1,721,240 research outputs found
Alkylidene and Arylidene Meldrum's Acid as a Versatile Reagent for Synthesis of Heterocycles
No full textMeldrum`s acid and its derivatives are excellent building blocks for synthesis of acyclic, carbocyclic and heterocyclic compounds.1 Herein recent (mainly year 2011 to 2015) trends on applications of arylidene/alkylidene Meldrum`s acid 1 (R1, R2 = H, Ar, Alk, -(CH2)n-) in the synthesis of heterocycles, and multicomponent reactions (MCR) involving their formation in situ are focused
Alkylidene and Arylidene Meldrum's Acid as a Versatile Reagent for Synthesis of Heterocycles
No full textMeldrum`s acid and its derivatives are excellent building blocks for synthesis of acyclic, carbocyclic and heterocyclic compounds.1 Herein recent (mainly year 2011 to 2015) trends on applications of arylidene/alkylidene Meldrum`s acid 1 (R1, R2 = H, Ar, Alk, -(CH2)n-) in the synthesis of heterocycles, and multicomponent reactions (MCR) involving their formation in situ are focused
Synthesis of Malonic Acid Monoanilides
No full textCleavage of Meldrum`s acid with anilides was studie
Thioalkylation of Meldrum 's Acid: Protected alkylidene derivatives of isopropylidene malonate
No full textThioalkylated Meldrum 's acid is easily by treatment of Meldrum 's acid with an aldehyde and thiophenol in the presence of catalytical amounts of piperidinium acetate (→ 1–6 , Table 1 ). The adducts 1–6 are crystalline, stable compounds and they can be caused to react directly with nucleophiles and dienes (see 3→7–12 , Scheme 1 ). The regeneration of the parent olefin is effected thereby by simply dissolving the adduct under neutral or basic conditions. Extension of this method to thiocarboxylic acids allowed the preparation of the corresponding formaldehyde derivatives 13 and 15 (Table 3 ).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37971/1/19880710816_ftp.pd
Síntese de potenciais antagonistas do receptor B1 da bradicinina contendo o heterociclo piridazinona
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2013.Uma série de 4,5-di-hidro-3(2H)-piridazinonas dissubstituídas nas posições 4 e 6 do heterociclo foi preparada com bons rendimentos. A metodologia utilizada na síntese do anel di-hidropiridazinônico foi a de Tóth, na qual empregou-se derivados do ácido de Meldrum e numa sequência de quatro etapas reacionais obteve-se o sistema heterocíclico com sucesso. Os derivados monoalquilados do ácido de Meldrum foram obtidos exclusivamente com bons rendimentos, assim como os derivados dialquilados. Uma modificação na metodologia de síntese dos potenciais antagonistas do receptor B1 foi feita, partindo-se do fenol 9a para introdução de sistemas como fenilacético e p-toluenossulfonila. Diferentes grupos ácidos foram incorporados na posição 4 da estrutura do heterociclo culminando em di-hidropiridazinonas contendo a porção fenoxifenilacético e fenoxifenilmetiltetrazol. A obtenção das piridazinonas dissubstituídas foi alcançada a partir da oxidação dos derivados da 4,5-di-hidro-3(2H)-piridazinona. Os intermediários bem como os produtos finais foram devidamente caracterizados por espectrometria de IV, RMN de 1H e 13C.Abstract : A series of 4,6-dissubstituted-4,5-dihydro-3(2H)-pyridazinones was prepared in good yields. The methodology employed on the synthesis of dihydropyridazinone ring was Tòth´s methodology, which made use of Meldrum´s acid derivates and in a four-step reaction sequence the heterocyclic system was sucessfully obtained. The monoalkylated derivates of Meldrum´s acid were obtained exclusively in good yields as well as the dialkylated derivates. A modification of the method of potencial receptor B1 antagonists synthesis was made, starting from phenol 9a to introduction of systems such as phenylacetic and p-toluenesulphonyl. Different acids groups were incorporated at position 4 of the heterocycle structure culminating in dihydropyridazinones containing the phenoxylphenylacetic group and the phenoxylphenyl group containing tetrazole. The obtation of dissubstituted pyridazinones derivates was achieved by oxidation reaction of 4,5-dihydro-3(2H)-pyridazinones derivates. The intermediates compounds as well as the final products were characterized by IR, 1H and 13C NMR spectroscometry
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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