Convenient synthesis of heterocyclic azo dyes in the class of pyranopyrazoles and chromenes

Article abstract of DOI:10.3184/174751918X15177611816526

A series of novel azo group fused 2H-chromenes and 4H-chromenes were synthesised as well as pyranopyrazole derivatives via the Knoevenagel condensation reaction of C-H acid compounds with 5-(arylazo)salicylaldehydes by a nucleophilic addition to the carbo

Full text of DOI:10.3184/174751918X15177611816526

68 RESEARCH PAPER
VOL. 42 FEBRUARY, 68–72
JOURNAL OF CHEMICAL RESEARCH 2018
Convenient synthesis of heterocyclic azo dyes in the class of pyranopyrazoles
and chromenes
Hamidreza Azari Arbabi, Siavash Salek Soltani, Hasan Salehi, Shahla Rezazadeh, Afsaneh Zonouzi
and Mansoureh Toosibashi*
School of Chemistry, University College of Science, University of Tehran, Tehran, Iran
A series of novel azo group fused 2H-chromenes and 4H-chromenes were synthesised as well as pyranopyrazole derivatives via the
Knoevenagel condensation reaction of C–H acid compounds with 5-(arylazo)salicylaldehydes by a nucleophilic addition to the carbonyl
group followed cyclisation.
Keywords: chromene, pyranopyrazole, azo dye, Knoevenagel condensation
Knoevenagel condensation, which was reported for the first
time by Emil Knoevenagel, is a nucleophilic addition of an
2-imino-6-(phenyldiazenyl)-2H-chromene-3-carbonitrile 5a, were
synthesised and also some new derivatives of azo ketocoumarins 3
were prepared using an optimised method.
1
active methylene component to carbonyl group of an aldehyde
or ketone followed by elimination of water to generate an
2
–6
Results and discussion
alkene. This is an easy way to prepare α,β-unsaturated
compounds. The existence of electron-withdrawing groups
adjacent to the methylene group is essential. This reaction is
The
three-component
reaction
of
5-(phenyldiazenyl)
salicylaldehyde (1 equiv.), malononitrile (1 equiv.) and 3-methyl-5-
pyrazolone (1 equiv.) in ethanol was chosen for initial optimisation
studies and pyranopyrazole 2a was isolated for the first time. The
reaction was carried out at ambient temperature in 30 min in the
presence of an aliphatic amine, such as triethylamine, diethylamine
and piperidine. Piperidine was the most efficient catalyst for the
synthesis of 2a (78% yield). The optimised conditions were then
utilised for a range of azosalicylaldehyde substrates. Both electron-
poor and electron-rich derivatives reacted well (Scheme 1).
7–10
usually catalysed by different weak and strong bases.
Knoevenagel condensation is utilised in the synthesis of
chromene and pyranopyrazole moieties, which are key core
substances in a variety of natural products and biological
11–15
structures.
Figure1showsdiversecompoundscontainingapyranopyrazole
or chromene nucleus with a variety of biological activities and
16–19
pharmaceutical properties (A–D).
Coupling of these scaffolds with the azo functional group
generates unique structures with photochemical and photophysical
properties as azo dye compounds. In this study, three novel azo
dyes in the class of pyranopyrazoles and chromenes, namely,
The formation of azopyranopyrazole derivatives 2a–h can be
explained by a domino process. In the first step, an arylidene
malononitrile intermediate is formed via Knoevenagel
condensation between a 5-(phenyldiazenyl)salicylaldehyde
derivative 1 and malononitrile. Then, Michael addition of
pyrazolone to arylidenemalononitrile is accomplished followed
by cyclisation and tautomerisation leading to product 2.
6
-amino-4-[2-hydroxy-5-(phenyldiazenyl)phenyl]-3-methyl-1,4-
dihydropyrano[2,3-c]pyrazole-5-carbonitrile 2a, 2-[2-amino-3-
cyano-6-(phenyldiazenyl)-4H-chromen-4-yl]malononitrile 4a and
OH
OH
OH
HN
EtO C
2
CN
S
NH
OH
N
O
N
O
Br
CN
NH
CN
N
NH
O
O
O
2
N
O
NH2
H
Br
A
B
C
D
Chk1 kinase inhibitor
Antioxidant
and antibiotic
Cytotoxic agent
Anticancer
and Bcl-2 inhibitor
Fig. 1 Structures of some bioactive compounds bearing pyranopyrazole and chromene moieties.
O
R
CN
CN
'
NH
R
N
N
N
Piperidine (5 mol%)
EtOH, r.t, 30 min
2a) R=H, R'=H
2b) R=Cl, R'=H
2c) R=Br, R'=H
2e) R=Br, R'=OMe
2f) R=Et, R'=H
+
R
HO
N
CHO
OH
CN
2g) R=Et, R'=OMe
N
N
2d) R=Cl, R'=OMe 2h) R=OMe, R'=H
N
O
NH2
H
1
2
'
R
Scheme 1 Synthesis of 6-amino-4-substituted-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile 2a–h.
*
Correspondent. E-mail: Toosibashi@ut.ac.ir

JOURNAL OF CHEMICAL RESEARCH 2018 69
Next, Knoevenagel condensation of a 5-(phenyldiazenyl)
salicylaldehyde derivative with ethylacetoacetate at
0 °C with 6–7 h stirring afforded the 6-(substituted phenyl)
Michael addition of malononitrile to the 2H-chromene 5
was also investigated. As a result, transformation to 4 was not
observed.
1
4
diazenylchromen-2-one derivatives 3a–f (Scheme 2). We
attempted to synthesise new derivatives of 3 compared with
previous studies.
A plausible mechanism for the reaction is shown in Scheme
4. By the reaction of compound 1 with malononitrile, the
arylidenemalononitrile intermediate A is formed, which can
then be converted in two ways. The first is intramolecular
cyclisation followed by tautomerisation to form product 5.
The second is Michael addition of a second equivalent of
malononitrile leading to intermediate B followed by cyclisation
and tautomerisation to obtain product 4.
