Synthesis and antimicrobial activity of some new pyrazole, fused pyrazolo[3,4-d]-pyrimidine and pyrazolo[4,3-e][1,2,4]-triazolo[1,5-c]pyrimidine derivatives

Article abstract of DOI:10.3390/molecules13071501

Hydrazonyl bromides 2a,b reacted with active methylene compounds (dibenzoylmethane, acetylacetone, ethyl acetoacetate, phenacyl cyanide, acetoacetanilide, ethyl cyanoacetate, cyanoacetamide and malononitrile) to afford the corresponding 1,3,4,5-tetrasubst

Full text of DOI:10.3390/molecules13071501

Molecules 2008, 13, 1501-1517; DOI: 10.3390/molecules13071501
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.org/molecules
Article
Synthesis and Antimicrobial Activity of Some New Pyrazole,
Fused Pyrazolo[3,4-d]-pyrimidine and Pyrazolo[4,3-e][1,2,4]-
triazolo[1,5-c]pyrimidine Derivatives
Nada M. Abunada 1,*, Hamdi M. Hassaneen 2, Nadia G. Kandile 3 and Omar A. Miqdad 1
1
Department of Chemistry, Faculty of Applied Sciences, Al-Aqsa University, 76888 Gaza, Palestine;
E-mail: miqdadomar@hotmail.com (O. A. Miqdad)
2
Department of Chemistry, Faculty of Science, Cairo University, Egypt; E-mail:
hamdi_251@yahoo.com (H. M. Hassaneen)
3
Department of Chemistry, University College for Women, Ain Shams University, Heliopolis, Cairo,
Egypt; E-mail: nadiaghk@yahoo.com (N. G. Kandile)
*Author to whom correspondence should be addressed; E-mail: nadanadannrs@yahoo.com
Received: 4 May 2008; in revised form: 21 July 2008 / Accepted: 22 July 2008 / Published: 29 July 2008
Abstract: Hydrazonyl bromides 2a,b reacted with active methylene compounds
(dibenzoylmethane, acetylacetone, ethyl acetoacetate, phenacyl cyanide, acetoacetanilide,
ethyl cyanoacetate, cyanoacetamide and malononitrile) to afford the corresponding 1,3,4,5-
tetrasubstituted pyrazole derivatives 5-12a,b. Reaction of 12a,b with formamide, formic
acid and triethyl orthoformate give the pyrazolo[3,4-d]pyrimidine, pyrazolo[3,4-
d]pyrimidin-4(3H)one and 5-ethoxymethylene-aminopyrazole-4-carbo-nitrile derivatives
13-15a,b, respectively. Compounds 15a,b reacted with benzhydrazide and hydrazine
hydrate to afford pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine and [4-iminopyrazolo-
[3,4-d]pyrimidin-5-yl]amine derivatives 16a,b and 17a,b. Reactions of compounds 17a,b
with triethyl orthoformate and carbon disulfide give the corresponding pyrazolo[4,3-e]-
[1,2,4]triazolo[1,5-c]pyrimidine derivatives 18a,b and 19a,b, respectively.
Keywords: Hydrazonyl bromides, pyrazolo[3,4-d]pyrimidine, pyrazolo[4,3-e][1,2,4]-
triazolo[1,5-c]pyrimidine, antimicrobial activity.

Molecules 2008, 13
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Introduction
Pyrazole and fused heterocyclic pyrazole derivatives constute an interesting class of heterocycles
due to their synthetic versatility and effective biological activities [1-3]. Pyrazolo[3,4-d]pyrimidine
derivatives have been found to possess antitumor and antileukemia activity [4-7], pyrazolo[4,3-e]-
1,2,4-triazolo[1,5-c]pyrimidine derivatives have been found to be highly potent and selective human
A3 [8-11], A2A [10] and A 2B [11] adenosine receptor antagonists. On the other hand, hydrazonyl
halides have been shown to be biologically active depending on the nature of the groups on the carbon
and nitrogen atoms. For example, C-acetyl and C-ethoxyhydrazonyl halides were reported to be active
against red spider mites on beans and apple trees [12], whereas their C-aryl and C-aroyl analogues
exhibit antiviral and antimicrobial [13] properties and C-alkylmethanohydrazonyl halides possess
miticidal, insecticidal and herbicidal properties [14]. Moreover, many selectively fluoro-substituted
organic compounds show peculiar pharmacological and agrochemical properties [15-20]. In
continuation of our work concerning the preparation of hydrazonyl halides [21-23] and their reactions
in the synthesis of heterocyclic compounds [24-27], we decided here, on one hand, to synthesize C-(4-
fluorophenyl)- [28], and C-(2,4-dichlorophenyl)-N-(4-nitrophenyl)methanohydrazonyl bromides [29],
which have received very little attention [29,30], surmising that both might have biological activity,
and, on the other hand, to synthesize some new heterocyclic derivatives with anticipated biological
activity.
Results and Discussion
Reaction of hydrazonyl bromides 2a,b with dibenzoylmethane in sodium ethoxide solution at room
temperature gave, as the sole separable product, 3-aryl-4-benzoyl-1-(4-nitrophenyl)-5-phenylpyrazoles
5a,b (Scheme 1).
Scheme 1
R
Br
+
Ar
_
C H
C
Ar
O
C2H5OH
r.t.
_
..
..
R CHC R'
+
Na
+
N N Ar'
H
N
R'
N
OH
Ar'
2a,b
3
R \ R'
Ar
R
H
R
Ar
5a,b COPh \ Ph
6a COCH3 \ CH3
7a,b COOEt \ CH3
8a CN \ Ph
9a,b NHCOPh \ CH3
_
H2O
OH
R'
N
N
R'
N
N
Ar'
Ar'
5-9
4
Ar = a, 4-FC6H4; b, 2,4-Cl2C6H3; Ar', 4-NO2C6H4

