Phosphorus oxychloride → 1-(4-bromo-phenyl)-6-chloro-3-cyclopropyl-1H-pyrimidine-2,4-dione

To 1-(4-bromo-phenyl)-3-cyclopropyl-pyrimidine-2,4,6-trione 32 (11.8 g) obtained in Step 2 was added water (1.31 ml) and phosphorus oxychloride (17.0 ml) was added dropwise with stirring at room temperature. After the completion of the dropwise addition, the mixture was stirred at 110° C. for 3 hrs. After allowing to cool to room temperature, the reaction mixture was added to ice water by small portions and the mixture was stirred. The mixture was stirred at room temperature and extracted with chloroform. The organic layer was washed with brine, and dried over anhydrous magnesium sulfate. Anhydrous magnesium sulfate was filtered off, and the filtrate was concentrated under reduced pressure. The residue was purified by column chromatography (hexane:ethyl acetate=2:1→chloroform:acetone=30:1) to give a 1:1.4 mixture (11.6 g, yield 93%) of 1-(4-bromo-phenyl)-6-chloro-3-cyclopropyl-1H-pyrimidine-2,4-dione 33 and 3-(4-bromo-phenyl)-6-chloro-1-cyclopropyl-1H-pyrimidine-2,4-dione 34 as a pale-yellow foamy oil.