Tungstate-loaded triazine-based magnetic poly(Bis-imidazolium ionic liquid): An effective bi-functional catalyst for tandem selective oxidation/Knoevenagel condensation in water

Article abstract of DOI:10.1016/j.polymer.2017.02.028

A novel bi-functional polymeric catalyst was synthesized by immobilization of tungstate anions onto the nitrogen rich poly(ionic liquid)/magnetic nanocomposite. The resulting catalyst has two types of catalytic sites: (i) immobilized WO₄ anions with bis-imidazolium ionic liquid cation for selective oxidation of alcohols and (ii) basic amine groups for Knoevenagel condensation between produced aldehyde and malononitrile. Due to the polymeric nature of the catalyst, large amounts of tungstate and basic nitrogen groups were presented on the solid surface which led to a decrease in the applied catalyst mass for catalytic reaction. High catalytic activity and excellent selectivity of catalyst in water medium make this protocol a green way for production of fine chemicals.

Full text of DOI:10.1016/j.polymer.2017.02.028

Accepted Manuscript
Tungstate-loaded triazine-based magnetic Poly(Bis-imidazolium ionic liquid):
An effective Bi-Functional catalyst for tandem selective oxidation/Knoevenagel
condensation in water
Nasrin Zohreh, Maryam Tavakolizadeh, Seyed Hassan Hosseini, Ali Pourjavadi, Craig
Bennett
PII:
S0032-3861(17)30151-9
10.1016/j.polymer.2017.02.028
JPOL 19429
DOI:
Reference:
To appear in: Polymer
Received Date: 15 December 2016
Revised Date: 3 February 2017
Accepted Date: 7 February 2017
Please cite this article as: Zohreh N, Tavakolizadeh M, Hosseini SH, Pourjavadi A, Bennett C,
Tungstate-loaded triazine-based magnetic Poly(Bis-imidazolium ionic liquid): An effective Bi-Functional
catalyst for tandem selective oxidation/Knoevenagel condensation in water, Polymer (2017), doi:
10.1016/j.polymer.2017.02.028.
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ACCEPTED MANUSCRIPT
Tungstate-Loaded Triazine-Based Magnetic Poly(Bis-imidazolium Ionic Liquid): An
Effective Bi-Functional Catalyst for Tandem Selective Oxidation/Knoevenagel
Condensation in Water
[
a]
[a]
[b]
[b]
Nasrin Zohreh,* Maryam Tavakolizadeh, Seyed Hassan Hosseini, Ali Pourjavadi, Craig
[
c]
Bennett
[
a]
Department of Chemistry, Faculty of Science, University of Qom, P. O. Box: 37185-359, Qom, Iran
[
b]
Polymer Research Laboratory, Department of Chemistry, Sharif University of Technology, Tehran, Iran
[
c]
Department of Physics, Acadia University, Wolfville, Nova Scotia, Canada
(
E-mail address: nasrin.zohreh@gmail.com, n.zohreh@qom.ac.ir; Phone/fax: +982532103488)
Abstract
A novel bi-functional polymeric catalyst was synthesized by immobilization of tungstate anions
onto the nitrogen rich poly(ionic liquid)/magnetic nanocomposite. The resulting catalyst has two
types of catalytic sites: (i) immobilized WO anions with bis-imidazolium ionic liquid cation for
4
selective oxidation of alcohols and (ii) basic amine groups for Knoevenagel condensation
between produced aldehyde and malononitrile. Due to the polymeric nature of the catalyst, large
amounts of tungstate and basic nitrogen groups were presented on the solid surface which led to
a decrease in the applied catalyst mass for catalytic reaction. High catalytic activity and excellent
selectivity of catalyst in water medium make this protocol a green way for production of fine
chemicals.
Keywords: Bi-functional catalyst; Magnetic catalyst; Oxidation; Knoevenagel condensation
1

