bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copper-catalyzed asymmetric allylic substitution reactions with organozinc and Grignard reagents
Authors: Geurts Koen , Fletcher Stephen P. , van Zijl Anthoni W. , Minnaard Adriaan J. , Feringa Ben L. 
Published: May 2008

Abstract
Asymmetric allylic alkylations (AAAs) are among the most powerful C-C bond-forming reactions. We present a brief overview of copper-catalyzed AAAs with organometallic reagents and discuss our own contributions to this field. Work with zinc reagents and phosphoramidite ligands provided a framework for later developments which employ Grignard reagents and ferrocenyl ligands. High yields and excellent regioselectivities and enantioselectivities are achieved. The AAAs may be more general than previously envisioned, in terms of using substrates functionalized with heteroatoms at various positions; heteroatom substituents at the γ-position provide densely functionalized building blocks. These h-AAA reactions rely on the design of appropriate substrates containing heteroatoms and have allowed us to demonstrate viable new approaches toward the synthesis of versatile organic building blocks. We illustrate that the chiral secondary allylic alcohols, primary homo-allylic alcohols and amines can readily be obtained in high enantiomeric purity in a catalytic asymmetric fashion by copper-catalyzed AAAs. Furthermore, we show that manipulation of the terminal olefin provides chiral building blocks where the ee of the starting materials is preserved.
Golden opportunities in catalysis
Authors: Krause Norbert , Belting Volker , Deutsch Carl , Erdsack Jörg , Fan Hong-Tao , Gockel Birgit , Hoffmann-Röder Anja , Morita Nobuyoshi , Volz Frank 
Published: May 2008

Abstract
The gold-catalyzed endo-cycloisomerization of allenes bearing nucleophilic substituents in the α- or β-position opens up a versatile access to various five- and six-membered heterocycles. Key features of these transformations are the high reactivity of the allene in the presence of Lewis-acidic, carbophilic gold(I) or gold(III) catalysts, and the chirality transfer from the allenic axis of chirality to the new stereogenic center in the cyclization product. Recent contributions of our group include the optimization of chirality transfer by using σ-donor ligands to gold, and applications in the total synthesis of natural products, e.g., of the β-carboline alkaloids (-)-isocyclocapitelline and (-)-isochrysotricine.
Rhodium-catalyzed CO gas-free carbonylative cyclization using aldehydes
Authors: Morimoto Tsumoru , Fujioka Masahiko , Fuji Koji , Tsutsumi Ken , Kakiuchi Kiyomi 
Published: May 2008

Abstract
A new protocol for CO gas-free carbonylation, in which aldehydes are used as a substitute for CO, is described. The protocol consists of two Rh-mediated processes; the Rh-mediated decarbonylation of aldehydes, which leads to the formation of Rh carbonyl, and subsequent Rh-catalyzed carbonylative cyclization utilizing the in situ formed Rh carbonyl species.
First palladium- and nickel-catalyzed oxidative diamination of alkenes: Cyclic urea, sulfamide, and guanidine building blocks
Authors: Muñiz Kilian , Hövelmann Claas H. , Streuff Jan , Campos-Gómez Esther 
Published: May 2008

AbstractWe recently reported the first catalytic diamination of alkenes. This protocol calls for the use of Pd(II) as catalyst in combination with PhI(OAc)2as terminal oxidant and furnishes the final diamines as cyclic ureas. It consists of an unprecedented two-step reaction of aminopalladation and Csp3-N-bond formation involving a Pd(IV) species. Introduction of Ni(II) catalysts for homogeneous oxidation allows for an efficient diamination with sulfamides, which lead to convenient liberation of the free diamines. In related protocols, the substrate scope of the diamination has been broadened to the formation of cyclic guanidines.
Asymmetric synthesis of planar-chiral ferrocenes by Mo- or Ru-catalyzed enantioselective metathesis
Authors: Ogasawara Masamichi , Watanabe Susumu , Nakajima Kiyohiko , Takahashi Tamotsu 
Published: May 2008

