Synthesis of 1-(1,2,4-triazol-3-yl)-1,2,3-triazoles

1-(1,2,4-Triazol-3-yl)-1,2,3-triazoles were obtained by 1,3-dipolar cycloaddition of 3-azido-1,2,4-triazole to acetylene derivatives. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 262–264, February, 1980.     

Microwave-assisted synthesis and crystal structure of some novel 1,2,4-oxadiazol-5-ylmethyl-1,2,3-triazoles

Microwave-assisted 1,3-dipolar cycloaddition of 5-azidomethyl 3-aryl-substituted 1,2,4-oxadiazoles to electron-deficient alkyne; phenyl propiolic acid affords a series of 1,2,3-triazole derivatives carrying 3-p-substitutedphenyl-1,2,4-oxadiazolyl methyl unit. The structures of all the cycloadducts were elucidated by IR, NMR (¹H, ¹³C, 2D), MASS (low and high resolution) spectra, X-ray diffraction data, and physical characteristics (melting points and R_f values).     

DFT studies on tautomerism of C5-substituted 1,2,4-triazoles

DFT (B3LYP/6-311++G**, B3PW91/6-311++G**) Gibbs free energy and single point CCSD(T)/6-311++G**//DFT total energy calculations were performed to investigate stability and tautomerism of C5-substituted 1,2,4-triazoles. Three different tautomers are possible for the substituted 1,2,4-triazoles: N1–H, N2–H, and N4–H. Unlike for the 1,2,3-triazoles, where the most stable is the N2–H tautomer regardless of substituent applied, for the 1,2,4-triazoles, the electron donating substituents (–OH, –F, –CN, –NH₂, and –Cl) and the C5-cation stablize the N2–H tautomer, whereas the electron withdrawing substituents (–CONH₂, –COOH, –CHO, –BH₂, and –CFO) and the C5-anion stablize the N1–H tautomer. Except for the C5-anion and C5-cation, the N4–H form is the least stable tautomer. The relative stability of the C5-substituted 1,2,4-triazole tautomers is strongly influenced by attractive and/or repulsive intramolecular interactions between substituent and electron donor or electron acceptor centres of the triazole ring.     

On the lead tetraacetate oxidation of 4-amino-1,2,4-triazoles, 1-amino- and 2-amino-1,2,3-triazoles

Lead tetraacetate oxidation of 4-amino-1,2,4-triazoles, 1-amino- and 2-amino-1,2,3-triazoles affords mainly fragmentation to nitriles or acetylenes, even in the presence of intramolecularly attached double bonds.

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Über die Bleitetraacetatoxidation von 4-Amino-1,2,4-triazolen, 1-Amino- und 2-Amino-1,2,3-triazolen (Kurze Mitteilung)

Zusammenfassung Bei der Oxidation von 4-Amino-1,2,4-triazolen, 1-Amino- und 2-Amino-1,2,3-triazolen mit Bleitetraacetat entstanden hauptsächlich Nitrile bzw. Acetylene durch Fragmentierung — trotz der Gegenwart von intramolekularen Doppelbindungen.

     

Quantum chemical study of tautomerism of bullvalene, bullvalenol, and the corresponding ketone

Using the quantum chemical method PBE0/cc-pVTZ, we determined structural parameters and dipole moments of bullvalene (tricyclo[3.3.2.0^4.6]deca-2,7,9-triene), 1-, 2-, 3-, and 4-hydroxytricyclo[3.3.2.0^4.6]-deca-2,7,9-trienes, and isomeric 2- and 3-ketones transforming into each other through the keto-enol tautomerism and Cope rearrangement with the triatomic ring migration. The dominant tautomer is 3-ketone containing a triatomic ring conjugated with the carbonyl group.     

An aqueous medium synthesis and tautomerism study of 3(5)-amino-1,2,4-triazoles

A catalyst-free highly efficient synthesis of 3(5)-amino-5(3)-(het)aryl-1,2,4-triazoles in aqueous medium was performed using conventional heating and microwave irradiation. The tautomerism in the products was investigated using NMR spectroscopy and X-ray crystallography. The effects of the substitution, temperature, solvents, and concentration on the tautomerism were studied. The triazoles were found to exist in 1H-forms, the 4H-form was not observed either in solid state or in solution. In general, 5-amino-1,2,4-triazoles were electronically preferred in the tautomeric equilibrium, but some exceptions from the established relationship were also identified.     

