Partenaires et organisations internationales
(Anglais)
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AT, BE, DK, FI, FR, DE, EL, HU, IE, IT, LV, MT, NL, NO, PL, PT, RO, SI, ES, SE, CH, UK
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Résumé des résultats (Abstract)
(Anglais)
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The aim of this COST network is to find new catalysts and ligands for transition-metal catalyzed reactions. The range of studies go from new reactions, to mechanistic aspects as well as to synthetic ones. In this context, asymmetric synthesis and catalysis is of prime importance. Although emphasis is put on Cu, other metals, such as Ir, Ru, Rh and Pd are also examined. Our group has concentrated its efforts on the design and synthesis of new chiral phosphoramidite ligands. They are prepared by assembling an atropoisomerically flexible biphenol part with a chiral C2 symmetrical amine. A variety of such ligands have been synthesized and tested in two reactions: the Cu-catalyzed conjugate addition and the Cu-catalyzed allylic substitution. More recently, we have found that some of these ligands are also very efficient in the Ir-catalyzed allylic alkylation. The asymmetric conjugate addition needs dialkyl zinc as primary source of organometallics. We noticed that tralkyl aluminium may react equally well with cyclic and acyclic enones. Moreover, they allow the reaction on trisubstituted enones (ee's up to 96.6%), a result previously unattainable. In the allylic substitution, our reacting system (RMgX, 1% CuBr, 1% L*) was extended to other substrates with equal success (ee's up to 98%), and applied to the synthesis of (R)-Naproxen, a well known non-steroidal anti-inflammatory. One of our best phosphoramidite ligands has found a new application in the Ir-catalzyed allylic alkylation. Not only it affords higher regio- (>99:1) and enantioselectivities (>98%), but also have a much higher turnover, allowing the reaction to proceed at room temperature in a couple of hours. This new topic is presently actively studied and applications to the synthesis of natural products is underway.
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