Trifluoroacetic acid → 5-(4-Chlorophenyl)-thiophene-2-carboxylic acid (2-oxoethyl)amide

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Reaction Steps

Add water (21 mL) followed by trifluoroacetic acid (100 g) to a 250 mL three-necked round bottom flask equipped with an overhead stirrer, nitrogen inlet/outlet, and thermocouple. To the stirring TFA solution, add 5-(4-chlorophenyl)-thiophene-2-carboxylic acid (2,2-diethyoxyethyl) amide (25 g, 0.07 mol) in one portion. Stir the reaction mixture for 4 h, pour onto ice/water (1200 mL), and stir for 1.25 h. Filter the resulting slurry and rinse the solid with water (500 mL) and heptane (500 mL), and then dry to give 18.65 g (95%) of the title compound as a yellow-white solid. LC-MS/ES m/z (35Cl)=278 (M−H)−. 1H NMR (500 MHz, CDCl3): δ 4.40 (d, J=4.0 Hz, 2H), 6.69 (bs, 1H), 7.26 (d, J=3.0 Hz, 1H), 7.40 (d, J=9.0 Hz, 2H), 7.53-7.58 (m, 3H), 9.78 (s, 1H).

Provenance & Evidence