Synthesis of ionic liquid functionalized SBA-15 mesoporous materials as heterogeneous catalyst toward knoevenagel condensation under solvent-free conditions

Article abstract of DOI:10.1002/ejic.200600289

1-Methyl-3-propylimidazolium chloride (MPImCl) and 1-propylpyridinium chloride (PPyCl) ionic liquid functionalized SBA-15 mesoporous materials were synthesized and used as heterogeneous catalysts in Knoevenagel reactions with excellent yields and reusabil

Full text of DOI:10.1002/ejic.200600289

SHORT COMMUNICATION
DOI: 10.1002/ejic.200600289
Synthesis of Ionic Liquid Functionalized SBA-15 Mesoporous Materials as
Heterogeneous Catalyst toward Knoevenagel Condensation under Solvent-Free
Conditions
[
a]
[a]
[b]
[a]
[a]
[a]
Yong Liu, Jiajian Peng, Shangru Zhai, Jiayun Li, Jianjiang Mao, Meijiang Li,
[a]
[a]
Huayu Qiu,* and Guoqiao Lai*
Keywords: Mesoporous materials / Heterogeneous catalysis / Ionic liquids
1
-Methyl-3-propylimidazolium chloride (MPImCl) and 1-pro-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
pylpyridinium chloride (PPyCl) ionic liquid functionalized
SBA-15 mesoporous materials were synthesized and used as
heterogeneous catalysts in Knoevenagel reactions with ex-
cellent yields and reusability.
Introduction
ysis but also as green catalysts themselves in many reactions
such as cycloaddition, Biginelli reaction, nitration,
The Knoevenagel condensation, one of the most impor-
tant preparation methods of substituted alkenes, is widely
employed to synthesize intermediates of fine chemicals
[6]
Beckmann rearrangement and Knoevenagel condensation
[7]
as well. However, in some cases ionic liquids are miscible
with some products or reactants, leaving separation and re-
use of catalyst still a problem. Thus, immobilization of ionic
liquids on solid-based materials is of particular interest. Re-
cently, several groups reported the successful synthesis of
(Scheme 1). Compared to traditional homogeneous cata-
lysts including organic bases (primary, secondary, tertiary
amines), ZnCl , LiCl, and cetyltrimethylammonium bro-
2
[
1]
mide (CTAB), solid-based heterogeneous catalysts are
more desirable for their advantages in separation and reus-
ability. In recent years, resins, zeolites, hydrotalcites etc.
have been applied to this reaction as heterogeneous cata-
[8]
silica-based ionic liquids, while reports on ordered ionic
liquids functionalized mesoporous materials are still quite
[9]
rare. Herein, we report the synthesis of MPImCl and ionic
liquid functionalized SBA-15 mesoporous material and its
catalytic activity toward Knoevenagel condensation under
solvent-free conditions. The resulting hetergeneous catalyst
could be easily recovered with high catalytic activity re-
maining after 10 cycles.
[
2]
lysts, among which organo-functionalized mesoporous sil-
icas are specially studied due to their unique properties such
as high surface area, uniform pore structure and controlla-
ble surface properties.[ Recently, synthesis and catalysis ac-
tivities of different structured mesoporous materials func-
3]
[
4]
tionalized by amino/diamino groups have been reported.
Results and Discussion
1-Methyl-3-[(triethoxysilyl)propyl]imidazolium chloride
(
MTESPImCl) and 1-[(triethoxysilyl)propyl]pyridinium
Scheme 1.
