Rapid and efficient acetylation of alcohols and phenols with acetic anhydride using tin(IV) porphyrin as catalyst

Article abstract of DOI:10.1081/SCC-120003629

The efficient and rapid esterification of alcohols and phenols in acetic anhydride was achieved by tin(IV) tetraphenylporphyrin perchlorate [Sn^IV (tpp) (ClO₄)₂] as catalyst in high yields. Sn^IV (tpp) (ClO₄)₂ showed highly catalytic activity on the acetylation reaction.

Full text of DOI:10.1081/SCC-120003629

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RAPID AND EFFICIENT ACETYLATION OF ALCOHOLS
AND PHENOLS WITH ACETIC ANHYDRIDE USING TIN(IV)
PORPHYRIN AS CATALYST
Shahram Tangestaninejad a , Mohammad Hossein Habibi a , Valiollah Mirkhani a & Majid
Moghadam a
a Department of Chemistry, Isfahan University, Isfahan, 81744, Iran
Published online: 17 Aug 2006.
To cite this article: Shahram Tangestaninejad , Mohammad Hossein Habibi , Valiollah Mirkhani & Majid Moghadam (2002):
RAPID AND EFFICIENT ACETYLATION OF ALCOHOLS AND PHENOLS WITH ACETIC ANHYDRIDE USING TIN(IV) PORPHYRIN AS
CATALYST, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:9,
1337-1343
To link to this article: http://dx.doi.org/10.1081/SCC-120003629
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SYNTHETIC COMMUNICATIONS, 32(9), 1337–1343 (2002)
RAPID AND EFFICIENT ACETYLATION
OF ALCOHOLS AND PHENOLS WITH
ACETIC ANHYDRIDE USING TIN(IV)
PORPHYRIN AS CATALYST
*
Shahram Tangestaninejad,
Mohammad Hossein Habibi, Valiollah Mirkhani,
and Majid Moghadam
Department of Chemistry, Isfahan University,
Isfahan 81744, Iran
ABSTRACT
The efficient and rapid esterification of alcohols and phenols
in acetic anhydride was achieved by tin(IV) tetraphenyl-
porphyrin perchlorate [SnIV (tpp) (ClO4)2] as catalyst in
high yields. SnIV (tpp) (ClO4)2 showed highly catalytic activity
on the acetylation reaction.
The protection of hydroxy groups by the formation of esters is of
great importance in organic synthesis.1 Protection of such functional groups
is often necessary during the course of various transformations in a synthetic
sequence, especially in nucleosides, carbohydrates, steroids and natural prod-
ucts. Many heterogeneous and homogeneous catalysts or reagents such as 4-
(dimethyl amino) pyridine (DMAP) and 4-pyrrolidinopyridine (PPY),2
*Corresponding author.
1337
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

1338
TANGESTANINEJAD ET AL.
scandium trifluromethanesulfonate [Sc(OTf)3],3 TaCl5,4 montmorillonite
K-10 and KSF,5 trimethylsilyl trifluromethanesulfonate (TMSOTf),6
Bu3P,7 CoCl2,8 iodine,9 Cu(NO3)2 ꢀ 3H2O,10 copper trifluro-methesulfonate
[Cu(OTf)2]11 and indium trifluromethanesulfonate-[ln(OTf)3]12 have been
reported as acylating agents. In some of these cases the yields are low or
stringent reaction conditions are used.
The successful applications of metalloporphyrins as mild Lewis acid
catalysts13–16 prompted us to explore the potential of these complexes as
catalysts for the conversion of alcohols and phenols to their corresponding
esters.
We found that SnIV(tpp)(ClO4)2 can act as an efficient catalyst for the
conversion of various alcohols and phenols to esters with acetic anhydride at
room temperature in high yields (Scheme 1).
Scheme 1.
1-Heptanol was chosen as a model substrate for the acylation reaction.
The reaction of this alcohol (1 mmol) in acetic anhydride (1 ml) in the
presence of 0.02 molar equivalent of SnIV(tpp)(ClO4)2 at room temperature
was completed within 5 min and the corresponding acetate was obtained in
99% yield. In the absence of SnIV(tpp)(ClO4)2 catalyst, the reaction was
much less efficient.
A series of primary and secondary alcohols were acylated with Ac2O in
the presence of 0.02 molar equivalent of SnIV(tpp)(ClO4)2 at room tempera-
ture in 60–99% yields (Table 1). Tertiary alcohols such as 1-adamantanol
and triphenylmethanol were also satisfactorily acetylated without any
elimination products (Table 1, Entries 20 and 21).
Under the same reaction conditions, phenols were converted to their
corresponding acetates in good to excellent yields (Table 2). The acetylation
of polyhydroxy phenols was also investigated and the corresponding
polyacetates were obtained in 66–99% yields (Table 2, Entries 3–7).
In conclusion, we have found that SnIV(tpp)(ClO4)2 is a mild and
efficient catalyst for acetylation of alcohols and phenols with acetic
anhydride. The advantage of this combination is that even hindered
substrates can be acylated in high yield under mild conditions.

ACETYLATION OF ALCOHOLS AND PHENOLS
1339
Table 1. Acetylation of Alcohols with Ac2O Catalyzed by
SnIV(tpp)(ClO4)2 at Room Temperature
Time
(min)
Yielda
(%)
Entry
1
Substrate
5
5
5
5
5
5
5
99
99
99
99
99
99
99
2
3
4
5
6
7
8
9
120
5
99
99
10
11
12
13
14
120
5
65
99
99
99
5
5
30
80
(continued )

1340
TANGESTANINEJAD ET AL.
Table 1. Continued
Time
(min)
Yielda
(%)
Entry
15
Substrate
5
99
16
60
99
17
18
19
40
60
15
92
65
99
20
15
30
99
70
21
aGC yields.
EXPERIMENTAL
All chemicals used were reagent grade. The tetraphenylporphyrin was
prepared and metallated according to the literature.17,18 SnIV(tpp)(ClO4)2,
was prepared as described by Arnold19 and Suda.13
General Procedure for Acetylation Reaction
In a round-bottom flask (25 ml) equipped with a magnetic stirrer, a
solution of alcohol or phenol (1 mmol) in Ac2O (1 ml) was prepared.
SnIV(tpp)(ClO4)2 (0.19 g, 0.02 mmol) was added to this solution and the

ACETYLATION OF ALCOHOLS AND PHENOLS
1341
Table 2. Acetylation of Phenols with Ac2O Catalyzed by
SnIV(tpp)(ClO4)2 at Room Temperature
Time
(min)
Yielda
(%)
Entry
1
Substrate
5
10
5
99
90
99
60
2
3
4
5
5
6
7
10
5
92
99
95
30
8
9
5
99
65
120
10
120
55
aGC yields.
reaction mixture was stirred at room temperature. The reaction was mon-
itored by GLC. After completion of the reaction, the mixture was directly
passed through a short column of silica-gel (1 : 1 hexane-ethyl acetate) to
remove the catalyst. The eluate was evaporated under reduced pressure and
the remaining residue was purified by silica-gel plate chromatography

1342
TANGESTANINEJAD ET AL.
(eluted with CCl4 : Et2O ¼ 9 : 1) to afford the corresponding ester without
any elimination products.
ACKNOWLEDGMENT
The partial support of this work by Isfahan University Research
Council is gratefully acknowledged.
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Received in Japan February 20, 2001