Chiral Nitroxide/Copper‐Catalyzed Aerobic Oxidation of Alcohols: Atroposelective Oxidative Desymmetrization

Abstract A series of chiral imidazolidinone‐based hydroxylamines were evaluated as catalysts for the aerobic oxidation of alcohols in the presence of Cu I OTf/bpy/NMI as co‐catalysts. In such conditions, the in situ produced nitroxides catalyze the oxidation of benzylic alcohols. When the imidazolidinone ring is substituted by a copper‐coordinating heterocycle, the outcome of the oxidation is clearly improved in terms of rate and maximal conversion. Enantiopure catalysts featuring a bipyridine unit covalently attached in close vicinity to the hydroxylamine could be readily prepared and used in the enantioselective aerobic oxidation of three model axially‐prochiral diols. These results demonstrate for the first time the validity of a O 2 /chiral nitroxide/copper combination for enantioselective oxidations.