Immobilization of phosphomolybdic acid nanoparticles on imidazole functionalized Fe3O4@SiO2: A novel and reusable nanocatalyst for one-pot synthesis of Biginelli-type 3,4-dihydro-pyrimidine-2-(1H)-ones/thiones under solven

Article abstract of DOI:10.1039/c4ra09929j

This article introduces Fe₃O₄@SiO₂-imid-H₃PMo₁₂O₄₀ nanoparticles as heterogenic catalyst for the synthesis of 3,4-dihydropyrimidinones under solvent-free condition. This reaction proceeds t

Full text of DOI:10.1039/c4ra09929j

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: J. javidi, M.
Esmaeilpour and F. nowroozi, RSC Adv., 2014, DOI: 10.1039/C4RA09929J.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Page 1 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
Graphical abstract
Fe3O4@SiO2-imid-PMAn: A novel and reusable nanocatalysts

RSC Advances
Page 2 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Immobilization of Phosphomolybdic Acid nanoparticles on Imidazole
Functionalized Fe3O4@SiO2: A novel and reusable nanocatalysts for one-pot
synthesis of Biginelli-type 3,4-dihydro- pyrimidine-2-(1H)-ones/thiones under
solvent-free conditions
Mohsen Esmaeilpour (1)*, Jaber Javidi (2)*, Fatemeh Nowroozi Dodeji(2)
(1) Chemistry Department, College of Science, Shiraz University, Shiraz, Iran
(2) Department of Pharmaceutics, School of Pharmacy, Shahid Beheshti University of Medical
Sciences, Tehran, Iran
*Corresponding author. Tel.: +98 7116137738, fax: +98 7112286008.
E-mail address: m1250m551085@yahoo.com (M. Esmaeilpour), JaberJavidi@sbmu.ac.ir (J.
Javidi),
Abstract
This article introduces of Fe3O4@SiO2-imid-H3PMo12O40 nanoparticles as heterogenic catalyst
for the synthesis of 3,4-dihydropyrimidinones under solvent-free condition. This reaction
proceeds through acetoacetate esters and aldehyde derivatives followed by cyclisation with an
urea to the dihydropyrimidinone. Excellent yields of dihydropyrmidinones are obtained within a
short reaction time. The suggested method offers several advantages such as short reaction times,
1

Page 3 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
high yields, easy purification, a cleaner reaction and ease of recovery and reusability of the
catalyst by a magnetic field. Also, the aforementioned nanocatalyst can be easily recovered by an
external magnetic field and reused for subsequent reactions at least 5 times without noticeable
deterioration in catalytic activity. Particle size distribution, surface area, magnetic properties and
percent of leaching of H3PMo12O40 (PMA) after any reaction were investigated by dynamic light
scattering (DLS), nitrogen physisorption method (BET) and Inductively Coupled Plasma (ICP)
analyzer.
Keywords
3,4-Dihydropyrimidine; Biginelli Reaction; Solvent-Free; Magnetic Nanocatalyst;
Heteropolyacids
Introduction
3,4-Dihydropyrimidin-2(1H)-ones are interesting compounds due to their biological
importance and exhibit a wide range of pharmaceutical and therapeutic properties.1 These
products are medicinally important as calcium channel blockers, anti-inflammatory
agents, antihypertensive, anti-tumor, anti-inflammatory, adrenergic and neuropeptide
antagonists.2 They are prepared by Biginelli reaction. The Biginelli’s reaction consists of
three compound condensation of an aldehyde, α,β-ketoester and urea in the presence of
an acid catalyst.3
2

RSC Advances
Page 4 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Recently, several procedures have been reported by Lewis acids and protic acids as
catalyst for the synthesis of dihydropyrimidinones derivatives.4 Although most of
reported methods are worthwhile, many of them have one or more of the following
drawbacks: tedious workup of the reaction mixture, difficulty in separation and recovery
of the catalyst, expensive moisture sensitive reaction conditions, toxic metals, low yields
and long reaction times.
Therefore, in spite of a large number of methods reported for this transformation,
development of more efficient, simple and milder protocols by suitable catalysts are
needed.
Brønsted acids such as Keggin-type heteropolyacids (HPAs) have been used as efficient
catalysts for a variety of organic reactions because of their superacidic and redox
properties, low toxicity, ease of handling, low cost, high thermal stability, high proton
mobility, water tolerance, stronger acids than homogeneous acid catalysts, development
of clean technologies, recoverability and reusability.5 Although HPAs in their acidic form
are versatile compounds, their main disadvantages are high solubility in polar solvents
and low surface area (<10 m2/g). Therefore, in a homogeneous reaction the isolation of
the products and the reuse of the catalyst after reaction become difficult.6 Therefore, in
order to overcome this problem, these materials disperse on supports (such as silica,
acidic ion-exchange resins, active carbon and etc.) which possess large surface area. The
3

Page 5 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
use of support allows the heteropolyacids to be dispersed over a large surface area and
increases theirs catalytic activity.7
Nanoparticles have properties intermediate between those of bulk and single particles.8
They are expected to be suitable candidates for the design of highly active and selective
catalysts. Nanostructured materials, a new branch of materials research, are attracting a
great deal of attention because of their potential applications in areas such as optics,9
ceramics,10 electronics,11 catalysis,12 magnetic data storage,13 and nanocomposites. The
unique properties and the improved performances of nanomaterials are determined by
their sizes, surface structures and inter-particle interactions.
In previous work,14 we introduce a simple, repaid, inexpensive and one step method,
solvothermal, for synthesis of H3PMo12O4 nanoparticles (PMAn) from H3PMo12O4 bulk
particles (PMAb). Acidity of as-prepared nanoparticles was investigated by pyridine
adsorption method. Results showed rising acidity by declining particle size of HPAs.
In recent years, nanomagnetic materials have emerged as viable alternatives to
conventional heterogeneous supports.15 The magnetic separation technology offers many
advantages over conventional filtration and other purification methods.
In family of nanomagnetic materials, magnetite (Fe3O4) exhibits excellent properties, so
that makes it great potential applications in magnetic bio-separations,16 drug delivery,17
magnetic resonance imaging (MRI) contrast agents,18 hyperthermia treatment of cancer
cells19 and catalysts20.
4

