Synthesis, characterization, and antibacterial evaluation of new alkyl 2-amino-4-aryl-4H-chromene-3-carboxylates

Article abstract of DOI:10.1007/s10593-015-1779-1

[MediaObject not available: see fulltext.] A series of alkyl 2-amino-4-aryl-4H-chromene-3-carboxylates was synthesized by an efficient, solvent-free one-pot three-component cyclocondensation of resorcinol, aromatic aldehydes, and ethyl or methyl cyanoacet

Full text of DOI:10.1007/s10593-015-1779-1

DOI 10.1007/s10593-015-1779-1
Chemistry of Heterocyclic Compounds 2015, 51(9), 808–813
Synthesis, characterization, and antibacterial evaluation
of new alkyl 2-amino-4-aryl-4H-chromene-3-carboxylates
Sedighe Gholipour1, Abolghasem Davoodnia1*, Mahboobeh Nakhaei-Moghaddam2
1 Department of Chemistry, Mashhad Branch, Islamic Azad University,
Mashhad 91735-413, Iran;
e-mail: adavoodnia@mshdiau.ac.ir, adavoodnia@yahoo.com
2 Department of Biology, Mashhad Branch, Islamic Azad University,
Mashhad 91735-413, Iran; e-mail: m.nakhaei@mshdiau.ac.ir
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2015, 51(9), 808–813
Submitted August 21, 2015
Accepted September 22, 2015
A series of alkyl 2-amino-4-aryl-4H-chromene-3-carboxylates was synthesized by an efficient, solvent-free one-pot three-component
cyclocondensation of resorcinol, aromatic aldehydes, and ethyl or methyl cyanoacetate using sodium carbonate as catalyst. The present
methodology offers several advantages, such as a simple procedure with ease of handling, short reaction time, high yields, and the
1
absence of any volatile and hazardous organic solvents. The products were characterized on the basis of IR, H NMR, and 13C NMR
spectral and microanalytical data and evaluated for their antibacterial activity against Gram-positive bacteria (Staphylococcus
epidermidis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) using paper disc diffusion technique.
Keywords: alkyl 2-amino-4-aryl-4H-chromene-3-carboxylates, ethyl cyanoacetate, methyl cyanoacetate, sodium carbonate, antibacterial
activity, cyclocondensation.
flowers of Wisteria sinensis and is one of their fragrance
components.10 Among different types of chromene systems,
2-amino-4H-chromenes have been reported to exhibit
highly useful proapoptotic properties for the treatment of a
wide range of cancer ailments.11 In cancer chemotherapy,
2-amino-4H-chromene II was marked for drug develop-
ment due to its high inhibition of tumor-associated Bcl-2
proteins.12 A modified 4H-chromene structure III was able
to induce apoptosis (programmed cell death) in several cancer
cell lines.13 2-Amino-4H-chromenes have also been shown
to exhibit antibacterial14–16 and antifungal16 activity.
The chromene moiety has emerged as a privileged
scaffold for drug design and discovery and generated great
attention because of certain natural and synthetic chromene
derivatives possess important biological properties such as
antitumor,1 antiviral,2 antivascular,3 antimicrobial,4 antihyper-
tensive,5 anticonvulsant,6 and TNF-α inhibitor activity.7
They have also been widely employed as cosmetics, pigments,8
and potent biodegradable agrochemicals.9 7-Hydroxy-
6-methoxy-4H-chromene I (Fig. 1) is an example of naturally
occurring 4H-chromene, which was obtained from the
Due to the aforementioned important properties of
chromene derivatives, considerable attention has been
focused on the development of environmentally friendly
methodologies for the synthesis of 2-amino-4H-chromene
scaffold. Several methods have been reported for the
synthesis of 2-amino-4H-chromene-3-carbonitriles such as
potassium carbonate-catalyzed conjugate addition-
cyclization reaction of malononitrile with Knoevenagel
adducts, previously formed from salicylaldehyde, and a
range of nucleophiles, such as oxindole, pyrazolone,
nitromethane, N,N-dimethylbarbituric acid, or indane-
dione;17 one-pot reaction of salicylaldehyde, malononitrile,
and nitroalkanes catalyzed by DBU;18 reaction of various
Figure 1. Structures of some biologically active 4H-chromenes.
