Sodium Hydroxide → N-(5-amino-2-chloro4-fluorophenyl)-1-chloromethanesulfonamide

74.5 g of crude N-[4-chloro-5-[[(chloromethyl)sulfonyl]amino]-2-fluorophenyl]acetamide (purity: 90%) was suspended in 355 mL of 6 N hydrochloric acid and heated to 95° C. After 1.5 hours the suspension turned into a solution. The mixture was cooled to room temperature and 90 mL of a NaOH solution (50%) was added (pH 3). The precipitated product was filtered and washed with water to yield, after drying, 62.8 g of the title compound as yellow crystals (purity: 86.4% by HPLC) which could be further purified by recrystallization as described above in Example 5.