Lanthanum-Catalyzed Asymmetric Cyclopropanation

Significance

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.