RSC Advances
Page 6 of 29
View Article Online
DOI: 10.1039/C4RA09929J
In our previous study21, PMAn were supported on magnetic Fe3O4@SiO2-imid
nanoparticles. Compared to other substrates (silica, acidic ion-exchange resins, active
carbon and nano titania7b), Fe3O4@SiO2–imid nanoparticles have various advantages
such as high loading capacity, low leaching and simple and efficient recovery procedure.
Fig. 1 presents the procedure for the preparation of Fe3O4@SiO2–imid–PMAn stepwise.
In this work, we tried to synthesize dihydropyrimidin derivatives with using
Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb catalysis.
Results and discussion
In our previous work21, the Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2–imid–PMAn nano
catalysts were characterized by various methods such as transmission electron
microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering
(DLS), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM) and
etc. As shown in Fig. 1 Fe3O4@SiO2–imid–PMAn nanoparticles have spherical shapes
with approximately 50 nm diameters. The size distribution of these is centered at a value
of 55 nm. The magnetic properties of Fe3O4, Fe3O4@SiO2, Fe3O4@SiO2-imid-PMAn
nanoparticles were measured by VSM at room temperature. All the samples show a
typical superparamagnetic behavior. Hysteresis phenomenon was not found and the
magnetization and demagnetization curves were coincident. The saturation magnetization
of samples (a–c) is 63.4, 39.7, 33.2 emu/g, respectively.
5

Page 7 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
Fig. 1 Preparation and characterization of Fe3O4@SiO2–imid–PMAn stepwise.
6

RSC Advances
Page 8 of 29
View Article Online
DOI: 10.1039/C4RA09929J
We wish to report that immobilization of phosphomolybdic acid on imidazole
functionalized Fe3O4@SiO2 (Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb)
catalyzed the Biginelli reaction of aromatic aldehydes, acetoacetate esters and urea to
yielding the dihydropyrimidinones. In pursuit of developing a solvent-free methodology
for the preparation of these biologically important compounds, we decided to explore the
use of these magnetic nanocatalysts for the synthesis of various substituted 3,4-
dihydropyrimidin-2(1H)-ones by Biginelli protocol under solvent-free condition (Scheme
1).
R1
O
C
N
C
O
C
X
C
O
O
C
N
C
R2
C
C
Magnetic nanocatalyst
Solvent-free, 80oC
R2
R2
C
+
+
X
C
C
N
N
R1
C
Scheme.1 Synthesize dihydropyrimidin derivatives with using Fe3O4@SiO2-imid-PMAn
nanocatalyst.
Initially the reaction between benzaldehyde (1mmol), acetoacetate esters (1mmol) and
urea (1.5mmol), as the model reaction was examined in the presence of various amount
of the nanocatalysts and the results are presented in Table 1, entries 1-5. The best result
was attributed to the reaction of benzaldehyde (1mmol), ethyl acetoacetate (1mmol) and
urea (1.5mmol) in presence of 0.03g or 0.04g of Fe3O4@SiO2-imid-PMAn or
Fe3O4@SiO2-imid-PMAb nanocatalysts at 80oC (Table1, entry 4). The results show
7

Page 9 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
clearly that nanocatalysts are effective for this transformation and in the absence of it, the
reaction did not take place even after higher reaction time (Table1, entry 1).
Table1 Optimization of synthesis of 3,4-dihydro- pyrimidin-2-(1H)-ones /thiones
Fe3O4@SiO2-imid-PMAn
Fe3O4@SiO2-imid-PMAb
Amount of
Entry
Solvent
Condition
80oC
Amount of
catalysts (g)
Time
(min)
Yieldb
(%)
Time
(min)
Yieldb
(%)
catalysts
(g)
Solvent-free
Trace
Trace
1
2
-
60
60
30
30
30
45
60
60
60
60
60
60
60
60
-
90
90
90
45
45
60
90
90
90
90
90
90
90
90
Solvent-free
Solvent-free
Solvent-free
Solvent-free
80oC
80oC
80oC
80oC
0.01
0.02
0.03
0.04
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
71
92
93
0.02
0.03
0.04
0.05
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.04
62
81
89
89
3
4
5
92
82
21
83
80
86
38
87
45
51
6
Solvent-free
Solvent-free
Toluene
THF
60oC
r.t
78
17
73
75
80
26
80
33
32
7
8
9
reflux
reflux
reflux
reflux
reflux
reflux
reflux
10
11
12
13
14
Ethanol
H2O
CH3CN
CHCl3
CH2Cl2
a Reaction condition: benzaldehyde (1 mmol), ethylacetoacetate (1mmol), urea (1.5 mmol).
b Isolated yield.
The effect of temperature was studied by carrying out the model reaction at different
temperatures under solvent-free condition (room temperature, 60◦C and 80oC) and the
best results were obtained at 80oC (Table 1, entries 4, 6 and 7). Then, the reactions were
conducted in refluxing toluene, THF, EtOH, H2O, CH3CN, CH2Cl2 and CHCl3 as
solvents and under solvent-less condition (Table1, entries 4 and 8-14). When the reaction
was performed in solvent-free, the progress of the reaction was higher in comparison with
8

