Chemistry Of Pyrazoles Research Articles

The reaction of acetylenes with aldazines in the NaOBut/DMSO system: a contribution to the pyrazole chemistry

Arylacetylenes readily react with aromatic aldazines in superbase medium NaOBut/DMSO (1 vol% EtOH) at room temperature to afford mainly 4-arylmethyl-3,5-diaryl-1H- pyrazoles in up to 47% yield along with minor amounts of 1-arylmethyl-3,5-diaryl-1H-pyrazoles and 1,2-diaryl-1,2- bis(3,5-diaryl-1H-pyrazol-1-yl)ethanes. The reaction is rationalized as proceeding via the diazaallyl anions, the adducts of acetylenic carbanions to a C=N bond, which further undergo the proton transfer processes and intramolecular cyclization to the above pyrazole derivatives.

A Brief Review on Antimicrobial Potential of Pyrazoles (From 2010-2018)

In the last few decades, pyrazole chemistry has attracted chemists’ and biologists’ attention mainly due to the discovery of the interesting properties of a great number of pyrazole derivatives. The resulting proliferation of research literature reflects the enormous biological potential of pyrazole derivatives as antitumor, anti-inflammatory, anti-HIV and antimicrobial agents. This review focuses on research concerning the antimicrobial activity of pyrazole derivatives conducted from 2010-2018, and is intended to assist in the development of a new generation of antimicrobial drugs.

Microwave‐assisted Vilsmeier‐Haack synthesis of Pyrazole‐4‐carbaldehydes

AbstractThe synthesis of 4‐formylpyrazoles using Vilsmeier‐Haack reagent is a common protocol in pyrazole chemistry. An efficient microwave‐assisted synthesis of 4‐formylpyrazoles by employing Vilsmeier‐Haack reagent (OPC‐VH) derived from phthaloyl dichloride/dimethylformamide has been described. This method offers the advantages of operational simplicity, avoiding the use of POCl3 as toxic reagents and reuse of the by‐product in the preparation of phthaloyl dichloride.

Pyrazole-based compounds in chitosan liposomal emulsion for antimicrobial cotton fabrics

The chemistry of pyrazoles has gained increasing attention due to its diverse pharmacological properties such as antiviral, antagonist, antimicrobial, anticancer, anti-inflammatory, analgesic, anti-prostate cancer, herbicidal, acaricidal and insecticidal activities. 1-Phenyl pyrazole-3, 5-diamine, 4-[2-(4-methylphenyl) diazenyl] and 1H- pyrazole-3 (1), 5-diamine, 4-[2-(4-methylphenyl) diazenyl] (2) were synthesized, characterized and encapsulated into liposomal chitosan emulsions for textile finishing. The chemical modifications of cotton fabrics were demonstrated by infrared analysis. Retention of the fabric mechanical properties was investigated by reporting the tensile strength values. Synthesized pyrazole-based compounds were screened for cytotoxicity against skin fibroblast cell line and showed very limited toxicity for both compounds. Antimicrobial potentials of the treated cotton fabrics were tested against bacterial strains E. coli ATCC 8379 and Staphylococcus aureus ATCC 25923.

Synthesis of Pyrazoles via Electrophilic Cyclization of Alkynes Containing Thiophene

Background: Pyrazole is a simple aromatic ring an organic compound of the heterocyclic series that characterized five-membered ring structure which comprises located adjacent two nitrogen atoms and three carbon atoms. In recent years interest in the pyrazole chemistry excessively has increased due to many a wide range of properties. Because they have a wide range of specific properties such as biological activities, pharmaceutical i.e., Pyrazoles were also applied successfully in many fields; medicine, agricultural, industry, pharmaceutical chemistry so that pyrazole chemistry was quite an interesting area of research for the synthesis of their derivatives and investigates new methods. Methods: Research and online content related to synthesis pyrazole and electrophilic cyclization of molecules are reviewed. Excerpts are used to illustrate key themes about chemistry of organic substances bearing pyrazole group. All the solvents and chemical materials were purchased. All the reagents were used directly without purification. Results: The new substitute α,β-alkynic hydrazones was prepared by heating directly from thiophene-2-acetyl chloride and terminal alkyne via a palladium-catalyzed coupling reaction then a series of the new substituted pyrazole derivatives were converted via electrophilic cyclization by catalyst and characterizations of each compound were indicated by the help of spectral data. Conclusion: The new different substitute pyrazoles were synthesized via copper mediated electrophilic cyclization. Firstly, the various hydrazones derivatives were carried out by the condensation reactions of the propargyl ketone that prepared from phenyl acetylene and acyl chloride with hydrazines. The various pyrazoles contain that thiophene were obtained by electrophilic cyclization copper(I) iodide and the various hydrazones. In addition, synthesized of substitute pyrazoles may be apply the other fields because of their diverse and potent biological properties. For this reason, the syntheses of different pyrazole compounds are becoming more importance. Keywords: Alkyne, electrophilic cyclization, hydrazine, hydrazone, pyrazole.

