Supported heteropoly acids offering strong option for efficient and cleaner processing for the synthesis of imidazole derivatives under solvent-free condition

Co(II)-Cu(II) mixed-oxide catalysts for single-step synthesis of 2,4,5-triaryl-1H-imidazole derivatives under microwave irradiation

In this study, a catalyst composite of Co-Cu was prepared from chloride-containing precursor of Co(II) and Cu(II) metals using the milky latex of the Euphorbia neriifolia plant following green principles of synthesis. The catalyst composite was characterized using XRD, EDAX, SEM, HR-TEM, FTIR, XPS and TOF-MS. The crystallinity of the mixed-oxide composite with a distorted octahedral nature was confirmed from analysis. Chemical charge analysis of the Co-Cu mixed phase based on XPS revealed Co2+ and Cu2+ oxidation states. This material was used for synthesizing 2,4,5-triaryl-1H-imidazole (TIMDZOL) derivatives. Analysis of reaction conditions revealed that EtOH : PEG at 8 : 2 ratio under microwave conditions showed better yields with less time and better reusability of the Co-Cu catalyst.

Synthesis of a bistriazolyl-phenanthroline-Cu(ii) complex immobilized on nanomagnetic iron oxide as a novel green catalyst for synthesis of imidazoles via annulation reactions

We designed and prepared a novel N-heterocycle-based nanocatalyst by a post synthetic method, namely the [Fe3O4@DAA-BTrzPhen-Cu(ii)] composite. In this method, bistriazolyl-phenanthroline groups were stepwise synthesized on an Fe3O4 substrate and used as a tetradentate nitrogenous ligand for coordinating to copper ions. The obtained nanocomposite was well characterized using FT-IR, PXRD, TGA, EDAX, ICP-OES, EDX-mapping, SEM, TEM, VSM and BET analyses, which confirm the formation of a thermostable crystalline spherical particle morphology with the particle size in the range of 17 nm to 25 nm and a magnetization value of 42 emu g-1. Also, the catalytic activity of [Fe3O4@DAA-BTrzPhen-Cu(ii)] as a novel and magnetically separable heterogeneous nanocatalyst was evaluated in preparing various tetrasubstituted imidazole derivatives from one-pot four-component condensation of anilines, aldehydes, 1,2-diketones and ammonium acetate, and favorable products were produced with excellent yields. The stability, low Cu leaching, and heterogenous nature of the nanocatalyst were confirmed by hot-filtration and leaching tests. The copper based nanocatalyst could be easily recovered by magnetic field separation and recycled at least 8 times in a row without noticeable loss in its catalytic activity.

Heterogenization of heteropoly compounds: a review of their structure and synthesis

The heterogenization of different types of heteropoly compoundsviasix popular methods from those published over the past recent 15 years is reviewed.

Shape-dependent catalytic activity of Fe3O4 nanostructures under the influence of an external magnetic field for multicomponent reactions in aqueous media

Fe₃O₄ nanostructures were synthesized under external magnetic field, shown shape-dependent catalytic activity for the synthesis of imidazole derivatives in water.