A mixture of 2.6 g of 5-(5-chlorovaleryl)-2-methoxy-benzenesulfonamide, 1.8 g of 1-(2-methoxyphenyl)piperazine, 1 g of sodium carbonate and 20 ml of dimethyl sulfoxide was stirred at 90° C. for 3 hours. After the reaction was finished, water was added to the reaction mixture and then the mixture was extracted with ethyl acetate. The extract was washed with water saturated with sodium chloride and dried over anhydrous sodium sulfate. The solvent was distilled away and the residue was dissolved in acetone followed by adding concentrated hydrochloric acid in required amount to produce crystals. The thus-produced crystals were recrystallized from methanol to obtain 2.8 g of the titled compound (yield: 61%).
