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General procedure for the synthesis of 3-bromo-6-fluoropyridine-2-carboxylic acid from 3-bromo-2-methyl-6-fluoropyridine: 3-bromo-2-methyl-6-fluoropyridine (5 kg) was dissolved in concentrated sulfuric acid (50 kg). After warming the reaction system to 60 °C, chromium trioxide (CrO3, 16 kg) was added in batches. After the addition was completed, the reaction was continued at 60 °C with stirring for 18 h, during which the progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction solution was adjusted to neutral with 20% sodium hydroxide (NaOH) solution. Subsequently, ethyl acetate (50 L × 3) was added to the reaction solution for extraction. The organic phases were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The resulting crude product was purified by slurrying with hexane, filtered and dried to give 3-bromo-6-fluoropyridine-2-carboxylic acid as a white solid (3.8 kg, 58% yield).

[1] Patent: CN108341769, 2018, A. Location in patent: Paragraph 0021; 0022; 0024; 0025; 0026; 0028
[2] Patent: CN108503581, 2018, A. Location in patent: Paragraph 0031-0032; 0039; 0041; 0043