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

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

Deadline for manuscript submissions: closed (30 April 2021) | Viewed by 55974

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

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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 (17 papers)

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Editorial

Jump to: Research, Review

3 pages, 188 KiB  
Editorial
Special Issue “Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds”
by Vera L. M. Silva and Artur M. S. Silva
Molecules 2021, 26(16), 4989; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26164989 - 18 Aug 2021
Cited by 2 | Viewed by 1646
Abstract
Pyrazoles and their reduced form, pyrazolines, are considered privileged scaffolds in medicinal chemistry, owing to their remarkable biological activities, physicochemical properties and occurrence in many low-molecular-weight compounds present in several marketed drugs (e [...] Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)

Research

Jump to: Editorial, Review

12 pages, 2860 KiB  
Article
Synthesis and Structural Characterization of a Silver(I) Pyrazolato Coordination Polymer
by Kiyoshi Fujisawa, Takuya Nemoto, Yui Morishima and Daniel B. Leznoff
Molecules 2021, 26(4), 1015; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26041015 - 15 Feb 2021
Cited by 7 | Viewed by 2147
Abstract
Coinage metal(I)···metal(I) interactions are widely of interest in fields such as supramolecular assembly and unique luminescent properties, etc. Only two types of polynuclear silver(I) pyrazolato complexes have been reported, however, and no detailed spectroscopic characterizations have been reported. An unexpected synthetic method yielded [...] Read more.
Coinage metal(I)···metal(I) interactions are widely of interest in fields such as supramolecular assembly and unique luminescent properties, etc. Only two types of polynuclear silver(I) pyrazolato complexes have been reported, however, and no detailed spectroscopic characterizations have been reported. An unexpected synthetic method yielded a polynuclear silver(I) complex [Ag(μ-L1Clpz)]n (L1Clpz− = 4-chloride-3,5-diisopropyl-1-pyrazolate anion) by the reaction of {[Ag(μ-L1Clpz)]3}2 with (nBu4N)[Ag(CN)2]. The obtained structure was compared with the known hexanuclear silver(I) complex {[Ag(μ-L1Clpz)]3}2. The Ag···Ag distances in [Ag(μ-L1Clpz)]n are slightly shorter than twice Bondi’s van der Waals radius, indicating some Ag···Ag argentophilic interactions. Two Ag–N distances in [Ag(μ-L1Clpz)]n were found: 2.0760(13) and 2.0716(13) Å, and their N–Ag–N bond angles of 180.00(7)° and 179.83(5)° indicate that each silver(I) ion is coordinated by two pyrazolyl nitrogen atoms with an almost linear coordination. Every five pyrazoles point in the same direction to form a 1-D zig-zag structure. Some spectroscopic properties of [Ag(μ-L1Clpz)]n in the solid-state are different from those of {[Ag(μ-L1Clpz)]3}2 (especially in the absorption and emission spectra), presumably attributable to this zig-zag structure having longer but differently arranged intramolecular Ag···Ag interactions of 3.39171(17) Å. This result clearly demonstrates the different physicochemical properties in the solid-state between 1-D coordination polymer and metalacyclic trinuclear (hexanuclear) or tetranuclear silver(I) pyrazolate complexes. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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16 pages, 3198 KiB  
Article
Boulton-Katritzky Rearrangement of 5-Substituted Phenyl-3-[2-(morpholin-1-yl)ethyl]-1,2,4-oxadiazoles as a Synthetic Path to Spiropyrazoline Benzoates and Chloride with Antitubercular Properties
by Lyudmila Kayukova, Anna Vologzhanina, Kaldybai Praliyev, Gulnur Dyusembaeva, Gulnur Baitursynova, Asem Uzakova, Venera Bismilda, Lyailya Chingissova and Kydyrmolla Akatan
Molecules 2021, 26(4), 967; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26040967 - 12 Feb 2021
Cited by 9 | Viewed by 2470
Abstract
The analysis of stability of biologically active compounds requires an accurate determination of their structure. We have found that 5-aryl-3-(2-aminoethyl)-1,2,4-oxadiazoles are generally unstable in the presence of acids and bases and are rearranged into the salts of spiropyrazolinium compounds. Hence, there is a [...] Read more.
