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(pressurized with 10 bar H2 each time), and then pressurized to the desired pressure with hydrogen.
Finally, the stirrer speed was adjusted and the temperature was set to the desired value. After the
completion of the hydrogenation process the reaction vessel was cooled to room temperature and the
pressure was relieved. Next the solvent was evaporated under reduced pressure to give a solid product
that was washed several times with diethyl ether and was purified by silica gel chromatography
(CH2Cl2/MeOH 95:5–92:8).
3.4. Synthesis of hydrogenation products
3-Benzyl-5-benzylidene-4-hydroxy-3-pyrroline-2-one (9) [28,40]: It was derived as a pale yellow solid
(from methanol), mp 188–189 °C; 1H-NMR (DMSO-d6): 3.58 (s, 2H, 7-H), 6.25 (s, 1H, 6-H), 7.22 (m,
13
6H), 7.35 (t, 2H), 7.55 (d, 2H, J = 7.2 Hz), 9.48 (s, 1H, NH), 11.04 ppm (s, 1H, (4)-OH). C-NMR
(DMSO-d6): 26.2 (C-7), 104.1 (C-3), 104.9 (C-6), 125.5 (C-l), 127.1 (C-f), 127.6/128.0/128.5/128.8
(C-b, C-c, C-d, C-e, C-h, C-I, C-j, C-k), 132.5 (C-5), 134.2 (C-a), 140.0 (C-g), 159.4 (C-4), 172.7 ppm
(C-2). HRMS calcd. for [C18H15NO2+23Na]+: 300.1000, found: 300.0999.
3-p-Methoxybenzyl-5-p-methoxybenzylidene-4-hydroxy-3-pyrroline-2-one (10): It was derived as a
1
pale yellow solid (from methanol), mp 189–190 °C; H-NMR (DMSO-d6): 3.49 (s, 2H, 7-H), 3.70 (s,
3H, OCH3 [C-l]), 3.77 (s, 3H, OCH3 [C-f]), 6.19 (s, 1H, 6-H), 6.82 (d, 2H, j- and k-H, J = 7.5 Hz),
6.92 (d, 2H, d- and e-H, J = 8.1 Hz), 7.14 (d, 2H, h- and i-H, J = 8.1 Hz), 7.49 (d, 2H, b- and c-H,
13
J = 8.7 Hz), 9.37 (s, 1H, NH), 10.85 ppm (s, 1H, (4)-OH); C-NMR (DMSO-d6): 25.5 (C-7), 55.0
(OCH3 [C-l]), 55.2 (OCH3 [C-f]), 104.4 (C-3), 105.1 (C-6), 113.6 (C-j, C-k), 114.2 (C-d, C-e), 127.0
(C-a), 129.1 (C-b, C-c), 130.5 (C-h, C-i), 130.9 (C-g), 132.3 (C-5), 157.4 (C-4), 158.6 (C-l), 159.2 (C-
f), 172.9 ppm (C-2). HRMS calcd. for [C20H19NO4+23Na]+: 360.1212, found: 360.1221.
3-p-Methoxybenzyl-5-p-methoxybenzylidene-4-methoxy-3-pyrroline-2-one (11): It was derived as a
1
pale yellow solid (from methanol), mp 184–185 °C; H-NMR (DMSO-d6): 3.71 (s, 3H, OCH3 [C-l]),
3.73 (s, 2H, 7-H), 3.78 (s, 3H, OCH3 [C-f]), 3.98 (s, 3H, OCH3 [C-4]), 6.13 (s, 1H, 6-H), 6.86 (d, 2H,
j- and k-H, J = 7.5 Hz), 6.92 (d, 2H, d- and e-H, J = 8.1 Hz), 7.11 (d, 2H, h- and i-H, J = 8.1 Hz), 7.51
(d, 2H, b- and c-H, J = 8.7 Hz), 9.78 ppm (s, 1H, NH); 13C-NMR (DMSO-d6): 26.4 (C-7), 55.0 (OCH3
[C-l]), 55.2 (OCH3 [C-f]), 59.0 (OCH3 [C-4]), 105.7 (C-3), 105.9 (C-6), 113.9 (C-j, C-k), 114.2 (C-d,
C-e), 126.7 (C-a), 128.7 (C-b, C-c), 130.1 (C-g), 130.7 (C-h, C-i), 132.6 (C-5), 157.5 (C-4), 158.7 (C-
l), 159.7 (C-f), 172.6 ppm (C-2). HRMS calcd. for [C21H21NO4+23Na]+: 374.1368, found: 374.1367.
3, 5-Dibenzyl-4-hydroxy-3-pyrroline-2-one (12): It was derived as a pale yellow solid (from methanol),
1
mp 72–73 °C; H-NMR (DMSO-d6): 2.87–3.05 (dd, 2H, 6-H), 3.16/3.22 (2s, 2H, 7-H), 4.17 (br, 1H,
5-H), 6.75 (d, 2H, J = 6.9 Hz), 7.08 (d, 3H, J = 6.6 Hz), 7.21 (m, 5H), 7.34 (s, 1H, NH), 10.81 ppm (s,
1H, (4)-OH). 13C-NMR (DMSO-d6): 26.2 (C-7), 36.5 (C-6), 56.0 (C-5), 104.6 (C-3), 125.1 (C-l), 126.2
(C-f), 127.7 (C-d, C-e, C-j, C-k), 128.1 (C-4), 128.6 (C-i), 129.1 (C-h), 129.7 (C-b, C-c), 136.2 (C-a),
140.1 (C-g), 168.6 ppm (C-2). HRMS calcd. for [C18H17NO2+23Na]+: 302.1157, found: 302.1199.