bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalysis with Soluble Hybrids of Highly Branched Macromolecules with Palladium Nanoparticles in a Continuously Operated Membrane Reactor
Authors: Sablong Rafael , Schlotterbeck Ulf , Vogt Dieter , Mecking Stefan 
Published: March 2003

AbstractThe continuous recovery and recycling of soluble metal nanoparticles by means of ultrafiltration is described, employing hybrids of palladium nanoparticles with highly branched amphiphilic polyglycerol as a catalyst for cyclohexene hydrogenation as a model reaction. In a continuously operated membrane reactor a productivity of 29000 TO over 30 exchanged reactor volumes was observed for nanoparticles of 2.2 nm size, with a maximum rate of 1200 TO h−1. Catalysis by soluble metal complexes can be excluded. After 30 hours of operation, some decrease in activity is observed which is due to deposition of palladium on the ultrafiltration membrane, however this material does not contribute to catalytic activity.
Phenol and Organic Bases Co‐Catalyzed Chemical Fixation of Carbon Dioxide with Terminal Epoxides to Form Cyclic Carbonates
Authors: Shen Yu‐Mei , Duan Wei‐Liang , Shi Min 
Published: March 2003

AbstractPhenol can efficiently catalyze the reactions of terminal epoxides with carbon dioxide in the presence of catalytic amounts of various organic bases such as 4‐dimethylaminopyridine (DMAP), pyridine, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene, and triethylamine to give the corresponding five‐membered cyclic carbonate in high yields (initial pressure 3.57 MPa; reaction temperature 120 °C). p‐Methoxyphenol with DMAP is the best combination to give the cyclic carbonate in the highest yield.
Catalytic Carbon‐Fluorine Bond Activation with Monocoordinated Nickel‐Carbene Complexes: Reduction of Fluoroarenes
Authors: Kuhl Sébastien , Schneider Raphaël , Fort Yves 
Published: March 2003

AbstractMonocoordinate nickel/N‐heterocyclic carbene complexes reveal unexpected reactivity towards aryl fluorides. Defluorination reactions were efficiently performed with a β‐hydrogen‐containing alkoxide (3 equiv.) in the presence of 3 mol % of [1:1] Ni(0)/IMes⋅HCl catalyst (IMes=1,3‐dimesitylimidazol‐2‐ylidene).
Asymmetric Synthesis with N‐Heterocyclic Carbenes. Application to the Copper‐Catalyzed Conjugate Addition
Authors: Alexakis Alexandre , Winn Caroline L. , Guillen Frederic , Pytkowicz Julien , Roland Sylvain , Mangeney Pierre 
Published: March 2003

AbstractChiral N‐heterocyclic carbenes are good ligands for the copper‐catalyzed conjugate addition of dialkylzinc reagents to various Michael acceptors. With as little as 4% of chiral ligand, the enantioselectivity may reach 93% on cycloheptenone.
Efficient and Eco‐Friendly Process for the Synthesis of Bis(1H‐indol‐3‐yl)methanes using Ionic Liquids
Authors: Yadav J. S. , Reddy B. V. S. , Sunitha S. 
Published: March 2003

AbstractIndoles react smoothly with carbonyl compounds in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF4) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF6) ionic liquids under mild reaction conditions to afford the corresponding bis‐indolylmethanes in excellent yields. These ionic liquids can be recovered and recycled in subsequent reactions without any apparent loss of activity.
Synthesis of Functionalised Phenylalanines Using Rhodium Catalysis in Water
Authors: Chapman Christopher J. , Frost Christopher G. 
Published: March 2003

AbstractThe efficient synthesis of substituted phenylalanine‐type amino acids using a rhodium‐catalysed, conjugate addition of arylboronic acids is described. The reactions are run in water and use a low loading (0.5 mol %) of rhodium catalyst.
Catalytic Asymmetric Alkylation in Water in the Presence of Surfactants
Authors: Sinou Denis , Rabeyrin Cedric , Nguefack Christelle 
Published: March 2003

