No description available.

In the first part of this study, four new chiral ligands (FAM) were synthesized and used in catalytic amounts in asymmetric 1,3-dipolar cycloaddition reactions of azomethine ylides. This method leads to the synthesis of chiral pyrrolidines, which are found in the structure of many biologically active natural compounds and drugs. It was found that using 10 mol% of one of these chiral ligands with different dipolarophiles (dimethyl maleate, dimethyl fumarate, methyl acrylate, tert-butyl acrylate, and Nmethylmaleimide), pyrrolidine derivatives could be synthesized in up to 94% yield and 95% ee. In the second part of the study, the catalytic activity of these chiral ligands were tested with titanium in asymmetric alkynylzinc addition reactions to aldehydes. By this method, chiral propargylic alcohols, which are important precursors for the natural products and pharmaceuticals can be synthesized. Using our catalyst, chiral propargylic alcohols were obtained in up to 96% yield and 98% ee. Although, most of the catalyst systems in the literature worked only with aromatic or aliphatic aldehydes and phenylacetylene, the catalyst system developed in this study worked with four different types of aldehydes (aromatic, aliphatic, heteroaromatic and a,b-unsaturated) and two different aliphatic acetylenes very successfully. Additionally, chiral ligand can be recovered in more than 90% yield and reused without losing its activity.

In this study new twelve phosphorus based chiral ligands were synthesized and characterized. Then the catalytic activity of these chiral ligands was tested with Cu(II) and Ag(I) salts in asymmetric 1,3-dipolar cycloaddition reactions of azomethine ylides. This method provides the synthesis of different pyrrolidine derivatives with up to four stereogenic centers. Pyrrolidine derivatives are found in the structure of many biologically active natural compounds and drugs. Therefore the asymmetric synthesis of these compounds is highly important and many groups are involved in this area. As the precursor of the azomethine ylides, N-benzyliden-glycinmethylester, N-(4-methoxy benzyliden)-glycinmethylester, N-(naphthalene-1-ylmethylene)-amino-acetic acid methyl ester, and N-(naphthalen-2-ylmethylene)-amino-acetic acid methyl ester were synthesized and used. As the dipolarophiles, methyl acrylate, dimethyl maleate and N-methyl maleimide were used. Using these imines and dipolarophiles with 6 mol % of one of the P-FAM chiral ligands in the presence of Ag(I) salt, pyrrolidine derivatives were synthesized in up to 95% yield and 89% enantioselectivity. Additionally, chiral ligand was recovered in more than 80% yield and reused without losing its activity.

