bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of β‐Lactams by Palladium(0)‐Catalyzed C(sp3)−H Carbamoylation
Authors: Dailler David , Rocaboy Ronan , Baudoin Olivier 
Published: May 2017

AbstractA general and user‐friendly synthesis of β‐lactams is reported that makes use of Pd0‐catalyzed carbamoylation of C(sp3)−H bonds, and operates under stoichiometric carbon monoxide in a two‐chamber reactor. This reaction is compatible with a range of primary, secondary and activated tertiary C−H bonds, in contrast to previous methods based on C(sp3)−H activation. In addition, the feasibility of an enantioselective version using a chiral phosphonite ligand is demonstrated. Finally, this method can be employed to synthesize valuable enantiopure free β‐lactams and β‐amino acids.
meso‐Cumulenic 2H‐Corroles from meso‐Ethynyl‐3H‐corroles
Authors: Ueta Kento , Naoda Koji , Ooi Shota , Tanaka Takayuki , Osuka Atsuhiro 
Published: May 2017

AbstractAlkynyl‐substituted 3H‐corrole 9 a was converted to [3]cumulenic 2H‐corrole 10 a by treatment with trimethylsilyl chloride (TMSCl), and 1,3‐butadiyne‐bridged 3H‐corrole dimer 11 b was transformed into [5]cumulene‐bridged 2H‐corrole dimer 12 b by oxidation with PbO2. Both 10 a and 12 b were metalated to form ZnII complexes 10 a‐Zn and 12 b‐Zn. The structures of 10 a‐Zn and 12 b‐Zn show planar conformations with bond‐length alternations that are analogous to those of tetraaryl [n]cumulenes. The cumulenic corrole dimers 12 b and 12 b‐Zn display large NIR absorption bands in the range of 700–1400 nm (maximum ϵ≈1.0×105 m−1 cm−1) owing to the effective π‐conjugation between the two corrole units through the [5]cumulene bridge.
A Dual Palladium and Copper Hydride Catalyzed Approach for Alkyl–Aryl Cross‐Coupling of Aryl Halides and Olefins
Authors: Friis Stig D. , Pirnot Michael T. , Dupuis Lauren N. , Buchwald Stephen L. 
Published: May 2017

AbstractWe report an efficient means of sp2–sp3 cross coupling for a variety of terminal monosubstituted olefins with aryl electrophiles using Pd and CuH catalysis. In addition to its applicability to a range of aryl bromide substrates, this process was also suitable for electron‐deficient aryl chlorides, furnishing higher yields than the corresponding aryl bromides in these cases. The optimized protocol does not require the use of a glovebox and employs air‐stable Cu and Pd complexes as precatalysts. A reaction on 10 mmol scale further highlighted the practical utility of this protocol. Employing a similar protocol, a series of cyclic alkenes were also examined. Cyclopentene was shown to undergo efficient coupling under these conditions. Lastly, deuterium‐labeling studies indicate that deuterium scrambling does not take place in this sp2‐sp3 cross coupling, implying that β‐hydride elimination is not a significant process in this transformation.
Isomerenselektive Erzeugung und spektroskopische Charakterisierung der Picolyl‐Radikale
Authors: Reusch Engelbert , Holzmeier Fabian , Constantinidis Philipp , Hemberger Patrick , Fischer Ingo 
Published: May 2017

AbstractStickstoff‐haltige resonanzstabilisierte Radikale wie Picolyl spielen eine wichtige Rolle in Verbrennungsprozessen und in der Astrochemie. Sie wurden jedoch bislang kaum untersucht, da es schwierig ist, sie isomerenselektiv zu erzeugen. Schwellenphotoelektronenspektren der drei Isomere des Picolyl‐Radikals, C6H6N, wurden mit Synchrotronstrahlung aufgenommen. Die Radikale wurden selektiv durch Pyrolyse aus Aminomethylpyridinen hergestellt. Ionisierungsenergien von 7.70, 7.59 und 8.01 eV wurden für 2‐, 3‐ bzw. 4‐Picolyl gemessen. Die beobachtete Schwingungsstruktur wurde einer Deformationsschwingung des aromatischen Rings zugeordnet. Die gewonnenen spektroskopischen Daten ermöglichen es, die verschiedenen Picolyl‐Isomere selektiv nachzuweisen, beispielsweise in der Flammenanalytik.
Enantioselective Synthesis of Tetrahydroquinolines by Borrowing Hydrogen Methodology: Cooperative Catalysis by an Achiral Iridacycle and a Chiral Phosphoric Acid
Authors: Lim Ching Si , Quach Thanh Truong , Zhao Yu 
Published: May 2017

