One-pot green synthesis of pyrrole derivatives catalyzed by nano sulfated zirconia as a solid acid catalyst

Article abstract of DOI:10.1002/cjoc.201100143

A new and efficient method for the preparation of N-substituted pyrroles from one-pot Paal-Knorr condensation has been accomplished using nano-crystalline sulfated zirconia (SZ) as the catalyst in ethanol at moderate temperature. This new protocol has the advantages of easy availability, stability, reusability and eco-friendliness of the catalyst, high to excellent yields, simple experimental and work-up procedure. The synthesized compounds were confirmed through spectral characterization using IR, ¹H NMR, ¹³C NMR and mass spectra. A new and efficient method for the preparation of N-substituted pyrroles from one-pot Paal-Knorr condensation has been accomplished using nano-crystalline sulfated zirconia (SZ) as the catalyst in ethanol at moderate temperature. This new protocol has the advantages of easy availability, stability, reusability and eco-friendliness of the catalyst, high to excellent yields, simple experimental and work-up procedure. Copyright

Full text of DOI:10.1002/cjoc.201100143

FULL PAPER
DOI: 10.1002/cjoc.201100143
One-pot Green Synthesis of Pyrrole Derivatives Catalyzed by
Nano Sulfated Zirconia as a Solid Acid Catalyst
,a
b
Teimouri, Abbas*
Chermahini, Alireza Najafi
a
Chemistry Department, Payame Noor University, 19395-4697, Tehran, Iran
Department of Chemistry, Faculty of Science, Yasouj University, Yasouj, P.O. Box 75918-671671, Iran
b
A new and efficient method for the preparation of N-substituted pyrroles from one-pot Paal-Knorr condensation
has been accomplished using nano-crystalline sulfated zirconia (SZ) as the catalyst in ethanol at moderate tempera-
ture. This new protocol has the advantages of easy availability, stability, reusability and eco-friendliness of the
catalyst, high to excellent yields, simple experimental and work-up procedure. The synthesized compounds were
1
13
confirmed through spectral characterization using IR, H NMR, C NMR and mass spectra.
Keywords sulfated zirconia, green synthesis, pyrrole, Paal-Knorr condensation
Introduction
various organic synthesis and transformation reactions
[
17]
having enormous industrial applications.
Reusable
Pyrroles and their derivatives are very important
heterocyclic compounds. They constitute the core unit
of many natural products, synthetic materials and me-
dicinal chemistry.
synthesis of pyrrole in the literature from conjugate ad-
heterogeneous catalysts have attracted a great deal of
interests in recent years. Since most of the catalysts are
expensive and contaminate the environment, the devel-
opment of efficient methods for recovery and reuse of
the catalysts is a very important aspect in this chemistry.
In continuation of our ongoing research for the de-
[
1,2]
There are several methods for the
[3]
[4]
dition reactions,
classical Hantzsch procedure,
[5]
1
,3-dipolar cycloaddition reaction, aza-Wittig reac-
velopment of simple and efficient methods for the syn-
[6]
[7]
tion, reductive coupling, titanium catalyzed hy-
[18-22]
thesis of various heterocyclic compounds,
herein,
[8]
[9]
droamination of diynes, annulations reactions, and
other multistep operations.
remains one of the most significant and simple methods
which consists of the cyclocondensation of primary
amines with 1,4-dicarbonyl compounds to produce
N-substituted pyrroles. Several catalysts have been used
we report the synthesis of pyrroles from 2,5-hexane-
dione and primary amines catalyzed using nano-crys-
talline sulfated zirconia (SZ) as a catalyst in ethanol at
moderate temperature.
[10]
The Paal-Knorr reaction
[
11]
[12]
[15]
Results and Discussion
in this reaction including ionic liquids,
zeolite,
[13]
[14]
Al
2
O
3
,
montmorillonite K10, silica sulfuric acid,
In a model between 2,5-diketone and aniline as an
aromatic amines, effect of the catalyst amount was in-
vestigated (Scheme 1 and Table 1). To minimize the
formation of by-products and to achieve good yield of
the desired product, the reaction is optimized by varying
the amount of catalyst (10, 25 and 50 mg). The per-
centage of the product formation using 10, 25 and 50
mg of SZ as catalyst was found 48%, 96% and 73%,
respectively (Table 1, Entries 1—3). When the catalyst
content was increased to 50 mg, the product formation
[16]
microwave and ultrasound irradiation. However, de-
spite the potential utility of these catalysts, many of
these methodologies for the synthesis of pyrroles are
associated with several shortcomings such as low yields,
prolonged reaction time, harsh reaction conditions, the
requirement of excess of catalysts, use of expensive re-
agents and high temperature. Thus, a milder, selective,
non-hazardous, inexpensive, recyclable, and eco-
friendly organic catalyst is still in demand.
