General procedure for the synthesis of piperazine-1-amide hydrochloride from tert-butyl 4-carbamoylpiperazine-1-carboxylate: To a dichloromethane (DCM, 2 mL) solution of tert-butyl 4-carbamoylpiperazine-1-carboxylate (0.16 g, 0.7 mmol) was added an ethyl acetate (EtOAc) solution of hydrochloric acid (4 M, 2 mL). The reaction mixture was stirred at room temperature for 30 min and then concentrated under reduced pressure to give piperazine-1-amide hydrochloride as a white solid (0.16 g, 100% yield). The product was characterized by 1H NMR (600 MHz, CD3OD): δ 3.71-3.73 (m, 4H), 3.25-3.27 (m, 4H); MS-ESI: m/z 130.10 [M + H - HCl]+.
