Synthesis and antitumor evaluation of some new fused and binary pyridines

Article abstract of DOI:10.1002/jhet.1020

Syntheses of some new heterocyclic compounds containing pyridone, thioxopyridine, halogenated-pyridine-carbonitriles, pyrazolopyridine, and pyridine derivatives were achieved. Besides, a modified synthetic method for the synthesis of 2-chloro-4,6-dimethyl-nicotinonitrile () through the reaction of acetylacetone and malononitrile as starting materials was implemented. The reaction of 2-chloronicotinonitrile with substituted amines to 2-aminonicotinonitrile were also investigated. Fused or binary pyridines were tested for cytotoxicity against well-known established model Ehrlich ascites cells in vitro. Compound exhibited a high antitumor activity compared with 5-fluorouracil.

Full text of DOI:10.1002/jhet.1020

Month 2013
Synthesis and Antitumor Evaluation of Some New Fused
and Binary Pyridines
a
a
b
Mohamed A. Waly, Ibrahim I. EL‐Hawary, Wafaa S. Hamama *
a
and Hanafi H. Zoorob
a
Department of Chemistry, Faculty of Science (Damietta), Mansoura University, Egypt
b
Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, ET-35516, Egypt
*
E-mail: wshamama@yahoo.com
Received December 21, 2010
DOI 10.1002/jhet.1020
Published online 00 month 2013 in Wiley Online Library (wileyonlinelibrary.com).
Syntheses of some new heterocyclic compounds containing pyridone, thioxopyridine, halogenated‐pyridine‐
carbonitriles, pyrazolopyridine, and pyridine derivatives were achieved. Besides, a modified synthetic method
for the synthesis of 2‐chloro‐4,6‐dimethyl‐nicotinonitrile (3) through the reaction of acetylacetone and malo-
nonitrile as starting materials was implemented. The reaction of 2‐chloronicotinonitrile 3 with substituted
amines to 2‐aminonicotinonitrile were also investigated. Fused or binary pyridines were tested for cytotoxicity
against well‐known established model Ehrlich ascites cells in vitro. Compound 13 exhibited a high antitumor
activity compared with 5‐fluorouracil.
J. Heterocyclic Chem., 00 (2013).
INTRODUCTION
RESULTS AND DISCUSSION
Synthesis of the pyridine ring system and its deriva-
tives occupy an important place in the realm of syn-
thetic organic chemistry due to their therapeutic and
pharmacological properties [1–3]. They have emerged
as integral backbones of over 7000 existing drugs [4].
The pyridine ring is also an integral part of anticancer
and anti‐inflammatory agents [5, 6]. Moreover, tetralins
In this work, we developed a convenient method for the
synthesis of 2‐chloro‐4,6‐dimethylpyridine‐3‐carbonitrile
(3) [15], through a reduced reaction sequence. Its
synthesis including the condensation of acetyl acetone
with malononitrile in the presence of a catalytic amount
of piperidine afforded 2‐imino‐4,6‐dimethyl‐2H‐pyran‐
3‐carbonitrile (1) followed by rearrangement of the
iminopyran derivative 1 in a mixture of acetic acid
and sulfuric acid gave to afford hydroxynicotinonitrile
derivative 2. Moreover, refluxing of compound 2 with
phosphorous oxychloride in acetonitrile catalyzed by
triethylamine (TEA) afforded 2‐chloronecotinonitrile
derivative 3 in good yield (82%). The conversion of 1
to 2 was attributed to the diministring yield of 2
(30%) which reduces the yield of its conversion to 2‐
chloronicotinonitrile 3, thus, lowering the overall yield
of obtaining 3 through this synthetic pathway. Conse-
quently, in this work, we alleviated the rearrangement
step of compounds 1–2 by chlorination of 1 with
phosphorous oxychloride in acetonitrile catalyzed by
TEA where by 2‐chloronicotinonitrile derivative 3 was
obtained with remarkably improved yield up to 96%
“
tetrahydronaphthalene” derivatives are of increasing
interest as many of these compounds play a vital role
in the biological activities, because of their biological
potentialities; for example, as potent agonists for D2‐
type receptors [7], as a treatment of Alzheimer’s disease
[
8], cardiovascular diseases [9], and as a preventer of
dopamine‐induced cell death [10]. On the other hand,
cyanopyridone and cyanopyridine derivatives have
promising antimicrobial [11] and anticancer activities
[
12]. The interest in 3‐cyano‐2(1H)‐pyridone and their
derivatives is due to their wide range of practical uses
as medicinal compounds. Recently, new pyridine
carbonitriles were reported as anti‐inflammatory agents
[
13] and pyrazolopyridine derivatives have been
recently reported as antitumor agents [14].