RSC Advances
Page 10 of 29
View Article Online
DOI: 10.1039/C4RA09929J
solvent conditions. Therefore, the solvent-free condition was used for the synthesis of
dihydropyrimidinones derivatives.
In order to study the generality of the procedure, a series of aromatic aldehydes with the
electron-donating and electron-withdrawing substituent were reacted with ethyl
acetoacetate and urea under the optimized conditions. The results are presented in Table
2. Aromatic aldehydes containing both electron donating and electron withdrawing
groups afforded high yields of the desired products.
Also heterocyclic aromatic compounds, such as furyl-2-carbaldehyde and thiophen-2-
carbaldehyde produced the corresponding dihydropyrimidinones in excellent yields
(Table 2, entries11and12). Also, more importantly acid sensitive aldehydes such as 2-
furfural, underwent condensation without formation of any side products (Table2,
entry11).
The reaction of other 1,3-dicarbonyl compounds such as acetylacetone also run with
benzaldehyde and urea in the presence of Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-
imid-PMAb nanoparticles under solvent free conditions and the corresponding
dihydropyrimidinones were obtained in high yields (Table2, entry 15). Also, the reaction
of benzaldehyde and its 4-chloro, 4-methyl and 4-methoxy derivatives were treated with
ethyl acetoacetate and thiourea in the presence of nanocatalysts under solvent-free at
80oC and the related Biginelli products were obtained in high yields (Table 2, entry16-
19).
9

Page 11 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
Table2 Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb -catalyzed one-pot
synthesis of 3,4-dihydro- pyrimidin-2(1H)-ones/thiones.a
Fe3O4@SiO2-imid-PMAn Fe3O4@SiO2-imid-PMAb
Time (min) Yieldb (%) Time (min) Yieldb (%)
m.p. (oC)
Entry
R1
R2
X
Found
Reported[Ref]
1
C6H5
OEt
205-206
206-208[22]
O
30
93
45
89
2
3
4-Br-C6H4
2-Cl-C6H4
4-Cl-C6H4
OEt
OEt
OEt
213-214
215-216
215-216
222-223
227-228
210
213-215[23]
216-218[24]
214-215[25]
221[26]
229-231[27]
209-211[25]
205-206[22]
262[28]
201-203[25]
203-205[29]
209-210[30]
225-227[27]
207-210[25]
233-236[31]
208-210[27]
180-182[27]
192-194[27]
152-153[32]
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S
35
35
35
25
25
20
35
40
40
25
30
40
30
30
30
25
30
35
86
88
90
92
90
94
91
91
90
95
92
85
92
88
91
90
89
87
55
50
50
30
30
30
50
60
60
30
60
60
50
50
45
45
45
45
81
83
87
89
92
91
88
85
82
91
85
80
89
88
84
88
86
83
4
5
2-NO2-C6H4 OEt
3-NO2-C6H4 OEt
4-NO2-C6H4 OEt
6
7
8
4-Me-C6H4
OEt
203-204
262-263
200-201
205-206
210-211
223-224
208-209
235-236
211
9
2-MeO-C6H4 OEt
4-MeO-C6H4 OEt
10
11
12
13
14
15
16
17
18
19
2-Furyl
OEt
2-Thiophene OEt
PhCH=CH
C6H5
OEt
OMe
CH3
OEt
OEt
OEt
C6H5
C6H5
4-Cl-C6H4
4-Me-C6H4
179-180
191-193
153
S
S
4-MeO-C6H4 OEt
S
a Reaction condition aldehyde (1 mmol), β-diketoester (1mmol), urea or thiourea (1.5 mmol),
Fe3O4@SiO2-imid-PMAn (0.03g) or and Fe3O4@SiO2-imid-PMAb (0.04g), solvent-free, 80oC.
bIsolated yield.
A comparison among Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb and the
other catalysts, which were reported in the literature, in synthesis of 3,4-dihydropyrimid-
inones revealed advantages of these magnetic nanocatalysts over the most of them in
term of higher yield and shorter reaction time (Table3). According to these findings,
10

RSC Advances
Page 12 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb led to the best result and
produced the maximum conversion in the shortest time (Table3, entry1,2).
Table3 Comparison of the catalytic efficiency of Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-
imid-PMAb with that of reported catalysts in the preparation of ethyl 6-methyl-2-oxo-4-phenyl-
1,2,3,4-tetrahydropyrimidine-5- carboxylate.
Entry
Catalyst
Fe3O4@SiO2-imid-PMAn
Time
30 min
45min
5h
6-7h
12h
6h
18h
48h
3h
Yielda (%)
literature reference
1
2
3
4
5
6
7
8
9
93
89
80
75
94
91
71
82
90
This work
This work
[24]
Fe3O4@SiO2-imid-PMAb
12-Molybdophosphoric acid
12-Tungstophosphoric acid (PWA)
Trichloroisocyanuric acid (TCCA)
Silica sulfuric acid
[33]
[34]
[35]
[3]
[28]
[36]
Sulfuric acid
Montmorilonite KSF
TiCl4-MgCl2·4CH3OH
L-Pyrrolidine-2-carboxylicacid-4-hydrogen
sulfate supported on silica gel
Amberlyst-70
Sm(ClO4)3
Chiral ligand/HCl
NH4H2PO4
poly(4-vinylpyridine-co-divinylbenzene)–Cu(II)
complex
10
6h
92
[37]
11
12
13
14
3h
9
6 day
2h
81
72
81
85
[38]
[39]
[40]
[41]
15
24h
70
[42]
aIsolated yield.
Considering the general mechanistic pathway, the suggested mechanism for the
formation of (3) using Fe3O4@SiO2-imid-PMAn or Fe3O4@SiO2-imid-PMAb is shown in
Scheme 2. Protonation of the carbonyl group by Brønsted acid generates an electrophilic
center on the carbonyl carbon atom, which is easily attacked by the urea to form
minimum intermediate (1), which is the key rate-limiting step. Interception of this
11

Page 13 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
minimum intermediate (1) by β-dicarbonyl produces an open chain ureide (2), which
subsequently cyclizes through dehydration process yielding compounds (3).
NH
H2PMo12O40
Si
N
H+
R2
O
O
R1
O
O
O
H
R1
H
X
R1
H
R1
H
OH
NH2
R2
H3C
NH
H3C
-H2O
X
+
N
NH2
N
NH2
X
X
(1)
(2)
H2N
NH2
R1
O
R1
O
H
R2
H3C
NH
R2
H3C
NH
-H2O
N
H
X
N
H
X
HO
(3)
Scheme.2 Proposed mechanism for synthesis of dihydropyrimidinones via Biginelli
condensation protocol.
However, magnetically supported catalysts can be recovered with an external magnet due
to the paramagnetic character of the support, resulting in remarkable catalyst recovery
without the need for a filtration step (Scheme3).
12

