bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Polymer‐Bound Monodentate‐P‐Ligated Palladium Complex as a Recyclable Catalyst for the Suzuki–Miyaura Coupling Reaction of Aryl Chlorides
Authors: Zhou Yun‐Bing , Li Cun‐Yao , Lin Min , Ding Yun‐Jie , Zhan Zhuang‐Ping 
Published: July 2015

AbstractA three‐fold cross‐linked polymer‐bound phosphine (POL‐Ph3P) with high phosphorus content has been prepared. The phosphorus‐containing polymer forms a monodentate‐P‐ligated palladium complex, which shows excellent activity in Suzuki–Miyaura cross‐coupling reactions of aryl chlorides. Importantly, the catalyst Pd/POL‐Ph3P is highly stable and can be reused for at least 10 times without losing reactivity.magnified image
Enantioselective Total Synthesis of (+)‐Gephyrotoxin 287C
Authors: Nemoto Tetsuhiro , Yamaguchi Mami , Kakugawa Kazumi , Harada Shingo , Hamada Yasumasa 
Published: July 2015

AbstractGephyrotoxin 287C, a bioactive alkaloid bearing a perhydropyrrolo[1,2‐a]quinoline skeleton with five stereocenters, is an attractive target for synthetic organic chemistry. We achieved an enantioselective total synthesis of (+)‐gephyrotoxin 287C, for which the key steps were palladium‐catalyzed asymmetric allylic amination using a chiral diaminophosphine oxide (DIAPHOX) preligand, diastereoselective intramolecular Mannich reaction, and tin tetrachloride‐catalyzed diastereoselective conjugate addition/protonation.magnified image
Dark matter searches
Authors: Baudis Laura 
Published: July 2015

One of the major challenges of modern physics is to decipher the nature of dark matter. Astrophysical observations provide ample evidence for the existence of an invisible and dominant mass component in the observable universe, from the scales of galaxies up to the largest cosmological scales. The dark matter could be made of new, yet undiscovered elementary particles, with allowed masses and interaction strengths with normal matter spanning an enormous range. Axions, produced non‐thermally in the early universe, and weakly interacting massive particles (WIMPs), which froze out of thermal equilibrium with a relic density matching the observations, represent two well‐motivated, generic classes of dark matter candidates. Dark matter axions could be detected by exploiting their predicted coupling to two photons, where the highest sensitivity is reached by experiments using a microwave cavity permeated by a strong magnetic field. WIMPs could be directly observed via scatters off atomic nuclei in underground, ultra low‐background detectors, or indirectly, via secondary radiation produced when they pair annihilate. They could also be generated at particle colliders such as the LHC, where associated particles produced in the same process are to be detected. After a brief motivation and an introduction to the phenomenology of particle dark matter detection, I will discuss the most promising experimental techniques to search for axions and WIMPs, addressing their current and future science reach, as well as their complementarity.
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Silver‐Catalyzed Cross‐Coupling of Isocyanides and Active Methylene Compounds by a Radical Process
Authors: Liu Jianquan , Liu Zhenhua , Liao Peiqiu , Zhang Lin , Tu Tao , Bi Xihe 
Published: July 2015

AbstractIsocyanides are versatile building blocks, and have been extensively exploited in CH functionalization reactions. However, transition‐metal‐catalyzed direct CH functionalization reactions with isocyanides suffer from over‐insertion of isocyanides. Reported herein is a radical coupling/isomerization strategy for the cross‐coupling of isocyanides with active methylene compounds through silver‐catalysis. The method solves the over‐insertion issue and affords a variety of otherwise difficult to synthesize β‐aminoenones and tricarbonylmethanes under base‐ and ligand‐free conditions. This report presents a new fundamental CC bond‐forming reaction of two basic chemicals.
Benzylic C(sp3)H Perfluoroalkylation of Six‐Membered Heteroaromatic Compounds
Authors: Kuninobu Yoichiro , Nagase Masahiro , Kanai Motomu 
Published: July 2015

AbstractSuccessful benzylic C(sp3)H trifluoromethylation, pentafluoroethylation, and heptafluoropropylation of six‐membered heteroaromatic compounds were achieved as the first examples of a practical benzylic C(sp3)H perfluoroalkylation. In these reactions, BF2CnF2n+1 (n=1–3) functioned as both a Lewis acid to activate the benzylic position and a CnF2n+1 (n=1–3) source. The perfluoroalkylation proceeded at both terminal and internal positions of the alkyl chains. Perfluoroalkylated products were obtained in moderate to excellent yields, even on gram scale, and in a sequential procedure without isolation of the intermediates. By using this method, trifluoromethylation of a bioactive compound, as well as introduction of a CF3 group into a bioactive molecular skeleton, proceeded regioselectively.
The Cleavage of a CC Bond in Cyclobutylanilines by Visible‐Light Photoredox Catalysis: Development of a [4+2] Annulation Method
Authors: Wang Jiang , Zheng Nan 
Published: July 2015

