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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

Metal template synthesis of hard-to-access mechanically interlocked molecules

Wu, Jhenyi January 2013 (has links)
The construction of mechanically interlocked molecules has been the subject of decades of research. The efficiency of strategies for preparing these molecules has increased continuously. In recent years, the transition metal templation strategy has played quite a remarkable role in the synthesis of entwined or mechanically bonded structures due to the metals’ diverse coordination chemistry and ability to chelate ligands. In the early stages of this method’s development, the metal ions were used as integral part of the scaffold for such components as rings and stoppers to generate the interlocked structures. In newly developed active metal templation strategies, metal ions are used to promote covalent bond forming reactions while simultaneously acting as structural supports. In this thesis, three main aspects are expanded for the discussion of the application of metal template strategies. First of all, the newly developed strategy - active metal template - will be described and exemplified using the Huisgen-Meldal-Fokin Cu(I)- catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC “click” reaction), the Cu(I)-mediated Cadiot-Chodkiewicz heterocoupling of an alkyne halide with a terminal alkyne, and the Ni(II)-catalyzed Csp3-Csp3 homocoupling reaction. Secondly, the thesis discusses the use of these strategies to obtain several hard-to-access structures, including the first high-yielding doubly threaded [3]rotaxanes, heterocircuitcatenanes and the one pot synthesis of homocircuit-catenanes, and the smallest molecular trefoil knot prepared to date. Lastly, as an extension of the metal temptation strategy, the final chapter of this thesis will discuss the assembly of inorganic metal-organic catenanes by metal coordination.
2

Mechanically interlocked architectures via active-metal template strategies

Hänni, Kevin D. January 2009 (has links)
In contrast to the classic ‘passive template’ approach, an ‘active-metal’ template strategy involves a metal centre which acts as both a template and the catalyst for covalent bond formation in the construction of mechanically interlocked architectures. The crucial formation of a covalent bond between two ‘half-threads’ is promoted by the catalyst and directed through the cavity of the macrocycle by the catalyst’s coordination requirements. The main attractive features of such a synthetic approach are the efficiency (as one step is required instead of two), the rapid assembly of inaccessible structures, the possibility of ‘traceless’ assemblies, the versatility, the possibility to use catalytic amount of the metal template and to provide mechanistic insight. This novel concept was successfully introduced by our group and applied to a wide range of well-known transition metal-catalysed reactions. The thesis will present several examples of active-metal template reactions for the synthesis of interlocked architectures, including Cu(I)-catalysed alkyne-azide cycloaddition (CuAAC popularised as the click reaction), Pd(II)-catalysed alkyne homocouplings Pd(II)-catalysed oxidative Heck cross-couplings and Lewis acids mediated Diels-Alder reactions.
3

Synthèse de [1]rotaxanes par la méthode de reconnaissance active pour le développement d'une polymérase artificielle autonome et adaptative / Synthesis of [1]rotaxanes by active metal template for the conception of an autonomous and adaptative artificial polymerase

Pairault, Noël 13 December 2016 (has links)
Cette thèse est consacrée à la mise au point d'une machine moléculaire artificielle sous la forme d'un [1]rotaxane, capable de synthétiser différents polymères de façon autonome. Au cours de cette étude, nous avons réalisé la première synthèse hautement diastéréosélective de [1]rotaxanes par la méthode de reconnaissance active catalysée au cuivre(I). Nous avons montré qu'un frein moléculaire est nécessaire pour assurer la stabilité de l'architecture entrelacée. De plus, l'utilisation d'un macrocycle avec une chaine latérale courte est indispensable pour favoriser la synthèse de lassos moléculaires. Enfin, le centre asymétrique du frein moléculaire guide la stéréosélectivité de la réaction. Ceci permet de faire la synthèse stéréodivergente de [1]rotaxanes à partir de macrocycles énantiomériquement purs. La seconde partie du projet concerne et de la processivité potentielle de ce type d'architecture moléculaire. Dans ce cadre, nous avons construit un [2]rotaxane présentant un stoppeur labile et une fonction thiol protégée sur la chaine latérale du macrocycle. La libération contrôlée du thiol induit la formation d'un [1]rotaxane piégé in situ par un nucléophile indiquant le potentiel de cette approche pour la conception de machines moléculaires fonctionnant de façon itérative. / This thesis is devoted to the development of an artificial molecular machine in the form of [1]rotaxane, designed to synthesize different kind of polymers autonomously. During this study, we accomplished the first highly diastereoselective synthesis of [1]rotaxanes by the copper(I)-catalysed active template method. We showed that a molecular brake was necessary to ensure the stability of the interlocked architecture. Moreover, the use of a short lateral chain of the macrocycle is essential to promote the synthesis of molecular lassos. Finally, the asymmetric center of the molecular brake induces the stereoselectivity of the reaction. This allows us to accomplish the stereodivergent synthesis of [1]rotaxanes from enantiomerically pure macrocycles. The second part of this project concerns the study of the potential processivity of this kind of molecular architecture. In this context, we built a [2]rotaxane which has a labile stopper and a protected thiol moiety on the lateral chain of the macrocycle. The controlled release of the thiol leads to the formation of a [1]rotaxane trapped in situ by a nucleophile, showing the potential of this approach for the design of molecular machines working processively.

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