2
0,21
As shown in Scheme 3, the catalytic reaction of
5
-(phenyldiazenyl)salicylaldehydes 1 and malononitrile was
performed in ethanol at room temperature to gain substituted
H-chromene 4 and 2H-chromene 5 derivatives. In initial
4
studies, a mixture of products 4 and 5 were afforded for many
conditions. The solvent quantity is very important for exclusive
synthesis of 4 or 5. With higher amounts of solvents, compound
Conclusion
4
was mostly obtained, but the reason is unclear. When the
An approach for the synthesis of a new series of azochromene
and azopyranopyrazole dyes was described. To the best of our
knowledge, this is the first report on the synthesis of these novel
pyrano[2,3-c]pyrazoles via a multicomponent pathway. The
solvent quantity was reduced, a mixture of products or only
compound 5 was obtained. However, in some cases, column
chromatography was required to obtain the less polar product 5.
O
O
3
a) R=H, R'=H
OEt
R
O
O
3b) R=H, R'=OMe
Piperidine (5 mol%)
+
N
R
N
3c) R=Et, R'=H
d) R=Cl, R'=H
3e) R=Et, R'=OMe
f) R=Cl, R'=OMe
0
EtOH, 40 C, 6-7 hours
3
N
CHO
OH
O
N
'
3
R
3
1
'
R
Scheme 2 Synthesis of 3-acetyl-6-(phenyldiazenyl)chromen-2-one derivatives 3a–f.
4
a) R=H, R'=H
b) R= p-Br, R'=H
c) R= p-Br, R'=OMe
4d) R= p-Cl, R'=H
e) R= p-Et, R'=H
4f) R= p-Et, R'=OMe
4g) R= p-NO , R'=H
4h) R= p-OMe, R'=H
i) R= H, R'=OMe
j) R= o, p-OMe, R'=H
4k) R= m, p-Me, R'=H
4
4
NC
CN
CN
N
N
CN
R
4
NC
eq
2
O
NH2
'
2
4
mi
n
R
3
0
r.t,
H,
EtO
N
CHO
OH
4
4
N
R
N
C
1 e
q
NC
CN
1
'
CN
R
R
5
a) R=H, R'=H
Et
OH
,
r.t
N
CN
NH
,
30
m
5b) R=Et, R'=H
5
5
in
N
c) R=Et, R'=OMe
d) R=OMe, R'=H
O
'
5e) R=Br, R'=H
f) R=Br, R'=OMe
5
R
5
5
g) R=Cl, R'=H
5
h) R=Cl, R'=OMe
Scheme 3 Reaction of 5-(phenyldiazenyl)salicylaldehyde derivatives 1 with malononitrile to afford products 4 and 5.
CN
PhN2
CN
N
PhN2
NC CN
CN
O
O
PhN2
CN
NH
NC
CN
NC
CN
NC CN
CN
CN
O
5
base PhN
2
PhN2
C
N
PhN2
CN
NH2
+
A
PhN2
CHO
OH
NH
O
O
H O
4
2
OH
1
B
NC
CN
CN
N
NC
CN
NC
CN
CN
CN
NC CN
PhN2
PhN2
CN
OH CN
PhN2
O
O
Scheme 4 Plausible route for the formation of azochromene dyes 4 and 5.

70 JOURNAL OF CHEMICAL RESEARCH 2018
reactions conditions are very mild with high yields and easy
purification. Moreover, our method provides an opportunity to
consider and study the biological activities of these heterocyclic
azo compounds. Its further applications in the field of azo
products synthesis are under investigation in our team and will
be reported in due course.
methoxyphenyl}-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-
carbonitrile (2e): Yellow-orange solid; yield 1.58 g (66%); m.p.
−1
2
1
48–250 °C; IR (KBr) (υ cm ): 3389 (OH), 2187 (CN), 1660 (C=N),
579, 1519 (C–N), 1473 (N=N), 1256 (C–N); H NMR (300 MHz,
1
DMSO-d ): δ 2.04 (s, 3H, CH ), 3.90 (s, 3H, CH ), 4.73 (s, 1H, CH),
6
3
3
6
.86 (s, 2H, NH ), 7.21 (d, J = 1.8 Hz, 1H, ArH), 7.35 (d, J = 1.8 Hz, 1H,
2
ArH), 7.72–7.80 (m, 4H, ArH), 9.0–10.5 (br s, 1H, OH), 10.5–12.0 (br
s, 1H, N–H). Anal. calcd for C H BrN O : C, 52.40; H, 3.56; N, 17.46;
Experimental
21
17
6
3
found: C, 52.47; H, 3.61; N, 17.40%.
6-Amino-4-{5-[(4-ethylphenyl)diazenyl]-2-hydroxyphenyl}-
-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (2f):
Yellow-orange solid; yield 1.54 g (77%); m.p. 220–222 °C; IR (KBr)
5
-(Phenyldiazenyl)salicylaldehyde derivatives
1
were prepared
2
2
according to a previous reported method. All of the reagents and
solvents were purchased from Merck, Sigma-Aldrich and Fluka.
They were used without any purification. TLC was carried out on
coated plastic sheets (25DCUV-254). Melting points were measured
on an electrothermal Gallenkamp melting point apparatus. Elemental
analysis for C, H and N were analysed using a Thermo Finnigan Flash
EA1112 instrument. IR spectra were obtained on a Shimadzu FT-
3
−
1
(
1
υ cm ): 3415, 3330 (NH ), 3263 (OH), 2186 (CN), 1643 (C=N), 1576,
2
1
539, 1509 (C–N), 1480 (N=N), 1256 (C–N); H NMR (300 MHz,
DMSO-d ): δ 1.20 (t, J = 7.5 Hz, 3H, CH ), 2.03 (s, 3H, CH ), 2.67
6
3
3
(
q, J = 7.5 Hz, 2H, CH ), 4.75 (s, 1H, CH), 6.83 (s, 2H, NH ), 7.14 (d,
2
2
1
13
J = 9 Hz, 1H, ArH), 7.37 (d, J = 8.1 Hz, 2H, ArH), 7.52 (d, J = 1.18 Hz,
H, ArH), 7.69–7.77 (m, 3H, ArH), 9.0–10.5 (br s, 1H, OH), 10.5–12.0
IR-4300 spectrophotometer using KBr discs. H NMR and C NMR
spectra were obtained on Bruker 250 and 300 MHz spectrometers in
CDCl and DMSO-d solutions and chemical shifts are noted in δ
1
(
br s, 1H, N–H). Anal. calcd for C H N O : C, 65.99; H, 5.03; N,
22 20 6 2
3
6
2
0.99; found: C, 65.90; H, 5.09; N, 21.05%.
