Electrophilic Fluorination of Silyl Dienol Ethers: a General and Selective Access to -Fluoro Enals

We describe the direct synthesis of gamma-fluoro enals from the corresponding silyl dienol ethers. This simple process operates under mild conditions and is compatible with a wide range of functionalities. The high gamma regioselectivity of this protocol was rationalized by means of theoretical calculations. The first general synthesis of gamma-fluoro alpha,beta-unsaturated aldehydes was achieved from the corresponding silyl dienol ethers and N-fluorobenzenesulfonimide (NFSI). The complete selectivity towards the gamma position was rationalized thanks to DFT calculations.image