P2O5/Al2O3 AS an efficient heterogeneous catalyst for the acetylation of alcohols, phenols, thiols, and amines under solvent-free conditions

Article abstract of DOI:10.1080/00397911.2010.492197

A convenient, rapid, and efficient method for the acetylation of alcohols, phenols, thiols, and amines has been developed by using acetic anhydride in the presence of a catalytic amount of P₂O₅/Al ₂O₃ under solvent-free conditions at room temperature. This reaction was studied under different conditions, and several solvents were examined for this conversion. However, in terms of reaction time and yield, it was found that the best result was obtained when the reaction was carried out under solvent-free conditions. Racemization of optically active alcohols and epimerization of sugars were not observed. The use of nontoxic and inexpensive materials, simple and clean workup, short reaction times, and good yields of the products are the advantages of this method.

Full text of DOI:10.1080/00397911.2010.492197

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P O /Al O as an Efficient Heterogeneous
2
5
2 3
Catalyst for the Acetylation of Alcohols,
Phenols, Thiols, and Amines Under
Solvent-Free Conditions
a
b c
d
Amin Zarei , Abdol R. Hajipour
& Leila Khazdooz
a
Department of Science, Islamic Azad University, Fasa Branch, Fasa,
Fars, Iran
b
Department of Pharmacology, University of Wisconsin, Medical
School, Madison, Wisconsin, USA
c
Pharmaceutical Research Laboratory, College of Chemistry, Isfahan
University of Technology, Isfahan, Iran
d
Department of Science, Islamic Azad University, Khorasgan Branch,
Isfahan, Iran
Version of record first published: 29 Apr 2011
To cite this article: Amin Zarei, Abdol R. Hajipour & Leila Khazdooz (2011): P O /Al O as an Efficient
2
5
2 3
Heterogeneous Catalyst for the Acetylation of Alcohols, Phenols, Thiols, and Amines Under Solvent-
Free Conditions, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 41:12, 1772-1785
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1
Synthetic Communications , 41: 1772–1785, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.492197
P O /Al O AS AN EFFICIENT HETEROGENEOUS
2
5
2
3
CATALYST FOR THE ACETYLATION OF ALCOHOLS,
PHENOLS, THIOLS, AND AMINES UNDER
SOLVENT-FREE CONDITIONS
1
Amin Zarei, Abdol R. Hajipour, and Leila Khazdooz
2,3
4
1
Department of Science, Islamic Azad University, Fasa Branch, Fasa,
Fars, Iran
2
Department of Pharmacology, University of Wisconsin, Medical School,
Madison, Wisconsin, USA
3
Pharmaceutical Research Laboratory, College of Chemistry,
Isfahan University of Technology, Isfahan, Iran
4
Department of Science, Islamic Azad University, Khorasgan Branch,
Isfahan, Iran
GRAPHICAL ABSTRACT
Abstract A convenient, rapid, and efficient method for the acetylation of alcohols, phenols,
thiols, and amines has been developed by using acetic anhydride in the presence of a
2 5 2 3
catalytic amount of P O /Al O under solvent-free conditions at room temperature. This
reaction was studied under different conditions, and several solvents were examined for this
conversion. However, in terms of reaction time and yield, it was found that the best result
was obtained when the reaction was carried out under solvent-free conditions. Racemization
of optically active alcohols and epimerization of sugars were not observed. The use of
nontoxic and inexpensive materials, simple and clean workup, short reaction times, and
good yields of the products are the advantages of this method.
2 5 2 3
Keywords Acetylation; alcohols; amines; P O =Al O ; thiols
INTRODUCTION
The acetylation of alcohols, phenols, thiols, and amines is an important and
widely utilized transformation in organic synthesis because of the ease of deprotec-
[
1,2]
tion.
Although a number of methods are available for the acetylation of some
functional groups, acetic anhydride in the presence of an acidic or basic catalyst is
the most commonly used reagent for this purpose. Some basic catalysts that have
Received November 8, 2009.
Address correspondence to Amin Zarei, Department of Science, Islamic Azad University, Fasa
Branch, P.O. Box 364, Fasa 7461713591, Fars, Iran. E-mail: aj_zarei@yahoo.com
1
772

