title: Fluorinated chiral secondary amines as catalysts for epoxidation of olefins with oxone.
abstract: We have synthesized a series of chiral cyclic secondary amines having different substitution patterns and have screened them as catalysts for the asymmetric epoxidation of olefins using Oxone. The highest enantiomeric excess (61%) occurred for the epoxidation of 1-phenylcyclohexene catalyzed by a secondary amine bearing a fluorine atom at the beta-position relative to the amino center. Our experimental results provide further support to the notion that the amine plays a dual role--as a phase transfer catalyst and an Oxone activator--in these epoxidation reactions. The slightly acidic reaction conditions we employed in this work obviate the need to preform ammonium salts, which are the actual catalysts that mediate the epoxidations.
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China.
authors.forename: Chun-Yu
authors.initials: CY
authors.lastname: Ho
authors.forename: Ying-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Man-Kin
authors.initials: MK
authors.lastname: Wong
authors.forename: Dan
authors.initials: D
authors.lastname: Yang