(
ppm) relative to TMS as standard.
6
-Amino- 4- {3- [(4-ethylphenyl) diazenyl] - 6-hydroxy-2-
Synthesis of azopyranopyrazole derivatives (2a–h); general procedure
methoxyphenyl}-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-
carbonitrile (2g): Orange solid; yield 1.68 g (78%); m.p. 232–234 °C;
Piperidine (5 mol%) was added to a solution of 5-(phenyldiazenyl)
salicylaldehyde derivative 1 (5 mmol), 3-methyl-5-pyrazolone (0.49 g,
−1
IR (KBr) (υ cm ): 3492 (NH ), 3390 (OH), 2187 (CN), 1656 (C=N),
2
1
5
mmol) and malononitrile (0.33 g, 5 mmol) in ethanol (25 mL) under
1576, 1515 (C–N), 1471 (N=N), 1256 (C–N); H NMR (300 MHz,
rapid stirring at ambient temperature. After 30 min, the precipitate
was collected and washed with cold ethanol to gain pure 2a–h in good
yield.
DMSO-d ): δ 1.19 (t, J = 7.5 Hz, 3H, CH ), 2.03 (s, 3H, CH ), 2.66
6
2
3
(q, J = 7.5 Hz, 2H, CH ), 3.90 (s, 3H, CH ), 4.73 (s, 1H, CH), 6.84 (s,
2
3
2H, NH ), 7.17 (s, 1H, ArH), 7.33 (s, 1H, ArH), 7.37 (d, J = 7.5 Hz, 2H,
2
6
-Amino-4-[2-hydroxy-5-(phenyldiazenyl)phenyl]-3-methyl-1,4-
ArH), 7.77 (d, J = 7.5 Hz, 2H, ArH), 9.0–10.5 (br s, 1H, OH) 10.5–12.0
13
dihydropyrano[2,3-c]pyrazole-5-carbonitrile (2a): Yellow-orange
solid; yield 1.34 g (72%); m.p. 225–227 °C; IR (KBr) (υ cm ): 3416,
330 (NH ), 3268 (OH), 2185 (CN), 1644 (C=N), 1577, 1538, 1510 (C–
N), 1478 (N=N), 1256 (C–N); H NMR (300 MHz, DMSO-d ): δ 1.96
s, 3H, CH ), 4.69 (s, 1H, CH), 6.77 (s, 2H, NH ), 7.07 (d, J = 8.75 Hz,
(br s, 1H, N–H); C NMR (75 MHz, DMSO-d ): δ 9.9, 15.2, 28.07,
6
−1
28.09, 55.07, 55.81, 101.2, 104.75, 117, 120.5, 122.5, 124.6, 128.7, 137.2,
3
140.2, 141.2, 147.6, 147.8, 150, 159. Anal. calcd for C H N O : C,
2
23 22
6
3
1
64.17; H, 5.15; N, 19.52; found: C, 64.11; H, 5.09; N, 19.60%.
6-Amino-4-{2-hydroxy-5-[(4-methoxyphenyl)diazenyl]phenyl}-3-
6
(
3
2
1
H, ArH), 7.45–7.77 (m, 7H, ArH), 9.0–10.5 (br s, 1H, OH), 10.5–12.0
methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (2h): Brown
solid; yield 1.25 g (62%); m.p. 246–248 °C; IR (KBr) (υ cm ): 3417,
−1
(
br s, 1H, N–H). Anal. calcd for C H N O : C, 64.51; H, 4.33; N,
2
0
16
6
2
2
2.57; found: C, 64.42; H, 4.39; N, 22.62%.
-Amino-4-{5-[(4-chlorophenyl)diazenyl]-2-hydroxyphenyl}-
-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (2b):
3331 (NH ), 3271 (OH), 2186 (CN), 1644 (C=N), 1578, 1538, 1502
2
6
(C–N), 1250 (C–N);
1
H NMR (300 MHz, DMSO-d ): δ 2.03 (s, 3H,
6
3
CH ), 3.83 (s, 3H, CH ), 4.75 (s, 1H, CH), 6.82 (s, 2H, NH ), 7.06 (d,
3
3
2
Yellow solid; yield 1.40 g (69%); m.p. 245–247 °C; IR (KBr) (υ
J = 8.5 Hz, 2H, ArH), 7.12 (d, J = 8.8 Hz, 1H, ArH), 7.49 (d, J = 1.96
Hz, 1H, ArH), 7.67 (dd, J = 8.8, 1.96 Hz, 1H, ArH), 7.80–7.88 (m, 2H,
ArH), 9.0–10.5 (br s, 1H, OH), 10.5–12.0 (br s, 1H, N–H). Anal. calcd
for C H N O : C, 62.68; H, 4.51; N, 20.88; found: C, 62.61; H, 4.45; N,
−1
cm ): 3416, 3331 (NH ), 3268 (OH), 2186 (CN), 1644 (C=N), 1577,
2
1
1
538, 1510 (C–N), 1479 (N=N), 1251 (C–N); H NMR (300 MHz,
DMSO-d ): δ 2.04 (s, 3H, CH ), 4.75 (s, 1H, CH), 6.85 (s, 2H, NH ),
6
3
2
21
18
6
3
7.14 (d, J = 8.75 Hz, 1H, ArH), 7.54 (d, J = 2.1 Hz, 1H, ArH), 7.58 (d, J
2
0.95%.
=
=
9 Hz, 2H, ArH), 7.71 (dd, J = 8.75 Hz, J = 2.1 Hz, 1H, ArH), 7.83 (d, J
9 Hz, 2H, ArH), 9.0–10.5 (br s, 1H, OH), 10.5–12.0 (br s, 1H, N–H).
Synthesis of 6-(substituted phenyl)diazenylchromen-2-one derivatives
(
3a–f); general procedure
Anal. calcd for C H ClN O : C, 59.05; H, 3.72; N, 20.66; found: C,
2
0
15
6
2
5
9.01; H, 3.80; N, 20.61%.
-Amino-4-{5-[(4-bromophenyl)diazenyl]-2-hydroxyphenyl}-
-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (2c):
Piperidine (5 mol%) was added to a solution of 5-(phenyldiazenyl)
salicylaldehyde derivative 1 (5 mmol) and ethyl acetoacetate (0.65 g,
5 mmol) in ethanol (20 mL) under stirring and heating at 40 °C for
6–7 h. After cooling, the precipitate was filtered and washed with cold
ethanol to afford pure product 3a–f in good yield.