The analysis of stability of biologically active compounds requires an accurate determination of their structure. We have found that 5-aryl-3-(2-aminoethyl)-1,2,4-oxadiazoles are generally unstable in the presence of acids and bases and are rearranged into the salts of spiropyrazolinium compounds. Hence, there is a significant probability that it is the rearranged products that should be attributed to biological activity and not the primarily screened 5-aryl-3-(2-aminoethyl)-1,2,4-oxadiazoles. A series of the 2-amino-8-oxa-1,5-diazaspiro[4.5]dec-1-en-5-ium (spiropyrazoline) benzoates and chloride was synthesized by Boulton–Katritzky rearrangement of 5-substituted phenyl-3-[2-(morpholin-1-yl)ethyl]-1,2,4-oxadiazoles and characterized using FT-IR and NMR spectroscopy and X-ray diffraction. Spiropyrazolylammonium chloride demonstrates in vitro antitubercular activity on DS (drug-sensitive) and MDR (multidrug-resistant) of MTB (M. tuberculosis) strains (1 and 2 µg/mL, accordingly) equal to the activity of the basic antitubercular drug rifampicin; spiropyrazoline benzoates exhibit an average antitubercular activity of 10–100 μg/mL on MTB strains. Molecular docking studies revealed a series of M. tuberculosis receptors with the energies of ligand–receptor complexes (−35.8–−42.8 kcal/mol) close to the value of intermolecular pairwise interactions of the same cation in the crystal of spiropyrazolylammonium chloride (−35.3 kcal/mol). However, only in complex with transcriptional repressor EthR2, both stereoisomers of the cation realize similar intermolecular interactions. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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12 pages, 2819 KiB  
Article
Approaches to the Synthesis of Dicarboxylic Derivatives of Bis(pyrazol-1-yl)alkanes
by Nikita P. Burlutskiy and Andrei S. Potapov
Molecules 2021, 26(2), 413; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26020413 - 14 Jan 2021
Cited by 6 | Viewed by 2470
Abstract
Carboxylation of bis(pyrazol-1-yl)alkanes by oxalyl chloride was studied. It was found that 4,4′-dicarboxylic derivatives of substrates with electron-donating methyl groups and short linkers (from one to three methylene groups) can be prepared using this method. Longer linkers lead to significantly lower product yields, [...] Read more.
Carboxylation of bis(pyrazol-1-yl)alkanes by oxalyl chloride was studied. It was found that 4,4′-dicarboxylic derivatives of substrates with electron-donating methyl groups and short linkers (from one to three methylene groups) can be prepared using this method. Longer linkers lead to significantly lower product yields, which is probably due to instability of the intermediate acid chlorides that are initially formed in the reaction with oxalyl chloride. Thus, bis(pyrazol-1-yl)methane gave only monocarboxylic derivative even with a large excess of oxalyl chloride and prolonged reaction duration. An alternative approach involves the reaction of ethyl 4-pyrazolecarboxylates with dibromoalkanes in a superbasic medium (potassium hydroxide–dimethyl sulfoxide) and is suitable for the preparation of bis(4-carboxypyrazol-1-yl)alkanes with both short and long linkers independent of substitution in positions 3 and 5 of pyrazole rings. The obtained dicarboxylic acids are interesting as potential building blocks for metal-organic frameworks. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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18 pages, 7699 KiB  
Article
Synthesis of 6,7-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by Azomethine Imine-Alkyne Cycloadditions Using Immobilized Cu(II)-Catalysts
by Urša Štanfel, Dejan Slapšak, Uroš Grošelj, Franc Požgan, Bogdan Štefane and Jurij Svete
Molecules 2021, 26(2), 400; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26020400 - 13 Jan 2021
Cited by 8 | Viewed by 2728
Abstract
A series of 12 silica gel-bound enaminones and their Cu(II) complexes were prepared and tested for their suitability as heterogeneous catalysts in azomethine imine-alkyne cycloadditions (CuAIAC). Immobilized Cu(II)–enaminone complexes showed promising catalytic activity in the CuAIAC reaction, but these new catalysts suffered from [...] Read more.
