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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Síntese e avaliação de derivados furânicos, tetraidrofurânicos e pirrólicos com potencial atividade  tripanocida / Synthesis and evaluation of furan, tetrahydrofuran and pyrrole derivatives with potential trypanocidal activity

Ana Paula Hartmann 13 July 2015 (has links)
A Doença de Chagas é causada pelo Trypanosoma cruzi, e possui duas fases clínicas, sendo o tratamento com o fármaco benznidazol eficaz somente na fase aguda, porém com diversos efeitos adversos ao longo do período do tratamento. Desta forma, consórcios vêm sendo estabelecidos entre \"governo - universidade - indústria\", com auxilio de capital nacional e estrangeiro para o desenvolvimento de novos fármacos. Apesar de diversas ferramentas disponíveis para o planejamento de novos compostos, a busca por produtos naturais ainda desperta interesse de muitos pesquisadores. Diversos trabalhos vêm descrevendo estudos de síntese e atividade tripanocida de lignanas, as quais merecem destaque, veraguensina (17) e grandisina (18). Devido à falta de tratamento e a alta toxicidade dos agentes disponíveis, este trabalho tem como objetivo sintetizar análogos dessas lignanas, relacionados a derivados de tetraidrofurânicos, furânicos, pirrólicos e de seus intermediários e testa-lasfrente à atividade tripanocida e citotóxica. O planejamento sintético envolveu a geração de derivados 1,4-diaril-2-butino-1,4-diol (28a-t) a partir da reação de condensação entre fenil carbinol (26) e aldeídos arílicos (27a-t) com diferentes padrões de substituiçõescom diversos grupos funcionais. Estes intermediários, obtidos em rendimentos moderados, foram convertidos aos correspondentes 1,4-diaril-1,4-diidroxílicos (30a-g), pela reação de redução em dióxido de platina e, posteriormente, oxidados a 1,4-diaril-1,4-dicetonas (29a-g). A partir da formação dos intermediários 29 e 30, os produtos de interesse, 2,5-diaril-furano (32a-g) e 2,5-diaril-tetraidrofurano (31a-g) foram preparados empregando reações de ciclização na presença de ácidos tríflico e trifluoroacético, respectivamente. Os intermediários e produtos obtidos em rendimentos de moderado a bom, totalizando 48 compostos, foram avaliados em ensaios de atividade tripanocida, envolvendo a cepa Tulahuen de T. cruzi, bem como ensaios de citotoxicidade. Considerando as cinco séries sintetizadas (28, 29, 30, 31 e 32), vale destacar que a maioria apresentou compostos com potente atividade tripanocida, a partir de 1,4 ?M, superior ao fármaco disponível benznidazol (7,9 ?M) e, adicionalmente, não apresentaram citotoxicidade em ensaios realizados por citometria de fluxo. / Chagas\' disease is caused by the Trypanosoma cruzi, whichhas two clinical stages. The treatment with the benznidazole is effective only in the acute stage, although with several side effects throughout the treatment period. Therefore, consortia are being established between \"government - university - industry\", with national and foreign financial support for drug discovery development. In spite of many available tools to design new compounds, the search for natural products still arouse interestfor a great number of researchers. Several papers have described studies of synthesis and trypanocidal activity of lignans, being veraguensin (17) and grandisin (18) worth to mention. Due to the lack of treatment and the high toxicity of the available drugs, this research has the aimto synthesize analogues from the above lignans, such astetrahydrofuran, furanic, pyrrolic derivatives and their intermediates,and test their trypanocidal activity and cytotoxicities. The synthetic strategy was based on the synthesis of 1,4-diarylacetylene-1,4-glycols (28a-t) via condensation reaction between phenyl carbinol (26) and substituted aryl aldehydes (27a-t) with several functional groups at different positionsof the aromatic ring. These intermediates, obtained in moderate yields, were converted to their corresponding 1,4-diaryl-1,4-dihydroxyl derivatives (30a-g) by the reduction reaction using platinum dioxide and, subsequently, oxidized to 1,4-diaryl-1,4-diketones (29a-g). From the synthesis of the intermediates 29 and 30, products of interest, 2,5-diaryl-furan (32a-g) and 2,5-diaryl-tetrahydrofuran (31a-g) were prepared from the cyclization reaction in the presence of the triflic and trifluoracetic acids, respectively. The intermediates and products, obtained in moderate to good yields, in a total of 48 compounds, were assessed in trypanocidal assays, using T. cruzi Tulahuen strain,as well as cytotoxicity assays. Considering the five synthesized series (28, 29, 30, 31 e 32), it is worth noting that the majority of the compounds showed potent trypanocidal activity from 1.4 ?M, higher than the available benznidazole (7,9 ?M) and, additionally, they were not cytotoxicin Flow Cytometry assays.
42