Nowadays, more and more heterogeneous Bronsted
acids, e.g., zeolites and montmorillonite clay are pre-
ferred from an economical perspective as well as from
an ecological viewpoint. Zirconia has attracted consid-
erable interest on account of its potential use as a cata-
lyst support. Recent investigations reveal that promoted
zirconia is an exceptionally good solid acid catalyst for
Scheme 1 Schematic representation of the reaction
O
CH3
Catalyst
CH3
H C
3
+ H N R
N R + 2H O
2
2
EtOH, reflux
O
2
1
CH3
3
*
E-mail: a_teimouri@pnu.ac.ir
Received July 18, 2011; accepted August 14, 2011; published online January 19, 2012.
372
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 372—376

One-pot Green Synthesis of Pyrrole Derivatives Catalyzed by Nano Sulfated Zirconia
decreased to 73% (Table 1, Entry 3). Therefore, it was
found that the use of 25 mg of the catalyst was sufficient
to promote the reaction, and greater amounts of the
catalyst did not improve the yields.
It is noteworthy to mention that in the absence of
catalyst, no product was found even after 180 min.
These results indicate that the catalyst exhibits a high
catalytic activity in this transformation.
reaction. After completion of the reaction, the catalyst
was separated by filtration, washed 3 times with 5 mL
acetone, then with doubly distilled water several times
and dried at 110 ℃. Then the recovered catalyst was
used in the next run. The results of three consecutive
runs showed that the catalyst can be reused several
times without significant loss of its activity (see Figure
1).
Table 1 Effect of catalyst type and amount of catalyst on the
synthesis of pyrroles
a
Entry Catalyst
Catalyst loading/mg Time/min Yield /%
1
2
3
4
SZ
SZ
10
25
50
—
100
75
48
96
73
—
SZ
90
no catalyst
180
Figure 1 The results obtained from catalyst reuse of nano-
crystalline sulfated zirconia in the pyrrole formation.
a
Isolated yields.
In order to optimize the reaction conditions, includ-
Several substituted aromatic amines reacted with
,5-diketone in the presence of solid acid catalyst to
give the corresponding pyrrole derivatives in good
yields. The nature of the substituents on the aromatic
aldehyde has not significant effect on yield of reaction.
The range of isolated yields obtained was found 81%—
ing solvents and temperature, the reaction of 2,5-di-
ketone and aniline as the aromatic amines was opti-
mized by time of the reaction and using various solvents
2
such as EtOH, MeOH, CH
tries 1—6). Reaction in toluene and dichloromethane
DCM) solvents gave low product yields even after 110
3
CN, and THF (Table 2, En-
(
9
4% for SZ as the catalyst.
and 150 min, respectively (Table 2, Entries 5 and 6).
Moreover the yields were moderate in case of methanol
and acetonitrile under reflux condition (Table 2, Entries
a
Table 3 Acid-catalzed synthesis of pyrrole derivatives
CH3
O
3
and 4). The best results were obtained when the reac-
CH3
Catalyst
H C
+
H N R
2
N R
+
2H O
tion was carried out in ethanol at reflux during 80 min
in the presence of catalyst (Table 2, Entry 2). Therefore,
ethanol was selected as a solvent for this reaction. Al-
though water is a desirable solvent for chemical reac-
tions for reasons of cost, safety and environmental con-
cerns, we found that using water in this reaction gave
moderate yields of products under reflux condition after
long reaction times (Table 2, Entry 1).
3
2
EtOH, reflux
O
CH3
Time (min)/
Yeild (%)
m.p./℃
(Lit. m.p.)
