Diisopropylamine → (1-(tert-Butoxycarbonyl)-4-fluoro-1H-indol-2-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of diisopropylamine (175 mL, 1.25 mol) in THF (800 mL) at 0° C. was added n-BuLi (500 mL, 1.25 mol, 2.5 M in hexane) dropwise. The mixture was stirred at 0° C. for 40 min. Then the mixture was cooled to −78° C. Tert-butyl 4-fluoro-1H-indole-1-carboxylate (118 g, 0.50 mol) in THF (300 mL) was added dropwise slowly, followed by triisopropyl borate (231 mL, 1.00 mol). The mixture was stirred at −78° C. for another 40 min. The reaction was monitored by HPLC. When the reaction was completed, the reaction was quenched with NH4Cl (sat. 500 mL). Then the mixture was adjusted to pH=6 with 1 N HCl. Extracted with EtOAc (2000 mL) and the combined organic layers were washed with brine (500 mL), dried over Na2SO4, filtered and concentrated. The obtained solid was recrystallized with EtOAc and PE to give (1-(tert-butoxycarbonyl)-4-fluoro-1H-indol-2-yl)boronic acid (93 g, yield: 64%, store in fridge). 1H-NMR (CDCl3, 400 MHz) δ 7.77 (d, J=8.4 Hz, 1H), 7.57 (s, 1H), 7.44 (s, 2H), 7.24 (m, 1H), 6.90 (m, 1H), 1.66 (s, 9H). MS (M+H)+: 280.

Provenance & Evidence