Acetylation of alcohols and phenols under solvent-free conditions using iron zirconium phosphate

Article abstract of DOI:10.1016/S1872-2067(14)60280-1

Iron zirconium phosphate (ZPFe) nanoparticles were found to function as an efficient catalyst for the acetylation of a wide range of alcohols and phenols using acetic anhydride, generating good to excellent yields under solvent-free conditions. The steric and electronic properties of various substrates had a significant influence on the reaction conditions required to achieve the acetylation. The catalyst used in the current study was characterized by inductively coupled plasma-optical emission spectrometry, X-ray diffraction, N₂ adsorption-desorption, scanning electron microscopy, and transmission electron microscopy. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 9.3 ? when Fe³⁺ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. This new method for the acetylation of alcohols and phenols has several important advantages, including mild and environmentally friendly reaction conditions, as well as good to excellent yields and a facile work-up.

Full text of DOI:10.1016/S1872-2067(14)60280-1

Chinese Journal of Catalysis 36 (2015) 595–602
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
Acetylation of alcohols and phenols under solvent‐free conditions
using iron zirconium phosphate
Abdol R. Hajipoura,b,*, Hirbod Karimia,c, Amir Mastia
a Pharmaceutical Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156, Iran
b Department of Neuroscience, University of Wisconsin, Medical School, Madison, WI 53706‐1532, USA
c Young Researchers and Elite Club, Shahreza Branch, Islamic Azad University, Shahreza, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
Iron zirconium phosphate (ZPFe) nanoparticles were found to function as an efficient catalyst for
the acetylation of a wide range of alcohols and phenols using acetic anhydride, generating good to
excellent yields under solvent‐free conditions. The steric and electronic properties of various sub‐
strates had a significant influence on the reaction conditions required to achieve the acetylation.
The catalyst used in the current study was characterized by inductively coupled plasma‐optical
emission spectrometry, X‐ray diffraction, N2 adsorption‐desorption, scanning electron microscopy,
and transmission electron microscopy. These analyses revealed that the interlayer distance in the
catalyst increased from 7.5 to 9.3 Å when Fe3+ was intercalated between the layers, whereas the
crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at
least six times without any discernible decrease in its catalytic activity. This new method for the
acetylation of alcohols and phenols has several important advantages, including mild and environ‐
mentally friendly reaction conditions, as well as good to excellent yields and a facile work‐up.
© 2015, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Received 24 November 2014
Accepted 26 December 2014
Published 20 April 2015
Keywords:
Iron zirconium phosphate
Nanoparticle
Acetylation
Alcohol
Phenol
Solvent‐free condition
Solid catalyst
Published by Elsevier B.V. All rights reserved.
1. Introduction
sesses excellent selectivity towards Pb2+, Zn2+, and Fe3+ as an
ion exchanger [15–17]. Furthermore, ZP has been shown to
α‐Zirconium phosphate (ZP) is one of the most important
compounds in inorganic chemistry, and the layered structure of
this material has led to its use in a variety of different fields
[1–3]. ZP behaves as a unique ion exchanger because of its ex‐
ceptionally poor aqueous solubility, high thermal stability, re‐
sistance to radiation and abrasive properties [4,5]. The H+ of
the P–OH moiety in ZP can be exchanged for various other ions,
resulting in an enlargement of the interlayer distance [6–9].
Several studies pertaining to the successful exchange of this
proton with various divalent and trivalent cations, including
Mn2+, Co2+, Ni2+, Cu2+, Fe2+, Fe3+, and Zn2+, have been presented
in the literature [10–14]. It has also been reported that ZP pos‐
exhibit antibacterial activity when loaded with Cu2+, Zn2+, or
Ce3+ [5,6,13,14]. There have also been several reports concern‐
ing the catalytic activities of ion‐exchanged materials of this
type, including the use of zinc zirconium phosphate (ZPZn) as a
catalyst in the acetylation of alcohols and phenols and the use
of copper zirconium phosphate (ZPCu) as a catalyst during the
selective oxidation of alcohols [18–24].
