How is 4-chloro-6,7-dihydro-5H-pyrrolo[2,3-d]pyrimidine (CAS: 16372-08-0) typically synthesized?

4-Chloro-6,7-dihydro-5H-pyrrolo[2,3-d]pyrimidine can be synthesized by the reaction of 1,2-dichloro-3,4-dihydro-5H-pyrrolo[2,3-d]pyrimidine with a chlorine-containing reagent. Common methods include the use of thionyl chloride or phosphorus oxychloride as the chlorinating agent. The synthetic process is typically carried out in a solvent like dichloromethane or toluene, with the reaction yielding up to 85% purity.