Département de chimie moléculaire

A series of chiral imidazolidinone-based hydroxylamines e.g., I were evaluated as catalysts for the aerobic oxidn. of benzyl alc./axially-prochiral diols 2,6-(CH₂OH)₂C₆H₃X [X = 2-F₃CC₆H₄, 2-(CH₃)₃C-6-H₃CC₆H₃O, 1-naphthyl] in the presence of CuOTf/bpy/NMI as co-catalysts. In such conditions, the in situ produced nitroxides catalyze the oxidn. of benzyl alc. When the imidazolidinone ring is substituted by a copper-coordinating heterocycle, the outcome of the oxidn. 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 prepd. and used in the enantioselective aerobic oxidn. of three model axially-prochiral diols. These results demonstrate for the first time the validity of a O₂/chiral nitroxide/copper combination for enantioselective oxidns.