PURPOSE: In the reaction between a fluorine-containing epoxy compound and a perfluoroketone, a catalyst amount of potassium fluoride is used to give the titled compound used as a starting compound for a chiral reagent with advantage in yield, operation and costs.

CONSTITUTION: The reaction between a fluorine-containing epoxy compound of formulaI(Rf is perfluoroalkyl) such as hexafluoro-1,2-epoxypropane and a perfluoroketone of formula III (R'f, Rf are identical or different perfluoroalkyl) in the presence of potassium fluoride is conducted at room temperature to give the compound of formula III. The amount of the potassium fluoride used 1/10W 1/20mol per mole of the perfluoroketone preferably and a some excessive amount of perfluoroketone is used to the above epoxy compound. The titled compound is used as a starting compound of a monomer as a constituent of fluoropolymers.