P
2
O
5
/Al
2
O
3
AS AN EFFICIENT CATALYST
1773
Scheme 1. Acetylation of alcohols, phenols, thiols, and amines.
been developed for acetylation include triethylamine, pyridine or 4-(dimethylamino)
[4]
[
3]
[5]
pyridine (DMAP), KF-Al O , and Py=basic alumina. Also, t-Bu P was intro-
2
3
3
[7]
[6]
[8]
[14]
[21]
duced for base-sensitive compounds. Among the acidic ones, CoCl , Me SiCl,
[
ZnO, trichloroisocyanuric acid,
Mg(NTf2)2,
HClO -SiO ,
montmorillonite K-10 clay,
[
ionic liquid, and various triflates
2
3
9]
[10]
[11]
[12]
[13]
ZrCl4,
[18]
Mg(ClO ) ,
CeCl ,
MoO Cl ,
2
InCl3,
BiOClO4,
3
[19]
2
[20]
[
15]
[16]
[17]
NBS,
Cu(BF ) ,
I ,
LiClO4,
Zn(ClO ) ,
4 2
2
4 2
[
22]
[23]
[24]
2
[27]
[25]
HBF -SiO ,
Nafion-H,
[30–34]
NH SO H,
2
cation-exchanged
[TMBSA][HSO4]
4
2
4
2
4
3
[26]
[28]
ZrOCl ꢀ 8H O,
2
2
29]
have been used for this purpose.
[36]
[
35]
Recently, 3-nitrobenzeneboronic acid,
37–39]
have been reported for the acetylation of alcohols.
La(NO ) ꢀ 6H O,
and heteropoly
3
3
2
[
acids
RESULTS AND DISCUSSION
Recently, the use of catalysts and reagents supported on solid supports were
developed because such reagents not only simplify purification processes but also
help to prevent release of reaction residues into the environment. Although there
[40–42]
are many reports using phosphorus pentoxide as a reagent in organic reactions,
P O is difficult to handle because of its moisture sensitivity at room temperature.
In continuation of our studies on the stabilization of P O on solid supports and
2
5
2
5
[43–47]
its applications in organic synthesis, herein we report an efficient, convenient,
and mild procedure for the acetylation of alcohols, phenols, thiols, and amines in
the presence of acetic anhydride and a catalytic amount of P O =Al O . The reaction
2
5
2
3
is easily carried out at room temperature under solvent-free conditions (Scheme 1).
To optimize the reaction conditions, initially we tried to convert 4-nitrophenol
(2 mmol) to 4-nitrophenylacetate with P O =Al O (0.06 g, 10 mol%) and acetic
2 5 2 3
anhydride (4 mmol, 0.40 mL) in various solvents and also under solvent-free
conditions (neat). As shown in Table 1, in comparison to conventional methods in
Table 1. Conversion of 4-nitrophenol to 4-nitrophenylacetate in different solvents
a
and under solvent-free conditions in the presence of P O =Al O
2 5 2 3
b
Entry
Solvent
Yield (%)
Time (min)
1
2
3
4
5
6
Diethyl ether
Dichloromethane
Acetonitrile
45
85
42
78
20
97
60
30
60
60
60
20
Cyclohexane
Ethyl acetate
Solvent-free
a
The yields refer to the isolated pure products.
The reaction was carried out in 5 mL of solvent at rt.
b

1774
A. ZAREI, A. R. HAJIPOUR, AND L. KHAZDOOZ
2 5 2 3
Table 2. Acetylation of alcohols, phenols, thiols, and amines catalyzed by P O =Al O under solvent-free
a,b,c
conditions at room temperature
Entry
1
Substrate
Product
Time (min) Yield (%)
20
20
97
90
2
3
20
92
4
5
6
20
20
20
93
96
92
7
8
20
20
20
97
95
96
9
d
1
0
D-Glucose
D-Glucose pentaacetate
120
20
85
93
1
1
1
1
1
2
3
4
20
10
20
95
88
92
15
20
94
(
Continued )

