bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transition‐Metal‐Free Intramolecular Carbene Aromatic Substitution/Büchner Reaction: Synthesis of Fluorenes and [6,5,7]Benzo‐fused Rings
Authors: Liu Zhenxing , Tan Haocheng , Wang Long , Fu Tianren , Xia Ying , Zhang Yan , Wang Jianbo 
Published: January 2015

AbstractIntramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by RhII catalysts with α‐diazocarbonyl compounds as the substrates. Herein a transition‐metal‐free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N‐tosylhydrazones as the diazo compound precursors and show wide substrate scope.
Feineinstellung der nucleophilen Reaktivität von Bor‐at‐Komplexen aus Aryl‐ und Heteroarylboronsäureestern
Authors: Berionni Guillaume , Leonov Artem I. , Mayer Peter , Ofial Armin R. , Mayr Herbert 
Published: January 2015

AbstractAus Thienyl‐ bzw. Furylboronsäureestern und Aryllithium‐Verbindungen hergestellte Bor‐at‐Komplexe wurden isoliert und durch Röntgenstrukturanalyse charakterisiert. Die Produkte und Mechanismen ihrer Reaktionen mit Carbenium‐ und Iminium‐Ionen wurden analysiert. Durch UV/Vis‐spektroskopische Verfolgung der Kinetik dieser Reaktionen wurde der Einfluss der Aryl‐Substituenten, der Diol‐Liganden (Pinakol, Ethylenglykol, Neopentylglykol, Brenzkatechin) und der Gegenionen auf die nucleophile Reaktivität der Bor‐at‐Komplexe untersucht. Eine Hammett‐Korrelation bestätigte die polare Natur ihrer Reaktionen mit Benzhydrylium‐Ionen, und die Korrelation lg k(20 °C)=sN(E+N) wurde verwendet, um die Nucleophilie der Bor‐at‐Komplexe zu bestimmen und mit der anderer Borate und Boronate zu vergleichen. Die Neopentylglykol‐ und Ethylenglykol‐Derivate sind 104‐mal reaktiver als die Pinakol‐ und Brenzkatechin‐Derivate.
A Complex Perovskite‐Type Oxynitride: The First Photocatalyst for Water Splitting Operable at up to 600 nm
Authors: Pan Chengsi , Takata Tsuyoshi , Nakabayashi Mamiko , Matsumoto Takao , Shibata Naoya , Ikuhara Yuichi , Domen Kazunari 
Published: January 2015

AbstractOne of the simplest methods for splitting water into H2 and O2 with solar energy entails the use of a particulate‐type semiconductor photocatalyst. To harness solar energy efficiently, a new water‐splitting photocatalyst that is active over a wider range of the visible spectrum has been developed. In particular, a complex perovskite‐type oxynitride, LaMgxTa1−xO1+3xN2−3x (x≥1/3), can be employed for overall water splitting at wavelengths of up to 600 nm. Two effective strategies for overall water splitting were developed. The first entails the compositional fine‐tuning of a photocatalyst to adjust the bandgap energy and position by forming a series of LaMgxTa1−xO1+3xN2−3x solid solutions. The second method is based on the surface coating of the photocatalyst with a layer of amorphous oxyhydroxide to control the surface redox reactions. By combining these two strategies, the degradation of the photocatalyst and the reverse reaction could be prevented, resulting in successful overall water splitting.
Oxide‐Supported IrNiOx Core–Shell Particles as Efficient, Cost‐Effective, and Stable Catalysts for Electrochemical Water Splitting
Authors: Nong Hong Nhan , Oh Hyung‐Suk , Reier Tobias , Willinger Elena , Willinger Marc‐Georg , Petkov Valeri , Teschner Detre , Strasser Peter 
Published: January 2015

AbstractActive and highly stable oxide‐supported IrNiOx core–shell catalysts for electrochemical water splitting are presented. IrNix@IrOx nanoparticles supported on high‐surface‐area mesoporous antimony‐doped tin oxide (IrNiOx /Meso‐ATO) were synthesized from bimetallic IrNix precursor alloys (PA‐IrNix /Meso‐ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA‐IrNix /Meso‐ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core–shell particles. The core–shell IrNiOx /Meso‐ATO catalyst displayed high water‐splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.
Pickering Interfacial Catalysis for Biphasic Systems: From Emulsion Design to Green Reactions
Authors: Pera‐Titus Marc , Leclercq Loïc , Clacens Jean‐Marc , De Campo Floryan , Nardello‐Rataj Véronique 
Published: January 2015