0009-3122/15/5109-0808©2015 Springer Science+Business Media New York
808

Chemistry of Heterocyclic Compounds 2015, 51(9), 808–813
Table 1. Optimization of the reaction conditions for the synthesis
In conclusion, we have reported a convenient method for
of compound 4a catalyzed by Na2CO3
the synthesis of some new alkyl 2-amino-4-aryl-4H-
resorcinols with benzylidene malononitriles using various
bases as catalyst;19–21 reaction of malononitrile with in situ
generated sensitive ortho-quinone methides from 2-(aryl-
sulfonyl)alkyl phenols;22 reaction of malononitrile with
photochemically generated ortho-quinone methides from
o-(dimethylaminomethyl)phenols or o-(hydroxymethyl)-
phenols;23 or stepwise condensation of salicylaldehydes
with 3 equiv of malononitrile.21 An improved method has
also been reported for the synthesis of 2-amino-4-aryl-4H-
chromene-3-carbonitriles via a one-pot three-component
cyclocondensation of resorcinol, an aromatic aldehyde, and
malononitrile in the presence of various catalysts.24–31
Despite the availability of a wide variety of synthetic routes
Na2CO3,
mol %
Time,
min
Yield,
%
Entry
Solvent
T, °C
1
2
–
–
110
80
120
40
35
35
35
30
30
30
30
25
25
20
20
30
60
35
35
40
45
30
60
70
70
65
75
74
70
82
80
84
95
94
94
50
85
80
78
72
5
–
3
5
–
110
toward 2-amino-4H-chromene-3-carbonitriles,
a closer
4
5
–
140
look at the literature disclosed that the synthesis of alkyl
2-amino-4-aryl-4H-chromene-3-carboxylates has been
largely overlooked and only a few examples of the synthesis
of ethyl 2-amino-4-aryl-4H-chromene-3-carboxylates have
been reported by stepwise reaction of an aromatic aldehyde
and ethyl cyanoacetate followed by cyclization with
activated phenols or resorcinol in the presence of piperidine
as catalyst after refluxing for several hours in ethanol.32,33
Inspired by these facts and due to our interest in the
synthesis of heterocyclic compounds with potential biolo-
gical activities,34–38 we report here our results from an
efficient solvent-free synthesis of alkyl 2-amino-4-aryl-4H-
chromene-3-carboxylates by one-pot, three-component
cyclocondensation reaction of resorcinol, aromatic
aldehydes, and ethyl or methyl cyanoacetate using Na2CO3
as catalyst. The products were also evaluated for their
antibacterial activity against Staphylococcus epidermidis
(S. epidermidis) ATCC 12228 and Staphylococcus aureus
(S. aureus) ATCC 6538 as Gram-positive and Escherichia
coli (E. coli) ATCC 8739 as Gram-negative bacteria using
paper disc diffusion technique.
5
10
10
10
15
15
15
20
20
20
25
20
20
20
20
20
–
80
6
–
110
7
–
140
8
–
80
9
–
110
10
11
12
13
14
15
16
17
18
19
–
140
–
–
80
110
–
140
–
110
H2O
MeOH
EtOH
MeCO2Et
CH2Cl2
Reflux
Reflux
Reflux
Reflux
Reflux
can be seen, the efficiency of the reaction is affected
mainly by the amount of Na2CO3 and reaction temperature.
The best result was obtained when the reaction was run at
110°C in the presence of 20 mol % of Na2CO3 (entry 12).
For showing the effect of solvent, the same model reaction
was also carried out in different solvents including H2O,
MeOH, EtOH, MeCO2Et, and CH2Cl2 in the presence of
20 mol % of the catalyst (entries 15–19). As shown, the
yield of the product 4a under solvent-free conditions was
greater and the reaction time was considerably shorter than
with the conventional methods. Therefore, our optimized
conditions are 20 mol % of Na2CO3 at 110°C under solvent-
free conditions. All subsequent reactions were carried out
using these conditions.
Encouraged by the remarkable results obtained in the
model reaction and to show the generality and scope of this
protocol, a range of alkyl 2-amino-4-aryl-4H-chromene-
3-carboxylates 4a–j were prepared by the reaction of resor-
cinol (1), aromatic aldehydes 2a–g, and ethyl or methyl
cyanoacetate 3a,b in the presence of Na2CO3 under the
optimized reaction conditions. The results are summarized
in Table 2. As shown, all reactions proceed very cleanly to
give the corresponding products 4a–j in high yields over
At first, the synthesis of compound 4a was selected as a
model reaction to optimize the reaction conditions. The
reaction was carried out by heating equimolar amounts of
resorcinol (1), benzaldehyde (2a), and ethyl cyanoacetate
(3a) under various conditions. We decided to investigate
the efficiency of Na2CO3 in the model reaction under
solvent-free conditions, which offers several advantages
such as being environmentally friendly, simpler work-ups,
cleaner products, enhanced selectivity, reduction of by-
products, and faster reactions. To find the optimum
reaction conditions, different parameters were studied for
the formation of compound 4a. The results are summarized
in Table 1. Low yield of the product was obtained in the
absence of the catalyst by heating the reaction mixture at
110°C under solvent-free conditions for 120 min (entry 1).
