Synthesis and characterization of BEA-SO3H as an efficient and chemoselective acid catalyst

Article abstract of DOI:10.1016/j.molcata.2010.11.013

BEA zeolite was synthesized under hydrothermal condition and modified with various amounts of chlorosulphonic acid. It was characterized by XRD, XRF, FT-IR, BET, thermogravimetric analysis and SEM techniques. Catalytic activity of BEA-SO₃H was tested for the synthesis of 1,1-diacetates from a variety of aromatic and aliphatic aldehydes including those carrying electron donating or withdrawing substituents by acetic anhydride. At optimized conditions, The BEA-SO₃H (28 wt.%) catalyst showed good yield at very short time for the synthesis and deprotection of 1,1-diacetates. Furthermore, BEA-SO₃H was found to be recyclable for the protection of aldehydes with acetic anhydride under solvent-free and room temperature conditions. This method is a green approach for the protection of aldehydes in the presence of ketones.

Full text of DOI:10.1016/j.molcata.2010.11.013

Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
Contents lists available at ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Synthesis and characterization of BEA-SO3H as an efficient and chemoselective
acid catalyst
Roozbeh Javad Kalbasia,b,∗, Ahmad Reza Massaha,b,∗, Anahita Shafieia,b
a Department of Chemistry, Islamic Azad University, Shahreza Branch, 311-86145, Shahreza, Isfahan, Iran
b Razi Chemistry Research Center, Islamic Azad University, Shahreza Branch, Shahreza, Isfahan, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 March 2010
Received in revised form 29 October 2010
Accepted 14 November 2010
Available online 21 November 2010
BEA zeolite was synthesized under hydrothermal condition and modified with various amounts of
chlorosulphonic acid. It was characterized by XRD, XRF, FT-IR, BET, thermogravimetric analysis and SEM
techniques. Catalytic activity of BEA-SO3H was tested for the synthesis of 1,1-diacetates from a variety of
aromatic and aliphatic aldehydes including those carrying electron donating or withdrawing substituents
by acetic anhydride. At optimized conditions, The BEA-SO3H (28 wt.%) catalyst showed good yield at very
short time for the synthesis and deprotection of 1,1-diacetates. Furthermore, BEA-SO3H was found to
be recyclable for the protection of aldehydes with acetic anhydride under solvent-free and room tem-
perature conditions. This method is a green approach for the protection of aldehydes in the presence of
ketones.
Keywords:
Beta zeolite
Chlorosulphonic acid
Aldehyde protection
Deprotection
© 2010 Elsevier B.V. All rights reserved.
1,1-Diacetates
1. Introduction
these methods have drawbacks, such as harsh acidic conditions,
long reaction times, need for expensive catalyst, stoichiometric or
The protection of carbonyl groups plays an important role in
organic synthesis as well as in the chemistry of drug design [1].
Acylal formation is one of the most widely used processes for
protection of carbonyl compounds. Due to the remarkable stability
of 1,1-diacetates (acylals) toward a variety of reaction conditions,
such as aqueous acids, neutral and basic media [2], synthesis of
them is one of the methods of choice to protect a carbonyl com-
pound in multi-step organic synthesis. Despite that numerous
electrophilic catalysts were shown to be effective in forming 1,1-
diacetates by the reaction of aldehydes or ketones with acetic
anhydride, new reports are still being published, disclosing the use
of new reagents. Strong protic acids, such as sulphuric acid [3,4],
phosphoric acid and methane sulphonic acid [5], NH2SO3H [6], and
Lewis acids, such as Bi(NO3)3·5H2O [7], ZrCl4 [8], FeCl3 [9], anhy-
drous FeSO4 [10], Bi(OTf)3 [11], PCl3 [12], and LiBr [13] have been
employed for the synthesis of 1,1-diacetates. Furthermore, there
are several inorganic heterogeneous catalysts, such as SiO2 [14],
zeolite [15], montmorilonite [16], amberlyst [17], AlPW12O40 [18]
and H6P2W18O62·24H2O [19] for this purpose. However, many of
excess amounts of reagents.
Many heterogeneous catalysts are less active than the homo-
geneous catalysts because the reaction rates are limited by the
transport of the reactant to the active sites on the particle surfaces.
The utility of heterogeneous catalysts can be improved by using
high surface area materials since the transport of the reactants to
the active site on particle surface can be enhanced by this method.
