New method for the annelation of a pyridine ring on derivatives of imidazole and benzimidazole

The interaction of (Z)-1,3-diaryl-4-bromo-2-buten-1-ones with 1-substituted (benz)imidazoles in benzene gave (Z)-1-R-3-(2,4-diaryl-4-oxo-2-butenyl)-1H-imidazolium bromides and (Z)-1-R-3-(2,4-diaryl-4-oxo-2-butenyl)-1H-benzimidazolium bromides which readily cyclize in the presence of base to form derivatives of 7,9-diarylpyrido[1,2-a]benzimidazole and 6,8-diarylpyrimidazo[1,2-a]pyridine. The effects of the nature of substituents in the benzene ring of the diarylbutenones and the substituent at N(1) in the (benz)imidazoles on the alkylation and cyclization reactions has been studied. The optimum conditions for the synthesis of the 5-R-4-hydroxy-2,4-diphenyl-4,5-dihydro-1H-pyrido[1,2-a]benz-imidazol-10-ium, 5-R-2,4-diaryl-4-hydroxy-4,5-dihydro-3H-pyrido[1,2-a]benzimidazol-10-ium, and 5-R-2,4-diaryl-5H-pyrido[1,2-a]benzimidazol-10-ium have been found.     

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

The formylation of pyrrolo[1,2-a]pyrazines containing alkyl, aryl, or hetaryl substituents in positions 1 and 6 of the heterocycle has been studied. It has been shown that formylation of 1-phenyl-and 1-(2 thienyl)pyrrolo[1,2-a]pyrazine occurs selectively at the α-position of the pyrrole ring. In all of the remaining examples the reaction course depends on substituent, reagent ratio, and reaction time. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 88–93, January, 2008.     

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.     

Fluorinated [1,2,4]triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines and [1,2,4]triazolo[5,1-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazines*

The reaction of 3-R-5-amino-1,2,4-triazoles with the ethyl ester of 2-fluoroacetoacetic acid gave 2-R-fluoro[1,2,4]triazolo[1,5-a]pyrimidin-7(4H)-ones. The reaction of a 3-R-1,2,4-triazolyl-5-diazonium salt with the ethyl ester of 2-fluoroacetoacetic acid and subsequent cyclization of the triazolylhydrazones lead to 7-R-3-fluoro[1,2,4]triazolo[5,1-c][1,2,4]triazin-4(1H)-ones.     

An efficient synthesis of 1,3-diaryl-pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxalines from 2-(1h-pyrrol-1-yl)phenylamines

The condensation of 1,3-diaryl-4-bromo-2-buten-1-ones with o-phenylenediamine leads to 2-[2,4-diaryl-1H-pyrrol-1-yl]phenylamines. Heating solutions of these compounds in formic acid leads to formylation and intramolecular condensation to give 1,3-diarylpyrrolo[1,2-a]quinoxalines. The acylation of 2-[2,4-diphenyl-1H-pyrrol-1-yl]phenylamine with acetic anhydride in acetic acid leads to an acetamide, which readily cyclizes to give 4-methyl-1,3-diphenylpyrrolo[1,2-a]quinoxaline upon heating with POCl₃.     

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

Reactions of 5-aryl- and 5,7-diaryl-1,3-dimethyl-2,4-dioxopyrano[4,3-d]pyrimidinium salts with hydrazine were studied. In the former case, the reaction products were the 6-amino-1,3-dimethyl-2,4-dioxopyrido[4,3-d]pyrimidinium salts. 5,7-Diarylpyrano[4,3-d]pyrimidinium salts were transformed into either the corresponding pyridinium salts or 1H-pyrimido-[5,4-d][1,2]diazepine-2,4(3H,9H)-diones, depending on the hydrazine concentration and the reaction time. For Part 1, see Ref. 1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1720–1725, May, 2008.     

Synthesis of substituted 7,8-di(propylsulfonyl)pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazines

Heating of pyrazinium salts with E-1,2-dichloro-1,2-di(propylsulfonyl)ethene in chloro-form in the presence of three-fold excess of Et₃N regiospecifically gives rise to substituted 7,8-di(propylsulfonyl)pyrrolo[1,2-a]pyrazines in high yields. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 424–426, February, 2008.     

