title: Asymmetric Synthesis of Bicyclic Nitrocyclopropanes from Primary Nitro Compounds and Stereoselective Formation of Tetrahydro-2H-cyclopenta[b]furans via Ring Expansion/Cyclization Reaction.
abstract: Optically active bicyclic nitrocyclopropanes are readily prepared from primary chiral nitro compounds, prepared by the conjugate addition of propionaldehyde to a nitro alkene in the presence of proline-derived organocatalysts. The one-step cyclopropanation took place smoothly in a highly stereoselective manner regardless of the stereogenic center adjacent to the allylic unit. Although the allylation reaction catalyzed by BF3·OEt2 provides a mixture of two possible diastereomers, subsequent oxidation of the alcoholic carbon after the formation of nitrocyclopropanes gave diastereomerically pure single products. As a result, separation of the diastereomers during the reaction sequence is unnecessary. Baeyer-Villiger oxidation of the bicyclic nitrocyclopropane ketones followed by enolization resulted in stereoselective formation of a novel cyclopenta[b]furan ring in good yield via ring expansion followed by transannular nucleophilic cyclization.
authors.affiliation: Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University , Ube 755-8611, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Kamimura
authors.affiliation: Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University , Ube 755-8611, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Moriyama
authors.affiliation: Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University , Ube 755-8611, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University , Ube 755-8611, Japan.
authors.forename: Takuji
authors.initials: T
authors.lastname: Kawamoto
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Ehime University , Matsuyama 790-8577, Japan.
authors.forename: Hidemitsu
authors.initials: H
authors.lastname: Uno