Diethyl Oxalate → (5S)-5-(1-methylethyl)-1-(phenylmethyl)-2,3-piperazinedione

Participants

Reaction Steps

[(2S)-2-Amino-3-methylbutyl](phenylmethyl)amine (Katritzky, A. R. Tetrahedron: Asymmetry 2002, 13, 933-938) (2.57 g, 13.4 mmol) was dissolved in 100 mL of EtOH with stirring. Diethyl oxalate (1.82 mL, 13.4 mmol) was added via syringe. The mixture was heated to reflux for 3.5 days and subsequently cooled to rt. The mixture was concentrated in vacuo. Purification by flash chromatography afforded the title compound of step A (2.43 g, 9.87 mmol, 74%). 1H NMR (400 MHz, DMSO-d6) δ 8.74 (br. s, 1H), 7.38-7.24 (m, 5H), 4.54 (AB, ΔνAB=88.7 Hz, JAB=14.7 Hz, 2H), 3.48 (dd, J=13.2, 4.2 Hz, 1H), 3.31 (dd, J=13.2, 6.2 Hz, 1H), 3.17 (m, 1H), 1.61 (m, 1H), 0.82 (d, J=6.8 Hz, 3H), 0.63 (d, J=6.8 Hz, 3H).

Provenance & Evidence