Journal articles: 'Pyrazoles'

1

Alsayari, Abdulrhman, Abdullatif Bin Muhsinah, Yahya I. Asiri, Jaber Abdullah Alshehri, Yahia N. Mabkhot, Mohammad Y. Alfaifi, Serag Eldin I. Elbehairi, Mater H. Mahnashi, and Mohd Zaheen Hassan. "Arylhydrazono/Aryldiazenyl Pyrazoles: Green One-Pot Solvent-Free Synthesis and Anticancer Evaluation." Letters in Organic Chemistry 17, no. 10 (November 17, 2020): 772–78. http://dx.doi.org/10.2174/1570178617666200320104923.

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The aim of this study was to synthesize and evaluate the biological activity of pyrazole derivatives, in particular, to perform a “greener” one-pot synthesis using a solvent-free method as an alternative strategy for synthesizing hydrazono/diazenyl-pyridine-pyrazole hybrid molecules with potential anticancer activity. Effective treatment for all types of cancers is still a long way in the future due to the severe adverse drug reactions and drug resistance associated with current drugs. Therefore, there is a pressing need to develop safer and more effective anticancer agents. In this context, some hybrid analogues containing the bioactive pharmacophores viz. pyrazole, pyridine, and diazo scaffolds were synthesized by one-pot method. Herein, we describe the expedient synthesis of pyrazoles by a onepot three-component condensation of ethyl acetoacetate/acetylacetone, isoniazid, and arenediazonium salts under solvent-free conditions, and the evaluation of their cytotoxicity using a sulforhodamine B assay on three cancer cell lines. Molecular docking studies employing tyrosine kinase were also carried out to evaluate the binding mode of the pyrazole derivatives under study. 1-(4-Pyridinylcarbonyl)-3- methyl-4-(2-arylhydrazono)-2-pyrazolin-5-ones and [4-(2-aryldiazenyl)-3,5-dimethyl-1H-pyrazol-1- yl]-4-pyridinylmethanones, previously described, were prepared using an improved procedure. Among these ten products, 1-isonicotinoyl-3-methyl-4-[2-(4-nitrophenyl)hydrazono]-2-pyrazolin-5-one (1f) displayed promising anticancer activity against the MCF-7, HepG2 and HCT-116 cell lines, with an IC50 value in the range of 0.2-3.4 μM. In summary, our findings suggest that pyrazoles containing hydrazono/ diazenyl and pyridine pharmacophores constitute promising scaffolds for the development of new anticancer agents.

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Elnagdi, Mohamed Hilmy, Ahmed Hafez Hussien Elghandour, Kamal Usef Sadek, and Mahmoud Mohamed Mahfouz Ramiz. "Studies on Condensed Pyrazoles. A New Route for Synthesis of Pyrazolo[4,3-c]pyrazoles." Zeitschrift für Naturforschung B 44, no. 8 (August 1, 1989): 951–54. http://dx.doi.org/10.1515/znb-1989-0816.

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A novel synthesis of pyrazolo[4,3-c]pyrazoles via 1,5-dipolar cyclization of products of coupling of 2,3-dimethyl-1-phenyl-5-oxo-3-pyrazolin-4-diazonium chloride with active methylene reagents is reported.

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Chauhan, Pankaj, Suruchi Mahajan, and Dieter Enders. "Asymmetric synthesis of pyrazoles and pyrazolones employing the reactivity of pyrazolin-5-one derivatives." Chemical Communications 51, no. 65 (2015): 12890–907. http://dx.doi.org/10.1039/c5cc04930j.

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The various catalytic asymmetric strategies employing organo- and metal-catalysts utilized pyrazolin-5-one derivatives for the synthesis of potentially bioactive enantiopure pyrazoles and pyrazolones are presented.

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Lin, Wei-Syuan, and Shigeki Kuwata. "Recent Developments in Reactions and Catalysis of Protic Pyrazole Complexes." Molecules 28, no. 8 (April 17, 2023): 3529. http://dx.doi.org/10.3390/molecules28083529.

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Protic pyrazoles (N-unsubstituted pyrazoles) have been versatile ligands in various fields, such as materials chemistry and homogeneous catalysis, owing to their proton-responsive nature. This review provides an overview of the reactivities of protic pyrazole complexes. The coordination chemistry of pincer-type 2,6-bis(1H-pyrazol-3-yl)pyridines is first surveyed as a class of compounds for which significant advances have made in the last decade. The stoichiometric reactivities of protic pyrazole complexes with inorganic nitrogenous compounds are then described, which possibly relates to the inorganic nitrogen cycle in nature. The last part of this article is devoted to outlining the catalytic application of protic pyrazole complexes, emphasizing the mechanistic aspect. The role of the NH group in the protic pyrazole ligand and resulting metal–ligand cooperation in these transformations are discussed.

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Queiroz, Jaqueline E., Lucas D. Dias, Giuliana M. Vila Verde, Gilberto L. B. Aquino, and Ademir J. Camargo. "An Update on the Synthesis and Pharmacological Properties of Pyrazoles Obtained from Chalcone." Current Organic Chemistry 26, no. 2 (January 2022): 81–90. http://dx.doi.org/10.2174/1385272826666220119110347.

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Abstract: A review concerning the synthesis and pharmacological properties of pyrazoles obtained from Chalcone described in the literature over the last 5 years (2016-2020) was presented and discussed. Among the synthetic approaches for pyrazoles described so far, the cyclization and acetylation method of α,β-unsaturated chalcones, and substituted hydrazine were selected and analyzed. 105 pyrazole derivatives (3-107) were evaluated as well as their pharmacological activities, namely, antineoplastic, anti-inflammatory, antioxidant, antibacterial, antifungal, antimycobacterial, antiplasmodial, Alzheimer's disease, enzymes inhibition (like acetylcholinesterase, carbonic anhydrase, and malonyl CoA decarboxylase), anticonvulsant, among others. Pyrazolic compounds are widely used in the design of the new drug with a wide spectrum of pharmacological approaches. Therefore, it is relevant to research the synthetic methods and therapeutic properties of different pyrazole derivatives.

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Milišiūnaitė, Vaida, Rūta Paulavičiūtė, Eglė Arbačiauskienė, Vytas Martynaitis, Wolfgang Holzer, and Algirdas Šačkus. "Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction." Beilstein Journal of Organic Chemistry 15 (March 14, 2019): 679–84. http://dx.doi.org/10.3762/bjoc.15.62.

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Fused pyrazole ring systems are common structural motifs of numerous pharmaceutically important compounds. Nevertheless, access to derivatives of the aromatic 2H-furo[2,3-c]pyrazole ring system is still quite limited, and their chemistry and functional properties remain largely underexplored. The current study investigates routes to construct this system from easily accessible starting materials using metal-catalyzed reactions. A simple and efficient procedure to access the 2H-furo[2,3-c]pyrazole ring system was developed by employing the silver(I) ion-mediated ring-closure reaction of 4-alkynyl-3-hydroxy-1-phenyl-1H-pyrazoles as a key step. The required intermediate hydroxyalkynyl substrates for this reaction were prepared by a Pd-catalyzed coupling of 4-iodo-1-phenyl-1H-pyrazol-3-ol with ethyne derivatives. The structures of the obtained target compounds were unequivocally confirmed by detailed 1H, 13C and 15N NMR spectroscopic experiments, HRMS and a single-crystal X-ray diffraction analyses. This silver(I)-mediated 5-endo-dig cyclization of readily available 4-alkynyl-3-hydroxy-1H-pyrazoles can be used as an efficient method to access many novel 2,5-disubstituted 2H-furo[2,3-c]pyrazoles.

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7

Lam, Linh, Sang H. Park, and Joseph Sloop. "Synthesis and Characterization of 3-Methyl-1-(4-(trifluoromethyl)phenyl)indeno [1,2-c]pyrazol-4(1H)-one." Molbank 2022, no. 4 (November 7, 2022): M1483. http://dx.doi.org/10.3390/m1483.

