Chitosan-Silica Sulfate Nano Hybrid as a Novel and Highly Proficient Heterogeneous Nano Catalyst for Regioselective Ring Opening of Epoxides via Carboxylic Acids

Article abstract of DOI:10.1002/hlca.201700144

The synthesis and characterization of chitosan-silica sulfate nano hybrid (CSSNH) as a novel and efficient heterogeneous nano catalyst involving acid-base bifunctional activity is described. The catalytic potency and activity of this eco-friendly catalyst was investigated in regioselective ring opening of epoxides with carboxylic acids to access structurally diverse 1,2-diol mono-esters in good to excellent yields. CSSNH catalyst was characterized using different microscopic and spectroscopic techniques encompassing scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N₂ adsorption isotherm, and Fourier transform infrared spectroscopy. The green nature, cheapness, efficiency, ease of preparation, handling and reusability of this new catalyst makes this catalyst to be useful for green industrial processes.

Full text of DOI:10.1002/hlca.201700144

Article Type: Full Paper
Chitosan-Silica Sulfate Nano Hybrid (CSSNH) as a Novel and Highly
Proficient Heterogeneous Nano Catalyst for Regioselective Ring Opening
of Epoxides via Carboxylic Acids
Somayeh Behrouz *,a, Mohammad Navid Soltani Rad *,a, Mohammad Amin Piltan a and Mohammad
Mahdi Doroodmand b
a Medicinal Chemistry Research Laboratory, Department of Chemistry, Shiraz University of
Technology, Shiraz 71555-313, Iran. E-mail: behrouz@sutech.ac.ir, soltani@sutech.ac.ir, Tel.: +98-71-
37261392; fax: +98-71-37354523
b Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
The synthesis and characterization of chitosan-silica sulfate nano hybrid (CSSNH) as a novel and
efficient heterogeneous nano catalyst involving acid-base bifunctional activity is described. The
catalytic potency and activity of this eco-friendly catalyst was investigated in regioselective ring
opening of epoxides with carboxylic acids to access structurally diverse 1,2-diol mono-esters in good
to excellent yields. CSSNH catalyst was characterized using different microscopic and spectroscopic
techniques encompassing scanning electron microscopy (SEM), transmission electron microscopy
(TEM), X-ray diffraction (XRD), N2 adsorption isotherm, and Fourier transform infrared spectroscopy
(FT-IR). The green nature, cheapness, efficiency, ease of preparation, handling and reusability of this
new catalyst makes this catalyst to be useful for green industrial processes.
Keywords: carboxylic acid • CSSNH • epoxide • heterogeneous catalyst • nano hybrid
Introduction
Epoxides as a carbon-electrophile play a significant role in organic synthesis due to their facile ring
opening reaction with vary nucleophiles [1]. In this regard, epoxides are extensively used for
preparation of numerous 1,2-difunctional compounds [2]. Although the ring opening reaction of
epoxides via diverse nucleophiles has been widely studied; however, there has been little attention
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to the ring opening of epoxides with carboxylic acids. The ring opening of epoxides with carboxylic
acids is a well-known strategy to obtain 1,2-diol mono-esters (β-hydroxy esters) as useful precursors
applied in production of surfactants especially for oil and gas industries [3], synthesis of
biocompatible and biodegradable polymers [4], biolubricants [5,6], fragrances and pharmaceuticals
[7,8]. Additionally, 1,2-diol mono-esters are valuable intermediates used in the total synthesis of
steroids and carbohydrates [9,10].
The ring opening reaction of epoxides with carboxylic acids are generally carried out under
different conditions including acidic, basic and neutral conditions [11]. However, most of the
reported methods suffer from one or more drawbacks such as harsh reaction condition, high catalyst
loading, low conversion and moderate yield, limited substrate scope, the use of expensive reagents
or catalysts, and finally the use of non-reusable and/or non-recyclable catalysts. In this context, the
search for a mild, green, and low-cost protocol for facile and efficient ring opening of epoxides with
carboxylic acids is still desired.
In recent decades, acid-base dual-activation which enables the cooperative activation of both
reactants has been the subject of considerable research interest since it mimics the enzymatic
process in nature [12]. This protocol is of great significance for efficient progress of nucleophilic
reactions under mild and convenient conditions. The dual-activation strategies generally include, (i)
the use of two separate catalysts and/or reagents, (ii) the use of one molecule having two separate
active cores as a bifunctional catalyst and/or reagent, and (iii) the use of one catalyst in which merely
activates one reactant and subsequently, the in situ generated reactive substrate that can promote
the activation of the other reactants [13-16]. The ring opening reaction of epoxides with different
nucleophiles using dual-activation catalysts is well established [12, 17-19]. In this context, the acid-
base dual-activation strategy has been successfully employed for the ring opening of epoxides with
carboxylic acids using FeCl3/Et3N and/or N-methylmorpholine [20] and also FeCl3/pyridine [21] in
homogeneous conditions.
Nowadays, the use of heterogeneous catalysts in organic reactions is highly preferred to
homogeneous catalysts owing to both environmental and economic aspects. In particular, there has
been a growing interest in the application of natural biopolymers as environmentally benign
materials for preparation of heterogeneous catalysts [22,23]. Along this line, polysaccharides as one
of the most abundant biomolecules in nature are extensively applied. Among polysaccharides,
chitosan (CS, Figure 1) has gained tremendous research interest due to its unique properties such as
biocompatibility and biodegradability, non-toxicity, inertness towards air and moisture,
hydrophilicity, chemical reactivity, excellent chelating ability, and the ease of chemical modification
owing to presence of hydroxyl and amino functionalities [24-26]. Chitosan is utilized as
environmental friendly material since it can be readily degraded by water and soil microorganisms. In
addition, chitosan is a very cheap natural biopolymer present in industrial waste and also easily can
be acquired by alkaline deacetylation of chitin from crustacean [27]. Thus, an increasing industrial
and scientific interest has been focused on the application of chitosan in different fields such as
pharmaceutical, drug delivery, cosmetics, food packaging, adhesives, waste water treatment,
membranes, surface conditioners, hydrogels, and fuel cells [28-30]. Aside from the extensive
utilization of chitosan as a biopolymer support for the synthesis of heterogeneous catalysts [31-37], it
can be efficiently used as the heterogeneous catalyst in its parental shape without any post-
modification [38-40].
