Synthesis, Antimicrobial and Antioxidant Activities of Novel 7-thioxo-4,6,7,8-tetrahydro-pyrazolo[4',3':5,6]pyrano[2,3-d]pyrimidin-5(1H)-ones Derived by SDS Catalyzed Multicomponent Reactions in Aqueous Micellar Media

Background: Surfactants as catalysts have found extensive utility in developing environmentally benign reaction conditions by reducing the resultant organic waste and the recyclability of the catalysts has made great advantages over other catalysts. The vital catalytic action can be attributed to its ability to solubilize insoluble substrate by forming colloidal mixtures. Objective: In this concern, we hypothesized, to develop a green protocol using micellar catalysts in aqueous media. Primarily expecting the reaction components should be ideally soluble at room temperature conditions under suitable catalysts. Method: Herein a highly efficient, one-pot four-component reaction involving thiobarbituric acid, hydrazine hydrate, ethyl acetoacetate and aromatic aldehydes for the synthesis of 7- thioxopyrazolopyrano- pyrimidinone derivatives has been accomplished using SDS (sodium dodecyl sulphate) as a catalyst. The procedure offers the advantages of green solvent, easy work-up avoiding the chromatographic separation and use of inexpensive, biodegradable, reusable catalyst. Results: These novel 7-thioxo-pyrazolopyrano-pyrimidinone derivatives were screened for antimicrobial and antioxidant activities. It was found that 3-methyl-4-(2,4-dichlorophenyl)-6,8-diethyl- 7-thioxo- 4,6,7,8-tetra-hydropyrazolo[4',3':5,6]pyrano[2,3-d]pyrimidin-5(1H)-one (5b) has shown high anti- fungal and anti-bacterial activities against the tested fungi and bacteria, which may be due to the presence of chlorine atoms. Four compounds, 5a, 5b, 5i and 5j were found to show high antioxidant activities. Conclusion: The thioxo-pyrazolo-pyranopyrimidinone motifs synthesized via the condensation protocol under micellar catalysis are found to be highly biological active entities. These series of novel compounds accounted for unique in-vitro assays.