Effect of poly(ethylene glycol)-400 and carbon on MoO3 nanocomposite materials and its catalytic activity for Biginelli reactions

Article abstract of DOI:10.1002/cjoc.201180355

The effect of addition of poly(ethylene glycol)-400 (PEG-400) and carbon (0, 1, 2 and 3 wt%) as substrates were investigated systematically to get the desired phase of carbon-doped MoO₃ material. The carbon source was prepared from the Acacia a

Full text of DOI:10.1002/cjoc.201180355

FULL PAPER
Effect of Poly(ethylene glycol)-400 and Carbon on MoO3
Nanocomposite Materials and Its Catalytic Activity
for Biginelli Reactions
Navgire, Madhukar
Yelwande, Ajeet
Arbad, Balasaheb
Lande, Machhindra*
Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, India
The effect of addition of poly(ethylene glycol)-400 (PEG-400) and carbon (0, 1, 2 and 3 wt%) as substrates
were investigated systematically to get the desired phase of carbon-doped MoO3 material. The carbon source was
prepared from the Acacia arabica plant wood. The resulting samples were calcined at 500 ℃. The effect of
PEG-400 and carbon composite on the structure, particle size and morphology were investigated. The prepared
samples were characterized by XRD, SEM-EDS and FT-IR techniques. The samples with PEG-400 and carbon ad-
dition give better control of particle size and porosity. The prepared catalysts were tested for the synthesis of
3,4-dihydropyrimidones via the Biginelli-type condensation reaction. This new method consistently has the advan-
tage of excellent yields (88%—93%) and short reaction times (1.5—3 h) than do classical Biginelli reaction condi-
tions.
Keywords carbon substrate, MoO3, PEG, Biginelli reaction, 3,4-dihydropyrimidones
Introduction
molybdenum oxide based materials are of great techni-
cal interest.10-14
Acid-catalysed organic reactions are numerous and
the usage of solid acid catalysts is very important in
several industrial and environmental processes.1-5 It can
be said that solid acids are the most important hetero-
geneous catalysts used today, considering in terms of
both the total amounts used and the final economic im-
pact.6
The Biginelli reaction is one of the most important
multi-component reactions for the synthesis of dihy-
dropyrimidinones. Dihydropyrimidinones are known to
exhibit a wide range of biological and therapeutic ac-
tivities such as antiviral, antitumor, antibacterial, and
anti-inflammatory, analgesic, blood platelets aggrega-
tion inhibitors, cardiovascular properties.15 The classical
Biginelli reaction requires long reaction times (20 h)
and often suffers from low yields of products in case of
substituted aromatic and aliphatic aldehydes.16 Multi-
step synthesis17 produces somewhat higher yields but
lacks the simplicity of original one-pot Biginelli proto-
col, hence the Biginelli reaction continues to attract the
attention of organic chemists interested in finding
milder and more efficient procedures for the synthesis
of dihydropyrimidinones. Recently several methods
have been reported for preparing dihydropyrimidines
using different Lewis acids such as BF3 OEt2, LaCl3,
Yb(OTf)3,18-20 as well as protic acids such as H2SO4,
HOAc, conc. HCl21-23 as promoters. Many other meth-
ods including microwave irradiations, ionic liquids and
clay24 are also reported. However, many of these meth-
ods are associated with expensive and toxic reagents,
stoichiometric amount of catalyst, reaction time, unsat-
isfactory yields, incompatibility with other functional
groups and involve difficult product isolation proce-
dures. Moreover, some of the methods are practical for
aromatic aldehydes only.25 Thus, there is still a need for
It clearly indicates the significance of these materials
and the scope of their commercial exploitation. The use
of conventional liquid acids and Lewis acids has sig-
nificant risks in handling, containment, disposal and
regeneration due to their toxic and corrosive nature.
