1,721,018 research outputs found
The dual role of ionic liquid BmimBF4, precursor of N-heterocyclic carbene and solvent, in the oxidative esterification of aldehydes
No full textRoom temperature ionic liquid BmimBF(4) (1-butyl-3-methylimidazolium tetrafluoroborate) has been utilized in the N-heterocyclic carbene-catalyzed oxidation of aldehydes to yield esters. In the presence of MnO2 as oxidant and of DBU and caesium carbonate as bases, aromatic, heteroaromatic and aliphatic esters have been isolated in good to excellent yields. The recyclability of the used ionic liquid along with the excess of inorganic reagents has been proved. The simple and cheap BmimBF4 ionic liquid played the dual role of precatalyst and solvent. This is the first time that such a reaction has been carried out with an ionic liquid as solvent. (C) 2013 Elsevier Ltd. All rights reserved
On the reactivity and stability of electrogenerated N-heterocyclic carbene in parent 1-butyl-3-methyl-1H-imidazolium tetrafluoroborate: Formation and use of N-heterocyclic carbene-CO2 adduct as latent catalyst
No full textA simple electrolysis (under galvanostatic conditions) of the room temperature ionic liquid 1-butyl-3-methyl-1H-imidazolium tetrafluoroborate, BMIm-BF4, yields, after bubbling CO2 into the catholyte, the adduct NHC-CO2. The considerable stability of this NHC-CO2 adduct, at room temperature, in the parent ionic liquid as solvent, has been compared with the one of free NHC in the same BMIm-BF4. The BMIm-BF4 solution containing NHC-CO2 adduct, suitably triggered (US irradiation or 120 degrees C), is able to release free NHC. The NHC-CO2 adduct usefulness has been demonstrated using it as efficient latent catalyst, in BMIm-BF4 as solvent, in the benzoin condensation and in the oxidative esterification of cinnamaldehyde with benzyl alcohol. (C) 2013 Elsevier Ltd. All rights reserved
An electrochemical alternative strategy to the synthesis of b-lactams via N-C4 bond formation
No full textA simple electrochemical synthesis of b-lactams has been developed using constant current electrolysis in a suitable solvent-supporting
electrolyte solutions, with subsequent addition of bromoamides. The regio- and stereo-selectivity of the electrochemically-induced cyclization
of bromoamides to b-lactams, via N C4 bond formation, has been evidenced. This synthesis avoids any addition of bases and probases and gives b-lactams in high yields
Saturated esters from α,β-unsaturated via reactions in ionic liquid catalyzed by electrogenerated N-heterocyclic carbenes
No full textElectrogenerated N-heterocyclic carbenes as organocatalysts. Use and reuse of ionic liquids as solvents and pre-catalysts in the transesterification/acylation reaction
No full textElectrochemically induced addition reactions in the absence of solvent and supporting electrolyte
No full textAbstract: Solvent- and supporting electrolyte-free
electrolysis in a two-compartment cell proved to be
effective for the direct electroactivation of CH
acid-containing compounds vs. catalytic addition processes.
Michael adducts (including quaternary carbon
centres) and 2-nitroalkanols were obtained in very
good yields and selectivity on application of a catalytic
amount of electricity under galvanostatic conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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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