La catalyse est la pierre angulaire de la chimie verte et elle permet de performer des transformations chimiques difficiles de manière efficace et sélective. Au niveau industriel, l'utilisation de la catalyse se traduit habituellement en une économie de temps et d'argent. Le développement de systèmes catalytiques pratiques s'est initialement fait à l'aide de métaux des secondes et troisièmes rangées de transition. Au cours des deux dernières décennies, ce domaine de recherche a atteint une certaine maturité. Néanmoins, les catalyseurs à base de métaux de transitions sont souvent dispendieux et polluants. Une quantité considérable de gaz à effet de serre est également engendrée par l'extraction minière de ces métaux. Afin de palier à ces problèmes, d'intéressantes alternatives commencent à faire leur place. Notamment, de nouvelles stratégies de catalyse sans métal de transition ont été développées et l'étude des mécanismes réactionnels nous permet de maximiser leur efficacité. Dans cette thèse, l'optimisation d'une paire de Lewis frustrée (FLP) de type aminoborane (1-NR₂-2-BH₂-C₆H₄) est exploré afin d'améliorer ses performances dans la borylation catalytique de liens C-H de molécules hétéroaromatiques (pyrroles, indoles, thiophènes). Dans les premiers chapitres, le mécanisme réactionnel de cette réaction de borylation est étudié en détail. Une première étude théorique nous permet de déterminer l'impact de l'ajout d'un groupement fonctionnel en position ortho du -BH₂ sur l'activation du lien C-H. Par la suite, la performance d'aminoboranes possédant un encombrement stérique varié au niveau de l'amine est testée pour la catalyse. Les résultats obtenus combinés avec des études cinétiques démontrent que l'aminoborane possédant un groupement pipéridyl effectue la borylation catalytique jusqu'à 15 fois plus rapidement que l'espèce possédant le groupement le plus encombrée tetraméthylpipéridyl. L'activation C-H est donc favorisée lorsque le site réactionnel est plus dégagé. Pour compléter l'étude du mécanisme de la borylation, nous avons également étudié l'étape de la métathèse des liens sigma, qui se révèle être un élément critique et important lors de la borylation du thiophène. En explorant la réaction de FLPs de type aminoborane, nous avons découvert que l'acide borique pouvait agir comme précatalyseur pour l'hydroboration catalytique de composés insaturés. Cette espèce de bore peu dispendieuse et stable peut être utilisée comme précatalyseur remplaçant le BH₃ qui est une molécule très réactive. Une étude mécanistique à l'aide de réactions stœchiométriques et d'analyses cinétiques démontre que la réaction d'hydroboration est plus rapide que la génération et la régénération du catalyseur. Finalement, un système catalytique à base d'acide borique utilisant l'irradiation micro-ondes sans conditions inertes a donc été développé pour l'hydroboration d'esters et d'alcynes. Une dernière étude portant sur la combinaison de deux types de chimie sans métal, les FLPs et les phosphines biphiliques, vient clore le travail présenté. Nous avons exploré deux stratégies pour évaluer s'il est possible de générer une synergie avec les deux systèmes. Tout d'abord, nous avons adapté le ligand de la phosphine triamide P{N[o-NMe-C₆H₄]₂} pour y installer une base de Lewis intramoléculaire. Des tests d'activation de l'hydrogène gazeux avec la phosphine biphilique modifiée nous ont permis de réaliser qu'il n'est pas possible d'atteindre de la réactivité FLP de cette manière. Nous avons ensuite décidé de mélanger la phosphine biphilique P{N[o-NMe-C₆H₄]₂} avec l'aminoborane de type FLP le moins encombrée (1-NMe₂-2-BH₂-C₆H₄). L'objectif était de produire un complexe sans métal ayant une plateforme d'oxydoréduction sur l'atome de phosphore et des orbitales vides et pleines fournies par l'acide de Lewis et la base de Lewis de l'aminoborane. Le complexe attendu n'est pas généré. À la place de celui-ci, une réaction entre les deux espèces produit le benzodiazaborole correspondant et un solide orangé insoluble. À