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Desymmetrization of Cyclohexanones Catalyzed by Chiral Ionic Liquids
S. Luo*, L. Zhang, X. Mi, Y. Qiao, J.-P. Cheng*
Institute of Chemistry, Chinese Academy of Sciences, Beijing and Nankai University, Tianjin, P. R. of China
23 January 2008 (online)
An organocatalytic desymmetrization of 4-substituted cyclohexanones (1) via Michael addition to nitroolefins (2) has been developed. Ketones 1 react with aromatic nitroalkenes 2 in the presence of chiral ionic liquid 3 (15 mol%) and salicylic acid (5 mol%) to give adducts of type 4 in high yields, diastereoselectivities and enantioselectivities. This transformation presumably proceeds via an enamine intermediate. A transition state illustrating the mode of face shielding by the imidazolium moiety to explain the observed relative and absolute configuration is proposed.