Cesium salt of 2-molybdo-10-tungstophosphoric acid as an efficient and reusable catalyst for the synthesis of uracil derivatives via a green route

Multicomponent synthesis of pyrimido[4,5-b] quinolines over a carbocationic catalytic system

Trityl chloride (TrCl) was efficiently used as a neutral catalyst for the multicomponent cyclization reaction of an aldehyde with dimedone and 6-amino-1,3-dimethyluracil for the preparation of pyrimido[4,5-b] quinolines in chloroform under reflux condition.

Cesium salt of tungstophosphoric acid/mesoporous (zirconia-silica) composite for highly efficient synthesis of 7-hydroxy-4-methyl coumarin and removal of methylene blue

The removal of harmful organic dyes from aqueous solutions has drawn the attention of scientists because of the substantial threat they pose to society's worldwide health. Hence, it is crucial to design an adsorbent that is both very effective in removing dyes and has the benefit of being inexpensive. In the present work, Cs salts of tungstophosphoric acid (CPW) supported mesoporous Zr-mSiO₂ (mZS) with varying extents of Cs ions have been prepared by a two-step impregnation technique. Accordingly, a lowering in the surface acidity modes was observed after Cs exchanged protons of H₃W₁₂O₄₀ and formed salts immobilized on the mZS support. After exchanging the protons with Cs ions, the characterization results revealed that the primary Keggin structure was unaltered. Moreover, the Cs exchanged catalysts had higher surface area than the parent H₃W₁₂O₄₀/mZS, suggesting that Cs reacts with H₃W₁₂O₄₀ molecules to create new primary particles with smaller sizes possessing inter-crystallite centers with a higher dispersion degree. With an increase in Cs content and thus a decrease in the acid strength and surface acid density, the methylene blue (MB) monolayer adsorption capacities on CPW/mZS catalysts were increased and reached an uptake capacity of 359.9 mg g^-1 for Cs₃PW₁₂O₄₀/mZS (3.0CPW/mZS). The catalytic formation of 7-hydroxy-4-methyl coumarin was also studied at optimum conditions and it is found that the catalytic activity is influenced by the amount of exchangeable Cs with PW on the mZrS support, which is in turn influenced by the catalyst acidity. The catalyst kept approximately the initial catalytic activity even after the fifth cycle.

Silica supported lanthanum trifluoroacetate and trichloroacetate as an efficient and reusable water compatible Lewis acid catalyst for synthesis of 2,4,5-triarylimidazoles via a solvent-free green approach

In the present research article, we have developed solid heterogenous silica supported lanthanum trifluoroacetate and trichloroacetate as green Lewis acid catalysts. These catalysts were synthesized by a novel, simple, cheap, clean, and environment friendly method. The physicochemical properties of the prepared catalysts were well studied and characterized by sophisticated spectroscopic techniques such as FTIR, TGA, XRD, EDX, SEM, TEM and BET analysis. The catalyst was utilized in the synthesis of arylimidazole derivatives via green protocols under solvent-free conditions at 70 °C with a higher yield, mild reaction conditions and a short reaction time. The catalyst works superiorly in water as well as in various organic solvents as a reusable and easily recoverable catalyst.