Alumina supported acidic ionic liquid: Preparation, characterization, and its application as catalyst in the synthesis of 1,8-dioxo-octahydroxanthenes

Article abstract of DOI:10.1080/15533174.2012.756897

Preparation of a novel heterogeneous acidic catalyst by impregnation of alumina support by N-(4-sulfonic acid)butyl triethylammonium hydrogen sulfate ([Et₃NC₄SO₃H][HSO₄]), an acidic ionic liquid, and its primary

Full text of DOI:10.1080/15533174.2012.756897

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Alumina Supported Acidic Ionic Liquid: Preparation,
Characterization, and Its Application as Catalyst in the
Synthesis of 1,8-dioxo-octahydroxanthenes
a
a
a
Mahsa Khoshnevis , Abolghasem Davoodnia , Atefeh Zare-Bidaki & Niloofar Tavakoli-
a
Hoseini
a
Department of Chemistry, Mashhad Branch , Islamic Azad University , Mashhad , Iran
Accepted author version posted online: 28 Jan 2013.Published online: 14 May 2013.
To cite this article: Mahsa Khoshnevis , Abolghasem Davoodnia , Atefeh Zare-Bidaki & Niloofar Tavakoli-Hoseini (2013)
Alumina Supported Acidic Ionic Liquid: Preparation, Characterization, and Its Application as Catalyst in the Synthesis of 1,8-
dioxo-octahydroxanthenes, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:9, 1154-1161,
DOI: 10.1080/15533174.2012.756897
To link to this article: http://dx.doi.org/10.1080/15533174.2012.756897
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:1154–1161, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.756897
Alumina Supported Acidic Ionic Liquid: Preparation,
Characterization, and Its Application as Catalyst in the
Synthesis of 1,8-dioxo-octahydroxanthenes
Mahsa Khoshnevis, Abolghasem Davoodnia, Atefeh Zare-Bidaki, and Niloofar
Tavakoli-Hoseini
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran
are produced[9] are still big challenges to overcome. The immo-
Preparation of a novel heterogeneous acidic catalyst by impreg- bilization of ILs on solid supports can solve these problems and
nation of alumina support by N-(4-sulfonic acid)butyl triethylam-
satisfy the requirements from chemical industry of the ease of
separation and recovery of catalyst from reaction mixture. By
transferring the catalytic property of a homogeneous catalyst to
a heterogeneous catalyst, the immobilization can combine the
monium hydrogen sulfate ([Et
3
NC
4
SO
3
H][HSO
4
]), an acidic ionic
[10]
liquid, and its primary application as a solid acidic supported cata-
lyst in the synthesis of 1,8-dioxo-octahydroxanthenes by reaction of
dimedone with aromatic aldehydes are described. Characterization
of the catalyst was performed by FT-IR, BET, TG/DTG, and XRD advantages of homogeneous ILs with those of heterogeneous
techniques. The results showed that the catalyst has high activity
catalysts. There are some reports for using of solid supports
and the desired products were obtained in high yields. Moreover,
the recovered catalyst was found to be reusable and a considerable
catalytic activity still could be achieved after third run.
[11–14]
for immobilizing the ILs.
In supported catalysts, the cat-
alytic behavior of the catalyst is strongly dependent on support
properties. Among the various supported catalysts, particularly,
alumina and silica supported reagents have advantages of low
cost, ease of preparation, and catalyst recycling.[
Keywords 1, 8-dioxo-octahydroxanthenes, alumina supported ionic
15–18]
liquid, heterogeneous catalysis, solvent-free condition
Xanthenes have received great attention because of their
wide range of therapeutic and biological properties, such
[
19]
[20]
as antibacterial,
antiviral,
and anti-inflammatory activi-
INTRODUCTION
Ionic liquids (ILs), which are generally defined as salts with
a melting point below 100 C, are fascinating materials that have
attracted rising interest in the last decade in organic chemistry as
catalysts or solvents and have been shown to promote a variety of
organic transformations effectively because they possess a num-
ber of unique physicochemical properties such as the negligible
vapor pressure, unique solvation properties, good ion conduc-
ties.[ Apart from their use as valuable synthetic precursors
21]
[
22]
[23]
◦
for many organic compounds
and dyes
they also found
uses in laser technologies,[ and fluorescent materials for vi-
24]
sualization of biomolecules.[ In particular, xanthenediones
20]
constitute a structural unit in a number of natural prod-
and have been used as versatile synthons because of
the inherent reactivity of the inbuilt pyran ring.
of the commonly used methods reported for the synthesis of
xanthenediones involves the condensation of aromatic
aldehydes with 1,3-cyclohexanedione or 5,5-dimethyl-1,3-
cyclohexanedione (dimedone). This reaction can be carried
out in the presence of various catalysts such as cyanuric
ucts[
25,26]
[
27]
One
[
1–4]
tivity, and catalytic activity and selectivity.
The introduction
of structural functionalities on the cationic or anionic part has
made it possible to design new ILs with specific properties.[
5]
SO3H-functionalized ILs can be used as highly efficient acid
catalysts and have been receiving extensive interest as green
substitute for H2SO4, HF, and AlCl3 catalysts in chemical pro-
chloride,[
28]
NaHSO4,
[29]
InCl3.4H2O,
[30]
Amberlyst-15,
[31]
SbCl /SiO , Dowex-50W,[33] polyaniline-p-toluenesulfonate
[
32]
cesses.[6–8]
However, the danger of catalyst leaching and the
3
34]
2
salt,[ Fe -montmorillonite,
3+
[35]
trimethylsilylchloride,
[36]
p-
difficulties of extracting products from ILs when polar products
dodecylbenzenesulfonic acid,[37] H3PW12O40/MCM-41,
[38]
[
39]
[40]
silica-supported preyssler nano particles (SPNP), SmCl3,
[
41]
[42]
Hydrotrope,
L-proline,
triethylbenzylammonium chlo-
ride,[ and PPA-SiO2.[44] However, some of these methodolo-
gies suffer from disadvantages, such as low yields, prolonged
reaction time, harsh reaction conditions, and the requirement of
excess catalysts. Therefore, the development of simple, efficient,
high-yielding, and environmentally friendly methods using
43]
Received 19 April 2012; accepted 4 December 2012.
The authors express their gratitude to the Islamic Azad University,
Mashhad Branch for its financial support.
Address correspondence to Abolghasem Davoodnia, Department of
Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran.
E-mail: adavoodnia@mshdiau.ac.ir.
1154

