Nickel oxide-catalyzed synthesis of 4-amino-2H-chromenes: ITS application in antimicrobial studies and towards protein docking

Article abstract of DOI:10.14233/ajchem.2019.21799

This work involves the synthesis of densely functionalized 2-amino-4H-chromenes by domino Knoevenagel-Michael-cyclization reaction of aromatic aldehydes, β-naphthol and malononitrile in the presence of a catalytic amount of a heterogeneous and reusable gr

Full text of DOI:10.14233/ajchem.2019.21799

Asian Journal of Chemistry; Vol. 31, No. 5 (2019), 1049-1056
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2019.21799
Nickel Oxide-Catalyzed Synthesis of 4-Amino-2H-Chromenes:
Its Application in Antimicrobial Studies and Towards Protein Docking
1
2,
2,*,
A. NEELA , T. CLARINA and V. RAMA
1Department of Chemistry, Rani Anna Govt. College for Women, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627012, India
2Department of Chemistry, Sarah Tucker College, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627012, India
*Corresponding author: E-mail: rama242002@gmail.com
Received: 5 November 2018;
Accepted: 18 December 2018;
Published online: 28 March 2019;
AJC-19329
This work involves the synthesis of densely functionalized 2-amino-4H-chromenes by domino Knoevenagel-Michael-cyclization reaction
of aromatic aldehydes, β-naphthol and malononitrile in the presence of a catalytic amount of a heterogeneous and reusable green NiO
nanoparticle at 50 °C. The biogenic nickel oxide nanoparticles are characterized by Fourier transform infrared radiation, X-ray diffraction
analysis, scanning electron microscopy and transmission electron microscopy. The synthesized chromenes are characterized by IR, NMR
spectra. The synthesized chromene derivatives are studied for microbial inhibition by Kirby-Bauer disc diffusion method using amikacin
and flucanazole as positive control. The compounds are found to have good to moderate antimicrobial activities. Their bio evaluation has
been carried out with a protein and identified promising ligands for Mycobacterium tuberculosis InhA through molecular docking.
Keywords: 2-Amino-4H-chromenes, Knoevenagel-Michael cyclization, Antimicrobial activity, Molecular docking.
also been isolated from the leaves. The active ingredients are
andrographolide and neoandrographolide, which are derivatives
of diterpenoids. Though the main component andrographolide
is slightly soluble in water [9], our focus on green synthesis
makes us to get water extract just to prepare NiO nanoparticles.
The emerging interest to synthesize nanoparticles of nickel oxide
is due to its high catalytic efficiency, strong adsorption ability.
The synthesis of 2-amino-4H-chromenes has already been
prepared by heating a mixture of malono-nitrile, aldehyde and
activated phenol in the presence of hazardous organic bases
such as piperidine [10]. Although different synthetic methods
are available to prepare these heterocyclic systems using
methane sulphonic acid, preyssler heteropoly acid, ammonium
acetate, N,N-dimethylamino-functionalized basic ionic liquid,
CuSO4·5H2O, DBU, chitosan, p-toluene sulfonic acid, Ca(OH)2,
nano-magnesium oxide, hexadecyltrimethyl ammonium
bromide (HTMAB), polyamine catalyst, 2,2,2-trifluoroethanol,
Mg/Al hydrotalcite, microwave-assisted, DBU, PbO, nitriles
have been reviewed [11-28]. To the best of our knowledge
there is no report in the literature using green NiO nanoparticle
as a catalyst for the synthesis of 2-amino-4H-chromenes. With
increasing emphasis on green chemistry, we wish to report a
INTRODUCTION
Green chemistry is increasingly seen as a powerful tool that
researchers can use to evaluate the environmental impact of
nanotechnology. Here an attempt is made to evaluate the catalytic
efficiency of nanoparticles, quantify the greenness of a chemical
process and also to factor in new avenues of synergistic
chromenes. Chromene derivatives are an important class of
heterocyclic compounds, widely distributed in natural products.
Chromene and its derivatives have also been recognized as one
type of ‘privileged medicinal scaffolds’ due to their unique
pharma-cological and biological activities. Among various
chromene family members, 2-amino-4H-chromenes are
especially important for medicinal applications including anti-
microbial [1], antiviral [2], mutagenicity [3], antiprolife-rative
[4], antitumor [5], cancer therapy [6] and central nervous
system activity [7,8]. This highly potent compound is prepared
by multi-component reactions (MCRs) using green NiO nano-
particles as an efficient catalyst. In this work, greener ecofriendly
process is done by water extract of Andrographis paniculata
plant. Andrographis paniculata contains diterpenes, lactones
and flavonoids. Flavonoids mainly exist in the root but have
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1050 Neela et al.
Asian J. Chem.
facile, three components procedure for the selective synthesis
of 2-amino-4H-chromenes using different aromatic aldehydes,
β-naphthol and malononitrile at 50 °C in the presence of green
NiO nanoparticles under stirring conditions. Encouraged by the
results, aromatic aldehydes (1a-j) bearing both electron-
withdrawing and electron donating groups are subjected to
three component condensation reaction to give 2-amino-4H-
chromene derivatives (4a-j) under optimized reaction condition
(15 mg NiO, 50 °C). Further, antimicrobial screening of these
synthesized compounds is done against some bacterial (Gram-
positive as well as Gram-negative) and fungal strains. Mycobac-
terium tuberculosis contains unique signature fatty acids, the
mycolic acids, that are unusually long chain α-alkyl, β-hydroxy
fatty acids of 60-90 carbons encoded by the Mycobacterium
gene InhA is a key catalyst in mycolic acid biosynthesis. Studies
over the years have established that InhA is the primary molecular
target for the past 40 years. Considering the possible application
in biomedical fields, protein docking has also been studied using
Auto dock 4.2 software package.
obtained product of NiO nanoparticle is stored in airtight
container for further analysis.