RSC Advances
Page 14 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Scheme.3 Catalyst ability to effective recovery at the end of reactions by external
magnetic field.
The activity of the recycle catalysts were also examined under the optimized conditions
and the desired products were obtained in high yields after 4 runs without distinct
deterioration in catalytic activity (Fig. 2).
13

Page 15 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
a Reaction condition: (A) benzaldehyde (1 mmol), ethyl acetoacetate (1mmol), urea or thiourea (1.5
mmol), Fe3O4@SiO2-imid-PMAn (0.03g), solvent-free, 80oC.
b Reaction condition: (A) benzaldehyde (1 mmol), ethyl acetoacetate (1mmol), urea or thiourea (1.5
mmol), Fe3O4@SiO2-imid-PMAb (0.04g), solvent-free, 80oC.
Fig.2 Recyclability of Fe3O4@SiO2-imid-PMAn (A) and Fe3O4@SiO2-imid-PMAb (B) in
the synthesis of 3,4-dihydro- pyrimidin-2-(1H)-ones under solvent-free conditions.
The amounts of the nano heteropolyacid leaching for the reactions under the optimized
conditions were detected. The molybdenum (Mo) amount in reaction medium after each
reaction cycle was measured through ICP and details are provided in Table 4. The
analysis of the reaction mixture by the ICP technique showed that the leaching of
H3PMo12O40 was negligible. Additionally, the size and surface area of catalysts after each
reaction cycle was investigated by DLS and nitrogen physisorption method (BET)
respectively and results are provided in Table 4. As shown, the size of catalysts will be
14

RSC Advances
Page 16 of 29
View Article Online
DOI: 10.1039/C4RA09929J
increased after each cycle. Generally, leaching of H3PMo12O40, increase of catalyst size
and decrease of surface area led to a decrease in the yield of reaction.
Table 4 Mean article size, surface area and ratio of PMAn leaching in each reaction cycle
Run
Mean article size (nm)a surface area (m2/g)b Ratio of leaching (%)c
1
2
3
4
5
55
59
62
68
73
422
410
392
386
377
0.09
0.11
0.15
0.20
0.33
a By DLS
b By BET
By ICP
c
Conclusion
In conclusion, we report here a high yielding one-pot synthesis of 3,4-dihydropyrimidin-
2- (1H)-ones and thione analogs from readily available aldehydes, acetoacetate esters and
urea or thiourea in presence of efficient magnetic nanocatalysts by Biginelli reactions
under solvent-free conditions. The protocol offers several advantages such as easy
preparation, heterogeneous nature and easy separation of the catalyst, short reaction
times, easy isolation, very good yields and simple work up procedures. Also, in solvent-
free reactions the purification process is simplified and the reaction is environmentally
friendly. The nanocatalysts could be successfully recovered and recycled at least for five
runs without noticeably decreasing in catalytic activity.
Experimental
General methods
15

Page 17 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
All starting materials were purchased from fluka. The reactions were monitored by thin
layer chromatography (TLC). 1H NMR, 13C NMR spectra were obtained at 250MHz
using a Bruker spectrometer in CDCl3 as the solvent and tetramethyl silane (TMS) as
internal reference. Fourier transform infrared (FT-IR) spectra were obtained using a
Shimadzu FT-IR 8300 spectrophotometer. Melting points were determined on a Mel-
Temp apparatus. Magnetic characterization was carried out on a vibrating sample
magnetometer (Meghnatis Daghigh Kavir Co., Iran) at room temperature, and dynamic
light scattering (DLS) was recorded on a HORIBA-LB550 instrument. A transmission
electron microscope (Philips EM208) with an accelerating voltage of 100 kV was used to
examine morphology, and size of the nanoparticles. All compounds were identified by
comparison of their spectral data and physical properties with those of the authentic
sample and all yields refer to isolated products.
General procedure
Preparation of Fe3O4@SiO2 Core-Shell
The core–shell Fe3O4@SiO2 nanospheres were prepared by a modified Stober method in
our previous work.12 In a typical procedure, the mixture of FeCl3.6H2O (1.3g, 4.8mmol)
in water (15ml) was added to the solution of polyvinyl alcohol (PVA 15000), as a
surfactant, and FeCl2.4H2O (0.9g, 4.5mmol) in water (15 ml), which was prepared by
completely dissolving PVA in water followed by addition of FeCl2.4H2O. The resultant
solution was left to be stirred for 30 min in 80oC. Then, hexamethylentetraamine
16

RSC Advances
Page 18 of 29
View Article Online
DOI: 10.1039/C4RA09929J
(HMTA) (1.0mol/l) was added drop by drop with vigorous stirring to produce a black
solid product when the reaction media reaches pH 10. The resultant mixture was heated
on water bath for 2h at 60oC and the black magnetite solid product was filtered and
washed with ethanol three times and was then dried at 80oC for 10h.Then Fe3O4
nanoparticle (0.50g, 2.1mmol) was dispersed in the mixture of ethanol (50mL), deionized
water (5mL) and tetraethoxysilane (TEOS) (0.20mL), followed by the addition of 5.0mL
of NaOH (10wt%). This solution was stirred mechanically for 30 min at room
temperature. Then the product, Fe3O4@SiO2, was separated by an external magnet, and
was washed with deionized water and ethanol three times and dried at 80oC for 10 h.
4.2.2. Preparation of H3PW12O40 nanoparticles (PMAn)
PMAn nanoparticles were prepared in our previous work.14 In a typical procedure, 5
mmol of bulk H3PMo12O40 (PMAb) was dispersed in 50 mL n-Octane and the resulting
dispersion was stirred vigorously for 30 min at room temperature to form a homogeneous
dispersion. This dispersion was transferred into a Teflon-lined stainless autoclave filling
80% of the total volume. The autoclave was sealed and maintained at 150oC for 12 h. The
autoclave was then cooled to room temperature. Finally, the resulted powder was filtered
and washed for several times by Octane, and dried in a vacuum at 80oC for 12 h.
Preparation of Fe3O4@SiO2-imid-PMAn
Fe3O4@SiO2 (1g) was added to the solution of 3-chlorotriethoxypropylsilane (1 mmol,
0.241 g) and imidazole (1 mmol, 0.0680 g) in p-xylene (20 mL) and the resultant mixture
17

