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Thesis advisor: Kian L. Tan / Thesis advisor: Dunwei Wang / Silicon nanowires are utilized to harvest the energy from visible light. The introduction of a nickel pre-catalyst, 1, allows for this energy to be stored in chemical bonds, which are subsequently used in the carboxylation of 4-octyne. / Thesis (MS) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Reproduction de : Thèse de doctorat : Génie des procédés et de l'environnement : Toulouse, INPT : 2005. / Titre provenant de l'écran-titre. Bibliogr. 136 réf.

Dans le monde actuel, le dioxyde de carbone (CO2) est le déchet majoritaire issu de l’utilisation des ressources fossiles mais il est encore peu utilisé dans les applications à grande échelle. Afin de tirer parti de son abondance, le développement de nouvelles transformations chimiques du CO2 pour accéder à des produits de chimie fine connait un intérêt croissant au sein de la communauté scientifique. Tout particulièrement, la formation de liaison(s) C-N à partir du CO2 et d’un substrat azotés permet d’accéder à des produits à hautes valeurs énergétiques et commerciales. Un second type de transformation désirable est la formation de liaison C-C à partir du CO2 afin de synthétiser des dérivés d’acides carboxyliques comme des esters. L’utilisation d’hydrosilanes, réducteurs doux, permet de travailler sous 1 bar de CO2 avec des catalyseurs à base de métaux peu coûteux et abondants tels que le fer et le zinc ou bien avec des organocatalyseurs. Les synthèses de formamides, de méthylamines ou d’aminals à partir du CO2 ont ainsi été développées par hydrosilylation. Enfin, la carboxylation des carbosilanes à partir du CO2 a été développée pour la première fois avec un catalyseur à base de cuivre. Dans le cas des 2-pyridylsilanes, l’utilisation de sels de fluorures pentavalents permet d’activer le substrat efficacement sans catalyseur. / In the current world, carbon dioxide (CO2) is the major waste of the massive utilization of fossil resources but only few applications have been developed using this compound. In order to take advantage of its abundancy, the development of novel chemical transformation of CO2 to produce fine chemicals is of high interest in the scientific community. In particular, the formation of C-N bond(s) from CO2 and amine compounds unlocks a new way to access high energy and value-added. A second type of highly desirable transformation is the formation of C-C bonds with CO2 so as to synthesize carboxylic acid derivatives. The utilization of hydrosilanes as mild reductants allows the reactions to proceed under 1 bar of CO2 with abundant and cheap metal-based catalysts (iron, zinc) or with organocatalysts. The synthesis of formamides, methylamines and aminals from CO2 are described herein. Ultimately, the catalytic carboxylation of carbosilanes has been achieved for the first time using copper-based complexes. In the specific case of 2-pyridylsilanes, the use of pentavalent fluoride salts allowed us to perform the reaction without catalyst.

Le marquage radioisotopique est un domaine d’intérêt d’un point de vue de la recherche fondamentale en santé et, de par ses nombreuses applications, aussi bien en industrie pharmaceutique et agrochimique que dans le milieu académique. Dans ce contexte, le carbone-14 joue un rôle primordial dans le développement de nouvelles drogues et dans les études ADME et toxicologiques. Les voies de synthèse traditionnelles impliquant le ¹⁴C sont longues et multi-étapes ce qui entrave la viabilité de cette stratégie. L’objectif de cette thèse est de développer de nouvelles techniques de radiomarquage par échange isotopique. Dans un premier temps, nos efforts se sont portés sur le développement d’un échange d’isotopes du carbone (EIC) dynamique entre le ¹³CO₂ ou le ¹⁴CO₂, une source fondamentale et facile d’accès de carbone radioactifs et des acides carboxyliques (hétéro)aromatiques par le biais d’une catalyse au cuivre. Le concept de EIC a ensuite été appliqué à d’autres fonctions, présentes dans de nombreux agents pharmaceutiques, les acides phénylacétiques. Une nouvelle approche, sans métaux de transition, a pu être décrite, permettant d’effectuer le marquage avec le ¹³CO₂, le ¹⁴CO₂ et le ¹¹CO₂. Enfin, un autre EIC faisant intervenir le cyanure comme source primaire de carbone radioactif a été conçu. Le développement de l’EIC a permis d’étendre le concept de marquage en dernière étape de synthèse à des substrats contenant une fonction nitrile ou acide carboxylique, en réduisant les coûts et en limitant la génération de déchets radioactifs. Ce concept, encore en voie de développement, offre des alternatives aux méthodes existantes. / Radioisotope labeling is a relevant topic both from a fundament research perspective and for health applications in academy and pharmaceutical and agrochemical industries. In this context, carbon-14 plays a basic role in drug development and ADME and toxicological studies. Traditional synthesis with radiocarbon (¹⁴C), based on lengthy and multistep approaches, have hampered the sustainable of the strategy. The aim of this thesis is to develop novel labeling techniques by isotope exchange. At first, our efforts were focused on the developement of a copper catalyzed dynamic carbon isotope exchange (CIE) using ¹³CO₂ and ¹⁴CO₂, a fundamental and readily available source of radiocarbon on (hetero)aromatic carboxylic acids. The concept of CIE was further extent to another relevant drug scaffolds such as phenyl acetic acids. Hence, it was described a transition metal-free approach able to exchange ¹³CO₂, le ¹⁴CO₂ and ¹¹CO₂, to the best of our knowledge this would be the first example. At last, another CIE with a different primary radiocarbon source such as cyanyde was envisioned. CIE technology expands the concept of late-stage carbon radiolabeling, with substrates bearing carboxylic acid and nitrile moieties, reducing the synthetic costs and limiting the generation of radioactive waste. This new process is still at its infancy and more work need to be done.