Entry Product
R
b
4
8—50
1
2
3
4
5
6
7
1a
1b
1c
1d
1e
1f
C H
6
5
30/94
60/90
60/85
60/90
85/81
60/90
[23]
(
(
(
48—50)
6
62—64)
5
0—62
4-ClC H
6
5
[24]
8—60
Table 2 The condensation reaction of 2,5-hexandione (1 mmol)
with aniline (1 mmol) under various reaction conditions at room
temperature
6 5
4-BrC H
[23]
56—58)
1
42—144
2 6
4-NO C H
5
[23]
(
144—146)
2—44
a
Entry
Solvent
Time/min
180
Yield /%
4
C
6
H
5
CH
4-CH
4-OCH
2
NH
2
[
23]
1
H
2
O
60
90
70
75
60
70
(40—42)
2—74
7
2
EtOH
80
3
C
6
H
5
[
24]
(
74—76)
6
60—62)
3
MeOH
90
2—64
4
CH
3
CN
120
1g
3
C
6
H
5
50/86
[23]
(
13
5
DCM
THF
150
a
1
The products were characterized by IR, H NMR, C NMR and
b
6
200
mass spectroscopy. Isolated yields. The reaction conditions:
aromatic amine (1 mmol), 2,5-diketone (1 mmol), 25 mg catalysts
in the ethanol as the solvent and under reflux condition.
a
Isolated yields.
One of the most important advantages of heteroge-
neous catalysis over the homogeneous counterpart is the
possibility of reusing the catalyst by simple filtration,
without loss of activity. The recovery and reusability of
the catalyst were investigated in the pyrrole formation
The actual mechanism of the reaction is unclear.
However, the proposed mechanism for the formation of
N-substituted pyrroles in the presence of nano-crystal-
line SZ as a catalyst is shown in Scheme 2. The
Chin. J. Chem. 2012, 30, 372—376
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
373

Teimouri & Chermahini
FULL PAPER
2
,5-hexandione (carbonyl groups) is first activated by
lowed by the hydrolysis with water. After 3 h aging at
room temperature, the resulting gel was dried at 110 ℃
for 12 h followed by calcination at 600 ℃ for 2 h.
Characterization X-ray diffraction pattern was
recorded on diffractometer (Philips X'pert) using Cu Kα
radiation (λ＝1.5405 Å), angle range was between 0°
and 80° (Figure 2). Crystallite size of the crystalline
phase was determined from the peak of maximum in-
catalyst. The primary amine attacks to form an interme-
diate. Cyclization and dehydration of intermediate gives
the final product and releases the catalyst for the next
catalytic cycle.
Scheme 2 The proposed mechanism for the formation of pyr-
roles
[
26]
tensity (2θ＝30.18°) by using Scherrer formula, with
a shape factor (K) of 0.9, as below: Crystallite size＝
Kλ/Wcos θ, where, W＝W －W and W is the broad-
H
H
O
CH3
O
O
CH3
H N R
2
b
s
b
CH3
CH3
s
ened profile width of experimental sample and W is the
O
H
H
standard profile width of reference silicon sample.
FT-IR spectra of the catalysts were recorded by FT-IR
－
1
HO
spectrophotometer in the range of 400—4000 cm with
CH3
－
1
a resolution of 4 cm by mixing the sample with KBr
(Figure 3).
NHR
CH
H C
3
CH3
H
N
3
OH
CH3
H O
R
2
OH
CH3
N R
H
N
R
-
2H O
2
CH3
CH3
HO
HO
Conclusions
In conclusion, a one-pot, mild, efficient, and envi-
ronmentally benign protocol has been developed for the
synthesis of N-substituted pyrroles catalyzed by clays,
zeolite and nano-crystalline SZ as catalyst in high yields.
Compared to previously reported methods, the mild re-
action conditions, easy work-up, clean reaction profiles,
lower catalyst loading and cost efficiency render this
approach as an interesting alternative to the existing
methods.
Figure 2 XRD pattern of sulfated-zirconia catalyst.
Experimental
Instruments and characterization
All reagents were purchased from Merck and Al-
drich and used without further purification. Products
were characterized by spectroscopy data (Mass, FT-IR,
1
13
Figure 3 FT-IR spectrum of sulfated-zirconia catalyst.
H NMR and C NMR spectra), elemental analysis
(
CHN) and melting points. A JASCO FT/IR-680 PLUS
Specific surface area, pore volume and pore size dis-
tribution of sulfated zirconia samples calcined at 600
spectrometer was used to record IR spectra using KBr
pellets. NMR spectra were recorded on a Bruker 400
Ultrasheild NMR and DMSO-d was used as solvent.
6
Melting points reported were determined by open capil-
lary method using a Galen Kamp melting point appara-
tus and are uncorrected. Mass spectra were recorded on
a Shimadzu Gas Chromatograph Mass Spectrometer
GCMS-QP5050A/Q P5000 apparatus.
