General procedure for the synthesis of tert-butyl 2-(4-chlorophenyl)piperazine-1-carboxylate from the compound (CAS: 769944-38-9): a solution of 4-(tert-butoxycarbonyl)-3-(4-chlorophenyl)piperazin-2-one (500 mg, 1.6 mmol) and acetic acid (929 μL, 16 mmol) was added to refluxing 1,4-dioxane (5 mL ), followed by sodium borohydride (608 mg, 16 mmol). The reflux reaction was continued. Upon completion of the reaction, the reaction was quenched with water, the organic phase was extracted with dichloromethane and washed with brine and the organic phase was dried. After removing the solvent under reduced pressure, the residue was purified by silica gel column chromatography to afford 4-(tert-butoxycarbonyl)-3-(4-chlorophenyl)piperazine (330 mg, 69% yield).1H-NMR (CDCl3) δ 1.46 (9H, s), 2.76-2.99 (3H, m), 3.13 (1H, dd, J = 13.0 Hz, 4.3 Hz), 3.45-3.49 (3H, m). 3.45-3.49 (2H, m), 3.92 (1H, m), 5.15 (1H, s), 7.27-7.33 (4H, m).
