5-Fluorobarbituric acid
Urea (1.50 g, 25 mmol) was added to the solution of sodium (1.2 g, 53 mmol) in anhydrous ethanol (50 mL) and the mixture was heated to reflux. Diethyl 2-fluoromalonate (4.45 g, 25 mmol) was added dropwise over 10 minutes and the mixture was heated at reflux for 1 h. After cooling to room temperature, the solution was filtered, the residue was washed with ethanol (20 mL), dissolved in water (30 mL) and acidified with HCl to pH 1. The precipitated product was recrystallized from the liquor to afford 5-fluorobarbituric acid (1.87 g, 51%) as a tan powder.
m.p.: >300 °C; ([M + H]+, 147.0206, C4H4FN2O3 requires: [M]+, 147.0204);
IR (neat,cm−1) 2926, 2828, 1578, 1383, 1241, 1128;
δF (D2O + NaOD, 376 MHz): – 191.95 (s);
δC (D2O + NaOD, 100 MHz) 131.89 (d, 1JCF 214.4, C–F), 157.77 (d, 4JCF 6.2, C–NH), 164.59 (d, 2JCF 13.4, CO);
m/z (ASAP) 147 (25%, [M + H]+).
- (a) E. D. Bergmann, S. Cohen and I. Dharak, J. Chem. Soc., 1959, 3286–3289
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