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Benzimidazole
Terms modified by Benzimidazole Selected AbstractsStudy of the adsorption of benzimidazole and 2-mercaptobenzothiazole on an iron surface by confocal micro-Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2004G. Wang Abstract Benzimidazole (BIMH) and 2-mercaptobenzothiazole (HMBT) dissolved in ethanol were chosen for the investigation of the interaction between organic molecules and surface atoms of iron or iron oxide by confocal micro-Raman spectroscopy. Both BIMH and HMBT show enhanced and highly structured spectra in the 200,1500 cm,1 region when the iron is at a potential of ca ,0.7 to ,0.9 V in a neutral medium. BIMH had a weak interaction with the iron surface in a basic medium but it was chemically adsorbed in a neutral medium. HMBT was chemically adsorbed on the iron via the exocyclic S and N atoms in acidic and neutral solutions, whereas in basic media it was bound electrostatically. Copyright © 2004 John Wiley & Sons, Ltd. [source] Total Synthesis and Biological Assessment of Benzimidazole-Based Analogues of Epothilone A: Ambivalent Effects on Cancer Cell Growth InhibitionCHEMBIOCHEM, Issue 1 2006Fréderic Cachoux Dr. Benzimidazole-based analogues of cis - and trans -Epo A, 2 and 3, have been prepared through stereoselective total synthesis. Both compounds are highly potent antiproliferative agents, but the effects of side-chain replacement on cellular activity are ambivalent. While significantly enhanced potency is observed against a drug-sensitive human cancer cell line, 2 and 3 more susceptible to P-gp-mediated drug efflux than Epo A or trans -Epo A. [source] ChemInform Abstract: Diversity-Oriented Synthesis of Benzimidazole, Benzoxazole, Benzothiazole and Quinazolin-4(3H)-one Libraries via Potassium Persulfate,CuSO4 -Mediated Oxidative Coupling Reactions of Aldehydes in Aqueous Micelles.CHEMINFORM, Issue 37 2010Atul Kumar Abstract The diversity-oriented synthesis of the title heterocycles in aqueous micelles shows the advantages of short reaction times, high yields, high chemoselectivities, low coast, and environmental friendliness. [source] ChemInform Abstract: Synthesis of Novel Synthetic Intermediates from the Reaction of Benzimidazole and Triazole Carbenes with Ketenimines and Their Application in the Construction of Spiro-Pyrroles.CHEMINFORM, Issue 15 2010Jun-Ming Mo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Second Generation of 2H-Benzimidazole 1,3-Dioxide Derivatives as anti-Trypanosomatid Agents: Synthesis, Biological Evaluation, and Mode of Action Studies.CHEMINFORM, Issue 9 2010Mariana Boiani Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Diversity-Oriented Synthesis of Benzimidazole and Benzoxa/(thia)zole Libraries Through Polymer-Supported Hypervalent Iodine Reagent.CHEMINFORM, Issue 30 2009Atul Kumar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis of Highly Functionalized 2-(Substituted Biphenyl) Benzimidazole via Suzuki,Miyaura Cross Coupling Reaction.CHEMINFORM, Issue 12 2008Ramanatham Vinodkumar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Regioselective Synthesis of Some Novel Pyrazoles, Isoxazoles, Pyrazolo[3,4-d]pyridazines and Isoxazolo[3,4-d]pyridazines Pendant to Benzimidazole.CHEMINFORM, Issue 23 2007Mohamed R. Shaaban Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Quinoxaline,Benzimidazole Rearrangement in the Synthesis of Benzimidazole-Based Podands.CHEMINFORM, Issue 13 2007V. A. Mamedov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Propionic Acids in Organic Synthesis: Novel Synthesis of Benzimidazole, 3,1-Benzoxazine, 3-Aminoquinazoline and 3-Aminothieno[2,3-d]pyrimidine Derivatives Containing 2-Naphthyl Propionyl Moiety.CHEMINFORM, Issue 21 2006Abdullah G. M. Al-Sehemi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Reactivity Studies on 4-Aminopyrones: Access to Benzimidazole and Benzimidazolone Derivatives.CHEMINFORM, Issue 52 2002Mohamed Amari Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of Some Benzimidazole-, Benzothiazole- and Pyridine-Derived Chelating Agents.CHEMINFORM, Issue 38 2002Jayakumar G. Gilbert Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Adamantylation of Imidazoles and Benzimidazole.CHEMINFORM, Issue 17 2002G. F. Raenko Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Facile Method for the Synthesis of Combinatorial Libraries of Benzimidazole, Benzothiazole, Benzoxazole, Perimidine and QuinazolinoneCHINESE JOURNAL OF CHEMISTRY, Issue 2 2009Majid. Abstract A highly yielding