SYNTHETIC COMMUNICATIONS®
1623
3-Amino-7-benzylidene-1,7-dihydro-4H-pyrazolo[4,3-c]pyridine-4,
6(5H)-dione (4a)
Yellow crystals, yield 66%, m.p. 240 °C, νmax/cm−1 (KBr) 3402 (NH2), 3200 (NH), 1692
1
(CO); H NMR (DMSO) δ ¼ 6.04 (s, 2H, NH2), 6.95–7.49 (m, 5H, Ar), 8.03 (s, 1H,
CH), 10.43 (s, 1H, NH), 12.09 (s, 1H, NH); m/z 254 ¼ (Mþ, 100%), 238 (22.9%), 210
(22.9%), 166 (24.2%), 127 (29.3%), 91 (64.0%), 77 (48.1%), 66 (20.8%), 51 (16.0%); Anal.
Calcd for C13H10N4O2: C, 61.41; H, 3.96; N, 22.04. Found: C, 61.59; H, 3.82; N, 22.31%.
General procedure of synthesis of compounds 6a–e
A solution of compound 2 (0.01 mol) and sodium acetate (0.01 mol) in N,N-
dimethylformamide (10 ml) was cooled in an ice bath at (0–5 °C) while being stirred. To
the resulting cold solution was added portionwise a cold solution of the appropriate
diazonium salt 5a–e prepared as usual by diazotizing the corresponding aromatic amine
(0.01 mol) in concentrated hydrochloric acid (3 ml) with sodium nitrite (0.01 mol) in water
(3 ml). After all the diazonium salt solution was added, the mixture was stirred for further
one hour. while cooling in an ice-bath. The solid that precipitated was filtered off,
washed with water, dried and finally crystallized from N,N-dimethylformamide to give
products 6a–e.
3-Amino-7-(2-(p-tolyl)hydrazono)-1,7-dihydro-4H-pyrazolo[4,3-c]pyridine-4,6
(5H)-dione (6b)
Orange crystals, yield 74%, m.p. 315 °C, νmax/cm−1 (KBr) 3419 (NH2), 3338, 3211, 3195
1
(3NH), 1691 (CO); H NMR (DMSO) δ ¼ 2.28 (s, 3H, CH3), 6.57 (s, 2H, NH2), 7.18
(d, 2H, J ¼ 8.7 Hz, CH), 7.22 (d, 2H, J ¼ 9 Hz, CH), 10.63 (s, 1H, NH), 12.10 (s, 1H,
NH), 12.58 (s, 1H, NH); m/z 284 ¼ (Mþ, 88.3%), 239 (9.0%), 213 (1.7%), 166 (5.6%),
135 (31.5%), 106 (92.0%), 91 (100%), 77 (69.6%), 65 (59.1%), 52 (42.6%); Anal. Calcd
for C13H12N6O2: C, 54.93; H, 4.25; N, 29.56. Found: C, 54.81; H, 4.43; N, 29.79%.
General procedure of synthesis of compounds 9a–d
A mixture of compound 2 (0.01 mol) and α,β-unsaturated ketones 7a–d (0.01 mol) in N,
N-dimethylformamide (10 ml) containing a few drops of piperidine was heated under
reflux for 6 hours and the reaction mixture was followed by TLC. The solid so formed
was filtered off and recrystallized from N,N-dimethylformamide to give the respective
products 9a–d.
2-Amino-8-(benzo[d][1,3]dioxol-5-yl)-6-phenyl-3H-pyrazolo[4,5,1-ij][1,6]
naphthyridine-3,5(4H)-dione (9d)
Brown crystals, yield 81%, m.p 285 °C, νmax/cm−1 (KBr) 3413 (NH2), 3117 (NH), 1681
1
(CO); H NMR (DMSO) δ ¼ 6.26 (s, 2H, CH2), 6.64 (s, 2H, NH2), 7.18 (s, 1H, Ar), 7.27
(d, 2H, J ¼ 8.4 Hz, Ar), 7.57–7.69 (m, 3H, Ar), 7.84–8.41 (m, 3H, Ar), 10.93 (s, 1H,
NH). 13C NMR (DMSO) δ ¼ 89.32, 101.75, 108.05, 110.10, 110.89, 117.75, 124.15,
128.97, 130.09, 130.77, 131.27, 131.61, 142.29, 145.04, 146.05, 147.64, 149.87, 160.27,
162.77; m/z 398 ¼ (Mþ, 2.8%), 386 (1.7%), 363 (0.4%), 343 (0.1%), 326 (0.1%), 317
(0.5%), 305 (1.4%), 281 (0.2%), 268 (0.8%), 247 (1.8%), 229 (0.9%), 213 (0.9%), 201