Oxidation of 1-(4′-substituted phenyl)-2-(4-methylphenyl)diazene — Benzylic substitution vs. C–azo bond breaking

Abstract

The low oxidation potential of 1-phenyl-2-(4-methylphenyl)diazene 4′-substituted with a dimethylamino or methoxy group (10 and 11) allows the easy single electron transfer with radical cation generation in the presence of FeCl3. At the same time, the stabilizing effect of the positive charge exerted by 4-dimethylaminophenyl > 4-methoxy groups on the intermediate carbocation favors the hydrogen atom elimination in comparison with proton loss. Whereas benzylic substitution towards di- and triarylmethane derivatives takes place starting from diazene 11, the oxidation of diazene 10 leads mainly to products of C–azo breaking. This difference is well-supported by the idea that the electron, in the first step of oxidation, is extracted from the azo and (or) from the amino nitrogen atom.Key words: diazenes, oxidation, single electron transfer, benzylic substitution, C–azo bond breaking.