[O:1]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[NH:4][CH2:3][CH2:2]1.C(=O)([O-])[O-].[K+].[K+].I[CH2:18][CH3:19]>CN(C=O)C>[CH2:18]([N:4]1[C:5]2[CH:10]=[CH:9][CH:8]=[CH:7][C:6]=2[O:1][CH2:2][CH2:3]1)[CH3:19]To a stirred solution of 3,4-dihydro-2H-benzo[1,4]oxazine (4.0 g, 29.6 mmol) in DMF (20 mL) was added potassium carbonate (10.22 g, 74.0 mmol). After stirring for five min. Iodo-ethane (3.5 mL, 44.4 mmol) was added and heated to 60° C. for overnight. Reaction mixture was cooled to room temperature, quenched by the addition of water (20 mL), extracted with ethyl acetate (3×25 mL). The organic layer was washed with water (30 mL), brine (30 mL), dried over sodium sulfate, concentrated and purified by silica gel column chromatography to furnish 4-ethyl-3,4-dihydro-2H-benzo[1,4]oxazine (2.7 g).
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