Synthesis method of 3,5-dichlorobenzoyl chloride

The invention discloses a synthesis method of 3,5-dichlorobenzoyl chloride. The synthesis method comprises the following steps: firstly, carrying out sulfonation reaction by taking benzoyl chloride as a raw material, secondly, conducting catalytic chlorination reaction and thirdly conducting sulfur dioxide removal chlorination reaction. The synthesis method is characterized in that the sulfur dioxide removal chlorination reaction in the third step is carried out under the catalysis of quaternary phosphonium salt. By adopting a method of catalyzing the sulfur dioxide removal chlorination, and compared with the existing technological method, the synthesis method has the characteristics of reducing the reaction temperature, quickening the reaction speed, being higher in the yield and content of products, and the like, and is suitable for industrial production.