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.     

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.     

Heterocyclisch anellierte Pyrazin-1,4-dioxide; 1. Mitt.: Die positionsselektive Synthese von Pyrido[2,3-b]pyrazin-1,4-dioxiden

The positionsselective synthesis of the title compounds5 is described and the structure established by reduction of5c to8 and synthesis of the latter by an unambiguous method.

     

Synthesis and chemical transformations of 2,3-dihydropyrrole-2,3-diones annelated on the [a] side by azaheterocycles. (Review)

Data on methods for the synthesis of 2,3-dihydro-2,3-pyrrolediones condensed with azaheterocycles on the [a] side are reviewed. Their reactions with nucleophilic reagents, allylboronation, reduction, and thermal transformations are discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 3–25, January, 2006.     

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.     

Reaction of 5-phenyl-2,3-dihydrofuran-2,3-dione with 6,7-dimethoxy-3,4-dihydroisoquinoline. Crystal structure of 1-benzoyl-8,9-dimethoxy-2,3,5,6-tetrahydropyrrolo[2,1-a]isoquinoline-2,3-dione

The reaction of 5-phenyl-2,3-dihydrofuran-2,3-dione with 6,7-dimethoxy-3,4-dihydroisoquinoline gave 1-benzoyl-2-hydroxy-8,9-dimethoxy-3,5,6,10b-tetrahydropyrrolo[2,1-a]isoquinolin-3-one and its oxidation product,viz., 1-benzoyl-8,9-dimethoxy-2,3,5,6-tetrahydropyrrolo[2,1-a]isoquinoline-2,3-dione. The last-mentioned compound was studied by X-ray structural analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1845–1848, October, 1997.     

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 reactions of 2-substituted 1-phenyl-4-oxo-1,4-dihydropyrido-[2,3-d]pyrimidines

2-Methyl-4-oxo-1-phenyl-1,4-dihydropyrido[2,3-d]pyrimidine was acylated by succinic and trifluoroacetic anhydrides and also underwent the Claisen reaction with diethyl oxalate and ethyl oxanilate to give acyl derivatives at the methyl group, which, according to UV, IR, and¹H NMR spectra, exist as enaminocarbonyl and iminoenol tautomers with intramolecular hydrogen bonds.Perm State Pharmaceutical Academy, Perm 614600, Russia. e-mail: GIO@pharm.perm.su. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1119–1122, August, 2000.     

Efficient synthesis of 2- and 3-substituted-2,3-dihydro [1,4]dioxino[2,3-b]pyridine derivatives

A versatile new approach for the synthesis in three steps of 2-substituted-2,3-dihydro[1,4]dioxino[2,3-b]pyridines B via a Smiles rearrangement using easily available reagents is described. A study illustrating the influence of experimental conditions on the progress of the reaction is reported.     

Synthesis of 2,3-Dihydrothiazolo[3,2-a]pyrimidin-5-ones by a Michael-type Tandem Reaction

Summary. Although various thiazoles are known in literature for their biological and pharmacological properties only a few multi-step synthesis pathways for the preparation of thiazolo[3,2-a]pyrimidinones have been reported, which are tedious and time-consuming. An alternative synthesis pathway is described, which allows the preparation of 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones in a one-step process based on a Michael-type tandem reaction. By heating of 2-thiobarbituric acid with ethyl 4-bromocrotonate in ethanol at 60°C for 2 h, a 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one was obtained in 73% yield, whereas carrying out the reaction at room temperature results in the formation of an unstable unsaturated ester. The structures of both, the α,β-unsaturated ester as well as the 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one were confirmed by NMR spectroscopy. Additionally, the structure of the 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one was investigated by single-crystal X-ray analysis. The described approach offers a significant improvement over previously reported synthesis pathways because it allows the simple preparation of 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones with good yields in a one-step reaction.     

Synthesis and reductive reactions of 2,3-dioxo-2,3-dihydrobenzo[<Emphasis Type="Italic">b</Emphasis>]furo[2,3-<Emphasis Type="Italic">f</Emphasis>]-, -[2,3-<Emphasis Type="Italic">g</Emphasis>]-, and -[3,2-<Emphasis Type="Italic">e</Emphasis>]indoles

The Sandmeyer reaction was used to prepare 2,3-dioxo-2,3-dihydrobenzo[b]furoindoles which could be reduced with diborane or with complex hydrides to give the corresponding unsubstituted as well as the 3-hydroxybenzo[b]furoindoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No 11, pp. 1683–1689, November, 2004.     

The mass spectral fragmentation of some 2,3-dihydro-5-trifluoromethyl-7-(p-R-phenyl)-1,4-diazepines

Summary Electron impact mass spectra of seven 2,3-dihydro-5-trifluoromethyl/methyl-7-(p-R-phenyl)-1,4-diazepinesR=H, CH₃, OCH₃, CF₃, Cl, Br) have been recorded and are discussed. These systems dissociate by scission of the C₂-C₃ bond followed by loss of H^. to give the [M-H]⁺ ion as the base peak. The fragmentation behaviour has been investigated using metastable scanning techniques and accurate mass measurements. The origin of some characteristic fragment ions is discussed.

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Massenspektroskopische Fragmentierung einiger 2,3-Dihydro-5-trifluormethyl-7-(p-R-phenyl)-1,4-diazepine

Zusammenfassung Die EI-Massenspektren von 7 2,3-Dihydro-5-trifluormethyl/methyl-7-(p-R-phenyl)-1,4-diazepinen (R=CH₃, OCH₃, CF₃, Cl, Br) werden vorgestellt. Diese Verbindungen fragmentieren unter Spaltung der C₂-C₃-Bindung. Anschließende Abspaltung von H^. führt zum Fragment [M-H]⁺, das als Basispeak auftritt. Das Fragmentierungsverhalten wurde mittels metastabiler Methoden und genauer Massenbestimmungen untersucht. Die Herkunft einiger charakteristischer Fragmentionen wird diskutiert.

     

Condensed Imidazo-1,2,4-azines. 31. Synthesis and Chemical Transformations of Substituted 1,2,4-Triazepino[2,3-a]benzimidazoles

By reaction of 1,2-diaminobenzimidazole with 1,3-diketones, acetoacetic ester and its derivatives, we have synthesized substituted 1,2,4-triazepino[2,3-a]benzimidazole and 5H-1,2,4-triazepino[2,3-a]benzimidazol-4-one. By reaction of 5H-2-methyl-1,2,4-triazepino[2,3-a]benzimidazol-4-one with aromatic aldehydes or phenyldiazonium chloride, we have obtained 3-arylidene(phenylazo) derivatives of this compound, and by reaction with P₂S₅ we have obtained 5H-2-methyl-1,2,4-triazepino[2,3-a]benzimidazole-4-thione. We have shown that when reacted with ammonia, primary or secondary amines, the latter forms 4-amino-substituted 2-methyl-1,2,4-triazepino[2,3-a]benzimidazole.     

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.     

Oxidative Recyclization of 4,6,7-Trichloro-5-hydroxy-2-(2-pyrimidylamino)-2,3-dihydrobenzo[b]furan

When 4,6,7-trichloro-5-hydroxy-2-(2-pyrimidylamino)- 2,3-dihydrobenzo[b]furan reacted with phenyliodoso diacetate, an unexpected oxidative recyclization was observed to give 3-(3,5,6-trichloro-1,4-benzoquinon-2-yl)imidazo[1,2-a]pyrimidine. 2-[N-2-(3,5,6-Trichloro-1,4-benzoquinon-2-yl)ethenylamino]pyrimidine is the intermediate product in the conversion.