Solvent-free Mizoroki–Heck reaction catalyzed by palladium nano-particles deposited on gelatin as the reductant, ligand and the non-toxic and degradable natural product support

Abstract

Gram-scale synthesis of uniform nano-particles of palladium supported on gelatin, as a reductant and ligand is described. These particles were prepared under green conditions without addition of any external reducing agent and ligand. No complicated work up process was needed for the isolation of the nano-particles. Full characterization of the supported palladium particles on gelatin was performed by UV–Vis spectra and also by SEM, TEM and AFM images. The amount of palladium particles on gelatin was determined by induced coupled plasma (ICP) analysis and atomic absorption spectroscopy (AAS) to be 0.09 mmol of Pd per gram of the gelatin. The supported nano-particles of palladium on gelatin were applied successfully as the catalyst in Mizoroki–Heck reaction. The reaction was conducted under solvent-free conditions using tri( n-propyl) amine as a base at 140 °C. This system showed high catalytic activity for the reaction of aryl iodides and aryl bromides with n-butyl acrylate and styrene. In the case of the reaction of aryl iodides with n-butyl acrylate, incredible reaction rates were observed which is unique in comparison with the other methods reported in the literature. The catalyst was recovered and recycled for ten consecutive runs. We have also checked the effect of one of the generated base adduct on the reaction rate.