Browsing by Author "Godard, Cyril"
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Item Highly Efficient Rh-catalysts Immobilised by π-π Stacking for the Asymmetric Hydroformylation of Norbornene under Continuous Flow Conditions(2019-04-18) Cunillera, Anton; Blanco, Carolina; Gual, Aitor; Marinkovic, Jakob Maximilian; Garcia-Suarez, Eduardo J.; Riisager, Anders; Claver, Carmen; Ruiz, Aurora; Godard, Cyril; Tecnalia Research & InnovationThe application of C1-symmetrical diphosphite ligands containing furanose backbone in the Rh-catalysed asymmetric hydroformylation of norbornene is described. The catalysts were highly active and produced exclusively exo-norbornanecarboxaldehyde with enantioselectivities (ee) up to 71 %. Considering these promising results, the ligands were modified with a pyrene moiety to accomplish their immobilisation onto carbon materials. The corresponding Rh complexes bearing the novel pyrene-tagged ligands were synthesised and immobilised onto multiwalled carbon nanotubes (MWCNT), reduced graphene oxide (rGO) and carbon beads (CBs). The novel catalytic systems were tested in the asymmetric hydroformylation of norbornene providing similar performance in terms of both activity and selectivity compared to the non-immobilised systems. The recyclability of the new heterogenised catalysts was studied in the target reaction in batch mode. Nevertheless, the recycling was unsuccessful due to catalyst leaching. When used under continuous flow mode, these catalysts revealed robust and provided even higher ee than the corresponding homogeneous systems.Item Selective Oxidative Carbonylation of Aniline to Diphenylurea with Ionic Liquids(2018-06-07) Zahrtmann, Nanette; Claver, Carmen; Godard, Cyril; Riisager, Anders; Garcia-Suarez, Eduardo J.; Tecnalia Research & InnovationA catalytic system for the selective oxidative carbonylation of aniline to diphenylurea based on Pd complexes in combination with imidazolium ionic liquids is presented. Both oxidants, Pd complexes, and ionic liquids affect the activity of the reaction, and the choice of oxidant determines the selectivity of the reaction. Together they allow the reaction to proceed under comparatively mild conditions without a loss of activity. Examination of the reaction by use of in situ NMR spectroscopy allowed us to observe an intermediate suggested only previously, which supported the proposed mechanism.