Synthesis method of chlorantraniliprole intermediate

The invention relates to the technical field of chemical synthesis, and particularly discloses a synthetic method of a chlorantraniliprole intermediate. The synthesis method comprises the following steps that under the condition of an organic solvent, a compound I, brominated salt and concentrated sulfuric acid serve as raw materials, a bromination reaction is conducted, a compound II is prepared, and the organic solvent is dichloroethane or chloroform; the molar ratio of the compound I to the sodium bromide is 1: (1-1.1); the molar ratio of the compound 1 to the concentrated sulfuric acid is 1: (2-4). According to the method, the bromination reaction is fully carried out due to the excessive use of concentrated sulfuric acid, so that the yield and the purity of the compound II are obviously improved, the yield can reach 95% or above, the purity can reach 98.0% or above, in addition, generation of a large amount of mixed acid wastewater is avoided, the types of three wastes are simplified, the environment-fri