Conformational energy (A-value) of the 4-phenyl-1,2,3-triazolyl group

Conformational energy (A-value) of the 4-phenyl-1,2,3- triazolyl group was estimated as 2.0 kcal mol–1 (8.5 kJ mol–1) using 1H NMR-based conformational study for a set of (4-phenyl-1,2,3-triazol-1-yl)cyclohexanes. This provides a reasonable estimation also for the conformational energy of 1,2,3-triazolyl group itself and its substituted analogues.     

CuI/l-proline catalyzed click reaction in glycerol for the synthesis of 1,2,3-triazoles

Despite the apparent simplicity of the copper(I) iodide catalyzed CuAAC reaction, the conversion of the catalytic species, i.e. Cu(I) to thermodynamically more stable Cu(II), via aerial oxidation or disproportionation is a major issue. To stabilize the Cu(I) species, the reaction is ideally carried out under an inert atmosphere in the presence of additives such as alcohols, amines, thiols, and aldehydes. Herein, we report the first CuI catalyzed click reaction without an inert atmosphere by employing the CuI/l-proline system in glycerol. The method showed remarkable stability towards sensitive functional groups such as acetonides and 1,2,4-trioxanes.     

A tandem of the Cornforth rearrangements of 4-(1,2,3-triazol-1-yl)iminomethyl-1,2,3-thiadiazole

The method for the synthesis of 5-(2,6-dimethylmorpholino)-1,2,3-thiadiazole-4-carbaldehyde was proposed. Its reaction with sodium 1-amino-4-(N-methyl)carbamoyl-1,2,3-triazol-5-olate proceeds through a tandem of the Cornforth rearrangements. The initially formed azomethine isomerizes into sodium 4"-(2,6-dimethylmorpholino)thiocarbonyl-4-(N-methyl)carbamoyl-1,1"-bis[1,2,3]triazolyl-5-olate, which then rearranges to give sodium 4-{N-[4-(2,6-dimethylmorpholinothiocarbonyl)-1,2,3-triazol-1-yl]carbamoyl}-1-methyl-1,2,3-triazol-5-olate.     

Quantum-chemical investigation of certain physicochemical properties of C-nitro-1,2,3-triazole and N-alkyl-4(5)-nitro-1,2,3-triazoles

Quantum-chemical calculations have been carried out on molecular electrostatic potentials, proton affinity in the gas phase, gas phase basicity, and pK _BH+ values in aqueous solution for C-nitro- and N-alkyl-4(5)-nitro-1,2,3-triazoles, and the relative stability of the isomeric N-alkyl-4(5)-nitrotriazoles (alkyl = Me, Et, i-Pr, t-Bu) in the gas phase and in aqueous solution. For all the studied substances in the gas phase the 2H-tautomer and the N(2)-isomers were considerably more stable than the corresponding N(1) compounds, and the 3H-tautomer and N(3)-isomer were the least stable. In aqueous solution 1- and 3-isomers had close values of energies, but in the case of C-nitro-1,2,3-triazole the 1H form became even more stable than the 2H-form. It was established which ring nitrogen atoms of 1,2,3-triazoles are protonated in the gas phase and in solution. The obtained data correlate well with the results of experimental investigations on the alkylation of 1,2,3-triazoles in acidic and basic media and of the experimental investigation on the alkylation of C-nitro-1,2,3-triazoles with diethyl sulfate carried out in the present work. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1816–1828, December, 2008.     

Binding affinity studies of 1,2,3-triazole copper(II) complexes to human serum albumin

Abstract

Two copper(II) complexes with tetradentate 1,4-disubstituted-1,2,3-triazole ligands, [CuL(MeCN)](ClO₄)₂ (1) and [CuL′](ClO₄)₂ (2), have been prepared and characterized by different techniques, including X-ray structure determination, spectroscopic, and electrochemical measurements, as reported elsewhere. Herein, we report the interactions of these complexes, and corresponding free ligands, with human serum albumin (HSA) verifying their relative thermodynamic stability and differences in binding to this protein. Interactions with HSA were verified by CD measurements monitored at 564?nm, up to stoichiometric ratio 2:1 [Complex]:[protein], according to competitive equilibria involving the insertion of copper at the selective N-terminal metal binding site in HSA, and additionally at a secondary nonselective site. Further interactions of these complexes with L-tryptophan residues, and probable supplementary site(s) for the binding, were followed by fluorescence measurements. Analogous experiments with the free L and L′ indicated much weaker interactions. Protein oxidation damage was observed for both complexes, monitored by carbonyl groups formation in the presence of H₂O₂, probably with the participation of reactive oxygen species. Density functional theory calculations exhibit metal-ligand binding interaction energies similar to [Cu(HSA-N_terminal)]⁺, and reinforced the experimental results, showing clearly that such triazole ligands are competitive toward copper(II) in biological medium.     

