Zirconium triflate grafted on SBA-15 as a highly efficient solid acid catalyst for ring opening of epoxides by amines and alcohols

Article abstract of DOI:10.1016/S1872-2067(17)62794-3

Metal (Al, Ti, Zr) triflate grafted mesoporous SBA-15 (AlTf/S, TiTf/S, ZrTf/S) samples were synthesized as inexpensive solid acid materials by a simple one-pot-two-step synthesis methodology. These materials were characterized by X-ray diffraction, N₂-sorption, thermogravimetric analysis, Fourier transform infrared spectroscopy (FT-IR), in-situ pyridine FT-IR spectroscopy, and elemental analysis. ZrTf/S was found to be a highly efficient and reusable solid acid catalyst for ring opening of epoxides with amines and alcohols and produced β-amino alcohols and β-alkoxy alcohols respectively under ambient reaction conditions. The ZrTf/S catalyst showed the highest activity, which was attributed to its high acidity compared with that of the Ti and Al containing samples.

Full text of DOI:10.1016/S1872-2067(17)62794-3

Chinese Journal of Catalysis 38 (2017) 758–766
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
Zirconium triflate grafted on SBA‐15 as a highly efficient solid acid
catalyst for ring opening of epoxides by amines and alcohols
Kamlesh N. Tayade a, Lianyue Wang a, Sensen Shang a, Wen Dai a, Manish Mishra b, Shuang Gao a,*
a Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
b Department of Chemical Engineering And Shah‐Schulman Center for Surface Science and Nanotechnology, Faculty of Technology, Dharmsinh Desai
University, Nadiad 387001, Gujarat, India
A R T I C L E I N F O
A B S T R A C T
Article history:
Metal (Al, Ti, Zr) triflate grafted mesoporous SBA‐15 (AlTf/S, TiTf/S, ZrTf/S) samples were synthe‐
sized as inexpensive solid acid materials by a simple one‐pot‐two‐step synthesis methodology.
These materials were characterized by X‐ray diffraction, N2‐sorption, thermogravimetric analysis,
Fourier transform infrared spectroscopy (FT‐IR), in‐situ pyridine FT‐IR spectroscopy, and elemental
analysis. ZrTf/S was found to be a highly efficient and reusable solid acid catalyst for ring opening of
epoxides with amines and alcohols and produced β‐amino alcohols and β‐alkoxy alcohols respec‐
tively under ambient reaction conditions. The ZrTf/S catalyst showed the highest activity, which
was attributed to its high acidity compared with that of the Ti and Al containing samples.
© 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Received 21 November 2016
Accepted 6 January 2017
Published 5 April 2017
Keywords:
Epoxide ring opening
Acid catalysis
Metal triflate
Grafted catalyst
Mesoporous silica
Published by Elsevier B.V. All rights reserved.
1. Introduction
unattractive considering their disadvantages, such as the use of
halogenated and/or toxic solvents and the difficultly of separa‐
Ring opening of epoxides is an important transformation in
organic synthesis because it provides access to valuable phar‐
maceuticals and intermediate chemicals [1–5]. Bifunctional
molecules of great significance can be synthesized by nucleo‐
philic attack of amines, azides, alcohols, and thiols on epoxide
rings. For example, β‐alkoxy alcohols are used as intermediates
for the synthesis of pharmaceutical compounds, such as anti‐
tumor and immunosuppressant drugs [6]. β‐Amino alcohols
are used for synthesizing β‐blockers, insecticidal agents, un‐
natural amino acids, chiral auxiliaries and oxazolines [2–5].
Several studies have reported the synthesis of β‐amino al‐
cohols and β‐alkoxy alcohols by aminolysis and alcoholysis of
epoxides, respectively, using homogeneous and heterogeneous
acid catalysts. However, homogeneous catalytic processes are
tion and poor reusability of the catalyst. Solid acid catalysts,
such as sulfonic acid functionalized SBA‐15 and Ti‐MCM‐41 [7],
Na‐Y zeolite [8], Cu‐MOF (Cu(bpy)(H2O)2(BF4)2(bpy)) [9],
mesoporous alumininosilicate [10], Fe(BTC) (where BTC is
1,3,5‐benzenetricarboxylate) [11], CuO/SiO2 [12], Ti‐SBA‐12
and Ti‐SBA‐16 [13], sulfonic acid functionalized mesoporous
carbon [14], graphite oxide [15], and mesoporous Zr‐beta zeo‐
lite [16], have been shown to be active and selective for ring
opening reactions of epoxides. However, these catalysts also
have some limitations, such as the need for longer reaction
times [7–15] and non‐ambient reaction conditions [11,12,14],
and tedious synthesis of the catalyst [7,16]. Therefore, the de‐
velopment of easy to synthesize, more efficient and environ‐
mentally benign catalysts is of great importance.
