Useful Electro-Oxidative Conversions of Aromatic Compounds

Abstract

Conditions for the direct and indirect side-chain oxidation of methylnaphthalenes were explored, together with substituent effects likely to influence the acidity of their radical-cations. That substituent effects alter the electron demand at side-chain positions was shown using chemical shifts (¹³C) at the benzylic carbons of 2-benzylnaphthalenes substituted at the para position of the benzyl group. However, the reactivity of 2-methylnaphthalenes in direct anodic oxidation ranges from exclusive dimerisation to exclusive nuclear substitution with negligible attack at the methyl group.

In contrast DDQ is an effective side-chain oxidant for electron-rich 2-methylnaphthalenes. An indirect method was devised in which non-stoichiometric amounts of DDQ are used with continuous anodic regeneration in an undivided cell and at constant current.