Synthesis of 1H-thieno[3,4-c]pyrazoles,thieno[3,4-b]furans,selenolo[3,4-b]furans and pyrrolo[3,4-d]thiazoles

Starting from the readily available aryl 2-methyl-5-phenyl-3-furyl ketones, 5-methyl-1H-1-phenylpyrazole-4-yl ketones and 4-methyl-2-phenyl-5-thiazolylcarboxaldehyde, a series of 2-phenyl-4-arylthieno[3,4-b]-furan, 2-phenyl-4-(p-methoxyphenyl)selenolo[3,4-b]furan, 4-aryl-1H-1-phenylthieno[3,4-c]pyrazole and 5-benzyl-2-phenylpyrrolo[3,4-d]thiazole were prepared in high yield.     

Efficient synthesis of fused perhydrofuro[2,3-b]pyrans (and furans) by ring opening of 1,2-cyclopropanated sugar derivatives

[structure: see text]. An efficient method has been developed for the construction of fused perhydrofuro[2,3-b]pyrans by diastereoselective ring opening of 1,2-cyclopropanated sugar derivatives. The methodology has been successfully applied to the synthesis of fused perhydrofuro[2,3-b]pyrano-gamma-butyrolactone derivatives.     

Synthesis of pyrido[3,4-b]pyrano[3,4-b]indoles

The synthesis of some pyrido[3,4-b]pyrano[3,4-b]indoles ( 3 ) from 3-hydroxy-4-(3-indolyl)piperidines ( 6 ) is reported.     

Synthesis of pyrazolo[3,4-b][1,4]diazepines and pyrazolo[3,4-b]pyrazines

The synthesis and structure elucidation of new pyrazolo[3,4-b][1,4]diazepines and pyrazolo[3,4-b]pyrazines are reported and the characterisation of isomers and tautomers by proton and carbon-13 nmr are discussed. In some case only NOE experiments allow us to identify the isomeric structure.     

Synthesis of highly functionalized indeno[1,2-b]furans

Some novel functionalized indeno[1,2-b]furans were synthesized from the reaction of indandione/indanone and aldehydes at room temperature followed by the reaction of the Knoevenagel condendensed intermediate with 4-hydroxycoumarins in the presence of iodine as catalyst in dimethyl sulfoxide (DMSO) under thermal conditions. The reaction involved in a condensation and Michael addition followed by lactone ring opening and intramolecular cyclization process to afford the product in high yield in easy work-up procedure.     

Synthesis of dihydrothieno[3,4-b]indoles

A new heterocyclic system — 3-imino-4-methyldihydrothieno[3,4-b]indole — was obtained by treatment of 1-methylindole-2-carboxylic acid thioamide with aldehydes or ketones in the presence of hydrogen chloride. Reactions involving saponification and acetylation of the imino group of the thieno ring and opening of the thieno ring by the action of LiAlH₄ to give a bis(indolylphenylmethyl) sulfide were carried out. A scheme is proposed in which the SH group of the thioamide adds to the carbonyl compound in the first step, after which the product undergoes intramolecular cyclization in the 3 position of indole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1327–1331, October, 1977.     

6-Amino-5-cyano-1H,4H-pyrazolo[3,4-b]pyrans

The reaction of 3-methyl-1-phenyl-5-pyrazolene with arylideneamino nitriles in alcohol leads to the formation of 3-methyl-4(1-aryl-2,2-dicyanoethyl)-5-pyrazolones, which are readily cyclized in the presence of bases to the corresponding 6-amino-5-cyano-3-methyl-4-aryl- 1H,4H-pyrazolo[3,4-b]pyrans. The structures of the intermediate and final products were confirmed by the IR, UV, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 801–806, June, 1982.     

Selenium heterocycles. XXXIII. Synthesis of thieno[3,4-b]furan,seleno[3,4-b]furan,thieno[3,4-b]indole and seleno[3,4-b]indole. four novel heterocycles

Starting from the readily available 2-methyl-3-benzoylfuran, 1-phenylthieno[3,4-b]furan and 1-phenyl-seleno[3,4-b]furan were prepared. Also, starting from phenyl 3-methylindol-2-yl ketone and aryl 2-methyl-indole-3-yl ketones a series of substituted thieno[3,4-b]indoles and substituted seleno[3,4-b]indoles were prepared.     

Synthesis of quinolono[4,3-b] and [3,4-b]carbazoles potential DNA binders

2-and 3-β-[arylvinyl]indoles, obtained by Wittig-Horner reaction of the corresponding N-benzenesulfonylbromomethylindoles with o-nitrobenzaldehydes, gave 2- and 3-arylcarbazoles respectively upon Diels-Alder reaction with DMAD. On reductive cyclisation, these carbazoles gave the title compounds.     

Synthesis of pyridazino[3,4-b]quinoxalines and pyrazolo[3,4-b]-quinoxaline by 1,3-dipolar cycloaddition reaction

The pyridazino[3,4-b]quinoxalines 6a,b and pyrazolo[3,4-b]quinoxaline hydrochloride 9 were synthesized by the 1,3-dipolar cycloaddition reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 5 with dimethyl or diethyl acetylenedicarboxylate and 2-chloroacrylonitrile, respectively. The reaction mechanisms were postulated for the formation of 6a,b and 9 .     

