Potassium Carbonate → N'-hydroxy-1-methyl-5-nitro-1H-pyrazole-3-carboximidamide

To a solution of 1-methyl-5-nitro-1H-pyrazole-3-carbonitrile (2.4 g, 15.8 mmol, Princeton) and hydroxylamine hydrochloride (3.29 g, 47.3 mmol) in EtOH (0.50 mL) was added potassium carbonate (10.9 g, 79 mmol) and the mixture was refluxed for about 2 h. The reaction mixture was filtered hot and the collected solid was rinsed with EtOH (50 mL) and then MeOH (100 mL). The filtrate was concentrated under reduced pressure. The crude material was partitioned between DCM (40 mL) and water (20 mL). The aqueous layer was acidified to about pH 2 using 1 N HCl and back extracted with DCM (20 mL). The aqueous layer was basified using saturated NaHCO3 and the precipitate was collected by vacuum filtration and dried to afford N′-hydroxy-1-methyl-5-nitro-1H-pyrazole-3-carboximidamide (1.24 g, 4.49 mmol, 67%). LC-MS (Table 1, Method g) Rt=1.07 min, m/z 186 (M+H)+. 1H-NMR (DMSO-d6, Bruker 400 MHz) δ 9.78 (s, 1H), 7.22 (s, 1H), 5.71 (s, 2H), 4.16 (s, 3H).