Preparation, GIAO NMR Calculations and Acidic Properties of Some Novel 4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives with Their Antioxidant Activities

Six novel 3-alkyl(aryl)-4-(p-nitrobenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5- ones (2a-f) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H- 1,2,4-triazol-5-ones (1a-f) with p-nitrobenzoyl chloride and characterized by elemental analyses and IR, ¹H-NMR, ¹³C-NMR and UV spectral data. The newly synthesized compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetone, isopropyl alcohol, tert-butyl alcohol and N,N-dimethylformamide, and the half-neutralization potential values and the corresponding pK_a values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic ¹H and ¹³C nuclear magnetic shielding constants of compounds 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data. Furthermore, these new compounds and five recently reported 3-alkyl-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3a–c,e,f) were screened for their antioxidant activities.     

Synthesis,Characterization and Conductivity Properties of Novel Oligomer Schiff Bases Derived from 4-Amino-3-hydrazino-5-mercapto-1, 2, 4-triazole and Their Reactions with VO(IV), Cu(II) Ions

A new Schiff base, 4-(4-hydroxysalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (4HSAHMT), and novel Schiff base oligomers of 4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole (SAHMT), 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (2HNAHMT), 4-(4-hydroxysalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (4HSAHMT) and 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (BrSAHMT) were synthesized via oxidative polymerization using NaOCl as the oxidant. The structures of the oligomers were supported by FT-IR, UV–Vis, ¹H-NMR, and ¹³C-NMR techniques. The compounds were further characterized by solubility tests, TG–DTA, and elemental analysis. The molecular weight distribution parameters of the compounds were determined by the size exclusion chromatography (SEC). According to SEC, the number average molecular weight (M _n ) values of O-SAHMT, O-BrSAHMT, O-4HSAHMT and O-2HNAHMT were 2,700, 2,100, 2,700 and 1,000 g mol^?1, respectively. The weight losses of O-SAHMT, O-BrSAHMT, O-4HSAHMT and O-2HNAHMT were 73, 76, 80 and 54 %, respectively, at 1,000 °C. TG analyses showed that the synthesized oligomers were stable toward thermal decomposition. The synthesized oligomers were converted to metal complexes with salts of VO(IV) and Cu(II). The doped and undoped electrical properties of oligomers and oligomer–metal complexes were determined by the four-point probe technique at room temperature and atmospheric pressure.     

The Triazole Ring as a Privileged Scaffold for Putative Antifungals: Synthesis and Evaluation of a Series of New Analogues

The significant antifungal activity of a series of novel 1,2,4-triazole derivatives against different strains of Candida albicans, Candida krusei and Aspergillus fumigatus, compared to the commercial fungicides ketoconazole and itraconazole, is reported. Systemic mycosis and invasive fungal infections, whether from immunodeficiency or hospital-acquired infection, have been on an upward trend for several years. The 1,2,4-triazole ring substituted with other aromatic and heteroaromatic systems plays an important role in the field of antifungal drug discovery and development. Thus, an extensive series of 29 triazoles, substituted in different positions with a variety of aromatic rings, has been designed, synthesized, and evaluated for their fungicidal activity. Almost all the agents tested in vitro showed high activity against all examined fungal strains. It is noteworthy that, in the case of A. fumigatus, all the examined compounds achieved equal or higher antifungal activity than ketoconazole, but less activity than itraconazole. Among all the derivatives studied, the dichlorourea analogue and bromo-substituted triazole stand out as the most promising compounds. Quantitative structure-activity relationship (QSAR) models were built for a systematic structure-activity relationship (SAR) profile to explain and potentially explore the potency characteristics of 1,2,4-triazole analogues.     

