Cyclization of N-alkylazinium cations with bifunctional nucleophiles. 11. Reactions of quinoxalinium salts with thioamides — Simple method for the synthesis of hydrogenated thiazolo[4,5-b]quinoxalines

Thioacetamides and thiobenzamides undergo cyclization with N-alkylquinoxalinium salts in the presence of bases to give 4-alkyl-3a,4,9,9a-tetrahydrothiazolo[4,5-b]quinoxalines.See [1] for communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 686–690, May, 1984.     

Cyclization of N-alkylazinium cations with bifunctional nucleophiles. 14. Reaction of quinoxalinium salts with mono- and N,N′-disubstituted amidines

Monosubstituted benzamidines undergo cyclization with quinoxalinum salts to give 1,2-disubstituted 3a,4,9,9a-tetrahydroimidazo[4,5-b]quinoxalines. The participation in similar cyclizations of N,N-disubstituted amidines with a CH-active group in the a position leads to 3a,4,9,9a-tetrahydropyrrolo[2,3-b]quinoxalines.See [1] for Communication 13.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 390–395, March, 1985.     

Cyclization of N-alkylazinium cations with binucleophiles. 8. Annellation of the imidazole ring with pyrazines and quinoxalines

Monosubstituted and N,N′-disubstituted thioureas enter into cyclization with pyrazinium and quinoxalinium ion to form imidazo[4,5-b]-annellated pyrazines and quinoxalines.     

Cyclization of N-alkylazinium cations with bifunctional nucleophiles. 10. Isomeric thiazolo[4,5-b]quinoxalines in reactions of N-methylquinoxalinium ions with dithiocarbamates

The cyclization of N-methylquinoxalinium iodide with ammonium salts of N-alkyl-dithiocarbamic acids in DMSO leads to 4-methyl-2,3,3a,4,9,9a-hexahydrothiazolo-[4,5-b]quinoxalines, whereas regioisomeric cycloadducts with a reversed orientation of the thiazole ring are formed in ethanol in the presence of diethylamine.See [1] for communication 9.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 680–685, May, 1984.     

Cyclization of N-alkyl azinium cations with bifunctional nucleophiles. 21. Regioisomeric 1,3,4-thiadiazino[5,6-b]quinoxalines

Thiobenzhydrazides undergo cyclization with N-alkyl-quinoxalinium salts to give 5-alkyl-substituted 1,4,4a,5,10,10a-hexahydro-1,3,4-thiadiazino[5,6-b]quinoxalines, which undergo isomerization to 10-alkyl-substituted thiadiazinoquinoxalines when they are heated in ethanol or in the presence of acids.See [1] for Communication 20.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 557–561, April, 1987.     

Features of the reaction of unsymmetrical 2-mercapto-imidazoles with aromatic and aliphatic ketones

The cyclization of unsymmetrical 2-mercaptoimidazoles with aliphatic and aromatic ketones has been studied. Using ¹H NMR and X-ray analysis it has been shown that 4-R¹-1H-2-mercaptoimidazoles undergo selective oxidative cyclization to the corresponding 3-R³-2-R²-6-R¹-imidazo[2,1-b][1,3]thiazoles while 6-R⁴-1H-2-mercaptobenzo[d]imidazoles give a mixture of 6-R⁴-3-R²-2-R³-benzo[4,5]imidazo[2,1-b][1,3]thiazole and 7-R⁴-3-R²-2-R₃-benzo[4,5]imidazo[2,1-b][1,3]thiazole in the ratio 1: 1. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 115–122, January, 2007.     

Fluoro-containing Heterocycles. IV. Synthesis of Benzimidazole Derivatives

2-Mercapto-5,6-difluorobenzimidazole reacts with aliphatic and alicyclic ketones in acetic acid in the presence of catalytic amount of sulfuric acid to afford fluorinated derivatives of 2,3-disubstituted benz[4,5]imidazo[2,1-b][1,3]thiazoles. Reaction with aromatic -haloketones occurs in another way: to furnish 2-phenylacylthio-5,6-difluorobenzimidazoles that in the system acetic anhydride-pyridine undergo cyclization into the corresponding fluorinated derivatives of benz[4,5]imidazo[2,1-b][1,3]thiazoles.     

