Using 3-iodo-4-methylaniline (1.97 g, 8.45 mmol) and pinacol ester of bis(diphenylphosphino)borate (2.32 g, 9.13 mmol) as raw materials, pinacol ester of bis(boronic acid) was dissolved in DMSO (23 mL) under the protection of argon gas, and potassium acetate (2.87 g, 29.2 mmol) and [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride were added sequentially ( 345 mg, 0.423 mmol). The reaction mixture was stirred at 80 °C for 4 hours. After completion of the reaction, ethyl acetate and water were added to the mixture, the insoluble material was removed by filtration through diatomaceous earth and the organic phase was extracted with ethyl acetate. The organic layer was washed sequentially with water and brine and dried over anhydrous magnesium sulfate. The solvent was removed by concentration under reduced pressure and the residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=6/1) to afford the target product 4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (Compound A4, 1.36 g, 69% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 1.33 (s, 12H), 2.42 (s, 3H), 3.51 (br s, 2H), 6.68 (dd, J = 8.1,2.7Hz, 1H), 6.97 (d, J = 8.1Hz, 1H), 7.11 (d, J = 2.7Hz, 1H).
