General procedure for the synthesis of methyl 4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate from methyl 3-bromo-4-methylbenzoate and pinacol ester of biboronic acid: Methyl 3-bromo-4-methylbenzoate (3 mL, 19.2 mmol) was dissolved in 1,4-dioxane (96 mL), bis(pinacolato ) diboron (7.31 g, 28.2 mmol) and potassium acetate (5.65 g, 57.6 mmol) were added. Subsequently, Pd(dppf)Cl2 (2.8 g, 3.84 mmol) was added to the reaction system. The resulting mixture was stirred at 90 °C for 16 h under argon protection. After completion of the reaction, the mixture was cooled to room temperature and the reaction was quenched by the addition of water. The reaction mixture was extracted with ethyl acetate (EtOAc), the organic layers were combined and dried over anhydrous magnesium sulfate. The organic phase was concentrated under reduced pressure and purified by silica gel column chromatography to afford the target product methyl 4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (off-white solid, 4.46 g, 84% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 8.40 (d, 1H), 7.97 (dd, 1H), 7.23 (d, 1H), 3.94-3.87 (m, 3H), 2.58 (s, 3H), 1.35 (d, 12H).
