Synthesis and properties of pyrimido[4,5-<Emphasis Type="Italic">a</Emphasis>]- and pyrido[4,3-<Emphasis Type="Italic">a</Emphasis>]carbazole derivatives

Methods for the synthesis of substituted pyrimido [4,5-a]- and pyrido[4,3-a]carbazoles were proposed. Condensation of 2-(dimethylaminomethylene)-6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one with guanidine and thiourea afforded 2-amino-8-methyl-6,11-dihydro-5H-pyrimido[4,5-a]carbazole and 8-methyl-3,5,6,11-tetrahydro-2H-pyrimido[4,5-a]carbazole-2-thione, respectively. The reaction of cyano(6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-ylidene)acetamide with dimethylformamide dimethyl acetal gave N-(dimethylamino-methylene)cyano(6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-ylidene)acetamide. Cyclization of the latter yielded 1-cyano-8-methyl-3,5,6,11-tetrahydro-2H-pyrido[4,3-a]carbazol-2-one.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2740–2744, December, 2004.     

Fluorine-containing pyrido[1,2-<Emphasis Type="Italic">a</Emphasis>]quinazolin-6-ones

Reactions of 2-aminopyridine and 2-amino-5-methylpyridine with 2,3,4,5-tetrafluorobenzoyl chloride afforded N,N’-diaroylpyridinium salts, which were converted into 6H-pyrido[1,2-a]quinazolin-6-ones by refluxing in toluene in the presence of triethylamine. The angular structure of the tricyclic derivatives obtained was confirmed by ¹⁹F and ¹³C NMR spectroscopy and 2D heteronuclear HetCOR and HMBC experiments.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2216–2220, October, 2004.     

Transformations of 8-substituted tetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrazines

The reactions of 8-chlorotetrazolo[1,5-a]pyrazine with N-, O-, and S-nucleophiles involve the ipso substitution of the chlorine atom. Heating of this compound with benzotriazole or phenyltetrazole results in elimination of the nitrogen molecule from one of the tetrazole rings to form new annelated azapentalenes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 334–338, February, 2007.     

Synthesis of 8,8-R,R-8,9-dihydro[1,2,4]triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]quinazolin-6(7<Emphasis Type="Italic">H</Emphasis>)-ones

Three-component condensation of 3-amino-1,2,4-triazole (or its 5-methyl and 5-methylthio derivatives), dimedone (or cyclohexane-1,3-dione), and dimethylformamide dimethyl acetal afforded 8,8-R, R-8,9-dihydro[1,2,4]triazolo[1,5-a]quinazolin-6(7H)-ones. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2805–2807, December, 2005.     

Nitration of Pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazines

We have synthesized nitro derivatives of pyrrolo[1,2-a]pyrazines using a nitrating mixture and acetyl nitrate. We have obtained the products of oxidation of the side chain of 1,6-substituted pyrrolo[1,2-a]-pyrazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1579–1586, October, 2005.     

Trifluoroacetylation of pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazines

A study was carried out on the reaction of pyrrolo[1,2-a]pyrazines containing an alkyl, aryl, or aralkyl substituent at C-1 with trifluoroacetic anhydride. Trifluoroacetylation products may be formed either by reaction in the pyrrole ring or at the aryl or aralkyl groups at C-1. Products of electrophilic substitution at C-6 are formed in the trifluoroacetylation of pyrrolo[1,2-a]pyrazines containing at C-1 a substituent bulkier than a methyl group but lacking substituents at C-6 (the α-position of the pyrrole ring). __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1226–1233, August, 2007.     

Pyrano[4,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidinium salts

5-Aroyl-1,3,6-trimethyluracils were converted to pyrano[4,3-d]pyrimidinium salts. Reactions of the salts obtained with ammonia, primary amines, and hydrazine were studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2251–2257, November, 2007.     

Alternative Routes to the Pyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazolo-[1,5-<Emphasis Type="Italic">c</Emphasis>]pyrimidine System

Formimidic acid esters derived from 1-substituted 5-aminopyrazole-4-carbonitriles reacted with carboxylic acid hydrazides on heating to give 2,7-disubstituted pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives as a result of double heterocyclization. The same compounds were obtained by thermal recyclization of 1-aroyl-2-(1-R-pyrazolo[3,4-d]pyrimidin-4-yl)hydrazines.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 934–938.Original Russian Text Copyright © 2005 by Tyurin, Vorob’ev, Minyaeva, Krasnikov, Mezheritskii.     

Chemical Reactions of 2-Methyl-5,7-diphenyl-6,7-dihydropyrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine

The hydrolysis, oxidation, reduction, alkylation, formylation, and nitrosation reactions of 2-methyl-5,7-diphenyl-6,7-dihydropyrazolo[1,5-a]pyrimidine have been studied.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 577–581, April, 2005.     

11H-isoindolo[2,1-<Emphasis Type="Italic">a</Emphasis>]benzimidazoles (Review)

Data on methods for the synthesis of isoindolo[2,1-a]benzimidazole and its derivatives and their chemical characteristics are reviewed. Data from quantum-chemical calculations of certain structures are presented. Possible practical applications of the compounds are indicated. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 323–351, March, 2007.     

Synthesis of 3-Aroylmethylene-1,6,7,11b-tetrahydro-2H-pyrazino-[2,1-<Emphasis Type="Italic">a</Emphasis>]isoquinolin-4-ones

The reaction of substituted methyl aroylpyruvates with 1-aminomethyl-1,2,3,4-tetrahydroisoquinoline dihydrochloride in the presence of AcOH gives 3-aroylmethylene-1,6,7,11b-tetrahydro-2H-pyrazino[2,1-a]isoquinolin-4-ones whose structures have been confirmed by IR, ¹H NMR, and mass spectrometry. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1218–1221, August, 2005.     

Condensed Tetrazolo-1,3,5-triazines. 2. Alkylation and Nucleophilic Substitution of 5-Trinitromethyltetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]-1,3,5-triazin-7-ones

A new heterocyclic compound, 3-methyl-5-trinitromethyltetrazolo[1,5-a]-1,3,5-triazin-7-one, was synthesized by the reaction of methyl iodide and the silver salt of 5-trinitromethyltetrazolo[1,5-a]-1,3,5-triazin-7-one. An X-ray diffraction structural analysis of this product was carried out and feasibility was demonstrated for the nucleophilic substitution of the trinitromethyl group in this compound by the action of phenol, phenol derivatives, and thiophenol.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 582–588, April, 2005.