Nitration of 1,3-dihydro-2<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-2-one derivatives

Nitration of 1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one and its N-methyl derivatives at 0–5°C and 60°C gives 5-nitro-and 5,6-dinitro-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones, respectively. The latter can also be obtained by nitration of 5-mononitro derivatives under similar conditions. The nitration of 6-chloro-and 6-bromo-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones and their N-methyl-substituted analogs leads to the formation of the corresponding 6-chloro(bromo)-5-nitro compounds. The same products are formed in the nitration of 5,6-dichloro-and 5,6-dibromo-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones. In this case, the process involves replacement of the halogen atom in position 5 of the pyridine fragment by nitro group. The nitration of 6-bromo-5-methyl-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one is accompanied by oxidation of the 5-methyl group to carboxy.     

Synthesis of naphtho[1,2-<Emphasis Type="Italic">e</Emphasis>]-pyrazolo[5,1-<Emphasis Type="Italic">b</Emphasis>][1,3]oxazines

The previously unknown heterocyclic system naphtho[1,2-e]pyrazolo[5,1-b][1,3]oxazine was synthesized by the condensation of 1-dimethylaminomethyl-2-naphthols with bromopyrazoles. It is proposed that the highly reactive o-methylenequinone of the naphthalene series is formed as an intermediate.     

Synthesis and functionalization of 7-hydroxyanthra[2,1-<Emphasis Type="Italic">b</Emphasis>]benzo[<Emphasis Type="Italic">d</Emphasis>]furan-8,13-diones

The diazotization of 1-amino-2-aryloxy-4-hydroxy-9,10-anthraquinones in various solvents and subsequent heating of the diazotization products lead to 7-hydroxyanthra[2,1-b]benzo[d]furan-8,13-diones. When consecutively treated with benzenesulfonyl chloride and amines, the products form 7-aminoanthra[2,1-b]benzo[d]furan-8,13-diones.     

Reactions of 1,3-Dialkyl-5-amino-1,3-dihydro-2<Emphasis Type="Italic">H</Emphasis>-imidazo-[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-2-ones with acetylacetone and ethyl acetoacetate

1,3-Dialkyl-5-amino-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones reacted with acetylacetone to give the corresponding 4-(1,3-dialkyl-2-oxo-1,3-dihydro-2H-imidazo[4,5-b]pyridin-5-ylamino)pent-3-en-2-ones which underwent intramolecular cyclization to 1,3-dialkyl-5,7-dimethyl-1,3-dihydro-2H-imidazo[4,5-b]-[1,8]naphthyridin-2-ones on heating in polyphosphoric acid or diphenyl ether. Analogous reaction of 1,3-dialkyl-5-amino-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones with ethyl acetoacetate led to the formation of ethyl 3-(1,3-dialkyl-2-oxo-1,3-dihydro-2H-imidazo[4,5-b]pyridin-5-ylamino)but-2-enoates whose cyclization afforded 1,3-dialkyl-8-hydroxy-7-methyl-1,3-dihydro-2H-imidazo[5,4-b][1,8]naphthyridin-2-ones.     

Reactions of 2-(2-propynylsulfanyl)-5,6,7,8-tetrahydrobenzo[<Emphasis Type="Italic">b</Emphasis>]thieno[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidin-4(<Emphasis Type="Italic">3H</Emphasis>)-one with arylsulfenyl chlorides

2-(2-propynylsulfanyl)-5,6,7,8-tetrahydrobenzo[b]thieno[2,3-d]pyrimidin-4(3H)-one with arylsulfenyl chlorides in chloroform gave products of anti-Markownikoff Ad _E-addition. The use of nitromethane as solvent in the presence of lithium perchlorate additives favored intramolecular electrophilic cyclization into 1-arylsulfanyl-1,2,6,7,8,9-hexahydro-4H-benzo[4,5]thieno[3,2-e][1,3]thiazolo[3,2-a]-pyrimidin-5-one.     

Synthesis of 13-alkylbenzo[<Emphasis Type="Italic">f</Emphasis>]isochromeno[4,3-<Emphasis Type="Italic">b</Emphasis>]indole-5,7,12(13<Emphasis Type="Italic">H</Emphasis>)-triones by reaction of 2-alkylamino-1,4-naphthoquinones with ninhydrin

Reactions of 2-alkylamino-1,4-naphthoquinones with 2,2-dihydroxy-1H-indene-1,3(2H)-dione afforded 13-alkylbenzo[f]isochromeno[4,3-b]indole-5,7,12(13H)-triones.     

