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

The invention relates to a preparation method of 4-(hydroxymethylphosphonyl)-2-oxobutyric acid, which comprises the following steps: a) mixing 3-chloropropionyl chloride, a first solvent, trimethylsilyl cyanide and cyanide, carrying out substitution reaction to obtain a feed liquid containing 4-chloro-2-oxobutyronitrile, and carrying out reduced pressure distillation and separation to obtain a 4-chloro-2-oxobutyronitrile intermediate; b) performing an Arbuzov reaction on the obtained 4-chloro-2-oxobutyronitrile intermediate and methyl phosphonite diester in a second solvent in the presence of cuprous iodide to obtain a (3-cyano-3-oxopropyl) methyl phosphinate feed liquid, and purifying the (3-cyano-3-oxopropyl) methyl phosphinate feed liquid to obtain a (3-cyano-3-oxopropyl) methyl phosphinate crude product; and c) mixing the obtained (3-cyano-3-oxopropyl) methyl phosphinate crude product with hydrochloric acid, carrying out hydrolysis reaction, and then carrying out purification treatment to obtain the 4-(hy