A solution of 4-[1-(4-pentafluoroethyloxy-phenyl)-1H-[1,2,4]triazol-3-yl]-benzoic acid (1.67 g, 4.2 mmol), diphenylphosphoryl azide (1.26 g, 4.58 mmol) and triethylamine (0.5 g, 5 mmol) in dry t-BuOH (10 mL) was heated to 75° C. for 90 min, resulting in dissolution of the starting acid and subsequent precipitation of the azide. The cooled solution was then poured onto ice (10 g), and the resulting mixture was filtered and dried to furnish the azide (0.80 g) as a white solid: mp 112-115° C. dec; 1H NMR (300 MHz, CDCl3) δ 8.62 (s, 1H), 8.33 (d, J=8.4 Hz, 2H), 8.16 (d, J=8.4 Hz, 2H), 7.85 (d, J=9 Hz, 2H), 7.42 (d, J=9 Hz, 2H); ESIMS m/z 425 (M+H).