This results indicate that the catalyst is necessary for the
reaction. We were pleased to see that the reaction was
efficiently catalyzed by Na2CO3 under solvent-free
conditions at elevated temperature leading to product 4a in
high yield (entry 2). Then the reaction was performed in
the presence of various amounts of the catalyst and also at
different temperatures under solvent-free conditions. As
809

Chemistry of Heterocyclic Compounds 2015, 51(9), 808–813
Table 2. Synthesis of alkyl 2-amino-4-aryl-4H-chromene-3-carboxylates 4a–j using Na2CO3 as catalyst*
Melting point, °C
Entry
Product
Ar
R
Time, min
Yield, %
Found
Reported
1
2
Ph
Et
Me
Et
20
15
20
15
15
15
10
20
20
20
95
98
90
92
90
90
95
95
90
95
217–219
230–231
218–220
227–229
219–221
228–229
211–213
191–192
197–199
232–234
219–22132
4a
4b
4c
4d
4e
4f
Ph
–
3
4-ClC6H4
4-ClC6H4
4-BrC6H4
4-BrC6H4
4-FC6H4
2-ClC6H4
4-MeOC6H4
3-BrC6H4
–
4
Me
Et
–
5
–
6
Me
Et
–
7
–
4g
4h
4i
8
Me
Et
–
191–19432
–
9
10
Me
4j
* Reaction conditions: resorcinol (1) (1 mmol), aromatic aldehyde 2a–g (1 mmol), ethyl or methyl cyanoacetate 3a,b (1 mmol), and anhydrous Na2CO3
(0.20 mmol, 20 mol %), 110°C, solvent-free.
short reaction times. According to 1H NMR spectral data in
Table 3. Antibacterial evaluation of compounds 4a–j using disc
aromatic region of chromene ring, resorcinol (1) reacts at
position C-4 instead of position C-2 because of the steric
hindrance between two hydroxyl groups or crowding of the
aryl group with the remaining OH group in the product,
and therefore 7-hydroxy-4H-chromenes 4a–j are formed
not the corresponding 5-hydroxy isomers 5.25–30
diffusion method
Inhibition zone, mm*
Compound
S. epidermidis
E. coli
6.7 0.2
7.0 0.6
7.0 0.0
6.0 0.0
6.0 0.0
7.3 0.2
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
7.7 0.2
8.0 0.0
7.7 0.2
6.0 0.0
7.3 0.2
7.7 0.2
7.3 0.2
6.0 0.0
6.0 0.0
7.3 0.2
6.0 0.0
30.3 0.5
6.0 0.0
4a**
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
7.0 0.0
6.0 0.0
6.0 0.0
6.0 0.0
6.7 0.2
6.0 0.0
6.0 0.0
7.0 0.0
6.0 0.0
20.3 0.5
4b**
4c**
The structure of all products 4a–j was deduced from
their spectral and microanalytical data. For example, the
1H NMR spectrum of compound 4f in DMSO-d6 showed
two sharp singlets at 3.50 and 4.80 ppm for methoxy and
methine groups, respectively, along with a signal at
7.62 ppm for the NH2 group, a signal at 9.62 ppm for the
OH proton, as well as the signals in the aromatic region due
to seven aromatic protons indicating the formation of com-
pound 4f. The IR spectrum showed absorption bands at
3423, 3308, and 3240 cm–1 for NH2 and OH groups.
Further proof came from 13C NMR spectrum which showed
the characteristic signals at 50.9, 76.4, and 169.0 ppm for
methoxy, methine, and carbonyl groups, respectively, as
well as other signals in the aromatic region. This
compound also gave satisfactory microanalytical data
corresponding to the molecular formula C17H14BrNO4.