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Pyrazoles have potential applications in the agrochemical and medicinal chemistry industries as pesticides, anti-inflammatory medications, and antitumor drugs. Fluorinated fused-ring pyrazoles may also possess medicinally useful properties. Herein, we report the acid-catalyzed synthesis of a new tricyclic, trifluoromethylated indenopyrazole, 3-methyl-1-(4-(trifluoromethyl)phenyl)indeno[1,2-c]pyrazol-4(1H)-one, from 2-acetyl-1,3-indanedione and 4-trifluoromethylphenylhydrazine. This isomeric pyrazole was obtained in yields ranging from 4–24%. NMR spectroscopic characterization and elemental analysis support the structural assignment, identity, and purity of the product.

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8

Lindsay-Scott, Peter J., and Eloise Rivlin-Derrick. "Regiocontrolled Synthesis of 6,7-Dihydro-4H-pyrazolo[5,1-c][1,4]oxazines." Synthesis 52, no. 01 (October 8, 2019): 105–18. http://dx.doi.org/10.1055/s-0037-1610734.

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Synthetic access to 6,7-dihydro-4H-pyrazolo[5,1-c][1,4]oxazines has been achieved in 3–4 steps from commercially available pyrazoles. Optimization of a protected hydroxyethyl group on N1 enabled the regiocontrolled construction of pyrazole-5-aldehydes in high yields; subsequent deprotection and reduction generated fused heterocyclic scaffolds bearing multiple substitution patterns. Moreover, the intermediate pyrazole lactols were shown to be versatile synthetic building blocks.

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Mantzanidou, Martha, Eleni Pontiki, and Dimitra Hadjipavlou-Litina. "Pyrazoles and Pyrazolines as Anti-Inflammatory Agents." Molecules 26, no. 11 (June 5, 2021): 3439. http://dx.doi.org/10.3390/molecules26113439.

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The five-membered heterocyclic group of pyrazoles/pyrazolines plays important role in drug discovery. Pyrazoles and pyrazolines present a wide range of biological activities. The synthesis of the pyrazolines and pyrazole derivatives was accomplished via the condensation of the appropriate substituted aldehydes and acetophenones, suitable chalcones and hydrazine hydrate in absolute ethanol in the presence of drops of glacial acetic acid. The compounds are obtained in good yields 68–99% and their structure was confirmed using IR, 1H-NMR, 13C-NMR and elemental analysis. The novel derivatives were studied in vitro for their antioxidant, anti-lipid peroxidation (AAPH) activities and inhibitory activity of lipoxygenase. Both classes strongly inhibit lipid peroxidation. Compound 2g was the most potent lipoxygenase inhibitor (IC50 = 80 µM). The inhibition of the carrageenin-induced paw edema (CPE) and nociception was also determined, with compounds 2d and 2e being the most potent. Compound 2e inhibited nociception higher than 2d. Pyrazoline 2d was found to be active in a preliminary test, for the investigation of anti-adjuvant-induced disease (AID) activity. Pyrazoline derivatives were found to be more potent than pyrazoles. Docking studies of the most potent LOX inhibitor 2g highlight hydrophobic interactions with VAL126, PHE143, VAL520 and LYS526 and a halogen bond between the chlorine atom and ARG182.

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10

Warkentin, John, and John Mck R. Woollard. "Photolysis of 5,5-dibenzyl-Δ3-1,3,4-oxadiazolines." Canadian Journal of Chemistry 75, no. 3 (March 1, 1997): 289–307. http://dx.doi.org/10.1139/v97-033.

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Photolysis of dibenzyl-Δ3-1,3,4-oxadiazolines (3) in the presence of dimethyl acetylenedicarboxylate (DMAD) gives only modest yields of the expected symmetrical 3,3-dibenzylcyclopropenes (4), but these are accompanied by more than six by-products, including unsymmetrical cyclopropenes, methylenecyclopropanes, and various pyrazoles. The origin of this array of products can be explained by a series of steps starting with photolysis of 3 to form a diazoalkane that undergoes 1,3-dipolar cycloaddition to DMAD, generating a 3H-pyrazole as initial product. The latter is further photolyzed to a symmetrical cyclopropene in competition with benzyl group migration by thermal 1,5-sigmatropic or ion-pair rearrangement to afford a 4H-pyrazole. The 4H-pyrazole in turn undergoes photolysis to an unsymmetrical cyclopropene, which rearranges to a methylenecyclopropane. The 4H-pyrazole also undergoes autoxidation, in the presence of air, to afford a benzoyl-4H-pyrazole. Additionally, in competition with rearrangement, the various pyrazoles lose a benzyl group or a methoxycarbonyl group to afford pyrazoles with one less substituent. Keywords: 5,5-dibenzyl-Δ3-1,3,4-oxadiazolines, photolysis of; 3,3-dibenzyl-3H-pyrazoles, rearrangement of; 3,4-dibenzyl-4H-pyrazoles, autoxidation of; 3,4-dibenzyl-4H-pyrazoles, photolysis of; cyclopropenes, rearrangement to methylenecyclopropanes.

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11

Andicsová, Anita, Angelika Lásiková, Marek Fronc, Jozef Kožíšek, and Daniel Végh. "3-(2-Heteroaryl)-pyrazolotetrazoles – a subunits for losartan-like structures." Acta Chimica Slovaca 5, no. 2 (November 1, 2012): 220–24. http://dx.doi.org/10.2478/v10188-012-0033-z.

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Abstract A modification of biphenylyltetrazole moiety of Losartan (A) by 3-(2-heteroaryl)-pyrazolotetrazole (B) is described. Ketone semicarbazones react with two moles of phosphorus oxychloride-dimethylformamide with the formation of 3-substituted pyrazol-4-carbaldehydes. The transformations of 3-substituted pyrazole-4- carboxaldehydes to 3-substituted pyrazole-4-nitriles were carried out by reaction of hydroxylamine in DMFA. The prepared cyano pyrazoles were converted to tetrazoles by heating with trimethylsilylazide and dibuthyltinoxide in toluene.

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12

Hartwig de Oliveira, Daniela, Fernanda Severo Sabedra Sousa, Paloma Taborda Birmann, Ana Paula Pesarico, Diego Alves, Raquel Guimarães Jacob, and Lucielli Savegnago. "Evaluation of antioxidant activity and toxicity of sulfur- or selenium-containing 4-(arylchalcogenyl)-1H-pyrazoles." Canadian Journal of Physiology and Pharmacology 98, no. 7 (July 2020): 441–48. http://dx.doi.org/10.1139/cjpp-2019-0356.

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Pyrazoles represent a significant class of heterocyclic compounds that exhibit pharmacological properties. The present study aimed to investigate the antioxidant potential of pyrazol derivative compounds in brain of mice in vitro and the effect of pyrazol derivative compounds in the oxidative damage and toxicity parameters in mouse brain and plasma of mice. The compounds tested were 3,5-dimethyl-1-phenyl-4-(phenylselanyl)-1H-pyrazol (1a), 3,5-dimethyl-4-(phenylselanyl)-1H-pyrazole (2a), 4-((4-methoxyphenyl)selanyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (3a), 4-((4-chlorophenyl)selanyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (4a), 3,5-dimethyl-1-phenyl-4-(phenylthio)-1H-pyrazole (1b), 3,5-dimethyl-4-(phenylthio)-1H-pyrazole (2b), 4-((4-methoxyphenyl)thio)-3,5-dimethyl-1-phenyl-1H-pyrazole (3b), 4-((4-chlorophenyl)thio)-3,5-dimethyl-1-phenyl-1H-pyrazole (4b), and 3,5-dimethyl-1-phenyl-1H-pyrazole (1c). In vitro, 4-(arylcalcogenyl)-1H-pyrazoles, at low molecular range, reduced lipid peroxidation and reactive species in mouse brain homogenates. The compounds also presented ferric-reducing ability as well nitric oxide-scavenging activity. Especially compounds 1a, 1b, and 1c presented efficiency to 1,1-diphenyl-2-picryl-hydrazyl-scavenging activity. Compounds 1b and 1c presented 2,20 -azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)-scavenging activity. In vivo assays demonstrated that compounds 1a, 1b, and 1c (300 mg/kg, intragastric, a single administration) did not cause alteration in the of δ-aminolevulinic acid dehydratase activity, an enzyme that exhibits high sensibility to prooxidants situations, in the brain, liver, and kidney of mice. Compound 1c reduced per se the lipid peroxidation in liver and brain of mice. Toxicological assays demonstrate that compounds 1a, 1b, and 1c did not present toxicity in the aspartate aminotransferase, alanine aminotransferase, urea, and creatinine levels in the plasma. In conclusion, the results demonstrated the antioxidant action of pyrazol derivative compounds in in vitro assays. Furthermore, the results showed low toxicity of compounds in in vivo assays.

