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Very High Yield (very + high_yield)
Selected AbstractsMetal Complexes of 4,11-Dimethyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) , Thermodynamic and Formation/Decomplexation Kinetic StudiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009Ivona Svobodová Abstract The macrocyclic ligand with two methylphosphonic acid pendant arms, 4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (1,8-H4Me2te2p, H4L3), was synthesized by a new simple approach. The product of the reaction of quarternized formaldehyde cyclam aminal with the sodium salt of diethyl phosphite was hydrolyzed to give a very high yield of the title ligand. The (H6L3)2+ cation in the solid state is protonated on all ring nitrogen atoms and on each phosphonate group. In the solid-state structure of [Cu(H3L3)][Cu(H2L3)]PF6·3H2O, neutral as well as positively charged complex species are present. Molecular structures of both species are very similar having the copper(II) ion in a coordination environment between square-pyramidal and trigonal-bipyramidal arrangements (, = 0.43 and 0.48) with one pendant arm non-coordinated. The ligand forms stable complexes with transition-metal ions showing a high selectivity for divalent copper atoms. The formation of complexes of the ligand with CuII, ZnII and CdII is fast, confirming the acceleration of complexation due to the presence of the strongly coordinating pendant arms. Acid-assisted decomplexation is fast for all three metal ions. Therefore, the copper(II) complex is not suitable for medicinal applications employing copper radioisotopes, but the title ligand motive can be employed in copper(II) separation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Regiospecific Synthesis of 4-Deoxy- D - threo -hex-3-enopyranosides by Simultaneous Activation,Elimination of the Talopyranoside Axial 4-OH with the NaH/Im2SO2 System: Manifestation of the Stereoelectronic EffectEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2006Emanuele Attolino Abstract A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-,- D - threo -hex-3-enopyranosides has been developed. The process involves a simultaneous activation,elimination of the OH-4 group of ,- D -talopyranosides and 2-acetamido-2-deoxy-,- D -talopyranosides, mediated by the NaH/N,N,-sulfuryldiimidazole system at ,30 °C. The same reaction applied on the analogous ,- D -galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri- O -benzyl-,- D -talo- and ,- D -galactopyranosides, the corresponding 4- O -imidazylates can be isolated by quenching the reactions at ,30 °C. Upon warming these crude products to room temperature, the ,- talo -4- O -imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its ,- galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the stereoelectronic effect exerted, exclusively in talo -configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3),H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A Simple Sol,Gel Synthesis of Superconducting MgB2 Nanowires,ADVANCED MATERIALS, Issue 14 2006M. Nath Superconducting MgB2 nanowires have been synthesized in a very high yield by a simple soft-chemical approach combining sol-gel chemistry and pyrolysis techniques (see main image in the figure; scale bar: 10,,m). The long thin nanowires show a superconducting transition temperature, Tc, of ca.,39,K, as shown in the magnetization curve in the inset of the figure. [source] Synthesis of pyridazine derivatives through the unexpected intermediate 5-amino- 4-cyano -2,3-dihydro-furan-2,3-disulfonic acid disodium saltJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2003Barbara Cacciari An unexpected compound (5-amino-4-cyano-2,3-dihydrofuran-2,3-disulfonic acid disodium salt, 4) was isolated from the reaction of glyoxale bis hydrogen sulfite disodium salt with malononitrile. Its structure was undoubtly identified through crystal structure analysis. Compound 4 was highly stable and it was isolated easily and in a very high yield. Its reactivity was studied in the reactions with some hydrazine derivatives in order to obtain different pyridazine analogs. [source] Human papillomavirus L1 protein expressed in tobacco chloroplasts self-assembles into virus-like particles that are highly immunogenicPLANT BIOTECHNOLOGY JOURNAL, Issue 