To a solution of 4-(5-(4-(perfluoroethoxy)phenyl)-1,3,4-oxadiazol-2-yl)benzoic acid (217 mg, 0.54 mmol) in isopropanol (5.4 mL) was added triethylamine (0.09 mL, 0.65 mmol) and diphenyl phosphorazidate (0.13 mL, 0.60 mmol) and the reaction was stirred at room temperature for 16 hours. The white precipitate that had formed was filtered and dried in a vacuum oven to provide 4-(5-(4-(perfluoroethoxy)phenyl)-1,3,4-oxadiazol-2-yl)benzoyl azide as a white solid (145 mg, 63%): mp 140° C. (dec); 1H NMR (400 MHz, DMSO-d6) δ 8.32 (m, 4H), 8.24-8.17 (m, 2H), 7.68 (d, J=8.9 Hz, 2H); 19F NMR (376 MHz, DMSO-d6) δ −85.25, −86.89; ESIMS m/z 426 ([M+H]+).
