Step 2: Synthesis of 1-(methylsulfonyl)piperazine
A mixture of tert-butyl 4-(methylsulfonyl)piperazine-1-carboxylate (1.0 g, 3.79 mmol) with trifluoroacetic acid (TFA, 0.86 g, 7.58 mmol) in dichloromethane (CH2Cl2, 10 mL) was stirred for 2 hours at room temperature. After completion of the reaction, the mixture was concentrated under reduced pressure to afford 1-(methylsulfonyl)piperazine as a yellow oil (0.5 g, 80.52% yield). The product was characterized by 1H NMR (400 MHz, CD3OD): δ 3.50-3.47 (m, 4H), 3.33-3.28 (m, 4H), 2.92 (s, 3H); ESI-MS m/z: 165 ([M + H]+).
