The first example for the generation of carbonyl ylides from palladium carbenes is reported. Systematic investigation of the substituents attached to the carbonyl group indicates that the employment of trifluoromethyl group as the substituent is very critical for the success of this transformation. The remarkable fluorine effect on the reactivity is very impressive, which allows the construction of various trifluoromethylated oxiranes in high yields and diastereoselectivities.magnified image