Synthesis 8-1-A; 4-Chloro-7H-pyrrolo[2,3-d]pyrimidine-5-carboxylic acid; Under dry nitrogen protection, n-butyllithium (n-BuLi) solution (4 mL, 1.5 M, 6 mmol) was slowly added dropwise to an anhydrous tetrahydrofuran (THF, 4.09 mmol) solution of 5-bromo-4-chloro-7H-pyrrolo[2,3-d]pyrimidine (0.95 g, 4.09 mmol). 15 mL) solution, keeping the reaction temperature at -78°C. The reaction mixture was stirred continuously at -78°C for 1 h. The reaction mixture was then stirred continuously at -78°C for 1 h. The reaction temperature was kept at -78°C. Subsequently, solid carbon dioxide (CO2) was added directly to the reaction system. The resulting suspension continued to be stirred at -78°C for 2 hr, after which it was slowly warmed up to room temperature. The reaction solution was adjusted to acidic (pH<7) with 1 M hydrochloric acid (HCl), and the resulting white precipitate was collected by filtration, washed thoroughly with deionized water, and dried to afford the target product, 4-chloro-7H-pyrrolo[2,3-d]pyrimidine-5-carboxylic acid, as a white solid (0.53 g, 66% yield). The product was characterized by 1H NMR (500 MHz, DMSO-d6): δ 8.30 (1H, s), 8.66 (1H, s); LC-MS retention time (Rt) 2.63 min; mass spectrum (m/z) 198 [MH+].
![5-Bromo-4-chloro-7H-pyrrolo[2,3-d]pyrimidine](/CAS/GIF/22276-95-5.gif)
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