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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

Gold(I)-Catalyzed Enantioselective Hydroamination of Unactivated Alkenes

Lee, seong du January 2012 (has links)
<p>Numerous methodologies for efficient formation of carbon-nitrogen bonds have been developed over the decades due to the widespread importance of nitrogen containing compounds in pharmaceuticals and bulk commercial chemicals. Among many methods, hydroamination, especially, has attracted enormous attention because of its atom-economical characteristic to synthesize amine moieties. As a result, numerous publications have been reported relating the hydroamination reaction using various metal catalysts. However, the hydroamination of unactivated alkenes still remains a challenge task because of the low reactivity of the CC double bond. Recent development of superior gold(I) catalysis in many organic transformations stimulated us to develop efficient gold(I)-catalyzed methods for enantioselective intra- and intermolecular hydroamination of unactivated alkenes. </p><p>A gold(I)-catalyzed system for enantioselective intramolecular hydroamination of unactivated alkenes has been developed. For the effective gold(I)-catalyzed method, various gold(I)-catalysts have been synthesized and tested. Among the catalysts, bis(gold) complexes containing an axially chiral bis(phosphine) ligand catalyze the enantioselective intramolecular hydroamination of unactivated alkenes with carboxamide derivatives, most effectively. The method was effective for both carbamates and ureas to form pyrrolidine derivatives with up to 85 % ee.</p><p>The first enantioselective intermolecular hydroamination of unactivated alkenes was realized by a gold(I)-catalyzed method. The gold(I) catalyst system adds cyclic ureas to unactivated 1-alkenes to produce corresponding enantiomerically enriched hydroamination product in good yield with enantioselectivity up to 78 % ee. </p><p>Polymer-embedded ligands have been synthesized to demonstrate proofs of concepts for fluxional mechanocatalysis. We applied a certain shear stress using a rheometer in the course of palladium-catalyzed asymmetric allylic alkylation to examine catalytic reactivity change under the mechanical force.</p> / Dissertation
2

Syntheses and catalytic properties of palladium (II) complexes of various new aryl and aryl alkyl phosphane ligands

Vuoti, S. (Sauli) 27 November 2007 (has links)
Abstract Thirty three aryl and aryl alkyl phosphane ligands were prepared and characterized for catalytic purposes. The aryl groups in both types of ligands were modified with alkyl substituents (methyl, ethyl, isopropyl, cyclohexyl, phenyl) or hetero substituents (methoxy, N,N-dimethylaniline, thiomethyl). The alkyl groups directly attached to the phosphorous atom were ethyl, isopropyl or cyclohexyl. Mono- and in some cases also dinuclear palladium (II) complexes of the ligands were prepared and characterized. The syntheses of the palladium complexes are solvent-dependent and afford either mono- or dinuclear complexes depending on the choice of the solvent. Additionally, two 2-mercaptobenzothiazole palladium complexes were synthesized and characterized. A rare distorted lantern-type structure was presented for the first time. The ligands were characterized by 1H, 13C, 31P NMR spectroscopy and mass spectrometry. The palladium complexes were characterized by 31P NMR spectroscopy, X-ray crystallography and elemental analysis. Links between the NMR data of the palladium complexes and ligands and their catalytic activity was screened and correlation found. The crystal structures of the palladium complexes were studied for possible attractive interactions between two ligands. Such interactions were found from two examples. There is an attractive interaction between the phenyl and quinolinyl moieties of 2-quinolinyldiphenyl phosphane. A similar interaction was found between the methyl substitute and phenyl ring of o-tolylphosphane. The ligands and palladium complexes presented in this thesis were prepared in hope of finding suitable catalysts for Suzuki coupling reactions of various bulky aryl halides and phenyl boronic acids to prepare sterically hindered bi- and triaryls under microwave irradiation. A selection of aryl alkyl phosphane ligands catalyzed the couplings of bulky aryl bromides and even unactivated aryl chlorides efficiently and produced high yields. The reaction conditions of a new catalyst system were optimized, and it was noticed that the addition of a small amount of water enhanced the purity and yield of the coupling products further.
3

Formation de composés polycycliques par activation de doubles liaisons : approche catalytique intra et intermoléculaire de réactions de type Friedel-Crafts : applications au domaine des arômes et parfums / Non disponible

Cacciuttolo, Bastien 14 February 2013 (has links)
L’utilisation de méthodologies de synthèse toujours plus performantes et respectueuses de l’environnement est un axe de recherche majeur de la chimie moderne. L’apport de la catalyse, avec l’utilisation de superacides de Lewis, a permis d’améliorer de nombreux processus synthétiques. Nous avons pu développer dans ce manuscrit des réactions de cycloisomérisation de type réaction de Friedel-Crafts qui donnent accès à un ensemble de structures polycycliques intéressantes avec de bons rendements et sélectivités. L’utilisation d’une quantité catalytique, entre 1 et 10 mol% de Bi(OTf)3, permet l’activation d’oléfines et d’allènes non activés ainsi que de systèmes 1,3-diéniques. Ce type de méthodologie, à économie d’atomes maximale, a permis de limiter la formation de sous-produits, le catalyseur pouvant être recyclé et réutilisé sans perte d’activité. Des approches intra- et intermoléculaires, des réactions cascades et tandems ainsi qu’une étude mécanistique ont été effectuées afin de mieux comprendre la réactivité et ses limitations, et ainsi atteindre une plus large gamme de structures. Les méthodologies développées ont été appliquées au domaine des arômes et parfums pour la synthèse d’analogues de la Calone 1951®, de chromanes, d’indanes et de tétralines fonctionnalisés, posant les bases de travaux futurs pour une meilleur compréhension des relations structures-odeurs / Efficient and ecofriendly synthetic methodologies have always constituted an important area of research in modern organic chemistry. Lewis superacid catalysis has contributed in the improvement of many synthetic processes. We have developed some cycloisomerization reactions including Friedel-Crafts type reaction, giving access to a set of interesting polycyclic structures with good yields and selectivities. The use of a catalytic amount of Bi(OTf)3 (1 to 10 mol%), has allowed the activation of olefins, non-activated allenes and of 1,3-dienic systems. This atom economy methodology can prevent the formation of by-products and the catalyst can be recycled without loss of activity. Intra- and intermolecular approaches, tandem and cascades reactions, as well as mechanistic studies were conducted to enable a better understanding of the reactivity and its limitations to reach a wider range of structures. The developed methodologies were applied to the field of flavors and fragrances in the synthesis of Calone 1951® analogues, and for the preparation of chromans, indanes and tetralins type functionalized structures, for a better understanding of the structure/odor relationship.

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