Synthesis Of High Purity Of Clomazone

Clomazone,a selective sprout herbicide, belonged to heterocyclic herbicide, which canmake plant die by affecting the biologic synthesis of carotene and chlorophyll to depressphotosynthesis. Clomazone is highly thought by both here and abroad for the characteristicof low-toxicity, wide weed control, long period of validity and increasing production.This paper reviews the preparation of clomazone and its intermediate. Analyze thecorrelated literature and design the route of high purity of clomazone.3-chloro-N-hydroxy-2,2-dimethyl propanamide which was synthesized from hydroxylaminehydrochloride and3-chloro-2,2-dimethyl propionyl chloride; The4,4-dimethyl-3-isoxazolindinone was prepared by cyclizing3-chloro-N-hydroxy-2,2-dimethyl propanamide with alkaline hydroxide; the2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone was obtained by benzylatingthe resulting4,4-dimethyl-3-isoxazolindinone with2-chlorobenzyl chloride, andeliminating by--product1-[(2-chlorophenyl)methoxy]-3,3-dimethyl-2-azetidinone bycontacting the product mixture with anhydrous hydrogen chloride, and further benzylatingfree isoxazolidinone with base. The structure of product and intermediate was confirmed onthe basis of experiment.The results show that the yield was83.7%and the purity was99.0%when the materialratio n(3-chloro-2,2-dimethyl propionyl chloride):n(hydroxylamine hydrochloride) was1:1.3, reaction temperature was0℃, pH7.0～7.2and the acylating reagent was aqueous30%sodium hydroxide solution in the process of oximation reaction. The purity was over97%when reaction time was18h, reaction temperature was20℃,pH was9.0±0.1in theprocess of cyclization reaction. The yield was87.5%and the purity was92.2%whenreaction time was6h and the material ratio was1:1reaction temperature was90℃, thedropping time of2-chlorobenzyl chloride was0.5h in the process of condensation reaction.The yield was93.9%and purity was95.3%in the process of purification with dry HCl gas.