The general procedure for the synthesis of 5-iodo-7H-pyrrolo[2,3-d]pyrimidin-4-amine using 4-amino-7H-pyrrolo[2,3-d]pyrimidine as starting material was as follows: 7H-pyrrolo[2,3-d]pyrimidin-4-amine (1.3 g, 9.7 mmol, 1.0 eq.) was dissolved in chloroform (45 mL) at room temperature, followed by the addition of N-iodo-substituted butylenedi imide (NIS, 2.18 g, 9.7 mmol, 1.0 equiv). The reaction mixture was heated to reflux for 2 hours. Upon completion of the reaction, the precipitate was collected by filtration and dried under vacuum to afford the target product 5-iodo-7H-pyrrolo[2,3-d]pyrimidin-4-amine (2.09 g, 83% yield) as a white solid.