Synthesis and characterization of ionic liquid based bifunctional periodic mesoporous organosilica supported potassium carbonate as very efficient nanocatalyst for the Knoevenagel condensation

Article abstract of DOI:10.1016/j.molcata.2016.01.001

A novel ionic liquid based bifunctional periodic mesoporous organosilica supported potassium carbonate (BPMO-IL-KCO₃) is prepared, characterized and its catalytic efficiency is studied in the Knoevenagel reaction. The BPMO-IL-KCO₃ wa

Full text of DOI:10.1016/j.molcata.2016.01.001

Accepted Manuscript
Title: Synthesis and Characterization of Ionic Liquid Based
Bifunctional Periodic Mesoporous Organosilica Supported
Potassium Carbonate as Very Efficient Nanocatalyst for the
Knoevenagel Condensation
Author: Dawood Elhamifar Somayeh Kazempoor
PII:
S1381-1169(16)30001-2
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.01.001
MOLCAA 9733
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Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
29-10-2015
31-12-2015
2-1-2016
Please cite this article as: Dawood Elhamifar, Somayeh Kazempoor, Synthesis
and Characterization of Ionic Liquid Based Bifunctional Periodic Mesoporous
Organosilica Supported Potassium Carbonate as Very Efficient Nanocatalyst for
the Knoevenagel Condensation, Journal of Molecular Catalysis A: Chemical
http://dx.doi.org/10.1016/j.molcata.2016.01.001
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Synthesis and Characterization of Ionic Liquid Based Bifunctional
Periodic Mesoporous Organosilica Supported Potassium Carbonate as
Very Efficient Nanocatalyst for the Knoevenagel Condensation
Dawood Elhamifar* and Somayeh Kazempoor
Department of Chemistry, Yasouj University, Yasouj, 75918-74831, Iran, E-mail: d.elhamifar@yu.ac.ir
Highlights ►
► ► ► Novel bifunctional ionic liquid based PMO supported K2CO3 was prepared and characterized
► Excellent properties of this nanomaterial were developed in details ► This material was applied as
an efficient nanocatalyst for the Knoevenagel reaction ► The Knoevenagel products were obtained in
high to excellent yields and selectivities ► This nanocatalyst was reused several times without
important decrease in efficiency ► ►
Graphical abstractA novel ionic liquid based bifunctional periodic mesoporous organosilica
supported potassium carbonate was prepared, characterized and its catalytic activity was
investigated in the Knoevenagel reaction. This catalyst exhibited high efficiency for the
preparation of different derivatives of Knoevenagel products under moderate reaction
conditions. Moreover, the catalyst was successfully recovered and reused several times
without important decrease in reactivity and stability.
Abstract
A novel ionic liquid based bifunctional periodic mesoporous organosilica supported potassium
carbonate (BPMO-IL-KCO3) is prepared, characterized and its catalytic efficiency is studied in the
Knoevenagel reaction. The BPMO-IL-KCO3 was prepared by chemical attachment of 1-methyl-(3-
trimethoxysilylpropyl)imidazolium chloride on an ionic liquid based PMO followed by treatment
with potassium carbonate under ambient temperature. This material was characterized with thermal
gravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, powder X-ray

diffraction (PXRD), scanning electron microscopy (SEM) and transmission electron microscopy
(TEM). The BPMO-IL-KCO3 was then successfully applied as efficient base catalyst in the
Knoevenagel condensation of different aldehydes with ethyl cyanoacetate and gave high to
excellent yields of the corresponding coupling products. The catalyst was recovered and reused
several times without significant decrease in activity and selectivity. The recovered catalyst was
also analyzed with TEM and nitrogen sorption experiment to investigate structural stability and
durability of the material under applied conditions.
Keywords: Bifunctional PMO• ionic liquid• basic PMO-IL• Knoevenagel condensation• recoverable
nanocatalyst
1. Introduction
The discovery of periodic mesoporous organosilicas (PMOs) with unique physiochemical properties,
high loading of organic functional groups in their framework as well as high thermal, mechanical and
chemical stability, and their expanding potential applications was a great achievement in the field of
material chemistry at last decade [1-3]. PMOs are synthesized by simultaneous hydrolysis and
condensation of bridged organosilane precursors in the presence of surfactant template as structure
directing agent [3]. To date, different approaches such as the selection of hydrolytic reaction conditions,
design of anionic or natural templates, development of new precursors, and the use of co-condensation
or grafting manners, have enabled the hierarchical structural control of PMOs from molecular- and
meso-scale structures to macroscopic morphology [3]. An interesting success of PMOs that combines
the unique framework properties with specific active sites is the making of bifunctional PMOs (BPMOs)
containing organic functional moieties both in pore wall and mesochannel [4, 5]. Due to high
accessibility and therefore high reactivity of mesochannel groups of BPMOs, they have excellent
efficiency especially in the catalytic processes [4, 5]. To date several BPMO materials with diverse

