Ligands carbènes N-hétérocycliques fonctionnalisés chiraux pour les réactions de couplage C-C asymétriques

L'accès à de nouvelles molécules bioactives nécessite des méthodologies de synthèse permettant l'obtention privilégiée d'un seul énantiomère. La catalyse asymétrique en général et la réaction de Suzuki-Miyaura asymétrique en particulier s'inscrivent dans cette démarche. Notre projet s'axe dans cette thématique, dans l'optique de développer de nouveaux catalyseurs chiraux pour la réaction de Suzuki-Miyaura asymétrique. Deux familles de complexes de palladium à ligands ferrocéniques chiraux bifonctionnels NHC/phosphine et NHC/amine ont été développés. La première famille de complexes a été synthétisée, caractérisée et utilisée dans la catalyse de la réaction de Suzuki-Miyaura asymétrique. L'accès à une deuxième famille de complexes à ligands hémilabiles NHC/amine a été possible via une voie de synthèse originale. De plus, un carbène libre imidazol-2-ylidène directement lié au ferrocène a été isolé et caractérisé. Enfin, dans l'objectif de développer de nouveaux catalyseurs électrochimiquement actifs, de nouveaux composés macrocycliques de type phthalocyanine présentant des unités ferrocéniques au sein de leur système pi ont été synthétisés.The access to new biologically active molecules requires synthetic methodologies that could allow the synthesis of only one enantiomer. Asymmetric catalysis in general and asymmetric Suzuki-Miyaura coupling in particular are part of this strategy. Our purpose in this field is to develop new chiral catalysts for the asymmetric Suzuki-Miyaura reaction. Two families of palladium complexes bearing chiral bifunctional ferrocenyl NHC/phosphine and NHC/amine ligands have been developed. The first family of complexes has been synthesised, fully characterised and used as catalysts for the asymmetric version of the Suzuki-Miyaura reaction. The second family of complexes bearing hemilabile NHC/amine ligands has been obtained via an original synthetic pathway. In addition, a free carbene directly connected to the ferrocenyl unit has been successfully isolated and characterised. Finally, in order to develop new redox-active catalysts, new phthalocyanine-type macrocycles containing ferrocenyl units fused in their pi system have been successfully synthesised

Synthesis and crystal structures of palladium complexes based on α\alpha -amino-oximes derived from (RR)-limonene and their application in allylic alkylation of 1,3-dioxo compounds

Coordination compounds Pd(L1)Cl$_{2}$, Pd(L2)Cl$_{2}$, and Pd(L3)Cl$_{2}$ have been synthesized from optically pure $\alpha$-amino-oxime ligands L1–L3 based on $(R)$-limonene. Structures of the new palladium complexes are characterized and described by NMR spectroscopy and X-rays. These $\alpha$-amino-oxime ligands were then evaluated in the palladium-catalysed allylation of 1,3-dioxo compounds

Synthesis and crystal structures of palladium complexes based on α\alpha -amino-oximes derived from (RR)-limonene and their application in allylic alkylation of 1,3-dioxo compounds

Coordination compounds Pd(L1)Cl$_{2}$, Pd(L2)Cl$_{2}$, and Pd(L3)Cl$_{2}$ have been synthesized from optically pure $\alpha$-amino-oxime ligands L1–L3 based on $(R)$-limonene. Structures of the new palladium complexes are characterized and described by NMR spectroscopy and X-rays. These $\alpha$-amino-oxime ligands were then evaluated in the palladium-catalysed allylation of 1,3-dioxo compounds

Synthesis of axially chiral biaryl compounds by asymmetric catalytic reactions with transition metals

International audienceAxially chiral biaryl structures are unique systems encountered in various synthetic compounds such as BINAP and BINOL, polymers, but also in natural products presenting a pharmaceutical interest such as Vancomycin, Steganacin or Korupensamine. The axial chirality of these products, so-called atropisomerism, is induced by the restricted rotation around the aryl–aryl bond. This review will summarize the different strategies imagined by chemists to control such chirality, focusing on asymmetric catalytic processes with transition metals. Only transition metal complexes bearing chiral ligands will be considered and the core of this review will consist of the enantioselective coupling of two achiral substrates

