Ultrasonic-assisted one-pot synthesis of pyrazolo[1,2-a][1,2,4]triazole-1, 3-diones

Article abstract of DOI:10.3987/COM-10-11959

A facile and efficient one-pot three-component synthesis of pyrazolo[1,2-a][1,2,4]triazole-1,3-diones via condensation reaction between malononitrile, 4-phenylurazole and aromatic aldehydes in ethanol under the catalytic effect of triethylamine and ultrasonic-irradiation conditions has been explored. The advantages of this protocol include a simple workup, high rates, use of inexpensive non-toxic catalyst, improved yields, and use of ethanol as a relatively environmentally benign solvent. The Japan Institute of Heterocyclic Chemistry.

Full text of DOI:10.3987/COM-10-11959

HETEROCYCLES, Vol. 81, No. 9, 2010
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HETEROCYCLES, Vol. 81, No. 9, 2010, pp. 2063 - 2073. © The Japan Institute of Heterocyclic Chemistry
Received, 8th April, 2010, Accepted, 30th July, 2010, Published online, 3rd August, 2010
DOI: 10.3987/COM-10-11959
ULTRASONIC-ASSISTED
ONE-POT
SYNTHESIS
OF
PYRAZOLO[1,2-a][1,2,4]TRIAZOLE-1,3-DIONES
Davood Azarifar* and Razieh Nejat Yami
Faculty of Chemistry, Bu-Ali Sina University, Zip Code 65178, Hamedan, Iran
*Corresponding author; E-mail: azarifar@basu.ac.ir
Abstract – A facile and efficient one-pot three-component synthesis of
pyrazolo[1,2-a][1,2,4]triazole-1,3-diones via condensation reaction between
malononitrile, 4-phenylurazole and aromatic aldehydes in ethanol under the
catalytic effect of triethylamine and ultrasonic-irradiation conditions has been
explored. The advantages of this protocol include a simple workup, high rates, use
of inexpensive non-toxic catalyst, improved yields, and use of ethanol as a
relatively environmentally benign solvent.
INTRODUCTION
With respect to a wide number of books,1 and articles2 published in recent years, applications of
ultrasounds in a so called “sonochemistry” have attracted much attention since it offers a versatile and
challenging technique in organic synthesis.3 Ultrasonic irradiation has been demonstrated to be quite
useful in a large variety of organic synthesis, providing high yields, short reaction times and mild
conditions.1,2 On the other hand, one-pot multi-component reactions have proven to be more
advantageous over conventional linear-type synthesis,4,5 since the multi-step reactions are usually
subjected to complex isolation procedures and produce significant amounts of waste materials. In addition,
multi-component processes provide rapid and efficient approach to organic transformations including
diverse synthesis of polyfunctionalized heterocycles.6 These compounds are of significant biological and
pharmaceutical importance that play vital roles in the drug discovery process.4,6 Polyfunctionalized
heterocyclic fragments form important moieties of a large number of a variety of natural products and
medicinal agents.4,6 As a result, the multi-component synthesis of polyfunctionalized heterocyclic
compounds is progressively becoming more challenging in organic and medicinal chemistry.7
Nitrogen-containing heterocyclic compounds are widespread in nature and have received considerable
attention due to their biological activities as pharmaceuticals, agrochemicals and functional materials.7-9

