Aluminum dodecatungstophosphate (AlPW12O40) as a non-hygroscopic Lewis acid catalyst for the efficient Friedel-Crafts acylation of aromatic compounds under solvent-less conditions

Article abstract of DOI:10.1016/j.tet.2004.09.049

Stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW ₁₂O₄₀), which is prepared easily from cheap and commercially available compounds was found to be an effective catalyst for Friedel-Crafts acylation reactions using carboxylic acids, acetic anhydride and benzoyl chloride in the absence of solvent under mild reaction conditions.

Full text of DOI:10.1016/j.tet.2004.09.049

Tetrahedron 60 (2004) 10843–10850
Aluminum dodecatungstophosphate (AlPW12O40) as a
non-hygroscopic Lewis acid catalyst for the efficient
Friedel–Crafts acylation of aromatic compounds under
solvent-less conditions
*
Habib Firouzabadi, Nasser Iranpoor and Farhad Nowrouzi
*
Department of Chemistry, Shiraz University, Shiraz 71454, Iran
Received 1 August 2004; revised 24 August 2004; accepted 16 September 2004
Available online 1 October 2004
Abstract—Stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW12O40), which is prepared easily from cheap and
commercially available compounds was found to be an effective catalyst for Friedel–Crafts acylation reactions using carboxylic acids, acetic
anhydride and benzoyl chloride in the absence of solvent under mild reaction conditions.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
have fair tolerance in aqueous solutions.12 It has been
demonstrated that the acidic cesium salts of HPAs are very
water-tolerant catalysts for hydration of olefins13 and
hydrolysis of esters.14 This nature was assigned to moderate
hydrophobicity of the catalysts.15
Heteropolyacids (HPAs) show very high catalytic activity
for some acid-catalyzed reactions. They have been used for
hydration of alkenes1–3 and polymerization of tetrahydro-
furan.4–6 Strong Brønsted acidity7,8 and the softness of the
heteropoly anions are responsible for their high catalytic
activities in these reactions.9 HPAs are usually solids that
are insoluble in non-polar solvents but highly soluble in
polar ones. The use of HPAs in non-polar solvents improves
product selectivity and also provides easy separation of
them.4 Heterogeneous catalysis has become attractive in
view of the increasingly strict environmental legislation, in
view of their isolation and separation from the reaction
media. Solid acid catalysts are harmless to the environment
with respect to corrosiveness, safety, quantity of waste, and
separability with certainly some exceptions.
We have recently started to study new catalytic applications
of heteropoly acids in organic reactions.16a–h
Friedel–Crafts acylation of aromatic compounds is the most
important and practical route for the synthesis of aromatic
ketones that are used in manufacturing of fine chemicals as
well as pharmaceuticals.17 The acylating agents for the
synthesis of aromatic ketones by Friedel–Crafts reactions
are mostly acid anhydrides or acyl chlorides. For this
purpose, varieties of catalysts have been reported.18,19
A
literature survey indicates that the use of carboxylic acids,
as acylating agents, are scarcely reported.20 Using car-
boxylic acids as acylating agents is a superior method with
respect to the procedures utilizing acyl chlorides and
anhydrides for the preparation of aryl ketones. Carboxylic
acids are stable and more available compounds and their
handlings are much easier than their corresponding acyl
chlorides and anhydrides.
Cesium salts of HPAs are good examples of active and
useful solid acid catalysts. They exhibit an excellent
performance in several organic reactions owing to their
high surface acidity and also probably to their unique
basicity.10,11 The catalytic activities of solid acids are
usually suppressed significantly in the presence of water.
Hence, although H-ZSM-5 has a high Si:Al ratio is known to
Now, we introduce aluminum dodecatungstophosphate
(AlPW12O40) as a stable, non-hygroscopic, easily available,
cheap and highly effective catalyst for Friedel–Crafts
acylation of aromatic compounds using carboxylic acids,
acetic anhydride and benzoyl chloride as acylating agents.
Keywords: Freidel–Crafts acylation; Poly oxometalate; Aluminum dodeca-
tungstophosphate; Solvent-free.
* Corresponding author. Tel.: C98 711 2284822; fax: C98 711 2280926
(H.F.); fax: C98 711 2280926 (N.I.); e-mail addresses:
firouzabadi@chem.susc.ac.ir; iranpoor@chem.susc.ac.ir
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.09.049

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H. Firouzabadi et al. / Tetrahedron 60 (2004) 10843–10850
2. Results and discussion
used for similar reaction and also does not require aqueous
workup which makes the process of the isolation of the
product much easier and not a time-consuming process.