Interaction of (z)-4-bromo-1,3-di(2-thienyl)- 2-buten-1-one with amines,synthesis of di(2-thienyl)azolo[<Emphasis Type="Italic">a</Emphasis>]pyridines

(Z)-4-Bromo-1,3-di(2-thienyl)-2-buten-1-one was obtained by the bromination of 1,3-di(2-thienyl)-2-buten-1-one by NBS in anhydrous CCl₄. The starting butanone was obtained by the condensation of 1-(2-thienyl)-1-ethanone by the action of SOCl₂. The reaction of (Z)-4-bromo-1,3-di(2-thienyl)-2-buten-1-one with tertiary amines such as Et₃N, pyridine, 1-alkyl-1,3-diazole, 1-alkylbenzimidazole, and 1-alkyl-1,2,4-triazole leads to quaternary salts. The azolium salts cyclize by the action of base to give di(2-thienyl)azolo[a]pyridinium derivatives. 3-Methyl-6,8-di(2-thienyl)[1,3]thiazolo[3,2-a]pyridin-4-ium and 2,4-di(2-thienyl)pyrido[2,1-b]benzothiazol-10-ium bromides were obtained by the same procedure but without separating the intermediate quaternary salts.     

Synthesis of diarylazolo[<Emphasis Type="Italic">a</Emphasis>]pyridines from [(<Emphasis Type="Italic">Z</Emphasis>)-2,4-diaryl-4-oxo-2-butenyl]azolium salts

A method for the synthesis of derivatives of [1, 3]thiazolo[3,2-a]pyridines, pyrido[2,1-b][1, 3]benzo-thiazole, [1, 3, 4]thiadiazolo[3,2-a]pyridine, and [1, 2, 4]triazolo[4,3-a]pyridine, which includes base initiated cyclization of quaternary azolium salts, formed by the interaction of (Z)-1,3-diaryl-4-bromo-2-buten-1-ones with 1-alkyl-1H-1,2,4-triazoles, 4-methyl-1,3-thiazole, 1,3-benzothiazole, and N-phenyl-1,3,4-thiadiazole-2-amine. Derivatives of 2-chloroimidazo[1,2-a]pyridine were obtained when 5-chloro-1-methyl-1H-imidazole was used.     

Synthesis of 1,2,3,9a-tetrahydro-9H-imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]indole-2-thione and 1,5,6,10b-Tetrahydroimidazo[2,1-<Emphasis Type="Italic">a</Emphasis>]-isoquinoline-2(3H)-thione derivatives

Thionation of 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one derivative with Lawessons reagent in boiling toluene afforded 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indole-2-thione derivative. Alkylation of the latter with ethyl iodide in DMF in the presence of a strong base gave 2-ethylthio-9,9,9a-trimethyl-9,9a-dihydro-3H-imidazo[1,2-a]indole. 1,5,6,10b-Tetrahydroimidazo[2,1-a]isoquinoline-2(3H)-thiones were synthesized by thionation of the corresponding carbonyl substrates.Published in Khimiya Geterotsiklicheskikh Soedinenii, No 11, pp. 1695–1700, November, 2004.     

Polyfunctional nitriles in the synthesis of derivatives of 1,3,4-thiadiazolo-[3,2-<Emphasis Type="Italic">a</Emphasis>]pyrimidines

A one-pot method has been developed for the synthesis of 2-R-7-methyl-5-oxo-5H-1,3,4-thia-diazolo[3,2-a]pyrimidine by condensation of β-alkylthio(alkoxy)propionitrile, thiosemicarbazide, and ethyl acetoacetate in PPA, and also (7-methyl-5-oxo-5H-1,3,4-thidiazolo[3,2-a]pyrimidin-2-yl)-acetamide from cyanoacetamide, thiosemicarbazide, and ethyl acetoacetate. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, 1096–1100, July, 2008.     

Synthesis of imidazo[4,5-<Emphasis Type="Italic">a</Emphasis>]acridones and imidazo[4,5-<Emphasis Type="Italic">a</Emphasis>]acridines as potential antibacterial agents

Abstract  New imidazo[4,5-a]acridone derivatives were synthesized from the rearrangement of 3H-imidazo[4′,5′:3,4]benzo[c]isoxazoles. New imidazo[4,5-a]acridines were obtained from the reaction of imidazo[4,5-a]acridones in boiling POCl₃. All of these compounds exhibited antimicrobial activities comparable to streptomycin as reference drug. Graphical abstract        

Fused polycyclic nitrogen-containing heterocycles 20. Thiazolo[3,4-<Emphasis Type="Italic">a</Emphasis>]quinoxalines from 4-hydroxy-2-phenyliminothiazolidines and C-substituted 1,2-phenylenediamines

The condensation of 4-hydroxy-3,5-diphenyl-2-phenyliminothiazolidine with 4,5-dimethyl-1,2-phenylenediamine affords 7,8-dimethyl-3-phenyl-1-phenyliminothiazolo[3,4-a]quinox-alin-4(5 H)- one; the condensation with 1,2-phenylenediamines containing different substituents at positions 4 and 5 gives both theoretically possible isomeric thiazolo[3,4-a]quinoxalines, which differ in the distribution of these substituents between positions 7 and 8 in the benzene ring of the quinoxaline system. 3a-Hydroxy-7,8-dimethyl-3-phenyl-l-phenylimino-3,3a-di-hydrothiazolo[3,4-a]quinoxalin4(5 H)- one was isolated and characterized as the intermediate of the reaction giving rise to thiazolo[3,4-a]quinoxaline from 4,5-dimethyl-1,2-phenylene-diamine. This intermediate is a covalent hydrate of the final product.     