l'aide d'études comparatives, nous sommes venus à la conclusion que le solide produit est un mélange de polymères de phosphore polyhydrures et que la réaction observée est caractéristique des aminophosphines possédant au moins un hydrogène. / Catalysis is the cornerstone of green chemistry, and it allows to perform efficient and selective transformations that are usually challenging to achieve. At the industrial level, catalysis usually offers time and cost-efficient processes. Initially, the development of practical catalysis was done using transition metals of the second and third rows. Over the last two decades, this field of research reached a certain level of maturity. However, the use of transition metal-based catalysts is generally expensive due to the costs associated with their production and their removal from final products. Additionally, a considerable amount of greenhouse gases is liberated during the mining processes of the metals. To overcome these problems, interesting alternatives are starting to appear. Notably new metal-free strategies have been developed and the study of the mechanism allows to maximize their efficiency. In this thesis, the optimisation of an aminoborane (1-NR₂-2-BH₂-C₆H₄) frustrated Lewis pair (FLP) is explored to improve its performance for the catalytic borylation of C-H bonds of heteroaromatic molecules (pyrroles, indoles, thiophenes). In the first chapters, the mechanism of this borylation reaction is thoroughly studied. First, a theoretical study allows us to evaluate the effect of adding a functional group in ortho position of the -BH₂ for the first reaction step of the catalytic cycle: C-H activation. Subsequently, the catalysis performance of aminoboranes with various steric hindrance were tested. These results combined with kinetic studies shows that the aminoborane with a piperidyl group can perform catalysis 15 times faster than the aminoborane with the most encumbered amino group tetramethylpiperidyl. Therefore, the C-H activation is favored when the reaction site is more accessible. To complete the mechanistic investigation of the borylation reaction, the sigma bond metathesis reaction step was also studied. We discovered that this step is a critical and important element for the borylation of thiophene. While screening the aminoborane FLPs reactivity, we discovered that boric acid could act as a precatalyst for the catalytic hydroboration of unsaturated compounds. This inexpensive and stable boron species can be used as a precatalyst to replace the very reactive BH₃. A mechanistic study done with stoichiometric reactions and kinetic analysis show that the hydroboration reaction is faster than the generation and the regeneration of the borane catalyst. Finally, a boric acid based catalytic system using microwave irradiation has been developed for the hydroboration of esters and alkynes. To conclude, a study on the combination of two metal-free strategies was done using FLPs and biphilic phosphines. We explored two strategies to evaluate if it is possible to generate a synergy with both systems. First, we installed an intramolecular Lewis base on the phosphine triamide P{N[o-NMe-C₆H₄]₂}. It was not possible to reach FLP reactivity when looking at hydrogen activation tests with the adapted biphilic phosphine. Following these results, we mixed the biphilic phosphine P{N[o-NMe-C₆H₄]₂} with the least sterically encumbered aminoborane FLP (1-NMe₂-2-BH₂-C₆H₄). The objective was to produce a metal-free complex with a redox platform on the phosphorus atom and with filled and vacant orbitals provided by the Lewis acid and the Lewis base of the aminoborane. Unfortunately, this complex was not generated. Instead, a reaction between the two species produced the corresponding benzodiazaborole and an insoluble orange solid. Using comparative studies, we concluded that the insoluble solid generated is a mixture of phosphorus polyhydride polymers and that the observed reaction is characteristic to aminophosphine bearing at least one hydrogen.

