9,9-bis(n-butyl)fluorene (26 g, 92 mmol) was used as raw material and mixed with N-bromosuccinimide (NBS, 16.5 g, 92 mmol) in acetone (200 mL). The reaction mixture was stirred at 80 °C for 3 h under nitrogen protection. After completion of the reaction, it was cooled to room temperature, the reaction solution was poured into cold water and extracted with dichloromethane (DCM, 3 x 200 mL). The organic layers were combined, washed with water, dried over anhydrous sodium sulfate, filtered and concentrated to dryness. The crude product was purified by silica gel short-column chromatography with petroleum ether as eluent to afford the target product 2-bromo-9,9-dibutylfluorene as a colorless solid (29.2 g, 92.7% yield); melting point 58-61 °C. 1H NMR (400 MHz, CDCl3) δ (ppm): 7.64-7.66 (m, 1H), 7.50-7.55 (m, 1H) , 7.43-7.47 (m, 2H), 7.31-7.34 (m, 3H), 1.88-1.96 (m, 4H), 1.03-1.12 (m, 4H), 0.68 (t, 6H, J=7.4Hz), 0.52-0.63 (m, 4H).
