Regioselective Alkylation of Thiazolylsulfonamides
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N-Benzyl-N-(5-tert-butyl-4-methyl-1,3-thiazol-2-yl)-3-nitrobenzene-
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sulfonamide (4b): mp 142–1438C. H NMR (CDCl3) d: 1.37 (9H, s), 2.33
(3H, s), 5.02 (2H, s), 7.24 (4H, m), 7.35 (2H, m), 7.64 (1H, t, J ¼ 7.8 Hz),
8.04 (1H, m), 8.38 (1H, ddd, J ¼ 1.0, 2.5, 8.3 Hz), 8.58 (1H, t, J ¼ 2.0 Hz).
FAB-MS m/z: 446 (Mþ þ1). Anal. calcd. for C21H23N3O4S2: C, 56.61; H,
5.20; N, 9.43; S, 14.39. Found: C, 56.65; H, 5.19; N, 9.39; S, 14.28.
Ethyl [5-tert-butyl-4-methyl-2-f[(3-nitrophenyl)sulfonyl]iminog-1,3-
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thiazol-3(2H)-yl]acetate (5a): mp 104–1058C (ethyl acetate–hexane). H
NMR (CDCl3) d: 1.24 (3H, t, J ¼ 7.0 Hz), 1.37 (9H, s), 2.21 (3H, s), 4.17
(2H, q, J ¼ 7.0 Hz), 4.71 (2H, s), 7.64 (1H, t, J ¼ 7.9 Hz), 8.28 (2H, m),
7.73 (1H, t, J ¼ 1.8 Hz). FAB-MS m/z: 442 (Mþ þ1). Anal. calcd. for
C18H23N3O6S2: C, 48.97; H, 5.25; N, 9.52; S, 14.53. Found: C, 48.99; H,
5.20; N, 9.47; S, 14.49.
N-[5-tert-Butyl-3-[2-(1,3-dioxolan-2-yl)ethyl]-4-methyl-1,3-thiazol-
2(3H)-ylidene]-3-nitrobenzenesulfonamide (6a): mp 212–2148C (ethyl
acetate–hexane). H NMR (DMSO-d6) d: 1.32 (9H, s), 1.85 (2H, m), 2.29
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(3H, s), 3.71 (2H, m), 3.84 (2H, m), 4.00 (2H, m), 4.81 (1H, t, J ¼ 4.4 Hz),
7.85 (1H, t, J ¼ 7.8 Hz), 8.25 (1H, m), 8.41 (1H, br d, J ¼ 2.4, 8.3 Hz),
8.49 (1H, t, J ¼ 2.0 Hz). FAB-MS m/z: 456 (Mþ þ1). Anal. calcd. for
C19H25N3O6S2: C, 50.09; H, 5.53; N, 9.22; S, 14.08. Found: C, 50.00; H,
5.64; N, 9.02; S, 13.98.
N-(5-tert-Butyl-4-methyl-1,3-thiazol-2-yl)-N-[2-(1,3-dioxolan-2-yl)-
ethyl]-3-nitrobenzenesulfonamide (6b): mp 185–1878C (ethyl acetate–
hexane). H NMR (DMSO-d6) d: 1.38 (9H, s), 1.86 (2H, m), 2.29 (3H, s),
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3.74 (2H, m), 3.85 (4H, m), 4.82 (1H, t, J ¼ 4.9 Hz), 7.95 (1H, t, J ¼ 8.3 Hz),
8.26 (1H, br d, J ¼ 7.8 Hz), 8.49 (1H, t, 2.0 Hz), 8.56 (1H, dd, J ¼ 1.5,
8.3 Hz). FAB-MS m/z: 456 (Mþ þ1). Anal. calcd. for C19H25N3O6S2: C,
50.09; H, 5.53; N, 9.22; S, 14.08. Found: C, 49.95; H, 5.60; N, 8.99; S, 13.85.
N-(5-Isopropyl-3-methyl-1,3-thiazol-2(3H)-ylidene)-3-nitrobenzene-
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sulfonamide (7a): mp 150–1518C (isopropanol). H NMR (DMSO-d6) d:
1.19 (6H, d, J ¼ 6.9 Hz), 2.95 (1H, heptet, J ¼ 6.9 Hz), 3.45 (3H, s), 7.22
(1H, s), 7.86 (1H, d, J ¼ 7.8, 8.3 Hz), 8.26 (1H, br d, J ¼ 7.8 Hz), 8.43 (1H,
ddd, J ¼ 1.0, 1.9, 8.3 Hz), 8.49 (1H, t, J ¼ 1.9 Hz). FAB-MS m/z: 342
(Mþ þ1). Anal. calcd. for C13H15N3O4S2: C, 45.73; H, 4.43; N, 12.31; S,
18.78. Found: C, 45.66; H, 4.31; N, 12.30; S, 18.89.
Methyl 5-Isopropyl-3-methyl-2-f[(3-nitrophenyl)sulfonyl]iminog-2,3-
dihydro-1,3-thiazole-4-carboxylate (8a): mp 120–1218C (ethyl acetate–
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hexane). H NMR (CDCl3) d: 1.29 (6H, d, J ¼ 6.8 Hz), 3.67 (3H, s), 3.68
(1H, heptet, J ¼ 6.8 Hz), 3.93 (3H, s), 7.88 (1H, br t, J ¼ 8.2 Hz), 8.29 (1H,
br d, J ¼ 7.7 Hz), 8.37 (1H, dd, J ¼ 2.0, 8.2 Hz), 8.79 (1H, t, J ¼ 2.0 Hz).
FAB-MS m/z: 400 (Mþ þ1). Anal. calcd. for C15H17N3O6S2: C, 45.10; H,
4.29; N, 10.52; S, 16.06. Found: C, 44.93; H, 4.10; N, 10.62; S, 16.09.
Methyl 5-tert-butyl-2-fmethyl[(3-nitrophenyl)sulfonyl]aminog-1,3-
thiazole-4-carboxylate (8b): mp 121–1238C (ethyl acetate–hexane). 1H
NMR (CDCl3) d: 1.36 (6H, d, J ¼ 6.9 Hz), 3.48 (3H, s), 3.89 (3H, s), 4.07