Thieno [2,3 -b] pyridines and thieno [ 3,2 -b] pyridines by the method of gould-jacobs

Bis(2-, and 3-thienylammonium) hexachlorostannates were condensed with ethoxymethylene derivatives of active methylene compounds in pyridine. The resulting condensation products IVa-IVc and Va-Vc on heating under reflux in Dowtherm or diphenyl ether provided various 4-hydroxythieno[2,3-b] pyridines (Ia-Ic) and 7-hydroxythieno[3,2-b]pyridines (IIa-IIc). The compound Ic on further transformations gave yet other derivatives If-Ik.     

A concise synthesis of functionalized 2,3-dihydrofuro[3,2-b], [3,2-c], and [2,3-b]pyridines

A strategy for the efficient and rapid one-pot synthesis of 2-aryl-2,3-dihydrofuro[3,2-b], [3,2-c], and [2,3-b]pyridines from readily available o-nitropicolines and aromatic aldehydes is described. The key transformation involves reaction of o-nitropicolines with aromatic aldehydes in the presence of TBAF and Hünig's base giving rise to functionalized products having molecular complexity suitable for further manipulation.     

Mass spectra of isomeric thieno [2,3-b]- and thieno[3,2-b]pyridines

The mass spectra of six isomeric thieno- and thionaphthenopyridines were studied for the first time, and the pathways of fragmentation of the molecular ions, which made it possible to isolate the peaks of the fragment ions that characterize the destruction of the pyridine and thiophene rings, were traced. It is shown that the character and type of conjugation of the heterorings can be distinguished by analyzing the mass-spectral data. The relationship between the intensity of the peak of the doubly charged molecular ion and the number of electrons in the system and the -donor character of the heteroring was illustrated by means of the literature data on the mass spectrometry of heteroaromatic systems with one heteroatom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 758–761, June, 1982.     

Thiazolo [3,2-a] pyridinium salts

The sulfides formed by the reaction of α-halo ketones or α-halo acetals with 2-mercaptopyridine may be cyclized in good yield to form thiazolo[3, 2-a]pyridinium salts. The presence of chloro or nitro substituents on the pyridine ring does not interfere with the synthesis. Nitration of 3-methylthiazolo[3, 2-a]pyridinium perchlorate has been found to occur at position 8.     

Hexahydrobenzothiazolo[3,2-a]pyridinium salts

Salts of hexahydrobenzothiazolo[3,2-a]pyridine are obtained by exchange reactions. Anions are placed in the order [(NC)₂CCHC(CN)₂]- > ClO₄ ^–>I₃ ^–>Br^– according to the ability to displace each other. X-ray structural and spectroscopic studies establish the cis-attachment of the thiazolidine and cyclohexane rings in the hexahydrobenzothiazolo [3,2-a]pyridinium salts studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1688, December, 1988.     

Oxazolo[3,2-a]pyridinium salts

The first synthesis of the aromatic oxazolo[3,2-a]pyridinium ring system has been accomplished by the cyclization of 1-acetonyl- or 1-phenacyl-2-pyridones. Through use of the analogous quinolones and 2-(p-bromophenacyl)-1-isoquinolone, benzologs of the new system have been prepared.     

New method for the synthesis of substituted thieno[3,2-b]pyridines and 5H-pyrano[2,3-d]thieno[3,2-b]pyridines derived from them

A new highly selective method was developed for the synthesis of substituted thieno[3,2-b]-pyridines based on the domino reaction of monopotassium salt (rather than dipotassium one) of carbamoylcyanodithioacetic acid with ethyl 4-chloroacetoacetate. Substituted 5H-pyrano[2,3-d]-thieno[3,2-b]pyridines were synthesized based on these thieno[3,2-b]pyridines.     

Oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts in organic synthesis

The methods for the synthesis of oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts and their reactivities are reviewed. Both systems exhibit ambident properties in reactions with nucleophiles; depending on the substituents and the reagents, both the oxazole and azine rings can undergo opening and transformations. A number of new methodologies involving oxazolopyridinium and oxazolopyrimidinium salts for the design of functionalized oxazoles, imidazoles, fused pyrroles, and other heterocyclic systems are generalized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 831–848, April, 2008.     

