Selective acetylation of alcohols and amines with ethyl acetate in the presence of H6[PMo9V3O40] as the catalyst

Article abstract of DOI:10.1007/s00706-007-0592-7

Acetylation of various alcohols and benzyl amine was tested in the presence of H₆[PMo₉V₃O₄₀], a mixed addenda heteropolyacid, in ethyl acetate under reflux condition. Phenols and anilines are not affected under the reaction conditions. Selective transestrification of alcohols can be achieved in the presence of phenol and aniline derivatives using this method. Springer-Verlag 2007.

Full text of DOI:10.1007/s00706-007-0592-7

Monatshefte fu¨r Chemie 138, 445–447 (2007)
DOI 10.1007/s00706-007-0592-7
Printed in The Netherlands
Selective Acetylation of Alcohols and Amines with Ethyl Acetate
in the Presence of H6[PMo9V3O40] as the Catalyst
Majid M. Heravi1;ꢀ, Khadijeh Bakhtiari1, Negar M. Javadi1,
Hossein A. Oskooie1, and Fatemeh F. Bamoharram2
1
Department of Chemistry, School of Sciences, Azzahra University, Vanak, Tehran, Iran
2
Department of Chemistry, Azad University of Mashhad, Mashhad, Iran
Received November 18, 2006; accepted (revised) November 23, 2006; published online March 16, 2007
# Springer-Verlag 2007
Summary. Acetylation of various alcohols and benzyl amine
ary hydroxy and amino groups. Thus, acylation by
was tested in the presence of H6[PMo9V3O40], a mixed ad-
denda heteropolyacid, in ethyl acetate under reflux condition.
Phenols and anilines are not affected under the reaction condi-
tions. Selective transestrification of alcohols can be achieved in
the presenceofphenolandaniline derivativesusingthismethod.
transestrification with an ester or an enol ester con-
stitutes a simple, practical, and selective alternative.
A variety of procedures involving different catalysts
have been developed for this transformation [15, 16]
and this process is under constant study to make it
more effective and selective [17, 18].
Keywords. Acetylation; Transestrification; Alcohols; Mixed
addenda heteropolyacids; Ethyl acetate.
Heteropolyacids, HPAs, catalyze a wide variety of
reactions in homogeneous or heterogeneous (liquid-
solid, gas-solid, or liquid–liquid biphasic) systems,
offering strong options for more efficient and clean-
er processing compared to conventional mineral
acids [19–22]. Catalysts based on heteropolyacids
as Brønsted acids have many advantages over liquid
acid catalysts. They are non-corrosive and environ-
mentally benign presenting fewer disposal problems.
Solid heteropolyacids have attracted much attention
in organic synthesis owing to easy work-up proce-
dures, easy filtration, and minimization of cost and
waste generation due to reuse and recycling of the
catalysts [23]. Being stronger acids, heteropolyacids
will have significantly higher catalytic activity than
conventional catalysts such as mineral acids, mixed-
oxides, zeolites, etc. In particular, in organic media
the molar catalytic activity of heteropolyacid is often
100–1000 times higher than that of H2SO4 [21, 22].
This makes it possible to carry out the catalytic pro-
cess at a lower catalyst concentration and=or at a
lower temperature. Further, heteropolyacid catalysis
Introduction
Acetylation of alcohols and amines is one of the
most frequently used transformations in organic syn-
thesis as it provides an efficient and inexpensive
means for protecting hydroxy and amino groups in a
multistep synthesis process [1, 2]. Esters are usually
synthesized from alcohols and carboxylic acids
[3, 4], or acid chloride and acid anhydride or an ester
[5, 6] as the acylating agent.
Many acidic [7] or basic [8] catalysts have been
used for this purpose. A variety of Lewis acids
such as Sc(NTf2)3 [9], TiCl(OTf)3 [10], TMSCl
and TMSOTf [11], La(Oi-Pr)3 [12], Sn(OTf)2 [13],
TiCl4=AgClO4 [14], have also been applied as cat-
alysts or reagents to mediate the reaction between
alcohols and acylating agent.
Most of the acidic and basic catalysts lack the
ability to differentiate between primary and second-
ꢀ
Corresponding author. E-mail: mmh1331@yahoo.com

