The general procedure for the synthesis of 1-(2-hydroxy-5-(trifluoromethyl)phenyl)ethanone from 1-(2-methoxy-5-(trifluoromethyl)phenyl)ethanone was as follows: ethanethiol (EtSH, 8.59 mL, 116 mmol) was slowly added to sodium hydride (NaH, 60% dispersed in mineral oil, 4.64 g, 116 mmol) at 0 °C in N,N- dimethylformamide (DMF, 300 mL) in suspension. After stirring the reaction mixture for 15 min, 1-(2-methoxy-5-trifluoromethylphenyl)ethanone (24.0 g, 110 mmol) was added and the mixture was subsequently heated to 100 °C and stirred continuously for 30 min. After completion of the reaction, it was cooled to room temperature and the reaction mixture was slowly poured into water, acidified with 1 M hydrochloric acid (HCl) to pH acidic and subsequently extracted with ethyl acetate (AcOEt). The organic phases were combined, washed sequentially with water and saturated brine, dried over anhydrous magnesium sulfate (MgSO4) and concentrated under reduced pressure to remove the solvent. The residue was purified by silica gel column chromatography using hexane/ethyl acetate (10:1, v/v) as eluent to afford the target product 1-(2-hydroxy-5-(trifluoromethyl)phenyl)ethanone (5k, 17.7 g, 79% yield) as a light yellow oil.
