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Recyclage de complexes bis(oxazolines)- cuivre chiraux pour la catalyse asymétrique : hétérogénéisation par interactions non-covalentes

Abstract : Chiral bis(oxazolines) associated to various metallic salts have been described as very powerful ligands for the catalytic C-C bond formation. The use of these chiral complexes as asymmetric catalysts allows for scalemic preparation of a wide range of functionalized synthons for the preparation of biologically active compounds. However, an important catalytic amount (around 10 mol%) is often needed to obtain high yields and enantioselectivities. Recycling these complexes can be interesting in terms of cost reduction and increase of the turn-over of these enantioselective reactions.These bisoxazolines were designed to allow recycling of the catalyst by heterogeneization thanks to a new methodology involving the formation of charge transfer complexes (CTC). This non-covalent interaction, linking the anthracenyle moiety and the trinitrofluorenone leads to precipitation of the catalytic species as a CTC due to the addition of pentane. This procedure has successfully been applied to the Diels-Alder reaction with copper complexes and we then endeavoured to carry out other transformations in order to broaden the scope of our methodology. We therefore attempted to carry out nitroaldolizations, carbonyle-ene and cyclopropanations reactions, both in mono- and multi-substrates procedures and in an original multi-reaction concept. Yields and enantioselectivities obtained with these new chiral catalysts compared satisfactorily with described homogeneous conditions. In the most cases, the CTC proved to be highly stable over the course of its different reuses.New supports allowing for CTC formation or π interactions have been prepared and tested in order to avoid having to precipitate the catalyst with pentane for recovery. This type of catalyst was subjected to the same, previously mentioned, reactions with modified supports such as polystyrene, silica or charcoal. These modifications made for efficient homogenous catalytical systems, whilst conserving high yields and enantioselectivities.
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Dorian Didier. Recyclage de complexes bis(oxazolines)- cuivre chiraux pour la catalyse asymétrique : hétérogénéisation par interactions non-covalentes. Autre. Université Paris Sud - Paris XI, 2011. Français. ⟨NNT : 2011PA112215⟩. ⟨tel-00856579⟩



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