Rapid and efficient method for acetylation of alcohols and phenols with acetic anhydride catalyzed by silica sulfate

Article abstract of DOI:10.1080/00397910500514295

A rapid and efficient method is described for acetylation of a series of alcohols and phenols with acetic anhydride catalyzed by silica sulfate solid acid at room temperature or at refluxing temperature in excellent yield. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910500514295

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Rapid and Efficient Method for Acetylation of
Alcohols and Phenols with Acetic Anhydride
Catalyzed by Silica Sulfate
Ying Zhao a , Li‐Bin Liu a , Zhuo Chen a , Tong‐Shuang Li a & Tong‐Shou Jin a
a Department of Chemistry, College of Chemistry and Environmental
Science, Hebei University, Baoding, China
Published online: 24 Feb 2007.
To cite this article: Ying Zhao , Li‐Bin Liu , Zhuo Chen , Tong‐Shuang Li & Tong‐Shou Jin (2006): Rapid and
Efficient Method for Acetylation of Alcohols and Phenols with Acetic Anhydride Catalyzed by Silica Sulfate,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
36:9, 1221-1227
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Synthetic Communicationsw, 36: 1221–1227, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500514295
Rapid and Efficient Method for Acetylation
of Alcohols and Phenols with Acetic
Anhydride Catalyzed by Silica Sulfate
Tong-Shou Jin, Ying Zhao, Li-Bin Liu, Zhuo Chen,
and Tong-Shuang Li
Department of Chemistry, College of Chemistry and Environmental
Science, Hebei University, Baoding, China
Abstract: A rapid and efficient method is described for acetylation of a series of
alcohols and phenols with acetic anhydride catalyzed by silica sulfate solid acid at
room temperature or at refluxing temperature in excellent yield.
Keywords: Acetylation, alcohol, phenol, silica sulfate
INTRODUCTION
The hydroxyl group is nucleophilic and easily oxidized by a wide range of
reagents. Because it can participate in a great number of transformations
under mild conditions, the most important thing in organic synthesis is to
ensure that a specific hydroxyl function in a multifunctional molecule is
protected from unwanted reactions. Esters are the most used protective
groups in organic synthesis.[1] The routine acylation of alcohols and phenols
is carried out by acetic anhydride or acetyl chloride in the presence of
tertiary amines such as triethylamine and pyridine.[2] Protonic acids, Lewis
acids, and several solid catalysts have recently been found to get better
results for the acetylation of alcohols and phenols.[3–10] Each of the
methods has its merits and shortcomings. These methods have not been
Received in Japan July 28, 2005
Address correspondence to Tong-Shou Jin, Department of Chemistry, College of
Chemistry and Environmental Science, Hebei University, No. 88 Hezuo Road,
Baoding 071002, China. E-mail: orgsyn@mail.hbu.edu.cn
1221

1222
T.-S. Jin et al.
entirely satisfactory; for example, triethylamine and pyridine have unpleasant
odor and are not easy to remove. In this article we reveal a novel method for
the acylation of alcohols and phenols with acetic anhydride catalyzed by silica
sulfate.
Silica sulfate, a new type of solid acid, has been studied recently.[11,12]
We believe that the silica sulfate is superior to the other reported acidic
solid supports or acidic resins, such as polysyrene sulfonic acid and Nafion-
H, for running reactions under heterogeneous conditions. Therefore, we are
interested in using this inorganic acidic resin as a new sulfuric acid
function. Herein we demonstrate a rapid and efficient method for acetylation
of a series of alcohols and phenols with acetic anhydride catalyzed by silica
sulfate solid acid at room temperature or at refluxing temperature (Scheme 1).
RESULTS AND DISCUSSION
The results of a series of alcohols and phenols with acetic anhydride catalyzed
by silica sulfate solid acid at room temperature or at refluxing temperature are
summarized in Table 1.
As shown in Table 1, a series of alcohols and phenols were treated with
acetic anhydride in the presence of silica sulfate in CH2Cl2, CHCl3 at room
temperature or at refluxing temperature. As for alcohols, primary (1, 2, 3, 4,
5, and 9) and secondary (6,7, 8, 9, and 10) alcohols can be easily acetylated
at room temperature. However, the hindered tertiary alcohol shows the
lowest activity. For example, triphenylmethanol (11) is acetylated with
acetic anhydride in the presence of silica sulfate at refluxing temperature
with a longer reaction time (3 h), but it remains unchanged. Therefore,
primary and secondary alcohols can be acetylated more easily than tertiary
alcohol.
The phenols with either electron-donating or electron-withdrawing
groups (12, 13, 14, 16, 17, 18, 19, 23, and 24) can afford high yields of
products at room temperature in a short time. When 2-nitrophenol (15) was
treated with acetic gave anhydride in the presence of silica sulfate, conversion
to 2-nitrophenyl acetate gave only 58% yield at room temperature in 3 h, but
only 5 min at refluxing CHCl3 under catalysis of silica sulfate gave 92% yield.
The explanation for this result may be the formation of a intramolecular
hydrogen bond in 2-nitrophenol, which would reduce the activity of the
molecule at room temperature, whereas heating destructs this structure.
Furthermore, we also find that polyhydroxy compounds could be transformed
Scheme 1.