General procedure for the synthesis of 2-amino-4H-
chromenes:A stoichiometric mixture of an aryl aldehyde (1.0
mmol), malononitrile (1.0 mmol), β-naphthol (1.0 mmol), NiO
(15 mg) and water (15 mL) as a solvent taken in a round bottom
flask, ball-milled for 30 min at 50 °C and then dried in an air
oven at 125 °C. The progress of the reaction is monitored
by TLC (ethyl acetate:n-hexane). Upon completion of the
reaction, the product is washed in hot water and purified by
recrystallization with hot ethanol. The scheme for the multi-
component reaction involving condensation of aromatic alde-
hyde (1), malononitrile (2) and the nucleophilic attack of the
phenolic -OH from naphthol (3) to the CN moiety to afford
2-amino-4H-chromenes is given in Scheme-I.
CN
H
Ar
NH2
OH
CN
Water
NiO/50oC
ArCHO
O
EXPERIMENTAL
CN
1
2
3
All chemicals and reagents are purchased from Merck
and Aldrich and used without further purification. Melting
points are determined with an Electrothermal 9100 melting
point apparatus and are uncorrected. FT-IR spectrum is recor-
ded on Shimadzu FT-IR 8300 series instrument in the range
of 4000-400 cm-1 using potassium bromide pellets. The phase
identity and crystalline size of NiO nanoparticles are charac-
terized by Shimadzu X-ray diffractometer (PXRD-7000) using
Cu-Kα-radiation of wavelength λ = 1.5406 Å. Morphological
features are studied using Hitachi-7000 scanning electron
microscopy and transmission electron microscopy. 1H NMR
and 13C NMR spectra (400MHz,100MHz) are recorded on a
DRX-500 Advance Bruker spectrometer. The percentage of
C, H, N in an organic compound is analyzed using the instru-
ment Elemental Vario EL III over a wide range of concen-
tration. The pharmacological activities against a few selected
microbial strains are tested by using Kirby-Bauer Disc Diffu-
sion method. The prediction of ligand with minimum energy
to target protein is done byAuto dock 4.2 software package. The
3D pose of bound ligand is visualized using different visua-
lizing tools like pymol, pyrx, which can infer the best fit of
ligand.
4 a-j
Scheme-I: Synthesis of 2-amino-4H-chromenes catalyzed by NiO
nanoparticles
Antibacterial assay: The synthesized compounds are
evaluated for their in vitro antibacterial activity against Gram-
negative bacteria such as Escherichia coli, Klebsiella pneumonia,
Pseudomonas aerugenisa, proteus mirabilis and Gram-positive
bacteria Staphylococcus aureus. They are also evaluated for
their in vitro antifungal activity against Candida albicans and
Aspergillus oryzae. Amikacin and flucanazole are used as
refere-nces to evaluate the potency of the compounds using
Kirby-Bauer disc-diffusion method. Most importantly, this
method undoubtedly permits the rapid and quick determination
of the efficiency of a drug by measuring diameter of the zones
of inhibition that result from diffusion of the agent into soaked-
in concentration of various products that can prevent the growth
of bacteria and then kept on the surface of the agar plates that
have been seeded with organism to be tested [29,30]. The plates
are transferred to a box like machine incubator at 37 °C for
approximately 10-20 min and allowed to dry and then placing
the developed mixture on the agar surface. The plates with the
help of a cotton swab are then inoculated with inoculums in
order to ensure the full growth and development of the organism.
As well-spaced intervals, the discs are transferred to the surface
of the agar plates, after incubation, the plates are carefully
examined with the growth inhibition, which is indicated by
the clear and a vivid zone around each disc. The size of the
zone determines the susceptibility of an organism to the drug.
Docking studies: For docking study, we have used Auto
dock 4.2 docking software. The structures of the synthesized
chromenes are drawn using Chem draw and are converted
into their respective pdb format. Molecules are then saved in
pdb format and are used as output file for Docking. A protein
structure (PDB ID:2NSD) is retrieved from Protein Data Bank
using RCSB PDB and is optimized by removing water mole-
Preparation of extract and synthesis of NiO nanopar-
ticles: Fresh leaves of Andrographis paniculata are collected
washed in running tap water and shade dried at room tempe-
rature. Dried leaves are powdered using a mixer mechanically,
sieved and subjected to Soxhlet extraction using deionized
water for 2 h. The aqueous solution obtained after extraction
is subjected to concentration under reduced pressure at 40
5
°C by rotary flash evaporator. To illuminate the effects of the
plant extract, different concentrations (5, 10, 15 and 20 mL)
are used by keeping the source of nickel nitrate at a constant
value. In this work, the reaction mixture is prepared by adding
15 mL of the plant extract (fuel) and nickel nitrate (0.1 g) as a
source of nickel under constant stirring until the colour changes
to black. Then it is kept in a preheated muffle furnace maintained
at 400 10 °C. NiO nanoparticles are formed after 3 h. The

Vol. 31, No. 5 (2019)
Nickel Oxide-Catalyzed Synthesis of 4-Amino-2H-Chromenes 1051
cules, residues and hydrogens are added. The minimized struc-
ture is used as the receptor protein for docking [31].
RESULTS AND DISCUSSION
Phytochemical screening: The leaf extract of the plant
Andrographis paniculata is screened for the presence of phyto-
chemical constituents using various tests and the results are
recorded in Table-1.