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OH
OH
O
O
SiO2
OSO3H
O
HO
O
HO
NH2
NHR
n
CS
R = H, COCH3
SSA
OH
OH
O
NH3
O
O
O
O
HO
SiO2
OSO3
O
S
HO
O
NH3
NHR
O
n
CSSNH
CSSNH
Figure 1. The general structure of chitosan (CS), silica sulfuric acid (SSA) and chitosan-silica sulfate nano hybrid (CSSNH).
In recent years, organic-inorganic hybrid materials or catalysts have gained particular attention [41]. Regarding to the benefits of
biopolymers as the green catalysts, the use of biopolymer-inorganic hybrid catalysts has been emerged as an attractive strategy in
preparation of new catalysts in organic reactions. In this context, there have been several reports on immobilization of chitosan or
chitosan-metal complexes on the surface of porous silica gel [42]. In most cases, the utilization of these hybrid catalysts have been
reported in oxidation and hydrogenation reactions, asymmetric dihydroxylation of olefins, and carbonylation reactions [42]. Molvinger and
co-workers have reported the application of chitosan-silica hybrid in reaction of lauric acid with glycidol [43].
Silica sulfuric acid (SSA, Figure 1) is an eco-friendly heterogeneous acid catalyst derived from silica gel which successfully applied in
numerous organic transformations [44]. However, to the best of our knowledge, there have been no reports yet on synthesis and
application of chitosan-silica sulfate nano hybrid (CSSNH) material as a green and economical organic-inorganic hybrid catalyst. In light of
the advantages of organic-inorganic hybrid catalysts and also inspired by the acid-base dual-activation strategy, hereby we describe the
synthesis and characterization of chitosan-silica sulfate nano hybrid (CSSNH) as a novel, environmental benign, and low-cost bifunctional
heterogeneous nano catalyst. The catalytic activity of this new biodegradable catalyst was investigated in the synthesis of 1,2-diol mono-
esters via regioselective ring opening reaction of epoxides with structurally diverse carboxylic acids in MeCN at reflux condition (Scheme 1).
Scheme 1. Synthesis of 1,2-diol mono-esters via ring opening reaction of epoxides with carboxylic acids using chitosan-silica sulfate nano hybrid (CSSNH).
Results and Discussion
Preparation of CSSNH
The process for the preparation of CSSNH is shown in Scheme 2. The first step of the catalyst
synthesis was initiated by preparing SSA. Due to our previous experience, the better result was
obtained when the activated SiO2 was applied instead of ordinary SiO2 to react with ClSO3H [45].
Thus, the exposure of normal silica with a flow of 8% O2 in an argon atmosphere was achieved for 1h
at 400 °C in a furnace. Then, ClSO3H (0.02 mol per 6.0 g silica) was added dropwise to the activated
silica followed by stirring the reaction mixture for 1h at room temperature. To prepare CSSNH,
chitosan was then added to an open-capped cylindrical pyrex-glass containing demineralized water.
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Subsequently, freshly prepared SSA was added portionwise to the mixture. When the pH of the
reaction mixture was reached to 7, the mixture was exposed to ultrasonic irradiation (30W) for 15
min. Filtration followed by drying provided CSSNH hybrid catalyst as a creamy solid (Figure 2).
Scheme 2. Preparation of chitosan-silica sulfate nano hybrid (CSSNH).
Figure 2. (A) SSA, (B) CS, (C) chitosan-silica sulfate nano hybrid.
Characterization of the catalyst nanostructure
The obtained CSSNH catalyst was characterized by various techniques involving scanning electron microscopy (SEM), transmission electron
microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption isotherm, and Fourier transform infrared spectroscopy (FT-IR). Figure 3
shows the SEM and TEM images of CSSNH catalyst, respectively.
Figure 3. (a) SEM and (b) TEM images of chitosan-silica sulfate nano hybrid (CSSNH).
The distribution of particle size for CSSNH catalyst has been indicated by corresponding TEM and SEM images. As it can be seen in Figure
4, about 45% of total CSSNH nanoparticles have size around 90 nm that clearly endorses the efficiency of applied procedure for
synthesizing CSSNH as a green nano-catalyst.
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50
40
30
20
10
0
55
60
82
90
120
150
200
Size distribution (nm)
Figure4. Histogram showing size distribution of chitosan-silica sulfate nano hybrid (CSSNH).
The Si morphology of CSSNH has also been characterized by patterned XRD as shown in Figure 5. As clearly shown, the diffractions
positioned at 2θ equal to 25 and 48° are assigned to Si morphology.
Figure 5. XRD pattern of chitosan-silica sulfate nano hybrid (CSSNH).
The nitrogen adsorption isotherm of CSSNH has also been shown in Figure 6. Based on the results, compared to the silica powder as the
adopted precursor, significant enhancement around 73 m2 g-1 was observed in the active surface during immobilization of chitosan.
The comparison between FT-IR spectra of CSSNH catalyst, CS and SSA is shown in Figure 7. The FT-
IR spectrum of chitosan shows a broad band at 3407 cm-1 which corresponds to the stretching
vibrations of O–H and N–H groups. The band at 2891 cm-1 displays the stretching vibrations of the C–
H bond. The absorption band present at 1568 cm-1 corresponds to the N–H bending vibration. The
bands around 1391 cm-1 are assigned to symmetric bending vibration of CH. The band at 1053 cm-1
indicates the stretching vibrations of the C–O bond. The FT-IR spectrum of SSA displays a band at 780
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cm-1 which is due to S–O stretching. A broad peak at 1007–1213 cm-1 is related to the stretching
symmetric and anti-symmetric Si–O–Si, symmetric and asymmetric stretching of O=S=O bonds. The
broad band at 3479 cm-1 is assigned to the stretching vibration of different hydroxyl moieties. The FT-
IR spectrum pattern of CSSNH catalyst displays a different fingerprint region at 400–1520 cm-1 in
comparison with that of pure chitosan which indicates a decisive interaction between chitosan and
SSA. Apparently, the peak at 1568 cm-1 is shifted to 1520 cm-1 after treating of chitosan with SSA. In
addition, the intensity of shifted N–H bending vibration at 1520 cm-1 is decreased which is due to the
protonated amino groups present in the synthesized catalyst.
Figure 7. The FT-IR spectrum of CS, SSA, and CSSNH catalyst.
