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Step-1: 2-Amino-4-fluorobenzoic acid (50 g, 322.6 mmol) was dissolved in 700 mL of N,N-dimethylformamide (DMF) followed by addition of N-chlorosuccinimide (41 g, 305.5 mmol) in batches. The reaction mixture was heated at 50 °C with stirring for 5 hours. Upon completion of the reaction, the mixture was cooled to room temperature and slowly poured into ice water to precipitate a solid. The solid was collected by filtration, dissolved in ethyl acetate (EtOAc) and washed with saturated sodium chloride solution (300 mL). The aqueous layer was back-extracted with ethyl acetate (3 x 200 mL). The organic phases were combined, dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure to give the product 2-amino-5-chloro-4-fluorobenzoic acid (42 g, 69% yield) as a brown solid.

[1] Patent: WO2016/171755, 2016, A1. Location in patent: Paragraph 0101
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