Sustainable construction: Admicellar catalysed synthesis of pyrimido[4,5-b]quinolines in an aqueous system

Article abstract of DOI:10.1039/c5ra00791g

A simple and highly efficient strategy has been documented for the rapid and convenient synthesis of 1-methyl-5-phenylbenzo[g]pyrimido[4,5-b]quinoline-2,4,6,11(1H,3H)-tetraone from aldehydes, 2-hydroxynaphthalene1,4dione and 6-aminouracil in the presence of nano ZnO under an aqueous admicellar system at 80°C. Results show that nano ZnO is a potential catalyst for the synthesis of pyrimido[4,5-b]quinoline. Nano ZnO was recovered and reused efficiently several times for the synthesis of the desired product which is an essential parameter of green synthesis. The reported method represents an eco-friendly alternative to classical protocols. Nano size of ZnO was confirmed by EDS, transmission electron microscopy (TEM) and XRD techniques.

Full text of DOI:10.1039/c5ra00791g

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Sustainable construction: admicellar catalysed
synthesis of pyrimido[4,5-b]quinolines in an
Cite this: RSC Adv., 2015, 5, 27603
aqueous system†
a
I. R. Siddiqui, Pragati Rai,a Rahila,a Hoezyfa Sagira and Prashant Singhb
*
A simple and highly efficient strategy has been documented for the rapid and convenient synthesis
of
1-methyl-5-phenylbenzo[g]pyrimido[4,5-b]quinoline-2,4,6,11(1H,3H)-tetraone
from
aldehydes,
2-hydroxynaphthalene1,4dione and 6-aminouracil in the presence of nano ZnO under an aqueous
admicellar system at 80 ꢀC. Results show that nano ZnO is a potential catalyst for the synthesis of
pyrimido[4,5-b]quinoline. Nano ZnO was recovered and reused efficiently several times for the synthesis
of the desired product which is an essential parameter of green synthesis. The reported method
represents an eco-friendly alternative to classical protocols. Nano size of ZnO was confirmed by EDS,
transmission electron microscopy (TEM) and XRD techniques.
Received 7th February 2015
Accepted 27th February 2015
DOI: 10.1039/c5ra00791g
www.rsc.org/advances
where the organic syntheses can be promoted by the nano
catalyst under admicellar system. Formation of admicelles plays
Introduction
vital role in many practical applications, including ore otation,
petroleum recovery, food science, agriculture etc. and can
notably improve the result of many reactions.
In recent years, with the vogue of green chemistry, eco-friendly
chemical processes or strategies have attracted tremendous
attention.1 Taking into consideration that organic solvents are
the main source of hazardous waste, the development of
methods with diminished use of organic solvents is of high
priority. Therefore, the use of water as a green solvent for
organic synthesis is economical and environmentally benign.
But in some cases, due to low solubility of the organic substrates
in aqueous medium, surfactants were efficiently used to facili-
tate the organic reactions through the formation of micelles.2
Recently, research has been conducted toward the synthesis
and use of metal oxide nanoparticles due to their distinctive
properties in comparison to the bulk metals.
Another foremost reaction template in aqueous medium
called ‘admicelle’ is a relatively new aspect in science. At a lower
surfactant concentration, admicelles are formed in water by the
adsorption of surfactant on solid–liquid interfaces of nano
particles.3 In aqueous condition, nanoparticles are accumulated
to form big particles having low catalytic activity and in these
cases, use of a surfactant forms admicelles. The hydrophobic
core present within admicelles furnishes a region which
dissolves the water-insoluble organic compounds. This
Furthermore, several studies have focused on ndings water-
compatible and reusable catalysts.4 Among various metal oxide
ZnO nanoparticles, have received considerable attention
because of their unique properties and remarkable applications
in various elds. It is well known that nano ZnO as a catalyst
plays an important role in synthetic organic chemistry because
of its high catalytic activity, reusability, easy handling and
nontoxicity.5a
Molecules which contain more than one nucleus recently
gain attention due to their remarkable chemical and biological
properties. Composite molecules are chemical units composed
of two (or more) structural units in which characteristics of
several components have been altered to give rise to altogether
new set of properties. Using the concept of molecular hybrid-
ization, pyrimidine and quinoline have been combined to
access
a hybrid molecule-pyrimido[4,5-b]quinoline which
possess broad range of biological proles. Their importance is
certied by the fact that a number of workers have documented
their synthesis.5b–d Although many publications have already
reported synthesis of pyrimido[4,5-b]quinoline but these
protocols suffers from various drawbacks such as use of
expensive catalysts, high amount of promoter, toxic or volatile
organic solvents, harsh reaction conditions or release of
hazardous wastes etc.
