Step 3: 15 g (59 mmol) of (4-((tert-butoxycarbonyl)amino)-3-fluorophenyl)boronic acid obtained from step 2 was reacted with 14 g (118 mmol) of pinacol in methanol for 1 h at room temperature with stirring. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming that the reaction was complete, 45 mL of water was added to the reaction mixture and the oily material started to crystallize after grinding. The precipitate was collected by filtration, washed with 70% methanol and dried to give 16 g (48 mmol) of N-Boc-3-fluoro-4-aminophenylboronic acid pinacol ester in 81% yield. The product was characterized by 1H-NMR (DMSO, 300 MHz): δ 9.11 (s, 1H), 7.73 (t, 1H), 7.38 (d, 1H), 7.28 (d, 1H), 1.43 (s, 9H), 1.25 (s, 12H).
