Preparation method of substituted phenylacetic acid derivative

The invention discloses a preparation method of a substituted phenylacetic acid derivative. The method comprises the following steps: 1, carrying out a sulfonylation reaction on substituted phenylglycine and sulfuryl chloride under the action of an alkali, and post-processing after completing the reaction to obtain an intermediate; and 2, carrying out a deamination reaction on the intermediate obtained in step 1 under the action of an organic acid and a reducing agent, and post-processing after completing the reaction to obtain the substituted phenylacetic acid derivative. The raw material phenylglycine used in the above route can be very easily purchased from the market, and is cheap and easily available. The preparation method has the advantages of short process route, mild reaction conditions, simple operation, high reaction yield and low total lost.