General procedure for the synthesis of 4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzaldehyde from 3-bromo-4-methylbenzaldehyde and pinacol bis(borate) ester: To a stirred solution of 3-bromo-4-methylbenzaldehyde (3.0 g, 15.1 mmol) in 1,4-dioxane (30 mL) was added pinacol bis(borate) ester ( 4.5 g, 17.7 mmol) and potassium acetate (2.98 g, 30.4 mmol). The reaction mixture was degassed with nitrogen for 20 min. Subsequently, Pd(dppf)Cl2 (0.62 g, 0.75 mmol) was added. The reaction system was heated and reacted at 90 °C overnight. After completion of the reaction, the mixture was diluted with water and extracted with ethyl acetate. The organic layer was washed sequentially with water and saturated saline and then concentrated. Purification by combiflash column chromatography afforded the target product 4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzaldehyde (3.4 g, 91.39% yield) as a yellow semi-solid.LCMS: (M + H)+ = 247.2; 1H NMR (CDCl3, 300MHz) δ 9.99 (s , 1H), 8.26 (s, 1H), 7.82-7.85 (dd, J=7.8, 1.5 Hz, 1H), 7.26-7.33 (m, 1H), 2.62 (s, 3H), 1.37 (s, 12H).