Among mesoporous silica zeolites, beta zeolite is one of the most
important high silica zeolites which have special catalytic proper-
ties because of its interconnected large pore network and strong
acidity [20–23]. There has been a great deal of investigations on its
synthesis and application [24–28].
In most cases, the incorporation of SO3H species into the
mesoporous silica and other inorganic materials is performed
with the organosilica or bridged organosilanes precursors. They
have extensively improved the hydrophobicity of mesoporous
silica material [29–53]. However, the organosilica and bridged
organosilane precursors either involve complicated synthesis and
purification method or are very expensive. Therefore, preparation
of acidic catalyst without using organosilica and bridged organosi-
lane precursors is highly desirable.
In this work, BEA zeolite was synthesized under hydrothermal
condition and modified with various amounts of chlorosulphonic
acid. Then the influence of the catalytic activity and the acidity of
the surface anchored sulphonic acid groups on the synthesis and
deprotection of acylals is considered.
∗
Corresponding authors at: Department of Chemistry, Islamic Azad University,
Shahreza Branch, 311-86145, Shahreza, Isfahan, Iran. Tel.: +98 321 3292072;
fax: +98 321 3293095.
E-mail addresses: rkalbasi@iaush.ac.ir, rkalbasi@gmail.com (R.J. Kalbasi),
massah@iaush.ac.ir (A.R. Massah).
1381-1169/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2010.11.013

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R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
Table 1
BEA-SO3H (28%) catalyzed protection of aldehydes under solvent-free condition.a
Entry
Aldehyde
Molar ratio (aldehyde:acetic anhydride)
Protection
Product
Time (min)
1
Yield (%)b
90
1
2
3
1:1
1:1
1:1
1
90
0
30
4
5
1:1
1:1
30
1
0
96
6
1:1
1
90
7
8
9
.1:15
.1:15
1:1
3
4
2
95
95
98
10
11
12
.1:15
1:1
2
1
2
90
90
80
1:1
13
1:1
20
10
14
15
.1:15
.1:15
1:1
4
30
1
85
0
16
90
a
Reaction conditions: acetic anhydride (2 mmol), catalyst (0.015 g), benzaldehyde (2 mmol), solvent-free, and room temperature.
Isolated yield.
b

R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
53
and 13C NMR. All melting points compared satisfactorily with those
reported in the literature.
2. Experimental
2.1. Instruments and characterization
2.2. Catalyst preparation
The catalyst was characterized by X-ray diffraction (Bruker
D8ADVANCE, Cu K␣ radiation), X-ray fluorescence (XRF) (Bruker
D8ADVANCE), FT-IR spectroscopy (Nicolet 400D in KBr matrix in
the range of 4000–400 cm−1), BET specific surface areas and BJH
pore size distribution (Series BEL SORP 18, at 77 K), thermal ana-
lyzer TGA (Setaram Labsys TG (STA); in a temperature range of
30–700 ◦C and heating rate of 10 ◦C/min in N2 atmosphere) and
SEM (Philips, XL30, SE detector).
Beta zeolite seeds (SiO2/Al2O3 = 50) were synthesized accord-
ing to a previously published method [54]. 0.189 g of aluminum
hydroxide (54% Al2O3, 46 wt.% H2O) was added to tetraethy-
lammonium hydroxide (TEAOH, 20%, aqueous solution) at room
temperature and the mixture was stirred for 15 min. Then, fume sil-
ica (6 g, 99.8%) was added drop-wise to the solution under stirring
at room temperature. After the mixture was homogenized, the tem-
perature was ramped to 75 ◦C and maintained at this temperature
for 1 h. The homogenous final gel was transferred into a Teflon-
lined stainless autoclave and placed at 140 ◦C for 12 days. Finally,
the solution was filtered and washed with deionized water and
then dried at 100 ◦C overnight. Template removal was performed
by calcination in air at 550 ◦C for 6 h.
The products were characterized by 1H and 13C NMR spectra
(Bruker DRX-500 Avance spectrometer at 500.13 and 125.47 MHz,
respectively), GC (Agilent 6820 equipped with a FID detector) and
GC–MS (Agilent 6890). Melting points were measured on an Elec-
trothermal 9100 apparatus and are uncorrected. All the products
are known compounds; they were characterized by IR, 1H NMR
Table 2
Deprotection of 1,1-diacetates over BEA-SO3H (28 wt.%) in ethanol.