chloride (TESPPyCl) were prepared by the reaction of 1-
methylimidazole or pyridine with (3-chloropropyl)triethoxy-
[
8a]
Ionic liquids, known as novel environmental benign me- silane, different from the literature not only because the
[
5]
dia, have attracted great interest in the last two decades
reactants were cheaper but also the corresponding pyridine
since they can serve not only as favorable solvents for catal- species could be obatined. The XRD patterns of the
MPImCl-SBA materials obtained with different MTES-
PImCl amounts are given in Figure 1. When the MTES-
Technology of the Ministry of Education, Hangzhou Teachers PImCl content in the initial mixture was 5%, one intense
[
a] Key Laboratory of Organosilicon Chemistry and Material
College,
diffraction peak together with two weak ones could been
seen (Figure 1, b), corresponding to the (100), (110), and
Hangzhou 310012, China
Fax: +86-571-28865135
E-mail: yjg@hztc.edu.cn
(200) planes of highly ordered SBA-15 structured mesopo-
[b] Department of Chemical Engineering and Materials, Dalian
Institute of Light Industry,
rous materials, respectively. As the MTESPImCl content in-
creased to 10%, the (110) and (200) peaks disappeared (Fig-
Dalian 116034, China
Eur. J. Inorg. Chem. 2006, 2947–2949
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2947

Y. Liu, J. Peng, S. Zhai, J. Li, J. Mao, M. Li, H. Qiu, G. Lai
SHORT COMMUNICATION
ure 1, c), indicating the decrease of pore regularity. With a display higher surface areas and larger pore diameters com-
further increase of the MTESPImCl content to 15%, no pared with MPImCl counterparts, and longer pre-hydroly-
characteristic peaks of SBA-15 mesoporous materials could sis time was found helpful to improve the structures of
be seen. It is noteworthy that when the pre-hydrolysis time products, which was in agreement with XRD results. Ele-
of tetraethyl orthosilicate (TEOS) was prolonged to 4 h, the mental analysis was used to obtain accurate amounts of the
order of pore structure (MTESPImCl content 10%) was ionic liquid attached to the mesopores. As summarized in
greatly improved (Figure 1, a). Similar phenomena have Table 1, loading amounts of PPy-SBA and MPImCl-SBA
been reported in the synthesis of sulfonic acid and ami- were comparable and increased with the increase of the
nopropyl functionalized SBA-15 mesoporous materials un- ionic liquid contents in the initial mixture. The effect of
[
4c,10]
der acid conditions
and could be explained by the fol- pre-hydrolysis time on the loading amounts was negligible.
lowing reasons: On one hand, MTESPImCl can perturb the Solid-state 29Si NMR spectroscopy and thermogravimetric
self-assembly of surfactant micelles and silica precursors; analysis (TGA) were also used to characterize the ionic li-
on the other hand, the cationic part of MTESPImCl proba- quid functionalized mesoporous materials and the results
bly interacts with ethoxy groups of TEOS, thus inhibiting well agree with that of the elemental analysis.
its hydrolysis and condensation. Therefore, prolonging the
pre-hydrolysis time of TEOS can prevent MTESPImCl Table 1. N adsorption-desorption and elemental analysis results of
2
ionic liquid functionalized SBA-15 materials.
from disturbing the mesophase. XRD results of PPy-SBA
materials also proved that orderd structures could be ob-
tained with TEOS pre-hydrolyzed for 4 h (Figure 2).
Ionic liquid,
amount [%]
S
BET
V
p
Pore diameter Loading amount
2
3
[m /g] [cm /g]
[nm]
[mmol/g]
–
, 0[a]
688
482
400
143
529
558
504
368
0.937
0.849
0.564
0.221
0.653
0.997
0.901
0.775
5.51
5.33
5.13
4.12
5.89
8.04
8.03
5.74
0
[
a]
MTESPImCl, 5
0.512
0.943
1.322
0.966
0.569
0.986
1.409
MTESPImCl, 10[
MTESPImCl, 15[
a]
a]
b]
[
MTESPImCl, 10
TESPPyCl, 5[
b]
[
b]
TESPPyCl, 10
TESPPyCl, 15[
b]
[
4
a] TEOS pre-hydrolysis time 40 min. [b] TEOS pre-hydrolysis time
h.
In view of the increasing emphasis on the adoption of
clean manufacturing processes and environmentally benign
technologies, clean, solvent-free and highly efficient cata-
Figure 1. XRD patterns of MPImCl-SBA materials with different lytic technologies for the chemical production are highly de-
MTESPImCl contents and different TEOS pre-hydrolyze times.
sirable, so we carried out the Koevenagel condensation of
various aldehydes with malononitrile/ethyl cyanoacetate at
100 °C under solvent-free conditions. 10% MPImCl-SBA
and 10% PPy-SBA were used as catalysts, respectively, and
the optimal amount of catalyst was determined to be
0
.8 mol-% based on the reaction of benzaldehyde with ma-
lononitrile (Table 2, Entries 1–3). As illustrated in Table 2
Entries 4, 6, 13, 15), the catalytic activities of PPy-SBA
(
were slightly lower than those of MPImCl-SBA; thus,
MPImCl-SBA was slected as catalyst for the other reac-
tions. As shown in Entries 7–10, reactions of malononitrile
with all tested aldehydes were complete in 3.5 h with excel-
lent yields (not lower than 87%), which was not lower (if
not higher) compared with those in traditional homogen-
Figure 2. XRD patterns of PPyCl-SBA materials with different
TESPPyCl contents with TEOS prehydrolyzed for 4 h; a: 5%, b:
[1,2]
eous systems.
The influence of substituents in the aro-
matic ring was negligible, indicating the high catalysis ac-
tivity of the MPImCl-SBA materials. In the case of ethyl
10%, c: 15%.
