bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric Transformations by Deprotonation Using Chiral Lithium Amides
Authors: S. Simpkins Nigel , D. Weller Michael 
Published: February 2015

AbstractLithium dialkylamides, especially lithium diisopropylamide (LDA), are valuable bases in organic synthesis but it is only since 1980 that their chiral counterparts have found application in reactions that can be broadly defined as asymmetric deprotonations. This chapter provides a comprehensive overview of all selective deprotonation processes mediated by chiral lithium amides, including desymmetrizations, kinetic resolutions, and other applications such as regioselective enolizations of chiral substrates.The chapter covers the entire substrate scope of chiral lithium amide deprotonation reactions, which includes rearrangement of epoxides to allylic alcohols, enolizations of carbonyl compounds (principally, but not exclusively, cyclic ketones), and metalations of organometallics (especially tricarbonyl(η6‐arene)chromium(0) complexes) and miscellaneous phosphorous‐ or sulfur‐containing compounds.It is possible to perform some benchmark reactions under “catalytic conditions,” i.e., using substoichiometic quantities of chiral lithium amide, particularly epoxide rearrangements. The capability of deprotonations, mediated by chiral lithium amides, to deliver non‐racemic intermediates with acceptable selectivity for target synthesis is amply illustrated by the examples included in the review. In particular, the desymmetrization of conformationally biased prochiral cyclic ketones has become a well‐established strategy for organic synthesis, and has seen significant application in target‐oriented synthesis.
The McMurry Coupling and Related Reactions
Authors: Takeda Takeshi , Tsubouchi Akira 
Published: February 2015

AbstractThe McMurry coupling reaction has been recognized as one of the most efficient methods for the synthesis of alkenes from carbonyl compounds. This reaction can be applied to the preparation of various alkenes that are otherwise difficult to prepare. For example, sterically congested tetrasubstituted alkenes as well as medium to large membered rings involving natural products may be accessed via this process. This coupling utilizes various low‐valent titanium reagents generated by the reduction of titanium (III or IV) chloride with K, Zn, LiAlH4, C8K, amongst others. Furthermore, a variety of low‐valent metal species other than titanium, including aluminum, zirconium, niobium, molybdenum, indium, tungsten, and samarium, have also been found to promote the reductive coupling of carbonyl compounds. The scope and limitations of these reagent systems are reviewed in this chapter, together with the stereochemistry and reaction mechanism. This reaction is categorized into four coupling modes: i) homocoupling giving symmetrical alkenes, ii) mixed coupling giving unsymmetrical alkenes, iii) intramolecular coupling giving cycloalkenes, and iv) tandem coupling giving cyclic polyenes. Characteristics of these reaction modes are described briefly. A selection of synthetic applications are reviewed, including examples of the preparation of sterically congested and strained alkenes, medium to large‐ring compounds, biologically active targets, as well as substrates applicable in material science. Experimental conditions used for this versatile process are summarized to assist the choice of suitable conditions.
Iron‐Catalyzed Cross‐Coupling Reactions
Authors: Nakamura Eiichi , Hatakeyama Takuji , Ito Shingo , Ishizuka Kentaro , Ilies Laurean , Nakamura Masaharu 
Published: February 2015

AbstractAbundant, inexpensive, and nontoxic iron salts can efficiently catalyze the cross‐coupling reaction of organic electrophiles with organometallic reagents. A large variety of aryl, acyl, alkenyl, allylic, benzylic, propargylic, and alkyl electrophiles can be successfully coupled with organomagnesium, ‐zinc, ‐copper, ‐manganese, and ‐boron reagents. Coupling reactions of two organometallic reagents under oxidative conditions and of two organic halides under reductive conditions are also discussed. The reaction mechanism is controversial and various mechanisms, sometimes interconnected, in which iron can adopt different oxidation states have been proposed. Electron‐transfer processes may also be involved.
The Boronic Acid Mannich Reaction
Authors: G. Pyne Stephen , Tang Minyan 
Published: February 2015

