Synthesis and characterization of a porous acidic catalyst functionalized with an imidazole ionic liquid, and its use for synthesis of phthalazinedione and phthalazinetrione heterocyclic compounds

Article abstract of DOI:10.1007/s11164-015-1997-2

A simple and convenient method has been used to prepare an [SBAIm] HSO₄ composite on SBA-15 mesoporous silica as support. The surface of the mesoporous silica was modified by reaction with the ionic liquid 1-(triethoxysilylpropyl)- 3-methylimid

Full text of DOI:10.1007/s11164-015-1997-2

Res Chem Intermed
DOI 10.1007/s11164-015-1997-2
Synthesis and characterization of a porous acidic
catalyst functionalized with an imidazole ionic liquid,
and its use for synthesis of phthalazinedione
and phthalazinetrione heterocyclic compounds
Jamal Davarpanah1 Parizad Rezaee2
•
•
Somayeh Elahi2
Received: 6 January 2015 / Accepted: 2 March 2015
Ó Springer Science+Business Media Dordrecht 2015
Abstract A simple and convenient method has been used to prepare an [SBA-
Im]HSO4 composite on SBA-15 mesoporous silica as support. The surface of the
mesoporous silica was modified by reaction with the ionic liquid 1-(triethoxysi-
lylpropyl)-3-methylimidazolium hydrogen sulfate (IL-HSO4). The resulting solid
acid was characterized by infrared spectroscopy (FTIR), transmission and scanning
electron microscopy, and thermogravimetric analysis. The acidic organocatalyst
enables environmentally benign one-pot synthesis of phthalazinedione and phtha-
lazinetrione heterocyclic compounds in ethanol.
Keywords Functionalized mesoporous silica Á Phthalazinedione and
phthalazinetrione Á Acidic ionic liquid Á Imidazolium ionic liquid Á Multicomponent
reactions
Introduction
Ionic liquids (IL), especially the imidazole type, have received much attention for
synthesis of heterogeneous catalysts. Owing to their high solubility, heterogeniza-
tion of IL is a very attractive means of overcoming the difficulty of recovery [1].
Development of supported ionic liquid catalysts (SILC) requires smaller amounts of
&
Parizad Rezaee
p.rezaee@iauabadan.ac.ir
Jamal Davarpanah
jamaldavarpanah@gmail.com
1
2
Chemistry Department, Production Technology Research Institute (ACECR), Ahvaz, Iran
Department of Chemical Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran
123