©
2013 HeteroCorporation

M. A. Waly, I. I. EL-Hawary, W. S. Hamama, and H. H. Zoorob
Vol
Scheme 1. Synthesis of 2-chloro-4,6-dimethylnicotinonitrile (3) and its reactions with amines.
1
1
(
Scheme 1). The H‐NMR spectra of iminopyran
and (NH ) groups, respectively. The H‐NMR spectrum
2
derivative 1 and hydroxynicotinonitrile 2 showed the
presence of exchangeable (NH) and hydroxy protons
at δ 12.3 and 12.2 ppm, respectively. Accordingly, 2‐
aminonicotinonitrile derivatives were synthesized
through the condensation of the corresponding amines
with 2‐chloronicotinonitrile derivative 3.
Aminonicotinonitriles were used as inhibitors for
nitrogen activated protein kinase‐2 for treating TNFα‐
mediated diseases in particular inflammations such as
arthritis [16]. Thus, the reactions of 2‐chloronicotinoni-
trile derivative 3 with methylamine, n‐butylamine,
ethylenediamine, and S‐methylisothiourea were imple-
mented. Refluxing of 3 with methylamine or butyl
showed two singlet signals at δ 5.0 and 11.1 ppm due
to (NH ) and (NH) protons, respectively. On the other
2
hand, it has been reported that the reaction of 3 with
thiourea afforded 2‐mercapto‐4,6‐dimethyl‐nicotinonitrile
(10) which reacted with hydrazine hydrate to afford
the corresponding pyrazolopyridine derivative 8 [15]
(Scheme 2).
Once more, insecticides, such as imidacloprid and
acetamprid (nicotinoids) [17], derived from pyridine
act on the central nervous system of insects causing
irreversible blockage of postsynaptic nicotenergic
acetylcholine receptor. Fipronil (fiproles) [18] derived
from pyrazole blocks the γ‐aminobutyric acid (GABA)
which regulated chloride channel in neurons, there by
antagonizing the calming effects of GABA. The substi-
tution pattern for the pyridine nucleus at the 2‐ or 3‐
position by different heterocyclic moieties markedly
modulates its biological properties. Also, it has been
found that pyridine derivatives work as insecticidal
amine in ethanol‐containing Na CO3 afforded the 2‐
2
aminonicotinonitrile derivatives 4 and 5, respectively
1
(
Scheme 1). Their H‐NMR spectra showed exchange-
able (NH) protons at 4.0 and 5.0 ppm, respectively.
The IR spectra of 4 and 5 showed absorption bands at
−
1
2
203 and 2206 cm
attributable to cyano groups,
respectively. Furthermore, condensation of 3 with S‐
methylisothiourea in ethanol and in the presence of
sodium carbonate afforded the S‐methylnicotinonitrile
derivative 6 instead of the fused pyridopyrimidine
derivative 7 (Scheme 1). The IR spectrum of 6 showed
the presence of the cyano absorption band at 2200
Scheme 2. Synthetic pathways for 4,6-dimethyl-1H-pyrazolo[3,4-b]
pyridin-3-amine (8).
CH3
NH2
S-methylisothiourea
EtOH, Na2CO3
NH2NH2.H2O
DMF
6
−
1
1
N
cm . Its H‐NMR spectrum showed signals at δ 2.3
s, 3H, CH -C═N), 2.5 (s, 3H, CH -C═C), and 2.6
3
H C
N
N
H
(
8
3
3
ppm (s, 3H, S‐CH ; Scheme 1).