1,2,4-三唑并[3,4-b]-1,3,4-噻二唑的合成、结构及生物活性

为了筛选出新的高活性化合物,以二氨基硫脲与有机羧酸为原料,回流反应生成中间体4-氨基-5-取代-1,2,4-三唑硫酮,再与羧酸在POCl3的催化下合成了3,6-双取代1,2,4-三唑并[3,4-b]-1,3,4-噻二唑新化合物。目标化合物通过IR、元素分析和1H NMR对其结构进行了表征。并初步测定了该化合物对5种植物病原菌(烟草赤星病、马铃薯干腐病、小麦赤霉病、番茄早疫病、西瓜枯萎病)的杀菌活性,结果表明此类化合物对所测菌种具有良好的杀菌、抑菌作用。     

含芳硫(芳氧)乙酸的新三唑类化合物的合成与生物活性研究

以苯(硫)酚、氯乙酸、N-溴代丁二酰亚胺和1-H-1,2,4-三氮唑为主要原料,通过O-烷基化、酯化、溴化、N-烷基化及水解反应合成了五种新型三唑类化合物。其结构经IR、1HNMR、EA和MS确证。初步生物活性测试表明,此类化合物有一定的杀菌活性。     

New Ammonium- and 1,2,4-Triazolium-Based Ionic Liquids for Wood Preservation

Biological activity of new potential wood preservatives—ammonium- and triazolium-based ionic liquids—was determined employing screening agar-plate, agar-block, and perlite-block methods. Experiments were carried out on Scots pine (Pinus sylvestris L.) and beech (Fagus sylvatica L.) wood. This study examined the effect of the ionic liquid structure on anti-fungal efficacy, depth of penetration, and fixation in wood. It was stated that the fungicidal value of new ammonium compounds depended, above all, upon the cation structure; for Coniophora puteana, it ranged from 2.7 kg m^?3 to 4.6 kg m^?3. These compounds effectively protected Scots pine wood against the action of mold fungi. Ammonium ionic liquids with a nitrite anion were characterized by strong fungitoxic properties, stronger than ammonium nitrates. The application in the amount of 15 g m^?2 caused an insignificant growth of mold fungi on the surface of Scots pine wood. For the mixture of 7.5% tebuconazole and 7.5% propiconazole dissolved in ionic liquids, the synergistic effect against mold fungi at the application of 15 g m^?2 was found. Dissolving tebuconazole in didecyldimethylammonium nitrate repeatedly lowered the fungicidal value against brown-rot fungi, as well as increased penetration of the ionic liquids in wood. This was associated with reduced viscosity of this ionic liquid caused by the addition of 1,2,4-triazole derivatives. Quaternary derivatives of 1,2,4-triazoles showed very high activity against blue stain and wood-decaying fungi. Additionally, most of the test compounds were well-fixed in Scots pine wood. The spectral study in infrared confirmed that nitrite, nitrate anions, and didecyldimethylammonium cation were retained in the treated wood.     

Syntheses and biological activities of novel diheterocyclic compounds containing 1,2,4‐triazolo[1,5‐a]pyrimidine and 1,3,4‐oxadiazole

In a search for novel agrochemicals with high activity and low toxicity, a series of diheterocyclic compounds containing 1,2,4‐triazolo[1,5‐a]pyrimidine and 1,3,4‐oxadiazole rings were designed and synthesized by a four‐step synthetic route starting from 2‐mercapto‐5,7‐dimethyl‐1,2,4‐triazolo[1,5‐a]pyrimidine. The structures of all the compounds synthesized were confirmed by ¹H NMR, mass spectroscopy and elemental analysis. The preliminary bioassay against Brassica campestris L and Echinochloa crusgalli Beavu indicated that the title compounds displayed herbicidal activity at the concentration of 100 ppm and that compounds 5a (R = CH₃), 5d (R = C₂H₅) and 5f (R = i‐Bu) were found to have particularly high activities. In addition, the results of an in vivo test at a concentration of 50 ppm showed that all the compounds prepared were highly active against Rhizoctonia slain, but not active against Fusarium oxysporum, Gibberella zeave and Phoma sparagi. A further in vivo test showed that compound 5j possessed better fungicidal activity against Rhizoctonia solani at a concentration of 200 ppm than Carbendazim and Validamycin A, which are well known for their fungicidal activity against Rhizoctonia solani. To our knowledge, this is the first report that 1,2,4‐triazolo[1,5‐a]pyrimidine derivatives display fungicidal activity against Rhizoctonia solani. © 2001 Society of Chemical Industry     

