Synthesis and Antioxidant Evaluation of Dihydropyrimidinone Integrated Pyrazoles

A series of novel ethyl 6-[2-(3-aryl-1-phenyl-1H-pyrazol-4-yl)vinyl]-2-oxo-4-phenyl- 1,2,3,4-tetrahydropyrimidine-5-carboxylates (9a-9d) has been synthesized by adopting a multistep synthetic strategy. The structure of the targets was confirmed on the basis of physical and spectral techniques. The synthetically achieved targets were evaluated for their antioxidant activity by in-vitro DPPH free radical scavenging assay. Of the chemical entities screened, most of them exhibit good to better radical scavenging profile and among those, the nitro substituent bearing molecule 9c displayed the highest activity (82%) with IC50 value 621.6 μM. Further, as a representative molecule, compound 9a has been subjected to density functional theory calculations employing B3LYP method with 6311(++G) basis set to optimize its structure.