Influência do cloreto de zinco na polimerização de resinas furânicas para moldes de fundição

Vale, Marcus Antonio 06 February 2015 (has links)
Made available in DSpace on 2016-03-15T19:36:47Z (GMT). No. of bitstreams: 1 Marcus Antonio Vale.pdf: 14954412 bytes, checksum: 3b3a2b0489271f2cd612006f585d47b6 (MD5) Previous issue date: 2015-02-06 / There are few manufacturing industries whose products covers such wide ranges in sizes, weight and complexity as the foundry industry. Smaller castings can be as small as a grain of rice and weight a fraction of gram, while the largest can reach hundreds of tons and be as big as a house. There is a wide range of metal casting processes, characterized mainly by the allow type and its pouring process and also by the mold type and its associated manufacturing process. In the particular case of molds, there are molds produced using sand bonded by chemical processes, or better, bonded by synthetic resin, which can be different in type and specific chemical composition. The resins developed for the automotive market has led to major changes in the manufacturing method of foundry molds. The polymerization of these resins and a subsequent curing are used to connect to the foundry sand in a rigid structure capable of receiving and holding liquid metal. Therefore, it is of fundamental importance to know the process of polymerization of these resins and their impact on the final properties of the obtained molds, especially in the mechanical characteristics. With respect to the sand-resin mixture (sand prepared), important factors are: the range of bench life time (gel time) which must be long enough to enable the manufacture of the mold, and cure speed should be fast enough to permit rapid rotation of the casting tooling and hence greater productivity. The bench life time interval is the maximum time (gel time) than the sand-resin mixture can be handled before starting the vitrification reaction of the resin (crosslinking chains), the extraction time is the time required for mold achieve an adequate minimum hardness to handling. The mixed sand life time is the maximum interval which the mixed sand can be handling before the polymerization of the resin used as bonding takes place. The hardening rate is the interval needed for the mold becomes hard enough to be handled. In this work was studied yhe influence of the addition of zinc chloride (in solution) in the sandfuran resin mixture, with the aim of reducing the relation between the extraction time intervals and time bench life. The results showed that addition of percentages of the order of 5.0% to 7.5% zinc chloride reduces this ratio between 10% and 17%; this means that the casting model may be extracted from the sand mass in a smaller time interval increasing the productivity of manufacturing molds. It was also observed that there was also an increase of about 9% to 18% in bench life intervals. / Poucos são os setores industriais de manufatura cujos produtos cobrem faixas tão amplas de tamanhos, peso e complexidade como o setor industrial de fundição. As menores peças fundidas podem ser tão pequenas quanto um grão de arroz e pesar uma fração de grama, enquanto as maiores podem atingir centenas de toneladas e ser tão grandes quanto uma casa. Existe uma gama considerável de processos de fundição, caracterizados principalmente pelo tipo de liga e seu processo de vazamento, pelo tipo de molde, e seu respectivo processo de fabricação. No caso específico dos moldes, têm-se moldes fabricados com areias aglomeradas por processos químicos, ou melhor, aglomerados com resinas sintéticas que podem ser de diferentes tipos e com composição química específica. As resinas desenvolvidas para o mercado automotivo deu origem a grandes mudanças na metodologia de fabricação dos moldes de fundição. A polimerização destas resinas e sua subsequente cura são usados para ligar à areia de fundição em uma rígida estrutura capaz de receber e manter metal líquido. Portanto, é de fundamental importância conhecer o processo de polimerização destas resinas e seu impacto nas propriedades finais dos moldes obtidos, principalmente nas características mecânicas. Com relação à mistura areia-resina (areia preparada), os fatores importantes são o intervalo de tempo de vida de banca (tempo de gelificação) que deve ser suficientemente longo para possibilitar a confecção do molde, e a velocidade de cura (vitrificação) que deve ser rápida suficiente para permitir a rápida rotatividade dos ferramentais de fundição e consequentemente uma maior produtividade. O intervalo de tempo de vida de banca é o tempo máximo (tempo de gelificação) que a mistura areia-resina pode ser manuseada antes de iniciar a reação de vitrificação da resina (reticulação das cadeias), o tempo de extração é o tempo necessário para o molde atingir uma dureza mínima adequada ao seu manuseio. Neste trabalho foi estudada a influência da adição de cloreto de zinco (em solução) na mistura areia-resina furânica, com o objetivo de reduzir a relação entre os intervalos de tempo de extração e tempo de vida de banca. Os resultados obtidos mostraram que percentuais de adição da ordem de 5,0% a 7,5% de cloreto de zinco reduzem esta relação entre 10% e 17%; o que significa que o modelo de fundição poderá ser extraído da massa de areia em um menor intervalo de tempo aumentando a produtividade de fabricação de moldes. Observou-se ainda que houve também um aumento da ordem de 9% a 18% nos intervalos de vida de banca.
43

