Zinc powder (200 g, 3.1 mol) was added to a solution of concentrated hydrochloric acid (500 mL) at -10 °C. After stirring for 45 minutes, 1H-pyrrole (50 g, 0.75 mol) was slowly added at -10°C through a dropping funnel. The reaction mixture was continued to be stirred at -10 °C for 30 min. Subsequently, concentrated hydrochloric acid (300 mL) was added and stirring was continued at -10 °C for 3 hours. Upon completion of the reaction, the solid product was collected by filtration and washed with distilled water (100 mL). The filtrate was adjusted to pH 14 with 2 M sodium hydroxide solution, followed by steam distillation until the distillate was no longer alkaline to litmus paper. The distillate was acidified with concentrated hydrochloric acid to pH 2. Finally, the solvent was removed by vacuum evaporation to afford the pure product 2,5-dihydro-1H-pyrrole hydrochloride (53 g, yield: 77%) as a red solid. The product was characterized by 1H NMR (400 MHz, MeOH-d4): δ 5.95 (s, 2H), 4.07 (s, 4H).