Page 19 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
was under reflux for 24h under nitrogen atmosphere. After refluxing for about 24 h, the
mixture was cooled to room temperature, filtered by an external magnet and the product
was washed with xylene to remove no reacted species and dried at 70 oC for 6 h.
Fe3O4@SiO2-imid (1.0g) was added to an acetonitrile solution of PMAn (1.0mmol) in
20mL was taken in a round-bottom flask. The mixture was refluxed for 24h under
nitrogen atmosphere. After 24h, the mixture was filtered by an external magnet, washed
with acetonitrile and dichloromethane, and dried at 70oC for 6h. Also, the same method
was used for the synthesis of Fe3O4@SiO2-imid-PMAb (PMAn = nano H3PMo12O40,
PMAb= H3PMo12O40).21
2.2.4. General procedure for the synthesis of 4-aryl-3,4-dihydropyrimidin-2(1H)-one
In a typical experiment, a mixture of aldehyde (10 mmol), β-diketoester (10 mmol) and
urea or thiourea (15 mmol) in solvent-free conditions was stirred for few minutes at 80oC,
in the presence of Fe3O4@SiO2-imid-PMAn (0.03g) or Fe3O4@SiO2-imid-PMAb (0.04g).
After completion of the reaction, ethyl acetate was added to the solidified mixture and the
insoluble catalyst was separated by magnetic field. The filtrate was dried and organic
medium was removed with a rotary evaporator under reduced pressure. Then, the
resulting solid product was recrystallized from ethanol to give pure product.
Spectral Data
18

RSC Advances
Page 20 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Ethyl-6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate (Table2,
entry 1)
White solid, m.p. 205-206 ◦C. 1H-NMR (250 MHz, CDCl3): δ= 1.15 (t, J= 7.1 Hz, 3H,
CH3CH2O-), 2.34 (s, 3H, CH3), 4.05 (m, 2H, CH2), 5.39 (s, 1H, CH), 5.70 (s, 1H, NH),
7.21-7.32 (m, 5H, Ar-H), 8.12 (s, 1H, NH). 13C-NMR (62.9 MHz, CDCl3): δ= 14.11,
18.65, 55.73, 59.99, 101.34, 126.58, 127.93, 128.69, 143.68, 146.26, 153.26, 167.23. IR
(KBr): 3244, 3116, 2931, 1728, 1701, 1651 cm-1.
Ethyl
4-(2-chlorophenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylate (Table 2, entry 3)
White solid, m.p. 215-216 ◦C. 1H-NMR (250 MHz, CDCl3): δ= 1.05 (t, J= 7.10 Hz, 3H,
CH3CH2-), 2.42 (s, 3H, CH3), 4.02 (q, J= 7.10 Hz, 2H, CH3CH2-), 5.85 (s, 1H, CH-),
5.87 (s, 1H, NH), 7.17-7.56 (m, 4H, Ar-H), 8.85 (s, 1H, NH). 13C-NMR (62.9 MHz,
CDCl3): δ= 13.97, 18.28, 52.10, 59.95, 98.82, 127.52, 127.99, 129.26, 129.77, 132.56,
139.52, 148.48, 153.24, 165.31. IR (KBr): 3232, 3112, 2920, 1701, 1643 cm-1.
Ethyl
4-(4-chlorophenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylate (Table 2, entry 4)
White solid, m.p. 215-216 ◦C. 1H-NMR (250 MHz, CDCl3): δ= 1.09 (t, J= 7.12 Hz, 3H,
CH3CH2-), 2.33 (s, 3H, CH3), 4.06 (m, CH3CH2-), 5.36 (s, 1H, CH-), 5.87 (s, 1H, NH),
7.27 (4H, Ar-H), 8.38 (s, 1H, NH). 13C-NMR (62.9 MHz, CDCl3): δ= 14.13, 18.68,
19

Page 21 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
55.02, 60.05, 127.79, 128.51, 128.65, 141.93, 146.18, 152.92, 158.86, 165.15. IR (KBr):
3244, 3116, 2927, 1705, 1651 cm-1.
Ethyl 6-methyl-4-(2-nitrophenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(Table 2, entry 5)
White solid, m.p. 222-223 ◦C. 1H NMR (250 MHz, DMSO-d6): δ= 1.09 (t, 3H, J=7.35
Hz, CH3, CH3CH2-), 2.26 (s, 3H, CH3), 3.86 (q, 2H, J=7.35 Hz, OCH2), 5.51 (d, 1H, J=
2.88 Hz, CH-), 7.01 (d, 1H, J=7.92 Hz, Ar-H), 7.14 (m, 1H, Ar-H), 7.19 (d, 1H, J= 6.23
Hz, Ar-H), 7.29 (m, 1H, Ar-H), 7.31 (s, 1H, NH), 9.09 (s, 1H, NH). 13C NMR (62.9
MHz, DMSO-d6): δ: 165.79, 156.54, 151.25, 150.13, 133.10, 128.11, 127.02, 119.32,
110.65, 97.10, 54.71, 49.13, 18.01, 17.04. IR (KBr): 3238, 3120, 2931, 1724, 1648, 1531,
1354 cm-1.
Ethyl 6-methyl-4-(3-nitrophenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(Table 2, entry 6)
Pale-yellow solid, m.p. 227-228 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.07 (t, J= 7.0
Hz, 3H, CH3CH2-), 2.48 (s, 3H, CH3), 3.96 (q, J= 1.8 Hz, 2H, CH3CH2-), 5.28 (s, 1H,
CH-), 7.66 (m, 2H, Ar-H), 7.87 (s, 1H, NH), 8.11 (m, 2H, Ar-H), 9.33 (s, 1H, NH). 13C-
NMR (62.9 MHz, DMSO-d6): δ= 13.91, 17.78, 53.46, 59.34, 98.26, 120.94, 122.29,
130.16, 132.93, 146.89, 147.64, 149.36, 151.74, 164.99. IR (KBr): 3328, 3101, 2931,
1708, 1627, 1527 cm-1.
20

