bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and Properties of Fluorous Quaternary Phosphonium Salts that Bear Four Ponytails; New Candidates for Phase Transfer Catalysts and Ionic Liquids
Authors: Emnet Charlotte , Weber Kathleen M. , Vidal José A. , Consorti Crestina S. , Stuart Alison M. , Gladysz J. A. 
Published: August 2006

AbstractThe fluorous tertiary phosphine [Rf6(CH2)2]3P [Rfn=CF3(CF2)n−1] and excess PhCH2Br, CH3(CH2)3OSO2CF3, or Rf6(CH2)2OSO2CF3 react (CF3C6H5, 45–110 °C) to give the phosphonium salts (PhCH2)[Rf6(CH2)2]3P+ Br− (2, 71 %), [CH3(CH2)3][Rf6(CH2)2]3P+ CF3SO3− (3, 65 %), or [Rf6(CH2)2]4P+ CF3SO3− (4, 83 %). The phosphines [Rf6(CH2)2]2[Rf8(CH2)2]P and [Rf8(CH2)2]3P are similarly elaborated with Rf6(CH2)2I, Rf8(CH2)2I, or Rf8(CH2)2Br (DMF, 115 °C) to [Rf8(CH2)2]4‐x[Rf6(CH2)2]xP+ I− (x=3, 7; 2, 8; 1, 9; 0, 10) or [Rf8(CH2)2]4P+ Br− (80–60 %). The salts exhibit melting points between 110 °C and 43 °C, with lower values favored by less symmetrical cations, Rf6 segments, and triflate and bromide anions. Solubilities decrease in the solvent sequence CF3C6F5 (all salts at least moderately soluble, room temperature)>acetone>THF>CF3C6H5>CF3C6F11>CH3C6H5, Et2O, CH2Cl2, hexane (all salts insoluble at elevated temperatures); some appreciably increase upon heating. Partition coefficients are very biased towards fluorous phases (>93:<7). The salts can be quite efficient at extracting picrate from water into CF3C6F5 (97–86 % for 2, 4, 9, 10) or CF3C6H5 (85–66 % for 2‐4), demonstrating their potential for phase transfer catalysis. A CF3C6F5 solution of Rf8(CH2)3I and aqueous NaCl react at 100 °C in the presence (but not the absence) of 9 to give Rf8(CH2)3Cl.
Immobilized Hydroxynitrile Lyases for Enantioselective Synthesis of Cyanohydrins: Sol‐Gels and Cross‐Linked Enzyme Aggregates
Authors: Cabirol Fabien L. , Hanefeld Ulf , Sheldon Roger A. 
Published: August 2006

AbstractThe hydroxynitrile lyases (HNLs) from Prunus amygdalus (PaHNL), Manihot esculenta (MeHNL), and Hevea brasiliensis (HbHNL) were successfully immobilized in sol‐gels. The cross‐linked enzyme aggregate (CLEA) of HbHNL was also prepared. These immobilized enzymes and the commercial PaHNL‐ and MeHNL‐CLEAs were employed for the enantioselective synthesis of cyanohydrins. The sol‐gels were highly efficient at low catalyst loading and particularly stable towards the organic solvent (diisopropyl ether) and substrate/product deactivation. The stabilization effect was inconsistent for CLEAs of different HNLs and significant deactivation of PaHNL‐ and HbHNL‐CLEAs in diisopropyl ether was observed. In contrast commercial MeHNL‐CLEA proved to be a remarkably robust and efficient biocatalyst in diisopropyl ether.
Supported Fluorous Phase Catalysis on PTFE, Fluoroalkylated Micro‐ and Meso‐porous Silica
Authors: Hope Eric G. , Sherrington James , Stuart Alison M. 
Published: August 2006

AbstractNew perfluoroalkylated micro‐ and mesoporous silica, along with powdered Teflon, have been evaluated as solid supports for supported fluorous phase catalysis in a model reaction; the hydrogenation of styrene using a fluorous analogue of Wilkinson’s catalyst. Each support material showed catalytic activity and catalyst‐leaching behaviour related to its surface area and was consistent with supported liquid phase catalysis. However, catalyst decomposition on the silica supports resulted in substantial reductions in activity on catalyst recycle. In contrast, although activity and leaching levels on PTFE were poorer, the supported catalyst was recycled successfully.
Methoxycarbonylation of Iodobenzene in Ionic Liquids. A Case of Inhibiting Effect of Imidazolium Halides
Authors: Zawartka W. , Trzeciak A. M. , Ziółkowski J. J. , Lis T. , Ciunik Z. , Pernak J. 
Published: August 2006