A clean synthesis of oxazino[5,6-<Emphasis Type="Italic">f</Emphasis>]quinolinone and naphtho[1,2-<Emphasis Type="Italic">e</Emphasis>]oxazinone derivatives

A clean, simple, one-pot, and efficient synthesis of 1,2-dihydro-1-aryl[1,3]oxazino[5,6-f]quinolin-3-one and 1,2-dihydro-1-arylnaphtho[1,2-e]-[1,3]oxazine-3-one derivatives was accomplished in good yields via reaction between 6-quinolinol or 2-naphthol, aromatic aldehydes, and methyl carbamate in aqueous medium catalyzed by TEBA (triethylbenzylammonium chloride). Correspondence: Mohammad Hossein Mosslemin, Department of Chemistry, Islamic Azad University, Yazd 8916871967, Iran.     

Synthesis and properties of cyanomethyl derivatives of imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyridine,imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrimidine,and imidazo[2,1-<Emphasis Type="Italic">b</Emphasis>]thiazole

2-Cyanomethyl derivatives were obtained of imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, and imidazo[2,1-b]thiazole, and their reactivity was investigated by an example of imidazo[1,2-a]pyridine: It was subjected to nitration, bromination, azo coupling and nitrosation. Acylation of the methylene group effected by amino acids esters with a subsequent addition of the amino group to the cyano group resulted in the formation of 5-amino-4-imidazo[1,2-a]-pyridin-2-yl-1-phenyl-1,2-dihydro-3H-pyrrol-3-one and 2-amino-1-ethyl-3-imidazol[1,2-a]pyridin-2-yl-4(1H)-quinolinone.     

Azacycloalkanes: XXXIX. New Syntheses of 1<Emphasis Type="Italic">H</Emphasis>-Pyrrole-1-carboxylic acid and 1,2-dihydropyrrolo-[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazin-3(4<Emphasis Type="Italic">H</Emphasis>)-one derivatives

New procedures have been developed for the synthesis of α-(2-formyl-1H-pyrrol-1-yl)-substituted carboxylic acids, α-(2-R-aminomethyl-1H-pyrrol-1-yl)-substituted carboxylic acids, and 1,2-dihydropyrrolo-[1,2-a]pyrazin-3(4H)-ones on the basis of furfurol and α-amino acids.     

Regioselectivity of cyclization of 3-allyl(propargyl)sulfanyl-5<Emphasis Type="Italic">H</Emphasis>-[1,2,4]triazino[5,6-<Emphasis Type="Italic">b</Emphasis>]indoles

The interaction of 3-allylsulfanyl-5H-[1,2,4]triazino[5,6-b]indole with iodine led to 1-iodomethyl-1,2-dihydro[1,3]thiazolo[2',3':3,4][1,2,4]triazino[5,6-b]indol-11-ium pentaiodide with an angular structure, on the basis of which 1-iodomethyl-1,2-dihydro[1,3]thiazolo-, 1-methylidene-1,2-di-hydro[1,3]thiazolo, and 1-methyl[1,3]thiazolo derivatives were obtained. The intramolecular cyclization of 3-propargyl(allyl)sulfanyl-5H-[1,2,4]triazino[5,6-b]indoles under the influence of concentrated sulfuric acid led to linear annelated products:3-methyl[1,3]thiazolo[3',2':2,3][1,2,4]tri-azino[5,6-b]indole or its 2,3-dihydro derivative.     

Three-component condensation of 4-aryl-1,4-dihydro-benzo[4,5]imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>][1,3,5]triazin-2-amines with formaldehyde and primary amines

Three-component cyclization of 4-aryl-1,4-dihydrobenzo[4,5]imidazo[1,2-a][1,3,5]triazin-2-amines with formaldehyde and primary amines gave the corresponding 6-unsubstituted or 6-aryl-2-alkyl-2,3,4,6-tetrahydro-1H-[1,3,5]triazino[1′,2′:3,4][1,3,5]triazino[1,2-a]benzimidazoles.     

Base-induced rearrangements of N-substituted 3-arylaminoisoxazol-5(2H)-ones to 2-arylaminoimidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyridines

New N-substituted derivatives of 2-substituted 3-phenylamino-and 3-(1-naphthyl)aminoisoxazol-5(2H)-ones were synthesized. The reaction of isoxazolones with 2-chloro-5-nitropyridine gave the corresponding isoxazolones with a nitropyridyl group substituted on N-2. Their rearrangements produced ethyl 2-arylaminoimidazo[1,2-a]pyridine-3-carboxylates in the presence of triethylamine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 751–757, May, 2008.     

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.