title: Asymmetric cyclization of omega-formyl-1,3-dienes catalyzed by a zerovalent nickel complex in the presence of silanes.
abstract: A nickel(0)-catalyzed asymmetric cyclization of omega-formyl-1,3-diene in the presence of silanes in which five- or six-membered carbocycles or pyrrolidine derivatives were afforded up to 86% ee by the use of (2R,5R)-2,5-dimethyl-1-phenylphospholane as a monodentate chiral ligand was investigated. The reaction course of this asymmetric cyclization can be explained for by two possible mechanisms: one in which the cyclization proceeds via a pi-allylnickel intermediate to produce a cyclized product having an internal olefin in the side chain, and one in which the cyclization proceeds via a sigma bond metathesis of silane and the nickel-oxygen bond of oxanickelacycle to produce a cyclized compound having a terminal olefin and/or an internal olefin in the side chain. It was speculated that both of these mechanisms operate in this asymmetric cyclization depending upon the nature of silanes and the reaction conditions.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sato
authors.forename: Nozomi
authors.initials: N
authors.lastname: Saito
authors.forename: Miwako
authors.initials: M
authors.lastname: Mori