethylbenzoyl)butylidene]-(1S,2S)-1,2-diphenylethylenediaminato}manganese(III) was determined by X-ray diffraction methods, which suggested that the bulkiness of the substituents in β-oxo aldimine ligand had played an important role in controlling the approach of sulfides to the manganese complex. Kinetic resolution took place during the subsequent oxidation process of sulfoxide into the corresponding sulfone, and the optical purity of the remaining sulfoxide increased.