1,721,005 research outputs found
Sintesi di Acidi 2-fenantrilpropionici e Strutture Fenantreniche Regioselettivamente Fluorurate a Potenziale Attività Farmacologica
No full textRecent Advances in Synthetic Strategies to 2,3-Dihydrobenzofurans
Full text linkThis review gives an overview on recent developments in methods for the construction of compounds with the 2,3-dihydrobenzo furan core in the period 2012 to 2019. Interest in 2,3-dihydrobenzofurans is constantly increasing. The methods are divided into intermolecular and intramolecular approaches. Intermolecular approaches are subdivided according to the parent intermediate for the key reaction, while intermolecular approaches are subdivided according by which bond is formed in the key reaction. The transformation of benzofurans to dihydrobenzofurans and other miscellaneous methods are also discussed. Approaches useful for the synthesis of natural products are emphasized. 1 Introduction 2 Intermolecular Approaches 2.1 o -Quinone Methides and o -Quinones 2.2 p -Quinone Methides and p -Quinones 2.3 Nitrogen-Containing Phenols and Quinones 2.4 o -Hydroxyphenylcarbonyl Derivatives and Phenols 2.5 Miscellaneous 3 Intramolecular Approaches 3.1 O-C2 Bond Forming 3.2 C2-C3 Bond Forming 3.3 C3-Aryl Bond Forming 3.4 O-Aryl Bond Forming 4 From BF to DHB 5 Rearrangements and Aromatizations
A HIGHLY REGIOSELECTIVE AND STEREOSELECTIVE-C5 OXYFUNCTIONALIZATION OF COPROSTANE STEROIDS BY DIOXIRANES - AN IMPROVED ACCESS TO PROGESTOGEN AND ANDROGEN HORMONES
No full textCoprostane steroids are selectively oxyfunctionalized at C5 by dimethyldioxirane and methyltrifluoromethyldioxirane to give useful intermediates for bioactive compounds
Last decade of unconventional methodologies for the synthesis of substituted benzofurans
No full textThis review describes the progress of the last decade on the synthesis of substituted benzofurans, which are useful scaffolds for the synthesis of numerous natural products and pharmaceuticals. In particular, new intramolecular and intermolecular C–C and/or C–O bond-forming processes, with transition-metal catalysis or metal-free are summarized. (1) Introduction. (2) Ring generation via intramolecular cyclization. (2.1) C7a–O bond formation: (route a). (2.2) O–C2 bond formation: (route b). (2.3) C2–C3 bond formation: (route c). (2.4) C3–C3a bond formation: (route d). (3) Ring generation via intermolecular cyclization. (3.1) C7a-O and C3–C3a bond formation (route a + d). (3.2) O–C2 and C2–C3 bond formation: (route b + c). (3.3) O–C2 and C3–C3a bond formation: (route b + d). (4) Benzannulation. (5) Conclusion
Desymmetrisation of meso-methyleyclooctanones. Highly enantioselective synthesis of C-8 syn-isoprenoid and syn,syn-deoxypropionate subunits from a bicyclo[3.3.1]nonane precursor
No full textThe methyl esters of 3R,7S-dimethyl- and 3R,5R,7S-trimethyl-8-hydroxyoctanoic acids have been prepared in good yields and with e.e. >98% by chemical elaboration of the known exo,exo-3,7-dimethylbicyclo[3.3.1]nonan-9-one, the key step involving the desymmetrisation of the intermediate meso-ketones cis-3,7-dimethyl- and cis,cis-3,5,7-trimethyl-cyclooctanone through the corresponding chiral enolates generated by the lithium amide of the (+)bis[(R)-(1-phenylethylamine)]. The very high enantioselectivity observed might be related to the conformational features of the eight-membered rin
Structural Insights into the TES/TFA Reduction of Differently Substituted Benzofurans: Dihydrobenzofurans or Bibenzyls?
No full textVarious polysubstituted benzofurans were reduced by using triethylsilane in trifluoracetic acid. 2,3-Dihydrobenzofurans or bibenzyl compounds were obtained in high yields, depending on the nature of the substituents at C2 and on the benzene ring of the core structure. A p -anisole substituent at C2 of benzofurans always led to the corresponding bibenzyls
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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