Hydrogenation and Hydrogenolysis. XV. Hydrogenation of Isomeric Anisidines with Platinum Metal Catalysts in Acetic Acid

Abstract

Abstract m-Anisidine was hydrogenolyzed to an extent of 92.5% in hydrogenation with a palladium catalyst in acetic acid at 60 °C and 90 kg/cm2. The amount of hydrogenolysis in o- and p-anisidine was only 2.1 and 2.5%, respectively. This great difference in hydrogenolysis between the isomers was not observed with rhodium and platinum catalysts. With m- and p-anisidines, selectivity at the initiation of hydrogenation was studied for the formation of N-cyclohexylanisidine intermediates and for other products by an extrapolation method. Extensive hydrogenolysis of m-anisidine and slight hydrogenolysis of o- and p-anisidines over palladium result from a high selectivity in the formation of the enamine or imine intermediates. The hydrogenation pathways leading to hydrogenolysis and secondary amine formation over the three platinum metals are discussed.