Preparation method of valproic acid

The invention belongs to the technical field of medicines, and particularly relates to a valproic acid preparation method which comprises the following steps: under the catalysis of heteropoly acid, malonic acid and acetone react in acetic anhydride to obtain malonic acid cyclic isopropyl ester; the preparation method comprises the following steps: under the catalysis of a phase transfer catalyst and potassium carbonate, carrying out a reaction on malonic acid cyclic isopropyl ester and halogenated propane, recovering a solvent after the reaction is completed, then adding alkali for hydrolysis, and then adding acid for neutralization to obtain 2, 2-dipropylmalonic acid; 2, 2-dipropylmalonic acid is heated for decarboxylation, and valproic acid is obtained; the whole reaction operation is green, environment-friendly, safe and simple, and the obtained product is high in yield and purity. 本发明属于医药技术领域，具体是涉及一种丙戊酸的制备方法,步骤为，在杂多酸催化下，丙二酸和丙酮在醋酸酐中进行反应，得到丙二酸环异丙酯；在相转移催化剂和碳酸钾催化下，丙二酸环异丙酯和卤代丙烷反应，反应完毕后回收溶剂，然后先加碱水解，再加酸中和，得到2,2