TABLE-1
PHYTOCHEMICAL SCREENING OF LEAF EXTRACT
Compound tested
Alkaloids
Tannins
Test
Inference
Dragendorffs reagent
Ferric chloride test
Shibata’s reaction
Hydrogen cyanide
Fehling’s test
–
–
+
+
+
+
Flavonoids
0
5
10
15
20
Cyanogenic glycosides
Reducing sugar
Terpenoid
Fig. 1. EDAX of NiO nanoparticles
Salkowski test
The particle size is calculated from X-ray diffraction images
of NiO powders using Scherrer’s formula [36] D = kλ/β cos θ
where, K is dimensionless number, which is equal to 0.89, λ
is the X-ray wavelength (1.5406 Å for Cu Kα1) employed
and β is full width at half maximum of a diffraction peak
(FWHM) and θ is the diffraction angle. The value of β is calcu-
lated from the following relation, β2 = βs2 – βo2. where, βs
is the measured line width at half maximum and β is the instru-
mental broadeningβo = 0.16 with the apparatus used. Crysta-
lline diameter is deduced for the greatest peak magnitude of
(2 0 0) through Scherrer’s equation. D = 0.89 λ/βcos θand found
as 8.5 nm. X-ray diffraction patterns with no notable diffraction
peaks aside from the typical peaks facilitated by the FCC phase
NiO nanoparticles with exceptional purity.
FT-IR analysis: The NiO nanoparticles are synthesized
in green and environmentally friendly via a simple precipitation
method using leaf extract of Andrographis paniculata and
nickel nitrate as fuel are characterized by various analytical
methods. FT-IR spectrum of biosynthesized NiO nanoparticles
was recorded to identify the capping and efficient stabilization
of the metal nanoparticles by biomolecules present in leaf extract.
The peak at 417 cm-1 belongs to (Ni---O) stretching frequency
[32,33]. The peak at 3516 cm-1 corresponds to alcohols and
phenols.A second typical absorption peak at 2359 cm-1 corres-
ponds to the presence of C=C from the aromatic rings and alkyne
bonds in the biomolecules and the observed peak at 1383 cm-1
is assigned to germinal methyl. These peaks denote stretching
vibrational bands responsible for compounds like flavonoids
and terpenoids and so may be held responsible for efficient capping
and stabilization of obtained NiO nanoparticles [34,35,40].
From the analysis of FT-IR studies, we confirmed that
phenolic compounds have the stronger ability to bind metal
indicating that could possibly form the metal nanoparticles to
prevent agglomeration and thereby stabilized the medium. This
suggests that the biological molecules could possibly perform
dual functions of formation and stabilization of NiO nanopar-
ticles in an aqueous medium.
EDAX: The energy dispersive analysis (Fig. 1) indicates
how the concentration of elements Ni, O and C varies periodi-
cally along the size of atoms being accompanied with maxima
of Ni along 52 %, O along 41 %, C along 7 % of distributions
and there is no evidence of impurity in the composition.
The purity and crystallinity of synthesized NiO nanopar-
ticles are examined using powder X-ray diffraction as shown
in Fig. 2. The peaks positions appearing at 37.5, 43.60, 63.1,
75.7 and 79.7 can be readily indexed as (111), (200), (220),
(311) and (222) crystal planes of the bulk NiO, respectively.
The XRD pattern shows that the samples are single phase and
no other impurities are detected in the distinct diffraction peak
except the characteristic peaks of face-centered cubic phase
NiO is detected. This result shows that the physical phases of
the NiO nanoparticles have higher purity prepared in this work.
The NiO lattice constant calculated from the XRD data is 4.1480 Å.
The obtained data is matched with the JCPDS file no 471049.
5000
4000
3000
2000
1000
0
0
10
20
30
40
50
(°)
Fig. 2. XRD images of NiO nanoparticles
60
70
80
90
2
θ
The sharpness and the intensity of the peaks are quite an
indication of the well crystalline nature of the prepared nano-
particles. Specific surface area has a particular importance in
case of adsorption, heterogeneous catalysis and reactions on
surfaces.
Calculation of specific surface area: The specific surface
area can be calculated by:

1052 Neela et al.
Asian J. Chem.
6000
SSA =
Sauter formula:
(1)
Density of the particle × D
where D is the size of the particles. The density of NiO is 6.68
g/cm3 and the size obtained from XRD study is 8.5 nm thus
the calculated value of the synthesized material NiO is 10567
m2/g. The surface of the synthesized materials is found to be
very large and hence the heterogeneous catalytic property is
in positive response.
SEM analysis: The surface features of the green synthe-
sized NiO nanoparticles are clearly examined through a scanning
electron microscope. The SEM micrographs (Fig. 3a,b) are
recorded at magnifications of 20,000x and 50,000x. From the
micrographs, it is suggested that the particles are polydispersity
and are mostly spherical in shape.
(a)
(b)
Fig. 4. a, b TEM images of NiO nanoparticles, c, d-SAED pattern & its
Histogram
CN
2
O
O
Ar
CH2(CN)2
NiO
NiO
H
Fig. 3. SEM images of NiO nanoparticles
CN
–H2O
–NiO
Ar
H
Ar
3
H
1
A few agglomerated nanoparticles are also observed in
NC
Ar
C
H
NiO
4
some places, thereby indicating possible sedimentation at a
later time. The biological molecules could possibly perform
dual functions of formation and stabilization of NiO nanopar-
ticles in the aqueous medium. The fine particle size results in
a large surface area that in turn, enhances the catalytic activity
of nanoparticles.
