bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using Soluble Polymers to Enforce Catalyst‐Phase‐Selective Solubility and as Antileaching Agents to Facilitate Homogeneous Catalysis
Authors: Liang Yannan , Harrell Mary L. , Bergbreiter David E. 
Published: May 2014

AbstractThe enforced phase‐selective solubility of polyisobutylene (PIB)‐bound RhII catalysts in biphasic heptane/acetonitrile mixtures can be used not only to recycle these catalysts but also to minimize bimolecular reactions with ethyl diazoacetate. When cyclopropanation and OH insertion reactions are carried out with PIB‐bound RhII catalysts either with or without addition of an unfunctionalized hydrocarbon polymer cosolvent, dimer by‐product formation is suppressed even without slow syringe pump addition of the ethyl diazoacetate. This suppression of by‐product formation is shown to be due to increased phase segregation of the soluble polymer‐bound catalyst and the ethyl diazoacetate reactant. These studies also reveal that added hydrocarbon polymer cosolvents can function as antileaching agents, decreasing the already small amount of a soluble polymer‐bound species that leaches into a polar phase in a biphasic mixture during a liquid/liquid separation step.
[3+2] Cycloaddition of Propargylic Alcohols and α‐Oxo Ketene Dithioacetals: Synthesis of Functionalized Cyclopentadienes and Further Application in a Diels–Alder Reaction
Authors: Fang Zhongxue , Liu Jianquan , Liu Qun , Bi Xihe 
Published: May 2014

AbstractCyclopentadienes are valuable intermediates in organic synthesis and also ubiquitous as the Cp ligands in organometallic chemistry. As part of ongoing efforts to develop novel organic reactions that employ functionalized alkynes, a [3+2] cycloaddition of propargylic alcohols and ketene dithioacetals has been developed, which leads to fully substituted 2,5‐dialkylthio cyclopentadienes in good to excellent yields. In an unusual dethiolating Diels–Alder reaction, the cyclopentadienes were further reacted with maleimides to afford a family of novel fluorescent polycyclic compounds.
Switchable Reconfiguration of an Interlocked DNA Olympiadane Nanostructure
Authors: Lu Chun‐Hua , Qi Xiu‐Juan , Cecconello Alessandro , Jester Stefan‐Sven , Famulok Michael , Willner Itamar 
Published: May 2014

AbstractInterlocked DNA rings (catenanes) are interesting reconfigurable nanostructures. The synthesis of catenanes with more than two rings is, however, hampered, owing to low yields of these systems. We report a new method for the synthesis of catenanes with a controlled number of rings in satisfactory yields. Our approach is exemplified by the synthesis of a five‐ring DNA catenane that exists in four different configurations. By the use of nucleic acids as “fuels” and “antifuels”, the cyclic reconfiguration of the system across four states is demonstrated. One of the states, olympiadane, corresponds to the symbol of the Olympic Games. The five‐ring catenane was implemented as a mechanical scaffold for the reconfiguration of Au NPs. The advantages of DNA catenanes over supramolecular catenanes include the possibility of generating highly populated defined states and the feasibility of tethering nanoobjects to the catenanes, which act as a mechanical scaffold to reconfigure the nanoobjects.
Selektive Funktionalisierung von P4 durch Metall‐vermittelte Bildung einer C‐P‐Bindung
Authors: Heinl Sebastian , Reisinger Sabine , Schwarzmaier Christoph , Bodensteiner Michael , Scheer Manfred 
Published: May 2014

AbstractEine neue einstufige und selektive Synthese für den ersten Schritt der Aktivierung von weißem Phosphor wurde unter Verwendung organischer Radikale entwickelt. Die Reaktion von NaCpR mit P4 in Gegenwart von CuX oder FeBr3 führt zur direkten Bildung der organisch substituierten P4‐Butterfly‐Verbindungen CpR2P4 (CpR: CpBIG=C5(4‐nBuC6H4)5 (1 a), Cp′′′=C5H2tBu3 (1 b), Cp*=C5Me5 (1 c) und Cp4iPr=C5HiPr4 (1 d)). Die Reaktion verläuft über die Aktivierung von P4 mittels CpR‐Radikalen, die durch Übergangsmetallen erzeugt wurden. Die neu gebildeten organischen P4‐Derivate wurden durch NMR‐Spektroskopie und Röntgenstrukturanalyse umfangreich charakterisiert.
Carbon–Carbon Cross‐Coupling Reactions Catalyzed by a Two‐Coordinate Nickel(II)–Bis(amido) Complex via Observable NiI, NiII, and NiIII Intermediates
Authors: Lipschutz Michael I. , Tilley T. Don 
Published: May 2014

