Some new pyrazole and pyrazolopyrimidines: Synthesis and antimicrobial evaluation

Article abstract of DOI:10.1002/jhet.1550

Novel β-enaminonitrile of 1-(6-phenyl-pyridazin-3-yl)-pyrazole derivative 2 was formed using (6-phenyl-pyridazin-3-yl)-hydrazine (1) and 2-ethoxymethylene-malononitrile. The β-enaminonitrile derivative 2 was in turn used as precursors for the preparation

Full text of DOI:10.1002/jhet.1550

Month 2013
Some New Pyrazole and Pyrazolopyrimidines: Synthesis and
Antimicrobial Evaluation
Ahmed H. Shamroukh,a,b Aymn E. Rashad,a,c Hatem S. Ali,d and Farouk M. E. Abdel-Megeida
*
aPhotochemistry Department, National Research Center, Dokki, Cairo, Egypt
bChemistry Department, Faculty of Science, Hail University, Hail, Saudi Arabia
cChemistry Department, Faculty of Science and Humanities, Shaqra University, Shaqra, Huraymila, Saudi Arabia
dFood Science and Nutrition Department, Faculty of Food Science and Agriculture, King Saud University, Riyadh,
Saudi Arabia
*
E-mail: ahshamroukh@yahoo.com
Received September 15, 2011
DOI 10.1002/jhet.1550
Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com).
Novel b-enaminonitrile of 1-(6-phenyl-pyridazin-3-yl)-pyrazole derivative 2 was formed using (6-phenyl-
pyridazin-3-yl)-hydrazine (1) and 2-ethoxymethylene-malononitrile. The b-enaminonitrile derivative 2 was
in turn used as precursors for the preparation of 1-(6-phenyl-pyridazin-3-yl)-pyrazoles (3, 9, 11), 1-(6-phenyl
-pyridazin-3-yl)-pyrazolo[3,4-d]pyrimidines (4–8, 13–16) and some of their corresponding N-acyclic
nucleosides (17, 18). All synthesized compounds were tested for their antimicrobial evaluation, and
compounds 3, 9, 17, and 18 showed more significant activity than the other tested compounds and some
known drugs (standers).
J. Heterocyclic Chem., 00, 00 (2013).
INTRODUCTION
pyridazine moiety into 1-position of the pyrazolo[4,3-d]
pyrimidine ring system to obtain a new heterocyclic ring
system that is expected to possess notable chemical and
biological activities.
The chemistry of pyrazolopyrimidine derivatives has
attracted the attention of numerous researchers over many
years because of their important biological activities [1–3].
The structural similarity of pyrazolo[3,4-d]pyrimidines with
purines [4] has made them a prime target for scientific
research; and in this context, several reports dealing with
the synthesis of these fused heterocyclic compounds have
been appeared in the literature [4–7]. Pyrazolopyrimidines
exhibited various biological activities such as antimicro-
bial [6] and antitumor [8]. In addition, a literature survey
revealed that pyrazolopyrimidines have been received
much attention on account of their neuroleptic [9], antihy-
pertensive [10,11], antileishmanial [12], analgesic [13],
and antimicrobial [14] activities. Also, the chemistry
of pyridazine derivatives has received great attention,
especially hydrazinopyridazine derivatives that were
prepared and tested for their biological activity [15].
In continuation of our previous work on pyridazines
and pyrazoles [15–17], we aimed to incorporate the
RESULTS AND DISCUSSION
This work is aimed at the synthesis of new compounds
related to b-enaminonitriles of pyridazinyl pyrazole deriva-
tives. In particular, 5-amino-1-(6-phenyl-pyridazin-3-yl)-
1H-pyrazole-4-carbonitrile (2) was used as key compound
for this study and for further syntheses of other fused
heterocyclic compounds. Compound 2 was prepared by
refluxing a mixture of 6-phenylpyridazin-3-ylhydrazine
(1) [18] and ethoxymethylenemalononitrile. The presence
of CN and NH2 groups in the spectral data of compound
2 assigned its structure (cf. Experimental). When
compound 2 was refluxed with triethyl orthoformate,
it afforded N-[4-cyano-2-(6-phenyl-pyridazin-3-yl)-2H-
pyrazol-3-yl]-formimidic acid ethyl ester (3). The IR
© 2013 HeteroCorporation

A. H. Shamroukh, A. E. Rashad, H. S. Ali, and M. E. Abdel-Megeid
Vol 000
1
spectrum of compound 3 showed absorption band for
bands for NH and C═O. Its H NMR spectrum revealed
band at 11.90 (s, 1H, NH, D2O exchangeable).
cyano group, while the absorption band characteristic for
1
the NH2 group disappeared. Also, its H NMR spectrum
The synthesis of methyl-[1-(6-phenyl-pyridazin-3-yl)-1H-
pyrazolo[3,4-d]pyrimidin-4-yl]-amine (6) was achieved by
treatment of compound 3 with alcoholic methylamine
(35% in methanol). The IR and H NMR spectra of com-
pound 6 revealed signals for NHCH3.