Typescript (photocopy).

[pt] Teologia e Literatura Fantástica: a redenção na Trilogia Cósmica de C. S. Lewis investiga a relação entre teologia e literatura, destacando a importância de se ultrapassar o racionalismo reducionista, seja na prática teológica, seja na vida cotidiana. Além disso, desenvolve o conceito de redenção cristã analisando a maneira como este tema é apresentado na literatura fantástica, especialmente a forma que ele é retratado na Trilogia Cósmica do escritor irlandês C. S. Lewis. A partir desses pontos, propõe-se a literatura fantástica como espaço potencial para a prática teológica. / [en] Theology and Fantastic Literature: the redemption in the Cosmic Trilogy C. S. Lewis investigates the relationship between Theology and Literature, highlighting the importance of overcoming reductionist rationalism, whether in practical theology, whether in daily life. It also discusses the concept of christian redemption, analyzing how this theme is presented in fantastic literature, especially the way it is portrayed in the Cosmic Trilogy by Irish writer C. S. Lewis. From these points, it is proposed the fantastic literature as a potential space for theological practice.

No intuito de subsidiar e orientar futuras pesquisas astroquímicas pela busca de novas espécies moleculares, foram calculadas diversas propriedades em nível CCSD/cc-pVQZ (como geometrias, cargas atômicas, momentos de dipolo, frequências vibracionais e intensidades fundamentais de infravermelho) de bases de Lewis (B) presentes no meio interestelar (B = CO, CS, SO, HCN, FCN, ClCN, BrCN, HNC, FNC, ClNC, BrNC, OCS, HCNO HOCN, HONC, HNCO, NCCN e CNNC) e de suas espécies protonadas. Além disso, o modelo Carga - Fluxo de Carga - Fluxo de Dipolo (CFCFD), em termos dos multipolos da Teoria Quântica de Átomos em Moléculas (QTAIM), foi empregado para o estudo das variações nas intensidades de infravermelho de modos de estiramento durante a protonação. Os resultados indicam que, dependendo da extremidade da molécula na qual o próton se liga, há fortalecimento ou enfraquecimento das bandas de infravermelho originais. Estes fenômenos parecem estar associados à alteração de carga inicial durante a protonação, com fluxos de carga e de dipolo coordenados com tais mudanças de carga iniciais durante as vibrações. No que concerne ao estiramento da ligação formada após a protonação, [B-H]+, a contribuição de carga é preponderante quando o próton se liga aos átomos mais eletronegativos e menos polarizáveis (O, N e F). Todavia, quando o próton se liga ao par eletrônico isolado do carbono (isonitrilas, CO e CS) ou a outros átomos como cloro, bromo e enxofre, a contribuição de fluxos de carga e de dipolo atômico se tornam mais relevantes. De qualquer maneira, a raiz quadrada da intensidade de infravermelho desta nova banda de absorção correlaciona-se com a carga do próton de forma linear. No que se refere à partição da energia eletrônica por meio da aproximação de Átomos Quânticos Interagentes, verifica-se que: (1) a energia de estabilização do próton é proporcional à carga eletrônica recebida da base; (2) a desestabilização da base aumenta quanto maior a quantidade de carga eletrônica doada para o próton e (3) a energia de interação dos fragmentos é bastante específica de cada sistema, o que origina uma separação em grupos de sistemas semelhantes. / In order to support and guide future astrochemical research related to the search for new molecular species, some properties were calculated at the CCSD/cc-pVQZ level (such as geometry, atomic charges, dipole moments, vibrational frequencies and fundamental infrared intensities) for Lewis bases (B) present in the interstellar medium (B = CO, CS, SO, HCN, FCN, ClCN, BrCN, HNC, FNC, ClNC, BRNC, OCS, HCNO, HOCN, HONC, HNCO, NCCN and CNNC) and its protonated species. In addition, the Charge - Charge Flux - Dipole Flux (CCFDF) model in terms of multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) was used to study the variations in the infrared intensities of stretching modes during protonation. The results indicate that there is strengthening or weakening of the original infrared bands depending on the molecule end to which the proton is attached. These phenomena appear to be associated with the initial redistribution of electronic charge during protonation, resulting in charge and dipole fluxes coordinated with such initial rearrangement during the vibrations. Moreover, regarding the stretching intensity of the bond formed after protonation, [BH]+, the charge contribution is predominant when the proton is bound to atoms more electronegative and less polarizable atoms (O, N and F). However, when the proton binds to the lone (electron) pair of carbon (isonitriles, CO and CS) or to other atoms such as chlorine, bromine and sulfur, the charge and dipole fluxes become more significant. Nevertheless, the square root of the intensity for this new infrared absorption band correlates linearly with the charge assumed by the proton. Finally, with respect to the electronic energy partition through the Interaction Quantum Atom proposal, it is seen that (1) the proton stabilization energy is proportional to the electronic charge received from the base; (2) the destabilization of the base increases in line with the amount of electronic charge lost to the proton and (3) the interaction energy between the fragments is very specific of each system, which results in group separations.

