5-Fluorobarbituric acid

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;

δ_F (D₂O + NaOD, 376 MHz): – 191.95 (s);  

δ_C (D₂O + NaOD, 100 MHz) 131.89 (d, ¹J_CF 214.4, C–F), 157.77 (d, ⁴J_CF 6.2, C–NH), 164.59 (d, ²J_CF 13.4, CO);  

m/z (ASAP) 147 (25%, [M + H]⁺).

1. (a) E. D. Bergmann, S. Cohen and I. Dharak, J. Chem. Soc., 1959, 3286–3289

http://pubs.rsc.org/en/content/articlehtml/2015/gc/c5gc00402k
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