Molecules 2008, 13
1503
The assignments of the structures of products 5a,b were based on their correct elemental analyses
1
and spectroscopic data. Their H-NMR spectra revealed only the expected aromatic proton multiplet
signals at δ 7.1-8.4 ppm. The IR spectra of each product showed two characteristic absorption bands at
1644-1650 cm-1 and 1593-1594 cm-1, assignable to a conjugated benzoyl carbonyl and C=N groups,
respectively.
Compound 5a was also obtained when the nitrilimine 3a [generated in situ from the reaction of
triethylamine with hydrazonyl bromide 2a] was reacted with dibenzoylmethane in tetrahydrofuran.
This finding supports the mechanism suggested earlier for a similar reaction [29], whereby the
carbanion – acting as a base – reacts with the hydrazonyl bromide to form a nitrilimine dipole 3, which
adds to the enol tautomers of the active methylene compounds used to form 4, which then loses one
molecule of water to give the pyrazole product.
Acetylacetone, ethyl acetoacetate, phenacyl cyanide, acetoacetanilide reacted with 2a,b under
similar reaction conditions and gave the corresponding pyrazole derivatives 6-9, respectively (Scheme
1). Similarly, 2a,b reacted with ethyl cyanoacetate and cyanoacetamide to give ethyl 5-amino-3-aryl-1-
(4-nitrophenyl)pyrazole-4-carboxylates 10a,b and 5-amino-3-aryl-1-(4-nitrophenyl)-pyrazole-4-
carboxamide derivatives 11a,b, respectively (Scheme 2). The structures were confirmed by the correct
elemental analyses (Table 2) and spectroscopic data (Table 3).
Scheme 2
O
H
Ar
Ar
COR
NH2
COR
NH
Br
Ar
R
NC CH2 C
+
_
N
N
N NHAr'
+
N
N
Na OC2H5
Ar'
Ar'
2a,b
10, 11
A, R = OC2H5
B, R = NH2
Ar = a, 4-FC6H4; b, 2,4-Cl2C6H3; Ar', 4-NO2C6H4
R
Br
+
Ar
_
C H
C
Ar
O
C2H5OH
r.t.
_
..
R CHC R'
+
Na
+
..
N N Ar'
H
N
R'
N
OH
Ar'
2a,b
3
R \ R'
Ar
R
H
R
Ar
5a,b COPh \ Ph
6a COCH3 \ CH3
7a,b COOEt \ CH3
8a CN \ Ph
9a,b NHCOPh \ CH3
_
H2O
OH
R'
N
N
R'
N
N
Ar'
Ar'
5-9
4

Molecules 2008, 13
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In addition, treatment of 2a,b with malononitrile in the presence of sodium ethoxide afforded the 5-
aminopyrazole-4-carbonitrile derivatives 12a,b (Scheme 3). The structural assignments of these
products were based on their elemental analyses and spectral data. Their IR spectra showed absorption
bands near υ 3420-3300 cm-1, assignable to the NH2 stretching vibrations and a characteristic band
1
near υ 2210 cm-1, corresponding to a C≡N linkage. Their H-NMR spectra showed a characteristic
signal near δ 6.80 ppm, assignable to the NH2 protons. The proposed structures of 12a,b were also
supported by their chemical reactivity. Thus, since they contain a β–enaminonitrile moiety, which is
well known to be highly reactive, they were used as intermediates for the synthesis of new
pyrazolo[3,4-d]pyrimidine derivatives. Refluxing compounds 12a,b with excess formamide and formic
acid gave the corresponding 4-amino-3-aryl-1-(4-nitrophenyl)pyrazolo[3,4-d]pyrimidine derivatives
13a,b and 3-aryl-1-(4-nitrophenyl)pyrazolo[3,4-d]pyrimidin-4-one derivatives 14a,b, respectively
(Scheme 3). The IR spectra of 13 and 14 displayed no cyano group absorptions.
Scheme 3
CN
CN
Br
+
Ar
H
_
N NHAr'
+
Na OC2H5
r.t.
2a,b
H2N
O
Ar
CN
Ar
HCOOH
heat
Ar
HCONH2
heat
N
N
N
NH2
N
N
N
N
N
N
N
Ar'
12a,b
Ar'
Ar'
14a,b
13a,b
Ac2O
heat
HC(OEt)3
Ar
N
CN
N=CHOEt
N
Ar'
15a,b
Ar = a, 4-FC6H4; b, 2,4-Cl2C6H3; Ar', 4-NO2C6H4
The condensations of compounds 12a,b with triethyl orthoformate at reflux afforded the
corresponding 5-ethoxymethyleneaminopyrazole-4-carbonitrile derivatives 15a,b, respectively
(Scheme 3). The confirmation of these structures was based on their analytical (Table 2) and
spectroscopic data (Table 3). The structures of 15a,b were further confirmed by their reactions with
benzhydrazide and hydrazine hydrate. Thus, treatment with benzhydrazide in tetrahydrofuran at reflux
temperature afforded 16a,b (Scheme 4). The IR spectra of the products confirmed the disappearance of
1
the nitrile absorption bands. The H-NMR spectra showed in each case a signal at δ 8.5 ppm,
corresponding to the pyrimidine proton. Furthermore, when compounds 15a,b were reacted with
hydrazine hydrate in tetrahydrofuran at ambient temperature they produced the corresponding [3-aryl-

