Isoxazole and its derivatives derived from natural resources are very few. However, they have several applications in pharmaceutical industries, including antimicrobial, antitumor, anticancer, antifungal, and antibacterial activities. As a result, this research aimed to design a novel one-pot green approach to synthesize new oxazole derivatives. The derivatives were further explored for their antibacterial and antioxidant activities together with their density functional theory (DFT) analysis. Characterization of newly synthesized moieties was done by IR, ¹H NMR, ¹³C NMR, CHN analysis, & single-crystal X-ray Crystallography. Further, these compounds were examined for their antibacterial potential by using Gentamycin as a standard drug against S. aureus and E. coli bacterial strains. The derivatives 4a, 4c, 4d, 4f, 4j, and 4k possessed excellent antibacterial potential against former, while 4c and 5 showed the highest activity against the later one. The derivatives were also analyzed for their antioxidant activities by using free radical scavenging (ABTS. & DPPH assays), and total antioxidant capacity. Here also, 4a, 4d, 4e, 4k, 4l, 4m, and 5 exhibited the most promising results. Finally, the DFT analysis was achieved by using the B3LYP methodology with a 6–311 + G(d,p) basis set to study the electronic structure of molecules and analysis of chemical reactivity descriptors such as hardness (η), Mulliken electronegativity (χ), chemical potential (μ) and electrophilicity (ω). These properties were calculated from the levels of the predicted frontier molecular orbitals and their energy gap.

Heterocyclic compounds are acquiring more importance in recent years because of their pharmacological activities. Compounds containing imidazole moiety have many pharmacological properties and play important role in biochemical processes. Imidazole is a natural compound which exists in many important natural molecules such as the amino acid histidine, vitamin B12, histamine, biotin and purines like adenine and guanine. Imidazole derivatives play significant roles in various pharmacological activities such as anticancer, antibacterial, antifungal, antiviral, anti-HIV and antitubercular. This article aims to review the work in the methods of synthesis using various catalytic system, solvent condition and pharmacological potential of 2,4,5-tri and 1,2,4,5-tetrasubstituted imidazoles reported during last 15 years.

Aims: In this article, we have developed an eco-friendly one-pot multi-component reaction methodology employed for the green synthesis of functionalized pyrazole derivatives viz cyclo-condensation of aromatic aldehydes, ethyl acetoacetate and phenyl hydrazine and/or hydrazine hydrate in the presence of cetyltrimethylammoniumbromide (CTAB) at 90°C temperature in an aqueous medium. Materials and Methods: In the present protocol, we developed a green method for the synthesis of functionalized pyrazole derivatives through one-pot, multi-component cyclo-condensation of aromatic aldehydes, phenyl hydrazine or hydrazine hydrate and ethyl acetoacetate using cetyltrimethylammoniumbromide (CTAB) as a catalyst in water as a solvent. Our methodology confers advantages such as short reaction time, atom economy, purification of the product without using column chromatographic and hazardous solvent. The reaction is being catalyzed by cetyltrimethylammoniumbromide (CTAB) and thus, products are formed under the green reaction conditions. Results and Discussion: Initially, the reaction of benzaldehyde and phenylhydrazine with ethyl acetoacetate was carried out in water at room temperature in the absence of the catalyst; no product was obtained after 24 h. When the reaction was carried out using L-proline as a catalyst in ethanol at 70°C, the yield of the product was 20%. Conclusion: This research not only provides a green and efficient method for the synthesis of sulfinic esters but also shows new applications of electrochemistry in organic synthesis. We consider that this green and efficient synthetic protocol used to prepare sulfinic esters will have good applications in the future. In conclusion, we have developed successfully a green and efficient one-pot multi-component methodology for the synthesis of substituted pyrazoles using CTAB as a catalyst in water as a solvent with excellent yields. Purifications of compounds were achieved without the use of traditional chromatographic procedures. This methodology has advantages of operational simplicity, clean reaction profiles and relatively broad scope, which make it more attractive for the diversity oriented synthesis of these heterocyclic libraries. In this methodology, we suggest a further alternative possibility for the formation of substituted pyrazoles. The compound 7h can be used as an anticancer drug in the pharma industry.