6
3
Yellow-orange solid; yield 1.53 g (68%); m.p. 236–238 °C; IR (KBr)
−1
(
1
υ cm ): 3423, 3332 (NH ), 3272 (OH), 2186 (CN), 1642 (C=N), 1576,
2
1
538, 1510 (C–N), 1477 (N=N), 1251 (C–N); H NMR (300 MHz,
3-Acetyl-6-(phenyldiazenyl)-2H-chromen-2-one (3a): Orange solid;
−1
2
DMSO-d ): δ 2.04 (s, 3H, CH ), 4.75 (s, 1H, CH), 6.85 (s, 2H, NH ),
yield 1.05 g (72%); m.p. 201–203 °C; IR (KBr) (υ cm ): 3049 (sp C–H),
3 1
6
3
2
7.16 (d, J = 8.72 Hz, 1H, ArH), 7.55–7.75 (m, 6H, ArH), 9.0–10.5 (br s,
2948 (sp C–H), 1735 (C=O), 1676 (C=O), 1477 (N=N); H NMR (300
MHz, DMSO-d ): δ 2.62 (s, 3H, CH ), 7.55–7.69 (m, 4H, ArH), 7.92–7.95
1H, OH), 10.5–12.0 (br s, 1H, N–H). Anal. calcd for C H BrN O : C,
2
0
15
6
2
6
3
5
3.23; H, 3.35; N, 18.62; found: C, 53.16; H, 3.41; N, 18.69%.
(t, 2H, ArH), 8.24 (dd, J = 7.5 Hz, 1H, ArH), 8.55 (s, 1H, ArH), 8.84 (s,
13
6
-Amino-4- {5- [(4-chlorophenyl) diazenyl]-2-hydroxy-3-
1H, =C–H); C NMR (75 MHz, DMSO-d ): δ 26.9, 121.5, 122.6, 126.6,
6
methoxyphenyl}-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-
carbonitrile (2d): Orange solid; yield 1.57 g (72%); m.p. 262–264 °C;
129.5, 138.2, 146.5, 151.3, 155.5, 171.5, 194.2. Anal. calcd for C H N O :
C, 69.86; H, 4.14; N, 9.58; found: C, 69.81; H, 4.08; N, 9.61%.
17
12
2
3
−1
IR (KBr) (υ cm ): 3385 (OH), 2187 (CN), 1658 (C=N), 1579, 1521 (C–
3-Acetyl-8-methoxy-6-(phenyldiazenyl)-2H-chromen-2-one (3b):
1
−1
N), 1473 (N=N), 1256 (C–N); H NMR (300 MHz, DMSO-d ): δ 2.04
Orange solid; yield 1.24 g (77%); m.p. 198–200 °C; IR (KBr) (υ cm ):
6
2
3
(
s, 3H, CH ), 3.90 (s, 3H, CH ), 4.73 (s, 1H, CH), 6.86 (s, 2H, NH ),
3053 (sp C–H), 2941 (sp C–H), 1736 (C=O), 1678 (C=O), 1462
3
3
2
1
7
(
.20 (d, J = 1.73 Hz, 1H, ArH), 7.34 (d, J = 1.73 Hz, 1H, ArH), 7.59
d, J = 8.6 Hz, 2H, ArH), 7.84 (d, J = 8.6 Hz, 2H, ArH), 9.0–10.5 (br s,
(N=N); H NMR (300 MHz, DMSO-d ): δ 2.54 (s, 3H, CH ), 4.02 (s,
6
3
3H, CH ), 7.58–7.63 (m, 3H, ArH), 7.77 (d, J = 1.5 Hz, 1H, ArH), 7.90
3
1
H, OH), 10.5–12.0 (br s, 1H, N–H). Anal. calcd. for C H ClN O : C,
(m, 2H, ArH), 8.13 (d, J = 2.5 Hz, 1H, ArH), 8.78 (s, 1H, =C–H). Anal.
21
17
6
3
5
7.74; H, 3.92; N, 19.24; found: C, 57.80; H, 3.96; N, 19.19%.
-Amino- 4- {5- [(4-bromophenyl) diazenyl]-2-hydroxy-3-
calcd for C H N O : C, 67.07; H, 4.38; N, 8.69; found: C, 67.01; H,
4.42; N, 8.61%.
18
14
2
4
6

JOURNAL OF CHEMICAL RESEARCH 2018 71
−
1
3
-Acetyl-6-[(4-ethylphenyl)diazenyl]-2H-chromen-2-one
(3c):
m.p. >250 °C; IR (KBr) (υ cm ): 3427 (N–H), 3334 (N–H), 2191
1
Orange solid; yield 1.10 g (69%); m.p. 148–150 °C; IR (KBr) (υ
cm ): 3048 (sp C–H), 2962 (sp C–H), 1742 (C=O), 1677 (C=O),
483 (N=N); H NMR (300 MHz, DMSO-d ): δ 1.22 (t, J = 7.5 Hz,
H, CH ), 2.58 (s, 3H, CH ), 2.70 (q, J = 7.5 Hz, 2H, CH ), 7.42 (d,
J = 8.1 Hz, 2H, ArH), 7.60 (d, J = 8.7 Hz, 1H, ArH), 7.81 (d, J = 8.1
Hz, 2H, ArH), 8.15 (m, 1H, ArH), 8.45 (d, J = 1.2 Hz, 1H, ArH), 8.78
(CN), 1644 (C=C), 1417 (N=N); H NMR (300 MHz, DMSO-d ): δ
6
−1
2
3
4.77 (s, 1H, C–H), 5.22 (d, J = 1.2 Hz, 1H, C–H), 7.35 (d, J = 9.0 Hz,
1H, ArH), 7.66–7.68 (m, 4H, N–H, ArH), 7.88–7.90 (m, 2H, ArH),
7.96 (dd, J = 8.7, 1.8 Hz, 1H, ArH), 8.09 (s, 1H, ArH). Anal. calcd for
C H ClN O: C, 60.89; H, 2.96; N, 22.42; found: C, 60.93; H, 2.91; N,
1
1
3
6
3
3
2
19
11
6
22.47%.