N
NiO
OH
Ar
O
C
N
N
NiO
OH
H
5
TEM analysis: TEM images of the prepared NiO nano-
particle samples are shown in Fig. 4a,b. It can be seen that the
NiO particles have nearly spherical shapes with weak agglome-
ration. Fig. 4c,d show the corresponding selected area electron
diffraction pattern and its Histogram. The SAED pattern consists
of five diffraction rings with different radii and one centre. The
diameter of the diffraction ring in SAED pattern is proportional
to (h2 + k2 + l2)1/2, where h, k, l are the Miller indices of the
planes corresponding to the ring, counting from the centre
1st, 2nd, 3rd, 4th and 5th rings correspond to (111), (200),
(220), (311) and (222) planes, respectively. Tropism of the
particles at random and small particles cause the widening of
diffraction rings that made up of many diffraction spots, which
indicate that the nanoparticles are polycrystalline structure.
The SAED pattern also confirms that the NiO nanopar-
ticles are face-centered cubic, which is consistent with the
above XRD results. The Histogram is drawn using MATLAB
software on SAED pattern. This gives a number of particles
distributed with respect to its size. A maximum number of
particles are in the range of 5 to 12 nm. This is reasonably good
concurrent with the corresponding parameter of XRD calcu-
lations obtained from Debye-Scherer equation.
–NiO
NC
Ar
C
NC
Ar
C
NH
NH
OH
H
H
NiO
NiO
OH
6
CN
CN
H
H
Ar
NH2
Ar
NH
H
NiO
–NiO
O
O
8
7
Scheme-II: A plausible reaction mechanism for the synthesis of 2-amino-
4H-chromenes
to generate 2-arylidenemalononitrile (3), which is formed by
Knoevenagel condensation of an activated aldehyde with malo-
nonitrile (2). 2-arylidenemalononitrile after activation with
NiO has undergone nucleophilic attack by β-naphthol (4) to
generate activated intermediate (5), which is simultaneously
aromatized (6), activated, undergoes Michael cyclization (7)
and NiO is recovered to give the product (8).
Preparation of 2-amino- 4H-chromenes catalyzed by
green NiO nanoparticles: A plausible reaction mechanism
for the synthesis of 2-amino-4H-chromenes is outlined in
Scheme-II. At first, aldehyde (1) is activated by NiO catalyst

Vol. 31, No. 5 (2019)
Nickel Oxide-Catalyzed Synthesis of 4-Amino-2H-Chromenes 1053
Initially, the efforts are focused on the evaluation of varying
parameters such as solvent and a catalytic amount of the catalyst
on the rate and the yields of obtained 2-amino-4H-chromenes
by reacting β-naphthol, aryl aldehydes and malononitrile from
the principles of green chemistry point of view.
The results in Table-2 suggest that water is the best solvent
in terms of yield and reaction time. In order to examine the
catalytic activity of NiO nanoparticles for the preparation of
chromenes a mixture of benzaldehyde (1 mmol), malononitrile
(1 mmol) and β-naphthol (1 mmol) is stirred in water. Optimi-
zation is carried out with variation in the reaction temperature
and catalyst amount. No product is observed at room tempe-
rature.As the temperature is increased to 50 °C the conversion
rate increased as well. From the optimization using a various
amount of catalyst loading, it is found that the optimal catalyst
amount is 15 mg (Table-3).
Spectral data
2-Amino-4-phenyl-4H-chromene-3-carbonitrile (4a):
White powder, FT-IR (KBr, νmax, cm–1): 3430 (NH2), 2223
(CN), 1686 (C=C), 1590 (C-O); 1H NMR (DMSO-d6, 400 MHz),
δH (ppm) 8.5 (s, 2H, NH2), 7.64-7.6 (m, 3H,ArH), 7.94-7.96 (d,
1H, ArH). Elemental analysis: Calculated (%) for C20H14N2O
(298.34): C, 80.51; H, 4.7; N, 9.3. Found: C, 80.32; H, 4.24;
N, 8.46.
2-Amino-4-(4-hydroxyphenyl)-4H-chromene-3-carbo-
nitrile (4b): White powder, FT-IR (KBr, νmax, cm–1): 3459
(NH2,OH), 3346 (CH), 2189 (CN), 1639 (C=C), 1593 (C-O);
1H NMR (DMSO-d6, 400 MHz), δ (ppm): 7.6 (d, 1H, ArH) 7-
7.4 (m, 3H) 9.7 (s, 2H, NH2). Elemental analysis: Calculated
(%) for C20H14N2O2 (314.34): C, 76.41; H, 4.4; N, 8.9. Found:
C, 76.30; H, 4.0; N, 8.9.
2-Amino-4-(3-hydroxyphenyl)-4H-chromene-3-carbo-
nitrile (4c): White powder, FT-IR (KBr, νmax, cm–1): 3431 (NH2,
1
OH), 3337 (CH), 2205 (CN), 1665 (C=C), 1590 (C-O); H
TABLE-2
NMR (DMSO-d6, 400 MHz), δ (ppm): 9.5 (s, 1H, OH), 7.06-
7.27 (m, 5H), 5.07 (s, 1H, H-4); Elemental analysis: Calculated
(%) for C20H14N2O2 (314.34): C, 76.41; H, 4.4; N, 8.9. Found:
C, 76.26; H, 4.0; N, 8.6.
EFFECT OF THE SOLVENT ON THE
YIELD, REACTION TIME AND YIELD
Solvent
Free
Time (h)
Yield (%)*
3
0.5
3
80
98
88
70
83
60
20
Water
2-Amino-4-(2-hydroxyphenyl)-4H-chromene-3-carbo-
nitrile (4d): Yellow powder, FT-IR (KBr, νmax, cm–1): 3456
(NH2, OH), 3334 (NH2), 2194 (CN), 1641 (C=C), 1573 (C-
O); 1H NMR (DMSO-d6, 400 MHz), δ (ppm): 8.3 (s, 1H), 7.4
(s, 2H, NH2), 7.57-7.59 (m, 3H, ArH), 6.63 (s, 2H, ArH).
