1,720,955 research outputs found
Reação multicomponente para a amino-organilcalcogenilação de maleimidas catalisada por nanopartículas de CuO.
No full textThe advancement of new green methodologies in organic synthesis is crucial for the safer and more sustainable production of compounds, especially in medicinal chemistry. Currently, a significant part of medicines is generated by total synthesis, where simple matter goes through several steps until the final product. Thus, continuous innovation in overview research, with an emphasis on ecological approaches, makes it possible to create new compounds through less aggressive processes.
This research project aims to develop more sustainable and environmentally friendly chemical methodologies, allowing the incorporation of organochalcogen groups (such as sulfur and selenium) through a multicomponent occurrence catalyzed by copper for the functionalization of maleimides. In this context, selenium plays a fundamental role due to its high reactivity and characteristics, making it an important ally in producing medicines and agrochemicals. Therefore, the main objective of this study is to create methods aligned with the principles of green chemistry for the synthesis of maleimides with biological potential.
The use of nanoparticles was investigated, and their interactions in the reaction medium and the variation in the concentration of the case were analyzed. In this context, 10 maleimide compounds were synthesized from commercial maleic anhydrides and anilines. For the chalcogenation of the derivatives, a system catalyzed by nanoparticles of copper (II) oxide, diphenyl diselenide, and secondary amines was used under optimized reaction conditions. This method resulted in the production of 26 compounds, with yields ranging from 53% to 96%. The characterization of the compounds was performed using 1 H and 13 C NMR spectroscopic techniques. These results, taken together, indicate the possibility of generating new compounds with unique properties, which are valuable in pharmaceutical research and materials chemistry.O avanço de novas metodologias verdes em síntese orgânica é crucial para a produção mais segura e sustentável de compostos, especialmente na química medicinal. Atualmente, uma parte significativa dos medicamentos é gerada por síntese total, onde substâncias simples passam por diversas etapas até o produto final. Assim, a contínua inovação em pesquisas de síntese, com ênfase em abordagens ecológicas, possibilita a criação de novos compostos por meio de processos menos agressivos. Este projeto de pesquisa visa desenvolver metodologias químicas mais sustentáveis e ambientalmente amigáveis, permitindo a incorporação de grupamentos organocalcogênios (como enxofre e selênio) através de uma reação multicomponente catalisada por cobre para a funcionalização de maleimidas. Nesse contexto, o selênio desempenha um papel fundamental devido à sua alta reatividade e versatilidade, tornando-o um aliado importante na produção de medicamentos e agroquímicos. Portanto, a principal finalizade deste estudo é criar métodos alinhados com os princípios da química verde para a síntese de maleimidas com potencial biológico.
O emprego de nanopartículas foi investigado, analisando suas interações no meio reacional e a variação na concentração do catalisador. Nessa conjuntura, foram sintetizados 10 derivados de maleimidas a partir de anidridos maleicos e anilinas comerciais. Para a calcogenação dos derivados, utilizou-se um sistema catalisado por nanopartículas de óxido de cobre (II), disseleneto de difenila e aminas secundárias, sob condições reacionais otimizadas. Esse método resultou na obtenção de 26 compostos, com rendimentos variando entre 53% a 96%. A caracterização dos compostos é realizada a partir de técnicas espectroscópicas de RMN 1H e 13C. Estes resultados, somados, indicam possibilidade de gerar novos compostos com propriedades únicas, valiosas em pesquisa farmacêutica e química de materiais
Aplicação de iodo hipervalente na selenilação de arenos ativados.
No full textThe development of environmentally friendly methods has been one of the most expanding areas in scientific research in recent years. The development of new methodologies, modifying techniques already known and used in the field, is a challenge for researchers. Therefore, this work aims at a method to functionalize sp2 carbon atoms attached to activated aromatic rings, using procedures that fit the sustainable foundations of green chemistry. Initially, the optimization of the method was carried out, using diphenyl diselenide and N,N-dimethylaniline as reference reagents, with several modifications in time, temperature and solvents. Thus, the reaction condition used 0.5 molar equivalent of PhICl2 as oxidizing agent, 1,4-Dioxane as solvent, at room temperature, in open atmosphere, for 30 minutes. This led to N,N-Dimethyl-4-(phenylselenyl)aniline in an isolated yield of 92%. Then, tests were conducted with different diselenides, in order to evaluate the efficiency of the methodology. The regioselectivity is seen from the greater coupling occurring in the –para position to anilines, and –ortho, when in the occurrence of substituents that weaken the ring resonance, or that present a steric effect. Furthermore, based on literature studies and control experiments, a mechanism was proposed, where there is the formation of the electrophilic species RYCl in situ, indicating an ionic pathway. Thus, it was possible to develop an efficient and more sustainable synthetic route for the chalcogenation of C(sp2)-H.O desenvolvimento de métodos ambientalmente amigáveis vem sendo uma das áreas em maior expansão nas pesquisas científicas dos últimos anos. A elaboração de novas metodologias, modificando técnicas já conhecidas e utilizadas no meio, é um desafio para os pesquisadores. Portanto, este trabalho tem como objetivo um método para funcionalizar átomos de carbono sp2 ligados a anéis aromáticos ativados, utilizando de procedimentos que se encaixam nos fundamentos sustentáveis da química verde. Inicialmente, foi realizada a otimização do método, utilizando disseleneto de difenila e N,N-dimetilanilina como reagentes de referência, com diversas modificações no tempo, temperatura e solventes. Dessa forma, a condição reacional utilizou 0,5 equivalente molar de PhICl2 como agente oxidante, 1,4-Dioxano como solvente, a uma temperatura ambiente, em atmosfera aberta, por tempo de 30 minutos. Com isso, chegou-se a N,N-Dimetil-4- (fenilselenil)anilina com um rendimento isolado de 92%. Em seguida, foram conduzidos testes com diferentes disselenetos, a fim de avaliar a eficiência da metodologia. A regiosseletividade é vista a partir do maior acoplamento ocorrido na posição –para às anilinas, e –orto, quando na ocorrência de substituintes que enfraquecem a ressonância do anel, ou que apresentem efeito estérico. Ademais, a partir de estudos da literatura e experimentos de controle feito, foi proposto um mecanismo, onde o há a formação da espécie eletrofílica RYCl in situ, indicando uma via iônica. Assim, foi possível desenvolver uma rota sintética eficiente e mais sustentável para a calcogenação do C(sp2)-H
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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