A solution of lithium diisopropylamide (0.02 mol) in THF/hexane, prepared from 0.02 mol of diisopropylamine in 25 ml of THF and 12.5 ml of a 1.6-molar solution of n-butyllithium in hexane, is added dropwise at 25° C. to a mixture of 0.02 mol of 1-(4'-pentylbiphenyl-4-yl)-2-(3,5-difluorophenyl)ethane, 0.02 mol of N,N-dimethylpropyleneurea, 0.02 mol of 1-iodopropane and 25 ml of THF. After stirring at room temperature for 1.5 hours, the reaction mixture is poured into water, the phases are separated, and the aqueous phase is extracted with 2×50 ml of methylene chloride. Drying over magnesium sulfate, evaporation of the solvent and chromatography give the pure product.
