4-Chloro-5-iodo-1H-pyrrolo[2,3-b]pyridine

651744-48-8

1015610-31-7

Step B: At -78 °C, sec-butyl lithium (S-BuLi, 59.3 mL, 71.2 mmol, 1.4 M in cyclohexane) was slowly added dropwise to a solution of 4-chloro-1-(triisopropylmethylsilyl)-1H-pyrrolo[2,3-b]pyridine (10.0 g, 32.4 mmol) in tetrahydrofuran (THF, 100 mL). The reaction mixture was stirred continuously at -78 °C for 30 min. Subsequently, iodine (I, 20.5 g, 80.9 mmol) in THF (50 mL) solution was added and the reaction continued to be stirred for 20 minutes at -78 °C. Upon completion of the reaction, saturated ammonium chloride solution (50 mL) and saturated sodium sulfite solution (50 mL) were added sequentially to quench the reaction. The mixture was extracted with hexane (200 mL) and the organic phase was washed with brine and dried over anhydrous sodium sulfate. After the solvent was removed by concentration under reduced pressure, the residue was dissolved in THF (50 mL) and tetrabutylammonium fluoride (TBAF, 32.4 mL, 32.4 mmol) was added. The reaction mixture was stirred at room temperature for 10 min, followed by the addition of water (20 mL) and ethyl acetate (100 mL). The organic layer was separated, washed with brine and dried over anhydrous sodium sulfate. After the solvent was removed by concentration under reduced pressure, the residue was suspended in dichloromethane (DCM, 20 mL) and stirred for 10 minutes. The solid formed was collected by filtration to afford the target product 4-chloro-5-iodo-1H-pyrrolo[2,3-b]pyridine (6.6 g, 73% yield) as a white solid.