Les matériaux conjugués sont de nos jours très utilisés dans de nombreuses applications ainsi qu’en recherche. L’enchainement des liaisons π-σ-π permet la délocalisation des électrons et d’obtenir différentes propriétés comme la conduction, la fluorescence, la chélation, etc. Ainsi, de nombreux dispositifs utilisent ces caractéristiques en vue d’obtenir de nouveaux matériaux révolutionnaires comme les cellules solaires, les transistors à effet de champs, les dispositifs électrochromiques, etc.. Les dispositifs électrochromiques font partie des dispositifs en vogue. Ils sont capables de changer de couleur selon le potentiel électrique appliqué. Ils se distinguent par la simplicité du mode de conception et ils ne nécessitent pas de fonctionner dans des conditions drastiques comme une atmosphère contrôlée. Ces dispositifs sont actuellement utilisés et commercialisés comme fenêtre intelligente, camouflage, papier électronique et carte de visite personnalisée pour n’en nommer que quelques-uns. Deux propriétés sont essentielles pour que des composés puissent être utilisés dans ces familles de dispositifs : la réversibilité à l’oxydation et la stabilité à l’air et à la lumière. Dans le groupe de recherche du professeur W.G. Skene, l’axe principal de recherche est basé sur la conception de nouveaux matériaux conducteurs comportant des liaisons azométhines. Les principaux matériaux étudiés sont des dérivés de thiophènes et de fluorènes. De précédents résultats ont montré que plusieurs produits issus de la réaction de condensation entre les dérivés du 2,5-diaminothiophène et de thiophènes diformylés menaient à des produits possédant d’excellentes propriétés photophysiques et électrochimiques. C’est en partant de ces résultats encourageants qu’il a été choisi de synthétiser une nouvelle famille de produits avec un nouveau substrat fonctionnalisé. Ce dernier possède d’excellentes propriétés électrochimiques et photophysiques : la triphénylamine. Deux familles de produits ont été synthétisées qui possèdent toutes comme cœur une triphénylamine. Cette dernière a été modifiée de façon à créer une, deux ou trois liaisons azométhines avec différents thiophènes. Deux dérivés du thiophène ont été choisis afin d’étudier l’influence des groupements donneurs et accepteurs sur ces nouveaux types de composés encore jamais étudiés. Les résultats des différentes synthèses et analyses ont été effectués par RMN, spectrométrie de masse, spectrométrie d’absorbance UV-Visible, fluorescence et voltampérométrie cyclique sont rapportées dans le présent recueil. / Conjugated materials are been used in many applications and fundamental research, owing in part to their high degree of conjugation. They further have opto-electronic properties that are compatible for use as conjugated materials in many devices including solar cells, organic field effect transistors, organic light emitting diodes and electrochromic devices. The latter are of particular interest because their colors that can be changed when a potential is applied. The advantage of these color switching materials compared to other opto-electronic devices is their simple fabrication that can be done under ambient conditions. Electrochromic devices have found many consumer applications including mirrors, tunable windows, camouflage and electronic paper, to name a few examples. The focus of our research group is the preparation of new conjugated materials based on azomethine. Previous efforts from the group demonstrated that azomethines having the required properties for use in electrochromic devices (electrochemical reversibility and air stability) were possible when using a 2,5-diaminothiophene derivative as a building block. It was also demonstrated that color tuning of both the neutral and oxidized states was possible when coupling 2,5-diaminothiophene with various heterocyclic arylaldehydes. Despite the many examples of azomethines studied in our group, fundamental structure-property relationships of these conjugated materials are still not understood. The objective of this thesis was therefore to prepare to new conjugated azomethines from triarylamine aldehydes. The objective was also to examine the opto-electronic properties of these novel azomethines, including the effect of the degree of conjugation and type of triphenylamine aldehyde precursor on the absorbance, electrochemical properties, and fluorescence.

No description available.

1-Aza-2-azoniaallene salts are reactive intermediates that undergo [3+2] cycloaddition with many different types of multiple bonds. For the past several years, the Brewer group has studied the reactivity of these intermediates in intramolecular reactions, and have discovered that these cationic heteroallenes can react through a variety of other, mechanistically distinct, pathways to give different classes of nitrogen heterocycles. For example, prior work in the Brewer group revealed that 1-aza-2-azoniaallene salts could react in an intramolecular [4+2] cycloaddition reaction to give protonated azomethine imine salts containing a 1,2,3,4-tetrahydrocinnoline scaffold. Further study of the scope and limitations of this Diels-Alder-like reaction are described herein. These studies primarily focused on how varying the N-aryl ring and alkene substituents affected the reaction. We discovered that in several instances, the metal mediated reaction did not facilitate the cycloaddition very well, so we searched for alternative ways to facilitate the reaction. We discovered that a non-metallic Lewis acid (TMSOTf) provided very clean products with α-chloroazo compounds. I hypothesized that changing the leaving group adjacent to the azo might further improve the reaction. With this in mind, I developed a technique to prepare α-trifluoroacetoxyazo compounds by treating aryl hydrazones with trifluoroacetoxy dimethylsulfonium trifluoroacetate. This technique is compatible with all types of functional groups including nitro aryl compounds, which gave low yields of the corresponding chloroazo derivatives. Importantly, these α-trifluoroacetoxyazo compounds gave even better cycloaddition results when treated with TMSOTf, and this method is more practical, more environmentally friendly, and greener than the metal mediated technique. This process even returned sterically hindered products in high yield, and provide a dearomatized non-protonated azomethine imine salt, which further verified the proposed mechanism of the [4+2] cycloaddition. Azomethine imines are well known to undergo 1,3-dipolar cycloadditions with alkenes. We wondered if the protonated azomethine imine salts generated by the [4+2] cycloaddition could be used in a subsequent base-mediated [3+2] cycloaddition to generate structurally complex tetra- or pentacyclic products. We were pleased to find that the protonated azomethine imines indeed reacted smoothly with a variety of π-system in the presence of triethylamine to give the corresponding cycloadducts in high yields with moderate to high diastereoselectivities. In an attempt to understand the diastereoselectivity of these [3+2] cycloadditions better, I modeled them computationally.

