1,720,979 research outputs found
Base-Mediated Transition-Metal-Free Dehydrative C−C and C−N Bond-Forming Reactions from Alcohols
No full textIn recent years, there has been an increasing interest in using alcohols as alkylating agents for C−C and C−N bond-forming processes employing mainly TM-catalysts. Although BH-catalysis looks like a green atom economy process since water is the only by-product, it often suffers from one or more drawbacks, such as the use of expensive noble metal complexes, capricious ligands, and toxic organic solvents. Therefore, straightforward, efficient, atom economy and environmentally benign alternative protocols are desirable. This review aims to summarize the current knowledge within the published literature about dehydrative processes developed without TM-catalysts. The most recent contributions to this topic have been reviewed keeping into account the new findings reported in this area. The features, strengths, and limitations of these alcohol-based C−C and C−N bond-forming processes has also been taken into account
A New Asymmetric Synthetic Route to Pheniramines via Hydroformylation of Functionalyzed Olefins
No full textAsymmetric Synthesis of 1-substituted-1-(pyridin-2-yl)methylamines by diastereoselective reduction of enantiopure sulfinimines
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Enantioselective Michael-Additions of Nitromethane to a,b-Unsaturated Ketones Catalyzed by Transition Metal Complexes with Chiral Nitrogen Ligands
No full textNickel(II) complexes with chiral chelating nitrogen ligands such as 2,2'-bipyridines, 1,10-phenanthrolines and 1,2-diamino compounds are satisfactory catalysts for the Michael addition of nitromethane to benzalacetone, chalcone and 2-cyclohexenone. Only the catalytic system derived from Ni(acac)2 and (+)-(S)-2-(anilinomethyl)pyrrolidine gave both good catalytic activity and asymmetric induction up to 24%. © 1989
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
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