Abstract
The boronic acid Mannich reaction is a three‐component reaction between a carbonyl compound (aldehyde or ketone), an amine (primary or secondary) and a boronic acid. This chapter addresses the mechanism, stereochemistry, and the scope and limitations of each of the three components of this reaction. Some typical experimental conditions are provided along with a comprehensive Tabular Survey.
This three‐component reaction is extremely versatile for preparing important chiral starting materials for the synthesis of molecules of biological interest, including chiral α‐amino acids, 1,2‐amino alcohols, 2‐aminoalkyl phenols, heterocycles, and alkaloids as shown in the general scheme below.
How well do regional climate models simulate the spatial dependence of precipitation? An application of pair‐copula constructions
Authors: Hobæk Haff Ingrid , Frigessi Arnoldo , Maraun Douglas 
Published: February 2015

AbstractWe investigate how well a suite of regional climate models (RCMs) from the ENSEMBLES project represents the residual spatial dependence of daily precipitation. The study area we consider is a 200 km × 200 km region in south central Norway, with RCMs driven by ERA‐40 boundary conditions at a horizontal resolution of approximately 25 km × 25 km. We model the residual spatial dependence with pair‐copula constructions, which allows us to assess both the overall and tail dependence in precipitation, including uncertainty estimates. The selected RCMs reproduce the overall dependence rather well, though the discrepancies compared to observations are substantial. All models overestimate the overall dependence in the west‐east direction. They also overestimate the upper tail dependence in the north‐south direction during winter, and in the west‐east direction during summer, whereas they tend to underestimate this dependence in the north‐south direction in summer. Moreover, many of the climate models do not simulate the small‐scale dependence patterns caused by the pronounced orography well. However, the misrepresented residual spatial dependence does not seem to affect estimates of high quantiles of extreme precipitation aggregated over a few grid boxes. The underestimation of the area‐aggregated extreme precipitation is due mainly to the well‐known underestimation of the univariate margins for individual grid boxes, suggesting that the correction of RCM biases in precipitation might be feasible.
Lösemittelgemische, Vorbemerkungen [Air Monitoring Methods in German language, 2014]
Authors: Tschickardt M. , Krämer W. , Breuer D. , Eisenhardt A. , Hebisch R. , Karmann J. , Moritz A. , Nitz G. , Schmitt R. , Schneider W. 
Published: February 2015

Abstract

Veröffentlicht in der Reihe
Analytische Methoden zur Prüfung gesundheitsschädlicher Arbeitsstoffe: Luftanalysen
, 18. Lieferung, Ausgabe 2014

Der Artikel enthält folgende Kapitel:
Tetrachlorethen [Air Monitoring Methods in German language, 2014]
Authors: Tschickardt M. , Krämer W. 
Published: February 2015

Abstract

Veröffentlicht in der Reihe
Analytische Methoden zur Prüfung gesundheitsschädlicher Arbeitsstoffe: Luftanalysen
, 11. Lieferung, Ausgabe 1998

Der Artikel enthält folgende Kapitel:

Grundlage des Verfahrens

Geräte, Chemikalien und Lösungen

Geräte

Chemikalien

Vorbehandlung der Adsorptionsröhrchen

Lösungen

Prüfgase und Vergleichsstandards

Probenahme und Probenaufbereitung

Gaschromatographische Arbeitsbedingungen

Analytische Bestimmung

Kalibrierung

Berechnung des Analysenergebnisses

Beurteilung des Verfahrens

Präzision und erweiterte Messunsicherheit

Wiederfindung und Einfluss der Luftfeuchte

Bestimmungsgrenze

Kapazität des Probenträgers

Lagerfähigkeit

Störeinflüsse

Diskussion
Sinonasal neuroendocrine carcinoma: a population‐based analysis of incidence and survival
Authors: Patel Tapan D. , Vazquez Alejandro , Dubal Pariket M. , Baredes Soly , Liu James K. , Eloy Jean Anderson 
Published: February 2015

