Imine-enamine tautomerism of dihydroazolopyrimidines. 3. 5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines

5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines were obtained by condensation of 3-amino-1,2,4-triazole with -dimethylaminopropiophenone hydrochlorides or crotophenone. The effect of steric and electronic factors on the position of the imine-enamine equilibrium in solutions of the synthesized substances is examined. 5-Phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyriniidine was subjected to x-ray diffraction analysis.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1539–1544, November, 1991.     

Imine-enamine tautomerism of dihydroazolopyrimidines 5. Steric effects and the tautomeric equilibrium for dihydro-1,2,4-triazolo[1,5-a]pyrimidines

The reaction of 3-amino-1,2,4-triazole with -dimethylaminopropiophenones or unsaturated ketones gives 5,7-disubstituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines. An increase in the bulk of the substituent at C₍₇₎ in the bicyclic system leads to relative stabilization of the enamine tautomer of these compounds. An x-ray diffraction structural analysis of 7-tert-butyl-5-(4-methoxyphenyl)-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine showed that the introduction of a tert-butyl group into the dihydropyrimidine ring leads to significant loss of planarity of this system.For Communication 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1357–1363, October, 1993.     

Imine-enamine tautomerism of dihydroazolopyrimidines. 6. Synthesis and tautomerism of thienyl derivatives of dihydro-1,2,4-triazolo-[1,5-a]pyrimidines

The cyclocondensation of thiophene analogs of chalcone with 3-amino-1,2,4-triazole gives 5- and 7-(α-thienyl)dihydro-1,2,4-triazolo[1,5-a]pyrimidines. The tautomer composition of synthesized compounds was analyzed. For communication 5, see [1]. Kharkov State University, 310077 Kharkov, Ukraine, Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 678–682, May, 1999.     

Tautomeric forms of 5-(2-hydroxyphenyl)-7-phenyldihydro-1,2,4-triazolo[1,5-a]pyrimidine

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1000–1001, July, 1989.     

Synthesis and structure of 4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidines

Kharkov State University, 310077 Kharkov and Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 981–986, July, 1994.Original article submitted May 11, 1994.     

Improved synthesis of 2-amino-1,2,4-triazolo[1,5-a]pyrimidines

An improved procedure is suggested for preparing 2-amino-1,2,4-triazolo[1,5-a]pyrimidines from 3,5-diamino-1,2,4-triazole and unsaturated aromatic ketones, with acetyl protection of the amino group in the step of oxidation of 2-amino-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines.     

Synthesis and electrophilic substitutions of novel pyrazolo[1,5-c]-1,2,4-triazolo[4,3-a]pyrimidines

5-Aryl-7-hydrazino-2-phenylpyrazolo[1,5-c]pyrimidines 1 were used as precursors for the preparation of a new series of 5-aryl-8-phenylpyrazolo[1,5-c]-1,2,4- triazolo[4,3-a]pyrimidines 2. The reactions of 2 with certain electrophilic reagents gave the respective 6-substituted derivatives 3-5 rather than the 7-isomeric products. Formylation of the key compounds 1 with ethyl formate yielded the formyl derivatives 6. Furthermore, boiling of compounds 1 with acetic acid afforded 7-acetylhydrazino-5-aryl-2-phenylpyrazolo[1,5-c]pyrimidines 7. Bromination of 7 yielded the dibromo- derivatives 8, while their iodination and nitration gave the monosubstituted derivatives 9 and 10, respectively. Also, treatment of 1 with boiling acetic anhydride yielded the triacetyl derivatives 11. The structure of synthesized products was confirmed by elemental analyses, IR, 1H NMR and MS spectra.     

Synthesis of 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamides

The 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamides are a new class of highly active herbicides. A novel cyclization method for the synthesis of these compounds is discussed.     

A new synthesis for 1,2,4-triazolo[1,5-a]-pyridines and 1,2,4-triazolo[1,5-a]isoquinolines

Summary Condensation of cyano acid hydrazide1 with cyclopentanone in refluxing ethanolic piperidine yields hydrazone2. With mixtures of aliphatic aldehydes and different active methylene reagents,2 reacts to 1,2,4-triazolo[1,5-a]pyridines (8a–f). Compound2 also reacts with arylidenes9a–g to give triazolopyridines10a–g. Reaction of2 with aromatic aldehydes affords compounds13a–c. Diazotation of2 with aryldiazonium chloride in ethanol at 0 °C leads to the azo adducts15a–d. The thieno-1,2,4-triazolopyridine16 is obtained by reaction of8a with elementary sulfur.16 undergoes cycloaddition with -nitrostyrene, maleic anhydride, N-arylmalemide, and acrylonitrile yielding the isoquinolines21–24. All new compounds have been characterized by their IR,¹H NMR, and mass spectra.

