title: Catalytic asymmetric bromination and chlorination of beta-ketoesters.
abstract: The first general catalytic asymmetric bromination and chlorination of beta-ketoesters has been developed. The reactions proceed for both acyclic and cyclic beta-ketoesters catalyzed by chiral bisoxazolinecopper(II) complexes giving the corresponding optically active alpha-bromo- and alpha-chloro-beta-ketoesters in high yields and moderate to good enantioselectivities. For the optically active chlorinated products the isolated yields are in the range of 88-99 % and the enantiomeric excesses up to 77 % ee, while the optically active brominated adducts are formed in 70-99 % isolated yield and up to 82 % ee. Based on the absolute configuration of the optically active products, the face selectivity for the catalytic enantioselective halogenation is discussed based on a bidentate coordination of the beta-ketoester to the chiral catalyst and a X-ray structure of chiral alpha,gamma-diketoesterenolatebisoxazolinecopper(II) complex.
authors.affiliation: The Danish National Research Foundation: Center for Catalysis, Department of Chemistry, Aarhus University, 8000 Aarhus C, Denmark.
authors.forename: Mauro
authors.initials: M
authors.lastname: Marigo
authors.forename: Nagaswami
authors.initials: N
authors.lastname: Kumaragurubaran
authors.forename: Karl Anker
authors.initials: KA
authors.lastname: Jørgensen