ALUMINA SUPPORTED ACIDIC IONIC LIQUID
1155
O
O
Ar
O
O
[Et3NC4SO3H][HSO4]/Al2O3
Solvent-free
+
Ar
H
O
O
1
20 °C
1
2a-j
3a-j
SCH. 1. [Et3NC4SO3H][HSO4]/Al2O3 catalyzed synthesis of 1,8-dioxo-octahydroxanthenes.
novel catalysts for the synthesis of these compounds is still Preparation of [Et NC SO H][HSO ]/Al O
3
3
4
3
4
2
in great demand.
The catalyst was prepared by impregnation method. Neutral
Based on these precedents and due to our interest in the alumina (Merck, Germany, 70–230 mesh, 1.0 g) was added to a
application of reusable catalysts in organic reactions[40–48] solution of [Et NC SO H][HSO ] (0.6 g) in methanol (5 mL)
3
4
3
4
herein firstly we report the preparation of a novel supported and water (5 mL). The mixture was stirred at room temperature
acidic IL by impregnation of alumina support by N-(4-sulfonic for 24 h to adsorb IL on surface of support. The methanol and
acid)butyl triethylammonium hydrogen sulfate (denoted as water were removed with rotary evaporator and the resulting
[
Et3NC4SO3H][HSO4]/Al2O3), and then investigate its catalytic solid powder was washed with cold acetonitrile, and dried in
◦
activity in the synthesis of 1,8-dioxo-octahydroxanthenes 3a–j vacuo at 100 C for 1 h.
by cyclocondensation of dimedone 1 with aromatic aldehydes
2a–j under solvent-free conditions (Scheme 1).
General Procedure for the Synthesis of
,8-dioxo-octahydroxanthenes 3a–j Catalyzed by
1
[Et3NC4SO3H][HSO4]/Al2O3
To a mixture of dimedone 1 (0.8 mmol), and an aro-
EXPERIMENTAL
matic aldehyde 2a–j (0.4 mmol), in a round bottom flask,
Et3NC4SO3H][HSO4]/Al2O3 (0.2 g) was added. The mixture
Chemicals and Apparatus
[
◦
All chemicals were available commercially and used with- was heated in the oil bath at 120 C for 30–40 min and the re-
out additional purification. The IL, [Et3NC4SO3H][HSO4], was action was monitored by TLC. Upon completion, the reaction
[
49]
synthesized according to the literature. Melting points were mixture was cooled to room temperature and hot acetonitrile
recordedona Stuart SMP3meltingpoint apparatus. The IRspec- was added. The catalyst was insoluble in hot acetonitrile and
tra were obtained using a Tensor 27 Bruker spectrophotome- could therefore be collected by a simple filtration. The filtrate
ter as KBr disks. Thermal gravimetric and differential thermal was heated in vacuo to evaporate the solvent. The solid residue
gravimetry (TGA/DTG) analyses were performed using air as was collected and recrystallized from ethanol to give compounds
◦
−1
oxidant at the heating rate of 5 C min in TGA-50, Shimadzu 3a–j in high yields.
system. The BET surface area of the material was measured
by nitrogen adsorption isotherm method with Quantachrome
Recycling and Reusing of the Catalyst
Due to the fact that the catalyst was insoluble in hot ace-
tonitrile, it could be recycled by simple filtration. The separated
instrument model Autosorb1, USA. X-ray diffraction (XRD)
was performed with a D8-Advance, Bruker X-ray diffractome-
ter (Germany) using graphite monochromatized high-intensity
◦
catalyst was washed with cold acetonitrile, dried at 100 C un-
1
CuKa radiation (k = 1.5406 Å). The H NMR (400 & 500 MHz)
der vacuum for 1 h, and reused in another reaction. The catalyst
could be used at least three times with only slight reduction in
its catalytic activity.
spectra were recorded with Bruker 400 and 500 spectrometers
(
Germany).
TABLE 1
N2 adsorption results of alumina, and [Et3NC4SO3H][HSO4]/Al2O3 in BET measurements
Pore volume
(mL.g )
2
−1
−1
Specific surface area (m .g )
Pore diameter (Å)
Sample
BET
BJHAds
DHAds
BJHAds
DHAds
BJHAds
DHAds
Alumina
113.8
000.0
121.3
000.2
122.6
000.5
61.92
20.53
61.92
20.53
0.233
0.002
0.231
0.002
[
Et3NC4SO3H][HSO4]/Al2O3

