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Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 34618

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Vera L. M. Silva

E-Mail Website
Guest Editor
LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: organic synthesis; development of sustainable organic synthesis methodologies; ohmic-heating-assisted synthesis; synthesis, functionalization and structural characterization of oxygen- and nitrogen-based heterocyclic compounds; development of molecules for medicinal applications
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Artur M. S. Silva

E-Mail Website
Guest Editor
LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: organic chemistry; green synthetic organic chemistry; synthesis of heterocyclic compounds; natural products; NMR techniques; synthesis of new compounds with biocidal and antioxidant activities
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Pyrazoles are considered privileged structures in medicinal chemistry due to their remarkable biological activities and occurrence in many low-molecular-weight compounds present in several marketed drugs (e.g., Celebrex® and Viagra®). Pyrazoles are also found within a variety of agrochemicals (fungicides, insecticides, and herbicides) and are versatile scaffolds for synthetic manipulations. The structural features of pyrazoles (mainly tautomerism, with possible implications for their reactivity), as well as their diverse applications, have stimulated the work of several research groups towards the synthesis and functionalization of pyrazole-type compounds and the study of their properties.

This Special Issue aims to provide a broad survey of the most recent advances in pyrazole chemistry. Original research articles or reviews that discuss new organic reactions and methodologies for the synthesis and functionalization of pyrazoles (including their reduced forms, pyrazolines), their use as ligands for the preparation of complexes, structural aspects and properties, and their applications in different fields are welcome.

Dr. Vera L. M. Silva
Prof. Dr. Artur M. S. Silva
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • pyrazoles
  • pyrazolines
  • synthesis
  • functionalization
  • transformation
  • complexes
  • applications

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Published Papers (16 papers)

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Editorial

Jump to: Research, Review

4 pages, 207 KiB  
Editorial
Special Issue “Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II”
by Vera L. M. Silva and Artur M. S. Silva
Molecules 2023, 28(15), 5873; https://doi.org/10.3390/molecules28155873 - 04 Aug 2023
Cited by 2 | Viewed by 670
Abstract
Pyrazole and its derivatives are considered privileged N-heterocycles with immense therapeutic potential [...] Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)

Research

Jump to: Editorial, Review

28 pages, 1987 KiB  
Article
Convenient Synthesis of N-Heterocycle-Fused Tetrahydro-1,4-diazepinones
by Karolina Dzedulionytė, Melita Veikšaitė, Vít Morávek, Vida Malinauskienė, Greta Račkauskienė, Algirdas Šačkus, Asta Žukauskaitė and Eglė Arbačiauskienė
Molecules 2022, 27(24), 8666; https://doi.org/10.3390/molecules27248666 - 07 Dec 2022
Cited by 5 | Viewed by 1814
Abstract
A general approach towards the synthesis of tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepin-4-one, tetrahydro[1,4]diazepino[1,2-a]indol-1-one and tetrahydro-1H-benzo[4,5]imidazo[1,2-a][1,4]diazepin-1-one derivatives was introduced. A regioselective strategy was developed for synthesizing ethyl 1-(oxiran-2-ylmethyl)-1H-pyrazole-5-carboxylates from easily accessible 3(5)-aryl- or methyl-1H-pyrazole-5(3)-carboxylates. [...] Read more.
A general approach towards the synthesis of tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepin-4-one, tetrahydro[1,4]diazepino[1,2-a]indol-1-one and tetrahydro-1H-benzo[4,5]imidazo[1,2-a][1,4]diazepin-1-one derivatives was introduced. A regioselective strategy was developed for synthesizing ethyl 1-(oxiran-2-ylmethyl)-1H-pyrazole-5-carboxylates from easily accessible 3(5)-aryl- or methyl-1H-pyrazole-5(3)-carboxylates. Obtained intermediates were further treated with amines resulting in oxirane ring-opening and direct cyclisation—yielding target pyrazolo[1,5-a][1,4]diazepin-4-ones. A straightforward two-step synthetic approach was applied to expand the current study and successfully functionalize ethyl 1H-indole- and ethyl 1H-benzo[d]imidazole-2-carboxylates. The structures of fused heterocyclic compounds were confirmed by 1H, 13C, and 15N-NMR spectroscopy and HRMS investigation. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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16 pages, 1803 KiB  
Article
Fluorinated and Non-Fluorinated 1,4-Diarylpyrazoles via MnO2-Mediated Mechanochemical Deacylative Oxidation of 5-Acylpyrazolines
by Greta Utecht-Jarzyńska, Anna Kowalczyk and Marcin Jasiński
Molecules 2022, 27(23), 8446; https://doi.org/10.3390/molecules27238446 - 02 Dec 2022
Cited by 7 | Viewed by 1318
Abstract
A solvent-free two-step synthesis of polyfunctionalized pyrazoles under ball-milling mechanochemical conditions was developed. The protocol comprises (3 + 2)-cycloaddition of in situ generated nitrile imines and chalcones, followed by oxidation of the initially formed 5-acylpyrazolines with activated MnO2. The second step [...] Read more.
A solvent-free two-step synthesis of polyfunctionalized pyrazoles under ball-milling mechanochemical conditions was developed. The protocol comprises (3 + 2)-cycloaddition of in situ generated nitrile imines and chalcones, followed by oxidation of the initially formed 5-acylpyrazolines with activated MnO2. The second step proceeds via an exclusive deacylative pathway, to give a series of 1,4-diarylpyrazoles functionalized with a fluorinated (CF3) or non-fluorinated (Ph, COOEt, Ac) substituent at C(3) of the heterocyclic ring. In contrast, MnO2-mediated oxidation of a model isomeric 4-acylpyrazoline proceeded with low chemoselectivity, leading to fully substituted pyrazole as a major product formed via dehydrogenative aromatization. The presented approach extends the scope of the known methods carried out in organic solvents and enables the preparation of polyfunctionalized pyrazoles, which are of general interest in medicine and material sciences. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Graphical abstract

