1,721,079 research outputs found
Palladium(0) olefin complexes and enantioselective allylic amination/alkylation with a P,N-auxiliary
No full textNew Pd(0) olefin complexes, 2-5, of a binaphthalene-based chiral P,N(oxazoline) auxiliary, (S,R)-2-[4-(isopropyl)oxazol-2-yl]-2'-diphenylphosphino-1,1'-binaphthyl 1, have been prepared (olefin = fumaronitrile, maleic anhydride, 4-cyclopentene-1,3-dione, and. dibenzylideneacetone). These compounds reveal different dynamic behavior in solution as shown by 2-D exchange spectroscopy. Ligand 1 affords excellent enantioselectivity (up to 99% ee) in the allylic amination of a 1,3-diphenyl allyl precursor. The solid-state structure of [Pd(eta(3)-PhCHCHCHMe)(1)]OTf, 15, has been determined and shows two different diastereomeric cations within one unit cell; that is both the si and re faces of the allyl crystallize together, the first example of this for a moderately large allyl ligand. The structure of PdCl(2)(1) is also reported and reveals las does that for 15) that the oxazoline ring of 1 is twisted relative to the P-Pd-N coordination plane, thus placing this ring substituent above and not below the coordination plane. A more exact solid-state structure for Pd(2)(dba)(3) has been determined
Chiral phosphito-thioether complexes of palladium(0) : comments on the Pd, Rh, and Ir regio-and-enantioselective allylic alkylations of PhCH=CHCH(OAc)R, R = H, Me, Et
No full textThe new chiral auxiliary (R)-2-ethylthio-1-(phenylethyl)-(R)-binaphthyl phosphite, 1, and three stable Pd(0) olefin complexes containing this chelate, 2-4, have been synthesized. The structure of the maleic anhydride complex 3 has been determined by X-ray diffraction methods. Solution details for 2-4 and aspects of their dynamics have been elucidated via 2-D NMR spectroscopy. The fumaronitrile complex 2 exchanges intramolecularly, whereas the maleic anhydride and pentenedione derivatives, 3 and 4, respectively, exchange intermolecularly. Ligand 1 has been used as auxiliary in the Pd, Rh, and Ir regio- and enantioselective allylic alkylation reactions of PhCH=CHCH(OAc)R, R = H, Me, Et, with the anion of dimethyl malonate. Modest to good selectivities are reported
Catalytic and structural studies on complexes of a binaphthyl-phosphino-oxazoline auxiliary : the meta dialkyl effect on enantioselectivity
No full textThe chiral phosphino-oxazoline ligand (S,R)-2-[4-(isopropyl)oxazol-2-yl]-2'-bis(3,5-dimethylphenylphosphino)-1,1'-binaphthyl, 6b, its Pd-dichloro complex, 9, the p-cyanoaryl complex [PdBr(p-NC-C6H4](6b)], 10, a model for the Heck reaction, the cationic 1,3-diphenylallyl derivative [Pd(eta(3)-PhCHCHCHPh)(6b)]OTf, 11, a model for the allylic allylation, and the Rh- and Ir-1,5-COD compounds [M(1,5-COD)(6b)]BF4, 12 and 13, respectively, have been prepared. In enantioselective catalytic experiments, the presence of the 3,5-dimethylphenyl groups generally increases the observed ee. The solid-state structure of PdCl2(6b), 9, has been determined. 2-D and variable-temperature NMR experiments suggest that one of the two 3,5-dimethyl P-aryl rings interacts selectively with the remaining ligands. Consequently, the entire chiral pocket becomes slightly more rigid and the correlation with substrate improves
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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