Synthesis of disubstituted imidazo[4,5-b]pyridin-2-ones

Regioselective palladium-catalyzed amination of 2-chloro-3-iodopyridine followed by a subsequent palladium-catalyzed amination leads to 2,3-diaminopyridines. Treatment with triphosgene affords highly functionalized unsymmetrical imidazo[4,5-b]pyridin-2-ones in just three synthetic steps. A two-step synthesis of pseudosymmetrically disubstituted imidazo[4,5-b]pyridin-2-ones, 1,4-disubstituted pyrido[2,3-b]pyrazinediones, and 1,3-disubstituted thiadiazolo[3,4-b]pyridin-2-ones is also described.     

Synthesis of 1-and 3-substituted imidazo[4,5-b]pyridin-2-ones

1-and 3-Substituted imidazo[4,5-b]pyridin-2-ones were synthesized by heating equimolar amounts of 3-amino-2-chloropyridine or 2-chloro-3-methylaminopyridine, urea, and the corresponding arylamine at 150–210°C. The reaction of 3-amino-2-chloropyridine with urea and p-phenylenediamine or p,p′-diaminobiphenyl at a ratio of 2:2:1 under analogous conditions gave 1,4-bis-(2-oxoimidazo[4,5-b]pyridin-3-yl)benzene or 1,4-bis(2-oxoimidazo[4,5-b]pyridin-3-yl)biphenyl, respectively.     

3 + 2] Cycloaddition reactions in the synthesis of triazolo[4,5-b]pyridin-5-ones and pyrrolo[3,4-b]pyridin-2-ones

The reaction of 5-benzenesulfonyl-3,4-dihydro-1 H-pyridin-2-one derivatives with azides or isocyanides provided two new classes of compounds, triazolo[4,5-b]pyridin-5-ones 3 or pyrrolo[3,4-b]pyridin-2-ones 4, respectively, in good yields and regioselectivity. A representative set of 20 compound 3 and 12 compound 4 was prepared.     

Synthesis and some reactions of 4-nitro derivatives of imidazo[4,5-c]pyridin-2-ones

Imidazo[4,5-c]pyridine and its N-methyl derivatives do not undergo nitration, but the 2-oxo derivatives of these compounds are easily nitrated when heated. Some properties of the resulting 4-nitroimidazo[4,5-c]pyridin-2-ones have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 97–102, January, 1986.     

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.     

Tautomerism of some imidazo[4,5-b]pyridine derivatives

It was shown by means of UV and IR spectroscopy and the ionization constants that the tautomeric equilibrium of 2-amino- and 2-mercapto derivatives of 3-methyl-3H-imidazo[4,5-b]pyridine is shifted to favor the amino and thione forms, respectively.     

Preparation of 2-aryl-substituted imidazo[4,5-b]pyridines and imidazo[4,5-c]pyridines

It is proposed that sulfur be used as the oxidizing agent in the synthesis of 2-arylimidazopyridines from o-diaminopyridines and aromatic (heteroaromatic) aldehydes. Benzyl alcohols and benzylpyridinium salts can be used in place of aldehydes. 2-Phenylimidazopyridines are also formed in the thermal oxidation with sulfur of o-diaminopyridines with a benzyl substituent attached to the ring or exocyclic nitrogen atoms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 639–645, May, 1987.     

Synthesis of imidazo[4,5-b]pyridines and imidazo[4,5-b]pyrazines by palladium catalyzed amidation of 2-chloro-3-amino-heterocycles

A facile synthesis of imidazo[4,5-b]pyridines and -pyrazines is described using a Pd-catalyzed amide coupling reaction. This reaction provides quick access to products with substitution at N1 and C2. A model system relevant to the natural product pentosidine has been demonstrated, as well as the total synthesis of the mutagen 1-Me-5-PhIP.     

