2-Iodoaniline → (2-Iodophenyl)hydrazine

21.9 g (100 mmol) o-iodophenyl amine was dissolved in 40 mL concentrated hydrochloric acid. At 0° C., 6.9 g (100 mmol) sodium nitrite (dissolved in 35 mL water) was added dropwise, and stirred at 0° C. for half an hour. Then, SnCl2.2H2O 64.7 g (300 mmol) (dissolved in 70 mL concentrated hydrochloric acid) was added dropwise slowly, and reacted for about 3 h until complete. It was filtered to obtain a white solid, washed with a saturated solution of sodium chloride, and then washed with a mixed solvent of petroleum ether and diethyl ether (1:1). Then, the solid was adjusted to be basic with sodium hydroxide solution. The solid impurity therein was filtered, the aqueous phase was extracted with dichloromethane several times, the organic phases combined, dried, rotate evaporated to dryness to obtain a colorless oil 10.3 g, at a yield of 44.0%.