1156
M. KHOSHNEVIS ET AL.
FIG. 1. FT-IR spectra of (a) [Et3NC4SO3H][HSO4], (b) Al2O3, and (c) [Et3NC4SO3H][HSO4]/Al2O3.
RESULTS AND DISCUSSION
FT-IR spectra of [Et3NC4SO3H][HSO4], Al2O3, and
Et3NC4SO3H][HSO4]/Al2O3 are compared in Figure 1. Be-
cause of overlaping with the bands of Al2O3, most of the bands
of [Et3NC4SO3H][HSO4] are not observable in the IR spectrum
of [Et3NC4SO3H][HSO4]/Al2O3 (Figure 1).
The data of specific surface area, pore size and pore volume
of Al2O3, and [Et3NC4SO3H][HSO4]/Al2O3 are presented in
Table 1. The specific surface area of the supported catalyst
[
Characterization of the Catalyst
The catalyst [Et3NC4SO3H][HSO4]/Al2O3 prepared by
impregnation of alumina support by [Et3NC4SO3H][HSO4]
was characterized by FT-IR spectroscopy, the N2 adsorp-
tion/desorption analysis (BET), thermal analysis (TG/DTG),
and X-ray diffraction (XRD) techniques.

ALUMINA SUPPORTED ACIDIC IONIC LIQUID
1157
measured by the BET method and other methods is near to zero
2
(
000.0–000.5 m /g). This may be due to the blockage of pores
by active species and shows the impregnation of alumina by
[Et3NC4SO3H][HSO4].
Thermal gravimetric (TGA) and differential thermal
gravimetry (DTG) analysis of the [Et3NC4SO3H][HSO4]/Al2O3
were investigated by raising its temperature at the rate of
◦
◦
5
C/min in air up to 1000 C to analyze its thermal decomposi-
tion behavior. Figure 2 shows the TGA/DTG curves of the pre-
pared [Et3NC4SO3H][HSO4]/Al2O3. Two main stages of mass
◦
loss were observed. The first small mass loss centered at 44.29 C
was assigned to the loss of physically adsorbed water molecules
◦
and the second mass loss centered at 358.85 C was probably
due to decomposition or removal of [Et3NC4SO3H][HSO4].
The XRD pattern of the Al2O3 and [Et3NC4SO3H][HSO4]/
Al2O3 are also presented in Figure 3.
FIG. 2. TGA and DTG curves of [Et3NC4SO3H][HSO4]/Al2O3 (color figure
available online).
FIG. 3. XRD patterns of (a) Al2O3 and (b) [Et3NC4SO3H][HSO4]/Al2O3.

