34). General procedure for the synthesis of 2-chloro-5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-pyrimidines: to a mixture of toluene (16 mL) and THF (4 mL) containing 5-bromo-2-chloropyrimidine (10 mmol, 1.93 g) and triisopropyl borate (12 mmol, 2.8 mL) at -78 °C, over a period of Hexane (1.58 M, 12 mmol, 7.6 mL) was added slowly and dropwise over 45 min. The reaction mixture was continued to be stirred at -78 °C for 1 hour. Subsequently, the mixture was slowly warmed to -20 °C and 1 M aqueous hydrochloric acid (20 mL) was added. After continued warming to room temperature, the precipitate was collected and washed with hexane to give a colorless powder (808 mg, 51% yield). A mixture of this powder (3.63 mmol, 575 mg), pinacol (3.81 mmol, 450 mg), and magnesium sulfate (18.15 mmol, 2.2 g) in toluene (10 mL) was stirred at room temperature for 15 hours. After completion of the reaction, the mixture was filtered and the filtrate was concentrated under reduced pressure. The resulting solid was washed with water to afford the target product 2-chloro-5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-pyrimidine (875 mg, quantitative yield); ESI-MS m/z: 159 [M + 1 - pinacol], retention time 1.75 min (condition A).