5 2008Alicia Fernández-San Millán Summary Cervical cancer is the second most prevalent cancer in women worldwide. It is linked to infection with human papillomavirus (HPV). As the virus cannot be propagated in culture, vaccines based on virus-like particles have been developed and recently marketed. However, their high costs constitute an important drawback for widespread use in developing countries, where the incidence of cervical cancer is highest. In a search for alternative production systems, the major structural protein of the HPV-16 capsid, L1, was expressed in tobacco chloroplasts. A very high yield of production was achieved in mature plants (~3 mg L1/g fresh weight; equivalent to 24% of total soluble protein). This is the highest expression level of HPV L1 protein reported in plants. A single mature plant synthesized ~240 mg of L1. The chloroplast-derived L1 protein displayed conformation-specific epitopes and assembled into virus-like particles, visible by transmission electron microscopy. Furthermore, leaf protein extracts from L1 transgenic plants were highly immunogenic in mice after intraperitoneal injection, and neutralizing antibodies were detected. Taken together, these results predict a promising future for the development of a plant-based vaccine against HPV. [source] Thermally stable and high molecular weight poly(propylene carbonate)s from carbon dioxide and propylene oxide,POLYMER INTERNATIONAL, Issue 10 2002Q Zhu Abstract The copolymerization of carbon dioxide and propylene oxide was carried out to afford alternating poly(propylene carbonate) in high yield. Thermal stable and high molecular weight copolymers were successfully obtained by optimizing the reaction conditions. The catalyst used was zinc glutarate supported on a perfluorinated compound containing 7,12 carbon atoms. Copolymerization parameters, such as the ratio of propylene oxide to catalyst, stirring strength and purity of propylene oxide, were studied. The alternating copolymer with a molecular weight of 56,100 in a very high yield (126,g polymer per gram of catalyst) was achieved, which is the highest yield ever reported. The thermal and mechanical properties of the alternating PPC copolymer were examined by the means of modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA) and tensile test. MDSC and TGA results showed that the alternating PPC copolymer exhibits an extremely high glass transition temperature (maximum 46.46,°C) and decomposition temperature (255.8,°C) when compared to those values reported in literature. Tensile test revealed that thin film of alternating PPC copolymer exhibits superior mechanical strength. © 2002 Society of Chemical Industry [source] Studies on the synthesis and thermal properties of alkoxysilane-terminated organosilicone dendrimersAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Kanak Saxena Abstract Silicone core dendrimers bearing terminal dialkoxy and trialkoxy silane groups were prepared in a three-step synthesis. Initially, the SiH terminated multifunctional silicone dendrimer, i.e. tetrakis(dimethylsiloxy)silane, was prepared by the reaction of tetraethoxysilane and dimethylethoxysilane. Tetrakis(dimethylsiloxy)silane on reaction with allylglycidylether in the presence of Speier's catalyst under pressure (100 psi) yielded epoxy-terminated dendrimer in very high yield (95%). The epoxy-terminated dendrimer was reacted with aminopropylalkoxysilanes to yield the next-generation dendrimer bearing dialkoxy and trialkoxy silane groups. The dendrimers were characterized by the usual physico-chemical techniques, i.e. elemental analysis, FT-IR, 1H, 13C and 29Si NMR. Thermal studies (Thermogravimetric analysis and Thermomechanical analysis) of the alkoxy terminated dendrimers and its cured products were also carried out. Copyright © 2010 John Wiley & Sons, Ltd. [source] Very High Yield Growth of Vertically Aligned Single-Walled Carbon Nanotubes by Point-Arc Microwave Plasma CVD,CHEMICAL VAPOR DEPOSITION, Issue 3 2005F. Zhong A very high yield, selective growth of dense, vertically aligned single-walled carbon nanotubes (SWNTs) has been demonstrated for the first time on Si substrates with a sandwich-like coating structure of Al2O3/Fe/Al2O3 at a low (600,°C) temperature by point-arc microwave plasma CVD. The SWNT film