BackgroundSinonasal neuroendocrine carcinoma (SNEC) is a rare, aggressive tumor usually associated with a poor prognosis. This study analyzes the clinicopathological characteristics and survival outcomes of SNEC using population‐based data.MethodsThe Surveillance, Epidemiology, and End Results (SEER) database (1973 to 2011) was queried for SNEC cases. Data analyzed included patient demographics, incidence, treatment modality, and survival.ResultsA total of 201 cases of SNEC were identified. Mean age at diagnosis was 55.8 ± 15.7 years. Overall 5‐year disease‐specific survival (DSS) rate for SNEC was 50.8%. Five‐year survival analysis for SNEC by site revealed DSS of 80.7%, 59.2%, 34.5%, and 33.0% for the sphenoid sinus, nasal cavity, maxillary sinus, and ethmoid sinus, respectively (p = 0.0014). Cox proportional hazard analysis revealed greater hazard of death for the maxillary (hazard ratio [HR] 2.14; 95% confidence interval [CI], 1.21 to 3.71; p = 0.0094) and ethmoid sinuses (HR 1.83; 95% CI, 1.05 to 3.16; p = 0.0345) when compared to the nasal cavity. Advanced stage disease (stages III to IV, 5‐year DSS 40.5%, p = 0.0008) was associated with poor survival outcomes. Survival was better among those treated with surgery (with [59.4%] or without [69.0%] radiotherapy) than those treated with primary radiotherapy alone (39.9%) (p < 0.0001).ConclusionSNEC commonly presents at an advanced‐stage with poor survival outcomes. Negative prognostic factors include primary tumor site and advanced stage disease. SNEC is a highly aggressive tumor necessitating surgery and/or surgery with adjuvant radiotherapy as the treatment of choice.
Enantioselektive Katalyse photochemischer Reaktionen
Authors: Brimioulle Richard , Lenhart Dominik , Maturi Mark M. , Bach Thorsten 
Published: February 2015

AbstractDie Natur des angeregten Zustands macht die Entwicklung chiraler Katalysatoren für enantioselektive photochemische Reaktionen zu einer enormen Herausforderung. Die Absorption eines 400‐nm‐Photons entspricht einer Energieaufnahme von etwa 300 kJ mol−1. Es bedarf innovativer Konzepte, um in einem derart großen Abstand vom Grundzustand Reaktionspfade zu eröffnen, die gezielt zu einem Enantiomer einer chiralen Verbindung führen. Hier werden die beiden wesentlichen Vorgehensweisen für homogen katalysierte, enantioselektive Prozesse diskutiert. Im ersten Teil werden chirale Photokatalysatoren besprochen, die in den photochemischen Schlüsselschritt eingreifen und in diesem Schritt eine asymmetrische Induktion bewirken. Im zweiten Teil werden Reaktionen vorgestellt, in denen die photochemische Anregung durch einen achiralen Katalysator erfolgt und die asymmetrische Induktion durch einen zweiten chiralen Katalysator gewährleistet wird (duale Katalyse).
A Trefoil Knotted Polymer Produced through Ring Expansion
Authors: Cao Peng‐Fei , Mangadlao Joey , Advincula Rigoberto 
Published: February 2015

AbstractA synthetic strategy is reported for the production of a trefoil knotted polymer from a copper(I)‐templated helical knot precursor through ring expansion. The expected changes in the properties of the knotted polymer compared to a linear analogue, for example, reduced hydrodynamic radius and lower intrinsic viscosity, together with an atomic force microscopy (AFM) image of individual molecular knots, confirmed the formation of the resulting trefoil knotted polymer. The strategies employed here could be utilized to enrich the variety of available polymers with new architectures.
Copper/Palladium Synergistic Catalysis for the syn‐ and anti‐Selective Carboboration of Alkenes
Authors: Logan Kaitlyn M. , Smith Kevin B. , Brown M. Kevin 
Published: February 2015

