Polyaniline/SiO2 Nanocomposite Catalyzed One-pot Three Component Synthesis of 3,4-dihydropyrimidin-2(1H)-one Derivatives

Abstract

An efficient and rapid protocol for the synthesis of one-pot 3,4-dihydropyrimidin-2(1H)-ones has been developed by the polyaniline/SiO2 catalyzed condensation of benzaldehydes, β-ketoesters and urea/ thiourea. Polyaniline/SiO2 nanocomposite was synthesized by chemical oxidative polymerization of aniline monomer on the surface of SiO2 in the presence potassium persulphate (K2S2O8) as oxidizing agent and sulfuric acid (H2SO4).The synthesized catalytic materials have been well characterized by means of transmission electron microscopy (TEM), thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Temperature programmed desorption (NH3-TPD) and Brunauer Emmett and Teller (BET) method. Solvent stability of catalyst was tested using UV-Visible spectroscopy. Thermal stability of Polyaniline is noticeably improved which may due to the insertion of polyaniline on the surface of SiO2. NH3-TPD was used to determine the acidic properties of solid catalyst Polyaniline/SiO2 indicate the weak, medium and strong acidic sites total acidic strength is found to be 0.2906 mmol/gm. The specific surface area and average pore diameter of 10 wt % polyaniline/SiO2 are found 75.3443 m²/g and 10.8823 nm. This protocol has several advantages such as good thermal stability, high yield, simple work up procedure, non-toxic, clean, and easy recovery and reusability of the catalyst system.