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1
. Introduction
The remarkable physicochemical properties of ionic liquids (ILs) make them unique materials
for various applications.[1-9] Over the last decade, many efforts have been made to develop the
application of ILs in the area of catalysis.[5, 6, 10-13] However, these specific homogenous IL
catalysts are minimally recyclable and, therefore, are not desirable for industrial applications.[14-
1
6] A standard solution for the recyclability issue is immobilization of homogenous IL catalysts
onto solid insoluble supports such as silica particles,[17-20] carbon-based materials[21-23] and
magnetic nanoparticles (MNPs).[24-26] The last approach is most desirable because their
magnetic property facilitates the catalyst separation using an external magnet.[25, 27-31] Despite
excellent recyclability and good catalytic performance of these supported IL catalysts, there is
one unsolved issue which has limited their widespread application. Since the surface areas of
solid supports are defined, they can only bear a limited quantity of IL molecules and therefore
the loading amounts of active catalytic species is usually very low in these catalysts.[25, 32, 33]
As a result, for a specific catalytic reaction, a large mass of such supported catalyst is needed
which leads to use of more solvent for mixing and product separation. To solve the low loading
problem, we have recently developed coating of MNPs by poly(ionic liquids) (PILs).[34-39]
Coating of solid supports with polymers increases the loading of active catalytic sites (which
usually are monomers of polymers).[40] The polymer chains can be covalently bonded to the
surface of the solid support by the head while the tail of the polymer chain can be grown without
considering the limited surface area.
One of the important organic transformations in industries and laboratories is selective oxidation
of substrates such as alcohols to the corresponding aldehydes.[41-46] The classical oxidation
methods include the use of stoichiometric amounts of strong oxidants such as chromium (VI)
2

ACCEPTED MANUSCRIPT
reagents [47, 48] and concentrated HNO
3
[49] which are environmentally hazardous and produce
large amounts of toxic wastes. A green protocol to replace the classical method for oxidation
reaction is using heterogeneous oxidation metal catalysts.[50-53] Some of these protocols are
based on the use of H O as co-catalyst which produces water as the only byproduct.[54-56]
2
2
However, for selective oxidations, H O should be applied in combination with metal
2
2
catalysts.[57-63] The most effective catalyst for oxidation reactions along with H O is tungstate
2
2
anions.[38, 64-70] However, the difference in solubility of tungstate anion and organic substrates
necessitates the use of phase transfer catalysts for these types of catalytic oxidations.[71, 72]
However, the recyclability of homogenous catalysts and phase transfer catalysts is still a major
problem.[54, 65, 72] A logical approach to this problem is heterogenization of the phase transfer
catalyst and tungstate anions.
In this work we have prepared a heterogeneous magnetic catalyst in which bis-imidazolium
tungstate ligands were immobilized onto the polymer coated MNPs. Using polymer coated MNP
as the support increased the loading amounts of immobilized tungstate anions. This catalyst was
then applied for one-pot tandem oxidation/Knoevenagel condensation between various alcohols
2 2
and active methylene compounds using H O as co-oxidant in water medium.[73-77] The
mechanism for the tandem reaction was also proposed. This study highlights the great potential
of polymer coated magnetic nanoparticles as bi-functional catalysts.
2
. Experimental
2
.1. Reagents and analysis
Azobisisobutyronitrile (AIBN, Kanto, 97%) was recrystallized from ethanol. Methyl acrylate
(MA) and N-methylimidazole (NMI) were distilled before use (Sigma-Aldrich). N,N'-
3