AbstractThe palladium(II) complexes, PdCl2(cod) (1), PdCl2[P(OPh)3]2 (2), [bmim]2[PdCl4] (3), and [bmpy]2[PdCl4] (4) (bmim=1‐butyl‐3‐methylimidazolium cation, bmpy=1‐butyl‐4‐methylpyridinium cation), were found to be active catalysts for the methoxycarbonylation of iodobenzene in ionic liquid (IL) media. The best results were obtained in pyridinium salts, [bmpy]X (X=Cl, Br, BF4, PF6) (76–100 % yield). In methoxycarbonylation reactions carried out in imidazolium salts, [bmim]BF4 and [bmim]PF6, the yield of benzoic acid methyl ester was slightly lower (50–78 % yield), whereas in [bmim]X (X=Cl, Br) the reaction was totally retarded. The inhibiting effect was not observed when a Me group was present at C‐2 (instead of a proton) on the imidazole ring. A palladium‐carbene complex, Pd(bmimy)2Br2 (5), obtained in the reaction of a palladium catalyst precursor with [bmim]Cl, presented much lower activity than precursors 1–4. Its formation may explain the observed inhibition of methoxycarbonylation in a [bmim]Cl medium.
Generation of Self‐Supported Noyori‐Type Catalysts Using Achiral Bridged‐BIPHEP for Heterogeneous Asymmetric Hydrogenation of Ketones
Authors: Liang Yuxue , Wang Zheng , Ding Kuiling 
Published: August 2006

AbstractThe programmed assembly strategy has been applied to the generation of self‐supported Noyori‐type catalysts for asymmetric hydrogenation of ketones by spontaneous hetero‐coordination of an achiral bridged diphosphine and chiral bridged diamine ligands with RuII metal ions. The immobilized catalyst demonstrates good enantioselectivity and activity in the heterogeneous catalysis of the hydrogenation of aromatic ketones and can be recovered and recycled for 4 times without obvious loss of selectivity and activity.
Liquid/Liquid Biphasic Recovery/Reuse of Soluble Polymer‐ Supported Catalysts
Authors: Bergbreiter David E. , Sung Shayna D. 
Published: August 2006

AbstractLiquid/liquid separations using gravity and two phases of different density are a practical and viable way to recover, separate and reuse soluble polymer‐supported catalysts. Such separations are facilitated by using polymers that have phase‐selective solubility under biphasic conditions. Such polymers can be designed to be soluble either in a non‐polar or a polar phase. Since catalyst and ligand loading can be at a low mole percent level on the polymer, the polymer’s intrinsic solubility can be maintained with a variety of ligands and catalysts making such separation strategies general. Catalysis with such soluble polymer‐supported species can either be carried out under biphasic or monophasic conditions. In the former case, aqueous/organic, fluorous/organic or other biphasic regimes can be used. In the later case, thermomorphic or latent biphasic conditions can be employed. In either case, catalyst separation and recovery can be accomplished simply without using significant quantities of additional solvent.
A Combinatorial Approach to Heterogeneous Asymmetric Aquacatalysis with Amphiphilic Polymer‐Supported Chiral Phosphine‐Palladium Complexes
Authors: Kobayashi Yukinari , Tanaka Daiki , Danjo Hiroshi , Uozumi Yasuhiro 
Published: August 2006

AbstractA library of amphiphlic polystyrene‐poly(ethylene glycol) (PS‐PEG) resin‐supported chiral phosphine ligands was prepared by the split method using porous miniature reactors. A polymeric (R)‐2‐(diphenylphosphino)binaphthyl (MOP) ligand anchored onto the PS‐PEG resin by an (S)‐alanine tether unit was identified through the library‐based screening to be an effective chiral ligand for the asymmetric palladium‐catalyzed π‐allylic substitution under heterogeneous aqueous conditions.
Hydroformylation of 1‐Octene in Supercritical Carbon Dioxide and Organic Solvents using Trifluoromethyl‐Substituted Triphenylphosphine Ligands
Authors: Koeken Ard C. J. , van Vliet Michiel C. A. , van den Broeke Leo J. P. , Deelman Berth‐Jan , Keurentjes Jos T. F. 
Published: August 2006

