A Highly Regio- and Stereoselective Synthesis of α-Fluorinated Imides via Fluorination of Chiral Enamides

A highly pi-facial selective and regioselective fluorination of chiral enamides is described. The reaction involves an enantioselective fluorination exclusively at the electron-rich enamide olefin with N-F reagents such as Selectfluor and N-fluoro-benzenesulfonimide [NFSI] accompanied by trapping of the beta-fluoro-iminium cationic intermediate with water. The resulting N,O-hemiacetal could be oxidized using Dess-Martin periodinane, leading to an asymmetric sequence for syntheses of chiral a-fluoro-imides and optically enriched a-fluoro-ketones.