Synthesis of pyrano[2,3-<Emphasis Type="Italic">f</Emphasis>]chromen-2,8-diones and pyrano[3,2-<Emphasis Type="Italic">g</Emphasis>]chromen-2,8-diones based on <Emphasis Type="Italic">o</Emphasis>-hydroxyformyl(acyl)neoflavonoids

Novel pyrano[2,3-f]chromen-2,8-diones and pyrano[3,2-g]chromen-2,8-diones were prepared based on modified analogs of natural o-hydroxyformyl(acyl)neoflavonoids. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–20, January–February, 2008.     

Ultrasound-Assisted Synthesis of 5<Emphasis Type="Italic">H</Emphasis>-Chromeno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine Derivatives

An environmentally friendly method has been developed for the preparation of 5H-chromeno[2,3-b]pyridine derivatives in an aqueous medium under ultrasound irradiation.     

A novel synthesis of 2-substituted 2H-imidazo[1,5-<Emphasis Type="Italic">b</Emphasis>]isoquinoline-1,5-diones by <Emphasis Type="Italic">in situ</Emphasis> desulfurization

A novel synthesis of 2-substituted 2H-imidazo[1,5-b]isoquinoline-1,5-diones by reductive desulfurization of a variety of 2-substituted 3-thioxo-2H-imidazo[1,5-b]isoquinoline-1,5-diones is reported with nickel boride in dry methanol at ambient temperature. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 404–408, March, 2008.     

Synthesis and structures of benzo[<Emphasis Type="Italic">cd</Emphasis>]furo[2,3-<Emphasis Type="Italic">f</Emphasis>]indol-4(5<Emphasis Type="Italic">H</Emphasis>)-one derivatives

A procedure was developed for the synthesis of derivatives of the new heterocyclic system, benzo[cd]furo[2,3-f]indole, based on the cyclodehydration of 6-acylmethyloxy-1-alkyl-benzo[cd]indol-2(1H)-ones. Either 7- or 8-aryl derivatives of benzo[cd]furo[2,3-f]indol-4(5H)-ones can be prepared depending on the reaction conditions. The molecular and crystal structures of 7- and 8-phenylbenzo[cd]furo[2,3-f]indol-4(5H)-ones were established by X-ray diffraction.     

Reactions of ethyl 6,6-dialkyl-8,9-dioxo-5,6,8,9-tetrahydrobenzo[<Emphasis Type="Italic">f</Emphasis>]pyrrolo[2,1-<Emphasis Type="Italic">a</Emphasis>]isoquinoline-10-carboxylates with <Emphasis Type="Italic">N</Emphasis>-nucleophiles

Reaction of enaminoesters, derivatives of 2,2-dialkyl-1,2,3,4-tetrahydrobenzo[f]isoquinoline, with oxalyl chloride leads to the formation of ethyl 6,6-dialkyl-8,9-dioxo-5,6,8,9-tetrahydrobenzo[f]pyrrolo[2,1-a]-isoquinoline-10-carboxylates. At reaction of the latter with ammonia and cyclic amines opening of pyrroledione cycle occurs and the formation of enaminoketoamides, and the reaction with o-phenylenediamine furnishes a fragment of benzimidazole. Hydroxylamine behaves as binucleophile and attacks not only lactam, but also the ester group, affording heterocyclic system of isoxazine-3,4,6-trione.     

New Synthesis of Pyrano[4,3-<Emphasis Type="Italic">d</Emphasis>]pyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]pyridines

A new efficient method has been developed for the synthesis of highly biologically active pyrano-[4,3-d]pyrazolo[3,4-b]pyridines on the basis of Smiles rearrangement of ethyl [(8-alkyl(aryl)-5-cyano-3,3-dimethyl-3,4-dihydro-1H-pyrano[3,4-c]pyridin-6-yl)oxy]acetates. Intermediate acetohydrazides have also been isolated. The proposed procedure is advantageous due to the possibility of avoiding experimentally difficult chlorination stage.     

