Microwave-accelerated three components cyclocondensation in the synthesis of 2,3-dihydroquinazolin-4(1H)-ones promoted by Cu-CNTs

Article abstract of DOI:10.1016/j.molcata.2013.01.031

Cu-CNTs efficiently catalyzes condensation reaction of isatoic anhydride, aldehydes, and primary amines or ammonium acetate to afford the corresponding 2,3-dihydroquinazolin-4(1H)-one derivatives successfully in high yield. The protocol proves to be effic

Full text of DOI:10.1016/j.molcata.2013.01.031

Journal of Molecular Catalysis A: Chemical 371 (2013) 135–140
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Microwave-accelerated three components cyclocondensation in the synthesis of
2,3-dihydroquinazolin-4(1H)-ones promoted by Cu-CNTs
Javad Safari∗, Soheila Gandomi-Ravandi
Laboratory of Organic Compound Research, Department of Organic Chemistry, College of Chemistry, University of Kashan, P.O. Box: 87317-51167, Kashan, Islamic Republic of Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Cu-CNTs efficiently catalyzes condensation reaction of isatoic anhydride, aldehydes, and primary amines
or ammonium acetate to afford the corresponding 2,3-dihydroquinazolin-4(1H)-one derivatives success-
fully in high yield. The protocol proves to be efficient and environmentally benign in terms of very easy
work-up, high yields, and ease of recovery of catalyst. In addition, the present method is superior in terms
of green media, the amount of catalyst and reaction time.
Received 21 December 2012
Received in revised form 27 January 2013
Accepted 28 January 2013
Available online xxx
© 2013 Elsevier B.V. All rights reserved.
Keywords:
Dihydroquinazolin-4(1H)-one
Synthesis
Catalyst
Cu-CNT composites
Microwave
1. Introduction
[14] and the condensation of isatoic anhydride, aldehydes, and
ammonium acetate or primary amine [15,16]. More attractive and
Heterocyclic chemistry occupies an important place in organic
chemistry research worldwide [1–4] and forms the basis of many
pharmaceutical, agrochemical and veterinary products. In the
broad class of heterocyclic compounds, the nitrogen heterocycles
play an important role. One of such systems is quinazolinones
as a class of N-heterocycles which have an important place in
medicinal and biological chemistry [5]. One of the main group
of quinazolinones, are 2,3-dihydroquinazolin-4(1H)-ones, which
have in particular have various biological activities, and are also
key intermediates for the synthesis of quinazolin-4(3H)-ones as
another member of this biologically important family [6–8]. These
exhibit broad spectrums of pharmacological and biological activ-
ities, such as antibacterial, antifertility, antifungal, antitumor, and
mono amine oxidase inhibitory activity [9]. In view of these useful
properties, various procedures have been reported for preparing
2,3-dihydroquinazolin-4(1H)-ones in literature, which including:
(a) the condensation reaction of anthranilamide with aldehyde
or ketone [6], (b) the reductive cyclization of o-nitrobenzamide
or o-azidobenzamide with aldehydes or ketones [10], (c) desul-
furization of 2-thioxo-4(3H)-quinazolinones [11], (d) a two-step
synthesis starting from isatoic anhydride and amines, followed
by annulation with ketones [12], (e) reaction of isatoic anhydride
with Schiff-bases [13], condensation of anthranilamide with benzil
convenient method for synthesis of such significant heterocycles
is three-component condensation of isatoic anhydride, aldehydes,
and amines. In this context, various catalysts have been reported
[17–28]. Some of these methodologies involve strongly acidic
conditions, toxic catalysts, hazardous organic solvents and long
reaction times. Thus, there is a need for an acidic and novel catalyst
that could overcome the above drawbacks.
CNTs have become one of the most active fields of nanoscience
and nanotechnology due to their exceptional properties that make
them suitable for many potential applications as high specific sur-
face areas, chemical stability and electrical conductivities [29].
The use of carbon nanotubes as support for transition metal cata-
lysts has recently been demonstrated [30–33]. Recently, CNT-based
composites have attracted much attention due to their unique
properties and promising applications [29,34,35]. In addition, the
advantages Cu-CNT composites are good thermal conductivity,
lower density than copper, good machinability and low coeffi-
cient of thermal expansion [36,37]. Therefore combining Cu with
CNTs to form metal/CNT nanocomposites produces synergistic
properties from both the metals and the CNTs. Some researchers
reported that the catalysts metal supported on multi-walled carbon
nanotubes exhibited much better activity than other carbon-
based supports for some hydrogenation reactions [38]. It is well
known that for CNTs without surface modification, there are
insufficient binding sites for anchoring the precursors of metal
ions or metal nanoparticles, which usually leads to poor disper-
sion and large metal nanoparticles, especially under high loading
∗
Corresponding author. Tel.: +98 0 361 591 2320; fax: +98 0 361 591 2397.
E-mail address: Safari@kashanu.ac.ir (J. Safari).
1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.01.031