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HETEROCYCLES, Vol. 81, No. 9, 2010
Among these, heterocycles possessing the urazole (1,2,4-triazolidine-3,5-diones) moieties have attracted
considerable attention as useful synthetic reagents in the laboratory as well as in industry. Urazoles have
found immense technological applications in the manufacture of herbicides and antifungal compounds.10
They have been also employed in the production of automobile air bags and in plastics as blowing agent
as well as in other polymeric materials.11,12 In addition, 1,2,4-triazolidine-3,5-dione moiety has a
documented prominence in a number of biological and medicinal agents such as antitumor drugs,13 and
hypolipidemically active compounds,14 pesticides15 and insecticides.16 Novel methods for preparing
heterocycles containing an urazole moiety have attracted much interest in recent years.17 On the other
hand, pyrazoles are another important class of N-heterocyclic compounds of diverse structures with a
wide range of interesting biological properties, such as analgesic, anti-pyretic, anti-bacterial,
anti-inflammatory, anti-diabetic and psychoanaleptic activities.18
Considering the important biological properties of the fused pyrazolourazoles, a number of methods have
been previously reported for the synthesis of these heterocycles.19 In 2010, Nikpassand et al.,20 have
reported
a
convenient ultrasound-promoted regioselective synthesis of fused polycyclic
4-aryl-3-methyl-4,7-dihydro-1H-pyrazolo[3,4-b]pyridines. Recently, Pizzuti and his co-workers have
efficiently utilized ultrasound in the synthesis of novel 4,5-dihydro-1H-pyrazole derivatives.21 Also, a
convenient protocol for the hydrochloric acid-catalyzed synthesis of 5-aryl-1,3-diphenylpyrazoles under
ultrasound irradiation has been reported.22 A one-pot easy conversion of Baylis-Hillman adducts into
arylpyrazoles under ultrasound irradiation have been recently reported.23
As part of our ongoing efforts on the synthesis of pyrazole derivatives,24 we report herein a one-pot
three-component condensation reaction between malononitrile, 4-phenylurazole and aromatic aldehydes
under catalytic effect of triethylamine and ultrasonic-irradiation conditions as a new approach for the
synthesis of new derivatives of pyrazolo[1,2-a][1,2,4]triazole-1,3-diones.
RESULTS AND DISCUSSION
With regard to the previous reports on three-component reactions for the synthesis of fused-ring
heterocycles including pyrazole-fused heterocycles,25-30 we were encouraged to preliminary examine
polycondensation reaction of a mixture of malononitrile 1, 4-phenylurazole 2, and benzaldehyde 3a in
ethanol using a catalytic amount of triethylamine as an inexpensive and readily available catalyst under
ultrasonic irradiation conditions. In this reaction, pyrazolo[1,2-a][1,2,4]triazole-1,3-dione 4a was afforded
in 93% yield after 45 min irradiation at 50 ºC. To achieve suitable reaction conditions, i.e., lower reaction
times and temperature for the synthesis of pyrazolo[1,2-a][1,2,4]triazole-1,3-diones 4, various solvents
and reaction conditions were investigated in the reaction of malononitrile 1, 4-phenylurazole 2, and
benzaldehyde 3a as a model reaction (Table 1). As shown in Table 1, the reaction worked out best at

