Recyclization of 1,3,4-Oxadiazoles and Bis-1,3,4-oxadiazoles into 1,2,4-Triazole Derivatives. Synthesis of 5-Unsubstituted 1,2,4-Triazoles

Efficient methods have been developed for obtaining precursors of stable carbenes, viz. 5-unsubstituted 3,4-diaryl-1,2,4-triazoles and 3,3′- or 4,4′-bridge linked bis-1,2,4-triazoles, by the recyclization of 5-unsubstituted 1,3,4-oxadiazoles or p-phenylenebis-1,3,4-oxadiazole with anilines or aromatic diamines in the presence of trifluoroacetic acid or with aniline hydrochlorides in pyridine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1026–1032, July, 2005.     

1,2,5-, 1,3,4- and 1,2,4-Oxadiazoles

Discrepancies found for some oxygen-containing compounds in a recent VESCF study of dipole moments have been further investigated by studying in detail furan, oxazole, isoxazole, and three isomeric oxadiazoles. In a preliminary geometrical study it was found that the method described previously for estimating ring angles and bond lengths satisfactorily accounted for observed geometries. However in those compounds where more than one ring atom carries lone pair -electrons, the electrostatic forces originating in these lone-pair dipoles have a considerable influence on ring geometry. When this is incorporated in the geometrical treatment, good agreement with known geometries is obtained.The effect of using Burns' rules for orbital exponents rather than Slater's rules to derive lone pair moments and the effect of including lone pair potentials in the hamiltonian have been studied. The best agreement between calculated and observed dipole moments (within 0.2 D) is obtained by using the BJ method that was used in the previous study but with revised values for some of the basic resonance integrals. The revised values are shown to be more in keeping with the relevant bond lengths and atomic numbers than the values previously used.

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Zusammenfassung Die in einer VESCF- (PPP mit Elektronegativitäts-Variation) Untersuchung über Dipolmomente aufgetretenen Abweichungen bei einigen O-haltigen Ringen wurden untersucht. Bei Ringen, die mehrere einsame Elektronenpaare tragen, muß die kürzlich angegebene einfache Methode zur Bestimmung der Geometrie durch zusätzliche Berücksichtigung der elektrostatischen Kräfte zwischen diesen Elektronenpaaren erweitert werden. Die Burnsschen Orbitalexponenten führen bei den einsamen Elektronenpaaren zu besseren Ergebnissen, als die Slaterschen. Die besten Dipolmomente werden mit der sog. BJ-Methode erhalten (Fehler < 0,2 D); allerdings wurden einige Resonanzintegrale gegenüber früheren Rechnungen abgeändert. Diese Resonanzintegrale entsprechen auch besser den Bindungslängen und Kernladungen.

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Résumé On a réétudié les contradictions trouvées pour certains composés oxygénés dans une étude récente des moments dipolaires par la méthode VESCF, en examinant en détail le furane, l'oxazole, l'isoxazole et trois oxadiazoles isomères. La méthode précédemment décrite pour l'estimation des angles du cycle et des longueurs de liaison rend compte de façon satisfaisante des géometries observées. Cependant dans les composés où plus d'un atome du cycle porte des paires libres d'électrons , les forces électrostatiques provenant de ces dipôles ont une influence considérable sur la géométrie du cycle. Lorsque l'on tient compte de cela dans le traitement de la géométrie, un bon accord est obtenu avec l'expérience.On a étudié l'effet provoqué par l'usage des règles de Burns plutôt que celles de Slater pour les exposants orbitaux pour l'obtention des moments des paires libres ainsi que l'effet de l'inclusion des potentiels des paires libres dans l'hamiltonien. Le meilleur accord entre moments dipolaires calculés et observés (á 0,2 D. près) est obtenu en utilisant la méthode BJ utilisée dans l'étude précédente mais avec des valeurs révisées pour certaines intégrales de résonance fondamentales. Ces nouvelles valeurs sont plus consistances avec les longueurs de liaison et les nombres atomiques que celles précédemment utilisées.

     

Synthesis and Biological Activities of Novel 1,4-Bridged Bis-1,2,4-Triazoles,Bis-1,3,4-Thiadiazoles and Bis-1,3,4-Oxadiazoles

Abstract

The terephthalic acid hydrazide(1) reacted with phenyl/benzyl isothiocyanate2a,bto yield the corresponding bis-thiosemicarbazides4a,b,viaacid hydrolysis of the intermediate 3whereas cyclization of4gave the bis-1,2,4-triazoles 5,6and bis-1,3,4-thiadiazoles7,8. Similarly, compound 1reacted with phenyl isocyanate9to give the bis-semicarbazide10, which was cyclized to the bis-oxadiazole 11and/or bis-1,2,4-triazole12in POCl_ti3and NaOH respectively.     