AbstractWe report the first example of an intermolecular [4+2] annulation of cyclobutylanilines with alkynes enabled by visible‐light photocatalysis. Monocyclic and bicyclic cyclobutylanilines successfully undergo the annulation with terminal and internal alkynes to generate a wide variety of amine‐substituted cyclohexenes including new hydrindan and decalin derivatives with good to excellent diastereoselectivity. The reaction is overall redox neutral with perfect atom economy.
Systemic Fluorescence Imaging of Zebrafish Glycans with Bioorthogonal Chemistry
Authors: Agarwal Paresh , Beahm Brendan J. , Shieh Peyton , Bertozzi Carolyn R. 
Published: July 2015

AbstractVertebrate glycans constitute a large, important, and dynamic set of post‐translational modifications that are notoriously difficult to manipulate and image. Although the chemical reporter strategy has been used in conjunction with bioorthogonal chemistry to image the external glycosylation state of live zebrafish and detect tumor‐associated glycans in mice, the ability to image glycans systemically within a live organism has remained elusive. Here, we report a method that combines the metabolic incorporation of a cyclooctyne‐functionalized sialic acid derivative with a ligation reaction of a fluorogenic tetrazine, allowing for the imaging of sialylated glycoconjugates within live zebrafish embryos.
Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity
Authors: Gu Cheng , Huang Ning , Wu Yang , Xu Hong , Jiang Donglin 
Published: July 2015

AbstractPorous organic polymers allow the integration of various π‐units into robust porous π‐networks, but they are usually synthesized as unprocessable solids with poor light‐emitting performance as a result of aggregation‐related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation‐induced‐emissive π‐systems. We developed a high‐throughput and facile method for the direct synthesis of large‐area porous thin films at the liquid–electrode interface. The approach enables the preparation of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub‐nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts‐per‐million levels in a selective manner.
{μ‐PbSe}: A Heavy CO Homologue as an Unexpected Ligand
Authors: Thiele Günther , Franzke Yannick , Weigend Florian , Dehnen Stefanie 
Published: July 2015

AbstractReactions of [K(18‐crown‐6)]2[Pb2Se3] and [K([2.2.2]crypt)]2[Pb2Se3] with [Rh(PPh3)3Cl] in en (ethane‐1,2‐diamine) afforded ionic compounds with [Rh3(PPh3)6(μ3‐Se)2]− and [Rh3(CN)2(PPh3)4(μ3‐Se)2(μ‐PbSe)]3− anions, respectively. The latter contains a PbSe ligand, a rather uncommon homologue of CO that acts as a μ‐bridge between two Rh atoms. Quantum chemical calculations yield a significantly higher bond energy for PbSe than for CO, since the size of the ligand orbitals better matches the comparably rigid Rh‐Se‐Rh angles and the resulting Rh⋅⋅⋅Rh distance. To rationalize the bent coordination of the ligand, orbitals with significant ligand contributions and their dependence on the bonding angle were investigated in detail.
A Divergent Enantioselective Strategy for the Synthesis of Griseusins
Authors: Zhang Yinan , Ye Qing , Wang Xiachang , She Qing‐Bai , Thorson Jon S. 
Published: July 2015

AbstractThe first enantioselective total synthesis of griseusin A, griseusin C, 4′‐deacetyl‐griseusin A, and two non‐native counterparts in 11–14 steps is reported. This strategy highlights a key hydroxy‐directed CH olefination of 1‐methylene isochroman with an α,β‐unsaturated ketone followed by subsequent stereoselective epoxidation and regioselective cyclization to afford the signature tetrahydro‐spiropyran ring. Colorectal cancer cell cytotoxicities of the final products highlight the impact of the griseusin tetrahydro‐spiropyran ring on bioactivity. As the first divergent enantioselective synthesis, the strategy put forth sets the stage for further griseusin mechanism‐of‐action and SAR studies.
A Stable Single‐Site Palladium Catalyst for Hydrogenations
Authors: Vilé Gianvito , Albani Davide , Nachtegaal Maarten , Chen Zupeng , Dontsova Dariya , Antonietti Markus , López Núria , Pérez‐Ramírez Javier 
Published: July 2015