Thus, there is need in the development of strong solid
acid catalysts which must be stable, regenerable and
active at moderate temperatures. Over the past few
years, the preparation and characterization of Molybde-
num based solid acids has been receiving much atten-
tion, among other solid acids such as clays, zeolites,
heteropolyacids and ion exchange resins, due to their
superior catalytic activity for hydrocarbon conver-
sions.7-9 Among these nanostructured metal oxides
MoO3, a wide band gap n-type semiconductor, is par-
ticularly interesting due to their potential applications. It
has been extensively investigated as a key material for
fundamental research and technological applications in
optical devices, smart windows, catalysts, sensors, lu-
bricants, electrochemical storage batteries, information
displays and optical filters. Molybdenum oxides and
*
E-mail: mkl_chem@yahoo.com; Tel.: 0091-0240-2403311; Fax: 0091-0240-2403335.
Received May 6, 2011; revised June 11, 2011; accepted June 21, 2011.
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Navgire et al.
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a simple and general procedure for one pot synthesis of
dihydropyrimidinone and thiones under mild conditions.
Although these methods each have their own merits,
they also suffer from the drawbacks with respect to re-
action time, cost of reagent and reaction work-ups.
Generally, small surface areas of the resulting cata-
lysts have attracted chemists to seek alternative prepara-
tion methods, which allow better control of the structure,
size, and morphology of the metal oxides. In this study,
a new additive using poly(ethylene glycol) (PEG) was
introduced. The PEG is water soluble organic polymer
having structure HO(CH2OCH2)nOH (molecular weight
ranging from 200 to 10000 g/mol). The effect of
PEG-400 (molecular weight around 400 g/mol) addition
on morphology of the molybdenum oxide was studied.
The improved desired properties of MoO3 by addition of
carbon substrate were explained by the high adsorption
of the impurities on the surface of added carbon and
their transfer to MoO3 surface. The carbon substrate
were prepared and utilized from natural sources of Aca-
cia arabica plant. This study describes a parametric de-
sign to determine the effect of PEG and natural carbon
obtained from Acacia arabica plant on morphology of
the molybdenum oxide calcined at 500 ℃.
carried out using Scanning Electron Microscopy with
Electron Dispersion Spectroscopy (SEM-EDS) charac-
terization conducted using a JEOL JEM 2300 (LA) in-
strument. The Fourier Transformation Infra-Red spectra
(FT-IR) were recorded on FT-IR spectrometer (JASCO
－
1
FTIR/4100, Japan) in the range of 4000—500 cm .
The microscopic nanostructures and particle size were
determined using a CM-200 PHILIPS Transmission
Electron Microscope (TEM) at 200 kV (L＝600, λ＝
0.025 Å).
The reagent grade chemicals were used in the prepa-
ration of the samples, ammonium heptamolybdate
(Ranbaxy Fine Chemicals), oxalic acid (Ranbaxy Fine
Chemicals), ammonia (Ranbaxy Fine Chemicals),
poly(ethylene glycol)-400 (PEG-400) (Qualigens Fine
Chemicals), without further purification.
Preparation of carbon substrate
The carbon was prepared from Acacia arabica plant
as a natural source. In the first step dried wood was
burnt in absence of air, then resulting charcoal was
crushed into fine powder. Finally, the obtained powder
material was calcined at 500 ℃ in high temperature
muffle furnace in air atmosphere. The temperature
stability of carbon is estimated to be up to 2800 ℃ in
vacuum and about 750 ℃ in air.26
In this article we reports the improvement in desired
properties of MoO3 by addition of PEG-400 substrate
which was explained by the better control of the struc-
ture, size, and morphology. Similarly, addition of carbon
also explains by high adsorption of the impurities on the
surface of added carbon and their transfer to MoO3 sur-
face. The carbon substrate was prepared and utilized
from natural sources like Acacia arabica plant. A series
of carbon-doped MoO3 nanocomposite materials were
prepared by sol-gel method. As a part of our research
interest towards the development of efficient, environ-
mentally benign and green synthetic methodologies us-
ing eco-friendly conditions, the motivation for this work
was the investigation of novel synthetic route to prepare
realistic solid acid catalytic model system based on mo-
lybdenum oxide by using PEG-400 and natural carbon,
which should give an efficient and environmentally
friendly process for the synthesis of 3,4-dihydro-
pyrimidones via the Biginelli-type condensation reac-
tion. The prepared catalyst is inexpensive, solid,
non-corrosive and recyclable. The short reaction time,
clean reaction condition, consistent yield and minimum
environmental effect are important features of the reac-
tion.
