Synthesis and characterization of nano acid catalyst derived from rice husk silica and its application for the synthesis of 3,4-dihydropyrimidinones/thiones compounds

In the present work, the extraction of silica nanoparticles from the rice husk followed by the modification using an acidic ionic liquid containing imidazolium butyl sulfonic acid through a sol-gel method (RH@ [SiPrImBuSO(3)H]CI) has been investigated. The composition, morphology and structural properties of the synthesized solid acid were analyzed by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis-derivative thermogravimetric (TGA-DTG), and nitrogen adsorption-desorption. The catalytic activity of the nanocomposite was examined through the one-pot condensation of aromatic aldehyde, beta-diketone, urea or thiourea under reflux condition. Diverse 3,4-dihydropyrimidinones/thiones derivatives were produced up to excellent yields in a short period of time. This nanocatalyst could be easily recovered, and reused without considerable loss of catalytic activity. This method seems to be a promising method for synthesizing organic chemicals. In addition to the conducted experiments, the H-1 and C-13 chemical shift and X-ray spectra values together with the structural parameters of 3,4-dihydropyrimidinones/thiones were computed and compared to the corresponding experimental values. As a result, the calculated H-1 and C-13 chemical shift and X-ray spectra show a good agreement with the experimental results. (C) 2019 Elsevier B.V. All rights reserved.