Ammonium chloride-promoted four-component synthesis of pyrrolo[3,4-b]pyridin-5-one

A novel multicomponent synthesis of 5-aminooxazole starting from simple and readily available inputs is described. Thus, simply heating a methanol solution of an aldehyde 3, an amine 4, and an alpha-isocyanoacetamide 5 provided the 5-aminooxazole (1) in good to excellent yield. The reaction of 1 with alpha,beta-unsaturated acyl chloride 13 lead to the formation of pyrrolo[3,4-b]pyridin-5-one (2) in a single operation. A triple domino sequence, acylation/IMDA/retro-Michael cycloreversion, is involved in this new scaffold-generating reaction. After the observation that ammonium chloride can significantly accelerate the oxazole formation in toluene, a one-pot four-component synthesis of 2 is developed.     

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.     

Isomerization of pyridazino [4,5-b] indoles to pyrrolo [3,4-b] indoles

The dihydropyridazine ring undergoes contraction to a dihydropyrrole ring to give 1-phenyl-2-benzylideneaminodihydropyrrolo[3,4-b]indol-3-ones when 1-phenyldihydropyridazino[4,5-b]indol-4-ones are treated with aromatic aldehydes under acid catalysis conditions. The reaction mechanism consists in the formation of a (3-indolyl)phenylmethyl cation, which leads to opening of the pyridazine ring and subsequent development of a bond between the carbonium center and the amide nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1406–1408, October, 1976.     

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 .     

Facile synthesis of some novel triazolo[3,4-b]thiadiazines and triazolo[4,3-b]tetrazines

4-Amino-5-ethyl-4H-1,2,4-triazole-3-thiol was used as a key intermediate for the synthesis of triazolo[3,4-b][1,3,4]thiadiazines, triazolo[4,3-b][1,2,4,5]tetrazines and Schiff’s base via reactions with various hydrazonoyl halides and salicyaldehyde, respectively. Moreover triazolyl-N-N′-triazole derivatives were prepared from reaction of Schiff’s base with various hydrazonoyl halides. The structures of all the newly synthesized heterocyclic compounds were established by considering elemental analysis and spectral data.     

Compounds in the pyrrolo[3′,4′:4,5] pyrrolo[3,4-b]indole series

Compounds in the new pyrrolo[3′,4′:4,5]pyrrolo[3,4-b]indole series have been produced by an imide cyclization of appropriate derivatives of pyrrolo[3,4-b]indole.     

Ethyl 5-amino-3-oxo-1,2-dihydro-1H-pyrazole-1-carboxylate in the selective synthesis of partially hydrogenated pyrazolo[3,4-b]pyridin-3-ones

Ethyl 5-amino-3-oxo-1,2-dihydro-1H-pyrazole-1-carboxylate undergoes selective cyclocondensation with 1,3-dicarbonyl compounds or their synthetic equivalents to give ethyl 3-oxo-1,2-dihydro-pyrazolo[3,4-b]pyridine-1-carboxylates which are readily converted to their 1-unsubstituted analogs.     

An efficient regioselective sonochemical synthesis of novel 4-aryl-3-methyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-6(7H)-ones

An efficient ultrasound-assisted preparation of a series of novel 4-aryl-3-methyl-4,5-dihydro-l//-pyrazolo[34-b]pyridin-6(7H)ones via the reaction of 5-amino-3-methyl-1H-pyrazole,Meldrum’s acid and various arylaldehydes using one-pot three-component approach is described.This rapid method produced the products in short reaction times(3-4 min) and excellent yields(87-95%).     

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.     

苯并吡喃[3,4-c]吡啶-5-酮类化合物的合成

以4-酮-3-甲酸甲酯哌啶盐酸盐为原料, 通过分子间环加成和N-烷基化反应, 合成了一系列潜在的多巴胺D₄受体配基苯并吡喃[3,4-c]吡啶-5-酮类化合物, 并用¹H NMR, IR, ESI-MS, 元素分析对其进行了表征.     

Solid-phase synthesis of imidazo[4,5-b]pyridin-2-ones and related urea derivatives by cyclative cleavage of a carbamate linkage

A solid-phase synthesis of substituted cyclic urea derivatives as potential heterocyclic library scaffolds is described. 2-Amino-3-nitropyridine is attached to Wang resin via a carbamate linkage. Reduction of the nitro group was achieved with SnCl(2).2H(2)O. Reductive alkylation with a range of substituted benzaldehydes followed by cyclative cleavage afforded a small library of 3-substituted imidazo[4,5-b]pyridine-2-ones in 33-45% yield and 59-88% purity. Subsequently, this methodology was applied to the synthesis of 3-substituted imidazo[4,5-f]quinolin-2-ones.     

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.     

Dihydropyrrolo[3,4-b]- and dihydropyrimido[4,5-b]indoles

Aromatic aldehydes react with indole-2-carboxylic acid azides under acid catalysis conditions to give the corresponding 3-(-halobenzyl)indoles, which react with aliphatic and aromatic amines to give the corresponding aminobenzylindoles. The latter undergo intramolecular cyclization to dihydropyrrolo[3,4-b]indoles at room temperature and are converted to dihydropyrimido[4,5-b]indoles through the Curtius rearrangement when they are heated to 80-110°C. Acetylation of the latter products gives N- and O-acetyl derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 935–939, July, 1982.     

Synthesis of 5H[l]benzopyrano[3,4-b]pyridin-5-one and its derivatives

3-Aminocoumarin undergoes the Skraup reaction to give a new ring system, 5H[l]benzo-pyrano[3,4-b]pyridin-5-one (IVa). When 3-aminocoumarin was condensed with the ethoxy methylene derivatives of active methylene compounds, ethyl acetoacetate, and dimethyl acetylenedicarboxylate, the intermediates Vla-VIf were formed which on thermal cyclizations afforded other derivatives of 5H[l ]benzopyrano[3,4-b]pyridin-5-one (IVb-IVf). The nitration of IVa gave IVg.     

Cycloaddition reactions of thiazolium azomethine ylides: application to pyrrolo[2,1-b]thiazoles

Thiazolium azomethine ylides, equipped with a C-2 methanethiol group, participate in an efficient [3 + 2] cycloaddition reaction with acetylene derivatives to yield unique pyrrolo[2,1-b]thiazoles. The elimination of the methanethiol leaving group from the cycloadduct has replaced the need for a separate oxidation step and suppresses ring-opening side reactions. Products were obtained in short synthetic sequences to demonstrate their use as a scaffold for compound libraries.     

The synthesis of 5-amino-v-triazolo[4,5-b] pyridin-7-one (l-deaza-8-azaguanine) and 5-amino-3-(β-D-ribofuranosyl)-v-triazolo[4,5-b] pyridin-7-one (1-deaza-8-azaguanosine)

The synthesis of l-deaza-8-azaguanine has been accomplished via a facile route from pyridine precursors. The site of rihosylation and anomeric configuration of l-deaza-8-azaguanosine and several closely related derivatives was accomplished by cmr and pmr, respectively.     

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.