Preparation of carbon-doped MoO3
Carbon-doped MoO3 catalysts were prepared by
conventional standard impregnation method. To im-
pregnate carbon-doped MoO3, the solution was obtained
by dissolving ammonium heptamolybdate (0.2 mol/L)
in deionized water. The system was kept under constant
stirring and sustaining the pH＝8 by simultaneous addi-
tion of 1∶1 NH4OH.27 The fine powdered carbon was
added with 0 wt% (CM-0), 1 wt% (CM-1), 2 wt%
(CM-2) and 3 wt% (CM-3), respectively. The excess
water was evaporated on the water bath with continuous
stirring. The resultant precursor was then dried at 110
℃ for 12 h and calcined at 500 ℃ for 2 h in air at-
mosphere.
Preparation of carbon-doped MoO3 with PEG-400
The series of modified samples with the addition of
carbon powder to solution containing PEG-400 on
MoO3 were prepared by simple impregnation method,
such as CPM-0, CPM-1, CPM-2, CPM-3 respectively.28
The fine powdered carbon (0, 1, 2, 3 wt%) was added in
the solution. Then excess water was evaporated with
continuous stirring. It was then dried at 110 ℃ for 12 h
and calcined at 500 ℃ for 2 h in air atmosphere.
Experimental
X-ray diffraction analyses (XRD) of the Molybde-
num oxide and carbon-doped MoO3 with and without
PEG-400 particles were performed using a Philips
X-ray diffractometer. The wavelength used for the XRD
analysis was 1.54 Å with radiation of CuKα. The dif-
fracting angle was varied between 20°—80°. Surface
morphology and elemental analysis of the samples were
General procedure for the synthesis of substituted
3,4-dihydropyrimidinones
As shown in Scheme 1, a mixture of aldehydes (1
mmol), ethyl acetoacetate (1 mmol) and urea/thiourea
(1.5 mmol) in the presence of carbon-doped MoO3 with
and without PEG-400 (0.2 mmol) in acetonitrile as sol-
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Effect of Poly(ethylene glycol)-400 and Carbon on MoO3 Nanocomposite Materials
vent was refluxed at 70—80 ℃ for an appropriate time
to gave 3,4-dihydropyrimidinone. After completion of
the reaction monitored by TLC (hexane/ethyl acetate,
8∶2), the reaction mixture was brought to room tem-
perature. Reaction mixture was washed by cold water to
remove excess urea or thiourea and then filtered. The
remaining solid material was washed with hot ethyl
acetate. The filtrate was concentrated and the solid
product was recrystallized from ethanol to give the pure
product. Many substitution patterns on the aromatic ring
could be introduced with high efficiency. We noted that
all aromatic aldehydes carrying either electron-donating
or electron-withdrawing substituents reacted well; giv-
ing moderate to excellent yields. The structure of all the
products was confirmed by comparing melting point
and spectral data with those in the literature.
4-(4-Fluorophenyl)-3,4-dihydro-6-methyl-5-propio-
nylpyrimidin-2(1H)-one (4e): 1HNMR (CDCl3, 300
MHz) δ: 8.08 (s, 1H), 7.85 (s, 1H), 7.65 (d, J＝9.08 Hz,
2H), 7.28 (d, J＝8.95 Hz, 2H), 5.45 (d, J＝2.20 Hz, 1H),
4.11 (q, J＝7.17 Hz, 2H), 2.37 (s, 3H), 1.28 (t, J＝7.16
－
1
Hz, 3H); IR (KBr) ν: 3232, 1724, 1631 cm .