2.1. Acylation of aromatic compounds with acetic
anhydride catalyzed by AlPW12O40
2.2. Benzoylation of aromatic compounds with benzoyl
chloride in the presence of AlPW12O40
The reaction of acetic anhydride and aromatic compounds
by Friedel–Crafts acylation reactions is the most practical
route for the synthesis of methyl aryl ketones. Investigation
of the application of AlPW12O40 as an easily available,
cheap and non-hygroscopic Lewis acid for this purpose is of
practical importance. In order to optimize the reaction
conditions, acylation of anisole with acetic anhydride in the
presence of different molar ratios of AlPW12O40 and various
solvents were studied (Scheme 1).
We have studied optimization of the reaction conditions for
the benzoylation of anisole under solvent-free conditions
(Scheme 3).
Scheme 3.
It was found that the reaction was complete after 2 h by
using of 4 mol% of the catalyst at 60–70 8C to produce ortho
and para isomers (1:4 ratio). We applied similar reaction
conditions for the preparation of other aryl ketones using
different aromatic compounds. The reactions proceeded
well and the desired products were isolated in excellent
yields (Table 4). We have observed that the rate of acylation
and benzoylation of 1,3-dimethoxy benzene was slower
than anisole. Para acylation or benzoylation of anisole do
not encounter that much steric resistance against the
approach of bulky Lewis acid complex and acylium ions
from the para position. However, in 1,3-dimethoxy benzene
the situation is quiet different and the bulky complex should
only approach from the ortho position of OMe groups which
encounters ortho steric effects. This effect causes retardation
in the rates of the reactions. Bezoylation of anthracene
under solvent-free conditions was sluggish in the presence
of this catalyst and gave a low yield. However, 9-
benzoylanthracene was isolated in 88% yield when the
reaction in n-hexane was heated under reflux conditions. We
also applied similar reaction conditions for benzoylation of
naphthalene. This reaction was not successful and a mixture
of 1 and 2 substituted benzoyl naphthalenes in low yields
plus unreacted starting material was isolated. Benzoylation
of benzene under similar reaction conditions failed.
However, this reaction was successful in a sealed tube at
120 8C overnight with 10 mol% of AlPW12O40 (97% GC
yield).
Scheme 1.
The results of this investigation are shown in Table 1. The
results indicate that the most suitable solvent for this
purpose is n-hexane in which the catalyst reacts under
completely heterogeneous conditions and the best result was
obtained when no solvent was used.
The optimum ratio of the catalyst was found to be 3 mol%
with respect to anisole for the reaction conducted in n-
hexane or solvent-less conditions. The optimized molar
ratio of acetic anhydride was found to be 2 mol equivalents
with respect to 1 mol equivalent of anisole under similar
reaction conditions (Scheme 2).
Scheme 2.
This reaction condition was applied for the preparation of
different aryl ketones from electron rich aromatic com-
pounds with success. The results of this study are tabulated
in Table 2.
In order to show the efficiency and the catalytic activity of
AlPW12O40 for the acylation of anisole with acetic
anhydride, we have tabulated our results in Table 3 with
some other recently used Lewis acids such as Sc(OTf)3,
Bi(OTf)3 and In(OTf)3.
2.3. Direct acylation of anisole with carboxylic acids in
the presence of AlPW12O40 as a reusable catalyst
We have also studied acylation of anisole with carboxylic
acids in the presence of 6 mol% of AlPW12O40 at 120 8C
(Scheme 4).
The results show that aluminum dodecatungstophosphate is
a more efficient and more effective catalyst than the triflates
Table 1. Effect of solvents upon Friedel–Crafts acylation of anisole catalyzed by AlPW12O40
Entry
Solvent
Temp. (8C)
T (h)
Conv. (%)a
1
2
3
4
5
6
CH2Cl2
CHCl3
CH3CN
CH3NO2
n-Hexane
None
40
62
82
100
69
60
5
3
3
4
2.5
1
63
76
38
63
93
100
a Conversion was determined by GC analysis.

H. Firouzabadi et al. / Tetrahedron 60 (2004) 10843–10850
10845
have found that this catalyst is reusable for these reactions
and can be easily recovered from the reaction mixture by
simple filtration followed by washing the mixture by n-
hexane/EtOAc (1:1). Drying of the catalyst was performed
at 120 8C under vacuum overnight. We have used the
recovered catalyst for the reaction of anisole with hexanoic
acid with success five times without noticeable change in its
catalytic activity. In Table 6, the results are compiled in
order to show the effectiveness of AlPW12O40 with respect
to the recently reported catalysts Cs2.5H0.5PW12O40 and
HZSM-5 for acylation of anisole with different carboxylic
acids. The results show that AlPW12O40 promotes the
reactions more effectively than the reported catalysts.
