A mixture of methyl 3-amino-2-(4-nitrophenyl)-6-(3-(trifluoromethyl)phenyl)isonicotinate (1 g, 2 4 mmol) in concentrated hydrochloric acid (20 mL, 37%) was cooled in an ice bath and a solution of sodium nitrite (0.99 g, 14.4 mmol) in water (0.5 ml) was added in small portions. The orange-red solution was stirred for 20 min and then a solution of sodium azide (0.94 g, 14.4 mmol) in water (0.5 mL) was added in portions. A precipitate formed and, after 30 min, the reaction was partitioned between DCM and water. The organic phase was washed with brine (2×50 mL), sat. aq. Na2CO3 solution, water, brine and then dried with sodium sulfate. Removal of the solvent followed by silica gel chromatography (elution with 40% EtOAc in hexane) afforded methyl 3-azido-2-(4-nitrophenyl)-6-(3-(trifluoromethyl)phenyl)-isonicotinate (1.0 g, 2 1 mmol, 89% yield). 1H NMR (500 MHz, chloroform-d) δ ppm 8.40 (2H, d, J=9.2), 8.33 (s, 1H), 8.29 (d, 1H, J=8.3), 8.22 (s, 1H), 8.07 (d, 2H, J=8.9), 7.74 (d, 1H, J=7.3), 7.66 (t, 1H, J=7.6), 4.12 (3H, s).
