1246765-28-5

943994-02-3

1246765-28-5

Step 2: 3-Oxo-2H,4H-benzo[b][1,4]oxazine-6-boronic acid pinacol ester (500 mg, 1.82 mmol), polymer-loaded phenylboronic acid (2200 mg, 6.4 mmol), and 1M aqueous hydrochloric acid solution (132 mg, 3.63 mmol) were mixed in acetonitrile (12 mL) and stirred at room temperature. After completion of the reaction, the reaction mixture was filtered and the filtrate concentrated to afford (3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)boronic acid as a solid (232 mg, 66% yield). The product was characterized by 1H NMR (400 MHz, methanol-d4): δ 4.79 (2H, s), 6.94 (1H, d, J = 8.0 Hz), 7.18 (1H, d, J = 1.2 Hz), 7.27 (1H, dd, J = 8.0,1.4 Hz).