The synthesized compounds 4a–j were screened for the
antibacterial activity against reference strains of S. epidermidis,
S. aureus, and E. coli bacteria. None of the compounds had
inhibition zone at a concentration of 2 mg/disc. The results, as
shown in Table 3, revealed that compounds 4a–c and 4f are
relatively effective against S. epidermidis at concentrations
≥ 3 mg/disc, while compounds 4c, 4g, and 4j show weak
antibacterial activity against E. coli only at a concentration
of 4 mg/disc. The minimum inhibitory concentration was
3 mg/disc for compounds 4a–c and 4f against S. epidermidis
and 4 mg/disc for compounds 4c,g,j against E. coli. None
4d**
4e**
4f**
4g**
4h**
4i**
4j**
4a***
4b***
4c***
4d***
4e***
4f***
4g***
4h***
4i***
4j***
DMSO
Gentamicin
* Diameter of each disc was 6.0 mm.
** Concentration 3 mg/disc.
*** Concentration 4 mg/disc.
810

Chemistry of Heterocyclic Compounds 2015, 51(9), 808–813
of the compounds showed antibacterial activity against
161.1; 161.2; 168.6. Found, %: C 68.72; H 5.11; N 4.67.
C17H15NO4. Calculated, %: C 68.68; H 5.09; N 4.71.
Ethyl 2-amino-4-(4-chlorophenyl)-7-hydroxy-4H-chro-
mene-3-carboxylate (4c). Yield 90%. IR spectrum, ν, cm–1:
3417, 3303, and 3247 (NH2 and OH), 1661 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 1.03 (3H, t, J = 7.2,
CH3); 3.92 (2H, q, J = 7.2, OCH2); 4.78 (1H, s, CH); 6.42
(1H, d, J = 2.0, H-8); 6.45 (1H, dd, J = 8.0, J = 2.0, H-6);
6.94 (1H, d, J = 8.0, H-5); 7.13 (2H, d, J = 8.4, H Ar); 7.25
(2H, d, J = 8.4, H Ar); 7.62 (2H, br. s, NH2); 9.67 (1H, s,
OH). 13C NMR spectrum, δ, ppm: 15.9; 60.2; 77.7; 103.7;
113.3; 113.8; 117.7; 129.7; 130.4; 131.4; 131.8; 149.3;
150.4; 158.5; 162.5; 170.0. Found, %: C 62.49; H 4.63;
N 4.09. C18H16ClNO4. Calculated, %: C 62.52; H 4.66; N 4.05.
Methyl 2-amino-4-(4-chlorophenyl)-7-hydroxy-4H-
chromene-3-carboxylate (4d). Yield 92%. IR spectrum, ν,
cm–1: 3417, 3376, and 3320 (NH2 and OH), 1666 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 3.48 (3H, s, OCH3);
4.80 (1H, s, CH); 6.42 (1H, d, J = 1.6, H-8); 6.46 (1H, d,
J = 8.4, H-6); 6.98 (1H, d, J = 8.4, H-5); 7.14 (2H, d,
J = 8.4, H Ar); 7.25 (2H, d, J = 8.4, H Ar); 7.63 (2H, br. s,
NH2); 9.63 (1H, s, OH). 13C NMR spectrum, δ, ppm: 50.9;
76.8; 102.6; 112.6; 117.3; 126.2; 127.1; 127.2; 128.7; 130.1;
149.0; 149.6; 157.3; 161.7; 169.2. Found, %: C 61.56;
H 4.23; N 4.19. C17H14ClNO4. Calculated, %: C 61.55;
H 4.25; N 4.22.
S. aureus at concentration of 3 or 4 mg/disc.
In conclusion, we have reported a convenient method for
the synthesis of some new alkyl 2-amino-4-aryl-4H-
chromene-3-carboxylates by one-pot three-component
cyclocondensation of resorcinol, aromatic aldehydes, and
ethyl or methyl cyanoacetate using sodium carbonate as
catalyst under solvent-free conditions. The method offers
several significant advantages, including short reaction
times, high yields of products, easy work-up, and the
absence of any hazardous organic solvents. Some of the
synthesized compounds have weak growth-inhibiting
effects on S. epidermidis and E. coli.
Experimental
IR spectra were obtained with KBr pellets using a
1
Tensor 27 Bruker spectrophotometer. H and 13C NMR
spectra were recorded on a Bruker 400 FT spectrometer
(400 and 100 MHz, respectively) in DMSO-d6 using TMS
as internal standard. Elemental analysis was performed on
a Thermo Finnigan Flash EA microanalyzer. Melting
points were recorded on a Stuart SMP3 melting point
apparatus. All chemicals were purchased from Merck and
Aldrich and used without additional purification.
