Carbon Dioxide → 5-Fluoro-4-thiouracil

Participants

Reaction Conditions

Reaction Steps

To a solution of phosphorus pentasulfide (102.6 g, 0.46 mol) in diglyme (1 L) was added 5-fluoropyrimidine-2,4(1H,3H)-dione (30 g, 0.23 mol). Solid sodium hydrogen carbonate (NaHCO3; 77.3 g, 1.04 mol) was added at a rate determined by the evolution of carbon dioxide. The reaction mixture was stirred overnight at 110° C. The yellow mixture was cooled and poured into 1 L of cold water. The precipitated solid product was isolated by filtration and purified by normal phase chromatography (gradient, 10 to 50% EtOAc/Petroleum ether) to give 5-fluoro-4-thioxo-3,4-dihydropyrimidin-2(1H)-one (13.4 g, 40%) as a yellow solid: mp 254-255° C.; 1H NMR (301 MHz, DMSO-d6) δ 7.81 (d, J=4.0 Hz, 1H); ESIMS m/z 145 ([M−H]−).

Provenance & Evidence