When compound 3, in dry ethanol, was stirred with
hydrazine hydrate at room temperature, it afforded 4-imino-
1-(6-phenyl-pyridazin-3-yl)-1,4-dihydro-pyrazolo[3,4-d]
pyrimidin-5-ylamine (7) (Scheme 1). The latter compound
was isomerized to the corresponding more thermodynami-
cally stable [1-(6-phenyl-pyridazin-3-yl)-1H-pyrazolo[3,4-d]
pyrimidin-4-yl]-hydrazine (8), upon refluxing in dry
dioxane in the presence of few drops of piperidine. Actually,
revealed the presence of OCH2CH3 and N═CH–O
signals. The synthesis of 4-amino pyrimidine derivative
4 was achieved by reacting compound 3 with ammonium
hydroxide solution (25%) to give 1-(6-phenyl-pyridazin-
3-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-ylamine (4) (Scheme 1).
The IR spectrum of compound 4 did not show the absorption
band of the cyano group and showed absorption band
1
1
for NH2. Its H NMR spectrum revealed band for NH2,
D2O exchangeable. Benzoylation of compound 4 with
benzoyl chloride, in dry dioxane, yielded N-[1-(6-phenyl-
pyridazin-3-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl]-benzamide
(5). The IR spectrum of compound 5 showed absorption
Scheme 1
CN
O
EtO
H
CN
CN
NHNH2
CN
N
N
NH2
N
CH3
N
N
Ac2O
heat
PPA/OPA
N
N
N
NHCOCH3
X
N
N
N
heat
heat
N
N
N
N
N
Ph
Ph
2
1
Ph
Ph
heat
N
HC(OEt)3
10
9
CN
CONH2
NH2
OEt
H2SO4, stirring, r.t.
N
N
N
N
N
N
N
N
Ph
3
Ph
11
NH4OH, EtOH, r.t.
MeNH3, EtOH, r.t.
N2H4, EtOH, r.t.
H2N
HN
NH2
N
N
N
CH3
HN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Ph
4
Ph
7
piperidine, dioxane
heat
Ph
PhCOCl, dioxane
heat
6
NH2
O
HN
Ph
HN
N
N
N
N
N
N
N
N
N
N
N
N
Ph
8
Ph
5
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2012
Synthesis, Reactions and Antimicrobial Evaluation of b-Enaminonitriles of Pyrazole
piperidine acts as a base in this Dimroth rearrangement reac-
tion, and the IR spectrum of compounds 7 and 8 did not show
any absorption band for the cyano group, whereas the IR and
1H NMR spectra showed absorption bands for NH and
NH2 groups.
2H-pyrazol-3-ylamine (12) (Scheme 2). The IR (KBr)
spectrum of compound 12 did not show the absorption
bands of the cyano group or carbonyl group and showed
absorption band for (NH2). The sequence of the formation
of compound 12 presumably took place via complete
hydrolysis of cyano group followed by decarboxylation.
The pyrazolo[3,4-d]pyrimidin-4-ones 13 and 14 could
be obtained directly by refluxing compound 11 with formic
acid or benzaldehyde in glacial acetic acid, respectively.
The IR and 13C NMR spectra of compounds 13 and 14
showed absorption bands for C═O and their H NMR
spectra showed signals at 12.50 and 12.70 (s, 1H, NH,
D2O exchangeable).
Compound 13 was converted to its corresponding 4-chloro
derivative by refluxing with phosphorus oxychloride to
give 4-chloro-1-(6-phenyl-pyridazin-3-yl)-1H-pyrazolo
[3,4-d]pyrimidine (15) (Scheme 2). The mass spectrum
of compound 15 showed the molecular ion peak M+ at
m/z 308 as the base peak as well as the presence of isotopic
pattern of chlorine atom. The pyrazolo[3,4-d]pyrimidine-
Acetylation of compound 2 with acetic anhydride in dry
pyridine yielded N-[4-cyano-2-(6-phenyl-pyridazin-3-yl)-
2H-pyrazol-3-yl]-acetamide (9) (Scheme 1). In an attempt
to cyclize compound 9 to pyrimidine derivative 10 by stir-
ring in a mixture of polyphosphoric acid (PPA) and ortho-
phosphoric acid (1:1) at room temperature, the unexpected
5-amino-1-(6-phenyl-pyridazin-3-yl)-1H-pyrazole-4-car-
boxylic acid amide (11) was obtained via deacetylation of
N-acetyl group besides the partial hydrolysis of cyano
group. The 1H NMR spectrum showed the absorption
bands of the two NH2 as well as C═O in IR spectrum.
Also, compound 11 was obtained directly by stirring of
compound 2 with concentrated sulfuric acid (98%).
