title: Novel intramolecular cyclopropanation reaction of unsaturated beta-keto esters.
abstract: [reaction: see text] Fused cyclopropane beta-keto esters are versatile intermediates for the synthesis of many biologically active natural products. Here we report a new intramolecular cyclopropanation reaction of unsaturated beta-keto esters. In the presence of I(2), Et(3)N, and Lewis acids such as Mg(ClO(4))(2) and Yb(OTf)(3), beta-keto esters 1 bearing various olefin substituents were transformed to fused cyclopropanes 2 in a highly stereospecific manner with moderate to good yields. The mechanism of the reaction was also investigated.
authors.affiliation: Department of Chemistry, The University of Hong Kong, P R China. yangdan@hku.hk
authors.forename: Dan
authors.initials: D
authors.lastname: Yang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gao
authors.forename: Chi-Sing
authors.initials: CS
authors.lastname: Lee
authors.forename: Kung-Kai
authors.initials: KK
authors.lastname: Cheung