Fe3O4@Silica Sulfuric Acid Nanoparticles as a Magnetically Recoverable Solid Acid Catalyst for the Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones

A new efficient method for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and spiroquinazolinones via a condensation reaction of aldehydes and ketones with anthranilamide in the presence of nano Fe3O4@SiO2-SO3H as catalyst in ethanol has been described. The reactions are completed in short times, and the corresponding dihydroquinazolinones are produced with high yields. The present procedure has several advantages, including short reaction times, high yields of products, facile experiment, simple work-up, eco-friendly reaction conditions, and reusability of the catalyst. The catalyst could simply be separated and recovered by an external magnet and reused in subsequent reactions with no considerable loss in activity.