4-(2-Chlorophenyl)-3,4-dihydro-6-methyl-5-propio-
nylpyrimidin-2(1H)-one (4f): 1HNMR (CDCl3, 300
MHz) δ: 8.38 (s, 1H), 8.11 (s, 1H), 7.35 (d, J＝9.10 Hz,
2H), 7.08 (d, J＝9.08 Hz, 2H), 5.45 (d, J＝2.18 Hz, 1H),
4.08 (q, J＝7.10 Hz, 2H), 2.36 (s, 3H), 1.19 (t, J＝7.44
－
1
Hz, 3H); IR (KBr) ν: 3250, 1741, 1654 cm .
1-(1,2,3,4-Tetrahydro-6-methyl-2-thioxo-4-p-tolyl-
1
pyrimidin-5-yl)propan-1-one (4g): H NMR (CDCl3,
300 MHz) δ: 8.05 (s, 1H), 7.75 (s, 1H), 7.26—7.40 (m,
4H), 5.35 (d, J＝3.05 Hz, 1H), 4.21 (q, J＝6.90 Hz, 2H),
2.45 (s, 3H), 1.31 (s, 3H), 0.90 (t, J＝7.80 Hz, 3H); IR
－
1
Scheme 1 Preparation of substituted 3,4-dihydropyrimidinones
from benzaldehyde, ethylacetoacetate and urea or thiourea by
using CPM-3 catalyst in acetonitrile solvent with reflux
(KBr) ν: 3240, 1722, 1638 cm .
1-(4-(4-Chlorophenyl)-1,2,3,4-tetrahydro-6-methyl-
2-thioxopyrimidin-5-yl)propan-1-one (4h): 1H NMR
(CDCl3, 300 MHz) δ: 8.75 (s, 1H), 8.51 (s, 1H), 8.25 (d,
J＝7.88 Hz, 2H), 7.88 (d, J＝7.58 Hz, 2H), 5.45 (d, J＝
2.05 Hz, 1H), 4.32 (q, J＝7.15 Hz, 2H), 1.71 (s, 3H),
1.32 (t, J＝7.01 Hz, 3H); IR (KBr) ν: 3245, 1725, 1632,
－
1
1575, 1545 cm .
1-(1,2,3,4-Tetrahydro-6-methyl-4-(3-nitrophenyl)-2-
thioxopyrimidin-5-yl)propan-1-one (4i): 1H NMR
(CDCl3, 300 MHz) δ: 8.15 (s, 1H), 8.08 (s, 1H), 7.25 (d,
J＝9.35 Hz, 2H), 7.18 (d, J＝9.00 Hz, 2H), 5.45 (d, J＝
2.05 Hz, 1H), 4.17 (q, J＝7.51 Hz, 2H), 1.88 (s, 3H),
1.19 (t, J＝7.10 Hz, 3H); IR (KBr) ν: 3250, 1741, 1654.
Results and discussion
Physical and spectroscopic data
XRD analysis
3,4-Dihydro-6-methyl-4-phenyl-5-propionylpyrimidin-
2(1H)-one (4a): HNMR (CDCl3, 300 MHz) δ: 8.40 (s,
In order to understand the phase symmetry of the
calcined samples, a systematic study on the XRD was
undertaken. Figure 1 shows that the highly intense
peaks were obtained at 2θ＝22.98°, 25.36°, 29.33°,
35.94°, 39.40°, 43.19° and 47.35°, corresponding to
planes (320), (400), (421), (440), (532), (542) and (552),
respectively, which predicts the cubic crystal symmetry
1
1H), 8.07(s, 1H), 7.26—7.38 (m, 5H), 5.45 (d, J＝2.15
Hz, 1H), 4.08 (q, J＝6.90 Hz, 2H), 2.36 (s, 3H), 1.19 (t,
－
1
J＝7.10 Hz, 3H); IR (KBr) ν: 3240, 1722, 1638 cm .