Pyrimido[4,5-b]quinoline derivatives have attracted consid-
erable interest because they exhibit promising biological activ-
ities such as antimalarial, anticancer, antimicrobial and anti-
inammatory.6 These advantages encouraged us towards the
phenomenon is termed as ‘adsolubilization’.
A reaction
template is thus formed on the surface of the nanoparticles
aLaboratory of Green Synthesis, Department of Chemistry, University of Allahabad,
Allahabad-211002, India. E-mail: dr.irsiddiqui@gmail.com
bNanotechnology Application Centre, University of Allahabad, Allahabad, 211002,
India
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c5ra00791g
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Scheme 1 Synthesis of 1-methyl-5-phenylbenzo[g]pyrimido[4,5-b]-
quinoline-2,4,6,11(1H,3H)-tetraone.
development of a new environmentally benign synthetic
method, of pyrimido[4,5-b]quinoline system by using equi-
molecular amounts of 2-hydroxynaphthalene1,4dione (1), 4-
chlorobenzaldehyde (2) and 6-aminouracil (3) in CTAB–water
system in the presence of nano ZnO. The general synthetic
protocol of the present investigation is shown in Scheme 1.
Fig. 2 XRD pattern of fresh nano ZnO (red line), reused ZnO (black
line) nano particle.
Result and discussion
ZnO nano particle was synthesised by using the reported
methodology7 with little modication. For a typical synthesis of
ZnO nano particle, appropriate amount of Zinc acetate was
taken in 100 ml of methanol and continuously stirred for
0.5 hours at room temperature. Simultaneously, KOH solution
was prepared in 100 ml of methanol. Now, both the solutions
were mixed with constant stirring for 10 hours. The nal solu-
tion was allowed to cool at room temperature and aged over-
night. This solution was centrifuged and washed several times
with absolute ethanol and water in order to remove unnecessary
impurities. The desired product was placed in a vacuum oven
ZnO nano particles were calculated by Debye–Scherrer's equa-
tion and observed around ꢁ15 nm in size. The morphology of
ZnO was noticed and found to be spherical in nature having
diameters ranging from 15 to 25 nm. On further investigation
(Fig. 3) the size and morphology of nano ZnO was analyzed by
TEM images and the inset of the g shows the representative
selected area electron diffraction (SAED) pattern which display
that the prepared ZnO nanoparticles were polycrystalline in
nature. The increased catalytic activity of the synthesized nano
ZnO over commercial bulk catalysts due to the higher surface to
volume ratio, thus resulting in higher surface concentrations of
the reactive sites.
ꢀ
for 10 h at 50 C to get powders of ZnO nanoparticles.
ZnO nano particles are characterized by EDS pattern which
displays the peak of oxygen and zinc showing the elemental
composition (Fig. 1). Fig. 2 shows the XRD pattern of ZnO nano
particles (red line). XRD spectra show broad peaks at the posi-
tions of 31.59ꢀ, 34.22ꢀ, 36.09ꢀ, 47.53ꢀ, 56.55ꢀ, 62.70ꢀ, 67.81ꢀ and
79.87ꢀ, which are in good agreement with the standard JCPDS
In our preliminary experiment, we have investigated the
optimization reaction condition regarding with both the cata-
lyst and the solvent. For this purpose, 2-hydroxynaphthalene1,4-
ꢀ
ꢀ
le for ZnO (JCPDS 36-1451, a ¼ b ¼ 3.249 A, c ¼ 5.206 A) and
can be indexed as the hexagonal wurtzite structure of ZnO
having space group P63mc. All the available reections of the
XRD phases have been tted with Gaussian distribution. The
broadening of XRD peaks (i.e. Scherrer's broadening) indicating
the formation of nano particles of ZnO. The particle size, d, of
Fig. 3 Shows the representative TEM image of the prepared nano
Fig. 1 Shows the EDS pattern of the ZnO nano particle.
27604 | RSC Adv., 2015, 5, 27603–27609
ZnO.