1,2,4-Oxadiazole-Based Bio-Isosteres of Benzamides: Synthesis,Biological Activity and Toxicity to Zebrafish Embryo

To discover new compounds with broad spectrum and high activity, we designed a series of novel benzamides containing 1,2,4-oxadiazole moiety by bioisosterism, and 28 benzamides derivatives with antifungal activity were synthesized. These compounds were evaluated against four fungi: Botrytis cinereal, FusaHum graminearum, Marssonina mali, and Thanatephorus cucumeris. The results indicated that most of the compounds displayed good fungicidal activities, especially against Botrytis cinereal. For example, 10a (84.4%), 10d (83.6%), 10e (83.3%), 10f (83.1%), 10i (83.3%), and 10l (83.6%) were better than pyraclostrobin (81.4%) at 100 mg/L. In addition, the acute toxicity of 10f to zebrafish embryo was 20.58 mg/L, which was classified as a low-toxicity compound.     

Inhibition of mild steel corrosion in hydrochloric acid solution by triazole derivatives: Part I. Polarization and EIS studies

A comparative study of 5-amino-1,2,4-triazole (5-ATA), 5-amino-3-mercapto-1,2,4-triazole (5-AMT), 5-amino-3-methylthio-1,2,4-triazole (5-AMeTT) and 1-amino-3-methylthio-1,2,4-triazole (1-AMeTT) as inhibitors for mild steel corrosion in 0.1 M HCl solution at 20 °C was carried out. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behaviour in the absence and presence of different concentrations of these inhibitors under the influence of various experimental conditions. Measurements of open circuit potential (OCP) as a function of time till reaching the steady-state potentials (E_st) were also established. The studies have shown that 5-AMT was the most efficient inhibitor reaching values of inhibition efficiency (IE%) up to 96% at a concentration of 10⁻³ M. Polarization curves showed that the four studied compounds act as mixed inhibitors. The potential of zero charge (PZC) of mild steel was determined in 0.1 M HCl in the absence and presence of the studied inhibitors. The effect of chemical structure of the four tested inhibitors was discussed. Results obtained from OCP versus time, polarization and impedance measurements are in good agreement.     

Synthesis and Evaluation of Some Triazole Derivatives as Corrosion Inhibitors and Biocides

Three compounds namely; 5-(phenyl)-4H-1,2,4-triazole-3-thiol, 3-(decylthio)-5-phenyl-1H-1,2,4-triazole and 3-(benzylthio)-5-phenyl-1H-1,2,4-triazole) were synthesized. The chemical structure of the prepared compounds was confirmed using FTIR and ¹H-NMR analysis. The compounds were tested as corrosion inhibitors against the corrosion of carbon steel in 1 M HCl using weight loss, polarization and electrochemical impedance methods. The results revealed that these compounds have significant inhibiting effects on the corrosion of carbon steel. Polarization studies showed that the compounds act as mixed-type inhibitors which retard the anodic and the cathodic reactions with a predominant effect towards the cathodic reaction. The prepared compounds were evaluated as antimicrobial agents against sulfate-reducing bacteria using the serial dilution method, which showed good biocidal action.     

An ab initio electronic structure study of methyl adsorption and reaction on cluster models for the diamond surface

Electronic structure calculations were carried out for a series of hydrogen-terminated carbon clusters designed to model the 100- and 111-diamond surfaces, C_d(100) and C_d(111). The subjects of the calculations were: (1) methyl radical (CH_3^·) adsorption on an activated diamond surface; and (2) hydrogen abstraction from adsorbed methyl via reaction with gas-phase atomic hydrogen. The largest clusters were treated at the MP2/6-31G*//HF/6-31G* level of theory. The results of higher level calculations on smaller clusters were used to estimate corrections to the MP2/6-31G*//HF/6-31G* energies. It is concluded that methyl adsorption is 6.8 kcal mol⁻¹ more exothermic on C_d(100) than on C_d(111). Also, the barrier for hydrogen abstraction from methyl adsorbed on C_d(100) is 2.4 kcal mol⁻¹ lower than that for abstraction from methyl adsorbed on the C_d(111) surface. Finally, the abstraction reaction energy is 0.8 kcal mol⁻¹ lower for methyl adsorbed on C_d(100) compared to methyl adsorbed on C_d(111).     