and fast method for the synthesis of heterocyclic compounds with trialkyl orthoformate using molecular sieve 3? as a catalyst is described. [source] The MHC class,II transactivator (CIITA) mRNA stability is critical for the HLA class,II gene expression in myelomonocytic cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 2 2005Andrea De Lerma Barbaro Abstract The human promyelocytic U937 cells express detectable levels of MHC class,II (MHC-II) molecules. Treatment with 12-o- - tetradecanoyl phorbol 13-acetate (TPA), inducing macrophage-like differentiation, produces a dramatic decrease of MHC-II expression as result of down-modulation of the activation of immune response gene,1 (AIR-1)-encoded MHC-II transactivator (CIITA). This event is specific, as MHC class,I remains unaffected. Similar results are observed with U937 cells expressing an exogenous full-length CIITA. Molecular studies demonstrate that TPA treatment affects the stability of CIITA mRNA rather than CIITA transcription. Importantly, cis -acting elements within the distal 650,bp of the 1035-bp 3,,untranslated region (3,UTR, nucleotides 3509,4543) are associated to transcript instability. Transcription inhibitors actinomycin,D and 5,6-dichlororibofuranosyl benzimidazole, and the translation inhibitor cycloheximide significantly rescue the accumulation of CIITA mRNA in TPA-treated cells. A similar effect is also observed after treatment with staurosporine and the PKC-specific inhibitor GF109203X. The instability of CIITA mRNA produced by TPA in U937 cells is not seen in B,cells. These results demonstrate the presence of an additional level of control of MHC-II expression in the macrophage cell lineage depending upon the control of CIITA mRNA stability, most likely mediated by differentiation-induced, 3,UTR-interacting factors which require kinase activity for their destabilizing function. [source] Synthesis, Cytotoxicity and Antibacterial Studies of p -Methoxybenzyl-Substituted and Benzyl-Substituted N-Heterocyclic Carbene,Silver ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2010Siddappa Patil Abstract p -Methoxybenzyl-substituted and benzyl-substituted N-heterocyclic carbene (NHC) [(3a,c) and (6a,c)] precursors were synthesised from the reaction of 1H -imidazole (1a), 4,5-dichloro-1H -imidazole (1b), and 1H -benzimidazole (1c) with p -methoxybenzyl bromide (2) and benzyl bromide (5). These NHC precursors were then treated with silver(I) acetate to yield the NHC,silver complexes [1,3-bis(4-methoxybenzyl)imidazol-2-ylidene]silver(I) acetate (4a), [4,5-dichloro-1,3-bis(4-methoxybenzyl)imidazol-2-ylidene]silver(I) acetate (4b), [1,3-bis(4-methoxybenzyl)benzimidazol-2-ylidene]silver(I) acetate (4c), (1,3-dibenzylimidazol-2-ylidene)silver(I) acetate (7a), (1,3-dibenzyl-4,5-dichloroimidazol-2-ylidene)silver(I) acetate (7b), and (1,3-dibenzylbenzimidazol-2-ylidene)silver(I) acetate (7c), respectively. The NHC precursor 3c, four NHC,silver complexes 4c and 7a,c were characterised by single-crystal X-ray diffraction method. The preliminary antibacterial activity of all the compounds was studied against Gram-negative bacteria Escherichia coli, and Gram-positive bacteria Staphylococcus aureus using the Kirby,Bauer disk-diffusion method. Almost all the NHC,silver complexes have shown high antibacterial activity compared to the NHC precursors. In addition, the NHC,silver complexes had their cytotoxicity investigated through MTT-based preliminary in vitro testing on the Caki-1 cell lines in order to determine their IC50 values. NHC,silver complexes 4a,c and 7a,c were found to have IC50 values of 7.3 (+/,6), 12.7(+/,3), 25.2 (+/,5), 2.5 (+/,3), 10.8 (+/,4) and 12.5 (+/,4) ,M respectively on the Caki-1 cell line. [source] Structural, Spectroscopic, and Proton-Coupled Electron-transfer Behavior of Pyrazolyl-3,5-bis(benzimidazole)-Bridged Homo- and Heterochiral RuIIRuII, OsIIOsII, and OsIIRuII 2,2,-Bipyridine ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2010Sujoy Baitalik Abstract The homo- and heterobimetallic complexes [(bpy)2MII(H2pzbzim)M,II(bpy)2](ClO4)3·nH2O (1, 3, 5) and their corresponding deprotonated complexes [(bpy)2MII(pzbzim)M,II(bpy)2](ClO4)·nH2O (2, 4, 6) [where MII, M,II = Ru (1, 2) = Os (3, 4); MII = Os and M,II = Ru (3, 5); bpy = 2,2,-bipyridine; H3pzbzim = pyrazole-3,5-bis(benzimidazole)] were synthesized, separated to their heterochiral (a, ,,/,,) and homochiral (b, ,,/,,) diastereoisomers, and characterized by elemental analyses, ESI-MS, and 1H NMR spectroscopy. The X-ray