The general procedure for the synthesis of 5-bromo-7-ethylindoline-2,3-dione from the compound (CAS: 849630-53-1) was as follows: to a mixed solution of sulfuric acid (100 mL) and water (10 mL) preheated to 80 °C (oil bath), N-(4-bromo-2-ethylphenyl)-2-hydroxyiminoacetamide (61.0 g, 225 mmol), and the dosing process was controlled to be completed within 20 min. After completion of dosing, the reaction mixture was continued to be heated at 80 °C (oil bath) for 15 min. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently diluted with ice water (500 mL) and extracted with ethyl acetate. The organic phase was washed with saturated sodium bicarbonate solution, dried over magnesium sulfate and concentrated under reduced pressure to afford the target product 5-bromo-7-ethylindoline-2,3-dione (42.3 g, 74% yield). The product was characterized by 1H NMR (DMSO-d6): δ 8.87 (s, 1H), 7.75 (d, 1H), 7.71 (d, 1H), 2.75 (q, 2H), 1.44 (t, 3H). In addition, the synthesis of 5-bromo-7-ethyl-1H-indole-2,3-dione can also be carried out with reference to the method of Example 36, with the difference that N-(4-bromo-2-ethylphenyl)-2-hydroxyiminoacetamide was used as the acetamide component, which ultimately resulted in the solid product, 5-bromo-7-ethylindoline-2,3-dione. esi (-) MS m/e = 252 (MH-).