AbstractA method for the diastereoselective carboboration of 1,2‐disubstituted styrenes with aryl/vinyl bromides and (Bpin)2 is reported. High diastereoselectivities and yields are observed for the formation of either diastereomer of the product from a single alkene isomer. These reactions provide access to a diverse range of structures from simple starting materials.
Enantioselective Catalysis of Photochemical Reactions
Authors: Brimioulle Richard , Lenhart Dominik , Maturi Mark M. , Bach Thorsten 
Published: February 2015

AbstractThe nature of the excited state renders the development of chiral catalysts for enantioselective photochemical reactions a considerable challenge. The absorption of a 400 nm photon corresponds to an energy uptake of approximately 300 kJ mol−1. Given the large distance to the ground state, innovative concepts are required to open reaction pathways that selectively lead to a single enantiomer of the desired product. This Review outlines the two major concepts of homogenously catalyzed enantioselective processes. The first part deals with chiral photocatalysts, which intervene in the photochemical key step and induce an asymmetric induction in this step. In the second part, reactions are presented in which the photochemical excitation is mediated by an achiral photocatalyst and the transfer of chirality is ensured by a second chiral catalyst (dual catalysis).
Highly Isoselective Coordination Polymerization of ortho‐Methoxystyrene with β‐Diketiminato Rare‐Earth‐Metal Precursors
Authors: Liu Dongtao , Yao Changguang , Wang Rong , Wang Meiyan , Wang Zichuan , Wu Chunji , Lin Fei , Li Shihui , Wan Xinhua , Cui Dongmei 
Published: February 2015

AbstractStereoselective coordination/insertion polymerization of the polar ortho‐methoxystyrene has been achieved for the first time by using the cationic β‐diketiminato rare‐earth‐metal species. High activity and excellent isoselectivity (mmmm>99 %) were acheived. The unmasked Lewis‐basic methoxy group does not poison the Lewis‐acidic metal center, but instead activates the polymerization through σ‐π chelation to the active species together with the vinyl group, thus lower the coordination and activation energies as compared with those of styrene derivatives lacking the methoxy group.
o‐Carborane‐Based Anthracene: A Variety of Emission Behaviors
Authors: Naito Hirofumi , Morisaki Yasuhiro , Chujo Yoshiki 
Published: February 2015

AbstractAn o‐carborane‐based anthracene was synthesized, and single crystals, with incorporated solvent molecules, were obtained from the CHCl3, CH2Cl2, and C6H6 solutions. The anthracene ring in the crystal is highly distorted by the formation of a π‐stacked dimer between the anthracene units. The crystals exhibited a variety of emission behaviors such as aggregation‐induced emission (AIE), crystallization‐induced emission (CIE), aggregation‐caused quenching (ACQ), and multichromism.
Auger Ionization Beats Photo‐Oxidation of Semiconductor Quantum Dots: Extended Stability of Single‐Molecule Photoluminescence
Authors: Yamashita Shin‐ichi , Hamada Morihiko , Nakanishi Shunsuke , Saito Hironobu , Nosaka Yoshio , Wakida Shin‐ichi , Biju Vasudevanpillai 
Published: February 2015

AbstractDespite the bright and tuneable photoluminescence (PL) of semiconductor quantum dots (QDs), the PL instability induced by Auger recombination and oxidation poses a major challenge in single‐molecule applications of QDs. The incomplete information about Auger recombination and oxidation is an obstacle in the resolution of this challenge. Here, we report for the first time that Auger‐ionized QDs beat self‐sensitized oxidation and the non‐digitized PL intensity loss. Although high‐intensity photoactivation insistently induces PL blinking, the transient escape of QDs into the ultrafast Auger recombination cycle prevents generation of singlet oxygen (1O2) and preserves the PL intensity. By the detection of the NIR phosphorescence of 1O2 and evaluation of the photostability of single QDs in aerobic, anaerobic, and 1O2 scavenger‐enriched environments, we disclose relations of Auger ionization and 1O2‐mediated oxidation to the PL stability of single QDs, which will be useful during the formulation of QD‐based single‐molecule imaging tools and single‐photon devices.
Anti‐inflammatory activity and molecular mechanism of delphinidin 3‐sambubioside, a Hibiscus anthocyanin
Authors: Sogo Takayuki , Terahara Norihiko , Hisanaga Ayami , Kumamoto Takuma , Yamashiro Takaaki , Wu Shusong , Sakao Kozue , Hou De‐Xing 
Published: February 2015