The protection and deprotection of organic functional
groups are important during multi‐step organic syntheses. The
particular functional group transformation chose is based on
considering the simplicity of the reaction, as well as the ability
to obtain high yields of the desired products and short reaction
* Corresponding author. Tel: +98‐0311‐3913262; Fax: +98‐0311‐3913252; E‐mail: haji@cc.iut.ac.ir
This work was supported by the Isfahan University of Technology (IUT), IR Iran.
DOI: 10.1016/S1872‐2067(14)60280‐1 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 36, No. 4, April 2015

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Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
times, and to achieve a low cost process with an easy work‐up
[25,26]. The acetylation of alcohols, phenols, thiols, and amines
is one of the most important and frequently used transfor‐
mations in organic synthesis, especially in the synthesis of nat‐
ural compounds, biologically active compounds, and polyfunc‐
tional molecules such as nucleosides, carbohydrates, chalcones,
flavanones, naphthoquinones, pesticides, and steroids. Acety‐
lated groups are also commonly found in cosmetics and food
stuffs, as well as in solvents, perfumes, plasticizers, flavors,
polymers, and pharmaceuticals [25–27]. One of the most com‐
mon examples of a compound containing an acetylated group is
acetylsalicylic acid (trademarked as Aspirin), which is pro‐
duced by the acetylation of salicylic acid with acetic anhydride
(AA) in the presence of an acid catalyst [28]. The acetyl group is
one of the most inexpensive and commonly used protecting
groups for –OH, –SH, and –NH2 moieties because the resulting
acetylated compounds are stable under a variety of reaction
conditions and in contact with a wide range of reagents. Fur‐
thermore, the acetyl group can be readily introduced using
inexpensive reagents and is easily removed by mild alkaline
hydrolysis [29–31].
A number of different procedures have been developed for
the acetylation of alcohols, phenols, amines, and thiols using
both homogeneous and heterogeneous catalysts. These have
included VIV(TPP)(OTf)2 [27], La(NO3)3·6H2O [29], B(C6F5)3
[30], NSPVPHS [31], ZnCl2 [32], borated zirconia [33], ZnO2
[34], Ce(OTf)3 [35], SiO2–ZnCl2 [36], H3PW12O40 [37], DMAP·HCl
[38], Cu(BF4)2 [39], silica‐bonded sulfamic acid [40], Cp2ZrCl2
[41], [TMBSA][HSO4] [42], [bmim][OTs] [43], [MMPPA][HSO4]
[44], SaSA [45], SBNPSA [46], SuSA [47], P(4‐VPT) [48],
acylimidazolium acetate [49], polyvinylpolypyrrolidoniume
tribromide [50], ZnAl2O4@SiO2 [51], P2O5/Al2O3 [52],
[Hmim]HSO4 [53], yttria–zirconia [54], CoCl2 [55],
MWCNTs‐C‐PO3H2 [56], NiCl2 [57], Ni/SiO2 [58], DBSA [59], rice
husk [60], anhydrous NiCl2 [61], LaFeO3/SiO2 [62], and
Fe/SBA‐15 [63]. However, most of these catalysts have both
advantages and limitations. Despite extensive interest in the
development of new methods of acetylation, there is still a re‐
quirement to develop simple, efficient, inexpensive, widely
applicable, reusable, and environmentally benign catalysts and
procedures capable of promoting the acetylation process. With
growing environmental concerns, one of the most promising
ways to achieve these goals appears to be the use of environ‐
mentally friendly insoluble catalysts and/or solvent‐free condi‐
tions. An insoluble catalyst may be readily recovered from the
post‐reaction mixture by simple filtration and potentially recy‐
cled and reused several times, making the process more eco‐
nomically and environmentally viable. Furthermore, reported
examples have demonstrated that heterogeneous catalysts
typically require less labor‐intensive work‐up procedures. Sol‐
vent‐free synthetic methods are also valuable for both envi‐
ronmental and economic reasons [22,24]. With this in mind,
and as part of ongoing work towards the development of effi‐
cient green catalysts for organic transformations [64,65] with a
particular emphasis on the acetylation and acylation of aro‐
matic compounds [52,53], we report herein the use of iron
zirconium phosphate (ZPFe) as an efficient catalyst for the
mild, simple acetylation of alcohols and phenols under sol‐
vent‐free conditions. This new ZPFe catalyst was characterized
by inductively coupled plasma‐optical emission spectroscopy
(ICP‐OES), X‐ray diffraction (XRD), N2 adsorption‐desorption,
scanning electron microscopy (SEM), and transmission elec‐
tron microscopy (TEM).
