Solvent-free and selective tosylation of alcohols and phenols with p-toluenesulfonyl chloride by heteropolyacids as highly efficient catalysts

Article abstract of DOI:10.1139/V06-066

Tosylation of some alcohols and phenols has been directly carried out with p-toluenesulfonyl chloride using heterodoxy acids (H₃PW ₁₂O₄₀, H₃PMo₁₂O₄₀, A ₃PW12O40, and AlPMo12O40) as catalysts in the absence of solvent. We found that heteropoly acids AlPW₁₂O₄₀ and AlPMo ₁₂O₄₀ were effective catalysts for the tosylation of alcohols and phenols. In the case of aliphatic alcohols, secondary alcohols undergo tosylation chemoselectively in the presence of primary hydroxyl groups. This new method consistently has the advantage of excellent yields and short reaction time.

Full text of DOI:10.1139/V06-066

812
Solvent-free and selective tosylation of alcohols
and phenols with p-toluenesulfonyl chloride by
heteropolyacids as highly efficient catalysts
Razieh Fazaeli, Shahram Tangestaninejad, and Hamid Aliyan
Abstract: Tosylation of some alcohols and phenols has been directly carried out with p-toluenesulfonyl chloride using
heterodoxy acids (H3PW12O40, H3PMo12O40, AlPW12O40, and AlPMo12O40) as catalysts in the absence of solvent. We
found that heteropoly acids AlPW12O40 and AlPMo12O40 were effective catalysts for the tosylation of alcohols and phe-
nols. In the case of aliphatic alcohols, secondary alcohols undergo tosylation chemoselectively in the presence of pri-
mary hydroxyl groups. This new method consistently has the advantage of excellent yields and short reaction time.
Key words: tosylation, p-TsCl, Keggin-type polyoxometalate, solvent-free reaction.
Résumé : La réaction de tosylation de quelques alcools et phénols a été réalisée directement par réaction avec du chlo-
rure de p-toluènesulfonyle en utilisant des acides hétérodoxes (H3PW12O40, H3PMo12O40, AlPW12O40 et AlPMo12O40)
comme catalyseurs, en l’absence de solvants. On a trouvé que les hétéropolyacides AlPW12O40 et AlPMo12O40 sont des
catalyseurs efficaces pour la tosylation des alcools et des phénols. Dans le cas des alcools aliphatiques, les alcools se-
condaires subissent une tosylation chimiosélective lorsqu’ils sont en présence de groupes hydroxyles primaires. Cette
nouvelle méthode présente les avantages d’excellents rendements et de temps de réaction courts.
Mots clés : tosylation, chlorure de p-tosyle, polyoxométallate de type Keggin, réaction sans solvant.
[Traduit par la Rédaction] Fazaeli et al. 818
Introduction
cohols give rearranged or polymeric products. Also, in this
case, primary and secondary alcohols behaved very simi-
larly. CoCl2·6H2O (8), silica chloride (9), and ZrCl4 (10)
have also been used to catalyze the tosylation of both
aliphatic and aromatic alcohols with p-TsOH. In these meth-
ods, tosylation of long-chain alcohols required longer reac-
tion times and the yields were poor.
Selective tosylation of a primary hydroxyl group in a mol-
ecule containing primary and secondary hydroxyl groups is
often required. The resulting sulfonates are the precursors
for epoxides enroute to the synthesis of a number of natural
products and drugs (11). It is important to realize a high
regioselectivity in the initial sulfonylation step to obtain
epoxides with high purity via cyclization of the product
hydroxyl sulfonates. Thus, there are a limited number of
suitable direct tosylation methods for alcohols with p-TsOH
and there is still a need to develop efficient protocols for this
purpose.
Herein, we wish to report a suitable method for direct
tosylation of alcohols with p-TsCl catalyzed by polyoxo-
metalates as Lewis acid catalysts (Scheme 1).
Polyoxometalates belong to a large class of nanosized
metal–oxygen cluster anions. The chemistry of polyoxo-
metalates (heteropolyacids and heteropolysalts), started by
Berzelius back in 1826, has now reached maturity. But it is
still a rapidly developing field interconnected with many dis-
ciplines (12).
Tosylation of alcohols is an important transformation in
organic synthesis (1, 2). The most widely used reagents, p-
toluenesulfonyl chloride (p-TsCl) or anhydride, are reactive
in comparison with p-toluenesulfonic acid (3). Preparation
of sulfonates generally relies on the use of the corresponding
sulfonyl chloride or anhydride in the presence of pyridine
(3b, 4), triethylamine (3a, 3c), 1,4-diazabicyclo[2.2.2]octane
(DABCO) (3d), or an aqueous base.
p-Toluenesulfonic acid (p-TsOH) has also been used (5)
as a tosylating agent, but in this case, expensive reagents
such as trialkyl orthoformates, alkylethers, esters, or 2-
alkoxybenzothiazolium salt are also necessary. Organic base
adducts of sulfonyls such as aryl sulfonyl methylimidazo-
lium salts, 1-phenylsulfonyl benzotriazole, and 1-(benzene-
sulfonyl)- and 1-(p-toluenesulfonyl)-3-methylimidazolium
triflates have also been employed for sulfonate synthesis (6).
The formation of the side products using these reagents in
the presence of a base is also a problem (1, 3b, 5).
Fe3+-montmorillonite clay has been reported to catalyze
the tosylation of alcohols with p-TsOH (7). This catalyst is
effective for tosylation of aliphatic alcohols, but aromatic al-
Received 7 November 2005. Published on the NRC Research
Press Web site at http://canjchem.nrc.ca on 17 May 2006.
R. Fazaeli and S. Tangestaninejad.1 Department of
Chemistry, Isfahan University, Isfahan, 81746-73441, Iran.
H. Aliyan. Department of Chemistry, Shahreza Islamic Azad
University 31186145, Shahreza, Isfahan, Iran.
The applications of polyoxometalates (POMs, especially
polyoxotungstates) for environmental protection and remedi-
ation have attracted much attention in recent years (13–19).
The majority of POMs have structures composed of molyb-
1Corresponding author (e-mail: stanges@sci.ui.ac.ir).
Can. J. Chem. 84: 812–818 (2006)
doi:10.1139/V06-066
© 2006 NRC Canada

