Sodium Hydroxide → 6-chloro-8-(methylthio)-2-(trifluoromethyl)-2H-chromene-3-carboxylic acid

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Reaction Steps

To a stirred solution of ethyl 6-chloro-8-(methylthio)-2-(trifluoromethyl)-2H-chromene-3-carboxylate (Step 3, 0.203 g, 0.575 mmol) in THF:EtOH:H2O (7:2:1, 5 mL), was added aqueous sodium hydroxide (0.63 mmol, 0.25 mL of 2.5 N soln.) and allowed to stir for two days. The resulting clear, yellow solution was concentrated in vacuo, was diluted with water (35 mL), and was acidified with concentrated HCl resulting in formation of a yellow suspension. Vacuum filtration of the suspension yielded the title compound as a yellow powder (0.132 g, 71%). 1HNMR (acetone-d6/300 MHz) 7.87 (s, 1H), 7.34 (d, J=2.2 Hz, 1H), 7.25 (d, J=2.2 Hz, 1H), 5.93 (q, 1H, J=7.05 Hz), 2.53 (s, 3H). LRMS m/z 323 (M−H); ESHRMS m/z 322.9782 (M−H, C12H7F3O3ClS, Calc'd 322.9757). Anal. Calc'd for C12H8F3O3ClS: C, 44.39; H, 2.48. Found: C, 44.63; H, 2.52.)

Provenance & Evidence