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Sophy, Mohamed Ahmed Elian, and Mohamed Ahmed Mahmoud Abdel Reheim. "Synthesis of Some New 1, 3, 4-Oxadiazole, Pyrazole, and Pyrimidine Bearing Thienopyrazole Moieties." Current Organic Synthesis 17, no. 8 (October 28, 2020): 661–70. http://dx.doi.org/10.2174/1570179417999200730215318.

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Aim and Objective: According to the literature survey, pyrazole is a unique template that is associated with several biological activities. This article highlighted the research work of many researchers reported in the literature for synthesis and different pharmacological activities of the pyrazole nucleus. In the present work, pyrazol- 3-one 1 was reacted with cyanoacetic acid hydrazide and elemental sulfur to afford the corresponding thieno[3,2-c]pyrazol-6-carbohydrazide 3 derivatives. The latter compound reacted with some electrophilic reagents such as DMF-DMA, triethylorthoformate, arylidenemalononitriles and chalcones under neat conditions to give substituted oxadiazole and pyrazole, respectively. The treatment of compound 3 with active methylene reagents such as acetylacetone, diethylmalonate, ethyl acetoacetate and ethyl cyanoacetate under suitable conditions afforded pyrazole derivatives 10, 11, 13, and 15, respectively. Novel pyrazolothienopyrimidine 27 and 30 were prepared from precursor 26 with carbon disulfide and triethylorthoformate, respectively. The chemical structures of the newly synthesized compounds were established by elemental and spectral analyses including IR, and 1HNMR in addition to 13C-NMR and mass spectra. Materials and Methods: A novel substituted pyrazole, pyrimidine and pyrazolothienopyrimidine were obtained via Gewald synthesis of thiophene and fused thiophene and Mannich reactions of 5-amino-3-phenyl-1Hthieno[ 3,2-c]pyrazole-6-carbohydrazide. Results and Discussion: A series of some newly azoles and azines were prepared via reaction of thieno[3,2- c]pyrazol-6-carbohydrazide derivative 3 as starting material with some electrophilic and nucleophilic reagents. The structures of target compounds were established by elemental analyses and spectral data. Conclusion: Pyrazole is a unique template that is associated with several biological activities. This article highlighted the research work of many researchers reported in the literature for synthesis and different pharmacological activities of the pyrazole nucleus. In the current investigation, we have developed new and efficient methods for the synthesis of thieno[3,2-c]pyrazol-6-carbohydrazide derivatives. In addition, we have explored the preparative potential of these substances as intermediates for the synthesis of substituted pyrazoles and fused pyrazoles 10-30, respectively.

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Bertolasi, Valerio, Paola Gilli, Valeria Ferretti, Gastone Gilli, and Cristina Fernàndez-Castaño. "Self-assembly of NH-pyrazoles via intermolecular N—H...N hydrogen bonds." Acta Crystallographica Section B Structural Science 55, no. 6 (December 1, 1999): 985–93. http://dx.doi.org/10.1107/s0108768199004966.

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The crystal structures of two NH-pyrazole derivatives forming intermolecular N—H...N hydrogen bonds are reported: 5-methyl-4-(3-methylpyrazol-5-yl)pyrazol-3-ol, C8H10N4O (P1), and 3-methyl-5-dihydro-1H-naphtho[1,2-d]pyrazole hemihydrochloride, C12H12N2.-C12H13N_{2}^{+}.Cl− (P2). 26 other structures are surveyed in order to obtain a deeper insight into the ways NH-pyrazoles self-assemble by means of intermolecular N—H...N hydrogen bonds in molecular crystals. A limited number of compounds form chains or dimers via homonuclear N+—H...N positive-charge-assisted hydrogen bonds, typical of proton sponges, which can be remarkably short [e.g. N...N 2.714 (3), N—H 1.09 (3), H...N 1.63 (3) Å, N—H...N 169 (3)° in (P2)]. Most pyrazoles, however, pack via neutral N—H...N bonds which are formally assisted by resonance (resonance-assisted hydrogen bond, RAHB) through the ...N=C—C=C—NH... iminoenamine fragment, contained in the ring, giving rise to dimers, trimers, tetramers and infinite chains of pyrazole molecules. Surprisingly, the resonance does not appear to shorten the N—H...N bond with respect to the accepted mean value N...N 2.97 (10) Å for non-resonant N—H...N bonds. It is shown that this is due to the internal π-delocalization of the pyrazole ring, which can be hardly increased by the hydrogen-bond interaction, except in symmetrically 3,5-substituted pyrazoles which display N...N distances as short as 2.82 Å, identical C—C and C—N distances in the two halves of the pyrazole molecule, and typical phenomena of N—H...N dynamical proton disorder, detectable by 15N-CP/MAS solid-state NMR.

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15

Usami, Yoshihide, Kodai Sumimoto, Azusa Kishima, Yuya Tatsui, Hiroki Yoneyama, and Shinya Harusawa. "Synthesis of Dihydropyrano[3,2-c]pyrazoles via Double Bond Migration and Ring-Closing Metathesis." Molecules 24, no. 2 (January 15, 2019): 296. http://dx.doi.org/10.3390/molecules24020296.

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Three types of pyrazole-fused heterobicycles, i.e., 1,5-, 1,7-, and 2,5-dihydropyrano[3,2-c]pyrazoles, were synthesized from 4-allyloxy-1H-pyrazoles. A sequence of the Claisen rearrangement of 4-allyloxy-1H-pyrazoles, ruthenium-hydride-catalyzed double bond migration, O-allylation, and ring-closing metathesis was employed in this study.

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Alsayari, Abdulrhman, Yahya I. Asiri, Abdullatif Bin Muhsinah, and Mohd Zaheen Hassan. "Anticolon Cancer Properties of Pyrazole Derivatives Acting through Xanthine Oxidase Inhibition." Journal of Oncology 2021 (July 5, 2021): 1–5. http://dx.doi.org/10.1155/2021/5691982.

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Background. Pyrazoles are an interesting class of compounds showing potent anticancer activities. Our previous studies have demonstrated the potent anticancer activity of pyrazole analogues. Therefore, we focused on developing anticancer agents through structure optimization of the pyrazolyl lead molecule. Methods. The pyrazole derivatives were prepared by the appropriate synthetic protocols. The antiproliferative activities were evaluated using a sulforhodamine B assay against three cancer cell lines. In vitro and in silico molecular docking studies employing xanthine oxidase were used to explore the mechanism by which pyrazole derivatives exert anticancer effects. Results. One of the pyrazole derivatives demonstrated the greatest promise as an anticancer agent against the human colon cancer cell line (IC50 4.2 μM), with a potent xanthine oxidase inhibitory activity (IC50 0.83 μM). Conclusion. In summary, our findings suggest that these pyrazolyl analogues containing a pyridine nucleus could serve as a promising lead molecule in the development of novel anticancer agents.

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Santos, Nádia E., Ana R. F. Carreira, Vera L. M. Silva, and Susana Santos Braga. "Natural and Biomimetic Antitumor Pyrazoles, A Perspective." Molecules 25, no. 6 (March 17, 2020): 1364. http://dx.doi.org/10.3390/molecules25061364.