A series of 12 silica gel-bound enaminones and their Cu(II) complexes were prepared and tested for their suitability as heterogeneous catalysts in azomethine imine-alkyne cycloadditions (CuAIAC). Immobilized Cu(II)–enaminone complexes showed promising catalytic activity in the CuAIAC reaction, but these new catalysts suffered from poor reusability. This was not due to the decoordination of copper ions, as the use of enaminone ligands with additional complexation sites resulted in negligible improvement. On the other hand, reusability was improved by the use of 4-aminobenzoic acid linker, attached to 3-aminopropyl silica gel via an amide bond to the enaminone over the more hydrolytically stable N-arylenamine C-N bond. The study showed that silica gel-bound Cu(II)–enaminone complexes are readily available and suitable heterogeneous catalysts for the synthesis of 6,7-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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13 pages, 2958 KiB  
Article
Fe(III) Complexes Based on Mono- and Bis-pyrazolyl-s-triazine Ligands: Synthesis, Molecular Structure, Hirshfeld, and Antimicrobial Evaluations
by Saied M. Soliman, Hessa H. Al-Rasheed, Jörg H. Albering and Ayman El-Faham
Molecules 2020, 25(23), 5750; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25235750 - 05 Dec 2020
Cited by 9 | Viewed by 2028
Abstract
The self-assembly of iron(III) chloride with three pyrazolyl-s-triazine ligands, namely 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)-1,3,5-triazine (PipBPT), 4-(4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-yl)morpholine (MorphBPT), and 4,4’-(6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4-diyl)dimorpholine (bisMorphPT) afforded [Fe(PipBPT)Cl2][FeCl4] ( [...] Read more.
The self-assembly of iron(III) chloride with three pyrazolyl-s-triazine ligands, namely 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)-1,3,5-triazine (PipBPT), 4-(4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-yl)morpholine (MorphBPT), and 4,4’-(6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4-diyl)dimorpholine (bisMorphPT) afforded [Fe(PipBPT)Cl2][FeCl4] (1), [Fe(MorphBPT)Cl2][FeCl4] (2), and [H(bisMorphPT)][FeCl4]. bisMorphPT.2H2O (3), respectively, in good yield. In complexes 1 and 2, the Fe(III) is pentacoordinated with three Fe-N interactions from the pincer ligand and two coordinated chloride anions in the inner sphere, and FeCl4¯ in the outer sphere. Complex 3 is comprised of one protonated ligand as cationic part, one FeCl4¯ anion, and one neutral bisMorphPT molecule in addition to two crystallized water molecules. Analysis of molecular packing using Hirshfeld calculations indicated that H…H and Cl…H are the most important in the molecular packing. They comprised 40.1% and 37.4%, respectively in 1 and 32.4% and 37.8%, respectively in 2. Complex 1 exhibited the most bioactivity against the tested microbes while 3 had the lowest bioactivity. The bisMorphPT and MorphBPT were inactive towards the tested microbes while PipBPT was active. As a whole, the Fe(III) complexes have enhanced antibacterial and antifungal activities as compared to the free ligands. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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29 pages, 10578 KiB  
Article
A Computational Study of Metallacycles Formed by Pyrazolate Ligands and the Coinage Metals M = Cu(I), Ag(I) and Au(I): (pzM)n for n = 2, 3, 4, 5 and 6. Comparison with Structures Reported in the Cambridge Crystallographic Data Center (CCDC)
by José Elguero and Ibon Alkorta
Molecules 2020, 25(21), 5108; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25215108 - 03 Nov 2020
Cited by 9 | Viewed by 2587
Abstract
The structures reported in the Cambridge Structural Database (CSD) for neutral metallacycles formed by coinage metals in their valence (I) (cations) and pyrazolate anions were examined. Depending on the metal, dimers and trimers are the most common but some larger rings have also [...] Read more.
