title: Nonradical zinc-Barbier reaction for diastereoselective synthesis of vicinal amino alcohols.
abstract: A new protocol for the synthesis of vicinal amino alcohols is described. The method employs a Barbier-type reaction between an imine and 3-benzoyloxyallyl bromide in the presence of zinc metal. The addition products are debenzoylated to afford amino alcohols in good yields and with diastereomeric ratios greater than 85:15 in favor of the anti isomer. A Hammett study has been performed which strongly indicates that the allylation does not follow a radical mechanism, but instead an organometallic reagent is formed which subsequently reacts with the imine. A computational study based on this mechanism reproduces the observed diastereoselectivity with high accuracy, but only when a sufficiently large portion of the substrate is included.
authors.affiliation: Center for Sustainable and Green Chemistry, Department of Chemistry, Technical University of Denmark, Building 201, Kemitorvet, DK-2800 Lyngby, Denmark.
authors.forename: Lise
authors.initials: L
authors.lastname: Keinicke
authors.forename: Peter
authors.initials: P
authors.lastname: Fristrup
authors.forename: Per-Ola
authors.initials: PO
authors.lastname: Norrby
authors.forename: Robert
authors.initials: R
authors.lastname: Madsen