Systematic evaluation of the palladium-catalyzed hydrogenation under flow conditions

Four types of heterogeneous Pd catalysts (10% Pd/C, 10% Pd/HP20, 0.5% Pd/MS3A, and 0.3% Pd/BN) were applied to the flow hydrogenation to systematically evaluate the appropriate conditions for the reduction of a wide variety of reducible functionalities. The use of 10% Pd/C and 10% Pd/HP20 allowed the hydrogenation of various reducible functionalities by a single-pass of the substrate-MeOH solution through the catalyst cartridge, while 0.5% Pd/MS3A and 0.3% Pd/BN catalyzed a novel chemoselective hydrogenation; only alkene, alkyne, azide, and nitro functionalities could be reduced with other coexisting reducible functionalities intact.