published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

No description available.

This thesis describes investigations on the topic of the versatile organic scaffold, 7-oxabenzonorbornadiene. The synthesis of 2-alkyl substituted furans via iron-catalyzed coupling of Grignard reagents and 2-bromofuran was optimized and various groups were coupled to furan. Primary and secondary alkyl groups were coupled with moderate to low yields of up to 56% were obtained. Furan-benzyne cycloaddition led to the formation of the corresponding C-1 substituted oxabenzonorbornadiene in yields of up to 70%. This methodology allows for access to uniquely substituted, strained bicyclic alkenes for further studies. The second part of this thesis describes the cyclopropanation of oxabenzonorbornadiene and the subsequent discovery of several reactions of the cyclopropane. The conditions for cyclopropanation were optimized, obtaining this product in yields of up to 98%. Treatment of this cyclopropane under electrophilic conditions led to the formation of (2-naphthyl)methanes in up to 98% yields, whereas treatment under nucleophilic conditions led to the formation of dihydronaphthols in up to >99% yield. The optimization of these reactions and mechanistic studies are described.

Despite the well-established use of organomagnesium reagents, research into the chemistry of the alkaline earth metals has received an increase in popularity over the last two decades, largely due to their applications as reagents and catalysts. Recently, sterically-demanding A-donor ligands have become more popular because of their ability to provide stable metal-donor interactions and achieve kinetic stabilisation of the complex by crowding the metal centre. Furthermore, the isolation of subvalent magnesium and calcium complexes which challenged established knowledge of the metals prompted further investigations into their stabilisation in low oxidation states.

3-acyltetramic acids, such as reutericyclin, belong to a group of natural products which contain a 5-membered pyrrolidine-2,4-dione heterocycle with an acyl group at the 3-position. Molecules containing this motif have been shown to contain a wealth of desirable bio-activity such as antibiotic, antitumor, antiviral, antiulcerative, fungicidal and cytotoxic properties. The motivation for synthetic efforts towards reutericyclin and analogues is that it has been shown to have potential as an antibiotic treatment against superbug C. difficile. Our synthetic approach used a pyrroloisoxazole bicyclic system as a masked form of the acyltetramic acid core structure, which enables us to make selective modifications towards these bio-active products and produce more analogues suitable for biological testing. We report the synthesis of several novel compounds closely related to a masked reutericyclin as well as elaborations at the C-3 methyl group through aldol chemistry. The route began with a naturally occurring amino acid that underwent N-protection, carboxyl reduction and conversion to an oxime. This oxime is precursor to a nitrile oxide used in a 1,3-dipolar cycloaddition to achieve a substituted isoxazole that was deprotected and, through an intramolecular peptide coupling reaction, provided the pyrroloisoxazole core as the masked acyltetramic acid. Acylation reactions were completed upon this pyrroloisoxazole using butyllithium as a base and a range of acyl chlorides. Other developments made in this synthesis were the isolation of the chlorinated oxime and its use in a solvent study and significant improvements in the peptide coupling reaction. Also, synthetic efforts were made to produce an analogue of the natural product laccarin A using this methodology.