Synthesis of 6-methyl-8<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">a</Emphasis>,<Emphasis Type="Italic">g</Emphasis>]quinolizin-8-imines <Emphasis Type="Italic">via Reissert</Emphasis> compounds

Alkylation of Reissert compounds derived from 3-methylisoquinolines with several 2-cyanobenzylbromides followed by hydrolytic cleavage provided the corresponding 1-benzyl-3-methylisoquinolines. Treatment of the latter with methylmagnesiumiodide caused cyclization to the title compounds rather than formation of 2-acetylbenzylisoquinolines.     

Alkylation of 2-(hydroxyimino)-5<Emphasis Type="Italic">H</Emphasis>-[1,3]thiazolo[3,2-<Emphasis Type="Italic">a</Emphasis>]-pyrimidin-3(2<Emphasis Type="Italic">H</Emphasis>)-ones

Alkylation products were obtained from ethyl 2-(hydroxyimino)-7-methyl-3-oxo-5-aryl-2,3- dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-6-carboxylates at the treatment with alkyl halides, dimethyl sulfate, and diazomethane. Diazomethane alkylated the initial substrate at the oxygen atom of the carbonyl group of the thiazolidine fragment, the other reagents, at the oxygen atom of the hydroxyimino group.     

Synthesis of 1-(1,3-dialkyl-2-oxo-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-imidazo-[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-5-yl)-5-oxopyrrolidine-3-carboxylic acids

Nitration of 2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one gave its 5-nitro derivative which was subjected to alkylation with dimethyl sulfate, diethyl sulfate, and benzyl(dimethyl)phenylammonium chloride. The resulting 1,3-dimethyl-, 1,3-diethyl-, and 1,3-dibenzyl-5-nitro-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones were reduced to the corresponding 1,3-dialkyl-5-amino-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones, and the latter reacted with itaconic acid to produce 1-(1,3-dialkyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-5-yl)-5-oxopyrrolidine-3-carboxylic acids. 1-(2-Oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-5-yl)-5-oxopyrrolidine-3-carboxylic acid was obtained by analogous reaction with 5-amino-2,3-dihydro-1H-imidazo[4,5-b]-pyridin-2-one.     

Reaction 5-(Arylmethylidene)pyrimidine-2,4,6(1<Emphasis Type="Italic">H</Emphasis>,3<Emphasis Type="Italic">H</Emphasis>,5<Emphasis Type="Italic">H</Emphasis>)-triones with L-Proline and Aldehydes

Boiling in toluene of 5-(arylmethylidene)pyrimidine-2,4,6(1H,3H,5H)-triones with L-proline and aldehyde led to the formation of previously unknown substituted 1′-arylhexahydro-1H-spiro[pyrimidine-5,2′-pyrrolysine]-2,4,6(1H,3Н,5Н)-triones.     

2-(2-thienyl)-6-methyl-6<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-<Emphasis Type="Italic">g</Emphasis>][1,3]benzothiazole: Synthesis and some transformations

Oxidation of N-(1-methylbenzimidazol-5-yl)thiophene-2-carbothioamide with potassium ferricyanide in an alkaline medium by Jacobson’s method afforded 2-(thien-2-yl)-6-methyl-6H-imidazo[4,5-g][1,3]benzothiazole. The latter enters into the electrophilic substitution reaction (nitration, bromination, formylation, acylation) exclusively at the position 5 of the thiophene ring. Characteristic reactions of nucleophilic substitution occurred at the imidazole ring. Quaternization with methyl iodide in benzene furnished the corresponding quaternary salt, whereas the Chichibabin amination with an excess of sodium amide in xylene gave negative result.     

Synthesis of [1,3]thiazolo[5,4-<Emphasis Type="Italic">b</Emphasis>]pyridine-2-carboxamides

[1,3]Thiazolo[5,4-b]pyridine-2-carboxamides were synthesized by reaction of 2-nitropyridin-3-amine with dithio esters containing a carbamoyl group.     

Reactions of 3-Aroylpyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxaline-1,2,4(5<Emphasis Type="Italic">H</Emphasis>)-triones with 2,3-Dihydrofuran and 3,4-Dihydro-2<Emphasis Type="Italic">H</Emphasis>-pyran

3-Aroylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones reacted with 2,3-dihydrofuran and 3,4-dihydro-2H-pyran to give mixtures of the corresponding hetero-Diels–Alder (furo- and pyrano[3″,2″: 5′,6′]pyrano- [4′,3′: 2,3]pyrrolo[1,2-a]quinoxalines) and Michael adducts (furyl- and pyranylpyrrolo[1,2-a]quinoxalines).