3
CH3
CN
On the other hand, the preparation of 2‐hyrazinoylni-
cotinonitrile 9 was achieved by condensation of 3 with
hydrazine hydrate at room temperature. However, the
formation of pyrazolopyridine derivative 8 was con-
ducted by refluxing of 9 in ethanol (Scheme 2). Its IR1
spectrum showed the absorption bands at 2212 cm−
attributable to cyano group besides absorption bands at
NH2NH2.H2O
r.t.
EtOH/ Reflux
3
H3C
H3C
N
9
NHNH2
S
CH3
CN
SH
H2N
NH2
NH NH .H O
2
2
2
N
−
1
1
0
3
392, 3327, and 3290 cm corresponding to (NH)
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
Antitumor Evaluation of Novel Pyridines
Scheme 3. Synthesis of fused or binary diazole, triazole, and tetrazole
derivatives.
[25], anxiolitic [26], and as inhibitors of mitogen‐activated
protein kinases [27, 28] or as growth hormone secretago-
gues [29]. They also can be used for the treatment of gastro-
intestinal disorders [30] and as antithrombotic agents [31].
Therefore, versatile and widely applicable methods for the
synthesis of these heterocycles are of considerable interest.
The preparations of these compounds are based on heterocy-
clic hydrazides as precursors. The [1,2,4]triazolo[4,3‐a]pyr-
idine ring system was prepared by different procedures
starting from the hydrazide derivative 9. Thus, the triazolo-
pyridine derivative 13 was synthesized through refluxing
of hydrazide 9 with triethylorthoformate in dimethylforma-
mide. Alternatively, the hydrazide derivative 9 with excess
formic or acetic acid afforded the [1,2,4]triazolo[4,3‐a]pyri-
dine derivatives 13 and 14, respectively (Scheme 3). The
IR spectra of 13 and 14 showed the cyano absorption bands
−1
1
at 2210 and 2213 cm , respectively. The H‐NMR spectra
of 13 showed the presence of C(1)‐H proton at δ 6.4 ppm,
1
whereas the H‐NMR spectra of 14 provided singlet signal
at δ 2.9 ppm due to C(1)‐CH protons.
3
The tetrazole unit that is not commonly used in
chemistry of natural products may be seen as a promis-
ing new un‐natural pharmacopoeiain medicinal chemis-
try because of its metabolic stability and its unique
structural and electronic feature [32]. The corresponding
N‐alkylated salts are used in photography, agriculture,
and dyes [33]. The synthesis of tetrazolopyridines cited
in literature from 2‐chloro‐4,6‐diarylnicotininitrile and
sodium azide in chlorobenzene and water catalyst by
tricapryl‐methylammonium chloride (Aliquat 336®)
[34]. Phase transfer catalysis makes it possible to carry
out azidolysis using sodium azide in a nonpolar solvent
such as chlorobenzene. The products are obtained in
quantitative yield in most cases; moreover, the solvent
was also recoverable [34]. The same reaction was tried
with different catalysts, such as tetrabutylammonium
bromide, benzyltriethylammonium chloride, tributylben-
zyl ammonium chloride, tetraethylammonium bromide,
and cetyltrimethyl ammonium chloride, but none of
these catalysts gave satisfactory results. Similar reaction
conditions using toluene, 18‐crown‐6, and sodium azide
found to increase the reaction time by 1 to 2 h [34].
