Arene Oxides as Intermediates in the Metabolism of Aromatic Substrates: Alkyl and Oxygen Migrations during Isomerization of Alkylated Arene Oxides

Phenolic products obtained on isomerization of the three arene oxides of toluene, the nine arene oxides ofortho-, meta -, andpara -xylene, the arene oxide of mesitylene, and 2-methyl and 1,2-dimethylnaphthalene-1,2-oxides are compared to the phenolic products obtained by hepatic metabolism of the parent aromatic hydrocarbons. The results are compatible with the intermediacy ofcertain of these arene oxides in the metabolic pathway from hydrocarbons to phenols. Migrations of methyl groups as well as a remarkable apparent migration of oxygen are observed. The isomerization of 1,4-dimethylbenzene oxide to 2,4-dimethylphenol is analogous to the methyl migration observed in the enzymatic conversion of 4-methylphenylalanine to 3-methyltyrosine with phenylalanine hydroxylase. There aremultiple pathways of isomerization of alkylarene oxides to phenols and they are determined by environmental and structural factors. The proportion and nature of products vary greatly with pH, which suggests the presence of different mechanisms for acid-catalyzed or spontaneous isomerizations of arene oxides.