AbstractWe report herein the highly enantioselective synthesis of 2‐substituted tetrahydroquinolines through borrowing hydrogen, a process recognized for its environmentally benign and atom‐economical nature. The use of an achiral iridacycle complex in combination with a chiral phosphoric acid as catalysts was the key to the development of this highly efficient and enantioselective transformation.
Selective Si−C(sp3) Bond Cleavage in (Aminomethyl)silanes by Carbanionic Nucleophiles and Its Stereochemical Course
Authors: Koller Stephan G. , Bauer Jonathan O. , Strohmann Carsten 
Published: May 2017

AbstractSelective cleavage of a silicon–carbon bond in tetraorganosilanes is still a great challenge. A new type of Si−C(sp3) bond cleavage in bench‐stable (aminomethyl)silanes with common organolithium reagents as nucleophiles has now been identified. Suitable leaving groups are benzyl, allyl, and phenylthiomethyl groups. A β‐donor function and polar solvents are essential for the reaction. Simple switching between α‐deprotonation and substitution is possible through slight modifications of the reaction conditions. The stereochemical course of the reaction was elucidated by using a silicon‐chiral benzylsilane. The new transformation proceeds stereospecifically with inversion of configuration and can be used for the targeted synthesis of enantiomerically pure tetraorganosilanes, which are otherwise difficult to access. Quantum chemical calculations provided insight into the mechanism of the new substitution.
Manganese‐Catalyzed Sustainable Synthesis of Pyrroles from Alcohols and Amino Alcohols
Authors: Kallmeier Fabian , Dudziec Beata , Irrgang Torsten , Kempe Rhett 
Published: May 2017

AbstractThe development of reactions that convert alcohols into important chemical compounds saves our fossil carbon resources as alcohols can be obtained from indigestible biomass such as lignocellulose. The conservation of our rare noble metals is of similar importance, and their replacement by abundantly available transition metals, such as Mn, Fe, or Co (base or nonprecious metals), in key technologies such as catalysis is a promising option. Herein, we report on the first base‐metal‐catalyzed synthesis of pyrroles from alcohols and amino alcohols. The most efficient catalysts are Mn complexes stabilized by PN5P ligands whereas related Fe and Co complexes are inactive. The reaction proceeds under mild conditions at catalyst loadings as low as 0.5 mol %, and has a broad scope and attractive functional‐group tolerance. These findings may inspire others to use Mn catalysts to replace Ir or Ru complexes in challenging dehydrogenation reactions.
Arsenic‐Rich Polyarsenides Stabilized by Cp*Fe Fragments
Authors: Schmidt Monika , Konieczny David , Peresypkina Eugenia V. , Virovets Alexander V. , Balázs Gabor , Bodensteiner Michael , Riedlberger Felix , Krauss Hannes , Scheer Manfred 
Published: May 2017