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methylenebisacrylamide (MBA), trichlorotriazine (TCT) and all other chemical compounds were
obtained from Merck and used without further purification.
The chemical structures of the samples were characterized by Fourier transform infrared (FT-IR)
spectroscopy using an ABB Bomem MB-100 spectrometer. Thermal gravimetric analysis (TGA)
-1
was performed using a TGA Q 50 thermogravimetric analyzer with a heating rate of 10 ˚C min
under a nitrogen atmosphere. A Philips CM30 transmission electron microscope (TEM) was
used to investigate the morphology of nanoparticles. Magnetization of the samples was measured
by vibrating sample magnetometer (Meghnatis Daghigh Kavir Co., Kashan, Iran). Tungstate ions
were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES, Perkin-
Elmer DV 4300). The X-ray diffraction (XRD) patterns were recorded on a RigalcuD/Max-3c X-
ray diffractometer. An X-ray fluorescence (XRF) (Philips 1404) was used for accurate elemental
analysis of samples. The products were determined by GC (Agilent) equipped with a flame
ionization detector using a HP-5 capillary column.
2
.2. Synthesis of catalyst (MNP@PIL/W)
Silica coated Fe nanoparticles (MNPs) were synthesized based on our previously reported
3
O
4
method.[78] MNP (1.0 g) was ultrasonically dispersed in dry ethanol (50 mL) and then NH (2
3
mL) was added to flask. Subsequently, 3-(trimethoxysilyl)propylmethacrylate (MPS) (3 mL) was
added and the mixture was stirred at 70 °C for 48 h. The MPS coated MNPs (MNP@MPS) were
magnetically separated and washed several times with methanol (4 × 50 mL) and dried under
vacuum at 50 °C.
Poly(aminoethyl acrylamide) coated MNPs was prepared based on our previous work.[79] In a
5
00 mL single-necked flask, a solution of MNP@MPS (0.50 g in 200 mL methanol), 2 g methyl
4

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acrylate, 0.5 g of MBA, and 70 mg of AIBN were mixed. The flask was completely
deoxygenated by bubbling purified argon for 30 min and then equipped with a fractionating
column, Liebig condenser, and a receiver. The polymerization process initiated when heating the
flask from ambient temperature to the boiling state in an oil bath. The reaction was ended after
about 130 mL of methanol was distilled from the reaction mixture within 5 h. The obtained
cross-linked poly(methylacrylate) coated MNP (MNP@PMA) were magnetically separated and
washed with water (2 × 100 mL) and methanol (3 × 50 mL) and dried under vacuum at 50 °C
(1.31 g product).
Subsequently, about 1.0 g of MNP@PMA was ultrasonically dispersed in 60 mL methanol, 25
mL ethylenediamine (EDA) was slowly added and the mixture was stirred at 60 °C for 72 h.
Cross-linked poly(aminoethyl acrylamide) coated MNP (denoted as MNP@PAEAm) was
magnetically separated and washed with methanol (3 × 50 mL) and then dried under vacuum at
5
0 °C for 12 h (0.88 g product).
In a round bottom flask, MNP@PAEAm (0.50 g) was ultrasonically dispersed in dry THF (30
mL). Following this, TCT (2.6 g, 14.0 mmol) and N,N′-diisopropylethylenediamine (2.6 mL,
2
0.0 mmol) were added and the flask was put in an ice bath. The mixture was stirred for 7 h
under N atmosphere. The product (MNP@PTCT) was magnetically separated and washed with
2
THF (5×15 mL) and dried under vacuum at room temperature (0.49 g).
Afterward, in a three-necked round bottom flask, MNP@PTCT (0.40 g) was dispersed in dry
CH CN (25 mL) and NMI (2 mL, 24 mmol) was added to flask. The flask was equipped with a
3
condenser and the mixture was refluxed for 2 days to produce MNP@PIL/Cl. The product was
separated using a magnet, washed with methanol (5×10 mL) anddried under vacuum at 50 ˚C
(0.39 g).
5

