International audienceNew chiral nitroxides based on the imidazolidin-4-one skeleton, and the corresponding hydroxylamines, have been prepared from cyclic nitrones by a straightforward reaction sequence. They were evaluated as catalysts in the aerobic oxidation of benzyl alcohol using different co-catalysts. Both the imidazolidinone nitroxides and hydroxylamines were proven to catalyze the reaction, with the ring substituent having an effect depending on the co-catalytic system. In some cases, rapid oxidation to benzaldehyde was accomplished at room temperature under an atmospheric O2 pressure. Moreover, atroposelective desymmetrization was achieved during the aerobic oxidation of a diol catalyzed by an enantiopure imidazolidinone nitroxide. Finally, the electrochemical behavior of the new hydroxylamines and nitroxides was investigated by cyclic voltammetry, which gave insights into the observed catalytic properties
International audienceA series of chiral imidazolidinone-based hydroxylamines were evaluated as catalysts for the aerobic oxidation of alcohols in the presence of CuIOTf/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 O2/chiral nitroxide/copper combination for enantioselective oxidations
Imidazolidinone Nitroxides as Catalysts in the Aerobic Oxidation of Alcohols, en Route to Atroposelective Oxidative Desymmetrization. -(CARBO LOPEZ, M.; ROYAL, G.; PHILOUZE, C.; CHAVANT, P. Y.; BLANDIN*, V.; Eur. J. Org. Chem. 2014, 22, 4884-4896, http://dx.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.