At -78°C, butyllithium (17 mL, 28 mmol) was added dropwise to a 50 mL 4/1 toluene/THF (4/1, 50 mL) solution of 3-bromo-2-methylpyridine (4.00 g, 23 mmol) and triisopropyl borate (6.40 mL, 28 mmol). The mixture was heated to -70°C over 30 minutes, then to 20°C. HCl (2 M) was added to bring the solution to pH 1. Water (20 mL) was then added, and the mixture was extracted with toluene. The aqueous layer was neutralized with 1 M NaOH and extracted with dichloromethane.
The aqueous layer was concentrated to dryness, and the white solid was washed with dichloromethane. The combined organic layers were dried over sodium sulfate, filtered, and concentrated to give 2.10 g of a yellow, oily 2-methylpyridine-3-boronic acid. ES+ = 138.2 (M+H).
