Synthèse des ligands chiraux DiPPAM et évaluation de leurs complexes métalliques pour la formation de liaison C-C

De nouveaux ligands chiraux tridentates P,N,O, les sels de phosphinoazométhinylate (les DiPPAMs), ont été développés. Une chimiothèque de 8 ligands a été synthétisée en une seule étape, sans aucune purification et avec des rendements quantitatifs. Des applications des DiPPAMs pour les réactions de couplages C-C ont été développées. De hautes énantiosélectivités ont été obtenues pour des additions conjuguées-1,4 et -1,6 catalysées au cuivre. Par ailleurs, un complexe Pd/DiPPAM a été isolé et évalué pour la réaction de Tsuji-Trostsur des substrats symétriques et dissymétriques. Des bons ee ont été obtenus dans le premier cas et un dédoublement cinétique a été observé lors d applications sur des substrats portant deux substituants différents sur les carbones allyliques terminaux.New chiral P,N,O ligands, the phosphinoazomethinaylate salts (DiPPAMs) were developed. A library of 8 DiPPAM ligands was prepared in one-step synthesis, without any purification and in quantitative yields. Applications of DiPPAMs for C-C bond formations were investigated. High enantioselectivities were obtained for 1,4- and 1,6-copper catalyzed conjugate additions. Furthermore, an original Pd/DiPPAM complex was synthesized and evaluated for Tsuji-Trost reaction on symmetric and dissymmetric substrates. Good ee s were obtained in the first case and a kinetic resolution was observed in the case of substrates bearing two different substituents on the external allylic carbones.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Asymmetric allylic alkylation (chap. 4)

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Enantioselective 1,4-conjugate addition of diethylzinc to (E)-alkenyl aryl ketones catalysed by Cu/DiPPAM complex

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Chiral phosphinoazomethinylate salts as new ‘one-step available’ ligands for copper-catalyzed asymmetric conjugate addition

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Copper-Catalyzed Asymmetric Conjugate Additions of Bis(pinacolato)diboron and Dimethylzinc to Acyl- N -methylimidazole Michael Acceptors: A Highly Stereoselective Unified Strategy for 1,3,5,... n (OH, Me) Motif Synthesis

International audienceA unified strategy for the construction of prevalent 1,3,5,...n (OH, Me) motifs based on consecutive copper-catalyzed asymmetric conjugate borylation (ACB) and methylation (ACA) reactions involving α,β-unsaturated 2-acyl-N-methylimidazoles is described. Good yields and high diastereoselectivities have been obtained in ACA and ACB reactions for both matched and mismatched pairs as illustrated in the synthesis of syn/anti and anti/anti (Me, OTBS,Me) and (OH, OTBS, Me) motifs

Non covalent immobilization of pyrene-tagged ruthenium complexes onto graphene surfaces for recycling in olefin metathesis reactions

International audienceSynthesis of Hoveyda-type ruthenium complexes, modified by pyrene tags on the NHC ligand and/or the benzylidene moiety, is described. Thanks to non-covalent it-err interactions these new complexes were immobilized on carbon supports [reduced graphene oxide (rGO) or graphene] and their activity and recoverability for metatheses reactions have been studied. A SIPr-based complex possessing the pyrene function on the benzylidene ligand (C2) delivered the best results for the ring closing metathesis of diethyldiallyl malonate as benchmark reaction. The presence of additional pyrene-functionalized styrenyl-ether as ligand to the rGO-supported catalyst (C2/L@rGO) noticeably improved the recycling procedure allowing supplementary efficient catalytic runs. This may be due either to a facilitated boomerang effect or to a gradual release of the active species in solution. Finally, catalyst C2/L@rGO was proven to be successfully used to promote metathesis reactions in a multisubstrate procedure, the same supported catalyst batch being successively engaged to transform three different substrates, in diene and ene-yne RCM reactions

Readily Accessible Unsymmetrical Unsaturated 2,6-Diisopropylphenyl N-Heterocyclic Carbene Ligands. Applications in Enantioselective Catalysis

International audienceA new multicomponent procedure was applied to the synthesis of (a)chiral bulky unsymmetrical unsaturated 2,6-diisopropylphenyl N-heterocyclic carbene (NHC) precursors with excellent selectivity (up to 95%) and good yields. This approach offers access to new chiral NHC ligands, which have found successful applications in both copper-catalyzed asymmetric allylic alkylation and copper-catalyzed asymmetric borylation

Cyclic(alkyl)(amino)carbene Ruthenium Complexes for Z-Stereoselective (Asymmetric) Olefin Metathesis

The first Z-stereoselective catechodithiolate ruthenium complexes containing cyclic(alkyl)(amino)carbene ligands are reported. Isolated in nearly quantitative yields or in-situ generated, these catalysts demonstrated remarkable Z selectivity (Z/E ratio up to >98/2) in ring-opening metathesis polymerization (ROMP), ring-opening-cross metathesis (ROCM) and cross-metathesis (CM). Thanks to the efficient chiral HPLC resolution of racemic CAAC-complex precursors, optically pure dithiolated complexes were also synthesized allowing to produce enantioenriched Z-ROCM products in >99/1 Z/E with good levels of enantioselectivity