GENERAL STEPS: Ethyl 2-chloro-3-oxopropionate (13) (4.48 g, 29.8 mmol, 1.00 equiv) and urea (1.79 g, 29.8 mmol, 1.00 equiv) were dissolved in 40 mL of water. The reaction mixture was stirred at 100 °C for 1 hour. After completion of the reaction, the light yellow suspension was cooled to room temperature and neutralized with saturated NaHCO3 solution. Subsequently, the reaction mixture was extracted with ethyl acetate (3 x 50 mL). The organic layers were combined, dried with anhydrous Na2SO4, filtered and concentrated under reduced pressure. The crude product was purified by fast liquid chromatography (silica gel, n-hexane/ethyl acetate = 1/2) to afford ethyl 2-aminooxazole-5-carboxylate (14) (2.40 g, 15.4 mmol, 51.3% yield).