AbstractRecently, the development of more sustainable catalytic systems based on abundant first‐row metals, especially nickel, for cross‐coupling reactions has attracted significant interest. One of the key intermediates invoked in these reactions is a NiIII–alkyl species, but no such species that is part of a competent catalytic cycle has yet been isolated. Herein, we report a carbon–carbon cross‐coupling system based on a two‐coordinate NiII–bis(amido) complex in which a NiIII–alkyl species can be isolated and fully characterized. This study details compelling experimental evidence of the role played by this NiIII–alkyl species as well as those of other key NiI and NiII intermediates. The catalytic cycle described herein is also one of the first examples of a two‐coordinate complex that competently catalyzes an organic transformation, potentially leading to a new class of catalysts based on the unique ability of first‐row transition metals to accommodate two‐coordinate complexes.
7‐Aryl‐7‐deazaadenine 2′‐Deoxyribonucleoside Triphosphates (dNTPs): Better Substrates for DNA Polymerases than dATP in Competitive Incorporations
Authors: Kielkowski Pavel , Fanfrlík Jindřich , Hocek Michal 
Published: May 2014

AbstractA series of 7‐substituted 7‐deazaadenine and 5‐substituted cytosine 2′‐deoxyribonucleoside triphosphates (dNTPs) were tested for their competitive incorporations (in the presence of dATP and dCTP) into DNA by several DNA polymerases by using analysis based on cleavage by restriction endonucleases. 7‐Aryl‐7‐deazaadenine dNTPs were more efficient substrates than dATP because of their higher affinity for the active site of the enzyme, as proved by kinetic measurements and calculations.
Carbon Dioxide Sensitivity of Zeolitic Imidazolate Frameworks
Authors: Mottillo Cristina , Friščić Tomislav 
Published: May 2014

AbstractZeolitic imidazolate frameworks of zinc, cobalt, and cadmium, including the framework ZIF‐8 commercially sold as Basolite Z1200, exhibit surprising sensitivity to carbon dioxide under mild conditions. The frameworks chemically react with CO2 in the presence of moisture or liquid water to form carbonates. This effect, which has been previously not reported in metal–organic framework chemistry, provides an explanation for conflicting reports on ZIF‐8 stability to water and is of outstanding significance for evaluating the potential applications of metal–organic frameworks, especially for CO2 sequestration.
Elucidating Diphosphoinositol Polyphosphate Function with Nonhydrolyzable Analogues
Authors: Wu Mingxuan , Chong Lucy S. , Capolicchio Samanta , Jessen Henning J. , Resnick Adam C. , Fiedler Dorothea 
Published: May 2014

AbstractThe diphosphoinositol polyphosphates (PP‐IPs) represent a novel class of high‐energy phosphate‐containing messengers which control a wide variety of cellular processes. It is thought that PP‐IPs exert their pleiotropic effects as allosteric regulators and through pyrophosphorylation of protein substrates. However, most details of PP‐IP signaling have remained elusive because of a paucity of suitable tools. We describe the synthesis of PP‐IP bisphosphonate analogues (PCP‐IPs), which are resistant to chemical and biochemical degradation. While the two regioisomers 1PCP‐IP5 and 5PCP‐IP5 inhibited Akt phosphorylation with similar potencies, 1PCP‐IP5 was much more effective at inhibiting its cognate phosphatase hDIPP1. Furthermore, the PCP analogues inhibit protein pyrophosphorylation because of their inability to transfer the β‐phosphoryl group, and thus enable the distinction between PP‐IP signaling mechanisms. As such, the PCP analogues will find widespread applications for the structural and biochemical characterization of PP‐IP signaling properties.
Allenamides as Orthogonal Handles for Selective Modification of Cysteine in Peptides and Proteins
Authors: Abbas Ata , Xing Bengang , Loh Teck‐Peng 
Published: May 2014

AbstractIn this study, a remarkably simple and direct strategy has been successfully developed to selectively label target cysteine residues in fully unprotected peptides and proteins. The strategy is based on the reaction between allenamides and the cysteine thiol, and proceeds swiftly in aqueous medium with excellent selectivity and quantitative conversion, thus forming a stable and irreversible conjugate. The combined simplicity and mildness of the process project allenamide as robust and versatile handles to target cysteines and has potential use in biological systems. Additionally, fluorescent‐labeling studies demonstrated that the installation of a C‐terminal allenamide moiety onto various molecules of interest may supply a new methodology towards the site‐specific labeling of cysteine‐containing proteins. Such a new labeling strategy may thus open a window for its application in the field of life sciences.
Antagonizing STAT3 Dimerization with a Rhodium(III) Complex
Authors: Ma Dik‐Lung , Liu Li‐Juan , Leung Ka‐Ho , Chen Yen‐Ting , Zhong Hai‐Jing , Chan Daniel Shiu‐Hin , Wang Hui‐Min David , Leung Chung‐Hang 
Published: May 2014

AbstractKinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti‐tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti‐tumor activity.
In situ processing of Nannochloropsis oculata algal biomass using a mixed bed ion‐exchange resin as a heterogeneous catalyst
Authors: Jamal Yousuf , Luo Guofan , Boulanger Bryan O. 
Published: May 2014

ABSTRACTIon‐exchange resins have the ability to convert microalgae‐derived lipids into esters and other recoverable organics. The presented research evaluated the use of mixed bed ion‐exchange resins for in situ processing of Nannochloropsis oculata algal biomass to recoverable organics within a co‐solvent system. The impact of various processing conditions (resin loading, resin type, biomass drying, solvent type, solvent volume, and biomass sonication) on the reaction yield of recoverable organics was investigated. Multiple analytical chemical approaches were used to characterize lipids within the biomass and to identify the converted reaction products. Each reaction system studied produced more than 20 recoverable organics in addition to the normally desired ester products. Phytol was observed as predominant reaction product in each system. The highest ester yield (approaching 60% biomass lipid to ester conversion) was observed with air‐dried algae processed at 50 °C at a mixing rate of 550 rpm for 2 h. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
The quantification of reticulocyte maturation and neocytolysis in normal and erythropoietin stimulated rats
Authors: Wiczling Paweł , Krzyzanski Wojciech , Żychlińska Natalia , Lewandowski Krzysztof , Kaliszan Roman 
Published: May 2014

ABSTRACTA technique has recently been proposed for obtaining the reticulocyte (RET) age distribution from the flow cytometric reticulocyte count. It allows for a quantitative characterization of reticulocyte dynamics. In this work this technique was applied to characterize the blood, bone marrow and spleen reticulocytes in homeostatic and erythropoietically stimulated rats in order to determine the reticulocyte maturation times in the bone marrow and blood; and to confirm the presence of ineffective erythropoiesis (neocytolysis). The latter was done by comparing the reticulocyte removal rate from blood with bilirubin formation after erythropoiesis stimulation. A single subcutaneous dose (4050 IU/kg) of recombinant human erythropoietin (rHuEPO) was administered to rats, then their reticulocytes were stained with thiazole orange and the distribution of the fluorescent signal measured using flow cytometry. The obtained signal distribution of the reticulocytes was transformed to the age distribution and a set of basic parameters reflecting reticulocyte dynamics was determined. Bilirubin concentrations were measured to directly assess the presence of reticulocyte irreversible removal. The bilirubin formation was found to be considerably modulated by rHuEPO and corresponded well to the determined reticulocyte removal rate. The initial increase and subsequent decrease of the reticulocyte maturation time in blood was quantitated and directly linked with RET mobilization from the bone marrow. A substantial number (60%) of reticulocytes is sequestrated during homeostasis in rats. This number increases and then decreases after rHuEPO administration, as also reflected by bilirubin formation. Flow cytometry seems to be an excellent method for studying RET dynamics and the presence of young RBC neocytolysis. Copyright © 2014 John Wiley & Sons, Ltd.
Highly Active and Recyclable Metal Oxide Catalysts for the Prins Condensation of Biorenewable Feedstocks
Authors: Costa Vinícius V. , Bayahia Hossein , Kozhevnikova Elena F. , Gusevskaya Elena V. , Kozhevnikov Ivan V. 
Published: May 2014

AbstractMetal oxides such as Nb2O5, Cr2O3, and especially a ZnIICrIII mixed oxide are demonstrated to be highly active and recyclable heterogeneous catalysts for Prins condensation, which provides a clean, high‐yielding route for the synthesis of nopol through the condensation of biorenewable β‐pinene with paraformaldehyde. ZnCr mixed oxide with an optimum Zn/Cr atomic ratio of 1:6 gave 100 % nopol selectivity at 97 % β‐pinene conversion, with the catalyst easily recovered and recycled. The acid properties of Nb2O5 and ZnCr mixed oxide were characterized by the diffuse reflectance IR Fourier transform spectroscopy of adsorbed pyridine and ammonia adsorption microcalorimetry. An appropriate combination of acid–base properties of ZnCr mixed oxide is believed to be responsible for its efficiency.
Pillar[5]arene‐Mediated Synthesis of Gold Nanoparticles: Size Control and Sensing Capabilities
Authors: Montes‐García Verónica , Fernández‐López Cristina , Gómez Borja , Pérez‐Juste Ignacio , García‐Río Luis , Liz‐Marzán Luis M. , Pérez‐Juste Jorge , Pastoriza‐Santos Isabel 
Published: May 2014