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The present review presents an overview of antitumor pyrazoles of natural or bioinspired origins. Pyrazole compounds are relatively rare in nature, the first ones having been reported in 1966 and being essentially used as somniferous drugs. Cytotoxic pyrazoles of natural sources were first isolated in 1969, and a few others have been reported since then, most of them in the last decade. This paper presents a perspective on the current knowledge on antitumor natural pyrazoles, organized into two sections. The first focuses on the three known families of cytotoxic pyrazoles that were directly isolated from plants, for which the knowledge of the medicinal properties is in its infancy. The second section describes pyrazole derivatives of natural products, discussing their structure–activity relationships.

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Secrieru, Alina, Paul Michael O’Neill, and Maria Lurdes Santos Cristiano. "Revisiting the Structure and Chemistry of 3(5)-Substituted Pyrazoles." Molecules 25, no. 1 (December 20, 2019): 42. http://dx.doi.org/10.3390/molecules25010042.

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Pyrazoles are known as versatile scaffolds in organic synthesis and medicinal chemistry, often used as starting materials for the preparation of more complex heterocyclic systems with relevance in the pharmaceutical field. Pyrazoles are also interesting compounds from a structural viewpoint, mainly because they exhibit tautomerism. This phenomenon may influence their reactivity, with possible impact on the synthetic strategies where pyrazoles take part, as well as on the biological activities of targets bearing a pyrazole moiety, since a change in structure translates into changes in properties. Investigations of the structure of pyrazoles that unravel the tautomeric and conformational preferences are therefore of upmost relevance. 3(5)-Aminopyrazoles are largely explored as precursors in the synthesis of condensed heterocyclic systems, namely pyrazolo[1,5-a]pyrimidines. However, the information available in the literature concerning the structure and chemistry of 3(5)-aminopyrazoles is scarce and disperse. We provide a revision of data on the present subject, based on investigations using theoretical and experimental methods, together with the applications of the compounds in synthesis. It is expected that the combined information will contribute to a deeper understanding of structure/reactivity relationships in this class of heterocycles, with a positive impact in the design of synthetic methods, where they take part.

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Lellek, Vit, Cheng-yi Chen, Wanggui Yang, Jie Liu, Xuebao Ji, and Roger Faessler. "An Efficient Synthesis of Substituted Pyrazoles from One-Pot Reaction of Ketones, Aldehydes, and Hydrazine Monohydrochloride." Synlett 29, no. 08 (February 15, 2018): 1071–75. http://dx.doi.org/10.1055/s-0036-1591941.

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An efficient, one-pot and metal-free process for the preparation of 3,5-disubstituted and 3,4,5-trisubstituted pyrazoles on multi-gram scale was developed. One-pot condensation of ketones, aldehydes and hydrazine monohydrochloride readily formed pyrazoline intermediates under mild conditions. Oxidation of pyrazolines, in situ, employing bromine afforded a wide variety of pyrazoles. The methodology offers a fast, and often chromatography-free protocol for the synthesis of 3,4,5-substituted pyrazoles in good to excellent yields. Alternatively, a more benign oxidation protocol affords 3,5-disubstituted or 3,4,5-trisubstituted pyrazoles by simply heating pyrazolines in DMSO under oxygen.

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Abaszadeh, Mehdi, Hassan Sheibani, and Kazem Saidi. "The Condensation of (Chlorocarbonyl)phenyl Ketene with Bisnucleophiles. Synthesis of 4-Hydroxy-5-phenylpyro-[2,3-c]pyrazol-6-ones and Formation of Pyrazolo[1,2-a]pyrazole-triones by Hydrogen Exchange in Unstable Mesoionic Compounds." Australian Journal of Chemistry 63, no. 1 (2010): 92. http://dx.doi.org/10.1071/ch09344.

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The addition of (chlorocarbonyl)phenyl ketene 2 to 5-alkylpyrazol-3(4H)-ones 1 led to the formation of 3-hydroxypyrazolo[1,2-a]pyrazole-dione/pyrazolo[1,2-a]pyrazole-trione derivatives 3. This is ascribed to hydrogen exchange in initially formed unstable, mesoionic pyrazolo[1,2-a]pyrazol-4-ium-5-olates. In contrast, condensation of the same ketene with 3-alkyl-1-phenyl-2-pyrazolin-5-ones 4 afforded 4-hydroxy-3-alkyl-1,5-diphenylpyrano[2,3-c]pyrazol-6-one derivatives 5. The latter reaction provides a new and rapid route to 4-hydroxy-2-pyrones fused to pyrazole rings, in good to excellent yields.

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Ramadan, El Sayed, Essam M. Sharshira, Ramadan I. El Sokkary, and Noussa Morsy. "Synthesis and antimicrobial evaluation of some heterocyclic compounds from 3-aryl-1-phenyl-1H-pyrazole-4-carbaldehydes." Zeitschrift für Naturforschung B 73, no. 6 (June 27, 2018): 389–97. http://dx.doi.org/10.1515/znb-2018-0009.

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AbstractA new series of chalcones, pyrazolinyl-pyrazoles, pyrazole-4-carbaldehyde oximes, pyrazole-4-carbonitriles, 5-pyrazolyl-1,2,4-triazolidine-3-thiones, and Knoevenagel condensation products was synthesized from 3-aryl-1-phenyl-1H-pyrazole-4-carbaldehydes. Most reactions were carried out either without solvent or in the presence of water as a green solvent. The structure of synthesized compounds was characterized by spectral and elemental analysis. The synthesized compounds were tested in vitro for their antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans in comparison with imipenem (intravenous β-lactam antibiotic) and clotrimazole (antifungal medication) as reference drugs by using the agar diffusion technique. 3-Aryl-1-phenyl-1H-pyrazole-4-carbonitriles 8b, 8c, and 8d showed significant antifungal activity against the fungus C. albicans.

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Urbonavičius, Arminas, Sonata Krikštolaitytė, Aurimas Bieliauskas, Vytas Martynaitis, Joana Solovjova, Asta Žukauskaitė, Eglė Arbačiauskienė, and Algirdas Šačkus. "Synthesis and Characterization of New Pyrano[2,3-c]pyrazole Derivatives as 3-Hydroxyflavone Analogues." Molecules 28, no. 18 (September 13, 2023): 6599. http://dx.doi.org/10.3390/molecules28186599.

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In this paper, an efficient synthetic route from pyrazole-chalcones to novel 6-aryl-5-hydroxy-2-phenylpyrano[2,3-c]pyrazol-4(2H)-ones as 3-hydroxyflavone analogues is described. The methylation of 5-hydroxy-2,6-phenylpyrano[2,3-c]pyrazol-4(2H)-one with methyl iodide in the presence of a base yielded a compound containing a 5-methoxy group, while the analogous reaction of 5-hydroxy-2-phenyl-6-(pyridin-4-yl)pyrano[2,3-c]pyrazol-4(2H)-one led to the zwitterionic 6-(N-methylpyridinium)pyrano[2,3-c]pyrazol derivative. The treatment of 5-hydroxy-2,6-phenylpyrano[2,3-c]pyrazol-4(2H)-one with triflic anhydride afforded a 5-trifloylsubstituted compound, which was further used in carbon–carbon bond forming Pd-catalyzed coupling reactions to yield 5-(hetero)aryl- and 5-carbo-functionalized pyrano[2,3-c]pyrazoles. The excited-state intramolecular proton transfer (ESIPT) reaction of 5-hydroxypyrano[2,3-c]pyrazoles from the 5-hydroxy moiety to the carbonyl group in polar protic, polar aprotic, and nonpolar solvents was observed, resulting in well-resolved two-band fluorescence. The structures of the novel heterocyclic compounds were confirmed by 1H-, 13C-, 15N-, and 19F-NMR spectroscopy, HRMS, and single-crystal X-ray diffraction data.

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23

Klein, Jean F., Jean Claude Pommelet, Josselin Chuche, José Elguero, Pilar Goya, and Ana Martinez. "SO2 extrusion in 1,2,6-thiadiazine 1,1-dioxides: a novel synthesis of pyrazoles." Canadian Journal of Chemistry 71, no. 3 (March 1, 1993): 410–12. http://dx.doi.org/10.1139/v93-060.

