Asymmetric induction and configurational correlations in oxidations at sulphur. Part V. Oxidations of optically active esters of o-(methylthio)benzoic acid by achiral peroxy-acids

Abstract

Oxidation of optically active esters of o-(methylthio)benzoic acid with achiral peroxy-acids (perbenzoic and 2,4,6-trimethylperbenzoic acids) yields mixtures of the corresponding diastereomeric sulphoxides, enriched in one of the components. Hydrolysis affords optically active o-methylsulphinylbenzoic acid. The absolute chirality of the latter depends on the chirality of the inducing alcohol. The optical yields are noticeably higher with the bulkier trimethylperbenzoic acid. The asymmetric induction is interpreted in terms of eclipsing effects of small, medium, and large groups. A correlation model, based on those conformations of the diastereomeric transition states which present the largest difference of steric compression, is suggested.