P
2
O
5
/Al
2
O
3
AS AN EFFICIENT CATALYST
1775
Table 2. Continued
Entry
Substrate
Product
Time (min) Yield (%)
16
20
92
1
1
7
8
20
40
90
90
1
2
9
0
20
30
88
91
2
2
2
2
2
1
2
3
4
5
45
50
60
20
20
92
90
88
95
96
2
2
2
6
7
8
40
25
50
90
94
90
(
Continued )

1776
A. ZAREI, A. R. HAJIPOUR, AND L. KHAZDOOZ
Table 2. Continued
Entry
Substrate
Product
Time (min) Yield (%)
29
40
88
3
3
3
0
1
2
20
20
25
93
97
96
3
3
3
25
92
4
5
25
20
93
92
3
3
6
20
94
84
e
37
120
e
e
3
3
8
9
120
120
87
85
4
0
1
2
20
20
20
92
90
4
4
95
(
Continued )

P
2
O
5
/Al
2
O
3
AS AN EFFICIENT CATALYST
1777
Table 2. Continued
Entry
Substrate
Product
Time (min) Yield (%)
43
60
96
a
b
The yields refer to the isolated pure products.
The products were characterized from their spectral (IR, H NMR) data and comparison with auth-
1
entic samples.
c
The substrate was reacted with 2 equiv of Ac
2
O per OH, SH, or NH
2
group unless otherwise stated.
d
Acetic anhydride was used as a solvent.
The substrate was reacted with 3 equiv of Ac
e
2
O.
the solvent, the yield of the reaction under solvent-free conditions is greater and the
reaction time is shorter. Therefore, we employed these conditions for the conversion
of various alcohols to their corresponding acetates under solvent-free conditions. In
the absence of catalyst, using the same reaction conditions, 4-nitrophenylacetate was
obtained in trace yield even after 1.5 h. We also studied this reaction with Al O
2
3
(0.03 g) in the absence of P O under the same conditions, and 4-nitrophenylacetate
was obtained in poor yield (20%) after 1.5 h. According to these results, P O is
2 5
2
5
necessary for this purpose.
As shown in Table 2, using this catalyst, different kinds of alcohols, phenols,
thiols, and amines were converted to their corresponding acetates in good yields
within short reaction times. The products were easily isolated by simple filtration.
Primary, secondary, and allylic alcohols underwent smooth acetylation at room tem-
perature without any by-products (Table 2, entries 1–18). Optically active menthol is
acetylated without racemization (Table 2, entry 15, observed [a] ¼ ꢁ78; reported
D
[
48]
[
a] ¼ ꢁ76). Also, t-butanol and 1-adamantol as tertiary alcohol can be acetylated
D
in good yields (Table 2, entries 19 and 20). Tetramethylsilane (TMS) and Tetrahy-
dropyran (THP) protecting groups were replaced by the acetyl group to prepare
the corresponding acetates (Table 2, entries 21–23). To extend the scope of the cata-
lyst, the acetylation of phenols was investigated. As shown in Table 2 (entries 24–36),
phenol and various substituted phenols were easily acetylated under the same con-
ditions. Moreover, no by-products (such as Fries rearrangement) were obtained
from any phenol derivations. We also investigated the reaction of 2-hydroxybenzal-
dehyde, 4-hydroxybenzaldehyde, and vanillin under the same conditions and
observed that both carbonyl and phenolic –OH groups were acylated (Table 2,
entries 37–39). The present method is suitable for the acetylation of electron-deficient
aryl amines (Table 2, entries 42 and 43).
To evaluate the role of Al O , we studied the acetylation of 4-nitrophenol, ben-
2
3
zyl alcohol, 2-hydroxybenzaldehyde, and thiophenol in the absence of Al O and
2
3
using P O alone. We found that the yields of the products by using the combination
2
5
of P O =Al O were greater (average, 10%) than those with P O alone under the
2
5
2
3
2
5
same conditions. In our previous work, we described the structure of P O =
2
5
[
47]
Al O .
2
It was found that P O reacted with Al O and bonded on the surface
2 5 2 3
3
of alumina. This structure has Brønsted and Lewis acidic sites dispersed on the