structures of 1a, 3a, and 5a show the involvement of two pyridine rings of two bpy ligands in strong intramolecular nonbonded ,,, interaction. The occurrence of a C,H···, interaction between an aromatic C,H and the ,-cloud of a pyridine ring leads to strong electronic shielding of this proton (1H NMR). In all cases, the two diastereoisomers show practically no differences in their absorption spectra, redox potentials, and pK values. The large shifts in the E1/2 values to less positive potentials and substantial redshifts in the MLCT bands that occur on deprotonation of 1, 3, and 5 are energetically correlated. From the profiles of E1/2(1), (2) vs. pH over the pH range 1,12, the equilibrium constants and standard redox potentials for all the complex species in the metal oxidation states II·II, II·III, and III·III and the bridged ligand in the protonation states H2pzbzim,, Hpzbzim2,, and pzbzim3, have been evaluated. Using these values the bond dissociation free energies for the benzimidazole N,H bonds have been estimated. Spectroelectrochemical studies have been carried out for 1a, 3a, and 5a in the range 400,1100 nm. With stepwise oxidation of the metal centers replacement of MLCT bands by LMCT bands occur gradually with the observation of sharp isosbestic points. In the case of 1a, a band observed at ,max = 910 nm for the RuIIRuIII species has been ascribed to intervalence charge transfer (IVCT) transition. [source] Betaine Adducts of N-Heterocyclic Carbenes: Synthesis, Properties, and ReactivityEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009Lionel Delaude Abstract N-Heterocyclic carbenes (NHCs) form stable zwitterionicadducts with a range of heteroallenes, ketenes, and allenes. Although the first representatives of this class of inner salts were first investigated as far back as the 1960s, they have enjoyed a sustained interest from the chemical community over the years. Depending on the nature of their anionic moiety, NHC betaines display a very broad palette of reactivities and have found applications in various fields of organic synthesis and catalysis. In this Microreview, the synthesis, properties, and reactivity of NHC betaines are surveyed. The NHCs under consideration include ylidenes derived from imidazole, benzimidazole, imidazoline, thiazole, or triazole, and the heteroallenes investigated so far are carbon dioxide, carbon disulfide, isocyanates, isothiocyanates, and their selenium analogues. A historical background is provided for each type of adduct under consideration, but emphasis is placed mainly on developments that have appeared in the literature within the past few years. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] A Polymer-Bound Oxidovanadium(IV) Complex Prepared from an L -Cysteine-Derived Ligand for the Oxidative Amination of StyreneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2008Mannar R. Maurya Abstract The ligand H2sal-cys (I) derived from salicylaldehyde and L -cysteine has been covalently bonded to chloromethylated polystyrene cross-linked with 5,% divinylbenzene. Upon treatment with [VO(acac)2] in dimethylformamide (DMF) the polystyrene-bound ligand PS-H2sal-cys (II) gave the oxidovanadium(IV) complex, PS-[VO(sal-cys)·DMF] (1). The corresponding neat complex, [VO(sal-eta)]2 (2), has also been prepared similarly in methanol. These complexes have been characterised by IR, electronic, EPR spectroscopic studies, magnetic susceptibility measurements and thermal as well as scanning electron micrographs studies. Complex [VO(sal-eta)]2 exhibits a medium intensity band at 980 cm,1 in the IR spectrum due to ,(V=O) stretch. Broad features of the EPR spectrum for the neat complex along with magnetic susceptibility studies suggest the presence of antiferromagnetic exchange interaction between two vanadium centers in close proximity. Both complexes catalyze the oxidative amination of styrene, in mild basic conditions, with secondary amines (diethylamine, imidazole, and benzimidazole) and gave a mixture of two aminated products in good yields. Amongst the two aminated products, the anti-Markovnikov product is favored over the Markovnikov one due to the steric hindrance posed by the secondary amines. The polymer-anchored heterogeneous catalyst is free from leaching during catalytic action and recyclable.