Entry
Substrate
Deprotection
Product
(min) Time
40
Yield (%)a
85
1
2
45
80
3
4
5
30
30
60
100
100
80
6
7
8
30
60
60
80
90
90
9
30
100
10
25
5
80
11
100
a
Isolated yield.

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R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
Table 3
The experimental results in synthesis of beta zeolite.
a
c
Product
SiO2/Al2O3
50
(TEA)2O/SiO2
0.15
H2O/SiO2
7
Temperature (◦C)
140
Time (day)
12
XRD crystallinity (%)b
100
SiO2/Al2O3
34.2
Zeolite beta (BEA)
a
Used in the synthesis procedure.
b
c
Reference zeolite crystallinity is calculated from the intensity of the most intense (3 0 2) reflection peak appearing at 22.4◦.
Estimated by XRF.
To synthesize BEA-SO3H (28 wt.%), 0.50 g of zeolite beta (BEA)
was added to a round-bottomed flask, then 0.192 g (1.65 mmol)
of chlorosulphonic acid was added dropwise during 30 min under
nitrogen atmosphere. The reaction mixture was stirred with a mag-
netic stirrer. After all chlorosulphonic acid was added, the reaction
mixture was stirred for another 30 min under nitrogen atmosphere.
Thenthe solutionwasfiltered and washed withwater (2 × 10 mL)to
remove the unreacted chlorosulphonic acid. Finally, the white solid
powder of BEA-SO3H (28 wt.%) was obtained. The composition of
the catalyst samples was obtained using XRF analysis. BEA-SO3H
(15 wt.%) and BEA-SO3H (34 wt.%) were synthesized similar to this
procedure with various amounts of chlorosulphonic acid.
Fig. 1. XRD powder patterns of the calcinated samples of zeolite beta catalysts con-
taining different amounts of loaded chlorosulphonic acid: (a) 0%, (b) 15%, (c) 28%,
(d) 34%, and (e) 56%.
2.3. General procedure for the synthesis of 1,1-diacetate
In the typical experiment, 2 mmol of acetic anhydride was
added to the mixture of catalyst (0.03 g, BEA-SO3H (28 wt.%)) and
benzaldehyde (2 mmol) in a round-bottomed flask. The reaction
mixture was stirred with a magnetic stirrer at solvent-free and
room temperature conditions. Course of the reaction was moni-
tored by TLC and GC. At the end of the reaction, the catalyst was
separated by filtration and washed with ethyl acetate (2 × 10 mL).
The solvent was evaporated under reduced pressure to give the cor-
responding pure 1,1-diacetate (acylal). The yield of 1,1-diacetates
with various aldehydes was tested at the optimized condition over
BEA-SO3H (28 wt.%) and the results are given in Table 1.
its crystallinity is lost to some extent, possibly by dealumination of
the zeolite. It can be seen that SiO2/Al2O3 ratio is about 34 wt.% for
synthesized beta zeolite (Table 3). After loading ClSO3H on the beta
zeolite (BEA-SO3H (28 wt.%)), the amount of SiO2/Al2O3 is about
37.5 wt.% (Table 4). These results show some dealumination of the
zeolite after loading ClSO3H. However, the crystallinity of the BEA
zeolite with 34% loaded acid still remained (Fig. 1d).
In addition, the X-ray fluorescence (XRF) results also show the
elemental composition of catalyst before and after washing the
catalyst with water (BEA-SO3H (28 wt.%)). It can be seen that the
proportion of SO3 in the catalyst was 22 wt.%, which was close to
28% ClSO3H of the value set in the catalyst design (Table 4). From
these data we can conclude that SO3H was grafted on the surface
of the catalyst by covalent bond. However, the amount of SO3 on
the surface of the catalyst did not change after washing the catalyst
with water. In addition, the proportion of SO3 in the catalyst was
estimated after the first and third cycles of the reaction (Table 4).
It can be seen that the amount of SO3 was constant. So it can be
concluded that there were no leaching of SO3 in the solution after
the third cycle of the reaction.
