5-Fluoro-4-thiouracil can be prepared from 5-fluorouracil as described (J. Med. Chem., Vol. 6, pp. 697-701 (1963)). 5-Fluoro-2(1H)-pyrimidinone can be subsequently prepared as described (Acta Chem. Scand., Vol. 23, pp. 294-299 (1969)). 5-Fluoro-2(1H)-pyrimidinone can then be converted to 2-methanesulfonyl-5-fluoropyrimidine by treatment with phosphorus oxychloride, followed by reaction with sodium methanethiolate and oxidation with m-chloroperbenzoic acid as described (Acta Chem. Scand., Vol. B39, pp. 696-696 (1985)). Conversion to the hydrazine is then effected by treatment of 2-methylsulfonyl-5-fluoropyrimidine with hydrazine hydrate in ethanol (Coll. Czech. Chem. Commun., Vol. 37, pp. 1721-17330 (1972)). Subsequent reaction of 2-methylsulfonyl-5-hydrazinopyrimidine with 4,4,4-trifluoro-1-phenyl-1,3-butanedione will then produce the title compound.