446
M. M. Heravi et al.
lacks side reactions such as sulfonation, chlorina-
tion, nitration, etc. which occur with mineral acids
[21, 22]. As stable, relatively nontoxic crystalline
substances, heteropolyacids are also preferable re-
garding safety and ease of handling.
The Keggin-type HPAs typically represented by
the formula H8-x[XM12O40], when X is the hetero-
atom (most frequently Pþ5 or Siþ4), x is the oxida-
tion state, and M is the addenda atom (usually Wþ6
or Moþ6), are the most important ones for catalysis
[19–22]. They have been widely used as acid and
oxidation catalysts for organic synthesis and found
several industrial applications.
Recently, we have reported acetylation of alco-
hols and phenols with acetic acid and acetic anhy-
dride in the presence of ferric perchlorate [24] or
H14[NaP5W30O110] [25]. In continuation of our in-
vestigation on the use of heteropolyacids as cata-
lysts for chemical preparations [26–31] we wish
now to report that the mixed addenda heteropolyacid
H6[PMo9V3O40] catalyzes the transestrification of
various alcohols and benzyl amines with ethyl acet-
ate very efficiently (Scheme 1).
Results and Discussion
When 2-chlorobenzyl alcohol was treated with ethyl
acetate in the presence of H6[PMo9V3O40] under re-
flux condition the corresponding acetate was obtain-
ed in good yield (Table 1, Entry 6). The reaction of
various benzyl alcohols with ethyl acetate under the
same condition afforded the corresponding products
in high yields. The results are summarized in Table 1.
In all cases, the reactions proceeded efficiently and
completed within 40–70 min. All of the products
were characterized by comparison of their spectra
and physical data with those reported in literature.
This method is effective for the preparation of ace-
tates from both electron-rich as well as electron-defi-
cient benzyl alcohols. Allylic, propargylic, primary,
and secondary alcohols were also successfully acety-
lated under these conditions. However, phenol and
aniline derivatives failed to react with ethyl acetate
to give the analogous products under these reaction
conditions. Moreover, treatment of benzyl amine and
ethyl acetate under the same reaction condition af-
forded N-benzylacetamide in 90% yield after 70 min
(see Table 1). In order to show the selectivity of the
procedure for the acetylation of different benzyl alco-
hols, we investigated the competitive reaction for the
preparation of benzyl acetates from benzyl alcohols in
the presence of phenols or anilines using a catalytic
Scheme 1
Table 1. Acetylation of alcohols and amines by transesterification with EtOAc using H6[PMo9V3O40] as the catalyst
Entry
Substrate
Product
Time=min
Yield=%a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
PhCH2OH
2-Me-PhCH2OH
2-OH-PhCH2OH
4-NO2-PhCH2OH
4-Br-PhCH2OH
2-Cl-PhCH2OH
4-OMe-PhCH2OH
Furyl-CH2OH
C2HCH2OH
PhCH2OAc
2-Me-PhCH2OAc2
2-OH-PhCH2OAc
4-NO2-PhCH2OAc
4-Br-PhCH2OAc
2-Cl-PhCH2OAc
4-OMe-PhCH2OAc
Furyl-CH2OAc
C2HCH2OAc
50
40
50
50
50
45
50
60
60
70
60
60
70
70
1440
1440
1440
1440
1440
1440
96
92
92
99
99
85
94
90
90
93
98
99
98
97
–
C2H3CH2OH
Ph2CHOH
CH3CH(OH)(CH2)5CH3
CH3CH(OH)(CH2)7CH3
PhCH2NH2
C2H3CH2OAc
Ph2CHOAc
CH3CH(OAc)(CH2)5CH3
CH3CH(OAc)(CH2)7CH3
PhCH2NHOAc
No reaction
PhNH2
4-NO2-PhNH2
4-Br-PhNH2
PhOH
4-Br-PhOH
2-NO2-PhOH
No reaction
No reaction
No reaction
No reaction
No reaction
–
–
–
–
–
a
Yields analyzed by GC

Selective Acetylation of Alcohols and Amines
447
amount of H6[PMo9V3O40] under reflux conditions.
We found that benzyl alcohols were converted to the
corresponding acetates in high selectivity in the pres-
ence of phenols or anilines. This suggested that selec-
tive preparation of acetates in the presence of phenols
or anilines could be achieved with this procedure.
In conclusion, H6[PMo9V3O40] was employed as
an effective heterogeneous catalyst for the transestri-
fication of alcohols in high yields in solution. The
catalyst is recyclable and was used in several runs
without loosing its catalytic activity. Relatively short
reaction time, very simple performance and work-up
procedure, high yields, easy recycling, and reusabil-
ity are worth of mentioning for the present protocol.
H6[PMo9V3O40] is non-corrosive and environmen-
tally benign and presents fewer disposal problems.
The use of this green, available, and inexpensive
solid acid catalyst allows replacement of the usual
soluble inorganic acids, contributing in this way to
the reduction of wastes.
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Experimental
All chemicals were purchased from commercial suppliers and
were used as received. All products were identified by their
spectra and physical data. Melting points were measured by
using the capillary tube method with an electrothermal 9100
apparatus. IR spectra were recorded from KBr disks on the
FT-IR Brucker Tensor 27. Mass spectra were recorded on MS
5973 Network Mass Selective detector. All the yields were
calculated from isolated products, and GC was used to estab-
lish their purities.
Acetylation of Alcohols Catalyzed by H6[PMo9V3O40]:
Typical Procedure
H6[PMo9V3O40] (0.03 g, 1 mol%), 0.10 g benzyl alcohol
(1mmol), and 0.9cm3 ethyl acetate (10 mmol) were refluxed
for 50min. The progress of the reaction was monitored by
TLC using petroleum ether-ethyl acetate as eluent. After com-
pletion of the reaction the catalyst was removed by filtration.
The solvent was evaporated under reduced pressure. The crude
product was purified by column chromatography over silica
gel to furnish pure benzyl acetate for which spectra are in full
agreement with data of an authentic sample. This procedure is
followed for acylation of all substrates included in Table 1. All
products are known compounds and were identified by com-
parison of their spectra with those of authentic samples.
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Acknowledgements
The authors are thankful to Azzahra University Council for the
partial financial support.
[31] Heravi MM, Motamedi R, Seifi N, Bamoharram FF
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