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Tetrabutylammonium Bromide (tetrabutylammonium + bromide)
Selected AbstractsTetrabutylammonium Bromide: An Efficient Medium for Dimethoxytritylation of the 5,-Hydroxyl Function of Nucleosides.CHEMINFORM, Issue 51 2004Ali Khalafi-Nezhad Abstract For Abstract see ChemInform Abstract in Full Text. [source] Molten Salt as a Green Reaction Medium: Efficient and Chemoselective Dithioacetalization and Oxathioacetalization of Aldehydes Mediated by Molten Tetrabutylammonium Bromide.CHEMINFORM, Issue 38 2004Brindaban C. Ranu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Evaluating Enzyme Cascades for Methanol/Air Biofuel Cells Based on NAD+ -Dependent EnzymesELECTROANALYSIS, Issue 7-8 2010Abstract Previous work by the group has entailed encapsulating enzymes in polymeric micelles at bioelectrode surfaces by utilizing hydrophobically modified Nafion membranes, which are modified in order to eliminate the harsh acidity of Nafion while tailoring the size of the polymer micelles to optimize for the encapsulation of an individual enzyme. This polymer encapsulation has been shown to provide high catalytic activity and enzyme stability. In this study, we employed this encapsulation technique in developing a methanol/air biofuel cell through the combined immobilization of NAD+ -dependent alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AldDH) and formate dehydrogenase (FDH) within a tetrabutylammonium bromide (TBAB) modified Nafion to oxidize methanol to carbon dioxide with poly(methylene green) acting as the NADH electrocatalyst electropolymerized on the surface of the electrode. The methanol biofuel/air cell resulted in a maximum power density of 261±7.6,,W/cm2 and current density of 845±35.5,,A/cm2. This system was characterized for the effects of degree of oxidation, temperature, pH, and concentration of fuel and NAD. [source] Efficient Copper(I)-Catalyzed C,S Cross Coupling of Thiols with Aryl Halides in WaterEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2008Laxmidhar Rout Abstract CuI efficiently catalyzes the C,S cross coupling of thiols with aryl halides in the presence of tetrabutylammonium bromide in water. The reactions with aryl thiols that have electron-withdrawing and -donating substituents are comparable and afford C,S cross-coupling products in high yield. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Fluorapatite-Supported Palladium Catalyst for Suzuki and Heck Coupling Reactions of HaloarenesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2007M. Lakshmi Kantam Abstract A fluorapatite-supported palladium catalyst (PdFAP) was synthesized by treatment of fluorapatite (prepared by incorporating the basic species fluoride ion into apatite in situ by co-precipitation) with bis(benzonitrile)palladium(II) chloride in acetone. The catalyst displayed high catalytic activity for Suzuki coupling of aryl iodides and bromides with boronic acids at room temperature and chloroarenes at 130,°C in the presence of tetrabutylammonium bromide to give biaryls in excellent yields. Heck olefination of chloroarenes was also successfully carried out by this catalyst. PdFAP was recovered quantitatively by simple filtration and reused with consistent activity. PdFAP was well characterized by XRD, FTIR, XPS, ICP-AES, CO2 TPD and CHN elemental analysis. [source] Liquid-Liquid-Liquid Phase Transfer Catalysis: A Novel and Green Concept for Selective Reduction of Substituted NitroaromaticsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Ganapati Abstract The selective reduction of nitroaromatics to the corresponding amines is an important transformation since many aromatic amines exhibit biological activities and find a multitude of industrial applications, being intermediates for the synthesis of dyes, pharmaceuticals and agrochemicals. A variety of nitroaromatics dissolved in organic solvents was reduced by using aqueous sodium sulfide, and tetrabutylammonium bromide (TBAB) as the phase transfer catalyst by choosing appropriate concentrations which resulted in three immiscible liquid phases. Compared to L-L PTC, the L-L-L PTC offers much higher rates of reaction, better selectivities and repeated use of catalyst. The selectivities for the desired products were 100%. [source] Synthesis of new photoresponsive polyesters containing norbornadiene residues by the polyaddition of donor,acceptor norbornadiene dicarboxylic acid diglycidyl ester with dicarboxylic acids and their photochemical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2001Yousuke Konno Abstract A donor,acceptor norbornadiene derivative, 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid diglycidyl ester (D,A NDGE), was synthesized by the reaction of the cesium salt of 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid with epibromohydrin in N -methyl- pyrrolidone (NMP). The polyaddition reactions of D,A NDGE with certain dicarboxylic acids were carried out with tetrabutylammonium bromide