How is 4-Chloro-6-iodo-1H-pyrrolo[2,3-d]pyrimidine (CAS: 876343-10-1) typically synthesized?

4-Chloro-6-iodo-1H-pyrrolo[2,3-d]pyrimidine is typically synthesized through the sequential addition of chlorine and iodine to 1H-pyrrolo[2,3-d]pyrimidine. This process involves nucleophilic substitution reactions where the chlorine and iodine atoms are installed at the appropriate positions. The reaction often requires the use of a catalyst and protective groups to control the reactivity and ensure high selectivity and yield.