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Complexes oléfiniques de titane : synthèse asymétrique et applications

Abstract : The Kulinkovich reaction, discovered in 1989, allows the titanium-mediatedtransformation of esters into cyclopropanols using Grignard reagents. This reaction wasextended to other substrates, notably nitriles which afford primary cyclopropylamines. First, a study of the asymmetric cyclopropanation of a cyanoester using a chiral titaniumcomplex has been carried out. A method allowing the fast assessment of the asymmetricinduction of chiral ligands has been worked out, and used to conduct a screening of chiraldiols. The best results were obtained with the original TADDOL, which furnished averageenantiomeric excesses, but our method remains an asset for the evaluation of other types ofchiral ligand.An original method for the formation of 1,4-diketones using an olefinic titanium complexhas been discovered, optimized, and explored. We established that 1,4-diketones are availablein two steps from carboxylic acids with modest to correct yields. The use of inexpensive andminimally toxic reagents as well as an access to a vast structural diversity allow our method tobe competitive beside those reported in literature.Several studies carried out previously by our team allowed the exclusive synthesis of the(Z) isomers of various 2,3-methanoaminoacids. In this present work, we developped asynthetic pathway towards (E) and (Z) isomers of orthogonaly protected 2,3-methanolysine,using the diastereoselective cyclopropanation of a benzylated cyanhydrin as key reaction. Theflexibility of this strategy allows to consider the preparation of (E) and (Z) isomers of variousother constrained aminoacid analogues.
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Paul Setzer. Complexes oléfiniques de titane : synthèse asymétrique et applications. Autre. Université du Maine, 2012. Français. ⟨NNT : 2012LEMA1007⟩. ⟨tel-00736642⟩

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