Synthesis
General procedure for the synthesis of 2-fluoro-3-methoxyaniline from 2-fluoro-3-methoxybenzoic acid: To a solution of 2-fluoro-3-methoxybenzoic acid (15.0 g, 88 mmol) and triethylamine (13.49 mL, 96.8 mmol) in toluene (300 mL) was added diphenylphosphoryl azide (20.9 mL, 96.8 mmol). The reaction mixture was heated to reflux for 1 hour. Subsequently, 2-methyl-2-propanol (12.5 mL, 132 mmol) was added and refluxing was continued for 5 hours. After completion of the reaction, the mixture was cooled to room temperature and concentrated under reduced pressure. The organic phase was separated by partitioning the residue between water and dichloromethane. The organic phase was dried with anhydrous sodium sulfate, filtered and passed through a short column of 1 inch silica gel and concentrated again. The resulting residue was dissolved in dichloromethane (200 mL), trifluoroacetic acid (25 mL) was added and stirred at room temperature overnight. Upon completion of the reaction, it was concentrated under reduced pressure and the residue partitioned between dichloromethane and saturated sodium bicarbonate solution. The organic phase was dried with anhydrous sodium sulfate, filtered and concentrated. Finally, purification by silica gel column chromatography (eluent: isohexane solution containing 15% ethyl acetate) afforded the target product 2-fluoro-3-methoxyaniline as a light yellow oil (10.8 g, 87% yield).1H NMR (400 MHz, CDCl3) δ 3.72 (2H, br s), 3.85 (3H, s), 6.34-6.41 (2H, m), 6.81-6.86 (1H, m).
References
[1] Patent: WO2005/47279, 2005, A1. Location in patent: Page/Page column 38
[2] Patent: WO2011/29392, 2011, A1
[3] Patent: WO2012/119559, 2012, A1
