To a solution of N-Boc-piperazine (5.0 g, 26.88 mmol) in anhydrous THF (50 mL) was added N,N'-thiocarbonyl diimidazole (5.48 g, 29.56 mmol) at room temperature and the reaction was stirred for 2 hours. Subsequently, the reaction mixture was heated to 50 °C for 1 hour. Upon completion of the reaction, the mixture was cooled to 0 °C and methanol ammonia solution (50 mL, 7 N) was slowly added. The resulting mixture was stirred at 60 °C for 20 hours. At the end of the reaction, the reaction mixture was diluted with water and extracted with EtOAc. The organic layers were combined and dried with anhydrous Na2SO4 and subsequently concentrated under vacuum. The crude product was purified by fast chromatography to afford the target compound 4-Boc-piperazine-1-thioamide. Yield: 4.0 g (92% yield) as a white solid.1H NMR (400 MHz, DMSO-d6) δ: 9.2 (m, 2H), 3.16-3.14 (m, 2H), 2.49-2.48 (m, 6H), 1.30 (s, 9H). lcms (method A): 246.2 (M + H), retention time 2.93 min. Purity 95.3% (max).