Synthesis and Bioactivity of 5-Substituted-2-furoyl Diacylhydazide Derivatives with Aliphatic Chain

A series of 5-substituted-2-furoyl diacylhydazide derivatives with aliphatic chain were designed and synthesized. Their structures were characterized by IR, ¹H NMR, elemental analysis, and X-ray single crystal diffraction. The anti-tumor bioassay revealed that some title compounds exhibited promising activity against the selected cancer cell lines, especially against the human promyelocytic leukemic cells (HL-60). Their fungicidal tests indicated that most of the title compounds showed significant anti-fungal activity. The preliminary structure-activity relationship showed that the aliphatic chain length and differences in the R² group had obvious effects on the anti-tumor and anti-fungal activities. The bioassay results demonstrated that the title compounds hold great promise as novel lead compounds for further drug discovery.     

A Cd/triazolate/carboxylate metal–organic framework with unprecedented (3,10)-connected topology based on tetranuclear clusters

Using 1,2,4-triazole and adipic acid as coligands, a novel three-dimensional metal–organic framework, namely {[Cd₄Cl(trz)₅(adi)]·H₂O}_n (1) (trz = 1,2,4-triazole, adi = adipic acid) was hydrothermally synthesized and characterized. The crystal structure reveals that three independent Cd(II) centers are linked via one μ₃-Cl and two μ₃-COO^? groups to form a unique [Cd₄Cl(CO₂)₂] tetranuclear cluster, which acts as a 10-connected node joining adjacent four tetranuclear subunits and six 3-connected trz nodes to give a novel (3,10)-connected topological net with the Schläfli symbol (4³)(4¹⁸6²⁵6²).     

5,7-二甲基-1,2,4-三唑并[1,5-a]嘧啶-2-芳磺酸酯新型化合物的合成及生物活性

三唑类化合物具有广泛的生物活性。以2-羟基-5,7-二甲基-1,2,4-三唑并[1,5-a]嘧啶为原料,在缚酸剂存在下,于室温分别和苯磺酰氯、对甲苯磺酰氯进行酯化反应,合成了两个新型的5,7-二甲基-1,2,4-三唑并[1,5-a]嘧啶-2-芳磺酸酯化合物a和b。产物经质谱、红外光谱、核磁共振谱确证。初步生物活性表明,该化合物具有一定的杀菌活性和除草活性,其中a有较高除草活性,而b对禾本科植物有较好的促进生长活性。     

1,2,4-三嗪酮类衍生物的合成研究及生物活性测试

以5-甲基-1,3,4-二唑-2(3H)-酮为原料,经过烷基化、扩环、水解和酰胺化等4步反应合成了12个新型的1,2,4-三嗪酮类化合物6a～6l,其结构经1H NMR、13C NMR和MS表征。初步生物活性测试结果表明,在50 g/mL质量浓度下,部分目标化合物对小麦赤霉病菌、辣椒枯萎病菌和苹果腐烂病菌表现出一定的生物活性。     

Structural and Preliminary Explosive Property Characterizations of New 3,4,5‐Triamino‐1,2,4‐triazolium (Guanazinium) Salts