AbstractTwo different in situ prepared catalysts generated from Rh(CO)2acac and trifluoromethyl‐substituted triphenylphosphine ligands have been evaluated for their activity and selectivity in the hydroformylation of 1‐octene. The solvents used were supercritical carbon dioxide, hexane, toluene, and perfluoromethylcyclohexane. The highest value for the turnover frequency, 9820 mol1‐octene molRh−1 h−1, has been obtained in supercritical carbon dioxide using ligand I, P[C6H3‐3,5‐(CF3)2]3. For both supercritical carbon dioxide and hexane employing ligand II, P(C6H4‐3‐CF3)3, a selectivity towards the linear aldehyde product, nonanal, and an n:iso ratio of 79.3 % and 4.6–4.8 have been obtained, respectively. These values are significantly higher than those obtained with triphenylphosphine as ligand (nonanal: 74–76 %, n:iso: 3.1–3.3). An increase in trifluoromethyl substitution on the triphenyl ligand results in an increase in the 1‐octene conversion rate, an increase in the n:iso ratio and a decrease in the overall selectivity towards aldehydes. In terms of turn‐over frequency and selectivity the three ligands give comparable results in supercritical carbon dioxide and hexane. This leads to the conclusion that the properties of supercritical carbon dioxide as a solvent for hydroformylation can be better compared with those of hexane rather than with those of toluene.
Palladium‐Catalysed Direct Regioselective Synthesis of Cyclic Ketals from Electron‐Rich Olefins and Aryl Bromides in Ionic Liquids
Authors: Hyder Zeynab , Mo Jun , Xiao Jianliang 
Published: August 2006

AbstractThe Heck reaction comprises one of the most important carbon‐carbon coupling reactions in organic synthesis. The popularity of the reaction is attributable to the broad availability of aryl halides and to the tolerance of the reaction for a wide variety of functional groups. Reported herein is a direct method for the highly regioselective preparation of 5‐membered and 7‐membered cyclic ketals in respectable to good yields from aryl bromides (1a–k) and electron‐rich olefins (2a and b). The reaction is performed with palladium catalysis using ionic liquid as solvent with no need for any halide scavengers, providing an alternative to the use of aryl triflates. The ionic liquid is found to direct the reaction pathway towards exclusive α‐arylation via a cationic route.
The Immobilization of Rhodium‐4‐(diphenylphosphino)‐2‐ (diphenylphosphinomethyl)‐pyrrolidine (Rh‐PPM) Complexes: A Systematic Study
Authors: Pugin Benoît , Blaser Hans‐Ulrich 
Published: August 2006

AbstractA modular toolbox for the immobilization of homogeneous catalysts to various supports is described. It consists of functionalized chiral diphosphines and three different linkers based on isocyanate chemistry and it is used to attach the 4‐(diphenylphosphino)‐2‐(diphenylphosphinomethyl)‐pyrrolidine (PPM) ligand to a large variety of soluble, swellable and non‐swellable solid organic polymers and to silica gels. As model reaction the hydrogenation of acetamidocinnamic acid derivatives, catalyzed with high enantioselectivity was chosen. Besides information on the usefulness of a particular type of support for synthetic applications, the experiments were also designed to address the question how parameters such as solubility, swellability, cage or pore size and solvent affect the rate and enantioselectivity of an immobilized catalyst. Rhodium complexes of ligands attached to soluble polymers and inorganic supports achieved ees up to 95 % and turnover frequencies between 700 and 1400 h−1, very close to the values of the homogeneous Rh catalyst (ee 95 %, TOF 1320 h−1). Insoluble or strongly cross‐linked organic polymers led to catalysts with lower enantioselectivity and activity. PPM ligands attached to water soluble dendrimer fragments allowed hydrogenation in water solution with ees up to 94 %, albeit with much lower activity compared to reactions in methanol with the homogeneous catalyst.
Asymmetric Catalytic Synthesis of Organic Compounds using Metal Complexes in Supercritical Fluids
Authors: Cole‐Hamilton David J. 
Published: August 2006

AbstractThe applications of metal‐based catalysts for the asymmetric synthesis of organic compounds in supercritical fluids are reviewed. Much of the work discussed concerns hydrogenation and hydroformylation of alkenes, but dihydoxylation and cyclopropanation reactions of alkenes are discussed as are asymmetric Diels–Alder reactions and aldol condensations. Supercritical fluids remove the need for harmful volatile organic solvents, but their use in separating the products from the catalyst by pressure swings or multiphasic systems is also described.
Continuous Asymmetric Hydrogenation in Supercritical Carbon Dioxide using an Immobilised Homogeneous Catalyst
Authors: Stephenson Phil , Kondor Betti , Licence Peter , Scovell Katherine , Ross Stephen K. , Poliakoff Martyn 
Published: August 2006

