Molecules 2012, 17
14632
3.3. Reaction of Enaminones 1a–d with Heterocyclic Amines
General procedure: To a solution of the appropriate enaminone 1a–d (5 mmol) in acetic acid (20 mL)
was added the appropriate heterocyclic amine (3-aminotriazole or 2-aminobenzimidazole, 5 mmol).
The mixture was stirred at reflux for 6 h then cooled. The formed solid was separated by filtration and
recrystallized from dioxane to give compounds 7a–d and 8a–d, respectively.
5-[2-Benzoylimino-3-(4-methoxyphenyl)-1,3,4-thiadiazol-5-yl]-[1,2,4]triazolo[1,5-a]pyrimidine (7a).
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Yellow solid (80% yield), mp 235–236 °C; IR (KBr) νmax 1604 (C=O), 1558 (C=N) cm−1; H-NMR
(DMSO-d6) δ 3.88 (s, 3H, OCH3), 7.48–7.59 (m, 5H, Ar-H), 7.24 (d, J = 8 Hz, 2H, ArH), 7.97 (d,
J = 8 Hz, 2H, Ar-H), 8.12 (d, 1H, J = 4.5 Hz, pyrimidinyl-H), 8.14 (d, 1H, J = 4.5 Hz, pyrimidinyl-H),
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9.05 (s, 1H, triazolyl-H); C-NMR (DMSO-d6) δ: 53.48, 115.58, 121.65, 125.79, 126.29, 128.80,
129.23, 129.53, 130.52, 130.98, 131.19, 143.87, 144.99, 147.10, 151.72, 159.83, 175.22. MS m/z (%)
430 (M++1, 6), 429 (M+, 40), 352 (3), 306 (26), 179 (2), 121 (43), 105 (100), 97 (8), 77 (66). Anal.
Calcd. for C21H15N7O2S (429.46): C, 58.73; H, 3.52; N, 22.83. Found: C, 58.53; H, 3.38; N, 22.64%.
5-[2-Benzoylimino-3-(4-methylphenyl)-1,3,4-thiadiazol-5-yl]-[1,2,4]triazolo[1,5-a]pyrimidine
(7b).
Yellow solid (79% yield), mp > 300 °C; IR (KBr) νmax 1602 (C=O), 1540 (C=N) cm−1; H-NMR
(DMSO-d6) δ 2.46 (s, 3H, CH3), 7.50–7.61 (m, 5H, ArH), 8.13 (d, J = 8 Hz, 2H, ArH), 8.16 (d, J = 8 Hz,
2H, ArH), 7.95 (d, J = 4.5 Hz, 1H, pyrimidinyl-H), 8.97 (s, 1H, triazolyl-H), 9.05 (d, J = 4.5 Hz, 1H,
pyrimidinyl-H); 13C-NMR (DMSO-d6) δ: 18.27, 114.01, 120.24, 123.27, 127.06, 128.18, 129.05,
130.47, 130.42, 132.48, 134.35, 142.54, 144.84, 148.21, 150.70, 158.16, 172.02. MS m/z (%) 414
(M++1, 3), 413 (M+, 11), 306 (10), 105 (100), 98 (2), 77 (62). Anal. Calcd. for C21H15N7OS (413.46):
C, 61.00; H, 3.66; N, 23.71. Found: C, 61.25; H, 3.47; N, 23.51%.
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5-[2-Benzoylimino-3-(4-chlorophenyl)-1,3,4-thiadiazol-5-yl]-[1,2,4]triazolo[1,5-a]pyrimidine
(7c).
Pale brown solid (76% yield), mp > 300 °C; IR (KBr) νmax 1610 (C=O), 1545 (C=N) cm−1; H-NMR
(DMSO-d6) δ 7.38 (d, J = 8 Hz, 2H, ArH), 7.49–7.96 (m, 5H, ArH), 8.12 (d, J = 8 Hz, 2H, ArH), 8.24
(d, J = 4.5 Hz, 1H, pyrimidinyl-H), 8.45 (d, J = 4.5 Hz, 1H, pyrimidinyl-H), 8.61 (s, 1H, triazolyl-H);
13C-NMR (DMSO-d6) δ: 114.21, 115.16, 118.27, 120.03, 122.10, 124.24, 126.57, 128.60, 135.28,
137.67, 142.11, 143.95, 147.09, 150.79, 155.20, 171.11. MS m/z (%) 435 (M++2, 3), 434 (M++1, 4),
433 (M+, 9), 356 (3), 306 (10), 105 (100), 98 (66), 77 (80). Anal. Calcd. for C20H12ClN7OS (433.87):
C, 55.36; H, 2.79; N, 22.60. Found: C, 55.26; H, 2.64; N, 22.49%.
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5-(2-Benzoylimino-3-(4-nitrophenyl)-1,3,4-thiadiazol-5-yl)-[1,2,4]triazolo[1,5-a]pyrimidine
(7d).
Brown solid (79% yield), mp > 300 °C; IR (KBr) νmax 1612 (C=O), 1540 (C=N) cm−1; H-NMR
(DMSO-d6) δ 7.53–7.64 (m, 5H, ArH), 8.26 (d, J = 8 Hz, 2H, ArH), 8.52 (d, J = 8 Hz, 2H, ArH), 8.56
(d, J = 4.5 Hz, 1H, pyrimidinyl-H), 8.59 (s, 1H, triazolyl-H), 9.00 (d, J = 4.5 Hz, 1H, pyrimidinyl-H);
13C-NMR (DMSO-d6) δ: the sample precipitated. MS m/z (%) 444 (M+, 17), 415 (3), 367 (4), 306 (4),
299 (2), 121 (3), 105 (100), 90 (4), 77 (42). Anal. Calcd. for C20H12N8O3S (444.43): C, 54.05; H, 2.72;
N, 25.21. Found: C, 54.18; H, 2.57; N, 25.05%.
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