12 pages, 1462 KiB  
Article
On the Question of the Formation of Nitro-Functionalized 2,4-Pyrazole Analogs on the Basis of Nitrylimine Molecular Systems and 3,3,3-Trichloro-1-Nitroprop-1-Ene
by Karolina Kula, Agnieszka Łapczuk, Mikołaj Sadowski, Jowita Kras, Karolina Zawadzińska, Oleg M. Demchuk, Gajendra Kumar Gaurav, Aneta Wróblewska and Radomir Jasiński
Molecules 2022, 27(23), 8409; https://doi.org/10.3390/molecules27238409 - 01 Dec 2022
Cited by 21 | Viewed by 1420
Abstract
Experimental and theoretical studies on the reaction between (E)-3,3,3-trichloro-1-nitroprop-1-ene and N-(4-bromophenyl)-C-arylnitrylimine were performed. It was found that the title process unexpectedly led to 1-(4-bromophenyl)-3-phenyl-5-nitropyrazole instead of the expected Δ2-pyrazoline molecular system. This was the result of a unique [...] Read more.
Experimental and theoretical studies on the reaction between (E)-3,3,3-trichloro-1-nitroprop-1-ene and N-(4-bromophenyl)-C-arylnitrylimine were performed. It was found that the title process unexpectedly led to 1-(4-bromophenyl)-3-phenyl-5-nitropyrazole instead of the expected Δ2-pyrazoline molecular system. This was the result of a unique CHCl3 elimination process. The observed mechanism of transformation was explained in the framework of the molecular electron density theory (MEDT). The theoretical results showed that both of the possible channels of [3 + 2] cycloaddition were favorable from a kinetic point of view, due to which the creation of 1-(4-bromophenyl)-3-aryl-4-tricholomethyl-5-nitro-Δ2-pyrazoline was more probable. On the other hand, according to the experimental data, the presented reactions occurred with full regioselectivity. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Figure 1

