title: Stereoselective construction of halogenated quaternary stereogenic centers via catalytic asymmetric Diels-Alder reaction.
abstract: Highly enantioselective Diels-Alder reactions of alpha-halo-alpha,beta-unsaturated ketones with Lewis acid-activated chiral oxazaborolidine 1 are described. The reaction with alpha-fluoroenones provided the corresponding cyclohexane derivatives having a fluorinated quaternary stereogenic center with up to 99% de and 94% ee. The reaction with alpha-bromo cyclic enones provided the corresponding bromo bicyclic adducts with up to 99% de and 95% ee. A brominated cis-fused bicyclic adduct derived from 2-bromocyclopenten-1-one and Dane's diene was converted to the trans-fused bicyclic system via reductive alkylation with the bulky aluminum reagent aluminum tris(2,6-diphenylphenoxide) (ATPH). With this process, formal syntheses of (+)-estrone and norgestrel have been demonstrated.
authors.affiliation: Department of Materials Science, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan. shiba@tutms.tut.ac.jp
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Shibatomi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Futatsugi
authors.forename: Fumito
authors.initials: F
authors.lastname: Kobayashi
authors.forename: Seiji
authors.initials: S
authors.lastname: Iwasa
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamamoto
mesh_terms: D000478:Alkylation; D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D003510:Cyclohexanes / Q000737:chemistry; D054879:Halogenation; D007659:Ketones / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013256:Steroids / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D003510:Cyclohexanes; D007659:Ketones; D013256:Steroids; C506365:Cyclohexane; D002244:Carbon