Résumé : Au cours de ce projet, la faisabilité de l’insertion du CO[indice inférieur 2] dans une fonction éther aliphatique à été démontrée pour la première fois. Cette découverte à été effectuée suite à la résolution cinétique et thermodynamique de la décarboxylation du diméthyle carbonate (DMC) en diméthyle éther (DME) et CO[indice inférieur 2] à la surface d’un catalyseur faujasite échangé avec du zinc(II) (Zn-FAU). Un profile réversible typique aux carbonates a été observé, soit que le CO[indice inférieur 2] est relâché à plus haute température et inséré aux plus basses températures. La structure de l’état de transition entre le DMC et DME a ensuite été résolue en corrélant des calculs en modélisation moléculaire aux mesures thermodynamiques effectuées entre le DMC et Zn-FAU. La méthode de calcul développée lors de l’analyse mécanistique a ensuite été appliquée à l’évaluation théorique de plusieurs structures catalytiques, ce qui a permis d’identifier les paramètres structurels des catalyseurs qui sont favorables à la réaction de carboxylation du DME. // Abstract : In this study, the feasibility of the insertion of CO[subscript 2] in an aliphatic ether function was demonstrated for the first time. This finding results from a thermodynamic and kinetic study on dimethyl carbonate (DMC) decarboxylation into dimethyl ether (DME) and CO[subscript 2] at the surface of a zinc(II) exchanged faujasite catalyst. The typical reversible profile of carbonates synthesis chemistry was observed, higher temperature being favorable to CO[subscript 2] release and lower temperature being favorable to CO[subscript 2] insertion. A structural resolution of the rate determining transition structure between DMC and DME was then achieved by correlating molecular modelling calculations to the thermodynamic measurements on DMC decarboxylation. The calculation method developed during the mechanistical analysis was further applied to theoretical catalyst activity screening, which allowed determining structural catalytic sites parameters that favor DME carboxylation over DMC decarboxylation.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

ATP-dependent phosphoenolpyruvate carboxykinase (E. C. 4.1.1.49; PCK) is an enzyme that catalyses the reversible conversion of oxaloacetate and ATP into phosphoenolpyruvate, ADP and CO2. PCK is made up of about 500 to 600 amino acid residues and is divided into two roughly equal domains. Upon binding of substrates, the two domains of PCK move towards each other. PCK is well known for its role in gluconeogenesis but in some species, it can have an anaplerotic role. In other species, PCK is important for metabolic steps involved in fermentation.<p>Presented in this thesis are five solved crystal structures of the ATP-dependent form of PCK. Three of the PCK crystal structures determined were from <i>Escherichia coli</i>; one was a complex of ATP, Mg2+ and CO2, the second structure was an ATP, Mg2+, Mn2+, CO2 and oxaloacetate complex and, the third <i>E. coli</i> structure was a Lys213Ser mutant complexed with ATP, Mg2+and Mn2+. Two <i>Anaerobiospirillum succiniciproducens</i> PCK crystal structures were also solved; one was in the native form and the other was an ATP-Mg2+-Mn2+-oxalate complex. <p>In the <i>E. coli</i>-PCK-ATP-Mg2+-CO2 crystal complex structure, the observed location of CO2 was in agreement with a previously determined <i>E. coli</i> PCK-CO2 crystal structure, which incorporated CO2 into the structure by a different technique. The findings from the <i>E. coli</i> PCK-ATP-Mg2+-CO2 crystal structure allowed the reaction mechanism presented in this work to be proposed.<p>The PCK-ATP-Mg2+-Mn2+-CO2-oxaloacetate structure is the first structure where oxaloacetate is observed bound to PCK. Surprisingly, the observed location of oxaloacetate in this structure is 5 Angstroms away from its expected position near Mn2+. Oxaloacetate is weakly bound to a non-catalytic region of the enzyme. It is proposed that when the domains of PCK move towards each other upon binding nucleotide, oxaloacetate experiences steric crowding which results in it being pushed towards the active site to react. <p>Previous kinetic studies on the <i>E. coli</i> PCK mutant Lys213Ser have determined that Mn2+ is unexpectedly inhibitory. A crystal structure of K213S-PCK-ATP-Mg2+-Mn2+ demonstrates that Mn2+ is tetrahedrally coordinated in the active site, not octahedrally as occurred in other structures. By having Mn2+ in the tetrahedral coordination state, substrate binding in the active site of PCK is altered in a way that does not allow catalysis to occur.<p>The two crystal structures of <i>A. succiniciproducens</i> PCK were useful in quantifying the substrate-induced domain movement. A surface active site lid made up of residues 385 to 405 that had never been observed in any of the previous PCK crystal structures was observed in the <i>A. succiniciproducens</i> PCK-ATP-Mg2+-Mn2+-oxalate crystal structure. Mutational studies of this lid have shown it to be essential for the function of PCK; however, its exact function is not certain. It has been proposed that the lid has multiple functions. One is to sequester the substrates from bulk solvent. Another function may be to assist in domain closure. The third function may be to assist in the proper positioning of substrates in the active site.

