Rearrangements in the acetolysis of exo-dehydro-2-norbornyl p-bromobenzenesulfonate

Abstract

exo-3-Deuteriodehydro-2-norbornyl p-bromobenzenesulfonate (VIIb) solvolyzes in glacial acetic acid to give about 7 % of an equimolar mixture of exo-3-deuteriodehydro-2-norbornyl acetate (VIId) and 7-deuteriodehydro-2-norbornyl acetate (VIIId), along with about 93 % of deuterated 3-nortricyclyl acetate (IId). The acetolysis is accompanied by a considerably more rapid scrambling of the p-bromobenzenesulfonate by internal return to 7-deuteriodehydro-2-norbornyl p-bromobenzenesulfonate (VIIIb), without attendant formation of deuterated nortricyclyl p-bromobenzenesulfonate (IIb). The data are consistent with the assumption that ion pairs involving a symmetrical nonclassical cation such as IV are produced in the ionization process, or with the assumption that rapidly equilibrating nonsymmetrical cations such as V and VI are involved, but are not consistent with the suggestion made earlier that the nonsymmetrical cation V is formed in the ionization step and isomerizes relatively slowly to its Wagner-Meerwein isomer VI.