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In this research, green procedure was employed for biosynthesis of magnetic nanoparticles of iron oxide (Fe3O4‐MNPs) by reduction of ferric chloride solution with Orange peel water extract. Also, dihydro‐2H‐cyclopenta[d][1,3]oxazole was generated through multicomponent reaction of 1,3‐oxazole‐2(3H)‐thione, dialkyl acetylenedicarboxylates, α‐haloketones, and Fe3O4‐MNPs as catalyst at ambient temperature in good yield. Initially, 1,3‐oxazole‐2(3H)‐thione derivatives as one of the precursors are produced through the reaction of alkyl bromides, isothiocyanate, sodium hydride, and Fe3O4‐MNPs as catalyst water at ambient temperature in 83–95% yields. Also, diphenyl‐picrylhydrazine radical trapping and ferric reduction activity potential assays are used for evaluation of antioxidant activity of some synthesized compounds. Among investigated compounds, 4b has good power for radical trapping activity and 4d has good reduction power to butylated hydroxytoluene and 2‐tert‐butylhydroquinone.

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Aims and Objective: In this work 1,3-oxazoles were generated using multicomponent reaction of α-bromo ketones, alkyl (aryl) isothiocyanates, sodium hydride and Fe3O4 MNPs in water at room temperature in good yields. The nanoparticles that is generated via biosynthesis method have potentially valuable in different purposes such as organic synthesis. Materials and Methods: To study antioxidant ability of some synthesized thioxo-1,3-oxazoles, diphenyl-picrylhydrazine (DPPH) radical trapping and power of ferric reduction testes are employed. Among studied thioxo-1,3-oxazoles, 4b have good power for radical trapping and reduction activity than to standard antioxidant such as BHT and TBHQ. In addition, the antimicrobial activity of some thioxo-1,3-oxazoles was studied employing the disk diffusion test on Gram-positive bacteria and Gram-negative bacteria. The results of disk diffusion test showed that compound 4a, 4b, 4d and 4f prevented the bacterial growth. Results: Without employing catalyst, these reactions have low yield and busy mixture. The synthesis of compound 4a as sample reaction have alike yield in the presence of ZnO-NPs and Fe3O4 MNPs (entry 20 and entry 30) but removal of catalyst from the mixture of reaction after completing of reaction is comfortable in present of Fe3O4 MNPs. Structures of 4a–4i are confirmed by IR, 1H NMR, 13C NMR mass spectra. Conclusion: The reaction of α-bromo ketones, isothiocyanate and sodium hydride in the presence of catalytic amount of Fe3O4 MNPs in water generate 1,3-oxazole derivatives in good yields. Some advantages of performing these reactions with present procedure are carrying out these reactions in water as green solvent and simple removal of catalyst.