* Corresponding author. Tel/Fax: +86‐411‐84379728; E‐mail: sgao@dicp.ac.cn
This work was supported by the CAS President’s International Fellowship Initiative (2016PT028) and the National Natural Science Foundation of
China (21273225 and 21403219).
DOI: 10.1016/S1872‐2067(17)62794‐3| http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 38, No. 4, April 2017

Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
759
Metal triflates (especially triflates of lanthanides and transi‐
tion metals) have received considerable attention as excellent
Lewis acid catalysts for several organic reactions over the past
two decades [17–22]. Consequently, supported metal triflates
have also been synthesized and used for important ac‐
id‐catalyzed reactions allowing easy separation, good reusabil‐
ity and enhanced activity [23–30].It is generally preferable for
the catalyst to be chemically grafted to rather than physically
adsorbed to the support because of the greater stability of
chemically grafted systems. In our previous reports, we devel‐
oped an aluminum triflate grafted on MCM‐41 as a cost effec‐
tive and easily synthesizable catalyst, which showed high acid‐
ity and water tolerance in ketalization of glycerol with acetone
into solketal at room temperature [31]. In the present work,
metal triflates of Al, Zr, and Ti grafted on SBA‐15 mesoporous
silica (AlTf/S, TiTf/S, and ZrTf/S, respectively) were prepared.
We aimed to generalize our one‐pot‐two‐step synthesis meth‐
odology and widening the applications of metal triflate grafted
catalysts to epoxide ring opening reactions as a more efficient,
low cost and environmentally benign catalyst system. SBA‐15
mesoporous silica was chosen as the support owing to its high
pore size, thick framework walls and good hydrothermal sta‐
bility and inter‐channel connectivity [32].
°C for 20 h. The gel produced was transferred to a Teflon‐lined
stainless steel autoclave and maintained at 80 °C for 2 d for the
hydrothermal synthesis. After 2 d, a white solid formed which
was filtered, washed with distilled water and then dried at 100
°C overnight. The dry solid powder was then calcined at 550 °C
for 4 h under an air flow to remove the template and obtain the
final SBA‐15 material.
Trifluoromethane sulfonic acid (0.1 g) was dissolved in 25
mL of toluene. This solution was added to a solution containing
zirconium propoxide (70% in propanol; 0.2951 g) dissolved in
25 mL of toluene and allowed to react for 2 h at r.t. under stir‐
ring. Dried SBA‐15 (150 °C for 4 h, 1 g) was then added to this
solution and allowed to react for 24 h at r.t. The solid was then
filtered and washed with toluene and dichloro‐
methane/acetonitrile (v/v = 1). The solid powder was then
dried at 100 °C for 24 h to obtain zirconium triflate grafted on
SBA‐15 (ZrTf/S) samples. Titanium isopropoxide (0.1895 g)
and aluminum isopropoxide (0.1362 g) were used to prepare
the titanium and aluminum triflate grafted SBA‐15 (TiTf/S and
AlTf/S) samples in a similar manner. The metal/Si molar ratio
was maintained at 1/25 for all sample preparations. A sche‐
matic representation of the ZrTf/S synthesis is shown in
Scheme 1. The synthesized catalyst samples were used for
aminolysis and alcoholysis of various epoxides by amines and
alcohols, respectively (Scheme 2).
2. Experimental
2.1. Materials
2.3. Material characterization
Pluronic P123 (PEO‐PPO‐PEO) polymer was purchased
from Sigma. Zirconium propoxide (70%) in propanol was pro‐
cured form Alfa‐Aesar. Tetraethyl orthosilicate (TEOS), HCl
(35%), titanium tetraisopropoxide, aluminum isopropoxide, all
epoxides, amines and alcohols were purchased from Si‐
nopharm Chemical Reagents Co. Ltd, Energy Chemical and J & K
Scientific, China. All the chemicals were used as received with‐
out any purification.