thickness increases continuously with the growth time, suggesting an almost unlimited life time for the catalyst. A film thickness of 420,,m, and production yield of SWNTs to catalyst of about 770,000,% can be achieved within 2,h. [source] Synthesis of ansa- [n]Silacyclopentadienyl,Cycloheptatrienyl,Chromium Complexes (n = 1, 2): Novel Precursors for Polymers Bearing Chromium in the BackboneCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2006Alexandra Bartole-Scott Abstract Reaction of [(,5 -C5H4Li)(,7 -C7H6Li)Cr],tmeda with a variety of dialkyl(dichloro)silanes in aliphatic solvents afforded the corresponding [1]silatrochrocenophanes. Structural characterization by X-ray diffraction analysis of the [1]silatrochrocenophanes bearing Me2Si, (iPr)2Si, and silacyclobutane bridges revealed tilt angles , of 15.56(12)°, 15.8(1)°, and 16.33(17)°, respectively. Analogously, a [2]silatrochrocenophane (6) was prepared in excellent yield by reaction of [(,5 -C5H4Li)(,7 -C7H6Li)Cr],tmeda with 1,2-dichloro-1,1,2,2-tetramethyldisilane. This complex also was characterized structurally and exhibited a tilt angle , of 2.60(15)°. The [1]silatrochrocenophane bearing the Me2Si bridge underwent facile and regioselective carbon,silicon bond cleavage with [Pt(PEt3)4] to give a very high yield of an oxidative addition product. The ring-opening polymerization of these novel [1]silatrochrocenophanes afforded ring-opened chromium-based polymers. [source] An Efficient Combined Electrochemical and Ultrasound Assisted Synthesis of Imidazole-2-ThionesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Marta Feroci Abstract The electrochemical reduction of 1,3-dialkylimidazolium ionic liquids gave the corresponding N-heterocyclic carbenes that, after reaction with elemental sulfur and ultrasound irradiation, yielded 1,3-dialkylimidazole-2-thiones in very high yields. The reaction is very clean, produces no side-products and avoids the use of any other added reagent. [source] Highly Enantio- and Diastereoselective Inverse Electron Demand Hetero-Diels,Alder Reaction using 2-Alkenoylpyridine N -Oxides as Oxo -HeterodienesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Santiago Barroso Abstract A general catalytic inverse electron demand hetero-Diels Alder reaction for 2-alkenoylpyridine N -oxides is presented. 2-Alkenoylpyridine N -oxides react very efficiently with alkenes in the presence of bisoxazolidine-copper(II) [BOX-Cu(II)] complexes to give chiral dihydropyrans bearing a pyridine ring at the 6-position with very high yields and excellent diastereo- and enantioselectivity. These heterodienes exhibited higher reactivity and enantioselectivity than the corresponding non-oxidized 2-alkenoylpyridines. [source] Activation of Elemental Sulfur by Electrogenerated Cyanomethyl Anion: Synthesis of Substituted 2-Aminothiophenes by the Gewald ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2008Marta Feroci Abstract The activation of elemental sulfur (S8) has been achieved by means of electrogenerated cyanomethyl anion [easily obtained by galvanostatic reduction from acetonitrile/tetraethylammonium hexafluorophosphate (MeCN-Et4NPF6)]. The "activated" sulfur reacted with ylidenemalononitriles to give substituted 2-aminothiophenes in very high yields. This variation of the Gewald reaction has been carried out using only catalytic amounts of electricity and supporting electrolyte. A proposed mechanism for the interaction between S8 and cyanomethyl anion is described. [source] Synthesis and characterization of end-functionalized carbosiloxane dendrimersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2002Chungkyun Kim Abstract Dendritic carbosilanes containing 48 and 96 functional groups on the periphery were prepared. The reaction of the fourth and fifth parent dendritic generations (G4-48Cl and G5-96Cl) with alcohol [9-anthracene methanol, 8-hydroxyquinoline, 4-hydroxyazobenzene, 2-hydroxymethylanthraquinone, and 5-(2-hydroxyethyl)-4-methylthiazole] in the presence of 1,1,2,2-tetramethylethyenediamine produced end-functionalized dendrimers with very high yields. The polydispersity indices of the prepared dendrimers revealed unchanged narrow values between the fourth and fifth generations. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 326,333, 2002 [source] | |||||||||||||