1,720,989 research outputs found
Palladium catalyzed molecular cascades for the synthesis of ethyl 2-methyl-2-(4-methyl-3-(morpholinomethyl)-2-oxopent-3-en-1-yl)-1-oxo-1,2,3,4,5,6-hexahydro-3aH-indene-3a-carboxylate
No full textRegiospecific pentamolecular queuing cascades involving the formation of five new bonds have been investigated. The process employs vinyl triflate as starter species together with excess dimethylallene and CO in the presence of in situ generated Pd(0) catalyst and morpholine as capping agent. The investigated reactions were properly tuned up for determining the best conditions allowing to maximizing the desired pentamolecular cascade pathway. The choice of the base, Pd-ligands and reaction temperature as well as the nature of the additive or its presence seem to be pivotal elements that must be tuned for realizing an efficient and reliable process
Solid phase synthesis of bicyclic pyrrolidines
No full textThe preparation of bicyclic pyrrolidines, stable and easy to isolate, is performed through both classical solution chemistry and on solid support. A new linker strategy is presented based on the concept of REM resin approach. Starting from a suitably derivatized Wang's resin, the linker can be REgenerated after cleavage of the product and functionalized to start a new synthetic cycle via a Michael reaction. In the present work a vinyl sulfone supported on a Wang's resin is able to undergo a Michael reaction with an amino acid derivative; the obtained adduct serves as a precursor for azomethine ylide generation, which is conveniently trapped with N-methyl-maleimide. The results are presented and discussed in the light of the experimental conditions applied as well as the method chosen for the cleavage of the product and resin regeneration
9-Anthraldehyde oxime: a synthetic tool for variable applications
No full textAbstract: Oximes are one of the most important and prolific functional groups in organic chemistry; among them, 9-anthraldehyde oxime represents a valuable example both from the preparative side and the synthetic applications. There are many strategies to prepare 9-anthraldehyde oxime from different functional groups that were summarized in the present review, focusing on the most recent and innovative. The main synthetic applications of 9-anthraldehyde oxime are presented and thoroughly discussed, focusing on the most recent and innovative synthetic strategies. Graphic abstract: [Figure not available: see fulltext.
Nitrosocarbonyl Carbohydrate Derivatives: Hetero Diels-Alder and Ene Reaction Products for Useful Organic Synthesis
No full textThe generation and trapping of two new nitrosocarbonyl intermediates bearing carbohydrate-based chiral substituents is achieved by the mild oxidation of the corresponding nitrile oxides with tertiary amine N-oxides. Their capture with suitable dienes and alkenes afforded the corresponding hetero Diels-Alder cycloadducts and ene adducts from fair to excellent yields. The entire methodology looks highly promising by the easy conversion of aldoximes into hydroxymoyl halides, widening the access to nitrosocarbonyls, versatile tools in organic synthesis
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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