Trinuclear Non-Heme Iron Complexes Based on 4-Substituted 2,6-Diacylpyridine Ligands as Catalysts in Aerobic Allylic Oxidations

Authors

  • Volker Rabe,

    1. Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, DE-70569 Stuttgart, (phone: +49-711-685-64565; fax: +49-711-685-64285)
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  • Wolfgang Frey,

    1. Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, DE-70569 Stuttgart, (phone: +49-711-685-64565; fax: +49-711-685-64285)
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  • Angelika Baro,

    1. Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, DE-70569 Stuttgart, (phone: +49-711-685-64565; fax: +49-711-685-64285)
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  • Sabine Laschat

    Corresponding author
    1. Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, DE-70569 Stuttgart, (phone: +49-711-685-64565; fax: +49-711-685-64285)
    • Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, DE-70569 Stuttgart, (phone: +49-711-685-64565; fax: +49-711-685-64285)
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Abstract

Taking the regio- and chemoselectivities of our iron complex precursors with pyridine core in aerobic oxidations into account, we envisioned a more effective influence on catalytic properties by the introduction of different substituents in 4-position of the pyridine moiety. The synthesis of these novel 4-substituted (pyridine-2,6-diyl)dipropanoic acids 4 is described. Analogously to the unsubstituted derivative, ligands 4 reacted with Fe(ClO4)3 to form trinuclear Fe3(μ3-O) complexes 3, which were tested in the aerobic Gif-type oxidation of α-pinene to myrtenol, verbenone, myrtenal, and pinene oxide. The electronic nature of the substituents was found to slightly effect the ratio of allylic oxidation/epoxidation, whereas its influence on the oxidation preference of secondary to primary C[BOND]H bonds is negligible as compared to the unsubstituted complex.

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