functionality have been prepared and applied as catalyst in different organic reactions [4-6]. As an
example, more recently we prepared a new BPMO based on ionic liquid and propylsulfonic acid groups
(BPMO-IL-SO3H) and studied its catalytic application in the esterification of carboxylic acids and
Biginelli reactions [6]. The BPMO-IL-SO3H gave well to excellent yield of desired products and could
be recovered and reused several times without significant decrease in efficiency, a feature that attributed
to the present of imidazolium moiety in the framework of the material [6].
On the other hand, the preparation of substituted alkenes through Knoevenagel reaction is one of the
most important organic processes which is very interested in between chemists due to its key role in the
production of biologically active compounds and fine chemicals [7, 8]. In the Knoevenagel process,
activated methylenes are reacted and condensed with carbonyls in the presence of acid or base catalysts
to prepare α,β-unsaturated products [7, 8]. Traditionally, a lot of organic and/or inorganic bases such as
pyridine, primary, secondary and tertiary amines, KHCO3, K2CO3, NaHCO3 and K2HPO4 have been
widely used as catalyst in the Knoevenagel condensation of a variety of different activated methylenes
with carbonyl compounds under homogeneous conditions [7, 9]. This reaction has also extensively been
performed in the presence of many homogeneous Lewis acid catalysts such as TiCl4, CuCl2, Al2O3,
LaCl3 and NbCl5 [7, 10]. However, since the homogeneous catalytic systems suffer from problems of
catalyst recovery, product separation and environmental pollution, therefore, several strategies have been
recently developed for the preparation of recoverable heterogeneous catalyst for this important reaction.
Along this line, several solid materials supported acid or base catalysts have been prepared for
catalyzing Knovenagel condensation under heterogeneous conditions [11-17]. Among different supports
applied in this regard, ordered mesoporous silicas are more attracted because of their high specific
surface area, high thermal and mechanical stability, uniform pore size distribution and good
recoverability [15-17]. Although, these successes have decreased some restrictions related to catalyst
recovery and product isolation, however, some limitations including the use of volatile organic solvents,
high catalyst loading and high reaction temperature are still observed in these systems. Hence, the
development of efficient environmental-friendly catalytic systems, especially metal-free, while

demonstrating excellent reactivity and reusability feature, is still a need for the Knoevenagel
condensation. Therefore, herein in continuation of our recent studies in the field of bifunctional PMOs
and according to importance of the Knoevenagel condensation in the synthetic organic chemistry, we
wish to disclose, for the first time, the preparation and characterization of a novel ionic liquid based
bifunctional periodic mesoporous organosilica with basic property (BPMO-IL-KCO3) as well as study
its catalytic application in the Knoevenagel condensation of different aldehydes with ethyl cyanoacetate
at ambient temperature (Scheme 1).
2. Experimental
2.1. Preparation of BPMO-IL-KCO3 nanocatalyst:
Firstly, the 1-methyl-(3-trimethoxysilylpropyl)imidazolium chloride ionic liquid was prepared by
reaction of N-methylimidazole (5 mmol) and 3-chloropropyl-trimethoxysilane (5 mmol) in toluene
under reflux conditions during 30 h [18]. The PMO-IL nanomaterial (see Supporting Information) was
then reacted with a substoichiometric amount of 1-methyl-(3-trimethoxysilylpropyl)imidazolium
chloride via a grafting approach to give ionic liquid based bifunctional PMO (BPMO-IL-Cl). Ionic
liquid based bifunctional PMO with basic property (BPMO-IL-KCO3) was then prepared by treatment of
BPMO-IL-Cl with potassium carbonate (Scheme 1). For this, the BPMO-IL-Cl (1g) was added to a flask
containing distilled water (50 mL) and vigorously stirred at room temperature. After complete dispersion
of BPMO-IL-Cl in water, potassium carbonate (5 mmol) was added and the mixture was stirred at the
same temperature for 24 h. The obtained precipitate was filtered and completely washed with distilled
water to remove KCl and unreacted potassium carbonate. The final material was dried for 12 h at 70 oC
and gave a white powder denoted as KCO3-containing ionic liquid based bifunctional PMO (BPMO-IL-
KCO3). The loading of the KCO3 was obtained to be 1.2 mmol/g by the means of the potassium content
obtained from energy-dispersive X-ray (EDX) spectroscopy.