Synthesis and transformation of N-oxides of some imidazo[4,5-b]pyrazine derivatives

The Böckelheide reaction was accomplished with a number of imidazo[4,5-b]pyrazine N-oxides, and the N-oxidation of the resulting acetoxy(hydroxy)methyl derivatives of imidazo[4,5-b]pyrazine and 6-bromo-1-methylimidazo[4,5-b]pyrazine was studied. The hydrolytic cleavage of 6-bromo-1-methylimidazo[4,5-b]pyrazine and its 4-N-oxide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 690–693, May, 1975.     

Aza and deaza analogs of purine nucleosides (review)

Methods for the preparation of aza and deaza analogs of purine nucleosides, viz., nucleosides of imidazo[4,5-d]-v-triazines, imidazo[4,5-b]pyridines, and imidazo[4,5-c]pyridines, and their properties are described. References to the synthesis of nucleosides of imidazo[4,5-d]pyridazines, imidazo[4,5-c]pyridazines, and imidazo[4,5-b]pyrazines are also given.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 147–161, February, 1981.     

Direct hydroxylation of N-substituted [4,5-b]pyridines and imidazo[4,5-c]pyridines

It is shown that when N-methyl (or benzyl) derivatives of imidazo[4,5-b]pyridine and N-methyl-substituted derivatives of imidazo[4,5-c]pyridine are heated with alkalis, the imidazole ring is always hydroxylated to give the corresponding 2-imidazolones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1252–1254, September, 1976.     

Regioselective,Unconventional Pictet–Spengler Cyclization Strategy Toward the Synthesis of Benzimidazole‐Linked Imidazoquinoxalines on a Soluble Polymer Support

A novel strategy for an unconventional Pictet–Spengler reaction has been developed for the regioselective cyclization of the imidazole ring system at the C2 position. The developed strategy was utilized to develop a diversity‐oriented parallel synthesis for bis(heterocyclic) skeletal novel analogs of benzimidazole‐linked imidazoquinoxalines on a soluble polymer support under microwave conditions. Condensation of polymer‐immobilized o‐phenylenediamines with 4‐fluoro‐3‐nitrobenzoic acid followed by nucleophilic aromatic substitution with an imidazole motif affords bis(heterocyclic) skeletal precursors for the Pictet–Spengler reaction. The unconventional Pictet–Spengler cyclization with various aldehydes was achieved regioselectively at the C2 position of the imidazole ring to furnish rare imidazole‐fused quinoxaline skeletons. During the Pictet–Spengler cyclization, aldehydes bearing electron‐donating groups afford 4,5‐dihydro‐imidazoquinoxalines, which then auto‐aromatize into benzimidazole‐linked imidazo[1,2‐a]quinoxalines. However, interestingly, aldehydes bearing electron‐withdrawing groups directly provide aromatized imidazo[1,2‐a]quinoxalines, which unexpectedly afford novel benzimidazole‐linked 4‐methoxy‐4,5‐dihydro‐imidazo[1,2‐a]quinoxalines after polymer cleavage.     

Cyclization of N-alkylazinium cations with bifunctional nucleophiles. 15. Isomerization of thiazolo[4,5-b]quinoxalines in the presence of acids

4-Alkyl-2-phenyl-3a,4,9,9a-tetrahydrothiazolo[4,5-b]quinoxalines undergo isomerization in chloroform in the presence of acids to the regioisomeric (with respect to them) 9-alkyl-substituted derivatives. Under the same conditions 2,4-dimethyl-3a,4-9,9a-tetrahydrothiazolo [4,5-b]quinoxaline undergoes isomerization to 4-methyl-1H-2,3,3a,4,9,9a-hexahydropyrrolo[2,3-b]quinoxaline-2-thione. It was demonstrated by means of deuterium labels that in both cases the isomerization proceeds through a step involving dissociation to a quinoxalinium cation and the corresponding thioamide.See [1] for Communication 14.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 396–403, March, 1985.     

Cyclization of N-alkylazinium cations with bisnucleophiles. 3. endo adducts in the reaction of quinoxalium salts with β-diketones and their x-ray diffraction analysis

The cyclization of N-alkylquinoxalinium salts with the anions of -dicarbonyl compounds proceeds regioselectively and stereoselectively and leads to endo-3a, 4,9,9a-tetrahydrofuro[2,3-b]quinoxalines. The structure of the cycloadducts was established on the basis of the ¹H and ¹³C NMR spectra and the results of x-ray diffraction analysis.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1392–1398, October, 1981.     