136
J. Safari, S. Gandomi-Ravandi / Journal of Molecular Catalysis A: Chemical 371 (2013) 135–140
R
O
O
CHO
NH2
N
O
Cu-CNTs
+
+
Solvent free
N
H
N
H
O
R
R'
4
1
3
2
R'
Scheme 1. Cu-CNTs catalyzed microwave-activated synthesis of 2,3-disubstituted-2,3-dihydroquinazolin-4(1H)-ones from isatoic anhydride, aromatic amine and aldehyde.
products were characterized by comparison of their spectral (1H
NMR, 13C NMR and MS) and physical data with those of authentic
samples. All yields refer to isolated products after purification.
conditions [39,40]. Herein we investigated the possibility of syn-
thesizing 2,3-dihydroquinazolin-4(1H)-one derivatives via one pot
three-component condensation of isatoic anhydride, aldehydes
and amines, in the presence of a catalytic amount of Cu-CNTs com-
posites under microwave irradiation (Schemes 1 and 2).
2.1. Catalyst preparation
Detailed procedure for preparing the Cu-CNT nanocomposites
is described elsewhere [41]. In brief, The CNTs were treated by
adding 40 mL of nitric acid and sulfuric acid (3:1 in volume) solu-
tion, then dropping 10 mL of ethanol into the solution slowly, to
increase their surface chemical activity via oxidation of the defect
sites before coating with copper. The solution was stirred at 70 ◦C
for 24 h. Then in a chemical reduction process, equal amounts of
0.01 M of Cu(NO3)2·3H2O aqueous solution and ethanol added to
the basic solution of NaOH and Na2CO3 (3:1 in volume) with pH
12. Acid-treated MWNTs were added to above aqueous solution
followed by dropping of a solution of 37% formaldehyde (10:1 of
formaldehyde and copper nitrate) under sonication for 2 h. Then,
the precipitate was separated by centrifugation and washed with
deionized water until pH 7. The solid samples were then calcined
at 350 ◦C for 2 h (Fig. 1).
2. Experimental
All chemicals and reagents were obtained from Merck and
Aldrich and were used without further purification. MWNTs were
purchased from Nanotech Port Co. (Taiwan). These MWNTs were
produced via the chemical vapor deposition (CVD, or sometimes
called catalytic pyrolysis) method. The outer diameter of CNT was
between 20 and 40 nm. Melting points were determined on an Elec-
trothermal MK3 apparatus and were uncorrected. 1H NMR and 13
C
NMR spectrums were recorded on Bruker DRX–400 spectrometer
at 400 and 100 MHz in DMSO-d6, respectively. The chemical shifts
are expressed in ı ppm using TMS as an internal standard and cou-
pling constants (J) are reported in hertz (Hz). Spin multiplicities
are given as s (singlet), d (doublet), t (triplet) and m (multiplet) as
well as b (broad). FT-IR spectra were recorded on a Perkin Elmer
FT–IR 550 spectrophotometer using KBr pellets and absorbencies
are reported in cm−1. Microwave oven reactions were performed
on a CEM–Discover Focused Monomode, microwave input power
300 W and microwave frequency 2450 MHz. ESI-MS analyses were
carried out on a MICROMASS QUATTRO II triple quadrupole mass
spectrometer. X-ray diffraction analysis was carried out using a
Holland Philips Xpert X-ray powder diffraction (XRD) diffractome-
ter (CuK, radiation, ꢀ = 0.154056 nm), at a scanning speed of 2◦/min
from 10◦ to 100◦ (2ꢁ). Scanning electron microscopy (SEM) images
were obtained using a FEI Quanta 200 SEM, operated at a 20 kV
accelerating voltage. Purity of the compounds synthesized was
monitored by TLC), visualizing with ultraviolet light. Elemental
analysis was performed using a Heraeus CHN-O-RAPID elemental
analyzer. UV–vis spectra of compounds were recorded on a UV-
Vis Varian Perkin-Elmer UV 550-S spectrophotometer. The known
2.2. General procedure for the synthesis of
2,3-dihydroquinazolin-4(1H)-ones under microwave irradiation
Cu-CNTs nanocomposite (0.04 g) as an efficient catalyst was
added to the mixture of isatoic anhydride (1 mmol), primary aro-
matic amine (1.1 mmol) or ammonium acetate (1.2 mmol) and
aldehyde (1 mmol). The resulting mixture was heated at microwave
oven under solvent free conditions with stirring for appropriate
time until reaction complete. After the complete disappearance
of the starting material, as monitored by TLC (eluent: petroleum
ether:ethyl acetate: 4:1), hot ethanol (15 mL) was added and the
catalyst was removed by filtration. The filtrate containing the cat-
alyst was evaporated under reduced pressure to give a solid, and
the recovered catalyst could be reused without a loss of catalytic
O
O
CHO
NH
O
Cu-CNTs
+
+
NH4OAc
Solvent free
N
H
N
H
O
R'
6
3
1
5
R'
Scheme 2. Cu-CNTs catalyzed microwave-activated synthesis of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones from isatoic anhydride, ammonium acetate and aldehyde.

