A green and practical method for the synthesis of novel pyrano[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrazoles and <Emphasis Type="Italic">bis</Emphasis>-pyrano[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrazoles using sulfonic acid-functionalized ionic liquid

An efficient and practical protocol was developed for the synthesis of novel pyrano[2,3-c]pyrazoles and bis-pyrano[2,3-c]pyrazoles by one-pot four-component reaction of arylaldehyde, ethyl acetoacetate, hydrazine hydrate and dimethyl malonate using SO₃H-functionalized ionic liquid [DMBSI]HSO₄ as a potential green catalyst under solvent-free condition. The method presented is mild, environmentally friendly, inexpensive and functionality tolerant and produces the desired pyranopyrazoles in short reaction times (17–24 min) and excellent yields (85–95%). In addition, the catalyst can be reused at least ten times without almost any change in its catalytic activity.     

Synthesis of pyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazolo[4,3-<Emphasis Type="Italic">c</Emphasis>]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol. Correspondence: Abolghasem Davoodnia, Department of Chemistry, School of Sciences, Islamic Azad University, Mashhad Branch, Mashhad 91735-413, Iran.     

Synthesis and reactions of some new selenolo[2,3-<Emphasis Type="Italic">c</Emphasis>]pyridazines

New series of selenolo[2,3-c]pyridazine and pyrimido[4',5':4,5]selenolo[2,3-c]pyridazine derivatives were prepared from 4-cyano-5,6-diphenylpyridazine-3(2H)-selenone. Elemental analysis, IR, ¹H NMR, and mass spectra confirmed the structures of the newly synthesized compounds.     

Green procedure for the synthesis of 1,4-dihydropyrano[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrazoles using saccharose

Saccharose was applied as an efficient and homogeneous catalyst for one-pot, four-component synthesis of 1,4-dihydropyrano[2,3-c]pyrazole derivatives from aromatic aldehydes, malononitrile, ethyl acetoacetate and hydrazine monohydrate under thermal solvent-free conditions. This protocol has a considerable number of advantages including mild condition, high yields, operational simplicity, environmentally benign and simple work-up procedures.     

Synthesis and antimicrobial screening of pyrano[3,2-<Emphasis Type="Italic">c</Emphasis>]chromene derivatives of 1<Emphasis Type="Italic">H</Emphasis>-pyrazoles

A new series of twenty four derivatives of pyrano[3,2-c]chromene IVa-x bearing 1H-pyrazole were synthesized by a one pot, base-catalyzed cyclocondensation reaction of 1H-pyrazole-4-carbaldehyde Ia-l, malononitrile II and 4-hydroxycoumarin IIIa-b. All the synthesized compounds were characterized by elemental analysis, FT-IR, ¹H NMR and ¹³C NMR spectral data. All the synthesized compounds were screened against six bacterial pathogens, namely B. subtilis, C. tetani, S. pneumoniae, S. typhi, V. cholerae, E. coli and for antifungal activity against two fungal pathogens, A. fumigatus and C. albicans using the broth microdilution MIC method. Some of the compounds were found to be equipotent or more potent than commercial drugs against most of employed strains, as evident from the screening data.      

Synthesis of substituted 2,4-dimethylthieno[3,2-<Emphasis Type="Italic">c</Emphasis>]quinolines

A procedure was developed for the synthesis of substituted 2,4-dimethylthieno[3,2-c]quinolines via intramolecular cyclization and subsequent aromatization of 3-(2-chloroprop-2-en-1-yl)-and 3-(2-oxopropyl)-2-methylquinoline-4-thiols. The latter were obtained by alkaline hydrolysis of the corresponding thiuronium salts which were prepared in turn by reactions of 4-chloro-3-(2-chloroprop-2-en-1-yl)-and 4-chloro-3-(2-oxopropyl)-2-methylquinolines with thiourea.     

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.     

Synthesis and X-ray study of 6<Emphasis Type="Italic">H</Emphasis>-chromeno[3,4-<Emphasis Type="Italic">e</Emphasis>][1,3,4]triazolo[2,3-<Emphasis Type="Italic">a</Emphasis>]pyrimidine

2-Dimethylamino methylenechromanone 1 reacted with 4H-1,2,4-triazol-3-amine in acetic acid to give only one isolated product which was identified by X-ray study as 6H-chromeno[3,4-e][1,3,4]triazolo[2,3-a]-pyrimidine. The molecular structure of 3, C₁₂H₈N₄O, was determined to be monoclinic, P2₁/c, a = 16.3875(5), b = 8.8378(3), c = 13.8392(5) Å, β = 101.190(1)°, V = 1966.22(11) ų, Z = 8.     

Synthesis of alkyl hexahydropyrazino-[1,2-<Emphasis Type="Italic">c</Emphasis>]pyrimidine-9-carboxylates

Cyclocondensation of 3-alkoxycarbonylmethylidenepiperazin-2-ones with α-chlorobenzyl isocyanates gave alkyl 8-aryl-1,6-dioxo-1,3,4,6,7,8-hexahydro-2H-pyrazino[1,2-c]pyrimidine-9-carboxylates. The use of 1-aryl-2,2,2-trifluoroethyl isocyanates in an analogous cyclization gave 6-aryl-1,8-dioxo-6-trifluoromethyl-1,3,4,6,7,8-hexahydro-2H-pyrazino[1,2-c]pyrimidine-9-carboxylates.     

