ABSTRACT The development of oxidation methodologies that proceed without molecular oxygen or stoichiometric oxidants, while employing environmentally benign solvents, is of paramount importance in sustainable synthetic chemistry. Herein, we report the oxidation of aryl aldehydes to the corresponding benzoic acid derivatives using commercially available palladium nanoparticles supported on aluminum oxyhydroxide in aqueous medium. The reaction proceeds under mild basic conditions at ambient temperature, with sodium borohydride acting as a hydride donor/modulator, promoting in situ formation of active hydride species on the catalyst surface. These species facilitate dehydrogenative oxidation of aldehydes via the hydrated (gem‐diol) intermediate, affording benzoic acid derivatives with concurrent evolution of molecular hydrogen. Under optimized conditions, 14 benzoic acid derivatives were synthesized within 6 h, with yields ranging from 50% to 95%. The products were fully characterized by NMR spectroscopy. The Pd/AlO(OH) catalyst was recovered and reused in three consecutive runs without significant loss of activity or yield. SEM/EDX analyses of fresh and reused catalysts revealed no significant morphological changes, and ICP‐OES confirmed negligible palladium leaching. The use of a commercially available, reusable catalyst for selective oxidation under oxygen‐free aqueous conditions provides a practical and sustainable strategy for the synthesis of industrially relevant benzoic acid derivatives.
Göksu et al. (Sat,) studied this question.