Quantum chemical study of the geometrical and electronic structure of niobium pentafluoride

The geometrical and electronic structure of various configurations of niobium pentafluoride is studied in the nonrelativistic approximation of the DV-X_α method. It is shown in a cluster approximation that the presence of the NbF₅ monomer in various geometrical configurations and of the cyclic [NbF₅]₃ trimer (D_3h symmetry) is most probable for the liquid and gaseous phases. Formation of infinite [NbF₅]_n chains is unlikely. For the most stable clusters, the calculated geometrical parameters are in satisfactory agreement with the available experimental data.     

Reactivity of N-(1,2,4-triazolyl)-substituted 1,2,3-triazoles

Synthetically useful rhodium(II) carbenes were obtained from N-(1,2,4-triazolyl)-substituted 1,2,3-triazoles and Rh(II) carboxylates. The electron-withdrawing 1,2,4-triazolyl group reveals the heretofore unknown reactivity of nonsulfonyl 1,2,3-triazoles, which exhibit the reactivity of diazo compounds. The resulting carbenes provide ready asymmetric access to secondary homoaminocyclopropanes (80-95% ee, dr >20:1) via reactions with olefins and also engage in efficient transannulation reactions with nitriles.     

Quantum chemical study of the tautomerism of 2-acetylcyclopentane-1,3-dione

An AM-1 LCAO MO calculation showed than the isomer with an enolized C=O bond in the sidechain stabilized by intramolecular hydrogen bonding is the thermodynamically most favorable among the three tautomers of 2-acetylcyclopentane-1,3-dione. The energy of the intramolecular hydrogen bond is about 8 kcal/mole.¹³ C NMR spectroscopy was used to show that 2-acetylcyclopentane-1,3-dione exists in the exocyclic enol form. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2377–2381, October, 1989.     

A survey of the lone pair effect on the ring geometry of 1,2,4-triazoles and analogous 1,2,3-triazoles and imidazoles : The structures of 1-methyl-5-amino-3-methylthio-1,2,4-triazole, 1-phenyl-5-amino-3-methylthio-1,2,4-triazole and 1-(4-methylbenzyl)-3-amino-5-methylthio-1,2,4-triazole

The structures of the title compounds have been established by X-ray crystallography from diffractometer data. Crystals of the first (I), C₄H₈N₄S, are monoclinic, space group P2₁/c, with a = 8.166(2), b = 10.481(1), c = 8.585(1) Å, β = 109.33(2)°, Z = 4, D_c = 1.381 g cm⁻³. Crystals of the second (II), C₉H₁₀N₄S, are monoclinic, space group P2₁/c, with a = 11.850(4), b = 7.898(1), c = 23.981 (6) Å, β = 117.23(2)°, Z = 8, D_c = 1.373 g cm⁻³. Crystals of the third (III), C₁₁H₁₄N₄S₁ are also monoclinic, space group P2₁/c with a = 12.829(3), b = 8.348(1), c = 11.088(4) Å, β = 94.40(4)°, Z = 4, D_c = 1.314 g cm⁻³. The structures, determined by direct methods (I, III) and Patterson synthesis (II) were refined to R = 0.039 for 1070 reflections of I, R = 0.040 for 2792 reflections of II and R = 0.041 for 1900 reflections of III. The characteristic features of the planar five-membered rings are studied in comparison with the analogous 1,2,3-triazoles and imidazoles. It is shown that these planar rings exhibit only two patterns of the endocyclic bond angles induced dominantly by the number and relative position of the N-lone pairs. A similar effect of the double bonds (attached to C atoms) is also discussed.     

5-卤代1,2,3,-三唑互变异构的密度泛函理论研究

用密度泛函B3LYP/6-311 G**方法,对气相和水相中的1,2,3三,-唑及5-卤(-F、C l和-B r)代1,2,3,-三唑互变异构体进行了几何构型全自由度优化,获得了它们在气相和水相中的几何结构和电子结构。计算结果显示,在气相和水相中1,2,3三-唑和5-卤代1,2,3三-唑的N2-H型要比对应的N1-H型和N3-H型稳定。讨论了不同的取代基团和溶剂化效应对互变异构体的几何结构、能量和电荷分布以及互变异构反应活化能的影响带。并进一步研究了N1-H、N2-H和N3-H型三唑之间的互变异构机理:(a)分子内质子转移;(b)水助质子转移。计算结果表明,途径(b)所需要的活化能较小,为120.06KJ/mol,途径(a)为204.12KJ/mol。     

1－（取代异噁唑基）－1，2，4．三唑和1－（取代嘧啶基）－1，2，4－三唑的合成及生物活性

合成了１５个新的１－（取代异噁唑基）－１，２，４－三唑和１－（取代嘧啶基）－１，２，４－三唑化合物，经元素分析、ＩＲ、１ＨＮＭＲ和ＭＳ证实其结构，并对其代表化合物进行了抑菌及植物生长调节活性的初步观察     

Efficient,mild synthesis of N-unsubstituted 1,2,3-triazoles from methanolysis of 1-sulfonyl-1,2,3-triazoles

A small library of diverse N-unsubstituted 1,2,3-triazoles was prepared from the corresponding 1-sulfonyl-1,2,3-triazoles, which were treated only with MeOH at reflux temperature. This process was carried out in good yields showing high efficiency and good functional group tolerance.     

