title: Lewis Acid Promoted [2 + 1] Cycloaddition Reactions of 1-Seleno-2-silylethene with Tricarbonyl-Substituted Olefins.
abstract: The reactions of 1-seleno-2-silylethenes 1 with highly electrophilic tricarbonyl-substitued olefins in the presence of Lewis acids have been investigated. The reaction of 1-(phenylseleno)-2-(trimethylsilyl)ethene (1a) with tris(alkoxycarbonyl) olefins 2 or 1,1-bis(alkoxycarbonyl)-2-acyl olefins 3 in the presence of ZnBr(2) at -30 degrees C gave cis-substituted cyclopropanes exclusively. The origin of the cis stereochemistry is ascribed to the synclinal addition path of the ZnBr(2)-coordinated electrophilic olefin to 1. Application of the highly functionalized selenium- and silicon-substituted cyclopropane products to the preparation of a useful synthetic intermediate 20 for the pyrethroid class of insecticides is also demonstrated.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kumagai
authors.forename: Takashi
authors.initials: T
authors.lastname: Takada
authors.forename: Shinichi
authors.initials: S
authors.lastname: Yamabe
authors.forename: Kagetoshi
authors.initials: K
authors.lastname: Yamamoto