Application of CSSNH catalyst in ring opening of epoxides via carboxylic acids
After synthesis and characterization of CSSNH catalyst then it was applied in synthesis of structurally diverse 1,2-diol mono-esters via
regioselective ring opening reaction of epoxides with carboxylic acids. Initially, efforts have been focused on optimizing the reaction
conditions. To this end, the reaction of cyclohexene oxide with benzoic acid in the presence of CSSNH catalyst was selected as the sample
reaction to afford 2-hydroxycyclohexyl benzoate. Thus, the influence of several effective factors on the reaction progress including solvent
type, temperature, and catalyst amount was studied in preparing 2-hydroxycyclohexyl benzoate.
In this concern, to indicate the significance of solvent, the sample reaction was carried out under
solvent-free conditions. However, the desired product was obtained in low yield even if the reaction
time was prolonged up to 18h (Table 1, entry 1). Thus, we screened the effect of various protic and
aprotic solvents on progress of the sample reaction (Table 1).
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Table 1. The influence of various solvents and temperatures on sample reaction using CSSNH catalyst a.
Entry
Solvent
Temperature (°C)
Time (h)
Yield b (%)
1
solvent-free c
H2O
100
r.t.
18
24
18
18
15
15
10
8
12
2
NR d
trace
20
3
H2O
40
4
H2O
60
5
H2O
80
26
6
H2O
90
32
7
H2O
reflux
100
100
reflux
reflux
reflux
reflux
r.t.
36
8
DMSO
DMF
57
9
8
60
10
11
12
13
14
15
16
17
18
acetone
CHCl3
toluene
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
12
14
10
4
45
28
30
96
18
10
9
trace
45
50
60
70
70
6
89
95 c
4
96
a Reaction conditions: benzoic acid (1 mmol), cyclohexene oxide (1.2 mmol), CSSNH catalyst (0.03 g), solvent (5 mL). b Isolated yield. c The reaction was tested in
a sealed tube. d No reaction.
As the results in Table 1 indicate, the solvent type has a substantial role in progress of the reaction.
Since the green nature of water, the use of this solvent in organic reactions has been an important
subject of many research interests. Hence, the sample reaction was examined in an aquatic media at
ambient temperature; however, no product was observed even in a trace amount (Table 1, entry 2).
To improve the reaction efficiency, the effect of different temperatures was studied on the sample
reaction when water was used as the solvent. As can be seen in Table 1, increasing the reaction
temperature affects the reaction progress to some extent (entries 2-7). In addition, when the
reaction was performed in refluxing water, the desired 1,2-diol mono-ester was obtained in 36%
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yield after 10h (entry 7). Thus, we focused on the use of several traditional organic solvents (Table 1).
As shown in Table 1, when the sample reaction was tested in DMSO or DMF (entries 8 and 9) the
moderate yields of product were obtained. The use of acetone, CHCl3, and toluene affords the
product in low yields (entries 10-12). Moreover, the use of MeCN led to desire product in a shorter
reaction time (Table 1, entry 13). Hence, MeCN was selected as the solvent of choice for all
subsequent reactions.
In another experiment, the influence of vary temperatures on progress of the sample reaction in MeCN was studied (Table 1, entries 13-
18). The obtained results indicate that increasing the reaction temperature can effectively accelerate the reaction rate and improve the
yield. Practically, the higher yield of the product in a shorter reaction time was acquired when the sample reaction was performed in
refluxing MeCN (Table 1, entry 13). In addition, more elevation in temperature provided no distinguishable raise on reaction progress
(Table 1, entry 18).
The catalyst loading is another important parameter in upgrading the ring opening reaction of
epoxides with carboxylic acids (Table 2). Apparently, in the absence of the catalyst, a very low yield of
product (<10%) was obtained (Table 2, entry 1). As shown in Table 2, the higher yield and rate of
sample reaction was gained when it was carried out in the presence of 0.03 g CSSNH catalyst (Table
2, entry 4). The reasonable yields of sample product were also afforded using lower amount of
catalyst when the reaction time was prolonged up to 7h (Table 2, entries 2 and 3). No further
improvement was observed when the catalyst amount was raised from 0.03 g up to 0.05 g (Table 2,
entries 5 and 6).
Table 2. Effect of various amounts of CSSNH on sample reaction a.
Entry
X g CSSNH
0
Time (h)
Yield b (%)
1
2
3
4
5
6
10
7
trace
80
0.01
0.02
0.03
0.04
0.05
7
89
4
96
4
96
4
95
a Reaction conditions: benzoic acid (1 mmol), cyclohexene oxide (1.2 mmol), CSSNH (X g), solvent (5 mL). b Isolated yield.
To prove the catalytic potency of CSSNH in ring opening reaction of epoxides with carboxylic acids, we carried out the sample reaction in
the presence of CS and/or SSA alone under the optimized conditions. Practically, performing the sample reaction under the optimized
conditions using CSSNH led to 2-hydroxycyclohexyl benzoate in 96% yield after 4 h. However, using CS and SSA as the reaction catalyst
under the optimized reaction conditions affords the corresponding product in 47% and 23% yields after 4 h, respectively. These results
indicate that neither CS nor SSA were as efficient as CSSNH for progress of the reaction.
Having optimized the reaction conditions, we then explored the versatility and scope of current protocol in ring opening reaction of
structurally diverse epoxides and carboxylic acids (Table 3). It is clear from Table 3 that CSSNH is a highly efficient and suitable
heterogeneous nano catalyst for regioselective ring opening of different epoxides with various carboxylic acids. The generality of this
protocol was confirmed with respect to aromatic (Table 3, entries 1-10), heteroaromatic (Table 3, entries 11 and 12), vinylic (Table 3, entry
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13) and long chain aliphatic carboxylic acids (Table 3, entries 14 and 15). Additionally, the N-protected amino acids can be successfully
applied in this protocol to provide the desired 1,2-diol mono-esters in excellent yields (Table 3, entry 16 and 17).
The chemoselectivity of the present method was assessed by its application for 3-hydroxyl benzoic acid (Table 3, entry 7). As shown in
Table 3, the corresponding 1,2-diol mono-ester was obtained in 92% yield as the sole product and the phenolic OH residue did not interfere
in the ring opening reaction of epoxide. Also, the method works well with structurally diverse epoxides involving terminal and vicinal
epoxides using CSSNH catalyst.
We further explored the capability of the present protocol for a large scale synthesis. To this end, the sample reaction was carried out on
a 100 mmol scale under the optimized reaction conditions which led to the formation of 2-hydroxycyclohexyl benzoate in 90% yield.
Table 3. Synthesis of 1,2-diol mono-esters using CSSNH catalyst.
