1,720,958 research outputs found
Easy access to (n+3)-dimethylamino-1-ethenylbicyclo[n.1.0]alkanes and their facile conversion to ring-annelated cyclopentadienes
No full textAminocyclopropanation of 1-ethenylcycloalkenes 2a-d with N,N-dibenzyl- and N,N-dimethylformamide, respectively, by treatment with cyclohexylmagnesium bromide in the presence of methyltitanium triisopropoxide yielded the exo-(n+3)-N,N-dimethylamino-1-ethenylbicyclo[n.1.0]alkanes 3a-d (58-72%). Compounds 7b-d could be transformed by thermal vinylcyclopropane to cyclopentene rearrangement to the corresponding exo-4-dimethyl-aminobicyclo[n.3.0]alk-1-enes 7b-d (84-90%). Elimination of the dimethylamino group led to the cyclopentadienes 11b-d and 12b-d (72-82%). The 5-dimethylamino-1-ethenylbicyclo[2.1.0]pentane did not undergo the typical vinylcyclopropane rearrangement, but ring-opening at the bridgehead-bridgehead bond to form 1-ethenyl-2-dimethylaminocyclopentene 8
Cyclopropyl building blocks for organic synthesis, 58 - A new short access to amino acids incorporating an aminocyclopropyl moiety from N,N-dibenzylcarboxamides
No full textOur recently reported titanium-mediated transformation of N,N-dialkylcarboxamides to cyclopropylamines has been applied to N,N-dibenzyl-2-benzyloxyacetamide using a variety of alkylmagnesium bromides to yield 1-(benzyloxymethyl)-1-(dibenzylamino)cyclopropane (15a, 48%) and 2-substituted analogs 15b-f (33-48%). These have been transformed in just a few steps into N-Boc-protected methyl esters of 1-ami-nocyclopropanecarboxylic acid (1, 29% overall), coronamic acid (2, 35%) and norcoronamic acid (21%), 2,3-methanoglutamic acid (21g, 19%) and 2,3-methanoornithine (21I, 12%). Similarly, the corresponding derivatives of 3,4-methano-gamma-aminobutyric acid (26, 23%) and 4-spirocyclopropane-gamma-butyrolactam (32, 44%) have been synthesized
Easy access to (n+3)-dimethylamino-1-ethenylbicyclo[n.1.0]alkanes and their facile conversion to ring-annelated cyclopentadienes
No full textAminocyclopropanation of 1-ethenylcycloalkenes 2a-d with N,N-dibenzyl- and N,N-dimethylformamide, respectively, by treatment with cyclohexylmagnesium bromide in the presence of methyltitanium triisopropoxide yielded the exo-(n+3)-N,N-dimethylamino-1-ethenylbicyclo[n.1.0]alkanes 3a-d (58-72%). Compounds 7b-d could be transformed by thermal vinylcyclopropane to cyclopentene rearrangement to the corresponding exo-4-dimethyl-aminobicyclo[n.3.0]alk-1-enes 7b-d (84-90%). Elimination of the dimethylamino group led to the cyclopentadienes 11b-d and 12b-d (72-82%). The 5-dimethylamino-1-ethenylbicyclo[2.1.0]pentane did not undergo the typical vinylcyclopropane rearrangement, but ring-opening at the bridgehead-bridgehead bond to form 1-ethenyl-2-dimethylaminocyclopentene 8
Cyclopropyl building blocks for organic synthesis, 58 - A new short access to amino acids incorporating an aminocyclopropyl moiety from N,N-dibenzylcarboxamides
No full textOur recently reported titanium-mediated transformation of N,N-dialkylcarboxamides to cyclopropylamines has been applied to N,N-dibenzyl-2-benzyloxyacetamide using a variety of alkylmagnesium bromides to yield 1-(benzyloxymethyl)-1-(dibenzylamino)cyclopropane (15a, 48%) and 2-substituted analogs 15b-f (33-48%). These have been transformed in just a few steps into N-Boc-protected methyl esters of 1-ami-nocyclopropanecarboxylic acid (1, 29% overall), coronamic acid (2, 35%) and norcoronamic acid (21%), 2,3-methanoglutamic acid (21g, 19%) and 2,3-methanoornithine (21I, 12%). Similarly, the corresponding derivatives of 3,4-methano-gamma-aminobutyric acid (26, 23%) and 4-spirocyclopropane-gamma-butyrolactam (32, 44%) have been synthesized
Primary 1-arylcyclopropylamines from aryl cyanides with diethylzinc and titanium alkoxides
No full text[GRAPHICS] 1-Aryl-substituted primary cyclopropylamines are conveniently prepared from aromatic nitriles and diethylzinc. The yields range from 40 to 56% for donor-substituted (five examples) to 62-82% for non- and acceptor-substituted substrates (nine examples)
ChemInform Abstract: A New Versatile Reagent for the Synthesis of Cyclopropylamines Including 4-Azaspiro(2.n)alkanes and Bicyclo(n.1.0)alkylamines.
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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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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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