The general procedure for synthesizing (2-chloro-3-fluorophenyl)hydrazine hydrochloride from 2-chloro-3-fluoroaniline was as follows: referring to the method of Example 189, a concentrated hydrochloric acid (70 mL) solution of 2-chloro-3-fluoroaniline (5.0 g) was slowly added dropwise to an aqueous (10 mL) solution of sodium nitrite (3.1 g), and the reaction temperature was maintained at -20 °C. The reaction mixture was stirred continuously at this temperature for 1.5 hours. Subsequently, a concentrated hydrochloric acid (20 mL) solution of tin(II) chloride (13 g) was slowly added dropwise at -20 °C and the reaction mixture was warmed to 0 °C with continued stirring for 1 hour. Upon completion of the reaction, the mixture was filtered, and the resulting solid was washed sequentially with water and hexane, and finally dried under reduced pressure to afford the target product (2-chloro-3-fluorophenyl)hydrazine hydrochloride as a yellow powder (4.3 g, 64% yield). The product was characterized by 1H-NMR (DMSO-d6): δ 6.91-7.02 (2H, m), 7.32-7.40 (1H, m), 8.35 (1H, brs), 10.23 (2H, brs), no other proton signals were detected.
