The invention belongs to the technical field of synthesis of ester compounds, and particularly relates to a preparation method of 2, 6-dichloro-4-cyanobenzoic acid methyl ester, which comprises the following steps: by taking dimethyl 2-aminoterephthalate as a
raw material, sequentially carrying out
substitution reaction,
deamination reaction,
hydrolysis reaction, amidation reaction and
dehydration reaction to obtain the 2, 6-dichloro-4-cyanobenzoic acid methyl ester. The 2, 6-dichloro-4-cyanobenzoic acid methyl ester is prepared by the method, and the yield reaches 59.28%. The N-chlorosuccinimide is used as a
chlorine source to carry out
substitution reaction on the 2-amino
dimethyl terephthalate, so that the potential safety
hazard caused by the traditional chlorination
reagent is avoided, and the tert-
butyl nitrite used in the
deamination reaction avoids the potential safety
hazard caused by the use of strong corrosive
sulfuric acid; the amidation reaction is completed in one step by adopting a condensing agent, so that the complicated operation caused by firstly preparing
acyl chloride and then carrying out
condensation reaction is avoided, and therefore, the preparation method has the characteristics of safe preparation process, environment friendliness, simplicity in operation and the like under the condition of ensuring the product yield and purity.