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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.
51

Explorations of Cascading Michael Additions

Young, Douglas M. 09 1900 (has links)
xx, 214 p. : ill. (some col.) / Intramolecular cascading Michael additions have the ability to transform simple, symmetric substrates into densely functionalized compounds containing new ring structures and chiral centers. The Rauhut-Currier (RC) reaction, also known as the vinylogous Morita-Baylis-Hillman reaction, utilizes this type of reactivity by cyclizing tethered, activated alkenes using phosphine or thiolate catalysis. This dissertation describes the expansion of the scope of the RC reaction, the introduction and importance of co-catalysts to cascading Michael additions, the development of the first amine-catalyzed RC reaction, and the transformation of cyclization products into fused, polycyclic aromatic compounds. Chapter I reviews the development and applications of the Rauhut-Currier reaction. Chapter II describes the regioselective synthesis of di-substituted indenes and introduces phenol as a rate- and selectivity-enhancing co-catalyst. Although tertiary amine nucleophiles were found to be inferior to phosphines as cyclization catalysts, chapter III discusses the ability of unhindered primary and secondary amines to undergo a diastereoselective, cascading aza-Michael-Michael addition to yield a wide variety of amino-indanes in the presence of an acid catalyst. Recognizing the importance of protic environments and small nucleophiles, the development of the first amine-catalyzed intramolecular RC is introduced in chapter IV. Chapter V describes the conversion of methyl ketone-substituted indenes to fluorene derivatives via an intramolecular aldol reaction. Chapter VI describes the serendipitous discovery and synthesis of indenopyrylium salts. Chapter VII details the novel production of indenopyridines from di-substituted indenes. Lastly, chapter VIII provides a summary and suggests future directions for this research. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Shih-Yuan Liu, Chairperson; Kenneth Doxsee, Advisor; David Tyler, Member; Michael Haley, Member; A. Dana Johnston, Outside Member
52

Conjugate additions and organocatalytic sequential reactions - new approaches to old reactions / Adições conjugadas e reações sequenciais organocatalíticas - uma nova abordagem para reações antigas