16 pages, 1857 KiB  
Article
Regioselective Synthesis, Structural Characterization, and Antiproliferative Activity of Novel Tetra-Substituted Phenylaminopyrazole Derivatives
by Matteo Lusardi, Aldo Profumo, Chiara Rotolo, Erika Iervasi, Camillo Rosano, Andrea Spallarossa and Marco Ponassi
Molecules 2022, 27(18), 5814; https://doi.org/10.3390/molecules27185814 - 08 Sep 2022
Cited by 5 | Viewed by 1337
Abstract
A small library of highly functionalized phenylaminopyrazoles, bearing different substituents at position 1, 3, and 4 of the pyrazole ring, was prepared by the one-pot condensation of active methylene reagents, phenylisothiocyanate, and substituted hydrazine (namely, methyl- and benzyl-hydrazine). The identified reaction conditions proved [...] Read more.
A small library of highly functionalized phenylaminopyrazoles, bearing different substituents at position 1, 3, and 4 of the pyrazole ring, was prepared by the one-pot condensation of active methylene reagents, phenylisothiocyanate, and substituted hydrazine (namely, methyl- and benzyl-hydrazine). The identified reaction conditions proved to be versatile and efficient. Furthermore, the evaluation of alternative stepwise protocols affected the chemo- and regio-selectivity outcome of the one-pot procedure. The chemical identities of two N-methyl pyrazole isomers, selected as prototypes of the whole series, were unambiguously identified by means of NMR and mass spectrometry studies. Additionally, semiempirical calculations provided a structural rationale for the different chromatographic behavior of the two isomers. The prepared tetra-substituted phenylaminopyrazoles were tested in cell-based assays on a panel of cancer and normal cell lines. The tested compounds did not show any cytotoxic effect on the selected cell lines, thus supporting their pharmaceutical potentials. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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16 pages, 3386 KiB  
Article
Reaction Products of β-Aminopropioamidoximes Nitrobenzenesulfochlorination: Linear and Rearranged to Spiropyrazolinium Salts with Antidiabetic Activity
by Lyudmila Kayukova, Anna Vologzhanina, Pavel Dorovatovskii, Gulnur Baitursynova, Elmira Yergaliyeva, Ayazhan Kurmangaliyeva, Zarina Shulgau, Sergazy Adekenov, Zhanar Shaimerdenova and Kydymolla Akatan
Molecules 2022, 27(7), 2181; https://doi.org/10.3390/molecules27072181 - 28 Mar 2022
Cited by 4 | Viewed by 1559
Abstract
Nitrobenzenesulfochlorination of β-aminopropioamidoximes leads to a set of products depending on the structure of the initial interacting substances and reaction conditions. Amidoximes, functionalized at the terminal C atom with six-membered N-heterocycles (piperidine, morpholine, thiomorpholine and phenylpiperazine), as a result of the spontaneous [...] Read more.
Nitrobenzenesulfochlorination of β-aminopropioamidoximes leads to a set of products depending on the structure of the initial interacting substances and reaction conditions. Amidoximes, functionalized at the terminal C atom with six-membered N-heterocycles (piperidine, morpholine, thiomorpholine and phenylpiperazine), as a result of the spontaneous intramolecular heterocyclization of the intermediate reaction product of an SN2 substitution of a hydrogen atom in the oxime group of the amidoxime fragment by a nitrobenzenesulfonyl group, produce spiropyrazolinium ortho- or para-nitrobenzenesulfonates. An exception is ortho-nitrobenzenesulfochlorination of β-(thiomorpholin-1-yl)propioamidoxime, which is regioselective at room temperature, producing two spiropyrazolinium salts (ortho-nitrobezenesulfonate and chloride), and regiospecific at the boiling point of the solvent, when only chloride is formed. The para-Nitrobezenesulfochlorination of β-(benzimidazol-1-yl)propioamidoxime, due to the reduced nucleophilicity of the aromatic β-amine nitrogen atom, is regiospecific at both temperatures, and produces the O-para-nitrobenzenesulfochlorination product. The antidiabetic screening of the new nitrobezenesulfochlorination amidoximes found promising samples with in vitro α-glucosidase activity higher than the reference drug acarbose. 1H-NMR spectroscopy and X-ray analysis revealed the slow inversion of six-membered heterocycles, and experimentally confirmed the presence of an unfavorable stereoisomer with an axial N–N bond in the pyrazolinium heterocycle. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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12 pages, 1542 KiB  
Article
An Orthogonal Synthetic Approach to Nonsymmetrical Bisazolyl 2,4,6-Trisubstituted Pyridines
by Arturo Gamonal Ruiz-Crespo, Laura Galán-Fernández, Paloma Martínez-Martín and Juan Carlos Rodríguez-Ubis
Molecules 2022, 27(5), 1746; https://doi.org/10.3390/molecules27051746 - 07 Mar 2022
Cited by 1 | Viewed by 1648
Abstract
A three-step synthetic route giving access to nonsymmetrical bisazolyl 2,4,6-trisubstituted pyridines with different substituents on the pyrazole, indazole, and pyridine heterocycles is described. From the readily available 4-bromo-2,6-difluoropyridine, both fluorine atoms allow for easy selective stepwise substitution, and the bromine atom provides easy [...] Read more.
A three-step synthetic route giving access to nonsymmetrical bisazolyl 2,4,6-trisubstituted pyridines with different substituents on the pyrazole, indazole, and pyridine heterocycles is described. From the readily available 4-bromo-2,6-difluoropyridine, both fluorine atoms allow for easy selective stepwise substitution, and the bromine atom provides easy access to additional functionalities through both Suzuki and Sonogashira Pd(0) cross-coupling reactions. These synthons represent optimal structures as building blocks in complexation and metalloorganic structures for the tuning of their chelating and photophysical properties. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Graphical abstract