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A novel synthesis of the pyrazole ring involving SO2 extrusion by flow vacuum pyrolysis in the 1,2,6-thiadiazine 1,1-dioxide system is described. The reaction has potential industrial significance for routes to pyrazoles or functionalized pyrazoles that do not involve hydrazines.

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24

Aonofriesei, Florin. "Polysorbate 21 Can Modulate the Antibacterial Potential of Two Pyrazol Derivatives." Biomolecules 12, no. 12 (December 6, 2022): 1819. http://dx.doi.org/10.3390/biom12121819.

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The combination of two compounds with known antimicrobial activity may, in some cases, be an effective way to limit the resistance to antibiotics of specific pathogens. Molecules carrying pyrazole moiety are well known for their bioactive properties and have wide applicability in the medical and pharmaceutical field. Surfactants have, among other useful properties, the ability to affect the growth of microorganisms. The paper reports on the effect of the combination of two pyrazole derivatives, (1H-pyrazol-1-yl) methanol 1-hydroxymethylpyrazole (SAM1) and 1,1′methandiylbis (1H–pyrazol) (AM1), with sorbitan monolaurate (polysorbate 21, Tween 21, T21) on the growth of Gram-positive and Gram-negative bacteria. The results demonstrated a different ability of this combination to inhibit Staphylococcus aureus and Escherichia coli. T21 intensified the inhibitory activity of the pyrazoles to a greater extent in the Gram-negative bacteria compared to the Gram-positive ones, a fact confirmed by time-kill experiments. The experimental data showed that the association of T21 with the pyrazoles led to the increased release of intracellular material and a more intense uptake of crystal violet, which indicates that the potentiation of the antibacterial effect was based on the modification of the normal permeability of bacterial cells. T21 acted as a modulating factor and increased the permeability of the membrane, allowing the accelerated penetration of the pyrazoles inside the bacterial cells. This fact is important in controlling the global increase in microbial resistance to antibiotics and antimicrobials and finding viable solutions to overcome the antibiotic crisis. The paper highlights the possibility of using non-toxic surfactant molecules in antimicrobial combinations with practical applications. This could widen the range of adjuvants in applications which would be useful in the control of resistant microorganisms.

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25

Rai, K. M. Lokanatha, K. B. Umesha, and M. A. Harish Nayaka. "Antioxidant and Antimicrobial Activity of 5-methyl-2-(5-methyl-1,3-diphenyl-1H-pyrazole-4-carbonyl)-2,4-dihydro-pyrazol-3-one." International Journal of Biomedical Science 5, no. 4 (December 15, 2009): 359–68. http://dx.doi.org/10.59566/ijbs.2009.5359.

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Cycloaddition of nitrile imines 4 generated in situ by the catalytic dehydrogenation of diphenyl hydrazones 3 using Chloramine-T (CAT) as oxidant in glacial acetic acid with enolic form of ethyl acetoacetate 5 afforded Ethyl 3-aryl-5-methyl-1-phenyl-1H-pyrazol-4-carboxylate 6 in 80% yield. The said pyrazoles 6 refluxed with 80% hydrazine hydrate using absolute alcohol as solvent for about 2-3 hours to produce the respective 5-methyl-1,3-diphenyl-1H-pyrazole-4-carboxylic acid hydrazide 7. The alcoholic solution of pyrazole acid hydrazides on heating with ethyl acetoacetate 5 to give the 5-methyl-2-(5-methyl-1,3-diphenyl-1H-pyrazole-4-carbonyl)-2,4-dihydro-pyrazol-3-one 8. The synthesized compounds were found to exhibit good antimicrobial and antioxidant activity as evaluated by 1,1-diphenyl-2-picryl Hydrazyl (DPPH) radical scavenging, reducing power and DNA protection assays.

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26

Meador, Rowan I. L., Nilamber A. Mate, and John D. Chisholm. "Acid Catalyzed N-Alkylation of Pyrazoles with Trichloroacetimidates." Organics 3, no. 2 (May 24, 2022): 111–21. http://dx.doi.org/10.3390/org3020009.

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N-Alkyl pyrazoles are important heterocycles in organic and medicinal chemistry, demonstrating a wide range of biological activity. A new method for the N-alkylation of pyrazoles has been developed using trichloroacetimidate electrophiles and a Brønsted acid catalyst. These reactions provide ready access to N-alkyl pyrazoles which are present in a variety of medicinally relevant lead structures. Benzylic, phenethyl and benzhydryl trichloroacetimidates provide good yields of the N-alkyl pyrazole products. Unsymmetrical pyrazoles provide a mixture of the two possible regioisomers, with the major product being controlled by sterics. This methodology provides an alternative to other alkylation methods that require strong base or high temperature.

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27

Lynch, Brian Maurice, Misbahul Ain Khan, Huk Chia Teo, and Francisco Pedrotti. "Pyrazolo[3,4-b]pyridines: Syntheses, reactions, and nuclear magnetic resonance spectra." Canadian Journal of Chemistry 66, no. 3 (March 1, 1988): 420–28. http://dx.doi.org/10.1139/v88-074.

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Efficient syntheses of approximately 70 simple substituted representatives of pyrazolo[3,4-b]pyridine 1 are reported from the following: (a) suitably substituted pyridines onto which a pyrazole ring is annelated, and (b) appropriately substituted pyrazoles onto which a pyridine ring is annelated. Selected examples of electrophilic, nucleophilic, and homolytic substitution reactions and group transformations are described, providing regiosynthetic paths to useful intermediate species. Some systematic aspects of substituent chemical shift influences in the 1H and 13C nuclear magnetic resonance spectra, aiding in structural assignments, are illustrated.

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Alsayari, Abdulrhman, Yahya I. Asiri, Abdullatif Bin Muhsinah, and Mohd Zaheen Hassan. "Synthesis and antimicrobial activity of aryldiazenyl/arylhydrazono pyrazoles." Journal of Chemical Research 45, no. 11-12 (November 2021): 1093–99. http://dx.doi.org/10.1177/17475198211057461.

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We report the design, synthesis, and in vitro antimicrobial evaluation of functionalized pyrazoles containing a hydrazono/diazenyl moiety. Among these newly synthesized derivatives, 4-[2-(4-chlorophenyl)hydrazono]-5-methyl-2-[2-(naphthalen-2-yloxy)acetyl]-2,4-dihydro-3 H-pyrazol-3-one is a promising antimicrobial agent against Staphylococcus aureus (minimum inhibitory concentration 0.19 μg mL−1). Structure–activity relationship studies reveal that the electronic environment on the distal phenyl ring has a considerable effect on the antimicrobial potential of the hybrid analogues. Molecular docking studies into the active site of S. aureus dihydrofolate reductase also prove the usefulness of hybridizing a pyrazole moiety with azo and hydrazo groups in the design of new antimicrobial agents.

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29

Petek, Nejc, Uroš Grošelj, Jurij Svete, Franc Požgan, Drago Kočar, and Bogdan Štefane. "Eosin Y-Catalyzed Visible-Light-Mediated Aerobic Transformation of Pyrazolidine-3-One Derivatives." Catalysts 10, no. 9 (September 1, 2020): 981. http://dx.doi.org/10.3390/catal10090981.

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By utilizing an underexplored reactivity of N1-substituted pyrazolidine-3-ones, we developed a visible-light-induced aerobic oxidation of N1-substituted pyrazolidine-3-one derivatives yielding the corresponding azomethine imines. The resulting azomethine imines can be further reacted with ynones in situ under copper catalyzed [3 + 2] cycloaddition reaction conditions yielding the corresponding pyrazolo[1,2-a]pyrazoles in good yields. The methodology can be extended to other 1-aryl-substituted pyrazolidinones which undergo endocyclic oxidation deriving the corresponding pyrazolones as single products.

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30

Gerster, Holger, Michael Keim, and Gerhard Maas. "Cycloaddition reactions of acetylenic iminium salts and diazoacetates leading to pyrazole iminium salts." Zeitschrift für Naturforschung B 74, no. 4 (April 24, 2019): 347–55. http://dx.doi.org/10.1515/znb-2019-0001.

