Potassium hydroxide monohydrate → 4-Hydroxy-6-chloro-8-trifluoromethoxychroman-4-yl carboxylic acid

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A solution of 4-hydroxy-6-chloro-8-trifluoromethoxychroman-4-yl carboxylic acid, methyl ester in iso-propanol (50 mL) was added to KOH/H2O (20%, 60 mL) and the mixture was refluxed overnight. The resultant solution was partially concentrated, and the remainder was acidified with H2SO4 (10%). The very turbid mixture was extracted with ether (3×), and the combined organic phase was dried (Na2SO4) and concentrated. The crude product was purified via prep-HPLC (CH3CN:0.1M ammonium acetate (30:60)). The fractions of interest were partly concentrated and extracted with ether. The combined organic layers were washed with water, dried (Na2SO4), and concentrated, yielding 0.24 g (10% over steps (vi)–(ix)).

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