Furopyridines. XIII. Reaction of 2-methylfuro[2,3-b]-, -[3,2-b]-, -[2,3-c]- and -[3,2-c]pyridines with lithium diisopropylamide

Lithiation of 2-methylfuro[2,3-b]- 1a , -[2,3-c]- 1c and -[3,2-c]pyridine 1d with lithium diisopropylamide at ?75° and subsequent treatment with deuterium chloride in deuterium oxide afforded 2-monodeuteriomethyl compounds 2a, 2c and 2d , while 2-methylfuro[3,2-b]pyridine 1b gave a mixture of 1b, 2b , 2-methyl-3-deuteriofuro[3,2-b]pyridine 2′b and 2-(1-proynyl)pyridin-3-ol 5 . The same reaction of 1a at ?40° gave 3-(1,2-propadienyl)pyridin-2-ol 3 and 3-(2-propynyl)pyridin-2-ol 4 . Reaction of the lithio intermediates from 1a, 1c and 1d with benzaldehyde, propionaldehyde and acetone afforded the corresponding alcohol derivatives 6a, 6c, 6d, 7a, 7c, 7d, 8a, 8c and 8d in excellent yield; while the reaction of lithio intermediate from 1b gave the expected alcohols 6b and 8b in lower yields accompanied by formation of 3-alkylated compounds 9, 11, 12 and compound 5 . While reaction of the intermediates from 1a, 1b and 1d with N,N-dimethylacetamide yielded the 2-acetonyl compounds 13a, 13b and 13d in good yield, the same reaction of 1c did not give any acetylated product but recovery of the starting compound almost quantitatively.     

Palladium-catalyzed direct arylation of pyridine N-oxide with 2-bromoacetanilides. Synthesis of benzisoxazolo[2,3-a]pyridinium tetrafluoroborates

The synthesis of a variety of novel benzisoxazolo[2,3-a]pyridinium tetrafluoroborates is described. These compounds are conveniently prepared from pyridine N-oxide via a microwave-promoted palladium-catalyzed direct arylation of pyridine N-oxide with 2-bromoacetanilides to give 2-(2-acetamidoaryl)pyridine N-oxides, followed by hydrolysis, diazotization and intramolecular displacement of nitrogen which affords the target benzisoxazolo[2,3-a]pyridinium tetrafluoroborates.     

苯并噁唑[3,2-a]吡啶盐两性离子化合物的合成

常温下,在丙酮与水的混合介质中(V:V=1:1),4-羟基香豆素类化合物与1,4-苯醌、2-甲氧基吡啶反应,生成5个未见文献报道的苯并噁唑两性离子化合物.产物经MS,1HNMR,元素分析表征,确定了其化学结构.     

2-Bromo-i-phenylethylidenemalononitrile in the synthesis of thieno[3,2-b]pyridines and thiazolo[4,5-b]pyridines

A novel regioselective synthesis of thieno[3, 2-blpyridines and thiazolo[4,5-blpyridines from 2-bromo-I-phenyl ethylidenemalononitrile is proposed. In the case of the thiazolo[4, 5-b]pyridines, the intermediate 5-(2, 2-dicyano-l-phenylvinyl)thiazoles were separated. Formation of the thiazolo(4,5-b]pyridines was confirmed by x-ray analysis.A. D. Zelinski Institute of Organic Synthesis, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 413–419, March, 1996. Original article submitted December 22, 1995.     

Synthesis of thiazolo- and oxazolo[3,2-a]pyridinium systems (review)

The published data on the synthesis of thiazolo- and oxazolo[3,2-a]pyridinium systems are systematized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1155–1164, September, 1991.     

2,3-Diphenylthiazolo[3,2-a]pyrimidinium salts

The corresponding 2,3-diphenyl[3,2-a]pyrimidinium salts were obtained by the condensation of 4,5-diphenyl-2-aminothiazole perchlorate with -diketones, -chlorovinyl ketones, -chlorovinyl aldehydes, and 1,1,3,3-tetraethoxypropane. The PMR spectra were used to prove the structures of the compounds obtained, particularly to select the structures of the isomeric salts obtained in the condensation with unsymmetrical -diketones, -chlorovinyl ketones, and -chlorovinyl aldehydes. As a rule, the latter give one isomer — the -unsubstituted (relative to the bridge nitrogen atom) derivative.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–631, May, 1972.     

Dehydrohalogenation of isomeric 2- and 3-bromomethyl substituted 2,3-dihydrooxazolo[3,2-a]pyridines

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