Nano-ZrO2 sulfuric acid: a heterogeneous solid acid nano catalyst for Biginelli reaction under solvent free conditions†
Nano-ZrO2 sulfuric acid [n-ZrO2–SO3H (n-ZrSA)] has been synthesized from the reaction of nano-ZrO2 with chlorosulfonic acid as sulfonating agent. This catalyst was characterized via FT-IR, XRD, TGA, FESEM, TEM, EDX, BET, BJH, ICP and pH analysis. We show that n-ZrSA catalyzed the Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)one derivatives in high yields under solvent-free conditions by the reaction of aldehyde, β-diketoester and urea (or thiourea). The main advantages of the catalyst are its non-toxic nature, high stability and reusability.