4692-98-2

87-48-9

4692-98-2

General procedure for the synthesis of 6-bromo-2H-benzo[d][1,3]oxazine-2,4(1H)-dione using 5-bromoindigo red as starting material: 5-bromoindigo red (II) (20.0 g, 88.49 mmol) was uniformly dispersed in dichloromethane (300 mL), and m-chloroperoxybenzoic acid (22.91 g, 132.73 mmol) was added in batches at room temperature. at room temperature. The reaction mixture was stirred at room temperature for 2 h. The reaction progress was monitored by thin layer chromatography (TLC) to confirm the completion of the reaction. Subsequently, the reaction system was cooled to 10°C with continuous stirring and sodium bisulfite solution was slowly added dropwise until the starch potassium iodide paper no longer showed color. The reaction solution was concentrated by rotary evaporation to remove dichloromethane, 50 mL of water was added to mix well with the residue, and then saturated sodium bicarbonate solution was added dropwise until no bubbles were produced. The resulting solid was collected by filtration, washed with a small amount of water and dried at 50 °C to give 20.99 g of 5-bromoisatoindirubic anhydride (III) in 98% yield.