Synthesis and characterization of ionic liquid immobilized on magnetic nanoparticles: A recyclable heterogeneous organocatalyst for the acetylation of alcohols

Article abstract of DOI:10.1016/j.jmmm.2015.10.044

Herein, we describe a simple and efficient procedure for the preparation of 3-((3-(trisilyloxy)propyl)propionamide)-1-methylimidazolium chloride ionic liquid supported on magnetic nanoparticle (TPPA-IL-Fe₃O₄). The structure of this magnetic ionic liquid is fully characterized by FT-IR, TGA, XRD, VSM, SEM, EDX and DLS techniques. TPPA-IL-Fe₃O₄ is employed as a catalyst for the acetylation of alcohols with acetic anhydride under mild and heterogeneous conditions at room temperature with good to excellent yields. The magnetic catalyst could be readily separate from the reaction media by simple magnetic decantation, and reused several times without significant loss of its catalytic activity.

Full text of DOI:10.1016/j.jmmm.2015.10.044

Author’s Accepted Manuscript
Synthesis and characterization of Ionic Liquid
immobilized on magnetic nanoparticles: A
recyclable heterogeneous organocatalyst for the
acetylation of alcohols
Arash
Norouzi
Ghorbani-Choghamarani,
Masoomeh
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PII:
S0304-8853(15)30678-8
http://dx.doi.org/10.1016/j.jmmm.2015.10.044
MAGMA60737
DOI:
Reference:
To appear in: Journal of Magnetism and Magnetic Materials
Received date: 29 March 2015
Revised date: 13 September 2015
Accepted date: 12 October 2015
Cite this article as: Arash Ghorbani-Choghamarani and Masoomeh Norouzi
Synthesis and characterization of Ionic Liquid immobilized on magnetic
nanoparticles: A recyclable heterogeneous organocatalyst for the acetylation of
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Synthesis and characterization of Ionic Liquid immobilized on magnetic
nanoparticles: A recyclable heterogeneous organocatalyst for the acetylation of
alcohols

Arash Ghorbani-Choghamarani and Masoomeh Norouzi
Abstract
Herein, we describe a simple and efficient procedure for the preparation of 3-((3-
trisilyloxy)propyl)propionamide)-1-methylimidazolium chloride ionic liquid supported on magnetic
nanoparticle (TPPA-IL-Fe O ). The structure of this magnetic ionic liquid is fully characterized by
(
3
4
FT-IR, TGA, XRD, VSM, SEM, EDX and DLS techniques. TPPA-IL-Fe O is employed as a
3
4
catalyst for the acetylation of alcohols with acetic anhydride under mild and heterogeneous
conditions at room temperature with good to excellent yields. The magnetic catalyst could be readily
separate from the reaction media by simple magnetic decantation, and reused several times without
significant loss of its catalytic activity.
Keywords
Magnetic nanoparticle, Immobilized ionic liquid, Acetylation, Alcohol.
1
. Introduction
The development of heterogeneous catalysts for organic synthesis has become a major area of research,
because of potential advantages of these materials over homogeneous systems (such as: simplified

Address correspondence to A. Ghorbani-Choghamarani, Department of Chemistry, Faculty of Science, Ilam
University, P.O. Box 69315516, Ilam, Iran; Tel/Fax: +98 841 2227022; E-mail address:
arashghch58@yahoo.comor a.ghorbani@mail.ilam.ac.ir