2. Experimental
2.1. Catalyst synthesis
All the reagents and solvents used in the current study were
purchased from the Merck Chemical Company and used with‐
out further purification. The catalyst was prepared according to
previously published procedures, with minor modifications
[2,8–10]. As an initial step, ZP was synthesized according to the
following procedure. ZrOCl2·8H2O (5 g) was heated under re‐
flux conditions in a solution of H3PO4 (50 mL, 12 mol/L) for 24
h. The resulting mixture was cooled to ambient temperature to
give a suspension. After filtration, the filter cake was washed
with a solution of H3PO4 (0.1 mol/L) until the filtrate was free
of chloride ions. The filter cake was then washed several times
with distilled water until the pH of the filtrate was neutral. The
remaining solid was dried in an oven at 110 °C for 24 h [2].
ZPFe was prepared through an ion‐exchange reaction [8–10].
Briefly, ZP (3 g) was dispersed in deionized water (50 mL) at
50 °C, and the resulting suspension was treated with a solution
of Fe(OAc)3 (100 mL, 0.1 mol/L) in water (providing an excess
of Fe3+). This mixture was then heated under reflux for 4 d. It is
noteworthy that the acetate ion performed effectively as a base
to keep the hydrogen ion concentration in the solution suffi‐
ciently low so as to achieve high loadings of the catalyst [8]. A
complete exchange between the cations and the hydrogen ions
of the P–OH groups could not be achieved in less than 3 d or
below 80 °C [13]. The resulting slurry was filtered while hot to
give a light yellow solid that was washed with distilled water
until no Fe3+ ions could be detected in the filtrate (that is, until
the filtrate was colorless). The solid product was then dried at
100 °C for 24 h before being calcined at 600 °C for 4 h to give
the final product, Fe1/3[Zr2(PO4)3], as a pale yellow solid
(Scheme 1).
2.2. Catalyst characterization
The chemical composition of the ZPFe catalyst was evaluat‐
ed both before and after the catalytic reaction by ICP‐OES using
an Optima 7300 V ICP‐OES spectrometer (PerkinElmer). Cata‐
OH
OH
P
P
110 o
C
H3PO4
White precipitate of
zirconium phosphate
Zr 4+ solution
Zr
Zr
100 oC, 24 h
24 h
Fe3+
O
O
P
O
P
P
Fe(AcO)3
Refluxe, 4 d
600 oC
4 h
Drying at 100 oC
24 h
Zr
Zr
Fe1/3[Zr2(PO4)3]
Scheme 1. Summary of the ZPFe preparation procedure.

Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
597
(002)
Scheme 2. Summary of the acetylation procedure.
ZPFe
lyst samples were also ground into fine powders and analyzed
by XRD on a Philips X’pert X‐ray diffractometer. The specific
surface areas of the samples were determined from their N2
adsorption–desorption isotherms, using the BET method, on a
Quantachrome ChemBET 3000 instrument. Each sample was
degassed at 400 °C for 2 h before being analyzed to remove any
adsorbed species from the surface. The surface morphologies of
the ZP and ZPFe materials were determined by SEM observa‐
tions employing a Philips XL microscope. TEM images of ZPFe
were obtained on a CENTRA 100 TEM system (Zeiss).
(002)
ZP
5
10
15
20
25
30
35
40
2/(o )
Fig. 1. XRD patterns of powdered ZP and unused ZPFe.
in the literature [8–10]. These results also demonstrate that
there was negligible leaching of iron ions into the reaction me‐
dia during the initial use of the catalyst.
2.3. General experimental procedure for the acetylation of
substrates under solvent‐free conditions
Figure 1 presents the powder XRD patterns of the ZP and
ZPFe materials, indicating characteristic reflections in the 2θ
range of 5°–40°. The diffraction peak generated by ZP at a 2θ of
approximately 12° was assigned to a d002 basal spacing of 7.5 Å
between planes, in good agreement with the patterns previ‐
ously reported for ZP and its derivatives having a hexagonal
crystal system [2].