AbstractPickering emulsions are surfactant‐free dispersions of two immiscible fluids that are kinetically stabilized by colloidal particles. For ecological reasons, these systems have undergone a resurgence of interest to mitigate the use of synthetic surfactants and solvents. Moreover, the use of colloidal particles as stabilizers provides emulsions with original properties compared to surfactant‐stabilized emulsions, microemulsions, and micellar systems. Despite these specific advantages, the application of Pickering emulsions to catalysis has been rarely explored. This Minireview describes very recent examples of hybrid and composite amphiphilic materials for the design of interfacial catalysts in Pickering emulsions with special emphasis on their assets and challenges for industrially relevant biphasic reactions in fine chemistry, biofuel upgrading, and depollution.
Synthesis of Polycyclic Tertiary Carbinamines by Samarium Diiodide Mediated Cyclizations of Indolyl Sulfinyl Imines
Authors: Rao Chintada Nageswara , Lentz Dieter , Reissig Hans‐Ulrich 
Published: January 2015

AbstractSamarium diiodide mediated cyclizations of N‐acylated indole derivatives bearing sulfinyl imine moieties afforded polycyclic tertiary carbinamines with moderate to excellent diastereoselectivities. Lithium bromide and water turned out to be the best additives to achieve these transformations in good yields. Using enantiopure sulfinyl imines the outcome strongly depends on the reactivity of the indole moiety. Whereas with unactivated indole derivatives desulfinylation and formation of racemic products was observed, indoles bearing electron‐withdrawing substituents at C‐3 afforded the polycyclic products with intact N‐sulfinyl groups and with excellent diastereoselectivity, finally allowing the preparation of enantiopure tertiary carbinamines. The mechanisms of these processes are discussed.
Heterogeneous Water Oxidation: Surface Activity versus Amorphization Activation in Cobalt Phosphate Catalysts
Authors: González‐Flores Diego , Sánchez Irene , Zaharieva Ivelina , Klingan Katharina , Heidkamp Jonathan , Chernev Petko , Menezes Prashanth W. , Driess Matthias , Dau Holger , Montero Mavis L. 
Published: January 2015

AbstractIs water oxidation catalyzed at the surface or within the bulk volume of solid oxide materials? This question is addressed for cobalt phosphate catalysts deposited on inert electrodes, namely crystallites of pakhomovskyite (Co3(PO4)2⋅8 H2O, Pak) and phosphate‐containing Co oxide (CoCat). X‐ray spectroscopy reveals that oxidizing potentials transform the crystalline Pak slowly (5–8 h) but completely into the amorphous CoCat. Electrochemical analysis supports high‐TOF surface activity in Pak, whereas its amorphization results in dominating volume activity of the thereby formed CoCat material. In the directly electrodeposited CoCat, volume catalysis prevails, but not at very low levels of the amorphous material, implying high‐TOF catalysis at surface sites. A complete picture of heterogeneous water oxidation requires insight in catalysis at the electrolyte‐exposed “outer surface”, within a hydrated, amorphous volume phase, and modes and kinetics of restructuring upon operation.
Revealing the Preferred Interlayer Orientations and Stackings of Two‐Dimensional Bilayer Gallium Selenide Crystals
Authors: Li Xufan , Basile Leonardo , Yoon Mina , Ma Cheng , Puretzky Alexander A. , Lee Jaekwang , Idrobo Juan C. , Chi Miaofang , Rouleau Christopher M. , Geohegan David B. , Xiao Kai 
Published: January 2015

AbstractCharacterizing and controlling the interlayer orientations and stacking orders of two‐dimensional (2D) bilayer crystals and van der Waals (vdW) heterostructures is crucial to optimize their electrical and optoelectronic properties. The four polymorphs of layered gallium selenide (GaSe) crystals that result from different layer stackings provide an ideal platform to study the stacking configurations in 2D bilayer crystals. Through a controllable vapor‐phase deposition method, bilayer GaSe crystals were selectively grown and their two preferred 0° or 60° interlayer rotations were investigated. The commensurate stacking configurations (AA′ and AB stacking) in as‐grown bilayer GaSe crystals are clearly observed at the atomic scale, and the Ga‐terminated edge structure was identified using scanning transmission electron microscopy. Theoretical analysis reveals that the energies of the interlayer coupling are responsible for the preferred orientations among the bilayer GaSe crystals.
Stable Heterocyclopentane‐1,3‐diyls
Authors: Hinz Alexander , Schulz Axel , Villinger Alexander 
Published: January 2015