Abstract
Kinetic resolution of planar-chiral 1,1'-diallylferrocene derivatives was realized by Mo- or Ru-catalyzed asymmetric ring-closing metathesis (RCM). The Mo catalyst showed much better performance than the Ru catalyst in the present reactions, and nearly perfect resolution of the racemic ferrocenes was achieved. This is the first example of highly enantioselective metal-catalyzed methods of preparing optically active planar-chiral metallocenes.
Nickel-catalyzed [2+2+2] cycloaddition of two alkynes and an imine
Authors: Ogoshi Sensuke , Ikeda Haruo , Kurosawa Hideo 
Published: May 2008

AbstractThe reaction ofN-benzenesulfonylbenzaldimine with Ni(cod)2and PCy3gave the corresponding η2-iminenickel complex quantitatively. Diphenylacetylene reacted with the η2-iminenickel complex to generate five-membered aza-nickelacycle. Insertion of second alkynes into the five-membered aza-nickelacycle led to the formation of the corresponding seven-membered aza-nickelacycles. Heating the solution of the seven-membered aza-nickelacycles induced the reductive elimination to give 1,2-dihydropyridine. In the presence of 10 mol % of Ni(cod)2and PMetBu2at 100 °C, the intermolecular [2+2+2] cycloaddition ofN-benzenesulfonylbenzaldimine and 2-butyne occurred to give the expected 1,2-dihydropyridine in 87 % yield. In the presence of PCy3, the reaction also proceeded catalytically, however, PMetBu2gave better results. Less bulky or less basic phosphine, PnBu3or P(o-tol)3, was not efficient for the reaction. Although Ni(0)-NHC complex was a good catalyst for [2+2+2] cycloaddition of two alkynes and a ketone or an aldehyde, this reaction did not proceed in the presence of an NHC ligand, 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene.
Toward the total synthesis of ritterazine N
Authors: Taber Douglass F. , Joerger Jean-Michel , Taluskie Karen V. 
Published: May 2008

AbstractZr-mediated equilibrating cyclocarbonylation of a designed triene led with high diastereocontrol to the ABC 6-6-5 tricyclic core of ritterazine N. The 5-5 EF spiroketal side chain of ritterazine N was prepared by equilibrating cyclization of an acyclic keto diol. The two components were coupled, and the D ring was assembled by intramolecular aldol condensation.
Rhenium-catalyzed synthesis of indene derivatives via C-H bond activation
Authors: Kuninobu Yoichiro , Nishina Yuta , Kawata Atsushi , Shouho Makoto , Takai Kazuhiko 
Published: May 2008

Abstract
Rhenium complex, [ReBr(CO)3(thf)]2-catalyzed reactions between aromatic imines and either acetylenes or α,β-unsaturated carbonyl compounds gave indene derivatives in good to excellent yields. These reactions proceed via C-H bond activation, insertion of acetylenes or α,β-unsaturated carbonyl compounds, intramolecular nucleophilic cyclization, and reductive elimination. Indene derivatives were also obtained from aromatic ketones and α,β-unsaturated carbonyl compounds in the presence of catalytic amounts of the rhenium complex and p-anisidine. Sequential ruthenium-catalyzed hydroamination of aromatic acetylenes with anilines, and rhenium-catalyzed reactions of the formed aromatic ketimines with α,β-unsaturated carbonyl compounds also provided indene derivatives.
New cyclizations via catalytic ruthenium vinylidenes
Authors: Varela Jesús A. , González-Rodríguez Carlos , Rubín Silvia G. , Castedo Luis , Saá Carlos 
Published: May 2008

Abstract
New carbocyclizations that proceed via catalytic metal-vinylidenes are presented. Metal-vinylidene catalytic species, which are easily accessible from terminal alkynes and catalytic amounts of transition-metal complexes, can be involved either in pericyclic reactions or in tandem processes triggered by nucleophilic attack at the electrophilic position of the vinylidene. In both cases, a wide variety of valuable cyclic compounds are easily accessible. Some recent carbocyclizations will be described.
What happens to international students’ English after one semester at university?
Authors: Storch Neomy , Hill Kathryn 
Published: May 2008

