A Novel One-Pot Method for Highly Regioselective Synthesis of Triazoloapyrimidinedicarboxylates Using Silica Sodium Carbonate

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.

Synthesis of pyrimidine-6-carbonitriles, pyrimidin-5-ones, and tetrahydroquinoline-3-carbonitriles by new superb oxovanadium(V)-[5,10,15,20-tetrakis(pyridinium)-porphyrinato]-tetra(tricyanomethanide) catalyst via anomeric based oxidation

Oxovanadium(V)-[5,10,15,20-tetrakis(pyridinium)-porphyrinato]-tetra(tricyanomethanide) [(VO)TPP][(TCM)₄] was designed, synthesized and characterized by various techniques such as FT-IR, EDX, SEM equipped with EDX mappings, CHN elemental analysis, ICP-OES, XRD, SEM, TEM, TGA, DTA, DRS, Kubelka-Munk function (Tauc's plot), and UV-Vis analyses. Then, [(VO)TPP][(TCM)₄] was used as a benign and expedient catalyst for the synthesis of numerous heterocyclic compounds such as 5-amino-7-(aryl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carbonitriles, 5-amino-7-(aryl)-[1,2,4]triazolo[1,5-a]pyrimidine-6-carbonitriles, 7-(aryl)-7,12-dihydro-5H-isochromeno[4,3-d][1,2,4]triazolo[1,5-a]pyrimidin-5-ones, and 4-(aryl)-2-(1H-indol-3-yl)-5,6,7,8-tetrahydroquinoline-3-carbonitriles under solvent-free conditions at 100 °C via a cooperative geminal-vinylogous anomeric based oxidation.

α-Aminoazoles/azines: key reaction partners for multicomponent reactions

Aromatic α-aminoazaheterocycles are the focus of significant investigations and exploration by researchers owing to their key role in diverse biological and physiological processes. The existence of their derivatives in numerous drugs and alkaloids is due to their heterocyclic nitrogenous nature. Therefore, the synthesis of a structurally diverse range of their derivatives through simple and convenient methods represents a vital field of synthetic organic chemistry. Multicomponent reactions (MCRs) provide a platform to introduce desirable structure diversity and complexity into a molecule in a single operation with a significant reduction in the use of harmful organic waste, and hence have attracted particular attention as an excellent tool to access these derivatives. This review covers the advances made from 2010 to the beginning of 2020 in terms of the utilization of α-aminoazaheterocycles as synthetic precursors in MCRs.

Strategies for synthesis of 1,2,4-triazole-containing scaffolds using 3-amino-1,2,4-triazole

1,2,4-Triazole-containing scaffolds are unique heterocyclic compounds present in an array of pharmaceuticals and biologically important compounds used in the drug-discovery studies against cancer cells, microbes, and various types of disease in the human body. This review article summarizes the pharmacological significance of the 1,2,4-triazole-containing scaffolds and highlights the latest strategies for the synthesis of these privileged scaffolds using 3-amino-1,2,4-triazole. This review stimulates further research to find new and efficient methodologies for accessing new 1,2,4-triazole-containing scaffolds which would be very useful for the discover of new drug candidates.

A three-component cyclocondensation reaction for the synthesis of new triazolo[1,5-a]pyrimidine scaffolds using 3-aminotriazole, aldehydes and ketene N,S-acetal

This study describes the use of 3-aminotriazole, different aldehydes and N-methyl-1-(methylthio)-2-nitroethenamine as a ketene N,S-acetal in a three-component condensation for the synthesis of a novel library of triazolo[1,5-a]pyrimidine scaffolds. The presence of trichloroacetic acid as a Brønsted-Lowry acidic promoter in acetonitrile or water solvent and room temperature condition resulting novel triazolo[1,5-a]pyrimidine systems named N-methyl-6-nitro-5-aryl-3,5-dihydro-[1, 2, 4]triazolo[1,5-a]pyrimidine-7-amine. The structure of products and direction of the N-cyclization could be confirmed using spectral data. The effect of various solvents on the progress of process was investigated in the paper. The presence of five nitrogen heteroatoms, the use of various aldehydes affording a range of skeletally distinct triazolo[1,5-a]pyrimidine-based heterocycles, the potency to create numerous hydrogen bonds in the product structure, and direction of cyclization are attractive features of this reaction.

A novel protocol for catalyst-free synthesis of fused six-member rings to triazole and pyrazole

Herein, an effectual, quick and novel method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine derivatives. This series of fused six-member rings to triazole and pyrazole was prepared via the catalyst-free reaction of dialkyl acetylenedicarboxylates and 3-substituted 1H-1,2,4-triazole or 3-amino-1H-pyrazole-4-carbonitrile. The structures of the prepared products were deduced from their Fourier-transform infrared, elemental analysis and proton and carbon-13 nuclear magnetic resonance spectral data. A novel and green method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine derivatives.

Aminoazole-Based Diversity-Oriented Synthesis of Heterocycles

The comprehensive review contains the analysis of literature data concerning reactions of heterocyclization of aminoazoles and demonstrates the application of these types of transformations in diversity-oriented synthesis. The review is oriented to wide range of chemists working in the field of organic synthesis and both experimental and theoretical studies of nitrogen-containing heterocycles.