2-Cyano-2-[(4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl)hydrazono]-N'-(4-methoxybenzylidene)-
acetohydrazide (4). Yield 2.89 g (74%); mp 257-258°C. IR spectrum, , cm-1: 3314, 3163 (2NH), 2180 (CN),
1650 (CO). 1H NMR spectrum (DMSO-d6), , ppm (J, Hz): 2.40 (3H, s, CH3); 2.55 (3H, s, CH3); 3.90 (3H, s,
OCH3); 6.90 (2H, d, J = 8.2, H Ar); 7.20 (1H, s, H-5); 7.40 (2H, d, J = 8.2, H Ar); 8.20 (1H, s, N=CH); 10.80
(1H, s, NH); 12.25 (2H, s, 2NH). Found, %: C 58.37; H 4.71; N 28.66. C19H18N8O2. Calculated, %: C 58.45;
H 4.65; N 28.70.
2-[(5-Bromo-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl)hydrazono]-2-cyano-N'-(4-methoxybenzyl-
idene)acetohydrazide (5). Yield 3.19 g (68%); mp 258-259°C. IR spectrum, , cm-1: 3325, 3214 (2NH), 2184
(CN), 1668 (CO). 1H NMR spectrum (DMSO-d6), , ppm (J, Hz): 2.40 (3H, s, CH3); 2.50 (3H, s, CH3); 3.85 (3H,
s, OCH3); 7.00 (2H, d, J = 8.0, H Ar); 7.40 (2H, d, J = 8.0, H Ar); 8.20 (1H, s, N=CH); 11.05 (1H, s, NH);
12.75 (2H, s, 2NH). Found, %: C 48.68; H 3.61; N 23.96. C19H17BrN8O2. Calculated, %: C 48.63; H 3.65;
N 23.88.
8-Aminopyrido[2',3':3,4]pyrazolo[5,1-c][1,2,4]triazine-7-benzylideneacetohydrazide Derivatives 6
and 7 (General Method). Compound 4 or 5 (0.005 mol) in acetic acid (20 ml) was heated under reflux for 30
min, and then allowed to cool. The solid product 6 or 7 was collected by filtration, washed with cold EtOH, and
recrystallized from EtOH–DMF mixture (1:1).
8-Amino-2,4-dimethylpyrido[2',3':3,4]pyrazolo[5,1-c][1,2,4]triazine-7-(4-methoxybenzylidene)-
acetohydrazide (6). Yield 1.78 g (91%); mp 300°C. IR spectrum, , cm-1: 3359, 3252, 3205 (NH2 and NH),
1660 (CO). 1H NMR spectrum (CDCl3–CF3COOD), , ppm (J, Hz): 2.90 (3H, s, CH3); 3.10 (3H, s, CH3); 3.85
(3H, s, OCH3); 7.00 (2H, d, J = 8.4, H Ar); 7.10 (1H, s, H-3); 7.40 (2H, d, J = 8.4, H Ar); 8.25 (1H, s, N=CH).
Found, %: C 58.54; H 4.70; N 28.78. C19H18N8O2. Calculated, %: C 58.45; H 4.65; N 28.70.
8-Amino-3-bromo-2,4-dimethylpyrido[2',3':3,4]pyrazolo[5,1-c][1,2,4]triazine-7-(4-methoxybenz-
ylidene)acetohydrazide (7). Yield 2.06 g (88%); mp 300°C. IR spectrum, , cm-1: 3386, 3277, 3204 (NH2 and
1
NH), 1661 (CO). H NMR spectrum (CDCl3–CF3COOD), , ppm (J, Hz): 2.90 (3H, s, CH3); 3.05 (3H, s, CH3);
3.85 (3H, s, OCH3); 7.00 (2H, d, J = 8.2, H Ar); 7.40 (2H, d, J = 8.2, H Ar); 8.30 (1H, s, N=CH). Found, %:
C 48.72; H 3.68; N 23.93. C19H17BrN8O2. Calculated, %: C 48.63; H 3.65; N 23.88.
3-Hydrazonopyrazolo[3,4-b]pyridine Derivatives 9a,b (General Method). A freshly prepared
solution of pyrazolopyridinediazonium chloride 2a (2.1 g, 0.01 mol) was added with continuous stirring to a
cold solution (0-5°C) of N'-acyl-2-cyanoacetohydrazide derivatives 8a or 8b (0.01 mol) and NaOAc (4.0 g, 0.05
mol) in EtOH (50 ml). The reaction mixture was allowed to stand in the cold for 2 h and then diluted with water.
The products so formed were collected by filtration and washed with water, followed by cold EtOH. The
isolated compounds were recrystallized from EtOH to give compounds 9a,b.
N'-Acetyl-2-cyano-2-[(4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl)hydrazono]acetohydrazide (9a).
Yield 2.17 g (69%); mp 285-286°C. IR spectrum, , cm-1: 3403, 3282, 3201 (3NH), 2192 (CN), 1698, 1657
(2CO). 1H NMR spectrum (DMSO-d6), , ppm: 2.10 (3H, s, COCH3); 2.50 (3H, s, CH3); 2.60 (3H, s, CH3); 7.00
(1H, s, H-5); 11.60 (2H, s, 2NH); 12.85 (1H, s, NH); 14.25 (1H, s, NH). Found, %: C 49.50; H 4.38; N 35.56.
C13H14N8O2. Calculated, %: C 49.68; H 4.49; N 35.56.
N'-Benzoyl-2-cyano-2-[(4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl)hydrazono]acetohydrazide
(9b). Yield 2.67 g (71%); mp 280-281°C. IR spectrum, , cm-1: 3416, 3284, 3199 (3NH), 2124 (CN), 1667,
1
1658 (2CO). H NMR spectrum (DMSO-d6), , ppm: 2.45 (3H, s, CH3); 2.60 (3H, s, CH3); 7.00 (1H, s, H-5);
7.30–7.50 (5H, m, H Ph); 10.35 (2H, s, 2NH); 12.20 (1H, s, NH); 13.75 (1H, s, NH). Found, %: C 57.59;
H 4.15; N 29.68. C18H16N8O2. Calculated, %: C 57.44; H 4.28; N 29.77.
8-Aminopyrido[2',3':3,4]pyrazolo[5,1-c]triazine-7-carboxylic Acid N'-acylhydrazide Derivatives
10a,b. Compound 9a,b (0.005 mol) in acetic acid (20 ml) was heated under reflux for 30 min and then allowed
to cool. The solid product 10a,b was collected by filtration, washed with cold EtOH, and recrystallized from
EtOH–DMF mixture (2:1).
8-Amino-2,4-dimethylpyrido[2',3':3,4]pyrazolo[5,1-c]triazine-7-carboxylic acid N'-Acetylhydra-
zide (10a). Yield 1.23 g (78%); mp 300°C. IR spectrum, , cm-1: 3378, 3180 (NH2 and NH), 1641 (br., CO).
1075