℃
were determined from N
isotherms at 77 K (ASAP 2010 Micromeritics) (Figure
). Surface area was calculated by using BET equation;
pore volume and pore size distribution were calculated
2
adsorption-desorption
4
[27]
by BJH method.
The samples were degassed under
vacuum at 120 ℃ for 4 h, prior to adsorption meas-
urement to evacuate the physisorbed moisture. The de-
tailed imaging information about the morphology and
surface texture of the catalyst was provided by SEM
Catalyst preparation
Synthesis of nano-crystalline sulfated zirconia
(
Philips XL30 ESEM TMP) (Figure 5).
Nano-crystalline sulfated zirconia has been prepared by
one step sol-gel technique.
volves the addition of concentrated sulfuric acid (1.02
mL) to zirconium n-propoxide precursor (30 wt%) fol-
[
25]
A typical synthesis in-
General procedure for the synthesis of pyrroles (3)
A solution of amine 1 (1 mmol) and 2,5-hexandi-
374
www.cjc.wiley-vch.de
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 372—376

One-pot Green Synthesis of Pyrrole Derivatives Catalyzed by Nano Sulfated Zirconia
2
.01 (s, 6H), 5.79 (s, 2H), 7.08 (d, J＝8.4 Hz, 2H), 7.57
13
(
1
d, J＝8.4 Hz, 2H); C NMR (DMSO-d
2.97, 106.13, 121.53, 128.67, 129.88, 132.32, 138.07;
FT-IR (KBr) ν: 3078, 2917, 1519, 1484, 1435, 1402,
6
, 400 MHz,) δ:
－
1
1
2
4
320, 1065, 998, 840, 760 cm ; MS (70 eV) m/z:
＋
50.10 (M ). Anal. calcd for C12
.86, N 5.60; found C 57.56, H 4.69, N 5.51.
-(4-Nitrophenyl)-2,5-dimethyl-1H-pyrrole
H12BrN: C 57.62, H
1
(1d):
1
m.p. 142—144 ℃; H NMR (DMSO-d
6
, 400 MHz) δ:
2
.10 (s, 6H), 5.78 (s, 2H), 7.06 (d, J＝8.1 Hz, 2H), 7.54
13
(
d, J＝8.1 Hz, 2H); C NMR (DMSO-d
6
, 400 MHz,) δ:
1
2.94, 106.16, 121.50, 128.61, 129.82, 132.28, 138.12;
－
1
FT-IR (KBr) ν: 3076, 2927, 1515, 1346, 856 cm ; MS
＋
Figure 4
N
2
adsorption-desorption isotherm of sulfated-zirconia
(70 eV) m/z: 216.09 (M ). Anal. calcd for C12
12 2 2
H N O :
catalyst.
C 66.65, H 5.59, N 12.96; found C 66.46, H 5.43, N
1
2.86.
-(4-Benzyl)-2,5-dimethyl-1H-pyrrole (1e): m.p. 42
44 ℃; H NMR (DMSO-d , 400 MHz) δ: 2.13 (s,
6
1
1
—
6
7
1
H), 5.09 (s, 2H), 5.95 (s, 2H), 6.87—6.90 (m, 2H),
13
.23—7.39 (m, 3H); C NMR (DMSO-d
6
, 400 MHz,) δ:
39.04, 129.07, 128.76, 128.25, 127.59, 105.63, 13.12;
FT-IR (KBr) ν: 3063, 2920, 2838, 1568, 1526, 1491,
－
1
＋
1
411, 1326 cm ; MS (70 eV) m/z: 185.28 (M ). Anal.
calcd for C13 15N: C 84.29, H 8.16, N 7.56; found C
4.16, H 8.11, N 7.53.
-(4-Methylphenyl)-2,5-dimethyl-1H-pyrrole (1f):
H
8
1
Figure 5 SEM micrograph of sulfated-zirconia catalyst.
1
m.p. 72—74 ℃; H NMR (DMSO-d
6
, 400 MHz) δ:
2
.08 (s, 6H), 2.30 (s, 3H), 5.71 (s, 2H), 7.12 (d, J＝8.8
one 2 (1 mmol) were thoroughly mixed in ethanol (10
mL), then catalyst (25 mg) was added. The mixture was
stirred at room temperature for the appropriate time ac-
cording to Table 2. The progress of the reaction was
monitored by TLC (Eluent: n-hexane∶ethylacetate, 3∶
1
3
6
Hz, 2H), 7.55 (d, J＝8.8 Hz, 2H); C NMR (DMSO-d ,
4
1
FT-IR (KBr) ν: 3078, 2915, 1523, 1478, 1429, 1412,
1
1
N 7.56; found C 84.08, H 8.41, N 7.44.