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Table 2 Optimization of catalyst on the yield of product in aqueous
dione (1), 4-chlorobenzaldehyde (2) and 6-aminouracil (3) were
chosen as model substrates for the synthesis of representative
compound (4a). Initially we have performed the reaction
employing nano ZnO as a catalyst and water as a solvent
because cyclization reactions occur more easily in polar
solvents8 and also from green synthesis point of view water has
been proved to be best for solution-phase chemistry.9
The reaction occurs but the product was obtained in traces
(Table 1, entry 1).
solution of CTABa
Entry
Catalyst
Amount (mol%)
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
InCl3
SiO2
15
15
15
15
5
10
15
20
10
10
10
10
10
6
30
32
25
22
54
73
95
95
Alumina
AcOH
Nano ZnO
Nano ZnO
Nano ZnO
Nano ZnO
To avoid this problem we turned our attention to use
cetryltrimethyl ammonium bromide (CTAB: cmc value
0.92 mM) as a surfactant. It is the best to utilize CTAB because it
acts as emulsifying agent when mixed with organic substrate to
form colloidal dispersion, which facilitate our model reac-
tions.10 Powdered activated carbon method11 or the potassium
ferrate method12 used for the removal of surfactant. We carried
out the reaction with 20 mM of CTAB in water, the reaction
occurs but again the yield was not good but improved as
compared to the previous observation. Inspired by this success,
the reaction was run with 50 mM of CTAB in 50 ml water. This
gave only 42% yield of the product (Table 1, entry 3). Delight-
fully, the reaction afforded maximum yield 65% (Table 1, entry
6) when the reaction was carried out with 80 mM of CTAB. No
improvement in yield was observed when concentration of
CTAB was further increased. Different types of other surface
active reagents like sodium dodecylsulfate (SDS: cmc value 8.1
mM) and tetradecyltrimethylammonium bromide (TTAB: cmc
value 3.8 mM) have been evaluated (Table 1, entries 11 and 12),
but they did not give satisfactory results in comparison to CTAB.
Thus 80 mM CTAB was sufficient to push the reaction
forward. To increase the yield of the product, we performed a
series of reactions by changing the concentration of the catalyst
i.e. nano ZnO, from 5 mol% to 20 mol%. Thus, 15 mol% of
catalyst was chosen as suitable quantity of the catalyst for the
reaction.
4
4
a
Reaction condition: all reaction were carried out using 2-
hydroxynaphthalene1,4-dione, (1 mmol), aldehydes (1 mmol), 6-
b
aminouracil (1 mmol), in CTAB–H2O (50 ml), at 80 ꢀC. Yield of
isolated product.
that nano ZnO was vital for this conversion in micellar system
we have performed this reaction in the presence of other cata-
lyst like InCl3, SiO2, Alumina and AcOH. The results are listed in
Table 2, which clearly indicate that nano ZnO is the suitable
catalyst for the proposed transformation. The most attractive
feature of this strategy is that this methodology involves nano
ZnO in a small amount. Only 15% nano ZnO is sufficient and
the amount of the product dramatically increases from 65% to
95%. When the reaction was performed with the decreased
amount from 15 mol% to 10 mol% and 5 mol%, the yield of the
product 4a was reduced (Table 2, entries 5 and 6), but the use of
20 mol% of nano ZnO did not affect the yield (Table 2, entry 8).
At last, we investigate the effect of other organic solvents (Table
3), but the result was not as good as it was in water (Table 4).
It was also noticed that the reaction temperature also play
important role in this synthesis. Reaction did not take place at
room temperature. When the temperature was increased the
ꢀ
yield of product also increased and 80 C was found optimum
temperature for maximum conversion. At increased concen-
tration of CTAB (just above CMC), we observed that there is no
improvement in the yield of the product. But, at very high
concentration of CTAB yield of the obtained product was very
low. The reason behind this problem is that at a high concen-
tration of CTAB (CMC), formation of micelles solubilizes the
organic compounds within its hydrophobic core.
Numerous parameters like solvent, catalyst and temperature
provide dramatic improvement in reaction. In order to show
Table 1 Effect of surfactant on the yield of the product in watera
Entry
Surfactant
Temp. (ꢀC)
Concentration
Yieldb (%)
1
2
3
4
5
6
7
8
—
80
80
80
80
80
80
80
r.t.
Reux
80
80
80
—
Trace
27
42
47
51
65
65
—
65
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
CTAB
SDS
20
50
60
70
80
90
80
80
100
80
80
Table 3 Optimization table for solvent for the synthesis of compound
4a
Entry
Solvent
Time (h)
Yieldb (%)
9
1
2
3
4
CH3CN
Toluene
EtOH
6
6
4
4
54
73
82
95
10
11
12
23
25
33
TTAB
H2O
a
a
Reaction condition: all reaction were carried out using 2-
Reaction condition: all reaction were carried out using 2-
hydroxynaphthalene1,4-dione, (1 mmol), 4-chloroaldehyde (1 mmol), hydroxynaphthalene1,4-dione, (1 mmol), 4-chlorobenzaldehyde (1
b
6-aminouracil (1 mmol), in surfactant, H2O (50 ml) at 80 ꢀC. Yield of mmol), 1-methyl 6-aminouracil (1 mmol), ZnO (15 mol%), in CTAB–
isolated product.
