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Transition-State Stabilization by a Secondary Substrate–Ligand Interaction: A New Design Principle for Highly Efficient Transition-Metal Catalysis

Authors

  • Tomáš Šmejkal,

    1. Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg (Germany), Fax: (+49) 761-2038715
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  • Denis Gribkov,

    1. Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg (Germany), Fax: (+49) 761-2038715
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  • Jens Geier,

    1. Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg (Germany), Fax: (+49) 761-2038715
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  • Manfred Keller,

    1. Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg (Germany), Fax: (+49) 761-2038715
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  • Bernhard Breit

    1. Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg (Germany), Fax: (+49) 761-2038715
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Abstract

A library of monodentate phosphane ligands, each bearing a guanidine receptor unit for carboxylates, was designed. Screening of the library gave some excellent catalysts for regioselective hydroformylation of β,γ-unsaturated carboxylic acids. A terminal alkene, but-3-enoic acid, was hydroformylated with a linear/branched (l/b) regioselectivity up to 41. An internal alkene, pent-3-enoic acid was hydroformylated with regioselectivity up to 18:1. Further substrate selectivity (e.g., acid vs. methyl ester) and reaction site selectivity (monofunctionalization of 2-vinylhept-2-enoic acid) were also achieved. Exploration of the structure–activity relationship and a practical and theoretical mechanistic study gave us an insight into the nature of the supramolecular guanidinium–carboxylate interaction within the catalytic system. This allowed us to identify a selective transition-state stabilization by a secondary substrate–ligand interaction as the basis for catalyst activity and selectivity.

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