Helical Chiral N-Heterocyclic Carbene Ligands in Enantioselective Gold Catalysis |
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| Authors: | Dr Lenka Pallova Dr Laura Abella Marion Jean Dr Nicolas Vanthuyne Cécile Barthes Dr Laure Vendier Prof Jochen Autschbach Dr Jeanne Crassous Dr Stéphanie Bastin Dr Vincent César |
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| Institution: | 1. LCC-CNRS, Université de Toulouse, CNRS, Toulouse, France;2. Department of chemistry, University at Buffalo-State University of New York, Buffalo, NY 14260 USA;3. Aix Marseille university, CNRS, Centrale Marseille, Ism2, Marseille, France;4. Institut des Sciences Chimiques de Rennes, UMR 6226, Institut de Physique de Rennes, UMR 6251, Campus de Beaulieu CNRS-Université de Rennes 1, 35042 Rennes Cedex, France |
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| Abstract: | The first chiral helicene-NHC gold(I) complexes efficient in enantioselective catalysis were prepared. The L-shaped chiral ligand is composed of an imidazo1,5-a]pyridin-3-ylidene (IPy) scaffold laterally substituted by a configurationally stable 5]-helicenoid unit. The chiral information was introduced in a key post-functionalization step of a NHC-gold(I) complex bearing a symmetrical anionic fluoreno5]helicene substituent, leading to a racemic mixture of complexes featuring three correlated elements of chirality, namely central, axial and helical chirality. After HPLC enantiomeric resolution, X-ray crystallography and theoretical calculations enabled structural and stereochemical characterization of these configurationally stable NHC-gold(I) complexes. The high potential in asymmetric catalysis is demonstrated in the benchmark cycloisomerization of N-tethered 1,6-enynes with up to 95 : 5 er. |
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| Keywords: | asymmetric catalysis chirality gold helicenes N-heterocyclic carbenes |
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