Synthesis and molecular structure of 2,4,8a-triaryl-6-methylperhydro[1,3,2]dioxaborinino[5,4-c]pyridines

Condensation of arylboronic acids with 4-hydroxy-3-(-hydroxybenzyl)-1-methyl-4-phenylpiperidine afforded 2,4,8a-triarylperhydro[1,3,2]dioxaborinino[5,4-c]pyridines. The molecular structure of 6-methyl-2,4,8a-triphenylperhydro[1,3,2]dioxaborinino[5,4-c]pyridine was established by X-ray diffraction analysis.     

Synthesis and spectral characteristics of 2-aryl-6-methyl-and 2-aryl-6-benzyl-4,8a-diphenylperhydro[1,3,2]dioxaborinino[5,4-c]pyridines

Aryl-N-methyl-and aryl-N-benzyl-B-substituted 4,8a-diphenylperhydro[1,3,2]dioxaborinino[5,4-c]pyridines, which are representatives of a new class of bicyclic compounds containing four heteroatoms, were synthesized from N-methyl-and N-benzyl-3-(α-hydroxybenzyl)-4-phenyl-γ-piperidols by cyclocondensation with arylboronic acids. The ¹H NMR and mass spectra of these compounds were examined as well as mass spectra of previously obtained analogs. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1253–1259, August, 2008.     

Synthesis of azolo[5,4-c]isoquinolines

Two pathways are presented for the synthesis of pyrazolo[5,4-c]isoquinoline derivatives: recyclization of 1-methyl-3-phenyl-4-cyano-6,7-dimethoxybenzo[c]pyrylium perchlorate upon treatment with hydrazine, and Bischler-Napieralski cyclization of substituted 5-amino-4-(3,4-dimethoxyphenyl)pyrazoles. A derivative of a new heterocyclic system, isoxazolo[5,4-c]isoquinoline, has also been obtained upon heating 5-amino-3-phenyl-4-(3,4-dimethoxyphenyl)isoxazole in a mixture of acetic anhydride and perchloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1092–1095, August, 1990.     

Recyclization of perhydrooxazolo[5,4-c]pyridines to 5,6,7,8-tetrahydrooxazolo[3,4-c]pyrimidines

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 855–856, June, 1991.     

The synthesis of pyrimido[4,5-c]pyridazines and pyrimido[5,4-c]pyridazines

The Hofmann reaction on 6-methylpyridazine-3,4-dicarboxamide (1) gave a mixture of 3-methylpyrimido[4,5-c]pyridazine-5,7-dione (2), 3-methylpyrimido[5,4-c]pyridazine-6,8-dione (3) and an acid (4) of unknown structure. The Hofmann reaction on pyridazine-3,4-dicarboxamide (9) gave a mixture of pyrimido[4,5-c]pyridazine-5,7-dione ( 10 ) and an acid ( 11 ) of unknown structure. The reaction of 3-amino-6-methylpyridazine-4-carboxamide ( 18 ) with ethyl orthoformate gave 3-methylpyrimido[4,5-c]pyridazin-5-one ( 21 ). 4-Aminopyridazine-3-carboxamide ( 36 ) upon fusion with urea gave pyrimido[5,4-c]pyridazine-6,8-dione ( 37 ) while with ethyl orthoformate 36 gave pyrimido[5,4-c]pyridazin-8-one ( 38 ). Pyrimido[5,4-c]-pyridazine-8-thione ( 39 ) was obtained by the action of phosphorus pentasulfide on 38. 4-Amino-3-cyanopyridazine ( 16 ) when treated with formamide produced 8-aminopyrimido[5,4-c]-pyridazine ( 41 ). The synthesis of 4-aminopyridazine-3-carboxamide ( 36 ) and 4-amino-3-cyanopyridazine ( 16 ), both key intermediates in the synthesis of the novel pyrimido[5,4-c]pyridazine ring system was accomplished by the Reissert reaction of 4-aminopyridazine-2-oxides and subsequent conversion of the nitrile to the amide.     

Hydroxyiminoisoquinolin-3(2H)-ones. 9. Synthesis of some oxazolo[5,4-c]-, thiazolo[5,4-c]- and 2,3-dihydro-1H-[1,4]oxazino[2,3-c]isoquinolines

4-Acetylamino-1-phenyl-1,4-dihydro-3(2H)-isoquinolinones and 4-amino-1-phenylisoquinolin-3-ol, prepared from the corresponding 4-hydroxyimino compounds, were converted into new isoquinolines containing fused oxazole, thiazole and 1,4-oxazine rings.     

