In-situ oxidation of 5-hydroxymethylfurfural to 5-formylfuran-2-carboxylic acid catalyzed by iron, manganese, copper and salicylic amantadine Schiff base ligands

To synthesize simple and efficient catalysts and their application in catalytic conversion of biomass platform compounds to prepare high value-added chemicals has always been the focus of researchers. In this paper, a catalyst composed of iron, manganese, copper and Schiff base ligand derived from amantadine salicylaldehyde was in-situ constructed to catalyze the selective oxidation of 5-hydroxymethylfurfural (HMF) to prepare 5-formyl-2-furancarboxylic acid (FFCA). The ligands and complexes were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and single crystal diffraction, and the reaction conditions such as oxidation reaction time, reaction temperature, molar ratio of MnCl₂·4H₂O to ligand, oxidant and catalyst dosage, etc, were optimized. Under the optimized conditions, 100% conversion of HMF and the FFCA with a yield of 52.1% can be obtained. Finally, on the basis of the reaction results, the HMF oxidation reaction process catalyzed by Mn metal complexes was analyzed.