HETEROCYCLES, Vol. 81, No. 9, 2010
2065
50 ºC under ultrasonic irradiation with a 20 mol% Et3N as the catalyst. Effects of solvents on the yield of
the product 4a were tested at ultrasonic-irradiation conditions. Ethanol (93%) was a much better solvent
in terms of yields than H2O (60%), acetonitrile (20%) and dichloroethane (< 10%). It is to mention that
the starting materials in the case of the solvents acetonitrile and dichloroethane were remained intact and
no by-products were detected. It was observed that, using lower or higher amounts of catalyst under the
same reaction time and temperature resulted in lower yields (Table 1). To study the effect of temperature,
º
the reaction was also performed at various temperatures (r.t, 30, 40, 50 and 60 C) under sonication.
Apparently, higher reaction temperature did not affect the reaction yield (Table 1). When the reaction was
carried out in the absence of the catalyst, no detectable amount of respective product was formed and the
starting materials remained almost intact. To show the role of ultrasound, the reaction was investigated
º
without ultrasonic irradiation at the same temperature (50 C) in various solvents. In all cases it was
observed that the use of ultrasound leads to the faster reaction and higher yields.
Table 1. Effect of reaction conditions.a
O
NH2
Ph
O
NH
NH
N
N
N
+
CN
N
NC
CN
+
PhCHO
1
2
3a
4a
O
O
Entry Conditions
Method
Catalyst (mol%)
Time (min) Yield (%)
1
2
3
4
5
6
7
8
EtOH / 50 ºC
EtOH / 50 ºC
EtOH/ 50 ºC
EtOH / 50 ºC
EtOH / 60 ºC
EtOH / 40 ºC
EtOH / 30 ºC
EtOH / rt
EtOH / 50 ºC
H2O / 50 ºC
H2O / 50 ºC
MeCN / 50 ºC
MeCN / 50 ºC
ClCH2CH2Cl / 50 ºC
1,2-Cl2C2H4 / 50 ºC
ultrasound
ultrasound
ultrasound
ultrasound
ultrasound
ultrasound
ultrasound
ultrasound
high speed stirring
ultrasound
high speed stirring
ultrasound
None
240
60
45
45
60
60
60
60
240
60
trace
55
93
94
94
Et3N (10)
Et3N (20)
Et3N (30)
Et3N (20)
Et3N (20)
Et3N (20)
Et3N (20)
Et3N (30)
Et3N (20)
Et3N (20)
Et3N (20)
Et3N (20)
Et3N (20)
Et3N (20)
86
<20
trace
trace
60
trace
20
trace
<10
trace
9
10
11
12
13
14
15
240
60
240
60
high speed stirring
ultrasound
high speed stirring
240
a Malononitrile (1 mmol), 4-phenylurazole (1 mmol), benzaldehyde (1 mmol).
This achievement encouraged us to extend this reaction to a variety of aromatic aldehydes 3b-p under
similar conditions (EtOH/Et3N/ultrasound), furnishing the respective pyrazolo[1,2-a][1,2,4]triazole-1,3-

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HETEROCYCLES, Vol. 81, No. 9, 2010
diones 4b-p in good to excellent yields in 30-60 min (Scheme 1). The results are summarized in Table 2.
13
The structures of the products 4a-p were fully established by their spectral (1H and C NMR, IR, MS)
and elemental analysis.
NH2
O
O
EtOH / 50 oC
))))))))
N
N
NH
NH
CN
N
+
N
+
RCHO
NC
CN
Et3N (20% mol)
30-60 min
R
1
O
2
O
3a-t
4a-t
Scheme 1
It is interesting to note that, the attempt to react the aliphatic aldehydes such as propanal 3q,
3-phenylpropanal 3r, n-heptanal 3s, and n-octanal 3t for the synthesis of their respective
pyrazolo[1,2-a][1,2,4]triazole-1,3-diones 4q-t under the same reaction conditions was failed (Table 2). 1H
NMR and IR spectral analysis of the reaction mixtures indicated no sign of the formation of respective
products and all three components of the reaction mixtures were found intact. This implies that the
present protocol cannot be suitable for the synthesis of pyrazolo[1,2-a][1,2,4]triazole-1,3-diones derived
from aqliphatic aldehydes. The lack of reactivity between the aliphatic aldehydes and malononitrile has
already been reported by X. Lu et al. in the one-pot synthesis of cyclopentenes.31
We were also interested in using similar reaction conditions (EtOH/Et3N/ultrasound), for the one-pot
reaction of ethyl cyanoacetate with benzaldehyde 3 and 4-phenylurazole 2, but unfortunately the reactions
were found sluggish and no pyrazolotriazole compound was detected.
Table 2. Ultrasonic-assisted synthesis of 1H-pyrazolo[1,2-a][1,2,4]triazole-1,3-diones.a
Product 4
R
Time (min)
Yield (%)b
a
b
c
d
e
f
g
h
i
Ph
45
30
30
30
60
30
30
30
60
60
30
30
30
93
92
90
91
86
91
90
93
85
83
90
94
92
2-ClC6H4
3-ClC6H4
4-ClC6H4
2,4-Cl2C6H3
2-NO2C6H4
3-NO2C6H4
4-NO2C6H4
4-FC6H4
4-MeC6H4
2-BrC6H4
3-BrC6H4
4-BrC6H4
j
k
l
m

