A solution of 6-methoxy-2-(4-methoxyphenyl)-3-[4-(2-piperidinoethoxy)benzoyl]benzo[b]thiophene hydrochloride (2.0 g) in 1,2-dichloroethane (20 mL) was treated with boron trichloride (2.0 mL). The resulting mixture was stirred at 35° C. for about 18 hours. A mixture of ethanol and methanol (10 mL, 95:5, 3A) was treated with the reaction mixture from above, causing the alcoholic mixture to reflux. Upon complete addition, the resulting crystalline slurry was stirred at 25° C. After one hour, the crystalline product was filtered, washed with cold ethanol (10 mL), and dried at 40° C. in vacuo to give 1.78 g of the title compound. The X-ray powder diffraction pattern is identical to that reported in Table 1.
