title: Asymmetric cyclopropanation of chalcones using chiral phase-transfer catalysts.
abstract: The first phase-transfer catalyzed cyclopropanation reaction of chalcones using bromomalonates as the nucleophiles in a Michael Initiated Ring Closing reaction (MIRC) was developed. Key to success was the use of a free OH-containing cinchona alkaloid ammonium salt catalyst and carefully optimized liquid/liquid reaction conditions. The reaction performed well for electron neutral and electron deficient chalcones giving the products in yields up to 98% and with enantiomeric ratios up to 91:9.
authors.affiliation: Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria.
authors.forename: Richard
authors.initials: R
authors.lastname: Herchl
authors.affiliation: Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria.
authors.forename: Mario
authors.initials: M
authors.lastname: Waser
keywords: Bifunctional; Cinchona alkaloids; Cyclopropanes; Organocatalysis; Phase-transfer catalysis