Electroorganic Reactions. 31. Quinonemethide Radical-Anions and Dianoins: Their Cathodic Generation and Reactivity

Article abstract of DOI:10.1021/jo00246a021

The cathodic reactions of a number of relatively stable quinonemethides have been examined in detail by cyclic voltammetry, controlled potential coulometry, and rigorous product analysis following preparative-scale electrolyses.The results of cyclic voltammetric experiments differ in some respects from those of earlier polarographic work.The lifetimes of the electrogenerated radical-anions and dianions, in the absence of added electrophile, are governed by steric hindrance.Hindered intermediates are relatively long-lived yet hydrogenate in the presence of proton donor and alkylate in the presence of methyl iodide.Less hindered analogue efficiently and rapidly dimerize, at carbon, with concomitant protonation or O-methylation depending on added electrophile.The ambident cathodically generated nucleophiles alkylate at both carbon and oxygen, and the competition is crucially dependent on the cation (Bu4N⁺ or Li⁺).Fuchsone 3 gives reduction products which vary with initial concentration and on the presence, or otherwise, of oxygen.Efficient reaction between oxygen and triarylmethyl radicals generated, e.g., from 3 has been demonstrated.