Aldehyde formation, phenoxyl radical

The catalytic mechanism of GOase has been extensively studied (Fig. 8) 63,64). The primary alcohol first coordinates to the active species A, leading to the formation of the metal-phenoxyl radical complex B. This species undergoes proton abstraction from the substrate by the axial tyrosinate (Tyr495), followed by a rapid intramolecular electron transfer from the intermediate ketyl radical anion with reduction of Cu to Cul The copper(I) species C reacts with dioxygen to form the hydroperoxo copper(II) complex D with the liberation of the aldehyde. Finally, dihydrogen peroxide is released to give back the active form of the enzyme. 

To mimic the function of GAO, a large number of copper(II)-phenoxide complexes have been synthesized, and these catalyze the aerobic oxidation of alcohols to aldehydes and/or ketones via formation of intermediate Cu(II)-phenoxyl radical complexes, followed by production of H2O2 as a coproduct. Stack and coworkers reported the first functional models (Fig. 11) (116,117). Wieghardt and co-workers reported on a dinuclear Cu(II)-phenoxyl complex, which can catalyze the oxidation of primary alcohols as well as secondary alcohols to ketones (118). Futhermore, Wieghardt and co-workers have synthesized various mononuclear copper complexes with imino-, thio-, and semiquinonate ligands, which affect similar chemistry (118-120). 

---