1,720,960 research outputs found
SONOCHEMISTRY: an alternative methodology to synthesis of 5-arylidenethiazolidine-2,4-diones
No full textThe efficient synthesis of sixteen (Z)-5-arylidene-2,4-thiazolidinediones by aldol
condensation reaction of 2,4-thiazolidinedione, mono- and di-substituted
arenealdehydes and KOH in ethanol using the ultrasound irradiation are reported.
The desired compounds were obtained in a few minutes (10-20min.) with moderated
to good yields (25-81%). The structure of all synthesized compound were confirmed
by Mass spectrometry and by hydrogen and carbon Nuclear Magnetic Resonance.
The sonochemistry has been showed as an alternative methodology in organic
synthesis once its biggest feature is the capacity to decrease the reaction time.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA sonoquímica tem se mostrado uma alternativa as metodologias convencionais
utilizadas em síntese orgânica, já que sua maior característica é a capacidade de
diminuir o tempo de reação. Esta dissertação apresenta e discute a síntese de
dezesseis 5-arilidenotiazolidina-2,4-dionas, a partir, da utilização da radiação
ultrassônica como fonte de energia alternativa. A obtenção desses compostos ocorre
através de reações entre a 2,4-tiazolidinadiona, dezesseis benzaldeídos (mono e
disubstituidos por diferentes grupos doadores e retiradores de elétrons) e hidróxido
de potássio, utilizando 10 mL de etanol como solvente. O tempo de reação variou
entre 10 e 20 minutos de sonicação, não mostrando relação entre os grupos
substituídos no anel aromático. Os produtos foram obtidos na forma de sólidos, em
alguns casos muito finos. Os rendimentos variaram de moderados a bons (25-81%).
Todas as moléculas sintetizadas tiveram suas estruturas químicas confirmadas por
Espectrometria de Massas e Ressonância Magnética Nuclear de Hidrogênio e
Carbono, foi percebido que a formação do isômero Z é o predominante nesta
síntese
SONOCHEMISTRY: an alternative methodology to synthesis of 5-arylidenethiazolidine-2,4-diones
No full textThe efficient synthesis of sixteen (Z)-5-arylidene-2,4-thiazolidinediones by aldol
condensation reaction of 2,4-thiazolidinedione, mono- and di-substituted
arenealdehydes and KOH in ethanol using the ultrasound irradiation are reported.
The desired compounds were obtained in a few minutes (10-20min.) with moderated
to good yields (25-81%). The structure of all synthesized compound were confirmed
by Mass spectrometry and by hydrogen and carbon Nuclear Magnetic Resonance.
The sonochemistry has been showed as an alternative methodology in organic
synthesis once its biggest feature is the capacity to decrease the reaction time.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA sonoquímica tem se mostrado uma alternativa as metodologias convencionais
utilizadas em síntese orgânica, já que sua maior característica é a capacidade de
diminuir o tempo de reação. Esta dissertação apresenta e discute a síntese de
dezesseis 5-arilidenotiazolidina-2,4-dionas, a partir, da utilização da radiação
ultrassônica como fonte de energia alternativa. A obtenção desses compostos ocorre
através de reações entre a 2,4-tiazolidinadiona, dezesseis benzaldeídos (mono e
disubstituidos por diferentes grupos doadores e retiradores de elétrons) e hidróxido
de potássio, utilizando 10 mL de etanol como solvente. O tempo de reação variou
entre 10 e 20 minutos de sonicação, não mostrando relação entre os grupos
substituídos no anel aromático. Os produtos foram obtidos na forma de sólidos, em
alguns casos muito finos. Os rendimentos variaram de moderados a bons (25-81%).