HETEROCYCLES, Vol. 81, No. 9, 2010
2067
n
o
p
q
r
s
pyridin-4-yl
pyridin-3-yl
4-NCC6H4
Et
3-PhC2H4
n-C6H13
45
30
60
120
120
120
120
87
91
90
-
-
-
t
n-C7H15
-
a
Malononitrile (1 mmol), 4-phenylurazole (1 mmol), aldehyde (1
mmol), triethylamine (0.02 g, 20 mol%), ultrasound, reaction
temperature 50 ºC.
b
Isolated yields.
A possible mechanism for the formation of 4a-t is proposed in Scheme 2. In this process the aldehyde 3
initially condenses with malononitrile 1 under the catalytic effect of Et3N to afford the dehydrated
condensed malononitrile derivative I. This step can be regarded as Knoevenagel addition. Then the
subsequent Michael type addition of the 4-phenylurazole 2 to I occurs to give the intermediate II
followed by successive cyclization to III and Et3N-catalyzed isomerization to afford the corresponding
product 4a-t.
Et3N
R
O
H
H
N
N
N
Et3N /
O
N
H
N
EtOH / 50 oC
)))))))))
NC
NC
NC
NC
C
NC
H
N
O
RCHO
+
N
- H2O
H
O
H
R
I
1
3
II
O
HN
O
H2N
N
NC
N
N
N
NC
N
H
N
H
O
R
O
R
4
III
Et3N
Scheme 2
In summary, we have developed a rapid and reliable synthetic procedure that provides access to hitherto
unknown pyrazolo[1,2-a][1,2,4]triazole-1,3-diones 4a-p in high yields and short reaction times by a
three-component cyclo-condensation reaction of aromatic aldehydes, malononitrile and 4-phenylurazole
using Et3N as an inexpensive and readily available catalyst under ultrasonic irradiation.

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HETEROCYCLES, Vol. 81, No. 9, 2010
EXPERIMENTAL
Chemicals used in this work were purchased from Fluka and Merk chemical companies and used without
purification. IR spectra were recorded on a Shimadzu 435-U-04 FT spectrophotometer from KBr pellets.
1H and 13C NMR spectra were measured for samples in DMSO-d6 with a 500 MHz Bruker instrument at
500.13 and 125.77 MHz respectively, using Me4Si as internal standard. Mass spectra were recorded with
a spectrometer FINNIGAN-MAT 8430 operating at an ionization potential of 70 ev. Melting points were
measured on a SMPI apparatus. Elemental analysis for C, H and N atoms were performed using a
Perkin–Elmer 2400 series analyzer. Ultrasonication was performed in a TRANSSONI 660/H ultrasound
cleaner with a frequency of 35 KHz and an output power of 70 W. The reactions were performed in open
vessels.
Typical procedure for the synthesis of pyrazolo[1,2-a][1,2,4]triazole-1,3-diones (4):
A mixture of malononitrile (0.07 g, 1 mmol), benzaldehyde (0.12 g, 1 mmol), 4-phenylurazole (0.18 g, 1
º
mmol), and Et3N (0.02 g, 20% mol) in EtOH (10 mL) was sonicated at 50 C for 45 min. After the
completion of the reaction as monitored by TLC analysis, the reaction mixture was filtered and the
precipitate was washed with ethanol (2 × 3 ml) to afford almost a pure product 4a. The structures of the
products 4a-p were fully established by their spectral (1H and 13C NMR, IR, MS) and elemental analysis
as given below.
7-1,3-dioxo-2,5-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbonitrile (4a)
White powder; mp >210 ºC; IR (KBr) (νmax/cm-1): 3431, 3317, 2191, 1774, 1712. MS, m/z (%): 331 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 5.95 (1H, s, CH), 7.08–8.12 (12H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.2, 63.3, 116.2, 126.1, 126.9, 127.7, 128.3, 128.5, 128.7, 129.5, 129.8, 130.2,
130.5, 133.4, 145.1, 150.1, 150.5, 153.3. Anal. Calcd for C18H13N5O2: C, 65.25; H, 3.93; N, 21.15%.
Found: C, 65.21; H, 3.86; N, 21.08%.
7-Amino-5-(2-chlorophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4b)
White powder; mp >218 ºC; IR (KBr) (νmax/cm-1): 3394, 3315, 2202, 1778, 1718. MS, m/z (%): 365 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 6.27 (1H, s, CH), 7.39–7.66 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.1, 61.6, 116.0, 125.9, 126.8, 128.0, 128.7, 128.8, 129.0, 129.5, 129.8, 130.3,
130.9, 131.7, 135.9, 150.1, 150.5, 153.5. Anal. Calcd for C18H12ClN5O2: C, 59.18; H, 3.28; N, 19.18%.
Found: C, 59.14; H, 3.25; N, 19.14%.
7-Amino-5-(3-chlorophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-

