Pyrimidines. 6. 6‐trifluoromethyl chloropyrimidines and related compounds

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.