Todas as moléculas sintetizadas tiveram suas estruturas químicas confirmadas por
Espectrometria de Massas e Ressonância Magnética Nuclear de Hidrogênio e
Carbono, foi percebido que a formação do isômero Z é o predominante nesta
síntese
Tetrahydronaphthyl-1-amine as precursor to obtain thiazolidinones and benzothiazepinones: Synthesis, atropisomerism and structural elucidation
No full textThe multicomponent one-pot by conventional heating methodology was applied to
development of four series of heterocycles containing nitrogen and sulfur. They were
synthetized from tetrahydronaphthalen-1-amines: 5,6,7,8-tetrahydronaphthalen-1-
amine (aromatic), R-1,2,3,4-tetrahydronaphthalen-1-amine (aliphatic) and (S)-
1,2,3,4-tetrahydronaphthalen-1-amine (aliphatic). Firstly, 5,6,7,8-
tetrahydronaphthalen-1-amine reacted with mercaptoacetic acid and arenealdehydes
having electron-withdrawing groups gave nine 2-aryl-3-(5,6,7,8-
tetrahydronaphthalen-1-yl)thiazolidin-4-one by satisfactory 47-70% yield. Also the
atropisomerism phenomenom was observed in several molecules of this series. It
was confirmed by variable-temperature nuclear magnetic resonance method. The
energy required for the interconversion of one atropisomer into another is around
16.7 kcal.mol-1
. Chemical quantum calculation displayed that more stable isomer has
the tethahidronaphthalene portion below the five-ring plane. NOESY showed that in
solution the same isomer is more stable. In turn, when the same aromatic amine
react with arenealdehydes bearing electron-donating groups and with two examples
having electron-withdrawing groups, by p-TSOH catalysis five 5-aryl-1,5,8,9,10,11-
hexahydronaphtho[1,2-e][1,4]thiazepin-2(3H)-one were obtained (56-72%). When
aliphatic amines of defined stereochemistry were used as precursor were synthetized
six 2-phenyl-3-R-(1,2,3,4-tetrahydronaphthalen-1-yl)thiazolidin-4-ones and six 2-
phenyl-3-S-(1,2,3,4-tetrahydronaphthalen-1-yl)thiazolidin-4-ones (14-70 %), after
purification some pairs of diastereoisomers were separated. The atropisomerism
phenomenon was also observed in examples this kind of thiazolidinones. All
compounds are unpublished and had their purities available and their structures
elucidated by mass spectrometry and nuclear magnetic resonance techniques and
available crystals by X-rayCoordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA metodologia multicomponente one-pot com aquecimento térmico convencional foi
aplicada para a síntese de quatro séries de heterociclos contendo nitrogênio e
enxofre, os quais foram sintetizados a partir de diferentes tetraidronafitilaminas:
5,6,7,8-tetraidronaft-1-ilamina (aromática), R-1,2,3,4-tetraidronaft-1-ilamina (alifática)
e S-1,2,3,4-tetraidronaft-1-ilamina (alifática). Primeiramente, ao reagir a 5,6,7,8-
tetraidronaftilamina com benzaldeidos substituídos por grupos retiradores de
elétrons e o ácido mercaptoacético, foram sintetizadas nove 2-(aril)-3-(5,6,7,8-
tetraidronaft-1-il)tiazolidin-4-onas com rendimentos entre 47-70%. A maioria dos
exemplos dessa série apresentou o fenômeno de atropoisomerismo, caracterizado
pelo método de ressonância magnética nuclear com variações de temperatura. A
partir dessa análise foi estimado que o ∆G‡ de interconversão entre os
atropoisômeros é de 16,7 Kcal.mol-1
. Cálculos teóricos quânticos indicaram que o
confôrmero mais estável é o que tem a porção alifática da tetraidronaftilamina abaixo
do plano do anel tiazolidinônico. Interações espaciais observadas no NOESY
demostraram que, em solução, este também é o confôrmero mais estável. Por sua
vez, quando esta mesma amina aromática reagiu com o ácido mercaptoacético, mas
com benzaldeidos substituídos por grupos doadores de elétrons e com dois
exemplos de retiradores de elétrons, em uma reação catalisada pelo ácido ptoluenosulfônico, foram sintetizadas cinco 5-(aril)-1,5,8,9,10,11-hexahidronafto[1,2-
e][1,4]tiazepin-2(3H)-onas (30-72 %). Quando utilizadas as aminas alifáticas de
estereoquímica definida como materiais de partida, foram sintetizadas seis 2-(aril)-3-
R-(1,2,3,4-tetraidronaft-1-il)tiazolidin-4-onas e seis 2-(aril)-3-S-(1,2,3,4-tetraidronaft1-il)tiazolidin-4-onas com rendimentos entre 14-70%. Após a purificação foram
obtidos exemplos dos pares de diastereoisômeros separados. Algumas moléculas
dessas duas séries também foram obtidas como uma mistura de atropoisômeros.
