In a three-necked flask equipped with a reflux condenser tube and a mechanical stirring device, 15.0 g of 4-nitrobenzenecarboximidamide (IV) prepared from Example 2, 20 mL of acetic acid, 45 mL of water, and 45 mL of ethanol (V water: V ethanol=1:1) were added, and the reaction was stirred and refluxed at 60° C. until complete dissolution. Subsequently, 20.3 g of iron powder (n4-nitrobenzenecarboximidamide IV: n iron powder = 1:4) was added to the reaction system, and the reaction was warmed up to 80 °C and continued to be stirred and refluxed for 4 hours. After completion of the reaction, it was filtered while hot. The filtrate was adjusted to pH 11~12 with 20% NaOH solution, at which time a large amount of flocculent precipitation was generated, and after filtration, the filtrate was adjusted to pH 1~2 with concentrated hydrochloric acid. the solution was concentrated until the crystals precipitated, and the resulting crystals were dried in vacuum at 100 ℃ to obtain 17.9 g of 4-nitrobenzenecarboximidamide dihydrochloride (I), as a white solid with 94.7% yield and 99.51% HPLC purity.