Bifunctional N-heterocyclic carbene ferrocenyl ligands - synthesis and palladium(II) complexes

International audienceTwo ferrocenylimidazolium tetrafluoroborate salts [R = Me, 7 and R = (2,4,6-trimethylphenyl), 8], precursors of new ferrocenylimidazol-2-ylidene bifunctional ligands, have been prepared for the first time. The free 1-(2-dimethylaminomethyl)ferrocenyl-3-methylimidazol-2-ylidene (12) was isolated and characterised by H-1 and C-13 NMR spectroscopy and represents the second example of an isolated and characterised imidazol-2-ylidene directly linked to ferrocene. Neutral (compound 13) and cationic (compound 14) palladium(II) complexes were obtained in moderate yields and characterised by H-1 and C-13 NMR spectroscopy and mass spectrometry

Caractérisations, Synthèses et propriétés catalytiques de complexes de Palladium et Molybdène coordinés par des ligands amino-oximes dérivés du (R)-limonène

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Synthesis and crystal structure of a new chiral alpha-aminooxime nickel(II) complex

International audienceA dinuclear nickel complex with (S)-limonene based amino­oxime ligand has been isolated and its crystal structure determined. The resolved structure of dichloridobis­{(2S,5R)-2-methyl-5-(prop-1-en-2-yl)-2-[(pyridin-2-yl)methyl­amino]­cyclo­hexan-1-one oxime}dinickel(II), [Ni2Cl2(C16H23ClN3O)2], at 100 K has monoclinic (P21) symmetry. The two NiII ions in the dinuclear complex are each coordinated in a distorted octa­hedral environment by three nitro­gen atoms, a terminal chloride and two μ bridging chlorides. Each oxime ligand is coordinated to nickel(II) by the three nitro­gen atoms, leading to two five-membered chelate rings, each displaying an envelope conformation. In the crystal, numerous inter­molecular and intra­molecular hydrogen bonds lead to the formation of a three-dimensional network structure

Palladium(ii) complexes with planar chiral ferrocenyl phosphane-(benz)imidazol-2-ylidene ligands

International audienceWe describe here the first examples of planar chiral ferrocenyl phosphane-benzimidazol-2-ylidene ligands and their coordination chemistry with palladium(ii). All ligand precursors, namely enantiopure ferrocenyl phosphane-(benz)imidazolium salts, and all enantiopure palladium complexes have been fully characterised by 1H, 31P and 13C NMR, mass spectrometry and X-ray diffraction methods for seven examples. The potential of these very bulky bidentate ligands in catalysis was evaluated and compared to their imidazol-2-ylidene analogues. The influence of sterics was shown to be non-negligible as the bulkiest ligand gave the lowest activities in the asymmetric Suzuki-Miyaura reaction

Ferreoelectricity in undoped ZnO nanorods

The technological interest in developing novel functional nano-objects that exhibit new properties arising from their nanoscopic nature is undoubtful. Although bulk ZnO is considered to be non-ferroelectric, herein, the ferroelectric behavior of undoped and self-standing ZnO nanoparticles is reported for the first time. The nanoparticles (NPs) under study are synthesized by an organometallic approach. When dispersed in a PMMA dielectric matrix, clear polarization loops and antisymmetric switching currents are recorded for the NPs with the larger volume, in coherence with the significant polar response of these NPs in solution, measured by polarization-resolved second harmonic scattering experiments. Structural characterizations reveal that ferroelectricity is related to the appearance of a new hexagonal crystalline phase, its unit cell being swelled with respect to the well-known wurtzite ZnO cell. The volume fraction of this new phase, the polar SHS response, and the amount of ferroelectric polarization response are all linearly linked, underlining the consistency between these complementary physical characterizations.IdEx Bordeau