General procedure for the synthesis of 2,6-dichlorophenylhydrazine hydrochloride from 2,6-dichloroaniline: 2,6-dichloroaniline (10.0 g, 61.72 mmol) was dissolved in an appropriate amount of solvent and cooled to -15 °C. At this temperature, aqueous sodium nitrite (5.11 g, 74.00 mmol) and hydrochloric acid were slowly added. The reaction mixture was stirred at 0-10°C for 15 minutes. The reaction mixture was filtered to remove insoluble matter and subsequently concentrated hydrochloric acid (34.7 g, 150 mmol) was added to the filtrate. The reaction system was maintained at -15 °C and stirring was continued for 30 min, after which the precipitate was collected by filtration to afford 15.00 g of the target product 2,6-dichlorophenylhydrazine hydrochloride. The product was characterized by 1H NMR (300 MHz, DMSO-d6): δ 7.18-7.28 (m, 1H), 7.39-7.52 (m, 2H), 10.30 (br s, 3H); the mass spectrum (MS) showed m/z: 176.90 (M)+.