Synthesis of alkyl 2-amino-4-aryl-4H-chromene-
3-carboxylates 4a–j (General method). A mixture of
resorcinol (1) (0.11 g, 1.0 mmol), an aromatic aldehyde 2a–g
(1.0 mmol), ethyl or methyl cyanoacetate 3a,b (1.0 mmol)
and anhydrous Na2CO3 (0.2 mmol, 20 mol %) was heated
in an oil bath at 110°C for 10–20 min. After completion of
the transformation (TLC control, eluent ethyl acetate–n-hexa-
ne), the reaction mixture was cooled to room temperature
and warm water was added. This resulted in the
precipitation of the product, which was collected by
filtration. The crude product was washed with warm water
repeatedly and recrystallized from EtOH to give
compounds 4a–j in high yields.
Ethyl
2-amino-4-(4-bromophenyl)-7-hydroxy-4H-
chromene-3-carboxylate (4e). Yield 90%. IR spectrum,
ν, cm–1: 3416, 3303, and 3244 (NH2 and OH), 1661 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 1.03 (3H, t, J = 6.8,
CH3); 3.92 (2H, q, J = 6.8, OCH2); 4.77 (1H, s, CH); 6.42
(1H, s, H-8); 6.46 (1H, d, J = 8.4, H-6); 6.94 (1H, d,
J = 8.4, H-5); 7.08 (2H, d, J = 8.0, H Ar); 7.38 (2H, d,
J = 8.0, H Ar); 7.61 (2H, br. s, NH2); 9.64 (1H, s, OH).
13C NMR spectrum, δ, ppm: 15.9; 60.2; 77.6; 103.7; 112.5;
113.8; 117.6; 120.3; 130.8; 131.5; 132.6; 149.7; 150.6;
158.5; 162.6; 169.8. Found, %: C 55.44; H 4.18; N 3.60.
C18H16BrNO4. Calculated, %: C 55.40; H 4.13; N 3.59.
Methyl 2-amino-4-(4-bromophenyl)-7-hydroxy-4H-
chromene-3-carboxylate (4f). Yield 90%. IR spectrum,
ν, cm–1: 3423, 3308, and 3240 (NH2 and OH), 1662 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 3.50 (3H, s, OCH3);
4.80 (1H, s, CH); 6.44 (1H, d, J = 2.4, H-8); 6.48 (1H, dd,
J = 8.4, J = 2.4, H-6); 6.99 (1H, d, J = 8.4, H-5); 7.10 (2H,
d, J = 8.4, H Ar); 7.40 (2H, d, J = 8.4, H Ar); 7.62 (2H,
br. s, NH2); 9.62 (1H, s, OH). 13C NMR spectrum, δ, ppm:
50.9; 76.4; 102.6; 112.7; 116.7; 119.2; 129.5; 130.2; 131.6
(2C); 148.4; 149.5; 157.4; 161.6; 169.0. Found, %:
C 54.32; H 3.74; N 3.69. C17H14BrNO4. Calculated, %:
C 54.28; H 3.75; N 3.72.
Ethyl
2-amino-7-hydroxy-4-phenyl-4H-chromene-
3-carboxylate (4a). Yield 95%. IR spectrum, ν, cm–1: 3438,
1
3372, and 3323 (NH2 and OH), 1666 (C=O). H NMR
spectrum, δ, ppm (J, Hz): 1.01 (3H, t, J = 6.4, CH3); 3.90
(2H, q, J = 6.4, OCH2); 4.75 (1H, s, CH); 6.40 (1H, s, H-8);
6.43 (1H, d, J = 8.0, H-6); 6.94 (1H, d, J = 8.0, H-5); 7.02–
7.25 (5H, m, H Ar); 7.57 (2H, br. s, NH2); 9.60 (1H, s, OH).
13C NMR spectrum, δ, ppm: 15.8; 60.1; 78.2; 103.7; 113.7;
113.8; 118.3; 127.3; 128.5; 129.7; 131.4; 150.2; 150.6;
158.3; 162.6; 170.0. Found, %: C 69.47; H 5.48; N 4.53.
C18H17NO4. Calculated, %: C 69.44; H 5.50; N 4.50.
Methyl 2-amino-7-hydroxy-4-phenyl-4H-chromene-
3-carboxylate (4b). Yield 98%. IR spectrum, ν, cm–1:
3418, 3306, and 3227 (NH2 and OH), 1664 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 3.49 (3H, s, OCH3);
4.79 (1H, s, CH); 6.43 (1H, d, J = 2.0, H-8); 6.47 (1H, dd,
J = 8.3, J = 2.0, H-6); 6.99 (1H, d, J = 8.3, H-5); 7.08 (1H,
t, J = 7.2, H Ar); 7.14 (2H, d, J = 7.3, H Ar); 7.20 (2H, t,
J = 7.6, H Ar); 7.60 (2H, br. s, NH2); 9.60 (1H, s, OH).