The structures reported in the Cambridge Structural Database (CSD) for neutral metallacycles formed by coinage metals in their valence (I) (cations) and pyrazolate anions were examined. Depending on the metal, dimers and trimers are the most common but some larger rings have also been reported, although some of the larger structures are not devoid of ambiguity. M06-2x calculations were carried out on simplified structures (without C-substituents on the pyrazolate rings) in order to facilitate a comparison with the reported X-ray structures (geometries and energies). The problems of stability of the different ring sizes were also analyzed. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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12 pages, 1702 KiB  
Article
C4-Alkylamination of C4-Halo-1H-1-tritylpyrazoles Using Pd(dba)2 or CuI
by Yoshihide Usami, Yuya Tatsui, Hiroki Yoneyama and Shinya Harusawa
Molecules 2020, 25(20), 4634; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25204634 - 12 Oct 2020
Cited by 7 | Viewed by 2495
Abstract
Alkylamino coupling reactions at the C4 positions of 4-halo-1H-1-tritylpyrazoles were investigated using palladium or copper catalysts. The Pd(dba)2 catalyzed C-N coupling reaction of aryl- or alkylamines, lacking a β-hydrogen atom, proceeded smoothly using tBuDavePhos as a ligand. As a [...] Read more.
Alkylamino coupling reactions at the C4 positions of 4-halo-1H-1-tritylpyrazoles were investigated using palladium or copper catalysts. The Pd(dba)2 catalyzed C-N coupling reaction of aryl- or alkylamines, lacking a β-hydrogen atom, proceeded smoothly using tBuDavePhos as a ligand. As a substrate, 4-Bromo-1-tritylpyrazole was more effective than 4-iodo or chloro-1-tritylpyrazoles. Meanwhile, the CuI mediated C-N coupling reactions of 4-iodo-1H-1-tritylpyrazole were effective for alkylamines possessing a β-hydrogen atom. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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16 pages, 6327 KiB  
Article
Synthesis and Antimicrobial Studies of Coumarin-Substituted Pyrazole Derivatives as Potent Anti-Staphylococcus aureus Agents
by Rawan Alnufaie, Hansa Raj KC, Nickolas Alsup, Jedidiah Whitt, Steven Andrew Chambers, David Gilmore and Mohammad A. Alam
Molecules 2020, 25(12), 2758; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25122758 - 15 Jun 2020
Cited by 36 | Viewed by 3348
Abstract
In this paper, synthesis and antimicrobial studies of 31 novel coumarin-substituted pyrazole derivatives are reported. Some of these compounds have shown potent activity against methicillin-resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentration (MIC) as low as 3.125 µg/mL. These molecules are equally potent [...] Read more.
In this paper, synthesis and antimicrobial studies of 31 novel coumarin-substituted pyrazole derivatives are reported. Some of these compounds have shown potent activity against methicillin-resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentration (MIC) as low as 3.125 µg/mL. These molecules are equally potent at inhibiting the development of MRSA biofilm and the destruction of preformed biofilm. These results are very significant as MRSA strains have emerged as one of the most menacing pathogens of humans and this bacterium is bypassing HIV in terms of fatality rate. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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16 pages, 4701 KiB  
Article
Selective Synthesis and Photoluminescence Study of Pyrazolopyridopyridazine Diones and N-Aminopyrazolopyrrolopyridine Diones
by Ching-Chun Tseng, Cheng-Yen Chung, Shuo-En Tsai, Hiroyuki Takayama, Naoto Uramaru, Chin-Yu Lin and Fung Fuh Wong
Molecules 2020, 25(10), 2409; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25102409 - 21 May 2020
Cited by 4 | Viewed by 2551
Abstract
The newly designed luminol structures of pyrazolopyridopyridazine diones and N-aminopyrazolopyrrolopyridine diones were synthesized from versatile 1,3-diaryfuropyrazolopyridine-6,8-diones, 1,3-diarylpyrazolopyrrolopyridine-6,8-diones, or 1,3-diaryl-7-methylpyrazolopyrrolopyridine-6,8-diones with hydrazine monohydrate. Photoluminescent and solvatofluorism properties containing UV–Vis absorption, emission spectra, and quantum yield (Φf) study of pyrazolopyridopyridazine diones and [...] Read more.
