A TEMPO-Free Copper-Catalyzed Aerobic Oxidation of Alcohols

The copper‐catalyzed aerobic oxidation of primary and secondary alcohols without an external N‐oxide co‐oxidant is described. The catalyst system is composed of a Cu/diamine complex inspired by the enzyme tyrosinase, along with dimethylaminopyridine (DMAP) or N‐methylimidazole (NMI). The Cu catalyst system works without 2,2,6,6‐tetramethyl‐l‐piperidinoxyl (TEMPO) at ambient pressure and temperature, and displays activity for un‐activated secondary alcohols, which remain a challenging substrate for catalytic aerobic systems. Our work underscores the importance of finding alternative mechanistic pathways for alcohol oxidation, which complement Cu/TEMPO systems, and demonstrate, in this case, a preference for the oxidation of activated secondary over primary alcohols. That's (non)radical: The employment of a tyrosinase‐based biomimetic catalyst led to the efficient oxidation of various alcohols (including secondary aliphatic ones) at ambient temperature, without the use of a radical co‐oxidant. The unique catalyst system provides complementary selectivity to previously described Cu‐based systems. DMAP=dimethylaminopyridine.