Unprecedented Asymmetric Epoxidation of Isolated Carbon-Carbon Double Bonds by a Chiral Fluorous Fe(III) Salen Complex: Exploiting Fluorophilic Effect for Catalyst Design

The first asymmetric epoxidation of isolated carbon-carbon double bonds by a chiral salen complex using ubiquitous Fe(III) as a center-metal is described. By simultaneously introducing fluorous tags and tert-butyl groups into the ligand of the salen complex, asymmetric epoxidation is achieved. The fluorous tags act as both the electron-withdrawing groups, to improve the catalytic activity for oxidation, and the driving force to form a unique asymmetric stereo environment. Crystallographic analysis of the complex revealed that the catalyst has a distinctive umbrella structure based on intramolecular fluorophilic effect. This is the first example of asymmetric catalytic space construction that exploits fluorous space-interaction of neighboring fluorous tags.