Electrochemical behaviour of veratrole and other catechol-based derivatives: Electrooxidative cleavage of its aromatic ring

The electrochemical oxidation of veratrole and related catechol-based derivatives was studied by electrolysis in a mildly alkaline aqueous solution at pH 9 with 50% of acetonitrile using three different electrode materials – boron-doped diamond, carbon fibres and platinum. Controlled-potential electrolysis followed by GC/MS analysis revealed the unexpected electrooxidative cleavage of the aromatic ring leading to muconic acid or the corresponding dialkyl esters as mixtures of cis,cis -, cis,trans - and trans,trans -isomers. The results indicate that the mechanism of the electrochemical ring-cleavage pathway is consistent with an overall four-electron oxidation process, where the initial formation of a reactive cation radical is followed by two hydroxylation steps and the oxidative cleavage of the vicinal diol.