Highly efficient hydrogenation and dehydrogenation of N-Heteroarenes catalyzed by mesoporous graphitic carbon nitride supported CoPD alloy nanoparticles

Abstract

The present study reports the preparation of a multifunctional nanocatalyst, namely mesoporous graphitic carbon nitride (m-gCN) supported cobalt-palladium (COPD) alloy nanoparticles (m-gCN/COPD), and its catalysis for two distinct organic transformations (hydrogenation and dehydrogenation of quinolines and tetrahydroquinolines) in order to obtain biologically important N-heterocyclic building blocks. The m-gCN/COPD nanocatalysts were prepared by following a two-step protocol comprising the synthesis of colloidal COPD alloy nanoparticles (NPs) via surfactant-assisted solvothermal co-reduction of metal precursors and the deposition of as-prepared COPD NPs on exfoliated m-gCN nanosheets in solution. After the characterization of m-gCN/COPD nanocatalysts, they were first utilized as catalyst in the synthesis of a variety of 1,2,3,4-tetrahydroquinoline derivatives via an efficient and environmentally friendly transfer hydrogenation methodology using ammonia borane (H3NBH3) as a hydrogen source in water. Next, the oxidation of 1,2,3,4-tetrahydroquinoline analogues was realized by using tert-butyl hydroperoxide (TBHP) as a green oxidant and m-gCN/COPD as catalysts. Additionally, m-gCN/COPD nanocatalysts are reusable in both reactions up to the five consecutive runs. Besides being novel, the presented catalytic hydrogenation and dehydrogenation protocols provides distinct advantageous such as using green reagents (H3NBH3 and TBHP) and water as the solvent for the synthesis of quinoline derivatives in the context of sustainable chemistry.