Orientador: Paulo Noronha Lisboa Filho / Banca: Renata Aquino da Silva de Souza / Banca: Fenelon Martinho Lima Pontes / O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter insitucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: A compreensão do comportamento estruturas, magnético e eletrônico para estes materiais ainda permanece um problema em aberto e tem exigido grandes esforços, principalmente, quando se refere aos diferentes estados de oxidação apresentados pelos elementos metálicos que as compõem. A flutuação de valência apresentada pelos ínos metálicos e a correspondente variação da estequiometria de oxgiênio nesses compostos são variáveis fundamentais para a correta interpretação de suas respostas físicas. Condições de preparo, como rota de síntese, tratamentos térmicos, razões de aquecimento e resfriamento, condições atmosféricas, são fatores a serem considerados nos estudos desses materiais, pois influenciam diretamente em suas composições estequiométricas. As manganitas aqui estudadas foram sintetizadas pela rota de síntese baseada no Método dos Precursores Poliméricos Modificados (MPPM), uma variação do Método Pechini (MP). Trata-se de um método químico para o preparo de amostras de óxidos metálicos e tem sido utilizado como uma excelente alternativa às tradicionais rotas físicas de síntese, como a rota de Reação em Estado Sólido (RES), pois permitem produzir amostras de excelente homogeneidade, bastante superiores às amostras convencionais preparadas via RES, maior controle no tamanho de partícula, por requerer temperaturas menoes para obtenção da fase cristalográfica do material, dentre outros fatores. Para a caracterização estrutural das amostras sintetizadas técnicas de Difração de Raios X (DRX) associada ao Método de Refinamento Rietveld (MRR) e Microscopia Eletrônica de Varredura (MEV) foram empregadas. Através da análise de DRX e refinamento Rietveld foi verificado a formação da fase cristalográfica dos materiais sintetizados, bem como foi possível identificar presença de fases secundárias para as manganitas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, NiMn2O4, CuMn2O4, CoMn2O4, Ni1-xCuMn2O4 and Ni1-xCoxMn2O4 (x=0,2; 0,4;0,6 e 0,8) oxide manganites with spinel structure were studied. The understangind of structural, magnetic and electrical response to these materials still remains an open question and requires large efforts, especially considering the valence fluctuation presented by metallic ions that compose these samples. The valence fluctuation presented by the metallic ions and the corresponding deficient oxygen stoichiometry are crucial factors to the correct description of the physical response in this material. Some factors, such as synthesis route, thermal history, heat and cooling rates, atmospheric gas flux, must be considered since they are directly responsible for the stoichiometric composition exhibited by these materials. In this study, manganite samples were synthesized by the Modified Polymeric Precursor Method (MPPM), a Pechini Method (PM) variation. MPPM is a chemical method to prepare metallic oxides samples and has been used as an excellent alternative to physical traditional synthesis routes, such as Solid State Reaction (SSR). MPPM allows to produce excellent homogeneous samples, with higher quality if compared to traditional ceramic routes, since this method is able to control the particle size considering heat-treatment lower tempeartures to obtain the crystallographic phase, among other advantages. The structural characterization was done by X Ray Diffraction (XRD) associated to Rietveld Refinament Method and Scanning Electron Micrograph (SEM). By the XRD and Rietveld refinament was observed the crystallographic phase was obtained, was also observed that the CoM2O4 and Ni-xCuxMn2O4 (with x > 0,6) manganites presented secondary phases. Magnetic behavior studies were also developed to these materials by DC magnetic measures... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:30:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-22Bitstream added on 2014-06-13T18:06:42Z : No. of bitstreams: 1 mazini_mc_me_bauru.pdf: 1283811 bytes, checksum: 358e012efa4b5f267477d338a13309e4 (MD5) / A compreensão do comportamento estruturas, magnético e eletrônico para estes materiais ainda permanece um problema em aberto e tem exigido grandes esforços, principalmente, quando se refere aos diferentes estados de oxidação apresentados pelos elementos metálicos que as compõem. A flutuação de valência apresentada pelos ínos metálicos e a correspondente variação da estequiometria de oxgiênio nesses compostos são variáveis fundamentais para a correta interpretação de suas respostas físicas. Condições de preparo, como rota de síntese, tratamentos térmicos, razões de aquecimento e resfriamento, condições atmosféricas, são fatores a serem considerados nos estudos desses materiais, pois influenciam diretamente em suas composições estequiométricas. As manganitas aqui estudadas foram sintetizadas pela rota de síntese baseada no Método dos Precursores Poliméricos Modificados (MPPM), uma variação do Método Pechini (MP). Trata-se de um método químico para o preparo de amostras de óxidos metálicos e tem sido utilizado como uma excelente alternativa às tradicionais rotas físicas de síntese, como a rota de Reação em Estado Sólido (RES), pois permitem produzir amostras de excelente homogeneidade, bastante superiores às amostras convencionais preparadas via RES, maior controle no tamanho de partícula, por requerer temperaturas menoes para obtenção da fase cristalográfica do material, dentre outros fatores. Para a caracterização estrutural das amostras sintetizadas técnicas de Difração de Raios X (DRX) associada ao Método de Refinamento Rietveld (MRR) e Microscopia Eletrônica de Varredura (MEV) foram empregadas. Através da análise de DRX e refinamento Rietveld foi verificado a formação da fase cristalográfica dos materiais sintetizados, bem como foi possível identificar presença de fases secundárias para as manganitas... / In this work, NiMn2O4, CuMn2O4, CoMn2O4, Ni1-xCuMn2O4 and Ni1-xCoxMn2O4 (x=0,2; 0,4;0,6 e 0,8) oxide manganites with spinel structure were studied. The understangind of structural, magnetic and electrical response to these materials still remains an open question and requires large efforts, especially considering the valence fluctuation presented by metallic ions that compose these samples. The valence fluctuation presented by the metallic ions and the corresponding deficient oxygen stoichiometry are crucial factors to the correct description of the physical response in this material. Some factors, such as synthesis route, thermal history, heat and cooling rates, atmospheric gas flux, must be considered since they are directly responsible for the stoichiometric composition exhibited by these materials. In this study, manganite samples were synthesized by the Modified Polymeric Precursor Method (MPPM), a Pechini Method (PM) variation. MPPM is a chemical method to prepare metallic oxides samples and has been used as an excellent alternative to physical traditional synthesis routes, such as Solid State Reaction (SSR). MPPM allows to produce excellent homogeneous samples, with higher quality if compared to traditional ceramic routes, since this method is able to control the particle size considering heat-treatment lower tempeartures to obtain the crystallographic phase, among other advantages. The structural characterization was done by X Ray Diffraction (XRD) associated to Rietveld Refinament Method and Scanning Electron Micrograph (SEM). By the XRD and Rietveld refinament was observed the crystallographic phase was obtained, was also observed that the CoM2O4 and Ni-xCuxMn2O4 (with x > 0,6) manganites presented secondary phases. Magnetic behavior studies were also developed to these materials by DC magnetic measures... (Complete abstract click electronic access below)

This work describes the design and synthesis of a set of four organic molecules that are intended to hydrogen-bond to each other in a pairwise manner. The four hydrogen-bonding units, termed ‘A’, ‘B’, ‘C’ and ‘D’, when placed in solution together, are designed so that A binds only to B, and C binds only to D. Each unit does not bind to itself, nor to either of the other two units to which binding is not intended. For example, A binds to B, but not to A, C, or D. Each unit contains an array of four hydrogen-bonds for strong binding to its partner, is designed to be as rigid as possible, as non-tautomeric as possible, and utilises a staggered non-symmetrical architecture. Of the four intended compounds, three were successfully synthesised (A, B and D). Units B and D were soluble in CDCl₃, but Unit A was not. Therefore, the design and synthesis of Unit A was amended, and two variants of Unit A that are both soluble in CDCl₃ were successfully synthesised. ¹H NMR binding experiments were performed between Unit B and each of the two variants of Unit A. Their binding behaviour was described. A binding constant could not be calculated because the units did not bind in a 1:1 fashion.