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For exchange of chloride with tungstate, MNP@PIL/Cl (0.30 g) was dispersed in DI water (25
mL) and Na WO .4H O (0.30 g, 0.82 mmol) was added to mixture. The mixture was stirred for 2
2
4
2
days at room temperature. The final product (MNP@PIL/W) was magnetically separated and
washed with water (5×10 mL) and methanol (5×10 mL) and dried under vacuum at 50 ˚C (0.29
g).
2
.3. General procedure for one-pot tandem oxidation/ Knoevenagel condensation catalyzed
by MNP@PIL/W
2 2
In a round-bottomed flask, 0.5 mmol alcohol, 0.75 mmol H O , 2 mL solvent water and 4 mol%
MNP@PIL/W (26 mg) were mixed and stirred at 90 °C for a defined time. After the completion
of the reaction, monitored by TLC, the reaction was cooled down to room temperature and then
0
.6 mmol malononitrile was added to solution and the mixture was stirred for another 2h. Ethyl
acetate was then added to the mixture and catalyst was separated by an external magnet and
washed with methanol, dried at 50 °C and stored for another run. The product was extracted by
ethyl acetate and analyzed by gas chromatography (GC).
3
. Results and Discussion
The catalyst was prepared in a few steps (scheme 1). First silica coated magnetic nanoparticles
MNPs) were prepared. Magnetic particles were then functionalized by MPS to generate vinyl
(
groups on the surface of the MNPs. The presence of vinyl groups on the surface of the MNPs
allow the covalent grafting of polymer chains to magnetic particles. The cross-linked
poly(methyl acrylate) (PMA) coated MNP was prepared through the distillation-precipitation-
polymerization method using MA, MBA and AIBN as monomer, cross-linker and initiator in the
presence of MNP@MPS as core. The resulting MNP@PMA was reacted with an excess amount
6

ACCEPTED MANUSCRIPT
of EDA and cross-linked poly(amino ethyl acrylamide) coated MNP was synthesized
(MNP@PAEAm). Coating of MNPs with PAEAm produces a magnetic support with numerous
amine groups on the surface. To immobilize tungstate ions, an ionic ligand should be initially
attached onto the surface of the support. For this purpose, a bis-imidazolium ligand was grafted
to MNP@PAEAm as depicted in scheme 1. After exchange of chloride with tungstate anion, the
final catalyst was ready (MNP@PIL/W).
Scheme 1
In each step of synthesis of the catalyst, FT-IR spectroscopy was used to verify the structure of
the sample. Figure S1 shows the FT-IR spectra of MNP(a), MNP@MPS (b), MNP@PMA (c)
-1
and MNP@PAEAm (d). The characteristic bands within 635, 1106, and 3200-3500cm in all
samples are attributed to stretching vibration of Fe-O, Si-O-Si, and O-H, respectively. The FT-IR
-1
spectrum of MNP@MPS showed absorption peaks at 1461 and 1713 cm attributed to C=C and
C=O bonds of MPS and confirmed the grafting of MPS. In the FT-IR spectrum of MNP@PMA,
-1
the characteristic peak of cross-linked poly(methyl acrylate) can be seen at 1735 cm attributed
to ester groups. This also was confirmed by the increasing intensity of the absorption peak at
2
929 related to stretching of the C-H bond of alkyl groups. Amidation of CO Me functional
2
groups of the polymer shell by ethylenediamine led to a decrease in C=O bond stretching band
-1
and appearance of amidic C=O band at 1654 cm in the MNP@AEAm spectrum. However,
some of the ester groups in the inner layer of the cross-linked polymer shell did not react with
EDA. These spectra show the characteristic peaks of each sample confirming the successful
synthesis of MNP@PAEAm.
7

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In the next steps, amine groups on the surface of MNP@PAEAm were reacted with TCT and
then N-methyl imidazole group added to this structure. The FT-IR spectra of these two steps are
shown in Figure 1b and c, but unfortunately the main characteristic peaks of TCT and bis-
imidazolium ligand are overlapped by strong peaks of PAEAm. However, after exchange of
-1
chloride with tungstate, a peak at 896 nm was observed that is attributed to stretching vibration
of W=O (comparing with FT-IR of Na WO , Figure 1e).
2
4
Figure 1
The TG analysis of samples in each step of synthesis of the catalyst shows that, after each
modification on the surface of the MNPs, weight loss increases (Figure 2). The TGA analysis of
MNP@MPS shows 2.20 % total weight loss at 250 ˚C (Figure 2a). From this weight loss, the
loading amount of MPS on the surface of MNPs was calculated as 0.17 mmol/g. All samples
show a weight loss at 100 ˚C which is attributed to loss of adsorbed water molecules. After this,
the main weight losses occur at around 300 ˚C which is associated with degradation of all
organic components on the samples. The TGA curves of MNP@PMA, MNP@PAEAm,
MNP@PTCT and MNP@PIL/W show 17.9, 24.0, 38.4 and 43.1% weight losses, respectively
(
Figure 2b-e). Due to the different structure of monomer and cross-linker on the surface of each
sample, the exact calculation of loading amount of each part is not possible. However, the results
of TGA clearly show that modification was successfully performed in each step of catalyst
preparation.
Figure 2
Table 1 shows the elemental analysis of MNP@MPS, MNP@PMA, MNP@PAEAm,
MNP@TCT and MNP@PIL/W. CHN analysis shows that content of C, H and N after each
8