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AbstractAcetylenic iminium triflates with the general formula [R–C≡ C–C(Ar)=N+R2 TfO−] were found to be excellent dipolarophiles in [3+ 2] cycloaddition reactions with diazoacetates leading to (1H-pyrazol-3(5)-yl)methanaminium triflates in high yields. The terminal acetylenic iminium salt (propyne iminium salt) [HC≡C–C(Ph)=N+Me2 TfO−] reacted with an equimolar amount of methyl diazoacetate instantaneously at 20°C to form the expected pyrazole in almost quantitative yield. When a 2:1 stoichiometry was applied, subsequent Michael addition of the pyrazole at the alkyne occurred and the bis(iminium) ditriflate 4 was obtained in high yield. By hydride reduction or hydrolysis of the iminium group, some of the highly hygroscopic pyrazole iminium salts were converted into neutral, twofold functionalized, di- and tri-C-substitued 1H-pyrazoles.

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31

Nikpour, Farzad, Sara Zandi, and Mahnaz Sharafi-Kolkeshvandi. "Electrochemically Catalyzed N–N Coupling and Ring Cleavage Reaction of 1H-Pyrazoles." Synthesis 53, no. 19 (July 12, 2021): 3591–96. http://dx.doi.org/10.1055/s-0040-1706050.

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AbstractThe electrocatalyzed N–N coupling and ring cleavage reaction of 3-methyl-, 3,5-dimethyl-, 3-methyl-5-phenyl- and 3,5-diphenyl-1H-pyrazole was investigated and led to the electro-organic synthesis of new heterocyclic compounds. The results revealed that electrochemically produced 1H-pyrazoleox plays the role of acceptor in a reaction with the starting molecule via a N–N coupling and ring cleavage reaction of pyrazoles. The proposed reaction sequence consists of anodic oxidation, dimerization, rearrangement and reduction. The electrochemically catalyzed reactions were accomplished under constant-current and constant-potential conditions using an undivided electrochemical cell with the advantages of mild reaction conditions, remarkable yields and environmental compatibility.

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32

Zandi, Sara, and Farzad Nikpour. "A convenient approach for the electrochemical bromination and iodination of pyrazoles." Zeitschrift für Naturforschung B 77, no. 1 (December 10, 2021): 35–40. http://dx.doi.org/10.1515/znb-2021-0148.

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Abstract Electrochemical bromination and iodination of some pyrazoles were investigated under constant-current (CC) electrolysis in an undivided electrochemical cell. Anodic oxidation of KX salt produces X2 in-situ which can be consumed as an expedient electrophile in pyrazoles aromatic electrophilic substitution reactions or may participate in an X–N coupling reaction with electrochemically catalyzed pyrazolesox to form the halogenated pyrazoles. All reactions proceeded without the need to use any hazardous reagents or catalysts. The reaction conditions are mild and environmentally compatible.

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33

Deacon, Glen B., Peter C. Junk, and Aron Urbatsch. "Lanthanoid and Alkaline Earth Complexes Involving New Substituted Pyrazolates." Australian Journal of Chemistry 65, no. 7 (2012): 802. http://dx.doi.org/10.1071/ch12069.

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From the pyrazoles 3,5-di-(2′-furanyl)pyrazole (fu2pzH), 3-phenyl-5-(2′-thienyl)pyrazole (PhtpzH) and 3-(2′-furanyl)-5-(2′′-naphthyl)pyrazole (funappzH), a range of alkaline earth and lanthanoid pyrazolate complexes has been prepared by redox transmetallation/protolysis reactions between free metals, Hg(C6F5)2 and the pyrazoles, by reaction of I2‐activated metals with the pyrazoles, and in one case by a similar reaction of unactivated metal, in the donor solvents tetrahydrofuran (thf) and 1,2-dimethoxyethane (dme). Thus the divalent [Ca(Phtpz)2(thf)4], [Ba(Phtpz)2(thf)4] and [Ca(funappz)2(thf)4]·(thf) complexes, the heteroleptic [Yb(Phtpz)I(thf)4] and the trivalent [La(fu2pz)3(thf)3]·2thf complex have been prepared and structurally characterized, as well as the dme complexes [Yb(Phtpz)2(dme)2] and [Eu(Phtpz)3(dme)2]. Highlights include the first trans-[LnII(pz)I(thf)4] complex, a rare transoid [Ln(pz)2(dme)2] complex and a complex with both chelating and unidentate dme. In all cases, the Phtpz complexes exhibit pronounced positional disorder of the 2-thienyl and phenyl groups in the solid state, as do the two polymorphs of the parent pyrazole.

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Hockstedler, Amy N., Beatrice A. Edjah, Saajid Z. Azhar, Hadrian Mendoza, Nicole A. Brown, Hayley B. Arrowood, Andrew C. Clay, et al. "13C NMR spectroscopy of heterocycles: 1-phenyl-3-aryl/t-butyl-5-arylpyrazoles." Heterocyclic Communications 23, no. 2 (April 1, 2017): 125–31. http://dx.doi.org/10.1515/hc-2017-0034.

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AbstractA series of chalcones 1–12 were converted to pyrazolines (1Pi–12Pi) by reaction with phenylhydrazine followed by DDQ oxidation to produce the corresponding pyrazoles (1Pz–12Pz). Three 1-phenyl-3-t-butyl-5-arylpyrazoles (13Pz–15Pz) were synthesized using an analogous approach. Molecular modeling studies predicted the 5-aryl group of the pyrazoles for both series to have a torsion angle of 52°–54° whereas the 1-phenyl group was predicted to have 35°–37° torsion angles. The 3-aryl group was predicted to be essentially coplanar (−3°) with the pyrazole system in the first series. 13C NMR data for both series, 1Pz–12Pz and 13Pz–15Pz, were collected in DMSO-d6 at 50°C. A plot of the C4 chemical shifts for 1Pz–12Pz versus Hammet constants for 5-aryl substituents yielded a very good linear correlation (R2=0.96) with a slope of 1.5. The chemical shift data for C4 showed little or no dependence on 3-aryl substituents. The result for 13Pz–15Pz, despite only three points, was consistent with the first series results and yielded a ρ value of 2.0. Distal transmission of substituent effects (5-aryl groups) to C4 of the pyrazole system was reduced by roughly 50–60% of that of the analogous planar isoxazole system, but are not consistent with results for the similarly twisted 4-bromoisoxazoles.

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35

Petek, Nejc, and Uroš Grošelj. "Photoinduced Ring Opening of Methyl 1-Aryl-5-oxo-6,7-dihydro-1H,5H-pyrazolo[1,2-a]pyrazole-2-carboxylates in the Presence of Diaryl Disulfides." Molbank 2023, no. 2 (June 15, 2023): M1670. http://dx.doi.org/10.3390/m1670.

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Among the methods used for the synthesis of functionalized heterocyclic compounds, photochemistry has gained immense popularity due to the reactivity of intermediates in photoinduced reactions. In this study, we report on the effect of diaryl disulfides as hydrogen atom transfer catalysts on the photoinduced transformations of pyrazolo[1,2-a]pyrazolones. After excitation with visible light, these compounds are susceptible to C–N bond cleavage, followed by intermolecular hydrogen atom abstraction. By modifying the reaction conditions, we have developed two novel methods for the synthesis of highly substituted pyrazoles.

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Kumar, Manoj, Shashi Sharma, Hardeep Singh Tuli, and Vinit Parkash. "Ferrocenyl Substituted Pyrazoles, Synthesis via novel route, Spectral Investigations and Their Biological Studies." Oriental Journal of Chemistry 35, no. 2 (April 28, 2019): 863–69. http://dx.doi.org/10.13005/ojc/350250.

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Ferrocenyl substituted heterocyclic compounds have wide range of medicinal approach. The synthesis of ferrocenyl substituted pyrazole is the new concern in these compounds with enhanced biological activities. This work focus on synthesis of ferrocenyl substituted pyrazoles via novel route. The synthesis of 1-phenyl-3-ferrocenyl-pyrazole was investigated involving Friedel Crafts Acylation like reaction conditions. The reaction proceeded through three stages using addition cyclo-condensation of acetyl ferrocene with phenyl hydrazine followed by cyclization using cyclizing reagent iodine in presence of NaHCO3. Individual product separated out having excellent yield (83%). Ferrocenyl substituted pyrazoles were characterized by spectroscopic methods (1H NMR, IR, GC-MS) and their biological properties have been screened.

