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A Facile Synthesis of Pyrido[ , :3,4]pyrazolo[1,5- a ]pyrimidine and Pyrido[ , :3,4]pyrazolo[5,1- c ][1,2,4]triazine Bearing a Thiophene Moiety  [PDF]
Tilal Elsaman,Mohamed Fares,Hatem A. Abdel-Aziz,Mohamed I. Attia,Hazem A. Ghabbour,Kamal M. Dawood
Journal of Chemistry , 2013, DOI: 10.1155/2013/463515
Abstract: Pyridinone derivative 8 was synthesized and transformed into the respective chloropyridine 9, which was allowed to react with hydrazine hydrate to afford pyrazolo[3,4-b]pyridin-3-amine derivative 11. Compound 11 was used as a key intermediate for a facile synthesis of the title compounds 14, 15, 17, 21a,b, and 24a–c where the reaction of 11 with some 1,3-dielecrophiles resulted in the formation of pyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines 14, 15, and 17, whereas diazotization of compound 11 gave the respective diazonium salt 18 which was coupled with some active methylene-containing compounds to give the corresponding hydrazones 19a,b and 22a–c. Cyclization of the latter hydrazones yielded the pyrido[2′,3′:3,4]pyrazolo[5,1-c][1,2,4]triazines 21a,b and 24a–c, respectively. 1. Introduction Thiophene moiety is present in a large number of bioactive molecules having diverse biological activities such as antiinflammatory [1], anticonvulsant [2], antibacterial [3], and antitumor [4] activities. Moreover, thiophene moiety is a well-known isostere for benzene; for example, the replacement of benzene ring of the antidepressant drug, Viloxazine, (I, Figure 1) led to a prolongation of half-life [5]. Figure 1: Chemical structures of Viloxazine ( I), Etazolate ( II), and Glicaramide ( III). On the other hand, several pyrazolo[3,4-b]pyridines revealed interesting biological properties including antimicrobial [6], antiviral [7], antiinflammatory [8], analgesic [9], and antitumor activities [10]. In addition, pyrazolo[3,4-b]pyridines represent the skeleton of pharmaceuticals possessing significant biological activities as represented by Etazolate (II, EHT-0202, Figure 1), an anxiolytic drug, which is now in clinical trials for the treatment of Alzheimer’s disease [11], and by Glicaramide (III, Figure 1), a potent antidiabetic agent [12]. Following a program dealing with the development of bioactive heterocyclic derivatives [13–15], we report herein a facile synthesis of new pyrazolo[3,4-b]pyridines 14, 15, 17, 21a,b, and 24a–c, bearing a thiophene moiety, as new bioactive candidates. 2. Experimental 2.1. General Melting points were determined on a Gallenkamp melting point apparatus and are uncorrected. Infrared (IR) spectra were recorded as KBr disks using the Perkin Elmer FT-IR Spectrum BX apparatus. NMR Spectra were measured in DMSO-d6 on a Jeol-NMR spectrometer operating at 400?MHz for 1H NMR and at 100?MHz for 13C NMR. Chemical shifts are expressed in δ values (ppm) relative to TMS as an internal standard. Coupling constants (J) are expressed in Hz. D2O was added
An Efficient and Convenient Synthesis of Certain 2-Thioxothiazole,2-oxo-1,2-dihydropridine, 2-Oxo-2H-pyran,2,4-diaminothiophene and Pyrazolo[5,1-c][1,2,4]triazine Derivatives Containing Antipyrine Moiety  [PDF]
Seif-Eldin Nasr Ayyad, Fathy Muhammad Abdelaziz El-Taweel, Abdel-Ghani Ali Elagamey, Tahani Mahmoud El-Mashad
International Journal of Organic Chemistry (IJOC) , 2012, DOI: 10.4236/ijoc.2012.22021
Abstract: 2-Thioxothiazole derivatives 5a-c were prepared by reacting a mixture of 1a-c, CS2/KOH and 4-(2-chloroacetyl)-1, 5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one(3). Reacting 2-cyano-N-(4-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-2H- pyrazol-4-yl)-2-thioxothiazol-3(2H)-yl)acetamide (5c) with mercaptoacetic acid, arylidenemalononitriles 8 and (E)- 3-(dimethylamino)-1-(furan-2-yl)prop-2-en-1-one (12) give 4-oxo-4,5-dihydrothiazole 6, 2-oxo-1,2-dihydropyridine 10 and 2-oxo-2H-pyran 15 respectively. Heating a mixture of 5c, malononitrile and elemental sulfur yield 2,4-diaminothio- phene 19. Coupling of 5c with the diazotized aminopyrazole 20 and aryldiazonium salts 23 give pyrazolo[5,1-c][1,2,4] triazines 22 and arylhydrazones 25 respectively.
