General procedure for the synthesis of (4-(methoxycarbonyl)-2-methylphenyl)boronic acid from methyl 4-iodo-3-methylbenzoate: to a 3-liter round-bottomed flask equipped with a mechanical stirrer, thermocouple, and dosing funnel were added 100 g of methyl 4-iodo-3-methylbenzoate and 1.0 L of anhydrous THF.The mixture was cooled to -25 °C, and over a period of 25 minutes 218 mL of isopropyl magnesium chloride (2 M of THF solution) while controlling the internal temperature to not exceed 0°C. Upon completion of the reaction, the mixture was aged at room temperature overnight. Subsequently, THF was removed by distillation under reduced pressure at a temperature below 45 °C. The resulting product slurry was cooled to room temperature and filtered. The filter cake was washed sequentially with water (3 x 500 ml) and toluene (2 x 250 mL), and finally dried under vacuum protected by nitrogen for 18 h. An off-white crystalline solid of (4-(methoxycarbonyl)-2-methylphenyl)boronic acid (64.3 g, 91% yield) was obtained.