J. Davarpanah et al.
ionic liquid and simultaneously minimizes limitations associated with their
viscosity, separation, corrosiveness, and toxicity. SILC have such interesting
advantages as facilitating separation workup and good recyclability. It has also been
reported that supported IL are more efficient than homogenous ionic liquids [2].
SILC have been used as organocatalysts which combine the benefits of IL and
heterogeneous catalysts [3].
In the work discussed in this paper, an imidazolium IL (ImIL) was successfully
used as a catalyst for a variety of reactions. ImIL based on 3-methylimidazolium
chloride have been efficiently used as ionic catalysts and solvents. Moreover,
Brønsted ionic solid acids (BISA), which contain an acid component in the cation or
anion, can act as catalysts in organic reactions. Many typical acid-catalyzed organic
reactions have been successfully performed in the presence of BISA [4, 5].
Substantial effort has been devoted to immobilization of IL on the surface of
supports, for example organic polymers, silica, and metal oxides [6–8].
Silica is usually used as a support for ionic liquids, because of its ready
availability and low cost. However, the wide-range pore distribution, irregular pore
shape, low pore volume, and low specific surface area of silica often result in
attachment of small amounts of ionic liquids, high mass-transfer resistance, and
poor catalytic activity [9]. Compared with amorphous silica gel, mesoporous silica
has excellent characteristics, for example controllable pore size, large number of
silanol groups, mechanical and chemical resistance, and high surface area, that
make it a preferable choice for use as a support [10, 11]. A few papers in the
literature report use of IL supported on porous silica prepared by post-grafting or
direct co-condensation [12].
One-pot multicomponent reactions (MCRs) have attracted much attention,
because of conversion of more than two educts directly into the desired products.
These coupling reactions have become important techniques for rapid generation of
a wide variety of organic molecules. The methods have much utility, particularly
when used for the preparation of medicinal heterocyclic compounds [13].
Among the large variety of heterocyclic compounds, those containing the
phthalazine group are well known in medicine and organic chemistry because of
their antimicrobial, anticonvulsant, antifungal, anticancer, and anti-inflammatory
activity [14]. Although a few methods, with distinct advantages, have recently been
reported for preparation of these compounds, by use of a variety of catalysts, the
methods suffer from such disadvantages as extended reaction times, unsatisfactory
yields, high cost, harsh reaction conditions, and use of toxic solvents and
stoichiometric amounts of catalyst; the catalysts are also environmentally
hazardous. Therefore, discovery of new catalysts for preparation of phthalazine
derivatives under mild conditions is of prime importance.
Considering these facts and as a part of our ongoing interest in the synthesis of
biologically relevant heterocyclic compounds [15–17], in this paper we report the
successful preparation of a mesoporous silica catalyst functionalized with methyl
imidazolium hydrogen sulfate ionic liquid, and its performance as acidic ionic
catalyst for synthesis of phthalazinedione and phthalazinetrione heterocyclic
compounds.
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Synthesis and characterization of a porous acidic catalyst…
Experimental
General
For direct synthesis of SBA-15, tetraethylorthosilicate (TEOS) was used as the silica
source and Pluronic P123 triblock copolymer (EO20PO70EO20, MW 5800) was used
as structure-directing agent; both were supplied by Aldrich. Other chemicals were
purchased from Fluka and Merck and used without further purification. Products
were characterized by comparison of their physical properties, and their IR,
1H NMR and 13C NMR spectra with those of standards. NMR spectra were
recorded by use of a Bruker Advance DPX 400 MHz instrument spectrometer, with
TMS as internal standard. IR spectra were recorded by use of a Bomem MB-series
1998 FTIR spectrometer.
Determination of product purity and monitoring of reactions were accomplished
by TLC on PolyGram silica gel SILG/UV 254 plates. Particle morphology was
examined by SEM (Philips XL30 scanning electron microscope) and TEM (Zeiss—
EM10C—80 kV).
Synthesis of [Si-Im]Cl
Methyl imidazole (10 mmol) and an equimolar amount of (3-chloropropyl)tri-
ethoxysilane were heated under reflux at 95 °C for 30 h under a nitrogen
atmosphere. The viscous oil precursor 1-methyl-3-(3-(triethoxysilyl)propyl)imida-
zolium chloride ([Si-Im]Cl) was obtained. It was used immediately in the next step
(Scheme 1) [18].
Catalyst preparation
Mesoporous silica SBA-15 was prepared as reported elsewhere [19]. SBA-15 (3 g,
previously dried overnight under vacuum at 180 °C) was added to a solution of
1-methyl-3-(3-(triethoxysilyl)propyl)imidazolium chloride ([Si-Im]Cl; 6.0 mmol) in
toluene (50 mL) and the mixture was heated under reflux for 24 h. After cooling to
room temperature, the reaction mixture was filtered, and the resulting solid ([SBA-
Im]Cl) was washed with toluene and diethyl ether, followed by drying at 50 °C
under reduced pressure. Finally, [SBA-Im]Cl (3.0 g) was suspended in dry CH2Cl2
(25 mL) in a three-necked, round-bottomed flask equipped with stirrer and ice bath.
During vigorous stirring, concentrated H2SO4 (97 %) (6.0 mmol) was added drop
by drop at 0 °C. The mixture was then warmed to room temperature, and heated
under reflux for 48 h. The solid was isolated by filtration, washed with ethanol, then
dried at room temperature.
When [SBA-Im]HSO4 (0.1 g) was placed in an aqueous solution of NaCl (1 M,
25 mL) of initial pH 6.0 and the resulting mixture was stirred for 24 h, the pH of
solution decreased to 2.7. This is equivalent to a loading of 0.5 mmol H? of the
acidic catalyst. This result was confirmed by back-titration analysis of the catalyst.
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J. Davarpanah et al.
OEt
P123, HCl, EtO Si OEt
OEt
SBA-15
Cl
N Me
N
EtO
EtO
N
Cl
+
EtO Si
EtO
EtO Si
EtO
N
Me
[Si-Im]Cl
SBA-15
[Si-Im]Cl
+
Me
N
N
HSO4
Si
Scheme 1 Synthesis of [SBA-Im]HSO4
Typical procedure for preparation of 3,4-dihydro-3,3-dimethyl-13-phenyl-
2H-indazolo[2,1-b]phthalazine-1,6,11-trione
A mixture of phthalhydrazide (0.16 g, 1 mmol), dimedone (0.14 g, 1 mmol),
benzaldehyde (0.13 g, 1.2 mmol), and [SBA-Im]HSO4 (0.1 g) was heated under
reflux in ethanol for 30 min. Progress of the reaction was monitored by TLC. After
completion of the reaction, the mixture was washed with hot ethanol and the catalyst
was isolated by filtration. The crude product was purified by recrystallization in
aqueous ethanol to afford the pure product, which was characterized by comparison
of its physical properties with those of a standard.
123