ACCEPTED MANUSCRIPT
modification increases confirming the successful modification in each step. The XRF analysis
shows 6.43 wt% chloride in the MNP@PTCT sample which is related to two unreacted chlorides
of grafted TCT molecules. From the weight percent of chloride, it can be concluded that the
loading amount of immobilized TCT on MNP@PTCT is around 0.91 mmol/g. Moreover, it was
found that the amounts of W and Cl in MNP@PIL/W are 0.59 and 14.09 wt%. The content of W
in this sample is related to 0.77 mmol/g of WO anions. Reduction of the Cl content in this
4
sample shows the successful exchange of WO
4
with chlorides. Moreover, the XRF analysis of
-
MNP@PIL/W did not detect any Na, confirming that there is no NaWO
4
or un-exchanged
2
-
Na
2
WO
4
. These results show that WO
4
is paired to one bis-imidazolium ligand.
Assuming that the only nitrogen source in MNP@PMA is MBA cross-linker, the amount of
cross-linking in MNP@PMA can be calculated using the N content of sample. It was found that
the content of MBA in MNP@PMA is about 1.84 wt%. Along with the TGA data (Figure 2b),
the content of poly(methyl acrylate) in MNP@PMA is about 13.86 wt% which is related to 1.61
mmol/g of CO Me groups in (17.9-2.2-1.84=13.86). Based on these results, the amount of
2
ethylenediamine in MNP@PAEAm was calculated as 1.24 mmol/g. The content of available
amine groups on the surface of MNP@PAEAm was also calculated by the back titration method
and it was found to be 1.11mmol/g which is in a good agreement with the NH content calculated
2
based on CHN analysis (see supporting information). The results of ICP analysis also showed
1
4.19 wt% of W in MNP@PIL/W which is closely agrees with the results of XRF.
Table 1
EDS analysis of MNP@PIL/W confirms the presence of C, N, O, Fe, Si and W (Figure 3). The
absence of Na and Cl in EDS analysis demonstrates that the ratio of bis-imidazolium cation to
WO anion is 2:1. Moreover, the absence of Na in this analysis shows that there is no physically
4
9

ACCEPTED MANUSCRIPT
adsorbed Na
2
WO
4
on the surface of catalyst. These results are in good agreements with the XRF
analysis.
Figure 3
TEM images of Fe O nanoparticles and MNP@PIL/W are presented in Figure 4a and b,
3
4
respectively. As shown, the size of magnetic Fe O nanoparticle is less than 10 nm (Figure 4a).
3
4
3 4
The TEM image of MNP@PIL/W shows gray material around the dark Fe O nanoparticles.
Based on the TEM analysis, the size of catalyst is more than 130 nm and several Fe
nanoparticles are entrapped within the polymeric matrix.
3 4
O
Figure 4
The XRD analysis of MNP@PIL/W (Figure 5a) shows that, the locations and intensities of the
diffraction peaks are identical to that of the pure Fe nanoparticle sample and consistent with the
3
O
4
standard pattern (JCPDS Card No. 79 - 0417 magnetite). The broad peak between 20-30 degrees is
attributed to amorphous silica and the polymeric shell. This pattern shows that the crystalline
3 4
phase of Fe O did not change during the catalyst preparation steps. The electron diffraction
pattern (RDP) of MNP@PIL/W also confirms the crystalline structure of the Fe O nanoparticles
3
4
(
Figure 5b)
Figure 5
Figure 6 shows the hysteresis loops of pure Fe
temperature. The maximum saturation magnetization of Fe
0.4 emu/g, respectively. The large decrease of saturation magnetization of MNP@PIL/W is
attributed to coating of non-magnetic silica and polymer shells around the magnetic
3
O
4
(a) and MNP@PIL/W (b) at room
3
O
4
and MNP@PIL/W are 54.2 and
2
1
0

