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.     

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.     

Reactions of 2,3-Dioxopyrrolo[2,1-<Emphasis Type="Italic">a</Emphasis>]isoquinolines with Active N-Nucleophiles

It is shown that 2,3-dioxopyrrolo[2,1-a]isoquinolines react readily with aliphatic diamines and hydroxyamine with opening of the dioxopyrrole ring and formation of the corresponding bisenaminoketoamides and hydroxamic acids. Reaction with the thiosemicarbazide and hydrazides of aromatic acids proceeds without opening of the pyrrole ring at the ketone carbonyl. Derivatives of hexahydropyridazine are formed when compounds with carboxyethyl groups at position 1 react with hydrazine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, 1383–1387, September, 2005.     

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.     

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.     

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.     

Contributions to syntheses of pyrrolo[2,1-a]phthalazines

Abstract  

Structural elucidation of the dihydro derivatives obtained as by-products in the classic salt method synthesis of pyrrolo[2,1-a]phthalazines and acetylenic dipolarophiles was achieved by X-ray diffraction analysis of a representative compound. In addition, new pyrrolo[2,1-a]phthalazines were obtained by a one-pot three-component reaction that avoids the formation of the dihydro derivative intermediates.     

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 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.     

Reaction of 2,3-Dioxopyrrolo-[2,1-<Emphasis Type="Italic">a</Emphasis>]isoquinolines with Aromatic and Secondary Aliphatic Amines

It has been found that 2,3-dioxopyrrolo[2,1-a]isoquinolines react with aromatic amines in glacial acetic acid and with heteroaromatic and secondary aliphatic amines in the absence of acid with opening of the pyrroledione ring to give 1,2,3,4-tetrahydroisoquinoline enamino ketoamides. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1378–1382, September, 2005.