[NH2:1][C:2]1[CH:3]=[C:4]([CH:7]=[CH:8][C:9]=1[OH:10])[C:5]#[N:6].C([O-])([O-])=O.[K+].[K+].Br[CH:18]([CH2:24]Br)[C:19]([O:21][CH2:22]C)=[O:20]>CC(C)=O.CO>[C:5]([C:4]1[CH:7]=[CH:8][C:9]2[O:10][CH:18]([C:19]([O:21][CH3:22])=[O:20])[CH2:24][NH:1][C:2]=2[CH:3]=1)#[N:6]3-Amino-4-hydroxy-benzonitrile (180 mg, 1.34 mmol) was dissolved in acetone (1.4 mL). To the solution was added K2CO3 (555 mg, 4.02 mmol) and ethyl 2,3-dibromopropanoate (380 mg, 1.46 mmol). The mixture was heated to reflux for 16 h. After cooling to room temperature the reaction mixture was filtered and concentrated in vacuo to give an oil. The oil was dissolved in methanol and was purified by silica gel chromatography (0-10% dichloromethane/hexanes) to afford methyl 6-cyano-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate (148 mg, 0.68 mmol). The methyl ester was isolated as methanol was used for loading the compound on silica resulting in transesterification. 1H NMR (400.0 MHz, DMSO-d6) δ 6.98 (dd, J=2.0, 8.2 Hz, 1H), 6.93-6.90 (m, 2H), 6.34 (s, 1H), 5.13 (t, J=3.3 Hz, 1H), 3.66 (s, 3H), 3.50-3.41 (m, 2H).
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