Influence of Achiral Phosphine Ligands on a Synergistic Organo- and Palladium-Catalyzed Asymmetric Allylic Alkylation |
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| Authors: | Dr David McLeod Dr Nicolaj Inunnguaq Jessen Dr Thanh V Q Nguyen Marcus Espe Dr Jeremy David Erickson Prof Dr Karl Anker Jørgensen Prof Dr Limin Yang Prof Dr K N Houk |
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| Institution: | 1. Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark;2. College of Materials, Chemistry and Chemical Engineering, Hangzhou Normal University, 311121 Hangzhou, P. R. China;3. Department of Chemistry and Biochemistry, Department of Biochemical and Biomolecular Engineering, University of California, 90095 Los Angeles, California, USA |
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| Abstract: | An unusual diastereodivergent stereoselective allylation reaction is presented. It consists of a palladium-catalyzed allylation reaction of an organocatalytically generated amino isobenzofulvene, where the diastereoselectivity is controlled by the electronic properties of a monodentate, achiral ligand on palladium. One major diastereoisomer is formed using triarylphosphines substituted with neutral or electron-donating substituents of the aryl group, while those with electron-withdrawing substituents favor the other diastereoisomer. The diastereoselectivity correlates with the Taft inductive parameter of substituents on the triarylphosphine ligand on palladium. The synergistic reaction involves both a catalytic secondary amine catalyst for the indene-aldehyde activation and the monodentate phosphine ligands on palladium, affording a highly enantioselective reaction with up to 98 % enantiomeric excess. Based on computational investigations, the role of the monodentate phosphine ligand on the diastereoselectivity is discussed. |
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| Keywords: | allylic alkylation asymmetric synthesis DFT calculations mechanism synergistic catalysis |
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