AbstractContinuous flow supercritical carbon dioxide (scCO2) has previously been shown (P. Stephenson, P. Licence, S. K. Ross, M. Poliakoff, Green Chem. 2004, 6, 521) to be a viable medium for conducting continuous asymmetric hydrogenation when it is combined with an appropriate enantioselective catalyst. Here we examine the use of a composite catalyst immobilisation system modified with several different types of asymmetric bisphosphine ligands in continuous flow scCO2. In particular, proprietary ligands from Solvias AG were found to be the most successful, with Josiphos 001 improving the enantiomeric excess (ee) to>80 % in the asymmetric hydrogenation of dimethyl itaconate (DMIT); this ee is higher than that reported for the batch hydrogenation of DMIT using a homogeneous catalyst fully dissolved in scCO2 (S. Lange, A. Brinkmann, P. Trautner, K. Woelk, J. Bargon, W. Leitner, Chirality 2000, 12, 450).
Purification of Fluorous Mitsunobu Reactions by Liquid‐Liquid Extraction
Authors: Curran Dennis P. , Bajpai Reena , Sanger Elizabeth 
Published: August 2006

AbstractSolvent tuning and partition coefficient measurements have identified suitable reagent and solvent combinations for the purification of fluorous Mitsunobu reaction products. The crude reaction mixtures are partitioned between 2/1 HFE‐7100/FC‐72 and DMF/10 % water to provide reagent (fluorous) and product (organic) fractions.
Silica‐Bound Homogenous Catalysts as Recoverable and Reusable Catalysts in Organic Synthesis
Authors: Corma Avelino , Garcia Hermenegildo 
Published: August 2006

AbstractVery frequently the most costly components in a chemical reaction are not the starting materials or the reaction products, but the catalyst. In addition to the advantages from the economic point of view, recovery and reuse of the catalyst is equally important in order to avoid wastes, so improving the greenness of the process. There is a current tendency to transform homogeneous into heterogeneous catalysis, that will even be accelerated in the near future. Starting from a successful homogeneous catalyst, one general methodology allowing its recovery and reuse is to immobilize a suitable derivative of the active catalyst on an insoluble solid support. When the catalyst does not deactivate and is sufficiently stable under the reaction conditions, the ultimate immobilization methodology is to attach covalently the catalytically active species to the support. In this contribution, after introducing some general principles describing the fundamentals of the covalent anchoring, the emphasis is placed more on giving an overview of the most important types of covalently anchored catalysts, including Brönsted and Lewis acids, covalently anchored bases and hydrogenation complexes. Hot topics such as silica‐bound organocatalysts and the application of periodic mesoporous organosilicas as heterogeneous catalysts is also covered.
Aspects of Immobilisation of Catalysts on Polymeric Supports
Authors: Dioos Bart M. L. , Vankelecom Ivo F. J. , Jacobs Pierre A. 
Published: August 2006

AbstractIn this review the authors intend to make a tutorial review on catalyst immobilisation from the viewpoint of the catalyst designer, emphasizing the use of promising concepts in this area, rather than trying to be exhaustive. The following topics are covered:
Numerical modeling of highly swirling flows in a through‐flow cylindrical hydrocyclone
Authors: Ko Jordan , Zahrai Said , Macchion Olivier , Vomhoff Hannes 
Published: August 2006

AbstractThis article aims to identify the most appropriate numerical methodology for simulating hydrocyclone flows with high swirl numbers. The numerical results are validated against the tangential velocity measurements from a cylindrical hydrocyclone with a swirl number of 8.1, which is twice the typical swirl magnitude of industrial hydrocyclones. The linear and quadratic formulations of the Reynolds stress transport (RST) model are used to simulate the anisotropic swirling turbulent flow three‐dimensionally in the commercial software package Fluent™. The tangential velocity profiles predicted by the quadratic RST model are in good agreement with experimental data. They also show Rankine vortex patterns over the entire flow domain. In contrast, the linear RST model fails to predict this important swirl flow feature. In addition, both models predicted a complex axial flow reversal pattern not previously reported in hydrocyclones. This study clearly shows that the quadratic RST model is preferable for future hydrocyclone simulations, especially when the swirl number is large. All necessary physical and numerical parameters used to obtain converged results are given in this article. © American Institute of Chemical Engineers AIChE J, 2006
Patched mutations and hairy skin patches: A new sign in Gorlin syndrome
Authors: Wilson Louise C. , Ajayi‐Obe Ekundayo , Bernhard Birgitta , Maas Saskia M. 
Published: August 2006