O objetivo deste trabalho foi investigar o uso de NbCl5 como ácido de Lewis em síntese orgânica (reações de abertura de epóxidos, reações de Diels-Alder e substituição eletrofílica de ciclo-enonas no anel furano e em reações de formação de beta-cloro-enonas e beta-etóxi-enonas a partir de beta-dicetonas e seus derivados acetilados. O comportamento de vários epóxidos quando tratados com NbCl5 foi estudado. Em geral verificou-se que os epóxidos estudados reagem rapidamente com NbCl5, levando geralmente à formação de mais de um produto (cloridrinas, 1,2-dióis, produtos contendo resíduos de solvente, como também produtos de rearranjo foram obtidos). Foi realizado um estudo detalhado verificando o efeito da temperatura (t.a., 0ºC ou -78ºC) e da concentração molar de NbCl5 nessas reações, com relação ao tempo e rendimento das reações, e à composição dos produtos. Reações entre diferentes ciclo-enonas (dienófilos de baixa reatividade) com ciclopentadieno e furanos (dienos) foram realizadas na presença de NbCl5. As reações mostraram que o NbCl5 é um bom ácido de Lewis para ativar reações de Diels-Alder ou substituição eletrofílica do hidrogênio pela ciclo-enona no anel furano. O produto de Diels-Alder foi obtido apenas na reação entre a ciclo-hexenona e o dieno mais reativo (ciclopentadieno). Dienos menos reativos, furano e 2-metil-furano levaram à formação de produtos de substituição eletrofílica do hidrogênio pela ciclo-enona no anel furano. beta-Dicetonas e seus derivados acetilados foram convenientemente transformados em beta-cloro-enonas e beta-etóxi-enonas pelo tratamento com NbCl5, em uma única etapa e em bons rendimentos. Observamos que quando as reações são realizadas em Et2O ou CH2Cl2 como solventes, apenas beta-cloro-enonas são formadas. Contudo, usando EtOAc como solvente, os resultados dependem da estrutura do substrato: substratos alfa-metilados formam exclusivamente beta-cloro-enonas (como nos outros solventes), enquanto os outros substratos levam à formação de beta-etóxi-enonas ou de misturas de beta-cloro-enonas e beta-etóxi-enonas. / The aim of this work was to investigate the use of NbCl5 as Lewis acid in organic synthesis (opening of epoxide rings, Diels-Alder and electrophilic substitution of cycloenones in furan ring reactions and in the formation of beta-chloroenones and beta-ethoxyenones from beta-diketones and the corresponding acetylated derivatives. The behaviour of several epoxides when treated with NbCl5 was studied. In general it was verified that the studied epoxides react rapidly with NbCl5, giving, in most cases, more than one product (chlorohydrins, 1,2-diols, products containing solvent residues as well as rearrangement products were obtained). A detailed study was performed to verify the effect of the temperature (rt, 0ºC or -78ºC) and of the NbCl5 molar concentration in the composition of the products, yield and time required for the reactions. Reactions between different cycloenones (dienophiles of low reactivity) with cyclopentadiene and furans (dienes) were performed in the presence of NbCl5. The reactions showed that NbCl5 is a good Lewis acid for Diels-Alder or electrophilic substitution of the hydrogen by the cycloenone system in furan ring. The Diels-Alder product was obtained only in reaction between the cyclohexenone and the highly reactive diene (cyclopentadiene). Less reactive dienes such as furan and 2-methylfuran gave electrophilic substitution of hydrogen by the cycloenone system in the furan ring. beta-Diketones and the corresponding acetylated derivatives were conveniently transformed in beta-chloroenones or beta-ethoxyenones by treatment with NbCl5, in one step and in good yields. When the reactions were carried out with Et2O or CH2Cl2 as solvents, only beta-chloroenones were obtained. However, with EtOAc as solvent, the results depend on the structure of the substrate: alpha-methylated substrates gave exclusively beta-chloroenones (as in other solvents), while the other substrates gave beta-ethoxyenones or mixtures of beta-ethoxyenones and beta-chloroenones.

Cette thèse a pour but d’étudier et d’approfondir les connaissances actuelles dans le domaine de la chimie des silyliums. Ces espèces cationiques semblables aux carbocations sont dotées d’une forte réactivité même vis-à-vis d’espèces très peu nucléophiles, ce qui leur confère des propriétés remarquables en tant qu’acide de Lewis. Les objectifs de cette thèse relèvent d’une tentative de dompter cette grande réactivité, via des méthodes de stabilisation du silylium, en conservant un bon compromis réactivité/stabilité. Un second axe de recherche envisagé est a visé d’application de ces silyliums en catalyse asymétrique et pour cela différents modèles ont été étudiés. Pour cela, l'introduction d'une chiralité centrée sur le silicium ou l'utilisation d'anion chiraux ont été étudiés. / The main objective of this thesis was to develop a better understanding of the silylium chemistry. These cationic three-coordinate silicon species similar to carbeniums are extremely reactive against any nucleophile and the extraordinarily high avidity of these cationic species for electron density make them remarkable Lewis acids. In this context, our aim during this thesis was to tame the reactivity of silyliums by means of introducing stabilisation at the cationic silicon center while preserving most of its reactivity. The study of new systems may provide informations on the way to find the best reactivity/stability compromise. Another part of this work was to focus on chirality in this stabilized silyliums to allow future asymmetric catalysis applications and the introduction of silicon-centered chirality but also chiral anions were probed.