ACCEPTED MANUSCRIPT
nanoparticles. Even with this reduction in the saturation magnetization, MNP@PIL/W can still
be easily separated from the solution by using an external magnet.
Figure 6
One-pot reactions catalyzed by multi-functional heterogeneous catalysts are an important
strategy for industrial production since they do not require isolation and purification of
intermediates, facilitating a greener process. The catalytic activity of MNP@PIL/W as a bi-
functional catalyst was examined in tandem oxidation/Knoevenagel condensation between
benzyl alcohol and malononitrile. This reaction can be performed in two steps under one-pot
condition: first, oxidation of benzyl alcohol and, second, amine promoted Knoevenagel
condensation to yield 2-benzylidenemalononitrile. Table 2 shows a control experiment for a
model reaction between benzyl alcohol and malononitrile. The reaction in the absence of catalyst
2 4
or un-supported Na WO gave no significant conversion of benzyl alcohol (Entry 1,2),
confirming that the oxidation of alcohol needs a phase transfer catalyst along with tungstate
catalyst. Using MNP@PIL/Cl gave only a 13% conversion to a mixture of benzaldehyde and
benzoic acid (Entry 3). However, using 5 mol% of MNP@PIL/W converts more than 96% of the
benzyl alcohol and produces 96% yield of desired product. The reaction gave almost same the
conversion with 4 mol% catalyst but reducing the amount of MNP@PIL/W to 3 mol% reduced
the conversion of alcohol to 87%. However, Knoevenagel condensation of produced
benzaldehyde was complete at this condition (Entry 6). In the next step, reaction time for each
step was optimized and it was found that oxidation reaction (Time A) and Knoevenagel
condensation (Time B) needs at least 4h and 2 h for completion, respectively (Entry 5,7-9). The
same reaction was performed in various solvents instead of water but the best result was obtained
in water (Entry 10-13). To understand the effect of the catalyst in tandem reaction, two other
1
1

ACCEPTED MANUSCRIPT
experiments were performed using benzaldehyde as the starting substrate (Entry 14,15). To
understand the effect of MNPs in catalytic activity of MNP@PIL/W, same catalyst was prepared
without the MNPs. The result showed that the absence of MNPs in catalyst structure did not
significantly affect on yield of products (Entry 16). The first experiment demonstrates that
Knoevenagel condensation did not proceed in the absence of any catalyst. In contrast, using
MNP@PIL/Cl without tungstate anion gave 99% yield of Knoevenagel product when the
reaction started with benzaldehyde instead of benzyl alcohol. This result confirms that tungstate
anions are not responsible for Knoevenagel condensation and that the basic amine groups on the
surface of solid supports play the key role in the second step. The results show that
MNP@PIL/W is highly selective for oxidation of benzyl alcohol and efficiently promotes the
Knoevenagel condensation under one-pot condition.
Table 2
The scope of the alcohol substrates was further extended to investigate the general utility of the
alcohol oxidation/ Knoevenagel condensation reaction sequence (Table 3). It can be seen that the
benzyl alcohols with both electro-donor and electron-withdrawing groups selectively oxidized to
the corresponding aldehydes and, in the next step, excellent yield of Knoevenagel product was
obtained. However, benzyl alcohols with high steric hindrance need longer reaction times and
gave lower yield of products. Secondary and aliphatic alcohols also produce the desired products
by this protocol.
Table 3
The recyclability experiment with MNP@PIL/W showed no obvious decrease in catalytic
th
activity after 5 runs (Figure 7 left). However, an increase in reaction time is observed after the 5
run which is attributed to loss of catalyst mass during catalyst separation and recovery. The right
1
2

