22276-95-5

541-41-3

144927-57-1

Under nitrogen protection, 5-bromo-4-chloro-7H-pyrrolo[2,3-d]pyrimidine (2.00 g, prepared with reference to Example 8 (1)) was dissolved in tetrahydrofuran (50 mL) and cooled to -80°C. A 2.64 M butyl lithium-hexane solution (7.2 mL) was slowly added dropwise, and after completion of the dropwise addition, the reaction mixture was stirred at -80°C for 30 minutes. Subsequently, a tetrahydrofuran (5 mL) solution of ethyl chloroformate (905 μL) was added and the reaction mixture was gradually warmed to room temperature and stirred overnight. Upon completion of the reaction, saturated aqueous ammonium chloride solution was added to the mixture to quench the reaction and the organic phase was extracted with ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with an eluent ratio of hexane/ethyl acetate (65/35 to 20/80) to afford ethyl 4-chloro-7H-pyrrolo[2,3-d]pyrimidine-5-carboxylate (1.43 g, 74% yield) as a colorless solid. Mass spectrum (APCI) m/z: 226/228 [M+H]+.