(Trifluoromethyl)trimethylsilane (28.4 g, 0.2 mol) was slowly added dropwise to a suspension of 2-thiophenecarboxaldehyde (11.2 g, 0.1 mol) and cesium fluoride (1.52 g, 0.01 mol) in 1,2-dimethoxyethane (70 mL) at 0 °C. The reaction mixture was warmed to 25 °C and stirred for 3 h until the feedstock was completely consumed. Subsequently, the reaction was quenched by the addition of 3N hydrochloric acid solution and stirring was continued for 0.5 h to ensure complete conversion of the intermediate to the target product 2,2,2-trifluoro-1-(thiophen-2-yl)ethanol. The reaction mixture was extracted with ethyl acetate and the organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (200 g silica gel, petroleum ether/ethyl acetate = 1% to 2% gradient elution) to afford the oily target product 125b (17.2 g, 97% yield).1H NMR (CDCl3) data were as follows: δ 7.39-7.38 (m, 1H), 7.19-7.18 (d, 1H, J=3.6 Hz), 7.05- 7.03 (m, 1H), 5.29-5.23 (m, 1H).
