[Br:1]Br.[CH3:3][S:4][C:5]1[N:10]=[C:9]([CH2:11][C:12]([C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[O:13])[CH:8]=[CH:7][N:6]=1>C(O)(=O)C>[Br:1][CH:11]([C:9]1[CH:8]=[CH:7][N:6]=[C:5]([S:4][CH3:3])[N:10]=1)[C:12]([C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)=[O:13]Bromine (24.1 g, 0.15 mol) is added with stirring to 2-(2-methylthio-pyrimidin-4-yl)-1-phenyl-ethanone (36.8 g, 0.15 mol) in acetic acid (300 ml) in such a way that the reaction temperature does not exceed +25° C. and the color of the bromine is discharged immediately. After the addition of the bromine solution the solvent is removed by evaporation under vacuum. The pH of the resulting oil is adjusted to 8 using an aqueous saturated sodium bicarbonate solution and the product is extracted several times with diethylther. Drying the combined extracts with magnesium sulfate, filtering and evaporation of the solvent gives the crude 2-bromo-2-(2-methylthio-pyrimidin-4-yl)-1-phenyl-ethanone in form of an oil of sufficient purity for the following step.
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