Aqueous High-Temperature Chemistry of Carbo- and Heterocycles. 30.1Aquathermolysis of Phenyl-Substituted Hydroxyquinolines

Abstract

A range of phenylquinolones and hydroxy-substituted phenylquinolines was synthesized and subjected to aquathermolysis in water alone, in 15% aqueous formic acid, and in 15% aqueous sodium formate at 315 and 460 °C. Thermal controls were obtained using cyclohexane as solvent. It was thought that the hydroxy substituent might provide a “handle” of activation for subsequent ring opening, denitrogenation, and possible biaryl cleavage pathways. At 350 °C all substrates tended to give mainly quinolines via deoxygenation as the main pathway. At 460 °C all substrates gave complex product slates with some ring opening to lower molecular weight products. Some denitrogenation was observed via ring opening and further reaction. Decarbonylation to yield indoles was also noted as a competing reaction pathway to quinoline ring opening. The indoles subsequently underwent ring opening reactions.