Iron oxide-pillared clay catalyzed the synthesis of acetonides from epoxides

Article abstract of DOI:10.1016/j.catcom.2014.05.002

FeO_x-pillared clays (FeO_x-pillared bentonite, FeO_x-pillared hectorite and FeO_x-pillared taeniolite) were synthesized by the intercalation of FeCl₃ into clay interlayers and calcination. The synthesize

Full text of DOI:10.1016/j.catcom.2014.05.002

Iron Oxide-pillared Clay Catalyzed the Synthesis of Acetonides from Epoxides
Piyarat Trikittiwong, Nipaka Sukpirom, Shogo Shimazu, Warinthorn Chavasiri
PII:
DOI:
Reference:
S1566-7367(14)00174-5
doi: 10.1016/j.catcom.2014.05.002
CATCOM 3896
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
20 April 2013
5 May 2014
8 May 2014
Please cite this article as: Piyarat Trikittiwong, Nipaka Sukpirom, Shogo Shimazu,
Warinthorn Chavasiri, Iron Oxide-pillared Clay Catalyzed the Synthesis of Acetonides
from Epoxides, Catalysis Communications (2014), doi: 10.1016/j.catcom.2014.05.002
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Iron Oxide-pillared Clay Catalyzed the Synthesis of Acetonides from
Epoxides
Piyarat Trikittiwonga, Nipaka Sukpiromb, Shogo Shimazuc,* and Warinthorn Chavasirib,*
aProgram in Petrochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
bDepartment of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
cDepartment of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, Chiba-shi 263-8522, Japan.
# Corresponding author, e-mail: warintho@yahoo.com, Tel: 662-218-7625
Abstract
FeOx-pillared clays (FeOx-pillared bentonite, FeOx-pillared hectorite and FeOx-pillared
taeniolite) were synthesized by the intercalation of FeCl3 into clay interlayers and calcination.
The synthesized catalysts were exploited for conversion of epoxides furnishing acetonides in
good to quantitative yields with short time under mild conditions. The catalysts could be
recovered and reused up to five times without appreciable loss of activity.
Keywords: Iron oxide pillared clays; Epoxides; 1,3-Dioxolanes

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1. Introduction
The protection of a carbonyl functional group from nucleophilic attack is still challenging
task. One of the most useful protecting methods for carbonyl compounds (aldehydes and
ketones) includes acetalization, thioacetalization and ketalization [1]. 1,3-Dioxolanes are widely
used to protect aldehydes and ketones. Epoxides are attractive intermediates due to their wide
range of regio-, chemo- and stereoselective transformations with concomitant ring opening. The
direct transformation of epoxides to acetonides was previously reported using several Lewis acid
catalysts such as anhydrous CuSO4 [2], BF3.OEt2 [3], CH3ReO3 [4], RuCl3 [5], TiO(TFA)2 and
TiCl3(OTf) [6], Fe(TFA)3 [7], K5CoW12O40·3H2O [8], Bi(TFA)3 [9], TABCO [10], SnCl2 [11],
Sn(tpp)(OTf)2 [12], Er(OTf)3 [13], and LiBF4 [14]. Some reported methods suffered from air- and
moisture-sensitive catalysts, expensive and toxic catalysts, high refluxing temperature, long
reaction time, difficulty in separation and recovery, less selectivity or yields and functional group
intolerance. In recent years, inorganic solid acids catalyzed organic reactions have gained
importance due to the proven advantage of heterogeneous catalysts such as simplified product
isolation, easy work-up, mild reaction conditions, shorter reaction time, easy recovery and
reusability of catalysts, better yield and a large reduction in the generation of wasteful products
[15].
Previously, certain clays such as K10-montmorillonite [16] and natural kaolinitic clay [17]
have been reported as an efficient catalyst in the synthesis of acetonides from epoxides.
Nonetheless, no report on the utilization of FeOx-pillared clays as catalysts has been addressed.
Herein, we report a new and efficient procedure for the preparation of acetonides from epoxides
by pillared clay catalysts under mild conditions.