Our attempts for the preparation of tetrazolopyridine
derivatives by methods that do not contain catalyst were
successful. Accordingly, the synthesis of tetrazolopyri-
dine ring system 16 based on 3 was discussed. 5,7‐
Dimethyltetrazolo[1,5‐a]pyridine‐8‐carbonitrile (16) was
synthesized either by refluxing of 3 with sodium azide
or by diazotization of the hydrazinyl derivative 9 with
sodium nitrite in diluted hydrochloric acid afforded the
same tetrazolopyridine derivative 16. The last procedure
passed through the formation of the intermediate 15,
which was cyclized in situ to the tetrazolopyridine de-
rivative 16 (Scheme 3). The IR spectra of 16 indicated
[
19] and antifungal agents [20]. Furthermore, pyrazole
and pyrazoline derivatives have also been found to
exhibit insecticidal [21], antifungal [22], and antibacte-
rial activities [23]. The effects of pyrazoline and pyra-
zole rings at position 2 of the pyridine nucleus
enhanced insecticidal, antifungal, and antibacterial
profiles of the compounds as compared to their parent
nucleolus [24]. Hence, it may be concluded that pyrazo-
lines and pyrazoles increases the insecticidal, antifungal,
and antibacterial activities. These findings prompted us
to synthesize a new series of pyridine derivatives by
incorporating pyrazole and pyrazoline moieties at
position 2, with a hope to get a better potential insecti-
cidal along with, antifungal, antibacterial, and biological
activities. Subsequently, refluxing of 2‐hydrazinyl‐4,6‐
dimethylpyridine‐3‐carbonitrile (9) with acetylacetone
or ethyl cyanoacetate in ethanol gave 4,6‐dimethyl‐2‐
(
(
3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine‐3‐carbonitrile
11) and 2‐(3‐amino‐4,5‐dihydro‐5‐oxopyrazol‐1‐yl)‐4,6‐
dimethylpyridine‐3‐carbonitrile (12), respectively (Scheme 3).
The IR spectra of 11 and 12 showed cyano absorption
−
1
bands at 2227 and 2260 cm , respectively. These data
reflected that the condensation of the hydrazide moiety
could condense faster with the activated methylene
carbonyl compounds than with the cyano group. Their
1
H‐NMR spectra indicated the presence of the pyrazolyl
C(4′)‐H protons at δ 6.0 and 4.0 ppm, respectively,
besides two singlet signals for compound 11 at δ 2.3
and 2.4 ppm due to C(3′)‐CH and C(5′)‐CH protons,
3
3
respectively, finally, exchangeable protons for compound
2 at δ 3.8 and 4.2 ppm for (NH ) and methylene
1
2
protons, respectively.
Triazolopyridines are important class of biologically ac-
tive heterocyclic compounds, which possess bactericidal
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

M. A. Waly, I. I. EL-Hawary, W. S. Hamama, and H. H. Zoorob
Vol
Table 1
In vitro cytotoxicity of pyridine derivatives using EAC assay.
EXPERIMENTAL
The completion of reaction was checked by tetramethylsi-
lane (TMS) by using Silica gel (Merck F, 254) and spots were
exposed to iodine vapor. Melting point (uncorrected) and were
determined on a Gallenkamp melting point apparatus. The IR
spectra were recorded on a Jasco 4100 FTIR spectrophotome-
%
Dead
Compounds
ED100 (μL)
ED50 (μL)
ED25 (μL)
−
1
1
13
5
3
4
5
6
8
9
1
1
1
1
‐FU
95.2
46.0
54.1
33.0
57.2
61.7
87.3
42.0
50.0
96.0
58.0
62.0
28.9
29.0
18.0
30.0
31.3
47.6
23.0
29.0
6.3
38.0
20.0
13.0
10.0
17.1
17.2
25.0
11.0
13.3
36.0
18.0
ter in KBr discs (υmax. in cm ). H‐NMR and C‐NMR
spectra were recorded on a Bruker Avance 300 spectrometer
operating at 300 and 75 MHz, respectively. Chemical shifts
were expressed in δ scale downfield as part per million
(
ppm) and TMS is used as an internal standard. The mass
spectrum was recorded on a Shimadzu GCMS‐QP 1000EX
mass spectrometer at 70 ev electron‐impact ionization. Ele-
mental analysis was recorded on PERKIN‐ELMER 2400 (C,
H, N, S, and O) elemental analyzer.
2‐Imino‐4,6‐dimethyl‐2H‐pyran‐3‐carbonitrile (1). A mixture
of acetylacetone (10.2 mL, 0.1 mol) and malononitrile (6.6
g, 0.1 mol) dissolved in ethanol (50 mL) and a catalytic
amount of piperidine (three drops) was refluxed for 3 h.
After cooling, the reaction mixture was poured into ice‐cold
water then the formed precipitate was filtered off, dried, and
recrystallized from methanol to give compound 1.
