Ethyl-4-(aryl)-6-methyl-2-(oxo/thio)-3,4-dihydro-1H-pyrimidine-5-carboxylates: Silica bismuth (III)triflate catalyzed synthesis and antioxidant activity

Novel ethyl-4-(aryl)-6-methyl-2-(oxo/thio)-3,4-dihydro-1H-pyrimidine-5-carboxylates were synthesized from one-pot, three-component Biginelli reaction of aryl aldehydes, ethyl acetoacetate and urea/ thiourea by catalytic action of silica supported Bismuth(III) triflate, a Lewis acid. All the synthesized compounds were structurally characterized by spectral (IR, H-1 NMR & C-13 NMR spectroscopic and Mass spectrometric) and elemental (C, H & N) analyses. The present protocol has deserved novel as, formed the products in high yields with short reaction times, involved eco-friendly methodology and reusable heterogeneous Lewis acid catalyst. The title compounds were screened for in vitro DPPH free radical scavenging antioxidant activity and identified 4i, 4j, 4h & 4f as potential antioxidants. The obtained in vitro results were correlated with molecular docking, ADMET, QSAR, Bioactivity & toxicity risk studies and molecular finger print properties and found that in silico binding affinities were identified in good correlation with in vitro antioxidant activity and studied the structure activity relationship. The molecular docking study has disclosed strong hydrogen bonding interactions of title compounds with aspartic acid (ASP197) aminoacid residue of 2HCK, a complex enzyme of haematopoietic cell kinase and quercetin. Results of toxicology study evaluated for potential risks of compounds have revealed title compounds as safer drugs. In ultimate the study has established ligand's antioxidant potentiality as they effectively binds with ASP197 amino acid of Chain A hence confirms the inhibition of growth of reactive oxygen species in vivo. In addition, the title compounds have been identified as potential blood-brain barrier penetrable entities and efficient central nervous system (CNS) active neuro-protective antioxidant agents.