Scheme 4.
This acylation was carried out with different carboxylic
acids (C2–C12) in good yields (Table 5). In this study, it was
observed that by increasing the chain length of the
carboxylic acids from C2 to C12 the regioselectivity of the
reactions increased and p-isomers were mostly produced.
We have not also observed any ester formation in any of the
reactions we conducted in the presence of AlPW12O40. We
Table 2. Acylation of aromatic compounds with acetic anhydride catalyzed by AlPW12O40
Entry
ArH
Time (h)
Product
Yielda (%)
Ref.
18p,t
1
0.75
94 (Ortho:ParaZ12:88)
18k,y
2
3
4
5
6
0.25
95
88b
93
18k
2
19a
0.6
6
18n
18f
91
2.5
92c
18l
7
5.5
90
18j
18i
18i
8
4
85
91
9
1.6
2.6
10
90d
1
a Isolated yields and the purity of the products were determined by H NMR spectroscopy and the ratio of the isomers was determined by GC.
b 2,6-Dimethoxyacetophenone was also detected in 12% yield.
c Other regioisomers were detected in 8%.
d Ac2O (4 equiv/mol) was used.

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H. Firouzabadi et al. / Tetrahedron 60 (2004) 10843–10850
Table 3. Comparison of the results used for the acylation of anisole with acetic anhydride catalyzed by AlPW12O40 and some other catalysts
Entry
Catalyst
Mol%
Temp. (8C)
T (h)
Yield (%)
Ref.
18l
1
2
3
4
5
Sc(OTf)3
Sc(OTf)3
Bi(OTf)3
In(OTf)3
AlPW12O40
20
20
5
1
3
50
50
50
50
60
18
2a
99
90
80
96
94
18n
18p
18w
2
1b
0.8
c
—
a 2 equiv of LiClO4 was used as an additive.
b 1 equiv of LiClO4 was used as an additive.
c Results are shown in Table 2.
Table 4. Benzoylation of aromatic compounds with benzoyl chloride catalyzed by AlPW12O40
Entry
ArH
Time (h)
Product
Yielda
Ref.
18p,t
1
2
94 (Ortho:ParaZ1:4)
18k
18d
2
3
4
5
6
1
97
90b
90
3.5
2
19b
18u
4.5
3.5
91
18q,v
92c
18q
7
2.5
91
18f
8
9
3
92d
18a
1.7
94
18x
10
4
88e
1
a Isolated yields and the purity of the products were determined by H NMR spectroscopy and the ratio of the isomers was determined by GC.
b Formation of 2,6-dimethoxybenzophenone was detected in 10%.
c Formation of 2,6-dimethylbenzophenone was detected in 8%.
d Other regioisomers were detected in 7%.
e Reaction was carried out in 2 mL of n-hexane under reflux conditions.

H. Firouzabadi et al. / Tetrahedron 60 (2004) 10843–10850
10847
Table 5. Acylation of anisole with carboxylic acids catalyzed by reusable
AlPW12O40 at 120 8Ca
catalyst. We observed that the reaction did not proceed at all
even after 24 h. We have found that this is a general method
and can be applied easily to a wide range of liquid and
crystalline carboxylic acids. Therefore, acylation of anisole
was conducted with acetic acid, octanoic acid, phenyl acetic
acid and benzoic acid in the presence of AlPW12O40
(3 mol%) and trifluoroacetic anhydride in excellent yields
(Table 7, entries 1–5). 2-Methylanisole was also acylated
with these acids in the presence of this catalyst and the
anhydride in excellent yields (90–96%) with high regios-
electivity (Table 7, entries 9–12). 1,2-Diethoxybenzene
reacted with the above acids under similar reaction
conditions to give the desired compounds as the sole
products of these reactions in 91–94% yields (Table 7,
entries 13–16). We also tried acylation of anthracene with
acetic acid, phenyl acetic acid and benzoic acid. The
reactions were slow and needed higher temperatures
therefore, the reactions were performed at 50 8C and the
desired ketones were isolated in 69–78% yields (Table 7
entries 17–19). The reaction of 2-methylnaphthalene with
acetic acid was also conducted at 50 8C in the presence of
the catalyst and trifluoroacetic anhydride. This reaction was
sluggish and after prolonged reaction times the desired
ketone was isolated in only 53% yield (Table 7 entry 20).
