The general procedure for the synthesis of (5-chloro-2-methylphenyl)hydrazine hydrochloride from 5-chloro-o-toluidine was as follows: 5-chloro-2-methylaniline (1.4362 g, 10.143 mmol, 1.00 eq.) was suspended in water (10 mL) under cooling conditions in an ice bath, followed by the addition of concentrated hydrochloric acid (10 mL). The reaction mixture was kept at 0 °C and an aqueous solution of sodium nitrite (0.791 g, 11.5 mmol, 1.13 eq.) was added slowly and dropwise (5 mL). After the reaction was carried out for 2 hours, the mixture was slowly added to a solution of concentrated hydrochloric acid (8 mL) of tin chloride dihydrate (5.88 g, 25.8 mmol, 2.55 eq.) that had been pre-cooled in an ice bath and stirred. Appropriate amount of water was added as necessary to maintain stirring while solid formation was observed. The reaction mixture was continued at 0 °C for 45 min. The white solid was collected by filtration and washed with ether (2 x 50 mL). The resulting solid was dried in vacuum to give 1.49 g (76% yield) of (5-chloro-2-methylphenyl)hydrazine hydrochloride. The product was characterized by 1H NMR (400 MHz, DMSO-d6) with chemical shifts δ: 10.08 (s, 3H), 7.98 (s, 1H), 7.13 (d, 1H), 6.97 (s, 1H), 6.91 (d, 1H), 2.14 (s, 3H).
