A synthesis method of 2-chloro-4-bromobenzonitrile comprises the following steps: S1, adding methylchloroaniline and
hydrobromic acid into a
solvent a, dropwise adding a
sodium nitrite solution, rapidly cooling to
room temperature after the reaction is completed, and filtering to obtain a compound I; s2, adding the compound I,
bromine and a
solvent b into a reaction kettle, stopping heating after the reaction is completed, naturally cooling to
room temperature, and filtering to obtain a compound II; s3, adding the compound II,
hydroxylamine hydrochloride and
sodium hydroxide into the reaction kettle, stopping heating after the reaction is completed, naturally cooling to
room temperature, and filtering to obtain a compound III; s4, adding the compound III into
thionyl chloride and a
solvent c, stopping heating after the reaction is completed, naturally cooling to room temperature, and filtering to obtain 2-chloro-4-bromophenoxybenzene; and (S5) carrying out
cyclohexane refining on the 2-chloro-4-bromobenzonitrile. According to the synthetic method of the 2-chloro-4-bromobenzonitrile, the 2-chloro-4-bromobenzonitrile is synthesized through four-step reaction of diazotization,
hydroformylation, oximation and nitrilation, and the method is simple in process, stable in quality, low in
energy consumption and easy to produce.