10 pages, 1394 KiB  
Article
Structural Requirements of 1-(2-Pyridinyl)-5-pyrazolones for Disproportionation of Boronic Acids
by Joungmo Cho, Venkata Subbaiah Sadu, Yohan Han, Yunsoo Bae, Hwajeong Lee and Kee-In Lee
Molecules 2021, 26(22), 6814; https://doi.org/10.3390/molecules26226814 - 11 Nov 2021
Cited by 2 | Viewed by 1413
Abstract
We observed an unusual formation of four-coordinate boron(III) complexes from the reaction of 1-(2-pyridinyl)-5-pyrazolone derivatives with arylboronic acids in the basic media. The exact mechanism is not clear; however, the use of unprotected boronic acid and the presence of a bidentate ligand appeared [...] Read more.
We observed an unusual formation of four-coordinate boron(III) complexes from the reaction of 1-(2-pyridinyl)-5-pyrazolone derivatives with arylboronic acids in the basic media. The exact mechanism is not clear; however, the use of unprotected boronic acid and the presence of a bidentate ligand appeared to be the key structural requirements for the transformation. The results suggest that base-promoted disproportionation of arylboronic acid with the assistance of the [N,O]-bidentate ligation of 1-(2-pyridinyl)-5-pyrazolone should take place and facilitate the formation of pyrazole diarylborinate. Experiments to obtain a deeper understanding of its mechanism are currently underway. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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28 pages, 3122 KiB  
Article
Synthesis and Antiproliferative Activity of 2,4,6,7-Tetrasubstituted-2H-pyrazolo[4,3-c]pyridines
by Beatričė Razmienė, Eva Řezníčková, Vaida Dambrauskienė, Radek Ostruszka, Martin Kubala, Asta Žukauskaitė, Vladimír Kryštof, Algirdas Šačkus and Eglė Arbačiauskienė
Molecules 2021, 26(21), 6747; https://doi.org/10.3390/molecules26216747 - 08 Nov 2021
Cited by 8 | Viewed by 2979
Abstract
A library of 2,4,6,7-tetrasubstituted-2H-pyrazolo[4,3-c]pyridines was prepared from easily accessible 1-phenyl-3-(2-phenylethynyl)-1H-pyrazole-4-carbaldehyde via an iodine-mediated electrophilic cyclization of intermediate 4-(azidomethyl)-1-phenyl-3-(phenylethynyl)-1H-pyrazoles to 7-iodo-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridines followed by Suzuki cross-couplings with various boronic acids and alkylation reactions. [...] Read more.
A library of 2,4,6,7-tetrasubstituted-2H-pyrazolo[4,3-c]pyridines was prepared from easily accessible 1-phenyl-3-(2-phenylethynyl)-1H-pyrazole-4-carbaldehyde via an iodine-mediated electrophilic cyclization of intermediate 4-(azidomethyl)-1-phenyl-3-(phenylethynyl)-1H-pyrazoles to 7-iodo-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridines followed by Suzuki cross-couplings with various boronic acids and alkylation reactions. The compounds were evaluated for their antiproliferative activity against K562, MV4-11, and MCF-7 cancer cell lines. The most potent compounds displayed low micromolar GI50 values. 4-(2,6-Diphenyl-2H-pyrazolo[4,3-c]pyridin-7-yl)phenol proved to be the most active, induced poly(ADP-ribose) polymerase 1 (PARP-1) cleavage, activated the initiator enzyme of apoptotic cascade caspase 9, induced a fragmentation of microtubule-associated protein 1-light chain 3 (LC3), and reduced the expression levels of proliferating cell nuclear antigen (PCNA). The obtained results suggest a complex action of 4-(2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-yl)phenol that combines antiproliferative effects with the induction of cell death. Moreover, investigations of the fluorescence properties of the final compounds revealed 7-(4-methoxyphenyl)-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridine as the most potent pH indicator that enables both fluorescence intensity-based and ratiometric pH sensing. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Graphical abstract