1778
A. ZAREI, A. R. HAJIPOUR, AND L. KHAZDOOZ
2 5 2 3
Scheme 2. Structure of P O =Al O .
surface of alumina. Furthermore, Al O as a support may also minimize cross con-
2
3
tamination between the product and H PO generated during the course of the reac-
3
4
[
47,49]
tion.
For these reasons, this can lead to significant improvements in its reactivity.
In the previous work, we determined the structure of P O =Al O (Scheme 2).
In this structure, the P-O-P bond is brittle and can be cleaved by different
2
5
2
3
Scheme 3. Suggested mechanism for the acetylation of alcohols to their corresponding acetates using a
2 5 2 3
catalytic amount of P O =Al O .

P
2
O
5
/Al
2
O
3
AS AN EFFICIENT CATALYST
1779
[
47,50]
nucleophiles.
the acetylation of alcohols using a catalytic amount of P O =Al O (Scheme 3).
Based on these results, we suggest the following mechanism for
2
5
2
3
Initially, acetic anhydride is activated by P O =Al O as intermediate (I). After that,
2
5
2
3
intermediate I is converted to intermediates II and III by nucleophilic attack of alco-
hol. As shown in Scheme 3, after the generation of intermediate III, the process of
acetylation is catalyzed with intermediate III.
EXPERIMENTAL
All reagents were purchased from Merck and Aldrich and used without further
purification. The products were characterized by comparison with authentic samples
1
and by spectroscopic data [Fourier transform–infrared (FT-IR, H NMR, and mp)].
1
H NMR spectra were recorded at 300 MHz. The spectra were measured in CDCl3
using tetramethylsilane (TMS) as the internal standard.
Preparation of P O /Al O
3
2
5
2
Phosphorus pentoxide (3 g) and 3 g of aluminium oxide (90 active acidic,
.063–0.200 mm) were mixed for 10 min in a round-bottomed flask until a fine and
0
homogenous powder was obtained. This reagent was heated in an oven at 120 C
ꢂ
[
45,47]
for 1 h and then stored in a sealed flask for later use.
General Experimental Procedure for the Acetylation of Alcohols
Under Solvent-Free Conditions
P O =Al O (0.06 g, 10 mol%) was added to a mixture of alcohol or phenol
3
2
5
2
(2 mmol) and acetic anhydride (4 mmol), and the reaction mixture was stirred at
room temperature for the specified time. The reaction was followed by thin-layer
chromatography (TLC). After completion of the reaction, the mixture was diluted
with CH Cl and filtered. The organic layer was washed with 10% NaHCO solution
2
2
3
and then dried over anhydrous Na SO . The solvent was evaporated under reduced
4
2
pressure to give the corresponding products. If necessary, the product was purified
by column chromatography on silica gel in cyclohexane=ethyl acetate.
Typical Experimental Procedure for the Preparation
of t-Butyl Acetate
ꢂ
P O =Al O (0.07 g, 2.4 mol%) was added at 0 C to a mixture of t-butanol
3
2
5
2
(10 mmol) and acetic anhydride (15 mmol), and the reaction mixture was stirred
for 5 min. Then the reaction mixture was brought to room temperature with constant
stirring and kept for 15 min. After completion of the reaction, the mixture was
extracted with diethyl ether (3 ꢃ 12 mL). The organic layer was washed with 10%
NaHCO solution and then dried over anhydrous Na SO . The solvent was
3
2
4
evaporated under reduced pressure to give t-butyl acetate in 88% yield.

