Difluorination of Functionalized Aromatic Olefins Using Hypervalent Iodine/HF Reagents

The hypervalent iodine/HF reagent consisting of PhIO and HF·py was found to be effective for fluorination of functionalized aromatic olefins bearing synthetically important carbonyl and hydroxyl groups. Fluorination of 1,3-diphenyl-2-propen-1-one with PhIO/HF·py reagent in CH₂Cl₂ at room temperature gave 3,3-difluoro-1,2-diphenyl-1-propanone in high yield. Other α-aryl-α,β-unsaturated ketones underwent the fluorination to yield aryl 2,2-difluoroethyl ketone derivatives in good to high yields. Catalytic fluorination of α-aryl-α,β-unsaturated ketones using a p-TolI/HF·py/mCPBA reagent system also worked well. Moreover, the fluorination of cinnamyl alcohol derivatives by PhIO/HF·py reagent proceeded smoothly to afford 2-aryl-3,3-difluoro-1-propanols in moderate yields.