Synthesis
Step 1) Reduction reaction: 2-fluoro-4-nitrophenol (5.0 g, 31.8 mmol) was dissolved in methanol (200 mL) and palladium/carbon catalyst (1.0 g, 10%) was added. The reaction mixture was stirred overnight at room temperature in a hydrogen atmosphere. Upon completion of the reaction, the mixture was filtered through a diatomaceous earth pad and washed with methanol (5 mL). The filtrate was concentrated under reduced pressure to give 4-amino-2-fluorophenol as a brown solid (4.02 g, yield >99%). Mass spectrum (ESI, cation mode) m/z: 128.1 [M+H]+.
References
[1] Patent: US2005/245530, 2005, A1. Location in patent: Page/Page column 35-36
[2] Patent: US2006/241104, 2006, A1. Location in patent: Page/Page column 14
[3] Patent: US2007/78140, 2007, A1. Location in patent: Page/Page column 25-26
[4] Patent: WO2014/22116, 2014, A2. Location in patent: Paragraph 0223
[5] Patent: US2015/37280, 2015, A1. Location in patent: Paragraph 0445; 0446