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HETEROCYCLES, Vol. 75, No. 6, 2008
compound 20 was separated at Rf = 0.32.
2,7-Diamino-3-benzyl-5-phenyl-4,5-dihydropyrazolo[1,5-a]pyrimidine-6-carbonitrile (19)
The solid, so formed after evaporation of the eluent, was recrystallized from petroleum ether to give a
faint brown product; yield 35 %; mp 179-180 ºC. Anal. Calcd for C20H18N6 (342.40): C, 70.16; H, 5.30; N,
24.54. Found: C, 70.07; H, 5.33; N, 24.13. IR (KBr): υmax = 3440, 3332 (NH2), 3381, 3329 (NH2), 3203
1
(NH), 2172 (CN); H NMR (400 MHz, DMSO-d6): δ, ppm = 3.56 (s, 2H, CH2), 5.02-5.11 (br, 3H, CH,
NH2, D2O exchangeable), 6.43 (br, 2H, NH2, D2O exchangeable), 7.13 (br, 1H, NH, D2O exchangeable),
13
7.20-7.34 (m, 10H, Ar-H); C NMR (600 MHz, DMSO-d6): δ, ppm = 158.35, 148.68, 145.17, 144.24,
141.98, 129.23, 128.93, 128.85, 128.30, 126.84, 126.41, 121.89, 88.19, 55.12, 54.01, 26.75. MS: m/z (%)
342 (M+, 80), 264 (35), 186 (40), 111 (80), 91 (100).
2,7-Diamino-3-benzyl-5-phenylpyrazolo[1,5-a]pyrimidine-6-carbonitrile (20)
The solid, so formed after evaporation of the eluent, was recrystallized from petroleum ether (60-80) to
give a faint yellow product; yield 55 %; mp 214-216 ºC. Anal. Calcd for C20H16N6 (340.14): C, 70.57; H,
4.74; N, 24.69. Found: C, 70.33; H, 4.73; N, 24.40. IR (KBr): υmax = 3443, 3352 (NH2), 3417, 3300
(NH2), 2212 (CN); 1H NMR (400 MHz, DMSO-d6): δ, ppm = 3.89 (s, 2H, CH2), 5.78 (br, 2H, NH2, D2O
13
exchangeable), 7.11-7.79 (m, 10H, Ar-H), 8.13 (br, 2H, NH2, D2O exchangeable); C NMR (600 MHz,
DMSO-d6): δ, ppm = 161.08, 158.56, 149.71, 146.50, 142.06, 138.88, 131.03, 130.29, 129.48, 129.23,
129.18, 126.71, 118.34, 96.45, 70.93, 27.44. MS: m/z (%) 340 (M+, 100), 324 (15), 297 (30), 263 (80),
195 (10), 153 (10), 127 (10), 104 (20), 77 (10).
Synthesis of 4,7-diamino-8-benzylpyrazolo[5,1-c][1,2,4]triazine-3-carbonitrile (22)
A solution of malononitrile (0.66 g, 0.01 mol) in EtOH (50 mL) was treated with sodium acetate (5 g).
The diazonium salt was then added gradually, with stirring, to the mixture. These diazonium salts was
prepared from compound 7a (1.88 g, 0.01 mol) dissolved in acetic acid (5 mL), concentrated
hydrochloric acid (2.5 mL), and sodium nitrite (0.69 g, 0.01 mol) according to the standard literature
procedures. After complete addition of the diazonium salt, the reaction mixture was kept at rt for 1 h. The
resulting solid product was filtered. The solid, so formed, was collected by filtration and recrystallized
from EtOH to give a yellow product; yield 80 %; mp 237-239 ºC. Anal. Calcd for C13H11N7 (265.28): C,
58.86; H, 4.18; N, 36.96. Found: C, 58.91; H, 4.14; N, 37.08. IR (KBr): υmax = 3314, 3162 (NH2), 3235,
3159 (NH), 2225 (CN); 1H NMR (400 MHz, DMSO-d6): δ, ppm = 4.21 (s, 2H, CH2), 7.17-7.32 (m, 7H,
Ar-H, NH2, D2O exchangeable), 9.28 (br, 1H, NH2, D2O exchangeable); 13C NMR (600 MHz,
DMSO-d6): δ, ppm = 146.06, 145.61, 143.15, 140.21, 128.41, 128.36, 126.11, 115.99, 112.46, 104.30,
28.20. MS: m/z (%) 265 (M+, 40), 250 (60), 222 (30), 170 (20), 129 (30), 84 (100), 66 (20).
Synthesis of compound 2-amino-3-benzyl-5-methylpyrazolo[1,5-a]pyrimidin-7(4H)-one (23)
Equimolecular amounts of 7a (1.88 g, 0.01 mol) and EtOAc (1.30 g, 0.01 mol) in ethanol (20 mL) were