1121057-75-7

75-36-5

1227068-67-8

4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2,3,6-tetrahydropyridine hydrochloride (Intermediate G3, 1.4 g, 5.70 mmol) was suspended in dichloromethane (DCM, 15 mL) and stirred at 0 °C. Subsequently, triethylamine (TEA, 2.384 mL, 17.10 mmol) and acetyl chloride (AcCl, 0.405 mL, 5.70 mmol) were sequentially added to the reaction system. The reaction mixture was gradually warmed to room temperature and stirring was continued for 30 minutes. Upon completion of the reaction, the reaction volume was concentrated to 1/3 of the initial volume and the residue was diluted with ethyl acetate (AcOEt, 150 mL). The organic phase was washed sequentially twice with water, once with 0.2 M aqueous hydrochloric acid, once with saturated aqueous sodium bicarbonate (NaHCO3) and finally dried over anhydrous sodium sulfate (Na2SO4). The solvent was removed under reduced pressure to give 1-acetyl-5,6-dihydro-2H-pyridine-4-boronic acid pinacol ester (1.24 g, 87% yield) as a pale yellow solid.UPLC-MS analysis resulted in a retention time of 0.83 min and a molecular ion peak of 252.3 [M+H]+, analytical method 9.