ELECTROCHEMICAL REDUCTION OF PARA-NITROPHENYL AZIDE - EVIDENCE CONSISTENT WITH THE FORMATION OF PARA-NITROPHENYLNITRENE ANION RADICAL AS A SHORT-LIVED INTERMEDIATE

The electrochemical reduction of p-nitrophenyl azide in DMF, acetonitrile, and butyronitrile is initially a one-electron process that affords the corresponding anion radical as a transient intermediate. Although p-02NC6H4N3*’ is too short-lived to be observed by our methods, product studies are consistent with a reaction pathway in which p-O2NC6H4N3*-decomposes by loss of dinitrogen to give the corresponding nitrene anion radical, p-O2NC6H4N*-, as a short-lived intermediate. In the absence of added reagents, 4,4'-02NC6H4N=NC6H4N022-is formed as the principal product via dimerization of anion radicals. In DMF, hydrogen atom abstraction and carbonyl addition/radical β-fragmentation are observed also as reaction pathways and become increasingly important processes with decreasing current density and increasing temperature. The products of the two latter reaction pathways are p-O2NC6H4NH-and p-O2NC6H4N-C0N(CH3)2, respectively. In the presence of the weak oxygen acid (CF3)2CHOH, reduction of p-02NC6H4N3is a two-electron process that yields dinitrogen and p-O2NC6H4NH2as products. In the presence of weak methylene carbon acids such diethyl malonate, a chain reaction involving diazo transfer ensues, producing the corresponding diazoalkane and p-02NC6H4NH2in high yields. © 1990, American Chemical Society. All rights reserved.