Molecules 2008, 13
1505
4-imino-1-(4-nitrophenyl)-1,4-dihydro-5H-pyrazolo[3,4-d]pyrimidin-5-yl]amine derivatives 17a,b
(Scheme 4). The structures proposed for these products were established from their correct elemental
analyses (Table 2) and spectroscopic data (Table 3). Their IR spectra revealed the absence of nitrile
absorption frequencies. The 1H-NMR spectra for 17a,b showed signals at δ 8.4 ppm, corresponding to
13
the pyrimidine proton, and 5.0 ppm, assignable to the NH2 protons. The C-NMR spectrum of 17b
was also compatible with the proposed structure.
Further confirmation of the structures of 17a,b was achieved from their reactions with triethyl
orthoformate and carbon disulfide. Thus, refluxing compounds 17a,b in an excess of triethyl
orthoformate gave products 18a,b, which were identified on the basis of correct elemental analyses
and spectroscopic data as 9-aryl-7-(4-nitrophenyl)pyrazolo[4,3-e][1,2,4]-triazolo[1,5-c]pyrimidine
derivatives (Scheme 4). The IR spectra of 18a,b displayed no absorption bands for the NH and NH2
groups, which were observable in compounds 17a,b. The 1H-NMR spectra showed signals near δ 9.7-
9.8 and 9.4-9.5 ppm, assignable to the pyrimidine and the triazole proton, respectively. In addition,
refluxing compounds 17a,b with carbon disulfide and potassium hydroxide in ethanol gave 19a,b,
which were identified as 9-aryl-7-(4-nitrophenyl)pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine-2-
thione derivatives (Scheme 4). The structures of the compounds produced were established by
spectroscopic data. The IR spectra revealed absorption bands corresponding to the NH and C=S
1
functions near 3421.1 or 3422.4 and 1240 cm-1, respectively. The H-NMR spectra exhibited two
singlets at δ 9.2 and 9.8 ppm, representing the protons of the pyrimidine and NH. Also, the mass
spectra of all prepared compounds were compatible with the proposed structures (Table 3).
Scheme 4
N
N
Ar
N
CH(OEt)3
N
N
N
heat
Ar'
18a,b
Ph
Ar
CN
HN
NH2
Ar
N
N
N
N
N
NH2NH2. H2O
N=CHOEt
PhCONHNH2
THF / heat
Ar
N
N
N
N
Ar'
N
N
Ar'
N
15a,b
17a,b
Ar'
S
16a,b
N
H
N
\KOH, heat
CS2
Ar
N
N
N
N
Ar'
19a,b
Ar = a, 4-FC6H4; b, 2,4-Cl2C6H3; Ar', 4-NO2C6H4

Molecules 2008, 13
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Antimicrobial Activity
Some of the prepared compounds (namely 2a,b, 6a, 9b, 17b and 18b) were screened for
antibacterial activity (in nutrient agar broth) and antifungal activity (in Dox's medium and Saboured's
agar) by the agar diffusion method [31,32] at a concentration 20 mg/mL using DMSO as solvent and
blank. The compounds were tested for their activities against Gram +ve bacteria (Staphylococcus
aureus) and Gram –ve bacteria (Escherichia coli), in addition to the pathogenic fungi Aspergillus
flavus and Candida albicans. The antimicrobial screening results were measured by the average
diameter of the inhibition zones, expressed in mm, and are presented in Table 1. As shown in the
results, all the tested compounds displayed significant activities against E. coli, S. aureus and C.
albicans, while only compound 2a was very active against A. flavus and showed almost the same
activity when compared with the usually used antifungal agents at the same concentration. Also, it was
observed that the hydrazonoyl bromide 2a has shown the highest activity toward all the tested
organisms among all the tested compounds.
Table 1. Antimicrobial activities of the tested compounds
Inhibition zone diameter (mm / mg sample)
Sample
E. coli
S. aureus
A. flavus
C. albicans
(G-)
0.0
15
12
13
12
13
10
32
--
(G+)
0.0
16
14
13
12
13
10
34
--
(Fungus)
0.0
(Fungus)
Control (DMSO)
0.0
14
12
12
10
12
9
2a
2b
13
0.0
6a
0.0
9b
0.0
17b
0.0
18b
0.0
Tetracycline
Flucoral
Amphotricine
--
--
14
16
20
--
--
16
Conclusions
In this report, the synthesis of new pyrazole derivatives 5-12 by the reaction of some active
methylene compounds with hydrazonoyl bromides 2a,b is reported. Also, the reaction of 12 with
formamide, formic acid and triethyl orthoformate afforded the corresponding pyrazolo[3,4-
d]pyrimidines 13, 14 and 5-ethoxymethyleneaminopyrazole-4-carbonitriles 15, respectively.
Compound 15 reacted with benzhydrazide and hydrazine hydrate to give the corresponding
pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines 16 and 5H-pyrazolo[3,4-d]pyrimidin-5-yl]amines 17.
Also, 17 reacted with triethyl orthoformate and carbon disulfide and gave the corresponding
pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines 18 and 19. The antibacterial and antifungal activity
screening data of some of the prepared compounds showed promising antibacterial and antifungal

Molecules 2008, 13
1507
activity. Compound 2a is the most effective one and it also exhibited high activity against the fungus
A. flavus.
Experimental
General
All melting points were measured on an Electrothermal melting point apparatus and are
uncorrected. The infrared spectra were recorded in potassium bromide pellets on a Pye Unicam SP 3-
300 or Shimadzu FT-IR 8101 PC infrared spectrophotometer. The 1H-NMR (200 MHz) and 13C-NMR
(50 MHz) spectra were recorded in (DMSO-d6) on a GEMINI-200 spectrometer using TMS as the
internal reference. Results are expressed in ppm and coupling constants (J) in Hertz. Mass spectra were
measured on a GCMS-QP 1000 EX spectrometer at 70 eV. Elemental analyses were carried out at the
Microanalytical Center of Cairo University, Giza, Egypt. Yields, analytical and spectroscopic data for
the products are given in Tables 2-3. The starting materials C-(4-fluorophenyl)-N-(4-
nitrophenyl)methanohydrazonyl bromide [2a [28], yellow solid, mp. 224-6 oC (from tetrahydrofuran),
o
lit. [28] mp. 202 C] and C-(2,4-dichlorophenyl)-N-(4-nitrophenyl)methanohydrazonyl bromide [2b,
[29], yellow solid, mp. 228-30 oC (from dioxane), lit. [29] mp. 212 oC] were prepared according to the
indicated literature methods.
Reaction of hydrazonyl bromides with active methylene compounds: General method for the synthesis
of 4,5-disubstituted-3-aryl-1-(4-nitrophenyl)pyrazoles 5-12
The appropriate active methylene compound (dibenzoylmethane, acetylacetone, ethyl acetoacetate,
phenacyl cyanide, acetoacetanilide, ethyl cyanoacetate, cyanoacetamide, malononitrile, 0.005 mol) was
added with stirring to an ethanolic sodium ethoxide solution [20 mL, prepared from sodium metal
(0.11 g, 0.005 mol) and absolute ethanol]. To the resulting solution the appropriate hydrazonyl
bromide 2a,b (0.005 mol) was added at room temperature. The mixture was stirred for 24 h, during
which the bromide dissolved and the crude pyrazole precipitated. The latter was collected, washed
with water, dried and crystallized from the indicated solvent.
4-Benzoyl-3-(4-fluorophenyl)-1-(4-nitrophenyl)-5-phenylpyrazole (5a). Off-white solid; mp. 185-8 oC
(from acetic acid).
4-Benzoyl-3-(2,4-dichlorophenyl)-1-(4-nitrophenyl)-5-phenylpyrazole (5b). Pale yellow solid; mp.
159-61 oC (from ethanol); lit. mp. 150 oC [29].
4-Acetyl-3-(4-fluorophenyl)-5-methyl-1-(4-nitrophenyl)pyrazole (6a). Pale yellow crystals; mp. 149-51
oC (from acetic acid).
Ethyl 3-(4-fluorophenyl)-5-methyl-1-(4-nitrophenyl)pyrazole-4-carboxylate (7a). Off-white solid; mp.
162-4 oC (from ethanol).

