Chlorosulfonic acid → 4-Methoxy-3-[4-(2,2,2-trifluoro-acetyl)-piperazin-1-yl]-benzenesulfonyl chloride

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Reaction Steps

A solution of 2,2,2-trifluoro-1-[4-(2-methoxy-phenyl)-piperazin-1-yl]-ethanone (14 g; 0.48 mol) in dichloromethane (20 mL) was added to chlorosulfonic acid (75 mL) in such a rate that the inner temperature did not exceed −5° C. After 10 min at this temperature, the solution was poured slowly onto ice-water (500 g), the precipitate was filtered and washed with cold water (2×200 mL) and cold diethyl ether (200 mL). The resulting solid was recrystallized from diethyl ether to give 4-methoxy-3-[4-(2,2,2-trifluoro-acetyl)-piperazin-1-yl]-benzenesulfonyl chloride as white powder (7.7 g; 41%), MS, MH+ 387, m. p. 125-127.3° C.

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