Phenylsulfonyl as a beta participating group

The phenylsulfonyl group (PhSO2) has been examined for its beta effect prop erties. The stereochemical relationship was varied between phenylsulfonyl a nd a nucleophilic leaving group (nucleofuge) separated by two carbons. Mech anisms were distinguished through solvent effects on rates and products. Wh en the stereochemistry between the two, groups was gauche, the only effect of phenylsulfonyl was strong inductive retardation in a mechanism involving solvent participation. With the antiperiplanar stereochemistry, however, t he mechanism clearly changed to carbocation formation with a small kinetic acceleration. Thus, phenylsulfonyl is a weak beta effect substituent. This remarkable property for a strongly electron-withdrawing group occurs most l ikely through hyperconjugation or possibly through anchimeric assistance.