N adsorption-desorption was carried out to supply fur- cyanoacetate, however, the yields decreased even if the reac-
2
ther information about the physical properties of the ionic tion time was prolonged to 6 h (Entries 9–15). Besides, alde-
liquid functionalized SBA-15 materials. As shown in hydes with electron-donating groups (Entries 11, 14, 15)
Table 1, surface areas, pore volumes and pore diameters of showed lower yields compared with the others. The reus-
the products all decreased as the ionic liquid content in- ability of the MPImCl-SBA materials was examined by the
creased from 0 to 15%, which could be attributed to the reaction of benzaldehyde with malononitrile. As shown in
increasing distribution of ionic liquid moieties in the inte- Entry 20, a yield as high as 86.1% was obtained in the 10th
rior mesopore surfaces. PPy-SBA materials were found to cycle.
2948
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 2947–2949

Ionic Liquid Functionalized SBA-15 Mesoporous Materials
SHORT COMMUNICATION
Table 2. Knoevenagel condensation of aldehydes with malono-
nitrile/ethyl cyanoacetate.
X-ray powder diffraction (XRD) data were acquired with a Rigaku
D/max 2500V/PC diffractometer with Cu-K radiation. N adsorp-
α 2
tion and desorption isotherms were measured with a Quantacrome
Autosorb-1 system at 77 K. Surface areas were calculated accord-
ing to the BET method with relative pressures in the range 0.2–0.3,
Ionic liquid
amount
Isolated
yield
[%]
Entry
R1
R2
Y
Time
[h]
[
mol-%]
0
and pore volumes were taken at the P/P = 0.9923 single point.
[
[
[
[
a]
a]
a]
b]
1
2
3
4
5
6
7
8
9
Ph
Ph
Ph
Ph
2-ClC
2-ClC
4-MeOC
4-ClC
4-HOC
4-MeC
Ph
Ph
Ph
2-ClC
2-ClC
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
CN
CN
CN
CN
CN
CN
CN
CN
CN
CN
CO
CO
CO
CO
CO
CO
CO
CO
CO
0.2
0.4
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
3.5
6.0
6.0
6.0
6.0
6.0
6.0
6.0
6.0
3.5
63.5
89.6
93.5
92.8
92.4
89.6
89.6
91.5
87.7
93.2
69.6
85.6
84.0
90.5
82.9
79.1
86.9
81.4
75.0
86.1
Pore diameters were determined from absorption branches accord-
ing to the Barrett–Joyner–Halenda (BJH) method. Loading
amounts of ionic liquids were caculated from the nitrogen contents
performed with an Elementar Vario EC III CHNOS element ana-
lyzer.
[
[
a]
b]
6
H
H
4
4
6
6
[
a]
H
4
[
a]
[
6 4
H
[
1] a) G. Jones, Org. React. 1967, 15, 204–599; b) R. P. Shanthan,
R. V. Venkataratnam, Tetrahedron Lett. 1991, 32, 5821–5823;
c) G. Gowravaram, B. V. S. Reddy, R. S. Babu, J. S. Yadav,
Chem. Lett. 1998, 773–774; d) S. Wang, Z. Ren, W. Cao, W.
Tong, Synth. Commun. 2001, 31, 673.
a]
6
H
4
[
a]
1
1
1
1
1
1
1
1
1
1
2
0
1
2
3
4
5
6
7
8
9
0
6
H
4
[
[
[
a]
a]
b]
2
Et
Et
Et
Et
Et
Et
Et
Et
Et
2
2
2
2
2
2
2
2
[
2] a) Y. Goa, P. Wu, T. Tatsumi, J. Catal. 2004, 224, 107–114; b)
[
a]
b]
6
H
H
4
4
6
J. Simpson, D. L. Rathbone, D. C. Billington, Tetrahedron Lett.
[
6
1
999, 40, 7031–7033; c) F. A. Khan, J. Dash, R. Satapathy,
[
a]
4-MeOC
H
4
S. K. Upadhyay, Tetrahedron Lett. 2004, 45, 3055–3058; d)
M. L. Kantam, B. M. Choudary, C. K. Venkat Reddy, K. K.
Rao, F. Figueras, Chem. Commun. 1998, 1033–1034.
[
a]
[
4-ClC
4-HOC
4-MeC
6
H
4
a]
6
H
H
4
4
[
a]
6
[
3] a) A. Corma, Chem. Rev. 1997, 97, 2373–2419; b) A. Sayari, S.
Hamoudi, Chem. Mater. 2001, 13, 3151–3168; c) C. Li, Catal.
Rev. 2004, 46, 419–492; d) R. Corriu, A. Mehdi, C. Reye, J.
Organomet. Chem. 2004, 689, 4437–4450.
4] a) S. G. Wang, Catal. Commun. 2003, 4, 469–470; b) Y. Kubota,
Y. Nishizaki, H. Ikeya, M. Saeki, T. Hida, S. Kawazu, M.
Yoshida, H. Fujii, Y. Sugi, Microporous Mesoporous Mater.
