PURIFICATION OF 2-NITRO-4-METHYLSULFONYLBENZOIC ACID Russian patent published in 2006 - IPC C07C317/24 C07C317/44 

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for purifying 2-nitro-4-methylsulfonylbenzoic acid from impurities. Method involves at least two of the following steps in any order: (a) dissolving 2-nitro-4-methylsulfonylbenzoic acid in water at pH about 3-7 followed by filtration; (b) contacting 2-nitro-4-methylsulfonylbenzoic acid aqueous solution with activated carbon at pH about 2-10; (c) treatment of 2-nitro-4-methylsulfonylbenzoic acid aqueous solution with the sufficient amount of a base for hydrolysis of unfavorable nitro- and dinitro-substituted impurities. Then the prepared aqueous solution containing 2-nitro-4-methylsulfonylbenzoic acid is kept at temperature up to about 95°C and pH value of this solution is brought about to pH providing crystallization of 2-nitro-4-methylsulfonylbenzoic acid at cooling. Also, invention describes a method for preparing mesotrion that comprises conversion of purified 2-nitro-4-methylsulfonylbenzoic acid to the corresponding acid chloroanhydride that is subjected to interaction with 1,3-dicyclohexanedione to yield mesotrion. The proposed method can be used in synthesis of herbicide for cereal crops and used for control of grassy and platyphyllous weeds before and after their germination.

EFFECT: improved purifying method of compound.

10 cl, 5 ex