AbstractAsymmetric palladium‐catalyzed alkylation of 1,3‐diphenyl‐2‐propenyl acetate with dimethyl malonate occurs in water in the presence of surfactants and a base. The efficiency as well as the enantioselectivity of the coupling reaction depend strongly on the nature and the concentration of the surfactant. The highest yield and enantioselectivity (up to 91%) was obtained using Binap as the ligand in the presence of a cationic surfactant, while neutral or zwitterionic surfactants gave poorer results; anionic surfactants gave no reaction at all. The best results were obtained using Na2CO3, NaHCO3, or K2CO3, among the bases used. The highest enantioselectivities were obtained when the reaction was performed in the presence of chiral atropoisomeric diphosphines such as Binap, Biphemp, or MeOBiphep. A supported cationic surfactant was also used successfully in this reaction, allowing an easier separation of the product.
Application of a Homogeneous Dodecakis(NCN‐PdII) Catalyst in a Nanofiltration Membrane Reactor under Continuous Reaction Conditions
Authors: Dijkstra Harm P. , Ronde Niek , van Klink Gerard P. M. , Vogt Dieter , van Koten Gerard 
Published: March 2003

AbstractA shape‐persistent nanosize dodecakis(NCN‐PdII‐aqua) complex (4b) was applied as a homogeneous catalyst in the double Michael reaction between methyl vinyl ketone and ethyl α‐cyanoacetate under continuous reaction conditions in a nanofiltration membrane reactor. Due to its macromolecular dimensions, the catalyst is retained in the reactor (R=99.5% determined by ICP‐AAS) during catalysis. In addition, the catalyst was found to be stable under the continuous reaction conditions as a constant activity was obtained at prolonged reaction times (26 h, 65 exchanged reactor volumes). The turnover number of the catalyst was thus increased by a factor greater than 40 from 80 (batch) up to >3000 mol/mol Pd. Further development of this technology will allow an increase of the number of (industrial) catalytic processes in which homogeneous catalysts are applied.
(−)‐Sparteine‐Mediated Directed ortho‐Metalation of N‐Cumyl‐N‐ethylferrocenecarboxamide. Versatile Routes to Functionalized Planar Chiral Ferrocenecarboxamides, Amines, Esters and Phosphines
Authors: Metallinos Costa , Szillat Hauke , Taylor Nicholas J. , Snieckus Victor 
Published: March 2003

AbstractN‐Cumyl‐N‐ethylferrocenecarboxamide 5 provides planar chiral carboxamides 6 in high yield and % ee via (−)‐sparteine‐mediated directed ortho‐metalation. Mild decumylation affords secondary amides 7, which serve as intermediates for a convenient and general route to the venerable Ugi planar chiral ferrocenylamines 13 and as versatile precursors for the preparation of novel chiral ferrocenes 15 and 20. The chiral TMS‐ferrocenyl derivative 7c is used to prepare the enantiomeric (S)‐7f, circumventing the lack of availability of (+)‐sparteine.
One‐Pot Homogeneous and Heterogeneous Oxidation of Glycerol to Ketomalonic Acid Mediated by TEMPO
Authors: Ciriminna Rosaria , Pagliaro Mario 
Published: March 2003

AbstractGlycerol, an increasingly abundant by‐product of biodiesel production, is selectively converted to ketomalonic acid in one pot at pH 10 using NaOCl as regenerating oxidant in water at 2 °C in the presence of catalytic Br− along with the radical TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl). The reaction can also be conducted at completion over a sol‐gel silica glass doped with the nitroxyl radical. Considering the stability and versatility of such doped glasses, these materials show real promise as reusable metal‐free catalysts for the conversion of a readily available and renewable biofeedstock into a highly valued compound.
A Simple and Convenient Method for Epoxidation of Olefins without Metal Catalysts
Authors: Klawonn Markus , Bhor Santosh , Mehltretter Gerald , Döbler Christian , Fischer Christine , Beller Matthias 
Published: March 2003

AbstractAn easy method for epoxidation of olefins using bleach (sodium hypochlorite) and either a stoichiometric or catalytic amount of bromide ion has been developed. Without any transition metal catalyst a variety of non‐activated olefins give epoxides in high yields and good selectivity at ambient conditions.
Easily Accessible Ring Opening Metathesis and Atom Transfer Radical Polymerization Catalysts based on Arene, Norbornadiene and Cyclooctadiene Ruthenium Complexes Bearing Schiff Base Ligands
Authors: Opstal Tom , Couchez Katrien , Verpoort Francis 
Published: March 2003

AbstractA group of four mixed ligand ruthenium(II)‐Schiff base complexes has been synthesized and characterized. These complexes are easily accessible from [RuCl2(p‐cymene)]2, [RuCl2(NBD)]n, [RuCl2(COD)]x and salicylaldimine salts. They have been found to serve as good catalyst precursors for ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) of different vinyl monomers. The catalytic activity and the control over the produced polymer can be dramatically improved after the addition of additives such as Et2AlCl and (n‐Bu)2NH.
Mono‐ and Bidentate Phosphine Ligands in the Palladium‐Catalyzed Methyl Acrylate Dimerization
Authors: Zimmermann Jörg , Tkatchenko Igor , Wasserscheid Peter 
Published: March 2003

