A. Perosa, M. Selva, P. Tundo
May 7, 1999
Citations
0
Influential Citations
16
Citations
Journal
Journal of Organic Chemistry
Abstract
A model halogenated aryl ketone (4-chloropropiophenone 1) was subjected to mild catalytic hydrodehalogenation (p[H2] = 1 atm, T = 50 °C) in a multiphase system consisting of isooctane and an alkaline aqueous phase, in the presence of onium salts as phase-transfer agents. The chemoselectivity of the reaction was sharply influenced by the KOH concentration of the aqueous phase: thus, the formation of 1-phenyl-1-propanol 4 was favored in a highly alkaline pH range (>13.5 by 50% to 5% KOHaq). Instead, up to 95% selectivity toward phenyl ethyl ketone 2 was observed if the pH was controlled (8 < pH < 13) by adjusting the KOHaq concentration in the range between 5 and 1%. Further investigation of the pH effect indicated that an acidic aqueous phase directed the reaction chemoselectivity toward the formation of products arising from aromatic ring reduction (i.e., cyclohexyl ethyl ketone 7 and 1-cyclohexyl-1-propanol 8) rather than from carbonyl hydrogenation or hydrogenolysis. Also aliphatic amines, used in plac...