Cycloaddition (4+1) formelle intermoléculaire entre un carbène libre riche en électrons et des carbonyles α,β-insaturés et transformations de l’orthoester obtenu en furanne et 5H-furanone

Croisetière, Jean-Philippe January 2017 (has links)
Le premier chapitre traite d’une réaction de cycloaddition (4+1) sur des énones et des énals à l’aide du diméthoxycarbène. Cette méthode permettrait d’obtenir des hétérocycles à cinq membres à partir de substrats linéaires simples et faciles à fabriquer. On retrouve dans ce chapitre l’optimisation de cette étape réactionnelle, ainsi que son utilisation pour préparer une gamme de substrats. Le second chapitre traite de la transformation des hétérocycles obtenus, et décrits au chapitre précédent, en furannes ainsi qu’en furanones. Cette méthode permet la transformation d’énones et d’énals en hétérocycles oxygénés à cinq membres en seulement deux étapes. On retrouve dans ce chapitre la description de plusieurs méthodes développées pour parvenir aux substrats, ainsi que les échecs rencontrés pour l’obtention de benzofuranne.
44

Heterogeneous catalytic conversion of biomass-derived carbohydrates to furanic biofuel additives and chemicals

Elsayed, Islam 13 December 2019 (has links)
Increasing energy demand and various problems associated with fossil fuels such as environmental pollution, global warming and diminishing petroleum reserves have greatly stimulated production of fuels and chemicals from renewable sources. Lignocellulosic biomass has been considered as one of the potential sources for a variety of fuels and industrial chemicals. 5-Hydroxymethylfurfural (HMF) has been identified as an excellent platform molecule because it is a flexible intermediate for the synthesis of bio-renewable fuels and materials. HMF can be easily obtained from acid-catalyzed hydration of biomass-derived carbohydrates (hexoses) in various media. HMF can be converted to energy products such as 2,5-bis(alkoxymethyl)furans (BAMFs), monomers for high-value polymers such as 2,5-bis(hydroxymethyl)furan (BHMF), and valuable intermediates for fine chemicals. Recently, magnetic nanoparticle based catalysts attracted more attention due to their good stability and easy separation from the reaction mixture by a permanent magnet. This unique magnetic separation property makes MNPs more effective than conventional filtration or centrifugation as it prevents loss of the catalyst. This dissertation work focuses on, firstly, studying the effectiveness of silica coated magnetite (Fe3O4) nanoparticles MNPs supported with sulfonic acid groups (Fe3O4@SiO2-SO3H) on the dehydration of glucose to HMF. Secondly, preparing a cost-effective catalytic transfer hydrogenation system for the selective transformation of HMF into BHMF via Meerwein-Ponndorf-Verley (MPV) reaction over the copper iron magnetic catalyst supported on activated carbon in ethanol solvent with the absence of molecular hydrogen. Thirdly, producing alkoxymethylfurans (AMFs) which are considered a potential biofuels by using two-step sequential reactions with cheap heterogeneous zinc-iron oxides magnetic nanocatalyst for the hydrogenation of HMF to furfuryl alcohols in various alcohols solvents in the absence of molecular hydrogen followed by solid Brønsted acid catalyst for the etherification reaction of furfuryl alcohol derivatives. All prepared heterogeneous catalysts were characterized by FTIR, XRD, H2-TPR, XPS, ICP-OES, HRTEM-EDX, and N2 adsorption-desorption isothermal analyses (BET and BJH) and were tested for recyclability. The chemical products were identified by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and products quantities were calculated by using calibration curves of chemical standards. Various reaction conditions such as reaction temperature, reaction time, catalyst amount, and alcohol type were optimized.
45

