Copper-Carbene Intermediates in the Copper-Catalyzed Functionalization of OH Bonds

• Published in: Chemistry : a European journal 2015-06, Vol.21 (27), p.9769-9775
• Main Authors: Pereira, Ana, Champouret, Yohan, Martín, Carmen, Álvarez, Eleuterio, Etienne, Michel, Belderraín, Tomás R., Pérez, Pedro J.
• Format: Article
• Language: English
• Subjects: Adducts; Carbenes; Catalysis; Catalysts; Chemical Sciences; Coordination chemistry; copper; diazo compounds; Displays; Insertion; Ligands; NMR spectroscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201500776

Copper–carbene [TpxCuC(Ph)(CO2Et)] and copper–diazo adducts [TpxCu{η1‐N2C(Ph)(CO2Et)}] have been detected and characterized in the context of the catalytic functionalization of OH bonds through carbene insertion by using N2C(Ph)(CO2Et) as the carbene source. These are the first examples of these type of complexes in which the copper center bears a tridentate ligand and displays a tetrahedral geometry. The relevance of these complexes in the catalytic cycle has been assessed by NMR spectroscopy, and kinetic studies have demonstrated that the N‐bound diazo adduct is a dormant species and is not en route to the formation of the copper–carbene intermediate. Copper–carbene complexes have been detected in the reaction of N2C(Ph)CO2Et with [TpMsCu(thf)], an intermediate relevant in the OH functionalization by carbene insertion (see scheme; TpMs=hydrotris(3‐mesityl)pyrazolylborate). The η1‐diazo adduct complex has also been characterized and determined to be the catalyst resting state during catalysis.