4-单取代-1,2,3-三氮唑的合成进展(Ⅱ)—通过去取代基反应

1,2,3-三氮唑衍生物是近些年研究热点化合物之一,随着4-单取代型衍生物在医药、农药、材料等领域的广泛应用,该类化合物的合成及应用近些年引起了广大研究者的关注并获得了可喜进展。本文阐述了4-单取代-1,2,3-三氮唑衍生物的合成发展历史,着重综述了近十年来该类唑衍生物的合成发展情况。内容主要涵盖二取代-1,2,3-三氮唑的去取代基反应,包括脱羧、脱苄基、脱羟(酰氧)基及脱取代乙基等反应。文章还包括一些合成方法及其产物的应用,并对一些重要的反应机理做了分析。文章最后对该类化合物的合成做了总结并展望了未来发展方向。     

Solvent controlled regioselective reaction of 1,2,3-benzotriazole (BtH) with pentafluorobenzene derivatives

Regioselective reaction of 1,2,3-benzotriazole (BtH) with pentafluorobenzene derivatives under base conditions was investigated and its regioselectivity strongly depends on solvent, base, and electron-withdrawing group at 4-position on the perfluorophenyl ring. Several Bt(N1)-substituted perfluorobenzenes were prepared by using this method.     

Synthesis and properties of nitro-1,2,3-triazoles (Review)

Published data on methods for the synthesis of substituted 4(5)-nitro-1,2,3-triazoles and their properties are reviewed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 3–25, January, 2008.     

Conformational fluxionality in a palladium(II) complex of flexible click chelator 4-phenyl-1-(2-picolyl)-1,2,3-triazole: A dynamic NMR and DFT study

An experimental and theoretical DFT study was carried out on the solution behavior in [D₇]DMF for bis-chelate complex [Pd(L)₂](BF₄)₂·2CH₃CN (L = 4-phenyl-1-(2-picolyl)-1,2,3-triazole). In structure of [Pd(L)₂]²⁺, the central square-planar palladium(II) cation is trans-chelated by two L substrates, each through the pyridine and the triazole N2 nitrogen atoms, forming two six-membered metallacycles. These can adopt boat-like conformations anti-trans-[Pd(L)₂]²⁺ and syn-trans-[Pd(L)₂]²⁺ in which the picolyl methylene carbons are anti or syn, respectively, relative to the palladium coordination plane. In solution, the boat-to-boat inversion at both metallacycles takes place. The conformers are in a dynamic equilibrium, which was monitored by variable-temperature (VT) ¹H NMR spectroscopy in the temperature range of 223-353 K. The equilibrium lies on the side of the anti-trans-[Pd(L)₂]²⁺ conformer and the corresponding reaction enthalpy and entropy is estimated to be 0.6 ± 0.5 kcal mol⁻¹ and 0.8 ± 1 cal mol⁻¹ K⁻¹, respectively. From the full-line-shape analysis of resonances in the VT ¹H NMR spectra, the activation enthalpy and activation entropy was determined to be 13.0 ± 0.4 kcal mol⁻¹ and 2.7 ± 1.6 cal mol⁻¹ K⁻¹, respectively. The activation entropy close to zero suggests a nondissociative mechanism for the isomerisation. DFT investigation revealed that the isomerisation proceeds through a one step mechanism with a barrier of 11.40 kcal mol⁻¹. The structures of the syn and anti conformers as well as that of the transition state were characterized. Energy decomposition analysis was carried out in order to explore the origins of the stability difference between the syn and anti isomers.     