1
3
4
6
31.0
ED100, ED50, and ED25 are the effective doses at 25, 50, and 100 μL,
respectively, of the compounds used. The dead % refers to the % of the
dead tumor cells and 5‐FU is 5‐fluorouracil as a well‐known cytotoxic
agent.
1
Yield (95%), mp 194–196°C; yellow powder; H‐NMR
the presence of absorption band of cyano group at 2210
−
1
−1
(CDCl
s, H, pyran), 12.3 (s, H, NH).
‐Hydroxy‐4,6‐dimethylpyridine‐3‐carbonitrile (2). A mixture
of 1 (3 g, 20 mmol), conc H SO (1 mL), and acetic acid (10
3 3 3
): δ, 2.3 (s, 3H, CH ‐C═C), 2.5 (s, 3H, CH ‐C═N), 6.1
cm and the tetrazolo ring at 3390 cm . Its mass spec-
(
+
trum showed the molecular ion peak at m/z 173 (M ,
6%; Scheme 3).
2
8
2
4
Biological activity.
To examine whether the newly
mL) was refluxed for 3 h. The reaction mixture was
evaporated under vacuum to remove excess acetic acid
followed by addition of ethanol where by compound 2 was
precipitated which was purified by crystallization from
methanol.
prepared compounds have a direct cytotoxic effect on
Ehrlich ascites cells (EAC) viability, the percentage of
viable cells was estimated by the trypan blue [35]
exclusion test. Ten fused or binary pyridines were
tested for cytotoxicity against well‐known established
Yield (30%); mp 285–287°C, (Lit. [15(a)] 286°C); white
1
crystalline solid; H‐NMR (CDCl
3
): δ, 2.3 (s, 3H, CH
3
-C═C),
model EAC in vitro. Results for the ED100, ED , and
2.4 (s, 3H, CH -C═N), 6.1 (s, H, pyridyl), 12.2 (s, H, OH).
50
3
ED25 values of the active compounds are summarized
in Table 1. The data showed clearly that compounds
2‐Chloro‐4,6‐dimethylpyridine‐3‐carbonitrile (3). Method (A).
A mixture of 2‐hydroxy‐4,6‐dimethylpyridine‐3‐carbonitrile
2) (3 g, 20 mmol) in acetonitrile (20 mL), excess POCl (6
3
mL, 40 mmol), and a catalytic amount of TEA (2 mL, 20
mmol) was added, and the reaction mixture was refluxed for
h. After cooling, the mixture was left in air until complete
(
8
,
9, and 13 showed high activities, whereas
compounds 4, 14, and 16 showed moderate activity;
on the other hand, the rest of compounds have weak
activities. From the structure activity relationship
3
evaporation of excess POCl . The reaction mixture was
3
(
SAR), we found that incorporation of cyclic and
poured onto ice‐cold water then the formed precipitate was
filtered off, dried, and recrystallized from hexane to give
compound 3.
Yield (82%); mp 95–96°C, white crystals.
Method (B). A mixture of 1 (3.9 g, 20 mmol), acetonitrile (20
3
mL), TEA (2 mL, 20 mmol), and excess POCl (6 mL, 40 mmol)
was added, and the reaction mixture was refluxed for 2 h. After
cooling, the reaction mixture was poured onto ice water; the
formed precipitate was filtered off, dried, and recrystallized
from hexane to give 3.
acyclic (N-N) moiety into the position 2 of pyridine
ring increases the activity of the tested compounds at
high concentration. Methyl group in compound 14
decreases the activity by about its half‐value than
compound 13 at high concentration (Table 1).
CONCLUSION
The prepared new ring systems seem to be interesting
for biological studies. Furthermore, the present investi-
gation offers rapid and effective new procedures for
the synthesis of a new class of fused or binary
pyridines. The new compounds were investigated for
their cytotoxicity against well‐known established model
EAC in vitro. Compound 13 exhibited a high antitumor
activity compared with 5‐fluorouracil.
Yield (96%); mp 95–96°C, [Lit. [15(b)] 94–95°C; Yield
−
1
1
(
2
77%)]; IR (KBr) ύ (cm ), 2223 (CN); H‐NMR (CDCl
.4 (s, 3H, CH -C═C), 2.5 (s, 3H, CH -C═N), 7.0 (s, H, pyridyl).
