bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dehydrative Direct CH Allylation with Allylic Alcohols under [Cp*CoIII] Catalysis
Authors: Suzuki Yudai , Sun Bo , Sakata Ken , Yoshino Tatsuhiko , Matsunaga Shigeki , Kanai Motomu 
Published: July 2015

AbstractThe unique reactivity of [Cp*CoIII] over [Cp*RhIII] was demonstrated. A cationic [Cp*CoIII] catalyst promoted direct dehydrative CH allylation with non‐activated allyl alcohols, thus giving C2‐allylated indoles, pyrrole, and phenyl‐pyrazole in good yields, while analogous [Cp*RhIII] catalysts were not effective. The high γ‐selectivity and C2‐selectivity indicated that the reaction proceeded by directing‐group‐assisted CH metalation. DFT calculations suggested that the γ‐selective substitution reaction proceeded by CH metalation and insertion of a CC double bond, with subsequent β‐hydroxide elimination. The [Cp*CoIII] catalyst favored β‐hydroxide elimination over β‐hydride elimination.
Mercury under Pressure acts as a Transition Metal: Calculated from First Principles
Authors: Botana Jorge , Wang Xiaoli , Hou Chunju , Yan Dadong , Lin Haiqing , Ma Yanming , Miao Mao‐sheng 
Published: July 2015

AbstractThe inclusion of Hg among the transition metals is readily debated. Recently, molecular HgF4 was synthesized in a low‐temperature noble gas but the potential of Hg to form compounds beyond a +2 oxidation state in a stable solid remains unresolved. We propose high‐pressure techniques to prepare unusual oxidation states of Hg‐based compounds. Using an advanced structure search algorithm and first‐principles electronic structure calculations, we find that under high pressure Hg in HgF compounds transfers charge from the d orbitals to the F, thus behaving as a transition metal. Oxidizing Hg to +4 and +3 yielded the thermodynamically stable compounds HgF4 and HgF3. The former consists of HgF4 planar molecules, a typical geometry for d8 metal centers. HgF3 is metallic and ferromagnetic owing to the d9 configuration of Hg, with a large gap between its partially occupied and unoccupied bands under high pressure.
Highly E‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes Under Chiral Iminophosphorane Catalysis
Authors: Uraguchi Daisuke , Yamada Kohei , Ooi Takashi 
Published: July 2015

AbstractA highly E‐selective and enantioselective conjugate addition of 2‐benzyloxythiazol‐5(4H)‐ones to β‐substituted alkynyl N‐acyl pyrazoles is achieved under the catalysis of a P‐spiro chiral iminophosphorane. Simultaneous control of the newly generated central chirality and olefin geometry is possible with a wide array of the alkynyl Michael acceptors possessing different aromatic and aliphatic β‐substituents, as well as the various α‐amino acid‐derived thiazolone nucleophiles. This protocol provides access to structurally diverse, optically active α‐amino acids bearing a geometrically defined trisubstituted olefinic component at the α‐position.
Tandem Chemoselective Suzuki–Miyaura Cross‐Coupling Enabled by Nucleophile Speciation Control
Authors: Seath Ciaran P. , Fyfe James W. B. , Molloy John J. , Watson Allan J. B. 
Published: July 2015

AbstractControl of boronic acid speciation is presented as a strategy to achieve nucleophile chemoselectivity in the Suzuki–Miyaura reaction. Combined with simultaneous control of oxidative addition and transmetalation, this enables chemoselective formation of two CC bonds in a single operation, providing a method for the rapid preparation of highly functionalized carbogenic frameworks.
[2+2] Photocycloaddition of Cinnamates in Flow and Development of a Thiourea Catalyst
Authors: Telmesani Reem , Park Sung H. , Lynch‐Colameta Tessa , Beeler Aaron B. 
Published: July 2015

