Background: Heterogeneous synthesis of nitrogen containing heterocyclic
compounds such as dihydropyrimidin-2(1H)-one/thione derivatives is an important
research. Use of nanocrystalline ZnO has demonstrated for heterocyclic compounds
which are routinely used in medicinal chemistry due to their therapeutic and pharmacological
properties. In this context the solvent free synthesis of pyrimidine derivatives
Methods: Synthesis of ZnO nanomaterials is carried out by precipitation method,
which is further used for synthesis of dihydropyrimidin-2(1H)-ones/thiones derivatives.
Stoichiometric amount of aromatic aldehydes (1), urea (2) and ethyl acetoacetate
(3) were taken in beaker. Then, 10 mmol percent nanocrystalline ZnO powder was
added as a catalyst in the reaction mixture which was subjected to heated at 55°C in microwave oven.
Results: Microwave assisted synthesis of 3,4-Dihydropyrimidin-2(1H)-ones/thiones has been successfully
carried out using eco-friendly ZnO nanoparticles as catalysts. Nanocrystalline ZnO of particle size
in the range 60-80nm was prepared by decomposing the Zinc Oxalate intermediate at 500ºC XRD
analysis indicates the formation of highly crystalline hexagonal phase of ZnO. Solvent free synthesis
using reported method have confer 95% yield which is greater than organic solvents such as DMF, Dioxane,
THF, Toluene for heterogeneous synthesis.
Conclusion: Successfully accomplished ‘green’ synthesis of dihydropyrimidone/thiones derivatives was
demonstrated. Use of nanocrystalline ZnO is found to be an efficient catalyst for heterogeneous Biginelli
reaction. Solvent free reactions gave the better yield compared to the use of organic solvents.