1,2-Dihydro-2-oxo-5-pyrimidinecarboxylic acid ethyl ester

The target compound ethyl 2-oxo-1,2-dihydropyrimidine-5-carboxylate was prepared by using urea and substituting 2,4-pentanedione as starting materials:

To a three-necked reaction flask equipped with a stirrer and a thermometer, urea, ethanol 35mL, substituting 2,4-pentanedione and hydrochloric acid 15mL were added in turn. the reaction was stirred for a period of time at a certain temperature, cooled naturally, and concentrated in a reduced-pressure water bath (water temperature <45 ) with a rotary evaporator. Decompression water bath concentration (water temperature <45 ), cooling, to the concentrate add ethanol, ether 20 ml, filtration, drying. 2-oxo-1,2-dihydropyrimidine-5-carboxylic acid, ethanol and acid catalysts, the reaction process heating evaporation of the water generated, no longer have water distillation, indicating the end of the reaction. After evaporating the excess ethanol, the solution was cooled. The product was washed repeatedly with water and 10% aqueous NaHCO3 to a pH of about 7. Reduced pressure distillation was carried out and the 112-114 C fraction was collected as the white crystalline product ethyl 2-oxo-1,2-dihydropyrimidine-5-carboxylate. The reaction process was changed from standing to stirring, which is favorable for accelerating the reaction rate and improving the yield; the product is easily soluble in water and organic solvents, and in the literature, it was filtered directly after the reaction, at this time, there existed water in the hydrochloric acid and ethanol added to the reaction system, and the direct filtration would make the product dissolved therein be lost, and we improved the process by firstly concentrating the reaction solution in the reduced-pressure water bath, to remove most of the water and ethanol, and then add a small amount of ethanol and ether to filter out the product, reducing the loss caused by filtration, thus increasing the yield.