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2. Experimental
2.1. General
Two types of the 2:1 layered clays were used as starting materials. Hectorite (Volclay Siam
Limited), with typical chemical analysis of (%wt): SiO2 61.78, Al2O3 1.58, MgO 20.32, Fe2O3
1.23, CaO 10.07, Na2O 2.80, K2O 0.33, was used as received. Bentonite clay (Cernic
International Co., LTD) with typical chemical analysis of (%wt): SiO2 63.60, Al2O3 17.60, Fe2O3
3.10, CaO 3.00, Na2O 3.40, K2O 0.50, was purified by fractionated centrifugation in order to
remove quartz and other dense impurities. De-ionized water was used throughout the study. For
.
preparation of catalysts, FeCl3 6H2O (Riedel-de Haën) and NaOH (Merck) were of laboratory
reagent grade. De-ionized water was used throughout the study.
For catalytic study, all
organic solvents were purified using standard distillation techniques. All reactants were
purchased from Fluka as laboratory reagent grade.
2.2. General preparation of acetonides
The mixture of epoxide 1 mmol and acetone (3 mL) was added to round bottle flask with
10%wt of catalyst to epoxide. The solution was continuous stirred for desired time and
temperature. After the specific time or the reaction was finished, the catalyst was filtered out of
the mixture, and washed the product out with EtOAc. The solvent was evaporated to dryness
under reduced pressure to afford the product. The reactions were monitored by TLC aluminium
sheets precoated with silica gel (Merck’s, Kieselgel 60 PF254). Products of the preparation of
acetonides from epoxides were monitored by Shimadzu GC 14-B (FID, HP-5 column) and
1
Shimadzu QP-5000 GCMS. The H NMR spectra were obtained in CDCl3 and determined by

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Mercury plus 400 NMR spectrometer operated at 399.84 MHz. All products were identified by
1H NMR.
2,2-Dimethyl-4-phenyl-1,3-dioxolane; 1H NMR (CDCl3) δ (ppm): 1.48 (3H, s), 1.52 (3H, s),
3.67 (1H, t), 4.27 (1H, dd, J = 8.6, 6.4 Hz), 5.05 (1H, dd, J = 8.6 Hz), 7.31 (5H, m).
1
2,2-Dimethyl-hexahydro-benzo[1,3]dioxole; H NMR (CDCl3) δ (ppm): 1.24-1.00 (4H, m),
1.35 (6H, s), 2.58-2.07 (4H, m), 4.34-4.05 (2H, m).
4-Decyl-2,2-dimethyl-1,3-dioxolane; 1H NMR (CDCl3) δ (ppm): 0.81 (3H, t), 1.14 (16H, m),
1.29 (3H, s), 1.34 (3H, s), 1.56 (2H, m), 3.42 (1H, dd, J = 8.8, 7.2 Hz), 4.00 (2H, m).
1
4-(Butoxymethyl)-2,2-dimethyl-1,3-dioxolane; H NMR (CDCl3) δ (ppm): 0.84 (3H, t), 1.30
(3H, s), 1.34 (3H, s), 1.48 (4H, m), 3.49 (3H, m), 3.67 (2H, m), 3.99 (1H, dd, J = 8.0, 6.8 Hz),
4.20 (1H, quin).
1
4-(tert-Butoxymethyl)-2,2-dimethyl-1,3-dioxolane; H NMR (CDCl3) δ (ppm): 1.13 (9H, s),
1.31 (3H, s), 1.38 (3H, s), 3.25 (1H, dd, J = 9.0, 6.4 Hz), 3.41 (1H, dd, J = 9.0, 5.6 Hz), 3.68 (1H,
dd, J = 8.0, 5.6 Hz), 4.01 (1H, dd, J = 8.0, 6.4 Hz), 4.13 (1H, quin).
1
4-(Isopropoxymethyl)-2,2-dimethyl-1,3-dioxolane; H NMR (CDCl3) δ (ppm): 1.09 (6H, d),
1.28 (3H, s), 1.34 (3H, s), 3.31 (1H, dd, J = 9.6, 6.0 Hz), 3.44 (1H, dd, J = 9.0, 6.4 Hz), 3.53 (1H,
septet), 3.65 (1H, dd, J = 8.0, 6.2 Hz), 3.98 (1H, dd, J = 8.0, 6.4 Hz), 4.16 (1H, quin).
1
2,2-Dimethyl-4-(phenoxymethyl)-1,3-dioxolane; H NMR (CDCl3) δ (ppm): 1.38 (3H, s),
1.45 (3H, s), 3.89 (2H, ddd, J = 5.0, 9.2, 15.2 Hz), 4.01 (1H, dd, J = 9.0, 4.6 Hz), 4.12 (1H, dd, J
= 14.4, 8.0 Hz), 4.45 (1H, quin), 6.91 (3H, m), 7.25 (2H, t).

