[CH3:1][N:2]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[O:5][CH2:4][C:3]1=O>C1COCC1>[CH3:1][N:2]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[O:5][CH2:4][CH2:3]1To a stirred solution of 4-methyl-4H-benzo[1,4]oxazin-3-one (2.18 g, 13.37 mmol) in THF (5 mL) was added borane-tetrahydrofuran complex (4.02 g, 46.8 mmol) at room temperature. After stirring the solution for 2 h, the reaction mixture was refluxed for 4 h. After complete conversion, reaction mixture was quenched by adding MeOH (10 mL) and evaporated the solvents. The residue obtained was extracted with ethyl acetate (30×2 mL) and the organic layer was washed with water (20 mL), brine (20 mL) and evaporation of solvent gave 4-methyl-3,4-dihydro-2H-benzo[1,4]oxazine 2.0 g.
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