AbstractCyclobutanes derived from the dimerization of cinnamic acids are the core scaffolds of many molecules with potentially interesting biological activities. By utilizing a powerful flow photochemistry platform developed in our laboratory, we have evaluated the effects of flow on the dimerization of a range of cinnamate substrates. During the course of the study we also identified a bis(thiourea) catalyst that facilitates better reactivity and moderate diastereoselectivity in the reaction. Overall, we show that carrying out the reaction in flow in the presence of the catalyst affords consistent formation of predictable cyclobutane diastereomers.
SiSi Double Bonds: Synthesis of an NHC‐Stabilized Disilavinylidene
Authors: Ghana Priyabrata , Arz Marius I. , Das Ujjal , Schnakenburg Gregor , Filippou Alexander C. 
Published: July 2015

AbstractAn efficient two‐step synthesis of the first NHC‐stabilized disilavinylidene (Z)‐(SIdipp)SiSi(Br)Tbb (2; SIdipp=C[N(C6H3‐2,6‐iPr2)CH2]2, Tbb=C6H2‐2,6‐[CH(SiMe3)2]2‐4‐tBu, NHC=N‐heterocyclic carbene) is reported. The first step of the procedure involved a 2:1 reaction of SiBr2(SIdipp) with the 1,2‐dibromodisilene (E)‐Tbb(Br)SiSi(Br)Tbb at 100 °C, which afforded selectively an unprecedented NHC‐stabilized bromo(silyl)silylene, namely SiBr(SiBr2Tbb)(SIdipp) (1). Alternatively, compound 1 could be obtained from the 2:1 reaction of SiBr2(SIdipp) with LiTbb at low temperature. 1 was then selectively reduced with C8K to give the NHC‐stabilized disilavinylidene 2. Both low‐valent silicon compounds were comprehensively characterized by X‐ray diffraction analysis, multinuclear NMR spectroscopy, and elemental analyses. Additionally, the electronic structure of 2 was studied by various quantum‐chemical methods.
Facing and Overcoming Sensitivity Challenges in Biomolecular NMR Spectroscopy
Authors: Ardenkjaer‐Larsen Jan‐Henrik , Boebinger Gregory S. , Comment Arnaud , Duckett Simon , Edison Arthur S. , Engelke Frank , Griesinger Christian , Griffin Robert G. , Hilty Christian , Maeda Hidaeki , Parigi Giacomo , Prisner Thomas , Ravera Enrico , van Bentum Jan , Vega Shimon , Webb Andrew , Luchinat Claudio , Schwalbe Harald , Frydman Lucio 
Published: July 2015

AbstractIn the Spring of 2013, NMR spectroscopists convened at the Weizmann Institute in Israel to brainstorm on approaches to improve the sensitivity of NMR experiments, particularly when applied in biomolecular settings. This multi‐author interdisciplinary Review presents a state‐of‐the‐art description of the primary approaches that were considered. Topics discussed included the future of ultrahigh‐field NMR systems, emerging NMR detection technologies, new approaches to nuclear hyperpolarization, and progress in sample preparation. All of these are orthogonal efforts, whose gains could multiply and thereby enhance the sensitivity of solid‐ and liquid‐state experiments. While substantial advances have been made in all these areas, numerous challenges remain in the quest of endowing NMR spectroscopy with the sensitivity that has characterized forms of spectroscopies based on electrical or optical measurements. These challenges, and the ways by which scientists and engineers are striving to solve them, are also addressed.
On the Role of Metals in Nitrogen‐Doped Carbon Electrocatalysts for Oxygen Reduction
Authors: Masa Justus , Xia Wei , Muhler Martin , Schuhmann Wolfgang 
Published: July 2015

