The invention discloses a synthetic process of 1-
alkyl-4-p-fluorophenyl-2,6-piperadinedione-3-formic ester. The synthetic process comprises the following steps of using 1-
alkyl-4-p-fluorophenyl-2,6-piperadinedione-3,5-diformic ester,
sodium hydroxide water solution and the like as raw materials and lower
fatty alcohol as a
solvent to undergo selective
hydrolysis reaction through a chemical method, cooling, diluting, filtering, recovering unreacted raw materials, acidifying the filtrate, filtering, washing and
drying in vacuum, thus obtaining an intermediate 1-
alkyl-4-p-fluorophenyl-2,6-piperadinedione-3-
formic acid-5-formic ester; then dissolving the intermediate in an
organic solvent, adding a small amount of catalyst to carry out decarboxylic reaction, cooling, filtering, adding water to the filtrate to be stirred for layering, recovering a
solvent at reduced pressure with an organic phase, and carrying out cooling
crystallization on the residues, thus obtaining the product 1-alkyl-4-p-fluorophenyl-2,6-piperadinedione-3-formic ester. The synthetic process is short in
route, is efficient, has the characteristics of cheap and accessible raw materials, high product yield, less three wastes and the like, and is suitable for large-scale industrial production.