4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydro-1,2-oxazol-3-yl]-2-methylbenzoic acid

4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydro-1,2-oxazol-3-yl]-2-methylbenzoic acid is an organic intermediate compound used in the synthesis of Fluralaner.

4-[5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydro-1,2-oxazol-3-yl]-2-methylbenzoic acid is prepared by the reaction of 2-methyl-4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzoic acid and 3-bromo-5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazole. The steps are as follows:
In a 100 mL three-necked flask, under nitrogen protection, add 3-bromo-5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazole (700 mg, 1.93 mmoL), 2-methyl-4-(4,4,5,5-tetramethyl-1,3-dioxaborolan-2-yl)benzoic acid (560 mg, 2.14 mmoL), potassium acetate (379 mg, 3.86mmol), 1,4-dioxane (15mL), water (1.5mL) and Pd(dppf)Cl2 (141mg, 0.19mmol), incubate the reaction at 85±5 for 8h, stop heating to room temperature, then Water (50 mL) was added to quench and then extracted with dichloromethane (45 mL×2), the organic phases were combined, the organic phase was washed once with saturated brine (50 mL), and then the organic phase was washed with anhydrous sodium sulfate (10.0 g). ) was dried for 2 h, the organic phase was concentrated to dryness under reduced pressure, and the concentrated residue was purified by silica gel column chromatography (developing solvent: n-heptane/ethyl acetate=10:1-3:1) to obtain 4-(5-(3 ,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydroisoxazol-3-yl)-2-methylbenzoic acid (694 mg, 86%) as a pale yellow solid.