Di-tert-butyl dicarbonate (0.40 g, 1.82 mmol) was added to an N,N-dimethylformamide (DMF) solution of 6-hydrazinylpyridine-3-carboxylic acid (0.346 g, 1.82 mmol) and triethylamine (0.32 mL, 2.36 mmol). The reaction mixture was stirred at 25 °C for 1 h to become homogeneous, and stirring was continued for 16 h. The reaction was carried out under reduced pressure. After completion of the reaction, the solvent was removed under reduced pressure. The residue was diluted with a solvent mixture of ethyl acetate/methanol (4:1, v/v) and purified by silica gel column chromatography, using ethyl acetate as eluent, to afford 6-[2-(tert-butoxycarbonyl)hydrazinyl]nicotinic acid (4b) as a light yellow solid (0.44 g, 96% yield).IR (ATR, cm-1): 3353, 3227, 2975, 1719, 1593, 1472, 1372, 1256, 1014, 867, 794, 520. 1H NMR (DMSO-d6, δ): 12.584 (s, 1H), 8.59 (s, 1H), 7.97 (d, J = 9 Hz, 1H), 6.54 (d, J = 9 Hz, 1H). 13C NMR (DMSO-d6, δ): 166.6 , 155.7, 150.5, 138.5, 116.7, 79.3, 28.1, 14.0. MS (ESI-): [M-H]- m/z 252.00. MS (ESI+): [M+H]+ m/z 254.07. HRMS (ESI+): [M+H]+ m/z 254.1145 (calculated values) C11H16N3O4, 254.1141).
![6-[2-(tert-Butoxycarbonyl)hydrazinyl]nicotinic acid](/CAS/GIF/133081-25-1.gif)