The cycloaddition reactions of a-acetyoxyl propynes with difluorocarbene, generated from the decomposition of FSO2CF2CO2SiMe3 in DG in the presence of 10% of NaF at 120℃ gave readily a-acetyoxyl gem-difluorocyclopropenes. When these fluorinated compounds were hydrolyzed under alkaline condition at 0℃, α-hydroxyl cyclopropenones were produced predominantly whereas treated with catalytic amounts of BF3·Et2O in Et2O, α-acetyoxyl cyclopropenones were obtained.