Monolayers of 1,2,3-propanetriol esters at the air-water interface: two-dimensional phases and miscibility

Monolayers of two glycerol esters, 1-monooleoylglycerol and 1-monostearoylglycerol, were studied at the air-water interface in the 15–30C temperature range.From the experimental isotherms (surface pressure vs area and surface potential vs area) the surface phases of the esters were inferred.The miscibility between the two esters was discussed in relationship to the interfacial orientations and distributions and to the surface phases of the esters.The results obtained supported and strengthened the empirical rule on miscibility previously found [1–7], i.e., for non-ionic compounds the same interfacial orientation of the hydrophobic chains is required in order to have bidimensional miscibility between the components.     

Synthesis and Application of Some Dianilinosilanes,Bis (Trimethylsilyl) Phenylenediamines and Dialkyl Benzo-1,3,2-Diazasilolines as Antioxidants

Negative hyperconjugation of the type n_N→σ* is responsible for the planar or almost planar geometry at nitrogen in certain S–N compounds.     

Synthesis of 2-(1,2,3-Thiadiazol-5-yl)-1H-benzimidazoles

We have developed a convenient preparative method for synthesis of previously unknown 2-(1,2,3-thiadiazol-5-yl)-1H-benzimidazoles based on reaction of benzoylhydrazones of 2-acylmethyl-1H-benzimidazoles with thionyl chloride. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1391–1393, September, 2005.     

Conformational Analyses of Physiological Binary and Ternary Copper(II) Complexes with l-Asparagine and l-Histidine; Study of Tridentate Binding of Copper(II) in Aqueous Solution

This study explores the structural properties and energy landscapes of the physiologically important bis(l -asparaginato)copper(II) [Cu(l -Asn)₂] and (l -histidinato)(l -asparaginato)copper(II) [Cu(l -His)(l -Asn)]. The conformational analyses in the gas phase and implicitly modeled water medium, and magnetic parameters of electron paramagnetic resonance spectra were attained using density functional theory calculations. The apical Cu^II coordination and hydrogen bonding were analyzed. Predicted lower-energy structures enabled the confirmation and, for apical bonding, also the refinement of structural proposals from literature. Available experimental results were indecisive regarding the amido-group binding in the Cu^II equatorial plane in solutions, but the examination of the relative stability of Cu(l -Asn)₂ conformers in 30 binding modes confirms the glycine-like mode as the most stable one. Previously reported experimental results for Cu(l -His)(l -Asn) were interpreted for l -His to have a tridentate histamine-like mode. However, the aqueous conformers with l -His in the glycinato mode are also predicted to have low energies, which does not contradict the tridentate l -His binding. The predicted magnetic parameters of conformers with an apical oxygen atom (intramolecular or from a water molecule) can reproduce the experimental data. An extent of conformational flexibility and abundance of l -His-containing ternary copper(II) amino acid complexes under physiological conditions may be related.     

Conformational study of the natural iron chelator myo-inositol 1,2,3-trisphosphate using restrained/flexible analogues and computational analysis

myo-Inositol 1,2,3-trisphosphate [Ins(1,2,3)P₃], a component in mammalian cells, possesses the correct chemical properties of an intracellular iron transit ligand. Here we have examined the conformation of the Ins(1,2,3)P₃-Fe³⁺ complex. The synthesis and antioxidant properties of 4,6-carbonate-myo-inositol 1,2,3,5-tetrakisphosphate [4,6-carbonate Ins(1,2,3,5)P₄], which is locked in the unstable penta-axial chair conformation and 1,2,3-trisphosphoglycerol, a flexible acyclic analogue of Ins(1,2,3)P₃, are reported. 4,6-Carbonate Ins(1,2,3,5)P₄ caused complete inhibition of iron-catalysed hydroxyl radical (HO) formation at 100 μM, thereby resembling Ins(1,2,3)P₃ and supporting a penta-axial chair binding conformation. In contrast, 1,2,3-trisphosphoglycerol was shown to have incomplete antioxidant properties. In support of experimental observations, we have applied high-level density functional calculations to the binding of Ins(1,2,3)P₃ to iron. This study provides evidence that Fe³⁺ binds tightly to the less stable penta-axial conformation of Ins(1,2,3)P₃ using terminal and bridging phosphate oxygens, thought to also contain a tightly bound water molecule or hydroxyl ligand in the complex.     