Although further heating of compound 11 in sulfuric
acid (98%) for 2 h afforded 2-(6-phenyl-pyridazin-3-yl)-
1
Scheme 2
CONH2
N
NH2
N
N
N
Ph
11
PhCHO, CH3COOH
heat
HCOOH
heat
H2SO4
reflux
O
O
H
N
H
N
N
NH2
N
N
Ph
N
N
N
N
N
N
N
N
N
N
N
Ph
Ph
Ph
12
13
14
POCl3
reflux
NaH, DMF,
O
Cl
Cl
or
OH
OR
S
O
Cl
H
N
N
N
N
N
N
N
N
thiourea,
N
N
N
N
dioxane, heat
N
N
N
N
N
N
Ph
Ph
Ph
16
15
17 R= CH3
18 R= H
Journal of Heterocyclic Chemistry
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A. H. Shamroukh, A. E. Rashad, H. S. Ali, and M. E. Abdel-Megeid
Vol 000
4-thione 16 was obtained by refluxing compound 15 with
BIOLOGICAL EVALUATION
thiourea in dry dioxane. The spectral data of compound
16 was in agreement with the proposed structure, in partic-
ular, the 13C NMR spectrum that revealed C═S at
170 ppm (cf. Experimental).
Antimicrobial activity of newly synthesized compounds
2–9 and 11–18 was tested in concentration of 0.1 g/mL by
using dimethylformamide as a solvent.
The synthesis of pyrimidine and fused heterocyclic
pyrimidine nucleosides has been extensively reported in
the literature [19,20]. However, there is still a great need
and interest to prepare more active acyclic pyrimidine
nucleosides with fewer side effects than those observed
for the already known derivatives. Therefore, when the
sodium salt of compound 13 (generated in situ) was
treated with 2-chloroethyl methyl ether or 2-chloroethanol,
CONCLUSIONS
Among the tested compounds, it was noticed that
pyrazole derivatives (compounds 3 and 9) and acyclic
nucleosides (compounds 17 and 18) showed more signifi-
cant antimicrobial activity than the other tested compounds
and some known drugs (standers).
Inhibition zone (mm)
Micro-organism
Bacteria
Tested compounds
and standers
Gram-positive
Gram-negative
Yeast
Fungi
Escherichia coli
Bacillus subtilis
Aspergillus niger
Candida albicans
Streptomycin
Erythromycin
Ampicillin
Amoxicillin
Fusidic acid
2
3
4
5
6
7
8
+++
À
+++
+++
À
+
À
+++
À
++
++
À
À
À
À
À
À
À
+++
++
+++
+
+++
++
+++
++
+
À
++
++
++
+
+++
+
+
++
++
+
À
À
++
++
++
++
À
+
++
À
À
++
+++
++
À
9
+++
À
+++
++
À
11
12
13
14
15
16
17
18
++
À
++
++
++
À
À
++
++
++
+
À
À
À
++
+
À
+
+++
+++
++
++
++
++
+++
+++
+++Highly sensitive (inhibition zone = 21–25 mm).
++Fairly sensitive (inhibition zone = 16–20 mm).
+Slightly sensitive (inhibition zone = 10–15 mm).
ÀNot sensitive.
EXPERIMENTAL
it afforded the corresponding N-acyclic nucleosides 17 and
18, respectively. The structure of the aforementioned acy-
clic nucleosides was confirmed with spectral data and their
1H NMR spectra revealed methoxyethyl and hydroxyethyl
signals. In addition, the IR and 13C NMR spectra revealed
that the site of attack was on the N-atom and not O-atom
(cf. Experimental).
All melting points are uncorrected and measured using Electro-
Thermal IA 9100 apparatus (Shimadzu, Japan). Infrared spectra
were recorded as potassium bromide pellets on a PerkinElmer
1650 spectrophotometer (PerkinElmer Inc., Norwalk, CT), National
1
Research Center, Cairo, Egypt. H NMR and 13C NMR spectra
were determined on a Jeol-EX-500 NMR spectrometer (JEOL,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2012
Synthesis, Reactions and Antimicrobial Evaluation of b-Enaminonitriles of Pyrazole
Tokyo, Japan) and chemical shifts were expressed as parts per mil-
lion; (d values, ppm) against TMS as internal reference, National
Research Center, Cairo, Egypt. Mass spectra were recorded on EI +
Q1 MSLMR UPLR, National Research Center, Cairo, Egypt.
Microanalyses were operated using Electrothermal IA 9100 appa-
ratus, (Electrothermal, Essex, U.K.), Organic Microanalysis Unit, Na-
tional Research Center, Cairo, Egypt. Column chromatography was
performed on (Merck) Silica gel 60 (particle size 0.06–0.20 mm).
Compound 1 was prepared according to a reported method [18].
5-Amino-1-(6-phenyl-pyridazin-3-yl)-1H-pyrazole-4-carbonitrile
(2). To a solution of 1.86g (0.01 mole) of compound 1 in 30mL
ethanol, 0.01mole of ethoxymethylenemalononitrile was added.
The reaction mixture was refluxed for 2 h. The formed precipitate
was filtered on hot, dried, and recrystallized from dioxane to give
compound 2 (2.52g, 96%); m.p. 251–252ꢀC. IR spectrum (KBr,
2 pyridazine-H), 8.80 (s, 1H, pyrazole-H), 9.00 (s, 1H, pyrimidine-
H) and 11.90 (s, 1H, NH, D2O exchangeable); MS, m/z (%): 393
(M+, 37.06), 364 (100), 316 (3.26), 289 (14.95), 262 (6.81), 234
(3.08), 140 (4.89), 115 (12.62), 105 (71.97), 77 (45.62). Anal.
