C([N:4]1[C:9](=[O:10])[NH:8][C:7](=[O:11])[C:6]([Br:12])=[N:5]1)(=O)C.N1C=CC=CC=1.[C:19](Cl)(=[O:26])[C:20]1[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=1>O1CCOCC1.CCOC(C)=O>[Br:12][C:6]1[C:7](=[O:11])[N:8]([C:19]([C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=2)=[O:26])[C:9](=[O:10])[NH:4][N:5]=1
2-acetyl-6-bromo-1,2,4-triazine-3,5(2H,4H)-dione (P6, 2.47 g, 10.56 mmol) was dissolved in 1,4-Dioxane (18 ml) and pyridine (2.56 ml, 31.7 mmol). The solution was cooled to 5° C. then benzoyl chloride (1.470 ml, 12.67 mmol) was added dropwise and the mixture was stirred at room temperature overnight. The day after the reaction mixture was diluted with AcOEt and washed with 0.5N HCl aq solution. Organic phase was separated, dried over Na2SO4, filtered and concentrated under reduced pressure. Crude product (brown oil) was purified by flash chromatography (SiO2, eluent: Cy to Cy/AcOEt 6:4) affording 6-bromo-4-(phenylcarbonyl)-1,2,4-triazine-3,5(2H,4H)-dione (1.46 g, 4.93 mmol, 46.7% yield) as a white powder.
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