title: Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes.
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.
authors.affiliation: Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen (Germany).
authors.forename: Jonathan
authors.initials: J
authors.lastname: Becker
authors.affiliation: Institut für Anorganische und Analytische Chemie, Johann Wolfgang Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany).|Current address: Max-Planck-Institute für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr (Germany).
authors.forename: Puneet
authors.initials: P
authors.lastname: Gupta
authors.affiliation: Universität Hamburg, Fachbereich Chemie, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany).
authors.forename: Friedrich
authors.initials: F
authors.lastname: Angersbach
authors.affiliation: Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Strasse 2, 24118 Kiel (Germany).
authors.forename: Felix
authors.initials: F
authors.lastname: Tuczek
authors.affiliation: Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Strasse 2, 24118 Kiel (Germany).
authors.forename: Christian
authors.initials: C
authors.lastname: Näther
authors.affiliation: Institut für Anorganische und Analytische Chemie, Johann Wolfgang Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany). max.holthausen@chemie.uni-frankfurt.de.
authors.forename: Max C
authors.initials: MC
authors.lastname: Holthausen
authors.affiliation: Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen (Germany). siegfried.schindler@anorg.chemie.uni-giessen.de.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Schindler
keywords: aldehydes; copper; density functional calculations; hydroxylation; transition states