Synthesis and characterization of a porous acidic catalyst…
Results and discussion
At the beginning of the 1990s, ordered mesoporous materials were discovered to
reduce the diffusion constraints encountered during use of microporous materials.
Among these ordered mesoporous materials, such silicate materials as SBA-15 have
attracted increasing attention in catalysis and as functional materials [20–25]. In this
study, SBA-15 was synthesized as reported elsewhere [19], by condensation of
TEOS in the presence of Pluronic P123 triblock copolymer as supramolecular
template. After calcination of the template, the surface of SBA-15 was modified
with imidazolium alkoxysilane, by use of a postgrafting procedure, to furnish [SBA-
Im]Cl. The resulting ionic solid was finally transformed into the target compound by
anion exchange with concentrated sulfuric acid.
Scheme 1 shows the synthetic pathway for preparation of [SBA-Im]HSO4 solid
acid catalyst.
The FTIR spectra of SBA-15, [Si-Im]Cl, and [SBA-Im]HSO4 are shown in
Fig. 1.
The FTIR spectra of SBA-15, [Si-Im]Cl, and [SBA-Im]HSO4 contained
characteristic peaks at 801, 620, and 1092 cm-1, most probably attributable to
symmetric and asymmetric stretching vibrations of Si–O bonds (Fig. 1).
The presence of peaks at 1200–1500 and 2870–3040 cm-1 in the FTIR spectra of
[Si-Im]Cl and [SBA-Im]HSO4 was most probably because of C–H bonds.
Characteristic peaks of [SBA-Im]HSO4 and [Si-Im]Cl, at approximately 1568 and
1644 cm-1 were attributed to C=C and C=N stretching vibrations, respectively, of
the imidazole ring, and a band at approximately 1465 cm-1 was characteristic of the
tertiary amine group.
The broad band at approximately 3450 cm-1 was ascribed to the stretching
vibrations of the SiO–H bond and the HO–H vibration of water molecules adsorbed
on the silica surface. The band at approximately 1635 cm-1 was also ascribed to the
bending vibration of water molecules adsorbed on the surface.
SBA-15
[Si-Im]Cl
[SBA-Im]HSO4
3400
2900
2400
1900
1400
900
400
Wavenumber (cm-1)
Fig. 1 FTIR spectra of SBA-15, [Si-Im]Cl, and [SBA-Im]HSO4
123

J. Davarpanah et al.
Scanning electron microscopy (SEM) is an important technique for determination
of size distribution, particle shape, surface morphology, and fundamental physical
properties. Figure 2 shows an SEM image of [SBA-Im]HSO4 particles. The image
is indicative of uniform particle size and hexagonal shape.
From the TEM image (Fig. 3), the pore structure and orderly pore arrangement
was clearly apparent, and confirmed the long-range and mesoporous ordering of this
organocatalyst.
Attachment of [Si-Im]Cl to the porous silica network was also confirmed by
thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The
weight loss with changing temperature was measured to estimate the rate of thermal
degradation. Figure 4 shows TGA the thermogram of the [SBA-Im]HSO4. The
Fig. 2 SEM image of [SBA-Im]HSO4
Fig. 3 TEM image of [SBA-Im]HSO4
123

Synthesis and characterization of a porous acidic catalyst…
Fig. 4 TGA–DTG and DTA profiles of [SBA-Im]HSO4
CHO
O
O
O
O
O
O
0.1 g cat, reflux
EtOH, 30 min
O
N
N
NH
NH
+
+
Scheme 2 The one-pot, three-component reaction of phthalhydrazide, dimedone, and benzaldehyde
123

J. Davarpanah et al.
Table 1 Results from one-pot, three-component reaction of phthalhydrazide (1 mmol), dimedone
(1 mmol), and benzaldehyde (1 mmol)
Entry
Solvent
Catalyst (g)
T (°C)
Time (min)
Yield (%)
1
–
–
100
60
60
60
30
60
60
60
60
30
30
60
Trace
40
2
H2O
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.075
0.05
–
Reflux
Reflux
Reflux
Reflux
Reflux
25
3
CH2Cl2
EtOH
CH3CN
EtOH–H2O
EtOH
EtOH
EtOH
EtOH
EtOH
35
4
90
5
35
6
70
7
50
8
50
60
9
Reflux
Reflux
Reflux
78
10
11
70
Trace
Scheme 3 Preparation of indazolo[2,1-b]phthalazinetriones and pyrazolo[1,2-b]phthalazinediones
catalyzed by [SBA-Im]HSO4
[SBA-Im]HSO4 hybrid material loses most of the weakly bonded water molecules
below 200 °C.
Secondary weight losses at approximately 200 and 590 °C are a result of
decomposition of the organic components of [Si-Im]HSO4.
The DTG curve of the catalyst also shows that most of the degradation occurred
at approximately 485 °C.
123

