RACEMIZATION METHOD OF (5R)-4-[5-(3,5-DICHLOROPHENYL)-5-(TRIFLUOROMETHYL)-4H-ISOXAZOL-3-YL]-2-METHYLBENZOIC ACID Russian patent published in 2023 - IPC C07D261/04 C07D261/08 

FIELD: organic chemistry.

SUBSTANCE: method for the racemization of (5R)-4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4H-isoxazol-3-yl]-2-methylbenzoic acid, an intermediate for the synthesis of the insecticide fluralaner. A method for racemization of mixture containing an enantiomeric excess of (5R)- and a deficiency of (5S)-4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4H-isoxazol-3-yl]-2-methylbenzoic acid, involves reacting of (5RS)-4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4H-isoxazol-3-yl]-2-methylbenzoic acid with an amine in an organic solvent selected from the group consisting of alcohol with 2-5 carbon atoms, tetrahydrofuran, dioxane, toluene, ethyl acetate and mixtures thereof to obtain a precipitate and a supernatant solution, separation of a supernatant solution containing a mixture containing (5R)- and (5S)- derivatives of methyl benzoic acid from the precipitate and interaction of the mixture with an alkaline compound in an alcohol of 2-8 carbon atoms to obtain a reacted mixture.

EFFECT: providing a racemization method for the further isolation of enantiopure or enantioenriched (5S)-4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4H-isoxazol-3-yl]-2-methylbenzoic acid for obtaining the preferred (S)-fluralaner.

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