1780
A. ZAREI, A. R. HAJIPOUR, AND L. KHAZDOOZ
Spectral Data for Some Representative Products
ꢁ
1
Benzyl acetate (Table 2, Entry 1). IR (KBr) cm : 3034, 2930, 1742, 1497,
1
1
5
455, 1380, 1362, 1228, 1026, 966, 750, 698. H NMR (300 MHz, CDCl ): d ¼ 7.38 (s,
3
H), 5.15 (s, 2 H), 2.12 (s, 3 H).
ꢁ
1
-Acetoxybenzyl acetate (Table 2, Entry 2). IR (KBr) cm : 3040, 2962,
2
741, 1611, 1587, 1492, 1455, 1370, 1228, 1177, 1111, 1026, 911, 835, 754. H
1
1
NMR (300 MHz, CDCl ): d ¼ 7.42 (d, J ¼ 7.6 Hz, 1 H), 7.34 (t, J ¼ 7.6 Hz, 1 H),
3
7
.22 (t, J ¼ 7.3 Hz, 1 H), 7.08 (d, J ¼ 7.9 Hz, 1 H), 5.07 (s, 2 H), 2.15 (s, 3 H), 2.05
(s, 3 H).
ꢁ
1
-Methoxybenzyl acetate (Table 2, Entry 3). IR (KBr) cm : 3020, 2942,
2
839, 1738, 1604, 1590, 1496, 1464, 1380, 1247, 1122, 1027, 964, 837, 755. H
1
2
NMR (300 MHz, CDCl ): d ¼ 7.35–7.25 (m, 2 H), 6.93 (t, J ¼ 7.3 Hz, 1 H), 6.87
3
(
d, J ¼ 8.1 Hz, 1 H), 5.18 (s, 2 H), 3.82 (s, 3 H), 2.09 (s, 3 H).
3
741, 1604, 1491, 1457, 1378, 1229, 1125, 1040, 897, 783, 743, 695. H NMR
ꢁ
1
-Methoxybenzyl acetate (Table 2, Entry 4). IR (KBr) cm : 2957, 2838,
1
1
(
3
300 MHz, CDCl ): d ¼ 7.22 (t, J ¼ 8.5 Hz, 1 H), 6.90–6.80 (m, 3 H), 5.03 (s, 2 H),
3
.75 (s, 3 H), 2.05 (s, 3 H).
ꢁ
1
-Methoxybenzyl acetate (Table 2, Entry 5). IR (KBr) cm : 3015, 2957,
4
838, 1737, 1613, 1518, 1464, 1379, 1240, 1176, 1125, 1031, 961, 823. H NMR
1
2
(
(
300 MHz, CDCl ): d ¼ 7.28 (d, J ¼ 8.5 Hz, 2 H), 6.88 (d, J ¼ 8.5 Hz, 2 H), 5.02
3
s, 2 H), 3.78 (s, 3 H), 2.05 (s, 3 H).