The newly designed luminol structures of pyrazolopyridopyridazine diones and N-aminopyrazolopyrrolopyridine diones were synthesized from versatile 1,3-diaryfuropyrazolopyridine-6,8-diones, 1,3-diarylpyrazolopyrrolopyridine-6,8-diones, or 1,3-diaryl-7-methylpyrazolopyrrolopyridine-6,8-diones with hydrazine monohydrate. Photoluminescent and solvatofluorism properties containing UV–Vis absorption, emission spectra, and quantum yield (Φf) study of pyrazolopyridopyridazine diones and N-aminopyrazolopyrrolopyridine diones were also studied. Generally, most of pyrazolopyrrolopyridine-6,8-diones 6 exhibited the significant fluorescence intensity and the substituent effect when compared with N-aminopyrazolopyrrolopyridine diones, particularly for 6c and 6j with a m-chloro group. Additionally, the fluorescence intensity of 6j was significantly promoted due to the suitable conjugation conformation. Based on the quantum yield (Φf) study, the value of compound 6j (0.140) with planar structural skeletal was similar to that of standard luminol (1, 0.175). Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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Review

Jump to: Editorial, Research

25 pages, 90668 KiB  
Review
Electrooxidation Is a Promising Approach to Functionalization of Pyrazole-Type Compounds
by Boris V. Lyalin, Vera L. Sigacheva, Anastasia S. Kudinova, Sergey V. Neverov, Vladimir A. Kokorekin and Vladimir A. Petrosyan
Molecules 2021, 26(16), 4749; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26164749 - 05 Aug 2021
Cited by 10 | Viewed by 2576
Abstract
The review summarizes for the first time the poorly studied electrooxidative functionalization of pyrazole derivatives leading to the C–Cl, C–Br, C–I, C–S and N–N coupling products with applied properties. The introduction discusses some aspects of aromatic hydrogen substitution. Further, we mainly consider our [...] Read more.
The review summarizes for the first time the poorly studied electrooxidative functionalization of pyrazole derivatives leading to the C–Cl, C–Br, C–I, C–S and N–N coupling products with applied properties. The introduction discusses some aspects of aromatic hydrogen substitution. Further, we mainly consider our works on effective synthesis of the corresponding halogeno, thiocyanato and azo compounds using cheap, affordable and environmentally promising electric currents. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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35 pages, 139203 KiB  
Review
Functional Pyrazolo[1,5-a]pyrimidines: Current Approaches in Synthetic Transformations and Uses As an Antitumor Scaffold
by Andres Arias-Gómez, Andrés Godoy and Jaime Portilla
Molecules 2021, 26(9), 2708; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26092708 - 05 May 2021
Cited by 57 | Viewed by 5722
Abstract
Pyrazolo[1,5-a]pyrimidine (PP) derivatives are an enormous family of N-heterocyclic compounds that possess a high impact in medicinal chemistry and have attracted a great deal of attention in material science recently due to their significant photophysical properties. Consequently, various [...] Read more.