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Access to 3-Methyl-4-methylene- N -tosylpyrrolidine and 3,4-DimethylN -tosylpyrroline by Ruthenium-Catalyzed Cascade Cycloisomerization/Isomerization ReactionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2004Ismail Özdemir Abstract New RuCl2(benzimidazole)(arene) complexes have been prepared. Upon reaction with 1,1-diphenylprop-2-ynol they generate catalyst precursors which perform the cycloisomerization of diallyltosylamide into 3-methyl-4-methylene- N -tosylpyrrolidine. The presence of N -(2,4,6-trimethylbenzyl)benzimidazole as ligand leads to a subsequent isomerization and gives the 3,4-dimethyl- N -tosylpyrroline. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Structural, Photophysical and Chiro-Optical Properties of Lanthanide Complexes with a Bis(benzimidazole)pyridine-Based Chiral LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2003Gilles Muller Abstract The neutral LnIII 1:1 nitrato complexes with the chiral ligand 2,6-bis(1- S -neopentylbenzimidazol-2-yl)pyridine (L11) have been synthesised and their stability constants measured in acetonitrile (log K1 = 4.0,6.4). The crystal and molecular structure of [Eu(NO3)3(L11)(MeCN)] shows the typical meridional planar coordination of L11 to the metal ion and low symmetry of the coordination polyhedron. The influence of the steric hindrance generated by the substituent at R2 on the crystal packing and bond lengths is discussed. Photophysical measurements show that ligand L11 induces a 3,,*-to-Ln energy-transfer process in the EuIII complex, while the TbIII compound is ten times less luminescent. Addition of a second molecule of L11 to give [Ln(ClO4)2(L11)2]+ leads to a large quenching of the EuIII luminescence (140-fold) due to several factors: a less efficient 1,,*,3,,* transfer (ca. fourfold), a smaller intrinsic quantum yield QEu (ca. threefold), and a substantially less efficient ligand-to-metal transfer (ca. 12-fold). In the case of the TbIII complex, the decrease in the energy of the triplet state reduces further the TbIII emission through increased back transfer. The specific rotary dispersion of the 1:1 and 1:2 complexes points to the chirality of the complexes arising mainly from the ligand, while the circularly polarized luminescence of these complexes with EuIII and TbIII displays a weak effect, pointing to a small diastereomeric excess in solution. Altogether, this study demonstrates that electronic, thermodynamic and photophysical properties of lanthanide complexes with aromatic terdentate ligands can be tuned by modifying the number and the arrangement of the ligands, as well as their substituents, particularly those in the R2 and R3 positions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Medium Effect on the Reaction of N -Butyl-2,4,6-trinitroaniline with NaOH,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2007María Laura Salum Abstract The kinetics of the reaction of N -butyl-2,4,6-trinitroaniline (3) with NaOH have been studied in 10 and 60,% 1,4-dioxane/H2O at 25 °C. In both cases, several processes were observed. In 10,% 1,4-dioxane/H2O the only product formed was 2,4,6-trinitrophenol (4), whereas in 60,% 1,4-dioxane/H2O a mixture of 4 and 5,7-dinitro-2-propyl-1H -benzimidazole 3-oxide (5) was observed in ratios that depend on the HO, concentration. A mechanism involving the formation of , complexes through the addition of one or two HO, anions to unsubstituted ring positions is proposed for 2,4,6-trinitrophenol formation. The presence of these complexes was confirmed by NMR studies in 60,% [D8]1,4-dioxane/D2O. The mechanism suggested for the formation of the N -oxide includes the cyclization of an N -alkylidene-2-nitrosoaniline-type intermediate as the rate-determining step. The decrease in solvent polarity produces a decrease in the observed rate constant for the formation of 4 of about one order of magnitude making the cyclization reaction a competitive pathway. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Second-Generation Inhibitors for the Metalloprotease Neprilysin Based on Bicyclic Heteroaromatic Scaffolds: Synthesis, Biological Activity, and X-Ray Crystal-Structure AnalysisHELVETICA CHIMICA ACTA, Issue 4 2005Stefan Sahli A new class of nonpeptidic inhibitors of the ZnII -dependent metalloprotease neprilysin with IC50 values in the nanomolar activity range (0.034,0.30,,M) were developed based on structure-based de novo design (Figs.,1 and 2). The inhibitors feature benzimidazole and imidazo[4,5- c]pyridine moieties as central scaffolds to undergo H-bonding to Asn542 and Arg717 and to engage in favorable , - , stacking interactions with the imidazole ring of His711. The platform is decorated with a thiol vector to