ꢁ
1
-Chlorobenzyl acetate (Table 2, Entry 6). IR (KBr) cm : 3066, 2950,
2
740, 1596, 1478, 1444, 1380, 1228, 1125, 1035, 918, 754. H NMR (300 MHz,
1
1
CDCl ): d ¼ 7.38–7.32 (m, 2 H), 7.28–7.20 (m, 2 H), 5.20 (s, 2 H), 2.10 (s, 3 H).
3
ꢁ
1
-Chlorobenzyl acetate (Table 2, Entry 7). IR (KBr) cm : 3050, 2961,
4
1
1
738, 1599, 1493, 1377, 1228, 1093, 1029, 967, 806. H NMR (300 MHz, CDCl ):
3
d ¼ 7.33 (d, J ¼ 8.95 Hz, 2 H), 7.28 (d, J ¼ 8.95 Hz, 2 H), 5.07 (s, 2 H), 2.1 (s, 3 H).
ꢁ
1
-Nitrobenzyl acetate (Table 2, Entry 8). IR (KBr) cm : 3074, 2939, 1737,
4
601, 1518, 1449, 1343, 1235, 1108, 1048, 921, 860, 741. H NMR (300 MHz,
1
1
CDCl ): d ¼ 8.25 (d, J ¼ 9.3 Hz, 2 H), 7.53 (d, J ¼ 9.3 Hz, 2 H), 5.22 (s, 2 H), 2.15
3
(s, 3 H).
ꢁ
1
Cinnamyl acetate (Table 2, Entry 9). IR (KBr) cm : 3027, 2943, 1735,
1
598, 1494, 1449, 1364, 1230, 1124, 1025, 967, 897, 746, 693. H NMR (300 MHz,
1
CDCl ): d ¼ 7.40–7.20 (m, 5 H), 6.65 (d, J ¼ 15.6 Hz, 1 H), 6.25 (dt, J ¼ 15.6 Hz,
3
1
J ¼ 7.8 Hz, 1 H), 4.70 (d, J ¼ 7.8 Hz, 2 H), 2.08 (s, 3 H).
2
ꢁ
1
1
1-Acetoxy-2-phenylethane (Table 2, Entry 12). IR (KBr) cm : 3029,
957, 1739, 1604, 1497, 1455, 1365, 1240, 1124, 1032, 896, 750, 700. H NMR
2
(
300 MHz, CDCl ): d ¼ 7.35–7.20 (m, 5 H), 4.30 (t, J ¼ 8.8 Hz, 2 H), 2.95 (t,
3
J ¼ 8.8 Hz, 2 H), 2.03 (s, 3 H).
-Acetoxy-1-phenylpropane (Table 2, Entry 16). IR (KBr) cm : 3033,
ꢁ
1
1
970, 2938, 2879, 1735, 1494, 1455, 1372, 1238, 1124, 1019, 965, 754, 700. H
1
2