Les azométhines contiennent des liaisons covalentes qui peuvent se former de façon réversible entre une amine et un aldéhyde. Cette réversibilité peut être exploitée pour échanger leurs composantes constitutionnelles. Les propriétés intrinsèques des azométhines peuvent être modulées en échangeant les composantes amines ou aldéhydes. L’échange des composantes constitutionnelles est possible en solution. Toutefois, les produits échangés doivent être purifiés pour éliminer les divers réactifs et produits échangés indésirables. Il est donc avantageux de simplifier l’étape de purification pour isoler le produit échangé désiré. Un moyen possible pour atteindre cet objectif est d’immobiliser l’amine ou l’aldéhyde sur une surface. Dans ce cas, les produits échangés souhaités peuvent être facilement isolés en rinçant la surface à la suite de cet échange. À cette fin, un monomère d’aldéhyde électroactif dérivé de la triphénylamine a été préparé. Il a été polymérisé thermiquement sur une électrode transparente. La polymérisation a été confirmée par les spectroscopies FT-IR ATR et Raman. Une série d’amines (aminocoumarines et diaminobenzothiadiazole) présentant chacune une couleur unique, une longueur d’émission et un potentiel d’oxydation électrochimique ont été choisis. Leur formation en azométhine et leur échange dynamique sur film mince d’aldéhyde électroactif ont donc pu être suivis électrochimiquement, par des spectroscopies UV-visibles et Raman, et par la fluorescence. Des composés modèles de ces fluorophores azométhines ont également été préparés pour l’analyse comparative de leurs propriétés électrochimiques et spectroscopiques, ainsi que pour la confirmation de l’échange des composantes. Il a été montré que les propriétés multiples (potentiel redox, couleur, longueur d’onde et rendement d’émission) du film électroactif pouvaient être simultanément modulées par la formation réversible d’azométhine. En immobilisant les azométhines sur une surface, leurs propriétés pourraient être modifiées de façon réversible par échange des composantes, soit en immergeant le substrat dans une solution d’amine, soit en enduisant la surface d’un jet d’amine suivi d’un rinçage. Ce processus direct permet de développer des surfaces dont les propriétés peuvent être constamment modifiées, tout en ouvrant la possibilité de réparer la surface et de restaurer les propriétés souhaitées par un échange dynamique de composantes. / Azomethines incorporate covalent bonds that can be reversibly formed between an amine and aldehyde. This reversibility can be exploited to exchange their constitutional components. The intrinsic properties of the azomethines can be modulated by exchanging either the amine or the aldehyde components. Exchanging the constitutional components is possible in solution. However, the exchanged products must be purified to remove the various reagents and undesired exchanged products. It is therefore advantageous to simplify the purification step for isolating the desired exchanged product. A possible means towards this goal is by immobilizing either the amine or the aldehyde on a surface. In such a case, the desired exchanged products can be readily isolated by rinsing the surface following the dynamic component exchange. Towards this end, an electroactive aldehyde monomer derived from triphenylamine was prepared. It was thermally polymerized on a transparent electrode. Polymerization was confirmed by FT-IR ATR and Raman spectroscopies. A series of amines (aminocoumarin and diaminobenzothiadiazole) each with a unique color, emission wavelength and electrochemical oxidation potential were chosen. Their azomethine formation and dynamic exchange with the electroactive aldehyde thin film could therefore be tracked electrochemically, by UV-visible and Raman spectroscopies, and by fluorescence. Model compounds of these azomethine fluorophores were also prepared for benchmarking their electrochemical and spectroscopic properties along with confirming component exchange. It was shown that multiple properties (redox potentials, color, emission wavelength, and emission yield) of the electroactive film could be simultaneously modulated by reversible azomethine formation. By immobilizing the azomethines on a surface, their properties could be reversibly modified by component exchange by either dipping the substrate in an amine solution or coating the surface with a spray of amine followed by rinsing. This straight-forward process provides the means for developing surfaces whose properties can be perpetually modified, while opening the possibility of repairing the surface and restoring desired properties by dynamic component exchange.