Calcd for C22H15N7O (393.39): C, 67.16; H, 3.84; N, 24.92;
Found: C, 67.13; H, 3.66; N, 25.05.
Methyl-[1-(6-phenyl-pyridazin-3-yl)-1H-pyrazolo[3,4-d]
pyrimidin-4-yl]-amine (6). Methylamine solution (20 mL, 35%)
was added to 20mL absolute ethanol containing 3.18 g (0.01 mol)
of compound 3, then the reaction mixture was stirred at room
temperature for 8 h. The formed precipitate was filtered off,
washed with ethanol, dried, and recrystallized from dimethyl
formamide to give compound 6 (2.34 g, 77%); m.p. 259–261ꢀC.
IR spectrum (KBr, n, cmÀ1): 3283 (NH); 1H NMR spectrum
(DMSO-d6, d ppm): 3.00 (s, 3H, CH3), 7.50–7.65 (m, 3H, Ar–H),
8.10–8.25 (m, 2H, Ar–H) and 8.30–8.70 (m, 5H, NH, D2O
exchangeable+ 2 pyridazine-H + pyrazole-H + pyrimidine-H); MS,
m/z (%): 303 (M+, 100), 288 (7.77), 276 (18.42), 247 (31.97), 220
(8.89), 206 (4.43), 144 (5.80), 115 (34.01), 77 (15.61). Anal.
Calcd for C16H13N7 (303.32): C, 63.35; H, 4.31; N, 32.32, Found:
C, 63.02; H, 4.49; N, 32.43.
4-Imino-1-(6-phenyl-pyridazin-3-yl)-1,4-dihydro-pyrazolo
[3,4-d]pyrimidin-5-ylamine (7). To a solution of 3.18g (0.01mol)
of compound 3 in 30 mL dry ethanol, 3 mL hydrazine hydrate (99%)
was added with stirring for 1 h at room temperature. The obtained
product was filtered, dried, and recrystallized from dry dioxane to
give compound 7 (2.80 g, 92%); m.p. 310–311ꢀC. IR spectrum
(KBr, n, cmÀ1): 3410, 3358 (NH2), and 3296 (NH); 1H NMR
spectrum (DMSO-d6, d ppm), 7.30–7.70 (m, 5H, 3Ar–H+NH2,
D2O exchangeable), 8.10 (s, 1H, pyrazole-H), 8.15–8.30 (m, 3H,
2Ar–H + pyridazine-H), 8.50 (d, J= 9.0 Hz, 1H, pyridazine-H), 8.60
(s, 1H, pyrimidine-H), and 12.60 (s, 1H, NH, D2O exchangeable);
MS, m/z (%): 304 (M+, 100), 290 (22.17), 261 (4.25), 235 (3.60),
197 (23.65), 171 (11.52), 152 (4.33), 115 (15.50), 102 (8.42), 77
(9.04). Anal. Calcd for C15H12N8 (304.32): C, 59.20; H, 3.97; N,
36.82; Found: C, 59.16; H, 3.79; N, 36.99.
1
n, cmÀ1): 3394, 3291 (NH2) and 2221 (CN); H NMR spectrum
(DMSO-d6, d ppm): 7.50–7.70 (m, 3H, Ar–H), 7.80 (s, 2H, NH2,
D2O exchangeable), 8.00 (s, 1H, pyrazole-H), 8.10À8.30 (m, 3H, 2
Ar–H + pyridazine-H) and 8.45 (d, J= 9.0 Hz, 1H, pyridazine-H);
MS, m/z (%): 262 (M+, 100), 233 (2.47), 197 (22.30), 185 (1.20),
155 (1.85), 140 (10.60), 115 (1.85), 104 (3.53), 102 (5.33), 93
(1.16), 89 (2.43), 77 (7.01). Anal. Calcd for C14H10N6 (262.27): C,
64.11; H, 3.84; N, 32.05; Found: C, 64.33; H, 3.70; N, 31.93.
N-[4-Cyano-2-(6-phenyl-pyridazin-3-yl)-2H-pyrazol-3-yl]-
formimidic acid ethyl ester (3). Compound 2, 2.62 g (0.01 mol)
was refluxed in 40 mL triethyl orthoformate for 5 h. The product
that separated on cooling was filtered off and recrystallized from
dry dioxane to give compound 3 (2.98 g, 94%); m.p. 170–172ꢀC.