recovery, reusability and the potential for incorporation in continuous reactors and microreactors), they
could be as environmentally benign chemical procedures for academia and industry [1,2].
In recent years, ionic liquids (ILs) based heterogeneous catalysis has attracted a considerable attention
under the heading of ‘‘green chemistry’’ as they permit mutual advantages of both homogeneous as well
as heterogeneous catalysts in organic synthesis [3-7].
They are non-volatile, non-flammable, thermally stable, and have excellent solvation properties [8-9],
because of their unique physicochemical properties, including negligible vapour pressure, wide liquid
range, higher ionic conductivity and excellent solubility [10-12].
Although ILs possess some advantages but their practical applications have been restricted by some
difficulties in its recovery which lead to economical and environmental problems. On the other hand, their
high viscosity not only limits their mass transfer during catalytic reactions but also makes their handling
difficult. Moreover, the use of relatively large amounts of ILs is costly and may cause toxicological
concerns. These problems can be overcome by immobilization of ILs on solid supports to obtain
heterogeneous catalysts [13-16].
In this regard, the use of supported magnetic nanoparticles (MNPs) materials has been efficiently
employed as heterogeneous catalysts. The main advantage of a catalytic system based on magnetic
nanoparticles is that the nanoparticles can be efficiently isolated from the reaction mixture through a
simple magnetic separation process after reaction completion [17]. In the other hand, nanoparticles have
emerged as efficient alternative support materials for the immobilization homogeneous catalyst [18, 19].
These nanoparticles, because of their high surface area and unique magnetic properties, have a broad
range of potential uses in disciplines including physics, biomedicine, biotechnology, material science and
catalysis support applications [20-22]. Additionally, the MNP-supported catalysts also show high
dispersion and reactivity with a high degree of chemical stability. By utilizing these advantages of
magnetic nanoparticles over other supporting materials, various catalysts and ligands have been
immobilized on these particles [23].
Protection of hydroxyl groups is very important for their organic and analytical chemistry applications
[
24, 25]. Among the protecting groups for alcohols, the acetate esters are the most important. Also
acetylation of hydroxyl groups is one of the most important and frequently used transformations in
organic synthesis, especially in the synthesis of natural compounds, biologically active compounds, and
polyfunctional molecules such as nucleosides, carbohydrates, flavanones, naphthoquinones, pesticides,
and steroids [26-29].

Acetic anhydride is a cheap and commercially available reagent, which it has frequently used for the
acetylation of hydroxyl groups, giving ammonia as only by-product. Various catalytic systems have been
developed for this transformation [30-33]. Although these methods provide good reaction conditions and
short reaction times, only a few procedures have been reported for the selective acetylation of alcohols in
the presence of other functional groups such as phenols and amines. There is therefore still an urgent need
for the development of new catalysts capable of affecting the chemoselective acetylation of hydroxyl
groups in the presence of other reactive groups.
In this regards, as part of our research program to develop selective, non-corrosiveness, low cost and ease
of isolation [34-39], we report here the preparation of 3-((3-(trisilyloxy)propyl)propionamide)-1-
methylimidazolium chloride ionic liquid supported on magnetic nanoparticle (TPPA-IL-Fe O ) as a novel
3
4
organocatalyst for the protection of the hydroxyl group in solvent-free media at room temperature.
2
2
. Experimental
.1 Materials
Chemicals were purchased from Fisher and Merck chemical companies. The reagents and solvents were
obtained from Sigma-Aldrich, Fluka or Merck and used without further purification. TPPA-IL-Fe O
3
4
,
were characterized using a Holland Philips X pert X-ray powder diffraction (XRD) diffractometer (Co
Ka, radiation= 0.154056 nm), at a scanning speed of 2◦/min from 10° to 100°. The particle size and
morphology were investigated using scanning electron microscopy (SEM) by FESEM-TESCAN MIRA3
on an accelerating voltage of 200 kV. IR spectra were recorded as KBr pellets on a VRTEX 70 model
BRUKER FT-IR spectrophotometer. The thermogravimetric analysis (TGA) curves are recorded using a
PL-STA 1500 device manufactured by Thermal Sciences. VSM measurements were performed using a
Vibrating Sample Magnetometer (VSM) MDKFD. The magnetization measurements were carried out in
an external field up to 15 kOe at several temperatures. Dynamic laser scattering (DLS) was performed on
1
13
Malvern ZEN 3600. H NMR and C NMR spectra were recorded with a Bruker DRX-400 spectrometer
at 400 and 100 MHz respectively.
2
.2 Preparation of magnetic Fe O nanoparticles (MNPs)
3 4
The mixture of FeCl .6H O (5.838 g, 0.022 mol) and FeCl .4H O (2.147 g, 0.011 mol) were dissolved in
3
2
2
2
1
1
00 mL of deionized water in a three-necked bottom (250 mL) at 80 °C under N atmosphere. Thereafter,
2
0 mL of aqueous NH solution (32%) was added into mixture within 30 min with vigorous mechanical
3