Table 1. Acetylation of alcohols and phenols catalyzed by silica sulfate
Solvent/
Bp (Torr) or Mp (8C)
Temp (8C)/T
(min)
Yield
(%)a
Entry
Substrate
1-Heptanol 1
1-Octanol 2
Product
Found
Reported[13]
1
2
3
4
5
6
7
8
9
CHCl3/rt/2
CHCl3/rt/1
CHCl3/rt/1
CHCl3/rt/2
CHCl3/rt/3
CHCl3/rt/3
CHCl3/rt/4
CHCl3/rt/1
CHCl3/rt/2
91
90
79
90
93
87
92
80
82
1-Heptanyl acetate
1-Octyl acetate
1-Octadecanyl acetate
Benzyl acetate
96–98/20
102–104/20
32–33
191–192/760
211.5/760
33
1-Octadecanol 3
Benzyl alcohol 4
2-Phenylethanol 5
Benzoin 6
115–117/20
122–124/20
82–83
134/102
232/760
83
2-Phenylethyl acetate
Benzoin acetate
Cyclohexyl acetate
Cholesteryl acetate
Betulin-3,22-diyl
diacetate
Cyclohexanol 7
Cholesterol 8
Betulinol 9
80–82/25
113–114
218–220
175/760
114–115
218–220
10
Diphenyl methanol 10
CHCl3/rt/1
90
Diphenyl methanyl
acetate
41–42
41–42
11
12
13
14
15
16
17
18
Triphenyl methanol 11
Phenol 12
CHCl3/62/180
CH2Cl2/rt/1.5
CHCl3/rt/3
CH2Cl2/rt/2
CHCl3/62/5
CH2Cl2/rt/3
CH2Cl2/rt/1
CH2Cl2/rt/1
NRb
87
94
94
92
98
93
94
Phenyl acetate
95–96/20
102–104/20
102–104/20
39–40
196/760
212/760
212–213/760
40–41
3-Methylphenol 13
4-Methylphenol 14
2-Nitrophenol 15
3-Nitrophenol 16
4-Nitrophenol 17
4-Chlorophenol 18
3-Methylphenyl acetate
4-Methylphenyl acetate
2-Nitrophenyl acetate
3-Nitrophenyl acetate
4-Nitrophenyl acetate
4-Chlorophenyl acetate
55–56
80–82
55–56
81–82
106–108/20
226–228/760
(continued)

Table 1. Continued.
Solvent/
Temp (8C)/T
(min)
Bp (Torr) or Mp (8C)
Yield
(%)a
Entry
19
Substrate
Product
Found
Reported[13]
2,4-Dichlorophenol 19
Catechol 20
CH2Cl2/rt/5
CHCl3/rt/1
CHCl3/rt/0.5
CHCl3/rt/1
86
88
91
83
2,4-Dichlorophenyl
acetate
124–126/20
62–63
244–245/760
20
21
22
Benzene-1,2-diyl
diacetate
63.5
Resorcinol 21
Benzene-1,3-diyl
diacetate
158–160/20
121–122
278/760
123–124
Hydroquinone 22
Benzene-1,4-diyl
diacetate
23
24
25
1-Naphthol 23
2-Naphthol 24
2,4,6-Tritertbutylphenol 25
CHCl3/rt/1
CH2Cl2/rt/1
CHCl3/62/60
90
88
NRb
1-Naphthyl acetate
2-Naphthyl acetate
48–49
69–70
48–49
70
aYields refer to isolated products.
bNo reaction.

