Mild fluorination of uracil derivatives by caesium fluoroxysulphate

Article abstract of DOI:10.1016/S0040-4020(01)88400-3

1,3-Dimethyl and 1,3-dimethyl-5-halo substituted uracil derivatives reacted with CsSO₄F under mild reaction conditions. Reactions carried out in an acetonitrile/water mixture or in a wide range of alcohols (methanol, ethanol, isopropanol and tert.butanol) resulted in the regioselective formation of the 5-fluoro-6-hydroxy or 5-fluoro-6-alkoxy-1,3-dimethyl-5,6-dihydrouracil derivatives, respectively, while the stereochemistry of the reaction was strongly syn predominant. Uracil was converted to 5-fluorouracil, and uridine to 5-fluorouridine, while the reaction of barbituric acid with CsSO₄F in acetonitrile as solvent produced 5,5-difluorobarbituric acid.