18 pages, 999 KiB  
Article
Convenient Synthesis of Pyrazolo[4′,3′:5,6]pyrano[4,3-c][1,2]oxazoles via Intramolecular Nitrile Oxide Cycloaddition
by Vaida Milišiūnaitė, Elena Plytninkienė, Roberta Bakšienė, Aurimas Bieliauskas, Sonata Krikštolaitytė, Greta Račkauskienė, Eglė Arbačiauskienė and Algirdas Šačkus
Molecules 2021, 26(18), 5604; https://doi.org/10.3390/molecules26185604 - 15 Sep 2021
Cited by 9 | Viewed by 2610
Abstract
A simple and efficient synthetic route to the novel 3a,4-dihydro-3H,7H- and 4H,7H-pyrazolo[4′,3′:5,6]pyrano[4,3-c][1,2]oxazole ring systems from 3-(prop-2-en-1-yloxy)- or 3-(prop-2-yn-1-yloxy)-1H-pyrazole-4-carbaldehyde oximes has been developed by employing the intramolecular nitrile oxide cycloaddition (INOC) reaction [...] Read more.
A simple and efficient synthetic route to the novel 3a,4-dihydro-3H,7H- and 4H,7H-pyrazolo[4′,3′:5,6]pyrano[4,3-c][1,2]oxazole ring systems from 3-(prop-2-en-1-yloxy)- or 3-(prop-2-yn-1-yloxy)-1H-pyrazole-4-carbaldehyde oximes has been developed by employing the intramolecular nitrile oxide cycloaddition (INOC) reaction as the key step. The configuration of intermediate aldoximes was unambiguously determined using NOESY experimental data and comparison of the magnitudes of 1JCH coupling constants of the iminyl moiety, which were greater by approximately 13 Hz for the predominant syn isomer. The structures of the obtained heterocyclic products were confirmed by detailed 1H, 13C and 15N NMR spectroscopic experiments and HRMS measurements. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Graphical abstract

13 pages, 2017 KiB  
Article
Synthesis, Characterization, and Biological Evaluation of Some Novel Pyrazolo[5,1-b]thiazole Derivatives as Potential Antimicrobial and Anticancer Agents
by Abdulrhman Alsayari, Abdullatif Bin Muhsinah, Yahya I. Asiri, Faiz A. Al-aizari, Nabila A. Kheder, Zainab M. Almarhoon, Hazem A. Ghabbour and Yahia N. Mabkhot
Molecules 2021, 26(17), 5383; https://doi.org/10.3390/molecules26175383 - 04 Sep 2021
Cited by 9 | Viewed by 2720
Abstract
The pharmacological activities of thiazole and pyrazole moieties as antimicrobial and anticancer agents have been thoroughly described in many literature reviews. In this study, a convenient synthesis of novel pyrazolo[5,1-b]thiazole-based heterocycles was carried out. The synthesized compounds were characterized by IR, [...] Read more.
The pharmacological activities of thiazole and pyrazole moieties as antimicrobial and anticancer agents have been thoroughly described in many literature reviews. In this study, a convenient synthesis of novel pyrazolo[5,1-b]thiazole-based heterocycles was carried out. The synthesized compounds were characterized by IR, 1H and 13C NMR spectroscopy and mass spectrometry. Some selected examples were screened and evaluated for their antimicrobial and anticancer activities and showed promising results. These products could serve as leading compounds in the future design of new drug molecules. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Graphical abstract

Review

Jump to: Editorial, Research

37 pages, 13175 KiB  
Review
Recent Developments in Reactions and Catalysis of Protic Pyrazole Complexes
by Wei-Syuan Lin and Shigeki Kuwata
Molecules 2023, 28(8), 3529; https://doi.org/10.3390/molecules28083529 - 17 Apr 2023
Cited by 5 | Viewed by 1700
Abstract
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(1 [...] Read more.
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. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Scheme 1