Reaction of 2‐chloronicotinonitrile derivative with
3
): δ,
3
3
3
amines. General procedure. A mixture of 3 (20 mmol) and
appropriate amine (1 mL), namely; methylamine or butylamine
in ethanol (20 mL) containing Na CO (1 g) was refluxed for
2
3
3
h. After cooling, the reaction mixture was poured into ice‐
cold water, and then the formed precipitate was filtered off,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
Antitumor Evaluation of Novel Pyridines
dried, and recrystallized from aqueous ethanol to give the
corresponding amino derivatives 4 and 5, respectively.
for 3 h. After cooling, the reaction mixture was poured into ice
water. The formed precipitate was filtered off, dried, and
recrystallized from methanol to give 11 and 12, respectively.
4
,6‐Dimethyl‐2‐(methylamino)pyridine‐3‐carbonitrile
−
1
(
3
4). Yield (81%); mp 70–72°C; IR (KBr) ύ (cm ), 2202 (CN);
390 (NH); H‐NMR (CDCl ): δ, 2.3 (s, 3H, CH -C═C), 2.5
4,6‐Dimethyl‐2‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine‐
3‐carbonitrile (11). Yield (89%); mp 83–85°C; IR (KBr) ύ
1
3
3
−1
1
(
(
(
s, 3H, NH-CH
3
), 3 (s, 3H, CH
3
-C═N), 4 (s, H, NH), 6.3 ppm
(cm ), 2227 (CN); H‐NMR (CDCl ): δ, 2.3 (s, 3H, CH ), 2.4
3 3
+
s, H, pyridyl); MS: (m/z, %): 161 (M , 100), 146 (2.5), 131
4.6); Calcd. for C
(s, 3H, CH ), 2.4 (s, 3H, CH -C═C), 2.5 (s, 3H, CH -C═N), 6.0
3
3
3
13
9
H
11
N
3
(161.2): C 67.06, H 6.88, N 26.07%.
(s, 1H, ═CH-), 7.0 (s, H, phenyl); C‐NMR (CDCl ): δ, 160.24
3
Found: C 67.16, H 6.80, N 26.09%.
(C), 160.20 (C), 154.10 (C), 150.10 (C), 147.17 (C), 122.10
2
‐(Butylamino)‐4,6‐dimethylpyridine‐3‐carbonitrile (5).
(CH), 114.41 (C), 108.46 (CH), 101.10 (C), 23.79 (CH ), 19.99
3
−1
+
Yield (75%), mp 126–128°C; IR (KBr) ύ (cm ), 2206 (CN);
3
2
(CH ), 19.90 (CH ), 12.50 (CH ). MS: (m/z, %): 226 (M , 100),
3
3
3
1
367 (NH); H‐NMR (CDCl ): δ, 0.9 (t, 3H, CH -CH ), 1.3 (s,
H, CH
211 (4.5), 186 (14.6), 159 (28.1), 145 (23.8), 131 (12.4); Calcd.
for C H N (226.28): C 69.00, H 6.24, N 24.76%. Found: C
3
2
3
2
-CH
3
), 1.6 (p, 2H, CH
2
-CH
2
-CH
3
), 2.4 (s, 3H, CH
3
-
13 14 4
C═C), 2.5 (s, 3H, CH
NH), 6.3 (s, H, pyridyl), MS: (m/z, %): 203 (M , 100), 188
18.5), 174 (13.8), 160 (31.1), 146 (28), 131 (2.4); Calcd. for
C H N (203.28): C 70.90, H 8.43, N 20.67%. Found: C 70.97,
3
-C═N), 3.5 (t, 2H, NH-CH
2
), 5.0 (s, H,
69.07, H 6.34, N 24.71%.
+
2‐(3‐Amino‐4,5‐dihydro‐5‐oxopyrazol‐1‐yl)‐4,6‐dimethyl-
pyridine‐3‐carbonitrile (12). Yield (80%); mp 160°C; IR
(
−1
12
17
3
(KBr) ύ (cm ), 1673 (CO), 2260 (CN), 3428, 3517 (NH );
2
H 8.48, N 20.77%.
