TSA-catalyzed regioselective synthesis of medicinally important 4-aryl-substituted dihydropyrimidine derivatives fused to pyrazole and triazole scaffolds via an efficient and green Domino reaction

Dihydroazolopyrimidines: Past, Present and Perspectives in Synthesis, Green Chemistry and Drug Discovery

Dihydroazolopyrimidines are an important class of heterocycles that are isosteric to natural purines and are therefore of great interest primarily as drug-like molecules. In contrast to the heteroaromatic analogs, synthetic approaches to these compounds were developed much later, and their chemical properties and biological activity have not been studied in detail until recently. In the review, different ways to build dihydroazolopyrimidine systems from different building blocks are described - via the initial formation of a partially hydrogenated pyrimidine ring or an azole ring, as well as a one-pot assembly of azole and azine fragments. Special attention is given to modern approaches: multicomponent reactions, green chemistry, and the use of non-classical activation methods. Information on the chemical properties of dihydroazolopyrimidines and the prospects for their use in the design of drugs of various profiles are also summarized in this review.

Nanocrystalline ZnO: A Competent and Reusable Catalyst for the Preparation of Pharmacology Relevant Heterocycles in the Aqueous Medium

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Nanoparticle catalyzed synthesis is a green and convenient method to achieve most of the chemical transformations in water or other green solvents. Nanoparticle ensures an easy isolation process of catalyst as well as products from the reaction mixture avoiding the hectic work up procedure. Zinc oxide is a biocompatible, environmentally benign and economically viable nanocatalyst with effectivity comparable to the other metal nanocatalyst employed in several reaction strategies. This review mainly focuses on the recent applications of zinc oxide in the synthesis of biologically important heterocyclic molecules under sustainable reaction conditions.

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Application of zinc oxide in organic synthesis: Considering the achievable advantages of this nanocatalyst, presently several research groups are paying attention in anchoring zincoxide or its modified structure in several types of organic conversions e.g. multicomponent reactions, ligand-free coupling reactions, cycloaddition reaction, etc. The advantages and limitations of this nanocatalyst are also demonstrated. The present study aims to highlight the recent multifaceted applications of ZnO towards the synthesis of diverse heterocyclic motifs. Being a promising biocompatible nanoparticle, this catalyst has an important contribution in the fields of synthetic chemistry and medicinal chemistry.

A nanocatalyst-assisted protocol to the synthesis of bis(pyrazolyl) methane derivatives bearing aroyl groups by the use of arylglyoxals in the presence of ZnO nanowires as a highly efficient, recyclable, and green catalyst

An efficient, promoted three-component (2+1) catalytic reaction between 3-methyl-1-phenyl-2-pyrazolin-5-one and arylglyoxal derivatives is described by the use of zinc oxide nanowires (ZnO NWs) as a green catalyst. By this achievement, some newly prepared bis(pyrazolyl)methane derivatives containing an aroyl group have been obtained. Starting materials were successfully condensed to obtain target products via three C–C bond formation in the presence of ZnO NWs as an efficient, cost-effective, environmentally friendly, and recyclable nanocatalyst. All synthesized products were obtained with good to excellent yields, and their structures were deduced by FTIR, 1H NMR, and 13C NMR spectroscopies and CHNS elemental analyses. It was shown that ZnO NWs can be separated, recovered after each run, and reused in further cycles (up to six runs) without significant loss of activity.

Tungstic acid-functionalized Fe3O4@TiO2: preparation, characterization and its application for the synthesis of pyrano[2,3-c]pyrazole derivatives as a reusable magnetic nanocatalyst

A new nanocatalyst based on the immobilization of tungstic acid onto 3-chloropropyl-grafted TiO₂-coated Fe₃O₄ nanoparticles (Fe₃O₄@TiO₂@(CH₂)₃OWO₃H) was prepared, characterized, and applied for the synthesis of pyrano[2,3-c]pyrazoles.