Elemental analysis: Calculated (%) for C20H14N2O2 (314.34):
C, 76.41; H, 4.4; N, 8.9. Found: C, 76.38; H, 4.3; N, 8.7.
2-Amino-4-(4-nitrophenyl)-4H-chromene-3-carbo-
nitrile (4e): Brown powder, FT-IR (KBr, νmax, cm–1): 3339
(NH2), 2190 (CN), 1635 (CO), 1585 (C=C), 1251 (C-O), 1379
(NO2); 1H NMR (DMSO-d6, 400 MHz), δ (ppm): 8.85 (s, 1H),
7.07 (t, J ¼ 8 HZ, 1H), 6.67–6.64 (m, 3H), 5.74 (s, 2H), 4.31
(s, 1H), 4.05–4.02 (m, 2H), 2.35 (s, 3H), 1.13 (t, 3H) Elemental
analysis: Calculated (%) for C20H13N3O3 (343.33): C, 69.95;
H, 3.8; N, 12.2. Found: C, 69.9; H, 3.6; N, 12.1.
2-Amino-4-(2-nitrophenyl)-4H-chromene-3-carbo-
nitrile (4f): Brown powder, FT-IR (KBr, νmax, cm–1): 3328
(NH2), 2202 (CN), 1693 (CO); 1369 (NO2); 1H NMR (DMSO-
d6, 400 MHz), δ (ppm): d 8.85 (s, 1H), 7.07 (t, 1H), 6.67–6.64
(m, 3H), 5.74 (s, 2H), 4.31 (s, 1H), 4.05–4.02 (m, 2H), 2.35
(s, 3H), 1.13 (t, 3H). Elemental analysis: Calculated (%) for
C20H13N3O3 (343.33): C, 69.95; H, 3.8; N, 12.2. Found: C,
69.9; H, 3.7; N, 12.3.
Ethanol
Water/ethanol (1:2)
n-Hexane
CH2Cl2
2
6.5
24
10
DMSO
TABLE-3
OPTIMIZATION OF REACTION CONDITION
Catalyst (mg)
Temp. (°C)
Yield (%)
5
10
15
25
50
50
60
70
89
Following this, a series of 2-amino-4H-chromenes have
been synthesized at 50 °C in the presence of a catalytic amount
(15 mg) of NiO nanoparticle via one-pot three-component
reactions of malononitrile, aromatic aldehydes and β-naphthol.
The synergistic effects of multicomponent reactions have been
successfully demonstrated to offer an easy way for the synthesis
of these compounds in excellent yields. In the scope and limi-
tations of this procedure, a series of experiments is carried out
using a variety of aromatic aldehydes (Table-4).
TABLE-4
PREPARATION OF 2-AMINO-4H-CHROMENES
Ar
Phenol
Product
4a
4b
4c
4d
4e
4f
4g
4h
4i
Time (min)
Yield (%)
m.p. found (°C)
273-275
274-277
228-230
254-256
185-186
260-262
244-246
221-223
240-244
272-274
m.p. reported
(278-279) [37]
C6H5
30
50
60
60
60
50
50
60
50
60
99
76
82
88
91
89
87
82
86
89
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
β-Naphthol
[37]
4-OH C6H4
3-OH C6H4
2-OH C6H4
4-NO2 C6H4
2-NO2 C6H4
C4H3S
C5H4N
C4H3O
5-Br-OHC6H3
(280-282) [37]
[37]
(225-227) [37]
[37]
(259-261) [37]
[37]
(187-188) [[3377]]
(262-268) [[3377]]
(240-243) [[3388]]
(224-226) [[3388]]
(246-248) [[3388]]
This work
4j

1054 Neela et al.
Asian J. Chem.
2-Amino-4-(thionyl)-4H-chromene-3-carbonitrile (4g):
The drug amikacin is used as a positive control for anti-
bacterial activity and Flucanazole as a positive control drug
for antifungal activity (Table-6).
Yellow powder, FT-IR (KBr, νmax, cm–1): 3422 (NH2), 2925
1
(C-H), 2222 (CN), 1464 (CO), 1630 (C=C), 1257 (C-S); H
NMR (DMSO-d6, 400 MHz), δ (ppm): 8.67 (s, 1H), 8.26 (d,
1H, ArH), 7.37-739 (m, 3H, ArH), 7.94 (d, 1H, ArH).
Elemental analysis: Calculated (%) for C18H12N2OS (304.37):
C, 71.0; H, 3.9; N, 9.2. Found: C, 71.3; H, 3.8; N, 9.4.
2-Amino-4-(pridyl)-4H-chromene-3-carbonitrile (4h):
Brown solid, FT-IR (KBr, νmax, cm–1): 3440 (NH2), 2204 (CN),
As seen from the data present in Table-6, it is evident that
among all the compounds (4b, 4c, 4d, 4i and 4j) show modest
inhibition whereas other compounds have either poor inhibi-
tory activity or do not show any inhibition. Interestingly, com-
pound 4g is the most potent for the inhibition of Klebsiella
pneumonia. Moreover, it is also evident that among all the
compounds (4b, 4c, 4i and 4j) show fungus inhibition whereas
other compounds do not show any inhibition.
Protein docking: The chromene ring is an important
pharmacophore in modern drug discovery. The knowledge
gained by various researchers has suggested that substituted
chromenes which interact easily with the receptors and possess
different pharmacological activities with lower toxicity. In this
study, we identify it via docking and their relative stabilities
are evaluated, using free energy simulations. Fig. 5 shows the
synthesized ligands used for docking.