HETEROCYCLES, Vol. 81, No. 9, 2010
2069
carbonitrile (4c)
White powder; mp >216 ºC; IR (KBr) (νmax/cm-1): 3445, 3330, 2197, 1772, 1715. MS, m/z (%): 365 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 6.17 (1H, s, CH), 7.23–7.80 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.2, 63.2, 116.3, 121.1, 126.8, 127.2, 128.1, 128.3, 128.8, 129.2, 129.8, 130.7,
135.2, 135.9, 145.6, 150.3, 150.6, 153.6. Anal. Calcd for C18H12ClN5O2: C, 59.18; H, 3.28; N, 19.18%.
Found: C, 59.12; H, 3.23; N, 19.08%.
7-Amino-5-(4-chlorophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4d)
White powder; mp >221 ºC; IR (KBr) (νmax/cm-1): 3455, 3325, 2200, 1783, 1719. MS, m/z (%): 365 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 5.89 (1H, s, CH), 7.42–7.67 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.2, 63.3, 116.3, 126.7, 126.8, 128.6, 128.8, 128.9, 129.0, 129.4, 129.5, 130.9,
133.2, 138.0, 145.4, 150.4, 150.5, 153.5. Anal. Calcd for C18H12ClN5O2: C, 59.18; H, 3.28; N, 19.18%.
Found: C, 59.13; H, 3.25; N, 19.12%.
7-Amino-5-(2,4-dichlorophenyl)-1,3-dioxo-2-phenyl-1,2,3-dihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4e)
White powder; mp >200 ºC; IR (KBr) (νmax/cm-1): 3475, 3336, 2200, 1783, 1750. MS, m/z (%): 399 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 6.22 (1H, s, CH), 7.43–7.70 (10H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 60.5, 61.1, 116.0, 126.7, 128.3, 128.7, 129.0, 129.2, 129.4, 129.9, 130.9, 131.0,
132.7, 134.0, 135.1, 150.2, 150.5, 153.5. Anal. Calcd for C18H11Cl2N5O2: C, 54.02; H, 2.77; N, 17.50%.
Found: C, 54.12; H, 2.71; N, 17.48%.
7-Amino-1,3-dioxo-5-(2-nitrophenyl)-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbo-
nitrile (4f)
º
Yellow powder; mp >215 C; IR (KBr) (νmax/cm-1): 3429, 3325, 2208, 1776, 1748. MS, m/z (%): 376
1
13
(M+). H NMR (500 MHz, DMSO-d6): δH 6.50 (1H, s, CH), 7.42–8.11 (11H, m, H–Ar and NH2). C
NMR (125 MHz, DMSO-d6): δC 60.0, 61.0, 116.0, 124.7, 126.7, 126.8, 128.7, 129.0, 129.4, 130.0, 130.9,
133.9, 134.7, 145.4, 147.5, 150.4, 150.6, 153.8. Anal. Calcd for C18H12N6O4: C, 57.44; H, 3.19; N,
22.34%. Found: C, 57.38; H, 3.15; N, 22.26%.
7-Amino-1,3-dioxo-5-(3-nitrophenyl)-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbo-
nitrile (4g)
White powder; mp >214 ºC; IR (KBr) (νmax/cm-1): 3437, 3317, 2196, 1770, 1728. MS, m/z (%): 376 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 6.08 (1H, s, CH), 7.43–8.35 (11H, m, H–Ar and NH2). C NMR

