The invention provides a preparation method of a herbicide oxadiazon intermediate 2, 4-dichloro-5-isopropoxy
phenylhydrazine, which comprises the following steps: by taking a
toluene solution of 2, 4-dichloro-5-isopropoxy
aniline as a
raw material, stirring to form a salt under an acidic condition, reacting with
cyanate at a certain temperature to generate
urea, degrading and rearranging by Hofmann in an alkaline environment, filtering, after recovering a
solvent at normal pressure, taking 2, 4-dichloro-5-isopropoxy
phenylhydrazine as a
raw material, adding
chloroform for extraction, and obtaining a
chloroform solution of the 2, 4-dichloro-5-isopropoxy
phenylhydrazine which can be directly used for an
acylation process to synthesize the oxadiazon key intermediate 2, 4-dichloro-5-isopropoxy phenylhydrazine. According to the method disclosed by the invention, a complicated
tin recovery process caused by reduction of diazonium salt by stannous
chloride in a traditional synthesis process is effectively avoided, and generation of a large amount of high-salt
wastewater in a
recovery section is avoided; on the other hand, alkalization operation is avoided,
solid materials are not added, the labor intensity is greatly reduced, and the production efficiency is effectively improved.