A method of producing a ??,??-unsaturated ketolactones represented by formula (3): ##STR16## wherein A represents a hydroxyl protection group; X1 and X2 represent a hydrogen atom or a halogen atom respectively, providing at least one of X1 and X2 is a halogen atom;R2 represents an alkyl group having 1 to 10 carbon atoms which may have a branch, a double bond, an alkoxy group, a phenyl group or a p