Functionalization of C-aryl glycals and studies toward the total synthesis of 5-hydroxyaloin A

Procko, Kristen Jean 16 February 2015 (has links)
In the context of ongoing efforts toward C-aryl glycoside synthesis, a recently developed approach to form C-aryl glycals from 2-deoxysugar lactones was expanded to form novel substrates. This approach has been applied to the synthesis of various furyl glycals, allowing access to C-aryl glycals via a benzyne furan (4+2) cycloaddition methodology. The hydroboration-oxidation of said C-aryl glycals has allowed access to C(2)-oxygenated C-aryl glycosides via the benzyne cycloaddition approach. An approach to the total synthesis of 5-hydoxyaloin A is detailed, in which regioselective benzyne furan (4+2) cycloadditions were achieved via the use of a silicon tether. Two approaches to the anthrone core have been applied; one in which an unsymmetrically-substituted aryl ring is first constructed by means of a silicon tether, and one in which the unsymmetrically-substituted ring is formed last, also utilizing a silicon tether. The latter approach has allowed access to the anthrone core of 5-hydroxyaloin A, and only a final desulfurization remains in order to access the natural product. / text
46

Furan measurement in transformer oil by UV-Vis spectroscopy using fuzzy logic approach

Lai, Sin Pin January 2009 (has links)
An Ultraviolet to Visible (UV-Vis) spectroscopic analysis based on fuzzy logic approach has been developed for furan content measurement in transformer oil. Following the successful identification and quantification of furan derivatives in transformer oil by ASTM D5837 standard, the new approach is able to approximate the furan content more conveniently and economically. As furan concentration level would determine the absorption intensity in UV-Vis spectral range, the fuzzy logic software model developed would exploit this characteristic to aggregate the furans content level in transformer oil. The UV-Vis spectral response at other ambient temperature is also studied. The proposed technique provides a convenient alternative to conventional method of furan measurement by High Performance Liquid Chromatography (HPLC) or Gas Chromatography Mass Spectrometry (GC/MS) in ASTM D5837 Standard.
47

N-alquilação regiosseletiva de pirazóis empregando 4-alcóxi(amino)-5-bromo-1,1,1-trifluorpent-3-en-2-onas / Regioselective N-alkylation of pyrazoles using 4-alkoxy(amino)-5-bromo-1,1,1-trifluoropent-3-en-2-ones"

