1-Boc-indole-4-boronic Acid Pinacol Ester

676448-17-2

73183-34-3

893441-86-6

KOAc (9 g, 91 mmol) was added to a solution of tert-butyl 4-bromo-1H-indole-1-carboxylate (9 g, 30 mmol) and bis(pinacolato)diboron (8.45 g, 33 mmol) in DMSO (180 mL). The suspension was purged with nitrogen (3 times) before addition of Pd(dppf)Cl2 (744 mg, 912 μmol). The reaction mixture was stirred at 80 °C for 12 hours. Upon completion of the reaction, the suspension was poured into water (400 mL) and extracted with EtOAc (300 mL × 2). The combined organic layers were washed with brine (200 mL), dried over Na2SO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (PE:EtOAc = 40:1) to afford tert-butyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole-1-carboxylate (7.8 g, 22.7 mmol, 75.8% yield) as a white solid. nmr (cdcl3, 400 MHz) δ ppm. 1.38 (s, 12H), 1.68 (s, 9H), 7.09 (d, J = 3.6 Hz, 1H), 7.30 (t, J = 7.6 Hz, 1H), 7.61 (d, J = 3.2 Hz, 1H), 7.70 (d, J = 7.2 Hz, 1H), 8.24 (d, J = 8 Hz, 1H); ESIMS measured value c19h26bno4 [m+h]+ 344.1.