ACCEPTED MANUSCRIPT
image in Figure 7 shows the leaching test for two steps of the catalytic reaction. In the first
experiment, leaching of catalyst was tested in oxidation reaction (line a and b). The results
showed that, after catalyst removal, oxidation did not proceed. Line c and d are related to
Knoevenagel reactions on benzaldehyde in the presence of MNP@PIL/W and after catalyst
removal, respectively. The results clearly show that the catalyst is truly heterogeneous and
leaching is negligible under this condition. Moreover, the ICP analysis of the product after hot
filtration testing showed no significant amount of tungstate, confirming the results of the
leaching experiments.
A possible reaction mechanism for oxidation/Knoevenagel condensation of benzyl alcohol
catalyzed by MNP@PIL/W includes 4 steps: (1) oxidation of immobilized WO anions to
4
WO (O ), (2) selective oxidation of alcohol to aldehyde, (3) deprotonation of malononitrile by
3
2
numerous amine groups on the surface of MNP@PIL/W and (4) promotion of the reaction of
malononitrile anion and aldehyde by ionic groups on the surface of MNP@PIL/W (Figure S2).
2
The hydrophobic -CH - chains on the surface of the catalyst are important the excellent oxidative
activity of the catalyst in water medium as it plays the role of phase transfer catalyst. On the
other hand, bis-imidazolium ligand can promote the Knoevenagel condensation with both basic
amine function on TCT, which can easily deprotonate malononitrile, and slightly acidic C-H of
imidazolium group which can protonate the oxygen of the aldehyde group.
Figure 7
4
. Conclusion
In summary, we have shown that MNP@PIL/W is an effective bi-functional catalyst for
oxidation/ Knoevenagel condensation of alcohols. The reaction proceeds in the absence of any
1
3

ACCEPTED MANUSCRIPT
phase transfer catalyst in water under mild conditions. Due to the polymeric nature of catalyst,
high amounts of tungstate and amine groups were loaded onto the surface of the catalyst which
led to a reduction in the amount of catalyst required for the reaction. Considering the versatile
structure of MNP@PIL/W catalyst, we believe that more bi-functional catalysts for one-pot
tandem reaction can be designed.
Acknowledgements
We are grateful for financial support by the Iran's National Elites Foundation.
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Scheme 1. Steps for preparation of MNP@PIL/W.
1
8

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Figure 1. FT-IR spectra of MNP@PAEAm (a), MNP@PTCT (b), MNP@PIL/W (c) N-
2 4
methylimidazole (d) and Na WO (e)
1
9

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Figure 2. TG analysis of MNP@MPS (a), MNP@PMA (b), MNP@PAEAm (c), MNP@PTCT
(d), MNP@PIL/W (e).
2
0

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Figure 3. EDS analysis of MNP@PIL/W.
2
1

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Figure 4. TEM images of Fe O nanoparticles (a) and MNP@PIL/W (b).
3
4
2
2

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Figure 5. XRD (a) and RDP (b) analysis of MNP@PIL/W.
2
3

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3 4
Figure 6. Room temperature magnetization curves of Fe O (a) and MNP@PIL/W (b).
2
4

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Figure 7. Left: recyclability experiments of MNP@PIL/W (two lines are related to time A and
B); Right: leaching test of MNP@PIL/W (a and b: oxidation of 1 to 2 with catalyst and after
catalyst removal, respectively; c and d: conversion of 2 to 3 with catalyst and after catalyst
removal, respectively).
2
5

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a
Table 1. Results of elemental analysis.
C
wt%)
1.58
11.42
13.96
14.36
25.30
H
N
(wt%)
-
0.34
3.82
7.70
9.15
Cl
(wt%)
W
(wt%)
Loading
(mmol/g)
MPS: 0.19
Sample
(
(wt%)
1.80
3.71
3.88
3.32
4.78
MNP@MPS
MNP@PMA
MNP@PAEAm
MNP@PTCT
-
-
-
-
-
-
-
b
-CO
2
Me :1.61
b
-NH : 1.24
2
6.43
0.59
TCT: 0.91
MNP@PIL/W
14.09
WO : 0.77
4
a
Weight percent of C, H and N elements were found by CHN analysis and Cl and W were
found by XRF.
Calculated based on CHN analysis along with TGA data.
b
2
6

