Step A: Boron tribromide (BBr3, 85.2 g, 341 mmol) was slowly added dropwise to a solution of 2-methoxy-5-(trifluoromethoxy)benzaldehyde (50.0 g, 227 mmol) in dichloromethane (DCM, 500 mL) at -20°C and under nitrogen protection. The reaction mixture was stirred at 0°C for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of ice chips, followed by pouring the mixture into an aqueous solution of saturated sodium bicarbonate (NaHCO3, 300 mL) and extracting with dichloromethane (DCM, 3 x 400 mL). The organic layers were combined, dried over anhydrous sodium sulfate and concentrated to give the crude product. The crude product was purified by silica gel column chromatography (eluent: hexane/ethyl acetate=20:1) to afford 2-hydroxy-5-(trifluoromethoxy)benzaldehyde (38.0 g, 81.0% yield). NMR hydrogen spectrum (400 MHz, CDCl3) δ 10.97 (s, 1H), 9.87 (s, 1H), 7.43-7.38 (m, 2H), 7.02 (d, J=8.0 Hz, 1H).