AbstractDiphosphadiazanediyl, [(μ‐NR)P]2 (R=Ter=2,6‐dimesitylphenyl), is known to readily activate small molecules with multiple bonds. CO is an especially intriguing species for activation, because either 1,1‐ or 1,2‐bridging mode would lead to a [1.1.1]bicycle or a carbene, respectively. The activation of CO with diphosphadiazanediyl already occurs at ambient temperatures (1 bar, 25 °C). However, CO is involved in an unprecedented ring expansion reaction under preservation of the biradical character, which leads to the formation of the first stable cyclopentane‐1,3‐diyl analogue displaying photochromic molecular switch characteristics.
Fine‐Tuning the Nucleophilic Reactivities of Boron Ate Complexes Derived from Aryl and Heteroaryl Boronic Esters
Authors: Berionni Guillaume , Leonov Artem I. , Mayer Peter , Ofial Armin R. , Mayr Herbert 
Published: January 2015

AbstractBoron ate complexes derived from thienyl and furyl boronic esters and aryllithium compounds have been isolated and characterized by X‐ray crystallography. Products and mechanisms of their reactions with carbenium and iminium ions have been analyzed. Kinetics of these reactions were monitored by UV/Vis spectroscopy, and the influence of the aryl substituents, the diol ligands (pinacol, ethylene glycol, neopentyl glycol, catechol), and the counterions on the nucleophilic reactivity of the boron ate complexes were examined. A Hammett correlation confirmed the polar nature of their reactions with benzhydrylium ions, and the correlation lg k(20 °C)=sN(E+N) was employed to determine the nucleophilicities of the boron ate complexes and to compare them with those of other borates and boronates. The neopentyl and ethylene glycol derivatives were found to be 104 times more reactive than the pinacol and catechol derivatives.
Engineered L‐Serine Hydroxymethyltransferase from Streptococcus thermophilus for the Synthesis of α,α‐Dialkyl‐α‐Amino Acids
Authors: Hernandez Karel , Zelen Igor , Petrillo Giovanna , Usón Isabel , Wandtke Claudia M. , Bujons Jordi , Joglar Jesús , Parella Teodor , Clapés Pere 
Published: January 2015

Abstractα,α‐Disubstituted α‐amino acids are central to biotechnological and biomedical chemical processes for their own sake and as substructures of biologically active molecules for diverse biomedical applications. Structurally, these compounds contain a quaternary stereocenter, which is particularly challenging for stereoselective synthesis. The pyridoxal‐5′‐phosphate (PLP)‐dependent L‐serine hydroxymethyltransferase from Streptococcus thermophilus (SHMTSth; EC 2.1.2.1) was engineered to achieve the stereoselective synthesis of a broad structural variety of α,α‐dialkyl‐α‐amino acids. This was accomplished by the formation of quaternary stereocenters through aldol addition of the amino acids D‐Ala and D‐Ser to a wide acceptor scope catalyzed by the minimalist SHMTSth Y55T variant overcoming the limitation of the native enzyme for Gly. The SHMTSth Y55T variant tolerates aromatic and aliphatic aldehydes as well as hydroxy‐ and nitrogen‐containing aldehydes as acceptors.
Investigation on jet stability, fiber diameter, and tensile properties of electrospun polyacrylonitrile nanofibrous yarns
Authors: Barua Bipul , Saha Mrinal C. 
Published: January 2015