1
H‐NMR (CDCl
3 3 3
): δ, 2.3 (s, 3H, CH -C═C), 2.5 (s, 3H, CH -
3
‐Cyano‐2‐methylmercapto‐4,6‐dimethylpyridine (6).
C═N), 3.7 (s, 2H, NH ), 4.0 (s, 2H, CH ), 6.6 (s, H, pyridyl);
2
2
A mixture of 3 (3.2 g, 20 mmol), S‐methylisothiourea sulphate
5.56 g, 20 mmol), and Na CO (3 g) in ethanol (20 mL) was
13
C‐NMR (CDCl ): δ, 171.8 (C), 162.83 (C), 162.80 (C),
3
(
2
3
155.10 (C), 152.70 (C), 120.79 (CH), 119.54 (C), 85.35 (C),
2.10 (CH ), 23.21 (CH ), 17.3 (CH ). MS: (m/z, %): 229
M , 100), 201 (35.3), 131 (25.4); Calcd. for C11
229.24): C 57.63, H 4.84, N 30.55, O 6.98%. Found: C
7.65, H 4.80, N 30.65, O 6.95%.
refluxed for 4 h. The reaction mixture was left in air until com-
plete evaporation of excess ethanol; the precipitate formed was
collected and recrystallized from ethanol to give 6.
7
(
(
2
3
3
+
1 5
H N O
−
1
1
Yield (70%); mp 81–83°C; IR (KBr) ύ (cm ), 2200 (CN); H‐
NMR (CDCl ): δ, 2.3 (s, 3H, CH -C═C), 2.5 (s, 3H, CH -C═N),
5
3
3
3
5
,7‐Dimethyl‐[1,2,4]triazolo[4,3‐a]pyridine‐8‐carbonitrile
13). A mixture of 9 (3.3 g, 20 mmol) and triethylorthoformate
2 mL) or formic acid (3 mL) was refluxed in DMF (20 mL) for 3
+
2
1
3
.6 (s, 3H, S-CH ), 6.7 (s, H, pyridyl), MS: (m/z, %): 178 (M ,
(
(
9 10 2
00), 163 (25.3), 148 (33.6), 131 (2.5); Calcd. for C H N S
(
178.25): C 60.64, H 5.65, N 15.72, S 17.99%. Found: C 60.69,
or 2 h, respectively. The reaction mixture was left to cool, poured
into ice water. The formed precipitate was filtered off, dried, and
recrystallized from ethanol to give 13.
H 5.75, N 15.70, S 17.91%.
4
,6‐Dimethyl‐3‐amino‐3H‐pyrazolo[3,4‐b]pyridine (8).
Method (A). A mixture of 2‐mercapto‐4,6‐dimethylpyridine‐3‐
carbonitrile (10) [15], (3.2 g, 20 mmol) or 2‐methylmercapto‐
−1
Yield (90%) and (85%); mp 150–152°C; IR (KBr) ύ (cm ),
210 (CN), 3270 (═CH); H‐NMR (CDCl ): δ, 2.3 (s, 3H,
1
2
3
4
,6‐dimethylpyridine‐3‐carbonitrile (6) (3.6 g, 20 mmol), and
CH
pyridyl); Calcd. for C
2.54%. Found: C 62.74, H 4.61, N 32.50%.
3
-C═C), 2.4 (s, 3H, CH
3
-C═N), 6.4 (s, H, CH), 6.4 (s, H,
hydrazine hydrate (50%, 50 mL) was refluxed in dimethylforma-
mide (20 mL) for 3 h. The reaction mixture was left to cool,
poured into ice water. The precipitate formed was filtrated off,
washed with water, and recrystallized from ethanol to give 8.
Yield (85%), (92%); mp 280–282°C, (Lit. [15] 280°C); IR
9 8 4
H N (172.19): C 62.78, H 4.68, N
3
3,5,7‐Trimethyl‐[1,2,4]triazolo[4,3‐a]pyridine‐8‐carbonitrile
(
14). A mixture of 9 (3.3 g, 20 mmol) and acetic acid (3 mL)
−
1
was refluxed for 2 h. The reaction mixture was left in air until
complete evaporation of excess acetic acid. The formed precipi-
tate was collected and recrystallized from ethanol to give 14.
