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.

     

Stable 1,2,4-triazolo[1,5-a]-pyrimidinium salts

2,3-Diamino-5,7-diaryl-1,2,4-triazolo[1,5-a]pyrimidinium salts have been synthesized by the cyclocondensation of 3,4,5-triamino-1,2,4-triazole with 1,3-diaryl-2,3-propanes, and their structures and chemical properties have been studied.Kharkov State University, Kharkov 310077, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, 796–804 June, 1999.     

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.     

Tricyclic heteroaromatic systems. 1,2,4-triazolo[1,5-a]quinoxaline

The parent 1,2,4-triazolo[1,5-a]quinoxaline was prepared by a few-step reaction from ethyl N¹-(2-nitrophenyl)-N³-ethoxalyloxamidrazonate, which afforded the key intermediate diethyl 1-(2-nitrophenyl)-1,2,4-triazole-3,5-dicarboxylate in satisfactory yield. The latter was cyclized, hydrolyzed, decarboxylated, reduced and dehydrogenated to yield the title compound.     

A convenient route to the 1,2,5-oxadiazole-substituted 1,2,4-triazolo[1,5-a]pyrimidine derivatives

Chemistry of Heterocyclic Compounds - A convenient synthesis of 1,2,4-triazole and 1,2,4-triazolo[1,5-a]pyrimidines with 3-amino-1,2,5-oxadiazole substituent starting from available...     

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.     

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.     

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.     

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.     

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.     

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.     

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).

     

Regioselectivity of N-substitution in bis-alkylation of 1,2,4-triazolo[1,5-a]benzimidazole-2-thione

Cyclization of the corresponding N-substituted 1,2-diaminobenzimidazoles with carbon disulfide in refluxing DMF leads to 3-methyl- and 3-benzyl-1,2,4-triazolo[1,5-a]benzimidazole-2-thiones. Based on the results of their S-alkylation, quantum chemical calculations by the density functional theory method, and 1D and 2D NMR spectroscopic studies, it was concluded that the bis-alkylation of N-unsubstituted 1,2,4-triazolo[1,5-a]benzimidazole-2-thione in the presence of a base proceeds with the formation of N(4)-derivatives of 2-alkylthio-1,2,4-triazolo[1,5-a]benzimidazole, rather than N(3)-derivatives as was believed earlier.     

Oxidative cyclization of 2-amino-1-arylideneaminobenzimidazoles into 1,2,4-triazolo[1,5-a]benzimidazoles

When heated in nitrobenzene, 1-arylideneamino-2-methylaminobenzimidazoles convert in a 20...30% yield into 2-aryl-3-methyl-1,2,4-triazolo[1,5-a]benzimidazoles. In addition, 2-methylaminobenzimidazole and the corresponding benzonitrile are formed as a result of a thermal splitting of the N-N bond. Under the same conditions, 2-amino-1-arylideneaminobenzimidazoles and 1-arylideneamino-3-methylbenzimidazoline-2-imines give only products of splitting off of the nitrile. In several cases, the subsequent reaction of the nitrile with 2-amino-1-methylbenzimidazole leads to the formation of benzamidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1226–1231, September, 1988.     

Crystal and molecular structure of 7-phenyl-1,2,4-triazolo[1,5-a]-1,3,5-triazine

The crystal and molecular structure of 7-phenyl-1,2,4-triazolo[1,5-a]-1,3,5-triazine were determined. It was shown that the amine nitrogen atom (N¹) of the triazole ring acts as a nucleophilic center in the cyclization of N-(1,2,4-triazol-5-yl)amidines with electrophilic reagents.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1386–1389, June, 1992.     

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.