Stereochemistry of the oxidation of imines derived from substituted cyclohexanones: Axial vs equatorial attack and evidence for delivery by an adjacent hydroxyl group

A set of conformationally biased imines derived from substituted cyclohexan ones and benzylamine or diphenylmethylamine, respectively, were oxidized to the corresponding oxaziridines. The structures of the oxaziridines were de termined via NMR comparison of two series of differently N-substituted oxaz iridines. Thus, those compounds having an axially disposed nitrogen substit uent displayed an upfield-shifted axial proton in a 1,3-relationship to the oxaziridine nitrogen in the N-diphenylmethyl series relative to the N-benz yl compounds. Analysis of the products obtained from these reactions sugges ts that (1) adjacent hydroxyl groups favor syn oxidant addition and (2) imi nes containing adjacent methoxy groups preferentially undergo attack anti t o the resident alkoxy substituent.