Triethylamine → 4-[3-(tert-Butoxycarbonylamino)pyrrolidin-1-yl]-2,3-difluorobenzoic acid ethyl ester

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A solution of 2,3,4-trifluorobenzoic acid ethyl ester (Example 1g, 3.70 g, 18.1 mmol), pyrrolidin-3-ylcarbamic acid tert-butyl ester (4.02 g, 21.6 mmol), and triethylamine (18.0 mL, 129 mmol) in acetonitrile (50 mL) is heated at 50° C. under nitrogen atmosphere for 4.5 hours. The solution is concentrated in vacuo and poured into a saturated NaHCO3 solution. The mixture is then extracted with chloroform, and the combined organic extracts are washed with brine, dried with Na2SO4, filtered, and the mixture concentrated in vacuo. The resulting residue is then purified by column chromatography (1:7 ethyl acetate/hexanes) to afford the title compound (4.70 g). 1H NMR (CDCl3): δ 7.59–7.49 (m, 1H), 6.35–6.26 (m, 1H), 4.88–4.84 (bd, 1H), 4.39–4.28 (m, 3H), 3.81–3.50 (m, 3H), 3.48–3.34 (m, 1H), 2.32–2.15 (m, 1H), 2.02–1.76 (m, 1H), 1.45 (s, 9H), 1.40 (t, 3H).

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