It is observed that among all the designed compounds,
the compound 4f shows better binding nature, which resulted
in a decrease in the energy value [39] and also the compound
4j. These compounds show a decreased energy values (-8.55),
(-8.32) which means that these compounds are more compa-
tible with the receptor than other designed chromene deriva-
tives and fit well in the receptor cavity forming energetically
most stable drug receptor complex. The energy values are
calculated and given in Table-7.
1
1472 (CO) 2881 (C-H); H NMR (DMSO-d6, 400 MHz), δ
(ppm): 8.6 (s, 1H), 7.1-7.33 (t, 8 H, 1H), 7.8 (d, 1H, ArH)
Elemental analysis: Calculated (%) for C19H13N3O (299.32):
C, 76.23; H, 4.3; N, 14.0. Found: C, 75.32; H, 4.24; N, 13.46.
2-Amino-4-(furfuryl)-4H-chromene-3-carbonitrile (4i):
FT-IR (KBr, νmax, cm–1): 3457 (NH2), 2227 (CN), 1606 (C=C),
1
1455 (CO), 1070 (C-C) H NMR (DMSO-d6, 400 MHz), δ
(ppm): 9.7 (s, 1H), 7.54-7.51 (t, 8 H, 1H), 7.27–7.23 (m, 3H);
Elemental analysis: Calculated (%) for C18H12N2O2 (288.30):
C, 74.99; H, 4.1; N, 9.7. Found: C, 74.32; H, 4.2; N, 8.46.
2-Amino-4-(5-bromo-2-hydroxyphenyl)-4H-chromene-
3-carbonitrile (4j): Yellow solid, FT-IR (KBr, νmax, cm–1): 3460
1
(NH2), 2189 (CN), 1479 (CO), 2883 (C-H), 595 (C-Br); H
NMR (DMSO-d6, 400 MHz): 8.3 (s, 1H), 7.29-7.25 (t, 8H,
1H), 7.59–7.56 (m, 3H); 13C NMR (100 MHz) 32.3, 37.1, 48.9,
115.5, 116.3, 117.2, 119.3, 124.2, 125.4, 128.7, 129.5134.1,
135.4, 146.9, 153.4, 160.3, 163.4 Elemental analysis: Calcu-
lated (%) for C20H13N2O2Br (392.30): C, 61.08.; H, 3.33; N,
7.12. Found: C, 60.72; H, 3.2; N, 7.16.
Recycling of the catalyst: The reusability study on the
catalyst is done by taking the condensation reaction of benzal-
dehyde, malononitrile and β-naphthol, as a model reaction
for the recovery investigations. The catalyst is recovered three
times by simple filtration and washed with acetone, dried in
an oven each time. The results are summarized in Table-5.
The catalytic activity of the catalyst is almost the same as
that of freshly used.
Conclusion
In the present investigation, a search of a new source for
the production of NiO nanoparticles is successfully carried
out. We have developed an efficient and green approach for
the one pot three components synthesis of chromenes using
NiO nanoparticles as a biodegradable, inexpensive and reusable
catalyst. The salient features of our methodology are simple
workup, devoid of toxic chemicals, less time consuming, high
yield products, easy isolation and also an agreement with the
overarching principles of green chemistry. We have utilized
the water extract of Andrographis paniculata, the natural and
low-cost biomaterial for the synthesis of NiO nanoparticles.
The components in the water extract serve as reducing, capping
and stabilizing agents for nanoparticle generation. FTIR analysis
evidences the organic groups involved in the bioconversion of
NiO nanoparticles. The EDAX spectrum analysis confirms the
generation of NiO nanoparticles. The XRD and SEM analysis
Antimicrobial evaluation: The synthesized chromene
derivatives (4a-j) are studied for microbial inhibition by Kirby-
Bauer disc diffusion method.
TABLE-5
REUSABILITY OF NiO NANOPARTICLES
Run
1
2
Time (h)
Yield (%)
1
1
1
98
96
93
3
TABLE-6
ANTIBACTERIAL AND ANTIFUNGAL ACTIVITIES OF SYNTHESIZED 2-AMINO-4H-CHROMENES
Control
(mm)
Bacteria/Fungus
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
Antibacterial
Escherichia coli
9
10
9
9
–
11
15
10
8
11
16
11
16
17
14
18
16
–
12
9
11
8
13
–
–
32
–
11
24
–
20
–
–
–
20
16
–
11
18
13
12
–
13
15
21
32
20
27
23
Klebsiella pneumonia
Pseudomonas aeruginosa
Proteus mirabilis
14
11
12
14
Staphylococcus aureus
11
–
Antifungal
Candida albicans
Aspergillus oryzae
10
–
12
15
17
25
18
–
10
–
17
–
10
–
17
–
28
27
16
16
24
28

Vol. 31, No. 5 (2019)
Nickel Oxide-Catalyzed Synthesis of 4-Amino-2H-Chromenes 1055
OH
HO
OH
O2N
CN
CN
CN
CN
CN
NH2
NH2
NH2
NH2
NH2
O
O
O
O
O
4c
4e
4b
4d
4a
OH
NO2
CN
CN
CN
CN
CN
NH2
NH2
NH2
NH2
NH2
N
O
Br
S
O
O
O
O
O
4g
4f
4h
4i
4j
Fig. 5. Structure of synthesized ligands used for docking
TABLE-7