as a catalyst in NMP, producing corresponding polyesters containing D,A norbornadiene (NBD) residues in the main chain in fair to good yields. The photoisomerization of the D,A NBD residues in the polyesters proceeded very smoothly, forming the corresponding quadricyclane groups. The photoreactivities of the D,A NBD residues in the polymer were 50 times higher than those of the NBD residues in the film state and 60 times higher than those in a tetrahydrofuran solution. The stored energy in the quadricyclane groups of the polymers was about 45,55 kJ/mol according to differential scanning calorimetry analysis of the irradiated polymer films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2683,2690, 2001 [source] Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium,Salen ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010William Clegg Prof. Abstract The development of bimetallic aluminium,salen complexes [{Al(salen)}2O] as catalysts for the synthesis of cyclic carbonates (including the commercially important ethylene and propylene carbonates) from a wide range of terminal epoxides in the presence of tetrabutylammonium bromide as a cocatalyst is reported. The bimetallic structure of one complex was confirmed by X-ray crystallography. The bimetallic complexes displayed exceptionally high catalytic activity and in the presence of tetrabutylammonium bromide could catalyse cyclic carbonate synthesis at atmospheric pressure and room temperature. Catalyst-reuse experiments demonstrated that one bimetallic complex was stable for over 60 reactions, though the tetrabutylammonium bromide decomposed in situ by a retro-Menschutkin reaction to form tributylamine and had to be regularly replaced. The mild reaction conditions allowed a full analysis of the reaction kinetics to be carried out and this showed that the reaction was first order in aluminium complex concentration, first order in epoxide concentration, first order in carbon dioxide concentration (except when used in excess) and unexpectedly second order in tetrabutylammonium bromide concentration. Further kinetic experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl bromide to reconvert the tributylamine into tetrabutylammonium bromide resulted in inhibition of the reaction. The reaction kinetics also indicated that no kinetic resolution of racemic epoxides was possible with this class of catalysts, even when the catalyst was derived from a chiral salen ligand. However, it was shown that if enantiomerically pure styrene oxide was used as substrate, then enantiomerically pure styrene carbonate was formed. On the basis of the kinetic and other experimental data, a catalytic cycle that explains why the bimetallic complexes display such high catalytic activity has been developed. [source] Tetraalkylammonium-Free Heck Olefination of Deactivated Chloroarenes by Using a Macrocyclic Catalyst PrecursorCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2010Christoph Röhlich Dipl.-Chem. Palladium reservoir: A macrocyclic dinuclear Pd complex is applied to the Heck coupling of strongly deactivated aryl chlorides. The complex serves as a very stable precatalyst, which releases active Pd under normal reaction conditions (see scheme). The controlled release and recapture of active Pd provides sufficient stabilization to supersede the addition of tetrabutylammonium bromide. Quantitative conversions can be achieved under additive-free conditions. [source] An Environmentally Benign Access to Dimethylated 1,6-Dihydropyrimidines Using Dimethyl Carbonate as Methylating Agent under MicrowaveCHINESE JOURNAL OF CHEMISTRY, Issue 2 2008Xi-Cun WANG Abstract An environmentally benign procedure for dimethylated 1,6-dihydropyrimidines has been developed by the reaction of 1,2,3,4-tetrahydropyrimidine-2-thiones with dimethyl carbonate, a non-toxic and environmentally friendly reagent. The methylation of 1,2,3,4-tetrahydropyrimidine-2-thione was promoted by MgO and tetrabutylammonium bromide (TBAB) under microwave. This protocol avoids the use of strong bases and highly toxic methylating agents such as methyl halide or dimethyl sulfate. Additionally, the possible role of MgO/TBAB in the reaction was also presented. [source] Highly Efficient Pd/C-Catalyzed Suzuki Coupling Reaction of p -(un)Substituted Phenyl Halide with (p -Substituted phenyl) Boronic AcidCHINESE JOURNAL OF CHEMISTRY, Issue 8 2007Ming-Gang Hu Abstract A highly efficient Pd/C-catalyzed ligandless, heterogeneous Suzuki reaction of p -(un)substituted phenyl halide with (p -substituted phenyl)boronic acid in DMF/H2O solvent in a short reaction time (0.5 h) at 75 °C was developed. The key for such a catalytic system was the addition of 1 equivalent of tetrabutylammonium bromide. A wide variety of substituents can be tolerated and high yields of cross coupling products were achieved. The palladium catalyst can be easily recovered and reused without significantly decreasing its efficiency. [source] | ||||||||||||||||||||||