By treatment with Br2CF2 and Ph3P, 4 unfunctionalized olefins, 4 enol ethers and 1 bis-enol ether were converted to gem-difluorocyclopropanes. Thus, RCH:CHOPr (R = H, Me) gave difluorocyclopanes I in 73 and 83% yield, resp. The yields were considerably increased and isomerizations at the double bonds were avoided if the reactions were carried out in the presence of a macrocyclic polyether such as 18-crown-6 and a moderate excess of reagents. [on SciFinder (R)]