General procedure for the synthesis of isopropenylboronic acid pinacol esters from pinacol, 2-bromopropene and compound (CAS:28049-80-1): 2-bromopropene (89.58 g, 0.741 mol) was dissolved in 750 mL of tetrahydrofuran, and slowly added dropwise from -10 °C to 0 °C with a mixture of bis(diisopropylamino)boron chloride (183 g, 0.74 mol) and lithium metal (10.4 g, 1.5 mol) mixture followed by 110 mL of tetrahydrofuran under strictly controlled reaction conditions. After the dropwise addition, the reaction was maintained at this temperature for 1 h. Then the temperature was raised to 25 °C and the reaction was continued for 5 h. The reaction was completed with the addition of pinacol. Upon completion of the reaction, pinacol (98.8 g), 2,6-di-tert-butyl-4-methylphenol (4.58 g) and 120 mL of tetrahydrofuran were added and the reaction mixture was heated to reflux. Purification by distillation under reduced pressure afforded 82.1 g of colorless transparent liquid isopropenylboronic acid pinacol ester in 66% yield and 99.7% GC purity. Finally, 2,6-di-tert-butyl-4-methylphenol (0.45 g) was added as a stabilizer for long-term storage.
