Synthesis of 5-Phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

Syntheses are reported for a series of 2-alkylamino-6-phenyl-4-trifluoromethylpyridines. The reaction of 3-cyano-2-(hydroxyalkylamino)-6-phenyl-4-trifluoromethylpyridines with thionyl chloride gave the corresponding 2-(chloroalkylamino)pyridines, 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydro-imidazo[1,2-a]pyridines, and 9-cyano-6-phenyl-8-trifluoromethyl-2,3,4-trihydropyrido[1,2-a]-pyrimidines. X-ray diffraction structural analysis was used to study 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine.     

Condensed isoquinolines 31. Reaction of 5-aryl-3-halo-12H-isoquino[2,3-a]quinazolines with electrophilic reagents

Treatment of 5-aryl-3-halo-12H-isoquino[2,3-a]quinazolines with electrophilic reagents readily forms their oxidation products. Acylation of the 3-chloro-5-phenyl-7,12-dihydroisoquino[2,3-a]quinazolinium perchlorate with Ac₂O in the presence of pyridine gave the product of electrophilic substitution at the C-7 atom 1-(3-chloro-5-phenyl-12H-isoquino[2,3-a]quinazolin-7-yl)-1-ethanone. By the same route phenacyl bromides react with the anhydro base 1 to give 5-aryl-7-(2-aryl-2-oxoethyl)-3-halo-isoquino[2,3-a]quinazolin-13-ium bromides. These salts readily react with nucleophilic reagents to form the products of addition at the C-12 atom. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1044–1052, July, 2008.     

Properties of 8-Cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

The alkylation, acylation, halogenation, nitration, oxidation, and hydrolysis reactions of 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine have been studied. It was found that the 6-halo derivatives add alcohol to give covalent solvates. X-ray analysis has been carried out on one of the solvates (6-chloro-8-cyano-7-ethoxy-5-phenyl-7-trifluoromethyl-1,2,3,7-tetrahydroimidazo[1,2-a]pyridine) as well as on 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine trifluoroacetate.     

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.

     

2-R-7-methyl[1,2,4]triazolo[2,3-a]pyrimidines: synthesis and structures

Reactions of 5-R-3-amino-1,2,4-triazoles with ethoxymethylideneacetylacetone and ethyl ethoxymethylideneacetoacetate proceeded regioselectively, giving 2-R-7-methyl[1,2,4]triazolo[2,3-a]-pyrimidines in good yields. The compounds obtained were characterized by elemental analysis, ¹H NMR spectroscopy, and X-ray diffraction analysis (for ethyl 2-ethylthio-7-methyl[1,2,4]triazolo[2,3-a]pyrimidine-6-carboxylate). The frontier orbitals, the molecular electrostatic potential, and the geometries of the reagent molecules were calculated by the DFT method (B3LYP/6-31G**). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1244–1248, June, 2008.     

Synthesis of 4-and 5-substituted 2-methyl-and 2-(2-carboxyethyl)-1,2,4-triazino-[2,3-a]benzimidazol-4(5)H-3-ones

Condensation of 2-alkylamino-1-aminobenzimidazoles and quaternary 1,2-diamino-3R-benzimidazolium salts with pyruvate and α-ketoglutaric acid has given 4-and 5-substituted 2-methyl-and 2-(2-carboxyethyl)-1,2,4-triazino[2,3-a]benzimidazol-4(5)H-3-ones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 738–747, May, 2006.     

Synthesis of pyrido[1,2-a]benzimidazoles from 2-acylmethyl-1H-benzimidazoles

Methods are proposed for the synthesis of previously unknown pyrido[1,2-a]benzimidazoles via the cyclocondensation of 2-acylmethyl-1H-benzimidazoles with malononitrile, triethylorthoformate ester, or ethoxymethylenemalononitrile. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1073–1079, July, 2006.     

Synthesis of Substituted 5,6-Dihydro-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepines

A one-pot synthetic approach to the novel 5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepines by thermal cyclization of 4-acylhydrazino-2,3-dihydro-1H-1,5-benzodiazepines is described.     

Properties of 2,3-dihydro-imidazolo[1,2-a]pyridines. (Review)

Published data on the physical and chemical characteristics of 2,3-dihydroimidazo[1,2-a]pyridines to 1998 are reviewed.Riga Technical University, Riga, Latvia; e-mail: mara@ktf.rtu.lv. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1027, August, 2000.     

Synthesis of 2,3-Dihydroimidazo[1,2-a]pyridines from 1,3-Diketones

A series of 2-hydroxy-, 2-chloro-, and 2-(2-hydroxyethylamino)-6-aryl-4-polyfluoroalkyl-3-cyanopyridines has been synthesized. The latter react with phosphorus oxychloride to give fluorine containing 2,3-dihydroimidazo[1,2-a]pyridines.     

Condensed isoquinolines 29. Oxidation reactions of 5-aryl-7,12-dihydroisoquino[2,3-a]quinazolinium salts

5-Aryl-7,12-dihydroisoquino[2,3-a]quinazolinium perchlorates are readily oxidized by atmospheric oxygen to form the products of oxidative coupling 5,5′-bis(aryl)-3,3′-dihalo[7,7′]bi[isoquino-[2,3-a]quinazoline-13,13′-diylium perchlorates. Heating 3-chloro-5-phenyl-7,12-dihydroisoquino-[2,3-a]quinazolinium perchlorate in nitrobenzene gives the 3-chloro-5-phenylisoquino[2,3-a]quinazolin-13-ium perchlorate. The aromatic 5-arylisoquino[2,3-a]quinazoline derivatives obtained react with nucleophilic reagents to form addition products at the C-12 atom. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 428–439, March, 2008.     

Synthesis of 8-tert-Butyl-9-oxo-1,2,4-triazolo[4,5-b]-1,2,4-triazolo[3,4-c]-1,2,4-triazine

8-tert-Butyl-9-oxo-1,2,4-triazolo[4,5-b]-1,2,4-triazolo[3,4-c]-1,2,4-triazine has been synthesized by the interaction of 6-tert-butyl-3-hydrazino-1,2,4-triazolo[3,4-c]-1,2,4-triazin-5-one with formic acid. The conditions of carrying out the reaction are discussed. Spectral characteristics are given.     

Formylation of Furyl-substituted Imidazo[1,2-a]pyridine, Imidazo[1,2-a]pyrimidine and Imidazo[2,1-b]thiazole

Vilsmeier formylation of 2-(2-furyl)-substituted imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, and also 6-(2-furyl)imidazo[2,1-b]thiazole with 1 mole of reagent occurs at the free position of the imidazole ring, while with an excess of the reagent it also occurs at the position 5 of the furyl group.     

Some chemical properties of 2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-one and 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones

We have studied the reaction of 2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-one and 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones with amines, alkylating reagents, and hydrogen peroxide. We have shown that the presence of an aryl substituent at the 2 position of [1,3-thiazino[3,2-a]benzimidazol-4-ones has a substantial effect on the direction of the reactions. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 445–452, March, 2006.     

Synthesis and properties of 1,2,4-triazolo[4,3-d]-1,2,4-triazolo-[3,4-f]furazano[3,4-b]pyrazines

New methods for the synthesis of 1,2,4-triazolo[4,3-d]-1,2,4-triazolo[3,4-f]furazano[3,4-b]pyrazines with functional substituents of various types are proposed and some properties of these compounds are studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1776–1778, October, 1993.