Sterically hindered aromatic compounds. IX. Electron spin resonance and product studies of the dediazoniation reaction

Abstract

An esr study of the dediazoniation of 2,4,6-tri-tert-butylaniline with butyl nitrite in methylene chloride indicated the formation of the 2,4,6-tri-tert-butylphenyl radical which was spin trapped by the butyl nitrite. The persistent 2,4,6-tri-tert-butylphenoxy radical was also formed. Product studies from reactions catalyzed by pivalic acid indicate a novel rearrangement of an ortho-tert-butyl group under dediazoniation conditions forming such products as: 3-(3,5-di-tert-butylphenyl)-2-methylpropene (4), 1-(3,5-di-tert-butylphenyl)-2-methylpropene (5), 3-(3,5-di-tert-butylphenyl)-2-methyl-2-propanol (6), 3-(3,5-di-tert-butylphenyl)-2-butoxy-2-methylpropane (7), 3-(3,5-di-tert-butylphenyl)-2-methyl-2-trimethylacetoxypropane (8), 2,4,6-tri-tert-butylphenyl trimethylacetate (9), and 2,4,6-tri-tert-butyl-1,4-quinol (10). The major products (4–7) are accounted for by a free radical pathway by rearrangement of the 2,4,6-tri-tert-butyl-phenyl radical. The minor products (esters 8 and 9) probably form by competing ionic reactions. N-Nitroso-2,4,6-tri-tert-butylacetanilide decomposes (at least in part) by a radical pathway leading to the rearranged radical (CH3)2ĊCH2—Ar which was spin trapped by the nitroso group of the substrate. Spin trapping experiments during the dediazoniation of 2,5-di-tert-butylaniline similarly gave evidence for the formation of aryl radicals.