AbstractThe redox chemistry of [Cp*Fe(η5‐As5)] (1, Cp*=η5‐C5Me5) has been investigated by cyclic voltammetry, revealing a redox behavior similar to that of its lighter congener [Cp*Fe(η5‐P5)]. However, the subsequent chemical reduction of 1 by KH led to the formation of a mixture of novel Asn scaffolds with n up to 18 that are stabilized only by [Cp*Fe] fragments. These include the arsenic‐poor triple‐decker complex [K(dme)2][{Cp*Fe(μ,η2:2‐As2)}2] (2) and the arsenic‐rich complexes [K(dme)3]2[(Cp*Fe)2(μ,η4:4‐As10)] (3), [K(dme)2]2[(Cp*Fe)2(μ,η2:2:2:2‐As14)] (4), and [K(dme)3]2[(Cp*Fe)4(μ4,η4:3:3:2:2:1:1‐As18)] (5). Compound 4 and the polyarsenide complex 5 are the largest anionic Asn ligand complexes reported thus far. Complexes 2–5 were characterized by single‐crystal X‐ray diffraction, 1H NMR spectroscopy, EPR spectroscopy (2), and mass spectrometry. Furthermore, DFT calculations showed that the intermediate [Cp*Fe(η5‐As5)]−, which is presumably formed first, undergoes fast dimerization to the dianion [(Cp*Fe)2(μ,η4:4‐As10)]2−.
Scandium‐Mediated Formation of a Bis(tetrahydropentalene)
Authors: Rausch Janek , Liebing Phil , Lorenz Volker , Hilfert Liane , Busse Sabine , Maichle‐Mössmer Caecilia , Edelmann Frank T. 
Published: May 2017

AbstractThe reactivity of Li[Sc(COT′′)2] (1; COT′′=1,4‐bis(trimethylsilyl)cyclooctatetraenyl) towards CoCl2 is considerably different from that of related lanthanide triple‐decker sandwich complexes. In addition to the expected triple‐decker complex Sc2(COT′′)3 (2), the complex Sc2{μ‐BTHP}(COT′′)2 (3) is formed, which comprises the novel BTHP2− ligand (BTHP2−=bis(3,5‐bis(trimethylsilyl)‐1,3a,6,6a‐tetrahydropentalene‐1‐yl)diide or bis(2,7‐bis(trimethylsilyl)bicyclo[3.3.0]octa‐2,7‐dien‐4‐yl)diide, C16H10(SiMe3)42−). The formation of 3 is likely facilitated by the fact that scandium prefers η8,η3 coordination rather than highly symmetric η8,η8 coordination, and the η3‐coordinated COT′′ ligand in 1 is activated owing to a loss of aromaticity. Acid hydrolysis of 3 leads to air‐stable H2BTHP (4).
Isomer‐Selective Generation and Spectroscopic Characterization of Picolyl Radicals
Authors: Reusch Engelbert , Holzmeier Fabian , Constantinidis Philipp , Hemberger Patrick , Fischer Ingo 
Published: May 2017

AbstractNitrogen‐containing resonance‐stabilized radicals such as the picolyl radical are important in combustion chemistry and astrochemistry. They have only been scarcely studied because an isomer‐selective generation is often difficult. Herein, we present threshold photoelectron spectra of the three picolyl radical isomers, C6H6N, that were obtained with synchrotron radiation. The radicals were selectively generated by flash pyrolysis from aminomethylpyridine precursors through deamination. Ionization energies of 7.70, 7.59, and 8.01 eV were determined for 2‐, 3‐, and 4‐picolyl, respectively. The observed vibrational structure was assigned to an in‐plane deformation mode of the aromatic ring. The spectroscopic insight gained in this study can be used to distinguish different picolyl isomers in on‐line combustion analysis, for example.
Intermolecular Charge‐Transfer Interactions Facilitate Two‐Photon Absorption in Styrylpyridine–Tetracyanobenzene Cocrystals
Authors: Sun Lingjie , Zhu Weigang , Wang Wei , Yang Fangxu , Zhang Congcong , Wang Shufeng , Zhang Xiaotao , Li Rongjin , Dong Huanli , Hu Wenping 
Published: May 2017

