The general procedure for the synthesis of 5-ethyl-2,4-piperidinedione from 1-Boc-5-ethyl-2,4-dioxopiperidine was as follows: 1-Boc-5-ethyl-2,4-dioxopiperidine was dissolved in trifluoroacetic acid (TFA, 10 mL), and the reaction was stirred for 2 h at room temperature. After completion of the reaction, the solvent was removed by rotary evaporator and the resulting residue was purified by column chromatography (eluent: hexane/ethyl acetate, 1:2, v/v) to afford 5-ethylpiperidine-2,4-dione in 52% yield. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-D6): δ 0.89 (t, J = 7.56 Hz, 3H), 1.35 (m, 1H), 1.69 (m, 1H), 2.39 (m, 1H), 3.14-3.38 (m, 4H), 8.05 (s, 1H); ESI (+) MS: m/z 142 (MH+) .