Entry
Product a
Time (h)
Yield b (%)
1
4
4
96
92
2
4
4
5
5
93
95
90
87
3
4
5
6
4
92
90
7
8
4.5
4
95
9
4.5
6
92
89
10
11
4
91
12
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5
93
13
4
4
95
92
14
15
6
6
91
94
16
17
a All products were characterized by 1H and 13C NMR, IR, CHN, and MS analysis. b Isolated yield.
The recyclability and reusability of the catalyst is a significant task as an evidence for its heterogeneous nature. Hence, the recoverability
and reusability of CSSNH catalyst was explored under the optimized conditions. In this context, after completion of the reaction, the
catalyst was recovered and dried. Then, it was directly applied in subsequent reaction while no fresh catalyst was added to the reaction
mixture. The obtained results demonstrated that CSSNH catalyst is a recoverable and reusable catalyst which can be efficiently employed
for at least 6 consecutive runs without significant decline in its activity (Table 4).
Table 4. The reusability of CSSNH catalyst a.
Run number b
Time (h)
Yield c (%)
1
2
3
4
5
6
4
4
4
5
5
6
96
96
94
93
92
91
a Reaction conditions: benzoic acid (1 mmol), cyclohexene oxide (1.2 mmol), CSSNH catalyst, MeCN (5 mL). b The entry number corresponds to the trial
number. c Isolated yield.
The ring opening reaction of epoxide with carboxylic acid generally produces two regioisomers 3
and 4 (Scheme 3). Under mild conditions, the reaction is achieved through the regioselective attack
of carboxylic acid to less hindered side of epoxide to afford product 3. However, product 4 can also
be obtained in harsh reaction conditions through nucleophilic attack to the more hindered carbon.
Moreover, it is well-indicated that the acyl migration of 1,2-diol mono-esters (i.e. isomerization) can
be happened through a five-membered ring intermediate 5 (Scheme 3) [46,47]. Thus, product 4 can
be also produced through the acyl transfer of initially generated 3. However, the ring opening of
epoxides with carboxylic acids was regioselectively achieved using the current catalyst in which
majorly led to isomers 3 in good to excellent yields. The regioisomers 4 were also obtained in trace
amounts.
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Scheme 3. Isomerization of 1,2-diol mono-esters.
A plausible mechanism is suggested to explain the acid-base dual-activation role of CSSNH in catalyzing the ring opening reaction of
epoxides with carboxylic acids (Scheme 4). As shown in Scheme 4, silica sulfate anion acts as the base and deprotonates the carboxylic acid
to produce the carboxylate anion I. On the other hand, protonated chitosan acts as the acid and interacts with epoxide oxygen (adduct II)
for activating the epoxide to undergo the nucleophilic attack. Then, treatment of I with II affords adduct III. Eventually, protonolysis of
adduct III generates the desired 1,2-diol mono-ester IV and librates the catalyst.
Scheme 4. A plausible reaction mechanism.
Using quantum chemical calculations, the full optimization of epoxide, carboxylic acid, CSSNH catalyst, anion I, adduct II, adduct III, SSA,
SSA anion, chitosan cation and product were performed by Gaussian 09 software [48]. In our calculations, benzoic acid (Scheme 4, R= Ph)
and 2-methyloxirane (Scheme 4, R’= Me) were applied as the model compounds. All calculations were carried out by density functional
theory (DFT) on the B3LYP/6-31+G(d,p) level of theory, containing polarizable and diffuse functions. The interaction energy (DE) was
estimated by employing the counterpoise (CP) method for the Gaussian basis set superposition error (BSSE) [49]. The results confirm the
formation of a relatively strong H-bond with 10.74 kcal/mol energy and 1.77 Å distance between oxygen atom of epoxide and NH of
chitosan residue (adduct II). This interaction plays a critical role for activation the epoxide toward the nucleophilic attack. In the last step,
the proton transfers from the NH of chitosan residue to the oxygen anion in adduct III which led to the formation of 1,2-diol mono-ester IV
and recycling the CSSNH catalyst. Table 5 shows the total (Hartree) and relative (kcal/mol) energies of optimized structure for the ring
opening reaction of 2-methyloxirane with benzoic acid in the presence of CSSNH. The reaction energy diagram for the proposed
mechanism is depicted in Figure 8.
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Table 5. The total and relative energies of optimized structure for the reaction between 2-methyloxirane and benzoic acid using CSSNH a.
Optimized geometry
Total energies (Hartree)
Relative energies (kcal/mol)
0.00
Epoxide+Carboxylic acid+CSSNH -4336.21530
Anion I+ Adduct II+SSA
Adduct III+SSA
-4336.03574
-4336.35742
-4336.25434
112.67
-89.18
Product IV+SSA
-24.50
a All calculations were performed using DFT on the B3LYP/6-31+G(d,p) level of theory
Figure 8. The reaction energy diagram for the proposed mechanism.
Conclusions
In summary, we have explained the synthesis, characterization and application of CSSNH as a new,
green, non-toxic, and inexpensive heterogeneous nano catalyst with dual mode of action. The
bifunctional activity of CSSNH catalyst was successfully applied in synthesis of 1,2-diol mono-esters
via regioselective ring opening of epoxides with carboxylic acids. The advantages of this approach
involve the green nature and reusability of the catalyst, high efficiency, mild reaction condition, low
catalyst loading, ease of operation, as well as applicability in large scale synthesis. Owing to
numerous benefits acquired by utilizing CSSNH, the expansion of other applications of this catalyst in
organic transformations is the subject of our future attempts.
Experimental Section
All chemical reagents were purchased from Fluka, Merck or Sigma-Aldrich. Solvents were purified by
standard procedures, and stored over 3Å molecular sieves. Reactions were followed by TLC using
SILG/UV 254 silica-gel plates. Column chromatography was performed on silica gel 60 (0.063-0.200
mm, 70-230 mesh; ASTM). Melting points were measured using Electrothermal IA 9000 melting point
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apparatus in open capillary tubes and are uncorrected. IR spectra were obtained using a Shimadzu
FT-IR-8300 spectrophotometer. Ultrasonication was performed using a horn sonicator, Misonix
model S-4000 (Qsonica LLC, Newtown, CT.) with a standard titanium tip diameters of ½”. The
transmission electron microscopy was employed using TEM (CN-10, Philips, 100 KV). The scanning
electron micrograph was attained using SEM (XL-30 FEG, Philips, 20 KV) instrument. The patterned X-
ray diffraction (XRD) was obtained using D8 Advance, Brüker AXS. The nitrogen adsorption isotherm
was achieved on lab-made Metrohm instrument. 1H- and 13C-NMR spectrum was recorded on Brüker
Avance-DPX-250/400 spectrometer operating at 250/62.5 MHz, respectively. Chemical shifts are
given in δ relative to tetramethylsilane (TMS) as an internal standard, coupling constants J are given
in Hz. GC/MS was performed on a Shimadzu GC/MS-QP 1000-EX apparatus (m/z; rel.%). Elemental
analyses were performed on a Perkin–Elmer 240-B micro-analyser.