IR spectrum (KBr, n, cmÀ1): 2229 (CN); 1H NMR spectrum
(DMSO-d6, d ppm): 1.30 (t, J = 7.3 Hz, 3H, OCH2CH3), 4.30 (q,
J = 7.3 Hz, 2H, OCH2CH3), 7.50–7.70 (m, 3H, Ar–H), 8.10–8.40
(m, 4H, 2 Ar–H + pyrazole-H + pyridazine-H), 8.50 (d, J = 9.0 Hz,
1H, pyridazine-H), and 8.65 (s, 1H, N = CH–O); MS, m/z (%):
318 (M+, 14.11), 289 (100), 273 (19.81), 197 (4.61), 155 (8.19),
140 (6.48), 115 (8.03), 102 (4.00), 77 (11.95). Anal. Calcd for
C17H14N6O (318.34): C, 64.14; H, 4.43;N, 26.39; Found: C,
64.21; H, 4.28; N, 26.40.
1-(6-Phenyl-pyridazin-3-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-
ylamine (4). Ammonium hydroxide solution (20 mL, 25%) was
added to 20mL absolute ethanol containing 3.18 g (0.01mol) of
compound 3, and the reaction mixture was stirred at room
temperature for 2 h. The formed precipitate was filtered off, dried,
and recrystallized from dioxane to give compound 4 (2.57 g,
89%), m.p. 300–301ꢀC. IR spectrum (KBr, n, cmÀ1): 3384, 3079
(NH2); 1H NMR spectrum (DMSO-d6, d ppm): 7.50–7.70 (m,
3 H, Ar–H), 7.80–8.30 (m, 4H, NH2, D2O exchangeable + 2Ar–
H), 8.40 (s, 1H, pyrazole-H) and 8.50–8.60 (m, 3H, 2 pyridazine-
H + pyrimidine-H); MS, m/z (%): 289 (M+, 100), 262 (33.29), 235
(13.84), 206 (6.77), 179 (2.24), 140 (8.60), 115 (23.93), 77 (5.09).
Anal. Calcd for C15H11N7 (289.28): C, 62.27; H, 3.83; N, 33.89;
Found: C, 62.39; H, 3.74; N, 33.87.
[1-(6-Phenyl-pyridazin-3-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-yl]-
hydrazine (8). Compound 7 (1.52g, 0.005 mol) in 20mL dry
dioxane containing few drops of piperidine was refluxed for 6 h.
Then the reaction mixture was evaporated under reduced pressure
and recrystallized from dioxane to give compound 8 (1.03 g,
68%), m.p. 337–338ꢀC. IR spectrum (KBr, n, cmÀ1): 3425, 3387
1
(NH2), and 3310 (NH); H NMR spectrum (DMSO-d6, d ppm):
6.40 (s, 2H, NH2, D2O exchangeable), 7.50–7.65 (m, 3H, Ar–H),
7.80 (s, 1H, NH, D2O exchangeable) and 8.10–8.60 (m, 6H,
2 Ar–H + pyrazole-H + 2 pyridazine-H + pyrimidine-H); MS, m/z
(%): 304 (M+, 5.19), 262 (100), 248 (1.57), 237 (1.49), 233
(3.23), 197 (38.35), 171 (9.96), 140 (15.58), 115 (20.71), 102
(15.75), 77 (13.76). Anal. Calcd for C15H12N8 (304.32): C, 59.20;
H, 3.97; N, 36.82; Found: C, 59.25; H, 3.83; N, 36.88.
N-[4-Cyano-2-(6-phenyl-pyridazin-3-yl)-2H-pyrazol-3-yl]-
acetamide (9). To a solution of compound 2 (2.62 g, 0.01mol)
N-[1-(6-Phenyl-pyridazin-3-yl)-1H-pyrazolo[3,4-d]pyrimidin-
4-yl]-benzamide (5). To a solution of 2.89g (0.01 mol) of
compound 4 in 50 mL dry dioxane, 1.4 mL (0.01 mol) benzoyl
chloride was added. The mixture was allowed to heat for 3 h, and
the excess solvent was removed under reduced pressure leaving an
oil that was washed with benzene to give a brown solid. The
remaining product was purified on silica gel using ethyl acetate:
pet. ether (40–60ꢀC) (2:1) as eluent to give compound 5 (2.44 g,
62%), m.p. 233–235ꢀC. IR spectrum (KBr, n, cmÀ1): 3244 (NH)
and 1698 (CO); 1H NMR spectrum (DMSO-d6, d ppm): 7.50–7.70
(m, 6H, Ar–H), 8.10–8.30 (m, 4H, Ar–H), 8.50–8.60 (m, 2H,
in 20mL dry pyridine, 10mL of acetic anhydride was added. The
reaction mixture was maintained at room temperature for 24 h,
which afforded no change, and then heated at 50ꢀC for 6 h, then
was evaporated under reduced pressure, and the remaining oil
product was purified with column chromatography (silica gel)
using pet. ether (40–60ꢀC):ethyl acetate mixture (1:1), as eluent to
give compound 9 (2.10g, 69%); m.p. 283–285ꢀC. IR spectrum
(KBr, n, cmÀ1): 3256 (NH), 2234 (CN) and 1702 (CO); 1H NMR
spectrum (DMSO-d6, d ppm): 2.10 (s, 3H, CH3), 7.55–7.65
(m, 3H, Ar–H), 8.20–8.30 (m, 3H, 2Ar–H + pyridazine-H), 8.50
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A. H. Shamroukh, A. E. Rashad, H. S. Ali, and M. E. Abdel-Megeid
Vol 000
(s, 1H, pyrazole-H), 8.60 (d, J = 9.0 Hz, 1H, pyridazine-H), and
11.20 (s, 1H, NH, D2O exchangeable); MS, m/z (%): 304 (M+,
11.13), 278 (3.13), 262 (100), 233 (1.54), 197 (16.12), 140 (5.24),
115 (5.94), 102 (2.84), 77 (5.54). Anal. Calcd for C16H12N6O
(304.31): C, 63.14; H, 3.97; N, 27.61; Found: C, 62.93; H, 4.02;
N, 27.70.