2.2. General procedure for the preparation of Knoevenagel products using BPMO-IL-KCO3
nanocatalyst
For this, BPMO-IL-KCO3 nanocatalyst (0.5 mol %) was added to a flask containing a homogeneous
ethanol solution of aldehyde (2 mmol) and ethyl cyanoacetate (2.2 mmol). The obtained mixture was
then magnetically stirred at 50 °C for an appropriate time indicated in Table 2. The reaction progress
was monitored by TLC. After completion of the reaction, warm ethanol (8 mL) was added and the
reaction mixture was separated from the catalyst by filtration and washing with ethanol. Pure products
were obtained after recrystallization in a mixture of hexane/ethanol solvent or isolated the residue by
column chromatography on silica.
2.3. General procedure for the recovery of BPMO-IL-KCO3 nanocatalyst in the Knoevenagel
reaction
For this, aldehyde (5 mmol), ethyl cyanoacetate (5.5 mmol) and BPMO-IL-KCO3 nanocatalyst (0.5 mol
%) were added to ethanol and the mixture was magnetically stirred at 50 °C. The reaction progress was
monitored by TLC. After the reaction was completed, warm ethanol (10 mL) was added and the
obtained solution was hotly filtered. The catalyst was separated from reaction mixture by further
washing with warm ethanol. Then this nanocatalyst was reused at the same conditions as the first run for
at least 7 times and gave corresponding Knoevenagel product in high yield and selectivity (Table 3).
2.4. General procedure for the hot filtration test in the Knoevenagel reaction
The hot filtration test was carried out in the reaction of benzaldehyde (2 mmol) with ethyl cyanoacetate
(2.2 mmol) in the presence of 0.5 mol % of catalyst in EtOH at 50 °C. After about 50 % of the reaction
was progressed, the obtained mixture was hotly filtered. The filtrate was then allowed to continue under
optimized conditions during 3 h and the reaction progress was monitored.
3. Results and Discussion

The ionic liquid based periodic mesoporous organosilica (PMO-IL) was first prepared according to
our recently reported procedure with a slight modification [18]. The PMO-IL nanomaterial was then
reacted with a substoichiometric amount of 1-methyl-(3-trimethoxysilylpropyl)imidazolium chloride via
a grafting approach to give ionic liquid based bifunctional PMO (BPMO-IL-Cl). Next, the BPMO-IL-Cl
was treated with potassium carbonate to produce bifunctional PMO-IL with basic property (BPMO-IL-
KCO3, Scheme 1). The BPMO-IL-KCO3 nanomaterial was then characterized with several techniques
such as nitrogen adsorption-desorption experiment, powder X-ray diffraction (PXRD), transmission
electron microscopy (TEM), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA),
and energy-dispersive X-ray (EDX) spectroscopy.
Nitrogen adsorption-desorption analysis of the BPMO-IL-KCO3 exhibited typically type IV isotherm
and H1 hysteresis loop with a relatively sharp capillary condensation step at a relative pressure of
approximately 0.70, and a very sharp capillary evaporation step centered at approximately 0.5 (Figure
1a). The BET surface area and total pore volume of the material were also found to be 523 m2/g and
0.92 cm3/g, respectively. The average pore diameter of BPMO-IL-KCO3, calculated using the Barrett–
Joyner–Halenda (BJH) method, showed a sharp pore-size distribution centered at 7.2 nm (Figure 1b).
These data successfully confirm the presence of a two dimensional (2D) hexagonal mesopore structure
with a narrow pore-size distribution for the material. Powder X-ray diffraction (PXRD) and transmission
electron microscopy (TEM) analyses of the BPMO-IL-KCO3 were carried out to get insight into the
structural feature of the material. The PXRD pattern of the catalyst illustrated one peak with high
intensity at 2Ө of 1 degree corresponding to d100 reflection and two peaks with low intensity at 2Ө of
1.62 and 1.84 corresponding, respectively, to d110 and d200 reflections. These strongly confirm the
presence of highly ordered mesostructure with two-dimensional hexagonal symmetry (p6mm) lattice for
the material (Figure 2). TEM image was in good agreement with the results of PXRD analysis and also
showed well ordered two-dimensional mesochannels for the material (Figure 3). The scanning electron
microscopy (SEM) image of the BPMO-IL-KCO3 was next carried out to show the morphology of the
material (Figure 4). This demonstrated a uniform and regular rope-like morphology for the material