(Vapor-liquid) equilibria and excess Gibbs free energy functions of (ethanol + glycerol), or (water + glycerol) binary mixtures at several temperatures

The vapor pressures of (ethanol + glycerol) and (water + glycerol) binary mixtures were measured by means of two static devices at temperatures between (273 and 353 (or 363)) K. The data were correlated with the Antoine equation. From these data, excess Gibbs free energy functions (G^E) were calculated for several constant temperatures and fitted to a fourth-order Redlich–Kister equation using the Barker method. The (ethanol + glycerol) binary system exhibits positive deviations in G^E where for the (water + glycerol) mixture, the G^E is negative for all temperatures investigated over the whole composition. Additionally, the NRTL, UNIQUAC and Modified UNIFAC (Do) models have been used for the correlation or prediction of the total pressure.     

Reaction of 5-Hydrazono-1,2,3-thiadiazoles with Toluene and Xylene in the Presence of PCl5

The treatment of 5-hydrazono-1,2,3-thiadiazoles by phosphorus pentachloride in toluene or xylene leads to an anomalous Dimroth rearrangement and the reaction of the mercapto function formed with the methyl group of the solvent to give 5-benzylmercapto-1,2,3-triazole.     

The Electro-Optical Kerr Effect in Conformational Analysis. New analytical methods (10)

Birefringence induced in a material by application of an electric field is known as the Kerr effect. The great sensitivity of this property to variations of molecular geometry and environment has made it the basis of a potent method for studying the conformations of molecules. It has, in addition, been effectively applied to investigations of the geometry of solvation and of solute aggregation. An outline is presented of the general technique of measurement of the Kerr effect, the extraction of directed effective polarizabilities of solute molecules and of structural groups, the calculation of theoretical Kerr constants for candidate structures of molecules, and the procedures used to determine solute conformations. The scope and limitations of the method are illustrated by specific conformational problems drawn from the literature. In the case of highly flexible molecules analysis of the measured Kerr constant is inhibited by uncertainties in conformational energy data. This paper is concerned mainly with the specification of detailed conformational energy data. This paper is concerned mainly with the specification of detailed conformational features of molecules. Reference is made, however, to the utilization of pulsed orienting fields to study shapes and dimensions of biological macromolecules.     

SYNTHESIS AND STRUCTURE OF Pd(II) COMPLEXES OF 1,2,3-TRIPHENYLGUANIDINE

Abstract

The formation of two complexes by reaction of [PdCl₄]^2- with 1,2,3-triphenylguanidine (PhNH)₂C=NPh under different metal/ligand ratios has been observed and the structure of the complex [(1,2,3-triphenylguanidine)₂PdCl₂] has been determined by X-ray diffraction methods. The ligands are coordinated as neutral monodentate molecules to the metal centre through their imine nitrogen atoms. The second Pd(II) complex is [Pd(1,2,3-triphenylguanidine)₄]²⁺ and was isolated by precipitation with ClO^? ₄.     

Synthesis of spiro bis(1,2,3-triazolium) salts as chiral ionic liquids

Unique chiral spiro ionic liquids based on 1,2,3-triazolium salts were synthesized via an intramolecular double Huisgen reaction. The optical resolution of the liquid precursors and subsequent dialkylations leads to chiral spiro triazolium salts on a gram scale.     

Synthesis and hydrolytic degradation of poly (glycerol succinate) based polyesters

The limited availability of petroleum resources motivates the research towards value-added products production from bio-resources. This study reports the synthesis of glycerol and succinic acid-based polyesters and their detailed characterization. The modification of poly (glycerol succinate) was done by using other diacids like glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. The sysnthesized polyesters were characterized using various techniques such as thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The addition of different dicarboxylic acids to poly (glycerol succinate) based co-polyesters increased the thermal stability of poly (Glycerol succinate). Glass transition temperatures were obtained in the range of ?17.2 to ?22.5 °C and it increased with chain length. The progress of reaction was monitored by determining acid number, ester number, and degree of esterification. The hydrolytic degradation of polyesters was carried out in acidic and basic medium. The polyesters was found to degrade under basic conditions whereas no weight loss of poly (glycerol succinate) was found under acidic conditions. Particularly, about 40% of poly (glycerol succinate) was degraded within 24 h under basic conditions (pH = 12). The analysis of morphology of polyesters during degradation showed that the increase in hydrolysis time increased the heterogeneity in polyester matrix.