AbstractThe notion of metal‐free catalysts is used to refer to carbon materials modified with nonmetallic elements. However, some claimed metal‐free catalysts are prepared using metal‐containing precursors. It is highly contested that metal residues in nitrogen‐doped carbon (NC) catalysts play a crucial role in the oxygen reduction reaction (ORR). In an attempt to reconcile divergent views, a definition for truly metal‐free catalysts is proposed and the differences between NC and M‐Nx/C catalysts are discussed. Metal impurities at levels usually undetectable by techniques such as XPS, XRD, and EDX significantly promote the ORR. Poisoning tests to mask the metal ions reveal the involvement of metal residues as active sites or as modifiers of the electronic structure of the active sites in NC. The unique merits of both M‐Nx/C and NC catalysts are discussed to inspire the development of more advanced nonprecious‐metal catalysts for the ORR.
Fused Thiophene‐Pyrrole‐Containing Ring Systems up to a Heterodecacene
Authors: Wetzel Christoph , Brier Eduard , Vogt Astrid , Mishra Amaresh , Mena‐Osteritz Elena , Bäuerle Peter 
Published: July 2015

AbstractA new class of π‐conjugated polycyclic hydrocarbons that promises interesting electronic properties is presented. The synthesis and extension of the S,N‐heteroacene series consisting of only five‐membered heterocyclic rings up to a very long, stable, and still soluble decacene SN10 is realized by multiple Pd‐catalyzed aminations of halogenated thiophene precursors as key reactions. These novel heteroacenes were characterized by optical spectroscopy and electrochemistry providing interesting structure–property relationships. Nearly complete bond‐length equalization in the inner part of the conjugated backbone and an unusual herringbone packing in the solid state underline the structural features of these novel systems.
HighlyE‐Selective and Enantioselective Michael Addition to Electron‐Deficient Internal Alkynes Under Chiral Iminophosphorane Catalysis
Authors: Uraguchi Daisuke , Yamada Kohei , Ooi Takashi 
Published: July 2015

AbstractA highly E‐selective and enantioselective conjugate addition of 2‐benzyloxythiazol‐5(4H)‐ones to β‐substituted alkynyl N‐acyl pyrazoles is achieved under the catalysis of aP‐spiro chiral iminophosphorane. Simultaneous control of the newly generated central chirality and olefin geometry is possible with a wide array of the alkynyl Michael acceptors possessing different aromatic and aliphatic β‐substituents, as well as the various α‐amino acid‐derived thiazolone nucleophiles. This protocol provides access to structurally diverse, optically active α‐amino acids bearing a geometrically defined trisubstituted olefinic component at the α‐position.
How Affect Shapes Risky Choice: Distorted Probability Weighting Versus Probability Neglect
Authors: Suter Renata S. , Pachur Thorsten , Hertwig Ralph 
Published: July 2015

AbstractPeople's choices between prospects with relatively affect‐rich outcomes (e.g., medical side effects) can diverge markedly from their choices between prospects with relatively affect‐poor outcomes (e.g., monetary losses). We investigate the cognitive mechanisms underlying this “affect gap” in risky choice. One possibility is that affect‐rich prospects give rise to more distortion in probability weighting. Another is that they lead to the neglect of probabilities. To pit these two possibilities against each other, we fitted cumulative prospect theory (CPT) to the choices of individual participants, separately for choices between options with affect‐rich outcomes (adverse medical side effects) and options with affect‐poor outcomes (monetary losses); additionally, we tested a simple model of probability neglect, the minimax rule. The results indicated a qualitative difference in cognitive mechanisms between the affect‐rich and affect‐poor problems. Specifically, in affect‐poor problems, the large majority of participants were best described by CPT; in affect‐rich problems, the proportion of participants best described by the minimax rule was substantially higher. The affect gap persisted even when affect‐rich outcomes were supplemented by numerical information, thus providing no support for the thesis that choices in affect‐rich and affect‐poor problems diverge because the information provided in the former is nonnumerical. Our findings suggest that the traditional expectation‐based framework for modeling risky decision making may not readily generalize to affect‐rich choices. Copyright © 2015 John Wiley & Sons, Ltd.
A Series of Multifunctional Metal–Organic Frameworks Showing Excellent Luminescent Sensing, Sensitization, and Adsorbent Abilities
Authors: Yi Fei‐Yan , Li Jian‐Ping , Wu Dai , Sun Zhong‐Ming 
Published: July 2015