Pyrazolo[1,5-a]pyrimidine (PP) derivatives are an enormous family of N-heterocyclic compounds that possess a high impact in medicinal chemistry and have attracted a great deal of attention in material science recently due to their significant photophysical properties. Consequently, various researchers have developed different synthesis pathways for the preparation and post-functionalization of this functional scaffold. These transformations improve the structural diversity and allow a synergic effect between new synthetic routes and the possible applications of these compounds. This contribution focuses on an overview of the current advances (2015–2021) in the synthesis and functionalization of diverse pyrazolo[1,5-a]pyrimidines. Moreover, the discussion highlights their anticancer potential and enzymatic inhibitory activity, which hopefully could lead to new rational and efficient designs of drugs bearing the pyrazolo[1,5-a]pyrimidine core. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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38 pages, 13911 KiB  
Review
Pyrazole Scaffold Synthesis, Functionalization, and Applications in Alzheimer’s Disease and Parkinson’s Disease Treatment (2011–2020)
by Xuefei Li, Yanbo Yu and Zhude Tu
Molecules 2021, 26(5), 1202; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26051202 - 24 Feb 2021
Cited by 38 | Viewed by 4765
Abstract
The remarkable prevalence of pyrazole scaffolds in a versatile array of bioactive molecules ranging from apixaban, an anticoagulant used to treat and prevent blood clots and stroke, to bixafen, a pyrazole-carboxamide fungicide used to control diseases of rapeseed and cereal plants, has encouraged [...] Read more.
The remarkable prevalence of pyrazole scaffolds in a versatile array of bioactive molecules ranging from apixaban, an anticoagulant used to treat and prevent blood clots and stroke, to bixafen, a pyrazole-carboxamide fungicide used to control diseases of rapeseed and cereal plants, has encouraged both medicinal and organic chemists to explore new methods in developing pyrazole-containing compounds for different applications. Although numerous synthetic strategies have been developed in the last 10 years, there has not been a comprehensive overview of synthesis and the implication of recent advances for treating neurodegenerative disease. This review first presents the advances in pyrazole scaffold synthesis and their functionalization that have been published during the last decade (2011–2020). We then narrow the focus to the application of these strategies in the development of therapeutics for neurodegenerative diseases, particularly for Alzheimer’s disease (AD) and Parkinson’s disease (PD). Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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30 pages, 8517 KiB  
Review
Homocoupling Reactions of Azoles and Their Applications in Coordination Chemistry
by Steffen B. Mogensen, Mercedes K. Taylor and Ji-Woong Lee
Molecules 2020, 25(24), 5950; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25245950 - 15 Dec 2020
Cited by 12 | Viewed by 3605
Abstract
Pyrazole, a member of the structural class of azoles, exhibits molecular properties of interest in pharmaceuticals and materials chemistry, owing to the two adjacent nitrogen atoms in the five-membered ring system. The weakly basic nitrogen atoms of deprotonated pyrazoles have been applied in [...] Read more.
Pyrazole, a member of the structural class of azoles, exhibits molecular properties of interest in pharmaceuticals and materials chemistry, owing to the two adjacent nitrogen atoms in the five-membered ring system. The weakly basic nitrogen atoms of deprotonated pyrazoles have been applied in coordination chemistry, particularly to access coordination polymers and metal-organic frameworks, and homocoupling reactions can in principle provide facile access to bipyrazole ligands. In this context, we summarize recent advances in homocoupling reactions of pyrazoles and other types of azoles (imidazoles, triazoles and tetrazoles) to highlight the utility of homocoupling reactions in synthesizing symmetric bi-heteroaryl systems compared with traditional synthesis. Metal-free reactions and transition-metal catalyzed homocoupling reactions are discussed with reaction mechanisms in detail. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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32 pages, 8639 KiB  
Review
Styrylpyrazoles: Properties, Synthesis and Transformations
by Pedro M. O. Gomes, Pedro M. S. Ouro, Artur M. S. Silva and Vera L. M. Silva
Molecules 2020, 25(24), 5886; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25245886 - 12 Dec 2020
Cited by 10 | Viewed by 3381
Abstract
The pyrazole nucleus and its reduced forms, pyrazolines and pyrazolidine, are privileged scaffolds in medicinal chemistry due to their remarkable biological activities. A huge number of pyrazole derivatives have been studied and reported over time. This review article gives an overview of pyrazole [...] Read more.