13C NMR spectrum, δ, ppm: 50.4; 76.3; 102.0; 112.0;
116.9; 125.7; 126.7; 128.2; 129.6; 148.4; 149.1; 156.7;
Ethyl 2-amino-4-(4-fluorophenyl)-7-hydroxy-4H-chro-
mene-3-carboxylate (4g). Yield 95%. IR spectrum, ν, cm–1:
3417, 3304, and 3244 (NH2 and OH), 1662 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 1.03 (3H, t, J = 6.8,
CH3); 3.93 (2H, q, J = 6.8, OCH2); 4.79 (1H, s, CH); 6.42
(1H, s, H-8); 6.46 (1H, d, J = 8.4, H-6); 6.94 (1H, d,
J = 8.4, H-5); 7.01 (2H, t, J = 8.4, H Ar); 7.14 (2H, t,
J = 7.2, H Ar); 7.61 (2H, br. s, NH2); 9.66 (1H, s, OH).
13C NMR spectrum, δ, ppm: 15.8; 60.2; 78.1; 103.7; 113.8;
811

Chemistry of Heterocyclic Compounds 2015, 51(9), 808–813
116.2; 116.4; 118.0; 130.3; 131.4; 146.5; 150.6; 158.4;
The authors express their gratitude to the Islamic Azad
University, Mashhad Branch for its financial support.
160.8; 162.5; 169.9. Found, %: C 65.62; H 4.95; N 4.27.
C18H16FNO4. Calculated, %: C 65.65; H 4.90; N 4.25.
Methyl 2-amino-4-(2-chlorophenyl)-7-hydroxy-4H-chro-
mene-3-carboxylate (4h). Yield 95%. IR spectrum, ν, cm–1:
3427, 3385, and 3315 (NH2 and OH), 1670 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 3.40 (3H, s, OCH3);
5.32 (1H, s, CH); 6.40 (1H, s, H-8); 6.43 (1H, d, J = 8.4,
H-6); 6.95 (1H, d, J = 8.4, H-5); 7.00–7.35 (4H, m, H Ar);
7.66 (2H, br. s, NH2); 9.66 (1H, s, OH). 13C NMR
spectrum, δ, ppm: 52.0; 76.9; 103.8; 113.9; 117.2; 129.0;
129.1; 130.6; 130.8; 131.3; 131.4; 132.7; 147.4; 150.4;
158.6; 162.8; 170.0. Found, %: C 61.61; H 4.26; N 4.18.
C17H14ClNO4. Calculated, %: C 61.55; H 4.25; N 4.22.
Ethyl 2-amino-7-hydroxy-4-(4-methoxyphenyl)-4H-
chromene-3-carboxylate (4i). Yield 90%. IR spectrum,
ν, cm–1: 3418, 3305, and 3243 (NH2 and OH), 1660 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 1.08 (3H, t, J = 6.8, CH3);
3.68 (3H, s, OCH3); 3.96 (2H, q, J = 6.8, OCH2); 4.74 (1H, s,
CH); 6.44 (1H, s, H-8); 6.48 (1H, d, J = 8.4, H-6); 6.78 (2H,
d, J = 8.4, H Ar); 6.96 (1H, d, J = 8.4, H-5); 7.05 (2H, d,
J = 8.4, H Ar); 7.55 (2H, br. s, NH2); 9.61 (1H, s, OH).
13C NMR spectrum, δ, ppm: 15.9; 56.5; 60.1; 78.4; 103.6;
113.6 (2C); 115.0; 118.7; 129.4; 131.4; 142.4; 150.6; 158.2;
158.7; 162.5; 170.0. Found, %: C 66.84; H 5.57; N 4.12.
C19H19NO5. Calculated, %: C 66.85; H 5.61; N 4.10.
Methyl 2-amino-4-(3-bromophenyl)-7-hydroxy-4H-
chromene-3-carboxylate (4j). Yield 95%. IR spectrum,
ν, cm–1: 3415, 3303, and 3261 (NH2 and OH) 1663 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 3.49 (3H, s, OCH3);
4.81 (1H, s, CH); 6.43 (1H, s, H-8); 6.48 (1H, d, J = 8.4,
H-6); 7.02 (1H, d, J = 8.4, H-5); 7.12–7.35 (4H, m, H Ar);
7.65 (2H, br. s, NH2); 9.65 (1H, s, OH). 13C NMR
spectrum, δ, ppm: 52.1; 77.3; 103.8; 113.9; 117.7; 123.1;
127.5; 130.3; 131.0; 131.3; 132.1; 150.6; 152.8; 158.6;
162.8; 162.9; 170.0. Found, %: C 54.30; H 3.77; N 3.69.