82 pages, 26827 KiB  
Review
Recent Applications of the Multicomponent Synthesis for Bioactive Pyrazole Derivatives
by Diana Becerra, Rodrigo Abonia and Juan-Carlos Castillo
Molecules 2022, 27(15), 4723; https://doi.org/10.3390/molecules27154723 - 23 Jul 2022
Cited by 41 | Viewed by 3311
Abstract
Pyrazole and its derivatives are considered a privileged N-heterocycle with immense therapeutic potential. Over the last few decades, the pot, atom, and step economy (PASE) synthesis of pyrazole derivatives by multicomponent reactions (MCRs) has gained increasing popularity in pharmaceutical and medicinal chemistry. [...] Read more.
Pyrazole and its derivatives are considered a privileged N-heterocycle with immense therapeutic potential. Over the last few decades, the pot, atom, and step economy (PASE) synthesis of pyrazole derivatives by multicomponent reactions (MCRs) has gained increasing popularity in pharmaceutical and medicinal chemistry. The present review summarizes the recent developments of multicomponent reactions for the synthesis of biologically active molecules containing the pyrazole moiety. Particularly, it covers the articles published from 2015 to date related to antibacterial, anticancer, antifungal, antioxidant, α-glucosidase and α-amylase inhibitory, anti-inflammatory, antimycobacterial, antimalarial, and miscellaneous activities of pyrazole derivatives obtained exclusively via an MCR. The reported analytical and activity data, plausible synthetic mechanisms, and molecular docking simulations are organized in concise tables, schemes, and figures to facilitate comparison and underscore the key points of this review. We hope that this review will be helpful in the quest for developing more biologically active molecules and marketed drugs containing the pyrazole moiety. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Graphical abstract

20 pages, 4590 KiB  
Review
Revisiting the Chemistry of Vinylpyrazoles: Properties, Synthesis, and Reactivity
by Vera L. M. Silva and Artur M. S. Silva
Molecules 2022, 27(11), 3493; https://doi.org/10.3390/molecules27113493 - 29 May 2022
Cited by 3 | Viewed by 1492
Abstract
Vinylpyrazoles, also known as pyrazolyl olefins, are interesting motifs in organic chemistry but have been overlooked. This review describes the properties and synthetic routes of vinylpyrazoles and highlights their versatility as building blocks for the construction of more complex organic molecules. Concerning the [...] Read more.
Vinylpyrazoles, also known as pyrazolyl olefins, are interesting motifs in organic chemistry but have been overlooked. This review describes the properties and synthetic routes of vinylpyrazoles and highlights their versatility as building blocks for the construction of more complex organic molecules. Concerning the reactivity of vinylpyrazoles, the topics surveyed herein include their use in cycloaddition reactions, free-radical polymerizations, halogenation and hydrohalogenation reactions, and more recently in transition-metal-catalyzed reactions, among other transformations. The current state of the art about vinylpyrazoles is presented with an eye to future developments regarding the chemistry of these interesting compounds. Styrylpyrazoles were not considered in this review, as they were the subject of a previous review article published in 2020. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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63 pages, 16829 KiB  
Review
1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research
by Andrzej Danel, Ewa Gondek, Mateusz Kucharek, Paweł Szlachcic and Arkadiusz Gut
Molecules 2022, 27(9), 2775; https://doi.org/10.3390/molecules27092775 - 26 Apr 2022
Cited by 6 | Viewed by 2897
Abstract
This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, [...] Read more.
This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, synthesis from anthranilic acid derivatives, multicomponent synthesis and others. The use of this class of compounds as potential fluorescent sensors and biologically active compounds is shown. This review intends to summarize the abovementioned aspects of 1H-pyrazolo[3,4-b]quinoline chemistry. Some of the results that are presented in this publication come from the laboratories of the authors of this review. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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Review
1H-Pyrazolo[3,4-b]pyridines: Synthesis and Biomedical Applications
by Ana Donaire-Arias, Ana Maria Montagut, Raimon Puig de la Bellacasa, Roger Estrada-Tejedor, Jordi Teixidó and José I. Borrell
Molecules 2022, 27(7), 2237; https://doi.org/10.3390/molecules27072237 - 30 Mar 2022
Cited by 19 | Viewed by 3334
Abstract
Pyrazolo[3,4-b]pyridines are a group of heterocyclic compounds presenting two possible tautomeric forms: the 1H- and 2H-isomers. More than 300,000 1H-pyrazolo[3,4-b]pyridines have been described which are included in more than 5500 references (2400 patents) [...] Read more.
Pyrazolo[3,4-b]pyridines are a group of heterocyclic compounds presenting two possible tautomeric forms: the 1H- and 2H-isomers. More than 300,000 1H-pyrazolo[3,4-b]pyridines have been described which are included in more than 5500 references (2400 patents) up to date. This review will cover the analysis of the diversity of the substituents present at positions N1, C3, C4, C5, and C6, the synthetic methods used for their synthesis, starting from both a preformed pyrazole or pyridine, and the biomedical applications of such compounds. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds II)
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