The pyrazole nucleus and its reduced forms, pyrazolines and pyrazolidine, are privileged scaffolds in medicinal chemistry due to their remarkable biological activities. A huge number of pyrazole derivatives have been studied and reported over time. This review article gives an overview of pyrazole derivatives that contain a styryl (2-arylvinyl) group linked in different positions of the pyrazole backbone. Although there are studies on the synthesis of styrylpyrazoles dating back to the 1970s and even earlier, this type of compound has rarely been studied. This timely review intends to summarize the properties, biological activity, methods of synthesis and transformation of styrylpyrazoles; thus, highlighting the interest and huge potential for application of this kind of compound. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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42 pages, 9647 KiB  
Review
Recent Advances in Synthesis and Properties of Nitrated-Pyrazoles Based Energetic Compounds
by Shijie Zhang, Zhenguo Gao, Di Lan, Qian Jia, Ning Liu, Jiaoqiang Zhang and Kaichang Kou
Molecules 2020, 25(15), 3475; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25153475 - 30 Jul 2020
Cited by 47 | Viewed by 5553
Abstract
Nitrated-pyrazole-based energetic compounds have attracted wide publicity in the field of energetic materials (EMs) due to their high heat of formation, high density, tailored thermal stability, and detonation performance. Many nitrated-pyrazole-based energetic compounds have been developed to meet the increasing demands of high [...] Read more.
Nitrated-pyrazole-based energetic compounds have attracted wide publicity in the field of energetic materials (EMs) due to their high heat of formation, high density, tailored thermal stability, and detonation performance. Many nitrated-pyrazole-based energetic compounds have been developed to meet the increasing demands of high power, low sensitivity, and eco-friendly environment, and they have good applications in explosives, propellants, and pyrotechnics. Continuous and growing efforts have been committed to promote the rapid development of nitrated-pyrazole-based EMs in the last decade, especially through large amounts of Chinese research. Some of the ultimate aims of nitrated-pyrazole-based materials are to develop potential candidates of castable explosives, explore novel insensitive high energy materials, search for low cost synthesis strategies, high efficiency, and green environmental protection, and further widen the applications of EMs. This review article aims to present the recent processes in the synthesis and physical and explosive performances of the nitrated-pyrazole-based Ems, including monopyrazoles with nitro, bispyrazoles with nitro, nitropyrazolo[4,3-c]pyrazoles, and their derivatives, and to comb the development trend of these compounds. This review intends to prompt fresh concepts for designing prominent high-performance nitropyrazole-based EMs. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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35 pages, 2516 KiB  
Review
Pyrazolyl-Ureas as Interesting Scaffold in Medicinal Chemistry
by Chiara Brullo, Federica Rapetti and Olga Bruno
Molecules 2020, 25(15), 3457; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25153457 - 29 Jul 2020
Cited by 18 | Viewed by 3870
Abstract
The pyrazole nucleus has long been known as a privileged scaffold in the synthesis of biologically active compounds. Within the numerous pyrazole derivatives developed as potential drugs, this review is focused on molecules characterized by a urea function directly linked to the pyrazole [...] Read more.
The pyrazole nucleus has long been known as a privileged scaffold in the synthesis of biologically active compounds. Within the numerous pyrazole derivatives developed as potential drugs, this review is focused on molecules characterized by a urea function directly linked to the pyrazole nucleus in a different position. In the last 20 years, the interest of numerous researchers has been especially attracted by pyrazolyl-ureas showing a wide spectrum of biological activities, ranging from the antipathogenic activities (bacteria, plasmodium, toxoplasma, and others) to the anticarcinogenic activities. In particular, in the anticancer field, pyrazolyl-ureas have been shown to interact at the intracellular level on many pathways, in particular on different kinases such as Src, p38-MAPK, TrKa, and others. In addition, some of them evidenced an antiangiogenic potential that deserves to be explored. This review therefore summarizes all these biological data (from 2000 to date), including patented compounds. Full article
(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)
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