A short and general synthesis of 1,3-dihydro-6-heteroaryl-5-perfluoroalkyl-2H-imidazo[4,5-b]pyridin-2-ones

Trifluoro or pentafluoroacylation of heteroaryl-enamines 2a,b gave the corresponding perfluoroacylated heteroaryl-enamines 3a-c . Heating the latter compounds with diethyl iminomalonate gave 2-amino-3-pyridinecarboxylates 4a-c . Hydrolysis to the free acids 5a-c , and reaction with diphenylphosphoryl azide afforded the desired 1,3-dihydro-6-heteroaryl-5-perfluoroalkyl-2H-imidazo[4,5-b]pyridin-2-ones 6a-c .     

Synthesis and PMR spectra of 2-hetaryl-substituted imidazo[4,5-b]-pyridines and imidazo[4,5-c]pyridines

A simple method for the synthesis of 2-hetarylimidazopyridines based on the oxidation with sulfur of a mixture of p-diaminopyridine and heterocyclic compounds that contain an active methyl group is proposed. The reaction of diamines with N-oxides of of - and -picolines and the intramolecular oxidative cyclization of 3-amino-4-(2-pyridylmethylamino)pyridine lead to the same result. The PMR spectra of the synthesized 2-pyridylimidazopyridines were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 940–947, July, 1989.     

Quaternization centers of N-methyl derivatives of imidazo[4,5-b]pyridine

It is shown that quaternization of isomers of 1-methylimidazo[4,5-b]pyridine and 3-methyl-imidazo[4,5-b]pyridine proceeds at different reaction centers — at the nitrogen atom of the imidazole ring in the first case and at the nitrogen atom of the pyridine ring in the second case.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1686–1688, December, 1973.     

Synthesis of imidazo[4,5-b]- and [4,5-c]pyridines

2-Arylimidazo[4,5-b]- and [4,5-c]pyridines have been prepared by treatment of the appropriate 2,3- or 3,4-diaminopyridine with an aromatic carboxylic acid in the presence of polyphosphoric acid. Other derivatives have been prepared by similar cyclisation of diaminopyridines using triethyl orthoformate, urea, thiophosgene and thiourea and the properties of some N-oxides have been investigated. A number of the arylimidazopyridines have been screened for mutagenicity.     

Pyridinethiones. VI. The synthesis of 2H-Thiopyrano[2,3-b]pyridin-2-ones

A general and versatile method for the preparation of 2H-thiopyrano[2,3-b]pyridin-2-ones is described. The starting materials, the β, β-disubstituted vinyl-1-t-butyl-2-(1H)pyridinethiones were prepared from the synthon 3-formyl-1-t-butyl-2-(1H)pyridinethione by condensation. ¹³H nmr spectra showed the vinyl double bond of the condensation products to have the trans configuration with the smallest group close to the sulfur atom. Some reactions of these new azaanalogues of thiocoumarins are reported.     

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.     

Synthesis and antituberculotic activity of some new imidazo[4,5-b]pyridine derivatives

The reactions of 2-acetylimidazo[4,5-b]pyridine hydrazone with some alkyl-and arylisothiocyanates and some orthoesters were carried out. Various new derivatives of the titled compound such as thiosemicarbazones, ethoxymethylenehydrazones, and derivatives of the new pyrido-[3′,2′:4,5]imidazo[1,2-d][1,2,4]triazine ring system were obtained. Biological data for selected compounds are presented. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1571–1579, October, 2006.     

Synthesis and properties of 4-haloimidazo[4,5-c]pyridin-2-ones

Summary The nitro group in 4-nitroimidazo[4,5-c]pyridin-2-ones is rather labile and may be replaced upon heating with hydrohalic acids to give the corresponding 4-halides. A methyl group at N₍₃₎ leads to a sharp increase in the lability of the nitro group, but the isomeric 5-vitro derivatives do not react with hydrobromic or hydrochloric acids. Some reactions and transformations of 4-chloroimidazo[4,5-clpyridin-2-one are examined.Translated from Khimiya Getcrotsiklichcskikh Soedinenii, No. 8, pp. 1071-1075, August, 1994.