surface. Thermal gravimetric analysis (TGA) of the material was also carried out to study the thermal
stability of the material (Figure 5). The first weight loss (4.69 %) in the temperature below 120 °C is
corresponded to removal of physosorbed water and alcoholic solvents remained from synthesis process.
The second weight loss (1.24 %) between 120 and 220 °C is attributed to elimination of surfactant
template, remained from extraction process. The third and main weight loss from 250 to 600 °C (23.82
%) is corresponded to methyl-propyl-imidazolium ionic liquids grafted onto solid surface and also
bis(propyl) imidazolium ionic liquids incorporated in the material pore wall. These observations confirm
successful immobilization and incorporation of ionic liquid moieties into/onto material network.
Energy-dispersive X-ray (EDX) spectroscopy of the BPMO-IL-KCO3 was carried out to be evidence for
the presence of C, O, Si, N and K in the material (Figure 6). The elemental distribution mapping of this
analysis demonstrated signals of carbon, oxygen, silicon, nitrogen and potassium in the sample. This
successfully confirms well immobilization and/or incorporation of ionic liquid and potassium carbonate
moieties onto/into material network. Importantly, the signal of chlorine should be observed at 2.65 KeV
[3e], however, this was not seen in the EDX spectrum of the BPMO-IL-KCO3 material confirming
successful replacement of chloride anions with KCO3 during anion exchange process.
After characterization, the catalytic application of BPMO-IL-KCO3 was investigated in the
Knoevenagel condensation of aldehydes with ethyl cynoacetate under different conditions. Firstly, the
effect of solvent and catalyst loading was investigated in the condensation of benzaldehyde with ethyl
cyanoacetate, as a model reaction, at 50 °C (Table 1). The results showed that in toluene low yield of
Knoevenagel product was obtained, while CH3CN and H2O delivered good yield of desired product.
Interestingly, in EtOH an excellent yield was obtained under the same conditions as before (Table 1,
entries 1-4). The study also showed that the reaction was strongly affected by the amount of the catalyst.
As shown in Table 1, by increasing the amount of catalyst from 0.15 to 0.5 mol% a significant increase
in the yield is observed (Table 2, entries 4–7), and the best result is obtained in the presence of 0.5 mol%
of catalyst. To show the impact of chemically grafted ionic liquid groups in the catalytic process, in the

next study the catalytic efficiency of PMO-IL-KCO3 was checked under the same reaction conditions as
BPMO-IL-KCO3 (Table 1, entry 4 vs. entry 8). Attractively, in the later case only 58 % of the
Knoevenagel product was obtained indicating the key role of grafted IL moieties in the catalytic process.
This result may be attributed to better accessibility and flexibility of highly active catalytic sites,
[methyl-propylimidazolium][KCO3] moieties, of BPMO-IL-KCO3 in comparison with PMO-IL-KCO3.
In another study the BPMO-IL-OH nanocatalyst was prepared by treatment of potassium hydroxide with
BPMO-IL using the same procedure as BPMO-IL-KCO3. Comparative efficiency tests were then
performed on BPMO-IL-KCO3 and BPMO-IL-OH catalysts in the Knoevenagel condensation of
benzaldehyde with ethyl cyanoacetate under the same conditions (Table 1, entry 4 vs. entry 9).
Interestingly, at the same reaction time as BPMO-IL-KCO3, BPMO-IL-OH gave 69% yield of the
desired product confirming that the efficiency of KCO3-containing BPMO-IL is much better than those
of hydroxyl-containing BPMO-IL. With the optimum conditions in hand, the scope and limitation of this
catalyst was next investigated in the Knovenagel condensation of various aldehydes with ethyl
cyanoacetate (Table 2). As mentioned above, benzaldehyde delivered excellent yield of corresponding
substituted alkene at 50 °C and short reaction time (Table 2, entry 1). The catalyst also demonstrated
excellent activity for other aromatic aldehydes bearing both electron donating and electron withdrawing
substituents (Table 2, eateries 2-12). As shown, 2-methyl-benzaldehyde, 4-methyl-benzaldehyde, 4-
methoxy-benzaldehyde, 4-hydroxy-benzaldehyde and 3-ethoxy-4-hydroxy-benzaldehyde (Table 2,
entries 2-6) delivered corresponding products in high yields (Table 2, entries 2-6). The electron
withdrawing groups containing aldehydes such as 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-
chlorobenzaldehyde,
3-bromobenzaldehyde, 3-nitrobenzaldehyde and 4-nitrobenzaldehyde also
afforded desired adducts in excellent yields (Table 2, entries 7-12). Importantly, the catalyst also showed
high efficiency for the less reactive orth-substituted benzaldehydes such as 2-methyl-benzaldehyde
(Table 2, entry 2) and 2-chlorobenzaldehyde (Table 2, entry 7). Interestingly, aliphatic aldehydes such as
butyl aldehyde and acetaldehyde also delivered good yield of the corresponding alkene products under
the same conditions as above (Table 2, entries 13, 14). These results successfully illustrate the high

