[CH3:1][CH:2]([CH3:17])[C:3]([C:5]1[CH:10]=[CH:9][C:8]([N:11]2[CH2:16][CH2:15][CH2:14][CH2:13][CH2:12]2)=[CH:7][CH:6]=1)=[O:4].ClS(O)(=O)=O.[Br:23]Br.[OH-].[Na+]>C(O)(=O)C>[Br:23][C:2]([CH3:17])([CH3:1])[C:3]([C:5]1[CH:10]=[CH:9][C:8]([N:11]2[CH2:16][CH2:15][CH2:14][CH2:13][CH2:12]2)=[CH:7][CH:6]=1)=[O:4]
34.70 g (0.15 mol) of 2-methyl-1-(4-piperidinophenyl)-propan-1-one are dissolved in 200 ml of glacial acetic acid. 0.58 g (5.0 mmol) of chlorosulfonic acid (corresponding to 0.33 ml) are added as catalyst. 24.0 g (0.15 mol) of bromine are then added dropwise at room temperature with thorough stirring in the course of approximately one hour. The solution is then poured onto ice and is brought to about pH 6 with dilute sodium hydroxide solution. The precipitated crystals are extracted with toluene. The toluene solution is dried with Na2SO4 and is concentrated at 40° C. under the vacuum of a rotary evaporator. The slowly crystallising, orange liquid is then reacted further.
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