AbstractWe report on the occurrence of discrete patches of unusually long pigmented hair on the skin of three patients with Gorlin syndrome from two unrelated families with confirmed heterozygous mutations in the Patched (PTCH) gene. The PTCH protein is a negative regulator of Hedgehog signaling, and the Sonic Hedgehog (SHH)‐PTCH pathway is known to play an important role in the formation and cycling of the hair follicle. We believe that the patches represent a genuine physical sign associated with Gorlin syndrome, and discuss molecular mechanisms by which they might arise. © 2006 Wiley‐Liss, Inc.
Cornelia de Lange syndrome: Parental preferences regarding the provision of medical information
Authors: Hinkson Deborah A.R. , Atenafu Eshetu , Kennedy Shelley J. , Vohra Sunita , Garg Deepak , Levin Alex V. 
Published: August 2006

AbstractWe surveyed 57 caregivers of children with Cornelia de Lange syndrome (CdLS) using a self‐report questionnaire designed to elicit their experiences with receiving information regarding health complications associated with this multisystem disorder. Their most frequent sources of information at the time of diagnosis were a health care provider (86%) and the CdLS Foundation (72%). Although most caregivers (82%) indicated a desire to receive information about all possible CdLS related health complications, on average they recalled receiving information on only 64% of their child's current or future health complications. For two of the top three complications (as ranked by caregivers), information was available to fewer than half of the caregivers at diagnosis. Only 40% of caregivers were satisfied with the amount of information received at diagnosis, while only 45% felt that the information they received was useful. Caregivers indicated a preference for receiving information in written format (59%) or verbally (39%). Our results indicate that caregivers of children with CdLS report a high need for information at diagnosis, regarding their child's actual or potential health complications. Dissatisfaction may result both from a deficiency in information provided, as well as a mismatch between issues mentioned and those that caregivers deem most important. Caregivers may benefit maximally from receiving information in person at the time of diagnosis as well as having an additional written source of information. These findings highlight the importance of complementary sources of information for caregivers and are likely to be relevant for other multisystem disorders. © 2006 Wiley‐Liss, Inc.
Autism spectrum disorder in Fragile X syndrome: Differential contribution of adaptive socialization and social withdrawal
Authors: Budimirovic Dejan B. , Bukelis Irena , Cox Christiane , Gray Robert M. , Tierney Elaine , Kaufmann Walter E. 
Published: August 2006

AbstractThe present study extends our previous work on characterizing the profile of social behavior abnormalities in boys with Fragile X (FraX) and autism spectrum disorder (ASD) using clinically oriented behavioral rating scales and standardized instruments. The goal was to further distinguish behavioral parameters contributing to the diagnostic classification of FraX + ASD. The study design included two cohorts of boys with FraX (3–8 years), a larger main cohort for cross‐sectional analyses (n = 56, 24 with ASD), and a longitudinal subset (n = 30, 11 with ASD) of the main cohort with up to 3 yearly observations. The focus was on the relative contribution of delayed adaptive socialization and social withdrawal, including item components of their corresponding rating instruments, to the diagnosis of ASD in boys with FraX. Using a combination of regression analyses, we demonstrated that: (1) as delayed socialization, social withdrawal is also a correlate of FraX + ASD; (2) items of social withdrawal scales representing avoidance were the main predictors of ASD status, particularly in older boys; (3) adaptive socialization skills reflecting rules of social behavior and recognition and labeling of emotions, linked to verbal reasoning abilities, were selectively associated with FraX + ASD; (4) adaptive socialization is the primary determinant over time of ASD status in boys with FraX; and (5) integrated adaptive socialization‐social withdrawal models allow the identification of distinctive FraX + ASD subgroups. Altogether, our findings suggest that two distinct but interrelated social behavior abnormalities, one linked to impaired cognitive processes (delayed socialization) and the second one to disturbance in limbic circuits (avoidance), play a role in the development of ASD in boys with FraX. © 2006 Wiley‐Liss, Inc.
Epiphyseal dysplasia and other skeletal anomalies in a patient with the 6p25 microdeletion syndrome
Authors: Kannu Peter , Oei Paul , Slater Howard R. , Khammy Ouda , Aftimos Salim 
Published: August 2006

AbstractThe 6p25 microdeletion syndrome comprises the Axenfeld–Rieger eye anomaly in association with a characteristic facies, developmental delay, hearing loss, and organ malformations. Skeletal anomalies in the form of hemivertebrae, clubfeet, and other positional joint anomalies have also been described in some patients. We report on a patient with a 2.2–2.4 Mb terminal microdeletion of the short arm of chromosome 6 who in addition had abnormalities of the proximal femoral and humeral epiphyses. We suggest that an epiphyseal dysplasia may be an additional clinical component of the 6p25 microdeletion syndrome. © 2006 Wiley‐Liss, Inc.