AbstractThe influence of several phosphine ligands on the activity, selectivity and stability of the catalytic system Pd(acac)2, ligand, [HOEt2][BF4] was studied in the dimerization of methyl acrylate (MA). It was found that the catalyst's activity increased with increasing the basicity of the monodentate ligands used, whereas bulky phosphines lowered the linearity of the dimers and the reaction rates. With chelating P N‐, P P‐, and P As‐ligands the Pd‐catalyst could be efficiently stabilized during the reaction. The use of 1‐dibutylphosphino‐2‐dimethylaminoethane as ammonium tetrafluoroborate salt allowed the highest overall activity.
Rhodium‐Catalysed Asymmetric Hydroformylation of Unsaturated Nitriles
Authors: Lambers‐Verstappen Mariëlle M. H. , de Vries Johannes G. 
Published: March 2003

AbstractAsymmetric hydroformylation of crotononitrile (1) and ally cyanide (2) was probed with the view to develop a synthesis for (R)‐4‐amino‐2‐methyl‐butan‐1‐ol. Hydroformylation of 1 under a variety of conditions mainly led to hydrogenated product. Hydroformylation of 2 with Rh/tris(2,4‐di‐tert‐butylphenyl) phosphite gave good selectivity to the formylated nitrile with an n/iso of 77:23. Asymmetric hydroformylation of 2 could be accomplished in 66% ee using Rh/(R,S)‐BINAPHOS.
Synthesis ofN‐Acetyl‐α‐aminobutyric AcidviaAmidocarbonylation: A Case Study
Authors: Gördes Dirk , Neumann Helfried , von Wangelin Axel Jacobi , Fischer Christine , Drauz Karlheinz , Krimmer Hans‐Peter , Beller Matthias 
Published: March 2003

AbstractThe synthesis ofN‐acetyl‐α‐aminobutyric acid by amidocarbonylation of propionaldehyde with acetamide in the presence of palladium catalysts is studied in detail. The influence of various reaction conditions and compositions (e.g., the co‐catalysts acid and bromide) on the yield ofN‐acetyl‐α‐aminobutyric acid is shown. For the first time it is demonstrated that the palladium‐catalyzed amidocarbonylations of aldehydes can be run with significantly lower halide concentrations (<30 mol %) without a major yield decrease. While phosphine‐free catalyst systems give best yields at low CO pressure, phosphine‐ligated palladium catalysts lead to better yields at higher CO pressure. At low palladium loadings (<0.1 mol %), unwanted condensation reactions of propionaldehyde become increasingly competitive.
Interstitial deletion of the short arm of chromosome 1: Attempt to establish a clinical phenotype (46,XX,del (1)(p22p32))
Authors: Mircher Clotilde , Rethore Marie‐Odile , Lespinasse James , Fert‐Ferrer Sandra , Lundsteen Claes , Kirchoff Maria 
Published: March 2003

AbstractA girl with a de novo interstitial deletion of the short arm of chromosome 1 (46,XX,del (1)(p22p32) is described with moderate developmental delay and minor phenotypic abnormality. These clinical manifestations are compared to previously reported patients with interstitial deletion of chromosome 1, in an attempt to identify a clinical phenotype which seems quite different from the syndrome linked to more terminal deletion of chromosome 1p, and perhaps from more proximal 1p deletion phenotype. © 2003 Wiley‐Liss, Inc.
Poland anomaly—report of an unusual family
Authors: Shalev Stavit A. , Hall Judith G. 
Published: March 2003

AbstractA family with classical Poland anomaly presenting in the son and a partially affected mother is reported. We hypothesize that Poland anomaly has a multifactorial basis involving vascular compromise in early development. Two possible predisposing factors are aberrant vascular formation and thrombophilia. The investigation of our family has not demonstrated an abnormality in coagulation, therefore, we surmise that an inherited structural variant of blood vessel formation is responsible. © 2003 Wiley‐Liss, Inc.
Copper Carbene Complexes: Advanced Catalysts, New Insights
Authors: Kirmse Wolfgang 
Published: March 2003