AbstractWe report the preparation and hydrogenation performance of a single‐site palladium catalyst that was obtained by the anchoring of Pd atoms into the cavities of mesoporous polymeric graphitic carbon nitride. The characterization of the material confirmed the atomic dispersion of the palladium phase throughout the sample. The catalyst was applied for three‐phase hydrogenations of alkynes and nitroarenes in a continuous‐flow reactor, showing its high activity and product selectivity in comparison with benchmark catalysts based on nanoparticles. Density functional theory calculations provided fundamental insights into the material structure and attributed the high catalyst activity and selectivity to the facile hydrogen activation and hydrocarbon adsorption on atomically dispersed Pd sites.
Metallic Single‐Unit‐Cell Orthorhombic Cobalt Diselenide Atomic Layers: Robust Water‐Electrolysis Catalysts
Authors: Liang Liang , Cheng Hao , Lei Fengcai , Han Jun , Gao Shan , Wang Chengming , Sun Yongfu , Qamar Shaista , Wei Shiqiang , Xie Yi 
Published: July 2015

AbstractThe bottleneck in water electrolysis lies in the kinetically sluggish oxygen evolution reaction (OER). Herein, conceptually new metallic non‐metal atomic layers are proposed to overcome this drawback. Metallic single‐unit‐cell CoSe2 sheets with an orthorhombic phase are synthesized by thermally exfoliating a lamellar CoSe2‐DETA hybrid. The metallic character of orthorhombic CoSe2 atomic layers, verified by DFT calculations and temperature‐dependent resistivities, allows fast oxygen evolution kinetics with a lowered overpotential of 0.27 V. The single‐unit‐cell thickness means 66.7 % of the Co2+ ions are exposed on the surface and serve as the catalytically active sites. The lowered Co2+ coordination number down to 1.3 and 2.6, gives a lower Tafel slope of 64 mV dec−1 and higher turnover frequency of 745 h−1. Thus, the single‐unit‐cell CoSe2 sheets have around 2 and 4.5 times higher catalytic activity compared with the lamellar CoSe2‐DETA hybrid and bulk CoSe2.
Combining polyhydroxyalkanoates with nanokeratin to develop novel biopackaging structures
Authors: Fabra Maria Jose , Pardo Pablo , Martínez‐Sanz Marta , Lopez‐Rubio Amparo , Lagarón Jose M. 
Published: July 2015

ABSTRACTThis work reports on the combination of polyhydroxyalkanoate (PHA)‐based materials and nanokeratin extracted from poultry feathers (a food by‐product) using different approaches. In the first approach, high‐barrier nanobiocomposites based on the combination of PHAs with a nanokeratin additive were successfully developed via both (i) direct melt compounding and (ii) preincorporated into an electrospun masterbatch of PHA which was subsequently melt compounded with PHA pellets. Enhanced barrier properties for the nanobiocomposites were obtained which were seen to depend on the PHA grade used. In the second approach, nanokeratin films were obtained via solution casting which were successfully hydrophobized by coating them with electrospun PHA fibers. The multilayered approach showed good adhesion and also lead to enhanced barrier performance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42695.
High shear melt‐processing of fiberglass‐reinforced poly(trimethylene) terephthalate composites
Authors: Lynch Jennifer Krystyna 
Published: July 2015

ABSTRACTAs the demand for polymer‐matrix composites (PMC) expands in order to replace traditional materials, processing of the PMC is increasingly vital, as the morphology and properties are processing dependent. Typically, thermoplastic PMCs are processed in at least two heat‐intensive steps, including a pre‐compounding step in order to achieve good mixing followed by a part fabrication step. The key aim of this study is to prepare a fiberglass‐reinforced poly (trimethylene terephthalate) (FG‐PTT) composite using a one‐step, high shear melt‐processing method that achieves both compounding and part fabrication. The morphology, thermal properties, and mechanical properties are characterized to determine the effect of FG reinforcement on this renewable biopolymer. This novel method produces a FG‐PTT composite with superior mixing and tensile strength, as well as enhanced toughness, in one processing step, reducing polymer degradation and fiber attrition, as well as, time, energy, and cost requirements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42714.
Competitive adsorption of Ag (I) and Cu (II) by tripolyphosphate crosslinked chitosan beads
Authors: Mao Chunxia , Imtiaz Syed Ahmad , Zhang Yan 
Published: July 2015

