Alkyl radical adducts of aromatic N-oxides as hydrogen-abstracting agents: The reactivity of phenazine-N,N′-dioxide-methyl radical adduct

An O-methylated analog of protonated phenazine-di-N-oxide radical anion abstracts hydrogen from primary and secondary alcohols in a slow (k ₁ < 500 M⁻¹ s⁻¹) bimolecular reaction. No kinetic evidence has been found for the unimolecular release of free methoxyl radicals through the homolytic N-OMe bond cleavage in these species. DFT calculations at the UB3LYP 6-31G(d) level indicate that protonated and O-alkylated radical anions of pyrazine, quinoxaline and phenazine di-N-oxides are close analogues of aromatic nitroxyl radicals with the highest spin density localized on the oxygen and nitrogen of the nitrone moiety.