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Ameziane El Hassani, Issam, Khouloud Rouzi, Hamza Assila, Khalid Karrouchi, and M’hammed Ansar. "Recent Advances in the Synthesis of Pyrazole Derivatives: A Review." Reactions 4, no. 3 (September 5, 2023): 478–504. http://dx.doi.org/10.3390/reactions4030029.

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Pyrazole, characterized by a five-membered heterocyclic structure featuring two neighboring nitrogen atoms, serves as a core element. Pyrazoles hold a privileged status as versatile frameworks in various sectors of the chemical industry, including medicine and agriculture. Previous reviews have extensively highlighted the significance of pyrazoles and their diverse biological activities, encompassing roles such as antituberculosis, antimicrobial, antifungal, anti-inflammatory, anticancer, and antidiabetic agents. Consequently, they have garnered substantial interest from researchers. The aim of this review is to offer a comprehensive overview of the published research related to the synthesis of pyrazole derivatives, encompassing a discussion of diverse methods for accessing the pyrazole moiety. These methods span from utilizing transition-metal catalysts and photoredox reactions to employing one-pot multicomponent processes, novel reactants, and innovative reaction types. It encompasses studies conducted by numerous scientists worldwide, showcasing collective efforts in advancing the methodologies and applications of pyrazole derivatives.

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38

Gill, Agagia, Udo R. Werz, and Gerhard Maas. "N-vinylation and N-allylation of 3,5-disubstituted pyrazoles by N–H insertion of vinylcarbenoids." Zeitschrift für Naturforschung B 70, no. 10 (October 1, 2015): 747–56. http://dx.doi.org/10.1515/znb-2015-0115.

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AbstractA vinylcarbenoid approach toward N-functionalization of NH-pyrazoles is presented. The rhodium(II)-catalyzed reaction of methyl styryl-diazoacetate (1) or dimethyl 2-diazoglutaconate (3) with 3,5-disubstituted pyrazoles gave products of carbenoid N–H insertion in high combined yields, although regioselectivity issues posed by the pyrazole or the vinylcarbenoid moiety as well as positional and configurational isomerism concerning the C,C double bond of the latter led to product mixtures. The ambident reactivity of the vinylcarbenoid derived from 1 could be steered by the catalyst: while Rh2(OAc)4 yielded products of direct carbenoid insertion preferentially, silver(I) catalysis strongly favored reaction at the vinylogous site of the carbenoid resulting in an N-allylation of the pyrazoles.

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Kumar, Munish, and Sharad Kumar Panday. "Pyrazole and Its Derivatives: An Excellent N-Hetrocycle with Wide Range of Biological Applications (A Review)." Oriental Journal Of Chemistry 38, no. 3 (June 30, 2022): 568–92. http://dx.doi.org/10.13005/ojc/380306.

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The pyrazole derivatives have been recognized as a unique heterocyclic molecule exerting broad range of biological activities such as analgesic, anti-viral, anti-histaminic, anti-microbial, anti-tumor, insecticides fungicides, anti-depressant, antipyretic, anti-inflammatory, angiotensin converting enzyme (ACE) inhibitory and estrogen receptor (ER) ligand activity etc. Pyrazoles also find applications in agrochemical and pharmaceutical industry. Pyrazoles have different chemical properties which may be attributed due to the effect of particular N-atoms present in pyrazole molecule. N-Atom present at position-2 having non Huckel lone pair is more reactive towards electrophiles while N-atom present at position-1 is unreactive. However, in the presence of strong base, the proton from N-atom at position-1 is abstracted thereby providing pyrazole anion after deprotonation, which in turn increases reactivity towards the electrophiles. There are wide range of drugs available in the market possessing pyrazole nuclei. The present manuscript is aimed to describe major developments achieved till date towards the synthesis and biological applications of pyrazole/pyrazole derivatives and is likely to be beneficial to the researchers working in the area.

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Zouaoui, Emna, and Mohamed Moncef El Gaïed. "Synthesis of Trifluoromethyl Heterocyclic Compounds." Journal of Chemical Research 2003, no. 4 (April 2003): 242–46. http://dx.doi.org/10.1177/1747519803200300404.

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Kumar, Manoj, Shashi Sharma, Hardeep Singh Tuli, and Rajshree Khare. "A Novel Synthesis, Characterization and Biological Studies of Ferrocenyl Substituted Pyrazoles." Asian Journal of Chemistry 31, no. 12 (November 16, 2019): 2729–32. http://dx.doi.org/10.14233/ajchem.2019.22161.

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It has been discovered that ferrocenyl substituted heterocyclic compounds have wide scope of restorative methodology. The combination of ferrocenyl substituted pyrazole is the new class in these compounds with upgraded natural activity. This work center around blend of ferrocenyl substituted pyrazoles through novel course. The combination of 1-phenyl-3-ferrocenyl-pyrazole was examined including addition-cyclocondensation like response conditions. The response continued through three phases using of expansion cyclo-buildup of acetyl ferrocene with phenyl hydrazine pursued by cyclizing reagent iodine with NaHCO3. In both syntheses, each time single product isolated having good yields (87 and 79 %). Ferrocenyl substituted pyrazoles were examined by spectroscopic techniques (1H NMR, IR, MS) and their biological properties have been screened.

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42

Kumar, Harish, Kushal Kumar Bansal, and Anju Goyal. "Synthetic Methods and Antimicrobial Perspective of Pyrazole Derivatives: An Insight." Anti-Infective Agents 18, no. 3 (September 11, 2020): 207–23. http://dx.doi.org/10.2174/2211352517666191022103831.

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Background: Due to newly emerging microbial infections and the development of resistance against cutting-edge therapeutics, innovative and robust medicinal agents are required. Small ring heterocycles, such as pyrazole and its derivatives have been acknowledged to possess myriad biological properties and the presence of pyrazole in clinics like celecoxib, phenylbutazone (anti-inflammatory), CDPPB (antipsychotic), rimonabant (anti-obesity), antipyrine, difenamizole (analgesic), fipronil (broad-spectrum insecticidal), betazole (H2-receptor agonist) and fezolamide (antidepressant) drugs has proven the pharmacological perspective of pyrazole nucleus. Objectives: The current review paper aimed at a recent update made on novel methodologies adopted in the synthesis of pyrazole derivatives with the emphasis on antibacterial (DNA gyrase inhibition) and antifungal activities. Methods: Pyrazole is one of the major tools to be investigated in drug design and discovery. Many studies have been reported by researchers that have claimed the significant biological potential of these derivatives. However, numerous studies on pyrazoles compounds shown to exhibit potential antifungal and antibacterial activities, the focus has also been made on DNA gyrase inhibition. Additionally, some important patents granted to this heterocyclic nucleus related to antimicrobial potential are also addressed appropriately. Results: DNA gyrase is a promising biotarget yet to be explored against a number of medicinal agents. The present work provides valuable insight into synthetic methods and antibacterials/antifungal significance of pyrazoles in general as well as new inhibitors of DNA gyrase in particular. Conclusion: The manuscript constitutes a valuable reference which advocates candidature of pyrazoles as a potential therapeutic alternative as antibacterial and antifungal agent.

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Kang, Eunsu, Hyun Tae Kim, and Jung Min Joo. "Transition-metal-catalyzed C–H functionalization of pyrazoles." Organic & Biomolecular Chemistry 18, no. 32 (2020): 6192–210. http://dx.doi.org/10.1039/d0ob01265c.

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Jansa, Josef, Ramona Schmidt, Ashenafi Damtew Mamuye, Laura Castoldi, Alexander Roller, Vittorio Pace, and Wolfgang Holzer. "Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents." Beilstein Journal of Organic Chemistry 13 (May 12, 2017): 895–902. http://dx.doi.org/10.3762/bjoc.13.90.

