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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Nouveaux développements de la chimie des proazaphosphatranes : de l’organocatalyse à la liaison halogène / New developments of proazaphosphatranes : from organocatalysis to halogen bonding

Yang, Jian 09 October 2018 (has links)
Au cours de ces travaux de thèse, nous avons exploré de nouvelles applications des proazaphosphatranes et de leurs dérivés, en particulier leur confinement dans une cage moléculaire. Dans la première partie, une bibliographie présente la littérature concernant (i) la découverte et les applications de proazaphosphatranes, (ii) les catalyseurs confinés dans des cages covalentes et (iii) la liaison halogène - une interaction non covalente émergente-. Par la suite, l’utilisation de proazaphosphatranes comme organocatalyseur très efficace pour la réaction de Strecker est décrit. Ensuite, un système FLP (paire de Lewis frustrée) comprenant un proazaphosphatrane encagé comme base de Lewis et du TiCl4 comme acide de Lewis a été utilisé pour catalyser la réaction de MBH (Morita-Baylis-Hillman). Finalement, un azaphosphatrane chloré a été synthétisé, et ses propriétés de reconnaissance vis à vis de différents anions halogénures, par liaison halogène, a été étudié. / In this dissertation, our goal is to explore new applications of proazaphosphatranes and their derivatives, especially in a confined space. In the first part, a comprehensive literature review regarding 1) discovery and application of proazaphosphatranes, 2) confined covalent cages based organo- and metal-catalysts, and 3) halogen bonding – an emergent noncovalent interaction has been demonstrated. Subsequently, proazaphosphatrane as highly efficient organocatalyst for the Strecker reaction is discussed. And a FLP (frustrated Lewis pair) system comprising an encaged proazaphosphatrane as Lewis base and TiCl4 as Lewis acid for MBH (Morita–Baylis–Hillman) reaction is reported. In the end, chlorinated azaphosphatrane is synthesized and studied in the recognition of different halide anions by halogen bonding, exhibiting a preferable affinity for chloride over bromide and iodide.
2

C2- and C3-symmetric ligands via ring-opening of aziridines

Lake, Fredrik January 2002 (has links)
This thesis deals with the design and synthesis of chiralenantiopure nitrogencontaining ligands and the use of theseligands in asymmetric catalysis. A modular synthetic approachto enantiopure nitrogen-containing ligands was developed. Thesynthetic method is based on the ring-opening of activatedchiral aziridines by nitrogen nucleophiles. The aziridines areconveniently prepared from amino alcohols. The structure oftheaziridine and of the nucleophile can be extensively varied andlibraries of ligands are easily prepared. The use of primaryamines affords C2-symmetric bis(sulfonamides), whereas the use ofammonia affords C3-symmetric tris(sulfonamides) that can beelaborated into the corresponding tetra-amines. The C2- and C3-symmetric ligands were used in the asymmetrictitaniummediated addition of diethylzinc to benzaldehyderesulting in modest enantioselection, 76% ee. A thoroughinvestigation of the reaction conditions revealed that theamount of Ti(OiPr)4has a decisive effect on the reaction rate and thestereochemical outcome of the reaction. The reaction timedecreased from about 90 hours to 15 minutes and theenantioselectivity changed from 26% of the (R)- enantiomer to72% of the (S)-enantiomer when the Ti(OiPr)4:benzaldehyde ratio was increased from 0.125:1 to1.48:1. Moreover, the titanium-mediated addition of diethylzincto benzaldehyde was studied in the presence of chiraladditives. The bis(sulfonamides) were also used in thecyclopropanation of cinnamyl alcohol. However, only lowenantioselection was observed, 27% ee. The C3-symmetric tetra-amines were reacted to formazaphosphatranes. These weak acids were only partiallydeprotonated by the strong base KOtBu to form the correspondingproazaphosphatranes. The unexpectedly strong basicity of theproazaphosphatranes was believed to be due to steric effects assuggested by DFT calculations. The tetra-amines and thesulfonamides were used for the preparation of metal complexesof Lewis acidic metals such as titanium(IV) andzirconium(IV). <b>Keywords:</b>asymmetric catalysis, aziridine, benzaldehyde,diethylzinc, enantioselective, ligand, proazaphosphatrane,ring-opening, sulfonamide, symmetry, titanium, zirconium
3

C2- and C3-symmetric ligands via ring-opening of aziridines

Lake, Fredrik January 2002 (has links)
<p>This thesis deals with the design and synthesis of chiralenantiopure nitrogencontaining ligands and the use of theseligands in asymmetric catalysis. A modular synthetic approachto enantiopure nitrogen-containing ligands was developed. Thesynthetic method is based on the ring-opening of activatedchiral aziridines by nitrogen nucleophiles. The aziridines areconveniently prepared from amino alcohols. The structure oftheaziridine and of the nucleophile can be extensively varied andlibraries of ligands are easily prepared. The use of primaryamines affords C<sub>2</sub>-symmetric bis(sulfonamides), whereas the use ofammonia affords C<sub>3</sub>-symmetric tris(sulfonamides) that can beelaborated into the corresponding tetra-amines.</p><p>The C<sub>2</sub>- and C<sub>3</sub>-symmetric ligands were used in the asymmetrictitaniummediated addition of diethylzinc to benzaldehyderesulting in modest enantioselection, 76% ee. A thoroughinvestigation of the reaction conditions revealed that theamount of Ti(OiPr)<sub>4</sub>has a decisive effect on the reaction rate and thestereochemical outcome of the reaction. The reaction timedecreased from about 90 hours to 15 minutes and theenantioselectivity changed from 26% of the (R)- enantiomer to72% of the (S)-enantiomer when the Ti(OiPr)<sub>4</sub>:benzaldehyde ratio was increased from 0.125:1 to1.48:1. Moreover, the titanium-mediated addition of diethylzincto benzaldehyde was studied in the presence of chiraladditives. The bis(sulfonamides) were also used in thecyclopropanation of cinnamyl alcohol. However, only lowenantioselection was observed, 27% ee.</p><p>The C<sub>3</sub>-symmetric tetra-amines were reacted to formazaphosphatranes. These weak acids were only partiallydeprotonated by the strong base KOtBu to form the correspondingproazaphosphatranes. The unexpectedly strong basicity of theproazaphosphatranes was believed to be due to steric effects assuggested by DFT calculations. The tetra-amines and thesulfonamides were used for the preparation of metal complexesof Lewis acidic metals such as titanium(IV) andzirconium(IV).</p><p><b>Keywords:</b>asymmetric catalysis, aziridine, benzaldehyde,diethylzinc, enantioselective, ligand, proazaphosphatrane,ring-opening, sulfonamide, symmetry, titanium, zirconium</p>

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