3,4-Dihydro-6-methyl-5-propionyl-4-p-tolylpyrimidin-
1
2(1H)-one (4b): HNMR (CDCl3, 300 MHz) δ: 8.10 (s,
1H), 7.94 (s, 1H), 7.26—7.38 (m, 5H), 5.35 (d, J＝2.05
Hz, 1H), 4.11 (q, J＝6.09 Hz, 2H), 2.35 (s, 3H), 1.71 (s,
3H), 1.19 (t, J＝7.80 Hz, 3H); IR (KBr) ν: 3240, 1722,
－
1
1638 cm .
4-(4-Chlorophenyl)-3,4-dihydro-6-methyl-5-propio-
nylpyrimidin-2(1H)-one (4c): 1HNMR (CDCl3, 300
MHz) δ: 8.08 (s, 1H), 7.85 (s, 1H), 7.58 (d, J＝9.90 Hz,
2H), 7.32 (d, J＝9.08 Hz, 2H), 4.38 (d, J＝6.80 Hz, 1H),
4.12 (q, J＝7.20 Hz, 2H), 2.37 (s, 3H), 1.28 (t, J＝7.15
－
1
Hz, 3H ); IR (KBr) ν: 3225, 1720, 1615 cm .
3,4-Dihydro-6-methyl-4-(3-nitrophenyl)-5-propionyl-
1
pyrimidin-2(1H)-one (4d): HNMR (CDCl3, 300 MHz)
δ: 8.38 (s, 1H), 8.15 (s, 1H), 7.75 (d, J＝9.18 Hz, 2H),
7.48 (d, J＝9.18 Hz, 2H), 5.05 (d, J＝2.25 Hz, 1H),
3.97 (q, J＝7.20 Hz, 2H), 2.42 (s, 3H), 1.30 (t, J＝7.24
Figure 1 XRD patterns of carbon sample prepared from Acacia
arabica.
－
1
Hz, 3H); IR (KBr) ν: 3232, 1724, 1631 cm .
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Navgire et al.
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of carbon substrate or fullerene. It was found that all the
XRD reflections of carbon substrate were matched us-
ing JCPDS card No. 79-701529 and lattice parameter
(a＝b＝c＝14.0408 Å).
Table 1 XRD analysis comparison data of CM-0 and CPM-3
2θ/(°)
(Calc.)
2θ/(°)
(Exp.)
CM-0 CPM-3 Grain size/
h k l
d/Å
d/Å
nm
1 1 0
0 4 0
0 2 1
1 1 1
0 6 0
1 4 1
2 1 0
0 0 2
2 4 0
1 7 1
2 5 1
1 9 0
2 7 0
0 7 2
2 3 2
3 0 1
0 2 3
23.334
25.078
27.330
33.763
38.987
42.393
46.258
49.269
53.229
57.698
62.867
64.958
66.768
69.551
72.877
76.542
78.878
23.313 3.80483 3.81257
10.16
09.11
09.76
07.64
06.40
06.29
06.13
08.54
05.50
08.98
10.08
08.03
05.38
06.82
07.21
07.57
08.58
Figure 2 (a—d) shows the XRD patterns of carbon
doped MoO3 without PEG-400 addition, i,e, CM-0,
CM-1, CM-2 and CM-3 samples which gives highly
intense and sharp peaks at 2θ＝23.36°, 25.75°, 27.30°,
33.61° and 38.96°, corresponding to the planes (110),
(040), (021), (111) and (060), respectively, indicating
orthorhombic crystal structure. The average particle
sizes of the powder were calculated using Debye-
Scherrer formula.30 It was noted that all the XRD peaks
are identified as MoO3 peaks from the JCPDS card
76-1003,31 with lattice parameter a＝3.9628 Å, b＝
13.8550 Å and c＝3.6964 Å. The strong and sharp
peaks suggest that the as-prepared materials are crystal-
line. Additional peak observed in Figure 2d at 2θ＝
30.00° for the plane corresponds to 421.
