Sulfuric Acid → 1-Amino-3-(4-chloro-2-fluoro-5-hydroxyphenyl)-6-trifluoromethyl-1,2,3,4-tetrahydropyrimidine-2,4-dione

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Conc. sulfuric acid (3 ml) was added to a solution of 1-amino-3-(4-chloro-2-fluoro-5-isopropyloxyphenyl)-6-trifluoromethyl-1,2,3,4-tetrahydropyrimidine-2,4-dione (4.5 g) in methylene chloride (50 ml) stirred at 0C . After 1 hour the mixture was diluted with water and processed. The oily product was chromatographed on silica gel eluting with ethyl acetate:hexane, 2:3, to give 1-amino-3-(4-chloro-2-fluoro-5-hydroxyphenyl)-6-trifluoromethyl-1,2,3,4-tetrahydropyrimidine-2,4-dione as a pale yellow amorphous solid (3.6 g,). 1H NMR (CDCl3,TMS): 7.27(1H, d, J=8.8 Hz), 6.88(1H, d, J=6.5 Hz), 6.28(1H, s), 5.86(1H, br. s), 4.61(2H, s)

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