performance of the designed catalyst for the preparation of a wide range of substituted alkenes which are
important intermediates in the field of pharmacology and chemistry.
The recoverability and reusability of the catalyst was then examined by carrying out runs of the
reaction with the same batch of the catalyst in the model reaction between benzaldehyde and ethyl
cyanoacetate. In order to regenerate the catalyst after each cycle, it was separated and washed completely
o
with ethanol and dried under vacuum at 70 C. This was then applied in aforementioned reaction under
conditions as before. Interestingly, the result illustrated that the catalyst could be recovered and reused at
least 7 times with remaining its efficiency (Table 3). Moreover, according to the elemental
analysis, no significant decrease of the K-loading in the recovered catalyst was detected after used,
indicating that the leaching of basic active sites could be essentially neglected.
To further investigate whether the catalyst works in a homogeneous or heterogeneous manner, a hot
filtration test was carried out in the reaction of benzaldehyde with ethyl cyanoacetate as a test model. For
this, after about 50 % of the reaction was progressed, the obtained mixture was hotly filtered. The
filtrate was then allowed to continue under optimized conditions. Importantly, no considerable reaction
progress was observed after 3 h. These observations verify that the leaching of KCO3 species were
negligible under applied conditions and the catalyst was most likely operating in a heterogeneous
manner. The recovered catalyst after fifth reaction cycle was analyzed by nitrogen-sorption experiment
and TEM analysis to investigate the structural and chemical stability of the material under applied
conditions. The TEM image of the recovered catalyst clearly demonstrated that the BPMO-IL-KCO3
catalyst remained well-defined ordered mesoporous structure after being reused for 4 times (Figure 7).
Moreover, the nitrogen adsorption-desorption and BJH pore size isotherms of the recovered BPMO-IL-
KCO3 illustrated a pattern the same as fresh catalyst (Figure 8). As shown the nitrogen-sorption
illustrated a type IV isotherm with H1 hysteresis loop. The BET surface area and mean pore volume of
this were decreased to 408 m2/g and 0.84 cm3/g, respectively (Table 1S). The BJH pore size distribution

