Diastereoselective oxidation of menthyl arenesulfenates to sulfinates and access to enantioenriched aryl methyl sulfoxides

Three aryl methyl sulfoxides were prepared via the following sequence: synthesis of the menthyl arenesulfenate from the corresponding thiol, diastereoselective oxidation leading to the sulfinate, then reaction with a Grignard reagent. The aryl moiety was substituted with a methyl ester on the ortho position or a nitro group on the ortho or the para position. The sulfenate esters were obtained in fair to excellent yield (42-82%). Four different oxidizing agents were tested to obtain the corresponding sulfinate esters with diastereomeric excesses (de) ranging from 10 to 48%. After separation of the diastereomers and reaction with methyl Grignard reagent, two enantiopure sulfoxides, and one enantioenriched sulfoxide (32% ee) were obtained.