coordinate to the ZnII ion and an aryl residue to occupy the hydrophobic S1, pocket, but lack a substituent for binding in the S2, pocket, which remains closed by the side chains of Phe106 and Arg110 when not occupied. The enantioselective syntheses of the active compounds (+)- 1, (+)- 2, (+)- 25, and (+)- 26 were accomplished using Evans auxiliaries (Schemes,2, 4, and 5). The inhibitors (+)- 2 and (+)- 26 with an imidazo[4,5- c]pyridine core are ca. 8 times more active than those with a benzimidazole core ((+)- 1 and (+)- 25) (Table,1). The predicted binding mode was established by X-ray analysis of the complex of neprilysin with (+)- 2 at 2.25-Å resolution (Fig.,4 and Table,2). The ligand coordinates with its sulfanyl residue to the ZnII ion, and the benzyl residue occupies the S1, pocket. The 1H -imidazole moiety of the central scaffold forms the required H-bonds to the side chains of Asn542 and Arg717. The heterobicyclic platform additionally undergoes ,-, stacking with the side chain of His711 as well as edge-to-face-type interactions with the side chain of Trp693. According to the X-ray analysis, the substantial advantage in biological activity of the imidazo-pyridine inhibitors over the benzimidazole ligands arises from favorable interactions of the pyridine N-atom in the former with the side chain of Arg102. Unexpectedly, replacement of the phenyl group pointing into the deep S1, pocket by a biphenyl group does not enhance the binding affinity for this class of inhibitors. [source] Phosphorus heterocycles from 2-(2-hydroxyphenyl)-1H -benzimidazoleHETEROATOM CHEMISTRY, Issue 4 2004Julio Hernández-Díaz Sixteen different P(III) and P(V) heterocycles derived from 2-(2-hydroxyphenyl)-1H-benzimidazole (1) are reported. In these heterocycles the phosphorus atom is part of a six-membered unsaturated ring. They were mainly studied by multinuclear NMR. The X-ray diffraction of 3,4- benzimidazole-5,6-benzo-2-dimethylamino-2-seleno- 1,3,2-oxazaphosphorinane is reported. Phosphoranes derived from 1 and 3,5-di-tert-butylcatechol, and bearing Cl, NMe2, or phenyl as substituent at phosphorus are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:307,320, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20021 [source] A combined computational and experimental approach for investigating a hydrogen-bonded supermolecular compound comprising benzimidazole and malonic acidINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2008Fang-Fang Jian Abstract A hydrogen-bonded tetramer supramolecular motif of 2:2 benzimidazole (BIZ) and malonic acid (MLA) has been synthesized and characterized by elemental analysis, infrared (IR), and X-ray single crystal diffraction. Thermal stability analyses demonstrate that this supramolecular adduct is a new material and it is not the ordinary superposition of the original monomers. Density function theory (DFT) calculations for the models of dimers, trimers, and tetramer comprising BIZ and MLA have been carried out at B3LYP/6-31G* and PBE1PBE/6-31G* levels of theory, respectively. By comparing the calculated results with the experiments (single crystal structure, IR spectra, and thermal analysis) and based on the statistic thermodymnamic calculations, it is concluded that the dimers cannot exist at room temperature and the tetramer can simulate the title supramolecular complex better than the two trimers. Further studies on the model of tetramer indicate that the hydrogen bond of N···HO is stronger than that of O···HN. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Application of the MTD-PLS method to heterocyclic dye,cellulose interactionsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2007Ludovic Kurunczi Abstract The minimal topologic difference method in a projection in latent structures variant procedure was applied to a series of heterocyclic monoazo dyes of the type: RC6H4N = NY (R = benzothiazole, benzimidazole, N-containing aromatic pentacycles; Y = , acid, H acid, chromotropic acid, R acid). A statistically excellent model was obtained: RX2 = 0.625, RY2 = 0.940, Q2 = 0.822. The analysis of this model reveals the nature of dye,fiber interactions, which determine the dye affinity. Hydrophobic character in the R group and H-bond donor groups in a specific Y substitution position augment the dye affinity for cellulose. An increase of the polar nature of atoms in R depletes the affinity. Also some lateral substituents belonging to the Y coupling components suffer steric hindrance, and their presence is detrimental for the affinity. