A nanocrystalline CdS thin film as a heterogeneous, recyclable catalyst for effective synthesis of dihydropyrimidinones and a new class of carbazolyl dihydropyrimidinones via an improved Biginelli protocol

Abstract

This is the first report on the use of a nanocrystalline cadmium sulphide (CdS) thin film coated glass reactor as an efficient tool for the synthesis of dihydropyrimidinones via multicomponent reactions of aldehydes, a β-ketoester, and urea/thiourea in ethanol at 78–80 °C. A nanocrystalline CdS thin film was prepared by the chemical bath deposition technique. The nanocrystalline CdS thin film was also effective for the efficient synthesis of a new class of carbazolyl dihydropyrimidinones and carbazolyl dihydropyrimidinthione derivatives in good yields. The CdS thin film was characterized by powder XRD, X-ray photoelectron spectroscopy, EDS analysis and FT-IR studies. The average crystallite size of 30.3 nm for the CdS nanoparticles was determined from the powder XRD plot using the Scherrer formula. Based on SEM analysis the particle size distribution of CdS nanoparticles is in the range of 23.2 to 33.9 nm. The effect of temperature, substituents and catalyst loading on the reaction was also studied. All the products were thoroughly characterized by ¹H-NMR, ¹³C-NMR, FT-IR, mass spectral and CHN analysis. Lipinski evaluations of the products were carried out to predict the oral bioavailability of the carbazolyl dihydropyrimidinones and carbazolyl dihydropyrimidinthiones. The advantages of this improved protocol for Biginelli reactions are high yields, easy separation, a recyclable catalyst, etc.