Composite catalytic preparation method of methyl 2-cyano-2-valproate

The invention relates to a preparation method of methyl 2-cyano-2-valproate as shown in a chemical structural formula I. The preparation method comprises the following steps: selecting methyl cyanoacetate and 1-chloropropane, and carrying out composite catalytic dipropylation under the action of potassium carbonate to prepare the methyl 2-cyano-2-valproate as shown in the formula I; the preparation reaction is as follows: the catalyst is composed of a catalyst A and a catalyst B; the catalyst A is selected from R4NX, R is C1-C5 linear alkyl, and X is F, Cl, Br, I or HSO4; the catalyst B is KX, wherein X is Br or I; the solvent is selected from one or two of THF (tetrahydrofuran), DMF (dimethyl formamide), DMC (dimethyl carbonate), DMSO (dimethyl sulfoxide), acetonitrile, propionitrile, butyronitrile, 1, 4-dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethyl acetate or butyl acetate. The invention also relates to an app