Molecules 2008, 13
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Ethyl 3-(2,4-dichlorophenyl)-5-methyl-1-(4-nitrophenyl)pyrazole-4-carboxylate (7b). Pale yellow
solid; mp. 114-6 oC (from ethanol); lit. mp. 121 oC [29].
3-(4-Fluorophenyl)-1-(4-nitrophenyl)-5-phenylpyrazole-4-carbonitrile (8a). Yellow crystals; mp. 188-
90 oC (from dioxane-ethanol).
3-(4-Fluorophenyl)-5-methyl-1-(4-nitrophenyl)-4-phenylaminocarbonylpyrazole (9a). Yellow crystals;
mp. 223-5 oC (from dioxane-ethanol).
3-(2,4-Dichlorophenyl)-5-methyl-1-(4-nitrophenyl)-4-phenylaminocarbonylpyrazole (9b). Pale brown
solid; mp. 208-10 oC (from acetic acid).
Ethyl 5-amino-3-(4-fluorophenyl)-1-(4-nitrophenyl)pyrazole-4-carboxylate (10a). Pale brown solid;
13
mp. 225-7 oC (from acetic acid); C-NMR: δ 164.2 (d, J = 253.4, C-F), 163.07 (C=O, ester), 151.50
(C=N), 151.41 (4-C pyrazole), 145.03 (C-p-NO2), 142.57 (C-NO2), 130.96 (d, J = 8.5, C-m-F), 128.74
(d, J = 3.4, C-p-F), 124.49, 123.24 (C-o, C-m-NO2), 114.10 (d, J = 21.6, C-o-F), 92.62 (C-5 pyrazole),
58.86 (OCH2CH3), 13.50 (OCH2CH3).
Ethyl 5-amino-3-(2,4-dichlorophenyl)-1-(4-nitrophenyl)pyrazole-4-carboxylate (10b). Yellow crystals
solid; mp. 229-30 oC (from dioxane-ethanol).
5-Amino-3-(4-fluorophenyl)-1-(4-nitrophenyl)pyrazole-4-carboxamide (11a). Brownish yellow solid;
mp.303-5 oC (from acetic acid).
5-Amino-3-(2,4-dichlorophenyl)-1-(4-nitrophenyl)pyrazole-4-carboxamide (11b). Yellow solid; mp.
261-3 oC (from dioxane-ethanol).
5-Amino-3-(4-fluorophenyl)-1-(4-nitrophenyl)pyrazole-4-carbonitrile (12a). Yellow solid; mp. 273-5
oC (from dioxane-ethanol).
5-Amino-3-(2,4-dichlorophenyl)-1-(4-nitrophenyl)pyrazole-4-carbonitrile (12b). Yellow solid; mp.
222-4 oC (from dioxane-ethanol).
Alternate preparation of 4-benzoyl-3-(4-fluorophenyl)-1-(4-nitrophenyl)-5-phenyl-pyrazole (5a).
A solution of triethylamine (0.7 ml, 0.005 mmol) in THF (5 mL) was added to a solution of
hydrazonyl bromide 2a (1.68 g, 0.005 mmol) and dibenzoylmethane (0.005 mmol) in THF (40 mL)
and the resulting mixture was stirred at room temperature for 4 h. The solvent was then evaporated and
the residue was triturated with ethanol whereupon it solidified. The solid was collected, washed with
water (10 mL) and crystallized from acetic acid to give the product, which was identical in all respects
1
(mp., IR, MS, H-NMR and elemental analysis) to compound 5a prepared by the general method.
Compound 5a was obtained in 59 % yield by this method.
Synthesis of [3-aryl-1-(4-nitrophenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl]amines 13a,b