Quantum chemical study of the electronic structure of NaX and NaY zeolites1

The CNDO/2 method is employed to determine S_III type positions for the location of Na cations in the faujasite zeolites. The minimum energy path of Na migration between these positions exhibiting an energy banier of 20 kJ/mol has been calculated.     

Quantum chemical study of the electronic structure and nature of the chemical bond for crystal modifications of metastable titanium dicarbide

A study was carried out on the electronic energy structure and nature of the chemical bond for a series of crystal modifications (like CaC₂, ThC₂, CsCl, or CaF₂) of metastable titanium dicarbide. The TiC₂ phase may be obtained as a film on the CaC₂ surface, and a metal-semiconductor heterojunction is formed. The possibilities of altering the electronic properties of this heterosystem are discussed. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 5, pp. 289–294, September–October, 1999.     

Mass-spectrometric study of isomeric 5-amino-1,2,3-thiadiazoles and 5-mercapto-1,2,3-triazoles

The behavior of the isomeric 5-amino-1,2,3-thiadiazoles and 5-mercapto-1,2,3-triazoles under electron impact was studied. It was shown that mass spectrometry can serve as a rapid and reliable method for the identification of these compounds. Key factors in the assignment of a compound to one or the other class are the peaks of the [M-N₂]⁺ ions, which are more intense in the case of the thiadiazoles, and the ions determined by the decomposition of the prototropic forms of the triazoles. The compositions of the ions were determined by the high-resolution mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 681–689, May, 1987.     

Quantum chemical study of the electronic structure of NiCH2 + in its ground state and low-lying electronic excited states

The electronic structure of NiCH(2) (+), representative of transition metal carbene ions, is investigated by means of several methods of quantum chemistry. The relative stabilities of the four low-lying doublet electronic states ((2)A(1), (2)A(2), (2)B(1), and (2)B(2)) are determined at the coupled cluster singles and doubles level (CCSD) and triples level [CCSD(T) and CCSDT-3] with both a Hartree-Fock and density functional theory (Kohn-Sham) reference. The equation-of-motion coupled cluster for treatment of excited states in singles and doubles approximation (EOM-CCSD) is used to characterize the transition energies from the (2)A(1) electronic ground state to the low-lying doublet excited states. The (2)A(2) and (2)B(1) states are nearly degenerate, found to be separated by 940 cm(-1) at the EOM-CCSD level, in agreement with the CASSCF energy ordering. The (2)B(2) state is calculated to be higher in energy by more than 1.0 eV. The spin purity of the low-lying doublet and quadruplet states described by CCSD calculations based on the unrestricted open-shell Hartree-Fock reference is discussed.     

Synthesis of 1,2,4-triazoles and 1,2,4-oxadiazoles

Monothiodiacylamines reacted regiosepecifically with hydrazines and hydroxylamine to give substituted 1,2,4-triazoles and 1,2,4-oxadiazoles in excellent yields.     

Quantum chemical calculations of the molecular structure of diphenylguanidine and experimental studies of its tautomerism in solution

MNDO-PM3 and AM1 quantum chemical calculations of the molecular structure of N,N′-diphenyl-guanidine (DPG) prove that the molecule preferably exists as an asymmetric tautomer with a basic center C = N−. IR and UV spectral data, dipole moments, and average molecular weights of DPG solutions in nonpolar and low-polar solvents confirm the results of calculations, indicating formation of hydrogen-bonded cyclic self-associates of DPG in solution. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 618–625, July–August, 1998.     

Ester,amide and ether derivatives of 1-(p-phenyl-substituted)-1,2,3-triazoles

This paper describes the preparation of three series of 1-phenyl-1,2,3-triazol derivatives with an ester, amide or ether group on the phenyl ring. These derivatives were obtained from 4-hydroxyphenyl- and 4-aminophenyltriazoles, previously synthesized by us, by means of a nucleophilic substitution reaction with acetic anhydride, acyl and alkyl halides. The largest part of compounds were tested in an agricultural chemicals, nutrition and animal health screening programme.