The ZPFe pattern indicates that the d‐spacing of the (002)
plane in this material was increased, demonstrating that Fe3+
ions intercalated into the ZP interlayers and thus increased the
ZPFe (1 mol%) was added to a mixture of alcohol (1 mmol)
and AA (2 mmol), and the resulting mixture was stirred at 40 °C
for a specified time (Scheme 2). Upon completion of the reac‐
tion (as determined by gas chromatography), the catalyst was
separated from the reaction mixture by centrifuge, after which
the supernatant was collected and diluted with a 10% NaHCO3
solution (10 mL) before being extracted with Et2O (2 × 10 mL).
The combined organic extracts were washed and then dried
over anhydrous CaCl2 before being evaporated to dryness un‐
der vacuum to give the desired product. In some cases, it was
necessary to purify the product by column chromatography on
a silica gel column with elution by a mixture of cyclohexane and
ethyl acetate.
d002 basal interlamellar spacing from the original value of 7.5 Å
to 9.3 Å. It is well known that the radii of the Fe3+ ion (0.64 Å)
and the hydrated Fe3+ ion (3.9 Å) are smaller than the basal
spacing of ZP (7.5 Å) [66,67]. These results therefore provide
evidence that Fe3+ ions were inserted into the ZP interlayers
and increased the basal spacing of the modified ZP during the
ion exchange process [4,9,10,17]. Taken together, the above
characterization data show that ZPFe had been successfully
synthesized. The XRD pattern of the ZPFe catalyst after the 7th
run demonstrates that the basal spacing of the ZP was ap‐
proximately 10.5 Å, a value only slightly larger than that of the
fresh ZPFe catalyst. This increase may have occurred because
of the presence of a reduced quantity of Fe3+ ions on the ZP
surface together with an increase in the number of water mol‐
ecules between the layers, meaning that Fe3+ ions may have
been washed off during the regeneration of the catalyst during
the process described in Section 2.4 (Table 1).
2.4. Recyclability studies
To examine the recyclability of the catalyst, the ZPFe was
recovered from the reaction media and re‐used. Following each
use, the catalyst was separated from the reaction mixture by
centrifugation, washed sequentially with ethanol and water,
dried at 110 °C for 2 h, and then activated at 450 °C for 2 h.
3. Results and discussion
3.1. Catalyst characterization
The data resulting from ICP‐OES analyses of the ZP and
ZPFe are shown in Table 1. The results obtained in the current
study for ZPFe were compared with those reported previously
Figure 2 shows a representative N2 adsorption–desorption
isotherm of ZPFe over the relative pressure range (p/p0) of
0.1–1.0. From these data, the ZPFe surface area was deter‐
mined to be 107.1 m2/g. The isotherm exhibits three adsorp‐
tion stages at p/p0 < 0.36, 0.36 < p/p0 < 0.92 and p/p0 > 0.92.
The isotherm also shows a typical type IV shape with a distinct
hysteresis loop, characteristic of a mesoporous material [68].
The hysteresis loop (type H3) is associated with the occurrence
of capillary condensation in the mesopores, indicating the
presence of a mesoporous structure in the ZPFe catalyst. The
observed increase in adsorption at higher p/p0 values shows
Table 1
Elemental compositions of iron zirconium phosphate catalysts (at%).
Sample
ZP
Fe
—
9.7
9.5
4.9
O
Zr
P
63.1
58.7
59.7
63.5
13.6
11.9
12.0
12.2
23.3
19.7
18.8
19.4
ZPFe
ZPFe a
ZPFe b
a After run 1.
b After run 7.

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Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
100
90
80
70
60
50
40
Adsorption
Desorption
0.0
0.2
0.4
0.6
0.8
1.0
p/p0
Fig. 2. N2 adsorption‐desorption isotherm of ZPFe.
Fig. 3. SEM images of ZP (a), unused ZPFe (b, c) and ZPFe after the 7th
run (d).
the presence of larger mesopores in the sample [9,10]. The
surface area of the ZPFe following the 7th run was found to be
82.3 m2/g.
Table 2
Conversions of phenol to phenylacetate in different solvents and under
solvent‐free conditions in the presence of ZPFe (1 mol%).
