1,2,4-Triazoles: Synthetic approaches and pharmacological importance. (Review)

Copper-catalyzed one-pot synthesis of 1,2,4-triazoles from nitriles and hydroxylamine

A simple and efficient copper-catalyzed one-pot synthesis of substituted 1,2,4-triazoles through reactions of two nitriles with hydroxylamine has been developed. The protocol uses simple and readily available nitriles and hydroxylamine hydrochloride as the starting materials and inexpensive Cu(OAc)2 as the catalyst, and the corresponding 1,2,4-triazole derivatives are obtained in moderate to good yields. The reactions include sequential intermolecular addition of hydroxylamine to one nitrile to provide amidoxime, copper-catalyzed treatment of the amidoxime with another nitrile, and intramolecular dehydration/cyclization. This finding provides a new and useful strategy for synthesis of 1,2,4-triazole derivatives.

Design, synthesis and anti-tobacco mosaic virus (TMV) activity of 5-chloro-N-(4-cyano-1-aryl-1H-pyrazol-5-yl)-1-aryl-3-methyl-1H-pyrazole-4-carboxamide derivatives

A series of novel pyrazole amide derivatives 3a-3p which take TMV PC protein as the target has been designed and synthesized by the reactions of 5-chloro-1-aryl-3-methyl-1H-pyrazole-4-carboxylic acids with 5-amino-1-aryl-1H-pyrazole-4-carbonitriles. All the compounds were characterized by 1H-NMR, mass spectroscopy and elemental analysis. Preliminary bioassays indicated that all the compounds acted against the tobacco mosaic virus (TMV) with different in vivo and in vitro modes at 500 μg/mL and were found to possess promising activity. Especially, compound 3p showed the most potent biological activity against tobacco mosaic virus (TMV) compared to ningnanmycin, and a molecular docking study was performed and the binding model revealed that the pyrazole amide moiety was tightly embedded in the binding sites of TMV PC (PDB code: 2OM3).

PEG-assisted two-component approach for the facile synthesis of 5-aryl-1,2,4-triazolidine-3-thiones under catalyst-free conditions

A straightforward and greener PEG-assisted protocol has been disclosed for the synthesis of 5-aryl-1,2,4-triazolidine-3-thiones via the reaction of aromatic aldehydes and thiosemicarbazides using very convenient neutral reaction conditions.

Recent advances bioactive 1,2,4-triazole-3-thiones

Triazoles are heterocyclic compounds which have a five-membered ring of two carbon atoms and three nitrogen atoms. These structures have been interest in the development of novel compounds with anticonvulsant, antidepressant, antioxidant, anti-inflammatory, analgesic, antinociceptive, antibacterial, antimycobacterial, antifungal, antiviral, anticancer, anti-parasitic, anti-urease and other activities. Therefore, many researchers have synthesized these compounds as target structures and evaluated their biological activities. This review contains various pharmacological activities of 1,2,4-triazole-3-thiones in one place and it is also the milestone for the new research towards this moiety.

Benzenesulfonamide bearing 1,2,4-triazole scaffolds as potent inhibitors of tumor associated carbonic anhydrase isoforms hCA IX and hCA XII

Three series of novel heterocyclic compounds (3a-3g, 4a-4g and 5a-5g) containing benzenesulfonamide moiety and incorporating a 1,2,4-triazole ring, have been synthesized and investigated as inhibitors against four isomers of the α-class carbonic anhydrases (CAs, EC 4.2.1.1), comprising hCAs I and II (cytosolic, ubiquitous isozymes) and hCAs IX and XII (transmembrane, tumor associated isozymes). Against the human isozymes hCA I and II, compounds of two series (3a-3g and 4a-4g) showed Ki values in the range of 84-868 nM and 5.6-390 nM, respectively whereas compounds of series 5a-5g were found to be poor inhibitors (Ki values exceeding 10,000 nM in some cases). Against hCA IX and XII, all the tested compounds exhibited excellent to moderate inhibitory potential with Ki values in the range of 2.8-431 nM and 1.3-63 nM, respectively. Compounds 3d, 3f and 4f exhibited excellent inhibitory potential against all of the four isozymes hCA I, II, IX and XII, even better than the standard drug acetazolamide (AZA) whereas compound of the series 5a-5g were comparatively less potent but more selective towards hCA IX and XII.