AbstractWe present a simple procedure for the synthesis of quasi‐spherical Au nanoparticles in a wide size range mediated by macrocyclic host molecules, ammonium pillar[5]arene (AP[5]A). The strategy is based on a seeded growth process in which the water‐soluble pillar[5]arene undergoes complexation of the Au salt through the ammonium groups, thereby avoiding Au nucleation, while acting as a stabilizer. The presence of the pillar[5]arene onto the Au nanoparticle particle surface is demonstrated by surface‐enhanced Raman scattering (SERS) spectroscopy, and the most probable conformation of the molecule when adsorbed on the Au nanoparticles surface is suggested on the basis of theoretical calculations. In addition, we analyze the host–guest interactions of the AP[5]A with 2‐naphthoic acid (2NA) by using 1H NMR spectroscopy and the results are compared with theoretical calculations. Finally, the promising synergetic effects of combining supramolecular chemistry and metal nanoparticles are demonstrated through SERS detection in water of 2NA and a polycyclic aromatic hydrocarbon, pyrene (PYR).
Two C3‐Symmetric Dy3III Complexes with Triple Di‐μ‐methoxo‐μ‐phenoxo Bridges, Magnetic Ground State, and Single‐Molecule Magnetic Behavior
Authors: Hänninen Mikko M. , Mota Antonio J. , Aravena Daniel , Ruiz Eliseo , Sillanpää Reijo , Camón Agustín , Evangelisti Marco , Colacio Enrique 
Published: May 2014

AbstractTwo series of isostructural C3‐symmetric Ln3 complexes Ln3⋅[BPh4] and Ln3⋅0.33[Ln(NO3)6] (in which LnIII=Gd and Dy) have been prepared from an amino‐bis(phenol) ligand. X‐ray studies reveal that LnIII ions are connected by one μ2‐phenoxo and two μ3‐methoxo bridges, thus leading to a hexagonal bipyramidal Ln3O5 bridging core in which LnIII ions exhibit a biaugmented trigonal‐prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self‐consistent field (CASSCF) calculations indicate that the magnetic coupling between the DyIII ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest DyO distance, the local magnetic moments are oriented almost perpendicular to the Dy3 plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the DyIII ions are separated by approximately 150 and 177 cm−1, for Dy3⋅[BPh4] and Dy3⋅0.33[Dy(NO3)6], respectively. As expected for these large energy gaps, Dy3⋅[BPh4] and Dy3⋅0.33[Dy(NO3)6] exhibit, under zero direct‐current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000 Oe, Dy3⋅[BPh4] exhibits two thermally activated processes with Ueff values of 34.7 and 19.5 cm−1, whereas Dy3⋅0.33[Dy(NO3)6] shows only one activated process with Ueff=19.5 cm−1.
Phosphorus Centers of Different Hybridization in Phosphaalkene‐Substituted Phospholes
Authors: Öberg Elisabet , Orthaber Andreas , Lescop Christophe , Réau Régis , Hissler Muriel , Ott Sascha 
Published: May 2014

AbstractPhosphole‐substituted phosphaalkenes (PPAs) of the general formula Mes*PC(CH3)(C4H2P(Ph))R 5 a–c (Mes*=2,4,6‐tBu3Ph; R=2‐pyridyl (a), 2‐thienyl (b), phenyl (c)) have been prepared from octa‐1,7‐diyne‐substituted phosphaalkenes by utilizing the Fagan–Nugent route. The presence of two differently hybridized phosphorus centers (σ2,λ3 and σ3,λ3) in 5 offers the possibility to selectively tune the HOMO–LUMO gap of the compounds by utilizing the different reactivity of the two phosphorus heteroatoms. Oxidation of 5 a–c by sulfur proceeds exclusively at the σ3,λ3‐phosphorus atom, thus giving rise to the corresponding thioxophospholes 6 a–c. Similarly, 5 a is selectively coordinated by AuCl at the σ3,λ3‐phosphorus atom. Subsequent second AuCl coordination at the σ2,λ3‐phosphorus heteroatom results in a dimetallic species that is characterized by a gold–gold interaction that provokes a change in π conjugation. Spectroscopic, electrochemical, and theoretical investigations show that the phosphaalkene and the phosphole both have a sizable impact on the electronic properties of the compounds. The presence of the phosphaalkene unit induces a decrease of the HOMO–LUMO gap relative to reference phosphole‐containing π systems that lack a PC substituent.
“Click” Chemistry Mildly Stabilizes Bifunctional Gold Nanoparticles for Sensing and Catalysis
Authors: Li Na , Zhao Pengxiang , Liu Na , Echeverria María , Moya Sergio , Salmon Lionel , Ruiz Jaime , Astruc Didier 
Published: May 2014

