1,720,964 research outputs found
Organocatalytic regio- and asymmetric C-selective SNAr reactions-stereoselective synthesis of optically active spiro-pyrrolidone-3,3 '-oxoindoles
No full textThe first example of catalytic enantioselective nucleophilic aromatic substitution of -dicarbonyl compounds is presented. An O-benzoylated cinchona alkaloid derivative catalyst gave a selective C-arylation reaction compared to, e.g., the corresponding benzylated catalyst which provided a 1:1 mixture of the C- and O-arylation products. The reaction proceeds well for various aromatic compounds with different 1,3-dicarbonyl compounds, and the optically active products are obtained in very high yields and with up to 92% ee. One further scope of the organocatalytic enantioselective nucleophilic aromatic substitution reaction is demonstrated by the synthesis of the optically active spiro-pyrrolidone-3,3′-oxoindole structure. Copyright © 2005 American Chemical Society
Organocatalytic enantioselective conjugate addition to alkynones
No full textThe first catalytic enantioselective addition of ?-dicarbonyl compounds to alkynones is presented. The conjugate addition proceeds in very high yields, giving a mixture of (Z)- and (E)-enones with up to 95% ee using the cinchona alkaloid [DHQ]2PHAL (5 mol %) as the catalyst. This organocatalytic enantioselective reaction has been further developed to a one-pot procedure to give the optically active (E)-enone adduct using first [DHQ]2PHAL (5 mol %), followed by Bu3P (10 mol %), as the catalysts
Improved asymmetric SNAr reaction of beta-dicarbonyl compounds catalyzed by quaternary ammonium salts derived from cinchona alkaloids
No full textChirally aminated 2-naphthols-organocatalytic synthesis of non-biaryl atropisomers by asymmetric Friedel-Crafts amination
No full textDirect organocatalytic and highly enantio- and diastereoselective Mannich reactions of alpha-substituted alpha-cyanoacetates
No full textMetal-free catalysis: Highly functionalized molecules with two contiguous stereocenters are easily accessed in high yield with high enantio- and diastereoselectivity by using a commercially available organocatalyst ((DHQD)2PYR, see scheme). The easily removed Boc protecting group in the product is an added value to this method as an important tool in asymmetric synthesis
Organocatalytic asymmetric hydroxylation of beta-keto esters: Metal-free synthesis of optically active anti-diols
No full textIntriguing behavior of cinchona alkaloids in the enantioselective organocatalytic hydroxyamination of alpha-substituted-alpha-cyanoacetates
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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
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