S. Goswami, A. K. Adak / Tetrahedron Letters 43 (2002) 8371–8373
8373
References
well with water and then with ethanol, and dried in
vacuum. The bright yellow solid (1.2 g, 70%, mp>350°C)
after pivaloylation with pivalic anhydride followed by
purification gave a cream coloured solid 1b (1.4 g, 78%,
mp 230–232°C). Compounds 1d, 1f and 2c were obtained
by condensation followed by direct acetylation of 1c, 1e
and 2b, respectively.
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6. Typical experimental procedure: A mixture of 2,5,6-tri-
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methylglyoxal (1.5 g, 40% in water) was placed in a
microwave oven (BPL 800G, indicates the commercial
name of the microwave oven) and subjected to irradiation
at 150 W for an optimised time (62 s). Water was then
added and the resulting slurry was centrifuged. The solid
separated was filtered through a sintered funnel, washed
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1
9. The H NMR spectra were found to be identical to those
reported earlier. Compound 1b (78%). Mp 320–322°C. 1H
NMR (CDCl3, 500 MHz): l 12.33 (br s, 1H, NH), 8.72
(s, 1H, C7-H), 8.35 (br s, 1H, NH), 2.75 (s, 3H, C6-CH3),
1.36 (s, 9H). Compound 1f (40%). Mp 108–110°C. 1H
NMR (CDCl3, 500 MHz): l 12.60 (br s, 1H, NH amide),
10.23 (br s, 1H, lactam NH), 8.94 (s, 1H, C7-H), 6.05 (d,
1H, C1%-H, J=8.9 Hz), 5.72 (dd, 1H, C%2-H, J=2.6, 2.6
Hz), 5.59–5.56 (m, 1H, C%3-H), 4.24 (qd, 2H, C%4-H2,
J=5.5, 5.5, 6.9 Hz, 6.9), 2.45 (s, 3H, -NHCOCH3), 2.15,
2.13, 2.05, 1.96 (4×s, 12H, -OCOCH3×4). [h]2D5 −17.31 (c
1, chloroform). Mass (FAB, MH+): 494 (100%). Com-
1
pound 2a (95%). H NMR (CDCl3, 500 MHz): l 8.58 (s,
1H, quinoxalin-2-yl), 7.92 (d, 1H, J=8.0 Hz), 7.87 (d,
1H, J=8.0 Hz), 7.60–7.54 (m, 2H), 2.66 (s, 3H). Com-
1
pound 2c (65%). Mp 110–112°C. H NMR (CDCl3, 500
MHz): l 8.84 (s, 1H, quinoxalin-2-yl), 8.10–8.08 (m, 2H),
7.79–7.77 (m, 2H), 6.33 (d, 1H, J=3.1 Hz), 5.79 (dd, 1H,
C2%-H, J=3.1, 3.1 Hz), 5.40–5.37 (m, 1H, C3%-H), 4.25 (qd,
2H, C4%-H2, J=2.7, 2.7, 5.0, 5.0 Hz), 2.22, 2.09, 2.04, 1.91
(4×s, 12H, 4×OCOCH3). Mass (FD, M+): 418 (100%).
10. (a) Russell, J. R.; Garner, C. D.; Joule, J. A. J. Chem.
Soc., Perkin Trans. 1 1992, 1245–1249; (b) Horton, D.;
Miller, M. J. J. Org. Chem. 1965, 30, 2457.
11. Goswami, S. P.; Adak, A. K. Synth. Commun. 2002, 33
(3).