This thesis is divided into four separate parts with amino alcohols as the common feature. The first part of the thesis describes the development of an efficient three-component approach to the synthesis of α-hydroxy-β-amino esters. Utilizing a highly diastereoselective Rh(II)-catalyzed 1,3-dipolar cycloaddition of carbonyl ylides to various aldimines, syn-α-hydroxy-β-amino esters are formed in high yields and excellent diastereoselectivities. An asymmetric version was also developed by employing chiral α-methylbenzyl imines as dipolarophiles yielding enantiomerically pure syn-α-hydroxy-β-amino esters. This methodology was also applied on a short asymmetric synthesis of the paclitaxel side-chain as well as in an asymmetric synthetic approach towards the proteasome inhibitor omuralide. Furthermore, the use of chiral Rh(II) carboxylates furnishes the syn-α-hydroxy-β-amino esters in moderate enantioselectivity (er up to 82:18), which indicates that the reaction proceeds via a metal-associated carbonyl ylide. The second part describes the development of a 1,3-dipolar cycloaddition reaction of azomethine ylides to aldehydes for the synthesis of α-amino-β-hydroxy esters. Different methods for the generation of the ylides, including Vedejs’ oxazole methology and an Ag(I)/phosphine-catalyzed approach have been evaluated. The best results were obtained with the Ag(I)/phosphine approach, which yielded the desired α-amino-β-hydroxy ester in 68% yield and 3.4:1 syn:anti-selectivity. The last two parts deals with the total synthesis of the amino alcohol-containing natural products D-erythro-sphingosine and (−)-stemoamide. The key transformation in the sphingosine synthesis is a cross-metathesis reaction for the assembly of the polar head group and the aliphatic chain. In the stemoamide synthesis, the key feature is an iodoboration/Negishi/RCM-sequence for the construction of the β,γ-unsaturated azepine core of stemoamide followed by a stereoselective bromolactonization/1,4-reduction strategy for the installation of the requisite C8-C9 trans-stereochemistry. / QC 20100820

No description available.

Polycyclic aromatic azomethine ylide (PAMY) is a versatile building block for the bottom-up construction of unprecedented nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs). Here, we demonstrate the 1,3-dipolar cycloaddition between PAMY and 1,4-diphenylbut-2-yne-1,4-dione as well as the subsequent condensation reaction with hydrazine, which led to synthesis of unique N-PAHs with a phenyl-substituted pyrrolopyridazine core (PP-1 and PP-2). The molecular structures of pristine PP-1 and tert-butyl-substituted PP-2 were verified by NMR and mass spectroscopy. Moreover, the structure of PP-2 was unambiguously elucidated by X-ray single crystal analysis. The optoelectronic properties were investigated by solvent-dependent UV-Vis absorption and fluorescence emission spectroscopy as well as cyclic voltammetry. Additionally, the density functional theory (DFT) calculations exhibited a push-pull behavior for PP-1 and PP-2. Furthermore, the in situ EPR/UV-Vis-NIR spectroelectrochemistry allowed the detailed insight into the spectroscopic properties and spin distribution of radical cation species of PP-2.