DOCKING RESULTS OF SYNTHESIZED 2-AMINO-4H-CHROMENES
Compound docked
Binding energy (Kcal/mol)
Types and number of interactions
Residues involved
MET A:161
PHE A:149
π-sulfur-1
π-π stacked-1
ALA A:191, PHE A:149
ILE A:194
Amide-π stacked -2
Hydrogen bond-1
π-alkyl-1
van der Walls-1
Carbon hydrogen bond
-8.27
4a
MET A:147
MET A 232
PRO A 193
PHE A:149
ALA A:191
ILE A:194
MET A:147
GLY A:192
PRO A 193
π-π stacked-1
Amide-π stacked -1
Hydrogen bond-1
π-alkyl-1
van der Walls-1
Carbon hydrogen bond
4b
-7.83
PHE A:149
ALA A:191
ILE A:194
π-π stacked-1
Amide-π stacked -1
Hydrogen bond-1
π-alkyl-2
4c
-7.93
-7.62
MET A:147, ILEA: 202
GLY A:192
van der Walls-1
PHE A:149
ILE A:194
MET A:199
GLY A:192
π-π stacked-1
Hydrogen bond-1
π-alkyl-1
4d
van der Walls-1
MET A:161
PHE A:149
ALA A:191
ILE A:194
MET A:147
MET A 232
TYR A: 158
π-sulfur-1
π-π stacked-1
Amide-π stacked -2
Hydrogen bond-1
π-alkyl-1
van der Walls-1
Carbon hydrogen bond
-8.08
4e
PHE A:149
π-π stacked-1
Hydrogen bond-3
π-alkyl-2
TYR A:158, LYS A:165, MET A:103
ALA A:191, ALA A:198
GLY A:96
-8.55
-7.80
-7.83
4f
4g
4h
van der Walls-1
PHE A:149
ALA A:191
TYR A:158
MET A:147
π-π stacked-1
Amide-π stacked -1
Hydrogen bond-1
π-alkyl-1
PHE A:149
ALA A:191
TYR A:158
π-π stacked-1
Amide-π stacked -1
Hydrogen bond-1
π-alkyl-2
MET A:147, ILE A:202

1056 Neela et al.
Asian J. Chem.
PHE A:149
ALA A:191
TYR A:158, ILE A:194
MET A:161
π-π stacked-1
Amide-π stacked -1
Hydrogen bond-2
π-alkyl-1
van der Walls-1
Hydrogen bond-2
π-alkyl-3
4i
-8.11
-8.32
PRO A:193
ILE A:194, TYR A:158
PROA:193, MET A:199, ALA A:191
MEY A 161
4j
van der Walls-1
π-σ-1
PHE A:149
13. N.K. Shah, N.M. Shah, M.P. Patel and R.G. Patel, J. Chem. Sci., 125,
525 (2013);
https://doi.org/10.1007/s12039-013-0421-y.
14. L. Chen, X.J. Huang, Y.Q. Li, M.Y. Zhou and W.J. Zheng, Monatsh.
Chem., 140, 45 (2009);
https://doi.org/10.1007/s00706-008-0008-3.
15. F.K. Behbahani and S. Maryam, J. Korean Chem. Soc., 57, 357 (2013);
https://doi.org/10.5012/jkcs.2013.57.3.357.
support the crystallinity and surface morphology of the
biosynthesized nanoparticles. The average crystallite size for
the intense peak measured is 8.5 nm from XRD analysis. TEM
and SAED analyses confirm the size of prepared NiO nanopar-
ticles. The synthesized compounds are screened for antibac-
terial activity and it is observed that 2-amino-4-(5-bromo-2-
hydroxyphenyl)-4H-chromene-3-carbonitrile) shows the modest
activity. In molecular docking studies, the docking scores
reveal the binding capacity between ligands and InhA enzyme.
The inhibition of InhA disrupts the biosynthesis of mycolic
acid which is a central constituent of bacterial cell wall. There-
fore, compounds 4f, 4j are stable and front-line ligands to
overcome the drug resistance of M. tuberculosis InhA protein.
16. Z. Afsaneh, M. Roghieh, S. Maliheh, K. Sussan, S.E. Ardestani and F.
Alireza, Iran. J. Pharm. Res., 12, 679 (2013).
17. H.M. Al-Matar, K.D. Khalil, H. Meier, H. Kolshorn and M.H. Elnagdi,
ARKIVOC, 288 (2008);
https://doi.org/10.3998/ark.5550190.0009.g27.
18. B. Baghernejad, M.M. Heravi and H.A. Oskooie, J. Korean Chem. Soc.,
53, 631 (2009);
https://doi.org/10.5012/jkcs.2009.53.6.631.
19. S.R. Kolla and Y.R. Lee, Tetrahedron, 67, 8271 (2011);
https://doi.org/10.1016/j.tet.2011.08.086.
ACKNOWLEDGEMENTS
20. D. Kumar, V.B. Reddy, B.G. Mishra, R.K. Rana, M.N. Nadagouda and
R.S. Varma, Tetrahedron, 63, 3093 (2007);
https://doi.org/10.1016/j.tet.2007.02.019.
The authors are grateful to SarahTucker College Tirunelveli,
India for the partial support of this work.
21. T.S. Jin,A.Q. Wang, X. Wang, J.S. Zhang and T.S. Li, Synlett, 871 (2004);
https://doi.org/10.1055/s-2004-820025.
22. R.L. Magar, P.B. Thorat, V.B. Jadhav, S.U. Tekale, S.A. Dake, B.R. Patil
and R.P. Pawar, J. Mol. Catal. Chem., 374-375, 118 (2013);
https://doi.org/10.1016/j.molcata.2013.03.022.
23. S. Khaksar,A. RouhollahpourandS.M.Talesh,J. Fluor. Chem.,141,11(2012);
https://doi.org/10.1016/j.jfluchem.2012.05.014.
24. M.P. Surpur, S. Kshirsagar and S.D. Samant, Tetrahedron Lett., 50, 719 (2009);
https://doi.org/10.1016/j.tetlet.2008.11.114.