H2O (50 ml), at 80 ꢀC. b Yield of isolated product.
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Table 4 Scope of substrate for the synthesis of compound 4a
Entry
2-hydroxynaphthalene1,4dione
Aldehydes (R1)
6-aminouracil (R)
Product 4
Yieldb (%)
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
4-Cl
4-Br
–H
–H
–H
–H
–H
–H
–H
–H
–Me
–Me
–Me
–Me
4a
4b
4c
4d
4e
4f
4g
4h
4i
95
95
93
89
93
93
94
95
95
95
95
92
4-NO2
–C6H5
3-Me
2-Me
4-Me
4-OMe
4-Cl
4-Br
4-Me
3-Me
9
10
11
12
4j
4k
4l
a
Reaction condition: all reaction were carried out using 2-hydroxynaphthalene1,4-dione, (1 mmol), aldehydes (1 mmol), 6-aminouracil (1 mmol),
nano ZnO, in CTAB–H2O (50 ml), at 80 ꢀC. b Yield of isolated product.
With the optimized conditions in hand, we explore the scope particle. Use of ZnO nano-particles promote the formation of
and limitation of this synthetic procedure by using variety of admicelles in aqueous medium and improved this reaction
reactants. A variety of aldehydes and aminouracil were used. procedure.
Interestingly, a wide range of aldehydes (containing electron
withdrawing and electron donating group) were undergoing reaction between starting material naphtha and aldehyde to
smooth transformation in this conversion. generate an intermediate. Then 6-aminouracil attacks to inter-
We speculated that the rst reaction is, probably involves the
The electronic effect and the nature of the substituent on the mediate I in Michael type fashion to generate another inter-
aldehyde do not show any obvious effects in terms of yield and mediate which undergoes intramolecular cyclisation by the
reaction time.
reaction of nucleophilic amino function to lead to the desired
Based on previously documented reactions and our experi- product in excellent yield. Compounds 4 and its derivatives are
ment plausible mechanism for the nano-ZnO catalysed forma- stable solids whose structures were conrmed by IR, 1H, 13C
tion of compounds 4 is depicted in Scheme 2. Organic reagents NMR spectroscopy and elemental analysis.
come closer to each other in the hydrophobic area of admicelles
In terms of green chemistry, efficient recovery and reus-
and the reaction between them is catalyzed by ZnO nano ability of the catalyst is very important, thus the recovery and
recyclability of nano ZnO were also examined. Aer the reaction
was completed, ethyl acetate was added to the reaction mixture.
The reaction mixture was stirred until complete dissolution of
desired product in ethyl acetate was observed. The two layers
were then separated. The aqueous layer was reused for the same
experiment for next cycles. There was no appreciable change
was observed in yield of desired product (shown in Fig. 4). This
was also conrmed by comparison of XRD pattern of the fresh
Scheme
2
Plausible mechanism for the synthesis of compound Fig.
4 Reusability of ZnO nano particles for the synthesis of
4a–4l.
compound 4.
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nano ZnO and the reused one aer h cycle. As displayed in was observed. The two layers were then separated. The aqueous
Fig. 2 XRD spectra of reused catalyst was found to be almost layer was reused for the same experiment for next cycles.
similar to the fresh one. The almost similar broadening in XRD
pattern of recovered ZnO nanoparticles do not aggregate during 11(1h,3h,5h,12h)-tetraone (4a). Orange powder; mp 294 C. IR
the reaction.
5-(4-Chlorophenyl)benzo[G]pyrimido[4,5-b]quinoline-2,4,6,
ꢀ
1
(KBr) (nmax/cmꢂ1): 3313, 3244, 1724, 1650, 1595, 1542. H NMR
(400 MHz, DMSO-d6): dH (ppm) 5.08 (s, 1H, CH), 7.26 (d, 3JHH
¼
8.4 Hz, 2H), 7.35 (d, 3JHH ¼ 8.5 Hz, 2H), 7.78–8.06 (m, 4H, H-Ar),
9.36 (s, 1H, NH), 10.20 (s, 1H, NH), 10.94 (s, 1H, NH). 13C NMR
(100 MHz, DMSO-d6): dC (ppm) 34.9, 89.0, 118.7, 126.7, 126.8,
128.8 (2 CH), 130.8 (2 CH), 130.9, 131.9, 132.5, 134.3, 135.8,
138.8, 144.4, 148.7, 150.2, 163.4, 179.7, 182.5. MS (EI, 70 eV): m/z
(%): 405 (M+, 10), 371 (10), 325 (45), 234 (28), 156 (26), 77 (78), 57
(80), 43 (100). For C21H12ClN3O4 (405.79): C, 62.16; H, 2.98; N,
10.36; found: C, 62.24; H, 2.86; N, 10.50.
