To a solution of [4-(2,5-dimethyl-phenyl)-piperazin-1-yl]-[1-(4-fluoro-2-methyl-phenyl)-piperazin-2-yl]-methanone hydrochloride (42 mg) in DMF (1 mL) was added 3-methoxybenzene sulfonyl chloride (21.4 mg) and triethyl amine (40 μL). The reaction mixture was stirred at ambient temperature for 2 h, was diluted with ethyl acetate and washed with a saturated aqueous solution of NaHCO3. The combined organic phases were washed with water and brine, dried (Na2SO4), filtered and evaporated. The crude product was purified by column chromatography (SiO2, n-heptane/ethyl acetate 2:1) to give [4-(2,5-dimethyl-phenyl)-piperazin-1-yl]-[1-(4-fluoro-2-methyl-phenyl)-4-(3-methoxy-benzenesulfonyl)-piperazin-2-yl]-methanone (42 mg) as white solid, MS: 581.3 ([M+H]+).
