142166-00-5

142166-01-6

Methyl 3-oxo-3,4-dihydro-2H-1,4-benzoxazine-7-carboxylate (1 g, 4.83 mmol) was used as starting material and mixed with boron trifluoride ethyl ether complex (1.273 mL, 10.14 mmol) in tetrahydrofuran (20 mL). The reaction mixture was stirred at 0 °C for 20 min. Subsequently, sodium borohydride (0.383 g, 10.14 mmol) was slowly added to the reaction system and stirring was continued at 0 °C for 1 h. The reaction was then brought to room temperature overnight. Upon completion of the reaction, ethyl acetate (~1 mL) was added to dilute the reaction, which was subsequently quenched by the addition of 1N aqueous hydrochloric acid. Extraction was carried out with ethyl acetate at room temperature, and the organic layer was separated, washed with saturated brine, dried over anhydrous sodium sulfate, and finally concentrated under reduced pressure to afford the target product, methyl 3,4-dihydro-2H-1,4-benzoxazine-7-carboxylate (0.916 g, 4.74 mmol, 98% yield), as a light yellow solid.