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2.3. General preparation of FeOx-pillared clay catalysts
FeOx-pillared clays were synthesized by intercalation of iron precursors, following by
calcinations at high temperature. Na-clays were dispersed in de-ionized water (10%wt) by
.
vigorous stirring for 1 day at RT. Then 1 M FeCl3 6H2O was slowly added in the suspended Na-
clay under stirring for 24 h at RT. The products were collected by centrifugation, and washed
with de-ionized water until chloride ions were eliminated. The as-synthesized products,
Fe-intercalated clays were dried followed by calcination at 300°C.
2.4. The characterization of FeOx-pillared clay catalysts
The prepared catalysts were characterized by XRD, surface area analyzer and NH3-TPD [18].
The XRD of raw clays and synthesized FeOx-pillared clays were measured by a Rigaku, Dmax
2200/utima+ X-ray powder diffractometer (40 Kv, 30 mA) with a monochromater and Cu K
radiation. The 2 was ranged from 2 to 30° with the scan speed of 3°/min and the scan step of
0.02°. The BET specific surface area of raw clays and synthesized FeOx-pillared clays were
obtained from surface area anylasis using the Quantachrome Autosorb-1 nitrogen adsorptometer.
Acidity of all catalysts was measured by temperature-programmed desorption (TPD) spectra of
ammonia were recorded by Quantachrome Autosorb-1-C equipped with thermal conductivity
detector.
Sample preparation for ICP: The 0.0400 g of a calcined catalyst, placed in a 100 mL Teflon
beaker, was soaked with 10 mL concentrated HCl and subsequently with 10 mL of 48% HF in
order to remove silica in the form of volatile SiF4 species. The mixture was heated but not boiled
to dryness on a hot plate. The removal of silica was repeated three times. Then, 10 mL of 6 M
HCl: 6 M HNO3 mixtures in the ratio of 1:3 was added and further heated to dryness. 5 mL of 6

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M HCl was added and the mixture was warmed for 5 min to complete dissolution. The solution
was transferred to 50 mL polypropylene volumetric flask and made up its volume by adding
deionized water. If the sample was not analyzed immediately, the solution was then transferred
into a plastic bottle with a treated cap underlined with a polypropylene seal.
3. Results and discussion
3.1. Catalytic activities of FeOx-pillared clay catalysts
A mild and efficient method for the direct conversion of epoxides to acetonides using FeOx-
pillared clays at RT in acetone was disclosed. A synthesis of 1 from styrene oxide with acetone is
displayed in Figure 1. Three FeOx-pillared clays (FeOx-pillared bentonite, FeOx-pillared
taeniolite and FeOx-pillared hectorite) were screened compared with raw clays (Table 1). The
quantitative yield of 1 was obtained using FeOx-pillared bentonite (10%wt) at RT for 5 min.
When the reaction was performed without catalyst, no product was observed. The comparative
examination on the effect of pillared clays was experimented. FeOx-pillared bentonite exhibited
the highest yield. These results were well corresponded with N2 adsorption-desorption, NH3-
TPD and ICP-OES experiments. The BET surface area, the amount of acidity and wt% of Fe
content of all catalysts are summarized (Table 2). The acidic character of pillared clays derived
from either Brønsted (weak acid sites) or Lewis site (strong acid sites). Weak acid site appeared
to be associated with the coordination of water with iron in pillars, while strong acid site was
attributed to Fe2O3. The nature and strength of acid sites were related to types of clays and
pillared species. These results pointed out that type of clays strongly affected on the acidity of
synthesized catalysts. FeOx-pillared clays gave much higher %yield than pure clays (Table 1)
corresponding well with the acidity and BET surface area observed.

