Synthesis
General procedure for the synthesis of 3-amino-4-fluorophenylboronic acid pinacol ester from 2-(4-fluoro-3-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl: First, a 500-mL Parr reactor flask was purged with nitrogen and 2-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2- based) aniline (13) (6.92 g, 25.9 mmol), ethyl acetate (150 mL) and 10% palladium carbon (50% wet, 150 mg dry wt.). Subsequently, the reaction flask was connected to a Parr hydrogenation unit, evacuated and filled with hydrogen to a pressure of 50 psi and reacted under shaking conditions for 2 hours. Upon completion of the reaction, the hydrogen was evacuated and filled with nitrogen. The catalyst was removed by filtration through a diatomaceous earth pad (521) and the filter cake was washed with dichloromethane (400 mL). The resulting filtrate was concentrated under reduced pressure to afford the target product 3-amino-4-fluorophenylboronic acid pinacol ester (14) in 100% yield (6.34 g) as a yellow oil. The product was characterized by 1H NMR (500 MHz, CDCl3): δ 7.22 (dd, 1H, J = 8.5,1.0 Hz), 7.16 (m, 1H), 6.97 (dd, 1H, J = 11.5,8.0 Hz), 3.68 (br s, 2H), 1.33 (m, 12H); MS (ESI+) m/z 238.2 (M + H).
