1,721,023 research outputs found
Reactions between organomagnesium reagents and nitroarenes: Past, present, and future
No full textGrignard reagents display useful diversity in their reactions with nitroarenes. Depending on the organomagnesium species used, these reactions, the results of which can be predicted from mechanistic studies, may lead to significantly diverse products (see scheme), and can be tailored towards the synthesis of substituted nitroarenes, indoles, and diarylamines. FG = functional group
The chemistry of thioacylsilanes
No full textThis review summarizes our work on the synthesis and the reactivity of thioacylsilanes and focuses on the differences between non-enethiolizable and enethiolizable thioacylsilanes
Sulfoxonium ylides: Simple compounds with chameleonic reactivity
Full text linkSulfur ylides first disclosed in 1930 started to gain more attention in the 1960s, thanks mainly to the studies by Corey and Chaykovsky on their use for the preparation of strained rings. More recently, the chemistry of these compounds has experienced important growth, in part due to the similarity of their reactivities with diazo compounds. This short review provides an overview on the great assortment of reactions of sulfoxonium ylides, outlining a comparison between the chemistry of these ylides and their congeners: sulfonium ylides and diazo compounds. Insertion reactions, cyclisation reactions and ring-opening reactions are highlighted, giving particular attention to catalytic asymmetric methodologies
Conformational studies by dynamic NMR. 72. Stereolabile enantiomers of acyl and thioacyl ferrocenes
No full textnon present
Divergent Reactivity of D-A Cyclopropanes under PTC Conditions, Ring-Opening vs. Decyanation Reaction
Full text linkThe divergent reactivity of D-A cyclopropane, under PTC conditions, is herein reported. Thus, a ring-opening or a decyanation reaction can be achieved by reacting 2-arylcyclopropane-1,1-dicarbonitriles 1 with thioacetic acid in different reaction conditions. The use of solid Cs2CO3 leads unexpectedly to the synthesis of new D-A cyclopropane derivatives via a decyanation reaction, followed by diastereoselective acetylation, whereas the use of an aqueous solution of Cs2CO3 results in a typical ring-opening reaction with the formation of S-thiolate products. Therefore, the use of tailored reaction conditions allows one to obtain either cyclic or open-chain products in moderate to good yields
New chemistry of α-silyl vinylsulfides
No full textα-Silyl Vinylsulfides, obtained in a stereoselective manner through enethiolizable silyl thioketones, can be used for the synthesis of vinylsulfides and vinylsilane with a specific geometry, and for the preraration of bicyclic and open chain thiofunzionalized enones
Catalyst- and Substrate-Dependent Chemodivergent Reactivity of Stabilised Sulfur Ylides with Salicylaldehydes
Full text linkStabilised sulfur ylides are synthetically appealing compounds, which reactivity under Brønsted acid catalysis has been poorly explored. Herein, we report a new catalyst- and substrate- dependent chemodivergent reaction between stabilised sulfur ylides and salicylaldehydes, leading to the (suprising) formation of 2H-chromenes or dihydrobenzofurans products. Particular attention was set on the unusual mechanisms involved. Two unique reaction routes including two ylide units in the reactions are proposed. These pathways were validated by performing a selectivity switch in some cases, enabled by the modulation of the nucleophilicity of the sulfur ylide, and by the loading of the Brønsted acid catalyst in the reaction
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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