General procedure for the synthesis of (9,9-diphenyl-9H-fluoren-2-yl)boronic acid from trimethyl borate and 2-bromo-9,9-diphenylfluorene: 10 g of 2-bromo-9,9-diphenylfluorene and 100 ml of anhydrous tetrahydrofuran were added to a 1-liter flask, and the mixture was cooled to -78 °C (using a bath of liquid nitrogen). Subsequently, 25.2 mL of n-butyllithium solution was added slowly and dropwise, followed by trimethyl borate. The reaction mixture was stirred at -78 °C and then allowed to warm naturally to room temperature. Then, an appropriate amount of dilute hydrochloric acid was added to carry out the hydrolysis reaction. Upon completion of the reaction, the mixture was extracted with ethyl acetate, the organic layer was separated and dried with anhydrous sodium sulfate. Finally, the solvent was removed by distillation under reduced pressure and the residue was eluted with hexane to afford 4 g of the target product (9,9-diphenyl-9H-fluoren-2-yl)boronic acid.
