Synthesis of compound C: Ammonia (2 mL) was slowly added dropwise to 4-trifluoromethylbenzoyl chloride (417 mg, 2 mmol) at room temperature while maintaining stirring. After the reaction continued for 3 h, the completion of the reaction was confirmed by thin layer chromatography (TLC, unfolding agent ratio of ethyl acetate:hexane = 1:2). The reaction mixture was poured into water (10 mL) and subsequently extracted with ethyl acetate (10 mL x 3). The combined ethyl acetate layers were washed sequentially with water (10 mL × 2) and saturated saline (10 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was distilled under reduced pressure to remove the solvent to give the crude product (355 mg, 2.0 mmol). The crude product was purified by solvent recrystallization from ethyl acetate/hexane mixture to give compound C (white needle-like crystals, 359 mg) in 95% yield. The melting point of the product was 186.5-187.5 °C. 1H-NMR (300 MHz, DMSO-d6) δ: 7.63, 8.19 (both broad peaks, 1H, NH or OH), 8.06 (double peak, 2H, J = 8.0 Hz, Ar-H), 7.84 (double peak, 2H, J = 8.0 Hz, Ar-H).
