Co-metal-free enantioselective conjugate addition reactions of zinc reagents |
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Authors: | Ay Sefer Nieger Martin Bräse Stefan |
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Institution: | Institute of Organic Chemistry, University of Karlsruhe (TH), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany. |
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Abstract: | Asymmetric conjugate addition of diethylzinc to cinnamaldehyde in a co-metal-free fashion by using N,O-ligands with planar and central chirality is described. Different modulations of the ligand structure, including several combinations of the chiral units, indicate that a 2.2]paracyclophane backbone is essential for the activity and the enantioselectivity of the generated active catalyst. By using the optimized ligand, an isolated yield of 90 % was obtained with up to 99 % ee. |
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Keywords: | asymmetric catalysis conjugate addition reactions enals N O‐ligands organozinc reagents |
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