also showed a peak with good density centered at 7.1 (Figure 8b, Table 1S). These observations exhibit
high hydrothermal, mechanical and chemical stability of the catalyst during applied conditions.
4. Conclusions
In conclusion, for the first time, a novel ionic liquid based bifunctional periodic mesoporous
organosilica with basic property (BPMO-IL-KCO3) was prepared, characterized and applied as effective
heterogeneous nanocatalyst in the Knoevenagel condensation. The powder X-ray diffraction,
transmission electron microscopy and nitrogen sorption analyses confirmed that the material had a well-
ordered two-dimensional hexagonal symmetry. The TG analysis showed high thermal stability of well
incorporated ionic liquid moieties in the material. Energy-dispersive X-ray analysis successfully proved
well immobilization and/or incorporation of ionic liquid and potassium carbonate moieties onto/into
material framework. The catalyst was effectively used in the Knoevenagel condensation of aldehydes
with ethyl cyanoacetate and afforded corresponding substituted alkenes in high to excellent yield. The
catalyst was also recovered and reused at least seven times without significant decrease in efficiency.
TEM image of the recovered BPMO-IL-KCO3 after fifth reaction cycle showed the presence of well-
ordered 2-dimensional hexagonal mesochannels indicating high chemical and structural stability of the
material under applied conditions. Other advantages of this study include mild reaction conditions, high
yield of products as well as high activity, stability and durability of the catalyst during reaction process.
According to abovementioned advantages, some applications of the BPMO-IL-KCO3 in the other base
catalyzed organic processes are underway in our laboratory.
Acknowledgments: The authors thank the Yasouj University and the Iran National Science Foundation
(INSF) for supporting this work.
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Scheme and Figure captions:
Scheme 1. Preparation of BPMO-IL-KCO3 nanocatalyst and its application in the Knoevenagel reaction
Figure 1. Nitrogen adsorption-desorption (a) and BJH pore size distribution (b) isotherms of the
BPMO-IL-KCO3 nanocatalyst
Figure 2. Powder X-ray diffraction (PXRD) pattern of the BPMO-IL-KCO3 nanocatalyst
Figure 3. TEM image of the BPMO-IL-KCO3 nanocatalyst
Figure 4. SEM image of the BPMO-IL-KCO3 catalyst
Figure 5. Thermal gravimetric analysis of the BPMO-IL-KCO3 nanocatalyst
Figure 6. Energy-dispersive X-ray (EDX) of the BPMO-IL-KCO3
Figure 7. TEM image of the recovered BPMO-IL-KCO3 after fifth reaction cycle
Figure 8. Nitrogen adsorption-desorption (a) and BJH pore size distribution (b) isotherms of the
recovered BPMO-IL-KCO3 nanocatalyst after fifth cycle
Table 1. The effect of the kind of catalyst, solvent and catalyst loading in the
Knoevenagel condensation of ethyl cynoacetate with benzaldehyde[a]
O
O
OEt
CN
O
Catalyst
H
NC
+
OEt
Catalyst
loading (mol
%)
Entry
1
Catalyst
Solvent
Toluene
Yield (%) [b]
37
BPMO-IL-KCO3
0.5

BPMO-IL-KCO3
BPMO-IL-KCO3
BPMO-IL-KCO3
BPMO-IL-KCO3
BPMO-IL-KCO3
BPMO-IL-KCO3
PMO-IL- KCO3
BPMO-IL-OH
0.5
0.5
0.5
0.4
0.3
0.15
0.5
0.5
H2O
CH3CN
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
2
3
4
5
6
7
8
9
78
75
96
75
57
26
58
69
[a] Reaction conditions: Benzaldehyde (2 mmol), ethyl cyanoacetate (2.2 mmol), solvent (5 mL),
50 °C, 80 min. [b] Isolated yields.
Table 2. The Knoevenagel condensation of aldehydes with ethyl cyanoacetate in the
presence of BPMO -IL-KCO3 nanocatalyst [a]
O
O
OEt
CN
O
H
BPMO-IL-KCO3
NC
+
OEt
R
R
Entry
1
Aldehyde
PhCHO
Time (min)
Yield (%)[b]
96
TON[c]
192
80
2
3
2-Me-PhCHO
4-Me-PhCHO
100
88
85
90
170
180
4
4-MeO-PhCHO
100
90
180

5
6
4-OH-PhCHO
100
100
88
86
176
172
3-EtO, 4-OH-
PhCHO
180
190
188
7
8
2-Cl-PhCHO
3-Cl-PhCHO
100
90
90
95
9
4-Cl-PhCHO
85
94
10
11
12
3-Br-PhCHO
3-NO2-PhCHO
4-NO2-PhCHO
90
30
30
92
95
97
184
190
194
13
14
Butylaldehyde
Acetaldehyde
105
105
75
74
150
148
[a] Reaction conditions: Aldehyde (2 mmol), ethyl cyanoacetate (2.2 mmol), catalyst (0.5
[b]
[c]
mol%), EtOH (5 mL), 50 °C
.
Isolated yields. TON = turnover number (defined as
mmol of product/mmol of catalyst).
Table 3. Reusability of the BPMO-IL-KCO3 catalyst in the Knoevenagel reaction of
benzaldehyde with ethyl cyanoacetate
Run
Time (min)
Yield (%)
TON
1
2
3
4
5
6
7
80
80
96
96
92
92
88
90
88
192
192
184
184
176
180
176
90
90
95
95
100

8
100
86
172