C17H14BrNO4. Calculated, %: C 54.28; H 3.75; N 3.72.
Antibacterial activity. The antibacterial activity of the
synthesized compounds was examined against S. epidermidis
ATCC 12228 and S. aureus ATCC 6538 as Gram-positive
and E. coli ATCC 8793 as Gram-negative bacteria using
disc diffusion method according to Kirby–Bauer
standards.39 Suspensions of the tested bacteria were
prepared with turbidity equivalent to McFarland tube
No. 0.5 (107–108 CFU/ml). Standard blank discs,
containing 2, 3, and 4 mg of the synthesized compounds,
were prepared using DMSO as solvent and placed on a
Mueller–Hinton agar pre-inoculated with 0.1 ml of
bacterial suspension. Discs of gentamicin 10 µg/disc and
DMSO were used as positive and negative controls,
respectively. All discs were fully dried before the applica-
tion on bacterial lawn. Plates were incubated for 18–24 h at
37°C, aerobically, and the diameter of inhibitory zones
around the discs was measured in millimeter. All
determinations were performed in triplicate, and average
value was reported as the inhibition zone (mean SEM).
Minimum inhibitory concentration was defined as the
lowest concentration of compound that inhibited the
growth of bacteria.
References
1. Raj, T.; Bhatia, R. K.; Sharma, M.; Saxena, A.; Ishar, M. Eur.
J. Med. Chem. 2010, 45, 790.
2. Conti, C.; Monaco, L. P.; Desideri, N. Bioorg. Med. Chem.
2014, 22, 1201.
3. Gourdeau, H.; Leblond, L.; Hamelin, B.; Desputeau, C.;
Dong, K.; Kianicka, I.; Custeau, D.; Boudreau, C.; Geerts, L.;
Cai, S.-X.; Drewe, J.; Labrecque, D.; Kasibhatla, S.; Tseng, B.
Mol. Can. Ther. 2004, 3, 1375.
4. Ashok, D.; Lakshmi1, B. V.; Ravi, S.; Ganesh, A.; Adam, S.
Chem. Heterocycl. Compd. 2015, 51, 462. [Khim Geterotsikl.
Soedin. 2015, 462.]
5. Johannes, C. W.; Visser, M. S.; Weatherhead, G. S.; Hoveyda, A. H.
J. Am. Chem. Soc. 1998, 120, 8340.
6. Bhat, M. A.; Siddiqui, N.; Khan, S. A. Acta Pol. Pharm.
2008, 65, 235.
7. Cheng, J.-F.; Ishikawa, A.; Ono, Y.; Arrhenius, T.; Nadzan, A.
Bioorg. Med. Chem. Lett. 2003, 13, 3647.
8. Ellis, G. In The Chemistry of Heterocyclic of Compounds.
Chromenes, Chromanes and Chromones; Weissberger, A.,
Taylor, EC, Eds.; John Wiley: New York, 1977., Chapter II, p. 11.
9. Hafez, E. A. A.; Elnagdi, M. H.; Elagamey, A. G. A.;
El-Taweel, F. M. A. A. Heterocycles 1987, 26, 903.
10. Joulain, D.; Tabacchi, R. Phytochemistry 1994, 37, 1769.
11. Nolan, K. A.; Zhao, H.; Faulder, P. F.; Frenkel, A. D.;
Timson, D. J.; Siegel, D.; Ross, D.; Burke Jr, T. R.; Stratford, I. J.;
Bryce, R. A. J. Med. Chem. 2007, 50, 6316.
12. Doshi, J. M.; Tian, D.; Xing, C. J. Med. Chem. 2006, 49,
7731.
13. Kemnitzer, W.; Drewe, J.; Jiang, S.; Zhang, H.; Crogan-
Grundy, C.; Labreque, D.; Bubenick, M.; Attardo, G.; Denis, R.;
Lamothe, S.; Gourdeau, H.; Tseng, B.; Kasibhatla, S.; Cai, S. X.
J. Med. Chem. 2008, 51, 417.
14. Zhang, G.; Zhang, Y.; Yan, J.; Chen, R.; Wang, S.; Ma, Y.;
Wang, R. J. Org. Chem. 2012, 77, 878.
