Silica sulfuric acid as an efficient reagent for the synthesis of symmetrical ethers under mild and heterogeneous conditions

Article abstract of DOI:10.1080/714040949

A mild and efficient method for the synthesis of symmetrical ethers using silica sulfuric acid is reported. All reactions are performed under compeletly heterogeneous conditions in good to high yields.

Full text of DOI:10.1080/714040949

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Phosphorus, Sulfur, and Silicon and the Related
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Silica Sulfuric Acid as an Efficient Reagent for the
Synthesis of Symmetrical Ethers Under Mild and
Heterogeneous Conditions
a
b
a
Farhad Shirini , Mohammad Ali Zolfigol & Kamal Mohammadi
a
Guilan University, Rasht, Iran
b
Bu-Ali Sina University, Hamadan, Iran
Published online: 18 Jun 2010.
To cite this article: Farhad Shirini , Mohammad Ali Zolfigol & Kamal Mohammadi (2003) Silica Sulfuric Acid as an Efficient
Reagent for the Synthesis of Symmetrical Ethers Under Mild and Heterogeneous Conditions, Phosphorus, Sulfur, and Silicon and
the Related Elements, 178:11, 2357-2361, DOI: 10.1080/714040949
To link to this article: http://dx.doi.org/10.1080/714040949
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Phosphorus, Sulfur, and Silicon, 178:2357–2361, 2003
Copyright ꢀC Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500390234821
SILICA SULFURIC ACID AS AN EFFICIENT
REAGENT FOR THE SYNTHESIS OF SYMMETRICAL
ETHERS UNDER MILD AND HETEROGENEOUS
CONDITIONS
a
b
Farhad Shirini, Mohammad Ali Zolfigol,
a
and Kamal Mohammadi
a
Guilan University, Rasht, Iran and Bu-Ali Sina University,
b
Hamadan, Iran
(
Received April 15, 2003; accepted May 15, 2003)
A mild and efficient method for the synthesis of symmetrical ethers
using silica sulfuric acid is reported. All reactions are performed under
compeletly heterogeneous conditions in good to high yields.
Keywords: Alcohols; heterogeneous conditions; silica sulfuric acid;
symmetrical ethers
1
The ether linkage is found prevalently in a variety of synthetic targets
2
3
including oligonucleotides and carbohydrates, and it also is recog-
4
nized as a crucial element in hydroxyl group protection.
Althogh a variety of methods are capable for the synthesis of
5−7
ethers,
most of them suffer from disadvantages such as long reac-
tion times and formation of by-products. Therefore, we decided to choose
a new reagent or reagent systems to overcome the above limitations.
In addition for our purpose both clean and easy work-up also were
important.
On the other hand, any reduction in the amount of sulfuric acid
needed and/or any simplification in handling procedures is required
8
for risk reduction, economic advantage, and environment protection.
In addition, there is current research and general interest in heteroge-
neous systems because of the importance such systems have in indus-
9
try and developing technologies. In continuation of our studies on the
Partial support of this work by the Research Affairs Office of Guilan University is
gratefully acknowledged.
Address correspondence to Farhad Shirini, Department of Chemistry, College of Sci-
ence, Guilan University, Rasht, Iran. E-mail: shirini@guilan.ac.ir
2
357

2
358
F. Shirini et al.
application of silica sulfuric acid,10−14 we found that this inorganic
acidic resin, as a new sulfuric acid function immobilized on the sur-
face of silica gel via covalent bonding, can be used as a proton source
for running reactions under heterogeneous conditions. Therefore, we
were interested in using this reagent for the synthesis of ethers. We
report here a simple and cheap method for the effective synthesis of
symmetrical ethers under heterogeneous conditions.
Different types of alcohols were subjected to etherification reaction
in the presence of silica sulfuric acid in refluxing n-hexane (Scheme 1,
Table I). The etherification reactions were performed under mild and
compeletly heterogeneous conditions and took place with good to excel-
lent yields. It is noted that the formation of alkene by-products which
is the common reaction in the dehydration of alcohols with H2SO4 was
not observed during the course of the reaction.
SCHEME 1
In conclusion the lowcost and the availability of the reagents, easy
and clean work-up, and high yield make this an attractive methodology.
We believe that the present methodology could be an important addition
to existing methodologies. The application of silica sulfuric acid in the
synthesis of unsymmetrical ethers is under way.
EXPERIMENTAL
Chemicals were purchased from Fluka, Merck, and Aldrich Chemical
Companies. Ethers were characterized by comparison of their spectral
1
(
IR, NMR) and physical data with that of authentic samples.
General Procedure for the Synthesis of Symmetrical
Ethers
Alcohol (1 mmol) was added to a suspension of silica sulfuric acid (0.2 g)
in n-hexane (3 mL). The resultant mixture was refluxed for the specified
time. The progress of the reaction was monitored by TLC or GC. The
reaction mixture was filtered on a silica gel pad and the residue was
washed with n-hexane (10 mL). The solvent was evaporated and the
ethers were obtained by distillation (Table I). If further purification

2359

2
360

Silica Sulfuric Acid as an Efficient Reagent
2361
was needed flash chromatography on silica gel provided highly pure
ethers.
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