stirring. The black precipitate solid was isolated by magnetic decantation, washed with double-distilled
water until neutrality, and further washed twice with ethanol and dried at 80 °C in vacuum.
2
.3 Preparation of Fe O -(3-aminopropyl)-triethoxysilane
3 4
The obtained magnetic nanoparticles (MNPs) powder (1.5 g) was dispersed in a mixture of ethanol and
water (250 ml, 1:1 by volume) by sonication for 30 min. Then 3-aminopropyl (triethoxy) silane (99%, 3
mL) was added to the mixture, and then kept under mechanical stirring under N atmosphere at room
2
temperature for 8 h. At the end of the reaction, the resulted product was washed with copious amounts of
deionized water and ethanol under magnetic decantation, and dried under vacuum at room temperature
overnight.
2
.4 Preparation of TPPA-IL-Fe O
3 4
The amino-functionalized MNPs (1 g) were dispersed in dry CH Cl (3 mL) by ultrasonic bath for 10
2
2
min, and the flask was cooled in an ice-water bath. Triethylamine (3.2 mL) was added and stirred for 30
min. Subsequently, acryloyl chloride (0.8 mL, 9.84 mmol) was added drop wise over a period of 30 min
at room temperature. The mixture was stirred at room temperature for 48 h. Then, the prepared
functionalized MNPs nanoparticles were separated by magnetic decantation and washed three times with
acetone and deionized water to remove the unattached substrates. The resulting product was dispersed in
methanol (10.0 mL), and stirred with 1-methylimidazole (2.0 mmol, 0.164 g). Subsequently, a
stoichiometric amount of concentrated HCl (97%, 0.2 mL) was added drop wise and the mixture stirred
for 1 h at 0 °C and then stirred for 1 week at room temperature. The solids were separated by a magnetic
field and washed with acetone. The resulting product was dried under vacuum for 12 h.
2
.5 General procedure for the preparation of alkyl acetates
To a stirred solution of 4-bromobenzylalcohol (1 mmol, 0.185 g) in freshly acetic anhydride (2 mmol,
.19 mL) TPPA-IL-Fe O (10 mg) was added and the reaction mixture was stirred at room temperature
0
3
4
for 20 min. The reaction progress was monitored by TLC (acetone: n-hexane, 2:8). After completion of
the reaction, the catalyst was separated by an external magnet and the mixture was diluted with CH Cl .
2
2
The organic layer was washed with NaHCO (5 mL) solution and water, then dried over anhydrous
3
Na SO . Finally, the organic solvents were evaporated and 4-bromobenzyl acetate was obtained in 96%
2
4
yield.

