<b>Aqueous High-Temperature Chemistry of Carbo- </b><b>and Heterocycles. </b><b>29.</b><b>¹</b><b> Reactions of Aryl </b><b>Hydrocarbons, Aryl </b><b><i>N-</i></b><b>Oxides, and Aryl Carbonyl </b><b>Compounds in Supercritical Water at 460 </b>°C

Abstract

A series of aryl hydrocarbons, aryl N-oxides, and aryl carbonyl compounds were subjected to thermolysis at 460 °C in water alone, in 15% aqueous formic acid, in 15% aqueous sodium formate, and, for comparison of purely thermal reactions, in cyclohexane. The runs were carried out initially for 7 min and, in most cases, also for 1 h. The aryl carbonyl substrates underwent mainly carbonyl reduction mainly under reducing conditions, with ring opening only observed in significant amounts for 1,4-naphthoquinone and 3,4-benzocoumarin. The arenes produced mainly reduction products with only low yields of ring-opened products observed. Aryl oximes underwent significant denitrogenation and subsequent reduction with only very little cleavage to simpler aromatic systems. The N-oxides underwent deoxygenation, and in the case of isoquinoline, ring opening of the heterocycle was prevalent. 2-Aminobiphenyl was denitrogenated and cleaved to simpler systems in cyclohexane, but in the aqueous systems it underwent mainly cyclization to yield carbazole with only low yields of denitrogenated products. 2-Phenylphenol was unreactive under aqueous conditions with only low yields of deoxygenated products observed.