General procedure for the synthesis of 8-bromo-1H-purine-2,6(3H,7H)-dione using 1H-purine-2,6(3H,7H)-dione as a raw material: weigh 15g of 1H-purine-2,6(3H,7H)-dione in a 250mL reaction flask, add 250mL of deionized water, and stir until complete dissolution. 7.6 mL of liquid bromine was added slowly dropwise, and the rate of dropwise acceleration was controlled to avoid violent reaction. The reaction mixture was heated to 100 °C and stirring was maintained until the color of the reaction solution faded completely from the red color of the bromine, indicating that the reaction was complete. The heating was stopped and the reaction mixture was cooled to room temperature. The reaction mixture was washed with a small amount of ice water to remove unreacted bromine. Subsequently, the reaction mixture was diafiltered and the solid product was collected. The filter cake was dried in a vacuum drying oven to give 18.4 g of 8-bromo-1H-purine-2,6(3H,7H)-dione.
