The general procedure for the synthesis of 8-bromo-1,3-dimethyl-1H-purine-2,6(3H,9H)-dione using 1,3-dimethyl-1H-purine-2,6(3H,9H)-dione as a starting material was as follows: the theophylline (10 g, 55.5 mmol) was dissolved in a mixed solvent of acetic acid/water (90 mL of acetic acid, 60 mL of water) at 50 °C, followed by the bromine (9.76 g, 61 mmol) was added slowly and dropwise. The reaction mixture was stirred continuously at 50 °C for 4 hours. Upon completion of the reaction, the mixture was cooled to room temperature to induce precipitation of the target product. The precipitate was separated by filtration and the filter cake was washed twice with distilled water and subsequently dried under vacuum to afford 8-bromo-1,3-dimethyl-1H-purine-2,6(3H,9H)-dione (13.6 g, 94.5% yield) as a white solid. The product was detected by LCMS and showed MH+ peak of 259.
