In a 500 mL round bottom flask, 1-bromo-3-iodobenzene (25.0 g, 88 mmol) was dissolved in 200 mL of tetrahydrofuran. The reaction solution was cooled to -78°C under nitrogen protection. n-Butyllithium (60.75 mL, 97 mmol) was slowly added dropwise to the cooled solution over a period of 30 minutes and stirring was continued at the same temperature for 1 hour. Subsequently, trimethyl borate (11 g, 106 mmol) was added dropwise at the same temperature, and then the mixture was gradually warmed to room temperature and stirred overnight. Upon completion of the reaction, 2 equivalents of hydrochloric acid was added dropwise to the reaction solution for acidification and stirring was continued for 1 hour. The reaction mixture was extracted with ethyl acetate, the organic layers were combined and concentrated under reduced pressure. The resulting crystals were dissolved in cold hexane to give Intermediate 11-a (12 g, 67.6% yield).
