Step 92b: Synthesis of 1-(triisopropylsilyl)pyrrole-3-boronic acid (Compound 0602-197)
To a stirring solution of 3-bromo-1-(triisopropylmethylsilyl)pyrrole (0601-197, 1 g, 3.31 mmol) in anhydrous THF (20 mL) under nitrogen protection, a THF solution of n-butyllithium (2.5 M, 1.58 mL, 3.96 mmol) was slowly added at -78 °C. Maintaining this temperature, stirring was continued for 30 minutes. Subsequently, trimethyl borate (687 mg, 6.6 mmol) was added dropwise to the reaction mixture. The reaction mixture was gradually warmed up to room temperature and stirring was continued for 1 hour. After completion of the reaction, the mixture was diluted with 200 mL of water and extracted with 200 mL of ethyl acetate. The organic phase was washed sequentially with 100 mL of water (twice) and 100 mL of brine and dried over anhydrous sodium sulfate. After concentration under reduced pressure, the crude product 0602-197 (280 mg, 32% yield) was obtained as an oil, which was used directly in the next step of the reaction without further purification.LCMS detection showed a molecular ion peak of 268 [M + 1]+.
