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Sulfated polysaccharides are widespread in nature. These compounds are implicated in a wide variety of important biological processes such as blood clotting, cell adhesion, and cell–cell communication. However, detailed characterization of their specific biological roles has proved to be very challenging. One reason for this is that the synthesis of even relatively small sulfated oligosaccharides still remains a considerable challenge. A general approach to the synthesis of sulfated carbohydrates was examined in which the sulfate group is incorporated at the beginning of the syntheses as a protected sulfodiester. Towards this end, a series of modified sulfuryl imidazolium salts were prepared and examined as reagents for incorporating 2,2,2-trichloroethyl-protected sulfate esters into monosaccharides.. A more efficient sulfating agent was obtained by incorporating a methyl group at the 2-position of the imidazolium ring. O-Sulfations that required prolonged reaction times and a large excess of the original sulfuryl imidazolium salt (SIS) which bears no alkyl groups on the imidazolium ring, were more readily achieved using the new reagent. Direct regioselective incorporation of TCE-protected sulfates into monosaccharides was achieved using the new imidazolium salt. We have also shown that the new SIS can also be used for the direct disulfation of monosaccharides and that trisulfated monosaccharides can also be prepared from the disulfated compounds. SIS’s bearing the TFE and phenyl groups, were readily prepared. In most instances, both TFE- and phenyl protected sulfated carbohydrates were easily prepared in good yields using SIS’s. Deprotection of the TFE group from secondary sulfates in carbohydrates and aryl sulfates was achieved in excellent yields using NaN3 in DMF. We applied the sulfate protecting group strategy towards the total synthesis of the tetrasaccharide portion of a disulfated glycosphingolipid called SB1a. Efficient routes were developed for the construction of the left- and right-hand protected disaccharide portions of the SB1a tetrasaccharide.

Sulfated polysaccharides are widespread in nature. These compounds are implicated in a wide variety of important biological processes such as blood clotting, cell adhesion, and cell–cell communication. However, detailed characterization of their specific biological roles has proved to be very challenging. One reason for this is that the synthesis of even relatively small sulfated oligosaccharides still remains a considerable challenge. A general approach to the synthesis of sulfated carbohydrates was examined in which the sulfate group is incorporated at the beginning of the syntheses as a protected sulfodiester. Towards this end, a series of modified sulfuryl imidazolium salts were prepared and examined as reagents for incorporating 2,2,2-trichloroethyl-protected sulfate esters into monosaccharides.. A more efficient sulfating agent was obtained by incorporating a methyl group at the 2-position of the imidazolium ring. O-Sulfations that required prolonged reaction times and a large excess of the original sulfuryl imidazolium salt (SIS) which bears no alkyl groups on the imidazolium ring, were more readily achieved using the new reagent. Direct regioselective incorporation of TCE-protected sulfates into monosaccharides was achieved using the new imidazolium salt. We have also shown that the new SIS can also be used for the direct disulfation of monosaccharides and that trisulfated monosaccharides can also be prepared from the disulfated compounds. SIS’s bearing the TFE and phenyl groups, were readily prepared. In most instances, both TFE- and phenyl protected sulfated carbohydrates were easily prepared in good yields using SIS’s. Deprotection of the TFE group from secondary sulfates in carbohydrates and aryl sulfates was achieved in excellent yields using NaN3 in DMF. We applied the sulfate protecting group strategy towards the total synthesis of the tetrasaccharide portion of a disulfated glycosphingolipid called SB1a. Efficient routes were developed for the construction of the left- and right-hand protected disaccharide portions of the SB1a tetrasaccharide.

Ionomers are valued for their exceptional physical properties, antimicrobial activity and superior adhesion to high surface energy solids and polymer blend components. Carboxylate, or sulfonate derivatives, of ethylene-rich thermoplastics are the most commercially available ionomers. Elastomeric ionomers bearing quaternary ammonium and phosphonium halide functionality have a literary standing in both scientific and patent-based publications. Currently cationic ionomers have shown great prominence in their inactivity to a wide range of bacteria and fungi. The specific focus of this research is in the derivatives of isobutylene-rich elastomers due to their exceptional impermeability, oxidative stability and vibration dampening characteristics. Imidazole-derived ionomers support a wider range of ionomer chemistry compared to ammonium and phosphonium analogues. N alkylation of nucleophiles including butyl imidazole, vinyl imidazole and 1,1’(1,4-butanediyl)bis(imidazole) by brominated poly(isobutylene-co-isoprene) yield thermally stable imidazolium bromide salts capable of supporting free radical cures and/or siliceous filler dispersions through further chemical modifications. The versatility of imidazole chemistry extends to the synthesis of isobutylene rich thermoset ionomers. This derives material properties from both a network of covalent crosslinks and a network of ion pair aggregates. Un-crosslinked elastomers are prone to creep and stress relaxation, hence a need for thermoset ionomer chemistry. Ion pairs are poorly solvated by the low dielectric constant of the polymer backbone and favoured thermodynamically by way of self assembly of the ionic functionality. The aggregation of ion pairs establishes a non covalent network of polymer chains whose dynamic mechanical properties approach those of conventional covalent thermosets comprised of carbon-carbon and/or sulfide crosslinks. However, the lability of this ionic network leads to a poor response to static loads leaving the thermoformable ionomers unqualified for engineering applications. A direct route is a more desirable method in preparing thermoset ionomers comprised of covalent crosslink networks and ionic functionality. In all, these reactive imidazolium ionomers look promising in supporting new value added applications for isobutylene rich derivatives, which include yet are not limited to elastomer thermosets, emulsions, filler composites and clay nanocomposites. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-12-11 15:34:32.691