AbstractCocrystals of 4‐styrylpyridine and 1,2,4,5‐tetracyanobenzene were successfully prepared by supramolecular self‐assembly. Donor–acceptor interactions between the molecular components are the main driving force for self‐assembly and contribute to intermolecular charge transfer. The cocrystals possess two‐photon absorption properties that are not observed in the individual components; suggesting that two‐photon absorption originates from intermolecular charge‐transfer interactions in the donor–acceptor system. The origin of two‐photon absorption in multichromophore systems remains under‐researched; thus, the system offers a rare demonstration of two‐photon absorption by cocrystallization. Cocrystal engineering may facilitate further design and development of novel materials for nonlinear optical and optoelectronic applications.
Regioselective Synthesis of Polycyclic and Heptagon‐embedded Aromatic Compounds through a Versatile π‐Extension of Aryl Halides
Authors: Fu Wai Chung , Wang Zheng , Chan Wesley Ting Kwok , Lin Zhenyang , Kwong Fuk Yee 
Published: May 2017

AbstractA versatile π‐extension reaction was developed based on the three‐component cross‐coupling of aryl halides, 2‐haloarylcarboxylic acids, and norbornadiene. The transformation is driven by the direction and subsequent decarboxylation of the carboxyl group, while norbornadiene serves as an ortho‐C−H activator and ethylene synthon via a retro‐Diels–Alder reaction. Comprehensive DFT calculations were performed to account for the catalytic intermediates.
Harnessing [1,4], [1,5], and [1,6] Anionic Fries‐type Rearrangements by Reaction‐Time Control in Flow
Authors: Kim Heejin , Inoue Keita , Yoshida Jun‐ichi 
Published: May 2017

AbstractA series of anionic Fries‐type rearrangements of carbamoyl‐substituted aryllithium intermediates were controlled by using flow microreactor systems. For the [1,4] and [1,5] rearrangements, the aryllithium intermediate formed before carbamoyl migration and the lithium alkoxide formed after carbamoyl migration can be selectively subjected to subsequent reactions with electrophiles by precisely controlling the residence time and temperature (−25 to −50 °C). In contrast, the [1,6] rearrangement is rather slow even at −25 °C. The absence of crossover products indicates the intramolecular nature of the carbamoyl group migration.
Divergent Synthesis of Disulfanes and Benzenesulfonothioates Bearing 2‐Aminofurans From N‐Tosylhydrazone‐Bearing Thiocarbamates
Authors: Mai Shaoyu , Song Qiuling 
Published: May 2017

AbstractAn efficient and convenient synthesis of valuable disulfanes and benzenesulfonothioates, having a 2‐aminofuran framework, has been developed by employing a copper‐catalyzed transformation of readily available N‐tosylhydrazone‐bearing thiocarbamates. This method features an inexpensive metal catalyst, mild reaction conditions, good functional‐group tolerance, short reaction times, and delivers valuable and complex products. A copper carbene generated from an N‐tosylhydrazone‐bearing thiocarbamate is proposed as the key intermediate for the transformation and it triggers the subsequent cascade. Remarkably, the Ts anion released from N‐tosylhydrazone further serves as a nucleophile, thus rendering the formation of benzenesulfonothioates under controlled conditions.
Graphene Oxide Conjugated Magnetic Beads for RNA Extraction
Authors: Pham Xuan‐Hung , Baek Ahruem , Kim Tae Han , Lee Sang Hun , Rho Won‐Yeop , Chung Woo‐Jae , Kim Dong‐Eun , Jun Bong‐Hyun 
Published: May 2017

AbstractA magnetic material that consists of silica‐coated magnetic beads conjugated with graphene oxide (GO) was successfully prepared for facile ribonucleic acid (RNA) extraction. When the GO‐modified magnetic beads were applied to separate the RNA from the lysed cell, the cellular RNAs were readily adsorbed to and readily desorbed from the surface of the GO‐modified magnetic beads by urea. The amount of RNA extracted by the GO‐modified magnetic beads was ≈170 % as much as those of the control extracted by a conventional phenol‐based chaotropic solution. These results demonstrate that the facile method of RNA separation by using GO‐modified magnetic beads as an adsorbent is an efficient and simple way to purify intact cellular RNAs and/or microRNA from cell lysates.
Observer Design for a Time Delay System via the Razumikhin Approach
Authors: Rehák Branislav 
Published: May 2017