(C-phenyl). MS, m/z (%): 290 (M+, 100), 261 (18.49), 235
(6.80), 206 (15.14), 179 (5.23), 140 (11.60), 115 (18.88), 102
(16.83), 77 (6.61). Anal. Calcd for C15H10N6O (290.27): C,
62.06; H, 3.47; N, 28.95; Found: C, 61.77; H, 3.56; N, 29.08.
1-(6-Phenyl-pyridazin-3-yl)-6-phenyl-1,5-dihydro-pyrazolo
[3,4-d]-pyrimidin-4-one (14).
An equimolar amount
of compound 11 (0.28 g, 0.001mol) and benzaldehyde in 25mL
glacial acetic acid was refluxed for 10 h. The formed solid was
filtered on hot, dried, and recrystallized from dimethylformamide
to give compound 14 (0.24g, 86%); m.p. 387–388ꢀC. IR
5-Amino-1-(6-phenyl-pyridazin-3-yl)-1H-pyrazole-4-carboxylic
acid amide (11).
Method A: A solution of 1.52 g (0.005 mol) of compound 9 in a
mixture of PPA and orthophosphoric acid (1:1) was stirred at
room temperature for 6 h. The reaction mixture was poured into
water, and the organic material was extracted with ethyl acetate.
The solvent was removed under reduced pressure leaving a solid
product that was recrystallized from dioxane to give compound 11
(0.82 g, 59%), m.p. 273–275ꢀC.
Method B: To 10 mL cold concentrated sulfuric acid (98%), 1.31 g
(0.005mol) of compound 2 was added, over a 5 min period with ice
bath cooling and stirring. After 10min, the ice bath was removed
and the mixture was stirred for an additional 15 min. The resulting
pale yellow solution was carefully pour onto ice chips and the result-
ing precipitate was collected, washed with water, dried, and recrys-
tallized from dioxane to give a compound (1.13g, 80.71%)
identical in all aspects with compound 11 (m.p., mixed m.p.,
TLC, and IR); m.p. 273–274ꢀC. IR spectrum (KBr, n, cmÀ1):
3440, 3324, 3200, 3120 (2NH2), and 1654 (CO); 1H NMR spec-
trum (DMSO-d6, d ppm): 6.95 (bs, 2H, NH2, D2O exchangeable)
7.40–7.90 (m, 5H, 3Ar–H + NH2, D2O exchangeable), 8.10 (s,
1H, pyrazole-H), 8.15–8.35 (m, 3H, 2Ar–H + pyridazine-H),
and 8.50 (d, J = 9.0 Hz, 1H, pyridazine-H); MS, m/z (%): 280
(M+, 100), 263 (43.0), 236 (3.0), 197 (26.0), 156 (4.0), 140
(8.0), 115 (3.50). Anal. Calcd for C14H12N6O (280.28): C,
59.99; H, 4.31; N, 29.98; Found: C, 59.87; H, 4.38; N, 29.95.
2-(6-Phenyl-pyridazin-3-yl)-2H-pyrazol-3-ylamine (12).
Compound 2, 1.31 g (0.005 mol), in 20 mL sulfuric acid (50%)
was refluxed for 2 h. The reaction mixture was cooled and
poured onto ice chips and the resulting precipitate was
collected, washed with water, dried, and purified with column
chromatography (silica gel) using chloroform: n-hexane (3:1)
as eluent to give compound 12 (0.58 g, 49%), m.p. 151–152ꢀC.
IR spectrum (KBr, n, cmÀ1): 3408, 3303 (NH2); 1H NMR
spectrum (DMSO-d6, d ppm): 5.50 (s, 1H, pyrazole-H), 7.00 (s,
2H, NH2, exchangeable with D2O), 7.40–7.60 (m, 4H, 3Ar–
H + pyrazole-H), 8.10–8.30 (m, 3H, 2Ar–H + pyridazine-H),
and 8.40 (d, J = 8.55 Hz, 1H, pyridazine-H); MS, m/z (%): 237
(M+, 100), 221 (2.61), 197 (32.35), 181 (2.71), 171 (2.02), 155
(4.05), 140 (24.30), 115 (22.22), 102 (5.30), 77 (12.99). Anal.
Calcd for C13H11N5 (237.26): C, 65.80; H, 4.67; N, 29.52;
Found: C, 65.89; H, 4.69; N, 29.33.