Todas as moléculas apresentadas nesse trabalho são inéditas na literatura e tiveram
suas purezas avaliadas e suas estruturas elucidadas por técnicas de espectrometria
de massas e ressonância magnética nuclear de 1H e
13C e por difração de raios X
em monocristal
Tetrahydronaphthyl-1-amine as precursor to obtain thiazolidinones and benzothiazepinones: Synthesis, atropisomerism and structural elucidation
No full textThe multicomponent one-pot by conventional heating methodology was applied to
development of four series of heterocycles containing nitrogen and sulfur. They were
synthetized from tetrahydronaphthalen-1-amines: 5,6,7,8-tetrahydronaphthalen-1-
amine (aromatic), R-1,2,3,4-tetrahydronaphthalen-1-amine (aliphatic) and (S)-
1,2,3,4-tetrahydronaphthalen-1-amine (aliphatic). Firstly, 5,6,7,8-
tetrahydronaphthalen-1-amine reacted with mercaptoacetic acid and arenealdehydes
having electron-withdrawing groups gave nine 2-aryl-3-(5,6,7,8-
tetrahydronaphthalen-1-yl)thiazolidin-4-one by satisfactory 47-70% yield. Also the
atropisomerism phenomenom was observed in several molecules of this series. It
was confirmed by variable-temperature nuclear magnetic resonance method. The
energy required for the interconversion of one atropisomer into another is around
16.7 kcal.mol-1
. Chemical quantum calculation displayed that more stable isomer has
the tethahidronaphthalene portion below the five-ring plane. NOESY showed that in
solution the same isomer is more stable. In turn, when the same aromatic amine
react with arenealdehydes bearing electron-donating groups and with two examples
having electron-withdrawing groups, by p-TSOH catalysis five 5-aryl-1,5,8,9,10,11-
hexahydronaphtho[1,2-e][1,4]thiazepin-2(3H)-one were obtained (56-72%). When
aliphatic amines of defined stereochemistry were used as precursor were synthetized
six 2-phenyl-3-R-(1,2,3,4-tetrahydronaphthalen-1-yl)thiazolidin-4-ones and six 2-
phenyl-3-S-(1,2,3,4-tetrahydronaphthalen-1-yl)thiazolidin-4-ones (14-70 %), after
purification some pairs of diastereoisomers were separated. The atropisomerism
phenomenon was also observed in examples this kind of thiazolidinones. All
compounds are unpublished and had their purities available and their structures
elucidated by mass spectrometry and nuclear magnetic resonance techniques and
available crystals by X-rayCoordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA metodologia multicomponente one-pot com aquecimento térmico convencional foi
aplicada para a síntese de quatro séries de heterociclos contendo nitrogênio e
enxofre, os quais foram sintetizados a partir de diferentes tetraidronafitilaminas:
5,6,7,8-tetraidronaft-1-ilamina (aromática), R-1,2,3,4-tetraidronaft-1-ilamina (alifática)
e S-1,2,3,4-tetraidronaft-1-ilamina (alifática). Primeiramente, ao reagir a 5,6,7,8-
tetraidronaftilamina com benzaldeidos substituídos por grupos retiradores de
elétrons e o ácido mercaptoacético, foram sintetizadas nove 2-(aril)-3-(5,6,7,8-
tetraidronaft-1-il)tiazolidin-4-onas com rendimentos entre 47-70%. A maioria dos
exemplos dessa série apresentou o fenômeno de atropoisomerismo, caracterizado
pelo método de ressonância magnética nuclear com variações de temperatura. A
partir dessa análise foi estimado que o ∆G‡ de interconversão entre os
atropoisômeros é de 16,7 Kcal.mol-1
. Cálculos teóricos quânticos indicaram que o
confôrmero mais estável é o que tem a porção alifática da tetraidronaftilamina abaixo
do plano do anel tiazolidinônico. Interações espaciais observadas no NOESY
demostraram que, em solução, este também é o confôrmero mais estável. Por sua
vez, quando esta mesma amina aromática reagiu com o ácido mercaptoacético, mas
com benzaldeidos substituídos por grupos doadores de elétrons e com dois
exemplos de retiradores de elétrons, em uma reação catalisada pelo ácido ptoluenosulfônico, foram sintetizadas cinco 5-(aril)-1,5,8,9,10,11-hexahidronafto[1,2-
e][1,4]tiazepin-2(3H)-onas (30-72 %). Quando utilizadas as aminas alifáticas de
estereoquímica definida como materiais de partida, foram sintetizadas seis 2-(aril)-3-
R-(1,2,3,4-tetraidronaft-1-il)tiazolidin-4-onas e seis 2-(aril)-3-S-(1,2,3,4-tetraidronaft1-il)tiazolidin-4-onas com rendimentos entre 14-70%. Após a purificação foram
obtidos exemplos dos pares de diastereoisômeros separados. Algumas moléculas
dessas duas séries também foram obtidas como uma mistura de atropoisômeros.
Todas as moléculas apresentadas nesse trabalho são inéditas na literatura e tiveram
suas purezas avaliadas e suas estruturas elucidadas por técnicas de espectrometria
de massas e ressonância magnética nuclear de 1H e
13C e por difração de raios X
em monocristal
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
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