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Table 2. Control experiment for oxidation/Knoevenagel condensation between benzyl
a
alcohol and malononitrile.
Cat. Loading
Time (h) Conv.
Yield (%)
Entry
Catalyst
-
Solvent
b
(mol%)
A
12
12
12
5
B
-
3
-
(%)
6
9
A
B
-
-
-
c
1
2
3
4
5
6
7
8
9
-
5
H O
2
4
2
c
Na WO4
H O
2
2
c
MNP@PIL/Cl
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
MNP@PIL/W
10 mg
H O
13
96
94
87
94
94
88
65
79
84
76
-
6
2
5
4
3
4
4
4
4
4
4
4
-
1mg
4
H O
2
2
2
2
1
2
4
3
2
2
5
2
2
-
-
-
-
12
96
94
87
94
82
84
16
51
72
43
-
2
H O
5
5
4
4
3
6
6
5
2
H
2
O
H O
2
H O
2
H O
4
2
1
1
1
1
1
1
1
0
1
2
3
4
5
6
Toluene
CHCl3
49
28
12
33
-
CH CN
3
THF
5
-
d
-
H
H
H
2
2
2
O
O
O
d
MNP@PIL/Cl
-
4
99
90
-
-
99
90
e
PIL/W
a
Reaction condition: benzyl alcohol (1 mmol), H O (1.5 mmol), 90 ˚C and after A time
2
2
malononitrile (1.2 mmol) at room temperature for B time. GC yield.
b
Conversions calculated based on initial mmol of benzyl alcohol.
Other product is benzoic acid.
Reaction started with benzaldehyde (1mmol) and malononitrile (1.2 mmol) at room
c
d
temperature.
e
Same catalyst without MNPs.
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Table 3. Tandem one-pot reaction of oxidation/ Knoevenagel condensation of
a,b
alcohols catalyzed by MNP@PIL/W.
H
H
H
H
CN
CN
CN
CN
CN
CN
CN
CN
CN
CN
H C
Br
H CO
3
3
Time A: 4h
Time B: 2h
Conv. : 94%
Time A: 4h
Time B: 2h
Time A: 5h
Time B: 2h
Time A: 6h
Time B: 2.5h
Conv. : 90%
Yield : 86%
Conv. : 96%
Yield : 94%
Conv. : 93%
Yield : 92%
Yield : 94%(87%)
OH
H
H
H
H
CN
CN
CN
CN
CN
CN
CN
NC
HO
O N
2
Time A: 8h
Time B: 3h
Conv. : 79%
Yield : 65%
Time A: 5h
Time B: 3h
Conv. : 91%
Yield : 90%
Time A: 3.5h
Time B: 1h
Conv. : 98%
Time A: 5h
Time B: 1.5h
Conv. : 95%
Yield : 95%(91%)
Yield : 98%(93%)
NO2
H
CH3
CN
CN
CN
CN
CN
CN
CN
Cl
Time A: 9h
Time B: 5h
Conv. : 39%
Time A: 5h
Time B: 3h
Conv. : 91%
Yield : 90%
Time A: 3h
Time B: 3h
Conv. : 88%
Yield : 81%(75%)
Time A: 10h
Time B: 5h
Conv. : 83%
Yield : 80%
Yield : 25%(23%)
H
CN
CN
CN
CN
CN
CN
Time A: 6h
Time B: 1h
Conv. : 99%
Yield : 95%
Time A: 9h
Time B: 5h
Conv. : 78%
Yield : 69%
Time A: 12h
Time B: 6h
Conv. : 90%
Yield : 84%
a
Reaction condition: Alcohol (0.5 mmol), MNP@PIL/W (4 mol%), H
2 2
O (0.75
mmol), H O (2 mL) at 90 ˚C and after A hours malononitrile (0.6 mmol) at room
2
temperature for B hours.
b
GC yield. The values in the parenthesis refer to the isolated yield.
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