1158
M. KHOSHNEVIS ET AL.
Catalytic Performance of [Et3NC4SO3H][HSO4]/Al2O3 in
the Synthesis of 1,8-dioxo-octahydroxanthenes
The performance of [Et3NC4SO3H][HSO4]/Al2O3 as a solid
acidic supported catalyst was evaluated in the synthesis of
TABLE 2
Effect of [Et3NC4SO3H][HSO4]/Al2O3 amount, solvent, and
a
temparature on the model reaction
Catalyst
(g)
T
( C)
Time
(min)
Yield
(%)b
1,8-dioxo-octahydroxanthenes. The possibility of performing
◦
Entry
Solvent
organic reactions under solvent-free conditions with solid
catalysts could enhance their efficiency from an economic as
well as an ecological point of view, so solvent-free chemical
reactions have received much attention. These reactions
offer several advantages in preparative procedures such as
environmental compatibility, simplification of work-ups,
formation of cleaner products, enhanced selectivity, reduction
of by-products, a reduction in waste produced, and much
improved reaction rates. Therefore, we decided to investi-
gate the efficiency of [Et3NC4SO3H][HSO4]/Al2O3 in the
synthesis of 1,8-dioxo-octahydroxanthenes under solvent-free 10
conditions. To find the optimal conditions, the synthesis of 11
compound 3d was used as a model reaction. The reaction was 12
carried out by heating a mixture of dimedone (0.8 mmol), and 13
1
2
3
4
5
6
7
8
9
None
0.06
0.06
0.06
0.10
0.10
0.10
0.14
0.14
0.14
0.20
0.20
0.20
0.20
0.26
0.20
0.20
0.20
0.20
0.20
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
120
80
100
120
80
100
120
80
100
120
80
100
120
140
120
90
50
40
30
50
40
30
50
40
30
40
30
30
30
30
30
30
30
30
30
None
54
57
75
67
69
63
70
75
72
78
81
85
84
86
68
69
69
67
86
4-chlorobenzaldehyde (0.4 mmol) in the presence of various 14
amounts of [Et3NC4SO3H][HSO4]/Al2O3 and at different 15
temperatures under solvent-free conditions (Table 2). As can 16
be seen, the efficiency of the reaction is affected mainly by 17
the amount of the catalyst and the reaction temperature. No 18
product was obtained in the absence of the catalyst (entry 1) 19
indicating that the catalyst is necessary for the reaction. The 20
H O
2
Reflux
Reflux
Reflux
Reflux
Reflux
CH CN
3
AcOEt
EtOH
CH Cl
2
2
◦
best result was conducted at 120 C in the presence of 0.2 g of
a0.8 mmol dimedone and 0.4 mmol 4-chloroben-
[
Et3NC4SO3H][HSO4]/Al2O3 (entry 13). An increase in the
zaldehyde.
reaction temperature and amount of the catalyst did not change
the yields significantly (entries 14 and 15).
For showing the effect of solvent, the same model reac-
tion was also carried out in different solvents including H2O,
CH3CN, AcOEt, EtOH, and CH2Cl2 in the presence of 0.2 g
of the catalyst (Table 2, entries 16–20). As shown, the com-
bThe yields were calculated based on 4-chlorobenza-
ldehyde and refer to the pure isolated product.
pound 3d was obtained in moderate yields in H2O, CH3CN, action times. On the other hand, easy separation of obtained
AcOEt, and EtOH (entries 16–19), but in high-yield in CH2Cl2 products from the catalyst makes this method useful for the
(entry 20) and also in solvent-free conditions (entry 13). Al- synthesis of 1,8-dioxo-octahydroxanthenes.
though, there is no significant difference between solvent-free
To show the merit of the present methodology, we compared
conditions and CH2Cl2 as solvent in the model reaction, based our results with those of the other methods reported for the
on our investigations, in CH2Cl2 as solvent, the catalyst has synthesis of 1,8-dioxo-octahydroxanthenes. This comparison is
poor reusability, but in solvent-free condition, the reusability shown in Table 4. As can be seen, our method reduces reaction
of [Et3NC4SO3H][HSO4]/Al2O3 was found to be favorable and times and produces high yields of the products.
it could be recovered and subsequently reused several times.
Reusability of a catalyst, especially for supported catalysts, is
Consequently, all subsequent reactions were carried out in the a very important parameter before recommending any catalyst
◦
presence of 0.2 g of the catalyst at 120 C under solvent-free for industrial-scale use. Therefore, in this work, the reusabil-
conditions.
3 4 3 4 2 3
ity of [Et NC SO H][HSO ]/Al O was also investigated. For
To evaluate the scope of this catalytic transformation, a range this purpose, the same model reaction was again studied under
of 1,8-dioxo-octahydroxanthenes were prepared by the reaction optimized conditions. After the completion of the reaction, the
of dimedone and aromatic aldehydes under optimized reaction catalyst was recovered according to the procedure mentioned
conditions. The results are summarized in Table 3. In all cases, in experimental section and reused for a similar reaction. The
aromatic aldehydes with electron-donating or -withdrawing sub- catalyst could be used at least three times with only slight reduc-
stituents reacted efficiently and quickly with dimedone, to give tion in the catalytic activity (85% for first use; 84% for second
cyclocondensation products 3a–j in high yields over short re- use; 82% for third use).

