The general procedure for the synthesis of 4-chloro-6-iodo-7H-pyrrolo[2,3-d]pyrimidines from 4-chloro-7-(phenylsulfonyl)-7H-pyrrolo[2,3-d]pyrimidines was carried out as follows: according to the literature [20], 4-chloro-7-(phenylsulfonyl)-7H-pyrrolo[2,3-d]pyrimidines (1) (5.42 g, 18.5 mmol) were subjected to iodination reaction. Upon completion of the reaction, a 9:1 mixture of 2:3 (6.0 g) was obtained. The mixture was mixed with THF (125 mL) and a methanolic solution of 5 M NaOH (21 mL). After stirring for 2 hours at room temperature, saturated aqueous NH4Cl solution (125 mL) was added and the mixture was concentrated. The precipitate formed was collected by filtration and washed with water. Subsequently, the precipitate was ground with boiling acetonitrile (1 g/10 mL) to give 4-chloro-6-iodo-7H-pyrrolo[2,3-d]pyrimidine (3.96 g, 14.2 mmol, 77% yield) as a white solid with a melting point of 219 °C (decomposition) (220 °C reported in literature [20]).1H NMR (400 MHz, DMSO-d6) δ: 12.57 (s, 1H), 8.51 (s, 1H), 6.88 (s, 1H). The obtained 1H NMR data were in agreement with those reported in the literature [20].