Copper–Carbene Intermediates in the Copper‐Catalyzed Functionalization of OH Bonds

Copper–carbene [TpxCuC(Ph)(CO2Et)] and copper–diazo adducts [TpxCu{η1-N2C(Ph)(CO2Et)}] have been detected and characterized in the context of the catalytic functionalization of OH bonds through carbene insertion by using N2C(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.