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Lanthanum-Catalyzed Asymmetric Cyclopropanation
H. Kakei, T. Sone, Y. Sohtome, S. Matsunaga*, M. Shibasaki*
The University of Tokyo, Japan
23 January 2008 (online)
The authors describe a catalytic asymmetric Corey-Chaykovsky cyclopropanation of enones with dimethyloxosulfonium methylide. The catalytic system is a lanthanum complex with lithium atoms and chiral BINOL-type ligands. The scope is broad and trans adducts are the sole isomers obtained in all cases. In a competition between double bonds of varying electronic properties, the reaction is highly chemoselective for the more electron-deficient olefin.