4
-Isopropylbenzyl acetate. 1H-NMR (CDCl , 400 MHz): δ 1.33 (d, J = 6.8 Hz, 6H), 2.15 (s, 3H), 2.98
3
13
(
m, 1H), 5.15 (s, 2H), 7.29 (d, J = 8.4 Hz, 2H), 7.36 (d, J = 8.4 Hz, 2H); C-NMR (CDCl , 100 MHz): δ
3
2
3
7
1, 24.1, 33.9, 66.3, 126.7, 128.6, 133.4, 149.1, 170.9.
-Flourobenzyl acetate. 1H-NMR (CDCl , 400 MHz): δ 2.096 (s, 3H), 5.1 (s, 2H), 7.14–7.23 (m, 3H),
3
1
3
.4–7.46 (m, 1H); C-NMR (CDCl , 100 MHz): δ 21.1, 65, 115.1, 122.5, 130.9, 139.5, 162.6, 170.7.
3
(3S,8S,9S,10R,13R, 14S, 17R)-10, 13-dimethyl-17-((R)-6- methylheptan-2-yl)-2, 3, 4, 7, 8, 9,
1
4
1
4
2
3
0,11,12,13,14,15,16,17- tetradecahydro-1H-cyclopenta[a]phenanthren-3-yl acetate. 1H-NMR (CDCl3,
00 MHz): δ 0.71(s, 3H), 0.89 (d, J = 6.8 Hz, 6H), 0.95 (d, J = 6.4 Hz, 4H), 1.07 (s, 4H), 1.15 (m, 7H),
.38 (m, 4H), 1.55 (m, 8H), 1.8–1.97 (m, 3H), 1.94–1.98 (s, 1H), 2.05 (s, 3H), 2.34 (d. J = 7.2 Hz, 2H),
1
3
.63 (m, J = 5.2 Hz, 2H), 5.398 (d, J = 4.4 Hz, 1H); C-NMR (CDCl , 100 MHz): δ 11.8, 18.7, 19.3, 21,
3
1.4, 22.6, 22.8, 23.8, 24.3, 27.8, 28, 28.2, 31.8, 31.9, 35.8, 36.2, 36.6, 37, 38.1,
. Results and discussion
The whole preparation route to obtain TPPA-IL-Fe O includes three steps as illustrated in Scheme
3
4
2
+
3+
1
. At first, the magnetite prepared by coprecipitation from Fe and Fe using NH solution. Then,
3
the 3-aminopropyltriethoxysilane was added to the ethanolic solution of Fe O nanoparticles to
3
4
achieve amine-coated Fe O nanoparticles through coordination bond with hydroxyl group. In the
3
4
second step, the reaction of amino groups with acryloyl chloride led to acryloxyl groups-
functionalized magnetic Fe O nanoparticles. Finally, the TPPA-IL-Fe O was prepared by the
3
4
3
4
Michael reaction of the acryloxyl groups with 1-methylimidazole in the presence of HCl.

Scheme 1. Synthesis of TPPA-IL-Fe O4
3
The prepared catalyst was characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), the
X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy
(EDX), vibrating sample magnetometer (VSM) and dynamic laser scattering (DLS).
3
.1. Catalyst characterizations
To identify the functional groups of TPPA-IL-Fe O , FT-IR analysis was carried out. Fig. 1 shows the
3
4
FT-IR spectra of Fe O nanoparticles, amine-functionalized Fe O , MNP-acryloxyl and TPPA-IL-Fe O
4
3
4
3
4
3
-1
along with their differential spectrum. The strong absorption at 580 cm was characteristic of the Fe–O
−
1
stretching vibration but for Fe O nanoparticles at 572 cm as a blue shift, due to the size reduction. The
3
4
−
1
broad band at 3500-3000 cm for MNP corresponds to the absorption of stretching vibration of hydroxyl
groups. The amine-functional groups of Fe O and the corresponding infrared absorption frequency are
3
4
shown in Fig. 1b. The spectra display a number of absorption peaks, indicating the 3-aminopropyl
−1
(triethoxy) silane was bonded on the surface of MNPs. The absorption around at 1111 and 1001 cm
corresponds to Si–O stretching vibration. The FT-IR spectroscopic analysis shows broad band at 3394

−
1
−1
cm , representing bonded –NH groups. The band observed at about 2922–2854 cm could be assigned
2
to the aliphatic C–H groups.
−
1
The spectrum of Fe O -acryloxyl Fig. 1c, a peak at wave number of 1710 cm is observed due to
3
4
−
1
stretching vibration of carboxyl group. An absorption band at 1642 cm correspondence to the C=C
−1
stretching mode, which conjugate with C=O bond (amide 1 band). The peak observed at 3020 cm
−
1
corresponds to the secondary amide group. The peak observed at 1245 and 1164 cm could be assigned
to C-N stretching and C–O stretching of ether groups, respectively.
−
1
IR spectra of TPPA-IL-Fe O have an adsorption band at 1160 cm , which is assigned to the C-N
3
4
-1
stretching vibration. Absorption peaks at 3170-3121 cm (C-H stretching vibration of imidazole ring) and
-1
absorption bands at nearly 1622 cm (C=N double bond) indicate the presence of imidazole rings,
therefore observation of these peaks in the IR spectra of TPPA-IL-Fe O proves that N-methylimidazole
3
4
was successfully attached to the surface of Fe O nanoparticles
3
4