Acid cyclization of amino-substituted heterocycles. Synthesis of 1,3-dioxo- pyrrolo[3,4-<Emphasis Type="Italic">c</Emphasis>]- and thieno[3,4-<Emphasis Type="Italic">c</Emphasis>]isoquino- lines and cinnolines

The reaction of 3-amino-4-(3,4-dimethoxyphenyl)maleimide and the methyl esters of 3-amino-4-(3,4-dimethoxyphenyl)-5-R-thiophene-2-carboxylic acids with carbonyl compounds and nitrous acid has been investigated. Dioxopyrrolo[3,4-c]- and thieno[3,4-c]isoquinolines and cinnolines were obtained. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 449-454, March, 2009.     

Regioselective Synthesis of Thieno[3,2-<Emphasis Type="Italic">c</Emphasis>][1]benzopyran-4-ones by Thio-<Emphasis Type="Italic">Claisen</Emphasis> Rearrangement

Summary. A number of thieno[3,2-c][1]benzopyran-4-ones, potential antiinflamatory, antipyretic, and antiallergic drugs, are synthesized in 65–80% yield by thermal thio-Claisen rearrangement of 4-allylthio[1]benzopyran-2-ones in refluxing quinoline for 0.5–8.0h. The 4-allylthio[1]benzopyran-2-ones are in turn prepared in 75–85% yield from 4-mercaptocoumarin and different allylic halides by phase-transfer-catalysed alkylation with TBAB or BTEAC catalyst in chloroform-aq. NaOH at room temperature.     

Fluorinated [1,2,4]triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines and [1,2,4]triazolo[5,1-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazines*

The reaction of 3-R-5-amino-1,2,4-triazoles with the ethyl ester of 2-fluoroacetoacetic acid gave 2-R-fluoro[1,2,4]triazolo[1,5-a]pyrimidin-7(4H)-ones. The reaction of a 3-R-1,2,4-triazolyl-5-diazonium salt with the ethyl ester of 2-fluoroacetoacetic acid and subsequent cyclization of the triazolylhydrazones lead to 7-R-3-fluoro[1,2,4]triazolo[5,1-c][1,2,4]triazin-4(1H)-ones.     

Transformations of 3,3,4-tricyano-3,4-dihydro-2<Emphasis Type="Italic">H</Emphasis>-pyran-4-carboxamides. Synthesis of pyrano[3,4-<Emphasis Type="Italic">c</Emphasis>]pyrrole derivatives

A procedure has been developed for the synthesis of polyfunctional pyrano[3,4-c]pyrrole derivatives via intramolecular cyclization involving vicinal cyano and carboxamide groups on a pyran ring. 3-Amino-1-oxo-1,3a,4,7a-tetrahydropyrano[3,4-c]pyrrole-3a,7a-dicarbonitrile thus obtained react with organic amines to give stable ammonium salts and undergo hydrolysis to 1,3-dioxo-1,2,3,3a,4,7a-hexahydropyrano[3,4-c]pyrrole-3a,7a-dicarbonitriles in the presence of sulfuric acid.     

Synthesis of derivatives of pyrido-[1,2-<Emphasis Type="Italic">c</Emphasis>][1,3,2]oxazaborinine and pyrido-[2,1,6-<Emphasis Type="Italic">f,g</Emphasis>][1,3,7,2]dioxazaphosphacyclo-decane

The condensation of 2,6-di(o-hydroxyphenyl)-3,5-diphenyl-γ-piperidone with boric and boronic acids gave a series of 1,3,4,11b-tetrahydro-2H-benzo[e]pyrido[1,2-c][1,3,2]oxazaborinin-2-ones. The action of phosphorus oxytrichloride on this piperidone gave a derivative of 8,10-dioxa-21-aza-9-phospha-pentacyclohenicosahexaene. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1882–1886, December, 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.     

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 2-alkyl-1-aryl-1,2-dihydrochromeno[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrrole-3,9-dione derivatives

A preparative procedure for the synthesis of 2-alkyl-1-aryl-1,2-dihydrochromeno[2,3-c]pyrrole-3,9-diones from methyl 4-(o-hydroxyphenyl)-2,4-dioxobutanoate, aromatic aldehyde, and aliphatic amine is described.     

Synthesis of 2,3-disubstituted derivatives of pyrano-, thiopyrano-, and benzoannelated pyrido[2,3-<Emphasis Type="Italic">b</Emphasis>]thieno[3,2-<Emphasis Type="Italic">d</Emphasis>]pyrimidines

A new methods have been developed for the synthesis of condensed pyrido[2,3-b]thieno[3,2-d]pyrimidines based on cyclic derivatives of 4-cyanopyridine-3-thiones. The presence of two different reactive functional groups NH₂ and CONH gives the possibility of carrying out different conversions of thieno[2,3-b]pyridines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1245–1252, August, 2008.