SEM images of ZP (Fig. 3(a)) demonstrate the presence of
hexagonal plates with well‐defined shapes and very smooth
surfaces. Figures 3(b) and (c) present SEM images of ZPFe,
from which it is evident that the structure of ZPFe was much
less ordered than that of ZP, and that the ZPFe particles had
aggregated to form both sheets and spheres of different shapes
and sizes [4,10].
Figure 4 shows TEM images of ZPFe. In these images, the
ZPFe catalyst can be seen to have retained the original mor‐
phology of ZP (a layered structure) and to consist of particles
approximately 150 nm in size. These images also show nano‐
particles of different sizes on the smooth surface of the ZP.
Entry
Solventa
Dichloromethane
Diethylether
Acetonitrile
Cyclohexane
Solvent‐freec
Yieldb (%)
Trace
Trace
Trace
52
Time (min)
120
1
2
3
4
5
120
120
60
15
90
a The reaction was carried out in 5 mL of solvent under reflux condi‐
tions.
b The yields refer to isolated pure products.
c The reaction was carried out at 40 °C.
each alcohol and phenol were converted to the corresponding
acetate in good yields following short reaction times when us‐
ing three or four equivalents of AA (Table 3, entries 8–10 and
20). Furthermore, the products were readily isolated from the
reaction mixtures by a simple filtration followed by a standard
work‐up procedure. Phenols reacted smoothly under the opti‐
mized conditions (Table 3, entries 1–15), with the correspond‐
ing acetates being formed in yields of 80%–95%. Furthermore,
no by‐products (such as those resulting from a Fries rear‐
rangement) were observed when reacting substituted phenols.
The presence of the electron‐donating substituents –CH3,
–OCH3 and –OH on the phenol ring significantly increased the
rate of the acetylation reaction (Table 3, entries 2–10), with
shorter reaction times being observed in these cases. In con‐
trast, the presence of electron withdrawing groups (carboxyl
and nitro groups and halogens) on the phenol ring decreased
3.2. Catalytic activity in acetylation and a proposed mechanism
The conversion of phenol (1 mmol) to phenyl acetate was
selected as a model reaction to optimize the reaction condi‐
tions. The conversion was performed in the presence of ZPFe
(1 mol%) and AA (2 mmol) in various solvents, as well as under
solvent‐free conditions. As shown in Table 2, the use of ZPFe as
a catalyst under solvent‐free conditions provided higher yields
and shorter reaction times than those achieved under conven‐
tional conditions.
Having determined the optimized conditions, we proceeded
to evaluate the scope and generality of the method using vari‐
ous alcohols and phenols (Table 3). The hydroxyl groups of
Fig. 4. TEM images of unused ZPFe under different magnifications ((a) and (b)) and ZPFe after the 7th run (c).

Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
599
Table 3
Acetylation of various alcohols with AA as catalyzed by ZPFe under solvent‐free conditions.
Entry
1
2
3
4
5
6
7
8
Substrate
C6H5OH
Product a
C6H5OAc
2‐Me‐C6H4OAc
Time (min)
15
Temperature (°C)
Substrate:AA molar ratio
Yield b (%)
40
40
40
40
40
40
40
40
40
40
60
60
60
60
60
40
40
40
40
40
40
40
40
40
40
40
1:2
1:2
1:2
1:2
1:2
1:2
1:2
1:3
1:3
1:4
1:2
1:2
1:2
1:2
1:2
1:2
1:2
1:2
1:2
1:3
1:2
1:2
1:2
1:2
1:2
1:2
90
91
95
87
94
92
95
91
90
88
82
87
80
89
90
92
91
92
95
92
84
82
95
92
95
87
2‐Me‐C6H4OH
4‐Me‐C6H4OH
2,6‐(Me)2‐C6H3OH
2,4‐(Me)2‐C6H3OH
4‐(CH3)3C‐C6H4OH
4‐MeO‐C6H4OH
4‐OH‐C6H4OH
3‐OH‐C6H4OH
2,3‐Di‐OH‐C6H3OH
4‐Cl‐C6H4OH
15
10
30
10
10
10
15
15
30
45
45
45
35
30
15
15
15
10
10
15
15
10
10
10
4‐Me‐C6H4OAc