ALUMINA SUPPORTED ACIDIC IONIC LIQUID
1159
TABLE 3
a
Synthesis of 1,8-dioxo-octahydroxanthenes 3a–j using [Et3NC4SO3H][HSO4]/Al2O3 as catalyst
Entry
Ar
Productsb
Time (min)
Yield (%)c
Br
O
O
O
3
Br
a
1
3-BrC6H4
30
97
O
O
O
3
b
2
3
4-BrC6H4
2-ClC6H4
30
40
98
84
Cl
O
O
O
3c
Cl
O
O
O
3
F
d
4
5
4-ClC6H4
4-FC6H4
30
35
85
80
O
O
O
3
OH
e
O
O
O
3
Me
f
6
7
4-HOC6H4
4-MeC6H4
40
40
88
89
O
O
2
O
3
OMe
g
O
O
O
3
h
8
4-MeOC6H4
40
78
(Continued on next page)

1160
M. KHOSHNEVIS ET AL.
TABLE 3
a
Synthesis of 1,8-dioxo-octahydroxanthenes 3a–j using [Et3NC4SO3H][HSO4]/Al2O3 as catalyst (Continued)
Entry
Ar
Productsb
Time (min)
Yield (%)c
NO2
O
O
O
3
NO2
i
9
3-O2NC6H4
30
94
96
O
O
O
3
j
10
4-O2NC6H4
30
a
b
◦
0
.8 mmol dimedone, 0.4 mmol aromatic aldehyde, and 0.20 g [Et
3
NC
4
SO
3
H][HSO
4
]/Al
2
O
3
at 120 C under solvent-free conditions.
All the products were characterized by IR spectral data and comparision of their melting points with those of authentic samples. Also, the
1
structures of some products were confirmed by H NMR spectral data.
c
The yields were calculated based on aromatic aldehyde and refer to the pure isolated product.
TABLE 4
Comparison of efficiency of various catalysts in the synthesis of 1,8-dioxo-octahydroxanthenes
Conditions
◦
Catalyst
Solvent
—
T ( C)
Time (min)
Yield (%)
Ref.
Dowex-50W
100
150–300
360
360
78–91
73–84
84–96
72–84
63–94
74–94
82–96
20–98
80–92
59–90
78–98
33
34
35
36
37
38
39
40
41
Polyaniline-p-toluenesulfonate salt H2O
reflux
reflux
reflux
3+
Fe -montmorillonite
Trimethylsilyl chloride
p-Dodecylbenzenesulfonic acid
H3PW12O40/MCM-41
SPNP
EtOH
CH3CN
H2O or EtOH
480–600
25–30 60–180 (ultrasound irradiation)
EtOH
H2O
reflux
reflux
120
80
60
120
300
180
480–1440
60–90
360
SmCl3
Hydrotrope
L-proline
—
H2O
ClCH2CH2Cl (DCE)
—
42
[
Et3NC4SO3H][HSO4]/Al2O3
30–40
This work
CONCLUSION
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[
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