ChemInform Abstract: Recent Advances in the Chemistry of Pyrazoles. Part 2. Reactions and N‐Heterocyclic Carbenes of Pyrazole

AbstractReview: 144 refs.

ChemInform Abstract: Recent Advances in the Chemistry of Pyrazoles. Properties, Biological Activities, and Syntheses

AbstractReview: 276 refs.

Recent Advances in the Chemistry of Pyrazoles. Part 2. Reactions and N-Heterocyclic Carbenes of Pyrazole

This review article summarizes progress in N-alkylations, N-alkenylations, N-and C-arylations and hetarylations, halogenations, as well as organometallic chemistry of pyrazoles mainly achieved during the last decade. In addition, the generation and chemistry of N-heterocyclic carbenes of pyrazole (pyrazol-3-ylidenes) and remote N-heterocyclic carbenes of pyrazole (pyrazol-4-ylidenes) are described.

Recent Advances in the Chemistry of Pyrazoles. Properties, Biological Activities, and Syntheses

Recent Advances in the Chemistry of Pyrazoles. Properties, Biological Activities, and Syntheses

Pyrazole Complexes and Supramolecular Chemistry

AbstractThis Microreview deals with the supramolecular chemistry of pyrazole metal complexes, in particular, complexes of pyrazoles with a nonsubstituted N–H group, which are able to engage in hydrogen bonding. The most pertinent general features of pyrazoles, in comparison with other heterocycles that are also popular ligands, and some aspects of the supramolecular chemistry of free pyrazoles are also included. In addition to the general supramolecular chemistry of pyrazole complexes, sections of this Microreview are devoted to liquid crystals, self‐assembled species, and hosts for anions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

ChemInform Abstract: Five Membered Ring Systems: With More than One N Atom

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Pyrazole chemistry. Part 4. Directed lithiation of 4-bromo-1-phenyl-sulphonylpyrazole: a convenient approach to vicinally disubstituted pyrazoles

4-Bromo-1 -phenylsulphonylpyrazole (10), obtained from 4-bromopyrazole (5) and benzenesulphonyl chloride, can be metallated regioselectively by phenyl-lithium to give the 5-lithio derivative (15) which upon quenching with appropriate electrophiles leads to the 4-bromo-1 -phenylsulphonyl-5-substituted pyrazoles (16)–(23), (25), and (26). Compounds (22), (23), and (25) were found to undergo isomerisation to afford the thermodynamically more stable 4-bromo-1 -phenylsulphonyl-3-substituted pyrazoles (11), (24), and (13) under the reaction conditions applied. The phenylsulphonyl protecting group then can be removed readily under alkaline conditions to yield the corresponding 4-, bromo-3(5)-substituted 1H-pyrazoles (6), (9), (28), (29), and (30).

Degenerate group movements. Degenerate acyl migrations in pyrazole chemistry

Variable-temperature n.m.r. studies show the existence of degenerate NN-acyl migration in 1-anilinocarbonyl-3,5-dimethylpyrazole (Ia).

Carbon-13 n.m.r. Spectroscopy of pyrazole and some substituted pyrazoles

The use of carbon-13 n.m.r. spectroscopy in pyrazole chemistry is demonstrated, and the results are shown to be in agreement with previously known physicochemical data.