A. Synthesis of ethyl 2-amino-4-fluorobenzoate
2-Amino-4-fluorobenzoic acid (1.57 g, 10.1 mmol) was dissolved in anhydrous ethanol (20 mL) and cooled to low temperature. Pure thionyl chloride (4.4 mL, 60 mmol) was added slowly and the reaction mixture was refluxed for 4 days. Subsequently, thionyl chloride (8 mL, 110 mmol) was added supplementally and the mixture was concentrated after the reaction was completed. It was diluted with ethyl acetate (EtOAc), washed with 2N sodium hydroxide (NaOH) solution, dried and concentrated in vacuum to give ethyl 2-amino-4-fluorobenzoate (1.73 g, 94% yield).
