Preparation method of 2-(4-bromomethylphenyl) propionic acid

The invention discloses a preparation method of 2-(4-bromomethylphenyl) propionic acid. The preparation method is characterized by comprising a preparation stage of 2-phenyl propionitrile, a preparation stage of 2-phenyl propionic acid and a preparation stage of 2-(4-bromomethylphenyl) propionic acid. The preparation stage of 2-phenyl propionitrile comprises the following steps: mixing benzyl cyanide, dimethyl carbonate and potassium carbonate; heating to 100-300 DEG C and carrying out thermal reaction for 5-50h under the pressure of 0.5-6MPa; and by the end of the reaction, carrying out filter pressing and rinsing to be neutral; distilling to removal excessive dimethyl carbonate; and carrying out high-vacuum rectification to obtain 2-phenyl propionitrile. Compared with the prior art, the preparation method disclosed by the invention has the following advantages and effects that the main raw material is benzyl cyanide which is subjected to methylation, hydrolysis reaction and bromomethylation to finally obtain the finished product; the purity of the finished product is high and the yield is up to 90% or above; and in addition, the preparation method has the advantages of simple production process, low production cost and low environment pollution.