ABSTRACTAlkalization of chitosan before crosslinking was applied in this study to enhance the adsorption capacity of the modified chitosan. Competitive adsorption of Ag (I) and Cu (II) from bimetallic solutions was studied using the newly synthesized tripolyphosphate crosslinked alkalized chitosan beads. Results indicated that alkalization before crosslinking helps to protect amine group from crosslinking and hence increases the uptake capacity and selectively of the synthesized beads toward Ag (I). The maximum uptakes of Ag (I) and Cu (II) were 82.9 and 15.5 mg g−1, respectively, at room temperature with an initial concentration of each metal being 2.0 mM and the sorbent dosage of 1.0 g L−1. The uptake of Ag (I) and Cu (II) by the beads can be better described by Langmuir isotherm and pseudo‐second rate equation. Analyses from FTIR and XPS confirmed that free amine, hydroxyl, and
groups are involved in metal binding with amine and hydroxyl groups more selective to Ag (I). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42717.
Evaluation of high temperature polymers in nanolayered films and gradient refractive index (GRIN) lenses
Authors: Yin Kezhen , Ji Shanzuo , Fein Howard , Ponting Michael , Olah Andrew , Baer Eric 
Published: July 2015

ABSTRACTA new polymer nanolayer gradient refractive index (GRIN) system with more robust thermal stability because of incorporation of a high glass transition temperature polyester, OKP4HT, was demonstrated. A combination of extruded nanolayered GRIN film systems, comprised of five unique polymer materials, were combined to produce laminate optics comprised of a large internal refractive index gradient distribution, n = 1.445 – 1.630, without degradation of optical transmissive properties. The optical performance of a series of varied magnitude GRIN lenses, ranging from Δn = 0 to 0.185, was evaluated. Increasing the lens refractive index range resulted in decreased optic sphericalaberrations that followed analytical predictions. An analytical approach was reported to correlate the polymer material upper service temperature (UST) to the onset of polymer material loss modulus as measured by DMTA. Thermo‐optical interferometry measurements of irreversible lens deformation confirmed the lenses UST at 125°C for the OKP4HT/PC system as compared to 75°C for a PMM/SAN17 system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42741.
DTI and VBM reveal white matter changes without associated gray matter changes in patients with idiopathic restless legs syndrome
Authors: Belke Marcus , Heverhagen Johannes T. , Keil Boris , Rosenow Felix , Oertel Wolfgang H. , Stiasny‐Kolster Karin , Knake Susanne , Menzler Katja 
Published: July 2015

AbstractBackground and PurposeWe evaluated cerebral white and gray matter changes in patients with iRLS in order to shed light on the pathophysiology of this disease.MethodsTwelve patients with iRLS were compared to 12 age‐ and sex‐matched controls using whole‐head diffusion tensor imaging (DTI) and voxel‐based morphometry (VBM) techniques. Evaluation of the DTI scans included the voxelwise analysis of the fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD).ResultsDiffusion tensor imaging revealed areas of altered FA in subcortical white matter bilaterally, mainly in temporal regions as well as in the right internal capsule, the pons, and the right cerebellum. These changes overlapped with changes in RD. Voxel‐based morphometry did not reveal any gray matter alterations.ConclusionsWe showed altered diffusion properties in several white matter regions in patients with iRLS. White matter changes could mainly be attributed to changes in RD, a parameter thought to reflect altered myelination. Areas with altered white matter microstructure included areas in the internal capsule which include the corticospinal tract to the lower limbs, thereby supporting studies that suggest changes in sensorimotor pathways associated with RLS.
Performance of Recombinant‐Whole‐Cell‐Catalyzed Reductions in Deep‐Eutectic‐Solvent–Aqueous‐Media Mixtures
Authors: Müller Christoph R. , Lavandera Iván , Gotor‐Fernández Vicente , Domínguez de María Pablo 
Published: July 2015

AbstractDeep‐eutectic solvents (DES) are cost‐effective, nonhazardous solvents that may be used in biocatalysis as nonconventional media that enable biotransformations with industrially sound high substrate loadings. Based on promising prognoses, this paper explores successfully the use of whole cells overexpressing oxidoreductases as biocatalysts for the stereoselective reduction of ketones in different DES–aqueous‐media solutions. Enzymes like Ralstonia sp. alcohol dehydrogenase (ADH) and horse liver ADH, overexpressed in Escherichia coli, remain active at different DES proportions (for example, DES:buffer, 80:20 v/v) to enable nonconventional biotransformations. Furthermore, the enantiomeric excesses obtained for a broad range of aromatic substrates increase significantly if DES is added, which provides a useful tool for combining high substrate loadings and improved enzymatic selectivities while working with nonhazardous solvents. Different DES are successfully employed, which gives hints of the potential that these emerging solvents may have.
Microwave Discharge Electrodeless Lamps. Part VIII: Continuous On‐Site Solar Energy Remediation of Contaminated Water
Authors: Horikoshi Satoshi , Nishimura Tomoki , Tsutsumi Hideya , Serpone Nick 
Published: July 2015