Asymmetric hydrogenation as a general route to polypropionates has been explored for allylic alcohols, acids, and derivatives, which has led to the generation of 2,4-dimethylated hexane derivatives. Quantitative yields in most cases and enantioselectivities greater than 98% were obtained. A remarkable stereofacial inversion was observed when an ester or acid was present in the allylic position instead of an alcohol or alcohol derivative. This led to the construction of all four diastereomers of the hexanol series from a single enantiomer of hydrogenation catalyst. Also described are an attempted synthesis of (-)-lardolure, a formal synthesis of the methyl ester portion of the preen gland extract from the domestic goose Anser anser, and a total synthesis of an extract from the fungi A. cruciatus. The synthesis of these compounds demonstrated shortcomings of the known catalyst system showing enantioselectivities for polymethylated compounds was high, while diastereoselectivity was low. Methodology to develop new N-heterocyclic carbene catalysts was developed using the cyanide coupling of aldimines to generate electronically tunable 1,3,4,5-tetraaryl complexes, and X-ray, IR, and calculations were used to elucidate their electronic characteristics. These studies indicate that the 4,5-positions have as great an influence on the metal-ligand bond as the 1,3-positions. In addition, they are among the most electron-donating 2- metalated N-heterocyclic carbenes found thus far. An intrinsic relationship between catalytic activity and electron donating ability was found in transfer hydrogenations.

Ce manuscrit présente la synthèse de nouveaux réseaux hybrides organiques/inorganiques à base de différents ligands imidazoliums. Trois ligands imidazoliums possédant chacun des caractéristiques spécifiques ont été synthétisés et utilisés avec l’objectif de parvenir à la formation de réseaux hybrides multiferroïques c’est-à-dire des réseaux qui possède à la fois un ordre magnétique et un ordre électrique. La modification du ligand a ainsi permis d’obtenir des composés répondant aux critères (de symétrie en particulier) à remplir pour la présence d’un ordre électrique. Pour construire le réseau inorganique magnétique nous avons travaillé sur la synthèse de composés à base de métaux de transition de la première série ou de lanthanides. L’ensemble des composés obtenus a été caractérisé par un ensemble de techniques (diffraction des rayons X, spectroscopie FTIR et UV-Vis, analyses thermiques et élémentaires). Les propriétés magnétiques, de luminescence et de ferroélectricité des composés ont aussi été étudiées. / This thesis presents the syntheses of new hybrid coordination networks based on imidazolium ligands. Three kinds of ligands possessing their own features were synthesized and used with the main objective to obtain multiferroic hybrid networks meaning networks which display a magnetic order and a ferroelectric order. The modification of the ligand allowed to obtain compounds filling criteria (on the symmetry) for a ferroelectric order. The magnetic inorganic network was built due to the synthesis of compounds based on first row metals or lanthanides. All compounds were characterized by several techniques (X-rays diffraction, spectroscopic measurements, thermal and elemental analyses). Magnetic, luminescence and ferroelectric properties were also studied.

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Palladium catalyzed Heck coupling with aryl and alkenyl halides has become a powerful means of carbon-carbon bond formation. This standard synthetic method has been developed to a high level of utility using various catalysts, conditions and substrates. Yet significant drawbacks remain, including poor reactivity, the need for high temperatures and base, limited substrate generality, and selectivity. Mixed products often suffer from olefin migration following insertion. N-Heterocyclic carbenes (NHC) have proven to be electron-rich donors which provide higher stability and reactivity than phosphines. In a previous paper reported by our research group the imidazolium-palladium carbene has proven to be highly efficient for the Suzuki-Miyaura cross couplings. The most active bis-2,6- diisopropylphenyl dihydroimidazolium chloride ligand 1 in that series together with palladium acetate were employed as the catalyst, to efficiently catalyze the Heck coupling of aryl diazonium ions with olefins with useful yields at room temperature. Added base is not needed either to form the carbene catalyst or for alkene product formation. Phase-Transfer Catalysis (PTC) is a very useful approach and has been widely used in synthetic organic chemistry. A novel class of fluoroanthracenylmethyl PTC catalysts were synthesized and explored for asymmetric glycolate and glycine alkylation. Phosphorous pentoxide was used for the challenging electron-deficient electrophilic aromatic substitution step. These new catalysts proved to have high selectivities for glycine alkylation under mild conditions.

Several new late transition metal complexes containing P-O and P-N ligands derived from 2-dicyclohexylphosphinoacetaldehyde were synthesized. A facile one-pot template method is used for the synthesis of P-N complexes, where the phosphine aldehyde and amine can undergo a condensation reaction to form a phosphine-imine metal complex in the presence of a metal precursor. Metal complexes with phosphino-enolate, imine, and oxime ligands are synthesized. Ni(II), Pt(II), Rh(I) and Ir(I) metal centres were investigated. The Rh(I) and Ir(I) complexes contain a 1,5-cyclooctadiene ligand, thus resembling Crabtree’s hydrogenation catalyst [Ir(COD)(py)(PCy3)][PF6]. These complexes are also active catalysts for olefin hydrogenation. Furthermore, the synthesis of a new chiral amine functionalized NHC ligand is explored, which has potential applications as a ligand in the metal-catalyzed enantioselective hydrogenation of polar bonds. This ligand is inspired by previous achiral hydrogenation catalysts reported by Morris et al. that displayed high activity for a variety of unsaturated substrates.

No description available.