(
s, 1H, =C–H). Anal. calcd for C H N O : C, 71.24; H, 5.03; N, 8.74;
2-{2-Amino-3-cyano-6-[(4-ethylphenyl)diazenyl]-4H-chromen-4-
yl}malononitrile (4e): Orange solid; yield 0.24 g (65%); m.p. >250 °C;
19
16
2
3
found: C, 71.19; H, 4.99; N, 8.80%.
-Acetyl-6-[(4-chlorophenyl)diazenyl]-2H-chromen-2-one
Yellow solid; yield 1.06 g (65%); m.p. 181–183 °C; IR (KBr) (υ cm ):
−1
3
(3d):
IR (KBr) (υ cm ): 3426 (N–H), 3334 (N–H), 2190 (CN), 1645 (C=C),
−
1
1
1417 (N=N); H NMR (300 MHz, DMSO-d ): δ 1.22 (t, J = 6.7 Hz,
6
2
1
3
052 (sp C–H), 1739 (C=O), 1671 (C=O), 1479 (N=N); H NMR
3H, CH ), 2.70 (q, J = 7.5 Hz, 2H, CH ), 4.77 (d, J = 3.3 Hz, 1H, C–H),
3
2
(
8
300 MHz, DMSO-d ): δ 2.59 (s, 3H, CH ), 7.82–7.90 (m, 4H, ArH),
.10–8.19 (m, 2H, ArH), 8.49 (s, 1H, ArH), 8.79 (s, 1H, =C–H). Anal.
5.21 (d, J = 3.9 Hz, 1H, C–H), 7.33 (d, J = 8.7 Hz, 1H, ArH), 7.43 (d,
J = 8.1 Hz, 2H, ArH), 7.66 (s, 2H, N–H), 7.81 (d, J = 8.1 Hz, 2H, ArH),
7.91–7.95 (m, 1H, ArH), 8.06 (s, 1H, ArH). Anal. calcd for C H N O:
6
3
calcd for C H ClN O : C, 62.49; H, 3.39; N, 8.57; found: C, 62.54; H,
17
11
2
3
21 16
6
3
.43; N, 8.50%.
-Acetyl-6-[(4-ethylphenyl)diazenyl]-8-methoxy-2H-chromen-2-
one (3e): Orange solid; yield 1.08 g (62%); m.p. 192–194 °C; IR (KBr)
C, 68.47; H, 4.38; N, 22.81; found: C, 68.50; H, 4.33; N, 22.74%.
3
2-{2-Amino-3-cyano-6-[(4-ethylphenyl)diazenyl]-8-methoxy-4H-
chromen-4-yl}malononitrile (4f): Orange solid; yield 0.27 g (69%);
−1
3
−1
(
υ cm ): 2933 (sp C–H), 1744 (C=O), 1678 (C=O), 1461 (N=N);
m.p. >250 °C; IR (KBr) (υ cm ): 3422 (N–H), 3334 (N–H), 2191
1
1
H NMR (300 MHz, DMSO-d ): δ 1.22 (t, J = 7.5 Hz, 3H, CH ), 2.65
(CN), 1648 (C=C), 1420 (N=N); H NMR (300 MHz, DMSO-d ): δ
6
3
6
(
q, 2H, CH ), 2.85 (s, 3H, CH ), 4.02 (s, 3H, CH ), 7.71–7.85 (m, 5H,
1.22 (t, J = 7.5 Hz, 3H, CH ), 2.70 (q, J = 7.5 Hz, 2H, CH ), 3.94 (s, 3H,
2
3
3
3
2
ArH), 8.09 (d, J = 1.8 Hz, 1H, ArH), 8.77 (s, 1H, =C–H). Anal. calcd
CH ), 4.75 (d, J = 3.0 Hz, 1H, C–H), 5.20 (d, J = 3.0 Hz, 1H, C–H), 7.43
3
for C H N O : C, 68.56; H, 5.18; N, 8.00; found: C, 68.49; H, 5.22; N,
(d, J = 7.8 Hz, 2H, ArH), 7.56 (s, 1H, ArH), 7.68 (s, 3H, ArH, N–H),
7.82 (d, J = 7.2 Hz, 2H, ArH). Anal. calcd for C H N O : C, 66.32; H,
4.55; N, 21.09; found: C, 66.36; H, 4.60; N, 21.01%.
2
0
18
2
4
8
.09%.
-Acetyl-6-[(4-chlorophenyl)diazenyl]-8-methoxy-2H-chromen-2-
one (3f): Orange solid; yield 1.08 g (61%); m.p. 175–177 °C; IR (KBr)
2
2
18
6
2
3
2-{2-Amino-3-cyano-6-[(4-nitrophenyl)diazenyl]-4H-chromen-4-
−1
3
yl}malononitrile (4g): Red solid; yield: 0.23 g (60%); m.p. >250 °C;
(
υ cm ): 2934 (sp C–H), 1738 (C=O), 1650 (C=O), 1474 (N=N);
1
IR (KBr) (υ cm−1): 3463 (N–H), 3350 (N–H), 2263 (CN), 2186 (CN),
H NMR (300 MHz, DMSO-d ): δ 2.57 (s, 3H, CH ), 3.76 (s, 3H, CH ),
6
3
3
1
7.57–7.93 (m, 6H, ArH), 8.18 (d, J = 1.8 Hz, 1H, ArH), 8.79 (s, 1H, =C–
1636 (C=C), 1416 (N=N); H NMR (300 MHz, DMSO-d
6
): δ 4.75 (d,
J = 3 Hz, 1H, C–H), 5.22 (d, J = 3.6 Hz, 1H, C–H), 7.37 (d, J = 8.7 Hz,
H, ArH), 7.70 (s, 2H, N–H), 8.00–8.05 (m, 3H, ArH), 8.16 (s, 1H,
ArH), 8.39 (d, J = 5.7 Hz, 2H, ArH). Anal. calcd for C H N O : C,
H); Anal. calcd for C H ClN O : C, 60.60; H, 3.67; N, 7.85; found: C,
18
13
2
4
1
6
0.66; H, 3.62; N, 7.79%.
Synthesis of 4H-chromene derivatives (4a–k); general procedure
-(Phenyldiazenyl)salicylaldehyde derivative (1 mmol) was
19
11
7
3
59.22; H, 2.88; N, 25.44; found: C, 59.28; H, 2.91; N, 25.50%.
