General procedure for the synthesis of 4'-bromo-4-biphenylboronic acid from triisopropyl borate and 4,4'-dibromobiphenyl: 4,4'-dibromobiphenyl (9.4 g, 30 mmol) was dissolved in anhydrous ethyl ether and cooled to -78 °C. Under nitrogen protection, n-butyllithium (2.5 M hexane solution, 2.1 g, 33 mmol) was slowly added dropwise, and after the drop was completed, the reaction was kept at -78 °C for 30 min. Subsequently, triisopropyl borate (8.5 g, 45 mmol) was added dropwise and the reaction was continued at -78 °C. After completion of the reaction, it was gradually warmed to room temperature, diluted with water and acidified with 2N HCl. The mixture was extracted with ethyl acetate, the organic layer was washed with water and dried over anhydrous magnesium sulfate. After filtration, the organic layer was concentrated, purified by silica gel column chromatography and finally recrystallized to obtain 4'-bromo-4-biphenylboronic acid (5.9 g, 71% yield).