Molecules 2008, 13
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A mixture of 5-amino-3-aryl-1-(4-nitrophenyl)pyrazole-4-carbonitrile 12a,b (0.005 mol) and
formamide (10 mL) was refluxed for 2-3 h. The solution was cooled, then poured onto water. The solid
that precipitated was collected and crystallized to give [3-(4-fluorophenyl)-1-(4-nitrophenyl)-1H-
pyrazolo[3,4-d]pyrimidin-4-yl]amine [13a, off-white solid; mp. >340 oC (from dimethylformamide] or
[3-(2,4-dichlorophenyl)-1-(4-nitrophenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl]amine [13b, off-white
solid; mp. 347-8 oC (from DMF)].
Synthesis of 3-aryl-1-(4-nitrophenyl)-1,4-dihydro-5H-pyrazolo[3,4-d]pyrimidin-4-ones 14a,b
A mixture of 5-amino-3-aryl-4-1-(4-nitrophenyl)pyrazole-4-carbonitrile 12a,b (0.005 mol) and
formic acid (20 mL) was refluxed for 1 h. The solution was cooled, and then poured on water. The
solid that precipitated was collected and crystallized from the indicated solvent to give 3-(4-
fluorophenyl)-1-(4-nitrophenyl)-1,4-dihydro-5H-pyrazolo[3,4-d]pyrimidin-4-one [14a, off-white solid;
o
mp. >340 C (from dimethylformamide] or 3-(2,4-dichlorophenyl)-1-(4-nitrophenyl)-1,4-dihydro-5H-
pyrazolo[3,4-d]pyrimidin-4-one [14b, white solid; mp. >345 oC (from DMF)].
Synthesis of 3-aryl-5-ethoxymethyleneamino-1-(4-nitrophenyl)pyrazole-4-carbonitriles 15a,b
A mixture of 5-amino-3-aryl-1-(4-nitrophenyl)pyrazole-4-carbonitrile 12a,b (0.005 mol), triethyl
orthoformate (3 mL) and acetic anhydride (20 mL) was heated under reflux for 5 h. After cooling the
precipitated solid was filtered off and recrystallized from the indicated solvent to give 5-ethoxy-
methyleneamino-3-(4-fluorophenyl)-1-(4-nitrophenyl)pyrazole-4-carbonitrile [15a, white solid; mp.
194-6 oC (from tetrahydrofuran)] or 5-ethoxymethyleneamino-3-(2,4-dichlorophenyl)-1-(4-nitro-
phenyl)pyrazole-4-carbonitrile [15b, white solid; mp. 226-7 oC (from THF)].
Synthesis of 9-aryl-7-(4-nitrophenyl)-2-phenyl-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines
16a,b
A mixture of 3-aryl-5-ethoxymethyleneamino-1-(4-nitrophenyl)pyrazole 15a,b (0.01 mol) and
benzhydrazide (0.01 mol, 1.36 g) in THF (30 mL) was refluxed for 12 h. The mixture was cooled and
the solvent was removed under reduced pressure and the resulting precipitate was purified by
crystallization from the indicated solvent to give 9-(4-fluorophenyl)-7-(4-nitrophenyl)-2-phenyl-7H-
pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine [16a, yellow solid; mp. >340 oC (from
dimethylsulfoxide)] or
9-(2,4-dichlorophenyl)-7-(4-nitrophenyl)-2-phenyl-7H-pyrazolo[4,3-e]-
[1,2,4]triazolo[1,5-c]pyrimidine [16b, yellow solid; mp. 334-6 oC (from dioxane)].
Synthesis of [3-aryl-4-imino-1-(4-nitrophenyl)-1,4-dihydro-5H-pyrazolo[3,4-d]pyrimidin-5-yl]amines
17a,b
Hydrazine hydrate (8 mL) was added to a suspension of 5-ethoxymethyleneamino-3-aryl-1-(4-
nitrophenyl)pyrazole-4-carbonitriles 15a,b (0.01 mol) in tetrahydrofuran (40 mL). The reaction
mixture was stirred at room temperature for 1 h. The precipitate which formed was filtered off, washed
with water, dried in air and crystallized from the indicated solvent to give [3-(4-Fluorophenyl)-4-
imino-1-(4-nitrophenyl)-1,4-dihydro-5H-pyrazolo[3,4-d]pyrimidin-5-yl]amine [17a, pale yellow solid;

Molecules 2008, 13
1510
o
mp. 266-8 C (from DMF)] or [3-(2,4-dichlorophenyl)-4-imino-1-(4-nitrophenyl)-1,4-dihydro-5H-
pyrazolo[3,4-d]pyrimidin-4-yl]amine [17b, pale yellow solid; mp. 256-8 oC (from DMF); 13C-NMR: δ
156.45 (C=N pyrimidine), 154.36 (C-5 pyrazole), 144.46, 144.27, 143.55, 134.98, 134.63, 134.21,
132.92, 129.36 (8C, ArC's), 127.50, 125.02, 124.98, 120.53, 120.21 (5C, ArCH's)].
Synthesis of 9-aryl-7-(4-nitrophenyl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines 18a,b
A mixture of [3-aryl-4-imino-1-(4-nitrophenyl)pyrazole-5-yl]amine 17a,b (0.005 mol) with (15 ml)
of triethyl orthoformate was refluxed for 1 h. After cooling, the precipitated product was collected by
filtration and crystallized from the indicated solvent to give 9-(4-fluorophenyl)-7-(4-nitrophenyl)-7H-
o
pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine [18a, pale yellow solid; mp. 304-6 C (from DMF-
ethanol)]
or
9-(2,4-dichlorophenyl)-7-(4-nitrophenyl)-7H-pyrazolo[4,3-e][1,2,4]-triazolo[1,5-
c]pyrimidine [18b, pale yellow solid; mp. 314-6 oC (from DMSO-ethanol)].
Synthesis of 9-aryl-7-(4-nitrophenyl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine-2(3H)-
thiones 19a,b
A mixture of [3-aryl-4-imino-1-(4-nitrophenyl)pyrazol-5-yl]amine 17a,b (0.01 mol) with carbon
disulfide (0.76 g, 0.01 mol) and potassium hydroxide (0.56 g, 0.01 mol) in ethanol (15 mL) was heated
under reflux for 10 h. After removal of ethanol, water was added and the resulting alkaline solution
was acidified with acetic acid and the precipitate formed collected by filtration, washed with water,
dried and crystallized from the indicated solvent to afford 9-(4-fluorophenyl)-7-(4-nitrophenyl)-7H-
pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine-2(3H)-thione [19a, yellow solid; mp. >350 oC (from
DMSO-ethanol)] or 9-(2,4-dichlorophenyl)-7-(4-nitrophenyl)-7H-pyrazolo[4,3-e][1,2,4]-triazolo[1,5-
c]pyrimidine-2(3H)-thione [19b, orange solid; mp. 306-8 oC (from DMF-ethanol)].
Table 2. Analytical data for the newly prepared compounds.
Analysis(%) Calcd./Found
Yield
%
76
Mol. Form.
Product
2a
Mol. Wt.
C13H9BrFN3O2
338.13
C
H
N
Cl
46.17
46.25
40.13
40.25
72.56
72.43
65.38
65.25
63.71
63.52
61.78
62.16
54.30
54.21
68.74
68.46
2.68
2.66
2.07
2.20
3.91
4.04
3.33
3.45
4.15
4.22
4.36
4.41
3.59
3.65
3.40
3.46
12.42
12.07
10.80
10.55
9.06
2b
5a
5b
6a
7a
7b
8a
93
66
62
71
64
53
48
C13H8BrCl2N3O2
389.03
18.22
18.04
C28H1 8FN3O3
463.45
8.94
C28H17Cl2N3O3
514.35
8.16
13.78
13.74
8.16
C18H14FN3O3
339.32
12.38
12.27
11.37
11.19
9.99
C19H16FN3O4
369.34
C19H15Cl2N3O4
420.24
16.87
16.64
9.87
C22H13FN4O2
384.36
14.57
14.46