[
a,c]
Ph
CN
[
[
a] MPImCl-SBA as catalyst. [b] PpyCl-SBA as catalyst.
c] MPImCl-SBA in the 10th cycle.
[
2
004, 70, 135–149; c) X. G. Wang, K. S. K. Lin, J. C. C. Chan,
In summary, ionic liquid functionalized SBA-15 mesopo-
S. Cheng, J. Phys. Chem. B 2005, 109, 1763–1769; d) D. Brunel,
Microporous Mesoporous Mater. 1999, 27, 329–344.
rous materials were synthesized and gave high yields and
good reusability in Koevenagel condensations. These mate-
rials might be used not only as heterogeneous catalysts in
reactions such as cycloaddition and Biginelli reactions but
also as support for transition metals (work in this direction
is in progress and will be reported soon).
[
5] a) T. Welton, Chem. Rev. 1999, 99, 2071–2083; b) J. Dupont,
R. F. Souza, P. A. Z. Suarez, Chem. Rev. 2002, 102, 3667–3692;
c) A. Ouadi, B. Gadenne, P. Hesemann, J. J. E. Moreau, I.
Billard, C. Gaillard, S. Mekki, G. Moutiers, Chem. Eur. J. 2006,
12, 3074–3081; d) M. Antonietti, D. Kuang, B. Smarsly, Y.
Zhou, Angew. Chem. Int. Ed. 2004, 43, 4988–4992; e) J. Du-
pont, J. Braz. Chem. Soc. 2004, 15, 341–350.
[
6] a) J. J. Peng, Y. Q. Deng, New J. Chem. 2001, 25, 639–641; b)
J. M. Sun, S. I. Fujita, M. Arai, J. Organomet. Chem. 2005,
6
2
2
2
90, 3490–3497; c) J. J. Peng, Y. Q. Deng, Tetrahedron Lett.
001, 42, 5917–5919; d) K. Qiao, C. Yokoyama, Chem. Lett.
004, 33, 808–809; e) J. J. Peng, Y. Q. Deng, Tetrahedron Lett.
001, 42, 403–405.
Experimental Section
In a typical procedure to synthesize MPImCl-SBA materials,
2
4.378 g of P123 (EO20PO70EO20) was dissolved in 115 g of H O to
[
7] a) J. R. Harjani, S. J. Nara, M. M. Salunkhe, Tetrahedron Lett.
002, 43, 1127–1130; b) D. C. Forbe, A. M. Law, D. W. Mor-
which 25 g of HCl was added. After 10.17 mL (0.045 mol) of TEOS
was added and pre-hydrolyzed for 40 min, 1.535 g (0.005) of MTE-
SPImCl was added. The mixture was stirred at 40 °C for 24 h and
then transferred into a Teflon-lined stainless steel autoclave and
kept at 100 °C for 24 h. The precipitate was filtered, subsequently
washed with distilled water and EtOH, and dried at 60 °C in air.
The template was removed by refluxing the as-synthesized material
in EtOH for 24 h. The Knoevenagel condensation was carried out
at 100 °C under solvent-free conditions. In a typical procedure,
2
rison, Tetrahedron Lett. 2006, 47, 1669–1703; c) P. Formentin,
H. Garcia, A. Leyva, J. Mol. Catal. A 2004, 214, 137–142.
[8] a) C. P. Mehnert, R. A. Cook, N. C. Dispenziere, M. Afeworki,
J. Am. Chem. Soc. 2002, 124, 12932–12933; b) C. P. Mehnert,
E. J. Mozeleski, R. A. Cook, Chem. Commun. 2002, 3010–
3
011; c) K. Qiao, H. Hagiwara, C. Yokoyama, J. Mol. Catal.
A 2006, 246, 65–69.
[
[
9] a) B. Gadenne, P. Hesemann, J. J. E. Moreau, Chem. Commun.
2
004, 1768–1769; b) M. H. Valkenberg, C. Castro, W. F.
1.82 g (0.025 mol) of malononitrile, 2.41 g (0.023 mol) of benzalde-
Hölderich, Green Chem. 2002, 4, 88–93.
10] D. Margolese, J. A. Melero, S. C. Christiansen, B. F. Chmelka,
G. D. Stucky, Chem. Mater. 2000, 12, 2448–2459.
Received: April 1, 2006
hyde and 0.22 g (0.2 mmol MPImCl) of 10% MPImCl-SBA were
mixed and allowed to react for an appropriate time. The products
were purified by column chromatography and the catalyst was fil-
tered, washed with CH
2
Cl
2
, and collected for reusability test.
Published Online: June 12, 2006
Eur. J. Inorg. Chem. 2006, 2947–2949
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2949