There is a common expectation, particularly amongst international students, that studying in an English-medium university should automatically produce a significant improvement in their English language skills. However, there is growing evidence to suggest that this is not necessarily the case.
This paper reports on a study which investigated the impact of one semester of study at a university on the English language proficiency of a sample of 40 international students. This was measured by comparing the students’ scores on a diagnostic English language test at the beginning and end of their first semester. A comparison of discourse measures of writing in terms of fluency, complexity and accuracy was also undertaken. Background information, including details of ESL support, if any, was collected for all participants via questionnaires, and interviews were conducted with a subset of the participants.
It was found that studying in an English-medium university generally led to an improvement in English language proficiency. The paper identifies a number of factors which appear to support language development, as well as factors that may inhibit it.
Has brief counselling an impact on the risk factors for cardiovascular disease in 40-year-old men. A three-year follow-up study
Authors: Näslindh-Ylispangar Anita , Sihvonen Marja , Sarna Seppo , Vanhanen Hannu , Kekki Pertti 
Published: May 2008

Abstract
The metabolic syndrome presents a serious challenge to health professionals. The aim of the present study is to analyze the impact of a brief counselling on cardiovascular risk factors among 40-year-old men. Forty-six males living in north-eastern Helsinki voluntarily completed the follow-up study between 2001 and 2004, and were assessed for clinical risk factors. The mean differences were determined by a paired t-test, and the interaction between groups and time by the F-test with repeated measures ANOVA. After baseline assessment and in 2002, males received a 45 minute nurse-delivered counselling session with self-administered protocol. Cardiovascular risk factors improved significantly (p<0.05) from baseline within months. However, the final measurements obtained after three years showed that almost all risk factors, except the low and high density lipoprotein, tended to revert back to baseline. The profiles were similar in all predictor groups. Brief counselling had an impact on risk factors measured in 2002, but only a partial effect on them in 2004. Conclusive results lead to the idea thatmore collaboration is needed between private health care agencies and official primary health care for ensuring the continuity of improved health habits among middle-aged males.
The mitochondrial localization of RelB and NFATx in immature T cells
Authors: Stasik Izabela , Rapak Andrzej , Zioło Ewa , Strządała Leon 
Published: May 2008

AbstractIn order to exert their activity, transcription factors must be transported to the nucleus. Certain transcription factors have also been found on mitochondria. Here, the localization of RelB and NFATx in the mitochondrial fractions of normal thymocytes and thymic lymphoma cells is shown for the first time. CREB was only found in the nucleus, while p50 (NFκB) was found in both the nucleus and the cytoplasm, but outside the mitochondria. The translocation of transcription factors to the mitochondria is differentially regulated. Unlike RelB, which is always present in the mitochondrial fraction, NFATx appeared on the mitochondria in cells treated with ionomycin together with an immunosuppressant and inhibitor of calcineurin (FK506). This data reveals that the mitochondrial localization of some transcription factors is precisely controlled by a calcium signal sensitive to FK506 in T cells.
Long‐term impacts of nitrogen and sulphur deposition on forest floor vegetation in the Northern limestone Alps, Austria
Authors: Hülber Karl , Dirnböck Thomas , Kleinbauer Ingrid , Willner Wolfgang , Dullinger Stefan , Karrer Gerhard , Mirtl Michael 
Published: May 2008

Abstract.Question: Are there effects of long‐term deposition of airborne nitrogen and sulphur on the forest floor vegetation from permanent plots collected in 1993 compared to 2005.Location: Northern limestone Alps in Austria.Methods: Single species responses were analysed by correlating trends in cover‐abundance values, as derived from marginal models, with Ellenberg indicator values. Changes in the species composition of plots were analysed by correlating changes in mean Ellenberg indicator values with the displacement of plots within a multidimensional scaling ordination.Results: Trends in single species abundance were positively correlated with indicator values of soil pH but were independent of nutrient availability. A general trend towards the homogenisation of vegetation, due to convergent time vectors of the relevés, became obvious. Oligotrophic sites previously situated at the distal ends of ordination axes shifted towards the centre since they were enriched by species preferring mesotrophic conditions. The bulk of plots with intermediate site conditions hardly showed any trends. A concomitant analysis demonstrated that temporal changes in species composition exceed the variation in cover abundance estimates among different field botanists.Conclusions: N deposition can lead to a homogenisation of forest floor vegetation. Larger limestone areas with diverse soil conditions, such as the Northern limestone Alps in Austria, as a whole are thus negatively affected by airborne N deposition. Nevertheless, the vegetation was at least as strongly affected by an increase of basiphilous species as a result of decreasing S deposition.
Mixing ratio and species affect the use of substrate‐derived CO2 by Sphagnum
Authors: Limpens J. , Robroek B.J.M. , Heijmans M.M.P.D. , Tomassen H.B.M. 
Published: May 2008