15. Kidwai, M.; Saxena, S.; Rahman Khan, M. K.; Thukral, S. S.
Bioorg. Med. Chem. Lett. 2005, 15, 4295.
16. Shah, N. K.; Shah, N. M.; Patel, M. P.; Patel, R. G. J. Chem.
Sci. 2013, 125, 525.
17. He, Y.; Hu, R.; Tong, R.; Li, F.; Shi, J.; Zhang, M. Molecules
2014, 19, 19253.
18. Zonouzi, A.; Mirzazadeh, R.; Safavi, M.; Ardestani, S. K.;
Emami, S.; Foroumadi, A. Iranian J. Pharm. Res. 2013, 12, 679.
19. Mohammed, F. K.; Soliman, A. Y.; Ssawy, A.; Badre, M. G.
J. Chem. Pharm. Res. 2009, 1, 213.
20. Kolla, S. R.; Lee, Y. R. Tetrahedron 2011, 67, 8271.
21. Anderson, D. R.; Hegde, S.; Reinhard, E.; Gomez, L.;
Vernier, W. F.; Lee, L.; Liu, S.; Sambandam, A.; Snider, P. A.;
Masih, L. Bioorg. Med. Chem. Lett. 2005, 15, 1587.
22. Caruana, L.; Mondatori, M.; Corti, V.; Morales, S.; Mazzanti, A.;
Fochi, M.; Bernardi, L. Chem.–Eur. J. 2015, 21, 6037.
23. Fujiwara, M.; Sakamoto, M.; Komeyama, K.; Yoshida, H.;
Takaki, K. J. Heterocycl. Chem. 2015, 52, 59.
24. Khaksar, S.; Rouhollahpour, A.; Talesh, S. M. J. Fluorine
Chem. 2012, 141, 11.
25. Habibi-Khorassani, S. M.; Hazeri, N.; Shahraki, M.; Abbasi, M.;
Karima, M.; Ali, M. Iran. J. Org. Chem. 2013, 5, 1163.
26. Dekamin, M. G.; Eslami, M.; Maleki, A. Tetrahedron 2013,
69, 1074.
27. Qareaghaj, O. H.; Mashkouri, S.; Naimi-Jamal, M. R.; Kaupp, G.
812

Chemistry of Heterocyclic Compounds 2015, 51(9), 808–813
Phosphorus, Sulfur Silicon Relat. Elem. 1995, 101, 207.
RSC Adv. 2014, 4, 48191.
34. Davoodnia, A.; Bakavoli, M.; Vahedinia, A.; Rahimizadeh, M.;
Roshani, M. Heterocycles 2006, 68, 801.
28. Safari, J.; Zarnegar, Z.; Heydarian, M. Bull. Chem. Soc. Jpn.
2012, 85, 1332.
35. Davoodnia, A.; Bakavoli, M.; Soleimany, M.; Tavakoli-
Hoseini, N. Monatsh. Chem. 2009, 140, 355.
36. Davoodnia, A.; Bakavoli, M.; Moloudi, R.; Khashi, M.;
Tavakoli-Hoseini, N. Chin. Chem. Lett. 2010, 21, 1-4.
37. Davoodnia, A.; Khashi, M.; Tavakoli-Hoseini, N.; Moloudi, R.;
Zamani, H. A. Monatsh. Chem. 2013, 144, 677.
38. Khashi, M.; Davoodnia, A.; Chamani, J. Phosphorus, Sulfur
Silicon Relat. Elem. 2014, 189, 839.
39. Bauer, A. W.; Kirby, W. M. M.; Sherris, J. C.; Turck, M.
Am. J. Clin. Pathol. 1966, 45, 493.
29. Makarem, S.; Mohammadi, A. A.; Fakhari, A. R.
Tetrahedron Lett. 2008, 49, 7194.
30. Kundu, S. K.; Mondal, J.; Bhaumik, A. Dalton Trans. 2013,
42, 10515.
31. Shekhar, A. C.; Kumar, A. R.; Sathaiah, G.; Raju, K.;
Rao, P. S.; Sridhar, M.; Narsaiah, B.; Srinivas, P. V. S. S.;
Sridhar, B. Helv. Chim. Acta 2012, 95, 502.
32. Al-Mousawi, S. M.; Elkholy, Y. M.; Mohammad, M. A.;
Elnagdi, M. H. Org. Prep. Proced. Int. 1999, 31, 305.
33. Radwan, S. M.; Bakhite, E. A.; Kamal El-Dean, A. M.
813