Molecules 2008, 13
1511
Table 2. Cont.
C23H17FN4O3
9a
58
47
52
56
53
51
64
61
93
85
88
83
87
82
54
52
67
63
56
61
52
53
66.33
65.96
59.11
58.97
58.37
58.36
51.32
51.55
56.30
56.29
48.99
49.10
59.44
59.37
51.35
51.35
58.28
58.26
50.89
51.17
58.12
58.15
50.76
50.85
60.15
60.18
53.03
53.02
63.85
63.88
57.38
57.40
55.88
55.90
48.93
48.91
57.60
57.58
50.72
50.70
53.06
53.03
47.17
47.19
4.11
4.17
3.45
3.49
4.08
4.18
3.35
3.51
3.54
3.61
2.82
3.01
3.11
3.01
2.42
2.47
3.16
3.15
2.51
2.55
2.86
2.88
2.25
2.33
3.72
3.71
3.04
3.06
3.12
3.10
2.60
2.61
3.31
3.03
2.89
2.91
2.68
2.66
2.12
2.14
2.47
2.46
1.97
2.00
13.45
13.39
11.98
11.76
15.12
14.89
13.30
13.19
20.05
19.87
17.85
17.63
21.66
20.98
18.71
18.45
23.99
24.01
20.94
20.81
19.93
19.90
17.41
17.36
18.46
18.44
16.27
16.27
21.72
20.71
19.52
19.51
26.83
26.80
23.50
23.54
26.12
26.15
23.00
22.98
24.06
24.07
21.39
21.41
416.40
C23H16Cl2N4O3
467.30
9b
15.17
15.05
10a
10b
11a
11b
12a
12b
13a
13b
14a
14b
15a
15b
16a
16b
17a
17b
18a
18b
19a
19b
C18H15FN4O4
370.33
C18H14Cl2N4O4
421.23
16.83
16.71
C16H12FN5O3
341.29
C16H11Cl2N5O3
392.19
18.07
18.16
C16H10FN5O2
323.28
C16H9Cl2N5O2
374.18
18.95
18.86
C17H11N6O2F
350.30
C17H10Cl2N6O2
401.20
17.67
17.74
C17H10N5O3F
351.29
C17H9Cl2N5O3
402.19
17.63
17.55
C19H14N5O3F
379.34
C19H13N5O3Cl2
430.24
16.48
16.47
C24H14N7O2F
451.41
C24H13N7O2Cl2
502.31
14.11
14.10
C17H12N7O2F
365.32
C17H11N7O2Cl2
416.22
16.99
17.01
C18H10N7O2F
375.31
C18H9N7O2Cl2
426.21
16.63
16.66
C18H10N7O2SF
407.38
C18H9N7O2SCl2
458.28
15.47
15.49