Fig. 1. FT-IR spectra of Fe O nanoparticles (a), amine-functionalized (b), MNP-acryloxyl (c), TPPA-IL-Fe O (d).
3
4
3
4
Thermal stability of Fe O and TPPA-IL-Fe O nanoparticles was investigated by TGA, which they are
3
4
3
4
presented in Fig. 2. MNP shows two-step weight loss behaviour (Fig. 2a), the initial weight loss up to 100
C is due to the removal of physically adsorbed solvents and surface hydroxyl groups. In addition, there is
°
a weight loss of about 3.5% displayed for MNPs in the temperature range of 200 and 474 °C is attributed
to dehydration of the surface –OH groups. There are two weight loss steps in TGA curve of TPPA-IL-
Fe O Fig. 2b. The first mass loss around 100 °C may be due to removal of surface adsorbed water of the
3
4
catalyst. The organic components were decomposed completely at 150-373°C. According to the TGA
results, the amount of TPPA–IL supported on Fe O was evaluated to be 16.3% (w/w).
3
4
1
00
95
90
85
80
75
70
65
a
b
0
100 200 300 400 500 600 700 800
Temperature (°C)
Fig. 2. TGA curves of Fe O (a), TPPA-IL-Fe O (b)
3
4
3
4
The crystalline structures of TPPA-IL-Fe O were investigated by powder X-ray diffraction (XRD)
3
4
(
Fig. 3). The XRD patterns of the synthesized particles show six characteristic peaks at (2θ = 21.3°,
5.2°, 41.5°, 50.6°, 63.2°, 67.5° and 74.4°), related to their corresponding indices ((1 1 1), (220),
311), (400), (422), (511), and (440) respectively. The sample show very broad peaks indicating the
3
(
ultra-fine nature and small crystallite size of the particles.
The average size of TPPA-IL-Fe O nanocatalyst diameter was calculated to be 19±1 nm from the
3
4
XRD results by Scherrer’s equation: D= kλ/ß Cosθ.
Where D is the average particle size of the phase under investigation, k is Scherrer's constant (0.9),
λ is the applied wavelength (1.5405 °A), ß is the corrected diffraction line full-width at half-
maximum (FWHM), applied to the principal diffraction peak corresponding to the plane (3 1 1) and
θ is the angle of diffraction. Finally, the analysis of the diffraction pattern showed the formation of

a cubic spinel structure, in the sample due to the strongest reflection that proceeds from the (3 1 1)
plane (Fig. 3), characteristic of such a phase.
Counts
160
140
120
100
(3 1 1)
80
60
40
20
0
(
2 2 0)
(
4 4 0)
(1 1 1)
(
4 0 0)
(
5 1 1)
(
4 2 2)
0
10
20
30
40
50
60
70
80
90 100
Position [°2Theta]
Fig. 3. XRD patterns TPPA-IL-Fe O4
3
Further characterization of TPPA-IL-Fe O nanoparticles was done using Scanning Electron Microscope
3
4
(
SEM) with different magnifications. The SEM image of the synthesized TPPA-IL-Fe O nanoparticle is
3 4
shown in the Figure 4 that indicates well dispersed particles that are more or less spherical. The size of
these particles is in the ranges from 8 nm to 18 nm, which confirms their nanostructure. The surface
morphology of the supported TPPA-IL was composed of relatively well formed and spherical particles
have uniform coating of the organic layers. The EDX spectrum of TPPA-IL-Fe O is shown in Fig. 4. The
3
4
result shows that the main elements in the TPPA-IL-Fe O nanoparticles are Fe, O, Si, N, Cl and C.
3
4

FeK
2000
1500
1000
O K
FeL
N K
500
ClK
ClK
FeK
C K
SiK
keV
0
0
5
10
Fig. 4. SEM images of TPPA-IL-Fe O nanoparticles with different magnifications. The EDX image TPPA-IL-Fe O
4
3
4
3
Vibrating sample magnetometer curve of TPPA-IL-Fe O at room temperature has been illustrated in Fig.
3
4
5
. The saturation magnetization value (Ms) for TPPA-IL-Fe O nanoparticle was found to be 43.9
3 4
−
1
emug .