Moraes, Paulo Alexandre de 19 August 2016 (has links)
This work presents the synthesis of three new series of nitrogen-heterocycles containing the substituent trifluoromethyl, exploiting the synthetic versatility and regioselectivity of 4-alkoxy-5-bromo-1,1,1-trifluorpent-3-en-2-ones and 4-amino-5-bromo-1,1,1-trifluoropent-3-en-2-ones in reactions with compounds containing nucleophilic nitrogen. Two series of 1-(3-alkoxy-5-trifluoromethyl-2,3-dihydrofuran-3-yl)-4,5-alkyl-3-(trifluoromethyl)-1H-pyrazoles were synthesized by the N-functionalization reaction of pyrazoles with 4-alkoxy-5-bromo-1,1,1-trifluorpent-3-en-2-ones, by Michael s nucleophilic addition. In the first step, there is a nucleophilic addition of the pyrazol molecule to the beta position of enones (Cβ), followed by an intramolecular cyclization reaction, where the furan ring is formed by replacement of the bromine atom by the carbonyl oxygen of enone, resulting in thirteen novel compounds with yields between 55-86%. The other compounds series, (E)-4-(amino)-1,1,1-trifluoro-5-(5-methyl-3- (trifluoromethyl)-1H-pyrazol-1-yl)pent-3-en-2-ones, was synthesized by N-alkylation reaction, through a bimolecular nucleophilic substitution (SN2) mechanism, with replament of the bromine atom, at five position (Cγ) of 4-amino-5-bromo-1,1,1-trifluoropent-3-en-2-ones, by the nucleophilic nitrogen of the pyrazoline ring. Seven N-alkylated products were obtained, with yields among 65-85%. In addition, the regioselectivity study of N-functionalized pyrazoles reactions is described, including the evaluation of reaction conditions and how substituents present in the pyrazole structure can influence the product formation, because many different steric and electronic factors. The obtained compounds were characterized by nuclear magnetic resonance 1H and 13C, mass spectrometry, elementary analysis and X-ray diffractometry. / A presente dissertação relata a síntese de três séries inéditas de heterociclos nitrogenados trifluormetil substituídos, que exploram a versatilidade sintética e a regiosseletividade das 4-alcóxi-5-bromo-1,1,1-trifluorpent-3-en-2-onas e das 4-amino-5-bromo-1,1,1-trifluorpent-3-en-2-onas, em reações com nucleófilos nitrogenados. As primeiras duas séries dos compostos 1-(3-alcóxi-5-trifluorometil-2,3-diidrofuran-3-il)-4,5-alquil-3-(trifluorometil)-1H-pirazóis, foram sintetizadas através do processo de N-funcionalização de pirazóis, a partir da reação com as 4-alcóxi-5-bromo-1,1,1-trifluorpent-3-en-2-onas, cujo o caminho mecanístico se deu através de uma reação de adição nucleofílica de Michael. Inicialmente, ocorre a adição do pirazol nucleofílico na posição beta (Cβ) das enonas bromadas, seguida de uma reação de ciclocondensação intramolecular formando o anel furano, com a substituição átomo de bromo pelo oxigênio enólico, resultando na formação de treze compostos inéditos, com rendimentos entre 55 e 86%. Outra série de compostos (E)-4-(amino)1,1,1-triflúor-5-(5-metil-3-(trifluormetil)-1H-pirazóis-1-il)pent-3-en-2-onas, foi sintetizada através da reação de N-alquilacão, via substituição nucleofílica bimolecular (SN2), onde o átomo de bromo na posição cinco (Cγ), das 4-amino-5-bromo-1,1,1-trifluorpent-3-en-2-onas, foi substituído pelo nitrogênio nucleofílico do anel pirazolínico, promovendo a formação de sete produtos N-alquilados, com rendimentos que variam entre 65 e 85%. Além disso, um estudo de regiosseletividade das reações N-funcionalizadas de pirazóis está descrito, onde a avaliação das condições reacionais e também de fatores estéricos e eletrônicos dos substituintes presentes nos substratos, foram determinantes para formação do produto formado. Os produtos obtidos neste trabalho foram caracterizados por ressonância magnética nuclear de 1H e 13C, espectrometria de massas de baixa e alta resolução, análise elementar e difratometria de Raio X.
48

Synthesis and molecular modelling of bio-based polyamides / Synthèse et modélisation moléculaire de polyamides biosourcés

