Aerobic oxidation of lignin model compounds catalyzed by the iron or copper/ABNO at room temperature with ambient air as the oxidant

Herein, we report a simple, efficient, and mild Fe(NO₃)₃·9H₂O or Cu(NO₃)₂·3H₂O/ABNO- catalytic system (ABNO=9-azabicyclo[3.3.1]nonane-N-oxyl), which was capable of oxidizing β-O-4 alcohol lignin model compounds to ketones at room temperature using ambient air as the oxidant. This versatile catalytic system exhibits excellent substrate scope and the corresponding products were obtained in good to excellent yields. The kinetic isotope effect shows that the CH bond breaking is the rate-determining step of the reaction. The experiment of gram scale proves that the catalytic system has good practicability.