Silica Sulfuric Acid-coated Fe3O4 Nanoparticles as a Highly Efficient and Reusable Solid Acid Catalyst for the Green Synthesis of 2,3- Dihydroquinazolin-4(1H)-ones under Solvent-free Conditions

An efficient and eco-friendly procedure for the synthesis of 2,3-dihydroquinazolin-4(1H)- ones and spiroquinazolinones in the presence of sulfuric acid functionalized silica-coated magnetite nanoparticles under solvent-free conditions has been described. The reactions are completed in short times, and the products are obtained in high isolated yields without any undesirable side reaction. This method has several advantages, including short reaction time, facile operation, easy work-up, ecofriendly reaction conditions, high isolated yields, and reusability of the catalyst. The catalyst could be easily separated and recovered from the reaction mixture by an external magnet and reused in subsequent reactions with no considerable loss in activity.