J. Safari, S. Gandomi-Ravandi / Journal of Molecular Catalysis A: Chemical 371 (2013) 135–140
137
Fig. 1. Schematic presentation of functional group formation and copper decoration on multi walled carbon nanotubes.
Table 2
Optimization of the condensation reaction power for synthesis of compound 4a in
various times.
Entry
P (w)
Time (min)
Yield (%)
1
2
3
4
5
6
30
45
50
65
70
85
35
20
15
5
5
3
56
72
87
99
95
92
of reagents were examined and the best result was obtained with
1:1:1.1:1.2 ratios of isatoic anhydride, aldehyde, and aniline or
ammonium acetate in the presence of 0.04 g of Cu-CNTs composite.
Presently organic reactions in solvent free media have attracted the
attention of researchers. Further because of the toxicity of organic
solvents, we considered the green media. When the reactions were
conducted in solvent free conditions, the expected products were
obtained with excellent yields in low reaction times. In order to
generalize the procedure, a variety of substituted aromatic alde-
hydes were screened under optimized conditions. To expand the
scope of amine substrates, a variety of amine derivatives were
applied to this protocol. Interestingly, in all cases, both electron-
rich and electron-deficient substrates worked well, and the desired
reactions took place successfully to afford the desired products in
good yields. These values are tabulated in Table 1. All these obser-
vations indicate that the electronic properties and the position of
the substituent group on the phenyl ring had no obvious influence
on this conversion.
The reaction temperature also played an important role in this
reaction. Therefore, we tried to optimize the reaction tempera-
ture in various times for the model reaction. As could be seen on
Table 2, the reaction at power 65 and 5 min proceeded in highest
yield. Using these optimized reaction conditions, the above men-
tioned cyclocondensation reaction proceeded well and afforded the
desired products in good to excellent yields. The catalytic activ-
ity of Cu-CNTs composite was evaluated for this model reaction,
and the results showed that Cu-CNTs composite could be used for
Fig. 2. Investigation of the amounts of catalyst effect on the preparation of 4a.
activity. The corresponding pure product was obtained by recrys-
tallization from ethanol.
3. Results and discussion
In order to exploit potential of Cu-CNTs composite for the syn-
thesis of 2,3-dihydroquinazolin 4(1H)-one derivatives, for the first
time three components one-pot condensation of isatoic anhydride,
aldehydes, and NH4OAc or primary amines in the presence of a cat-
alytic amount of Cu-CNTs composite as an efficient catalyst under
microwave-activated conditions was investigated. We studied the
potential use of Cu-CNTs as the catalytic agent on the condensa-
tion. To improve the yield and optimize the reaction conditions,
the effect of amount of catalyst on the condensation using the
model reaction of isatoic anhydride, benzaldehyde and aniline was
studied by varying the amount of Cu-CNTs without solvent under
microwave irradiation (Fig. 2). The results indicated clearly that Cu-
CNTs was a superior catalyst and successfully promoted this three
components condensation with high yields. As it was shown from
Fig. 2, the best result has been obtained with an amount of 0.04 g
Cu-CNTs composite. It is worth mentioning that all these results
clearly showed the efficiency of this catalytic system in the syn-
thesis of 2,3-dihydroquinazolin-4(1H)-ones. Different molar ratios
Table 1
Cu-CNTs composite mediated synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives under microwave irradiation without any solvent.
Entry
Product
Amine(R)/Ammonium salt
Rꢀ
Time (min)
Yield (%)
M.p (◦C)
Found
Ref.
Reported
1
2
3
4
5
6
7
8
9
4a
4b
4c
4d
4e
4f
4g
5h
5i
H
H
H
5
12
17
20
10
23
15
15
12
10
99
90
93
87
95
89
92
89
91
95
214–215
223–225
241–243
248–250
220–222
269–272
235–237
223–225
265–267
198–200
214–216
222–224
244–245
249–252
219–223
270–274
235–238
225–227
266–267
199–201
[42]
[43]
[44]
[25]
[27]
[45]
[27]
[46]
[47]
[48]
4-Me
4-OMe
4-Me
4-Br
4-Cl
4-F
2,3-Cl2
2-F
4-Me
4-OH
H
4-Me
H
NH4OAc
NH4OAc
NH4OAc
10
5j
4-NO2