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HETEROCYCLES, Vol. 81, No. 9, 2010
(125 MHz, DMSO-d6): δC 60.8, 63.0, 116.3, 121.5, 123.6, 126.8, 128.7, 129.0, 130.6, 130.9, 133.6, 141.5,
148.1, 150.3, 150.5, 153.7. Anal. Calcd for C18H12N6O4: C, 57.44; H, 3.19; N, 22.34%. Found: C, 57.41;
H, 3.08; N, 22.30%.
7-Amino-1,3-dioxo-5-(4-nitrophenyl)-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbo-
nitrile (4h)
º
Yellow powder; mp >218 C; IR (KBr) (νmax/cm-1): 3399, 3332, 2211, 1786, 1745. MS, m/z (%): 376
1
13
(M+). H NMR (500 MHz, DMSO-d6): δH 5.97 (1H, s, CH), 7.44–8.32 (11H, m, H–Ar and NH2). C
NMR (125 MHz, DMSO-d6): δC 61.0, 63.2, 116.37, 124.2, 126.9, 128.4, 128.9, 129.1, 129.6, 131.0, 46.28,
47.8, 150.37, 150.6, 153.7. Anal. Calcd for C18H12N6O4: C, 57.44; H, 3.19; N, 22.34%. Found: C, 57.38;
H, 3.13; N, 22.32%.
7-Amino-1,3-dioxo-5-(4-fluorophenyl)-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4i)
White powder; mp >222 ºC; IR (KBr) (νmax/cm-1): 3367, 3311, 2198, 1784, 1724. MS, m/z (%): 349 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 5.88 (1H, s, CH), 7.25–7.60 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.3, 63.4, 116.4, 126.7, 126.8, 128.6, 128.9, 129.2, 129.3, 129.4, 129.5, 129.9,
131.0, 135.3, 145.4, 150.0, 150.4, 153.5. Anal. Calcd for C18H12FN5O2: C, 61.89; H, 3.44, N, 20.05%.
Found: C, 61.86; H, 3.45; N, 19.97%.
7-Amino-1,3-dioxo-2-phenyl-5-p-tolyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbonitrile
(4j)
º
Yellow powder; mp >217 C; IR (KBr) (νmax/cm-1): 3368, 3318, 2190, 1772, 1711. MS, m/z (%): 345
(M+). 1H NMR (500 MHz, DMSO-d6): δH 2.48 (3H, s, CH3), 5.81 (1H, s, CH), 7.28–7.55 (11H, m, H–Ar
and NH2). 13C NMR (125 MHz, DMSO-d6): δC 25.1, 61.3, 63.2, 116.4, 126.3, 126.5, 128.3, 128.8, 129.0,
129.5, 129.7, 129.9, 133.1 137.7, 144.2, 150.1, 150.6, 153.4. Anal. Calcd for C19H15N5O2: C, 66.08; H,
4.35; N, 20.29%. Found: C, 66.04; H, 4.32; N, 20.23%.
7-Amino-5-(2-bromophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4k)
White powder; mp >223 ºC; IR (KBr) (νmax/cm-1): 3490, 3325, 2185, 1782, 1748. MS, m/z (%): 410 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 6.28 (1H, s, CH), 7.30–7.68 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DM SO-d6): δC 61.3, 63.7, 116.1, 121.7, 126.7, 126.8, 128.6, 128.7, 129.0, 129.4, 129.7, 130.5,
131.0, 133.0, 137.5, 150.1, 150.5, 153.5. Anal. Calcd acetonitrile (20%) and dichloroethane for for
C18H12BrN5O2: C, 52.68; H, 2.92; N, 17.07%. Found: C, 52.63; H, 2.87; N, 17.02%.

