Monatshefte fu¨r Chemie 138, 867–869 (2007)
DOI 10.1007/s00706-007-0684-4
Printed in The Netherlands
CuSO4 as a Mild, Green, and Efficient Catalyst for the One-pot Conversion
of THP Ethers to Acetates
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Karim Asadolah and Majid M. Heravi
Department of Chemistry, School of Sciences, Azzahra University, Vanak, Tehran, Iran
Received March 19, 2007; accepted March 27, 2007; published online June 22, 2007
# Springer-Verlag 2007
Summary. An efficient direct conversion of THP ethers into
drawbacks, such as high temperature, long reaction
times, unsatisfactory yields, and applicability for
THP ethers of only primary alcohols [4].
the corresponding acetates was achieved with acetic anhydride
in the presence of CuSO4 ꢁ 5H2O as an available and green
catalyst in high yields.
Keywords. THP ethers; Acetates; Acetylation; CuSO4;
One-pot.
Results and Discussion
We have recently observed that THP ethers can be
readily converted into the corresponding acetate by
reacting with AcOH in the presence of ferric per-
chlorate [5]. Armed with this experience and while
working with copper(II) sulfate as a green and avail-
able catalyst [6], we observed that benzyl THP ether
can be directly converted into the corresponding ac-
etate with Ac2O in the presence of a catalytic amount
of CuSO4 ꢁ 5H2O in CH2Cl2. The reaction could also
be extended to conversion of several THP ethers.
The details are described in this paper.
Introduction
The interconversion of one protecting group into
another is highly important and useful in multistep
organic and total synthesis. Thus, in recent years a
vast variety of methods has been developed to un-
cover a number of new reagents and catalysts for
such interconversion [1]. Tetrahydropyranyl (THP)
ethers constitute one of the most useful and common
protecting group of alcohols [2].
At the outset, alcohols were protected as the THP
ethers by a known method [7]. We decided to study
the direct conversion of these THP ethers to their
corresponding acetate using acetic anhydride in the
presence of Lewis acids. This conversion has been
already reported in the presence of Cu(OTf )2 [8].
Due to its rather high price we decided to introduce
a milder, less expensive, green, and easily available
reagent. Our first choice was CuSO4 ꢁ 5H2O as a
green and available Lewis acid. We found that
in the presence of a catalytic amount (5 mol%) of
CuSO4 ꢁ 5H2O, THP ethers can be efficiently con-
verted to their corresponding acetates with acetic
anhydride in CH2Cl2 under reflux condition in 3 h
The acetylation of alcohols is a useful transforma-
tion in day-to-day synthetic organic chemistry. There
are several methods for conversion of alcohols into
acetates under acidic and basic conditions [3]. THP
ethers are not suitable for use under acidic condi-
tions. On the other hand, acetates are stable to acids.
Thus, the interconversion of THP ethers to the cor-
responding acetates is a useful and important trans-
formation. Nowadays, this kind of interconversions
is rather limited. The methods available have their
own merits but several of them suffer from serious
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Corresponding authors. E-mail: mmh1331@yahoo.com