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The developed iron oxide-pillared bentonite provided the excellent yield within 5 min
revealing its remarkably efficient catalyst for the conversion of styrene oxide to its acetonide.
This process was found to be comparable with that previously reported using homogeneous
catalyst [19]. Nonetheless, the easy work-up protocol and reusability of exploited clay system
would lead this procedure more advantage.
O
O
O
O
iron oxide-pillared bentonite
RT, 5 min
+
H3C CH3
quantitative yield
O
O
FeCl3
RT, 12 min
Figure 1. Synthesis of acetonides from epoxides
92% yield

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Table 1
Conversion of styrene oxide to 1 catalyzed by different FeOx-pillared clays catalysts
Entry
Catalysts
FeOx-pillared bentonite
FeOx-pillared hectorite
FeOx-pillared taeniolite
bentonite
Yield (%)
quanta
83b
1
2
3
4
5
6
7
77b
tracec
tracec
tracec
0c
hectorite
taeniolite
none
Reaction conditions: styrene oxide (1 mmol), acetone (3 mL), catalyst 10 wt% to styrene
oxide at 30°C for a5 min; b30 min; c24 h.
Table 2
The amount of acidity and surface area
Entry
Catalysts
Wt% Fe Surface
acidity (mmol/g)
weak strong
acid sites acid sites
Total amount
of acidity
(mmol/g)
3.73
content
area
(m2/g)
155.52
122.30
20.33
65.05
57.11
3.53
1
2
3
4
5
6
FeOx-pillared bentonite
FeOx-pillared hectorite
FeOx-pillared taeniolite
bentonite
10.14
9.54
4.22
3.49
0.95
0.35
0.62
0.73
0.61
0.14
0.04
0.43
3.11
1.43
0.91
1.12
0.51
-
2.16
1.52
1.26
hectorite
0.55
taeniolite
0.43

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When the amount of catalyst increased from 2 to 10 wt%, the yield of product was increased.
Almost quantitative yield of product was achieved when 10 wt% of iron oxide-pillared bentonite
to styrene oxide was employed. The lower amount of catalyst was used, the lower yield was
detected. Using 30 wt% of catalyst, the yield of product was comparable with that using 10 wt%
of catalyst. Thus, the suitable amount of iron oxide-pillared bentonite was 10 wt% (Table 3).
Table 3
Effect of the amount of iron oxide-pillared bentonite
Entry
Fe-pillared bentonite
% Yield
% Styrene oxide
(wt%)
(recovered)
1
2
3
4
2
5
83
91
94
95
17
8
10
30
0
0
Reaction conditions: styrene oxide 1 mmol, acetone in excess (3 mL), iron oxide-pillared
bentonite varied at RT (30°C) for 5 min.
High to excellent yields of acetonides were obtained in all cases (Table 4). Styrene oxide was
stirred in the presence of 10%wt FeOx-pillared bentonite and acetone at RT for 5 min to produce
acetonide in quantitative yield. For cyclic epoxide (cyclohexene oxide) and terminal aliphatic
epoxide (1-dodecene oxide), 94 and 92% yields were achieved after 2 h (entries 2-3,

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respectively). The FeOx-pillared bentonite could also catalyze the efficient reaction of the
epoxides with ethereal linkage on the epoxide ring such as butyl glycidyl ether, tert-butyl
glycidyl ether, 2,3-epoxypropyl isopropyl ether and 2,3-epoxypropyl phenyl ether with acetone
to give their corresponding 1,3-dioxalones in high yields (entries 4-7). All products were
identified by GC and 1H NMR compared with authentic samples.

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Table 4
Conversion of epoxides to acetonides catalyzed by FeOx-pillared bentonite
Entry
Epoxides
Acetonides
Yield (%)
O
O
O
1
quant
O
O
2
3
4
5
6
94
O
O
O
O
92
88
O
O
O
O
O
O
O
O
O
O
63
90
92
O
O
O
O
O
O
O
O
O
O
7
Reaction conditions: epoxide (1 mmol), acetone (3 mL), 10 wt% FeOx-pillared bentonite to epoxide at
60°C for 2 h.