RSC Advances
Page 22 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Ethyl 6-methyl-4-(4-nitrophenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(Table 2, entry 7)
White solid, m.p. 210 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.07 (m, 3H, CH3CH2-),
2.24 (s, 3H, CH3), 3.95 (m, 2H, CH3CH2-), 5.25 (s, 1H, CH-), 7.49 (m, 2H, Ar-H), 7.87
(s. 1H, NH), 8.21 (m, 2H, Ar-H), 9.33 (s, 1H, NH). 13C-NMR (62.9 MHz, CDCl3): δ=
19.23, 23.05, 58.85, 64.602, 103.36, 129.03, 132.85, 151.78, 154.58, 156.94, 157.16,
170.25. IR (KBr): 3232, 3117, 2916, 1705, 1647 cm-1.
Ethyl
4-(2-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylate (Table 2, entry 9)
White solid, m.p. 262-263 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.00 (t, J= 7.04 Hz,
3H, CH3CH2-), 2.47 (s, 3H, CH3), 3.76 (s, 3H, -OCH3), 3.90 (m, 2H, CH3CH2-), 5.46
(s, 1H, CH-), 6.81-7.23 (m, 5H, Ar-H, NH), 9.08 (s, 1H, NH). 13C-NMR (62.9 MHz,
DMSO-d6): δ= 13.94, 17.63, 48.80, 55.29, 58.93, 111.04, 120.07, 127.00, 128.63,
146.17, 156.45, 167.41. IR (KBr): 3251, 2958, 1724, 1701, 1635 cm-1.
Ethyl
4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylate (Table 2, entry 10)
White solid, m.p. 200-201◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.07 (m, 3H,
CH3CH2-), 2.22 (s, 3H, CH3), 3.69 (s, 3H, -OCH3), 3.91 (m, 2H, CH3CH2-), 5.08 (s,
1H, CH-), 6.75 (m, 2H, Ar-H), 7.11 (m, 2H, Ar-H), 7.65 (s, 1H, NH), 9.14 (s, 1H, NH).
13C-NMR (62.9 MHz, DMSO-d6): δ= 14.03, 17.69, 53.27, 54.97, 59.08, 99.49, 113.62,
21

Page 23 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
127.33, 136.99, 147.94, 152.11, 158.37, 165.30. IR (KBr): 3251, 3112, 2923, 1705, 1651
cm-1.
Ethyl
4-(furan-2-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(Table 2, entry 11)
Black solid, m.p. 205-206 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.14 (t, J= 5.27 Hz,
3H, CH3CH2-), 2.20 (s, 3H, CH3), 4.02 (q, J= 7.04 Hz, 2H, CH3CH2-), 5.19 (s, 1H,
CH), 6.06-6.12 (m, 1H, Ar-H), 6.24-6.34 (m, 1H, Ar-H), 7.35 (m, 1H, Ar-H), 7.72 (s, 1H,
NH), 9.21 (s, 1H, NH). 13C-NMR (62.9 MHz, DMSO-d6): δ= 13.88, 14.07, 53.20,
59.15, 105.20, 110.27, 113.58, 142.06, 143.56, 150.50, 156.41, 158.67. IR (KBr): 3201,
3250, 2896, 2850, 1693 cm-1.
Ethyl 6-methyl-2-oxo-4-(thiophen-2-yl)-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(Table 2, entry 12)
White solid, m.p. 210-211 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.17 (m, 3H,
CH3CH2-), 2.20 (s, 3H, CH3), 4.04 (q, J= 7.05 Hz, 2H, CH3CH2-), 5.39 (s, 1H, CH-),
6.87-6.93 (m, 2H, Ar-H), 7.17.(m, 1H, Ar-H), 7.88.(s, 1H, NH), 9.48 (s, 1H, NH). 13C-
NMR (62.9 MHz, DMSO-d6): δ= 14.08, 17.61, 49.28, 59.30, 99.71, 123.44, 124.56,
126.60, 148.59, 148.70, 152.19, 164.95. IR (KBr): 3332, 3240, 3116, 2981, 1701, 1647,
1230, 1095 cm-1.
Ethyl 6-methyl-2-oxo-4-styryl-1,2,3,4-tetrahydropyrimidine-5-carboxylate (Table 2,
entry 13)
22