The reaction of 2-methoxynaphthalene with acetic acid,
octanoic acid, phenyl acetic acid and benzoic acid went
smoothly at room temperature in excellent yields (Table 7,
entries 21–24). Acylation of furan and pyrrole is not a
straightforward reaction and usually in the presence of acid
catalysts undergo polymerization reactions. We found that
AlPW12O40 is a suitable catalyst for such important
acylation reactions.
Entry
Acid
Acetic
Propionic
Butyric
Hexanoic
Hexanoic
Octanoic
Dodecanoic
Benzoic
Time (h)
Yield (%)b Ref. 20b
1
2
3
4
5
6
7
8
3
3.5
5
3
1.5
4
85c
88d
87
0e
91
85
90
92
8
10
a The catalyst was filtered, washed with n-hexane: ethyl acetate, dried at
120 8C/(K20) Torr/overnight and reused.
b Isolated yield based on carboxylic acid conversion determined by 1H
NMR spectroscopy and GC analysis.
c 12% regioisomer was determined.
d 8% regioisomer was detected.
e Reaction was carried out in the presence of 1 g silica gel.
Table 6. Comparison of some of the results obtained using AlPW12O40 with
some other catalysts used for acylation of anisole with carboxylic acidsa
Acid
Cat.
HZSM-5
40%CsPW/SiO2
AlPW12O40
HZSM-5
40%CsPW/SiO2
AlPW12O40
HZSM-5
Yield (%) (para-product)
Acetic
0.025
62
73
19.92
63.2
91
Hexanoic
Octanoic
4
40%CsPW/SiO2
AlPW12O40
HZSM-5
32.9
85
0
Dodecanoic
40%CsPW/SiO2
AlPW12O40
24.8
91
a The results were extracted from Ref. 20b,c.
Acylation of furan with acetic acid, phenyl acetic acid and
benzoic acid was conducted in the presence of TFAA and
AlPW12O40 at 0 8C successfully in 94–98% isolated yield
(Table 7, entries 25–27).
2.4. Acylation of aromatic compounds with carboxylic
acids in the presence of trifluoroacetic anhydride
catalyzed with AlPW12O40 at room temperature
Acylation of pyrrole also conducted smoothly in the
presence of TFAA, AlPW12O40 with acetic and benzoic
acids at K23 8C. The desired pyrrole ketones were isolated
in 92–98% yield (Table 7, entry 28–29). The formation of
any polymeric materials was not observed in these
reactions.
In this part of our studies, we have found that with 3 mol%
of AlPW12O40 in the presence of trifluoroacetic anhydride
(1.4 equiv) acylation of anisole proceeded easily in 0.25 h in
an excellent yield (Scheme 5).
3. Conclusion
AlPW12O40 is a cheap, easily available, non-hygroscopic,
heterogeneous, non-corrosive and environmentally benign
compound. In this work it has been used as an effective
catalyst for the efficient preparation of ketones via Friedel–
Crafts acylation reactions with acetic anhydride, benzoyl
chloride and with a range of easily available caboxylic acids
in the presence of triflouroacetic anhydride. This general
method can be applied easily to a wide range of liquid and
crystalline carboxylic acids. The method has many
advantages such as cheapness and availability of reactants
and also non-aqueous and easy work-up of the reaction due
to the heterogeneous conditions. The isolation of products
was easily accomplished by a simple extraction and
evaporation of the organic solvent.
Scheme 5.
In order to show the effect of the catalyst in this reaction, we
performed acylation of anisole with acetic acid in the
presence of trifluoroacetic anhydride (1.4 equiv) at room
temperature in the absence of the catalyst. We have
observed that the corresponding ketone was produced in
88% yield (GC) after 4 h (Table 7, entry 1) whereas the
desired ketone was isolated in 94% yield after 0.25 h in the
presence of the catalyst (Table 7, entry 2). We also tried
the reaction of anisole with TFAA in the presence of the

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H. Firouzabadi et al. / Tetrahedron 60 (2004) 10843–10850
Table 7. AIPW12O40 catalyzed acylation of aromatic compounds with compounds with carboxylic acids in the presence of trifluoroacetic anhydride
Entry
ArH
RCO2H
Product
Time (h)
Yield (%)a
Ref.