General procedure for synthesis of SSA [45]
Activation of silica gel: In a tubing thermal furnace (internal diameter: 2.0 cm, length: 25 cm), a
sample of normal silica gel (12.0 g) was exposed to a flow of 8% O2 in an argon atmosphere for 1 h at
400 °C in which afforded the activated silica gel.
Synthesis of SSA: In a 50 mL suction flask containing activated silica gel (6.0 g) equipped with a gas
inlet tube and a constant-pressure dropping funnel, was added dropwise ClSO3H (0.02 mol per 6.0 g
silica gel) using the dropping funnel over a period of 1 h at room temperature followed by stirring the
reaction mixture . The in situ generated HCl gas was absorbed over cold H2O through the gas inlet
tube. After complete addition of ClSO3H to the reaction mixture, the mixture was stirred for
additional 30 min. SSA (7.6 g) was obtained as a white solid which was directly used in the next step.
General procedure for synthesis of CSSNH
In an open-capped cylindrical pyrex-glass (50 mL), was added chitosan (1 g, medium molecular
weight, Aldrich, CAS No: 9012-76-4) in demineralized water (10 ml). Then, pH of the mixture was
reduced to 7 by adding SSA (0.5 g). The mixture was kept at room temperature and irradiated at 30W
power (cup horn: 20 kHz) in ultrasonic apparatus for 15 min. Afterward, the catalyst was filtered off
and dried in a vacuum oven at 50 C for 2 h and stored in a sealed vessel at refrigerator.
General procedure for synthesis of 1,2-diol mono-esters using CSSNH catalyst
To a round bottom flask (50 mL) was added a mixture of appropriate carboxylic acid (1 mmol),
epoxide (1.2 mmol), and CSSNH (0.03 g) in MeCN (5 mL). The reaction mixture was refluxed until TLC
monitoring indicated no further improvement in the conversion (Table 3). Afterward, the catalyst
was filtered off and washed with hot MeCN. The filtrate was evaporated to remove the solvent.
Then, water (15 mL) was added to the remaining foam and it was subsequently washed with CHCl3 (2
× 10 mL). The organic layer was dried (Na2SO4) and evaporated. The crude product was purified by
column chromatography on silica gel eluting with a mixture of n-hexane/EtOAc.
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Recycling the catalyst
After completion of the reaction as indicated by TLC monitoring (Table 3), the catalyst was vacuum-
filtered from the reaction mixture using a sintered glass funnel and washed with MeCN (2 × 2 mL).
Subsequently, the catalyst was kept in a vacuum oven at 50 C for 2h. The recovered catalyst was
then applied in next reaction without further purification.
2-Hydroxycyclohexyl Benzoate (entry 1).
Column chromatography purification on silica gel with n-hexane-EtOAc (5:2) gave white crystals (0.21
g, 96%); mp 104-105 ºC; Rf 0.73 (50% n-hexane-EtOAc). IR (KBr): 3600-3100 (br), 3050, 2985, 1730,
1
1260 cm-1. H NMR (250 MHz, CDCl3): δppm = 8.00-7.20 (m, 5 H, aryl), 4.80-4.76 (m, 1 H, PhCO2CH),
13
3.68-3.64 (m, 1 H, HCOH), 2.26 (s, 1 H, OH, exchangeable with D2O), 2.10-1.26 (m, 8 H, (CH2)4). C
NMR (62.5 MHz, CDCl3): δppm = 165.98, 133.54, 130.19, 129.59, 128.78, 80.43, 75.44, 30.79, 30.48,
23.80, 23.69. MS [m/z (%)]: 220.11 (9.1). Anal. Calcd for C13H16O3: C, 70.89; H, 7.32. Found: C, 70.80;
H, 7.37.
2-Hydroxypropyl Benzoate (entry 2).
Column chromatography purification on silica gel with n-hexane-EtOAc (7:2) gave a colorless oil (0.16
g, 92%); Rf 0.54 (50% n-hexane-EtOAc). IR (liquid film): 3600-31500 (br), 3100, 2950, 1735, 1265 cm-1.
1H NMR (250 MHz, CDCl3): δppm = 8.20-7.31 (m, 5 H, aryl), 4.53-4.42 (m, 1 H, CH(OH)CH3), 4.42-4.21
(m, 2 H, PhCO2CH2), 2.34 (br s, 1 H, OH, exchangeable with D2O), 1.38-1.22 (d, J = 5.9 Hz, 3 H, CH3). 13C
NMR (62.5 MHz, CDCl3): δppm = 167.24, 135.01, 134.98, 130.00, 127.63, 70.21, 66.20, 20.00. MS [m/z
(%)]: 180.08 (7.9). Anal. Calcd for C10H12O3: C, 66.65; H, 6.71. Found: C, 66.74; H, 6.78.
2-Hydroxy-3-(iso-propyloxy)propyl Benzoate (entry 3).
Column chromatography purification on silica gel with n-hexane-EtOAc (5:2) gave a colorless oil (0.22
g, 93%); Rf 0.83 (50% n-hexane-EtOAc). IR (liquid film): 3600-3100 (br), 3050, 2980, 1735, 1265 cm-1.
1H NMR (250 MHz, CDCl3): δppm = 8.24-7.28 (m, 5 H, aryl), 4.63-4.46 (dd, J = 2.6, 5.2 Hz, 2 H,
PhCO2CH2), 4.26-4.00 (quint, J = 5.2, 1 H, HCOH), 3.76-3.44 (m, 3 H, (CH3)2CHO, CH2O(iso-Pr)), 3.33 (br
13
s, 1 H, OH, exchangeable with D2O),1.35-1.00 (d, J = 6.0 Hz, 6 H, 2 CH3). C NMR (62.5 MHz, CDCl3):
δppm = 163.71, 134.32, 131.36, 131.02, 127.64, 74.81, 70.33, 70.02, 66.32, 22.23. MS [m/z (%)]:
238.12 (10.5). Anal. Calcd for C13H18O4: C, 65.53; H, 7.61. Found: C, 65.58; H, 7.69.