25.692
27.294
—
3.46471
3.2663 3.26487
33.615 2.66388 2.66391
38.933 2.30947 2.31146
42.312 2.13012 2.13435
46.157 1.96485 1.96510
49.292 1.84684 1.84719
53.218
—
1.71981
57.759 1.59417 1.59491
62.939 1.47614 1.47555
64.806 1.43729 1.43748
66.821
—
1.39893
69.699 1.34777 1.34803
72.922 1.29654 1.29620
76.511
78.878
—
—
1.24409
1.21258
logy of MoO3 samples with and without PEG-400 and
carbon addition. Figure 3 (b—c) shows morphology of
pure CM-0 with crystalline nature. It can be seen that
the samples CM-3 show agglomeration and randomness
in the particle size without porosity in Figure 3 (d—e).
Further, the samples CPM-3 show decrease in the parti-
cle size and development of porous surface in Figure 3
(f—g). From the SEM micrograph it can be seen that
effect of addition of PEG-400 as a surfactant clearly
shows alteration in particle size and morphology with
increasing porosity.
Figure 2 The XRD patterns of carbon doped MoO3 with and
without PEG-400 addition. (a) CM-0, (b) CM-1, (c) CM-2, (d)
CM-3, (e) CPM-0, (f) CPM-1, (g) CPM-2, (h) CPM-3.
Elemental compositions of carbon doped MoO3 with
and without PEG-400 were presented in Table 2. The
observed Mo∶C∶O atomic ratios are fairly close to
the expected bulk ratios indicating also a rather good
distribution of the metal species inside the samples. It
showed that, the minimum stoichiometric ratio of de-
sired elements in the CM3 and CPM3 maintained.
The Figure 2 (e—h) shows the XRD patterns of
carbon doped MoO3 with PEG-400 addition, i.e. CPM-0,
CPM-1, CPM-2 and CPM-3, which identifies the planes
(110), (040), (021), (111) and (060), corresponding to
orthorhombic crystal symmetry. Due to addition of
PEG-400, it was interestingly noted that the high inten-
sity peak was observed at 38.95° (2θ for hkl 060). The
XRD analysis comparison data of pure MoO3 and 3%
carbon doped MoO3 with PEG-400 were summarized in
Table 1. It was observed that all the XRD peaks are ex-
actly matched with literature values for MoO3 peaks. A
single orthorhombic structure was found for the entire
range of concentration of carbon.32,33 Similar peak ob-
served in Figure 2h at 2θ 30.00° for the plane corre-
sponds to 421.
FT-IR analysis
Figure 4a shows the FT-IR spectra of the carbon
substrate. The spectrum of the carbon substrate shows
broad peaks at 3400 cm－ due to OH stretching vibra-
1
tion modes of the absorbed water, the peak at 1384 and
1576 cm－ could be assigned for C—C and C＝C vi-
1
bration respectively.34 Figure 4b shows the FT-IR spec-
tra of CM-0 (pure MoO3). A band at 878 cm－ is char-
1
acteristics of terminal molybdenum oxygen double bond
(Mo＝O). The bands at 1439 and 1577 cm－ were at-
1
SEM and EDS analysis
tributed to C—C and C＝C vibrations. The broad band
around 3499 cm－ 1 was due to O—H stretching vibration
modes of the adsorbed water on the surface of the pow-
der.35
To study the surface topography and elemental
composition, the SEM and EDS were investigated sys-
tematically. Figure 3a shows flakes structure of carbon.