138
J. Safari, S. Gandomi-Ravandi / Journal of Molecular Catalysis A: Chemical 371 (2013) 135–140
Fig. 3. Recyclability of the catalyst for the one-pot synthesis of 4a.
five successive runs without significant decrease in its catalytic
activity (Fig. 3). In general, the target compounds were obtained
in excellent yields under the optimized conditions and the desired
products were isolated by a clean and simple work-up procedure.
All of the products are known compounds and their structure were
confirmed by comparison of their physical and spectral data with
those of authentic samples.
Characterization of Cu/CNTs has been performed by X-ray
diffraction. As shown in Fig. 4, the peaks of CNT were 26.48 and
44.68, and broad diffraction peaks with 2 at 43.78, 48.42 and 74.95,
corresponding to Cu. Fig. 5 shows the TEM and SEM images of CNTs
and Cu coated on CNT. The CNTs are very pure and their surface
is smooth. In comparing b with c, when CNTs coated with Cu, the
surface of CNTs was rough. Also SEM images show that the CNTs
are dispersed uniformly and combined well in the Cu.
Fig. 4. XRD diffraction of Cu-CNT composites.
form the quinazolinone core. First the isatoic anhydride is activated
with coated metal by the coordination with carbonyl groups fol-
lowed by nucleophilic attack of amine on the carbonyl unit to form
intermediate I. Then decarboxylation resulting intermediate I into
the formation of intermediate II followed by proton transfer yields
2-amino-N-substituted-amide III. Condensation of the promoted
aldehyde with the amino group of 2-amino-N-substituted-amide
III then produces an imine intermediate IV. The part of amide in
intermediate III could be converted into its tautomer in the pres-
ence of metal. Meanwhile, the part of imine in intermediate IV could
be activated by catalyst. Thus, intermediate V could be prepared by
intermolecular nucleophilic attack of the amide nitrogen on acti-
vated imine carbon, followed by a 1,5-proton transfer to produce
the final products.
On the basis of our experimental results and by referring to the
literature, a plausible mechanism of the three components reaction
is proposed in Scheme 3. Catalyst also might assist in improving
reactivity of carbonyl units and finally in promoting cyclization to
Fig. 5. Images of the samples (a) TEM of unpurified CNTs; (b) SEM of purified CNTs; (c) SEM of copper-coated CNTs.

J. Safari, S. Gandomi-Ravandi / Journal of Molecular Catalysis A: Chemical 371 (2013) 135–140
139
TNC- Cu
O
NH4OAc / NH2R
TNC- Cu
O
O
Cu-CNT
R
N
H
O
Cu-CNT
O
N
H
- CO2
H
O
NH
N
H
O
O
O
Cu-CNT
O
O
I
R
N
R
N
H
H
N
H
N
H
Ar
II
1,5-H shift
OH
O
R
R
TNC- Cu
N
N
OH
N
H
N
Ar
R
NH2
N
V
III
Cu-CNT
H
Ar
O
Cu-CNT
Ar
IV
Scheme 3. Plausible reaction pathway in the synthesis of mono- and disubstituted quinazolinones.
4. Conclusions
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In summary, we have successfully demonstrated for the
first time that Cu-CNTs nanocomposite could be used as an
excellent and efficient catalyst for convenient synthesis of
2,3-dihydroquinazolin-4(1H)-one derivatives under solvent free
conditions and microwave irradiation. The novelty and synthetic
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Appendix A. Supplementary data
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molcata.2013.01.031.
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