RSC Advances
Page 24 of 29
View Article Online
DOI: 10.1039/C4RA09929J
Pale- yellow solid, m.p. 223-224 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.15-1.27 (m,
3H, CH3CH2-), 2.47 (s, 3H, CH3), 4.04-4.13 (m, 2H, CH3CH2-), 4.70 (d, J= 2.8 Hz,
1H, CH), 6.13-6.21 (dd, J= 5.8, 5.95 Hz, 1H, CH=C-H), 6.38 (d, J=15.8, 1H, H-C=CH),
7.44-7.26 (m, 5H, Ar-H), 7.54 (s, 1H, NH), 9.15 (s, 1H, NH). 13C-NMR (62.9 MHz,
DMSO-d6): δ= 14.18, 17.69, 51.82, 59.15, 97.70, 126.26, 127.51, 127.74, 128.04,
129.89, 136.16, 148.49, 152.57, 165.14. IR (KBr): 3241, 1704, 1650, cm-1.
5-Acetyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (Table 2, entry 15)
Pale- yellow solid, m.p. 235-236 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 2.08 (s, 3H,
CH3), 2.27 (s, 3H, CH3CO-), 5.23 (s, 1H, CH-), 7.21-7.33 (m, 5H, Ar-H), 7.80 (s, 1H,
NH), 8.97 (s, 1H, NH). 13C-NMR (62.9 MHz, DMSO-d6): δ= 18.84, 30.24, 53.74,
109.53, 126.35, 127.28, 128.46, 144.15, 148.07, 152.09, 194.24. IR (KBr): 3294, 3116,
2920, 1701, 1616 cm-1.
Ethyl
6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate
(Table 2, entry 16)
White solid, m.p. 211 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.08 (m, 3H, CH3CH2-),
2.27 (s, 3H, CH3), 3.99 (m, 2H, CH3CH2-), 5.09 (s, 1H, CH-), 6.89 (m, 2H, Ar-H), 7.09-
7.30 (m, 2H, Ar-H), 9.58 (s, 1H, NH), 10.27 (s, 1H,NH). 13C-NMR (62.9 MHz, DMSO-
d6): δ= 13.96, 17.07, 55.01, 59.47, 100.88, 113.79, 127.55, 135.64, 144.68, 158.66,
165.09, 173.94. IR (KBr): 3328, 3174, 1670, 1573 cm-1.
23

Page 25 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
Ethyl
4-(4-chlorophenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-
carboxylate (Table 2, entry 17)
White solid, m.p. 179-180 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.09 (m, 3H,
CH3CH2), 2.27 (s, 3H, CH3), 3.97 (m, 2H, CH3CH2-), 5.14 (s, 1H, CH-), 7.16- 7.23 (m,
2H, Ar-H ), 7.38-7.42 (m, 2H, Ar-H), 9.65 (s, 1H, NH), 10.59 (s, 1H, NH). 13C-NMR
(62.9 MHz, DMSO-d6): δ= 13.93, 17.12, 53.38, 59.59, 100.21, 128.25, 128.53, 132.20,
142.31, 145.32, 164.92, 174.17. IR (KBr): 3325, 3178, 2985, 1674, 1573, 1195 cm-1.
Ethyl 4-(4-methoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimid- ine -5-
carboxylate (Table 2, entry 19)
Yellow solid, m.p. 153 ◦C. 1H-NMR (250 MHz, DMSO-d6): δ= 1.05 (m, 3H, CH3CH2-
), 2.27 (s, 3H, CH3), 3.69 (s, 3H, -OCH3), 3.99 (m, 2H, CH3CH2-), 5.09 (s, 1H, CH-),
6.86 (m, 2H, Ar-H), 7.13 (m, 2H, Ar-H), 9.58 (s, 1H, NH), 10.27 (s, 1H,NH). 13C-NMR
(62.9 MHz, DMSO-d6): δ= 19.21, 22.32, 58.63, 60.26, 64.73, 106.13, 119.04, 132.80,
140.89, 149.93, 163.92, 170.34, 179.19. IR (KBr): 3313, 3170, 1666, 1573 cm-1.
Acknowledgements
Authors are grateful to the council of Iran National Science Foundation and University of
Shiraz for their unending effort to provide financial support to undertake this work.
References
24

RSC Advances
Page 26 of 29
View Article Online
DOI: 10.1039/C4RA09929J
1 (a) A.K. Sharma, S. Jayakumar, M.S. Hundal, M.P. Mahajan, J. Chem. Soc. Perkin Trans.
2002, 1, 774; (b) S. Sasaki, N. Cho, Y. Nara, M. Harada, S. Endo, N. Suzuki, J. Med. Chem.
2003, 46, 113; (c) S. Bartolini, A. Mai, M. Artico, N. Paesano, D. Rotili, C. Spadafora, J. Med.
Chem. 2005, 48, 6776; (d) A.R. Khosropour, I. Mohammadpoor-Baltork, H. Ghorbankhani,
Catal. Commun., 2006, 7, 713.
2 (a) C. O. Kappe, Eur. J. Med. Chem., 2000, 35, 1043; (b) C. O. Kappe, O. V. Shishkin, G.
Uray, P. Verdino, Tetrahedron, 2000, 56, 1859.
3 D. Shobha, M.A. Chari, A. Mano, S.T. Selvan, K. Mukkanti, A. Vinu Tetrahedron, 2009, 65
10608.
4 (a) R. Ghosh, S. Maiti, A. Chakraborty, J. Mol. Catal. A: Chem. 2004, 217, 47; (b) A.S.
Paraskar, G.K. Dewker, A. Sudalai, Tetrahedron Lett. 2003, 44, 3305; (c) S. Tu, F. Fang, S.L.
Zhu, T.X. Zhang, Q. Zhuang, Synlett. 2004, 3, 537; (d) X.H. Chen, X.Y. Xu, H. Liu, L.F. Cun,
L.Z. Gong, J. Am. Chem. Soc. 2006, 128, 14802; (e) W.Y. Chen, S. Qin, J. R. Jin, Catal.
Commun. 2007, 8, 123; (f) M.M. Heravi, L. Ranjbar, F. Derikvand, B. Alimadadi, Mol. Divers.
2008, 12, 191.
5 M. Esmaeilpour, J. Javidi, F. Dehghani, F. Nowroozi Dodeji, New J. Chem., 2014,
38, 5453.
6 L. T. Aany Sofia, A. Krishnan, M. Sankar, N. K. Kala Raj, P. Manikandan, P. R. Rajamohanan
and T. G. Ajithkumar, J. Phys. Chem. C, 2009, 113, 21114.
7 (a) Z. Zhang, F. Zhang, Q. Zhu, W. Zhao, B. Ma and Y. Ding, J. Colloid Interface Sci., 2011,
360, 189;(b) A. Davood, K. Seyed-Mola and N. Razieh, J. Chem. Sci., 2014, 126, 95.
25