AbstractMicrowave discharge electrodeless lamps (MDELs) have been examined for continuous on‐site field treatment of contaminated water using solar cells to provide the necessary electrical power. The equipment aimed to decontaminate water in areas impacted by natural disasters such as the extensive earthquake that hit Eastern Japan in 2011. An energy‐saving semiconductor microwave generator provided the microwaves to activate the MDELs in a microwave/UV reactor setup operated using a single‐mode applicator and an E/H tuner. The herbicide 2,4‐dichlorophenoxyacetic acid degraded within a shorter time compared to methylene blue at a defined flow rate through the microwave/UV reactor. Sterilization of natural water contaminated with the bacterial microorganism Escherichia coli was complete within 20 min.
Raman Spectroscopy in Lithium–Oxygen Battery Systems
Authors: Gittleson Forrest S. , Yao Koffi P. C. , Kwabi David G. , Sayed Sayed Youssef , Ryu Won‐Hee , Shao‐Horn Yang , Taylor André D. 
Published: July 2015

AbstractElectrochemical processes in lithium–oxygen (Li–O2 or Li–air) batteries are complex, with chemistry depending on cycling conditions, electrode materials and electrolytes. In non‐aqueous Li–O2 cells, reversible lithium peroxide (Li2O2) and irreversible parasitic products (i.e., LiOH, Li2CO3, Li2O) are common. Superoxide intermediates (O2−, LiO2) contribute to the formation of these species and are transiently stable in their own right. While characterization techniques like XRD, XPS and FTIR have been used to observe many Li–O2 species, these methods are poorly suited to superoxide detection. Raman spectroscopy, however, may uniquely identify superoxides from O−O vibrations. The ability to fingerprint Li–O2 products in situ or ex situ, even at very low concentrations, makes Raman an essential tool for the physicochemical characterization of these systems. This review contextualizes the application of Raman spectroscopy and advocates for its wider adoption in the study of Li–O2 batteries.
Following Adsorbate Coverage on Anodes of High‐Temperature Polymer Electrolyte Membrane Fuel Cells in the Presence of CO and H2O by using In Operando X‐ray Absorption Spectroscopy
Authors: Caldwell Keegan M. , Kaserer Sebastian , Roth Christina , Ramaker David E. 
Published: July 2015

AbstractApplication of the Δμ X‐ray absorption near‐edge spectroscopy analysis technique to a polybenzimidazole‐membrane‐based high‐temperature (170 °C) polymer electrolyte membrane fuel cell (PEMFC) under varying conditions reveals binding‐site details for H, CO, and biphosphate on a platinum nanoparticle anode surface. A synergistic interplay between CO and biphosphate adsorption is found, so that with increasing CO in the gas feed (below 3–4 % in H2), an increased biphosphate coverage becomes visible, apparently because small amounts of adsorbed CO force more localization of the phosphate species, which is believed to be adsorbed on top of the existing H overlayer. Increasing the concentration of CO (well above 4 %) causes CO poisoning to takeover and dramatically decrease the activity, though, compared to low‐temperature PEMFCs, huge amounts of CO can still be tolerated. Adding small amounts of water (less than 7 mg min−1) with CO to the anode feed reduces the amount of adsorbed phosphate and, thereby, increases the activity.
Vertically Oriented Polymer Electrolyte Nanofiber Catalyst Support for Thin Film Proton‐Exchange Membrane Fuel Cell Electrodes
Authors: Babu S. Komini , Atkinson Robert W. , Papandrew Alexander B. , Litster Shawn 
Published: July 2015

AbstractPolymer electrolyte fuel cells are highly efficient and offer high power density, but high precious‐metal loading and degradation of carbon‐supported platinum (Pt) catalysts still hinder commercialization. Ionomer binders in conventional electrodes also introduce undesirable, high oxygen‐transport resistance. This paper presents an alternative composite Nafion nanofiber catalyst support electrode, in which the nanofibers provide robust internal proton transport to a conformal Pt catalyst coating without impeding O2 transport. The high‐surface‐area electrodes are prepared by solution casting ionomer onto a sacrificial template to simultaneously fabricate the nanofibers and the membrane. Thin Pt films are deposited on the nanofibers using either physical vapor deposition or chemical vapor deposition. The electrochemical characterization of the nanofiber electrodes demonstrates the high current density and specific activity of this nanofiber approach relative to prior electrodes fabricated by depositing Pt directly onto other Nafion surfaces.