| Abstract: | A study of the chlorination of 6-trifluoromethylpyrimidines was made. On sequential treatment of 6-tri-fluoromethyluracil (6) with phosphorus oxychloride and phosphorus pentachloride, 2,4-dichloro-6-trifluoro-methylpyrimidine (7) (25%) and 4-chloro-6-trifluoromethylpyrimidin-2-yldichlorophosphate (8) (53%) were obtained. Compound 8 was converted to 7 by treatment with hydrogen chloride in phosphorus oxychloride in 72% yield. In a one-pot synthesis, 77% of 7 was obtained from 6. The preparation of 2,4,5-trichloro-6-tri-fluoromethyluracil (16) proceeded similarly. Although the pyrimidinyldichlorophosphate ester has been proposed as the intermediate in converting a pyrimidinol to a chloropyrimidine, these are the first examples of such compounds to be isolated, characterized, and made to yield the ring-chlorinated pyrimidines. |