AbstractControlling the selectivity of reactive intermediates is a major goal of organic chemists. Carbenes generated by thermal or photochemical extrusion of nitrogen from diazo compounds defy external control and tend to give complex product mixtures. However, the catalyzed decomposition of diazo compounds gives rise to highly selective “carbenoids” which have found extensive application in synthesis although little is known of their precise nature. On the other hand, a large variety of carbene metal complexes have been prepared and characterized which more or less lack carbenoid reactivity. Structural evidence for the transients of catalyzed diazo decomposition is becoming available through experiment and computation. Although the present report focuses on copper complexes, outstanding results with other metals are also covered.
meso Compounds: Stepchildren or Favored Children of Stereoselective Synthesis?
Authors: Hoffmann Reinhard W. 
Published: March 2003

AbstractAfter more than a quarter of a century of development, the methodology of stereoselective synthesis appears to be fully matured. In line with this, the potential that meso compounds offer in stereoselective synthesis is clearly recognized. The use of meso compounds in synthesis is, however, in no way commensurate with this potential, because, ironically, the synthesis of meso compounds in the first place is a problem of stereoselective synthesis. Present‐day methodology does not provide many useful solutions to this problem. This Review therefore addresses the strategies available for the synthesis of more elaborate meso compounds whose stereogenic centers have a distance >1,4 between them. meso Compounds with more than four stereogenic centers are also considered. The criteria used in choosing from several strategies in the synthesis of such compounds are discussed.
Drying and semidrying oil macromonomers. III. Styrenation of sunflower and linseed oils
Authors: Akbas T. , Beker Ü. G. , Güner F. S. , Erciyes A. T. , Yagci Y. 
Published: March 2003

AbstractStyrenation of drying and semidrying oils, namely sunflower and linseed oils, via the macromer technique was studied. For this purpose, the macromonomers of the oils were prepared by transesterification of methyl methacrylate (MMA) with the corresponding partial glycerides (PG). Subsequent styrenation was achieved by free radical copolymerization of the macromonomers with styrene using benzoyl peroxide as the initiator. The viscosity and the film properties of the products were studied and compared. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2373–2376, 2003
Synthesis and characterization of novel grafted amphoteric poly(propylene) fabrics
Authors: Mosleh S. , Gawish S. M. 
Published: March 2003

AbstractNovel grafted amphoteric poly(propylene) (PP) fabrics were prepared by γ‐irradiation, which induced grafting of methacrylic acid (MA) onto PP fabric. A subsequent reaction of PP–MA grafted chains with freshly prepared (3‐chloro‐2‐hydroxylpropyl)amine or diamine chloride compounds followed by purification yielded the corresponding amphoteric PP fabrics. The latter were characterized by elemental microanalysis for the determination of the percentage nitrogen. Fourier transform infrared and scanning electron microscopy were performed on methacrylic and amphoteric PP fabrics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2504–2510, 2003
Effects of blend ratio and vulcanizate powders on the processability of silicone rubber/fluororubber blends
Authors: Ghosh Arun , Kumar B. , Bhattacharya A. K. , De S. K. 
Published: March 2003

AbstractWhile silicone rubber has a much lower shear viscosity than that of fluororubber, the viscosity of silicone rubber/fluororubber blends is closer to that of silicone rubber. All rubber compositions show pseudoplastic behavior. While the viscosity of a 50/50 silicone rubber/fluororubber blend increases on replacement of the silicone rubber by silicone rubber vulcanizate powder (SVP), the effect of fluororubber replacement by the corresponding fluororubber vulcanizate powder (FVP) on the shear viscosity is less pronounced. The difference in viscosity between SVP‐replaced silicone rubber and FVP‐replaced fluororubber becomes less prominent at higher shear rates. Fluororubber exhibits a higher extrudate die swell than that of silicone rubber. The die swell of the silicone rubber/fluororubber blends is higher than are the figures obtained by the additivity rule. Replacement of constituent rubbers in the blend by the corresponding vulcanizate powders causes an increase in the die swell. While the silicone rubber extrudate surface is smooth, the fluororubber extrudate shows melt fracture. The extrudate surfaces of the silicone rubber/fluororubber blends are similar to that of the silicone rubber extrudate. Replacement of constituent rubbers by the corresponding vulcanizate powders increases the roughness of the extrudate surface, which is more prominent in the case of silicone rubber replacement by SVP. SVP can replace 50% of silicone rubber and FVP can replace 75% of fluororubber in the 50/50 silicone rubber/fluororubber blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2377–2387, 2003
A novel synthesis method for the preparation of aromatic poly(imide benzoxazole) from trimellitic anhydride chloride and bis(o‐aminophenol)
Authors: Hsu Steve Lien‐Chung , Chang Keng‐Chuan , Huang Yuan‐Pin , Tsai Shih‐Jung 
Published: March 2003