2.4. General procedure for deprotection of 1,1-diacetate
A mixture of 1-phenylmethanediacetate (1 mmol) and BEA-
SO3H (28%) (0.02 g) in ethanol (96%, 5 mL) was stirred vigorously for
specified time at 50 ◦C (Table 2). After completion of the reaction,
as indicated by TLC, the catalyst was filtered and washed with Et2O
(2 × 10 mL). The solvent was evaporated under reduced pressure.
The resultant product was passed through short column of silica gel
(n-hexane–ethylacetate, 9:1) to afford pure aldehyde. The yield of
aldehydes with various 1,1-diacetates was tested at the optimized
condition over BEA-SO3H (28%) and the results are given in Table 2.
The infrared spectra of the BEA zeolite and the samples with
various amounts of ClSO3H supported on BEA zeolite are presented
in Fig. 2. In the sample BEA zeolite the broad peaks in the range
of 3200–3600 cm−1 may be attributed to the hydroxyl stretching
of hydrogen bonded internal silanol groups and O–H stretching of
water, while the peak at 1620–1640 cm−1 corresponds to bend-
ing mode of O–H of water. Besides those, the peaks around 800
3. Results and discussion
3.1. Characterization of the catalyst
The synthesis experimental results are summarized in Table 3.
In the reaction, the maintained time of the alumino silicate solution
into the Teflon-lined stainless autoclave has a great influence on the
size of the product. By increasing maintained time, the size of the
zeolite beta crystals increased.
Table 4
Summary of composition of BEA-SO3H (28 wt.%) determined by XRF.
Catalyst
Composition of catalyst by XRF (wt.%)
XRD powder patterns of the calcinated samples of zeolite beta
with different amount of loaded chlorosulphonic acid (a–e) are
presented in Fig. 1. Fig. 1a exhibited the typical pattern of highly
crystalline zeolite beta with broad and sharp reflections [55] and no
other phase impurities were observed. Relative crystallinity is cal-
culated from the intensity of the most intense (3 0 2) reflection peak
appearing at 22.4◦ of highly crystalline zeolite beta (Table 1). The
XRD analysis of the BEA-SO3H zeolites (Fig. 1) shows that by load-
ing the zeolite with ClSO3H and during the calcination processes,
SiO2
Al2O3
SO3
BEA-SO3H (28 wt.%)a
BEA-SO3H (28 wt.%)b
BEA-SO3H (28 wt.%)c
BEA-SO3H (28 wt.%)d
74.11
76.32
76.23
76.19
1.91
2.03
2.03
2.03
22.52
21.87
21.79
21.68
a
Before washing with water.
After washing with water.
After first cycle of the reaction.
b
c
d
After third cycle of the reaction.

R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
55
in the range of 750–1000 cm−1 may be attributed to the S–O bond. It
should be mentioned that with increasing amount of ClSO3H loaded
on the BEA zeolite, the intensity of the peaks related to S O and S–O
increases.
The N2 adsorption–desorption isotherm of beta zeolite with
various amounts of loaded chlorosulphonic acid is summarized in
Fig. 3. The pore volume data of all these materials are summarized
in Table 5. It is known that calcined BEA zeolite has a large pore vol-
ume (0.271 cm3/g), indicative of its potential application as a host in
materials. After being modified with ClSO3H it exhibits a lower pore
volume in comparison with that of pure BEA zeolite, which might
be due to the presence of SO3H groups on the pore surface. The
pore volume decreased with increasing amount of loaded chloro-
sulphonic acid. This means that the chlorosulphonic acid is grafted
onto the pore wall surface of beta zeolite materials (Table 5).
Typical SEM images are displayed in Fig. 4. No amorphous and
impurity phase existed in the all samples. The pure silica BEA zeo-
lite showed truncated square bipyramidal morphology and the
crystal size was 200 nm (Fig. 4a). The decrease in crystals size
and bipyramidal morphology was observed when the amount of
loaded acid in the sample was increased. However, the crystal
size and morphology of the BEA zeolite with 34% loaded acid still
remained.
TG/DTA measurement of the samples showed three weight loss
intervals mainly at 160–190 ◦C, 200–300 ◦C and 800–820 ◦C (Fig. 5).
The first step at 160–190 ◦C is in a good agreement with the weight
loss of chlorosulphonic acid, which is on the external or nearby
surface of beta zeolite. The peak is observed at 200–300 ◦C due to
the weight loss of SO2 and Cl2 molecules on the silica surface [59].
