Synthesis and application of Fe3O4@RHA nanocatalyst in the synthesis of polyhydroquinolines and dihydropyrimidinones (statistical approach to optimize parameters)

Abstract

In this study, rice husk ash as silica source was obtained and then, by adding Fe₃O₄, Fe₃O₄@RHA core-shell nanocatalyst was prepared. The Fe₃O₄@RHA nanocatalyst was identified using VSM, XRD, FE-SEM, EDX, and FT-IR analysis, and the optimization of the effective parameters in the reaction was done using response surface methodology (RSM). This nanocatalyst had spherical particles with an average particle size of about 30 nm and good magnetic properties of about 42 emu/gr. The Fe₃O₄ particles encapsulated in RHA were easily recovered and showed good catalytic activity. Using Fe₃O₄@RHA biosynthesized nanocatalyst, polyhydroquinoline derivatives were obtained through multi-component condensation of ammonium acetate, aldehyde, ethyl acetoacetate, and dimedone, under solvent-free conditions at 80 °C, as well as dihydropyrimidinone derivatives through multi-component reactions by condensation of urea, aromatic aldehyde, and β-Keto ester under solvent-free conditions at 70 °C. Fe₃O₄@RHA nanocatalyst was introduced as a heterogeneous, stable, and environmentally compatible catalyst; in its production, dangerous materials, reagents, and solvents were avoided and it is environmentally friendly. In addition, it has the advantage of being recyclable, resulting in short reaction time, high product yield, and economically good performance.