3-(Allyloxy)-2-hydroxypropyl Benzoate (entry 4).
Column chromatography purification on silica gel elution with n-hexane-EtOAc (5:2) gave a colorless
oil (0.22 g, 95%); Rf 0.60 (50% n-hexane-EtOAc). IR (liquid film): 3600-3150 (br), 3050, 2980, 1735,
1
1250 cm-1. H NMR (250 MHz, CDCl3): δppm = 8.31-7.42 (m, 5 H, aryl), 6.00-5.72 (m, 1 H, =CHCH2),
5.23-4.89 (dd, J = 10.4, 7.7 Hz, 2 H, =CH2), 4.42-4.17 (d, J = 4.4 Hz, 2 H, PhCO2CH2), 4.11-4.00 (m, 1 H,
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HCOH), 4.00-3.81 (d, J = 5.5 Hz, 2 H, HCOHCH2O), 3.50-3.38 (m, 2 H, =CHCH2O), 2.76 (s, 1 H, OH,
13
exchangeable with D2O). C NMR (62.5 MHz, CDCl3): δppm = 167.22, 136.28, 135.01, 130.24, 129.62,
129.40, 117.28, 74.41, 71.22, 69.32, 65.13. MS [m/z (%)]: 236.26 (10.2). Anal. Calcd for C13H16O4: C,
66.09; H, 6.83. Found: C, 66.17; H, 6.92.
3-Butoxy-2-hydroxypropyl 3-methylbenzoate (entry 5).
Column chromatography purification on silica gel elution with n-hexane-EtOAc (10:1) gave a yellow
oil (0.24 g, 90%); Rf 0.91 (50% n-hexane-EtOAc). IR (liquid film): 3510-3190 (br), 3061, 2972, 1730,
1238 cm-1. 1H NMR (250 MHz, CDCl3): δppm = 7.76-7.73 (m, 2 H, aryl), 7.27-7.17 (m, 2 H, aryl), 3.01 (s, 1
H, OH, exchangeable with D2O), 4.33-4.27 (m, 2 H, CO2CH2), 4.05-4.03 (m, 1 H, HCOH), 3.49-3.36 (m, 4
H, CH2OCH2), 2.28 (s, 3H, PhCH3), 1.49-1.43 (m, 2 H, OCH2CH2), 1.31-1.22 (m, 2 H, CH2CH3), 0.78 (t, J =
7.3 Hz, 3 H, CH2CH3). 13C NMR (62.5 MHz, CDCl3): δppm = 164.92, 139.05, 133.43, 131.03, 130.75,
128.95, 126.90, 74.58, 71.33, 68.36, 67.15, 32.69, 24.10, 19.91, 14.30. MS [m/z (%)]: 266.15 (13.7).
Anal. Calcd for C15H22O4: C, 67.64; H, 8.33. Found: C, 67.51; H, 8.21.
3-Butoxy-2-hydroxypropyl 4-tert-butylbenzoate (entry 6).
Column chromatography purification on silica gel elution with n-hexane-EtOAc (10:1) gave a yellow
oil (0.27 g, 87%); Rf 0.92 (50% n-hexane-EtOAc). IR (liquid film): 3500-3200 (br), 3075, 2943, 1733,
1
1242 cm-1. H NMR (250 MHz, CDCl3): δppm = 8.01-7.95 (m, 2 H, aryl), 7.47-7.43 (m, 2 H, aryl), 4.40-
4.37 (m, 2 H, CO2CH2), 4.19-4.15 (m, 1 H, HCOH), 3.57-3.46 (complex, 5 H, CH2OCH2, OH), 1.59-1.53
13
(m, 2 H, OCH2CH2), 1.41-1.33 (complex, 11 H, CH2CH3, C(CH3)3), 0.88 (t, J = 7.3 Hz, 3 H, CH2CH3). C
NMR (62.5 MHz, CDCl3): δppm = 164.11, 154.68, 130.15, 127.74, 124.26, 74.78, 72.39, 69.45, 68.26,
41.02, 32.74, 30.96, 19.15, 14.97. MS [m/z (%)]: 308.20 (18.1). Anal. Calcd for C18H28O4: C, 70.10; H,
9.15. Found: C, 70.19; H, 9.31.
2-Hydroxy-3-phenoxypropyl-3-hydroxy Benzoate (entry 7).
Column chromatography purification on silica gel with n-hexane-EtOAc (5:3) gave pale yellow crystals
(0.26 g, 92%); mp 63-65 ºC; Rf 0.53 (50% n-hexane-EtOAc). IR (KBr): 3600-3140 (br), 3100, 2980,
1730, 1250 cm-1. 1H NMR (250 MHz, CDCl3): δppm = 7.86-6.93 (m, 9 H, aryl), 4.63-4.50 (dd, J = 2.2, 4.9
Hz, 2 H CO2CH2), 4.50-4.32 (quint, J = 4.9, 1 H, HCOH), 4.29-4.00 (dd, J = 2.0, 4.9 Hz, 2 H, PhOCH2),
13
4.00-3.00 (br s, 1 H, HOPh, exchangeable with D2O), 2.50 (s, 1 H, OH, exchangeable with D2O). C
NMR (62.5 MHz, CDCl3): δppm = 167.33, 159.23, 156.31, 131.32, 130.29, 130.02, 123.62, 123.02,
122.07, 116.24, 115.00, 69.68, 69.41, 66.32. MS [m/z (%)]: 288.10 (12.5). Anal. Calcd for C16H16O5: C,
66.66; H, 5.59. Found: C, 66.74; H, 5.48.
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2-Hydroxy-3-phenoxypropyl-4-chloro Benzoate (entry 8).
Column chromatography purification on silica gel elution with n-hexane-EtOAc (7:3) gave a colorless
oil (0.28 g, 90%); Rf 0.73 (50% n-hexane-EtOAc). IR (liquid film): 3600-3150 (br), 3100, 2985, 1730,
1240 cm-1. 1H NMR (250 MHz, CDCl3): δppm = 7.93-7.91 (d, J = 7.8 Hz, 2 H, aryl), 7.52-7.42 (d, J = 7.8 Hz,
2 H, aryl), 7.42-7.16 (m, 2 H, aryl), 7.16-6.83 (m, 3 H, aryl), 4.81-4.52 (dd, J = 4.9, 1.9 Hz, 2 H, p-
ClPhCO2CH2), 4.42-4.38 (quint, J = 4.9, 1 H, HCOH), 4.29-4.00 (dd, J = 4.9, 2.2 Hz, 2 H, CH2OPh), 2.50
13
(s, 1 H, OH, exchangeable with D2O). C NMR (62.5 MHz, CDCl3): δppm = 166.34, 158.24, 136.29,
132.67, 132.11, 130.44, 130.00, 126.68, 115.00, 69.36, 69.24, 65.98. MS [m/z (%)]: 306.07 (13.7).