AbstractQuestion:Can mixing ratio and species affect the use of substrate‐derived CO2 by Sphagnum?Location:Poor fen in south Sweden and greenhouse in Wageningen, The Netherlands.Methods:Two mixing ratios of Sphagnum cuspidatum and S. magellanicum were exposed to two levels of CO2 by pumping CO2 enriched and non‐enriched water through aquaria containing the species mixtures in the greenhouse.Results:Enhanced CO2 stimulated the production of S. cuspidatum, but only in aquaria co‐dominated by S. magellanicum, coinciding with higher CO2 concentrations in the water layer. The denser growing S. magellanicum seemed to reduce gas escape from the water, resulting in accumulation of dissolved CO2. Adding CO2 did not affect species replacement.Conclusions:The use of substrate‐derived CO2 for Sphagnum production depended on species identity and mixing ratio. The effect of mixing ratio on CO2 concentrations in the water layer suggests that species composition may affect both the efficiency with which substrate‐derived CO2 is trapped and subsequently used. This could result in hitherto unexplored feedbacks between vegetation composition and gas exchange.
Activity and Heart Rate-based Measures for Outpatient Cardiac Rehabilitation
Authors: Sarela A. , Bidargaddi N. P. 
Published: May 2008

Summary

Objectives:
Derive activity and heart rate (HR) monitor-based clinically relevant measures for outpatient cardiac rehabilitation (CR).

Methods:
We are currently collecting activity/ ECG data from patients undergoing cardiac rehabilitation over duration of six weeks. From these data sets, we a) derive various measures which can be used in assessing home-based CR patients remotely and b) investigate the usefulness of continuous ambulatory HR and heart rate variability (HRV) for various core components of CR.

Results:
The information provided by these measures is interpreted according to the CR guidelines framework by American Association of Cardiovascular and Pul - monary Rehabilitation (AACVPR), thus showing how these tools can be used in assessing the progress of patients’ condition. The usefulness and significance of these measures from a health care professional perspective is also presented by evaluating them against the existing hospital-based measures through examples.

Conclusions:
Hospital-based CR programs, despite their clinical benefits are severely under-utilized and resource-demanding. Ambulatory monitoring technologies, which provide a means for continuous physiological monitoring of patients at home compared to hospital-based tools, can enable home-based CR. The clinically relevant measures derived from these tools not only reflect patients´ condition in a similar way as conventional tools but also show the continuous status of functional capacity (FC).
Offene Gerüststrukturen von Übergangsmetallen
Authors: Natarajan Srinivasan , Mandal Sukhendu 
Published: May 2008

AbstractIn den letzten Jahren hat sich gezeigt, dass neben anorganischen Silicaten und Phosphaten auch Carboxylate, Arsenate, Sulfate, Selenate, Selenite, Germanate und Phosphite offene Gerüststrukturen bilden können. Von besonderem Interesse sind die organisch‐anorganischen Hybridverbindungen, die sich aus der Kombination der reichen Koordinationschemie der zentralen Metall‐Ionen vieler dieser Strukturtypen mit der Flexibilität und der Funktionalität organischer Verbindungsglieder (“Linker”) ergeben. Vor allem die Übergangsmetalle scheinen besonders viele Varianten zu liefern, was in den bevorzugten Koordinationsweisen, Ligandengeometrien und Valenzzuständen begründet ist. Außerdem lässt die Kombination der magnetischen Eigenschaften von Übergangsmetallen mit den Kanalstrukturen offener Gerüste interessante Anwendungen erwarten. In diesem Aufsatz werden die Synthesen, Strukturen und Eigenschaften einer Reihe von Übergangsmetallverbindungen mit offenem Gerüst vorgestellt.
Testing of polysulfone for applications in nuclear facilities
Authors: Plaček V. , Hnát V. , Pejša R. , Kohout T. 
Published: May 2008

