26 g (60.4 mmol) of methyl (2E)-3-(4-{difluoro[4-(4,4,4-trifluorobutoxy)phenyl]methoxy}-phenyl)prop-2-enoate is dissolved in 400 ml of dioxane. 30 ml of NaOH (30%) diluted in 250 ml of water is added to the solution. The mixture is heated to 55° C. for 2 hours. The mixture is cooled to room temperature and is carefully acidified to pH=2 with a HCl solution (25%) and is stirred for 15 min. The product is filtrated off and dried at room temperature under vacuum for 10 h to give 20 g of (2E)-3-(4-{difluoro[4-(4,4,4-trifluorobutoxy)phenyl]methoxy}-phenyl)prop-2-enoic acid as a colourless powder.