5
1
2
-{2-Amino-3-cyano-6-[(4-methoxyphenyl) diazenyl]-4H-
dissolved in ethanol (20 mL). Then malononitrile (0.13 g, 2 mmol) and
a catalytic amount of piperidine (5 mol%) were added and the resulting
solution was stirred at room temperature for 30 min. The precipitate
was filtered and washed with cold ethanol to afford product 4a–k.
chromen-4-yl}malononitrile (4h): Orange solid; yield 0.26 g (71%);
−1
m.p. >250 °C; IR (KBr) (υ cm ): 3412 (N–H), 3329 (N–H), 2191 (CN),
1
1
3
648 (C=C), 1413 (N=N); H NMR (300 MHz, DMSO-d ): δ 3.85 (s,
6
H, CH ), 4.76 (d, J = 3.3 Hz, 1H, C–H), 5.20 (d, J = 3.6 Hz, 1H, C–H),
3
2
-(2-Amino-3-cyano-6-(phenyldiazenyl)-4H-chromen-4-yl)
7.13 (d, J = 8.4 Hz, 2H, ArH), 7.31 (d, J = 8.7 Hz, 1H, ArH), 7.65 (s,
malononitrile (4a): Yellow-orange solid; yield 0.21 g (63%); m.p.
2H, N–H), 7.86–7.91 (m, 3H, ArH), 8.02 (s, 1H, ArH). Anal. calcd for
C H N O : C, 64.86; H, 3.81; N, 22.69; found: C, 64.80; H, 3.77; N,
22.75%.
−1
>
250 °C; IR (KBr) (υ cm ): 3442 (N–H), 3326 (N–H), 2193 (CN),
2
0
14
6
2
1
2147 (CN), 1640 (C=C), 1419 (N=N); H NMR (250 MHz, DMSO-d ):
6
δ 4.80 (d, J = 3.75 Hz, 1H, C–H), 5.24 (d, J = 3.75 Hz, 1H, C–H), 7.36
2-[2-Amino-3-cyano-8-methoxy-6-(phenyldiazenyl)-4H-chromen-
4-yl]malononitrile (4i): Orange solid; yield: 0.22 g (60%); m.p.
(d, J = 8.75 Hz, 1H, ArH), 7.60–7.67 (m, 3H, ArH), 7.70 (s, 2H, N–H),
−1
7
=
.88–7.91 (m, 2H, ArH), 7.98 (dd, J = 9.0, 2.0 Hz, 1H, ArH), 8.11 (d, J
>250 °C; IR (KBr) (υ cm ): 3429 (N–H), 3336 (N–H), 2190 (CN),
13
1
1.75 Hz, 1H, ArH); C NMR (75 MHz, DMSO-d ): δ 32.9, 37.7, 49.3,
1647 (C=C), 1420 (N=N); H NMR (300 MHz, DMSO-d ): δ 3.96
6
6
113.2, 113.4, 118.1, 119.5, 119.6, 123, 124.4, 124.5, 129.9, 132, 149.2,
(s, 3H, CH ), 4.76 (d, J = 3.3 Hz, 1H, C–H), 5.20 (d, J = 3.9 Hz, 1H,
3
1
52.1, 152.3, 163.6. Anal. calcd for C H N O: C, 67.05; H, 3.55; N,
C–H), 7.58–7.61 (m, 4H, ArH), 7.69–7.71 (s, 3H, N–H, ArH), 7.88 (d,
19
12
6
2
4.69; found: C, 67.11; H, 3.61; N, 24.60%.
-(2-Amino-6-[(4-bromophenyl)diazenyl]-3-cyano-4H-chromen-
-yl)malononitrile (4b): Brown solid; yield 0.28 g (66%); m.p.
J = 6.6 Hz, 2H, ArH). Anal. calcd for C H N O : C, 64.86; H, 3.81; N,
22.69; found: C, 64.82; H, 3.85; N, 22.74%.
2
0
14
6
2
2
4
>
2-{2-Amino-3-cyano-6-[(2,4-dimethoxyphenyl)diazenyl]-4H-
chromen-4-yl}malononitrile (4j): Brown solid; yield: 0.24 g (59%);
−1
250 °C; IR (KBr) (υ cm ): 3429 (N–H), 3336 (N–H), 2192 (CN),
1
−1
1643 (C=C), 1416 (N=N); H NMR (300 MHz, DMSO-d ): δ 4.78 (d,
m.p. >250 °C; IR (KBr) (υ cm ): 3470 (N–H), 3351 (N–H), 2184
6
1
J = 3.3 Hz, 1H, C–H), 5.21 (d, J = 3.9 Hz, 1H, C–H), 7.35 (d, J = 8.7
Hz, 1H, ArH), 7.68 (s, 2H, N–H), 7.79–7.81 (m, 4H, ArH), 7.96 (dd, J
(CN), 1633 (C=C), 1417 (N=N); H NMR (300 MHz, DMSO-d ): δ
6
3.86 (s, 3H, CH ), 3.96 (s, 3H, CH ), 4.80 (d, J = 3.3 Hz, 1H, C–H),
3
3
=
8.7, 2.1 Hz, 1H, ArH), 8.10 (d, J = 1.8 Hz, 1H, ArH). Anal. calcd for
5.19 (d, J = 3.6 Hz, 1H, C–H), 6.62 (dd, J = 9.3, 1.2 Hz, 1H, ArH), 6.77
(d, J = 1.2 Hz, 1H, ArH), 7.29 (d, J = 8.7 Hz, 1H, ArH), 7.59 (s, 1H,
ArH), 7.62 (s, 2H, N–H), 7.82 (d, J = 8.7 Hz, 1H, ArH), 7.96 (s, 1H,
ArH). Anal. calcd for C H N O : C, 62.99; H, 4.03; N, 20.99; found:
C H BrN O: C, 54.43; H, 2.64; N, 20.05; found: C, 54.38; H, 2.60; N,
19
11
6
2
0.09%.
-(2-Amino-6-[(4-bromophenyl)diazenyl]-3-cyano-8-methoxy-4H-
chromen-4-yl)malononitrile (4c): Orange solid; yield 0.30 g (67%);
2
21
16
6
3
C, 63.03; H, 4.00; N, 20.91%.