Anal. Calcd for C16H15ClO4: C, 62.65; H, 4.93; Cl, 11.56. Found: C, 62.60; H, 5.02; Cl, 11.51.
2-Hydroxy-3-phenoxypropyl-4-methoxy Benzoate (entry 9).
Column chromatography purification on silica gel with n-hexane-EtOAc (5:2) gave white crystals (0.29
g, 95%); mp 82-84 ºC; Rf 0.56 (50% n-hexane-EtOAc). IR (KBr): 3600-3150 (br), 3100, 2980, 1735, 1250
cm-1. 1H NMR (250 MHz, CDCl3): δppm = 8.21-7.90 (d, J = 8.8 Hz, 2 H, aryl) 7.49-7.41 (d, J = 8.8 Hz, 2 H,
aryl), 7.00-6.72 (m, 5H, aryl), 4.73-4.51 (dd, J = 1.9, 5.1 Hz, 2 H, p-MeOPhCO2CH2), 4.50-4.41 (quint, J
= 5.1 Hz, 1 H, HCOH), 4.39-4.21 (dd, J = 2.0, 5.1 Hz, 2 H, CH2OPh), 3.90 (s, 3 H, OMe), 3.00 (s, 1 H, OH,
13
exchangeable with D2O). C NMR (62.5 MHz, CDCl3): δppm = 167.42, 165.00, 160.00, 133.64, 130.00,
123.62, 122.19, 115.00, 114.91, 70.26, 70.00, 65.00, 55.31. MS [m/z (%)]: 302.12 (11.7). Anal. Calcd
for C17H18O5: C, 67.54; H, 6.00. Found: C, 67.65; H, 6.14.
2-Hydroxyoctyl Benzoate (entry 10).
Column chromatography purification on silica gel with n-hexane-EtOAc (7:2) gave white crystals (0.23
g, 92%); mp 48-50 ºC; Rf 0.81 (50% n-hexane-EtOAc). IR (KBr): 3600-3160 (br), 3100, 2980, 1730, 1250
1
cm-1. H NMR (250 MHz, CDCl3): δppm = 8.25-7.32 (m, 5 H, aryl), 4.53-4.23 (m, 2 H, PhCO2CH2), 4.19-
3.86 (m, 1 H, HCOH), 2.45 (s, 1 H, OH, exchangeable with D2O), 1.75-1.25 (m, 10 H, (CH2)5), 1.00-0.75
13
(t, J = 6.6 Hz, 3 H CH3). C NMR (62.5 MHz, CDCl3): δppm = 167.24, 135.06, 130.09, 130.01, 127.68,
70.71, 69.11, 35.06, 32.71, 30.04, 25.22, 24.54, 15.10. MS [m/z (%)]: 250.16 (7.3). Anal. Calcd for
C15H22O3: C, 71.97; H, 8.86. Found: C, 72.05; H, 8.89.
2-Hydroxy-2-methylpropyl nicotinate (entry 11).
Column chromatography purification on silica gel with n-hexane-EtOAc (1:1) gave brwon solid (0.17
g, 89%); mp 159-161 ºC; Rf 0.10 (50% n-hexane-EtOAc). IR (KBr): 350-3179 (br), 3040, 2972, 1734,
1
1235 cm-1. H NMR (250 MHz, DMSO-d6): δppm = 9.29 (s, 1 H, aryl), 9.00 (d, J = 7.6 Hz, 1 H, aryl), 8.87
(d, J = 7.6 Hz, 1 H, aryl), 8.14-8.09 (m, 1 H, aryl), 5.88 (s, 1 H, OH, exchangeable with D2O), 4.71 (s, 2 H,
13
CO2CH2), 1.17 (s, 6 H, 2 CH3). C NMR (62.5 MHz, DMSO-d6): δppm = 166.30, 152.04, 150.19, 136.83,
126.17, 122.53, 76.91, 68.73, 27.38. MS [m/z (%)]: 195.09 (10.4). Anal. Calcd for C10H13NO3: C, 61.53;
H, 6.71; N, 7.18. Found: C, 61.64; H, 6.86; N, 7.31.
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2-Hydroxy-2-methylpropyl furan-2-carboxylate (entry 12).
Column chromatography purification on silica gel with n-hexane-EtOAc (10:1) gave a brown oil (0.17
g, 91%); Rf 0.78 (50% n-hexane-EtOAc). IR (liquid film): 3500-3180 (br), 3064, 2987, 1732, 1240 cm-1.
1H NMR (250 MHz, CDCl3): δppm = 7.61-7.59 (m, 1 H, C(5)-H, furan), 7.25-7.23 (m, 1 H, C(3)-H, furan),
6.53-6.50 (m, 1 H, C(4)-H, furan), 4.18 (s, 2 H, CO2CH2), 2.81 (s, 1 H, OH, exchangeable with D2O), 1.29
13
(s, 6 H, 2 CH3). C NMR (62.5 MHz, CDCl3): δppm = 159.74, 147.38, 144.97, 117.61, 112.18, 74.27,
67.34, 26.47. MS [m/z (%)]: 184.07 (9.5). Anal. Calcd for C9H12O4: C, 58.69; H, 6.57. Found: C, 58.80; H,
6.71.
2-Hydroxy-3-(methacryloyloxy)propyl Benzoate (entry 13).
Column chromatography purification on silica gel with n-hexane-EtOAc (5:3) gave a colorless oil (0.24
g, 93%); Rf 0.56 (50% n-hexane-EtOAc). IR (liquid film): 3600-3150 (br), 3050, 2980, 1730, 1720, 1250,
1
1230 cm-1. H NMR (250 MHz, CDCl3): δppm = 8.41-7.36 (m, 5 H, aryl), 6.21 (s, 1 H, =CHaHb), 5.63 (s, 1
H, =CHaHb), 4.64-4.50 (m, 2 H, PhCO2CH2), 4.49-4.23 [m, 3 H, HCHOH, CH2=C(Me)CO2CH2], 3.33 (br s, 1
H, OH, exchangeable with D2O), 2.05 (s, 3 H, CH3). 13C NMR (62.5 MHz, CDCl3): δppm = 167.21, 166.32,
136.22, 135.09, 130.06, 130.01, 128.51, 125.22, 69.90, 65.22, 65.09, 20.31. MS [m/z (%)]: 264.10
(8.7). Anal. Calcd for C14H16O5: C, 63.63; H, 6.10. Found: C, 63.75; H, 6.14.
