0.39 ml of azodicarboxylic acid diisopropyl ester is added at 0° C. to 0.52 g of triphenylphosphine in 20 ml of tetrahydrofuran. After 30 minutes, 289 mg of 3-(4-hydroxyphenyl)cyclohexanone and 554 mg of 3-[2,6-dichloro-4-(3,3-dichloro-allyloxy)-phenoxy]-propan-1-ol in 10 ml of tetrahydrofuran are added dropwise thereto. After 24 hours at room temperature, the reaction mixture is concentrated and the residue is purified over silica gel. 3-(4-{3-[2,6-Dichloro-4-(3,3-dichloro-allyloxy)-phenoxy]-propoxy}-phenyl)-cyclohexanone is obtained in the form of a colourless oil.