Conclusion
In conclusion, the present work disclose environmentally
benign multicomponent protocols for the synthesis of 1-methyl-
5-phenylbenzo[g]pyrimido[4,5-b]quinoline-2,4,6,11(1H,3H)-tet-
raone, employing CTAB–H2O as the reaction medium and nano
ZnO as the catalyst. This strategy is endowed with several
advantages such as use of aqueous medium, catalytic reaction,
excellent yield and ease of operation. The mild reaction condi-
tions and eco-friendly practicability made this methodology an
attractive approach to prepare pyrimido[4,5-b]quinoline deriv-
atives in good amount.
5-(4-Bromophenyl)benzo[G]pyrimido[4,5-b]quinoline-2,4,6,
ꢀ
11(1h,3h,5h,12h)-tetraone (4b). Orange powder; mp 299 C. IR
(KBr) (nmax/cmꢂ1): 3403, 3246, 3054, 1734, 1664, 1603, 1575. 1H
NMR (400 MHz, DMSO-d6): dH (ppm) 5.12 (s, 1H, CH), 6.92–7.98
(m, 8H, H-Ar), 9.31 (s, 1H, NH), 10.16 (s, 1H, NH), 10.84 (s, 1H,
NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 35.5, 87.0, 119.7,
124.3, 126.5, 126.9, 129.8 (2 CH), 131.4 (2 CH), 132.2, 134.5,
135.8, 138.7, 149.0, 154.7, 159.2, 163.3, 181.5, 184.5. MS (EI, 70
eV): m/z (%): 449 (M+, 8), 371 (12), 373 (50), 278 (30), 156 (22), 76
(80), 57 (80), 43 (100). For C21H12BrN3O4 (450.24): C, 56.02; H,
2.69; N, 9.33; found: C, 56.18; H, 2.58; N, 14.35.
Experimental
Material and methods
All chemical were reagent grade purchased from Aldrich and
Alfa Aesar and were used without purication. NMR spectra
were recorded on a BRUKER AVANCE II-400FT Spectrometer
(400 for 1H NMR, 100 MHz for 13C) using DMSO as solvent and
TMS as an internal reference. ESI-MS were recorded on a
Quattro II (ESI) spectrometer.
5-(4-Nitrophenyl)benzo[G]pyrimido[4,5-b]quinoline-2,4,6,
11(1h,3h,5h,12h)-tetraone (4c). Red powder; mp 297 ꢀC. IR (KBr)
(nmax/cmꢂ1): 3359, 3241, 3074, 1720, 1684, 1632, 1578. 1H NMR
(400 MHz, DMSO-d6): dH (ppm) 5.23 (s, 1H, CH), 7.35 (d, 3JHH
¼
8.5 Hz, 2H), 7.46 (d, 3JHH ¼ 8.5 Hz, 2H), 7.75–8.12 (m, 4H, H-Ar),
9.30 (s, 1H, NH), 10.20 (s, 1H, NH), 10.84 (s, 1H, NH). 13C NMR
(100 MHz, DMSO-d6): dC (ppm) 37.1, 87.9, 119.2, 126.8, 126.9,
128.8 (2 CH), 130.9 (2 CH), 131.1, 132.0, 132.7, 134.5, 136.0,
138.9, 144.9, 151.2, 160.0, 163.4, 181.7, 183.5. MS (EI, 70 eV): m/z
(%): 416 (M+, 15), 371 (16), 340 (54), 245 (34), 156 (18), 76 (84), 57
(76), 43 (100). For C21H12N4O6 (416.34): C, 60.58; H, 2.91; N,
13.46; found: C, 60.74; H, 2.86; N, 13.50.
Characterization techniques used
The prepared nanoparticles of ZnO were thoroughly character-
ized by X-ray diffraction (XRD) and transmission electron
microscopy (TEM) in order to elaborate structural properties in
precise 75 manner. XRD was performed on Rigaku D/max-2200
PC diffractometer operated at 40 kV per 40 mA, using CuKa1
ꢀ
radiation with wavelength of 1.54 A in the wide angle region
from 20ꢀ to 80ꢀ on 2q scale. The size and morphology of
prepared nanoparticles were found using a transmission elec-
tron 80 microscope (model Tecnai 30 G2S-Twin electron
microscope) operated at 300 kV accelerating voltage by dis-
solving the as synthesized powder sample in ethanol and then
placing a drop of this dilute ethanolic solution on the surface of
a carbon coated 200 mess copper grid.
