1,720,967 research outputs found
Synthesis of morpholino nucleosides starting from enantiopure glycidol
No full textThe synthesis of modified morpholino monomers was performed in a few steps through the condensation between 6-hydroxymethyl-morpholine acetal and nucleobases under Lewis acid conditions. The key common precursor of the targets - 6-hydroxymethyl-morpholine acetal - is easily synthesised via oxirane ring opening of optically pure glycidol using N-nosyl aminoacetaldehyde as a nucleophile, followed by an O-benzoylation/ring-closure tandem reaction sequence. Using readily available building blocks, this strategy allows access to diversified optically pure morpholino monomers in good yields and anomeric ratios
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
Copper(II)-catalyzed three-component arylation/hydroamination cascade from allyl alcohol: access to 1-Aryl-2-sulfonylamino-propanes
Full text linkA new straightforward approach to 1-aryl-2-aminopropanes using easily accessible substrates has been developed. Simple allyl alcohol is shown to be an ideal synthetic equivalent of the C3 propane-1,2-diylium bis-cation synthon in three-component cascade reactions with arenes and sulfonamide nucleophiles to regioselectively afford 1-aryl-2-aminopropanes. The reaction is catalyzed by Cu(OTf)2 and is expected to involve a Friedel-Crafts-type allylation of the arene, followed by hydroamination
Copper-Catalyzed/Hypervalent Iodine-Mediated Functionalization of Unactivated Compounds
Full text linkThe functionalization of unactivated substrates through the combination of copper catalysts and hypervalent iodine reagents represents a versatile tool in organic synthesis to access various classes of compounds. The hypervalent iodine derivatives can be used simply as oxidizing agents to regenerate the catalytic species or they can associate the functionalization of the starting material. In this review, special attention will be paid to methodologies which provide the introduction of nucleophiles into the reagent by use of suitable benziodoxol(on)es or iodonium salts. Many reactions concern C- and N-arylations, but may also involve formation of different carbon-carbon and carbon-nitrogen bonds, carbon-oxygen as well as carbon-halogen and carbon-phosphorus bonds
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
Palladium-Catalyzed/Mn(OAc)3-Mediated 1,2-Diazidation and 1,2-Acetoxy/Hydroxylation of N-Allyl Sulfonamides
No full textPalladium-catalyzed conditions for diazidation or acetoxy/hydroxylation of N-allyl sulfonamides by using Pd(OAc)(2) as the catalyst combined with Mn(OAc)(3) & sdot; 2H(2)O have been developed. The 1,2-diazidation reaction of the carbon-carbon double bond occurs in mild conditions (i. e. NaN3 as azide source in THF at room temperature), whereas the 1,2-acetoxy/hydroxylation requires an excess of Mn(OAc)(3) & sdot; 2H(2)O. The well-known ability of this reagent to act through single-electron transfer (SET) makes plausible a radical mechanism involving high valent palladium complexes
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