One-flask synthesis of 1,3,5-trisubstituted 1,2,4-triazoles from nitriles and hydrazonoyl chlorides via 1,3-dipolar cycloaddition

One-flask synthesis of 1,3,5-trisubstituted 1,2,4-triazoles from nitriles and hydrazonoyl chlorides via 1,3-dipolar cycloaddition.

Synthesis of New [1,2,4]Triazolo[3,4-b][1,3,4]thiadiazines and Study of Their Anti-Candidaland Cytotoxic Activities

New triazolothiadiazine derivatives5a–hwere synthesized from 4-amino-3-(4-pyridyl)-5-mercapto-4H-1,2,4-triazole (3) with substituted aryl hydrazonoyl chlorides4a–h. The compounds were testedin vitroagainst elevenCandidaspecies and compared with standard drug ketoconazole. Among these compounds, the compounds bearingp-chlorophenyl5e,p-methoxyphenyl5c, phenyl5a,andp-sulphonamidophenyl5gsubstituents on triazolothiadiazine system were found to be the most effective derivatives againstCandidaspecies. Compound5ewas the most effective compound againstC. parapsilosis(ATCC 22019),C. albicans(ATCC 66027),C.specie [blood] 12810, andC.specie [urine] 300 with MIC value of 6.25 μg/mL, whereas ketoconazole exhibits the inhibitory activity with MIC value of 3–30 μg/mL against all tested strains. It was clear that there is a positive correlation between anti-Candidalactivity andp-chlorophenyl substitution on triazolothiadiazine ring. All the synthesized compounds were also investigated for their potential cytotoxicity on noncancer cell line (MCF-12) using WST-1 assay. Three compounds5d,5a,and5hwere found to have the same IC50value as that of standard drug ketoconazole against noncancer cell line MCF-12 (IC50≥ 1.0 × 105 μg/mL).

Multicomponent synthesis of 1-aryl 1,2,4-triazoles

A multicomponent (single reactor) process for the synthesis of 1-aryl 1,2,4-triazoles was explored and developed. This transformation prepared the 1,2,4-triazole directly from anilines, amino pyridines, and pyrimidines. The reaction scope was explored with 21 different substrates, and the position of the nitrogen atoms in the newly formed ring was established by (15)N labeling and NMR spectroscopy.

Synthesis, structural characterization and comparison of experimental and theoretical results by DFT level of molecular structure of 4-(4-methoxyphenethyl)-3,5-dimethyl-4H-1,2,4-triazole

4-(4-Methoxyphenethyl)-3,5-dimethyl-4H-1,2,4-triazole (3) was synthesized from the reaction of ethyl N'-acetylacetohydrazonate (1) with 2-(4-methoxyphenyl)ethanamine (2). The structure of the title compound 3 has been inferred through IR, (1)H/(13)C NMR, mass spectrometry, elemental analyses and combination of X-ray crystallography and theoretical methods. In addition to the molecular geometry from X-ray determination, the molecular geometry and vibrational frequencies of the title compound 3 in the ground state, were calculated using the density functional method (B3LYP) with the 6-31G(d) basis set. The calculated results show that the optimized geometry can well reproduce the crystal structure and the theoretical vibrational frequencies show good agreement with experimental values. The nonlinear optical properties are also addressed theoretically. The predicted nonlinear optical properties of 3 are greater than ones of urea. In addition, DFT calculations of molecular electrostatic potentials and frontier molecular orbitals of the title compound were carried out at the B3LYP/6-31G(d) level of theory.