5-Phenylbenzo[G]pyrimido[4,5-b]quinoline-2,4,6,11(1h,3h,
ꢀ
5h,12h)-tetraone (4d). Red powder; mp 300 C. IR (KBr) (nmax
/
cmꢂ1): 3410, 3249, 3065, 1715, 1645, 1603, 1560. H NMR (400
MHz, DMSO-d6): dH (ppm) 5.22 (s, 1H, CH), 7.12–8.01 (m, 9H, H-
Ar), 9.28 (s, 1H, NH), 10.10 (s, 1H, NH), 10.81 (s, 1H, NH). 13C
NMR (100 MHz, DMSO-d6): dC (ppm) 35.5, 86.6, 119.7, 124.3,
126.5, 126.9, 127.8 (2 CH), 128.9 (2 CH), 131.5, 132.5, 134.2,
135.3, 139.8, 151.1, 155.7, 159.2, 163.5, 181.8, 185.5. MS (EI, 70
eV): m/z (%): 371 (M+, 5), 328 (12), 295 (42), 200 (30), 156 (22), 76
(80), 43 (100). For C21H13N3O4 (371.35): C, 67.92; H, 3.53; N,
11.32; found: C, 68.05; H, 3.50; N, 11.45.
1
General procedure for the synthesis of 2,4,6-substituted
pyrimidine-5-carbonitriles
Aldehydes (1 mmol), 6-aminouracil (1.0 mmol) and the 2-
hydroxynaphthalene1,4dione were added in the mixture of
CTAB (80 mM)–H2O (50 ml) and nano ZnO (15 mol%) at 80 ꢀC.
Aer completion of reaction the reaction mixture was being
cooled and solid product was separated.
5-o-Tolylbenzo[G]pyrimido[4,5-b]quinoliꢀne-2,4,6,11(1h,3h,
5h,12h)-tetraone (4e). Red powder; mp 277 C. IR (KBr) (nmax
/
cmꢂ1): 3415, 3246, 3056, 1713, 1656, 1603, 1532. H NMR (400
MHz, DMSO-d6): dH (ppm) 2.76 (s, 3H, Me), 5.16 (s, 1H, CH),
7.00–8.03 (m, 8H, H-Ar), 9.30 (s, 1H, NH), 10.19 (s, 1H, NH),
10.85 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 21.2,
1
Reusability of ZnO nano particle
Aer completion of the reaction, 10 ml of ethyl acetate were 35.4, 86.7, 116.9, 123.9, 126.3, 126.8, 127.3, 127.9, 128.6, 131.2,
added to the reaction mixture. The reaction mixture was stirred 132.5, 134.1, 135.1, 135.3, 137.9, 139.1, 151.0, 158.2, 163.5,
until complete dissolution of desired product in ethyl acetate 181.4, 183.3. MS (EI, 70 eV): m/z (%): 385 (M+, 10), 309 (44), 214
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(26), 156 (20), 91 (74), 57 (82), 43 (100). For C22H15N3O4 (385.37): 35.3, 86.1, 119.5, 124.0, 126.5, 126.9, 130.0 (2CH), 131.4, 131.6
C, 68.57; H, 3.92; N, 10.90; O, 16.61; found: C, 68.81; H, 3.75; N, (2CH), 132.5, 134.3, 135.2, 139.0, 151.0, 155.2, 156.3, 164.3,
10.91.
181.8, 186.6. MS (EI, 70 eV): m/z (%): 477 (M+, 5), 338 (22), 321
5-m-Tolylbenzo[G]pyrimido[4,5-b]quinoline-2,4,6,11(1h,3h, (32), 235 (100), 156 (76), 76 (80). For C23H16BrN3O4 (478.29): C,
5h,12h)-tetraone (4f). Red powder; mp 282 ꢀC. IR (KBr) (nmax
/
57.76; H, 3.37; N, 8.79; found: C, 57.86; H, 3.35; N, 8.83.
