Neighbouring-group participation by sulphinyl-oxygen. Part III. Stereomutations at the sulphur atom in norbornene disulphoxides

Abstract

5,6-Bisphenylsulphinylnorborn-2-enes are converted into iodohydrins by reactions involving intramolecular nucleophilic attack by sulphinyl-oxygen at an electrophilic carbon, and concomitant nucleophilic attack at sulphur by a water molecule, with inversion of chirality of the sulphinyl group. The reaction is strictly conditioned by steric factors. Under the conditions in which a sulphinyl group with appropriate configuration reacts, a second sulphinyl group in an unfavourable position in the same molecule remains unaltered. Conversion of 5,6-endo-anti,exo-syn-bisphenylsulphinylnorborn-2-ene into the endo-syn,exo-syn-isomer, and vice-versa, via iodohydrins, constitutes a Walden cycle at the sulphur atom.