General procedure for the synthesis of 1-cyclohexylpiperazine from tert-butyl 4-cyclohexylpiperazine-1-carboxylate: tert-butyl 4-cyclohexylpiperazine-1-carboxylate (1.38 g, 5.15 mmol) was dissolved in a mixture of ethanol/hydrochloric acid (15 mL), and the reaction was stirred for 18 h at room temperature. After completion of the reaction, the solvent was removed by distillation under reduced pressure. To the residue, 5 mL of water was added and the aqueous phase was washed with ethyl acetate (5 mL × 3). Subsequently, the aqueous phase was adjusted to pH 7~8 with base and extracted with ethyl acetate (10 mL × 3). All organic phases were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to give 0.78 g of 1-cyclohexylpiperazine (confirmed by LC-MS and TLC, yield: 90.1%).