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Ein neuer Syntheseweg für 1,2,4-Triazolo[1,5-a]pyridine und 1,2,4-Triazolo[1,5-a]isochinoline

Zusammenfassung Kondensation des Cyanohydrazids1 mit Cyclopentanon in ethanolischem Piperidin bei Rückflußtemperatur ergibt das Hydrazon2. Mit Gemischen aus aliphatischen Aldehyden und verschiedenen Verbindungen mit aktiven Methylengruppen reagiert2 zu 1,2,4-Triazolo[1,5-a]pyridinen (8a–f). Verbindung2 reagiert außerdem mit den Arylidenen9a–g zu den Triazolopyridinen10a–g. Umsetzung von2 mit aromatischen Aldehyden führt zu den Verbindungen13a–c. Diazotierung von2 mit Aryldiazoniumchloriden in Ethanol bei 0°C ergibt die Azoaddukte15a–d. Das Thieno-1,2,4-triazolylpyridin16 erhält man durch Reaktion von8a mit elementarem Schwefel.16 geht it -Nitrostyrol, Maleinsäureanhydrid, N-Arylmaleimid und Acrylnitril eine Cycloaddition zu den Isochinolinen21–24 ein. Alle neuen Verbindungen wurden durch ihre IR-,¹H-NMR- und Massenspektren charakterisiert.

     

Molecular structure and tautomeric conversions of 5-(4-dimethylaminophenyl)-7-phenyl-6,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine

The x-ray structure is solved and the three-dimensional structure is analyzed for 5-(4-dimethylaminophenyl)-7phenyl-6,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine. Its reverse isomerization into the 4,7-dihydro species is studiedTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 933–936, July, 1992.     

Carbocycle annelated 1,2,4-triazolo[1,5-α]pyrimidines

Reaction of 3-amino-1,2,4-triazole with mono- and dibenzalcycloalkanones gives 4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines annelated by five-, six-, or seven-membered carbocycles. They can be dehydrogenated to the corresponding heteraromatics. The spectra-luminescent properties of the compounds obtained are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 105–108, January, 1991.     

Chemical conversions of 5,7-disubstituted dihydro-1,2,4-triazolo[1,5-a]pyrimidines

Hydrolysis, oxidation, reduction, alkylation, and nitrosation of aromatic-substituted dihydro-1,2,4-triazolo-[1,5-a]pyrimidines have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1638–1642, December, 1990.     

An unequivocal synthesis of some substituted 1,2,4-triazolo[1,5-a]pyrimidines

An unequivocal synthesis of 5-chloro-7-methyl- (8) and 7-methyl-1,2,4-triazolo[1,5-a]pyrimidine (10) from 2-amino-4-chloro-6-methylpyrimidine (5) through the corresponding amidine6 and formamide oxime7 was developed. It was unambigously shown by comparison of the chemical shifts and the magnitude of coupling constants that the compounds obtained by condensation of 3-amino-1,2,4-triazole (12) and ethyl acetoacetate (13) and some further transformations are isomeric 5-methyl substituted 1,2,4-triazolo[1,5-a]pyrimidines1,9, and11.

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Eine eindeutige Synthese einiger substituierter 1,2,4-Triazolo[1,5-a]pyrimidine

Zusammenfassung Es wurde ein eindeutiger Syntheseweg für 5-Chlor-7-methyl- (8) und 7-Methyl-1,2,4-triazolo[1,5-a]pyrimidin (10) ausgehend von 2-Amino-4-chlor-6-methylpyrimidin (5) über das entsprechende Amidin6 und das Formamidoxim7 entwickelt. Durch Vergleich von chemischen Verschiebungen und Kopplungskonstanten konnte eindeutig gezeigt werden, daß die Verbindungen, die bei der Kondensation von 3-Amino-1,2,4-triazol (12) and Ethylacetoacetat (13), sowie einige weitere Transformationsprodukte, isomere 5-Methylsubstituierte 1,2,4-Triazolo[1,5-a]pyrimidine sind (1,9,11).

     

Identification by NMR spectroscopy of some isomeric 1,2,4-triazolo[4,3-a] and [1,5-a]pyrimidines

The title compounds have been prepared with four known procedures. The mixtures of isomers obtained have been separated by countercurrent distribution and the single isomers identified by NMR spectroscopy.     

Nitroazines 18. Arylation and destruction of 6-nitro-1,2,4-triazolo[1,5-a]pyrimidines

6-Ntiro-7-aryl-1,2,4-triazolo[1,5-a]pyrimidines were synthesized by treatment of the corresponding 7-oxo compounds with phosphorus oxychloride in the presence of N,N-dialkylanilines. The 7-(N-methyl-p-methoxyphenylamino) derivatives were formed under the same conditions with N,N-dimethyl-p-anisidine. The nitroarylazolopyrimidines produced underwent destruction to give -nitroacetophenones on treatment with water. The influence of substituenis on the course of the reaction is shown and the mechanism is discussed.For Communication 17 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1546–1554, November, 1992.     

2-Substituted 7-amino-1,2,4-triazolo[1,5-a]-[1,3,5]triazines

3-Substituted 5-amino-1-guanyl-1,2,4-triazoles have been obtained which, on reaction with orthoformic ester or 100% formic acid, form 2-substituted 7-amino-1,2,4-triazolo[1,5-a]-[1,3,5]triazines.     

2,3-Diamino-5-aryl-7-(4-nitrophenyl)-1,2,4-triazolo[1,5-a]pyrimidinium-6-olates

The corresponding triazolopyrimidinium salts and 1,2,4-triazolo[1,5-a]pyrimidinium-6-olates were formed from the reaction of 3,4,5-triamino-1,2,4-triazole and 1-aryl-3-(4-nitrophenyl)-2,3-dibromopropanones. The structure of one of the latter has been established by X-ray crystallography.