Crystalline form of benzothiophene compound and process for preparation thereof

Example 1

Preparation of Raloxifene Hydrochloride

[0091]To 400 ml of tetrahydrofuan, 100 g of raloxifene base was charged and 150 ml of hydrogen chloride gas in isopropyl alcohol was added at 5-10° C. (over a time period of about 1 hour). The reaction mass was stirred at 25-30° C. for 15 minutes, heated to 30-35° C. and maintained for 1 hour. The reaction mass was cooled to 0-5° C. and maintained for 30 minutes. The material was filtered, washed with chilled tetrahydrofuran followed by chilled methanol and vacuum dried for 30 minutes. The material was further dried under vacuum initially at 40-45° C. for about 2 hours and then at 50-55° C. for 8 hours.

Example 2

Preparation of Raloxifene Hydrochloride Monohydrate

[0092]To dried raloxifene hydrochloride (of example 1), 700 ml of methanol, 300 ml of water, 10 ml of dimethyl formamide and sodium metabisulphite solution (0.5 g of sodium metabisulphite dissolved in 5 ml of water) was charged. The reaction mass was heated to reflux (67-72° C.) and maintained for 1 hour to obtain a clear solution. 5 g of activated charcoal was slurried in 30 ml of methanol, the contents were heated to reflux, maintained for 1 hour and filtered over hyflo and washed with 400 ml of a methanol:water mixture (1:1). The pH of the clear filtrate was adjusted to 1.50 to 2.00 using a 1:1 mixture of water and concentrated hydrochloric acid at 60-65° C. The reaction mass was concentrated to 1100 ml under vacuum. The reaction mass was cooled gradually to 25-30° C. under stirring and further stirred for 30 minutes. The obtained material was filtered, washed with 25 ml of methanol and vacuum dried. The material was furthe