2,6‐(Me)2‐C6H3OAc
2,4‐(Me)2‐C6H3OAc
4‐(CH3)3C‐C6H4OAc
4‐MeO‐C6H4OAc
4‐AcO‐C6H4OAc
3‐AcO‐C6H4OAc
2,3‐Di‐AcO‐C6H3OAc
4‐Cl‐C6H4OAc
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
4‐Br‐C6H4OH
4‐Br‐C6H4OAc
4‐NO2‐C6H4OH
2‐OH‐C6H4CO2H
4‐OH‐C6H4CO2H
2‐Naphthol
4‐NO2‐C6H4OAc
2‐AcO‐C6H4CO2H
4‐AcO‐C6H4CO2H
2‐Naphthyl acetate
C6H5CH2OAc
2‐MeO‐C6H4CH2OAc
4‐MeO‐C6H4CH2OAc
4‐AcO‐C6H4CH2OAc
4‐Cl‐C6H4CH2OAc
4‐NO2‐C6H4CH2OAc
1‐Hexyl acetate
Cyclohexyl acetate
3‐Methylbutyl acetate
(CH3)3C‐OAc
C6H5CH2OH
2‐MeO‐C6H4CH2OH
4‐MeO‐C6H4CH2OH
4‐OH‐C6H4CH2OH
4‐Cl‐C6H4CH2OH
4‐NO2‐C6H4CH2OH
1‐Hexanol
Cyclohexanol
3‐Methyl‐1‐butanol
(CH3)3C‐OH
20
a All products were characterized by comparison of GC‐MS, IR and 1H NMR spectral data with those of authentic samples or reported data.
b Isolated yield.
the reaction rate (Table 3, entries 11–15). The optimized reac‐
tion conditions were also successfully applied to obtain the
acetylation of benzylic alcohols bearing either electron‐with‐
drawing or electron‐donating groups, without the formation of
any by‐products resulting from oxidation reactions (Table 3,
entries 17–22). In the case of deactivated aromatic rings (Table
3, entries 21 and 22), the acetylated products were obtained in
much lower yields and required longer reaction times than the
corresponding activated aromatic systems (Table 3, entries
18–20). It was also observed that the reaction times required
for the acetylation of the phenols were longer than those re‐
quired for the benzylic alcohols.
This difference in the reaction times was attributed to the
lower nucleophilicity of phenols compared with benzylic alco‐
hols because of the delocalization of the lone pairs of electrons
on the phenolic oxygen throughout the benzene ring
[43,49,51]. To further extend the scope of the ZPFe catalyst, we
also investigated the acetylation of several aliphatic alcohols,
including 1‐hexanol, cyclohexanol, 3‐methyl‐1‐butanol and
tert‐butanol, under the optimized conditions (Table 3, entries
23–26).
benzyl alcohol in the absence of the catalyst. As expected, no
products were formed in any of these reactions, demonstrating
the importance of the catalyst in the acetylation process. All the
acetylated products formed in the current study were charac‐
terized by gas chromatography‐mass spectrometry (GC‐MS,
Agilent 5975C), Fourier transform infrared spectroscopy
1
(FT‐IR, JASCO FT‐IR 680 plus) and H nuclear magnetic reso‐
nance (NMR, Bruker‐Avance AQS 400 MHz spectrometer). The
resulting spectra were compared with data obtained from
standard samples or data from the literature [28,44,45,47–53].
The reusability of the ZPFe catalyst was investigated under
the optimum reaction conditions for the acetylation of phenol,
and the results are shown in Table 4. The elemental composi‐
tion of the catalyst remained largely unchanged following its
7th use, although the amount of iron in the catalyst was re‐
duced by almost 50% compared with the first run (Table 1).
The recycled ZPFe catalyst gave a similar product yield to the
The acetylation reactions of 1‐hexanol cyclohexanol and
3‐methyl‐1‐butanol proceeded much more rapidly than the
acetylation of tert‐butanol, most likely because of the steric
hindrance provided by the tert‐butyl group. A schematic rep‐
resentation of the ZPFe‐mediated acetylation process is pro‐
vided in Scheme 3. To develop a better understanding of the
role of the ZPFe catalyst in the acetylation reaction, we also
investigated the acetylation of phenol, 4‐hydroxyphenol and
Scheme 3. Summary of the acetylation mechanism.