Two new highly stable energetic salts were synthesized in reasonable yield by using the high nitrogen‐content heterocycle 3,4,5‐triamino‐1,2,4‐triazole and resulting in its picrate and azotetrazolate salts. 3,4,5‐Triamino‐1,2,4‐triazolium picrate (1) and bis(3,4,5‐triamino‐1,2,4‐triazolium) 5,5′‐azotetrazolate (2) were characterized analytically and spectroscopically. X‐ray diffraction studies revealed that protonation takes place on the nitrogen N1 (crystallographically labelled as N2). The sensitivity of the compounds to shock and friction was also determined by standard BAM tests revealing a low sensitivity for both. B3LYP/6–31G(d, p) density functional (DFT) calculations were carried out to determine the enthalpy of combustion (Δ_cH (1) =−3737.8 kJ mol⁻¹, Δ_cH (2) =−4577.8 kJ mol⁻¹) and the standard enthalpy of formation (Δ_fH° (1) =−498.3 kJ mol⁻¹, (Δ_fH° (2) =+524.2 kJ mol⁻¹). The detonation pressures (P (1) =189×10⁸ Pa, P (2) =199×10⁸ Pa) and detonation velocities (D (1) =7015 m s⁻¹, D (2) =7683 m s⁻¹) were calculated using the program EXPLO5.     

Structure and Tautomerism of ANTA (aminonitrotriazole)

Energy and dipole moment calculations show 3-nitro-5- amino-1,2,4-triazole is the most stable tautomer of ANTA either in the gas phase and polar solvents, in agreement with X-ray findings. Our calculations predict that the 5-nitro-3-amino-1,2,4-triazole tautomer is more sensitive to shock or impact. Some discrepancies between semiempirical (AMI and PM3) calculations and ab initio (up to 6-31G*//6-31G) are studied.     

Six- and four-coordinated zinc(II) complexes exhibit strong blue fluorescent properties

A new ligand, 4-(p-chlorophenyl)-1,2,4-triazole (^pCltrz), and its complexes, [Zn(^pCltrz)₆]₂(ClO₄)₂ · H₂O (1) and [Zn(^pCltrz)₂Cl₂] (2), were synthesized. The structure of 1 exhibits the first case that zinc(II) ion coordinated with six triazole ligands to form octahedral environment. Both 1 and 2 display very strong blue photoluminescence as the result of the fluorescence from the intraligand emission excited state.     

Synthesis and characterization of novel optically active and flame‐retardant heterocyclic polyimides

Tetrachlorophthalic anhydride (1) was reacted with L ‐leucine (2) in toluene solution at refluxing temperature in the presence of triethylamine and the resulting imide‐acid (4) was obtained in quantitative yield. The compound (4) was converted to the N‐(tetrachlorophthaloyl)‐L ‐leucine acid chloride (5) by reaction with thionyl chloride. The reaction of this acid chloride (5) with isoeugenol (6) was carried out in chloroform and novel optically active isoeugenol ester derivative (7) as a chiral monomer was obtained in high yield. The compound (7) was characterized by ¹H‐NMR, IR, Mass and elemental analysis, and then was used for the preparation of model compound (10) and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione, PhTD (8) was allowed to react with compound (7). The reaction is very fast, and gives only one diastereomer of (10) via Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer (7) with bistriazolinediones [bis‐(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (11) and 1,6‐bis‐(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (12) were carried out in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and give novel optically active polymers (13) and (14) via repetitive Diels–Alder‐ene polyaddition reactions. The resulting polymers are optically active, thermally stable, and flame resistant. All of the above compounds were fully characterized by IR, ¹H‐NMR, elemental analysis, and specific rotation. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 240–248, 2000     

Synthesis and structural characterization of a disulphide-bridged tetranuclear palladium(II) complex derived from 3,5-diacetyl 1,2,4-triazole bis(4-ethylthiosemicarbazone)

A novel tetranuclear [Pd₄(μ₂-η²-S₂)(H₂L¹)₂] complex, where H₂L¹ is the anion of 3,5-diacetyl-1,2,4-triazole bis(4-ethylthiosemicarbazone), was synthesized and structurally characterized by single crystal X-ray diffraction. The molecular structure shows an unexpected μ₂-η²-S₂ bridge, which is shared by all the four palladium atoms. Each trideprotonate 3,5-diacetyl-1,2,4-triazole bis(4-ethylthiosemicarbazone) ligand acts as a hexadentate in a symmetrical manner bridging two metal ions through the two adjacent nitrogen atoms of the central triazole ring. The molecular packing is characterized by hydrogen bond interactions to form a 3D supramolecular architecture with channels running down the c¹ axis in which the lattice water molecules are encapsulated.