Ethanol → 6-(pentafluoroethyl)-2-(trifluoromethyl)-2H-1-benzopyran-3-carboxylic acid

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Reaction Steps

To a stirred solution of the ethyl ester (Step 1) (0.090 g, 0.231 mmol) in THF:EtOH:H20(7:2:1) (4 mL) was added aqueous NaOH solution (0.11 mL, 2.5 M). After stirring 16 hours, the reaction was partially concentrated in vacuo to remove the organic solvents, diluted with H2O, and washed with diethyl ether. The resulting aqueous phase was acidified with concentrated HCl, extracted with diethyl ether, dried over MgSO4, filtered and concentrated in vacuo yielding an oil. The oil was purified by flash chromatography (silica, hexanes-ethyl acetate, 3:1 with 5% acetic acid). This procedure yielded the title acid (0.020 g, 24%) as a white powder: mp 162.3–164.7° C. 1H NMR (acetone-d6/300 MHz) 8.05 (s, 1H), 7.90 (s, 1H), 7.74 (d, 1H, J=8.7 Hz), 7.29 (d, 1H, J=8.7 Hz), 5.97 (q, 1H, J=6.8 Hz). FABLRMS m/z 361 (M−H). ESHRMS m/z 361.0111 (M−H, Calc'd 361.0094).

Provenance & Evidence