Molecules 2008, 13
1512
Table 3. Spectroscopic data of the newly prepared compounds.
Product
MS
IR (KBr)
3258.2 (NH), 3087.7
1H-NMR (DMSO-d6)
7.25-8.54 (m, 8H, ArH), 10.54 (s,
1H, NH).
2a
2b
5a
339 (M++2, 98.1), 337 (M+, 100.0),
339 (88.3), 290 (9.3), 259 (10.2), 188 (CH-aromatic),
(17.6), 122 (48.7), 95 (64.8), 90
(43.3), 75 (51.7), 63 (54.1), 51 (21.3),
50 (18.3).
391 (M++4, 20.2), 389 (M++2, 47.3),
387 (M+, 30.5), 309 (28.3), 307
(38.8), 262 (43.9), 173 (54.0), 137
(39.9), 100 (29.4), 90 (45.7), 63
(100.0), 50 (34.4).
463 (M+, 97.0), 386 (94.0), 340
(45.7), 207 (26.8), 105 (40.4), 77
(100.0), 51 (39.6).
1595.6 (C=N).
3254.5 (NH), 3089.2
(CH-aromatic),
7.23-8.56 (m, 7H, ArH), 10.25 (s,
1H, NH).
1595.3 (C=N).
3115.6, 3080.1 (CH-
aromatic), 1644.1 (CO
benzoyl), 1593.8
(C=N).
7.14-8.32 (m, 18H, ArH).
5b
6a
7a
514 (M++2)-1, 0.5), 480 (39.5), 478
(100.0), 432 (20.9), 105 (8.2), 77
(25.4), 51 (8.2).
340 (M++1, 40.4), 339 (M+, 41.1),
324 (100.0), 278 (43.7), 279 (40.5),
117 (13.0), 76 (27.1), 50 (13.7).
369 (M+, 100.0), 324 (82.6), 278
(35.2), 117 (12.4), 76 (26.0), 50
(13.9).
3082.2 (CH-
7.19-8.42 (m, 17H, ArH).
aromatic), 1650.4
(CO), 1594.7 (C=N).
3084.4 (CH-
2.45 (s, 3H, CH3), 2.61 (COCH3),
aromatic), 1668.7 (CO 7.21-8.26 (m, 8H, ArH).
acetyl), 1593.5 (C=N).
3117.1, 3090.8 (CH-
1.19 (t, 3H, J = 7.2, COOCH2CH3),
aromatic), 1706.3 (CO 2.65 (s, 3H, CH3), 4.21 (q, 2H, J =
ester), 1594.4 (C=N).
3088.7 (CH-
7.2, COOCH2CH3), 7.23-8.45 (m,
8H, ArH).
7b
384 (M-35) (100.0), 386 (37.2), 356
(80.4), 367 (85.8), 311 (39.6), 310
(38.8), 117 (18.6), 76 (48.6), 51
(11.0), 50 (18.8).
384 (M+, 100.0), 337 (34.3), 76
(15.7), 50 (11.8).
1.20 (t, 3H, J = 7.3, COOCH2CH3),
aromatic), 1699.7 (CO 2.64 (s, 3H, CH3), 4.22 (q, 2H, J =
ester), 1595.5 (C=N).
7.3, COOCH2CH3), 7.24-8.45 (m,
7H, ArH).
8a
9a
3068.2 (CH-
7.23-8.45 (m, 13H, ArH).
aromatic), 2225.3
(C≡N), 1596.7 (C=N).
3239.7 (NH), 3061.9
(CH-aromatic),
416 (M+, 13.8), 324 (100.0), 278
(31.9), 65 (18.4).
2.63 (s, 3H, CH3), 7.14-8.27 (m,
13H, ArH), 11.60 (s, 1H, NH).
1657.6 (CO amide),
1596.2 (C=N).
9b
466 (M+, 4.3), 468 (M++2, 2.9), 431
(40.2), 374 (100.0), 328 (47.4), 117
(16.9), 65 (70.3), 50 (8.9).
3418.1 (NH), 3080.8
(CH-aromatic),
2.64 (s, 3H, CH3), 7.16-8.27 (m,
12H, ArH), 11.60 (s, 1H, NH).
1656.4 (CO amide),
1596.6 (C=N).
10a
370 (M+, 59.2), 324 (100.0), 277
(10.5), 146 (23.1), 90 (11.9), 76
(12.3), 63 (8.6), 50 (8.7).
3458.5, 3327.9 (NH2), 1.16 (t, 3H, J = 7.3, COOCH2CH3),
3112.8 (CH- 4.17 (q, 2H, J = 7.3, COOCH2CH3),
aromatic), 1675.4 (CO 6.84 (s, 2H, NH2), 7.21-8.43 (m,
ester), 1613.5 (C=N). 8H, ArH).

Molecules 2008, 13
1513
Table 3. Cont.
420 (M+, 18.0), 422 (M++2, 9.7), 385 3203.5, 3326.4 (NH2), 1.18 (t, 3H, J = 7.2, COOCH2CH3),
10b
11a
(100.0), 311 (14.4), 196 (20.0), 136
(10.1), 90 (22.8), 76 (38.5), 63
(23.0), 50 (20.7).
341 (M+, 62.3), 324 (100.0), 325
(77.9), 278 (13.1), 146 (37.6), 122
(12.0), 95 (17.5), 90 (27.0), 76
(30.6), 63 (26.7), 50 (24.4).
3076.4 (CH-
4.18 (q, 2H, J = 7.2, COOCH2CH3),
aromatic), 1680.6 (CO 6.84 (s, 2H, NH2), 7.22-8.43 (m,
ester), 1619.2 (C=N).
3495.3, 3371.8,
3277.3 (two NH2),
3119.9 (CH-
7H, ArH).
6.83 (s, br., 2H, NH2), 7.19-8.43 (m,
10H, ArHs, NH2).
aromatic), 1643.1 (CO
amide), 1585.9
(C=N).
11b
393 (M++2, 7.2), 391 (M+, 11.5), 356 3496.1, 3376.4,
6.83 (s, br., 2H, NH2), 7.21-8.45 (m,
9H, ArH, NH2).
(100.0), 357 (84.8), 310 (18.2), 91
(14.6), 76 (19.4), 63 (21.7), 50
(21.8).
3284.4 (two NH2),
3087.3 (CH-
aromatic), 1646.5 (CO
amide), 1588.3
(C=N).
12a
12b
13a
13b
14a
14b
15a
324 (M++1, 100.0), 323 (M+, 97.2),
3429.5, 3300.7 (NH2), 6.84 (s, 2H, NH2), 7.14-8.27 (m,
8H, ArH).
278 (14.8), 177 (13.6), 156 (16.4), 75 3079.7 (CH-
(23.6), 76 (26.9), 63 (18.3), 50
(23.5).
373 (M+, 100.0), 375 (M++2, 82.6),
327 (12.3), 292 (41.5), 173 (13.8),
129 (20.0), 76 (63.6), 63 (42.6), 50
(53.4).
350 (M+, 100.0), 304 (9.8), 303
(12.1), 276 (5.4), 156 (14.5), 122
(6.3), 63 (7.6), 50 (7.8).
aromatic), 2209.1
(C≡N), 1600.8 (C=N).
3447.7, 3320.8 (NH2), 6.86 (s, 2H, NH2), 7.12-8.27 (m,
3031.3 (CH-
7H, ArH).
aromatic), 2217.9
(C≡N), 1596.7 (C=N).
3480.8, 3290.2 (NH2), 5.02 (s, br., 2H, NH2), 7.33-8.58 (m,
3069.3 (CH-
aromatic), 1653.2
(C=N).
9H, ArH, pyrimidine-H).
402 (M++2, 72.6), 400 (M+, 100.0),
319 (35.4), 161 (44.2), 92 (26.5), 91
(31.9), 77 (46.9), 63 (49.6), 51
(46.9), 50 (54.0).
3470.2, 3318.7 (NH2), 6.20 (s, 2H, NH2), 7.14-8.27 (m,
3070.6 (CH-
aromatic), 1657.4
(C=N).
7H, ArH), 9.11 (s, 1H, pyrimidine).
351 (M+, 100.0), 248 (10.0), 184
(31.6), 157 (17.2), 145 (16.7), 133
3318.2 (NH), 3042.5 7.29-8.50 (m, 9H, ArH,
(CH-aromatic), pyrimidinone-H), 12.72 (s, br., 1H,
NH pyrimidinone).
(10.6), 90 (10.6), 76 (19.3), 75 (19.2), 1686.1 (C=O),
63 (19.8), 50 (31.1).
1590.1 (C=N).
3446.3 (NH), 3071.3 7.15-8.27 (m, 7H, ArH), 8.75 (s,
403 (M++2, 11.8), 401 (M+, 17.6),
366 (100.0), 368 (36.5), 320 (24.9),
90 (12.8), 76 (23.5), 63 (21.4), 50
(32.1).
(CH-aromatic),
1690.1 (CO), 1589.2
(C=N).
1H, pyrimidinone), 11.16 (s, 1H,
NH pyrimidinone).
379 (M+, 100.0), 351 (15.6), 350
(19.3), 323 (55.0), 276 (16.9), 145
(12.6), 76 (15.3), 50 (11.5).
3098.0 (CH-
1.35 (t, 3H, J = 7.0, CH3), 4.42 (q,
2H, J = 7.0, OCH2), 7.38-8.42 (m,
8H, ArH), 8.69 (s, 1H, N=CH).
aromatic), 2997.7,
2945.9 (CH-
aliphatic), 2232.4
(C≡N), 1630.5
(C=N).