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] A Lutidine-Bridged Bis-Perimidinium Salt: Synthesis and Application as a Precursor in Palladium-Catalyzed Cross-Coupling ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Tao Tu Abstract A novel lutidine-bridged bis-perimidinium dibromide 3 was synthesized in quantitative yield from cheap commercial starting materials. The bisylidene prepared therefrom in situ upon deprotonation is a potent precatalyst in palladium-catalyzed Heck and Suzuki cross-coupling reactions under aerobic conditions, and is efficient even with a ppm scale catalyst loading. Its stronger ,-donor character is held to be responsible for its superior catalytic performance compared with imidazole- and benzimidazole-based analogues bearing the same skeleton precursors. [source] Thermal aging of a blend of high-performance fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Carlos Arrieta Abstract The focus of this work is the study of the thermal aging of high-performance fibers used in the making of fire protective garments. Accelerated thermal aging tests were carried out on fabric samples made up of a blend of Kevlar® (poly p -phenylene terephthalamide) and PBI (poly benzimidazole) staple fibers, as well as on yarns pulled from this fabric, by means of exposure to elevated temperatures, comprised between 190°C and 320°C. All samples underwent loss of breaking force retention. The material thermal life, defined as the time required for the fibers to attain a 50% reduction of the original breaking force, ranged between a dozen of days at the lowest exposure temperature, to less than an hour at the highest. Breaking force data were fitted using the Arrhenius model following two different approaches, namely the extrapolated thermal life value and the shift factors yielded by the time-temperature superposition (TTS). The Arrhenius model seemed to describe appropriately the overall aging process, as inferred from the excellent fit obtained when using both approaches, although activation energies provided from both approaches are different. To follow the chemical evolution of the material with thermal aging, Fourier-transform infrared (FTIR) analyses were conducted. The qualitative analysis of the FTIR spectra showed little evidence of chemical changes between the aged and the nonaged samples, indicating either that the aging process carries on without significant modification of the chemical structure of the fibers, or that FTIR is not an appropriate method to spot such a modification. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Synthesis of novel pyrazolo[3,4- d]pyridazine, pyrido[1,2- a]benzimidazole, pyrimido[1,2- a]benzimidazole and triazolo[4,3- a]pyrimidine derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2008Mohamed R. Shaaban 4-Acetyl-5-methyl-1-phenyl-1H -pyrazole reacts with dimethylformamide dimethylacetal (DMF-DMA) to afford the corresponding (E)1-(5-methyl-1-phenyl-1H -pyrazol-4-yl)-3-(N,N -dimethylamino)-2-propen-1-one. The latter product undergoes regioselective 1,3-dipolar cycloaddition with nitrilimines and nitrile oxides to afford the novel 3-aroyl-4-(5-methyl-1-phenyl-1H -pyrazol-4-yl)carbonyl-1-phenylpyrazole and 3-aroyl-4-(5-methyl-1-phenyl-1H -pyrazol-4-yl)carbonyl isoxazole derivatives, respectively. It reacts also with 1H -benzimidazole-2-acetonitrile, 2-aminobenzimidazole and 3-amino-1,2,4-triazole to afford the novel pyrido[1,2- a]benzimidazole, pyrimido[1,2- a]benzimidazole and the triazolo[4,3- a]pyrimidine derivatives, respectively. The reaction of 3-aroyl-4-(5-methyl-1-phenyl-1H -pyrazol-4-yl) carbonyl-1-phenylpyrazole derivatives with hydrazine hydrate led to a new pyrazolo[3,4- d]pyridazine derivatives. [source] Regioselective synthesis of some novel pyrazoles, isoxazoles, pyrazolo[3,4- d]pyridazines and isoxazolo[3,4- d]pyridazines pendant to benzimidazoleJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2007Mohamed R. Shaaban 2-Acetyl-1-methyl-1H -benzimidazole reacts with dimethylformamide-dimethyl-acetal (DMF-DMA) to afford the corresponding E -1-(1-methyl-1H -benzimidazol-2-yl)-3- N,N -dimethylaminoprop-2-enone. The latter compound reacts regioselectively with some nitrilimines and nitrile oxides to afford the corresponding pyrazole and isoxazole derivatives, respectively. These reaction products react with hydrazine hydrate to give the novel pyrazolo[3,4- d]pyridazine and isoxazolo[3,4- d]pyridazine derivatives, respectively. [source] | ||||||||||||||||||||||||||||||||||