Mesoporous SBA‐15 and the samples ZrTf/S, TiTf/S and
AlTf/S were characterized with the following analytical tech‐
niques. Powder X‐ray diffraction (XRD) analysis was performed
on a PANalytical X’Pert3 powder diffractometer with Cu Kα
radiation (λ = 1.5418 Å; 1 Å = 0.1 nm) in the 2θ range of 0.5° to
10° with a scanning rate of 0.02°/s. The N2 sorption at liquid
nitrogen temperature (–196 °C) for determination of pore size
and pore volume, and the BET surface area measurements
were performed on a Quantachrome Quadrasorb SI. The sam‐
ples were degassed at 180 °C for 4 h before the measurements.
The C, H, S elemental analysis was performed with a VarioEL
elemental analyzer. Metal content was determined by induc‐
tively coupled plasma atomic emission spectroscopy (ICP‐AES)
with a PerkinElmer OPTIMA 3300DV. A sample (50 mg) was
dissolved in 40% HF solution (5–10 drops) followed by addi‐
tion of a 5 wt% boric acid solution and made up to 100 mL in a
volumetric flask. The resulting solutions were then analyzed by
2.2. Synthesis of metal triflate grafted SBA‐15 samples
Mesoporous silica SBA‐15 was prepared by a reported
method using pluronic P123 polymer as template under acidic
conditions. Typically, 4 g of P123 was dissolved in 30 mL water
and 90 mL of HCl solution (2 mol/L). TEOS was added drop‐
wise with stirring to the polymer solution and allowed to stir at
room temperature for 15 min. The mixture was then aged at 40
Tf
Tf
Tf
O
O
#
#
OPr
Zr
O


OHOHOHOHOH
Zr
Zr
H
H
H
H
Zr
O O O O
O
Toluene
rt, 2 h
O O O O
O
PrO
PrO
Tf-OH
SBA-15
+
PrO
OPr
+
OPr
PrO
Tetrahedral
Zr triflate
Toluene
rt, 24 h
Octahedral
Zr triflate
Triflic acid
Zirconium
propoxide
monotriflate
Zirconium
propoxide
ZrTf/S
..
* Brosted acid site
# Lewis acid site
Scheme 1. One‐pot‐two‐step synthesis of ZrTf/S and diagram of the Brönsted (B) and Lewis (L) acid sites in the ZrTf/S sample.

760
Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
R'
HN
OH
H
Aminolysis
Alcoholysis
O
OH
+
N
+
+
R'
H2N
R
R
R'
R
Major product (A)
Minor product (B)
Epoxide
Amine
R''
O
SBA-15
ZrTf/S
TiTf/S
OH
O
O
+
OH
R
R
R''
R''
HO
R
Major product (C)
Minor product (D)
Epoxide
Alcohol
Scheme 2. Ring opening of epoxides by amines and alcohols to synthe‐
sis β‐amino alcohols and β‐alkoxy alcohols.
ICP‐AES. Thermogravimetric analysis (TGA) was performed
with a NETZSCH STA 449 F3 Jupiter under an air flow of 50
mL/min from 40 to 800 °C. Diffuse reflectance UV‐visible spec‐
troscopy was performed with a PerkinElmer LAMBDA 950
UV/Vis/NIR spectrophotometer at r.t.; samples were activated
at 100 °C for 1 h prior to the analysis. Fourier transform infra‐
red (FT‐IR) spectroscopy was performed with a Thermo Ni‐
colet iS50 FT‐IR spectrometer. In‐situ FT‐IR under vacuum with
pyridine‐adsorbed and pyridine‐desorbed samples at different
temperatures was performed with a Bruker TENSOR27 in‐
strument. A neat sample disk was evacuated at 10−2 Pa at 200
°C for 1 h followed by pyridine adsorption for 5 min. FT‐IR
spectra were then recorded after desorbing pyridine at 100,
150, and 200 °C for 20 min under vacuum. The acidity was cal‐
culated from the following equation:
AlTf/S
1
2
3
4
5
O
2 /( )
Fig. 1. Powder XRD patterns of SBA‐15 and metal triflate grafted on
SBA‐15 samples.
lowing equations:
Conversion = (Initial epoxide mass ‒ final epoxide
mass)/Initial epoxide mass  100%
Selectivity for A = GC Peak area of A/GC peak area of all the
products  100%
Similarly, selectivity for product B in aminolysis and selec‐
tivity for products C and D in alcoholysis reactions were calcu‐
lated.
