General procedure for the synthesis of 3-(methoxycarbonyl)-4-methylphenylboronic acid pinacol ester from methyl 5-iodo-2-methylbenzoate and pinacol ester of bisboronic acid: methyl 5-iodo-2-methylbenzoate (0.25 mol), pinacol ester of bisboronic acid (100 g, 0.40 mol) and potassium acetate (92 g, 0.93 mol) were added to DMF (800 mL) , which was subsequently degassed with nitrogen. [1,1'-Bis(diphenylphosphino)ferrocene]palladium(II) dichloride complex with dichloromethane (6 g) was added and the reaction mixture was heated to 100 °C and kept for 18 hours. After completion of the reaction, it was cooled to room temperature, filtered through diatomaceous earth and washed with ethyl acetate (3 x 1 L). The filtrates were combined, washed with brine (3 x 500 mL), dried over anhydrous sodium sulfate and concentrated in vacuum. The residue was washed with petroleum ether (2 × 500 mL), filtered and dried to afford 3-(methoxycarbonyl)-4-methylphenylboronic acid pinacol ester as a yellow powder (60 g, 87% yield), which was used directly in the next reaction.