Reactivity of Amidinium Salts' Access to Benzo[4,5]imidazo[2,1-b]Thiazoles

Abstract

We present the synthesis of benzimidazole substituted at the 1 and 2 positions. The appropriate 2-thioalkyl-substituted benzimidazoles undergo intramolecular cyclization for occuring [4,5] imidazo[2,1-b] thiazoles derivatives.     

咪唑并吡啶类化合物的合成及其应用*

咪唑并吡啶类化合物具有与吲哚、氮杂吲哚等类似的特殊结构和良好的生物活性,在医药和农药工业有着广泛的应用,成为有机化学家和药物化学家的研究热点。咪唑并吡啶类化合物主要有咪唑并[4,5-b]吡啶、咪唑并[4,5-c]吡啶、咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶等4个类型。本文阐述了近年来咪唑并吡啶类化合物的合成研究进展和应用情况,主要介绍了咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶这两类化合物的合成方法和在医药及农药领域的应用。     

Thionation of imidazopyridines

Direct thionation of imidazo[4,5-b]pyridines and imidazo[4,5-c]pyridines results in the formation of their 2-thioxo derivatives, usually in high yield. The thione structure of the imidazopyridines obtained has been confirmed from their IR spectra in the solid state and in solution. The general nature of the thionation of imidazole, benzimidazole, imidazo[4,5-b]pyridine, imidazo[4,5-c]pyridine, and purine has been noted as one of the distinctive chemical properties of compounds in this series of nitrogen heterocycles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 799–804, June, 1988.     

Heterocyclization of functionalized heterocumulenes with C,N- and C,O-binucleophiles: IV. Reactions of 1-chloroalkylheterocumulenes and <Emphasis Type="Italic">N</Emphasis>-(1-chloroalkylidene)carbamates with 2-benzimidazolylacetonitriles and methyl 2-benzimidazolylacetates

1-Chloroalkyl isocyanates and 1-chloroalkylcarbodiimides undergo regioselective cyclization with nitriles and esters of 2-benzimidazolylacetic acid to give derivatives of 1-oxo and 1-arylimino-1,2,3,5-tetrahydrobenzo[4,5]imidazo[1,2-c]pyrimidine respectively. The cyclocondensation of 1,1-dichloroalkyl isocyanates or N-(1-chloroalkylidene)carbamates with nitriles and esters of 2-benzimidazolylacetic acid afforded 1,5-dihydrobenzo[4,5]imidazo[1,2-c]pyrimidin-1-one derivatives.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 11, 2004, pp. 1715–1724.Original Russian Text Copyright © 2004 by Vovk, Lebed, Pirozhenko, Tsymbal.For communication III see [1].     

N-oxides of imidazo[4,5-b]quinoxalines and imidazo[4,5-b]pyrazines

The N-oxides and N,N-dioxides of methyl derivatives of imidazo[4,5-b]quinoxaline and imidazo[4,5-b]pyrazine were synthesized. The higher reactivity of the 2-methyl group in the N-oxides of 2-methylimidazo[4,5-b]quinoxaline as compared with the corresponding unoxidized derivatives was demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1266–1270, September, 1972.     

Unusual cyclization of N-imidazolyl quinone imines with the formation of thiadiazole ring and its subsequent recyclization

2,6-Di-tert-butyl-4-{[2-(2-aryl-2-oxoethylthio)-1H-imidazol-1-yl]imino}cyclohexa-2,5-dien-1-ones under the action of bases give products of the 2,3-dihydroimidazo[2,1-b]thiazol- 3-ol series by subsequent recyclization reaction of the intermediate imidazo[2,1-b][1,3,4]thiadiazoles. The structure of imidazo[2,1-b]thiazol-3-ol is supported by the X-ray diffraction. The features of the cyclization processes of quinone imine derivatives were stimulated by DFT calculations using the wB97XD/6-311++G** method.     

Synthesis of 9-(trifluoromethyl)pyrido[1′,2′:1,2]-imidazo[4,5-b]quinoxalines

9-(Trifluoromethyl)pyrido[1′,2′:1,2]imidazo[4,5-b]quinoxalines (9-CF₃-PIQs) were obtained from the cyclization of 2-amino-3-chloro-6-(trifluoromethyl)quinoxaline ( 1a ) with some substituted pyridines. 3-[2-(4-Pyridyl)ethenyl]-9-CF₃-PIQ, one of thus obtained 9-CF₃-PIQs, cyclized with another molecule of 1a to produce the dihydro bis-PIQ-ethene derivative.