-(4-Methoxyphenyl)-2,5-dimethyl-1H-pyrrole (1g):
m.p. 62–64 ℃; H NMR (DMSO-d
00 MHz,) δ: 12.91, 21.2, 106.27, 121.50, 128.61,
＋
29.83, 132.30, 138.05; MS (70 eV) m/z: 201.21 (M );
－
1
327, 1061, 998, 840, 760 cm ; MS (70 eV) m/z:
1
). After completion of the reaction, 10 mL ethanol was
＋
85.16 (M ). Anal. calcd for C13H15N: C 84.28, H 8.16,
added, and the catalyst was removed by filtration.
Evaporation of the solvent under reduced pressure gave
the products. The filtrate was evaporated and the residue
was purified by column chromatography and by recrys-
tallization to afford the pure product.
1
1
6
, 400 MHz) δ: 2.13
(
s, 6H), 3.80 (s, 3H), 5.75 (s, 2H), 7.02 (d, J＝8.9 Hz,
1
3
2
6
H), 7.51 (d, J＝8.9 Hz, 2H); C NMR (DMSO-d , 400
1
-(4-Phenyl)-2,5-dimethyl-1H-pyrrole (1a): m.p. 48
1
MHz,) δ: 12.91, 55.2, 106.19, 121.50, 128.58, 129.80,
—
50 ℃; H NMR (DMSO-d
6
, 400 MHz) δ: 2.04 (s,
132.38, 138.17; FT-IR (KBr) ν: 3074, 2923, 1511, 1476,
6
3
1
3
9
H), 5.94 (s, 2H), 7.20—7.24 (m, 2H), 7.40—7.52 (m,
H); C NMR (DMSO-d , 400 MHz) δ: 13.02, 105.63,
6
27.61, 128.23, 128.78, 129.02, 139.04; FT-IR (KBr) ν:
－
1
13
1
430, 1410, 1317, 1060, 996, 840, 760 cm ; MS (70
＋
eV) m/z: 201.21 (M ). Anal. calcd for C13H15N: C 77.58,
H 7.51, N 6.96; found C 77.51, H 7.38, N 6.74.
059, 2920, 1598, 1510, 1494, 1403, 1320, 1216, 1031,
－
1
＋
98 cm ; MS (70 eV) m/z: 171.08 (M ). Anal. calcd
13N: C 84.16, H 7.65, N 8.18; found C 79.86, H
.45, N 8.08.
-(4-Cholorophenyl)-2,5-dimethyl-1H-pyrrole (1b):
for C12
7
H
Acknowledgement
Supports from the Payame Noor University in Isfa-
han research council and helps of Yasouj University are
gratefully acknowledged.
1
1
m.p. 60——62 ℃; H NMR (DMSO-d
6
, 400 MHz) δ:
2
.06 (s, 6H), 5.96 (s, 2H), 7.01 (d, J＝8.6 Hz, 2H,), 7.83
13
(
1
d, J＝8.6 Hz, 2H); C NMR (DMSO-d
3.06, 92.98, 106.18, 128.66, 130.17, 138.34, 138.74;
FT-IR (KBr) ν: 3073, 2916, 1583, 1484, 1434, 1403,
6
, 400 MHz,) δ:
References
[
1] Pescheko, C.; Winklhofer, C.; Ter, A.; Steglich, W. Synthesis 2006,
－
1
1
2
5
321, 1053, 997, 838, 760 cm ; MS (70 eV) m/z:
3048.
＋
05.08 (M ). Anal. calcd for C12
.88, N 6.81; found C 69.89, H 5.75, N 6.74.
-(4-Bromophenyl)-2,5-dimethyl-1H-pyrrole (1c):
H12ClN: C 70.06, H
[2] Lee, D.; Swager, T. M. J. Am. Chem. Soc. 2003, 125, 6870.
[
[
3] Dieter, R. K.; Yu, H. Org. Lett. 2000, 2, 2283.
4] Palacios, F.; Aparico, D.; Santos, J. M.; Vicario, J. M. Tetrahedron
2001, 57, 1961.
1
1
6
m.p. 58——60 ℃; H NMR (DMSO-d , 400 MHz) δ:
[
5] Berree, F.; Marchand, E.; Morel, G. Tetrahedron Lett. 1992, 33,
Chin. J. Chem. 2012, 30, 372—376
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
375

Teimouri & Chermahini
FULL PAPER
6
155.
