13391-28-1

13196-10-6

GENERAL STEPS: 5-methoxybenzofuran (0.5 g, 3.37 mmol) was dissolved in dichloromethane (DCM, 7 mL) under ice-bath cooling conditions and boron tribromide (3.4 mL, 3.37 mmol, 1 M DCM solution) was added slowly. The reaction mixture was stirred at 0 °C for 1 h. An equal amount of boron tribromide (3.4 mL) was added again. Subsequently, the reaction mixture was brought to room temperature and stirring was continued for 2 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the completion of the reaction, the reaction mixture was slowly poured into ice water and the pH was adjusted with sodium carbonate (Na2CO3) to 7. The aqueous phase was extracted with dichloromethane (DCM, 2×), the organic phases were combined and washed with saturated brine, dried over anhydrous sodium sulphate (Na2SO4) and concentrated under reduced pressure. The resulting light brown solid product (0.36 g, yield 79.6%) was pure enough to meet the requirements of the subsequent reaction and did not require further purification. The structure of the product was confirmed by 1H NMR (400 MHz, CD3OD): δ 7.59 (d, J = 2.0 Hz, 1H), 7.35 (d, J = 9.2 Hz, 1H), 7.01 (d, J = 2.4 Hz, 1H), 6.82 (dd, J = 8.8 Hz, J = 2.8 Hz, 1H), 6.67 (m, 1H), 4.73 (s 1H).