1,720,957 research outputs found
Bicyclobutanes as unusual building blocks for complexity generation in organic synthesis
No full textBicyclobutanes are among the most highly strained organic compounds and are intriguing building blocks in organic synthesis. This review provides an overview of the recent developments in bicyclobutane synthesis, their synthetic utility and their modes of reactivity
Assessing an Elusive 3,4‐Dimethyl‐Chloroborole
No full textAbstract
The attempted syntheses of 3,4‐dimethylborole derivatives further bearing bulky SiMe2t‐Bu groups in 2,5‐position are reported. Isolation of base‐stabilized adducts to the chloroborole were achieved. The respective free borole was found to be unstable and revealed 1,3‐hydrogen atom shift isomerization to a 1‐bora‐1,3‐butadiene with an s‐trans orientation and lacking cyclic conjugation of the π‐system. Computational probing indicates elevated C−H acidity of methyl groups attached to the butadiene backbone in boroles, exceeding the C−H acidity of respective boron‐bound methyl groups. Derivatization attempts of the new chloroborole are reported.A chloroborole with a new substitution pattern is presented. Methyl groups in the butadiene backbone are revealed to allow rearrangement to form non‐cyclo‐conjugate borabutadienes. The thermodynamic driving force is loss of anti‐aromatic destabilization. Computationally, methyl groups in the backbone of boroles are found to be more C−H acidic than methyl groups attached to the boron atom.
imageFonds der chemischen Industrie is acknowledged for funding (Liebig Fellowship)Boehringer Ingelheim Foundation
Photocatalytic Oxidative Activation of Bicyclo[1.1.0]butanes for Formal [2σ+2π] Cycloadditions
No full textWe report the discovery of an example of oxidative bicyclo[1.1.0]butane activation. This reactivity stands in contrast to well-established strain-release nucleophile addition and reductive activation and opens up further possibilities for exploiting bicyclo[1.1.0]butanes in synthesis. Using a strongly oxidizing acridinium organophotocatalyst, the formal [2σ+2π] cycloaddition between bicyclo[1.1.0]butanes and alkenes or aldehydes leads to the corresponding bicyclo[2.1.1]hexanes or oxabicyclo[2.1.1]hexanes. The subtle interplay between bicyclo[1.1.0]butane and alkene identity dictates the mechanism of the reaction, with regiodivergent pathways providing complementary reaction products in up to >20:1 regioselectivity. A mechanistic investigation including electrochemical, photophysical, radical trapping, and computational studies support the oxidative mechanisms proposed
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
