Using 2,4-dichloro-7H-pyrrolo[2,3-d]pyrimidine (1.00 g, 5.32 mmol) and p-toluenesulfonyl chloride (1.115 g, 5.85 mmol) as the raw materials, the two were dissolved in dichloromethane (20 mL) along with tetrabutylammonium hydrogen sulfate (0.090 g, 0.27 mmol) at room temperature. Subsequently, 50% aqueous sodium hydroxide solution (1 mL) was added to the reaction mixture and stirred at room temperature for 30 min. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the completion of the reaction, the reaction mixture was diluted with deionized water and dichloromethane and the organic layer was separated. The organic layer was concentrated by vacuum evaporation to give a light yellow solid. The crude product was purified by column chromatography (100% dichloromethane as eluent) to afford the target product 2,4-dichloro-7-toluenesulfonyl-7H-pyrrolo[2,3-d]pyrimidine (1.76 g, 97% yield) as a white solid. The mass spectrum (LCMS) showed [M + H]+ m/z 342. 1H NMR (400 MHz, chloroform-d) δ ppm: 8.14 (d, J = 8.59 Hz, 2H), 7.78 (d, J = 3.79 Hz, 1H), 7.39 (d, J = 8.59 Hz, 2H), 6.70 (d, J = 3.79 Hz, 1H). 2.45 (s, 3H).