Reductive amination of furfural and furfurylamine with methoxides and MIL-53-NH2(Al)-derived Ru catalyst

Difurfurylamine (DiFAM)2 is a valuable chemical used in pharmaceuticals or polymers, but an efficient synthesis is rarely reported. One such method involves the imination of furfural (FAL)3 and furfurylamine (FAM)4 to form difurfurylimine (DiFIM),5 followed by the hydrogenation of DiFIM to produce DiFAM. This process can be carried out effectively using Ru nanoparticles and borohydrides as catalyst and reducing agent, respectively. Understanding the mechanism of this reaction is crucial for designing similar systems in the future. The materials Ru@Al2O3 and Ru/γ-Al2O3 were synthesized via in situ synthesis and impregnation, respectively. Characterization was then performed to verify the physicochemical properties of the materials. The catalytic reaction was carried out in an 80 °C oil bath with stirring for 1 h. Simulations were performed using density functional theory (DFT).6 Ru@Al2O3 obtained from MIL-53-NH2(Ru, Al) demonstrated a higher dispersion of Ru NPs due to their interaction with the –NH2 ligands on MIL-53-NH2(Al). Moreover, DFT calculations predicted that the methanolysis products of borohydrides could reduce the activation energy of the reaction by forming a stable transition state. These factors combined to yield an impressive ca. 92% of DiFAM and provide new insights for designing hydrogenation systems.