AbstractThe paper presents an algorithm for the observer design for linear systems with time delay. The observer design is based on a solution of a set of linear matrix inequalities. They are derived using the Razumikhin functional. Quantization effects on the observation error are also studied, a bound on the observation error caused by quantization is derived. Two illustrative examples are presented.
Feedback between surface air temperature and atmospheric circulation in high‐temperature weather in East China: a diurnal perspective
Authors: Zeng X.‐M. , Zuo C. , Zhang Y. , Wang N. , Zheng Y. , Chen C. 
Published: May 2017

AbstractThis study proposes the generality of surface air temperature (SAT)–atmospheric circulation feedback during high‐temperature weather in late July 2003 over East China by using the Advanced Research Weather Research and Forecasting model (WRF; Version 3) simulations with a succession of 24‐h integrations, i.e. on a daily scale, the SAT increase leads to a weakened ridge of the western Pacific subtropical high in the lower troposphere (i.e. negative feedback), whereas it leads to a strengthened ridge in the upper troposphere (i.e. positive feedback) and vice versa. Additionally, using the balance equation of temperature, the feedbacks are clarified from the diurnal‐variation perspective. This shows many complex details, e.g. the changes in geopotential heights are more complex than those in air temperatures, and the overall daily feedback appears to be dominated by the feedback during the phase with intense daytime surface heating. All of the WRF‐modified land surface conditions can lead to large changes in the maximum, minimum, and average SATs over the mean diurnal scale, with generally larger differences induced by land surface schemes than those induced by initial soil moisture, suggesting that the SAT–circulation feedback can be greatly reduced (or amplified) by different land conditions over the diurnal weather scale and that diurnal variations could substantially contribute to longer timescale climate.
Beitrag zur Abbildung von Schlitzwänden in räumlichen Finite‐Elemente‐Berechnungen
Authors: Klein Linus , Moormann Christian 
Published: May 2017

AbstractBei der Herstellung wasserdruckhaltender Baugruben sowie zur Gewährleistung geringer aushubbedingter Verformungen angrenzender baulicher Anlagen werden häufig Schlitzwände eingesetzt. Im Zuge der Durchführung numerischer Berechnungen mit räumlichen Finite‐Elemente‐Modellen zur Untersuchung des Verformungsverhaltens der Baugrube und der Verformungsauswirkungen auf Bauwerke im Umfeld stellt sich die Frage, welchen Einfluss die Schlitzwandfugen auf das Trag‐ und Verformungsverhalten der Baugrube haben. Basierend auf einer Betrachtung der zur Ausführung kommenden Fugensysteme sowie der bestehenden Ansätze zur Berücksichtigung der Schlitzwandfugen werden in dem Beitrag die Ergebnisse einer numerischen Parameterstudie, in deren Rahmen unterschiedliche Modellierungsansätze für die Schlitzwandfugen bei Verwendung von Volumen‐ und Schalenelementen zur Abbildung der Verbauwände betrachtet werden, vorgestellt. Dabei wird der Einfluss der Schlitzwandfugen auf die Horizontalverformungen und Biegemomentenbeanspruchung der Verbauwände, die Setzungen der Geländeoberfläche sowie die Verteilung des entlang der Verbauwände einwirkenden Erddrucks untersucht. Die Ergebnisse zeigen, dass die Schlitzwandfugen einen gewissen, jedoch geringfügigen Einfluss auf die auftretenden Verformungen von Verbauwand und Geländeoberfläche haben. Auch die Verteilung des einwirkenden Erddrucks entlang der Verbauwand sowie deren Biegebeanspruchung werden nicht maßgeblich beeinflusst. Unter Berücksichtigung der gewonnenen Erkenntnisse wird ein Vorschlag zur einfachen Berücksichtigung des Einflusses von Schlitzwandfugen bei der Durchführung von numerischen Verformungsberechnungen unter Einsatz von Schalenelementen entwickelt.
Dokumentation der Entwicklung des m‐Faktors und neuer Aspekt der Verbrennungseffizienz
Authors: Hahn Sarah‐K. , Rost Michael , Kusche Christian , Knaust Christian , Krause Ulrich 
Published: May 2017

