Earth-Abundant Heterogeneous Cobalt Catalyst for Selective Ring Hydrogenation of (Hetero)arenes and Gram-Scale Synthesis of Pharmaceutical Intermediates

It is highly desired but scientificallyas well as technologicallychallenging to develop non-noble metal-based hydrogenation catalyststhat can substitute noble metal-based ones. Herein, we present a facileand environmentally friendly approach for synthesizing pine needlebiomass-derived nitrogen-doped carbon-supported Co3O4 nanoparticles (Co3O4/PNC). The wholeprocess involves the impregnation of pine needles with cobalt nitratesalt and subsequent pyrolysis at 500 & DEG;C under a nitrogen atmosphere.Applying this Co3O4/PNC nanocatalyst, a broadrange of substituted phenols and functional organic chemicals, including N- and O-heteroarenes, could be efficientlytransformed into their corresponding ring-hydrogenated products ingood-to-excellent yields (>55 examples). In addition, this catalyticapproach has proved useful for the preparation of seven key drug intermediateson a gram scale, which are commonly used in manufacturing active pharmaceuticalingredients in bulk quantities. Advantageously, cyclohexanecarboxylicacid, a key pharmaceutical building block of praziquantel, was synthesizedfrom polystyrene in a two-step process. The pivotal physicochemicalproperties of fresh and spent Co3O4/PNC nanocatalystswere thoroughly investigated by high-resolution transmission electronmicroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, N-2 adsorption-desorption, Raman analysis, H-2-temperature programmed reduction, and CO2-temperature-programmeddesorption analysis. The cobalt content in the Co3O4/PNC nanocatalyst was estimated by inductively coupled plasmaatomic emission spectroscopy analysis. Besides, the Co3O4/PNC nanocatalyst is stable, easily recovered, and reusedeffectively for four catalytic cycles with no loss of activity orselectivity. Furthermore, density functional theory calculations wereperformed to get more insights into the reaction mechanism.