Electron-transfer processes: oxidation of α- and β-alkenylbenzenes by peroxydisulfate in acetic acid

Oxidation of α- and β-unsaturated alkylbenzenes by peroxydisulphate in acetic acid gives side-chain acetoxylation with formation of the corresponding glycol diacetates and compounds (10), respectively. The reaction is catalysed by transition-metal salts, among which cupric acetate gives the best results. Generally, electron-releasing substituents on the benzene ring increase the yield and improve the selectivity. The same substrates are oxidized in water under Ag+ catalysis to the corresponding aldehydes. The different behaviour in the two solvents is ascribed to the difference in reactivity between the primary oxidation products and the starting olefin, whereas the initial oxidation step is suggested to occur in both cases via an electron-transfer process from the olefin to the sulphate radical anion