Several workers have reduced acidic polysaccharides for structural studies, for sorption studies, and for studies on chemical reactivity. All these investigators have used reduction procedures which have not been extensively studied and do not completely reduce the acidic groups. In addition, it is not known to what extent the other functional groups such as esters and hemiacetal are reduced. The goal of the present study is to obtain a further understanding of the reduction with both a Lewis acid, diborane, and a Lewis base, lithium borohydride, by comparison of the percent reduction of the functional groups on an acidic polysaccharide. Alginic acid from the stipes of the brown algae Laminaria hyperborea was selected as the acidic polysaccharide for study.

Thesis (M.A.)--Boise State University, 2009. / Includes bibliographical references (leaves 73-77).

Four analogues of the Lewis X trisaccharide antigen (β-D-Galp(1→4)[α-L-Fucp(1→3)]-D-GlcNAcp) in which the galactosyl residue is modified at O-4 as a methyloxy, deoxychloro, deoxyfluoro or deoxy were synthesized. The preparation of the modified 4-OMe, 4-Cl, 4-F and 4-H trichloroacetimidate galactosyl donors is described as well as their use in the glycosylation of an N-acetylglucosamine glycosyl acceptor. The resulting disaccharides were deprotected at O-3 of the glucosamine residue and fucosylated giving access to the desired protected Lewis X analogues. One step global deprotection (Na/NH3) of the protected 4”-methoxy and 4”-deoxy analogues, and two step deprotections (removal of a p-methoxybenzyl with DDQ, then Zemplén deacylation) of the 4”-deoxychloro and 4”-deoxyfluoro protected Lex analogues gave the desired compounds in good yields. The relative binding energies of the 4” manipulated Lewis X methyl glycoside analogues for anti-Lewis X mAb SH1 were determined using competitive ELISA procedures. The binding experiments revealed that substitution of the 4” site with a deoxychloro, deoxyfluoro or deoxy function had a large differential change in the free energy of binding; yet they did not completely abolish cross reactivity with native Lewis X. Substitution with a methyloxy function eliminated recognition by anti-Lewis X monoclonal antibody SH1. / NSERC

This study examines the links between architecture and literature through the work of English author/mathematician/geometrician Lewis Carroll/Charles L. Dodgson. The premise is that throughout Carroll's work, questions concerning the position of the body in relation to its surroundings---the possibility for one to forge a sense of place---are recurrent. Carroll stages a series of bodily movements in space: changes in scale, transformations, alterations, translations from bottom to top, from left to right, from the inside to the outside, and so on. Reading the work, one is constantly reminded that one's perception of space, as well as one's understanding of where one stands, are phenomena that take place in language, through utterances, through words. Approaching Carroll's work with particular attention to the space of bodily movements and to plays on language, one can access a subterranean architectural discourse. This discourse is oblique, suggested rather than explicit, but nonetheless raises pertinent questions concerning the formation of architectural meaning: the relationship of sense to its limits---to nonsense---in architecture. / The following texts are studied: Carroll's two architectural pamphlets; the two Alice stories with their convoluted spaces; a long epic poem dealing with the space of discovery; a drama on geometry and a logical exposition on the paradoxes of movement. Throughout Carroll's multifaceted work, nonsense guides the construction of the texts. Working at the limits of language and literary genres, Carroll's parodies possess strong allegorical powers: sense travels obliquely and the work remains enigmatic. However, the reader somehow understands the work; the experience of the work produces a certain kind of knowledge. / In architecture, meaning is also tied to its outer limits---to the polysemy of nonsense. Through one's experience of space, a stable and orderly building becomes heterogeneous, loaded with qualities and symbols. A sense of place emerges and meaning momentarily appears along the sinuous paths that run between bodily movements, thoughts, dreams, desire and words.