1,720,968 research outputs found
Synthesis and applications of fused N- and O-heterocyclic systems from nitrodienic building-blocks
No full textN-containing and O-containing heterocycles are widely distributed in natural products essential for life and are often responsible for the pharmaceutical activity of a lot of drugs and lead-compounds. Exploiting the electrophilic nature of functionalized nitrodienic building-blocks, combined with an opportune nuclophile, new protocols for the synthesis of fused N- and O-heterocycles, has been developed.
When using 2-aminopyridines or pyrrole as nucleophiles in the reaction with a suitable nitrodienic building block, it is possible to obtain imidazo[1,2-a]pyridines and 7-aryl-6-nitroindoles respectively. The particular substitution of these N-heterocycles was exploited to obtain fused heteropolycles systems: starting from imidazo[1,2-a]pyridines, through a photoinduced 6π-electrocyclization, new fused fluorescent polycycles were synthetized, and their fluorescent properties have been analysed, while performing a classical Cadogan reaction on 7-aryl-6-nitroindoles lead to functionalized pyrrolo[3,2-c]carbazoles.
Pyrrolo[3,2-c]carbazoles can react with nitrosoalkenes, leading to the products of alkylation, and this reaction has been studied in collaboration with the Organic Chemistry Group of the University of Coimbra.
Since the green approach in organic chemistry is gaining more and more importance, the possibility to use heterogeneous catalysis of Graphene Oxide (GO) in the synthesis of heterocycles, starting from nitrovinylic moieties, has also been investigated.
Finally, from the reaction between some particular nitrostilbenes and 2-naphthtol or 8-hydroxyquinoline, it was possible to synthetize a small library of dihydronaphtho- and naphthofuran derivatives. Naphthofurans obtained shown a good fluorescence, and their nature of diarylethenes made them promising substrates for a 6π-electrocyclization, with further expansion of the aromatic system, and the formation of a new benzenic ring, leading to new fused O-heterocyclic systems
A convenient access to imidazo[1,2-a]pyridines and fluorescent polycycles from nitrodienic building-blocks
No full textSynthesis of 2-Aryl-3-Vinylimidazo[1,2-a]Pyridines and fluorescent polycycles from nitrodienic building-blocks
No full textSynthesis of poly-functionalized Imidazo[1,2-a]Pyridines and fluorescent polycycles starting from the ring-opening of nitrothiophenes
No full textRecent advances in the use of conjugated nitro or dinitro-1,3-butadienes as building-blocks for the synthesis of heterocycles
No full textThe nitrovinyl moiety is surely one of the most reactive fragments in organic chemistry, continuously employed to explore original pathways and reach new targets. The short review herein represents an update on the potentialities in synthesis of conjugated mononitro or dinitro-1,3-butadienes: in such building blocks, the electrophilicity of the nitrovinyl moiety couples and takes advantage from the presence of a second, conjugated, vinyl moiety, most often leading to the eventual formation of diverse and/or diversely-functionalized heterocycles. The review will thus first of all provide chemists with recent, original protocols to such an important class of organic compounds as heterocycles, materials of choice for a lot of practical applications in different fields of human life
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
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