Diisopropylamine → 2-(2,4-Difluoroanilino)-4,5-difluorobenzoic acid

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Lithium diisopropylamide is generated at −5° C. by combining diisopropylamine (7.2 mL, 51 mmol) and n-butyllithium (33 mL, 53 mmol) in anhydrous tetrahydrofuran (150 mL) under an inert atmosphere. After 0.5 hour, the solution is cooled to −78° C. and 2,4-difluoroaniline (3.46 mL, 34 mmol) is added and stirred for 2 hours. 2,4,5-Trifluorobenzoic acid (3.0 g, 17 mmol) is added, and the mixture is subsequently allowed to warm to room temperature over 18 hours. A saturated solution of hydrogen chloride/dioxane (10 MIL) is added, and after 1 hour, the mixture is concentrated to a solid. The solid is dissolved in chloroform and washed with 1.0 M hydrochloric acid, water, and brine. The solution is dried, concentrated in vacuo, and purified by column chromatography (3:1 ethyl acetate/hexanes) to give 2-(2,4-difluoroanilino)-4,5-difluorobenzoic acid as a solid (2.18 g). 1H NMR (CDCl3): δ 8.95 (bs, 1H), 7.80–7.75 (m, 2H), 7.50–6.85 (m, 3H), 6.62–6.40 (m, 1H). MS EI: m/z 286 (M+).

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