Fluorinated chiral secondary amines as catalysts for epoxidation of olefins with oxone.
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.
Ho
Chun-Yu
CY
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China.
Chen
Ying-Chun
YC
Wong
Man-Kin
MK
Yang
Dan
D