Synthesis of some new of thieno[2,3-b]pyridines, pyrazolo[1,5-a]pyrimidine, [1,2,4]triazolo[1,5-a]pyrimidine, pyrazolo[5,1-c]triazine and pyrimido[1,2-a]benzimidazole derivatives containing pyridine moiety  [cached]
Mahmoud Abdallah Mohamed,Eman Kamal Ahmad Abdelall,Yasser Hassan Zaki,Abdou Osman Abdelhamid
European Journal of Chemistry , 2011, DOI: 10.5155/eurjchem.2.4.509-513.463
Abstract: pyrazolo[1,5-a]pyrimidine, [1,2,4]triazolo[1,5-a]pyrimidine and pyrimido[1,2-a] benzimidazole derivatives were synthesized by reaction of sodium salt of 3-hydroxy-(1-pyridin-2-yl)prop-2-en-1-one or sodium salt of 3-hydroxy-1-(pyridin-3-yl)prop-2-en-1-one with different heterocyclic amines in piperidenium acetate. Also, 3-amino-6-(2-pyridyl)thieno[2,3-b]pyridine derivatives were synthesized via reaction of pyridine-2-thione with various halogenated compounds. The structures of the newly synthesized compounds were confirmed by elemental analysis, spectral data, X-ray and alternative synthetic routes whenever possible.
Efficient Routes to Pyrazolo[3,4-e][1,2,4]triazines and a New Ring System: [1,2,4]Triazino[5,6-d][1,2,3]triazines  [PDF]
Hamad Mohamed Al-Matar,Khaled Dessouky Khalil,Doa’a Mohamed Al-Dorri,Mohamed Helmy Elnagdi
Molecules , 2010, DOI: 10.3390/molecules15053302
Abstract: Arylhydrazonomalononitriles 1a,b react with phenylhydrazine to yield amidrazones 2a,b that cyclize to give 2-aryl-5-phenylhydrazono-2,5-dihydro-[1,2,4]-triazine-6-carbonitriles 5a,b upon reaction with dimethylformamide dimethylacetal (DMFDMA). Refluxing 5a,b in glacial acetic acid resulted in the formation of the pyrazolo-1,2,4-triazines 6a,b. Compounds 6a,b were also formed upon treatment of 3-amino-4-phenylhydrazono-1-phenyl-2-pyrazolin-5-ones 7a,b with DMFDMA. Reacting these triazinyl arylhydrazononitriles 5a,b with hydroxylamine hydrochloride in ethanolic sodium acetate afforded amidrazones 8a,b that are readily cyclized in refluxing dimethylformamide into [1,2,4]triazino[1,2,3]triazines 10a,b.
Microwave Assisted Synthesis of Some New Fused 1,2,4-Triazines Bearing Thiophene Moieties With Expected Pharmacological Activity  [PDF]
Hosam A. Saad,Mohamed M. Youssef,Mosselhi A. Mosselhi
Molecules , 2011, DOI: 10.3390/molecules16064937
Abstract: Rapid and efficient solvent-free synthesis of 4-amino-3-mercapto-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one 1 under microwave irradiation is described. Some new fused heterobicyclic nitrogen systems such as 1,2,4-triazino[3,4-b][1,3,4]thiadiazinones, 1,3,4-thiadiazolo[2,3-c][1,2,4]triazinone and pyrazolo[5,1-c]-[1,2,4]triazine-7-carbonitrile, have been synthesized by treatment of 1 with bifunctional oxygen and halogen compounds, CS2/KOH and malononitrile via heterocyclization reactions, in addition to some uncondensed triazines. Structures of the products have been deduced from their elemental analysis and spectral data (IR, 1H-NMR, 13C-NMR). Select new synthesized compounds were screened as anticancer agents, with some showing activity as cytotoxic agents against different cancer cell lines.
Pyrazolo[4,3-e][1,2,4]triazines: Purine Analogues with Electronic Absorption in the Visible Region  [PDF]
Mariusz Mojzych,Andrzej Rykowski,Jacek Wierzchowski
Molecules , 2005, DOI: 10.3390/10101298
Abstract: Synthesis of several pryrazolo[4,3-e][1,2,4]-triazines is described. Theabsorption spectrum of some 5-substituted derivatives was found to extend to the visibleregion. These compounds were found to inhibit some enzymes of purine metabolism, likexanthine oxidase or bacterial purine-nucleoside phosphorylase with Ki values in the 10-3 –10-5 M range.