50
40
30
20
10
0
-
10000
-5000
0
5000
10000
-
-
-
-
-
10
20
30
40
50
Applied Field (Oe)
Fig. 5. VSM curve of TPPA-IL-Fe O at r.t.
3
4
The dynamic laser scattering (DLS) measurement of TPPA-IL-Fe O nanoparticle was shown in Fig. 6.
3
4
The hydrodynamic diameter of the nanoparticles in water was found to be mono disperse with mean values of 31.1 nm,
slightly larger than observed from XRD report due to the effect of both solvation, and the presence of ionic liquid
immobilized onthesurfaceofFe O nanoparticles.
3
4

Fig. 6. The dynamic laser scattering (DLS) measurement of nano TPPA-IL-Fe O4
3
3
.2. Catalytic studies
The effectiveness of the prepared TPPA-IL-Fe O as heterogeneous, reusable and inexpensive catalyst
3
4
was tested in the acetylation of alcohols under nearly neutral conditions (Scheme 2).
Scheme 2. Preparation of acetates.
Further efforts were focused on optimizing of reaction conditions, and these results are summarized in
Table 1. Initially, we carried out the acetylation of 4-bromobenzyl alcohol with acetic anhydride as
acetylating agent in the presence of catalytic amounts of TPPA-IL-Fe O in various organic solvents. But
3
4
reaction didn’t complete after 24 hours under solvent conditions. Eventually, we decided to carry out the
acetylation reaction in the absence of the solvent for the all reactions (solvent-free conditions).
To investigate the effect of the catalyst concentration, systematic studies are carried out in the presence of
different amounts of the catalyst (1, 5, 8, 10 mg) under solvent-free conditions, affording with 22%, 28%,

8
6% and 96% isolated yields, respectively. Thus, the best yield is found in the presence of 10 mg of
TPPA-IL-Fe O , and the use of higher amounts of catalyst (30 mg) does not improve the result to an
3
4
appreciable extent (Table 1, entry 5).
Table 1. Optimization of the catalyst amount of TPPA-IL-Fe O4
3
b
Entry
Catalyst amount (mg)
Yield (%)
1
2
3
4
5
6
1
22
28
5
8
10
86
96
30
95
No catalyst
Trace
a
Reaction conditions: 4-Bromo benzylalcohol (1 mmol), Acetic anhydride (2 mmol), room
temperature.
b
Yields refer to isolated pure product.
A variety of alcohols were efficiently esterificated to their corresponding acetate compounds under
standard reaction conditions, and the results are shown in Table 2. The catalytic system was then applied
to various benzylic, allylic, and aliphatic alcohols. The acetylation of para-, meta- and ortho-substituted
primary benzyl alcohols were performed to the corresponding substituted acetate in good to excellent
yields (Table 2, entries 1–10).
It seems that the reaction rates of benzyl alcohols with electron‐donating and electron‐ withdrawing
group’s substituent had no significant effect on the reaction time and yields. Next, we turned our attention
to non-benzylic primary alcohols, which were selectively converted to their corresponding acetates with
high efficiency at the same reaction conditions (Table 2, entry 11).
These results encouraged us to evaluate the acetylation of long chain aliphatic alcohols (such as 1-
hexanol) under similar reaction conditions (Table 2, entry 12). Also, cinnamyl alcohol, an allyllic alcohol,
was selectively converted to the corresponding acetate, which carbon double bond was intact during the
acetylation reaction (Table 2, entry 13).
Furthermore, the presence protocol was also applicable to the acetylation of secondary alcohols under the
same reaction conditions. Aliphatic and benzylic secondary alcohols were effectively esterificated to the
corresponding acetates (Table 2, entries 14–18), but the reaction rate is slower than primary ones. For
example, the acetylation of benzhydrol afforded benzhydryl acetate taking 3h in 91% yield (Table 1, entry
1
4).

a
Table 2. Acetylation of alcohols
b
Entry
1
Substrate
Product
Time (min) Yield (%)
2
2
3
0
94
96
2
3
4
70
80
96
94
5
6
25
60
93
94
7
150
270
83
58
8
9
60
7h
80
98
97
96
1
1
0
1
1
1
2
3
5h
50
98
97
1
1
4
5
180
240
91
95

