The general procedure for the synthesis of 1-methylpiperazin-2-one hydrochloride from tert-butyl 4-methyl-3-oxopiperazine-1-carboxylate was as follows: 4N HCl-dioxane solution (20 mL) was added to tert-butyl 4-methyl-3-oxopiperazine-1-carboxylate (2.06 g) and the reaction mixture was stirred for 1 hour at room temperature. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. Toluene was added to the residue and the solvent was again removed by azeotropic distillation under reduced pressure. The residue was dried to give 1-methylpiperazin-2-one hydrochloride as an oil (1.44 g, 99% yield). The product was characterized by 1H-NMR (400 MHz, DMSO-d6): δ 2.86 (3H, s), 3.34 (2H, br m), 3.50 (2H, m), 3.64 (2H, s). Mass spectra (ESI) showed m/z: 115 ([M + H]+).