1
cmꢂ1): 3327, 3266, 3051, 1723, 1655, 1612, 1525. H NMR (400
1,3-Dimethyl-5-m-tolylbenzo[G]pyrimido[4,5-b]quinoline-
MHz, DMSO-d6): dH (ppm) 2.70 (s, 3H, Me), 5.21 (s, 1H, CH), 2,4,6,11(1h,3h,5h,12h)-tetraone (4k). Red powder; mp 195 ꢀC. IR
7.01–8.12 (m, 8H, H-Ar), 9.25 (s, 1H, NH), 10.15 (s, 1H, NH), (KBr) (nmax/cmꢂ1): 3325, 1705, 1656, 1570, 1520. H NMR (400
1
10.83 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 23.5, MHz, DMSO-d6): dH (ppm) 2.22 (s, 3H, Me), 3.14 (s, 3H, NMe),
35.5, 86.4, 117.5, 124.1, 126.4, 126.9, 127.3, 128.0, 128.6, 131.5, 3.36 (s, 3H, NMe), 5.80 (s, 1H, CH), 6.94–8.02 (m, 8H, H-Ar),
132.5, 134.3, 135.3, 135.6, 138.0, 139.4, 151.5, 160.2, 163.3, 13.06 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm)
181.9, 183.5. MS (EI, 70 eV): m/z (%): 385 (M+, 8), 294 (40), 214 22.0, 29.0, 31.2, 35.5, 86.7, 111.8, 124.6, 126.5, 126.9, 127.2,
(22), 156 (28), 91 (70), 57 (78), 43 (100). For C22H15N3O4 (385.37): 128.0, 128.8, 131.4, 132.6, 134.3, 135.3, 135.4, 137.9, 139.1,
C, 68.57; H, 3.92; N, 10.90; found: C, 68.70; H, 3.85; N, 10.86.
151.0, 155.2, 164.5, 181.9, 184.3. MS (EI, 70 eV): m/z (%): 413
5-p-Tolylbenzo[G]pyrimido[4,5-b]quinoliꢀne-2,4,6,11(1h,3h, (M+, 8), 275 (16), 257 (22), 235 (100). For C24H19N3O4 (413.43): C,
5h,12h)-tetraone (4g). Red powder; mp 311 C. IR (KBr) (nmax
/
69.72; H, 4.63; N, 10.16; found: C, 69.86; H, 4.53; N, 10.05.
1
cmꢂ1): 3401, 3254, 3059, 1713, 1655, 1608, 1515. H NMR (400
1,3-Dimethyl-5-p-tolylbenzo[G]pyrimido[4,5-b]quinoline-
MHz, DMSO-d6): dH (ppm) 2.18 (s, 3H, Me), 5.05 (s, 1H, CH), 2,4,6,11(1h,3h,5h,12h)-tetraone (4l). Red powder; mp 263 ꢀC. IR
7.01 (d, 3JHH ¼ 7.7 Hz, 2H), 7.19 (d, 3JHH ¼ 7.7 Hz, 2H), 7.79–8.05 (KBr) (nmax/cmꢂ1): 3356, 1721, 1655, 1565. H NMR (400 MHz,
1
(m, 4H, H-Ar), 9.20 (s, 1H, NH), 10.13 (s, 1H, NH), 10.88 (s, 1H, DMSO-d6): dH (ppm) 2.26 (s, 3H, Me), 3.10 (s, 3H, NMe), 3.32 (s,
NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 21.0, 35.3, 86.5, 3H, NMe), 5.51 (s, 1H, CH), 6.98 (d, 3JHH ¼ 7.8 Hz, H-Ar), 7.20 (d,
114.9, 126.7, 126.8, 129.0 (2 CH), 130.5 (2 CH), 130.8, 131.3, 3JHH ¼ 7.9 Hz, H-Ar), 7.75–8.04 (m, 4H, H-Ar), 9.03 (s, 1H, NH).
132.5, 134.3, 135.8, 138.8, 144.4, 148.7, 159.2, 163.4, 179.8, 13C NMR (100 MHz, DMSO-d6): dC (ppm) 22.2, 28.9, 31.5, 36.5,
183.1. MS (EI, 70 eV): m/z (%): 385 (M+, 5), 294 (45), 214 (30), 156 88.7, 116.0, 124.3, 126.5, 126.9, 128.8 (2CH), 130.7 (2CH), 131.6,
(20), 76 (78), 57 (82), 43 (100). For C22H15N3O4 (385.37): C, 68.57; 134.5, 135.3, 135.4, 136.9, 139.4, 151.0, 158.2, 163.5, 180.7,
H, 3.92; N, 10.90; found: C, 68.50; H, 3.87; N, 10.81.
184.1. MS (EI, 70 eV): m/z (%): 413 (M+, 10), 322 (6), 275 (20), 235
5-(4-Methoxyphenyl)benzo[G]pyrimido[4,5-b]quinoline-2,4, (100), 156 (72), 76 (80). For C24H19N3O4 (413.43): C, 69.72; H,
6,11(1h,3h,5h,12h)-tetraone (4h). Orange powder; mp 301 ꢀC. IR 4.63; N, 10.16; found: C, 69.78; H, 4.45; N, 10.21.
