Citric Acid → 5-(3,3,3-trifluoropropyl)-1H-pyrrole-2-carboxylic acid

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Reaction Steps

2-(3,3,3-Trifluoro-propyl)-1H-pyrrole (8.15 mmol, 1.33 g) was added to a solution of trichloroacetyl chloride (8.15 mmol, 0.91 ml) in diethyl ether (10 ml). The resulting solution was held at room temperature for 1 h, then concentrated under reduced pressure. The resulting solid was dissolved in 1:1 dioxane-water (20 ml), treated with lithium hydroxide (24.5 mmol, 0.59 g), and heated to reflux for 30 minutes. After cooling to room temperature, the solution was acidified with saturated aqueous citric acid (20 ml), then extracted with ethyl acetate (2×50 ml). The combined organics were concentrated under reduced pressure. Purification of the resulting solid by silica gel chromatography provided 1.15 g (68%) of 5-(3,3,3-trifluoropropyl)-1H-pyrrole-2-carboxylic acid. 1H NMR (CDCl3) δ 9.33 (1H, br s), 6.99 (1H, dd, J=3.7, 2.5), 6.07 (1H, t, J=3.3), 2.96-2.89 (2H, m), 2.55-2.39 (2H, m).

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