These observations can be seen in the DSC curve of beta zeolites
with various amounts of loaded chlorosulphonic acid (Fig. 6). DSC
isotherms of BEA-SO3H catalysts show two endothermic processes
due to the decomposition of ClSO3H. The other weight loss intervals
correspond to the concurrent decomposition of beta zeolite struc-
ture by increasing temperatures. To prove this speculation, XRD
data of the catalyst post-TGA were used. As we can see from Fig. 7,
the XRD pattern of the catalyst was completely changed because of
the decomposition of beta zeolite structure by increasing temper-
ature. The XRD pattern displays the characteristic spectral profile
of an amorphous aluminosilicate, with an amorphous halo present
in the 2ꢀ = 23. This typical halo results from the dispersion of the
angles and bond distances between the basic structural units (sili-
cates and aluminates), which destroys the structure periodicity and
produces a non-crystalline material.
Fig. 2. FT-IR spectra of the calcinated samples of zeolite beta catalysts containing
different amounts of loaded chlorosulphonic acid: (a) 0%, (b) 15%, (c) 28%, and (d)
34%.
and 1090 cm−1 are attributed to the symmetric and asymmetric
stretching vibrations of the Si–O–Si groups, respectively [56]. The
band at 470 cm−1 is assigned to the bending vibrations of Si–O–Si
or Al–O–Si groups. The high crystallinity of zeolite samples can
be ascertained from their framework IR spectra, which show in
the 500–650 cm−1 region the features characteristic of zeolite beta
[55]. In the samples with various amounts of ClSO3H loaded on
BEA zeolite, some additional peaks; the asymmetric and symmetric
stretching of S O bond at 1229–1290 and 1177 cm−1, respectively,
confirm the presence of SO3H in BEA-SO3H [57,58]. The other peaks
3.2. Catalytic activity for synthesis and deprotection of
1,1-diacetate (acylal)
A wide variety of aromatic and aliphatic aldehydes (Table 1)
underwent smooth reaction to give the corresponding acylals in
good yield. As shown in Table 1, the results reveal that the BEA-
SO3H catalysis generally results in good yields with aromatic
aldehydes including those carrying electron donating or withdraw-
ing substituents even when moderately hindered aldehydes were
used, with the advantages of mild reaction conditions. The tol-
erance of various functional groups under the present reaction
Table 5
The BET results of beta zeolite (BEA) and BEA-SO3H synthesized with different
amounts of chlorosulphonic acid.
Sample
VP (cm3 g−1
)
BEA
0.271
0.115
0.104
0.069
BEA-SO3H (15%)
BEA-SO3H (28%)
BEA-SO3H (34%)
Fig. 3. Nitrogen adsorption–desorption analysis of beta zeolite with various
amounts of loaded chlorosulphonic acid: (a) 15%, (b) 28%, and (c) 34%.

56
R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
Fig. 4. SEM images of the calcinated samples of beta zeolite catalysts containing different amounts of loaded chlorosulphonic acid: (a) 0%, (b) 15%, (c) 28%, and (d) 34%.
conditions is worthy of mention, where the acid sensitive or oxi-
dizable groups such as methoxy, nitro, chloro, and double bonds
do survive under such condition. Aldehydes with withdrawing
substituents gave high although unmaximized yields, for exam-
ple it is worth that o-nitrobenzaldehyde and m-nitrobenzaldehyde
acetalised produced good yields (entries 7 and 14, 95% and 85%).
Moreover, it should be noted that aliphatic aldehydes afforded the
corresponding acylals within a short reaction time and good yield
(entries 1 and 2). Compounds such as acetophenone (entry 3) and
2-butanone (entry 4) were not converted into the corresponding
1,1-diacetates at optimum conditions even for 30 min. Further-
more, the results reveal that BEA-SO3H shows good activity for the
deprotection of 1,1-diacetates (Table 2).
3.2.1. Effect of the amount of loaded chlorosulphonic acid
In order to investigate the effect of the amount of loaded acid, the
activities of catalysts including various amounts of loaded chloro-
sulphonic acid on zeolite beta for synthesis of 1,1-diacetate (acylal)
were compared. The results are listed in Table 6. The variation in
Fig. 5. Thermogravimetric analysis (TG) of beta zeolite catalysts containing different
Fig. 6. DSC curves of beta zeolite catalysts containing different amounts of loaded
amounts of loaded chlorosulphonic acid: (a) 0%, (b) 15%, (c) 28%, and (d) 34%.
chlorosulphonic acid: (a) 0%, (b) 15%, (c) 28%, and (d) 34%.

