Preparation method of 4-(hydroxymethylphosphonyl)-2-oxobutyric acid

The invention provides a preparation method of 4-(hydroxymethylphosphonyl)-2-oxobutyric acid, which comprises the following steps: a) mixing methyl phosphonite monoester, a first solvent, an initiator and acryloyl chloride, carrying out addition reaction, and carrying out reduced pressure distillation to obtain (3-chloro-3-carbonyl propyl) methyl phosphonate feed liquid; b) mixing the (3-chloro-3-carbonyl propyl) methylphosphonate feed liquid obtained in the step a) with sodium cyanide, a second solvent and a catalyst, carrying out substitution reaction, and purifying to obtain (3-cyano-3-carbonyl propyl) methylphosphonate feed liquid; and c) uniformly mixing the (3-cyano-3-carbonyl propyl) methylphosphonate feed liquid obtained in the step b) with water, cooling to 10-40 DEG C, dropwise adding hydrochloric acid for acidification, continuously stirring for 0.1-1 hour after dropwise adding, then carrying out hydrolysis reaction, and finally carrying out purification treatment to obtain the 4-(hydroxymethylphos