18p,t
18p,t
20b,d
1
2
3
4
5
RZMe
4
0.25
1.5
2
88b,c
94c
91
94
96
RZMe
RZC7H15
RZPhCH2
RZPh
18w
18p,t
2.5
18y
18c
18k
6
7
8
RZMe
RZPhCH2
RZPh
2
2.5
3.75
97
90
91
18y
18c
9
RZMe
0.12
0.4
0.34
0.75
96
92
93
90
10
11
12
RZPhCH2
RZC7H15
RZPh
—
18k
19a
13
14
15
16
RZMe
0.65
1.5
2.5
3.5
93
94
91
91
RZC7H15
RZPhCH2
RZPh
—
—
19b
18i
17
18
19
RZMe
RZPhCH2
RZPh
2.5
10
8.5
78d
71d
69d
18b
18x
18j
20
RZMe
2
53e
18i
21
22
23
24
RZMe
0.25
0.34
2
98
95
90
88
18m
18m
18a
RZC7H15
RZPhCH2
RZPh
8
18n
19c
25
26
27
RZMe
RZPhCH2
RZPh
1.25
1.5
2.5
94f
95f
98f
18g
18h
18h
28
29
RZMe
RZPh
0.25
0.4
92g,h
98g
1
a Isolated yields and the purity of the products were determined by H NMR spectroscopy, 13C NMR spectroscopy and GC.
b Reaction was performed without using AlPW12O40
c 8% of regioisomer was detected.
.
d Reaction was carried out in 2 mL n-hexane at 50 8C.
e Reaction was carried out at 50 8C.
Reaction was carried out at 0 8C with 2 equiv of furan.
f
g Reaction was carried out in 2 mL n-hexane at K23 8C.
h 8% 3-acetyl pyrrole was detected by GC.
4. Experimental
compounds, carboxylic acids, acetic anhydride and acyl
chloride were purified by distillation or recrystallization
before use. The purity determination of the products was
accomplished by GC on a Shimadzu model GC-14A
instrument or by TLC on silica gel polygram SIL G/UV
254 plates. The FTIR spectra were recorded on a Shimadzu
model 8300 instrument. The NMR spectra were recorded on
4.1. General remarks
Chemicals were purchased from Fluka or Merck and
AlPW12O40 was prepared from H3PW12O40 and aluminium
nitrate according to the literature method.21 Aromatic

H. Firouzabadi et al. / Tetrahedron 60 (2004) 10843–10850
10849
a Bruker Advance DPX 250 MHz spectrometer and in all
cases CDCl3 was used as a solvent and TMS as an internal
standard.
4.6. Spectral data of the unknown ketones prepared by
the presented protocol
4.6.1. Table 7 entry 11: RZC7H15. Colourless viscous oil,
[Found: C, 77.38; H, 9.65. C16H24O2 requires C, 77.41; H,
9.65%]. Bp (P/32 mmHg)Z218 8C IR (KBr) (n C]O)Z
1610, 1691 cmK1 dH (250 MHz, CDCl3) 7.83–7.77 (2H, m,
Ph), 6.83 (1H, d, JZ8.4 Hz), 2.92 (t, 2H, JHHZ12 Hz, –
COCH2CH2), 2.25 (s, 3H), 1.67 (m, 2H), 1.56 (m, 2H), 1.42
4.2. Typical procedure for acylation of anisole with
acetic anhydride; a
2
Anisole (2 mmol, 0.216 g), acetic anhydride (4 mmol,
0.408 g) and AlPW12O40 (0.06 mmol, 0.232 g) were
combined, and the mixture was stirred at 60–70 8C for
45 min (Table 3). After completion of the reaction
(monitored by TLC and GC), Et2O (10 mL) and powder
of sodium hydrogen carbonate (0.8 g) was added to the
mixture in order to destroy the unreacted acetic anhydride.
The solid phase was isolated and washed with Et2O (2!
5 mL). Evaporation of the combined ethereal solutions
afforded the almost pure product in 94% yield (0.504 g).
2
(m, 2H), 1.36 (m, 2H), 1.21 (m, 2H), 0.88 (t, 3H, JHH
Z
7.5 Hz, CH3CH2). 13C NMR: d (ppm)Z199.53, 161.59,
130.7, 129.72, 128.1, 126.6, 109.15, 55.4, 38.2, 31.7, 29.4,
24.7, 22.6, 16.2, 14.1. MS (20 eV): m/z (%)Z248 (MC,
3.1), 177 (6.9), 164 (71.5), 150 (10.1), 149 (100), 91 (23.5),
41 (16.2).
