Oxidation of Alkylbenzenes by S2O82--CuII in Acetic Acid and Acetonitrile

Article abstract of DOI:10.1021/jo00173a026

Oxidation of a series of toluenes by K2S2O8 or (NH4)2S2O8 + Cu(OAc)2 in acetic acid or acetonitrile is little affected by added water or acetate and gives benzyl acetates or benzaldehydes, respectively, in good yields.Data are consistent with initial formation of aromatic radical cations, proton loss to give benzyl radicals, and oxidation to final products by Cu^II.Benzyl alcohols, but not acetates, are selectively oxidized, suggesting partial equilibration of radical cations, with rates of proton loss determining product distributions.Oxidation of cumene gives chiefly α-methylstyrene which is oxidized futher to 2-phenylpropanal.Products from p-ethyltoluene and p-cumene indicate that, on a statistical basis, loss of secondary and tertiary protons is more rapid than loss of primary protons, contrary to some previous reports.These systems appear promising for studying fragmentation patterns of aromatic radical cations in general.