ABSTRACTElectrospinning is a flexible and efficient method for producing nanofibers by using relatively dilute polymer solution. However, there are many parameters related to material and processing that influence the morphology and property of the nanofibers. This study investigates the influence of electric field and flow rate on diameter and tensile properties of nanofibers produced using polyacrylonitrile (PAN)‐dimethylformamide (DMF) solution. Stability of the spinning jet is investigated via fiber current measurement and an image system at different electric fields and solution flow rates. It is observed that a set of electric field and flow rate conditions favor producing thinnest, strongest, and toughest nanofibers during electrospinning process. Other conditions may lead to instability of the Taylor cone, discontinuous jet, larger diameter fiber, and lower mechanical properties. Finally, a simple dynamic whipping model is adopted to correlate the nanofiber diameter with volumetric charge density and is found to be excellent validating our experimental results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41918.
Unexpected Metal‐Free Transformation of gem‐Dibromomethylenes to Ketones under Acetylation Conditions
Authors: Kimura Rino , Sawayama Yusuke , Nakazaki Atsuo , Miyamoto Kazunori , Uchiyama Masanobu , Nishikawa Toshio 
Published: January 2015

AbstractNovel conditions for the transformation of gem‐dibromomethylenes to ketones are described. gem‐Dibromo compounds were treated with acetic anhydride and triethylamine in dichloromethane/water at room temperature under an air atmosphere to give the corresponding ketones in moderate yields. A radical mechanism is proposed based on experimental results.
Direct Oxidative Arylation of Aryl CH Bonds with Aryl Boronic Acids via Pd Catalysis Directed by the N,N‐Dimethylaminomethyl Group
Authors: Zhang Ji‐Cheng , Shi Jiang‐Ling , Wang Bi‐Qin , Hu Ping , Zhao Ke‐Qing , Shi Zhang‐Jie 
Published: January 2015

AbstractBiaryl skeletons were directly constructed via palladium‐catalyzed ortho‐arylation of N,N‐dimethyl benzylamine with aryl boronic acids with high efficiency and high regioselectivity under open‐flask conditions. The N,N‐dimethylaminomethyl group was first applied as a directing group in such an oxidative coupling. Various substrates proved to be efficient coupling partners, furnishing the corresponding ortho‐monoarylated or ‐diarylated arenes in moderate to good yields under mild conditions.
Modification of Bafilomycin Structure to Efficiently Synthesize Solid‐State NMR Probes that Selectively Bind to Vacuolar‐Type ATPase
Authors: Shibata Hajime , Tsuchikawa Hiroshi , Hayashi Tatsuru , Matsumori Nobuaki , Murata Michio , Usui Takeo 
Published: January 2015

AbstractBafilomycin (Baf) is one of the most potent inhibitors of vacuolar‐type ATPase, which is strongly implicated in age‐related diseases. However, the binding site of the antibiotic on the protein remains unclear because of the complexity of the structure of Baf bound to the target subunit in the transmembrane region. For conducting structural studies by applying solid‐state NMR, which is one of the most promising methodologies available for structural analysis in membrane system, preparing bioactive fluorinated Baf analogues is essential. In this study two Baf analogues were carefully designed and efficiently synthesized through the convergent coupling of three segments. Biological evaluation revealed that the activity of 24‐F‐Baf was comparable to that of Baf, indicating its utility as a potential probe for solid‐state NMR analysis. By contrast, desmethylated 24‐F‐Baf exhibited markedly diminished activity. The absence of two methyl groups caused a critical conformational change in the macrocyclic core structure necessary for binding to the target protein.
Feinbetonmatrix für Textilbeton
Authors: Lieboldt Matthias 
Published: January 2015