AbstractA series of highly luminescent‐active metal–organic frameworks (MOFs) 1–3 with hierarchical pores have been rationally constructed and fully characterized. The predesigned semi‐rigid hexacarboxylate ligand hexa[4‐(carboxyphenyl)oxamethyl]‐3‐oxapentane acid (H6L) has been adapted with various space‐directed N donors (i.e., 2,2’‐bipyridine, 4,4′‐di(1H‐imidazol‐1‐yl)‐1,1′‐biphenyl, and 1,3,5‐tri(1H‐imidazol‐1‐yl)benzene) from a bidentate V‐shape to a tridentate Y‐shape. This family of multifunctional MOF materials represents a variety of potential applications in the following aspects: first, as luminescent sensors that show a fast and sensitive detection for pollutant CrO42− and Cr2O72− ions in aqueous media; second, as adsorbents that can rapidly remove harmful organic dyes; third, as an antenna that can effectively sensitize visible‐light‐emitting Tb3+ ions. These multifunctional MOF materials combine optical‐sensing, adsorption, and sensitization properties, thus are very useful in many potential applications. Furthermore, these materials have proved to be reusable.
CaII‐Catalyzed Alkenylation of Alcohols with Vinylboronic Acids
Authors: Lebœuf David , Presset Marc , Michelet Bastien , Bour Christophe , Bezzenine‐Lafollée Sophie , Gandon Vincent 
Published: July 2015

AbstractDirect alkenylation of a variety of alcohols with vinylboronic acids has been accomplished using the air‐stable calcium(II) complex Ca(NTf2)2 under mild conditions with short reaction times. For reluctant transformations, an ammonium salt was used as an additive to circumvent the reactivity issue.
Self‐Assembly of Amphiphilic Janus Dendrimers into Mechanically Robust Supramolecular Hydrogels for Sustained Drug Release
Authors: Nummelin Sami , Liljeström Ville , Saarikoski Eve , Ropponen Jarmo , Nykänen Antti , Linko Veikko , Seppälä Jukka , Hirvonen Jouni , Ikkala Olli , Bimbo Luis M. , Kostiainen Mauri A. 
Published: July 2015

AbstractCompounds that can gelate aqueous solutions offer an intriguing toolbox to create functional hydrogel materials for biomedical applications. Amphiphilic Janus dendrimers with low molecular weights can readily form self‐assembled fibers at very low mass proportion (0.2 wt %) to create supramolecular hydrogels (G′≫G′′) with outstanding mechanical properties and storage modulus of G′>1000 Pa. The G′ value and gel melting temperature can be tuned by modulating the position or number of hydrophobic alkyl chains in the dendrimer structure; thus enabling exquisite control over the mesoscale material properties in these molecular assemblies. The gels are formed within seconds by simple injection of ethanol‐solvated dendrimers into an aqueous solution. Cryogenic TEM, small‐angle X‐ray scattering, and SEM were used to confirm the fibrous structure morphology of the gels. Furthermore, the gels can be efficiently loaded with different bioactive cargo, such as active enzymes, peptides, or small‐molecule drugs, to be used for sustained release in drug delivery.
Hydrogen‐Bonding Pincer Complexes with Two Protic N‐Heterocyclic Carbenes from Direct Metalation of a 1,8‐Bis(imidazol‐1‐yl)carbazole by Platinum, Palladium, and Nickel
Authors: Marelius David C. , Darrow Evan H. , Moore Curtis E. , Golen James A. , Rheingold Arnold L. , Grotjahn Douglas B. 
Published: July 2015