Cousin, Thibault 19 March 2013 (has links)
Dans le contexte actuel de raréfaction des ressources fossiles, le développement des polymères biosourcés est d'une grande importance. Le travail de cette thèse consiste donc en la synthèse et le développement d'un polyphtalamide amorphe à base d'acide furan-2,5-oique. Dans un premier temps, un protocole de modélisation moléculaire permettant de calculer la Tg de polyphthalamides a été développé. Pour cela, des PPA modèles (basés sur un mélange d'acides isophtaliques et téréphtaliques ainsi que l'hexaméthylène diamine) ont été synthétisés et caractérisés. En comparant les Tg obtenues par modélisation et par mesure en DSC, le protocole de modélisation a été validé. Dans un deuxième temps, ce protocole a été appliqué à des PPA à base de FDCA. Ces polymères ont également été synthétisés et caractérisés. Il en ressort que le PA 6-F subit une importante décarboxylation durant sa synthèse, l’empêchant d'atteindre une masse molaire importante. Il a aussi été montré que l'ajout de FDCA dans des copolyphthalamides diminuait leurs propriétés thermiques et mécaniques. / In the current context of oil resources rarefaction, the development of biobased polymers is of major importance. The present work focused on the development of a biobased amorphous polyphthalamide, based on furan-2,5-dicarboxylic acid. The first part of the study was devoted to the development of a molecular modelling protocol that could calculate the glass transition temperature of polyphthalamides with accuracy. In order to do this, model polyphthalamides based on isophthalic, terephthalic acid and hexamethylene diamine were synthesized and characterized as well as simulated. By comparison between simulated and measured Tg, the protocol was validated. In a second part of the study, this protocol was applied to FDCA based polyphthalamides. These PPA were also synthesized. It was found that the PA 6-F undertakes a decarboxylation, preventing it from reaching high a molar mass. It was also found that the mechanical and thermal properties decrease as the amount of FDCA in the copolymers increases.
49

Oberflächenfunktionalisierung von Poly(dimethyl)siloxan

Ullmann, Robert 07 March 2013 (has links) (PDF)
Im Rahmen der vorliegenden Arbeit werden die Synthese und Charakterisierung eines thermisch-kontrollierten und eines photochemisch-kontrollierten reversiblen Polymersystems vorgestellt. Weiterhin werden Poly(dimethyl)siloxan-Oberflächen mit Amino-, Isocyanat-, Furan-, Maleimid- und Cumarin-Gruppen funktionalisiert. Hierbei werden sowohl bekannte als auch neuartige Wege der Oberflächenmodifizierung vergleichend untersucht und bewertet. Ausgehend von den hergestellten Cumarin-funktionalisierten Poly(dimethyl)siloxan-Oberflächen wird eine Anbindung des synthetisierten photochemisch-kontrollierten reversiblen Polymersystems an diese Oberflächen untersucht. Des Weiteren wird die Anbindung des synthetisierten thermisch kontrollierten reversiblen Polymersystems sowohl an den hergestellten Maleimid- als auch an den Furan-funktionalisierten Poly(dimethyl)siloxan-Oberflächen analysiert. Basierend auf den vorgestellten Cumarin-Funktionalisierungen werden photoaktive Oberflächen beschrieben und mittels ATR-IR-spektroskopischer und UV/Vis-spektroskopischer Methoden analysiert.
50

Som om dagen tar slut : En ekokritisk läsning av subjektspositionen i fyra samtida bilderböcker

Manfredson Holmberg, Lisa January 2022 (has links)
This assignment aims to explore and analyze the picture books I skogen by Eva Lindström, Furan by Lisen Adbåge, Om dagen tar slut by Lisa Hyder and Naturen by Emma AdBåge, through an ecocritical study of subjekt formations. The studying of children's literatre, in relatoin to both the anthropocene and environmenantal discourse, gives an insight into the way man and nature are narrated and how subject positions are challenged. When analyzing such subjects this essay uses The Nature in Culture Matrix, created by the research group Nature in Children's Literature and Culture. The main concepts presented throughout this text include anthropocentrism, ecocentrism, celebrated nature and problematasing nature. This thesis examines how modern picture books protest against the former independent, free and courageous child that was encouraged to put themselves before others. Such a chliche is evident when characters defy a common pattern of action and how anthropomorphizations of nature can highlight the ecocritical way of thinking. It is further evident that pictre books, through intrigue, problematize the human subject and draw parallels to everything that is living. To conclude, the results show that the child as a subject either is challenged or replaced by nature.

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