−1
m.p. >250 °C; IR (KBr) (υ cm ): 3429 (N–H), 3337 (N–H), 2191 (CN),
2-{2-Amino-3-cyano-6-[(3,4-dimethylphenyl)diazeny])-4H-chromen-
4-yl}malononitrile (4k): Orange solid; yield 0.24 g (66%); m.p. >250 °C;
1
1648 (C=C), 1422 (N=N); H NMR (300 MHz, DMSO-d ): δ 3.95 (s,
6
−1
3H, CH ), 4.76 (d, J = 2.7 Hz, 1H, C–H), 5.20 (d, J = 3.6 Hz, 1H, C–H),
IR (KBr) (υ cm ): 3417 (N–H), 3330 (N–H), 2192 (CN), 1647 (C=C),
3
1
7.59 (s, 1H, ArH), 7.70–7.72 (m, 3H, N–H, ArH), 7.80–7.81 (m, 4H,
1415 (N=N); H NMR (300 MHz, DMSO-d ): δ 2.30 (s, 3H, CH ), 2.32
6
3
ArH); Anal. calcd for C H BrN O : C, 53.47; H, 2.92; N, 18.71; found:
(s, 3H, CH ), 4.76 (d, J = 3.3 Hz, 1H, C–H), 5.21 (d, J = 3.9 Hz, 1H, C–H),
2
0
13
6
2
3
C, 53.40; H, 2.99; N, 18.76%.
-{2-Amino-6-[(4-chlorophenyl)diazenyl]-3-cyano-4H-chromen-
-yl}malononitrile (4d): Yellow-orange solid; yield 0.26 g (71%);
7.31–7.36 (m, 2H, ArH), 7.61–7.66 (m, 4H, N–H, ArH), 7.92 (dd, J = 9.0,
2
1.2 Hz, 1H, ArH), 8.04 (s, 1H, ArH). Anal. calcd for C H N O: C, 68.47;
21
16
6
4
H, 4.38; N, 22.81; found: C, 68.39; H, 4.44; N, 22.75%.

72 JOURNAL OF CHEMICAL RESEARCH 2018
Synthesis of 2H-chromene derivatives (5a–h); general procedure
C H ClN O: C, 62.25; H, 2.94; N, 18.15; found: C, 62.32; H, 3.01; N,
16 9 4
A solution of malononitrile (0.13 g, 2 mmol / 2 mL ethanol) was added
dropwise to a stirring solution of 5-(phenyldiazenyl)salicylaldehyde
derivative 1 (2 mmol) in ethanol (15 mL) in the presence of piperidine
18.10%.
6-[(4-Chlorophenyl)diazenyl]-2-imino-8-methoxy-2H-chromene-3-
carbonitrile (5h): Orange solid; yield 0.42 g (63%); m.p. 231–233 °C;
(5 mol%) at ambient temperature. The resulting mixture was stirred for
−1
IR (KBr) (υ cm ): 3284 (N–H), 2235 (CN), 1659 (C=N), 1425 (N=N);
30 min. Then the precipitate was filtered, washed with cold ethanol and
1
H NMR (300 MHz, DMSO-d ): δ 3.92 (s, 3H, CH ), 7.37–7.91 (m,
6
3
purified with column chromatography (ethyl acetate: n-hexane; 70:30 v/v)
to obtain the less polar product 5a–h.
6
H, ArH), 8.48 (s, 1H, =C–H), 9.22 (s, 1H, N–H). Anal. calcd for
C H ClN O : C, 60.28; H, 3.27; N, 16.54; found: C, 60.33; H, 3.22; N,
17
11
4
2
2
-Imino-6-(phenyldiazenyl)-2H-chromene-3-carbonitrile
(5a):
16.60%.
Yellow-orange solid; yield 0.32 g (59%); m.p. 176–178 °C; IR (KBr)
−
1
1
(
(
υ cm ): 3307 (N–H), 2230 (CN), 1661 (C=N), 1422 (N=N); H NMR
Acknowledgement
250 MHz, DMSO-d ): δ 7.30 (d, J = 8.0 Hz, 1H, ArH), 7.53–7.57 (m,
6
3H, ArH), 7.90–7.94 (m, 2H, ArH), 8.02 (d, J = 2.25 Hz, 1H, ArH),
The authors gratefully acknowledge support from the University
of Tehran.
8
.10 (d, J = 8.75 Hz, 1H, ArH), 8.45 (s, 1H, =C–H), 8.86 (s, 1H, N–H);
1
3
C NMR (75 MHz, DMSO-d ): δ 105.2, 114.9, 115.1, 119.1, 120.9,
6
123.2, 124.6, 124.7, 129.8, 132.5, 149.2, 150.1, 152.6, 154.6. Anal. calcd
Electronic Supplementary Information
for C H N O: C, 70.06; H, 3.67; N, 20.43; found: C, 70.11; H, 3.61; N,
16
10
4
The ESI is available through: http://ingentaconnect.com/
content/stl/jcr/2018/00000042/00000002/art00002
Received 23 October 2017; accepted 6 January 2018
Paper 1705066
2
0.51%.
-[(4-Ethylphenyl)diazenyl]-2-imino-2H-chromene-3-carbonitrile
5b): Orange solid; yield 0.33 g (54%); m.p. 157–159 °C; IR (KBr) (υ
6
(
−1
1
cm ): 3303 (N–H), 2231 (CN), 1659 (C=N), 1422 (N=N); H NMR
https://doi.org/10.3184/174751918X15177611816526
Published online: 8 February 2018
(
300 MHz, DMSO-d ): δ 1.22 (t, J = 7.5 Hz, 3H, CH ), 2.70 (q,
6
3
J = 7.5 Hz, 2H, CH ), 7.36 (d, J = 8.7 Hz, 1H, ArH), 7.43 (d, J = 8.1 Hz,
2
2
H, ArH), 7.81 (d, J = 8.1 Hz, 2H, ArH), 8.06–8.09 (m, 2H, ArH), 8.50
(
s, 1H, =C–H), 9.10 (s, 1H, N–H). Anal. calcd for C H N O: C, 71.51;
References
18
14
4
H, 4.67; N, 18.53; found: C, 71.57; H, 4.61; N, 18.59%.
-[(4-Ethylphenyl)diazenyl]-2-imino-8-methoxy-2H-chromene-3-
carbonitrile (5c): Orange solid; yield 0.37 g (56%); m.p. 189–191 °C;
1
2
E. Knoevenagel, Ber. Dtsch Chem. Ges., 1894, 27, 2346.
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Huaxue, 2007, 27, 483.
