1,720,974 research outputs found
Three-component carboacylation of alkenes via cooperative nickelaphotoredox catalysis
No full textVarious commercially available acyl chlorides, aldehydes, and alkanes were exploited for versatile three-component 1,2-carboacylations of alkenes to forge two vicinal C–C bonds through the cooperative action of nickel and sodium decatungstate catalysis. A wealth of ketones with high levels of structural complexity was rapidly obtained via direct functionalization of C(sp(2))/C(sp(3))–H bonds in a modular manner. Furthermore, a regioselective late-stage modification of natural products showcased the practical utility of the strategy, generally featuring high resource economy and ample substrate scope
Electrochemical Rearrangement for Remote Functionalizations of Unactivated Alkenes
No full textAn electrochemical strategy for the dual functionalizations of unactivated alkenes through an intramolecular migration process was realized in the absence of sacrificial chemical oxidants and noble-metal catalysts under mild reaction conditions. The electrochemistry enabled a (hetero)aryl migration while providing access to alkenyl/alkynyl-migration products. Thus, electricity was employed for the formation of functionalized fluoroalkyl radicals through activation of C−H/C−Br bonds from fluorinated esters. Thereby, we obtained a variety of di and mono-fluorinated alkyl products with good functional group tolerance as well as chemo, and regioselectivities. Likewise, defluorinative allylation of α-carbonyl alkyl bromides proved viable. The reaction mechanism was established by experiments and computations.European Research Council http://dx.doi.org/10.13039/501100000781Alexander von Humboldt-Stiftung http://dx.doi.org/10.13039/100005156China Scholarship Council http://dx.doi.org/10.13039/501100004543Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165
Photoelectrochemical nickel-catalyzed carboacylation/silanoylation of alkenes with unactivated C/Si–H bonds
No full textA photoelectrochemical approach for the carboacylation/silanoylation of alkenes with alkanes/hydrosilanes is described. The method offers a new perspective for chemists to rapidly obtain various ketones with high levels of structural complexity.Direct and selective installation of two different functional groups into the unsaturated bonds of alkenes constitutes a long-standing goal in organic synthesis. Herein, we first report a photoelectrochemical approach for the carboacylation/silanoylation of alkenes with unactivated alkanes/hydrosilanes
via
the LMCT process. A number of ketones with high complexity and diversity were rapidly obtained from commercially available materials in an economical and sustainable manner. Furthermore, this protocol can be scaled up to the gram-level. This paired electrocatalysis strategy features excellent regioselectivity, and ample substrate scope, is external-oxidant-free, and features a high resource economy. A series of mechanistic experiments were performed to determine the preferred pathway for the photoelectrochemical Ni(
i
)/Ni(
ii
)/Ni(
iii
) cycles in these transformations.A photoelectrochemical approach for the carboacylation/silanoylation of alkenes with alkanes/hydrosilanes is described. The method offers a new perspective for chemists to rapidly obtain various ketones with high levels of structural complexity.Direct and selective installation of two different functional groups into the unsaturated bonds of alkenes constitutes a long-standing goal in organic synthesis. Herein, we first report a photoelectrochemical approach for the carboacylation/silanoylation of alkenes with unactivated alkanes/hydrosilanes
via
the LMCT process. A number of ketones with high complexity and diversity were rapidly obtained from commercially available materials in an economical and sustainable manner. Furthermore, this protocol can be scaled up to the gram-level. This paired electrocatalysis strategy features excellent regioselectivity, and ample substrate scope, is external-oxidant-free, and features a high resource economy. A series of mechanistic experiments were performed to determine the preferred pathway for the photoelectrochemical Ni(
i
)/Ni(
ii
)/Ni(
iii
) cycles in these transformations.National Natural Science Foundation of China https://doi.org/10.13039/501100001809Deutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Ruthenium(II)-Catalyzed Remote C–H Alkylation of Arenes Using Diverse N-Directing Groups through Aziridine Ring Opening
No full text
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
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
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