Fabrication of uniform Pd nanoparticles immobilized on crosslinked ionic chitosan support as a super-active catalyst toward regioselective synthesis of pyrazole-fused heterocycles.

Selection of biodegradable chitosan as a raw material is a smart technique due to its easy modifiability and high renewability. Herein, taking advantage of these functional characteristics, an ionic biopolymer support is produced from copolymerization of allylated chitosan (with 48 % degree of substitution) and polymerizable ionic liquid ([MEVIm]Br). Next, palladium nanoparticles are successfully stabilized in this designed support through a facile manner based on interconnected porous network, ionic nature and rich functional groups. Then, the Pd@CS-PIL structure was utilized as a heterogeneous catalyst for regioselective synthesis of pyrazole-fused heterocycles. The as-synthesized Pd@CS-PIL was characterized by various techniques such as XRD, EDX, FESEM, elemental mapping, TEM, BET, ICP, TGA, and FT-IR to better determine the structure, morphology, purity and physical properties. The obtained results revealed that the proposed nanostructure provides favorable porosity with significant specific surface area (139.2 m2.g-1), Pd nanoparticles with high dispersion (mean diameter âˆ¼ 22.8 nm) and crosslinked nature with good thermal stability (50 % weight loss about 600 °C). Therefore, Pd@CS-PIL nanostructure showed the key features of a super-active catalyst, and pharmaceutical pyrazole-fused scaffolds were produced in favorable yields (86-96 %) under ultrasound conditions.

Ultrasound-Engineered fabrication of immobilized molybdenum complex on Cross-Linked poly (Ionic Liquid) as a new acidic catalyst for the regioselective synthesis of pharmaceutical polysubstituted spiro compounds.

A novel supported molybdenum complex on cross-linked poly (1-Aminopropyl-3-vinylimidazolium bromide) entrapped cobalt oxide nanoparticles has been successfully fabricated through two different procedures, i.e. ultrasound (US) irradiations (100 W, 40 kHz) and reflux. The efficiency of the two different methods was comparatively investigated on the fundamental properties of proposed catalyst using diverse characterization techniques. Based on the obtained results, the ultrasonication method provides controlled polymerization process; as a result, well connected polymeric network is formed. In addition, the use of ultrasound waves turned out to be able to increase the particles uniformity, specific surface area (from 79.19 to 223.83 m2/g), and the onset thermal degradation temperature (Td) value (from 248 to 400 °C) of the prepared catalyst which intensifies the catalytic efficiency. Besides, US-treated catalyst demonstrated high chemical stability and maintained its cross-linked network after eight cycles recovery, while the cross-linked network of catalyst obtained under silent condition was completely disrupted. Furthermore, the ultrafast multi-step fabrication procedure was performed in less than 6 h under ultrasonic condition while a similar process promoted by a mechanical stirring method came to a conclusion after 5-6 days. Accordingly, the utility of the ultrasound irradiation was proved, and US-treated catalyst was applied for improved synthetic methodology of spiro 1,4-dihydropyridines and spiro pyranopyrazoles through different acidic active sites. Due to the significant synergistic influence between the proposed catalyst and US irradiation, a variety of novel and recognized mono-spiro compounds were fabricated at room temperature in high regioselectivity.

The influence of the polymerization approach on the catalytic performance of novel porous poly (ionic liquid)s for green synthesis of pharmaceutical spiro-4-thiazolidinones.

Although poly (ionic liquids) (PILs) have attracted great research interest owing to their various applications, the performance of nanoporous PILs has been rarely developed in the catalysis field. To this end, a micro-mesoporous PIL with acid-base bifunctional active sites was designed and fabricated by two different polymerization protocols including hydrothermal and classical precipitation polymerization in this paper. Based on our observations, hydrothermal conditions (high temperature and pressure) enabled the proposed sonocatalyst to possess a great porous structure with a high specific surface area (S BET: 315 m2 g-1) and thermal stability (around 450 °C for 45% weight loss) through strengthening cross-linking. In a comparative study, the preferred nanoporous PIL was selected and utilized as the sonocatalyst in a multicomponent reaction of isatins, primary amines, and thioglycolic acid. In the following, a variety of new and known pharmaceutical spiro-4-thiazolidinone derivatives were synthesized at room temperature and obtained excellent yields (>90%) within short reaction times (4-12 min) owing to the substantial synergistic effect between ultrasound irradiation and magnetically separable catalyst.

Synthesis of some Novel Imidazoles Catalyzed by Co3O4 Nanoparticles and Evaluation of their Antibacterial Activities.

