Electrocatalytic reduction of quinoline and its oxy derivatives

Electrocatalytic hydrogenation of quinoline, quinoline N-oxide, 8-oxyquinoline, and 5,7-dibromo-8-oxyquinoline is studied in an aqueous alkali catholyte solution with the additive of organic solvents on skeleton catalysts (Ni, Co, Cu, Fe) used for cathode activation. It is shown that the main product of hydrogenation of quinoline and quinoline N-oxide is 1,2,3,4-tetrahydroquinoline, whereas that of hydrogenation of 8-oxyquinoline, and its dibromo derivative, is 1,2,3,4-tetrahydro-8-oxyquinoline. A conclusion is made on the basis of chromatographic analysis as to the consecutive-parallel processes of deoxidation and hydrogenation of the N-heterocycle under electrocatalytic reduction of quinoline N-oxide.