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.