AbstractA large family of bifunctional 1,2,3‐triazole derivatives that contain both a polyethylene glycol (PEG) chain and another functional fragment (e.g., a polymer, dendron, alcohol, carboxylic acid, allyl, fluorescence dye, redox‐robust metal complex, or a β‐cyclodextrin unit) has been synthesized by facile “click” chemistry and mildly coordinated to nanogold particles, thus providing stable water‐soluble gold nanoparticles (AuNPs) in the size range 3.0–11.2 nm with various properties and applications. In particular, the sensing properties of these AuNPs are illustrated through the detection of an analogue of a warfare agent (i.e., sulfur mustard) by means of a fluorescence “turn‐on” assay, and the catalytic activity of the smallest triazole–AuNPs (core of 3.0 nm) is excellent for the reduction of 4‐nitrophenol in water.
Sequential Hydroformylation/Diels–Alder Processes: One‐Pot Synthesis of Polysubstituted Cyclohexenes, Cyclohexadienes, and Phthalates from Alkynes
Authors: Fang Xianjie , Jackstell Ralf , Beller Matthias 
Published: May 2014

AbstractA novel, one‐pot hydroformylation/Diels–Alder sequence for the synthesis of multisubstituted cyclohexenes, cyclohexadienes, and phthalates has been developed. Various alkynes were efficiently converted into the corresponding products in good yields and with excellent diastereoselectivity through palladium‐catalyzed hydroformylation followed by an AAD‐type reaction (AAD: Amides–Aldehydes–Dienophiles). In view of the availability of the substrates, the atom‐efficiency of the overall process, and the convenient introduction of substituents in the cyclohexene ring, this method complements current methods for the preparation of polysubstituted cyclohexane derivatives.
Electrophilic Trifluoromethylthiolation of Carbonyl Compounds
Authors: Alazet Sébastien , Zimmer Luc , Billard Thierry 
Published: May 2014

AbstractA general method for the α‐trifluoromethylthiolation of carbonyl compounds, without prefunctionalization, has been developed. Aldehydes, ketones, esters, amides, keto‐esters, alkaloids, and steroids have been trifluoromethylthiolated with good yields. This work, proposing a new reagent for electrophilic trifluoromethylthiolation, provides a route towards the original synthesis of various trifluoromethylthiolated molecules for further applications.
Rapeseed Proteins for Paperboard Coating
Authors: Oviedo Jesus Palomino , Metz Robert , Schulz John , Tressel Ralf‐Peter , Pudel Frank 
Published: May 2014

AbstractProtein samples of rapeseed were prepared with different compositions as protein isolate, protein concentrate and acetylated protein concentrate. They showed functional properties which are consolidated in the coating. The manufactured protein samples were tested in a pilot‐scale paperboard coating plant. The results indicated that the use of rapeseed proteins in the coating preparation is technically feasible and that the color and roughness of the coated paperboard show no negative effect on the quality. Industry printing experiments with this coated paperboard achieved the standard quality.
Orbital Effect‐Induced Anomalous Anion–π Interactions between Electron‐Rich Aromatic Hydrocarbons and Fluoride
Authors: Shi Guosheng , Yang Jinrong , Ding Yihong , Fang Haiping 
Published: May 2014

AbstractAnion–π interactions generally exist between an anion and an electron‐deficient π‐ring because of the electron‐accepting character of the ring. In this paper, we report orbital effect‐induced anomalous binding between electron‐rich π systems and F− through anion–π interactions calculated at the MP2/6‐31+G(d,p) and ωB97X‐D/6‐31+G(d,p) levels of theory. We find that anion–π interactions between F− and electron‐rich π rings increase markedly with increasing number of π electrons and size of the π rings. This is contrary to intuition because anion–π interactions would be expected to gradually decrease because of gradually increasing Coulombic repulsion between the negative charge of the anions and gradually increasing number of π electrons of the aromatic surfaces. Energy decomposition analysis showed that the key to this anomalous effect is the more effective delocalization of negative charge to the unoccupied π* orbitals of larger π rings, which is termed an “orbital effect”.