[Br:1]Br.[CH2:3]([S:19]([NH:22][C:23]1[CH:24]=[C:25]([C:29](=[O:31])[CH3:30])[CH:26]=[CH:27][CH:28]=1)(=[O:21])=[O:20])[CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][CH2:15][CH2:16][CH2:17][CH3:18].C(Cl)Cl>C(O)(=O)C>[CH2:3]([S:19]([NH:22][C:23]1[CH:24]=[C:25]([C:29](=[O:31])[CH2:30][Br:1])[CH:26]=[CH:27][CH:28]=1)(=[O:20])=[O:21])[CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][CH2:15][CH2:16][CH2:17][CH3:18]Bromine, 4.72 g (1.52 ml) was added to 25 g (0.059 M) of the product of Step A in 75 ml of glacial acetic acid at 70° C. Decolorization of bromine was instant. The reaction was followed by thin layer chromatography (CH2Cl2, silica gel) until the starting material was practically absent. The solid precipitated on cooling was collected by filtration, recrystallized from hexane to give 23.5 g of product (about 80% based on m-aminoacetophenone): mp 92°-5° C. Mass spectrum showed some dibrominated material.
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