C(B)= 1.88 IA(B)R2/W
C(L)= 1.42 IA(L)R2/W
where C is concentration of B or L sites (mmol/g), IA is the in‐
tegrated absorbance of B or L band (cm−1), R is the radius of
catalyst disk (cm), and W is the mass of the disk (mg).
3. Results and discussion
3.1. Characterization of AlTf/S, TiTf/S, and ZrTf/S samples
2.4. Catalytic evaluation of metal triflate grafted SBA‐15
samples
Various physicochemical characterization results are shown
in Table 1. Metal (Al, Zr, Ti) content as measured by ICP‐AES
showed a metal:Si ratio of 1:24.6, 1:26.5, and 1:24.9 for the
AlTf/S, TiTf/S, and ZrTf/S samples, respectively (Table 1). The
XRD patterns of the SBA‐15, ZrTf/S, TiTf/S, and AlTf/S revealed
characteristic reflections of a mesoporous structure showing
peaks for (100), (110), and (200) planes at low angles indicat‐
ing that the mesoporous structure of SBA‐15 was intact in all
the synthesized samples (Fig. 1). A decrease in the intensity of
the X‐ray reflection was indicative of grafting of the metal tri‐
flates. N2‐sorption results also revealed a type IV isotherm, and
a decrease in surface area, pore size, and volume indicate
grafting of the metal triflate moiety to the mesoporous struc‐
ture of SBA‐15 (Table 1, Fig. 2). The SBA‐15 sample showed the
Catalytic activity of the synthesized ZrTf/S, TiTf/S and
AlTf/S samples was evaluated by aminolysis and alcoholysis of
the epoxides. The epoxides were reacted with amines or alco‐
hols at defined reaction conditions in the presence of the acti‐
vated (100 °C, 2 h) catalyst samples prepared in this study. The
reaction mixtures were analyzed by gas chromatography (Ag‐
ilent 7890) with a GSBP‐5 non‐polar column and FID detector
for measuring epoxide conversion and product selectivity. The
products formed in the reactions were characterized by GC‐MS
(Agilent 9375MSD with 7890A GC) analysis and the data were
matched with those reported in the literature. Conversion of
epoxide and product selectivity was calculated from the fol‐
Table 1
Physicochemical properties of SBA‐15, ZrTf/S, TiTf/S, and AlTf/S samples.
CF3SO3− (mmol/g)
Pore volume
(cm3/g)
Amount of C by
CHS (mmol/g)
Amount of
acidity d
Material
SBET (m2/g)
Pore size (nm)
Si/metal a
By TGA b
By CHS c
SBA‐15
AlTf/S
TiTf/S
ZrTf/S
772
575
552
514
7.5
7.6
7.7
6.4
0.95
0.75
—
—
0.58
—
—
—
—
—
24.6
26.5
24.9
0.53
0.55
0.58
0.71
0.67
0.59
0.55
0.60
0.61
0.37
0.52
a From ICP‐AES analysis.
b Calculated from mass loss in TGA in temperature range 230–380 °C.
c Calculated from C, H, S elemental analysis.
d By FT‐IR of pyridine adsorbed samples after desorption at 200 °C under vacuum (10−2 Pa).

Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
761
700
600
500
400
300
200
100
ZrTf/S
SBA-15
AlTf/S
TiTf/S
ZrTf/S
TiTf/S
AlTf/S
SBA-15
4000 3600 3200 1800 1600 1400 1200 1000 800 600
0.0
0.2
0.4
0.6
0.8
1.0
Wavenumber (cm1)
p/p0
Fig. 4. FT‐IR spectra of SBA‐15, AlTf/S, TiTf/S, and ZrTf/S samples.
Fig. 2. N2 adsorption‐desorption isotherms of SBA‐15, ZrTf/S, TiTf/S,
and AlTf/S samples.
and that at ~1650 cm−1 was attributed to bending vibrations of
water molecules associated with surface silanol groups. These
characterization results confirmed the successful grafting of the
metal triflates onto the SBA‐15 mesoporous surface. Thus, it is
likely that our one‐pot‐two‐step metal triflate‐grafting ap‐
proach may be extended to other metal triflates [31].
highest BET surface area of 772 m2/g, which decreased to 575,
552, and 514 m2/g for the AlTf/S, TiTf/S, and ZrTf/S samples,
respectively, after the metal triflate was grated. The TGA analy‐
sis results revealed a mass loss of 0.58, 0.59, and 0.55 mmol/g
for the AlTf/S, TiTf/S, and ZrTf/S samples respectively in the
temperature range of 230 to 380 °C. This mass loss can be at‐
tributed to decomposition of the CF3SO3− moiety present in the
samples (Table 1; Fig. 3). The C, H, S elemental analysis showed
The FT‐IR spectrum measured after in‐situ pyridine adsorp‐
tion under vacuum showed bands at 1546 and 1640 cm−1,
which were assigned to the pyridinium ions adsorbed at B sites.