Solid Phase Luminescence and Thermal Transformations of Palladium(II) Complexes with 3-(2-Pyridyl)-1,2,4-Triazoles

Theoretical and Experimental Chemistry - The thermal behavior and luminescent properties of palladium(II) Pd(LR)2 complexes with 3-(2-pyridyl)-5-R-1,2,4-triazoles (LR , where R = H, Ph, Me) in...     

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.     

3-(2-吡啶基)-1,2,4-三唑衍生物的合成

1,2,4-三唑是五员含氮杂环化合物,其五员环上的三个N原子均可以同金属配位,因此它与金属离子的结合力很强,配位方式也很丰富,所构筑出来的配合物在生物、医药、磁性材料、手性催化剂、电致发光材料等方面都存在着诱人的应用前景,因而成为化学界和生物界的研究热点[1-4].     

Microwave Assisted Synthesis and Antimicrobial Activity of Novel 1,3,4-Thiadiazoles and 1,2,4-Triazoles Derived from 2-(3-Fluorophenyl)-4-methylthiazole-5-carbohydrazide

Russian Journal of General Chemistry - The precursors 2-{[2-(3-fluorophenyl)-4-methyl-1,3-thiazol-5-yl]carbonyl}-N-phenylhydrazinecarbothioamides are synthesized from...     

Iron(II) Complexes with 4-R-1,2,4-Triazoles (R = Ethyl,Propyl, Isopropyl): Synthesis and Properties

Fe(II) complexes with 4-R-1,2,4-triazoles of compositions FeL₃A₂ · nH₂O (where L is 4-propyl-1,2,4-triazol; A is Br^- (n = 4), CF₃SO₃ ^- (n = 5)), and FeL₂A₂ · nH₂O (where L are 4-ethyl-, 4-propyl-, 4-isopropyl-1,2,4-triazoles (Ettrz, Prtrz, Iprtrz, respectively), A = NCS^-, NO₃ ^- (n = 0-2)) were synthesized. Magnetochemical studies revealed that FeL₃A₂ · nH₂O complexes exhibit reversible spin transition (ST) ¹ A ₁ ⁵ T ₂ that is accompanied by thermochromism (a reversible change of color rose white). The temperatures of direct (T _s) and reverse (T _s) spin transitions are, respectively, 252 and 247 K for Fe(rtrz)₃Br₂ · 4H₂O and 207 and 202 K for Fe(rtrz)₃(CF₃SO₃)₂ · 5H₂O. Dehydration of the complexes is attended by significant changes in the type and temperatures of ST.     

Synthesis of (2-chloroquinolin-3-yl)-1,3,4-thiadiazole-2-carboxamides

(2-Chloroquinolin-3-yl)-1,3,4-thiadiazole-2-carboxamides were synthesized from hydrazones obtained via the reaction of 3-formyl-2-chloroquinoline with oxamic acid thiohydrazides.

     

Synthesis of 3-(5-Aryl-1,3,4-oxadiazol-2-yl)chromones

A general procedure was proposed for the synthesis of 3-(5-aryl-1,3,4-oxadiazol-2-yl)chromones by reaction of 3-formylchromone with aroylhydrazines, transformation of the corresponding acylhydrazones into 1,3-dipoles by the action of bromine in the presence of sodium acetate, and intramolecular ring closure.     

Synthesis of 4-(pyrazol-5-yl)-1,2,4-triazole-3-thiones

Condensation of pyrazolyl isothiocyanates 2 with N-substituted hydrazines provided the 2-methyl/phenyl-4-(pyrazol-5-yl)thiosemicarbazides 3 . Cyclization of 3 with formic acid-acetic anhydride or with triethyl orthoacetate-acetic anhydride provided 4-(pyrazol-5-yl)-l,2,4-triazole-3-thiones 4a-f and 5-methyl-4-(pyrazol-5-yl)-1,2,4-triazole-3-thiones 4g-I respectively.     

Synthesis of 3-(5-Aryl-1,3,4-oxadiazol-2-yl)chromones

A general method was proposed for the synthesis of 3-(5-aryl-1,3,4-oxadiazol-2-yl)chromones starting from 3-formylchromone. This aldehyde yields acylhydrazones, from which the corresponding unstable nitrile imines are generated. These intermediates undergo intramolecular 1,3-dipolar cycloaddition.     

Synthesis and functionalization of the 3-(1,3,4-oxadiazol-2-yl)-1h-indoles

A modified method is proposed for the preparative synthesis of 3-(1,3,4-oxadiazol-2-yl)-1H-indoles in high yield. We are the first to demonstrate the functionalization of this heterocyclic system by alkylation. In particular, syntheses are reported for [3-(1,3,4-oxadiazol-2-yl)-1H-indol-1-yl]acetic acids and their amide derivatives.     