AbstractDelphinidin 3‐sambubioside (Dp3‐Sam), a Hibiscus anthocyanin, was isolated from the dried calices of Hibiscus sabdariffa L, which has been used for folk beverages and herbal medicine although the molecular mechanisms are poorly defined. Based on the properties of Dp3‐Sam and the information of inflammatory processes, we investigated the anti‐inflammatory activity and molecular mechanisms in both cell and animal models in the present study. In the cell model, Dp3‐Sam and Delphinidin (Dp) reduced the levels of inflammatory mediators including iNOS, NO, IL‐6, MCP‐1, and TNF‐α induced by LPS. Cellular signaling analysis revealed that Dp3‐Sam and Dp downregulated NF‐κB pathway and MEK1/2‐ERK1/2 signaling. In animal model, Dp3‐Sam and Dp reduced the production of IL‐6, MCP‐1 and TNF‐α and attenuated mouse paw edema induced by LPS. Our in vitro and in vivo data demonstrated that Hibiscus Dp3‐Sam possessed potential anti‐inflammatory properties. © 2015 BioFactors, 41(1):58–65, 2015
A non‐chromatographic method for the removal of endotoxins from bacteriophages
Authors: Branston Steven D. , Wright Jason , Keshavarz‐Moore Eli 
Published: February 2015

ABSTRACTThe Ff filamentous bacteriophages show potential as a new class of therapeutics, displaying utility in materials science as well as pharmaceutical applications. These phages are produced by the infection of E. coli, a Gram‐negative bacterium which unavoidably sheds endotoxins into the extracellular space during growth. Since endotoxin molecules are highly immunoreactive, separation from the phage product is of critical importance, particularly those developed for human therapeutic use. The properties of M13, one of the Ff group, present a purification challenge chiefly because the standard scalable method for endotoxin removal from proteins—anion exchange chromatography—is not applicable due to pI similarity between the particles. This article examines the potential of polyethylene glycol (PEG)–NaCl precipitation as a scalable method for the separation of endotoxins from phage M13. Precipitation of M13 by 2% (w/v) PEG 6 000, 500 mM NaCl reduced endotoxin contamination of the phage product by 88%, but additional precipitation rounds did not maintain this proportional decrease. Dynamic light scattering was subsequently used to determine the effectiveness of a detergent to disassociate endotoxin molecules from M13. As a result, PEG–NaCl precipitation was supplemented with up to 2% (v/v) Triton X‐100 to improve separation. A 5.7 log10 reduction in endotoxin concentration was achieved over three rounds of precipitation whilst retaining over 97% of the phage. This method compares favorably with the well‐known ATPS (Triton X‐114) technique for endotoxin removal from protein solutions. Biotechnol. Bioeng. 2015;112: 1714–1719. © 2015 Wiley Periodicals, Inc.
Collaborative consumption: determinants of satisfaction and the likelihood of using a sharing economy option again
Authors: Möhlmann Mareike 
Published: February 2015