R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
57
120
100
80
60
40
20
0
0
0.01
0.02
0.03
0.04
Amount of catalyst (g)
Fig. 8. Effect of catalyst amount. Reaction conditions: acetic anhydride (2 mmol),
benzaldehyde (2 mmol), catalyst (BEA-SO3H (28%)) solvent-free, room temperature,
1 min.
Table 8
Recyclability of the catalyst for synthesis of 1,1-diacetate.a
Cycle
Yield of acylal (%)b
Time (min)
1
2
3
4
96
96
94
93
1
1
1
1
Fig. 7. XRD powder pattern of BEA-SO3H (28 wt.%) catalyst post-TGA.
Table 6
Effect of amount of loaded chlorosulphonic acid on synthesis of 1,1-diacetate.a
a
Reaction conditions: acetic anhydride (2 mmol), catalyst (0.015 g), benzalde-
hyde (2 mmol), solvent-free, and room temperature.
Catalyst
Yield of acylal (%)b
Time (min)
b
Isolated yield.
BEA
15
50
96
70
30
1
1
BEA-SO3H (15%)
BEA-SO3H (28%)
BEA-SO3H (34%)
3.2.3. Effect of catalyst amount
1
Fig. 8 displays the effect of the amount of BEA-SO3H (28 wt.%)
on the yield of 1,1-diacetate (acylal). It can be seen that the yield
of acylal increased from 70% to 96% when the amount of BEA-SO3H
(28 wt.%) increased from 0.01 g to 0.015 g. With excess amount of
catalyst, the yield obviously increased, because of the availability
of more acid sites. With further increase in catalyst amount, the
percentage of yield remains constant. 0.015 g catalyst is selected
for further experimental studies due to its optimum performance.
a
Reaction conditions: acetic anhydride (2 mmol), catalyst (0.015 g), benzalde-
hyde (2 mmol), solvent-free, and room temperature.
b
Isolated yield.
loaded chlorosulphonic acid (15–34 wt.% acid) has different effects
on the yield of the product. In the presence of the optimized cat-
alyst (BEA-SO3H (28 wt.%)), over 95% yield is observed. In order
to investigate effect of the support (BEA-SO3H) for synthesis of
1,1-diacetate, we used ClSO3H (with the same ratio of the opti-
mized catalyst) without any support as catalyst by keeping other
parameters constant. After 40 min, about 46% yield was observed.
Therefore, BEA zeolite as a support is very useful for the synthesis
of 1,1-diacetate.
3.3. Reusability study
Reusability of the catalyst is tested by carrying out repeated
runs of the reaction on the same batch of the catalyst. After each
cycle the catalyst was filtered off, washed with ethyl acetate and
dried at 120 ◦C and then reused for successive cycles. It is evident
that the catalyst worked well up to the third cycle. The results are
summarized in Table 8.
3.2.2. Effect of solvent
For optimization of the reaction conditions, we have tried the
conversion of benzaldehyde (2 mmol) to the corresponding acylal
with acetic anhydride (2 mmol) in the presence of various solvents
and also under solvent-free conditions at room temperature. In
comparison with conventional methods, the yield of the product
under solvent-free conditions is higher and reaction time is less
(Table 7). Therefore, we have employed the solvent-free conditions
for the conversion of various aldehydes to the corresponding acylals
(Table 1).
XRD powder pattern of the reused catalyst (after third cycle of
the reaction) is presented in Fig. 9. These data showed that the
Table 7
Effect of solvent on synthesis of 1,1-diacetate.a
Solvent
Time (min)
Yield of acylal (%)b
Ethylacetate
Acetonitrile
Dichloromethane
n-Hexane
4
3
3
3
1
50
70
80
70
96
Solvent-free
a
Reaction conditions: acetic anhydride (2 mmol), catalyst (0.015 g), benzalde-
hyde (2 mmol), and room temperature.
Fig. 9. XRD powder pattern of (a) fresh BEA-SO3H (28 wt.%) catalyst and (b) BEA-
SO3H (28 wt.%) catalyst after the third cycle of the reaction.
b
Isolated yield.

