1000340-39-5

68-12-2

918515-16-9

Step 2: 3-bromo-4-chloro-7-azaindole (8 g, 34.632 mmol) was dissolved in THF (160 mL) and cooled to -78 °C. Under nitrogen protection, n-butyllithium (1.6 M in hexane, 50 mL, 79.63 mmol) was slowly added and stirred for 30 min keeping the temperature at -78 °C. Subsequently, N,N-dimethylformamide (5.056 g, 69.264 mmol) was slowly added and stirring was continued at -78 °C. The reaction mixture was gradually warmed to 25 °C and stirred at this temperature for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of water (2 mL). The reaction mixture was concentrated under reduced pressure, treated with saturated aqueous ammonium chloride solution (28 mL), the precipitated solid was collected and dried under reduced pressure. Purification by silica gel column chromatography afforded 4-chloro-1H-pyrrolo[2,3-b]pyridine-3-carbaldehyde (3.5 g, 52% yield) as a light yellow solid. The product was confirmed by 1H NMR (CDCl3): δ 12.6-12.8 (br s, 1H), 10.4-10.6 (s, 1H), 8.26-8.3 (d, 1H), 8.12-8.18 (s, 1H), 7.26-7.3 (d, 1H). The mass spectrum (ESI) showed a molecular ion peak (M+1) of 181, which is consistent with the calculated value of the molecular formula C8H5ClN2O.