P
2
O
5
/Al
2
O
3
AS AN EFFICIENT CATALYST
1781
NMR (300 MHz, CDCl ): d ¼ 7.35 (s, 5 H), 5.70 (t, J ¼ 7.4 Hz, 1 H), 2.08 (s, 3 H),
3
1
.90 (m, 2 H), 0.90 (t, J ¼ 8.1 Hz, 3 H).
-Acetoxy-1-phenylethane (Table 2, Entry 17). IR (KBr) cm : 3050,
ꢁ
1
1
982, 1743, 1495, 1453, 1371, 1240, 1209, 1065, 943, 761, 699. H NMR
1
2
(
1
300 MHz, CDCl ): d ¼ 7.38–7.25 (m, 5 H), 5.88 (q, J ¼ 6.5 Hz, 1 H), 2.07 (s, 3 H),
3
.54 (d, J ¼ 6.5 Hz, 3 H).
-Oxo-1,2-diphenylethyl acetate (Table 2, Entry 18). IR (KBr) cm
ꢁ
1
2
065, 2955, 1733, 1697, 1596, 1497, 1449, 1371, 1232, 1180, 1054, 972, 916, 758,
:
3
6
1
96. H NMR (300 MHz, CDCl ): d ¼ 7.97 (d, J ¼ 8.2 Hz, 2 H), 7.55–7.45 (m, 3
3
H), 7.40–7.30 (m, 5 H), 6.88 (s, 1 H), 2.20 (s, 3 H).
ꢁ
1
1
-Adamantyl acetate (Table 2, Entry 20). IR (KBr) cm : 2911, 2853, 1732,
1
1
3
456, 1367, 1354, 1243, 1060, 1016, 863. H NMR (300 MHz, CDCl ): d ¼ 2.15 (bs,
3
H), 2.10 (bs, 6 H), 1.97 (s, 3 H), 1.66 (bs, 6 H).
ꢁ
1
Phenyl acetate (Table 2, Entry 24). IR (KBr) cm : 3065, 2930, 1764, 1593,
1
492, 1371, 1193, 1012, 924, 891, 814, 749, 692. H NMR (300 MHz, CDCl ):
1
3
d ¼ 7.40 (d, J ¼ 7.9 Hz, 2 H), 7.25 (t, J ¼ 7.5, 1 H), 7.13 (t, J ¼ 7.9 Hz, 2 H), 2.30
(s, 3 H).
ꢁ
1
-Methylphenyl acetate (Table 2, Entry 25). IR (KBr) cm : 3034, 2925,
4
762, 1593, 1507, 1431, 1369, 1217, 1196, 1164, 1018, 940, 908, 845, 806. H
1
1
NMR (300 MHz, CDCl ): d ¼ 7.18 (d, J ¼ 7.9 Hz, 2 H), 6.97 (d, J ¼ 7.9, 2 H), 2.35
3
(s, 3 H), 2.27 (s, 3 H).
ꢁ1
2-Chloro-6-nitrophenyl acetate (Table 2, Entry 28). IR (KBr) cm : 3092,
939, 2874, 1787, 1596, 1533, 1455, 1350, 1179, 1121, 1078, 898, 798, 754, 712. H
1
2
NMR (300 MHz, CDCl ): d ¼ 7.98 (d, J ¼ 8.7 Hz, 1 H), 7.75 (d, J ¼ 8.25 Hz, 1 H),
3
7
.35 (t, J ¼ 8.2 Hz, 1 H), 2.44 (s, 3 H).
ꢁ
1
,3-Dimethylphenyl acetate (Table 2, Entry 29). IR (KBr) cm : 3045,
2
926, 1764, 1582, 1469, 1371, 1213, 1184, 1062, 1010, 926, 864, 779, 730.
1
2
H
NMR (300 MHz, CDCl ): d ¼ 7.10 (t, J ¼ 7.5 Hz, 1 H), 7.05 (d, J ¼ 7.35 Hz, 1 H),
3
6
.85 (d, J ¼ 7.5 Hz, 1 H), 2.32 (s, 3 H), 2.30 (s, 3 H), 2.07 (s, 3 H).
-tert-Butylphenyl acetate (Table 2, Entry 30). IR (KBr) cm : 3043, 2963,
ꢁ
1
4
908, 1765, 1602, 1509, 1463, 1368, 1267, 1201, 1110, 1016, 911, 852, 698. H NMR
1
2
(
300 MHz, CDCl ): d ¼ 7.45 (d, J ¼ 8.25 Hz, 2 H), 7.25 (d, J ¼ 8.25 Hz, 2 H), 2.30 (s, 3
3
H), 1.36 (s, 9 H).
ꢁ
1
-Nitrophenyl acetate (Table 2, Entry 31). IR (KBr) cm : 3084, 2937,
4
852, 1760, 1615, 1591, 1521, 1486, 1348, 1192, 1102, 1011, 915, 866, 746, 701. H
1
2
NMR (300 MHz, CDCl ): d ¼ 8.28 (d, J ¼ 8.9 Hz, 2 H) 7.30 (d, J ¼ 8.9 Hz, 2 H),
3
2
.35 (s, 3 H).
ꢁ
1
,4-Diacetoxy benzene (Table 2, Entry 32). IR (KBr) cm : 3073, 2930,
1
761, 1507, 1417, 1369, 1216, 1173, 1014, 921, 851, 764. H NMR (300 MHz,
1
1
CDCl ): d ¼ 7.1 (s, 4 H), 2.28 (s, 6 H).
3