AbstractPincer protic N‐heterocyclic carbene (PNHC) complexes were synthesized by direct metalation, the formation of a metal carbon bond from an unfunctionalized CH bond in a single synthetic step. Significantly, direct metalation succeeded even for a first‐row metal, nickel. The chloride complexes were isolated and then converted to the acetate, triflate, or in the platinum case, a hydride analogue. Crystal structures and 1H, 13C, and 15N NMR data, as well as IR spectra, document the effects of intramolecular hydrogen bonding and the planar but flexible pincer framework. Anti‐Markovnikov addition of OH bonds to alkynes, including catalyzed alkyne hydration, were demonstrated on the Pt triflate analog.
Bisamidate Prodrugs of 2‐Substituted 9‐[2‐(Phosphonomethoxy)ethyl]adenine (PMEA, adefovir) as Selective Inhibitors of Adenylate Cyclase Toxin from Bordetella pertussis
Authors: Česnek Michal , Jansa Petr , Šmídková Markéta , Mertlíková‐Kaiserová Helena , Dračínský Martin , Brust Tarsis F. , Pávek Petr , Trejtnar František , Watts Val J. , Janeba Zlatko 
Published: July 2015

AbstractNovel small‐molecule agents to treat Bordetella pertussis infections are highly desirable, as pertussis (whooping cough) remains a serious health threat worldwide. In this study, a series of 2‐substituted derivatives of 9‐[2‐(phosphonomethoxy)ethyl]adenine (PMEA, adefovir), in their isopropyl ester bis(L‐phenylalanine) prodrug form, were designed and synthesized as potent inhibitors of adenylate cyclase toxin (ACT) isolated from B. pertussis. The series consists of PMEA analogues bearing either a linear or branched aliphatic chain or a heteroatom at the C2 position of the purine moiety. Compounds with a small C2 substituent showed high potency against ACT without cytotoxic effects as well as good selectivity over human adenylate cyclase isoforms AC1, AC2, and AC5. The most potent ACT inhibitor was found to be the bisamidate prodrug of the 2‐fluoro PMEA derivative (IC50=0.145 μM). Although the bisamidate prodrugs reported herein exhibit overall lower activity than the bis(pivaloyloxymethyl) prodrug (adefovir dipivoxil), their toxicity and plasma stability profiles are superior. Furthermore, the bisamidate prodrug was shown to be more stable in plasma than in macrophage homogenate, indicating that the free phosphonate can be effectively distributed to target tissues, such as the lungs. Thus, ACT inhibitors based on acyclic nucleoside phosphonates may represent a new strategy to treat whooping cough.
Differential effects of social and physical environmental enrichment on brain plasticity, cognition, and ultrasonic communication in rats
Authors: Brenes Juan C. , Lackinger Martin , Höglinger Günter U. , Schratt Gerhard , Schwarting Rainer K.W. , Wöhr Markus 
Published: July 2015

ABSTRACTEnvironmental enrichment (EE) exerts beneficial effects on brain plasticity, cognition, and anxiety/depression, leading to a brain that can counteract deficits underlying various brain disorders. Because the complexity of the EE commonly used makes it difficult to identify causal aspects, we examined possible factors using a 2 × 2 design with social EE (two vs. six rats) and physical EE (physically enriched vs. nonenriched). For the first time, we demonstrate that social and physical EE have differential effects on brain plasticity, cognition, and ultrasonic communication. Expectedly, physical EE promoted neurogenesis in the dentate gyrus of the hippocampal formation, but not in the subventricular zone, and, as a novel finding, affected microRNA expression levels, with the activity‐dependent miR‐124 and miR‐132 being upregulated. Concomitant improvements in cognition were observed, yet social deficits were seen in the emission of prosocial 50‐kHz ultrasonic vocalizations (USV) paralleled by a lack of social approach in response to them, consistent with the intense world syndrome/theory of autism. In contrast, social EE had only minor effects on brain plasticity and cognition, but led to increased prosocial 50‐kHz USV emission rates and enhanced social approach behavior. Importantly, social deficits following physical EE were prevented by additional social EE. The finding that social EE has positive whereas physical EE has negative effects on social behavior indicates that preclinical studies focusing on EE as a potential treatment in models for neuropsychiatric disorders characterized by social deficits, such as autism, should include social EE in addition to physical EE, because its lack might worsen social deficits. J. Comp. Neurol. 524:1586–1607, 2016. © 2015 Wiley Periodicals, Inc.
Data‐Driven Optimal Transport
Authors: Trigila Giulio , Tabak Esteban G. 
Published: July 2015