Molecules 2008, 13
1514
Table 3. Cont.
3088.3, 3004.5 (CH-
aromatic), 2950.3
15b
431 (M++2, 71.3), 429 (M+, 89.1),
368 (37.0), 366 (100.0), 320 (51.3),
1.36 (t, 3H, J = 7.0, CH3), 4.43 (q,
2H, J = 7.0, OCH2), 7.61-8.44 (m,
7H, ArH), 8.70 (s, 1H, N=CH).
292 (27.3), 195 (27.2), 156 (19.7), 90 (CH-aliphatic),
(22.8), 76 (56.1), 63 (31.5), 50 (48.0). 2221.9 (C≡N),
1629.9 (C=N).
16a
16b
451 (M+, 100.0), 393 (6.5), 284
3063.6, 3010.0 (CH-
7.43-8.12 (m, 13H, ArH), 8.56 (s,
1H, pyrimidine).
(11.0), 95 (6.3), 77 (8.2), 76 (8.5), 50 aromatic), 1635.2
(6.4).
(C=N).
503 (M++2, 58.1), 501 (M+, 100.0),
466 (73.1), 420 (28.5), 291 (10.4),
290 (10.1), 289 (12.8), 153 (11.3),
127 (10.0), 103 (18.9), 90 (12.4), 77
(42.2), 76 (28.3), 63 (13.1), 50 (17.9).
365 (M+, 100.0), 350 (8.0), 290
(10.2), 157 (6.0), 114 (6.7), 95 (8.6),
76 (9.4), 75 (12.0), 63 (8.6), 50
(11.3).
3086.8 (CH-
aromatic), 1643.7
(C=N).
7.42-8.08 (m, 12H, ArH), 8.54 (s,
1H, pyrimidine).
17a
17b
3430.6-3353.5 (NH,
NH2), 3067.1 (CH-
aromatic), 1582.3
(C=N).
5.01 (s, br., 2H, NH2), 7.16-8.56
(m, 8H, ArH, NH), 8.45 (s, 1H,
pyrimidine).
417 (M++2, 52.0), 415 (M+, 91.3),
382 (70.9), 380 (100.0), 363 (56.1),
334 (30.6), 307 (28.6), 215 (30.1),
187 (37.8), 150 (38.3), 122 (36.7),
114 (34.3), 90 (32.1), 77 (36.7), 76
(62.8), 63 (62.2), 50 (75.0).
3326.2-3270.3 (NH,
NH2), 3082.5 (CH-
aromatic), 1597.1
(C=N).
5.02 (s, br., 2H, NH2), 7.19-8.59
(m, 8H, ArH, NH), 8.47 (s, 1H,
pyrimidine).
18a
18b
375 (M+, 100.0), 329 (14.2), 275
(12.9), 208 (36.4), 90 (13.1), 75
(30.2), 63 (15.9), 50 (28.0).
427 (M++2, 36.7), 425 (M+, 55.5),
390 (36.6), 344 (30.0), 337 (19.9),
298 (21.2), 257 (41.4), 215 (44.2),
187 (100.0), 145 (27.8), 136 (23.1),
123 (21.2), 90 (50.6), 75 (30.1), 63
(44.9), 50 (27.9).
3087.1 (CH-
aromatic), 1629.7
(C=N).
7.58-8.59 (m, 8H, ArH), 9.43, 9.78
(two s, 2H, triazole, pyrimidine).
3036.1, 3095.8 (CH-
aromatic), 1635.7
(C=N).
7.62-8.66 (m, 7H, ArH), 9.52, 9.85
(s, 2H, triazole, pyrimidine).
19a
19b
407 (M+, 65.1), 325 (95.9), 257
(13.0), 146 (100.0), 136 (19.0), 121
(26.0), 106 (12.3), 95 (27.9), 90
3421.1 (NH), 3077.2 7.56-8.66 (m, 8H, ArH), 9.24 (s,
(CH-aromatic),
1632.1 (C=N),
1H, pyrimidine), 9.89 (s, 1H, NH).
(34.6), 75 (33.8), 63 (27.9), 50 (42.4). 1242.3 (C=S).
427 (M++2(-32), 65.9), 425 (M+(-32), 3422.4 (NH), 3096.9 7.54-8.67 (m, 7H, ArH), 9.22 (s,
100.0), 390 (56.0), 344 (41.1), 208
(14.5), 145 (16.7), 76 (26.2), 75
(23.6), 63 (18.6), 50 (32.4).
(CH-aromatic),
1649.5 (C=N),
1246.2 (C=S).
1H, pyrimidine), 9.88 (s, 1H, NH).
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