The general procedure for the synthesis of 4-bromobenzamidine hydrochloride from 4-bromobenzonitrile was as follows: hydrogen chloride gas was passed into a mixture of chloroform (300 mL) and ethanol (100 mL) containing 4-bromobenzonitrile (18.2 g) at -65 °C for 35 min. Subsequently, the reaction system was slowly warmed to room temperature and stirred continuously at that temperature overnight. Upon completion of the reaction, the solvent was removed by vacuum evaporation and the resulting residue was redissolved in ethanol (400 mL). Ammonium carbonate (48.0 g) was added to this solution and the reaction mixture was stirred at room temperature for 20 hours. At the end of the reaction, water (300 mL) was added and the ethanol was removed by vacuum concentration. The resulting precipitate was collected by filtration, washed with water and dried under vacuum to afford the target product 4-bromobenzamidine hydrochloride (22.9 g, 97% yield) as a white solid. The product was detected by 1H NMR (DMSO-d6), showing δ 2.55-4.60 (2H, broad peak), 6.30-8.90 (6H, multiple peaks); FAB-MS showed m/z 199,201 [(M + H)+].
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