AbstractThe problem of optimal transport between two distributions ρ(x) and μ(y) is extended to situations where the distributions are only known through a finite number of samples {xi} and {yj}. A weak formulation is proposed, based on the dual of the Kantorovich formulation, with two main modifications: replacing the expected values in the objective function by their empirical means over the {xi} and {yj}, and restricting the dual variables u(x) and v(y) to a suitable set of test functions adapted to the local availability of sample points. A procedure is proposed and tested for the numerical solution of this problem, based on a fluidlike flow in phase space, where the sample points play the role of active Lagrangian markers. © 2016 Wiley Periodicals, Inc.
“On–Off” RGD Signaling Using Azobenzene Photoswitch‐Modified Surfaces
Authors: Vaselli Elisa , Fedele Chiara , Cavalli Silvia , Netti Paolo A. 
Published: July 2015

AbstractPhotoresponsive surfaces were developed by modifying glass slides with switchable Gly‐Arg‐Gly‐Asp‐Ser (GRGDS) peptides to investigate light‐controlled cell adhesion. The GRGDS peptide sequence was attached to an azobenzene moiety and then “clicked” to silanized glass substrates. The photoresponsive behavior of such cell‐instructive materials (CIMs) was first checked by contact angle technique and by recording local changes in wettability owing to the isomerization of the azobenzene domain upon light stimulus. “On–off” switching was observed for at least five cycles when illuminated consecutively with UV and visible‐light sources. Finally, cell‐adhesion studies with human umbilical vein endothelial cells (HUVECs) validated our system as an effective light‐responsive CIM platform and the possibility of dynamically controlled cell adhesion in situ was envisioned.
Comparison of macroinvertebrate communities of intermittent and perennial streams in the dry forest of Guanacaste, Costa Rica
Authors: de Szoeke Suzanne M. , Crisman Thomas L. , Thurman Paul E. 
Published: July 2015

AbstractThe 7 m‐wide Canal Oeste passes over a series of first‐order, intermittent streams on hillsides on its way to irrigate the lowlands of Guanacaste, Costa Rica. Streams passing under lined portions of the canal have maintained intermittent flow, while those under unlined portions of the canal have become perennial, thus providing a unique opportunity to examine the impact of drastically altered hydrology on macroinvertebrate communities of dry forest streams. Macroinvertebrates were studied from the end of the dry season through a wet season. Macroinvertebrate recolonization of intermittent streams at the beginning of the wet season was rapid, led by small bodied taxa such as chironomids and oligochaetes with short life cycles and/or great tolerance for low oxygen and spates. As additional, less tolerant taxa arrived, most likely aerially from adjacent perennial streams, the fauna of intermittent streams progressively became similar to that of perennial streams of the area within 3–4 months of rewetting. The great resilience of the macroinvertebrate community is clearly demonstrated by its ability to adjust with few modifications to a complete switch from intermittent to perennial hydroperiod. Copyright © 2015 John Wiley & Sons, Ltd.
Copper‐Catalyzed Domino Reactions for the Synthesis of Phenothiazines
Authors: Huang Manna , Huang Dongting , Zhu Xinhai , Wan Yiqian 
Published: July 2015

AbstractA method for the one‐pot synthesis of phenothiazines from benzothiazoles and aryl ortho‐dihalides was explored. Preliminary work on the mechanism of the reaction suggested that it follows a domino process, including the hydrolysis of benzothiazoles followed by C–S coupling and C–N coupling. The low loading of the catalyst system (5 mol‐% for both copper and ligand), the mild experimental conditions (90 °C, 12 h), and the use of a green reaction medium make this synthesis very attractive to academia and industry.