Development of new and efficient copper(<scp>ii</scp>) complexes of hexyl bis(pyrazolyl)acetate ligands as catalysts for allylic oxidation
Serena Gabrielli, Maura Pellei, Iole Venditti, Ilaria Fratoddi, Chiara Battocchio, Giovanna Iucci, Irene Schiesaro, Carlo Meneghini, Alessandro Palmieri, Enrico Marcantoni, Luca Bagnarelli, Riccardo Vallesi, Carlo Santini
Abstract
In this study, two new hexyl bis(pyrazol-1-yl)acetate ligands and related copper(ii) complexes were prepared and fully characterized in the solid state and in solution. Their electronic and molecular structures were investigated by X-ray photoelectron spectroscopy and near edge X-ray absorption; their ligand molecular structural stability upon coordination to copper was also investigated. The Cu(ii) complexes were studied as new catalysts in copper-catalyzed C-H oxidation for allylic functionalization (the Kharasch-Sosnovsky reaction) avoiding the use of any external reducing agents. Using 5 mol% of these catalysts and tert-butylperoxybenzoate as the oxidant, allylic benzoates were obtained in up to 90% yield: the general reaction time was decreased to 6 h and a 5 to 1 ratio of the alkene and tert-butylperoxybenzoate was used to overcome the two most important limitations on their use in chemistry.