Teresa Corona1, Lídia Ribas1, Mireia Rovira1, Erik R Farquhar2, Xavi Ribas3, Kallol Ray4, Anna Company5. 1. Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, Campus Montilivi, E, 17003, Girona, Catalonia, Spain. 2. Case Western Reserve University Center for Synchrotron Biosciences and Center for Proteomics and Bioinformatics, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York, 11973, USA. 3. Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, Campus Montilivi, E, 17003, Girona, Catalonia, Spain. xavi.ribas@udg.edu. 4. Department of Chemistry, Humboldt Universität zu Berlin, Brook-Taylor Strasse 2, 12489, Berlin, Germany. kallol.ray@chemie.hu-berlin.de. 5. Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, Campus Montilivi, E, 17003, Girona, Catalonia, Spain. anna.company@udg.edu.
Abstract
High-valent terminal copper-nitrene species have been postulated as key intermediates in copper-catalyzed aziridination and amination reactions. The high reactivity of these intermediates has prevented their characterization for decades, thereby making the mechanisms ambiguous. Very recently, the Lewis acid adduct of a copper-nitrene intermediate was trapped at -90 °C and shown to be active in various oxidation reactions. Herein, we describe for the first time the synthesis and spectroscopic characterization of a terminal copper(II)-nitrene radical species that is stable at room temperature in the absence of any Lewis acid. The azide derivative of a triazamacrocyclic ligand that had previously been utilized in the stabilization of aryl-CuIII intermediates was employed as an ancillary ligand in the study. The terminal copper(II)-nitrene radical species is able to transfer a nitrene moiety to phosphines and abstract a hydrogen atom from weak C-H bonds, leading to the formation of oxidized products in modest yields.
High-valent terminal n class="Chemical">copper-nitrene species have been postulated as key inpan>termediates inpan> n class="Chemical">copper-catalyzed aziridination and amination reactions. The high reactivity of these intermediates has prevented their characterization for decades, thereby making the mechanisms ambiguous. Very recently, the Lewis acid adduct of a copper-nitrene intermediate was trapped at -90 °C and shown to be active in various oxidation reactions. Herein, we describe for the first time the synthesis and spectroscopic characterization of a terminal copper(II)-nitrene radical species that is stable at room temperature in the absence of any Lewis acid. The azide derivative of a triazamacrocyclic ligand that had previously been utilized in the stabilization of aryl-CuIII intermediates was employed as an ancillary ligand in the study. The terminal copper(II)-nitrene radical species is able to transfer a nitrene moiety to phosphines and abstract a hydrogen atom from weak C-H bonds, leading to the formation of oxidized products in modest yields.
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