AIM AND OBJECTIVE: The multi-component condensation of benzil, primary amines, ammonium acetate and various aldehydes was efficiently catalyzed using cobalt oxide nanoparticles under ultrasonic irradiation. This approach describes an effective and facile method for the synthesis of some novel 1,2,4,5-tetrasubstituted imidazole derivatives with several advantages such as high yields and short reaction times and reusability of the catalyst. Moreover, the prepared heterocyclic compounds showed high antibacterial activity against some pathogenic strains. MATERIALS AND METHOD: The facile and efficient approaches for the preparation of Co3O4 nanoparticles were carried out by one step method. The synthesized heterogeneous nanocatalyst was characterized by spectroscopic analysis including EDX, FE-SEM, VSM, XRD and FT-IR analysis. The as-synthesized cobalt oxide nanoparticles showed paramagnetic behaviour in magnetic field. In addition, the catalytic influence of the nanocatalyst was examined in the one-pot reaction of primary amines, benzil, ammonium acetate and diverse aromatic aldehydes under ultrasonic irradiation. All of the 1,2,4,5-tetrasubstituted imidazoles were investigated and checked with m.p., 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The antibacterial properties of the heterocycles were evaluated in vitro by the disk diffusion against pathogenic strains such as Escherichia coli (EC), Bacillus subtillis (BS), Staphylococcus aureus (SA), Salmonellatyphi (ST) and Shigella dysentrae (SD) species. RESULTS: In this research cobalt oxide nanostructure was used as a robust and green catalyst in the some novel imidazoles. The average particle size measured from the FE-SEM image is found to be 20-30 nm which confirmed to the obtained results from XRD pattern. Various electron-donating and electron-withdrawing aryl aldehydes were efficiently reacted in the presence of Co3O4 nanoparticles. The role of the catalyst as a Lewis acid is promoting the reactions with the increase in the electrophilicity of the carbonyl and double band groups. To investigate the reusability of the catalyst, the model study was repeated using recovered cobalt oxide nanoparticles. The results showed that the nanocatalyst could be reused for five times with a minimal loss of its activity. CONCLUSION: We have developed an efficient and environmentally friendly method for the synthesis of some tetrasubstituted imidazoles via three-component reaction of benzil, primary amines, ammonium acetate and various aldehydes using Co3O4 NPs. The present approach suggests different benefits such as: excellent yields, short reaction times, simple workup procedure and recyclability of the magnetic nanocatalyst. The prepared 1,2,4,5-tetrasubstituted imidazoles revealed high antibacterial activities and can be useful in many biomedical applications.

Magnetite Nanoparticles-Supported APTES as a Powerful and Recoverable Nanocatalyst for the Preparation of 2-Amino-5,10-dihydro- 5,10-dioxo-4H-benzo[g]chromenes and Tetrahydrobenzo[g]quinoline-5,10- diones.

AIM AND OBJECTIVE: This study introduces a green and effective approach for the preparation of biologically-active heterocyclic compounds including 2-amino-5,10-dihydro-5,10-dioxo-4Hbenzo[ g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones using one-pot multi-component reactions in the presence of Fe3O4@SiO2-NH2 nanocomposite. The preparation and use of aminofunctionalized Fe3O4@SiO2 as a powerful and reusable nanocatalyst is described. The catalyst was characterized by spectral techniques including FT-IR, SEM, XRD, EDX and VSM analysis. This method offers the advantages of high yields, short reaction times, comfortable work-up and reusability of the catalyst. MATERIAL AND METHOD: The amino-functionalization silica-coated magnetite nanocomposite was prepared by three step method and the structure elucidation of the nanocatalyst has been done using various spectroscopic analyses. Then, the Fe3O4@SiO2-NH2 nanocomposite was used in the multicomponent synthesis of 2-amino-5,10-dihydro-5,10-dioxo-4H-benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones under reflux conditions. All of the products were analyzed with m.p., 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The study on the recoverability of the nanocatalyst showed the recovered Fe3O4@SiO2-NH2 nanocomposite could be reused sixth consecutive times with a little-decreased activity. RESULTS: Amino-functionalized SiO2 coated Fe3O4 nanocomposite exhibited superparamagnetic behavior and strong magnetization at room temperature. The average crystallite sizes of the catalyst was about 50-60 nm. The obtained magnetic nanocomposite showed excellent catalytic activity as a new heterogeneous magnetic catalyst for the synthesis of some benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones. We propose that NH2 groups on the surfaces of nanocomposite act as the Brønsted base and cause to dehydrogenation of substrates to promote the reactions. CONCLUSION: It was found that Fe3O4@SiO2-NH2 nanocomposite act as an eco-friendly and efficient catalyst for one-pot synthesis of three/four component condensation reactions. In this research, aminofunctionalized Fe3O4@SiO2 was used as recoverable catalyst for the synthesis of 2-amino-5,10- dihydro-5,10-dioxo-4H-benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones under reflux conditions. The significant advantages of this method are the reasonably simple work-up, little catalyst loading, short reaction times, excellent yields, non-hygroscopic quality and reusability of the nanocatalyst which is in good agreement with green chemistry disciplines.