Selective Hydrogenation of Benzylidenethiazolidinedione Exocyclic Alkene with Anti-poisoning Nitrogen-Doped Carbon Supported Palladium Catalysts

Pioglitazone has been developed as an effective insulin-sensitizing agent for the treatment of type II diabetes mellitus. Selective hydrogenation of the benzylidenethiazolidinedione exocyclic alkene is a committed step in the industrial manufacturing of pioglitazone. However, the strong coordination between metallic sites of commercial hydrogenation catalysts and benzylidenethiazolidinedione might cause catalyst poisoning and lead to poor activity and selectivity. In this context, an effective and anti-poisoning catalyst with highly dispersed palladium nanoparticles supported on biomass-derived nitrogen-doped carbon with mesoporous structures has been established. A systematic investigation of the structure-activity relationship was performed with a series of Pd/CNx by regulating the ratio of precursors D-glucosamine hydrochloride (GAH) and melamine, and it demonstrated that large specific surface area, rich pore structure and strong Pd-N interaction were essential for the high catalytic performance. The optimal Pd/CN1.2 catalyst exhibited nearly 100% conversion and 95.5% selectivity under optimized reaction conditions. Remarkably, compared with commercial Pd/C catalyst, Pd/CN1.2 displayed almost twice the catalytic productivity and provided better poisoning resistance and leaching resistance. Moreover, its stability was also acceptable and good activity could be maintained after exposed in the air for 4 months.