Synthesis of furazano[3,4-b]pyrazine derivatives

Various furazano [3, 4-b] pyrazine derivatives were synthesized by condensation of 3, 4-diaminofurazan with substituted phenylglyoxals, cyclic di- and triketones, and diethyl acetylenedicarboxylate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 613–615, May, 1978.     

Synthesis of novel pyridazino[3,4-b]quinoxalines

The pyridazino[3,4-b]quinoxaline 12 was synthesized by the cyclization of the α-arylhydrazonoacyl-hydrazide 11. The reaction of compound 12 with phosphoryl chloride gave pyridazino[3,4-b]quinoxaline 13, whose reactions with sodium azide or cyclic secondary amines provided pyridazino[3,4-b]quinoxalines 14,17 and 18, respectively. The acylhydrazide 15 was also cyclized to pyridazino[3,4-b]quinoxaline 16.     

Synthesis of Pyrazolo[3,4-b]- and Pyrido[2,3-b]-1,5-benzodiazepines

Abstract

3-Dimethylaminomethyleno-4-phenyl-1H-1,5-benzodiazepin-2-one (1) was synthesized and reacted with hydrazines, active nitriles, and amino-heterocyclic compounds to give fused heterocyclic compounds 2–14.     

A Facile and Efficient Synthesis of Thieno[2,3-c]furans and Furo[3,4-b]indoles via a Pummerer-Induced Cyclization Reaction

The alpha-thiocarbocation generated from the Pummerer reaction of an o-heteroaroyl-substituted sulfoxide is intercepted by the adjacent keto group to produce an alpha-thio-substituted heteroaromatic isobenzofuran. In the presence of a suitable dienophile, the reactive o-xylylene undergoes a Diels-Alder cycloaddition followed by an acid-catalyzed ring-opening and aromatization to give heteroaromatic naphthalene derivatives. This one-pot procedure occurs smoothly with electron-deficient dienophiles. The tandem Pummerer cyclization-cycloaddition sequence also occurs intramolecularly using unactivated alkenyl tethers of variable length. With acetylenic dienophiles, the primary cycloadducts undergo in situ ring-opening to produce hydroxynaphthalene derivatives. In the absence of a dienophile, it was possible to prepare 4-(ethylthio)-6-phenylthieno[2,3-c]furan and 1-ethyl-4-(phenylsulfonyl)-4H-furo[3,4-b]indole. Various synthetic approaches were used for the preparation of the requisite thiophene- and indole-derived sulfoxide precursors. The facility of the tandem Pummerer-Diels-Alder reaction was very dependent on the experimental conditions used to promote the reaction. The best results were achieved by employing a mixture of acetic anhydride and toluene which contained a catalytic quantity of p-toluenesulfonic acid. The presence of the acid effectively drives the reaction in the desired direction by preventing formation of the acetoxy sulfide, which corresponds to the normal Pummerer product.     

Synthesis of hexahydroazonino[5,6-b]indoles from hexahydroazepino[4,3-b]-and-[3,4-b]indoles and activated alkynes

A reaction of substituted hexahydroazepino[4,3-b]-and-[3,4-b]indoles with activated alkynes was studied. A one-step method for the synthesis of isomeric hexahydroazonino[5,6-b]indoles different by positions of the double bond in the azonine ring was developed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2244–2250, November, 2007.     

Synthesis of 3-aryl-6H-isoxazolo[3,4-d]pyrazolo[3,4-b]pyridines and 3-aryl-6H-isoxazolo[5,4-d]pyrazolo[3,4-b]pyridines

The synthesis and characterization of a number of 3-aryl-6H-isoxazolo[3,4-d]pyrazolo[3,4-b]pyridines and 3-aryl-6H-isoxazolo[5,4-d]pyrazolo[3,4–6]pyridines from common precursors, 5-benzoyl-4-chloro-1H-pyrazolo-[3,4-b]pyridines, has been described. The structures were determined by unambiguous chemical synthesis and by isolation and ¹³C nmr analysis of some key, isolated, intermediates. The ability of these compounds to displace [3H]flunitrazepam from CNS binding sites was also observed.     

Synthesis and alkylation of pyrazolo[3,4-c]isoquinolines and hexahydrocyclohepta[d]pyrazolo[3,4-b]pyridines

The condensation of 1-acyl-2-(morpholin-4-yl)cycloalkenes with 3-amino-1-phenyl-1H-pyrazol-5(4H)-ones gave the corresponding 2,3,6,7,8,9-hexahydropyrazolo[3,4-c]isoquinoline and 3,6,7,8,9,10-hexahydrocyclohepta[ d]pyrazolo[3,4-b]pyridine derivatives. Alkylation of 2,3,6,7,8,9-hexahydropyrazolo[3,4-c]-isoquinolines with alkyl halides occurred at the nitrogen atom in the 3-position. The structure of 7-methyl-2,5-diphenyl-2,3,6,7,8,9-hexahydro-1H-pyrazolo[3,4-c]isoquinolin-1-one was proved by X-ray analysis.     

A Facile Synthesis of Pyrazolo[3,4-b]pyridines

Pyrazolo[3,4-b]pyridines (4) and (5) have been obtained by the condensation of 3-(alkyl/aryl)-5-amino-1-phenyl-1H-pyrazole-4-carboxaldehydes (3) with active methylene compounds viz: diethyl malonate and malononitrile.