Add 0.98 mmol of 60% sodium hydride suspended in oil to a solution of 0.82 mmol of 6-hydroxy-2-{4-[bis-(4-fluorophenyl)methyl]piperazin-1-ylcarbonyl}-1,4-benzodioxin in 10 cm3 of N,N-dimethylformamide under a nitrogen atmosphere. Stir for 15 minutes at room temperature, then add dropwise 0.98 mmol of methyl iodide. Stir for 2 hours at room temperature and then concentrate to dryness under reduced pressure and purify the resulting crude product by chromatography on a silica column (eluant:petroleum ether/ethyl acetate, 50:50). 6-Methoxy-2-{4-[bis-(4-fluorophenyl)methyl]piperazin-1-ylcarbonyl}-1,4-benzodioxin is thereby obtained in a yield of 83%.