Figure 2 (b—g) shows the variation in morpho-
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Effect of Poly(ethylene glycol)-400 and Carbon on MoO3 Nanocomposite Materials
Figure 4 (c—e) shows the FT-IR spectra of CM-1,
CM-2 and CM-3 respectively. A sharp band appearing
in the range 875—885 cm－ is due to the terminal mo-
1
lybdenum-oxygen double bond (Mo＝O). The bands at
1410—1600 cm－ were attributed to C—C and C＝C
1
vibrations, the additional band around 2926 cm －
1
probably may be due to CH2 and or C(OH) stretching
mode. While broad band around 3381—3464 cm－ was
1
due to O—H stretching vibration modes of the adsorbed
water.36 Figure 5 (a—d) shows the FT-IR spectra of
CPM-0, CPM-1, CPM-2 and CPM-3. The bands ob-
served were similar to the samples without addition of
PEG-400. We cannot find any bands for PEG-400, be-
cause the flash point of PEG is in between 182—287
℃.
Figure 3 The SEM image of (a) carbon, (b) and (c) CM-0, (d)
and (e) CM-3, (f) and (g) CPM-3.
Figure 5 IR spectra of (a) CPM-0, (b) CPM-1, (c) CPM-2, (d)
CPM-3.
Table 2 EDS elemental quantitative analysis
TEM analysis
Elemental atomic wt%
Entry
Sample
The TEM images shown in Figure 6 indicate the ob-
tained nano-sized particles for clarity. The TEM image
of pure MoO3 in Figure 6a shows the presence of highly
crystalline nano rods of MoO3 with particles size varing
in between 15.34 to 20.70 nm. It can be also seen that in
Figure 6 (c, d) the average particle size of modified
sample of carbon doped MoO3 with PEG-400 addition
(CPM-3) is in the range of 10.42 to 18.57 nm. From the
electron diffraction patterns (EDP) shown in Figure 6b,
R was measured to obtain the d value using the fol-
lowing equation with known values of λ and L.
Mo
13.12
9.58
O
C
1
2
CM-3
44.09
34.51
42.79
55.91
CPM-3
L
λ
Rd
＝
where, R is the distance of a diffraction spot from the
direct beam spot on the diffraction pattern, d is the
spacing of the planes; L is the effective camera length
and λ is wavelength of radiation. The value of λL is
referred to as the camera constant of the microscope.
The obtained d values of 3.86, 3.50, and 3.04 indicated
the (320), (400), and (421) surfaces of the orthorhombic
form of MoO3.
Figure 4 IR spectra of (a) carbon, (b) CM-0, (c) CM-1, (d)
CM-2, (e) CM-3.
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affected the product yield. Among these catalysts,
CPM-3 was proved to be the best as compared to the
others (Table 4, Entry 8). The CPM-3, the catalytic ma-
terial exhibits very good catalytic activity in the synthe-
sis of substituted 3,4-dihydropyrimidinones with excel-
lent to high yield in very shorter reaction time. That
might be due to small particle size and high porosity.
The possible mechanism for the preparation of substi-
tuted 3,4-dihydropyrimidinones by using CPM-3 cata-
lyst is presented in Scheme 2. In order to strengthen the
novelty of present method, we have compared our re-
sults with some reported procedures using some other
catalysts such as Cu(NH2SO3)2, Bi(NO3)3, Pb(NO3)2, aq.
Zn(BF4)2, H2SO4/SiO2.38-42 It was observed that CPM-3
catalytic materials give high yields within very short
reaction times in comparison with earlier reported
methods.
Figure 6 TEM images of (a) pure MoO3, (b) pure TiO2, (c)
MoO3 doped TiO2 and (d) high magnification of MoO3 doped
TiO2.