Bands at 1450 and 1610 cm−1 were assigned to pyridine ad‐
sorbed at L acid sites and a further band at 1490 cm−1 was as‐
signed to pyridine adsorbed to both B and L acid (B+L) sites
(Fig. 5) [36−38]. The greatest acidity was observed for ZrTf/S
(0.52 mmol/g) (Table 1) while TiTf/S and AlTf/S showed
slightly lower acidity (0.37 and 0.34 mmol/g, respectively). The
acidity reduced gradually with increasing desorption tempera‐
ture; however, even after desorption at 200 °C the samples
continued to show moderate strength and high acidity. UV‐vis
diffuse reflectance spectra revealed metal‐ligand (O2– and
−
the presence of 0.53, 0.55, and 0.58 mmol/g of the CF3SO3
moiety in the AlTf/S, TiTf/S, and ZrTf/S samples, respectively,
which is in accordance with the TGA results (Table 1). The
amount of C detected in the samples was consistent with the
amount of triflate added during synthesis and suggested nearly
complete reaction of the alkoxide metal precursor with triflic
acid and the silica surface. The FT‐IR spectra of these synthe‐
sized samples also showed characteristic absorption bands at
~580 and ~645 cm−1 attributed to the –CF3 asymmetric de‐
formation and SO3 symmetric deformation vibrations, respec‐
tively (Fig. 4) [33–35]. A very weak band observed at ~760
cm−1 was attributed to C–S stretching vibrations. IR bands at
~1290 and 1030 cm−1 were attributed to S =O stretching vibra‐
tions, which were observed as a shoulder in all samples (except
SBA‐15) merged with the characteristic Si–O–Si bands of silica
in the same region [7,33–35]. The strong and broad band be‐
tween 3600 and 3200 cm−1 was attributed to O–H stretching
−
CF3SO3 ) charge transfer interactions of the metal in the ZrTf/S,
TiTf/S, and AlTf/S samples (Fig. 6) [39−41]. The peak at ~220
nm indicated the presence of tetrahedral coordinated metal
centers (CF3SO3–M–(O–Si)3; M = Zr, Ti, Al). The broad absorp‐
tion band observed in all samples from around 260 to 300 nm
could be assigned to octahedral and pentahedral coordinated
metal centers generated from interactions with neighboring
0.9
AlTf/S
100
98
96
94
92
90
TiTf/S
ZrTf/S
L
0.6
0.3
B+L
B
200 o
C
0.0
0.9
0.6
0.3
150 oC
0.0
0.9
88
ZrTf/S
0.6
0.3
86
TiTf/S
100 o
C
84
AlTf/S
1450
1475
1500
1525
1550
1575
1600
1625
1650
100
200
300
400
500
600
700
800
Wavenumber (cm1)
Temperature (oC)
Fig. 5. FT‐IR spectra of pyridine adsorbed ZrTf/S, TiTf/S, and AlTf/S
samples indicating L and B acidic sites.
Fig. 3. TGA plots of synthesized ZrTf/S, TiTf/S, and AlTf/S samples.

762
Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
100
90
0.12
0.10
0.08
0.06
0.04
0.02
0.00
80
ZrTf/S
AlTf/S
TiTf/S
70
AlTf/S
TiTf/S
ZrTf/S
60
50
40
30
20
5
10
15
20
25
30
200
250
300
350
400
Wavelength (nm)
Reaction time (min)
Fig. 7. Comparison of catalytic activity of synthesized samples for
epoxide ring opening of styrene oxide by aniline. Reaction conditions:
styrene oxide (5 mmol), aniline (5 mmol), catalyst (25 mg), 35 °C.
Fig. 6. Diffuse reflectance UV‐visible spectra of ZrTf/S, TiTf/S, and
AlTf/S samples.
hydroxyl groups, as shown in Scheme 1.