1
spectrum (KBr, n, cmÀ1): 3448 (NH) and 1687 (CO); H NMR
spectrum (DMSO-d6, d ppm): 7.50–7.70 (m, 6H, Ar–H), 8.10–
8.30 (m, 4H, Ar–H), 8.50–8.70 (m, 3H, pyrazole-H + 2
pyridazine-H) and 12.70 (s, 1H, NH, D2O exchangeable); 13C
NMR spectrum (DMSO-d6, d ppm): 108 (C3a), 137 (C3), 140
(C6), 159 (C7a), 161 (C═O), 122, 126, 153, and 156 (C5, C4,
C6, and C3 pyridazine), 113, 118, 119,120, 121, 124, 130, and
132 (C-phenyl). MS, m/z (%): 366 (M+, 100), 262 (85.45), 206
(5.74), 179 (1.37), 140 (9.80), 115 (14.24), 104 (69.35), 77
(5.46). Anal. Calcd for C21H14N6O (366.37): C, 68.84; H, 3.85;
N, 22.94; Found: C, 68.62; H, 3.98; N, 22.88.
4-Chloro-1-(6-phenyl-pyridazine-3-yl)-1H-pyrazolo[3,4-d]
pyrimidine (15). Compound 13 (1.45 g, 0.005 mol) in
10 mL phosphorus oxychloride was refluxed for 10 h, then
the reaction mixture was cooled and poured into ice-water.
The formed solid was filtered off, dried, and purified on
silica gel using chloroform:n-hexane (1:1) as eluent to give
compound 15 (0.85 g, 55%) yield, m.p. 264–266ꢀC. 1H
NMR spectrum (DMSO-d6, d ppm): 7.55–7.70 (m, 3H, Ar–
H), 8.20–8.30 (m, 2H, Ar–H), 8.50 (d, J = 9.0 Hz, 1H, pyrida-
zine-H), 8.62 (d, J= 9.0 Hz, 1H, pyridazine-H), 9.00 (s, 1H,
pyrazole-H), and 9.10 (s, 1H, pyrimidine-H); MS, m/z (%):
310 (M+, Cl37, 38.41), 308 (M+, Cl35, 100), 244 (11.11),
218 (11.28), 190 (4.88), 140 (14.02), 115 (25.35). 101
(20.93), 77 (8.15). Anal. Calcd for C15H9ClN6 (308.73): C,
58.35; H, 2.93; N, 27.22; Found: C, 58.30; H, 2.94; N, 27.26.
1-(6-Phenyl-pyridazin-3-yl)-1,5-dihydro-pyrazolo[3,4-d]
pyrimidine-4-thione (16). Compound 15 (1.54 g, 0.005 mol)
and thiourea (0.38 g, 0.005 mol) in 40 mL dry dioxane was
refluxed for 4 h. The formed precipitate was collected and
dissolved in NaOH (20 mL, 10%). Then the mixture was
filtered off, and the filtrate was precipitated with HCl (0.1 N).
The solid product was collected and recrystallized from
dimethylformamide to give a compound 16 (1.16 g, 76%) m.
p. 336–337ꢀC. IR spectrum (KBr, n, cmÀ1): 3025 (NH),
1
and 1365 (C═S); H NMR spectrum (DMSO-d6, d ppm):
1-(6-Phenyl-pyridazin-3-yl)-1,5-dihydro-pyrazolo[3,4-d]
7.55–7.65 (m, 3H, Ar–H), 8.15–8.30 (m, 2H, Ar–H),
8.35–8.45 (m, 2H, pyrazole-H + pyridazine-H), 8.50–8.60
(m, 2H, pyridazine-H + pyrimidine-H), and 14.00 (s, 1H,
NH, D2O exchangeable); 13C NMR spectrum (DMSO-d6,
d ppm): 107 (C3a), 137 (C3), 141 (C6), 159 (C7a), 170
(C═S), 122, 126, 153, and 156 (C5, C4, C6, and C3
pyridazine), 113, 118, 121, 130, and 132 (C-phenyl).
MS, m/z (%): 306 (M+, 100), 277 (6.05), 272 (1.13), 252
(5.29), 218 (1.33), 176 (1.79), 140 (2.18), 115 (8.64),
102 (2.72), 77 (1.99). Anal. Calcd for C15H10N6S
(306.34): C, 58.80; H, 3.29; N, 27.43; S, 10.46; Found:
C, 58.92; H, 3.33; N, 27.10; S, 10.57.
pyrimidin-4-one (13).
Compound 11, 1.4 g (0.005 mol) in
20 mL formic acid (85%) was refluxed for 5 h. The reaction
mixture was cooled and poured into water, and the formed
solid was filtered off, dried, and recrystallized from
dimethylformamide to give a compound 13 (1.40 g, 79%); m.p.
