max was also investigated when 0.1 ml of base (0.1 M KOH) and 0.1 ml of acid (0.1 M HCl) was added to the
dye solutions in MeOH (1 ml; because of low solubility, concentration of dyes cannot be calculated exactly).
Elemental analysis was performed on a Leco CHNS-932 analyzer. Melting points were determined on an
Electrothermal 9100 melting point apparatus and are uncorrected.
Chemicals were obtained from Sigma-Aldrich Chemical Company and were used for syntheses without
further purification. The solvents used were of spectroscopic grade.
4-Amino-8-arylazo-7-methylpyrazolo[5,1-c][1,2,4]triazine-3-carboxylic Acid Ethyl Esters 4a-m
(General Method). Nitrosylsulfuric acid was prepared by dissolving NaNO2 (1.00 g, 14.5 mmol) in conc. H2SO4
(7 ml) at 70°C. 4-Aryl-3-methylazo-1H-pyrazol-5-amine 2a-m (2.0 mmol) was dissolved in hot glacial AcOH (2.5
ml) and rapidly cooled in an ice/salt bath to -5°C. The solution was then added in portions over 30 min to
nitrosylsulfuric acid at 0-5°C, and the mixture was stirred for a further 1 h at this temperature. Then the resulting
diazonium salt solution was added in portions over 30 min to a vigorously stirred solution of ethyl cyanoacetate
(0.22 g, 2.0 mmol) in pyridine (10 ml) at 0-5°C, maintaining the pH at 7-8 by simultaneous addition of solid
NaOAc. The mixture was then stirred for 2 h at 0-5°C. The progress of the reaction was followed by TLC on silica
gel plates using EtOAc–petroleum ether mixture, 5:2, as eluent. The resulting solid 3a-m was filtered off, washed
with cold water, and dried, then dissolved in glacial AcOH (30 ml), and refluxed for 4 h. The solvent was then
evaporated in vacuo and the remaining product was collected by filtration, dried, and recrystallized from DMF–
H2O, 3:1.
REFERENCES
1.
2.
3.
F. Freeman, Synthesis, 925 (1981).
Y. Tominaga, Y. Honkawa, M. Hara, and A. Hosomi, J. Heterocycl. Chem., 27, 775 (1990).
U. Hanefeld, C. W. Rees, A. J. P. White, and D. J. Williams, J. Chem. Soc., Perkin Trans. 1, 13, 1545
(1996).
4.
5.
6.
A. G. A. Elagamey and F. M. A.-A. El-Taweel, J. Prakt. Chem., 333, 333 (1991).
F. M. A. Latif, M. A. Barsy, E. A. Elrady, and M. Hassan, J. Chem. Res., Synop., 12, 696 (1999).
K. Senga, T. Novinson, R. H. Springer, R. P. Rao, D. E. O'Brien, R. K. Robins, and H. R. Wilson,
J. Med. Chem., 18, 312 (1975).
7.
8.
9.
S. P. Singh and D. Kumar, Heterocycles, 31, 855 (1990).
L. H. Sternbach, Prog. Drug Res., 22, 229 (1978).
N. Jaiswal, R. Jaiswal, J. Barthwal, and K. Kishor, Indian J. Chem., Sect. B: Org. Chem. Incl. Med.
Chem., 20B, 252 (1981).
10.
11.
S. G. Küçükgüzel, S. Rollas, H. Erdeniz, M. Kiraz, A. C. Ekinci, and A. Vidin, Eur. J. Med. Chem., 35,
761 (2000).
L. R. S. Dias, M. J. Alvim, A. C. C. Freitas, E. J. Barreiro, and A. L. P. Miranda, Pharm. Acta Helv., 69,
163 (1994).
12.
13.
J. W. Lyga, R. M. Patera, M. J. Plummer, B. P. Halling, and D. A. Yuhas, Pestic. Sci., 42, 29 (1994).
M. J. Genin, C. Biles, B. J. Keiser, S. M. Poppe, S. M. Swaney, W. G. Tarpley, Y. Yagi, and
D. L. Romero, J. Med. Chem., 43, 1034 (2000).
14.
15.
16.
17.
18.
19.
N. Ertan, Dyes Pigm., 44, 41 (2000).
A. K. Khalil, M. A. Hassan, M. M. Mohamed, and A. M. El-Sayed, Dyes Pigm., 66, 241 (2005).
A. Emandi, I. Serban, and R. Bandula, Dyes Pigm., 41, 63 (1999).
P. C. Tsai and I. J. Wang, Dyes Pigm., 64, 259 (2005).
Y. W. Ho, Dyes Pigm., 64, 223 (2005).
F. Karcı, N. Şener, M. Yamaç, İ. Şener, and A. Demirçalı, Dyes Pigm., 80, 47 (2009).
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