Using an efficient and eco-friendly approach, 14 4-aryl-7,7-dimethyl-1,2,3,4,5,6,7,8-octahydroquinazolin-2,5-diones (and six of their 2-thione analogues) were prepared in good yields and in short reaction times by a three-component reaction of an araldehyde, dimedone and urea (or thiourea) using Fe3O4 nanoparticles in aqueous ethanol under reflux conditions. The Fe3O4 nanoparticles, which were easily prepared and could be recycled, were fully characterised by TEM, SEM, XRD, EDX, VSM and FTIR analysis.
The reaction between dimedone, an aromatic aldehyde and urea catalysed by ZnO nanoparticles (ZnO NPs) in refluxing ethanol as a solvent provided a simple and efficient one-pot route for the synthesis of octahydroquinazolinone derivatives in excellent yields.
3,4-dihydropyrimidin-2(1H)-one and octahydroquinazolinone derivatives were obtained in high-to-excellent yields and short reaction times using SCMNPs@CA-EA-SO3H as a green and heterogeneous solid acid catalyst in a one-pot multi-component condensation of ethyl acetoacetate or dimedone, urea, and aldehyde compounds under solvent-free conditions. More importantly, the green catalytic system could be easily collected from the reaction solution utilizing an external magnet and reused for five runs with a negligible decrease in yields and reaction rate.