AbstractA poly(imide benzoxazole) was prepared directly from trimellitic anhydride chloride and 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane (BisAPAF) monomers in a two‐step method. In the first step, a poly(hydroxyamide amic acid) precursor was synthesized by the low‐temperature solution polymerization in an organic solvent. Subsequently, thermal cyclodehydration of the poly(hydroxyamide amic acid) precursor at 350°C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.22 dL/g. The cyclized poly(imide benzoxazole) showed a glass transition temperature (Tg) at 329°C and a 5% weight loss temperature at 530°C in nitrogen and at 525°C in air. The poly(imide benzoxazole) is amorphous as evidenced by the wide‐angle X‐ray diffraction measurement. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2388–2391, 2003
Analysis of surface degradation of silicone rubber due to tracking—A physicochemical approach
Authors: Sarathi R. , Maheswar Rao Uma 
Published: March 2003

AbstractThe tracking phenomenon for silicone rubber material under AC and DC voltages, with ammonium chloride as the contaminant, has been studied. The tracking phenomenon is explained in detail with a leakage current measurement. The tracking time depends on the conductivity and the flow rate of the contaminant. The surface condition of the aged specimens was characterized with contact angle measurements. The thermal and chemical stabilities of the material were identified with a methodical experimental study. Physicochemical analysis by wide‐angle X‐ray diffraction (WAXD), thermogravimetric differential thermal analysis (TG‐DTA), and the differential scanning calorimetry (DSC) indicated that the mechanism of the tracking process is due to surface degradation. The tracking time is different for AC and DC voltages. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2392–2399, 2003
Surface modification of thermotropic poly(oxybenzoate‐co‐oxynaphthoate) copolyester by remote oxygen plasma for copper metalization
Authors: Lim Sang Kyoo , Inagaki N. 
Published: March 2003

AbstractPoly(oxybenzoate‐co‐oxynaphthoate) (POCO) film surfaces were modified with remote oxygen plasma, and the effects of the modification on the adhesion between the copper layer and POCO were investigated. The remote‐oxygen‐plasma treatment led to a noticeable decrease in the contact angle, which was mainly due to the CO functional groups on the surface. The modification of the POCO surface by remote oxygen plasma was effective in improving the adhesion with copper metal. The peel strength for the copper metal/POCO system was enhanced from 10 to 127.5 mN/5 mm by the surface modification. The failure mode of the copper metal/POCO system was an interface layer between the oxidized micro‐POCO fibril surface and the copper metal layer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2400–2408, 2003
Temperature‐dependence modeling of highly crosslinked polymer networks
Authors: Yin S. , Pizzi A. 
Published: March 2003

AbstractThe dependence on the temperature of the state of a highly crosslinked polymer network can be modeled as a function of well‐defined molecular‐level network parameters to yield a simple applied model equation. The tightness and strength (modulus of elasticity) of the crosslinked networks formed, as well as any further tightening of the network due to further curing, can easily be compared with the parametersA,M, and α (the coefficient of branching) and them/Eratio and, therefore, with parameters directly related to molecular‐level characteristics of the system. The crosslinking contribution to the network is represented byAandM, the former representing the frequency of crosslinking and the latter having the dimensions of an energy. The ratiom/E, that is, the ratio of the average number of degrees of freedom of chain segments between crosslinking nodes (m) to the average energy of nonbonded atom interactions between the same segments (E), and α model the noncrosslinked contribution to the characteristics of the network. These are the same parameters that appear in the simple equation modeling the dependence of the characteristics of the network on the temperature within a limited temperature range. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2416–2426, 2003
New developments in flame retardancy of glass‐reinforced epoxy composites
Authors: Kandola Baljinder K. , Horrocks A. Richard , Myler Peter , Blair Dana 
Published: March 2003

AbstractThis work involves the development of novel glass fiber–reinforced composite materials containing a commercially available epoxy resin, a phosphate‐based intumescent, and inherently flame‐retardant cellulosic (Visil, Sateri) and phenol–formaldehyde (Kynol) fibers. The intumescent and flame‐retardant fiber components were added both as additives in pulverized form and fiber interdispersed with the intumescent as a fabric scrim for partial replacement of glass fiber. Thermal stability, char formation, and flammability properties of these novel structures were studied by thermal analysis, limiting oxygen index, and cone calorimetry. The results are discussed in terms of effect of individual additive component on thermal degradation/burning behavior of neat resin. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2511–2521, 2003