Role of the In Situ Generated Acidic Protons and Cl Species for 2,5-Hexanedione Production from the New Platform Molecule 5-(Chloromethyl)furfural

Synthesis of 2,5-hexanedione (HD) from 5-(chloromethyl)furfural (CMF) with polymethylhydrosiloxane (PMHS) as the hydrogen donor is reported for the first time. It was found that the yield of HD was up to 78% at 160 °C for 30 min. The in situ generated acidic protons could significantly promote the coupling reaction (hydrodechlorination, hydrogenolysis, and hydrolysis) from the perspective of kinetics and thermodynamics. After modifying Pd nanoparticles (NPs) with the in situ generated Cl species, the step sites could more easily adsorb the substrate molecules in comparison to the corner sites. The differential charge proved the electron transfer from Pd NPs to Cl species and substrate molecules. This work elucidates the role of acidic protons and the migration mechanism of Cl species, which could provide an experimental and theoretical basis for the development of future catalytic systems and the synthesis of biomass-derived chemicals.