3.2. Catalytic evaluation of metal triflate grafted on SBA‐15
samples for epoxide ring opening reaction
may reduce the product formation rate (Table 2). The solvent
had no significant effect on the selectivity of the products. The
reusability of the ZrTf/S sample was evaluated for four reaction
cycles. In the reusability study for aminolysis, the reaction
mixture was filtered after completion of the reaction to sepa‐
rate the used ZrTf/S. The used ZrTf/S sample was washed with
petroleum ether and activated at 100 °C for 2 h before the next
reaction cycle. In the aminolysis reaction, conversion of styrene
oxide and selectivity for the β‐amino alcohol were unaffected
(94% and 95%, respectively) after four cycles. For a reusability
study of alcoholysis, the reaction mixture was filtered after
completion of the reaction to separate the used ZrTf/S catalyst.
The ZrTf/S sample was directly activated at 100 °C for 2 h be‐
fore the next reaction cycle. The activity of ZrTf/S was also
unaffected after recycling for the alcoholysis reaction up to four
reaction cycles (98% conversion of styrene oxide and 96%
selectivity for β‐alkoxy alcohol (C+D)).
The catalytic activity of the AlTf/S, TiTf/S, and ZrTf/S sam‐
ples was compared for the ring opening of styrene oxide with
aniline (Fig. 7). The ZrTf/S sample clearly showed the highest
activity for this reaction giving 94% conversion of the epoxide
in 30 min, while the selectivity of all the samples was compara‐
ble (>96%). The highest activity of ZrTf/S may be attributed to
its stronger Lewis acidity (0.52 mmol/g) than those of the
TiTf/S and AlTf/S catalysts (Fig. 5).
3.2.1. Reaction condition optimization
For optimization of reaction conditions (Table 2), we ini‐
tially reacted styrene oxide with aniline in a 25‐mL round bot‐
tom flask at 25 °C in acetonitrile as a solvent in the presence of
25 mg of the activated (100 °C, 2 h) ZrTf/S sample. These con‐
ditions produced 52% conversion of the epoxide and 95% se‐
lectivity for the desired β‐amino alcohol products (A+B) at 25
°C. A similar reaction was performed in toluene and under con‐
ditions with no solvent. Under these reaction conditions 71%
conversion and 94% selectivity was observed in toluene, while
the reaction without solvent afforded 91% conversion of the
epoxide with 95% selectivity. At 35 °C we achieved an even
higher conversion of 94% with 96% selectivity. Thus, the cata‐
lytic performance of the ZrTf/S sample was better under sol‐
vent free conditions, which can be explained by the fact that
dilution of the reaction mixture in the solvent assisted reaction
Table 2
Reaction condition optimization for epoxide ring opening of styrene
oxide with aniline and with methanol catalyzed by ZrTf/S (25 mg)a.
Temp./Time
(°C/min)
25/30
Epoxide
conversion (%)
Selectivity
(%)
95
Entry
Solvent
1
2
3
acetonitrile
toluene
—
52
71
91
25/30
25/30
94
95
3.2.2. Aminolysis of epoxides with amines over ZrTf/S
4
35/30
35/30
35/30
35/30
35/30
35/10
35/10
—
—
—
—
—
—
—
—
94
95
93
93
94
100
98
99
100
98
96
97
96
96
95
98
96
95
Various epoxides were then reacted with amines in the
presence of the ZrTf/S sample at 35 °C and at an equimolar
ratio to explore the substrate scope (Table 3). Styrene oxide
reacted with aniline very efficiently to produce β‐amino alcohol
with 94% conversion of styrene oxide and 91% selectivity for
isomer A and 96% total selectivity for (A+B) in 0.5 h. Cyclo‐
hexene oxide reacted with aniline to selectively produce the
β‐amino alcohol with 89% conversion of the epoxide in 1 h. The
reactivity of styrene oxide was much higher than that of cyclo‐
hexene oxide because the intermediate carbocation formed
from styrene oxide is stabilized by resonance with the aromatic
ring and is highly susceptible to nucleophilic attack (Scheme 3).
5 (1st recycle)
6 (2nd recycle)
7 (3rd recycle)
8 (4th recycle)
9
10 (1st recycle)
11 (2nd recycle) 35/10
12 (3rd recycle) 35/10
13 (4th recycle) 35/10
—
—
99
96
a Entries 1–8: Styrene oxide (5 mmol), aniline (5 mmol); selectivity for
(A+B).
Entries 9–13: Styrene oxide (2 mmol), methanol (25 mmol); selectivity
for (C+D).

Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
763
Table 3
Aminolysis of epoxides with different amines using ZrTf/S (25 mg) at 35 °Ca.
Epoxide
(5 mmol)
Amine
(5 mmol)
Time
(h)
Epoxide conversion
(wt%)
Selectivity for A/B
Entry
1
(wt%)
O
0.5
94
91/5
H2N
H2N
2
3
4
5
6
O
O
O
O
O
1
3
3
3
89
88
79
78
12
100
97
99
99
83
Cl
H2N
H2N
CH3
OCH3
H2N
5
(at 45 °C)
H2N
O
5
7
19
61/7
H2N
(at 45 °C)
O
8
9
1
1
100
86
80/10
79/12
Cl
H2N
H2N
H2N
O
O
O
O
10
1
97
88/6
a Entries 2–6: product selectivity includes both stereoisomers (trans‐ and cis‐) and is calculated form GC.
-amino/ -alkoxy alcohol
Epoxide
R
Nu
R
R

R
Nucleophile
R'
O

O
O
R' Nu
OH
R' Nu
H
H
Carbocation
generation and
nucleophile attack
Epoxide adsorption
on acidic site
Protonation of "O"
of epoxide
Product desorption
= acidic site over ZrTf/S
Scheme 3. Plausible reaction pathway of epoxide ring opening reaction over ZrTf/S.
Similarly, the effect of nucleophilicity of the amine was ob‐
90%, 91%, and 94% total selectivity for (A+B).
served in the reaction of cyclohexene oxide with p‐Cl, p‐CH3,
and p‐OCH3 aniline, which afforded 88%, 79%, and 78% con‐
version with 97%, 99%, and 99% selectivity, respectively (Ta‐
ble 3). Cyclohexene oxide also reacted with cyclohexyl amine
giving 12% conversion and 83% selectivity after 5 h at 45 °C.
The low conversion may be explained by the strong adsorption
of the aliphatic amine to acidic sites of ZrTf/S, which caused
poisoning of the active sites and lowered product formation.
Styrene oxide with cyclohexyl amine also gave reduced product
conversion (19%) owing to a similar effect (Table 3). These
results demonstrate the excellent activity of the catalyst, even
in the presence of highly basic amines. Epichlorhydrin, al‐
lylglycidyl ether, and phenyl glycidyl ether also reacted with
aniline affording 100%, 86%, and 97% epoxide conversion
with 80%, 79%, and 88% selectivity for product isomer A, and
3.2.3. Alcoholysis of epoxides with alcohols
The ZrTf/S sample also catalyzed epoxide ring opening with
various alcohols efficiently at 35 °C (Table 4). Initially, cyclo‐
hexene oxide was reacted with methanol in an equimolar ratio
(1:1, 5 mmol), which resulted in 100% conversion of epoxide
but only 73% selectivity for the desired product. At higher mo‐
lar ratios of cyclohexene oxide to methanol (2:25 and 2:50), a
very high selectivity for the desired product (96% and 98%)
was achieved within 10 min (Table 4). Styrene oxide reacted
with methanol to give 100% conversion and 95% selectivity to
2‐methoxy‐2‐phenylethanol (product isomer C) at a 2:25 molar
ratio in 10 min. Although these conditions gave complete con‐
version, only 66% selectivity for product isomer C was
achieved at an equimolar ratio. The by‐product formed was

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Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
Table 4
Alcoholysis of epoxides with different alcohols catalyzed by ZrTf/S (25 mg) at 35 °Ca.
Time
(min)
10
Epoxide conversion
Selecitivity for C/D
Entry
1
Epoxide
Alcohol
(wt%)
100
100
100
100
72
100
99
(wt%)
98
96
73
89
30
77
39
2 mmol
2 mmol
5 mmol
2 mmol
5 mmol
2 mmol
5 mmol
CH3OH
50 mmol
25 mmol
5 mmol
25 mmol
5 mmol
25 mmol
5 mmol
O
OH
2
3
15
15
O
O
HO
OH
4
2 mmol
2 mmol
25 mmol
25 mmol
30
99
73
87
O
HO
5
6
20
10
100
O
O
2 mmol
5 mmol
CH3OH
100
100
95/3
66/2
25 mmol
5 mmol
O
O
O
OH
7
8
2 mmol
2 mmol
2 mmol
25 mmol
25 mmol
25 mmol
30
15
100
99
62/8
73/8
80/9
HO
HO
9
20
20
97
2 mmol
5 mmol
2 mmol
5 mmol
2 mmol
25 mmol
5 mmol
100
47
90/8
62/5
95/4
93/4
90/8
O
O
O
O
10
CH3OH
25 mmol
5 mmol
100
16
11
12
CH3OH
CH3OH
20
20
O
25 mmol
100
Cl
a Entries 1–5: Product selectivity includes both stereoisomers (trans‐ and cis‐) and is calculated form GC.