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Table 5 reveals the scope of the reaction with other carbonyl compounds such as
acetophenone, cyclohexanone and benzaldehyde. The reactions could proceed well with these
selected carbonyl compounds (entries 2-4). Without FeOx-pillared bentonite, no reaction
occurred.
Table 5
Reaction of carbonyl compounds with styrene oxide catalyzed by FeOx-pillared bentonite
Entry
Carbonyl compounds
1,3-Dioxolane
Yield (%)
O
Ph
O
1
H3C
H3C
>99
H3C CH3
O
O
Ph
O
Ph
2
3
4
83
77
85
Ph
CH3
O
O
H3C
Ph
Ph
O
O
O
O
O
Ph
Ph
H
H
Reaction conditions: carbonyl compound (2 mmol), styrene oxide (1 mmol), CH2Cl2 (3 mL), 10 wt%
FeOx-pillared bentonite to styrene oxide at refluxing CH2Cl2 for 2 h.
The proposed mechanism is presented (Scheme 1). The Lewis acid-mediated reaction of an
epoxide with a carbonyl compound was reported to proceed via the coordination of a metal oxide

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of the catalyst with the epoxide oxygen [13], followed by nucleophilic ring-opening of the
epoxide by the carbonyl oxygen and finally 1,3-dioxolane ring formation.
R3
R3
R4
R4
O
O
R1
R1
R1
R2
R2
R2
O
O
O
FeOx-pillared clay
FeOx-pillared clay
FeOx-pillared clay
R2
O
R1
R2
R1
OFeOx-pillared clay
R2
R1
O
OFeOx-pillared clay
R3
O
O
R4 R3
R4 R3
R4
Scheme 1. The Proposed Mechanism
3.2 Catalytic activities of reused of FeOx-pillared bentonite
FeOx-pillared bentonite could be easily recovered, simply by filtering the catalyst, washing
with EtOAc, drying at 100°C in oven for 2 h and calcination. The recovered FeOx-pillared
bentonite was used in the next run. The results are summarized (Table 6).

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Table 6
Activity of regenerated FeOx-pillared bentonite by calcination at 300°C for the conversion of
styrene oxide to acetonide
Entry
Times
% Yield of 1
1
2
3
4
5
1
2
3
4
5
99
99
88
76
74
Reaction conditions: styrene oxide (1 mmol), acetone (3 mL), catalyst 10 wt% to styrene oxide at 30°C
for 5 min.
In order to investigate for the reusability of the prepared FeOx-pillared bentonite, the reused
catalyst was employed in the next run. After reusing twice, 88% of acetonide was detected. The
regenerated FeOx-pillared bentonite exhibited lower activity than the original catalyst. This may
derive from the collapse of d001 spacing owing to the calcination process. The analysis of the
BET specific surface areas of the regenerated FeOx-pillared bentonite exhibited the lower value
than the original catalyst: 155.52 and 114.04 m2/g, respectively. There are two reasons: (i) the re-
calcination process at 300°C was not enough to remove all organic residues that blocked the
pores of the catalyst, and (ii) the collapse of the d-spacing also caused the smaller pores.
However, re-calcination process at higher 300°C may cause the pillared structure change or
collapse.

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The attempt to utilize this catalyst was carried out. The new protocol was accomplished
by simply filtering FeOx-pillared bentonite from the reaction mixture, drying at 100°C in oven
for 2 h and not calcinating. The process opened the good opportunity to exploit this catalyst at
least five times without appreciable loss of activity as summarized (Table 7).
Table 7
Activity of regenerated FeOx-pillared bentonite by not calcination for the conversion of styrene
oxide to acetonide
Entry
Times
% Yield of 1
1
2
3
4
5
1
2
3
4
5
99
93
96
92
98
Reaction conditions: styrene oxide (1 mmol), acetone (3 mL), catalyst 10 wt% to styrene oxide at 30°C
for 5 min.
4. Conclusion
FeOx-pillared bentonite as a highly effective catalyst for the conversion of epoxides to
acetonides was described. The reaction furnished 2,2-dimethyl-4-phenyl-1,3-dioxolane in
quantitative yield with short reaction time under mild conditions. The reaction worked smoothly
for a wide range of epoxides and carbonyl compounds. The calcination step was not requited for
the reuse of catalyst. Up to five times of this catalytic system could be achieved without
appreciable loss of activity.