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R.J. Kalbasi et al. / Journal of Molecular Catalysis A: Chemical 335 (2011) 51–59
CH3
C(OAc)2
O
OAc
OAc
BEA-SO3H (28 wt.%)
Ac2O (1 mmol)
+
CHO
1 mmol
+
CH3
0 %
96 %
1 mmol
Scheme 1. Chemoselectivity of the catalyst (BEA-SO3H (28%)).
Table 9
crystallinity of the catalyst did not change after the third cycle of
the reaction. In addition, the XRF results also show the elemental
composition of the catalyst after the first and third cycle of the
reaction (Table 4). However, the amount of SO3 on the surface of
the catalyst was not changed after the reaction. Also, SiO2/Al2O3
ratio of the catalyst did not change after the reaction and we can
conclude that the catalyst is stable in these conditions.
Comparison of the efficiency of BEA-SO3H with other catalysts in the protection of
4-nitrobenzaldehyde using acetic anhydride as acylation reagent.
Catalyst
Molar ratio
(alde-
hyde:acetic
anhydride)
Temperature
Time
Yield
(%)
Reference
NBS
1
2
Room
temperature
Room
8 h
98
88
90
[60]
[61]
InCl3
4 h
3.4. Chemoselectivity and shape-selectivity of the catalyst
temperature
LiBF4
ZrCl4
2
3
60 ◦
C
23 h
30 min 92
[62]
[8]
In order to examine the chemoselectivity of the present method,
equimolar mixtures of ketone (acetophenone) and aldehyde (ben-
zaldehyde) were allowed to react with acetic anhydride in the
presence of BEA-SO3H (28 wt.%) as a catalyst. As shown in Scheme 1,
the catalyst was able to discriminate between ketone and aldehyde
and showed a high chemoselectivity. Therefore, the present proce-
dure is a selective preparation of the 1,1-diacetates from aldehydes
in the presence of ketones.
Room
temperature
Room
temperature
Room
temperature
Room
LiOTf
8–5
3
15 h
4 h
94
94
[63]
[64]
[65]
Cu(OTf)2
Sc(OTf)2
1.5
10 min 99
temperature
Y zeolite
Beta zeolite
HZSM-5
(15)a
BEA-SO3H
(28 wt.%)
3
1
3
70 ◦C
7 h
1.5 h
4 h
93
93
24
[66]
[67]
[68]
60 ◦C
In order to examine the shape-selectivity of the cat-
Room
temperature
Room
alyst,
2-propylbenzaldehyde,
3-propylbenzaldehyde
and
4-propylbenzaldehyde were allowed to react with acetic anhydride
in the presence of the BEA-SO3H (28 wt.%) as a catalyst. As shown in
Scheme 2, the catalyst was able to discriminate between the alde-
hydes with different steric effects. As we can see from Scheme 2,
1,1-diacetate was produced only from 4-propylbenzaldehyde.
From these data we can conclude that the reaction just occurs in
the micropores of the catalyst and it does not occur on the outer
surface of the catalyst or in the solution with leached SO3H species.
1
4 min
95
This work
temperature
a
Si/Al molar ratio.
nitrobenzaldehyde using acetic anhydride as an acylating reagent
at very short time.
4. Conclusion
3.5. Comparison with other catalysts in synthesis of acylal
In conclusion, herein we report a mild and efficient catalyst for
the preparation of 1,1-diacetates from aldehydes in the presence of
acetic anhydride under solvent-free conditions at room tempera-
ture. This method is selective for the preparation of 1,1-diacetates
from aldehydes in the presence of ketones. 1,1-Diacetates can be
conveniently deprotected by using BEA-SO3H in methanol. Good
yields were obtained within short reaction times; reusability of
the catalyst, non-toxic nature and mild conditions are some of the
notable features of this protocol.
A comparison of the catalytic activity values of various catalysts
for the synthesis of acylals is given in Table 9. As can be seen, the
BEA-SO3H (28%) catalyst shows good yield for the protection of 4-
CHO
BEA-SO3H (28 wt.%)
No Reaction
Ac2O (2 mmol)
Acknowledgement
AcO
OAc
CHO
CHO
The support from Islamic Azad University, Shahreza Branch
(IAUSH) Research Council and Center of Excellence in Chemistry
is gratefully acknowledged.
BEA-SO3H (28 wt.%)
Ac2O (2 mmol)
3 %
OAc
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