Unexpected substituent effect in the stereoselective synthesis of trifluoromethyl group containing cyclopropane lactones

Methyl or phenyl substitution in the allylic position of malonic esters of (E)-3-phenyl-3-trifluoromethyl-2-propen-1-ol resulted in unexpected and unprecedented stereospecific formation of the corresponding cyclopropane lactone derivatives by a multistep reaction with iodine in the presence of potassium carbonate and phase transfer catalyst.