(KBr) (nmax/cmꢂ1): 3429, 3176, 3054, 1704, 1679, 1609, 1532. 1H
NMR (400 MHz, DMSO-d6): dH (ppm) 3.64 (s, 3H, OMe), 5.01 (s,
Acknowledgements
1H, CH), 6.75 (d, 3JHH ¼ 7.7 Hz, 2H, H-Ar), 7.20 (d, 3JHH ¼ 7.6 Hz,
2H, H-Ar), 7.80–8.02 (m, 4H, H-Ar), 9.30 (s, 1H, NH), 10.16 (s, P. Rai and Rahila thanks to CSIR for their Senior Research
1H, NH), 10.90 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6): dC Fellowship. H. Sagir thanks to UGC for her Junior Research
(ppm) 32.5, 55.7, 86.5, 114.3 (2 CH), 124.4, 126.2, 126.7, 129.7, Fellowship. Authors gratefully acknowledge the SAIF, Punjab
130.1, 130.5, 133.1, 133.2, 133.7, 135.3, 137.9 (2 CH), 144.7, University, Chandigarh, for providing all the spectroscopic data
159.2, 163.4, 179.8, 183.0. MS (EI, 70 eV): m/z (%): 401 (M+, 15), and Nanotechnology Application Centre, University of Allaha-
358 (14), 325 (30), 230 (26), 156 (22), 57 (76), 43 (100). For bad for powder XRD and EDS.
C
22H15N3O5 (401.37): C, 65.83; H, 3.77; N, 10.47; found: C, 65.87;
H, 3.75; N, 10.59.
Notes and references
5-(4-Chlorophenyl)-1,3-dimethylbenzo[G]pyrimido[4,5-b]-
quinoline-2,4,6,11(1h,3h,5h,12h)-tetraone (4i). Orange powder;
1 (a) T. H. Istvan and T. A. Paul, Chem. Rev., 2007, 107, 2167; (b)
P. Rai, M. Srivastava, J. Singh and J. Singh, RSC Adv., 2013, 3,
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2 (a) P. D. Maria, A. Fontana, C. Gasbarri and G. Siani,
Tetrahedron, 2005, 61, 7176; (b) T. Dwars, E. Paetzold and
G. Oehme, Angew. Chem., Int. Ed., 2005, 44, 7174; (c)
M. Srivastava, J. Singh, S. B. Singh, K. Tiwari, V. K. Pathak
and J. Singh, Green Chem., 2012, 14, 901.
mp 251 C. IR (KBr) (nmax/cmꢂ1): 3401, 1715, 1653, 1580, 1516.
ꢀ
1H NMR (400 MHz, DMSO-d6): dH (ppm) 3.18 (s, 3H, NMe), 3.35
(s, 3H, NMe), 5.64 (s, 1H, CH), 7.11–7.89 (m, 8H, H-Ar), 13.10 (s,
1H, NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 29.0, 31.3,
35.3, 86.1, 118.9, 124.1, 126.7, 126.9, 130.3 (2CH), 131.4, 131.5
(2CH), 132.6, 134.3, 135.2, 138.9, 151.1, 155.2, 156.4, 164.3,
181.6, 186.6. MS (EI, 70 eV): m/z (%): 433 (M+, 5), 322 (8), 271
(30), 235 (100), 156 (72), 76 (82), 57 (26). For C23H16ClN3O4
(433.84): C, 63.67; H, 3.72; Cl, 8.17; N, 9.69; found: C, 63.84; H,
3.55; N, 8.28.
3 Y. Zhang, Y. Chen, P. Westerhoff, K. Hristovski and
J. C. Crittenden, Water Res., 2008, 42, 2204.
4 (a) P. Rai, M. Srivastava, J. Singh and J. Singh, New J. Chem.,
2014, 38, 3181; (b) J. A. Gladysz, Pure Appl., ed. U. M.
Lindstorm, Wiley-Blackwell, New York, NY, 2007; (c)
M.-O. Simon and C. J. Li, Chem. Soc. Rev., 2012, 41, 1415.
5 (a) J. A. Gladysz, Chem. Rev., 2002, 102, 321; (b) R. M. Singh,
N. Sharma, R. Kumar, M. Asthana and S. Upadhyay,
Tetrahedron, 2012, 68, 10318; (c) Y. M. Elkholy and
5-(4-Bromophenyl)-1,3-dimethylbenzo[G]pyrimido[4,5-b]-
quinoline-2,4,6,11(1h,3h,5h,12h)-tetraone (4j). Orange powder;
mp 229 C. IR (KBr) (nmax/cmꢂ1): 3395, 1700, 1656, 1573, 1512.
ꢀ
1H NMR (400 MHz, DMSO-d6): dH (ppm) 3.12 (s, 3H, NMe), 3.36
(s, 3H, NMe), 5.79 (s, 1H, CH), 7.19–7.9 (m, 8H, H-Ar), 13.16 (s,
1H, NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 29.1, 31.3,
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