Step II: Synthesis of tert-butyl 4-[[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]methyl]piperazine-1-carboxylate (V-1). Under argon protection, tert-butyl 4-(4-bromobenzyl)piperazine-1-carboxylate (7.5 g, 21.1 mmol), pinacol ester of bis(boronic acid) (8 g, 31.7 mmol) and potassium acetate (4.1 g, 42.2 mmol) were dissolved in DMSO (50 mL). Subsequently [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride (0.77 g, 1.06 mmol) was added. The reaction mixture was stirred at 90 °C for 16 hours. The reaction progress was monitored by TLC. Upon completion of the reaction, water (100 mL) was added to the mixture and the product was extracted with ethyl acetate (50 mL x 3). The organic phases were combined, washed sequentially with water (100 mL) and brine (100 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: 2-20% methanol gradient in dichloromethane) to afford the target compound 4-(4-Boc-piperazinylmethyl)phenylboronic acid pinacol ester V-1 (7 g, 82% yield).LCMS: m/z 403.3 ([M+H]+).