Acetylation of Alcohols and Phenols
1225
into the corresponding polyacetates (9, 20, 21, and 22). In addition, 2,4,6-
tritertbutylphenol 25 treated with acetic anhydride remained unchanged in
the presence of silica sulfate in refluxing CHCl3 for 1 h. This result may be
due to the steric effect.
The catalyst was easily regenerated by washing with diethyl ether,
followed by drying at room temperature for 4 h. The catalyst could be
reused five times for the synthesis of 16 without significant loss of activity.
In conclusion, silica sulfate is good for acetylation of alcohols, phenols,
and polyhydroxy compounds. This method offers several advantages
including mild reaction conditions, cleaner reactions, and high yield of
products, as well as simple experimental and isolation procedures, which
make it a useful and attractive process for the acetylation.
EXPERIMENTAL
Melting and boiling points are uncorrected. Liquid alcohols and phenols were
purified by distillation before use. The products were characterized by their
1
melting or boiling points and/or IR and H NMR. IR spectra were recorded
1
on a Bio-Rad FIS-40 spectrometer (KBr). H NMR spectra were measured
on an Avance-400 spectrometer using TMS as internal standard and CDCl3
as solvent.
Preparation of the Catalyst[12]
Silica gel (100 g) was soaked with CH2Cl2 (50 mL), and then chlorosulfonic
(58.3 g, 0.5 moL) acid was added slowly with stirring at room temperature.
After the addition was completed, the mixture was shaken for 60 min. The
solvent was evaporated under reduced pressure. A white solid powder was
obtained and stored in a desiccator until use.
General Procedure
Mixture of the alcohol or phenol (1, 1 mmol), acetic anhydride (2, 2 mmol),
silica sulfate (80 mg), and solvent (CH2Cl2 or CHCl3, 5 mL) is stirred at
room temperature or refluxing temperature for the length of time indicated
in Table 1. The progress of the reactions is monitored by TLC. After com-
pletion of the reaction, the solvent was evaporated and diethyl ether
(10 mL) was added to the mixture. The catalyst was removed by filtration
and washed with diethyl ether (2 ꢀ 5 mL). The filtrate was washed with 5%
HCl (10 mL), 5% NaHCO3 (10 mL), and brine (2 ꢀ 10 mL) successively.
After drying with anhydrous sodium sulfate, the solvent was evaporated
under reduced pressure and the crude product purified by reduced pressure
distillation or recrystallization from 95% ethanol to get the pure product.

1226
T.-S. Jin et al.
Selected Spectral Data of Some Products
1-Octyl acetate: dH 0.88 (3H, t, –CH3), 1.20–1.43 [10H, m, CH3(CH2)5-],
1.78 (2H, m, CH2CH2 OOC CH3), 2.04 (3H, s, –OCOCH3), 4.05 (2H, t,
–CH2OCOCH3).
Benzyl acetate: dH 2.07 (3H, s, –OCOCH3), 5.09 (2H, s, ArCH2-), 7.26–7.36
(5H, m, –C6H5).
2-Phenylethyl acetate: dH 2.04 (3H, s, 1-OCOCH3), 2.82 (2H, t, J ¼ 7 Hz,
2-CH2), 4.83 (2H, t, J ¼ 7 Hz, 1-CH2), 7.15–7.38 (5H, m, 2-C6H5).
1–Octadecanyl acetate: dH 0.89 (3H, t, –CH3), 1.27 [30H, m, CH3(CH2)15-],
1.80
(2H,
m,
–CH2OCOCH3), 2.02 (3H, s, –OCOCH3).
–CH2CH2OOC
CH3),
4.34
(2H,
t,
Benzoin acetate: dH 7.30–8.01 (10H, m, Ar-H), 5.82 (1H, s, –CH), 2.03 (3H,
s, –OCOCH3).
Cyclohexyl acetate: dH 1.25–1.60(10H, m, –C6H11), 3.02 (1H, m,
–CHOOCCH3), 2.00 (3H, s, –OCOCH3).
Cholesteryl acetate: dH 5.39 (1H, d, J ¼ 4.4 Hz, 6-H), 4.64 (1H, m, 3a-H),
1.04 (3H, s, 19-CH3), 0.94 (3H, d, J ¼ 6.4 Hz, 21–CH3), 0.88 (6H, d,
J ¼ 6.4 Hz, 26, 27–CH3), 0.70 (3H, s, 18–CH3), 2.05 (3H, s, 3-OCOCH3).
Betulinyl-3,22-diyl diacetate:dH 4.71 (1H, s, 29-H), 4.61 (1H, s, 29-H0),
4.27 (1H, d, J ¼ 11.2 Hz, 28-H), 3.87 (1H, d, J ¼ 11.2 Hz, 28-H0), 2.32
(1H, m, 3-H), 1.66–1.08 (complex, CH2, CH), 1.70 (3H, s, 30–CH3), 1.41,
1.05, 0.99, 0.87, 0.85 (15H, all s, 5 ꢀ CH3), 2.09 (3H, s, 3-OCOCH3), 2.06
(3H, s, 22–OCOCH3).
4-Methylphenyl acetate: dH 2.01 (3H, s, –OCOCH3), 2.25 (3H, s, -Ar-CH3),
6.92 (2H, d, 20,60-Ar-H), 7.04 (2H, d, 30,50-Ar-H).
4–Chlorophenyl acetate: dH1.98 (3H, s, –OCOCH3), 6.98 (2H, d, 20,60-Ar-
H), 7.25 (2H, d, 30,50-Ar-H).
ACKNOWLEDGMENTS
The project was supported by the National Natural Science Foundation of
China (29872011 and 29572039), Educational Ministry of China, Educational
Department of Hebei Province (990104), and the Science and Technology
Commission of Hebei Province.
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