Boron trifluoride etherate → 4-(2-Chlorobenzylthio)-4-(2-fluorophenyl)-1-methylpiperidine hydrochloride

Participants

Reaction Steps

59.7 g of 2-chlorobenzylmercaptan, followed by 55 ml of boron trifluoride etherate are added to 25 g of 4-(2-fluorophenyl)-4-hydroxy-1-methylpiperidine of Example 1a in 55 ml of acetic acid. The reaction is stirred at 55°-65° C. for 20 hours. The excess acid is removed under reduced pressure at 80°-100° C. The oily residue is then equilibrated with 200 ml of 2 N hydrochloric acid and 200 ml of ether. The ether, and two more 125 ml portions of ether, is decanted off. The oil and water mixture is diluted to 650 ml volume with water and is stored at 0° C. for about three days to produce crystals. The mixture is diluted and filtered. The precipitate is washed with water and ether, and dried. The solid is recrystallized (acetone:ether) to a broad melting (122°-129° C.) solid. A portion of the solid is placed in water, basified with 10% aqueous NaOH, extracted into ether, washed, dried and treated with ethereal hydrogen chloride to give a white powder. The powder is recrystallized from acetone-ether to give a white crystalline solid, m.p. 173°-175° C. of 4-(2-chlorobenzylthio)-4-(2-fluorophenyl)-1-methylpiperidine hydrochloride.

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