HETEROCYCLES, Vol. 81, No. 9, 2010
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7-Amino-5-(3-bromophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4l)
White powder; mp >221 ºC; IR (KBr) (νmax/cm-1): 3428, 3335, 2208, 1783, 1722. MS, m/z (%): 410 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 5.88 (1H, s, CH), 7.40–7.68 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.1, 63.1, 116.4, 121.9, 126.0, 126.8, 128.6, 128.9, 129.4, 129.6, 130.9, 131.0,
131.4, 141.8, 145.4, 150.1, 150.4, 153.5. Anal. Calcd for C18H12BrN5O2: C, 52.68; H, 2.92; N, 17.07%.
Found: C, 52.65; H, 2.89; N, 16.98%.
7-Amino-5-(4-bromophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4m)
White powder; mp >224 ºC; IR (KBr) (νmax/cm-1): 3449, 3323, 2200, 1782, 1718. MS, m/z (%): 410 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 5.77 (1H, s, CH), 7.00–7.60 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 60.8, 61.3, 116.4, 126.5, 126.9, 127.8, 128.7, 129.0, 129.5, 129.9, 130.2, 131.1,
133.3, 137.7, 144.5, 150.1, 150.5, 153.3. Anal. Calcd for C18H12BrN5O2: C, 52.68; H, 2.92; N, 17.07%.
Found: C, 52.62; H, 2.90; N, 17.02%.
7-Amino-1,3-dioxo-2-phenyl-5-(pyridin-4-yl)-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbo-
nitrile (4n)
White powder; mp >198 ºC; IR (KBr) (νmax/cm-1): 3392, 3319, 2200, 1786, 1725. MS, m/z (%): 332 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 6.17 (1H, s, CH), 7.23–7.98 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 61.2, 63.3, 116.3, 126.1, 126.5, 127.2, 128.5, 128.8, 129.2, 129.5, 129.8, 130.7,
135.2, 146.2, 150.1, 150.3, 153.6. Anal. Calcd for C17H12N6O2: C, 61.44; H, 3.61; N, 25.30%. Found: C,
61.40; H, 3.56; N, 25.23%.
7-Amino-1,3-dioxo-2-phenyl-5-(pyridin-3-yl)-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-carbo-
nitrile (4o)
White powder; mp >195 ºC; IR (KBr) (νmax/cm-1): 3415, 3317, 2194, 1789, 1725. MS, m/z (%): 332 (M+).
13
1H NMR (500 MHz, DMSO-d6): δH 5.96 (1H, s, CH), 7.42–8.61 (11H, m, H–Ar and NH2). C NMR
(125 MHz, DMSO-d6): δC 60.6, 61.9, 116.3, 123.9, 126.7, 128.6, 128.9, 129.4, 130.9, 134.5, 134.8, 148.4,
149.9, 150.1, 150.4, 153.6. Anal. Calcd for for C17H12N6O2: C, 61.44; H, 3.61; N, 25.30%. Found: C,
61.37; H, 3.58; N, 25.25%.
7-Amino-5-(4-cyanophenyl)-1,3-dioxo-2-phenyl-1,2,3-trihydropyrazolo[1,2-a][1,2,4]triazole-6-
carbonitrile (4p)
White powder; mp >225 ºC; IR (KBr) (νmax/cm-1): 3373, 3311, 2233, 2192, 1778, 1724. MS, m/z (%): 356

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HETEROCYCLES, Vol. 81, No. 9, 2010
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(M+). H NMR (500 MHz, DMSO-d6): δH 5.96 (1H, s, CH), 7.42–7.93 (11H, m, H–Ar and NH2). C
NMR (125 MHz, DMSO-d6): δC 60.8, 63.3, 111.4, 116.3, 118.5, 126.8, 127.9, 128.6, 128.9, 130.9, 132.8,
144.3, 150.2, 150.5, 153.6. Anal. Calcd for for C19H12N6O2: C, 64.04; H, 3.77; N, 23.59%. Found: C,
64.02; H, 3.74; N, 23.55%.
ACKNOWLEDGEMENTS
We wish to thank the research council of Bu-Ali sins University, Hamadan, Iran, for financial support to
carry out this research.
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