AbstractCollaborative consumption, often associated with the sharing economy, takes place in organized systems or networks, in which participants conduct sharing activities in the form of renting, lending, trading, bartering, and swapping of goods, services, transportation solutions, space, or money. In this paper, a framework on the determinants of choosing a sharing option is developed and tested with two quantitative studies by applying partial least squares path modeling analysis. In study 1, users of the B2C car sharing service car2go (N = 236), and in study 2, users of the C2C online community accommodation marketplace Airbnb (N = 187) are surveyed. The results reveal the satisfaction and the likelihood of choosing a sharing option again to be predominantly explained by determinants serving users' self‐benefit. Utility, trust, cost savings, and familiarity were found to be essential in both studies, while service quality and community belonging were identified solely in study 1. Four proposed determinants had no influence on any of the endogenous variables. This applies to environmental impact, internet capability, smartphone capability, and trend affinity. Finally, research and managerial implications are discussed. Copyright © 2015 John Wiley & Sons, Ltd.
Improving Oxygen Electrochemistry through Nanoscopic Confinement
Authors: Doyle Andrew D. , Montoya Joseph H. , Vojvodic Aleksandra 
Published: February 2015

AbstractThe front cover artwork for Issue 05/2015 is provided by Dr. Aleksandra Vojvodic and co‐workers from Stanford University and the SUNCAT Center for Interfacial Science and Catalysis, USA. The image shows a schematic of the catalytic oxygen “evolution” reaction inside a well‐defined ruthenium oxide nanochannel structure. See the Communication itself at http://dx.doi.org/10.1002/cctc.201402864.
(E)‐,(Z)‐Parallel Preparative Methods for Stereodefined β,β‐Diaryl‐ and α,β‐Diaryl‐α,β‐unsaturated Esters: Application to the Stereocomplementary Concise Synthesis of Zimelidine
Authors: Ashida Yuichiro , Sato Yuka , Suzuki Takeyuki , Ueno Kanako , Kai Ken‐ichiro , Nakatsuji Hidefumi , Tanabe Yoo 
Published: February 2015

AbstractParallel and practical methods for the preparation of both (E)‐ and (Z)‐β‐aryl1‐β‐aryl2‐α,β‐unsaturated esters 1 and (E)‐ and (Z)‐α‐aryl1‐β‐aryl2‐α,β‐unsaturated esters 2 are described. These methods involve accessible, robust, stereocomplementary N‐methylimidazole (NMI)‐mediated enol tosylations (14 examples, 70–99 % yield), as well as stereoretentive Suzuki–Miyaura cross‐couplings (36 examples, 64–99 % yield). The highlighted feature of the present protocol is the use of parallel and stereocomplementary approaches to obtain highly (E)‐ and (Z)‐pure products 1 and 2 by utilizing sequential enol tosylations and cross‐coupling reactions. An expeditious and parallel synthesis of (E)‐ and (Z)‐zimelidine (3), which is a highly representative selective serotonin reuptake inhibitor (SSRI), was performed by utilizing the present methods.
Rapid Sonochemical Synthesis of Luminescent and Paramagnetic Copper Nanoclusters for Bimodal Bioimaging
Authors: Wang Chuanxi , Cheng Hao , Sun Yuanqing , Lin Quan , Zhang Chi 
Published: February 2015

AbstractHerein, luminescent and magnetic copper nanoclusters (CuNCs) are synthesized by a one‐pot sonochemical route using glutathione (GSH) as a reducing and stabilizing agent. The resultant CuNCs show red fluorescence and paramagnetic properties at room temperature. In addition, the as‐prepared GSH‐CuNCs are water‐soluble, exhibit low toxicity, and have multifunctional surface chemistry due to the GSH protective layer. Folic acid (FA) was covalently anchored to the GSH‐CuNCs, and the nanoprobes were used for highly selective, targeted fluorescent imaging (FI) of gastric cancer HeLa cells with laser scanning confocal microscopy. Finally, the as‐prepared GSH‐CuNCs could work as T1 contrast agents for magnetic resonance imaging (MRI) due to their paramagnetic properties. These findings highlight the fascinating features of luminescent and magnetic CuNCs, which are a promising platform for bimodal MRI/FI of cancer cells.