Step 2. Methyl 3-amino-4-hydroxybenzoate (4.2 g, 25.4 mmol) was dissolved in dimethylformamide (85 mL) and K2CO3 (14.2 g, 102.9 mmol, 4 eq.) and 1,2-dibromoethane (19.3 g, 102.9 mmol, 4 eq.) were added sequentially. The reaction mixture was stirred at 70 °C overnight. Upon completion of the reaction, the insoluble solids were removed by filtration. The filtrate was concentrated under reduced pressure to remove the solvent and the residue was purified by fast column chromatography (eluent: heptane/ethyl acetate gradient) to afford methyl 3,4-dihydro-2H-benzo[1,4]oxazine-6-carboxylate (3.65 g, light yellow solid). The product was identified by mass spectrometry (ISP): m/e = 235.1 (M + CH3CN+); NMR hydrogen spectrum (300 MHz, CDCl3) δH: 7.36 (1H, dd, J = 8.5, 2.0), 7.30 (1H, d, J = 2.0), 6.78 (1H, d, J = 8.5), 4.30 (2H, m), 3.85 (3H , s), 3.43 (2H, m).
![3,4-Dihydro-2H-benzo[1,4]oxazine-6-carboxylic acid methyl ester](/CAS/GIF/758684-29-6.gif)