[NH2:1][C:2]1[C:11]([C:12]2[CH:17]=[CH:16][C:15]([N+:18]([O-:20])=[O:19])=[CH:14][CH:13]=2)=[N:10][C:9]([Br:21])=[CH:8][C:3]=1[C:4]([O:6][CH3:7])=[O:5].N([O-])=O.[Na+].[N-:26]=[N+:27]=[N-].[Na+].CCOCC>C(O)(C(F)(F)F)=O.C(Cl)Cl.C1COCC1>[N:1]([C:2]1[C:11]([C:12]2[CH:13]=[CH:14][C:15]([N+:18]([O-:20])=[O:19])=[CH:16][CH:17]=2)=[N:10][C:9]([Br:21])=[CH:8][C:3]=1[C:4]([O:6][CH3:7])=[O:5])=[N+:26]=[N-:27]Methyl 3-amino-6-bromo-2-(4-nitrophenyl)isonicotinate (7.2 g, 20 5 mmol) was dissolved in TFA (70 mL) and the yellow solution was cooled in an ice bath. Sodium nitrite (2.82 g, 40.9 mmol) was added in small portions with stirring to give a dark yellow mixture. After 30 min, sodium azide (13.29 g, 204 mmol) was added in small portions followed by Et2O (20 mL). The light yellow mixture was stirred in the ice-bath for 30 min and then partitioned between DCM and water. The organic phase washed with water (3×250 mL), sat. aq. Na2CO3 solution (3×250 mL), brine, dried with sodium sulfate, and the solvent removed. Silica gel chromatography (30% THF in DCM) afforded methyl 3-azido-6-bromo-2-(4-nitrophenyl)isonicotinate (6.8 g, 16.5 mmol, 81% yield). 1H NMR (500 MHz, DMSO-d6) δ ppm 8.37 (2H, d, J=8.85 Hz), 8.06 (1H, s), 8.02 (2H, d, J=9.16 Hz), 3.97 (3H, s).
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