(
2
KBr) ύ (cm ), 1620 (C═N), 3179 (NH), 3286, 3387 (NH ).
Method (B) A mixture of 9 (3.2 g, 20 mmol) and hydrazine hy-
drate (50%, 50 mL) in ethanol (20 mL) was refluxed for 3 h. The
reaction mixture was left to cool and poured into ice water. The
precipitate formed was filtrated off, washed with water, dried,
and recrystallized from n‐butanol to give 8.
−
1
Yield (80%); mp 135–137°C; IR (KBr) ύ (cm ), 2213 (CN);
1
H‐NMR (CDCl
C═N), 2.9 (s, 3H, CH
(186.21): C 64.50, H 5.41, N 30.09%. Found: C
4.61, H 5.55, N 30.18%.
3
): δ, 2.4(s, 3H, CH
3 3
-C═C), 2.5 (s, 3H, CH -
), 7.0 (s, H, pyridyl); Calcd. for
3
10 10 4
C H N
Yield (80%); yellow crystalline solid, identical data to that
obtained in Method (A).
6
5,7‐Dimethyltetrazolo[1,5‐a]pyridine‐8‐carbonitrile (16).
2‐Hydrazinoyl‐4,6‐dimethylpyridine‐3‐carbonitrile (9).
A mixture of 3 (3.2 g, 20 mmol) and hydrazine hydrate (5 mL,
00 mmol) in ethanol (20 mL) was stirred for 5 h, and the
obtained solid was collected by filtration and dried to give 9 as
yellow crystalline solid.
Method (A) A mixture of 3 (3.2 g, 20 mmol), sodium azide (2 g)
in ethanol (20 mL) was refluxed for 3 h. After cooling, the reaction
mixture was poured into ice water. The formed precipitate was fil-
tered off, dried, and recrystallized from ethanol to give 16, yield
(86%); mp > 300°C.
1
Yield (91%) with colored change, mp 130°C; IR (KBr) ύ
−
1
1
(
(
(
cm ), 2212 (CN), 3392 (NH), 3290, 3327 (NH
CDCl ): δ, 2.4 (s, 3H, CH -C═C), 2.5 (s, 3H, CH
s, 2H, NH ), 6.5 (s, H, pyridyl), 11.7 (s, H, NH). MS: (m/z,
2
); H‐NMR
Method (B) Compound 9 (3.3 g, 20 mmol) with NaNO (1 g, 15
2
-C═N), 5.0
mmol) and HCl (3 mL) was stirred in an ice bath. The formed
precipitate was filtered off and recrystallized from ethanol to
give 16.
3
3
3
2
+
%
): 162 (M , 100), 131 (32.5); Calcd. for C H N (162.19): C
8 10 4
−
1
1
5
9.24, H 6.21, N 34.54%. Found: C 59.33, H 6.28, N 34.64%.
Reaction of 2‐hydrazinoylnicotinonitrile derivative 9 with
Yield (75%); mp > 300°C; IR (KBr) ύ (cm ), 2220 (CN); H‐
NMR (CDCl ): δ, 2.46 (3H, s, CH -C═N), 2.53 (3H, s, CH
C═C), 6.8 (H, s, pyridyl); MS: (m/z, %): 173 (M , 100), 145
(4.6), 131 (2.5), 119 (6.3); Calcd. for C (173.17): C
55.48, H 4.07, N 40.44%. Found: C 55.41, H 4.16, N 40.51%.
-
3
3
3
+
active methylene compounds. General procedure. A mixture
of 9 (3.3 g, 20 mmol) and acetylacetone or ethyl cyanoacetate
8 7 5
H N
(
2 mL, 20 mmol) in ethanol (20 mL) was refluxed with stirring
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

M. A. Waly, I. I. EL-Hawary, W. S. Hamama, and H. H. Zoorob
Vol
Antitumor activity. Different concentrations of the tested
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−
1
compounds were prepared (ED100, ED , and ED 1 g mL
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25
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet