Highly efficient and green chemical synthesis of imidazolyl alcohols and N-imidazolyl functionalized β-amino compounds using nanocrystalline ZSM-5 catalysts

Article abstract of DOI:10.1016/j.apcata.2014.03.006

A solvent free protocol is developed for the synthesis of imidazolyl alcohols and N-imidazolyl functionalized β-amino compounds. Imidazolyl alcohols were synthesized by the ring opening of epoxides with imidazoles and N-imidazolyl functionalized β-amino compounds were synthesized by the hydroamination reaction of imidazoles and activated olefins. These reactions were catalyzed by a variety of crystalline heterogeneous catalysts such as Al/Zr substituted nanocrystalline ZSM-5 (M-Nano-ZSM-5), conventional M-ZSM-5 (where M = Zr, Al), and Zr substituted amorphous mesoporous catalysts (Zr-SBA-15 and Zr-KIT-6). Among these catalysts, nanocrystalline Zr-Nano-ZSM-5 exhibited the highest activity and regioselectivity. Structure activity relationship is explained based on the catalytic activity, acidity measurements, reactivity of reactants (imidazoles/epoxides/methyl acrylate), competitive adsorption, nature, and type of catalysts. Zr-Nano-ZSM-5 exhibited exceptionally high catalytic activity compared to the catalysts reported in the literature for the synthesis of imidazolyl alcohols and other imidazole derivatives.

Full text of DOI:10.1016/j.apcata.2014.03.006

Applied Catalysis A: General 477 (2014) 8–17
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Highly efficient and green chemical synthesis of imidazolyl alcohols
and N-imidazolyl functionalized ␤-amino compounds using
nanocrystalline ZSM-5 catalysts
Rajkumar Korea, Biswarup Satpatib, Rajendra Srivastavaa,∗
a Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, India
b Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A solvent free protocol is developed for the synthesis of imidazolyl alcohols and N-imidazolyl function-
alized ␤-amino compounds. Imidazolyl alcohols were synthesized by the ring opening of epoxides with
imidazoles and N-imidazolyl functionalized ␤-amino compounds were synthesized by the hydroam-
ination reaction of imidazoles and activated olefins. These reactions were catalyzed by a variety of
crystalline heterogeneous catalysts such as Al/Zr substituted nanocrystalline ZSM-5 (M-Nano-ZSM-5),
conventional M-ZSM-5 (where M = Zr, Al), and Zr substituted amorphous mesoporous catalysts (Zr-SBA-
15 and Zr-KIT-6). Among these catalysts, nanocrystalline Zr-Nano-ZSM-5 exhibited the highest activity
and regioselectivity. Structure activity relationship is explained based on the catalytic activity, acidity
measurements, reactivity of reactants (imidazoles/epoxides/methyl acrylate), competitive adsorption,
nature, and type of catalysts. Zr-Nano-ZSM-5 exhibited exceptionally high catalytic activity compared
to the catalysts reported in the literature for the synthesis of imidazolyl alcohols and other imidazole
derivatives.
Received 22 January 2014
Received in revised form 28 February 2014
Accepted 3 March 2014
Available online 13 March 2014
Keywords:
Nanocrystalline zeolites
Zirconosilicates
Imidazolyl alcohols
Aminolysis
Hydroamination
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
complexes can be supported or encapsulated in the mesoporous
material for efficient recycling [12].
Heterocyclic compounds are building blocks of many bio-
logically important molecules such as deoxyribonucleic acid,
hemoglobin, chlorophyll, proteins etc. Heterocyclic compounds are
synthetic intermediates for the production of agrochemicals, drugs,
insecticides, herbicides, etc. [1]. 1,3-diazoles (imidazole deriva-
tives) are important heterocyclic synthetic precursor [2–4]. Among
imidazole derivatives, imidazolyl alcohols are one of the important
building blocks for the synthesis of antiprotozoal (metronidazole,
ornidazole, and secnidazole) and antifungal drugs (miconazole
and econazole) [5]. Compounds containing imidazole moiety play
important roles in the green chemistry and catalysis. Most of the
commercial ionic liquids and ionic liquids based research are based
on imidazole. Because of the functionalization ability of imidazole
ring, a wide range of ionic liquids were prepared and investigated
in the catalytic reactions [6–9]. Imidazole based ligands are known
to make a wide range of homogeneous complexes [10,11]. These
Several routes are known for the synthesis of imidazolyl alcohols
that include N-alkylation of imidazole and ring opening of epox-
ides with imidazole [13–18]. Among these, ring opening of epoxide
with imidazole nucleophile is the best synthetic route [14–18].
Epoxides are three-member heterocyclic ring that are more reac-
tive than ethers due to ring strain. When nucleophiles attack the
electrophilic C of the C O bond, ring opening of epoxide takes
place due to the cleavage of C O bond of epoxide. Ring opening
of epoxide with imidazole nucleophile is either un-catalyzed (but
occurs at very high temperature and high pressure) or catalyzed
by acid or base catalysts [14–18]. Catalysts reported for this reac-
tion are suffered from several disadvantages such as high pressure,
high temperature, longer reaction time (7 days), use of solvent,
use of excess amount of expensive reagents or catalysts, use of
microwave radiation, and in-efficient recycling of the catalyst. Very
recently, a three-step synthetic route is reported for the preparation
of imidazolyl alcohol, which involves: (a) silylation of imidazole,
(b) ring-opening of epoxide with silylated imidazole catalyzed by
LiBr, and (c) desilylation with KF [18]. Imidazole derivatives can
also be synthesized by the hydroamination reaction of imidaz-
ole and activated olefins using the acid/base catalysts [19–31].
∗
Corresponding author. Tel.: +91 1881 242175; fax: +91 1881 223395.
E-mail addresses: rajendra@iitrpr.ac.in, chemi rajendra@yahoo.co.in
(R. Srivastava).
http://dx.doi.org/10.1016/j.apcata.2014.03.006
0926-860X/© 2014 Elsevier B.V. All rights reserved.

R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
9
Catalysts reported for this reaction are suffered from one or more
disadvantages such as longer reaction time (24 h), use of solvent,
use of excess amount of expensive reagents or catalysts, and in-
efficient recycling of the catalyst. Therefore, it is very important
to develop one-step, economical, and reusable catalyst based syn-
thesis methodology for the preparation of imidazolyl alcohols and
other imidazole derivatives.
were prepared using ZrIPO by following the reported procedures
[47,48].
2.2. Material characterization
X-ray diffraction (XRD) patterns were recorded in the 2ꢀ range
of 5–60◦ for wide angle and 0.5–5◦ for low angle with a scan
speed of 1◦/min on a PANalytical X’PERT PRO diffractometer
using Cu K␣ radiation (ꢁ = 0.1542 nm, 40 kV, 40 mA) and a pro-
portional counter detector. N2 adsorption measurements were
performed at 77 K by Quantachrome Instruments Autosorb-IQ
volumetric adsorption analyzer. Sample was out-gassed at 573 K
for 3 h in the degas port of the adsorption apparatus. The spe-
cific surface area of zeolites was calculated from the adsorption
data points obtained at P/P0 between 0.05 and 0.3 using the
Brunauer–Emmett–Teller (BET) equation. The pore diameter was
estimated using the Barret–Joyner–Halenda (BJH) method. Scan-
ning electron microscopy (SEM) measurements were carried out on
a JEOL JSM-6610LV to investigate the morphology of the zeolites.
The detailed TEM structural analysis of the developed morpholo-
gies were carried out using FEI, Tecnai G2 F30, S-Twin microscope
operating at 300 kV equipped with a GATAN Orius CCD cam-
era. High-angle annular dark field scanning transmission electron
microscopy (HAADF-STEM) employed here using the same micro-
scope, which is equipped with a scanning unit and a HAADF
detector from Fischione (model 3000). The compositional analy-
sis was performed by energy dispersive X-ray spectroscopy (EDS,
EDAX Instruments) attachment on the Tecnai G2 F30. The sample
was dispersed in ethanol using ultrasonic bath, mounted on a car-
bon coated Cu grid, dried, and used for TEM measurements. Acidity
was examined by temperature-programmed desorption (TPD) with
ammonia using a Quantachrome Autosorb-IQ. Before TPD experi-
ments, catalyst was pre-treated in He (50 mL/min) at 873 K for 1 h.
After cooling down to 343 K, a mixture of NH3 in He (10:90) was
passed (75 mL/min) at 343 K for 1 h. Then, the sample was sub-
sequently flushed by He stream (50 cm3/min) at 373 K for 1 h to
remove physisorbed ammonia. The TPD experiments were carried
out in the range of 373–973 K at a heating rate of 10 K/min. The
ammonia concentration in the effluent was monitored with a gold-
plated, filament thermal conductivity detector. Fourier transform
infrared (FTIR) spectra were recorded on a Bruker spectropho-
Our research is focused on the synthesis of ionic liquid and
zeolite based catalysts and finds their applications in the selec-
tive synthesis of important organic molecules. Among the ionic
liquid and zeolite based catalysts, zeolite based catalysis is more
attractive due to user-friendliness, easy recovery, and recyclabil-
ity. Zeolites have been given significant attention due to their acidic
properties, shape selectivity, and redox properties (obtained by the
isomorphous substitution of transition metal ions in the frame-
work) [32–34]. However, the application of conventional zeolite
is limited in the synthesis of large organic molecules due to the
pore diffusion limitations. To overcome this problem, our group
and other catalysis/material scientists have developed synthesis
strategies for the preparation of nanocrystalline zeolites having
inter/intra-crystalline mesopores that enhance the diffusion of
reactant/product molecules and improve the lifetime of catalyst
[35–46]. A variety of ionic/non-ionic/polymeric soft templates and
hard templates (based on silica and carbon materials) have been
reported for the synthesis of nanocrystalline zeolites [42–46].
In this study, one-step, eco-friendly, solvent free catalytic route
is reported for the synthesis of imidazolyl alcohols using Al/Zr con-
taining nanocrystalline ZSM-5 catalysts (hereafter represented as
M-Nano-ZSM-5, where M = Al, Zr) (Scheme 1). Application of these
catalysts is extended in the synthesis of other imidazole deriva-
tives by the hydroamination reaction of imidazole and activated
olefin (Scheme 1). For comparative study, microporous ZSM-5 cata-
lysts (M-ZSM-5) and amorphous mesoporous zirconosilicates (such
as Zr-SBA-15 and Zr-KIT-6) were also investigated. Zr-Nano-ZSM-
5 exhibited exceptionally high catalytic activity compared to the
catalysts reported in the literature for the synthesis of imidazolyl
alcohols and other imidazole derivatives.
2. Experimental
2.1. Material preparation
tometer in the region 400–4000 cm−1 (spectral resolution = 4 cm−1
;
number of scans = 200). Samples were prepared in the form of
KBr pellets (1 wt.%). Diffuse reflectance UV–visible (DRUV–vis)
measurements were conducted using a Shimadzu UV-2550 spec-
trophotometer equipped with an integrating sphere attachment
(ISR 2200). Spectral grade BaSO4 was used as a reference mate-
rial. 1H/13C NMR spectra were recorded on a JEOL (JNM-ECS400
Spectrometer; 400 MHz).
2.1.1. Synthesis of nanocrystalline ZSM-5 catalysts
In a typical synthesis of Zr-Nano-ZSM-5, required amount
of zirconium (IV) isopropoxide (ZrIPO) was added to 23.72 g
of tetraethylorthosilicate (TEOS) and the resultant solution was
stirred for 15 min under ambient condition until reaction mix-
ture becomes clear solution (Solution A). PrTES (PrTES = propyl
triethoxy silane) (1.74 g) was mixed with TPAOH (42.7 g) to form
solution B. Solution A was added slowly to the solution B, fol-
lowed by the addition of 52 mL of distilled water. The resultant
gel was further homogenized for 3 h under stirring. The reaction
mixture was transferred to a Teflon-lined stainless steel autoclave,
and hydrothermally treated at 443 K for 5 days under static condi-
tions. The final product was filtered, washed with distilled water,
and dried at 373 K. Material was calcined at 823 K for 15 h under
air for surfactant removal to obtain Zr-Nano-ZSM-5. Materials pre-
pared with different Si/Zr ratio are represented as Zr-Nano-ZSM-5
(x), where x = Si/Zr ratio.
2.3. Procedure for catalytic reactions
For the synthesis of imidazolyl alcohols, equimolar amounts
(5 mmol) of epoxide and imidazole were taken in
a 50 mL
round-bottomed flask. Required amount of catalyst was added
to the reaction mixture and the reaction flask was placed in a
temperature-controlled oil bath. The reaction flask was attached
to a water-cooled condenser. The reaction was conducted at a
specific temperature for a desired period of time. The progress of
the reaction was monitored by gas chromatograph. Products were
characterized by using various spectroscopic tools that matched
well with the reported literature [13–17].
For the synthesis of other imidazole derivatives reported in
this study, reactions were performed by reacting activated olefins
(3 mmol) and imidazoles (2 mmol). A known amount of catalyst
was added to the reaction mixture and reaction flask was placed in
Al-Nano-ZSM-5 (50) was synthesized by following the reported
procedure using PrTES as an additive [39]. Conventional Zr-ZSM-5
(50) and Al-ZSM-5 (50) were synthesized using the similar proce-
dure that was adopted for the preparation of Zr-Nano-ZSM-5 (50)
and Al-Nano-ZSM-5 (50), respectively, but in the absence of PrTES.
For comparative study, mesoporous Zr-KIT-6 and Zr-SBA-15 (50)

10
R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
Scheme 1. Proposed mechanism for the (a and b) ring opening of epoxide with strong/weak nucleophiles, and (c) hydroamination reaction over metallosilicate catalyst.
a temperature-controlled oil bath. The reaction flask was attached
to a water-cooled condenser. The reaction was conducted at a spe-
cific temperature for a desired period of time. The progress of
the reaction was monitored by gas chromatograph. Products were
characterized by using various spectroscopic tools that matched
well with the reported literature [19–31].
with H1 hysteresis loops (Fig. S1b), which matched well with the
reported literature [47,48]. Surface area and pore volume obtained
from the sorption data are provided in Table 1.
Zr-ZSM-5 (50) exhibited capsule like morphology with a par-
ticle size of approximately 100 nm, whereas Zr-Nano-ZSM-5 (50)
exhibited irregular aggregated nanoparticle morphology (Fig. S2).
SEM image of Zr-SBA-15 (50) shows many wheat-like aggregated
microstructures, whereas Zr-KIT-6 exhibited irregular flake like
morphology (Fig. S2). Detailed nanostructure is already reported
for the conventional M-ZSM-5, Zr-SBA-15, and Zr-KIT-6 [47,48].
Catalytic investigation (described below) confirms that Zr-Nano-
ZSM-5 (50) exhibited the highest activity; therefore in-depth study
was made for Zr-Nano-ZSM-5 (50) using HR-TEM.
TEM image of Zr-Nano-ZSM-5 (50) shows the irregular aggre-
gated nanoparticle morphology with 10–20 nm particle size (Fig. 2a
and b). To investigate the chemical composition of the dots and
surrounding matrix, high-angle annular darkfield (HAADF) analysis
was performed (Fig. 2c). It provides the Z-contrast image, where the
intensity of scattered electrons is proportional to the square of the
atomic number Z. EDX spectrum from a region marked by yellow
area in Fig. 2c confirms the presence of O, Zr, and Si atoms (Fig. 2d).
Comparison of concentrations across the structure was made by
EDX line profile. The representative EDX line profile across the line
shown in Fig. 2c shows the elemental distribution of Si, O, and Zr
(Fig. 2e–h).
3. Results and discussion
3.1. Catalyst characterization
XRD patterns of M-Nano-ZSM-5 and conventional M-ZSM-5
samples were found to be identical and show the characteristic
peaks of crystalline MFI framework structure (Fig. 1a) [39]. The
low-angle XRD patterns of the mesoporous Zr-KIT-6 and Zr-SBA-
15 samples are consistent with the reported literature (Fig. S1a)
[47,48]. Furthermore, only a broad, wide-angle XRD patterns in the
2ꢀ range of 22–26◦ were observed, which confirm that Zr-KIT-6 and
Zr-SBA-15 are amorphous in nature.
Zr-Nano-ZSM-5 (50) exhibited type-IV isotherm similar to that
of mesoporous materials (Fig. 1b). The major difference between Zr-
Nano-ZSM-5 isotherm and Zr-ZSM-5 isotherm is a distinct increase
of N2 adsorption in the region 0.4 < P/P0 < 0.9, which is interpreted
as a capillary condensation in mesopore void spaces. The meso-
pores show a broad pore size distribution in the range of 5–50 nm
(inset of Fig. 1b). The N2-adsoption investigation reveals that the
external surface area and pore volume of Zr-Nano-ZSM-5 (50) are
much higher than that of conventional Zr-ZSM-5 (50) (Table 1). Zr-
SBA-15 (50) and Zr-KIT-6 (50) samples exhibited type IV isotherms
Zr-Nano-ZSM-5 (50) and Zr-ZSM-5 (50) exhibited UV absorp-
tion band in the range of 205–210 nm and a less distinguished
overlapped absorption in the range of 215–230 nm (Fig. 1c).
UV absorption band in the range of 205–210 nm is attributed

R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
11
500
0.75
(b)
Zr-ZSM-5
(a)
450
0.60
Zr-Nano-ZSM-5
Al-Nano-ZSM-5
Zr-Nano-ZSM-5
400
350
300
250
200
150
100
50
0.45
0.30
0.15
0
20
40
60
Pore size (nm)
Zr-ZSM-5
Al-ZSM-5
40
0.0
0.2
0.4
0.6
0.8
1.0
10
20
30
50
Relative pressure (p/p0)
Zr-Nano-ZSM-5
960
(d)
(c)
Zr-ZSM-5
800
ZSM-5
550
Zr-Nano-ZSM-5
Zr-ZSM-5
1228
1100
200
250
300
350
400
450
500
1400
1200
1000
Wavenumber8(0c0m-1)600
Wavelength (nm)
Fig. 1. (a) Wide angle XRD patterns, (b) N2-adsorption isotherms (inset shows pore size distribution), (c) Diffuse reflectance UV–vis spectra, and (d) FT-IR spectra of
Zr-Nano-ZSM-5 (50) and Zr-ZSM-5 (50).
to mono-atomically dispersed Zr4+ ions in tetra-coordinated
geometry, whereas the absorption in the range of 215–230 nm
corresponds to Zr(OH)(OSi)3 structure [49]. These absorption
bands arise due to ligand-to-metal (O2− → Zr4+) charger transfer
transitions. The electronic transition for Zr(OH)(OSi)3 occurs at
lower energy (at higher wavelength) than that of Zr(OSi)4 due to
the differences in the electron donating capacities of OH− and OSi−
ligand groups (electron donating capacity of HO− > OSi−). Hence,
Table 1
Textural properties of metallosilicates synthesized in this work.
b
Materials
Si/Ma
Input
SBET (m2/g)
Ext. SA (m2/g)
VTotal (mL/g)
Total acidityc (mmol/g)
Output
Al-ZSM-5 (50)
Al-Nano-ZSM-5 (50)
Zr-ZSM-5 (50)
Zr-Nano-ZSM-5 (50)
Zr-SBA-15 (50)
Zr-KIT-6 (50)
50
50
50
50
50
50
50
52.4
52.8
61.5
57.8
59.1
58.4
58.5
332
535
463
565
920
1040
542
71
255
130
260
740
810
256
0.26
0.57
0.27
0.55
1.43
1.78
0.51
1.34
1.19
0.77
0.83
0.61
0.65
0.85
Zr-Nano-ZSM-5 (50) (recycled catalyst)
a
Obtained by ICP analysis.
b
SBET calculated from the adsorption data obtained in the region of 0.05 < P/P0 ≤ 0.3.
c
Obtained by NH3 TPD analysis.

12
R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
Fig. 2. (a and b) TEM image, (c) HAADF image, (d) EDX spectrum of the area highlighted in panel (c), and (e–h) EDX line profile of the line shown in panel (c) for Zr-Nano-ZSM-5
(50).
the energy gap between oxygen and Zr molecular orbitals is lower
in the case of Zr(OH)(OSi)3 than that of Zr(OSi)4. The UV absorp-
tion band of Zr-SBA-15 (50) and Zr-KIT-6 (50) samples matched
well with the reported spectra [47,48]. These material exhibited
UV absorbance in the range of 205–215 nm and a less distinguished
overlapped absorption in the range of 215–250 nm. In addition to
these absorptions, an additional weak absorption band centered at
280 nm was also observed for Zr-SBA-15/Zr-KIT-6, which can be
correlated to extra framework ZrO2 species [47,48].
Temperature programmed desorption of ammonia (NH3-TPD)
was employed to gain insights into the acidity of the solid materi-
als investigated in this study (Table 1). As shown in Table 1, the
acidity of Zr containing materials was found to be less than Al
containing materials. The order of total acidity of various catalysts
prepared with Si/M = 50 was found to be Al-ZSM-5 > Al-Nano-ZSM-
5 > Zr-Nano-ZSM-5 > Zr-ZSM-5 > Zr-KIT-6 > Zr-SBA-15.
3.2. Catalytic activity
FT-IR spectra of various materials investigated in this study
exhibited common peaks at 800 cm−1, 1100 cm−1, and 1230 cm−1
(Fig. 1d) [50]. The absorption at 550 cm−1 observed in the case of
M-Nano-ZSM-5 and M-ZSM-5 is due to the pentasil framework
vibration of MFI framework structure. This peak was not observed
in the FT-IR spectra of Zr-SBA-15 and Zr-KIT-6 (Fig. S1c). The
3.2.1. Synthesis of imidazolyl alcohols
Imidazolyl alcohols were synthesized by the ring opening of
epoxide with imidazole (aminolysis reaction) in the presence of
various catalysts prepared in this study (Table 2). To optimize the
reaction condition, styrene oxide and imidazole were chosen. Two
isomerized products A and B were obtained by the ring opening
of styrene oxide with imidazole (Scheme 1). Under our reaction
condition, only trace amount of product (<1%) was obtained in
the absence of catalyst (Table 2). Both, the nature and type of the
catalyst influenced the epoxide conversion and product selectiv-
ity. Zr-ZSM-5 (50) was found to be more active than Al-ZSM-5
(50), which is reverse the acidity order obtained from NH3-TPD
(Table 2). This result suggests that Zr incorporation in the frame-
work is favorable for the synthesis of imidazolyl alcohols by the
ring opening reaction of epoxide. Nanocrystalline ZSM-5 materials
absorption peak at 800 cm−1 is due to Si
ing, and absorption peaks at 1100 cm−1 and 1230 cm−1 are assigned
to asymmetric stretching of Si Si. It may be noted that no FT-
O Si symmetric stretch-
O
IR signal was observed at 960 cm−1 for Si-ZSM-5 sample. Whereas,
a weak IR absorption at 960 cm−1 for Zr containing ZSM-5 mate-
rials and a sharp but low intense peak at 970 cm−1 was observed
for Zr-SBA-15/Zr-KIT-6. This FT-IR peak confirmed the incorpora-
tion of metal ions in the framework structure and assigned to an
asymmetric stretching mode of a [SiO4] unit bonded to a Zr4+ ion
(O3Si
O Zr) [50].

R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
13
Table 2
Comparative catalytic activity of various metallosilicates in the synthesis of imidazolyl alcohols.
.
E. N.
Catalyst
Nucleophile (R)
Epoxide
Conv. (%)
Product sel. (%)
Average TOF (h−1
)
A
B
1
2
3
4
5
6
7
8
9
None
Al-ZSM-5 (50)
H
H
H
H
H
H
H
H
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = Ph
Rꢀ = CH3
Rꢀ = Ph
<1%
8
–
–
68
63
62
83
88
88
86
81
82
84
90
88
37
38
17
12
12
14
19
18
16
10
12
Al-Nano-ZSM-5 (50)
Zr-ZSM-5 (50)
Zr-Nano-ZSM-5 (30)
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (100)
Zr-SBA-15 (50)
15
49
96
82
61
31
30
52
31a
43a
131
491
576
774
1084
298
285
491
293
406
Zr-KIT-6 (50)
H
CH3
H
10
11
12
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (50)
H
13
Zr-Nano-ZSM-5 (50)b
H
78
736
Reaction conditions: catalyst (25 mg), imidazole (5 mmol), styrene oxide (5 mmol), reaction temperature (318 K), reaction time (45 min).
Average TOF (h−1) = Turnover frequency [moles of styrene oxide converted per mole of active metal (Zr/Al) per hour].
a
Reaction temperature (303 K).
Only one product was obtained.
b
exhibited higher catalytic activity than that of conventional ZSM-
5 materials. Among all ZSM-5 materials investigated in this study,
Zr-Nano-ZSM-5 exhibited the highest catalytic activity. Intercrys-
talline mesopores and large external surface area of nanocrystalline
ZSM-5 provide better accessibility of the reactant molecules to
the active sites and facile diffusion of product molecules through
mesopores, compared to the conventional ZSM-5 materials. Fur-
ther catalytic investigation reveals that amorphous mesoporous
Zr-SBA-15 (50) and Zr-KIT-6 (50) exhibited less activity than Zr-
Nano-ZSM-5 (50). This result confirms that Zr incorporation in the
crystalline zeolite framework is required for high activity.
Influence of reaction parameters such as role of solvent, reac-
tion temperature, amount of catalyst, Si/Zr ratio were investigated
by taking Zr-Nano-ZSM-5 (50) as a catalyst, styrene oxide and imid-
azole as model substrates. Catalytic activity of Zr-Nano-ZSM-5 (50)
was found to be significantly higher in the absence of solvent, when
compared to the reactions performed in a solvent medium (Table
S1). This reduction in the catalytic activity can be correlated to
the competitive adsorption of reactant and solvent molecules. This
competitive adsorption creates obstacle for the reactant molecules
to reach active sites in the presence of solvent molecule; therefore,
catalytic activity was decreased. When the reaction was performed
under solvent free condition, only reactant molecules are acces-
sible to the active sites and high catalytic activity was achieved.
With increase in the temperature from 303 to 333 K, conversion of
styrene oxide increased from 43 to 94 mol% (Fig. S3). Amount of
catalyst influences the conversion of styrene oxide. With increase
in the amount of catalyst, epoxide conversion increased (Fig. S3).
However, when average TOF was taken into account, catalytic activ-
ity obtained with 25 mg of catalyst was found to be better than
that of 50 mg of catalyst for 5 mmol of styrene oxide. Influence
of Si/Zr molar ratio shows that catalyst prepared with high Si/Zr
ratio exhibited higher activity (Compare average TOF of entries 5–7,
Table 2). This result confirmed that all Zr sites present in the cat-
alyst (prepared with high Si/Zr) are involved in the reaction. The
comparative catalytic activity data summarized in Table 3 shows
that nanocrystalline Zr-Nano-ZSM-5 investigated in this study
exhibited significantly higher activity than various catalysts
reported in the literature for the aminolysis reaction of imidazole
with styrene oxide.
It is known in the literature that Lewis acid catalyst provides
good selectivity for amino alcohol A, when strong nucleophile is
used. Strong nucleophile attacks the least hindered carbon of epox-
ide and follows SN2 mechanism to produce amino alcohol A. In
contrast, high selectivity for amino alcohol B was obtained when
weak nucleophile was reacted with epoxide. Weak nucleophiles
are susceptible to attack on the stable carbocation formed by the
epoxide (Scheme 1a and b) [15]. To evaluate the scope of this reac-
tion for the synthesis of a wide range of imidazolyl alcohols, various
epoxides (propylene oxide, cyclohexene oxide, and styrene oxide)
and imidazoles (imidazole and 2-methyl imidazole) were cho-
sen. Order of catalytic activity for imidazole and various epoxides
follows the order: styrene oxide > cyclohexene oxide > propylene
oxide (Table 4). When the reaction of styrene oxide with various
amines was analyzed, it was found that the reactivity and selectivity
can be correlated with the basicity of the amines (strong nucleo-
philes/higher basic amines have higher pKa value) (Table 4). Strong
nucleophiles produced high selectivity for product A (but with low
average TOF), whereas weak nucleophiles produced high selectivity
for product B (with high average TOF). The reactivity difference can
be explained by the competitive adsorption of amines and styrene
oxide over Zr-Nano-ZSM-5 (50) (Table 4). FT-IR provides evidence
that imidazole is preferentially adsorbed on the catalyst surface
during the ring opening reaction of imidazole and styrene oxide
(Fig. S4). When the relative adsorption ratio of amine/styrene oxide
was found to be greater than 2, then product A was found in higher
selectivity than product B. Competitive adsorption study provides
evidence for the difference in the product selectivity observed for
weak and strong nucleophiles (Table 4). In the first step, strong
nucleophiles (for example imidazole) adsorbed on the active sites
and the adsorbed nucleophiles attack on the less hindered side
of styrene oxide (either adsorbed or present in the bulk) to form
more selective product A. While, in the case of weak nucleophile
(aniline), it was less adsorb on the active sites when compared to

14
R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
Table 3
Comparative catalytic activity data for the aminolysis and hydroamination reactions over various catalysts reported in the literature with Zr-Nano-ZSM-5 (50).
Ring opening reaction of styrene oxide with imidazole
E. No.
Catalyst
Solvent
Temp./time
Styrene oxide conv. (%)
Lit. Ref.
1
2
3
4
5
6
SiO2 with high pressure (10 kbar)
High pressure (10 kbar)
CH3CN
CH3CN
Neat
Neat
CH3OH
Neat
RT/7 days
338 K/3 days
RT/24 h
360/510 W with pressure
333 K/6 h followed by RT/3 h
318 K/45 min
47
60
90
60
78
96
[14]
[15]
[17]
[16]
[18]
This work
Y(NO3)3·6H2O
Microwave irradiation (360/510 W)
Steps involved: (a) silylation, (b) LiBr, and (c) desilylation with KF
Zr-Nano-ZSM-5 (50)
Hydroamination reaction of imidazole with methyl acrylate
E. No.
Catalyst
Solvent
Temp./time
Yield of product [C] (%)
Lit. Ref.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
KF/Al2O3
CH3CN
Neat
Neat
Neat
Neat
DMF
CH3CN
Neat
Neat
Neat
RT/18 h
323 K/6 h
RT/6 h
96
85
90
93
90
90
95
0
90
92
50
52
89
96
[19]
[24]
[26]
[27]
[28]
[29]
[25]
[30]
[20]
[21]
[22]
[23]
[31]
This work
[Ti4H11(PO4)9]·nH2O
Bmim]OH
[Bmim]Im
Cu(acac)2in [bmim][BF4]
PS–imCuI
RT/1 h
333 K/8 h
348 K/4 h
RT/14 h
RT/2 h
RT/24 h
RT/45 min
RT/9 h
333 K/4 h
RT/6.5 h
318 K/5 min
DBU
[DBU]-derived ionic liquid
Y(NO3)3·6H2O
Vanadyl(IV) acetate
I2
Silica-supported AlCl3
PEG-400 as solvent
Zr-Nano-ZSM-5 (50)
CH2Cl2
Neat
0.5 mL of PEG-400
Neat
styrene oxide. Styrene oxide is adsorbed on the active acid sites to
form stable carbocation, which was attacked by the weak nucle-
ophile (either adsorbed or present in solution) to form product B
in the high selectivity. As shown in Table 4, strong nucleophile
(having pKa > 7) such as imidazole, butylamine, and cyclohexy-
lamine afforded high selectively for product A, while weak
nucleophile (pKa < 7) such as aniline afforded higher selectivity for
product B.
Further, the aminolysis reaction of styrene oxide (5 mmol)
with equimolar amount of imidazole (2.5 mmol) and 2-methyl
imidazole (2.5 mmol) was investigated. Table 5 shows that aminol-
ysis products (6 + 7) selectivity obtained by the reaction of
imidazole and styrene oxide was found to be more than the
products (8 + 9) selectivity obtained by the reaction on 2-methyl
imidazole and styrene oxide. This confirms the high reactivity
of imidazole when compared to 2-methylimidazole. Similarly,
Table 4
Competitive adsorption of styrene oxide & various nucleophiles (along with pKa) at Zr-Nano-ZSM-5 (50) and the catalytic activity for the ring opening reaction of styrene
oxide with these nucleophiles.
.
Adsorbent
(SO + Nu)
Amount adsorbed
mmol/g catalyst
Relative adsorption ratio: amine/SO
Average TOF (h−1
)
Product selectivity (%)
pKa value of amine
Amine
0.56
SO
0.04
14.0
2.2
774a
101a
88
86
12
14
14.5
10.6
0.38
0.36
0.14
0.17
0.17
0.18
2.1
100a
85
4
15
96
10.6
4.1
0.77
7040b
25 mg of Zr-Nano-ZSM-5 (50) was suspended for 15 min in equimolar amounts (1 mmol) of styrene oxide (SO), amines as a nucleophile (Nu) dissolved in 5 mL of
dichloromethane as a solvent and addition n-decane (1 mmol) used for standard. The catalyst was, then, separated and the concentration of the substrate in the liquid
portion was determined by gas chromatography. The amount adsorbed on the catalyst surface was determined by difference.
Average TOF (h−1) = Turnover frequency [moles of epoxide converted per mole of active Zr per hour].
a
Average TOF at 318 K after 45 min of the reaction.
Average TOF at 318 K after 5 min of the reaction.
b

R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
15
Table 5
Competitive aminolysis reactions of substituted imidazole and epoxides over Zr-Nano-ZSM-5 (50).
.
Nucleophiles(mmol)
Epoxides (mmol)
Conv. (%)
Product selectivity (%)
(1)
(2)
(3)
(4)
(5)
(6) + (7)
(8) + (9)
(10) + (11)
(12)
2.5
5
5
2.5
–
–
5.0
2.5
2.5
–
2.5
–
–
–
2.5
42
61
55
52
39
–
–
–
45
–
–
–
48
21a
41
Reaction conditions: Zr-Nano-ZSM-5 (50) (25 mg), reaction temperature (318 K), reaction time (45 min).
Average TOF (h−1) = Turnover frequency [moles of epoxide converted per mole of active metal Zr per hour].
a
Reaction temperature (303 K).
aminolysis reaction of imidazole (5 mmol) with equimolar amount
of styrene oxide (2.5 mmol) and propylene oxide/cyclohexene
oxide (2.5 mmol) was investigated. Catalytic activity data shown
in Table 5 confirms that the different ratio of the observed prod-
ucts is due to the different reactivity of epoxides. Reactivity of
propylene oxide is less compared to styrene oxides, therefore more
selectivity was observed for the products obtained from the aminol-
ysis reaction of styrene oxide and imidazole when compared to
propylene oxide and imidazole. Based on the amount of prod-
ucts obtained by the aminolysis reaction of imidazole and styrene
oxide/cyclohexene oxide, one can conclude that both epoxides have
almost similar reactivity toward imidazole.
TOF of entries 5–7, Table 6). The comparative catalytic activity data
summarized in Table 3 shows that nanocrystalline Zr-Nano-ZSM-
5 investigated in this study is more active than various catalysts
reported in the literature for the hydroamination reaction of methyl
acrylate with imidazole.
Imidazole is activated at the acid sites of zeolite (I) in the first
step to form intermediate (II) by acid-base interaction, followed by
Michael addition of methyl acrylate to give the intermediate (III)
(Scheme 1c). The intermediate (III), then, releases the anti-adduct
(product IV) to regenerate acid sites of the catalyst (I). Let’s assume
that methyl acrylate is adsorbed at acid sites of zeolite catalyst,
which is followed by the formation of corresponding cation. In this
mechanism, unfortunately, nucleophile (imidazole) attacks pref-
erentially to the ␣-carbon of methyl acrylate to give Markovnikov
adduct. But this second possibility is ruled out in our study, because
no Markovnikov adduct was formed. Since our catalyst is an acid
catalyst, therefore, the adsorption of imidazole on acid sites of zeo-
lite by acid–base interaction is more appropriate (and does occur
as shown above in the competitive adsorption studies) than that of
methyl acrylate to yield acrylate cation.
To evaluate the scope of this methodology for the synthesis of
wide range of imidazole derivatives, imidazole/2-methylimidazole
was reacted with various activated olefins (Table 6). Reactions
of imidazole with methyl acrylate, ethyl acrylate, and acryloni-
trile produced almost similar yields of the corresponding products.
However, less product yield was observed when the reaction was
performed with 2-cyclohexenone. Significantly, longer reaction
time is required for the hydroamination reaction of ethyl cinna-
mate. Furthermore, the product yield was less when 2-methyl
imidazole was reacted with methyl acrylate when compared with
product yield obtained using imidazole. The result confirms that
the reaction is influenced by the reactivity of the substrate. Imidaz-
ole (pKa = 14.5) having high pKa value offered high yield of desired
product when compared to 2-methylimidazole (pKa = 7.86).
The competitive hydroamination reactions of various amines
with different olefins were investigated. Depending on amine and
olefin reactivity, selectivity of the product varies. For example,
equimolar amounts of aniline (1.0 mmol) and imidazole (1.0 mmol)
were reacted with methyl acrylate (2 mmol) in the presence of Zr-
Nano-ZSM-5 (50). After 5 min, only N-alkylation of imidazole was
obtained exclusively with 72% conversion of methyl acrylate and
100% selectivity (entry No. 2, Table 7). It is highly probable that
aniline chemisorbs on some acid sites that is responsible for the
reduction of product yield. Under the reaction condition, no aniline
derived product was observed. However, when aniline was reacted
3.2.2. Synthesis of N-imidazolyl functionalized ˇ-amino
compounds
A wide range of imidazole derivatives can be synthesized by
the hydroamination reaction of imidazole and activated olefins
(Scheme 1). The conjugate addition of imidazole and methyl
acrylate was investigated over various catalysts prepared in this
study (Table 6). The order of catalytic activity of various catalysts
was found to be Zr-Nano-ZSM-5 (50) > Zr-ZSM-5 (50) > Zr-SBA-
15 (50) ≈ Zr-KIT-6 (50) > Al-Nano-ZSM-5 (50) > Al-ZSM-5 (50). This
observation confirmed that, Zr incorporation in the crystalline
zeolite framework is ideally suited for the synthesis of imidaz-
ole derivatives. Influence of reaction parameters such as role of
solvent, reaction temperature, amount of catalyst, Si/Zr ratio was
investigated by taking Zr-Nano-ZSM-5 (50) as a catalyst, methyl
acrylate and imidazole as model substrates. The catalytic activity
of Zr-Nano-ZSM-5 (50) was found to be more when reaction was
performed in the absence of solvent (Table S2). Solvent molecules,
especially polar solvent molecules can block the active sites due
to the competitive adsorption of reactant and solvent molecules.
This competitive adsorption creates hindrance for the reactant
molecules to reach active sites in the presence of solvent molecules;
therefore, low catalytic activity was observed. With increase in the
temperature from 298 to 333 K, reaction yield was increased from
18 to 99 mol% (Fig. S5). It is interesting to note that unlike the con-
ventional process, the reaction of methyl acrylate with imidazole
occurs even at ambient conditions (298 K). Amount of catalyst also
influences the reaction yield. With increase in the amount of cata-
lyst, product yield also increased (Fig. S5). When average TOF was
taken into account, 25 mg of catalyst exhibited better activity than
that of 50 mg of catalyst for 2 mmol of reactants. Influence of Si/Zr
molar ratio was investigated and it was found that materials pre-
pared with high Si/Zr exhibited higher activity (Compare average

16
R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
Table 6
Comparative catalytic activity of various metallosilicates in the hydroamination reaction.
.
Entry No.
Catalyst
Nucleophile (R)
Acceptor
Yield of product [C] (%)
Average TOF (h−1
)
1
None
H
–
19
31
52
96
81
58
42
43
59
83
84
67a
–
585
2
Al-ZSM-5 (50)
H
3
Al-Nano-ZSM-5 (50)
Zr-ZSM-5 (50)
H
955
4
H
1870
2073
3250
3708
1453
1474
2367
3330
3370
19
5
Zr-Nano-ZSM-5 (30)
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (100)
Zr-SBA-15 (50)
H
6
H
7
H
8
H
9
Zr-KIT-6 (50)
H
10
11
12
13
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (50)
Zr-Nano-ZSM-5 (50)
CH3
H
H
H
14
Zr-Nano-ZSM-5 (50)
H
53
2126
Reaction conditions: catalyst (25 mg), imidazole (2 mmol), methyl acrylate (2 mmol), reaction temperature (318 K), reaction time (5 min).
Average TOF (h−1) = Turnover frequency [moles of imidazole converted per mole of active metal (Zr/Al) per hour].
a
Reaction temperature (353 K), time (12 h). [C] = N-imidazolyl functionalized ␤-amino compounds.
with methyl acrylate at 353 K for 12 h, almost quantitative yield of
the product was obtained. These investigations confirm that rate of
the reaction of imidazole with methyl acrylate is very high when
compared to the rate of the reaction of aniline with methyl acrylate.
Within the small reaction time (5 min), aniline was not able to form
the product. It may be noted that, equimolar amounts of styrene and
methyl acrylate were reacted to imidazole (2 mmol) in the presence
of Zr-Nano-ZSM-5 (50), and then only hydroamination product
Table 7
Competitive hydroamination reactions of olefins and amines over Zr-Nano-ZSM-5 (50).
.
Nucleophile (mmol)
Olefins (mmol)
Conv. (%)
Product selectivity (%)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
10
55
100
7
10
48
46
100
11
12
13
14
15
16
17
18
1
1
1
1
2
2
2
1
–
–
–
–
–
–
–
1
–
–
–
–
–
–
–
1
–
–
–
–
–
–
–
1
–
–
–
2
2
2
2
1
1
1
–
–
–
–
1
–
–
–
–
–
–
–
1
–
–
–
–
–
–
–
1
67
72
96
97
77
78
40
–
–
–
–
52
–
–
–
–
–
–
–
–
–
–
–
–
0
45
–
–
–
–
–
0
–
–
–
–
–
–
–
60
–
–
–
–
–
33
–
–
–
–
–
–
90
–
–
54
–
–
–
–
–
–
–
Reaction conditions: Zr-Nano-ZSM-5 (50) (25 mg), reaction temperature (318 K), reaction time (5 min).

R. Kore et al. / Applied Catalysis A: General 477 (2014) 8–17
17
corresponding to the reaction of imidazole and methylacrylate was
Appendix A. Supplementary data
obtained. This confirms the sluggish rate of the reaction of styrene
with imidazole. Several such examples are provided in Table 7.
Recyclability of Zr-Nano-ZSM-5 (50) was investigated in the
aminolysis reaction of imidazole with styrene oxide and the
hydroamination reaction of imidazole and methyl acrylate. At the
end of each cycle, 5 mL of dichloromethane was added and the cata-
lyst was separated by centrifugation, dried at 373 K and then used in
the next cycle. Recycling experiments confirmed that no significant
loss in the activity was observed after 5 recycles (Fig. S6). ICP analy-
sis confirmed that Zr was not leached during the reaction. Textural
characterizations using XRD and surface area analysis confirmed
that the catalyst is stable.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.apcata.2014.03.006.
References
[1] V.F.D. Álvaro, A.F. Brigas, E.G. Derouane, J.P. Lourenc¸ o, B.S. Santos, J. Mol. Catal.
A: Chem. 305 (2009) 100–103.
[2] M.R. Grimmet, in: A.R. Katritzky, C.W. Rees, E.F.V. Scriven (Eds.), Comprehensive
Heterocyclic Chemistry II, Pergamon, Oxford, 1996, pp. 77–220.
[3] M. Botta, F. Corelli, F. Gasparrini, F. Messina, C. Mugnaini, J. Org. Chem. 65 (2000)
4736–4739.
[4] T. Eicher, S. Hauptmann, The Chemistry of Heterocycles, Georg Thieme Verlag,
New York, 1995.
Nanocrystalline ZSM-5 was obtained by the addition of PrTES
in the synthesis composition of conventional ZSM-5. PrTES con-
tains only three hydrolysable moieties with one hydrophobic alkyl
group that are unfavorable for the formation of extended tetrahe-
dral SiO2 linkages. Consequently, the zeolite growth is significantly
retarded at the organic and inorganic interfaces, resulting in the
formation of aggregated ZSM-5 zeolite nanocrystals as observed in
the TEM images (Fig. 2). Mesopores in zeolites are formed due to
the crystal packing of these nanosized zeolite particles. Catalytic
activities in the ring opening of epoxide with strong/weak amine
nucleophiles and hydroamination reaction of activated olefins with
imidazole suggest that isomorphous substitution of Zr in the zeolite
MFI framework is responsible for the high activity. Acidity mea-
surements confirmed that zeolites with high acidity are not suitable
for these reactions. When acidity and activity are taken into the
consideration for Al incorporated ZSM-5 materials and Zr incor-
porated ZSM-5 materials, one can conclude that fine tuning in the
acidity by incorporating suitable metal ion in the MFI-framework
is the required for these reactions. It seems that Zr incorporation
[5] D.M. Gabriella, L.R. Guiseppe, P. Di Alessandra, R. Rino, B. Alberto, C. Chiara,
S. Anna, M. Giovanni, C. Emmanuele, A. Marino, S. Romano, J. Med. Chem. 48
(2005) 4378–4388.
[6] R. Kore, R. Srivastava, J. Mol. Catal. A: Chem. 376 (2013) 90–97.
[7] R. Kore, T.J. Dhilip Kumar, R. Srivastava, J. Mol. Catal. A: Chem. 360 (2012) 61–70.
[8] R. Kore, R. Srivastava, J. Mol. Catal. A: Chem. 345 (2011) 117–126.
[9] R. Kore, R. Srivastava, Tetrahedron Lett. 53 (2012) 3245–3249.
[10] D. Joseph, K. Mukesh, Z. Matthias, T.P. Elizabeth, Organometallics 32 (2013)
966–979.
[11] P.L. Arnold, M. Rodden, K.M. Davis, A.C. Scarisbrick, A.J. Black, C. Wilson, Chem.
Commun. (2004) 1612–1613.
[12] R. Kore, M. Tumma, R. Srivastava, Catal. Today 198 (2012) 189–196.
[13] S. Tang, G.A. Baker, H. Zhao, Chem. Soc. Rev. 41 (2012) 4030–4066.
[14] H. Kotsuki, K. Hayashida, T. Shimanouchi, H. Nishizawa, J. Org. Chem. 61 (1996)
984–990.
[15] H. Kotsuki, M. Wakao, H. Hayakawa, T. Shimanouchi, M. Shiro, J. Org. Chem. 61
(1996) 8915–8920.
[16] H. Desai, B.R. D’Souza, D. Foether, B.F. Johnson, H.A. Lindsay, Synthesis 6 (2007)
902–910.
[17] M.J. Bhanushali, N.S. Nandurkar, M.D. Bhor, B.M. Bhanage, Tetrahedron Lett. 49
(2008) 3672–3676.
[18] M.A. Jalila, S.M. Masum, Tetrahedron Lett. 53 (2012) 3049–3051.
[19] J. Nath, M.K. Chaudhur, Tetrahedron Lett. 46 (2005) 3279–3282.
[20] M.J. Bhanushali, N.S. Nandurkar, S.R. Jagtap, B.M. Bhanage, Catal. Commun. 9
(2008) 1189–1195.
[21] R. Trivedi, P. Lalitha, S. Roy, Synth. Commun. 38 (2008) 3556–3566.
[22] K.J. Borah, M. Phukan, R. Borah, Synth. Commun. 40 (2010) 2830–2836.
[23] M.R. Saidi, Y. Pourshojaei, F. Aryanasab, Synth. Commun. 39 (2009) 1109–1119.
[24] J. Nath, M.K. Chaudhur, Catal. Lett. 133 (2009) 388–393.
[25] C.E. Yeom, M.J. Kim, B.M. Kim, Tetrahedron 63 (2007) 904–909.
[26] L. Yang, L.W. Xu, W. Zhou, L. Li, C.G. Xia, Tetrahedron Lett. 47 (2006) 7723–7726.
[27] X. Chen, X. Li, H. Song, Y. Qian, F. Wang, Tetrahedron Lett. 52 (2011) 3588–3591.
[28] M. Lakshmi Kantam, B. Neelima, C.V. Reddy, R. Chakravarti, Ind. Eng. Chem. Res.
46 (2007) 8614–8619.
[29] L. Li, Z. Liu, Q. Ling, X. Xing, J. Mol. Cat. A: Chem. 353–354 (2012) 178–184.
[30] A.G. Ying, L. Liu, G.F. Wu, G. Chen, X.Z. Chen, W.D. Ye, Tetrahedron Lett. 50
(2009) 1653–1657.
[31] D. Kumar, G. Patel, B.G. Mishra, R.S. Varma, Tetrahedron Lett. 49 (2008)
6974–6976.
provides optimum acidity for these reactions. Due to large ionic
4+
radius (0.73 A for Zr and 0.54 A for Al3+) and larger electronega-
tive difference between M4+ and oxygen attached to epoxide ring
(2.11 and 1.8 for O Zr and O Al, respectively), zirconosilicates can
polarize the O Zr bond more efficiently. The high polarizability
of zirconosilicates is responsible for the weakening of O C bond
(of epoxide ring) and facile reaction of amine to epoxide to form
desired product.
˚
˚
4. Conclusions
Nanocrystalline Zr-Nano-ZSM-5 prepared using propyltri-
ethoxy silane exhibited large external surface area, mesopore
volume, and possess intercrystalline mesopores. Zr-Nano-ZSM-5
exhibited exceptionally high catalytic activity compared to cat-
alysts reported in the literature for the synthesis of imidazolyl
alcohols and N-imidazolyl functionalized ␤-amino compounds.
Based on catalytic activity, acidity measurements, adsorption
experiments, and textural properties, one can conclude that opti-
mum Zr polarizability, acidity, large external surface area, and
intercrystalline mesopores are responsible for such a high activ-
ity of Zr-Nano-ZSM-5. Therefore, it can be concluded that by fine
tuning of textural and acidic properties, it is possible to develop a
highly efficient catalyst for a particular type of reaction.
[32] M.E. Davis, Nature 417 (2002) 813–821.
[33] F. Schüth, W. Schmidt, Adv. Mater. 14 (2002) 629–638.
[34] C.S. Cundy, P.A. Cox, Chem. Rev. 103 (2003) 663–701.
[35] R. Kore, B. Satpati, R. Srivastava, Chem. Eur. J. 17 (2011) 14360–14365.
[36] R. Kore, B. Satpati, R. Srivastava, ACS Catalysis 3 (2013) 2891–2904.
[37] R. Kore, R. Sridharkrishna, R. Srivastava, RSC Advances 3 (2013) 1317–1322.
[38] R. Kore, R. Srivastava, RSC Advances 2 (2012) 10072–10084.
[39] R. Srivastava, N. Iwasa, S.-I. Fujita, M. Arai, Chem. Eur. J. 14 (2008) 9507–9511.
[40] R. Srivastava, M. Choi, R. Ryoo, Chem. Commun. (2006) 4489–4491.
[41] M. Choi, H.S. Cho, R. Srivastava, C. Venkatesan, D.H. Choi, R. Ryoo, Nat. Mater. 5
(2006) 718–723.
[42] Y. Tao, H. Kanoh, L. Abrams, K. Kaneko, Chem. Rev. 106 (2006) 896–910.
[43] J. Pérez-Ramírez, C.H. Christensen, K. Egeblad, C.H. Christensen, J.C. Groen,
Chem. Soc. Rev. 37 (2008) 2530–2542.
[44] C.J.H. Jacobsen, C. Madsen, J. Houzvicka, I. Schmidt, A. Carlsson, J. Am. Chem.
Soc. 122 (2000) 7116–7117.
[45] K. Egeblad, C.H. Christensen, M. Kustova, C.H. Christensen, Chem. Mater. 20
(2008) 946–960.
[46] K. Na, C. Jo, J. Kim, K. Cho, J. Jung, Y. Seo, R.J. Messinger, B.F. Chmelka, R. Ryoo,
Science 333 (2011) 328–332.
Acknowledgements
[47] A. Ramanathan, B. Subramaniam, R. Maheswari, U. Hanefeld, Microporous
Mesoporous Mater. 167 (2013) 207–212.
[48] D.M. Do, S. Jaenicke, G.K. Chuah, Catal. Sci. Technol. 2 (2012) 1417–1424.
[49] P. Ratnasamy, D. Srinivas, H. Knözinger, Adv. Catal. 48 (2004) 1–169.
[50] R. Szostak, Molecular Sieves: Principles of Synthesis and Identification, Van
Nostrand Reinhold, New York, 1989, pp. 317.
Authors are thankful to DST for financial assistance through DST
project SB/S1/PC-91/2012. R.K. is grateful to CSIR, New Delhi for
SRF fellowship. We acknowledge Director, IIT Ropar for constant
encouragements.