A mixture of 3-(1-piperazinyl)-1,2-benzisothiazole (4.0 g, 18.2 mmol), 1-[4-(2-chloroethoxy)-3-methoxyphenyl]-ethanone (4.3 g, 20.0 mmol), K2CO3 (3.0 g, 21.8 mmol), acetonitrile (125 ml) and a catalytic amount of KI was heated to reflux and stirred under nitrogen for 24 hours. At this point, an additional amount of K2CO3 (1.0 g, 7.2 mmol) and alkylating agent (0.4 g, 1.7 mmol) was added to the reaction mixture and heating at reflux was resumed for 24 hours. The reaction was cooled to ambient temperature and filtered. The filter cake was washed with acetonitrile and the filtrate was concentrated to afford a dark oil. The oil was extracted with methylene chloride, and the organic extract was washed with water, dried with MgSO4 and concentrated to yield 9.2 g of an oil. Purification by preparative HPLC (Waters Associates Prep LC/System 500 utilizing 2 silica gel columns and 3% methanol/methylene chloride as eluent) provided 3.8 g of a soft, beige gum, which readily solidified. The compound was recrystallized twice from ethanol to give 2.1 g (28%) of -[4-[2-[4-(2-benzisothiazol-3-y)--piperazinyl]ethoxy]-3-methoxyphenyl]ethanone as a beige solid, m.p.=98°-100° C.