6
−1
IR (KBr) (υ cm ): 3288 (N–H), 2190 (CN), 1663 (C=N), 1424 (N=N);
3
4
1
H NMR (300 MHz, DMSO-d ): δ 1.19 (t, J = 7.8 Hz, 3H, CH ), 2.67
6
3
S. Kantevari, R. Bantu and L. Nagarapu, J. Mol. Catal. A Chem., 2007,
(
q, J = 7.5 Hz, 2H, CH ), 3.97 (s, 3H, CH ), 7.42 (d, J = 7.8 Hz, 2H,
2
3
2
69, 53.
ArH), 7.66–7.71 (m, 2H, ArH), 7.77–7.84 (m, 2H, ArH), 8.46 (s, 1H,
C–H), 9.18 (s, 1H, N–H). Anal. calcd for C H N O : C, 68.66; H,
5
6
7
M. Feroci, M. Orsini, L. Palombi and A. Inesi, Green Chem., 2007, 9, 323.
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8, 597.
=
19
16
4
2
4
.85; N, 16.86; found: C, 68.57; H, 4.90; N, 16.81%.
-Imino-6-[(4-methoxyphenyl) diazenyl]-2H-chromene-3-
carbonitrile (5d): Orange solid; yield 0.37 g (61%); m.p. 172–174 °C;
2
8
9
−1
IR (KBr) (υ cm ): 3305 (N–H), 2191 (CN), 1649 (C=N), 1417 (N=N);
1
H NMR (300 MHz, DMSO-d ): δ 3.86 (s, 3H, CH ), 7.11 (d, J = 7.8
6
3
Hz, 2H, ArH), 7.30 (d, J = 8.1 Hz, 1H, ArH), 7.81 (d, J = 7.5 Hz, 2H,
ArH), 8.07–8.13 (m, 2H, ArH), 8.54 (s, 1H, =C–H), 9.12 (s, 1H, N–H).
10
E. Palao, A.R. Agarrabeitia, J. Bañuelos-Prieto, T.A. Lopez, I. Lopez-
Arbeloa, D. Armesto and M.J. Ortiz, Org. Lett., 2013, 15, 4454.
Anal. calcd for C H N O : C, 67.10; H, 3.97; N, 18.41; found: C, 67.17;
17
12
4
2
11 C.H. Chang, H.C. Cheng, Y.J. Lu, K.C. Tien, H.W. Lin, C.L. Lin, C.J. Yang
and C.C. Wu, Org. Electron., 2010, 11, 247.
12 C. Qi, Y. Xiong, V.E. Lux, H. Cong and J.A. Porco Jr., J. Am. Chem.
Soc., 2016, 138, 798.
13 K.M. Meepagala, A.S. Estep and J.J. Becnel, J. Agric. Food Chem., 2016, 64,
4914.
14 N. Kumarswamyreddy and V. Kesavan, Org. Lett., 2016, 18, 1354.
H, 4.01; N, 18.49%.
- [(4-Bromophenyl) diazenyl] -2-imino-2H-chromene-3-
carbonitrile (5e): Orange solid; yield 0.39 g (55%); m.p. 225–227 °C;
6
−1
IR (KBr) (υ cm ): 3297 (N–H), 2235 (CN), 1656 (C=N), 1413 (N=N);
1
H NMR (300 MHz, DMSO-d ): δ 7.39 (d, J = 8.7 Hz, 1H, ArH),
6
7.63–7.82 (m, 4H, ArH), 8.06–8.14 (m, 2H, ArH), 8.52 (s, 1H, =C–H),
15
A. Khazaei, M.A. Zolfigol, F. Karimitabar, I. Nikokar and A.R.M. Zare,
RSC Adv., 2015, 5, 71402.
R.P. Pandit and Y.R. Lee, Mol. Divers., 2014, 18, 39.
9
.14 (s, 1H, N–H). Anal. calcd for C H BrN O: C, 54.41; H, 2.57; N,
16 9 4
1
5.86; found: C, 54.48; H, 2.49; N, 15.80%.
-[(4-Bromophenyl)diazenyl]-2-imino-8-methoxy-2H-chromene-3-
1
6
6
−1
17 N. Radulovic, G. Stojanovic, R. Vukicevic, V. Dekic, B. Dekic and R. Palic,
carbonitrile (5f): Orange solid; yield 0.44 g (58%); IR (KBr) (υ cm ):
Monatsh. Chem., 2006, 137, 1477.
1
3287 (N–H), 2232 (CN), 1659 (C=N), 1425 (N=N); H NMR (300
18
M. Khoobi, A. Foroumadi, S. Emami, M. Safavi, G. Dehghan, B.H.
Alizadeh, A. Ramazani, S.K. Ardestani and A. Shafiee, Chem. Biol. Drug.
Des., 2011, 78, 580.
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Dies and A.M. El-Agrody, Molecules, 2017, 22, 479.
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P. Sivaguru, R. Sandhiya, M. Adhiyaman and A. Lalitha, Tetrahedron
Lett., 2016, 57, 2496.
MHz, DMSO-d ): δ 3.95 (s, 3H, CH ), 7.68–7.87 (m, 6H, ArH), 8.48 (s,
6
3
1
H, =C–H), 9.22 (s, 1H, N–H). Anal. calcd for C H BrN O : C, 53.28;
17 11 4 2
H, 2.89; N, 14.62; found: C, 53.33; H, 2.96; N, 14.57%.
- [(4-Chlorophenyl) diazenyl]-2-imino-2H-chromene-3-
carbonitrile (5g): Orange solid; yield 0.38 g (62%); m.p. 205–207
19
6
2
0
−
1
°
(
C; IR (KBr) (υ cm ): 3297 (N–H), 2248 (CN), 1656 (C=N), 1417
1
21
N=N); H NMR (300 MHz, DMSO-d ): δ 7.37 (d, J = 8.7 Hz, 1H,
6
ArH), 7.62–7.69 (m, 2H, ArH), 7.86–7.92 (m, 2H, ArH), 8.09–8.14
m, 2H, ArH), 8.52 (s, 1H, =C–H), 9.14 (s, 1H, N–H). Anal. calcd for
22 S.F. Kamazani, S.S. Soltani and A. Zonouzi, Orient. J. Chem., 2016, 32,
(
2543.