Heterocyclic polyfluoro-compounds. Part XIX. Synthesis of and nucleophilic substitution in some 2,4,6-trifluoropyrimidines; formation of trifluoromethylpyrimidines by pyrolysis of tetrafluoropyrimidine

Abstract

Reaction of tetrachloropyrimidine with anhydrous potassium fluoride at 530° gives tetrafluoropyrimidine, 5-chloro-2,4,6-trifluoropyrimidine, and a 90 : 8 : 2 mixture of 2,4,6-trifluoro-5-trifluoromethyl-, 2,4,5-trifluoro-6-trifluoromethyl- and 4,5,6-trifluoro-2-trifluoromethyl-pyrimidine; the first two components of the mixture can be detected in the product of pyrolysis of tetrafluoropyrimidine at 550°. Fluorination of 2,4,6-trichloro-5-nitropyrimidine with potassium fluoride at 250° gives 2,4,6-trifluoro-5-nitropyrimidine, and similar treatment of 2,4,6-trichloro-5-cyanopyrimidine yields 5-cyano-2,4,6-trifluoro-, 4-chloro-5-cyano-2,6-difluoro-, 2,4-dichloro-5-cyano-6-fluoro-, and 4,6-dichloro-5-cyano-2-fluoro-pyrimidine. The above 5-substituted 2,4,6-trifluoropyrimidines and 2,4,6-trifluoropyrimidine itself are readily attacked by methanol–sodium carbonate, aqueous ammonia, or propenyl-lithium with displacement of ring fluorine as fluoride; the observed orientations of attack are discussed.