predominantly the acid catalyzed Meinwald rearrangement
product [10] (phenylacetaldehyde), which also highlights the
acidic nature of the catalytic sites on the ZrTf/S sample. Sec‐
ondary, tertiary, and benzylic alcohols also reacted with cyclo‐
hexene oxide as well as styrene oxide, to give complete conver‐
sion and excellent selectivity at a 2:25 ratio of epoxide to alco‐
hol. Cyclohexene oxide reacted completely with i‐propanol and
cyclohexanol giving 89% and 77% selectivity in 15 min. Simi‐
larly, t‐butanol and benzyl alcohol also reacted with cyclohex‐
ene oxide with 73% and 87% selectivity in 20 and 30 min, re‐
spectively (Table 4). Styrene oxide reacted with t‐butanol,
benzylalcohol, and cyclohexanol giving 62%, 73%, and 80%
selectivity for product isomer C and 70%, 81%, and 89% selec‐
tivity for (C+D), respectively, with nearly complete conversion.
Such remarkable catalytic activity at low epoxide to alcohol
molar ratios and at ambient reaction conditions makes our
ZrTf/S catalyst stand out from previously reported Cu‐MOF [9],
mesoporous aluminosilicate [10], Fe(BTC) [11], CuO/SiO2 [12],
and sulfonic acid functionalized mesoporous carbon [14] based
catalysts. Similarly, epichlorohydrin, allylglycidyl ether and
phenyl glycidyl ether reacted with methanol affording excellent
conversion (100%) and 90%, 90%, and 95% selectivity for
product isomer C and 98%, 99%, and 98% selectivity for (C+D)
in 20 min.
When the epoxide molecule adsorbs to the ZrTf/S catalyst,
acidic site is activated, which induces polarization causing
electron deficiency on the highest substituted carbon of the
epoxide ring (Scheme 3). The nucleophile (amine/alcohol) then
attacks this electron deficient carbon followed by protonation
of the epoxide O by a proton from the nucleophile to ultimately
form the final product β‐amino/β‐alkoxy alcohol.
4. Conclusions
We have successfully demonstrated a general one‐pot‐ two‐
step method for synthesis of metal triflate grafted mesoporous
silica catalyst. The ZrTf/S catalyst prepared in the study was
found to be easily synthesized, reusable and highly efficient for
catalysis of epoxide ring opening by alcohols and amines. The
ZrTf/S sample showed higher catalytic activity than the AlTf/S
and TiTf/S samples owing to its higher acidity. Furthermore,
high catalytic activity for epoxide ring opening with poor nu‐
cleophiles was obtained.
Acknowledgments
Authors are thankful to Chinese Academy of Sciences (CAS)
and Dalian Institute of Chemical Physics, CAS for providing
financial support and CAS President’s International Fellowship
Initiative funding.
3.2.4. Plausible reaction pathway

Kamlesh N. Tayade et al. / Chinese Journal of Catalysis 38 (2017) 758–766
765
Graphical Abstract
Chin. J. Catal., 2017, 38: 758–766 doi: 10.1016/S1872‐2067(17)62794‐3
Zirconium triflate grafted on SBA‐15 as a highly efficient solid acid catalyst for ring opening of epoxides by amines and
alcohols
Kamlesh N. Tayade, Lianyue Wang,Sensen Shang, Wen Dai, Manish Mishra, Shuang Gao *
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China; Dharmsinh Desai University, India
We report the synthesis of zirconium triflate grafted mesoporous SBA‐15 (ZrTf/S) using a simple one‐pot‐two‐step synthesis. ZrTf/S
showed excellent activity for ring opening of epoxides by various amines and alcohols under ambient conditions.
[17] S. Kobayashi, M. Sugiura, H. Kitagawa, W. W. L. Lam, Chem. Rev.,
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