AbstractPolysulfone Tecason S samples, designed for use in nuclear facilities, were aged under different conditions to simulate their long‐term use in nuclear power plants. The specimens, with thicknesses of 4 mm, were irradiated with 60Co γ rays in oxygen and/or in air at different temperatures and thermally aged at 180°C. For all samples, the glass‐transition temperature, the stepwise change in the heat capacity at the glass‐transition temperature, and the oxidative induction temperature were measured with differential scanning calorimetry. Simultaneously, the mechanical properties were determined and correlated with the results obtained by differential scanning calorimetry. Although the material was aged under very harsh conditions (irradiation in oxygen with absorbed doses up to 500 kGy and thermal aging at 180°C up to 115 days), the detected changes were relatively small. Nevertheless, a tendency of the glass‐transition temperature and oxidative induction temperature to decrease with advanced material degradation was evident. The color changes of the cross‐sectional slices of some samples clearly indicated that the degradation was due to diffusion‐limited oxidation not homogeneously distributed throughout the sample bulk. In addition, samples from the near surface layers and from the center of the sample were examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Development and electrical conductivity behavior of copper‐powder‐filled‐epoxy graded composites
Authors: Chand Navin , Nigrawal Archana 
Published: May 2008

AbstractThis article reports the development and direct‐current (dc) conductivity behavior of copper‐powder‐filled‐epoxy graded composite. Copper‐powder‐filled‐epoxy composites with 10 wt % copper powder and epoxy resin were developed. dc conductivity measurements were performed on the graded composites with an electrometer in the temperature range of 28–146°C. The dc conductivity decreased with an increase in the distance in the direction of the centrifugal force, and this showed the formation of a graded structure. The dc conductivity increased as the copper powder content increased. Two‐phase conduction occurred in all the copper‐filled‐epoxy graded samples. The activation energy calculated with an Arrhenius equation for one sample was 0.88 eV, and this was mainly due to conduction electronic. Another sample had an activation energy of 1.33 eV. Three samples exhibited ionic conduction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A thermal expulsion approach to homogeneous large‐volume methacrylate monolith preparation; Enabling large‐scale rapid purification of biomolecules
Authors: Danquah Michael K. , Ho Jenny , Forde Gareth M. 
Published: May 2008

AbstractNumerous efforts have been dedicated to the synthesis of large‐volume methacrylate monoliths for large‐scale biomolecules purification but most were obstructed by the enormous release of exotherms during preparation, thereby introducing structural heterogeneity in the monolith pore system. A significant radial temperature gradient develops along the monolith thickness, reaching a terminal temperature that supersedes the maximum temperature required for structurally homogenous monoliths preparation. The enormous heat build‐up is perceived to encompass the heat associated with initiator decomposition and the heat released from free radical‐monomer and monomer–monomer interactions. The heat resulting from the initiator decomposition was expelled along with some gaseous fumes before commencing polymerization in a gradual addition fashion. Characteristics of 80 mL monolith prepared using this technique was compared with that of a similar monolith synthesized in a bulk polymerization mode. An extra similarity in the radial temperature profiles was observed for the monolith synthesized via the heat expulsion technique. A maximum radial temperature gradient of only 4.3°C was recorded at the center and 2.1°C at the monolith peripheral for the combined heat expulsion and gradual addition technique. The comparable radial temperature distributions obtained birthed identical pore size distributions at different radial points along the monolith thickness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
PdII‐Catalyzed Domino Heterocyclization/Cross‐Coupling of α‐Allenols and α‐Allenic Esters: Efficient Preparation of Functionalized Buta‐1,3‐dienyl Dihydrofurans
Authors: Alcaide Benito , Almendros Pedro , Martínez del Campo Teresa , Carrascosa Rocío 
Published: May 2008

AbstractA mild, palladium(II)‐catalyzed reaction of α‐allenols with α‐allenic esters in a heterocyclization/cross‐coupling sequence, applicable to a wide range of substitution patterns, has been developed for the preparation of 2,3,4‐trifunctionalized 2,5‐dihydrofurans. Our studies indicate high levels of chemo‐ and regiocontrol. The possibility of using optically active substrates as well as substrates of increased steric demand, such as tertiary α‐allenols, makes this novel sequence of heterocyclization/cross‐coupling an attractive method in organic synthesis. The current mechanistic hypothesis invokes a regiocontrolled palladium(II)‐mediated intramolecular oxypalladation of the free allenol component, that then undergoes a cross‐coupling reaction with the allenic ester partner, followed by a trans‐β‐deacyloxypalladation with concomitant regeneration of the PdII species.