Synthesis and Antibacterial Activities of Novel 2,5-Diphenylindolo[2,3-e] Pyrazolo[1',5':3",4"]pyrimido[2",1"-c] [1,2,4]triazines  [PDF]
Kamal F.M. Atta,Omaima O.M. Farahat,Somaya M. Ghobashy,Mohamed G. Marei
Molecules , 2011, DOI: 10.3390/molecules161210387
Abstract: The formation of (E)-3-{2-(2,5-diphenylpyrazolo[1,5-c]pyrimidin-7-yl)hydrazono}indolin-2-ones 3 has been achieved by condensation of equimolar amounts of 7-hydrazino-2,5-diphenylpyrazolo[1,5-c]pyrimidine (1) and isatin (or isatin derivatives) 2 at room temperature. The (E)-products could be isomerized into corresponding the (Z)-3 isomers. Reactions of the latter fused heterocyclic hydrazones towards different electro-philic reagents yielded the corresponding 3-substituted derivatives 4–7. Dehydrative cyclisation of the hydrazones 3 using phosphorus oxychloride afforded the 2,5-diphenyl- indolo[2,3-e]pyrazolo[1',5':3",4"]pyrimido[2",1"-c][1,2,4] triazines 13. The polyfused heterocyclic ring system 13 underwent electrophilic substitution reactions at position 4 rather than at position 3. The 3-bromo isomer of 17 was prepared by a sequence of reactions starting from 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H)-thione (11). The orientation of the electrophilic attack was supported by spectroscopic and chemical evidence. Some of the synthesized compounds were found to possess slight to moderate activity against the microorganisms Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa.
Reactions with hydrazonoyl halides 66: Synthesis of some new 1,3,4-thiadiazoles, triazolino[4,3-a]pyrimidines and isoxazolo[3,4-d]pyridazines containing coumarin moiety  [cached]
Abdou Osman Abdelhamid,Abdelgawad Ali Fahmi,Abeer Bahlol Ali
European Journal of Chemistry , 2011, DOI: 10.5155/eurjchem.2.4.544-551.478
Abstract: 2,3-Dihydro-1,3,4-thiadiazoles, triazolino[4,3-a]pyrimidines, isoxazoles and isoxazolo[3,4-d]pyridazines containing coumarin moities were synthesized from the reactions of methyl (or benzyl) carbodithioate, pyrimidine-2-thione and 3-(3-(dimethylamino)acryloyl)-2H-chromen-2-one derivatives with C-coumarinoyl-N-phenylhydrazonoyl bromide. The structures of all the newly synthesized compounds were confirmed by elemental analyses and spectral data.
Benzyl 5-phenylpyrazolo[5,1-a]isoquinoline-1-carboxylate  [cached]
Yu-Kun Lu,Xiao Yao,Li-Wen Luo,Ren-Qing Lü
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811050586
Abstract: In the title compound, C25H18N2O2, the pyrazolo[5,1-a]isoquinoline ring system is approximately planar [maximum deviation = 0.027 (2) ] and is oriented at dihedral angles of 57.22 (6) and 71.36 (7)° with respect to the two phenyl rings. The phenyl rings are twisted to each other by a dihedral angle of 66.33 (8)°. A weak intramolecular C—H...O hydrogen bond occurs. In the crystal, weak C—H...π interactions are present.
Heterocyclic o-Aminonitriles: Preparation of Pyrazolo[3,4-d]-pyrimidines with Modification of the Substituents at the 1- Position  [PDF]
Eljazi I. Al-Afaleq,Samar A. Abubshait
Molecules , 2001, DOI: 10.3390/60700621
Abstract: Novel 1-[6-(p-tolyl) pyridazin-3-yl]pyrazole-o-aminonitriles (3a-c) were formed using 3-hydrazino-6-(p-tolyl)pyridazine (2) and ketene S,S-acetals (1a), S,Nacetals (1b) or tetracyanoethylene (1c). The pyrazole-o-aminonitriles (3a-c) were in turn used as precursors for the preparation of previously unreported 1-[6-(p-tolyl)-pyridazin-3-yl]pyrazolo[3,4-d]pyrimidines (8, 9, 13-20) and 7-[6-( p-tolyl) pyridazin-3-yl]2-arylpyrazolo[3,4-d]1,2,4-triazolo[5,1-f]pyrimidines (10-12) which are expected to possess considerable chemical and pharmacological activities.
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