Feu, Karla Santos 01 April 2016 (has links)
Submitted by Ronildo Prado (ri.bco@ufscar.br) on 2018-09-17T13:47:42Z No. of bitstreams: 1 TeseKSF.pdf: 23261470 bytes, checksum: 5b1d96df4f120f2aa4446a1eda8ba6c0 (MD5) / Approved for entry into archive by Ronildo Prado (ri.bco@ufscar.br) on 2018-09-17T13:47:54Z (GMT) No. of bitstreams: 1 TeseKSF.pdf: 23261470 bytes, checksum: 5b1d96df4f120f2aa4446a1eda8ba6c0 (MD5) / Approved for entry into archive by Ronildo Prado (ri.bco@ufscar.br) on 2018-09-17T13:48:07Z (GMT) No. of bitstreams: 1 TeseKSF.pdf: 23261470 bytes, checksum: 5b1d96df4f120f2aa4446a1eda8ba6c0 (MD5) / Made available in DSpace on 2018-09-17T13:49:31Z (GMT). No. of bitstreams: 1 TeseKSF.pdf: 23261470 bytes, checksum: 5b1d96df4f120f2aa4446a1eda8ba6c0 (MD5) Previous issue date: 2016-04-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / This thesis consists in a collection of projects wherein the focus is the application of organocatalysts to accelerate the reactions, its primary function, as to induce asymmetry to the synthetic targets, within a perspective of sustainable chemistry. Thus, this thesis was arranged in four sections, the first two being about conjugate additions reactions; the third one related to 1,6-Friedel-Crafts/ 1,4-oxa-Michael cascade, and finally the fourth related to a formal [3 + 3] cycloaddition reaction. The first chapter describes the application of ionic liquids as basic catalysts in the conjugate addition of diketones to nitroolefins irradiated by ultrasound. Thus, the Michael adducts, which are important synthetic building blocks were synthesized efficiently under solvent free conditions. In the second chapter is presented the formal synthesis of Pregabalin Phenibut and Bacoflen. The synthetic intermediate of theses are obtained via a conjugate addition of aldehydes to nitroolefins, using an organocatalyst developed by our group in PEG-400, as recyclable solvent. In this regard, a collection of Michael adducts was synthesized within the principles of green chemistry in good yields and selectivities. The third section describes the first organocatalytic asymmetric cascate 1,6- Friedel-Crafts / 1,4- Oxa-Michael of hydroxyarenes to 2,4-dienal for the construction of chiral chromans, which are important bioactive compounds. A collection of chiral chromans was synthesized with high yields and selectivities (94-99% ee). Furthermore, several manipulations were made including the formation of a macrocyclic lactam. Finally, the fourth section dedicated to the formal [3 + 3] cycloaddition of azomethine imine with methyl isocyanoacetates leading to 1,2,4 triazines derivatives, which are relevant biological activity heterocyclic. We used either organocatalytic approach as cooperative catalysis (organocatalysis and metal catalysis). This work is still in the primary stages, however the product has been obtained with up to (42% ee, 69% yield), as just one diastereomer. / Essa tese consiste em uma coleção de projetos cujo foco central foi a aplicação de organocatalisadores tanto para acelerar as reações, sua função primária, quanto para induzir assimetria aos alvos sintéticos, dentro de uma ótica da química sustentável. Assim, a presente tese foi organizada em quatro capítulos, sendo os dois primeiros envolvendo reações de adições conjugadas, o terceiro referente a uma reação cascata tipo Friedel-Crafts seguida de oxa-Michael e por fim o quarto referente a uma reação de cicloadição formal [3+3]. O primeiro capítulo refere-se a aplicação de uma classe de líquidos iônicos de tarefa específica, como catalisadores básicos em reações de adição conjugada de dicetonas à nitroolefinas irradiadas por ultrassom. Desta forma, em uma condição livre de solventes, foram sintetizados de forma eficiente, uma coleção de adutos de Michael, os quais são importantes blocos de construção sintéticos. No segundo capítulo apresenta-se a síntese formal dos fármacos Pregabalina, Phenibut e Bacofleno. O intermediário sintético dos medicamentos citados são produtos de adição conjugada de aldeídos à nitroolefinas, os quais foram facilmente sintetizados utilizando um organocatalisador desenvolvido pelo próprio grupo em PEG-400, como solvente reciclável. Assim foi sintetizado uma coleção de adutos de Michael em bons rendimentos e seletividades, dentro dos príncipios da química verde. O terceiro capítulo descreve o primeiro exemplo de adição-1,6 tipo Friedel-Crafts seguida de adição- 1,4 Oxa-Michael organocatalítica assimétrica de hidroxiarenos a 2,4-dienais para a construção de cromanos enantioenriquecidos. Foram sintetizados uma coleção de cromanos quirais com altos rendimentos e seletividades (94-99% ee), os quais, posteriormente sofreram uma série de manipulações, incluindo uma macrolactamização.Por fim, o quarto capítulo dedica-se a cicloadição formal [3+3] de azometina imina com isocianoacetato de metila, levando a produtos derivados do 1,2,4 triazenos, heterocíclicos de relevante atividade biológica. Utilizou-se tanto a organocatálise, quanto a catálise cooperativa (organocatálise e catálise metálica) como ferramentas sintéticas. Este trabalho está ainda nas etapas iniciais, sendo os resultados preliminares, entretanto o produto já foi obtido com até (42% de ee e 69%) de rendimento, sendo a síntese diastereoseletiva.
53

Estudos do efeito da composicao quimica e da conformacao mecanica na cinetica de recristalizacao de ligas Al-Mg-Zr

BUSO, SIDNEI J. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:49:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:37Z (GMT). No. of bitstreams: 1 09673.pdf: 6473990 bytes, checksum: f8b53c5c1d35245956acaf44b35ed078 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
54

Efeito de tratamentos termicos e da adicao de cromo nas propriedades mecanicas de ligas Fe-24 atAl

PAOLA, JEAN C.C. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:42:50Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:27Z (GMT). No. of bitstreams: 1 06112.pdf: 5630844 bytes, checksum: d96c90e096947d42a20110e42e3cc1e8 (MD5) / Dissertacao(Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
55

Tracing Translation Universals and Translator Development by Word Aligning a Harry Potter Corpus

Helgegren, Sofia January 2005 (has links)
For the purpose of this descriptive translation study, a translation corpus was built from roughly the first 20,000 words of each of the first four Harry Potter books by J.K. Rowling, and their respective translations into Swedish. I*Link, a new type of word alignment tool, was used to align the samples on a word level and to investigate and analyse the aligned corpus. The purpose of the study was threefold: to investigate manifestations of translation universals, to search for evidence of translator development and to study the efficiency of different strategies for using the alignment tools. The results show that all three translation universals were manifested in the corpus, both on a general pattern level and on a more specific lexical level. Additionally, a clear pattern of translator development was discovered, showing that there are differences between the four different samples. The tendency is that the translations become further removed from the original texts, and this difference occurs homogeneously and sequentially. In the word alignment, four different ways of using the tools were tested, and one strategy was found to be more efficient than the others. This strategy uses dynamic resources from previous alignment sessions as input to I*Trix, an automatic alignment tool, and the output file is manually post-edited in I*Link. In conclusion, the study shows how new tools and methods can be used in descriptive translation studies to extract information that is not readily obtainable with traditional tools and methods.
56

Influencia do teor de cromo e de tratamentos termicos na microestrutura e no comportamento mecanico de ligas intermetalicas ordenadas a base de Fesub3 Al