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Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
Although some of the other catalysts performed well for the
Table 4
same reaction (Table 5, entries 2, 6, and 10), they invariably
needed longer reaction times to generate suitable yields (Table
5, entries 3, 6, 7, 9, 11, 13, and 14) or required the use of a sol‐
vent (Table 5, entries 4, 6, 7, 9, and 12). It is noteworthy that
the more reactive compound acetyl chloride was required in
one case, involving reaction at room temperature (Table 5,
entry 5). Furthermore, this reaction required a longer reaction
time to afford a similar yield of the acetylated product to the
current protocol. Some of the previously reported protocols
used acetic acid as the acetylating agent, which is a much
greener reagent than acetyl chloride (Table 5, entries 4, 8, and
15). However, these reactions also required longer reaction
times (3–15 h), high temperatures (70–110 °C) and a large
Percent yields obtained during catalyst reuse under the optimum reac‐
tion conditions for acetylation of phenol.
Run
Yield (%)
Fresh
90
1
90
2
90
3
88
4
87
5
85
6
83
7
70
Reaction conditions: Phenol (1 mmol), Ac2O (2 mmol), catalyst (1
mol%), 40 °C.
freshly prepared catalyst up until the 6th cycle.
The catalytic efficiency of ZPFe was compared with those
reported for several catalysts and reaction protocols, and the
results are summarized in Table 5. Using the current method,
phenol was converted to acetyl phenol in 91% yield following a
reaction time of less than 15 min at 40 °C (Table 5, entry 18).
Table 5
Comparison of protocols for the acylations of phenol and benzyl alcohol.
Entry
Catalyst
T (°C)
Time (min)
Ac2O (equiv.)
Yield (%)
Solvent
Ref.
1
2
3
4
5
6
7
8
ZPZn
B(C6F5)3
ZnCl2
60
RT
RT
110
RT
RT
80
45
15
150
840
60
150
210
180
600
30
2
1.2
1
5 a
1.2 b
1.5
1.2
5 a
1.1
1
3 mLc
2
1.5
3 mLc
5a
89
92
40
10
90
98
83
3
99
97
—
97
99
—
77
90
95
90
92
70
—
—
—
Toluene
—
CH3CN
CH3CN
—
[22]
[30]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[43]
[44]
[46]
[54]
[58]
[61]
Borate zirconia
ZnO
Ce(OTf)3
SiO2‐ZnCl2
H3PW12O40
DMAP·HCl
Cu(BF4)2
70
9
RT
RT
RT
50
RT
RT
110
65
Toluene
—
—
10
11
12
13
14
15
16
17
18
19
20
Silica sulfamic acid
[bmim][OTs]
[MMPPA][HSO4]
SBNPSA
Yttria–zirconia
Ni/SiO2
180
10
[bmim][BF4]
120
180
900
240
30
15
15
15
—
—
—
CH3CN
—
—
1.5
4
2
2
2
NiCl2
ZPFe
ZrOCl2·8H2O
ZP
RT
40
40
This work
This work
This work
—
—
40
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
ZPZn
B(C6F5)3
ZnCl2
60
RT
RT
110
80
RT
30
2
180
840
180
15
600
120
120
120
45
240
240
30
2
1.2
1
91
98
63
25
90
93
93
99
99
85
91
94
98
98
91
90
75
—
—
—
Toluene
CH3CN
—
—
—
—
CH2Cl2
—
—
—
—
—
—
—
[22]
[30]
[32]
[34]
[36]
[40]
[41]
[42]
[44]
[45]
[46]
[54]
[55]
Borated zirconia
SiO2‐ZnCl2
Silica sulfamic acid
Cp2ZrCl2
[TMBSA][HSO4]
[MMPPA][HSO4]
SaSA
SBNPSA
Yttria–zirconia
CoCl2
5a
1.2
3 mLc
1
1.1
1.1
1.2
3 mLc
5a
2
4
2
2
RT
RT
R T
Reflux
RT
110
RT
RT
40
40
40
NiCl2
ZPFe
ZrOCl2·8H2O
ZP
[61]
15
15
15
This work
This work
This work
2
a Acetic acid as the acetylating agent.
b Acetyl chloride as the acetylating agent.
c Ethyl formate as the acetylating agent.

Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
601
excess of acid acetic in almost all cases. The acetylation of phe‐
nol was also investigated using ZrOCl2·8H2O and ZP under our
optimized reaction conditions (Table 5, entries 19 and 20).
ZrOCl2·8H2O gave an excellent yield of the desired product, but
was much more difficult to recover and reuse than the ZPFe
catalyst. ZP gave a lower yield (70%) than ZPFe. The use of
ZPZn as a catalyst, however, provided a similar result to that
obtained when using ZPFe (Table 5, entry 1), with a 20 mol%
loading of ZPZn providing the acetyl phenol product in 89%
yield following a reaction time of 45 min [22].
2H), 3.65 (s, 3H), 2.2 (s, 3H); IR (KBr): 3011, 2943, 2826, 1729,
1613, 1518, 1460, 1363, 1243, 1176, 1120, 1031, 960, 823
cm–1.
3‐Methylbutyl acetate (Table 3, entry 23). 1H NMR (400
MHz, CDCl3): δ = 4.18 (t, J = 6.6 Hz, 2H), 2.1 (s, 3H), 1.58–1.67
(m, 1H), 1.43–1.5 (m, 2H), 0.96 (d, J = 3.4, 6H); IR (KBr): 2962,
2935, 1743, 1465, 1430, 1249, 1172, 1136, 1065, 962, 857
cm–1.
4. Conclusions
Based on this comparison process, ZPFe was identified as
the best catalyst for this transformation in terms of the reaction
time and the loading of the catalyst. Benzyl alcohol was also
acetylated under the optimized conditions to give the acetylat‐
ed product in 91% yield following a reaction time of 15 min at
40 °C (Table 5, entry 35). This protocol was also compared with
a variety of different previously reported procedures for the
same transformation, and the results are shown in Table 5.
When the reaction was conducted at room temperature in the
presence of a different catalyst, longer reaction times were
generally required to reach completion (Table 5, entries 23,
27–29, and 33). The use of ZPZn, ZrOCl2·8H2O or ZP as a cata‐
lyst under the optimized conditions provided the desired
product in yields of 91%, 90% and 75%, respectively (Table 5,
entries 21, 36, and 37). However, large excesses of the catalyst
were required in all three cases, and significant difficulties
were encountered during the recovery of these catalysts. These
reactions also resulted in lower yields of the product. There
were some benefits to using these catalysts, in that they used
acetic acid as the acetylating agent rather than AA, even though
all required longer reaction times, higher temperatures and a
large excess of acetic acid to reach completion (Table 5, entries
24 and 32). 1H NMR and FT‐IR spectral data for selected com‐
pounds from Table 3 are provided below.
ZPFe is an inexpensive, noncorrosive and environmentally
benign catalyst that can be readily prepared from simple start‐
ing materials. This catalyst was characterized using various
analytical methods and the results were in agreement with
those reported previously in the literature. In this study, we
have developed a simple and efficient procedure for the acety‐
lation of a variety of different alcohols in good yields over short
reaction times. There are several notable advantages to this
methodology, including a broad substrate scope, the use of AA
as an acetylating agent, excellent product yields and a simple
work‐up procedure resulting from the heterogeneous condi‐
tions.
Acknowledgments
We gratefully acknowledge the funding support received for
this project from the Isfahan University of Technology (IUT), IR
Iran.
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Abdol R. Hajipour et al. / Chinese Journal of Catalysis 36 (2015) 595–602
Graphical Abstract
Chin. J. Catal., 2015, 36: 595–602 doi: 10.1016/S1872‐2067(14)60280‐1
Acetylation of alcohols and phenols under solvent‐free
conditions using iron zirconium phosphate
Abdol R. Hajipour*, Hirbod Karimi, Amir Masti
Isfahan University of Technology, Iran;
University of Wisconsin, USA;
Islamic Azad University, Iran
Iron zirconium phosphate was prepared and applied as an
efficient and reusable nanocatalyst for the acetylation of al‐
cohols with good yields. This method conforms to several of
the guiding principles of green chemistry.
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