4.6.2. Table 7 entry 14: RZC7H15. Light yellow solid,
mpZ43 8C, [Found: C, 73.94; H, 9.57. C18H28O3 requires
C, 73.97; H, 9.58%] IR (KBr) (n C]O)Z1677 cmK1, dH
(250 MHz, CDCl3) 6.5–7.4 (m, 3H, Ph), 4.08 (q, 4H), 2.9 (t,
4.3. Typical procedure for benzoylation of anisole with
benzoyl chloride
2
2
2H, JHHZ12 Hz, –COCH2CH2), 1.5 (t, 6H, JHHZ15 Hz,
OCH2CH3), 1.71 (m, 2H), 1.41 (m, 2H), 1.3 (m, 2H), 1.18
(m, 2H), 0.98 (m, 2H), 0.81 (t, 3H, 2JHHZ7.5 Hz, CH3CH2).
dC (63 MHz, CDCl3)Z196.6, 153.2, 148.8, 144, 130.4,
122.9, 120, 115, 112.4, 64, 42, 32, 30, 23, 15, 14, MS
(20 eV): m/z (%)Z292 (MC, 10.8), 221 (8.6), 208 (100),
193 (73.2), 180 (14.8), 165 (38.4), 137 (36.3), 109 (17.5), 81
(14), 57 (16.1).
Anisole (2 mmol, 0.216 g), benzoyl chloride (3 mmol,
0.421 g) and AlPW12O40 (0.08 mmol, 0.232 g) were
combined and the mixture was stirred at 60–70 8C for 2 h
(Table 4, entry 1). After completion of the reaction
(monitored by TLC and GC), Et2O (10 mL) and powder
of sodium hydrogen carbonate (0.8 g) was added to the
reaction mixture in order to destroy the unreacted benzoyl
chloride. The solid phase was recovered by filtration and
was washed with Et2O (2!5 mL). Evaporation of the
combined ethereal solutions afforded the almost pure
product in 94% yield (0.796 g).
4.6.3. Table 7 entry 15: RZPhCH2. Yellow solid, mpZ
82 8C, [Found: C, 76.1; H, 7.02. C18H20O3 requires C,
76.05; H, 7.04%] IR (KBr) (n C]O)Z1700, 1596 cmK1dH
(250 MHz, CDCl3) 7.34–7.2 (5H, m, Ph), 7.62 (1H, d, JZ
8.37 Hz), 7.46 (1H, s),6.86 (1H, d, JZ8.4 Hz), 4.22 (2H, s),
4.08–4.19 (4H, m, –OCH2CH3), 1.5–1.41 (6H, m,
OCH2CH3). dC (63 MHz, CDCl3)Z196.3, 148, 144,
135.1, 131, 130, 129.3, 128, 126, 120, 114, 64.4, 45.13,
14.6. MS (20 eV): m/z (%)Z284 (MC, 3.3), 194 (12.5), 193
(100), 165 (32.1), 137 (27.3), 109 (10.4), 91 (19.5).
4.4. General procedure for acylation of anisole with
carboxylic acids
To a mixture of carboxylic acid (2 mmol) and anisole
(100 mmol), AlPW12O40 (12 mol%, 0.362 g) was added and
the reaction mixture was stirred at 120 8C for the appropriate
reaction times (Table 5). After completion of the reaction
(monitored by TLC and GC), the catalyst was filtered. The
unreacted anisole was separated by vacuum distillation and
the desired ketone was isolated with high purity (GC) in
good yield.
Acknowledgements
The authors are thankful to Iran TWAS Chapter Based at
ISMO and the Shiraz University Research Council for the
support of this work.
4.5. General procedure for acylation of aromatic
compounds using carboxylic acids and triflouroacetic
anhydride (TFAA) catalyzed with AlPW12O40
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tet.2004.09.
049
Aromatic compound (2 mmol), carboxylic acid (2 mmol),
trifluoroacetic anhydride (2.8 mmol, 0.39 mL) and
AlPW12O40 (0.03 mmol, 0.174 g) were mixed together
and stirred by a magnetic stirrer at room temperature for
the appropriate reaction times (Table 7). After completion
of the reaction (monitored by TLC and GC), Et2O (10 mL)
and powder of sodium hydrogen carbonate (1.2–1.5 g) was
added to destroy the unreacted TFAA or carboxylic acid.
The solid phase was recovered by filtration and was washed
with Et2O (2!5 mL). Evaporation of the combined ethereal
solutions afforded the highly pure product.
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