1
6
80
95
1
1
7
8
120
120
80
86
a
Reaction conditions: substrate (1 mmol), acetic anhydride (2 mmol), catalyst 10 mg, room temperature.
Yields refer to isolated pure products.
b
We investigated the reaction of tertiary alcohols with acetic anhydride under described conditions. It was
observed that they have not reacted under the described experimental conditions (Scheme 3). Excellent
chemoselectivity was seen for the conversion of secondary alcohols in the presence of tertiary alcohols
such as 1-admantanol. Interestingly, the designed catalyst was capable to affect the chemoselective
acetylation of hydroxyl groups in the presence of other reactive groups. Also the acetylation of 4-
bormobenzylalcohol did occur selectively in the presence of phenols and the hydroxyl group of phenol
was intact during this reaction (Scheme 3).
Scheme 3. Chemoselectivity of the acetylation.
In order to investigate the efficiency of this new procedure in comparison with known reported
procedures in the literature, the results for the acetylation of hydroxyl groups, compared with the best of

the well-known data from the literature as outlined in the Table 3. As shown in Table 3, the previously
reported procedures suffer from one or more disadvantages such as longer reaction time and low yields of
products.
Table 3. Comparison of different methods used for the acetylation of 4-bormobenzylalcohol using
acetic anhydride with different catalysts
a
Entry
Catalyst and Reaction conditions
TPPA-IL-Fe O at rt
Time (h)
0.33
4
Yield (%)
Ref.
1
2
3
4
5
96
94
94
88
85
this work
[40]
3
4
K CoW O .3H O at reflux
5
12 40
2
Silphos [PCl _n(SiO )n] at reflux
12
[41]
3
2
Acylimidazolium acetate
2.6
[42]
Mg(HSO ) , CH Cl at reflux
1.5
[43]
4
2
2
2
a
Isolated yield.
A plausible mechanism for described transformation has been shown in Scheme 4. Based on this
mechanism, the TPPA-IL-magnetic nanoparticles act as a Lewis acid in the reaction that activates the
acetic anhydride followed by nucleophilic addition of alcohols, which produces the corresponding
acetate.
Scheme 4. Proposed mechanism for the acetylation of alcohols

The reusability of the catalysts is an important advantage and makes them useful for commercial
applications. In this aim, the activity of TPPA-IL-Fe O was investigated in the acetylation of 4-
3
4
bormobenzylalcohol over nine runs, during which a small appreciable loss was observed in the catalytic
activity (Fig. 6). After each run, the solid catalyst was magnetically separated and washed with organic
solvents such as CH Cl and the residue was used in the next run alternatively.
2
2
1
00%
8
6
4
2
0%
0%
0%
0%
0%
1
2
3
4
5
6
7
8
9
Cycle
Fig. 6. Reusability of the nanocatalyst
3
. Conclusions
In conclusion, in this project we have synthesised a novel supported ionic liquid on magnetic
nanoparticles. This ionic liquid was fully characterized. Also we have developed an efficient procedure
for the chemoselective acetylation of alcohols with acetic anhydride. Attractive features of this method
are the simple experimental procedure, good yields and green content of the procedure. This catalytic
system showed an excellent reactivity combined with efficient catalyst recyclability without any
decreases in activity.
Acknowledgements
This work was supported by the research facilities of Ilam University, Ilam, Iran.
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26.
Highlights
TPPA-IL-Fe O were prepared and well characterized
3
4
TPPA-IL-Fe O could be easily separated from solution with an external magnet
3
4
The TPPA-IL-Fe O was characterized by, FT-IR, SEM, TGA, DLS, EDS and VSM
3
4
The catalytic activity of TPPA-IL-Fe O was investigated in acetylation of alcohols
3
4
Graphical abstracts

Synthesis and characterization of Ionic Liquid immobilized on magnetic
nanoparticles: A recyclable heterogeneous organocatalyst for the acetylation of
alcohols
*
Arash Ghorbani-Choghamarani and Masoomeh Norouzi