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Reactions of fluorinated anilines with stoichiometric Ti(NMe2)4 in mesitylene (typically for 23 h at 120 °C) afforded moderate to high yields of the corresponding N,N-dimethyl-o-phenylenediamine derivatives resulting from defluoroamination of a fluorine atom ortho to the NH2 of the starting aniline. Reactivity increased with additional ring fluorination in general accordance with established regiochemical (activating and deactivating) trends. Based on results, we propose a metal-mediated, SNAr-based mechanism. We report the scope and limitations of this reaction and discuss trends in reactivity according to a putative mechanistic scheme. / Master of Science / This thesis describes reactions of fluorinated anilines with titanium amides to make fluorinated 1,2-phenylenediamines. The reaction gives high to moderate yields, and is highly selective for ortho substitution. The scope of the reaction, trends in reactivity among substrates, product characterization, and reaction mechanism are discussed. This reaction is of interest because fluorinated aniline derivatives are a privileged structural motif in pharmaceuticals and agricultural chemicals. The first chapter presents an overview of C-F bond activation and key background information. Chapter 2 is a description of the experiments and an in-depth analysis of their results. Chapter 3 presents detailed characterization data for substances generated in this research. Chapter 4 comprises some concluding remarks and plans for possible future extensions of the research.

Au cours de cette thèse, nous nous sommes intéressés à la préparation de nouveaux catalyseurs dérivés de la pyridine. En utilisant l’échelle de réactivité de Mayr, nous avons également cherché à quantifier l’effet d’un transfert de charge sur la nucléophilicité d’une pyridine. De plus, à travers un volet de trois méthodologies, nous avons étudiés leur activité en organocatalyse en tant que catalyseur sur des composés de natures très différentes (nitroalcènes, β-lactames et furan-2,3-diones). Enfin, dans un autre registre, nous avons développé la synthèse de nouvelles cages organiques chirales et fonctionnalisées parformation de liaisons imines réversibles. Nous avons également évalué leurs performances entant que cryptants. / During my PhD, we were interestedin the synthesis of new organocatalystsderivated from pyridine. Then, we tried toquantify a charge transfer effect towardpyridine nucleophilicity using a physicalorganic chemistry tool: the Mayr’s RelativityScale. Moreover, we also evaluated theircatalytic activity through three variousmethodologies involving different kind ofcompounds: nitroalkenes, β-lactams and furan-2,3-diones.To finish, we developed a straightforwardsynthesis of chiral, tunable and functionnalizedorganic cage compounds by imine reversiblebond formation. We also evaluated theirperformances as cryptands.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

This thesis deals with the development and application of new synthetic methodology for stereo- or regioselective construction of carbon-carbon bonds in organic synthesis. The first part of this thesis describes the development of a divergent protocol for stereoselective synthesis of chiral aminodiols by employing Mukaiyama aldol additions to syn- and anti-α-amino-β-silyloxy aldehydes. The stereoselectivity of the nucleophilic attack is governed by either chelation to the α-amino moiety or by nucleophilic attack in the Felkin-Anh sense. This study is also directed towards the elucidation of the factors that dictate aldehyde π-facial selectivity in substrate-controlled nucleophilic additions to these and similar systems. In the second part, a highly stereoselective [3 + 2]-annulation reaction of N-Ts-α-amino aldehydes and 1,3-bis(silyl)propenes for stereoselective construction of densely functionalized pyrrolidines is presented. In addition, this methodology is also implemented as a keystep in a synthetic approach towards the polyhydroxylated pyrrolidine and pyrrolizidine alkaloids DGDP and (+)-alexine from a common late pyrrolidine intermediate. Finally, a divergent protocol for regioselective opening of vinyl epoxides using alkyne nucleophiles is described, in which the regioselectivity of the nucleophilic attack is controlled by the choice of reaction conditions. The regioselectivities of the SN2 and SN2’ processes are, however, significantly influenced by the nature of the alkyne substituents and the best results are obtained using ethoxyacetylene. The SN2 opening of vinyl epoxides with ethoxyacetylene as nucleophile is also shown to provide a straightforward entry to functionalized γ-butyrolactones. / QC 20100917

Les β-lactones étant présentes dans de nombreux composés naturels biologiquement actifs, cette famille de molécules a été intensivement étudiée aussi bien d’un point de vue structural que pour leur réactivité, contrairement aux β-thiolactones. Afin d’établir un parallèle entre ces deux familles, nous avons étudié leur stabilité thermique en comparant les vitesses d’extrusion de CO2 et COS. Le suivi réactionnel a été réalisé par UV-spectrométrie de masse sur des β-lactones di-, tri- et tétrasubstituées et les β-thiolactones correspondantes, dans deux solvants (un polaire, l’autre apolaire). Utilisant la même stratégie, nous nous sommes intéressés à l’ouverture de ces hétérocycles par différents nucléophiles ainsi que la formation cinétique compétitive des β-(thio)lactones à partir d’un intermédiaire commun. Les similitudes entre les β-lactones et β-thiolactones soulignées par ces investigations, ont révélé la possible utilisation de ces dernières comme substitut des premières. La deuxième partie de ce manuscrit concerne la synthèse de mimes des O-sialosides présents dans de nombreux processus biologiques mais sensibles à l’hydrolyse enzymatique. A partir de dérivés de l’acide N-acétylneuraminique, nous avons développé des méthodes de C- et S-glycosylations électrophiles α-sélectives, et efficaces malgré la présence d’un groupement électroattracteur en C2 et du méthylène en C3 favorisant la formation du glycal. Ces techniques de synthèse, conduisant à des rendements et sélectivités excellents, pourront trouver des applications pour la synthèse de glycomimétiques. / Β-Lactones are present in many biologically active natural products; consequently, much attention has been focused on these compounds concerning structural properties as well as reactivity, unlike β-thiolactones. In order to compare these two compounds families, we have studied their thermal stability investigating the rate of CO2 and COS extrusion. Reactions were monitored by UV-mass spectrometry starting from di-, tri- and tetrasubstituted β-lactones and the corresponding β-thiolactones, in two different solvents (one polar, the other apolar). Using the same strategy, we worked on heterocycles opening by various nucleophiles. We have also studied the competitive kinetic formation of β-(thio)lactones from a common intermediate. These investigations permitted to show the similarities between these two families and revealled the possible use of β-thiolactones as β-lactone surrogates. O-Sialosides are present in many biological processes but are sensitive to enzymatic hydrolysis. We have worked on N-acetylneuraminic acid derivatives to develop a new method leading to α-selective C- and S-glycosylations, which is efficient in spite of the presence of a withdrawing group at C2 and methylene at C3 which increase glycal formation. This method leads to excellent yield and selectivity and could find applications on glycomimetic synthesis.