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A synthesis of tetrasubstituted pyrazoles containing two, three or four pyridinyl substituents is described. Hence, the reaction of 1,3-dipyridinyl-1,3-propanediones with 2-hydrazinopyridine or phenylhydrazine, respectively, affords the corresponding 1,3,5-trisubstituted pyrazoles. Iodination at the 4-position of the pyrazole nucleus by treatment with I2/HIO3 gives the appropriate 4-iodopyrazoles which served as starting materials for different cross-coupling reactions. Finally, Negishi cross-coupling employing organozinc halides and Pd catalysts turned out to be the method of choice to obtain the desired tetrasubstituted pyrazoles. The formation of different unexpected reaction products is described. Detailed NMR spectroscopic investigations (1H, 13C, 15N) were undertaken with all products prepared. Moreover, the structure of a condensation product was confirmed by crystal structure analysis.

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Bharathi, R. "In vitro and molecular docking studies of an antiinflammatory scaffold with human peroxiredoxin 5 and tyrosine kinase receptor." Bioinformation 16, no. 11 (November 30, 2020): 929–36. http://dx.doi.org/10.6026/97320630016929.

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A new series of 4-(3-(2-amino-3,5-dibromophenyl)-1-(4-substitutedbenzoyl)-4,5-dihydro-1H-pyrazol-5-yl)benzonitrile (4a-h) compounds were synthesized and evaluated for in-vitro anti-inflammatory activities. The spectral (IR, NMR) and elemental analyses data of the product indicated the formation of new pyrazoles 4a-h. Compound 4e exhibited potent anti-inflammatory property with 85.45 % inhibitions. This value was compared with standard diclofenac sodium. This data is explained using molecular docking analysis of receptor-ligand binding. These results demonstrated that pyrazole derivatives are potential inhibitors of Human Peroxiredoxin 5 and Tyrosine kinase receptor in the treatment of inflammation related illness.

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Rey, Marine, and Stéphane Beaumont. "Molybdenum-Mediated One-Pot Synthesis of Pyrazoles from Isoxazoles." Synthesis 51, no. 20 (August 26, 2019): 3796–804. http://dx.doi.org/10.1055/s-0039-1690615.

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A one-pot approach for the direct synthesis of substituted pyrazoles from isoxazoles is reported. The process involves isoxazole N–O bond cleavage mediated by a molybdenum complex, in situ hydrolysis of the resulting β-amino enone to the corresponding 1,3-diketone, followed by pyrazole formation in the presence of hydrazine or substituted hydrazine. Good to excellent yields and regioselectivities are obtained with nonsymmetric isoxazoles. By using readily available starting materials, a wide range of substituted pyrazoles may be synthesized by this method.

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Aegurla, Balakrishna, Nisha Jarwal, and Rama Krishna Peddinti. "Denitrative imino-diaza-Nazarov cyclization: synthesis of pyrazoles." Organic & Biomolecular Chemistry 18, no. 31 (2020): 6100–6107. http://dx.doi.org/10.1039/d0ob01200a.

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This iodine-catalysed expedient process furnished functionally-rich pyrazoles regioselectively in ethanol under aerobic conditions. The cascade reaction for the pyrazole formation proceeds through enamine–imino diaza-Nazarov 4π-electrocyclization.

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48

Potapov, Andrei S., Evgenia A. Nudnova, Vladimir D. Ogorodnikov, Tatiana V. Petrenko, and Andrei I. Khlebnikov. "Synthesis of New Bitopic Tetra(pyrazolyl)-Ligands with Neopentane and O-Xylene Backbones." Scientific World Journal 2012 (2012): 1–5. http://dx.doi.org/10.1100/2012/798271.

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Several new bitopic pyrazole-containing ligands were prepared from the corresponding pyrazoles and tetrahalogen or tetratosyloxy derivatives of o-xylene and neopentane in a superbasic medium (KOH-DMSO).

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49

Volkova, Darya S., Arkadiy A. Popov, Evgeny V. Root, Alexey A. Kukushkin, and George A. Suboch. "SUBSTITUTED 4-NITROSOPYRAZOLES IN THE DIELS-ALDER REACTION." Siberian Journal of Life Sciences and Agriculture 13, no. 5 (October 29, 2021): 104–19. http://dx.doi.org/10.12731/2658-6649-2021-13-5-104-119.

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Background. 4-Nitrosopyrazoles have become widespread in the pharmaceutical industry and in chemistry due to their high reactivity and biological activity. However, the interaction of 3,5-substituted 4-nitroso-1H-pyrazoles with diene hydrocarbons has not been studied to date. Purpose. Study of diene condensation of tetraphenylcyclopentadienone with 3,5-dimethyl-4-nitroso-1H-pyrazole and 3(5)-methyl-4-nitroso-5(3)-phenyl-1H-pyrazole; proof of the structure of the obtained compounds; prediction of potential positive biological activity. Materials and methods. Research methods include: directed organic synthesis, thin-layer chromatography, chromato-mass spectra, prediction of biological activity using the PASS-online web-resource. Results. Substituted oxazines, pyrazoles and but-2-en-1-ones were synthesized. Fragmentation decays based on the mass spectrum of the obtained compounds confirm their molecular weight and structure. The PASS-online program predicts potential biological activity. Conclusion. Substituted oxazines, pyrazoles and but-2-en-1-ones were obtained for the first time by the Diels-Alder reaction, the structure of which was proved by HPLC/MS. Based on the output data of the PASS-online program, the synthesized substances are taurine dehydrogenase inhibitors and exhibit antitumor effect.

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50

Frampton, Christopher S., Michael W. Majchrzak, and John Warkentin. "Sense of sequential 1,5-sigmatropic rearrangements of dimethyl-3,3-dialkyl-3H-pyrazole-4,5-dicarboxylates. Crystal and molecular structures of two dimethyl-4,5-dialkyl-1H-pyrazole-1,3-dicarboxylates." Canadian Journal of Chemistry 69, no. 3 (March 1, 1991): 373–78. http://dx.doi.org/10.1139/v91-057.

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3,3-Dialkyl-3H-pyrazole-4,5-dicarboxylic acid dimethyl esters (4), obtained by cycloaddition of R1R2C=N+=N− (R1 = R2 = CH3; R1 = CH3, R2 = CH2CH3) to CH3O2CC≡CCO2CH3, rearrange thermally by 1,5-sigmatropic alkyl shifts to both N and C. The latter rearrangement is followed by two successive 1,5-sigmatropic shifts of a methoxycarbonyl group. Final products of the threefold rearrangement were shown to be 4,5-dialkyl-1H-pyrazole-1,3-dicarboxylic acid dimethyl esters (6), rather than the isomeric 3,4-dialkyl-1H-pyrazole-1,5-dicarboxylic acid dimethyl esters (7), by means of single crystal X-ray diffraction. Those products therefore result from alkyl migration to C-4 of 4, followed by sequential migration of the methoxycarbonyl group, initially at C-4, to C-3 and then to N-2 of 4. In the initial alkyl migration step, ethyl migrates in preference to methyl, and in subsequent migration steps the methoxycarbonyl group migrates faster than the ethyl or methyl group. Crystals of 4-ethyl-5-methyl-1H-pyrazole-1,3-dicarboxylic acid dimethyl ester (6b) are monoclinic, of space group P21/n, with a = 7.907(1) Å, b = 11.087(2) Å, c = 13.199(3) Å, V = 1124.9(4) Å 3, Dc = 1.34 g cm−3, Dm = 1.33 g cm−3 for Z = 4, and R1 = 0.0772 (R2 = 0.0626) for 1474 reflections (R1 = 0.0428, R2 = 0.0422 for 903 reflections with I > 3σ(I)). The structure of 6a is similar. Key words: 3,3-dialkyl-3H-pyrazoles, 1,5-sigmatropic rearrangements of; 4,5-dialkyl-1H-pyrazoles, crystal and molecular structures; 1,5-sigmatropic rearrangements of pyrazoles, sense of.

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Journal articles on the topic 'Pyrazoles'

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