Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes |
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| Authors: | Jonathan Becker Puneet Gupta Dr. Friedrich Angersbach Prof. Dr. Felix Tuczek Prof. Dr. Christian Näther Prof. Dr. Max C. Holthausen Prof. Dr. Siegfried Schindler |
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| Affiliation: | 1. Institut für Anorganische und Analytische Chemie, Justus‐Liebig‐Universit?t Gie?en, Heinrich‐Buff‐Ring 58, 35392 Gie?en (Germany);2. Institut für Anorganische und Analytische Chemie, Johann Wolfgang Goethe‐Universit?t Frankfurt, Max‐von‐Laue‐Strasse?7, 60438 Frankfurt am Main (Germany);3. Current address: Max‐Planck‐Institute für Kohlenforschung, Kaiser‐Wilhelm‐Platz?1, 45470 Mülheim an der Ruhr (Germany);4. Universit?t Hamburg, Fachbereich Chemie, Martin‐Luther‐King‐Platz 6, 20146 Hamburg (Germany);5. Institut für Anorganische Chemie, Christian‐Albrechts‐Universit?t zu Kiel, Max‐Eyth‐Strasse?2, 24118 Kiel (Germany) |
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| Abstract: | The formation of a bis(μ‐oxido)dicopper complex with the ligand 2‐(diethylaminoethyl)‐6‐phenylpyridine (PPN) and its subsequent hydroxylation of the pendant phenyl group (studied earlier by Holland et al., Angew. Chem. Int. Ed. 1999 , 38, 1139–1142) has been reinvestigated to gain a better understanding of such systems in view of the development of new synthetic applications. To this end, we prepared a simple copper imine complex system that also affords selective o‐hydroxylation of aromatic aldehydes by using dioxygen as the oxidant: Applying the ligand N′‐benzylidene‐N,N‐diethylethylenediamine (BDED), salicylaldehyde was prepared in good yields and we show that this reaction also occurs through an intermediate bis‐μ‐oxido copper complex. The underlying reaction mechanism for the PPN‐supported complex was studied at the BLYP‐D/TZVP level of density functional theory and the results for representative stationary points along reaction paths of the BDED‐supported complex reveal a closely related mechanistic scenario. The results demonstrate a new facile synthetic way to introduce OH groups into aromatic aldehydes. |
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| Keywords: | aldehydes copper density functional calculations hydroxylation transition states |
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