AbstractZur Herstellung von dünnen, leistungsfähigen Verstärkungsschichten mit feinmaschigen Bewehrungsstrukturen, wie beispielsweise Carbongelege, können nur spezielle Feinbetonmatrices verwendet werden, welche sich deutlich von konventionellen Betonen unterscheiden. Die granulometrische und mineralogische Zusammensetzung des Feinbetons muss sowohl auf die Eigenschaften der aus feinen Multifilamentgarnen bestehenden textilen Gelege als auch auf die Verarbeitungsprozesse abgestimmt sein. Im Rahmen der Grundlagenforschung wurden geeignete Rezepturen entwickelt und hinsichtlich des Verbundverhaltens mit der Bewehrung und der Dauerhaftigkeit eingehend untersucht. Jedoch sind diese Rezepturen wegen der zahlreichen trockenen und flüssigen Komponenten für eine baustellengerechte Anwendung ungeeignet. Es musste eine Trockenmischung entwickelt werden, die adäquate Eigenschaften aufweist. Im Folgenden werden die Anforderungen an den Feinbeton und die Umsetzung in einer praxistauglichen Werktrockenmischung erläutert. Im Besonderen wird auf die in der systemisch zugehörigen allgemeinen bauaufsichtlichen Zulassung geforderten Eigenschaften sowie die Qualitätssicherung und Verarbeitungsprozesse des Feinbetons eingegangen.Fine‐grained concrete matrix for TRC – requirements, adaption to construction site operation, propertiesFor the preparation of thin, capable reinforcement layers with finely woven reinforcement structures, such as carbon fabrics, only special matrices of fine concrete can be used, which significantly differ from conventional concretes mixtures. The granulometric and mineralogical composition of the fine concrete shall be adjusted to both, the properties of the textile fabrics consisting of fine multifilament yarn, as well as to the processing processes. In the context of fundamental research suitable formulations have been developed and investigated concerning the bond behavior of the reinforcement and the durability. However, these formulations are inappropriate regarding the numerous dry and liquid components of a construction site application. A dry mixture had to be developed which has adequate properties. Hereinafter the requirements of the fine concrete and the implementation of a practical factory dry mixture are explained. Specifically, the characteristics that are required by the general technical approval, just as the quality management and processing processes of the fine concrete will be explained.
Nutzung der abZ “Verfahren zur Verstärkung von Stahlbeton mit TUDALIT® (Textilbewehrter Beton)”
Authors: Assmann Ulrich , Offermann Peter 
Published: January 2015

AbstractMit der Marke TUDALIT® sind höchste Ansprüche an die Leis‐tungsfähigkeit der Materialien und an die Qualität der Ausführung verbunden. Auf diese hohen Qualitätsstandards hat sich der Verband TUDALIT e.V., dem Forscher, Hersteller, Planer und Anwender angehören, verständigt. Die TUDAG ist Inhaber der allgemeinen bauaufsichtlichen Zulassung und eröffnet allen interessierten Bauschaffenden die Lizenznahme unter der Voraussetzung, dass die hohen Standards der Marke TUDALIT® zwingend eingehalten werden.Use of the general technical approval “method of strengthening of steel reinforced concrete with TUDALIT® (textile reinforced concrete)”.With the brand TUDALIT®, high demands on the performance of the materials and the quality of construction work are connected. The members of the Association TUDALIT e. V. – these are researchers, manufacturers, designers and users – have made an agreement about these high quality standards. The TUDAG is the owner of general technical approval and opens up license acquisition to all interested builders on condition that the high standards of the brand TUDALIT® are complied.
Textilbeton – Eigenschaften des Verbundwerkstoffs
Authors: Lorenz Enrico , Schütze Elisabeth , Weiland Silvio 
Published: January 2015

AbstractWerden textile Bewehrungsgelege in Feinbeton eingebettet, entsteht der Verbundwerkstoff textilbewehrter Beton oder kurz Textilbeton. Wie bei jedem Verbundwerkstoff ist es in der Regel nicht möglich, aus den Eigenschaften der Ausgangsstoffe direkt auf das Verbundtragverhalten zu schließen. Dafür sind Kenntnisse über die Verbundeigenschaften zwischen Filamenten, Garn bzw. Textil und Matrix entscheidend. Neben der Charakterisierung und Identifikation der einzelnen Systemkomponenten sind zur allgemeinen Beschreibung des Tragverhaltens auch experimentelle Untersuchungen am Verbundwerkstoff erforderlich, die als Basis für Materialoptimierung, Identifikation von Tragmechanismen sowie Anwendung von Berechnungsmodellen dienen. Im Beitrag werden die grundlegenden Zulassungsversuche zur Ermittlung und Überprüfung der Material‐ und Bemessungskennwerte von Textilbeton zur Bauwerksverstärkung vorgestellt.Textile Reinforced Concrete – properties of the composite materialBy embedding a textile reinforcement into a fine‐grained concrete the composite material textile reinforced concrete is created. As with any composite material, it is not generally possible to deduce the structural behavior of the composite from the properties of the raw materials. This is why a profound knowledge of the bond behavior between filaments, rovings or textile and the concrete matrix is essential. In addition to the characterization and identification of the individual system components, experimental investigations on the composite material are necessary to describe the material behavior. These form the basis for material optimization, the identification of bearing mechanisms and the application of analytical models. This publication presents the fundamental approval tests that were conducted to determine and verify the material and characteristic values of textile reinforced concrete for the strengthening of bending‐stressed steel reinforced concrete members.