333432-28-3

121-43-7

28320-31-2

333432-28-3

2-Bromo-9,9-dimethyl-9H-fluorene (100 g, 366 mmol) was dissolved in 1000 mL of tetrahydrofuran under nitrogen protection and cooled to -78 °C. At this temperature, a hexane solution of 1.6 M n-butyllithium (275 mL, 439 mmol) was slowly added dropwise. After the dropwise addition was completed, the reaction mixture was kept at -78 °C and continued to be stirred for 1 hour. Subsequently, the reaction mixture was slowly warmed to room temperature and trimethyl borate (49.5 g, 476 mmol) was added dropwise and stirring was continued for 1 hour at room temperature. Upon completion of the reaction, 1 M aqueous hydrochloric acid was added slowly and stirred for 30 minutes at room temperature. The organic layer was separated and concentrated under reduced pressure and the resulting crude product was recrystallized with a mixed solvent of dichloromethane and hexane to afford the title compound 9,9-dimethyl-2-boronic acid fluorene (70 g, 80% yield).