2-Hydroxy-3-phenoxypropyl decanoate (entry 14).
Column chromatography purification on silica gel with n-hexane-EtOAc (10:1) gave a yellow oil (0.31
g, 95%); Rf 0.95 (50% n-hexane-EtOAc). IR (liquid film): 3530-3190 (br), 3050, 2973, 1735, 1248 cm-1.
1H NMR (250 MHz, CDCl3): δppm = 7.31-7.24 (m, 2 H, aryl), 6.99-6.88 (m, 3 H, aryl), 4.31-4.12 (complex,
3 H, CO2CH2, HCOH), 4.02-3.99 (m, 2 H, CH2OPh), 2.88 (s, 1 H, OH, exchangeable with D2O), 2.31 (t, J =
7.4 Hz, 2 H, CH2CO2), 1.64-1.56 (m, 2 H, CH2CH2CO2), 1.32-1.25 (complex, 12 H, CH3(CH2)6), 0.84 (t, J =
13
6.9 Hz, 3 H, CH3). C NMR (62.5 MHz, CDCl3): δppm = 174.45, 156.38, 129.41, 120.53, 114.69, 70.24,
68.11, 67.91, 33.51, 31.96, 30.43, 29.81, 29.51, 29.22, 25.21, 22.46, 15.42. MS [m/z (%)]: 322.21
(18.6). Anal. Calcd for C19H30O4: C, 70.77; H, 9.38. Found: C, 70.64; H, 9.27.
2-Hydroxy-3-phenoxypropyl 2-ethylhexanoate (entry 15).
Column chromatography purification on silica gel with n-hexane-EtOAc (10:1) gave a colorless oil
(0.27 g, 92%); Rf 0.95 (50% n-hexane-EtOAc). IR (liquid film): 3517-3194 (br), 3061, 2978, 1733, 1239
1
cm-1. H NMR (250 MHz, CDCl3): δppm = 7.30-7.24 (m, 2 H, aryl), 6.98-6.88 (m, 3 H, aryl), 4.31-4.20
(complex, 3 H, CO2CH2, HCOH), 4.02-3.99 (m, 2 H, CH2OPh), 2.94 (s, 1 H, OH, exchangeable with D2O),
2.32-2.29 (m, 1 H, CHCO2), 1.63-1.49 (m, 4 H, (CH2CH2CH), 1.29-1.23 (m, 4 H, 2 CH2CH3), 0.91-0.83 (m,
6 H, 2 CH3). 13C NMR (62.5 MHz, CDCl3): δppm = 174.82, 158.17, 129.74, 120.81, 115.20, 70.98, 69.19,
68.04, 47.86, 30.65, 29.47, 24.39, 22.96, 14.94, 12.29. MS [m/z (%)]: 294.18 (17.3). Anal. Calcd for
C17H26O4: C, 69.36; H, 8.90. Found: C, 69.50; H, 9.06.
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2-Hydroxycyclohexyl 2-benzamidoacetate (entry 16).
Column chromatography purification on silica gel elution with EtOAc gave a white foam (0.25 g,
1
91%); Rf 0.62 (EtOAc). IR (liquid film): 3500-3170 (br), 3050, 2948, 1735, 1695, 1250 cm-1. H NMR
(250 MHz, CDCl3): δppm = 7.81-7.78 (m, 2 H, aryl), 7.68 (s, 1 H, NH, exchangeable with D2O), 7.46-7.34
(m, 3 H, aryl), 4.69-4.68 (m, 1 H, CO2CH), 4.15 (complex, 3 H, NCH2, HCOH), 3.49 (s, 1 H, OH,
exchangeable with D2O), 1.95 (br s, 2 H, CH2), 1.65 (br s, 2 H, CH2), 1.23 (br, 4 H, 2 CH2). 13C NMR (62.5
MHz, CDCl3) δppm: 170.16, 168.21, 133.44, 131.77, 128.49, 127.21, 79.27, 72.32, 42.24, 32.77, 29.98,
23.86, 23.76. MS [m/z (%)]: 277.13 (9.4). Anal. Calcd for C15H19NO4: C, 64.97; H, 6.91; N, 5.05. Found:
C, 64.85; H, 6.97; N, 5.19.
2-Hydroxy-2-methylpropyl 2-benzamidoacetate (entry 17).
Column chromatography purification on silica gel elution with n-hexane-EtOAc (1:1) gave a bright
brown foam (0.24 g, 94%); Rf 0.2 (50 % n-hexane-EtOAc). IR (liquid film): 3450-3190 (br), 3046, 2965,
1
1732, 1691, 1254 cm-1. H NMR (250 MHz, CDCl3): δppm = 7.85 (s, 1 H, NH, exchangeable with D2O),
7.75-7.73 (m, 2 H, aryl), 7.39-7.24 (m, 3 H, aryl), 4.09 (d, J = 5.1 Hz, 2 H, NCH2), 3.92 (s, 2 H, CO2CH2),
3.67 (s, 1 H, OH, exchangeable with D2O), 1.11 (s, 6 H, 2 CH3). 13C NMR (62.5 MHz, CDCl3) δppm
:
170.13, 168.42, 133.32, 131.79, 128.46, 127.25, 72.50, 69.45, 41.94, 25.91. MS [m/z (%)]: 251.12
(14.9). Anal. Calcd for C13H17NO4: C, 62.14; H, 6.82; N, 5.57. Found: C, 62.23; H, 6.97; N, 5.76.
Supplementary Material ((optional))
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/MS-number.
Acknowledgements
The author is thankful from the Shiraz University of Technology Research Councils for partial support
of this work.
Author Contribution Statement
S. Behrouz and M. N. Soltani Rad have designed the project and experiments, synthesized the
catalyst, carried out the spectroscopic data analyses and wrote the manuscript. M. A. Piltan achieved
the synthesis of all compounds using the catalyst. M.M. Doroodmand performed catalyst
characterization and data analyses.
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