Table 4 Effect of carbon and PEG-400 content of the catalyst
Catalytic activity results
Entry
Catalyst
CM-0
Time/min
180
120
120
90
Yield/%
In order to get best experimental results, we have
considered the model reaction of Biginelli’s one-pot
condensation reaction, i.e. that the reaction of aldehydes
(1.0 mmol) with urea or thiourea (1.2 mmol) and ethyl
acetoacetate (1.2 mmol) using 0.1 g of catalyst in ace-
tonitrile (10 mL) as solvent at ambient temperature. The
reaction is very fast and 93% conversion was observed
in 90—180 min. In this study, the effect of different
solvent was investigated and the results are given in
Table 3. The choice of solvent proved critical. The re-
sults showed that the examined solvents were not suit-
able separately. The best result was found to be with 0.1
g of CPM-3 catalyst, affording 93% yield of product. It
was observed that the acetonitrile is a much better sol-
vent in terms of yields (93%) than all other tested sol-
vents such as methanol, dichloromethane, THF, water,
H2O-THF and toluene.37
1
2
3
4
5
6
7
8
51
CM-1
62
CM-2
65
CM-3
76
CPM-0
CPM-1
CPM-2
CPM-3
120
120
90
55
70
82
90
93, 91, 91a
Reaction condition: benzaldehyde (1.0 mmol) with ethyl aceto-
acetate (1.2 mmol) and urea (1.2 mmol) using 0.1 g of catalyst in
10 mL acetonitrile solvent in refluxing. a Yield of product with
catalyst reused up to three times.
Therefore, the CPM-3 catalytic material in acetoni-
trile solvent system in refluxing was used for the prepa-
ration of different derivatives of 3,4-dihydropyrimidi-
nones with electron donating as well as withdrawing
substituent. Similarly, we study the tolerance of various
functional groups such as methyl, chlorides, nitro and
fluorides, etc. to the reaction conditions. Aromatic
aldehyde with these functional groups reacted smoothly
and produced the corresponding dihydropyrimidinones
in high yields and high purity. Thiourea has been used
with similar success to provide corresponding
S-dihydropyrimidinones analogues, which are also of
interest due to their biological activities (Table 5). The
catalyst was recovered by filtration of reaction mixture
under hot condition. The recovered catalyst was washed
several times with acetone and dried at 100 ℃. The
separated catalyst was again reused for the same reac-
tion. In these cases the yield of product to be 93%, 91%,
91% in successive three-time use. Thus the activity of
catalyst was found to be diminished after its recyclabil-
ity.
Table 3 Comparative study of different solvent system
Entry
Solvent
EtOH
Time/min
180
Yield/%
35
1
2
3
4
5
6
7
8
9
Acetic acid
CH3CN
CH3OH
CH2Cl2
THF
180
40
90
93
120
82
120
76
180
65
H2O
180
40
H2O-THF
Toluene
180
70
180
60
Reaction condition: benzaldehyde (1.0 mmol) with ethyl aceto-
acetate (1.2 mmol) and urea (1.2 mmol) using 0.1 g of CPM-3
catalyst in 10 mL solvent in refluxing.
We initially studied the effect of prepared catalysts
for the Biginelli’s one-pot condensation reaction. As
shown in Table 4, the choice of catalyst significantly
The reaction proceeds efficiently under these condi-
tions and the dihydropyrimidinones are produced in
2054
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© 2011 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2011, 29, 2049— 2056

Effect of Poly(ethylene glycol)-400 and Carbon on MoO3 Nanocomposite Materials
Scheme 2 Possible mechanism for the preparation of substituted 3,4-dihydropyrimidinones by using CPM-3 catalyst
Table 5 Preparation of different derivatives of 3,4-dihydropyrimidinones
Entry
R
X
O
O
O
O
O
O
S
Time/min
85
Yield/%
93
m.p. (Rep.)/℃
200—202
214—216
212—213
225—226
219—222
175—177
193—195
204—205
—
m.p. (Found)/℃
206—208
212—214
215—216
227—229
215—218
178—180
192—194
205—207
236—238
a
b
c
d
e
f
H
4-CH3
4-Cl
3-NO2
2-Cl
4 -F
135
88
120
90
150
90
140
81
125
89
g
h
i
4-CH3
3-NO2
4-F
160
87
S
140
91
S
145
90
Reaction condition: benzaldehyde (1.0 mmol) with ethyl acetoacetate (1.2 mmol) and urea (1.2 mmol) using 0.1 g of CPM-3 in 10 mL
acetonitrile solvent in refluxing to 90 min.
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yields as well as simple experimental and isolation pro-
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for large scale synthesis of these compounds.
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