Sodium Hydroxide → 4-Bromo-2-fluoro-6-(methylthio)benzoic acid

To a 20 L flask was charged dimethyl formamide (14.5 L, 10.0 vol), followed by sodium hydroxide (293.7 g, 1.2 eq) and the reaction mass cooled to −15 to −10° C. 4-bromo-2,6-difluorobenzoic acid (1450 g, 1.0 equiv) was added over a period of 10-15 min at −15 to −10° C. and stirred for an additional 10-15 min. Sodium thiomethoxide (514.6 g, 1.2 equiv) was added over a period of 5-10 min at −10 to −5° C. On completion of the addition the temperature of the reaction was raised to 25-28° C. over a period of 45 to 60 min and maintained at that temperature 1.5-2 h. The temperature of the reaction was then raised to 60-65° C. over a period of 30-60 min and maintained at 60-65° C. for 5 h until the reaction was deemed complete. The reaction mixture was then cooled to 20-25° C. and quenched with a cooled (5-10° C.) solution of 2N HCl (5.045 L of 12N HCl in 30.3 L water). Following the quench, ethyl acetate (14.5 L, 10 vol) was added and the mixture stirred for 10-15 min. The phases were separated and the aqueous layer was extracted with ethyl acetate (7.25 L, 5 vol). The two phases were separated and the combined organic layer was washed with a brine solution (725 g of NaCl in 3.625 L of water). The phases were separated and the organic layer was washed with water (5.0 vol, 7.25 L). The phases were separated and the organic layer was dried over sodium sulfate (1450 g). The organic layer was filtered to remove the sodium sulfate, which was then washed with ethyl acetate (2.9 L, 2 vol). The organic layer was concentrated under reduced pressure at 45-50° C./30-40 mm Hg to ˜1 to 1.2 volumes and petroleum ether (7.25 L, 5 vol) was added at 40-45° C. over a period of 15-20 min. The solution was cooled to 20-25° C. over a period of 20-25 min. The solid was filtered and washed with petroleum ether (2.9 L, 2.0 vol) and the product dried under vacuum at 25-28° C., 0.4 to 0.7 mbar to afford 1410 g (87%, 99.40 Area %) of the intermediate 6-fluoro-4-bromo-2-methylsulfanyl-benzoic acid.