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Acknowledgements
We gratefully thank the Natural Products Research Unit, Department of Chemistry, Faculty of
Science, Chulalongkorn University, Thailand and Department of Applied Chemistry and
Biotechnology, Faculty of Engineering, Chiba University, Japan for the provision of chemicals
and laboratory facilities. Financial support from Office of the Higher Education Commission is
also indebted.
References
[1] (a) D.M. Clode, Chem. Rev. 79 (1979) 491-513. (b) A. Mori, H. Yamamoto, J. Org. Chem.
50 (1985) 5444-5446. (c) K. Hirano, T. Iwahama, S. Sakaguchi, Y. Ishii, Chem. Commun.
(2000) 2457-2458. (d) B. Wang, Y. Gu, G. Song, T. Yang, L. Yang, J. Suo, J. Mol. Catal. A:
Chem. 233 (2005) 121-126. (e) R. Balamurugan, R.B. Kothapalli, G.K. Thota, J. Org.
Chem. 8 (2011) 1557-1569. (f) S. Madabhushi, K.K.R. Mallu, N. Chinthala, C.R. Beeram,
V.S. Vangipuram, Tetrahedron Lett. 53 (2012) 697-701. (g) J.K. Augustine, A. Bombrun,
W.H.B. Sauer, P. Vijaykumar, Tetrahedron Lett. 53 (2012) 5030-5033.
[2] R.P. Hanzlik, M. Leinwetter, J. Org. Chem. 43 (1978) 438-440.
[3] D.S. Torok, J.J. Figueroa, W.J. Scott, J. Org. Chem. 58 (1993) 7274-7276.
[4] Z. Zhu, J.H. Espenson, Organometallics. 16 (1997) 3658-3663.
[5] N. Iranpoor, F. Kazemi, Synth. Commun. 28 (1998) 3189-3193.
[6] N. Iranpoor, B. Zeynizadeh, J. Chem. Res. (1998) 466-467.
[7] N. Iranpoor, H. Adibi, Bull. Chem. Soc. Jpn. 73 (2000) 675-680.
[8] M.H. Habibi, S. Tangestaninejad, V. Mirkhani, B. Yadollahi, Catal. Lett. 75 (2001) 205-207.

ACCEPTED MANUSCRIPT
17
[9] I. Mohammadpoor-Baltork, A.R. Khosropour, H. Aliyan, Synth. Commun. 31 (2001) 3411-
3416.
[10]H. Firouzabadi, N. Iranpoor, H.R. Shaterian, Bull. Chem. Soc. Jpn. 75 (2002) 2195-2205.
[11]J.R.Vyvyan, J.A. Meye, K.D. Meyer, J. Org. Chem. 68 (2003) 9144-9147.
[12]M. Moghadam, S. Tangestaninejad, V. Mirkhani, R. Shaibani, Tetrahedron 60 (2004) 6105-
6111.
[13]A. Procopio, R. Dalpozzo, A. De Nino, L. Maiuolo, M. Nardi, B. Russo, Adv. Synth. Catal.
347 (2005) 1447-1450.
[14]F. Kazemi, A.R. Kiasat, S. Ebrahimi, Synth. Commun. 35 (2005) 1441-1445.
[15](a) J.H. Clark, Acc. Chem. Res. 35 (2002) 791-797. (b) T. Okuhara, Chem. Rev. 102 (2002)
3641-3666.
[16]I. Bucsi, A. Meleg, A. Molnar, M. Bartok, J. Mol. Catal. A: Chem. 168 (2001) 47-52.
[17]D. Ponde, H.B. Borate, A. Sudalai, T. Ravlndranathan, V.H. Deshpande, Tetrahedron Lett.
37 (1996) 4605-4608.
[18] T. Piyarat, S. Nipaka, and C. Warinthorn, J. Mol. Catal. A: Chem. 378 (2013) 76-81.
[19] S. Sumit, S. K. Mandal, C. R. Subhas, Tetrahedron Lett. 49 (2008) 5928-5930.

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Graphical abstract

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Highlights
•FeOx-pillared bentonite efficiently catalyzed the conversion of epoxides.
•The reaction furnished acetonides in excellent yields under mild reaction conditions.
•The quantitative yields was obtained using 10wt% of catalysts at RT for 5 min.
•Up to five times of this catalytic system could be achieved without loss of activity.