Oxidation by cobalt(III) acetate. Part 10. Effects of ring substituents on the product distributions in the oxidation of β-methylstyrenes by cobalt(III) acetate in acetic acid

Abstract

The oxidation of ring-substituted β-methylstyrenes by cobalt(III) acetate in acetic acid has been studied by product analysis and the relative rates were measured by a competition method. Electron-releasing groups (p-MeO, p-Me, and p-Bu^t) accelerated both the reaction rate and the formation of glycol monoacetates, while electron-withdrawing groups (p-Cl and m-Cl) not only retarded the reaction but also favoured the formation of allylic acetate instead of glycol monoacetate. The good relationship of relative rates with δ⁺ in the Hammett plot showed that both products were derived from the same intermediate. The reaction mechanism is discussed in connection with the stabilities of radical cations formed by a one-electron transfer from the olefins to cobalt(III) acetate.