[18] Chermahini, A. N.; Teimouri, A.; Momenbeik, F.; Zarei, A.;
Dalirnasab, Z.; Ghaedi, A.; Roosta, M. J. Heterocycl. Chem. 2010,
47, 913.
[
[
6] Katritzky, A.; Steel, P. J. J. Org. Chem. 1994, 59, 4551.
7] Furstner, A.; Weintritt, H.; Hupperts, A. J. Org. Chem. 1995, 60,
6
637.
8] Ramanathan, B.; Keith, A. J.; Armstrong, D.; Odom, A. L. Org. Lett.
004, 6, 2957.
[19] Dabbagh, H. A.; Teimouri, A.; Chermahini, A. N. Appl. Catal. B:
Environ. 2007, 76, 24.
[20] Chermahini, A. N.; Teimouri, A.; Moaddeli, A. Heteroatom Chem.
2011, 22, 168.
[21] Teimouri, A.; Chermahini, A. N. Polyhedron 2011, in press.
[22] Teimouri, A.; Chermahini, A. N. J. Mol. Catal. A: Chem. 2011, 346,
39.
[
[
2
9] (a) Arcadi, A.; Rossi, E. Tetrahedron 1988, 54, 15253; (b) Lee, C. F.;
Yang, I. M.; Hwu, T. Y.; Feng, A. S.; Tseng, J. C.; Luh, T. Y. J. Am.
Chem. Soc. 2000, 122, 4992.
[
[
10] Balme, G. Angew. Chem., Int. Ed. 2004, 43, 6238.
11] Wang, B.; Gu, Y.; Luo, C.; Yang, T.; Yang, L.; Suo, J. Tetrahedron
Lett. 2004, 45, 5873.
[23] Satyanarayana, V. S. V.; Sivakumar, A. Ultrason. Sonochem. 2011,
18, 917.
[
[
[
[
[
[
12] Sreekumar, R.; Padmakumar, R. Synth. Commun. 1998, 28, 1661.
13] Kidwai, K.; Rastogi, S. J. Heterocycl. Chem. 2006, 43, 1231.
14] Abid, M.; Spaeth, A.; Török, B. Adv. Synth. Catal. 2006, 348, 2191.
15] Veisi, H. Tetrahedron Lett. 2010, 51, 2109.
16] Zhang, Z. H.; Li, J. J.; Li, T. S. Ultrason. Sonochem. 2008, 15, 673.
17] (a) Indovina, V.; Pietrogiacomi, D.; Campa, M. C. Appl. Catal. B:
Environ. 2002, 39, 115; (b) Pietrogiacomi, D.; Campa, M. C.; Tuti, S.
Appl. Catal. B: Environ. 2003, 41, 301; (c) Li, N.; Wang, A.; Tang, J.
Appl. Catal. B: Environ. 2003, 43, 195; (d) Tsyntsarski, B.; Avreyska,
V.; Kolev, H.; Marinova, T.; Klissurski, D.; Hadjiivanov, K. J. Mol.
Catal. A: Chem. 2003, 193, 139; (e) Demirci, U. B.; Garin, F. J. Mol.
Catal. A: Chem. 2002, 188, 233.
[24] Shi, Z. Y.; Jin, L.; Ling, X. Chin. Chem. Lett. 2010, 21, 664.
[25] (a) Argauer, R. J.; Landolt, G. R. US 3702886, 1972; (b) Dwyer, J.
Chem. Ind. 1984, 258; (c) Guth, J. L. in Zeolite Microporous Solids:
Synthesis, Structure, and Reactivity, Kluwer Academic, The Nether-
lands, 1992, p. 49; (d) Choudhary, V. R.; Panjala, D.; Banerjee, S.
Appl. Catal. A: Gen. 2002, 231, 243.
[26] (a) Mishra, M. K.; Tyagi, B.; Jasra, R. V. J. Mol. Catal. A: Chem.
2004, 223, 61; (b) Tyagi, B.; Mishra, M. K.; Jasra, R. V. Catal.
Commun. 2006, 7, 52.
[27] Cullity, B. D.; Stock, S. R. Elements of X-ray Diffraction, 3rd ed.,
Prentice Hall, Upper Saddle River, NJ, 2001, p. 388.
(Pan, B.)
376
www.cjc.wiley-vch.de
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 372—376