ATP-dependent phosphoenolpyruvate carboxykinase (E. C. 4.1.1.49; PCK) is an enzyme that catalyses the reversible conversion of oxaloacetate and ATP into phosphoenolpyruvate, ADP and CO2. PCK is made up of about 500 to 600 amino acid residues and is divided into two roughly equal domains. Upon binding of substrates, the two domains of PCK move towards each other. PCK is well known for its role in gluconeogenesis but in some species, it can have an anaplerotic role. In other species, PCK is important for metabolic steps involved in fermentation.<p>Presented in this thesis are five solved crystal structures of the ATP-dependent form of PCK. Three of the PCK crystal structures determined were from <i>Escherichia coli</i>; one was a complex of ATP, Mg2+ and CO2, the second structure was an ATP, Mg2+, Mn2+, CO2 and oxaloacetate complex and, the third <i>E. coli</i> structure was a Lys213Ser mutant complexed with ATP, Mg2+and Mn2+. Two <i>Anaerobiospirillum succiniciproducens</i> PCK crystal structures were also solved; one was in the native form and the other was an ATP-Mg2+-Mn2+-oxalate complex. <p>In the <i>E. coli</i>-PCK-ATP-Mg2+-CO2 crystal complex structure, the observed location of CO2 was in agreement with a previously determined <i>E. coli</i> PCK-CO2 crystal structure, which incorporated CO2 into the structure by a different technique. The findings from the <i>E. coli</i> PCK-ATP-Mg2+-CO2 crystal structure allowed the reaction mechanism presented in this work to be proposed.<p>The PCK-ATP-Mg2+-Mn2+-CO2-oxaloacetate structure is the first structure where oxaloacetate is observed bound to PCK. Surprisingly, the observed location of oxaloacetate in this structure is 5 Angstroms away from its expected position near Mn2+. Oxaloacetate is weakly bound to a non-catalytic region of the enzyme. It is proposed that when the domains of PCK move towards each other upon binding nucleotide, oxaloacetate experiences steric crowding which results in it being pushed towards the active site to react. <p>Previous kinetic studies on the <i>E. coli</i> PCK mutant Lys213Ser have determined that Mn2+ is unexpectedly inhibitory. A crystal structure of K213S-PCK-ATP-Mg2+-Mn2+ demonstrates that Mn2+ is tetrahedrally coordinated in the active site, not octahedrally as occurred in other structures. By having Mn2+ in the tetrahedral coordination state, substrate binding in the active site of PCK is altered in a way that does not allow catalysis to occur.<p>The two crystal structures of <i>A. succiniciproducens</i> PCK were useful in quantifying the substrate-induced domain movement. A surface active site lid made up of residues 385 to 405 that had never been observed in any of the previous PCK crystal structures was observed in the <i>A. succiniciproducens</i> PCK-ATP-Mg2+-Mn2+-oxalate crystal structure. Mutational studies of this lid have shown it to be essential for the function of PCK; however, its exact function is not certain. It has been proposed that the lid has multiple functions. One is to sequester the substrates from bulk solvent. Another function may be to assist in domain closure. The third function may be to assist in the proper positioning of substrates in the active site.

Thèse de doctorat : Physique et Chimie de la Matière et des Matériaux : Nancy 1 : 2008. / Titre provenant de l'écran-titre.