A novel preparation of thiazolo[5,4-c]pyridines and the synthesis of some imidazo[4,5-c]pyridines and oxazolo[4,5-c]pyridines

Diethoxymethyl acetate was used to cyclize o-disubstituted aminopyridines to oxazolo[4,5-c]pyridines and imidazo[4,5-c]pyridines. All the possible imidazole-methylated imidazo[4,5-c]pyridines were prepared. A novel synthesis of 2-substituted thiazolo[5,4-c]pyridines and 4-amino-3-pyridinethiol was discovered.     

Synthesis of 2-aryl-6-carbethoxythiazolo[4,5-c]pyridine and 7-chloro-2-phenylthiazolo[5,4-c]pyridine

Starting from readily available 2-aryl-5-formyl-4-mehtylthiazole, 2-aryl-6-carbethoxythiazolo[4,5-c]pyridine was prepared. β-(2-Phenylthiazol-4-yl)acrylic acid was converted to the corresponding azide (VI). Cyclization of compound VI afforded 2-phenylthiazolo[5,4-c]pyridin-7(6H)one. Reaction of the latter with phosphorous oxychloride gave 7-chloro-2-phenylthiazolo[5,4-c]pyridine.     

New [g]-fused [1,2,4]triazolo[1,5-c]pyrimidines: Synthesis of pyrido[3,2-e] and [4,3-e][1,2,4]triazolo[1,5-c]pyrimidine,pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine and [1,2,4]triazolo[1,5-c]pteridine derivatives

A number of 2-aryl-substituted pyrido[3,2-e] and [4,3-e][1,2,4]triazolo[1,5-c]pyrimidines and [1,2,4]triazolo[1,5-c]pteridines 11,12a,b,e , their corresponding 5-carbonyl derivatives 7,8a,b,e and some pyrimido[5,4-e][1,2,4]triazolo[1,5-c]pyrimidin-5-ones 7,8c,d have been synthesized, according to different pathways. The new tricyclic heterocycles were prepared with the aim of studying their possible benzodiazepine receptors affinity.     

Synthesis of 2H-Thiopirano[3,4-c]pyrazol-7-one Derivatives as the First Example a New Heterocyclic System

Russian Journal of General Chemistry - A series of ethyl 4-[(Z)-(4-oxo-2-thioxo-1,3-thiazolidin-5-ylidene)methyl]-1-aryl-1H-pyrazole-3-carboxylates was obtained as a result of the reaction of ethyl...     

Synthesis of a New Heterocyclic System. 7-Methyl-1-phenyl-5,7-dihydro[1,2]diazepino[5,4-b]carbazol-4(3H)-one

Russian Journal of Organic Chemistry - 7-Methyl-1-phenyl-5,7-dihydro[1,2]diazepino[5,4-b]carbazol-4(3H)-one representing a new heterocyclic system has been synthesized starting from...     

Etude des conditions d'accés aux 6H-, 7H- et 11H-pyrimidino-[4,5-a], [4,5-b], [5,4-a] [5,4-b] et [5,4-c]carbazoles. 1

The synthesis of dihydropyrimidinocarbazoles 12,15 and 18 was achieved by cyclization of tetrahydrocarbazolones with triformamidomethane. The oxidation with potassium permanaganate of dihydropyrimidinocarbazoles gave the pyrimidinocarbazoles 13,16 and 19. The application of the Sandemeyer reaction to amiononitrocarbazoles gave cyanonitrocarbazoles which could be reduced to aminocyanocarbazoles 1 and 7. Intramolecular cyclization of the carbazoles 1 and 7 afforded 3,4-dilhydro-4-oxo-6H-pyrimidino[5,4-b]carbazole 2 and 1,2-dighydro-1-oxo-6H-pyrimidino[5,4-b]carbazole 10 was obtained by cyclization of quinazolinyl hydrazone 9 with hydrochloric acid and acetic acid. The structure of the derivatives was determined by ¹H-nmr and the Overhauser effect.     

A facile synthesis of 2-aminothiazolo[5,4-b]- and 2-aminothiazolo[4,5-c] pyridines

The hydrochlorides of the title compounds are obtained in moderate yields by refluxing 2-chloro-3-aminopyridine or 3-amino-4-chloropyridine, respectively, with an alkyl. Aralkyl-, or aryl isothiocyanate in absolute ethanol solution. A proof is presented that the 2-aminothiazolopyridine hydrochloride and not the isomeric o-chloropyridylthiourea is the product of this reaction. The free-bases may be obtained from the hydrochlorides with aqueous sodium bicarbonate. A mechanism for the formation of the thiazole ring is briefly considered. The interactions of 2-chloro-3-aminopyridine with l-substituted-5-mereapto-1H-tetrazoles are also described.