Pd/C Catalyzed Decarboxylation-Transfer Hydrogenation of Quinoline Carboxylic Acids

Abstract:: Pd/C catalyzed decarboxylation-transfer hydrogenation of quinoline carboxylic acids and transfer hydrogenation of quinolines had been developed for the synthesis of 1,2,3,4-tetrahydroquinolines. These two processes were implemented smoothly using Pd/C (0.9 mol%) as catalyst with ammonium formate as hydrogen source in ethanol at 80 oC. The reaction system also can be applied to transfer hydrogenation of benzo[h]quinoline and 2,9-dimethyl-1,10-phenanthroline with good to excellent yields. And the gram scale and recycling of catalyst had been tested with good results. Furtherly, the mechanism of Pd/C catalyzed reduction of quinoline carboxylic acids and quinolines had been proposed.