Page 27 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
8 M. Salavati-Niasari, J. Javidi, F. Davar, Ultrason. Sonochem., 2010, 17, 870.
9 K. Lance Kelly, Eduardo Coronado, Lin Lin Zhao, and George C. Schatz , J. Phys. Chem. B,
2003, 107, 668.
10 D. Vollath, D.Vinga Szabó, J. Hauβelt, J. Eur. Ceram. Soc. 1997, 17, 1317.
11 W. Lu, C. M. Lieber, Nat. Mater., 2007, 6, 841.
12 M. Esmaeilpour, A. R. Sardarian, J. Javidi, Appl. Catal. A-Gen. 2012, 445– 446, 359.
13 G. Reiss, A. Hütten, Nat. Mater., 2005, 4, 725.
14 J. Javidi, M. Esmaeilpour, Z. Rahiminezhad, F. Nowroozi Dodeji, J. Clust. Sci., 2014, 25,
1511.
15 (a) S. Shylesh, J. Schweizer, S. Demeshko, V. Schunemann, S. Ernst, W.R. Thiel, Adv. Synth.
Catal., 2009, 351, 1789; (b) E. Mohsen, J. Jaber, M. A. Mehdi, N. D. Fatemeh, J. Iran. Chem.
Soc., 2014, 11, 499.
16 I.J. Bruce, T. Sen, Langmuir, 2005, 21, 7029.
17 (a) C. Alexiou, R .Jurgons, R. Schmid, A. Hilpert, C. Bergemann, F. Parak, H. Iro, J. Magn.
Magn. Mater., 2005, 293, 389; (b) J.L. Zhang, R.S. Srivastava, R.D.K. Misra, Langmuir, 2007,
23, 6342.
18 Y.M. Huh, E.S. Lee, J.H. Lee, Y.W. Jun, P.H. Kim, C.O. Yun, J.H. Kim, J.S. Suh, Adv.
Mater. 2007, 19, 3109.
19 (a) M.F. Kircher, U. Mahmood, R.S. King, R. Weissleder, L.A. Josephson, Cancer Res.,
2003, 63, 8122; (b) J. Jaber, E. Mohsen, Colloids Surf., B, 2013, 102, 265; (c) H. Pardoe, P.R.
Clark, T.G. Pierre, P.Moroz, S.K.A. Jones, Magn. Reson. Imag., 2003, 21, 483.
26

RSC Advances
Page 28 of 29
View Article Online
DOI: 10.1039/C4RA09929J
20 (a) E.W. Wong, M.J. Bronikowski, M.E. Hoenk, R.S. Kowalczyk, B.D. Hunt, Chem. Mater.
2005, 17, 237; (b) M. Esmaeilpour, J. Javidi, F. Nowroozi Dodeji, H. Hassannezhad, J. Iran.
Chem. Soc., 2014, 11, 1703.
21 M. Esmaeilpour, J. Javidi, M. Zandi, Mater. Res. Bull., 2014, 55, 78.
22 D.S. Bose, L. Fatima, H.B. Mereyala, J. Org. Chem., 2003, 68, 587.
23 D. Russowsky, F.A. Lopes, V.S.S., Silva, K.F.S. Canto, M.G. Montes Doca, M.N. Godoi, J.
Braz. Chem. Soc., 2004, 15, 165.
24 M.M. Heravi, K. Bakhtiari, F.F. Bamoharram, Catal. Commun., 2006, 7, 373.
25 E.H. Hu, D.R. Silder, U.H. Dolling, J. Org. Chem., 1998, 63, 3454.
26 A. Shaabani, A. Bazgir, Tetrahedron Lett., 2004, 45, 2575.
27 N.Y. Fu, Y.F. Yuan, Z. Cao, S.W. Wang, J.T. Wang, C. Peppe, Tetrahedron, 2002, 58, 4801.
28 F. Bigi, S. Carloni, B. Frullanti, R. Maggi, G. Sartori, Tetrahedron Lett., 1999, 40, 3465.
29 C.V. Reddy, M. Mahesh, P.V.K. Raju, T.R.Babu, V.V.N. Reddy, Tetrahedron Lett., 2002, 43,
2657.
30 G. Sabithia, G. S. K. K. Reddy, C. S. Reddy, J. S. Yadav, Synlett, 2003, 6, 858.
31 M. Gohain, D. Prajapati, J.S. Sandhu, Synlett, 2004, 2, 235.
32 C.O. Kappe, J. Org. Chem., 1997, 62, 7201.
33 M.M. Heravi, F. Derikvand, F. Bamoharram, J. Mol. Catal. A: Chem., 2005, 242, 173.
34 M.A. Bigdeli, S. Jafari, Gh. H. Mahdavinia, H. Hazarkhani, Catal. Commun., 2007, 8, 1641.
35 P. Salehi, M. Dabiri, M.A. Zolfigol, M.A.B. Fard, Tetrahedron Lett., 2003, 44, 2889.
36 A. Kumar, R.A Maurya, J. Mol. Catal. A: Chem. 2007, 272, 53.
37 A. Ghorbani-Choghamarani, P. Zamani, Chin. Chem. Lett, 2013, 24, 804.
27

Page 29 of 29
RSC Advances
View Article Online
DOI: 10.1039/C4RA09929J
38 S.H. Chandak, N.P. Lad, P.P. Upare, Catal. Lett. 2009, 131, 469.
39 C.J. Liu, J.D. Wang, Molecules, 2010, 15, 2087.
40 D. Ding, C.G. Zhao, Eur. J. Org. Chem, 2010, 3802.
41 R. Tayebee, B. Maleki, M. Ghadamgahi, Chinese. J. Catal, 2012, 33, 659.
42 R.V. Yarapathi, S. Kurva, S. Tammishetti, Catal. Commun, 2004, 5, 511.
28