25. D.S. Raghuvanshi and K.N. Singh, ARKIVOC, 305 (2010);
https://doi.org/10.3998/ark.5550190.0011.a25.
26. J.M. Khurana, B. Nand and P. Saluja, Tetrahedron, 66, 5637 (2010);
https://doi.org/10.1016/j.tet.2010.05.082.
27. A.V.B.K. Borhade, B.K. Uphade and D.R. Tope, J. Chem. Sci., 125,
583 (2013);
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
regarding the publication of this article.
REFERENCES
1. M.M. Khafagy, A.H.F. Abd El-Wahab, F.A. Eid and A.M. El-Agrody,
Farmaco, 57, 715 (2002);
https://doi.org/10.1016/S0014-827X(02)01263-6.
2. W.P. Smith, L.S. Sollis, D.P. Howes, C.P. Cherry, D.I. Starkey, N.K.J.
Cobley, H. Weston, J. Scicinski, A. Merritt, A. Whittington, P. Wyatt,
N. Taylor, D. Green, R. Bethell, S. Madar, R.J. Fenton, P.J. Morley, T.
Pateman and A. Beresford, Med. Chem., 41, 787 (1998);
https://doi.org/10.1021/jm970374b.
https://doi.org/10.1007/s12039-013-0396-8.
28. A.A. Harb, A.M. El-Maghraby and S.A. Metwally, Coll. Czech. Chem.
Commun., 57, 1570 (1992);
3. K. Hiramoto, A. Nasuhara, K. Michiloshi, T. Kato and K. Kikugawa,
Mutat. Res., 395, 47 (1997);
https://doi.org/10.1016/S1383-5718(97)00141-1.
4. G. Bianchi and A. Tava, Agric. Biol. Chem., 51, 2001 (1987);
https://doi.org/10.1080/00021369.1987.10868286.
5. S.J. Mohr, M.A. Chirigos, F.S. Fuhrman and J.W. Pryor, Cancer Res.,
35, 3750 (1975).
6. D.R. Anderson, S. Hegde, E. Reinhard, L. Gomez, W.F. Vernier, L.
Lee, S. Liu, A. Sambandam, P.A. Snider and L. Masih, Bioorg. Med.
Chem. Lett., 15, 1587 (2005);
https://doi.org/10.1135/cccc19921570.
29. B. Mahesh and S. Satish, World J. Agric. Sci., 4, 839 (2008).
30. K. Soo-Hwan, H.S. Lee, D.S. Ryu, S.J. Choi and D.S. Lee, Korean J.
Microb. Biotechnol., 39, 77 (2011).
31. O. Trott and A.J. Olson, J. Comput. Chem., 31, 455 (2010).
32. H.T. Zhang, J. Ding and G.M. Chow, Mater. Res. Bull., 44, 1195 (2009);
https://doi.org/10.1016/j.materresbull.2008.09.042.
33. B.S. Siddiqui, F. Afshan, Ghiasuddin, S. Faizi, S.N.H. Naqvi and R.M.
Tariq, Phytochemistry, 53, 371 (2000);
https://doi.org/10.1016/j.bmcl.2005.01.067.
https://doi.org/10.1016/S0031-9422(99)00548-8.
7. F. Eiden and F. Denk, Arch. Pharm., 324, 353 (1991);
https://doi.org/10.1002/ardp.19913240606.
8. S. Makarem, A.A. Mohammadi and A.R. Fakhari, Tetrahedron Lett.,
49, 7194 (2008);
34. Q. Huang, D. Li, Y. Sun, Y. Lu, X. Su, H. Yang, Y. Wang, W. Wang, N.
Shao, J. Hong and C. Chen, Nanotechnology, 18, 105104 (2007);
https://doi.org/10.1088/0957-4484/18/10/105104.
35. J. Parekh and S.V. Chanda, Turk. J. Biol., 31, 53 (2006).
36. D. Mandal, M.E. Bolander, D. Mukhopadhyay, G. Sarkar and P.
Mukherjee, Appl. Microbiol. Biotechnol., 69, 485 (2006);
https://doi.org/10.1007/s00253-005-0179-3.
37. X.-S. Wang, G.-S. Yang and G. Zhao, Tetrahedron, 19, 709 (2008);
https://doi.org/10.1016/j.tetasy.2008.02.018.
38. A.F. Latif, Indian J. Chem., 29B, 664 (1990).
39. R. Siva Kumar, P. Kumarnallasivan, P.R. Vijai Anand, R. Pradeepchandran,
K.N. Jayaveera and R.Venkatnarayanan, Der Pharm. Chem., 2, 100 (2010).
40. T. Clarina, G.R. Priya Dharsini and V. Rama, Chem. Sci. Trans., 6, 523 (2017);
https://doi.org/10.7598/cst2017.1413.
https://doi.org/10.1016/j.tetlet.2008.10.006.
9. M. Chen, C. Xie and L. Liu, J. Chem. Eng. Data, 55, 5297 (2010);
https://doi.org/10.1021/je100344z.
10. A.G.A. Elagamay and F.M.A.A. El-Taweel, Indian J. Chem., 29B, 885
(1990).
11. M.M. Heravi, B. Baghernejad and H.A. Oskooie, J. Chin. Chem. Soc.
(Taipei), 55, 659 (2008);
https://doi.org/10.1002/jccs.200800098.
12. M.M. Heravi, K. Bakhtiari, V. Zadsirjan, F.F. Bamoharram and O.M.
Heravi, Bioorg. Med. Chem. Lett., 17, 4262 (2007);
https://doi.org/10.1016/j.bmcl.2007.05.023.