COUTO, ANTONIO A. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:43:09Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:23Z (GMT). No. of bitstreams: 1 06209.pdf: 16796127 bytes, checksum: ee7da755adc485834808ec1efbe10133 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
57

Estudo de mecanismos de propagacao de discordancias em intermetalicos ordenados Nisub3Al pelo metodo de atrito interno

MOURISCO, AROLDO J. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:43:48Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:46Z (GMT). No. of bitstreams: 1 06774.pdf: 10158756 bytes, checksum: 5149634807182733ed057dd54ba6924b (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
58

Estudos do efeito da composicao quimica e da conformacao mecanica na cinetica de recristalizacao de ligas Al-Mg-Zr

BUSO, SIDNEI J. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:49:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:37Z (GMT). No. of bitstreams: 1 09673.pdf: 6473990 bytes, checksum: f8b53c5c1d35245956acaf44b35ed078 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
59

Efeito de tratamentos termicos e da adicao de cromo nas propriedades mecanicas de ligas Fe-24 atAl

PAOLA, JEAN C.C. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:42:50Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:27Z (GMT). No. of bitstreams: 1 06112.pdf: 5630844 bytes, checksum: d96c90e096947d42a20110e42e3cc1e8 (MD5) / Dissertacao(Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
60

Comportamento piezomagnético da liga Fe-Ga e Fe-Ga-B com 18,6 %at. de Ga e 2%at. de B / Comportamento piezomagnético das ligas Fe-Ga e Fe-Ga-B com 18,6 %at. de Ga e 2%at. de B

Fábio Martins Cardoso 21 November 2017 (has links)
No presente trabalho foram produzidas duas ligas policristalinas de Fe-Ga e Fe-Ga-B para estudar a influência do boro nas propriedades piezomagnéticas da liga Fe-Ga. As propriedades piezomagnéticas foram obtidas a partir de medidas de magnetostricção (λ) em função de campo magnético (H) pelo coeficiente d33 = dλ/dH e medidas de indução magnética (B) em função da tensão compressiva aplicada (σ) pelo coeficiente d*33 = dB/dσ. A composição escolhida foi com 18,6% de Ga para ambas as ligas, que é a composição que possui o maior valor de magnetostricção na liga binária. A análise da microestrutura indicou a presença das fases Fe(Ga)-α (A2) e Fe3Ga (D03) para ambas as ligas e da fase Fe2B para a liga ternária. A presença da fase Fe2B causou o refinamento dos grãos e consequentemente um pequeno aumento do campo coercitivo da liga Fe-Ga-B se comparada à liga Fe-Ga e, além disto, aumentou o campo de saturação. Consequentemente os coeficientes piezomagnéticos da liga com boro foram duas vezes menores que da liga Fe-Ga. A igualdade d33* = d33 não é satisfeita para a liga Fe-Ga nem para a Fe-Ga-B, significando que os experimentos não foram realizados em condições estritamente reversíveis. Atribui-se esta irreversibilidade à alta velocidade de carregamento usada nos experimentos de B vs σ. No entanto, a dependência dos coeficientes piezomagnéticos do campo magnético e da tensão compressiva aplicada da liga Fe-Ga-B é bem menor que da liga Fe-Ga e os valores obtidos de ~ 4 nm/A são suficientemente adequados para muitas aplicações. / In this work were maked two polycrystalline alloys of Fe-Ga e Fe-Ga-B for to study the influence of borun in the piezomagnetc properties of the Fe-Ga alloys. The piezomagnetc properties were obteined from magnetostrictive measuments (λ) in function of magnetic field (H) by the coefficient d33 = dλ/dH and magnetic induction measuments (B) in function of compressive stress applied (σ) by the coefficient d*33 = dB/dσ. The chosen composition were 18.6% of Ga to both alloys, which is the composition for the largest magnetostriction to the binary alloy. The microstructural analysis indicated the presence of the phases Fe(Ga)-α and Fe3Ga (D03) for the both alloys and Fe2B phases to the ternary alloy. The presence of the Fe2B caused the refinament of the grains and consequently a small increase in the coercive field of the Fe-Ga alloy and, in addition, increased the saturation field. Consequently, the piezomagnetic coefficients of the boron alloys were twice as low as that of the Fe-Ga alloy. The equality d33* = d33 was not satisfied for the Fe-Ga and to Fe-Ga-B meaning that the experiments were not performed under strictly reversible conditions. This irreversibility was attributed to the high loading speed used in the experiments of B vs σ. However, the dependence of the piezomagnetic coefficients of the magnetic field and the applied compressive stress of the Fe-Ga-B alloy is much lower than that of the Fe-Ga alloy and the values obtained from ~ 4nm/A are sufficiently suitable for many applications.

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