AbstractVor dem Hintergrund der Zurückziehung der DIN 18230 Teil 2 zur Bestimmung des m‐Faktors von Materialien für die Brandlastbewertung im Industriebau müssen neue Wege gefunden werden, wie das Abbrandverhalten alternativ quantifiziert werden kann. Der Beitrag fasst die Entstehung und die Entwicklung der Bestimmungsweise von Abbrandfaktoren zusammen und gibt Ausblick auf eine neue Möglichkeit zur Bewertung von Brandlasten, die Verbrennungseffizienz.
Experimentelle Untersuchungen zum Trag‐ und Verformungsverhalten brandbeanspruchter Tunnelschalen
Authors: Siemon Matthias , Zehfuß Jochen 
Published: May 2017

AbstractEreignisse wie der Brand im Eurotunnel, bei dem über eine Länge von 500 m Betonabplatzungen von bis zu 30 cm Tiefe auftraten, resultierten in der Einführung unterschiedlicher Anforderungen, um das Abplatzen sowohl in Bezug auf die Abplatztiefe als auch die betroffene Fläche auf ein verträgliches Maß zu begrenzen. Im Vergleich zu Bränden im Hochbau ist bei Tunnelbränden mit hohen Aufheizraten der brandbeanspruchten Bauteile zu rechnen. Aus diesem Grund kommt bei der versuchstechnischen Bewertung von Tunnelbauteilen für Eisenbahntunnel in Deutschland die sogenannte EBA‐Tunnelbrandkurve zum Einsatz, die anhand von Großversuchen an Eisenbahnwaggons abgeleitet wurde.Das Tragverhalten von Tunnelbauteilen unter Brandbeanspruchung wurde in den vergangenen Jahren im Rahmen verschiedener Forschungsvorhaben untersucht. Die in diesem Beitrag vorgestellten Ergebnisse basieren auf einem von der Deutschen Bahn beauftragten Vorhaben zur Untersuchung und Überprüfung von zwei Betonrezepturen sowie dem Nachweis der Standsicherheit der Tunnelinnenschale im Brandfall mithilfe von Großversuchen. Für diese Versuche wurden maßstabsgetreue Tunnelsegmente abgeleitet, die hinsichtlich ihrer Abmessungen, Konstruktion und Bewehrungsführung der maßgebenden Stelle eines real existierenden Eisenbahntunnels entsprachen.Vor dem Start der Beflammung wurden die Probekörper mithilfe von horizontal und vertikal angeordneten hydraulischen Pressen belastet. Die Prüfkräfte wurden in Vorberechnungen bestimmt und berücksichtigen die gebettete Lagerung der Tunnelinnenschale, den Boden‐ und Wasserdruck, das Eigengewicht sowie die thermisch induzierten Zwangkräfte aufgrund Brandbeanspruchung. Um weitere Zwangkräfte während des Versuchs zu verhindern, wurde der Probekörper statisch bestimmt gelagert und die Versuchslasten kraftgesteuert eingeleitet.
The Common Ratio Effect in Choice, Pricing, and Happiness Tasks
Authors: Schneider Mark , Shor Mikhael 
Published: May 2017

AbstractThe Allais common ratio effect is one of the most robust violations of rational decision making under risk. In this paper, we conduct a novel test of the common ratio effect in which we elicit preferences for the common ratio choice alternatives in choice, pricing, and happiness rating tasks. We find large shifts in preference patterns across tasks, both within and between subjects. In particular, we find that both the consistency and distribution of responses differ systematically across tasks, with modal choices replicating the Allais preference pattern, modal happiness ratings exhibiting consistent risk aversion, and modal prices maximizing expected value. We discuss the predictions of various cognitive explanations of the common ratio effect in the context of our experiment. We find that a dual process framework provides the most complete account of our results. Surprisingly, we also find that although the Allais pattern was the modal behavior in the choice task, none of the 158 respondents in our experiment exhibited the Allais pattern simultaneously in choice, happiness, and pricing tasks. Our results constitute a new paradox for the leading theories of choice under risk. Copyright © 2017 John Wiley & Sons, Ltd.