1782
A. ZAREI, A. R. HAJIPOUR, AND L. KHAZDOOZ
ꢁ1
1
,3-Diacetoxy benzene (Table 2, Entry 33). IR (KBr) cm : 3075, 2939,
1
1
752, 1599, 1485, 1445, 1372, 1225, 1125, 1015, 965, 916, 783, 698. H NMR
300 MHz, CDCl3): d ¼ 7.35 (t, J ¼ 8.0 Hz, H), 6.98 (dd, J1 ¼ 8.0 Hz,
J ¼ 1.76 Hz, 2 H), 6.92 (t, J ¼ 1.76 Hz, 1 H), 2.25 (s, 3 H).
(
1
2
ꢁ
1
,2-Bis(4-acetoxyphenyl)propane (Table 2, Entry 34). IR (KBr) cm :
2
055, 2965, 1752, 1601, 1508, 1371, 1228, 1169, 1019, 911, 851. H NMR
1
3
(
(
300 MHz, CDCl ): d ¼ 7.22 (d, J ¼ 8.8 Hz, 4 H), 6.97 (d, J ¼ 8.8 Hz, 4 H), 2.28
3
s, 6 H), 1.67 (s, 6 H).
ꢁ1
1-Acetoxy naphthalene (Table 2, Entry 35). IR (KBr) cm : 3062, 2935,
769, 1598, 1577, 1509, 1461, 1390, 1369, 1201, 1155, 1078, 1014, 916, 893, 866,
1
7
1
97, 772, 744. H NMR (300 MHz, CDCl ): d ¼ 7.89–7.83 (m, 2 H), 7.73 (d, J ¼ 8 Hz,
3
Hz, 1 H), 7.53–7.42 (m, 3 H), 7.24 (d, J ¼ 7.5 Hz, 2 H), 2.45 (s, 3 H).
ꢁ1
2-Acetoxy naphthalene (Table 2, Entry 36). IR (KBr) cm : 3057, 2925,
757, 1597, 1509, 1464, 1438, 1372, 1220, 1136, 1015, 964, 926, 824, 759. H
1
1
NMR (300 MHz, CDCl ): d ¼ 7.88–7.77 (m, 3 H), 7.57 (d, J ¼ 1.87 Hz, 1 H),
3
7
.53–7.43 (m, 2 H), 7.22 (dd, J ¼ 8.2 Hz, J ¼ 1.87 Hz, 1 H), 2.35 (s, 3 H).
1
2
1,1-Diacetoxy-1-(2-acetoxyphenyl)methane (Table 2, Entry 38). IR
KBr) cm : 3050, 2985, 1760, 1750, 1610, 1530, 1490, 1380, 1250, 1205, 1160,
ꢁ
1
(
1
1
070, 990, 950, 810, 750. H NMR (300 MHz, CDCl ): d ¼ 7.75 (s, 1 H), 7.25–7.15
3
(m, 2 H), 7.10–7.00 (m, 2 H), 2.18 (s, 3 H), 1.94 (s, 6 H).
1,1-Diacetoxy-1-(4-acetoxy-3-methoxyphenyl)methane (Table 2, Entry
9). IR (KBr) cm : 3050, 2950, 1770, 1750, 1610, 1500, 1465, 1385, 1250, 1205,
ꢁ1
3
1
1
H), 3.85 (s, 3 H), 2.35 (s, 3 H), 2.20 (s, 6 H).
070, 990, 780. H NMR (300 MHz, CDCl ): d ¼ 7.60 (s, 1 H), 7.25–7.05 (m, 3
3
CONCLUSION
We have shown that P O =Al O is an efficient catalyst for the acylation of
2
5
2
3
alcohols, phenols, thiols, and amines using acetic anhydride under solvent-free con-
ditions at room temperature. The advantages of this method over earlier reported
processes are its simplicity, clean and rapid reactions, good yields, absence of organic
solvents, and retention of chirality. The use of an inexpensive and nontoxic catalyst
is another advantage of this method. In contrast to other acids, this compound does
not need special precautions for storage and handling, and it can be stored on the
benchtop for weeks without losing its catalytic activity.
ACKNOWLEDGMENTS
We gratefully acknowledge the funding support received for this project from
the Islamic Azad University of Fasa and Isfahan University of Technology (IUT).

P
2
O
5
/Al
2
O
3
AS AN EFFICIENT CATALYST
1783
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O
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