4.87 g of para-toluenesulfonyl chloride (25.5 mmol) are slowly added to a solution of 6.70 g of (4-fluoro-4-hydroxymethylpiperidin-1-yl)-(3-chloro-4-fluorophenyl)methanone (23.12 mmol) in 40 ml of pyridine cooled to 0° C. and maintained under a nitrogen atmosphere. The mixture is stirred for 12 hours at room temperature and then it is poured into ice-cold water, extracted with chloroform and then the organic phase is washed with a 1N aqueous solution of hydrochloric acid. The organic phase is dried over magnesium sulfate, filtered and then concentrated under vacuum. The title product is purified by recrystallization from a dichloromethane/diisopropyl ether mixture. 7.73 g of a white crystalline powder are obtained.