345–346ꢀC. IR spectrum (KBr, n, cmÀ1): 3058 (NH), and 1665
(CO); 1H NMR spectrum (DMSO-d6, d ppm): 7.55–7.70 (m,
3H, Ar–H), 8.20–8.30 (m, 3H, 2Ar–H + pyrazole-H), 8.37 (d,
J = 9.0 1H, pyridazine-H), 8.50–8.60 (m, 2H, pyridazine-
H + pyrimidine-H), and 12.50 (s, 1H, NH, D2O exchangeable);
13C NMR spectrum (DMSO-d6, d ppm): 108 (C3a), 137 (C3),
140 (C6), 159 (C7a), 159 (C═O), 122, 126, 153, and 156
(C5, C4, C6, and C3 pyridazine), 113, 118, 121, 130, and 132
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2012
Synthesis, Reactions and Antimicrobial Evaluation of b-Enaminonitriles of Pyrazole
GENERAL PROCEDURE FOR SYNTHESIS OF
2) Yeast: Candida albicans
3) Fungi: Aspergillus niger
COMPOUNDS 17 AND 18
To a solution of compound 13 (0.01 mol) in dry DMF
(50 mL), 50% oil-immersed sodium hydride (0.20g) was
added. Thereafter, the reaction mixture was stirred at room
temperature for 1 h. Then, 2-chloroethyl methyl ether or 2-
chloroethanol (0.02 mol) was added and the reaction mix-
tures were stirred at 70ꢀC for 3 and 5 h, respectively. After
evaporation under reduced pressure, the residues were puri-
fied on silica gel column using chloroform: methanol (9:1)
Medium.
The cap-assay method containing (g/l):
peptone 6.0, yeast extract 3.0, meat extract 1.5, glucose
1.0 and agar 20.0 were used. The medium was sterilized
and divided while hot (50–60ꢀC) in 15 mL. Portions
among sterile petri-dishes of 9 cm diameter.
One milliliter of the spore suspension of each micro-
organism was spread all over the surface of the cold solid
medium placed in the petri-dish.
Method [21]. A total of 0.5 g of each tested compounds
was dissolved in 5 mL of dimethylformamide. An amount
of 0.1 mL of test solution was placed on Whatman paper
disc of 9 mm diameter, and the solvent was left to
evaporate. These saturated discs were placed carefully on
the surface of the inoculated solid medium; each petri-
dish contains at least three discs. The petri-dishes were
incubated at 5ꢀC for an hour to permit good diffusion
and then transferred to an incubator of 85ꢀC overnight,
then examined. The results were then recorded by
measuring the inhibition zone diameters.
as an eluent to give compounds 17 and 18, respectively.
5-(2-Methoxyethyl)-1-(6-phenyl-pyridazin-3-yl)-1,5-dihydro-
pyrazolo[3,4-d]pyrimidin-4-one (17). (1.49 g, 43%); m.p.
219–220ꢀC. IR spectrum (KBr, n, cmÀ1): 1691 (C═O); 1H
NMR spectrum (DMSO-d6, d ppm): 3.30 (s, 3H, OCH3),
3.65 (t, J = xx Hz, 2H, CH2O), 4.10–4.25 (t, J = xx Hz, 2H,
NCH2), 7.50–7.75 (m, 3H, Ar–H), 8.15–8.30 (m, 2H, Ar–
H), 8.37 (d, J = 9.0 Hz, 1H, pyridazine-H), and 8.45–8.60
(m, 3H, pyridazine-H + pyrazole-H + pyrimidine-H); 13C
NMR spectrum (DMSOd6,d ppm): 32 (CH2O), 58 (OCH3),
69 (CH2N), 108 (C3a), 137 (C3), 140 (C6), 159 (C7a), 162
(C═O), 122, 126, 153, and 156 (C5, C4, C6, and C3
pyridazine), 113, 118, 121, 130, and 132 (C-phenyl); MS,
m/z (%): 378 (M+, 8.35), 333 (17), 320 (100). MS, m/z
(%): 348 (M+, 18.93), 303 (4.66), 290 (100), 261 (16.28),
248 (3.29), 235 (6.11), 155 (4.09), 140 (2.77), 115 (6.45),
77 (4.25). Anal. Calcd for C18H16N6O2 (348.36): C, 62.06;
Acknowledgments. The authors extend their appreciation to the
Deanship of Scientific Research at King Saud University
for funding the work through the research group project No.
RGP-VPP-032.
H, 4.63; N, 24.13; Found: C, 62.09; H, 4.41; N, 24.23.
5-(2-Hydroxyethyl)-1-(6-phenyl-pyridazin-3-yl)-1,5-dihydro-
pyrazolo[3,4-d]pyrimidin-4-one (18). (1.60 g, 48%); m.p.
REFERENCES AND NOTES
293–295ꢀC. The IR spectrum (KBr, n, cmÀ1): 3415–3350
1
(OH) and 1722 (C═O). Its H NMR spectrum (DMSO-d6,
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BIOLOGICAL EVALUATION
Micro-organisms’ species:
1) Bacteria
a) Gram-negative bacteria, Bacillus subtilis
b) Gram-positive bacteria, Escherichia coli
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

A. H. Shamroukh, A. E. Rashad, H. S. Ali, and M. E. Abdel-Megeid
Vol 000
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet