Selective CF Bond Activation in 1,1‐Difluorocyclopropanes: Synthesis of Functionalized Monofluoroalkenes

Functionalized monofluoroalkenes (3‐arylated and 5‐oxygenated 1‐aryloxy‐2‐fluoro‐1‐alkenes) are synthesized via selective activation of the CF bonds in 2‐aryloxy‐1,1‐difluorocyclopropanes that are readily prepared from aryl vinyl ethers. Treatment of these difluorocyclopropanes with Me 2 AlCl promotes fluoride abstraction followed by cyclopropane ring opening to generate α,β‐unsaturated oxocarbenium ions. These cations are subsequently trapped with nucleophiles, such as arenes and silyl enol ethers (Friedel–Crafts‐ and aldol‐type reactions), to provide functionalized 2‐fluoro‐1‐alkenes. Because of the instability of vinyl cations, further fluoride abstraction is suppressed, resulting in completely selective CF bond activation.