Synthesis
General steps for the synthesis of 2-fluoro-3-hydroxybenzaldehyde from 2-fluoro-3-methoxybenzaldehyde:
Step 1: Synthesis of 2-fluoro-3-hydroxybenzaldehyde. BBr3 (4 mL, 4 mmol, 1.0 M solution in heptane) was slowly added dropwise to a dichloromethane solution of 2-fluoro-3-methoxybenzaldehyde at -78 °C. The reaction mixture was stirred at -78 °C for 1 hour, followed by a slow warming to 0 °C and continued stirring for 2 hours. The reaction mixture was poured into water and extracted with ethyl acetate (3 x 10 mL). The organic phases were combined, washed sequentially with water and saturated saline and dried over anhydrous sodium sulfate. The solvent was concentrated under reduced pressure and the residue was purified by silica gel column chromatography with the eluent being a 0-20% ethyl acetate-hexane solvent mixture to afford the target product 2-fluoro-3-hydroxybenzaldehyde (158 mg, 28% yield) as a white solid. MS data: MS m/z 141 [M + H]+.
References
[1] Journal of Medicinal Chemistry, 1986, vol. 29, # 10, p. 1982 - 1988
[2] Journal of Medicinal Chemistry, 2014, vol. 57, # 11, p. 4584 - 4597
[3] Patent: WO2005/82890, 2005, A1. Location in patent: Page/Page column 70
[4] Patent: WO2008/51494, 2008, A1. Location in patent: Page/Page column 115
[5] Patent: WO2013/61052, 2013, A1. Location in patent: Page/Page column 65