Synthesis and characterization of a porous acidic catalyst…
After characterization of the [SBA-Im]HSO4 catalyst, to investigate its activity in
the one-pot multicomponent synthesis of phthalazinedione and phthalazinetrione
heterocyclic compounds we focused on systematic evaluation of different condi-
tions for the model three-component coupling of phthalhydrazide (1 mmol),
dimedone (1 mmol), and benzaldehyde (1.1 mmol) (Scheme 2). Different amounts
of catalyst, solvents, and temperatures were screened to test the efficiency of the
catalyst; the results obtained are summarized in Table 1.
Table 2 Results from one-pot, three-component reaction of phthalhydrazide (1 mmol), diketone (1 m-
mol), and aldehyde (1 mmol) in ethanol, catalyzed by [SBA-Im]HSO4
Entry
Aldehyde
(X)
Diketone
Product
Time
(min)
Yield (%)
O
O
O
O
1
H
30
90
O
N
N
O
O
NO2
O
O
O
O
2
3
4
4-NO2
20
90
85
84
N
N
O
O
OMe
O
O
4-OCH3
35
35
N
N
O
O
Me
O
4-CH3
O
N
N
O
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J. Davarpanah et al.
Table 2 continued
Entry Aldehyde
Diketone
Product
Time
Yield (%)
(X)
(min)
Cl
O
O
5
4-Cl
30
87
O
O
N
N
O
O
O
O
6
7
3-F
25
35
88
83
F
O
N
N
O
O
OH
O
O
4-OH
O
N
N
O
O
Cl
O
O
O
O
8
9
3-Cl
30
25
86
89
O
N
N
O
NO2
O
3-NO2
O
N
N
O
123

Synthesis and characterization of a porous acidic catalyst…
Table 2 continued
Entry
Aldehyde
(X)
Diketone
Product
Time
(min)
Yield (%)
O
O
O
O
O
10
H
35
30
86
O
N
N
H3C
CH3
CH3
CH3
O
NO2
11
12
13
4-NO2
88
86
87
O
O
H3C
CH3
O
N
N
CH3
CH3
Cl
O
O
O
O
4-Cl
3-F
35
30
O
H3C
CH3
O
N
N
CH3
CH3
O
O
F
O
N
N
H3C
CH3
CH3
CH3
O
Subsequently, the optimum conditions were used to study the scope and
limitations of the method. A wide range of substituted aldehydes, phthalhydrazide,
and cyclic or acyclic diketones (dimedone and acetylacetone) were reacted in the
presence of [SBA-Im]HSO4 (0.1 g) in ethanol under reflux conditions (Scheme 3;
Table 2).
As shown in Table 2, aromatic aldehydes with electron-releasing and electron-
withdrawing groups were uniformly transformed into the corresponding phtha-
lazinedione and phthalazinetrione heterocyclic compounds in high yields within
25–35 min.
To investigate the activity of the catalyst after recycling, it was reused five times
for one-pot multicomponent condensation of phthalhydrazide, dimedone, and
benzaldehyde in ethanol under reflux. In this procedure, after completion of each
123

J. Davarpanah et al.
90
89
89
88
87
88
No of runs
Fig. 5 Recyclability of catalyst
reaction hot ethanol was added and the catalyst was isolated by filtration. The
recovered catalyst was washed with ethanol, dried, and reused (Fig. 5). The results
illustrated in Fig. 5 showed the catalyst could be reused for up to five cycles without
losing its activity.
Conclusion
In this research, a mesoporous silica catalyst functionalized with the acidic methyl
imidazolium ionic liquid, [SBA-Im]HSO4, was successfully prepared and charac-
terized by FTIR, TGA-DTA, SEM, and TEM. The catalytic activity of this solid
acid nanocomposite was investigated in the one-pot synthesis of 2H-indazolo[2,1-
b]phthalazine-1,6,11-trione and 1H-pyrazolo[1,2-b]phthalazine-5,10-dione deriva-
tives by a three-component reaction of phthalhydrazide, cyclic or acyclic diketones,
and aromatic aldehydes. Advantages of this reaction are clean reaction profiles,
short reaction times, easy to handle procedure, and a catalyst with high activity and
good recyclability. Subsequent reuse of the catalyst showed that catalysis was
wholly heterogeneous.
Acknowledgments We gratefully acknowledge support of this work by the Abadan branch of Islamic
Azad University.
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