Design, spectral characterization and biological studies of transition metal(II) complexes with triazole Schiff bases

A new series of three biologically active triazole derived Schiff base ligands L(1)-L(3) have been synthesized in equimolar reaction of 3-amino-1H-1,2,4-triazole with pyrrol-2-carboxaldehyde, 4-bromo-thiophene-2-carboxaldehyde, and 5-iodo-2-hydroxy benzaldehyde. The prepared Schiff bases were used for further complex formation reaction with different metal elements like Co(II), Ni(II), Cu(II) and Zn(II) as chlorides by using a molar ratio of ligand:metal as 2:1. The structure and bonding nature of all the compounds were identified by their physical, spectral and analytical data. All the metal(II) complexes possessed an octahedral geometry except the Cu(II) complexes which showed a distorted octahedral geometry. All the synthesized compounds, were studied for their in vitro antibacterial, and antifungal activities, against four Gram-negative (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and against six fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) by using agar-well diffusion method. It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. In vitro Brine Shrimp bioassay was also carried out to investigate the cytotoxic properties of these compounds. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

Effect of Microwave Irradiation on the Synthesis of 1,2,4-Triazol-3-One Derivatives and their Antimicrobial Activities

An easy efficient method for the synthesis of N-(3,5-dichlorophenyl)-5-alkyl/aryl-3H-1,2,4-triazol-3-one derivatives under microwave irradiation has been developed using the reaction of 3,5-dichloroaniline and ethoxycarbonylhydrazones. This reaction occurs more efficiently and faster than the conventional heating method. We obtained 5-mercapto-1,3,4-oxadiazol derivatives by this method. The newly synthesised compounds have been tested for their antimicrobial activity against Enterobacter cloaceae, Escherichia coli, Klebsiella pneumonie, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhimurium, Yersinia pseudotuberculosis, Bacillus subtilis and Staphylococcus aereus.

Design, synthesis and antimicrobial evaluation of novel 2-aryl-thiazolidin-4-one derivatives

Novel 2-arylthiazolidin-4-one derivatives (8a-q and 11) have been synthesized in good-to-excellent yields (70-96%) by one-pot three-component condensation-cyclization reaction of aromatic or aliphatic primary amines, aromatic aldehydes, and thioglycolic acid in polypropylene glycol at 110°C temperature. The in vitro antimicrobial activity of the synthesized 2-arylthiazolidin-4-ones was investigated against a panel of six pathogenic fungal strains, a Gram-positive and three Gram-negative bacteria. Results revealed that the compounds (8a-d) bearing 3-(4-(1H-imidazolylmethyl)phenyl)-substituent displayed significant antibacterial efficacy specifically against Klebsiella pneumoniae (minimum inhibitory concentration 12.5 μg/mL). In addition, some of the synthesized compounds have also shown antimicotic activity against Sporothrix schenckii, Trichophyton mentagrophytes, and Aspergillus fumigatus at the concentration of 50 μg/mL.

Rapid synthesis of 1,3,5-substituted 1,2,4-triazoles from carboxylic acids, amidines, and hydrazines

A general method for the synthesis of 1,3,5-trisubstituted 1,2,4-triazoles has been developed from reaction of carboxylic acids, primary amidines, and monosubstituted hydrazines. This highly regioselective and one-pot process provides rapid access to highly diverse triazoles.

Nucleosides 5(15): synthesis of novel 1,2,4-triazolo[3,4-c]-1,2,4-triazole nucleosides

Ribosylation of 3-methylthio-5-phenyl-1,2,4-triazole (1) with ribose derivative 2 gave the protected 1,2,4-triazole-nucleoside 3, which reacted with hydrazine hydrate to afford the 3-hydrazino-1,2,4-triazole derivative 5. Reaction of 5 with aromatic aldehydes yielded the corresponding hydrazones 6, which cyclized under bromination in acetic acid to give 8. Debenzoylation of 8 afforded novel 1,2,4-triazolo[3,4-c]-1,2,4-triazole nucleosides 9.