2-芳基-5-(6-哒嗪酮-3-基)-1,3,4-噁二唑的合成

1,4,5,6-四氢-6-哒嗪酮-3-甲酰肼(1)和1,6-二氢-6-哒嗪酮-3-甲酰肼(2)与芳香醛反应得到相应的芳香醛腙3a～3g和5a～5g, 再将3a～3g, 5a～5g在溴的作用下, 合环得到一系列1,3,4-噁二唑的衍生物4a～4g和6a～6g. 化合物的结构经1H NMR, IR, MS和元素分析得以证实.     

Synthesis of 2-amino-5-(5R-1,2,4-oxadiazolyl-3)-1,3,4-oxadiazoles

The interaction of 2-amino-1,3,4-oxadiazole-5-carboxamidoxime with nitriles in the presence of ZnCl₂ and HCl or with trichloroacetic anhydride affords 2-amino-5-(5R-1,2,4-oxadiazolyl-3)-1,3,4-oxadiazoles. Their reactions with N-nucleophiles have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2100–2103, December, 1993.     

5-Acylmethyl-3-(2-pyridyl)-1,2,4-triazines: Synthesis and Complexes with Cu(II)

5-Acylmethyl-3-(2-pyridyl)-1,2,4-triazines are easily prepared from accessible 3-(2-pyridyl)-1,2,4-triazine 4-oxides by reaction of the latter with acetophenone or trifluoroacetone in the presence of NaH. The compounds obtained behaved as efficient ligands in reaction with CuCl₂ furnishing dimeric neutral complexes with Cu(II) whose structure was investigated by means of X-ray diffraction analysis.     

Syntheses of (3-Benzyl-4-Aroyl-1,2,4-Triazole-5-yl)[5-(3,4,5-Trimethoxylphenyl)-1,3,4-Oxadizole-2-yl] Sulfides

2-5-Disubstituted-1,3,4-oxadiazoIesand3,4-disubstituted-l,2.4-triazoleshavebeenreportedtopossessanhb8cterial'-',antiinflamatory';activity,andtobepIantgrowthpromoters"'.lnearlierreports'-',wedescribedthereactionof2-methylsulphon}!l-5-phenyl-l-3,4-oxadiazolewithavarietyofnucleophilicreagents,suchas,amine,azide.hy'drazine-andaryloxy.Inordertoscreennewcompoundsforphysiologicalactivity-wewouldliketodescribeanovelsynthesisofl2new(3-benZyl-4-aroyl-l,2,4-triazoIetrimethoxylphenyl)-1'3,4-oxadiaz(2)byn…     

3-(4-Phenyl-1,2,4-triazol-3-yl)chromones

The condensation of 4-phenyl-1,2,4-triazol-3-ylacetonitrile with 2-methyl-, 4-ethylresorcinol, and with pyrogallol gave α-(4-phenyl-1,2,4-triazol-3-yl)-2,4-dihydroxyacetophenones. Upon treatment with acid anhydrides and chlorides and subsequent hydrolysis these form 7-hydroxy-3-(4-phenyl)-1,2,4-triazol-3-yl)chromones with different substituents in both the benzene and the pyrone rings. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1676–1684, November, 2005.     

Synthesis and Crystal Structure of 2,5-Di- （pyridin-3-yl）-1,3,4-oxadiazolendium Nitrate

In order to continue our studies on the synthesis, properties and coordination of s-tetrazine, 3,6-di-(pyridin-3-yl)-s-tetrazine (II, 3-dptz) was synthesized and characterized by 1H- NMR, MS and IR spectra. And the coordination reaction of 3-dptz with nitrate of Cu(II) was studied. 3-dptz reacting with CuII salt [Cu(NO3)2·2H2O] generates a new salt, nitrate of 2,5-di-(pyridin-3- yl)-1,3,4-oxadiazolene (III). III was determined by IR spectra and single-crystal X-ray diffraction to give the following crystal data: space group P21/c, a = 4.9112(1), b = 8.4101(3), c = 29.499(1) , β = 93.266(2)o, V = 1216.44(7) nm3, Mr = 287.24, Z = 4, Dc = 1.568 g/cm3,μ= 0.122 mm-1, F(000) = 592, R = 0.0430 and wR = 0.1240. The results show that III is composed of one cation and one nitrate anion. The cation consists of one H+ and one 2,5-di-(pyridin-3-yl)-1,3,4-oxadiazol molecule, with the former being attached to the latter via electrovalent bond with N3 atom. And the O(42) atom in the nitrate anion is disordered. Intra- and intermolecular H-bonds are observed in the crystal of the title compound. The mechanism of metal-assisted decomposition was also discussed briefly.