[NH2:1][C:2]1[CH:3]=[CH:4][C:5]([Cl:8])=[N:6][CH:7]=1.N([O-])=O.[Na+].[N-:13]=[N+:14]=[N-].[Na+]>C(O)(C(F)(F)F)=O.O>[N:1]([C:2]1[CH:3]=[CH:4][C:5]([Cl:8])=[N:6][CH:7]=1)=[N+:13]=[N-:14]5-Amino-2-chloropyridine (2.28 g; 17.7 mmol; 1.0 eq.) was dissolved in TFA (7 mL). Sodium nitrite (1.35 g; 19.5 mmol; 1.1 eq.) was then added portion wise to this solution maintained at 0° C. Reaction mixture was stirred at 0° C. for 30 min before the addition of and ice-cold solution of sodium azide (1.15 g; 17.7 mmol; 1.0 eq.) in water (8 mL). It was stirred at 0° C. for 1 h. TFA was then removed and the residue was dissolved in EtOAc. Organic phase was washed with an aqueous saturated solution of NaHCO3, brine, dried over magnesium sulfate, filtered and concentrated. The crude obtained was purified by flash chromatography on silica (heptane:EtOAc, gradient from 95:5 to 80:20) to afford the title compound as a brown oil (1.89 g, 69%). 1H NMR (300 Mz, DMSO-d6) δ 8.23 (dd, J=0.6, 2.9 Hz, 1H), 7.68 (dd, J=2.9, 8.6 Hz, 1H), 7.54 (dd, J=0.6, 8.6 Hz, 1H).
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