Fazaeli et al.
813
Scheme 1.
All solvents were reagent grade. All reaction mixtures
were stirred magnetically and were monitored by TLC. IR
spectra were recorded on a PerkinElmer FT-IR Impact 400D
p-TsCl, POM
R-OTs
1
spectrophotometer with KBr. H and 13C NMR spectra were
R-OH
Solvent-free, r.t.
recorded on a Bruker AW 500 MHz spectrometer.
General procedure for tosylation
POM = HTP, HMP, AlTP, AlMP
The solvent-free method has an operationally simple pro-
cedure. An alcohol or phenol (1 mmol) and POM
(AlPW12O40, AlPMo12O40, H3PW12O40, or H3PMo12O40,
0.03 mmol) and p-TsCl (1.2 mmol) were ground together in
a mortar and pestle at room temperature for several minutes
to form the tosylates. In cases when the mixture stuck to the
walls of the mortar, it was taken off the walls with a spatula
and grounding was redone. The progress of the reaction was
monitored by GC and TLC. After complete disappearance of
the starting material, the mixture was poured into a satd.
NaHCO3 solution, extracted with CH2Cl2 (3 × 20 mL), and
the organic phase was dried over Na2SO4. The residue was
subjected to column chromatography over silica gel using
EtOAc–hexane (1:4) as eluent to produce pure tosylate. The
structures of the products were established from their spec-
tral (1H and 13C NMR, IR, and MS) data.
denum and tungsten polyhedrons. Other elements occur in
small amounts in these structures. Polyoxotungstates and
polyoxomolybdates decompose in alkaline media to form
simple tungstate and molybdate ions, and therefore, they can
be determined in these forms (20).
The relative activity of Keggin heteropolyacids primarily
depends on their acid strength. Other properties, such as the
oxidation potential as well as the thermal and hydrolytic sta-
bility, are also important.
Tungsten heteropolyacids are usually the catalysts of
choice because of their stronger acidity, higher thermal sta-
bility, and lower oxidation potential compared with molyb-
denum acids. Generally, if the reaction rate is controlled by
the catalyst acid strength, H3PW12O40 shows the highest cat-
alytic activity in the Keggin series. The acids H3PW12O40,
(HTP) and H3PMo12O40, (HMP) are readily available and
most frequently used as catalysts. These acids have rela-
tively high thermal stabilities and decompose at 465 and
375 °C, respectively (12).
Preparation of aluminum dodecatungstophosphate
(AlPW12O40) was reported in 1982 by Ono (21) from the re-
action of aluminum nitrate and dodecatungstophosphoric
acid in a quantitative yield. We have also prepared aluminum
dodecatungstophosphate (AlPW12O40 or AlTP) and alumi-
num dodecamolybdophosphate (AlPMo12O40 or AlMP) by
the addition of aluminum nitrate or aluminum carbonate to
the aqueous solution of tungstophosphoric acid or moly-
bdatophosphoric acid, respectively, which on complete evap-
oration of water gave the desired compound as white (AlTP)
and yellow (AlMP) powders in quantitative yield. AlTP pre-
pared by both protocols gave satisfactory analytical results
within the range of the experimental error. This salt is a wa-
ter stable and nonhygroscopic compound (21–23).
Selected spectroscopic data
Cyclopentyl p-toluenesulfonate (Table 1, n)
Thick oil. IR (film, cm–1): 1172, 1354. 1H NMR
(200 MHz, CDCl3) δ: 1.54–1.78 (8H, m, -[CH2]4-), 2.43
(3H, s, CH3), 4.49 (1H, m, CHO-), 7.32 (2H, d, m-H, J =
8.1 Hz), 7.78 (2H, d, o-H, J = 8.1Hz). MS (EI) m/z: 240
(M+, 2), 172 (61), 107 (33), 91 (100), 65 (34).
Cyclohexyl p-toluenesulfonate (Table 1, m)
Thick oil. IR (film, cm–1): 1170, 1351. 1H NMR
(200 MHz, CDCl3) δ: 1.30–1.78 (10H, m, -[CH2]5-), 2.44
(3H, s, CH3), 4.49 (1H, m, CHO-), 7.32 (2H, d, m-H, J =
8.8 Hz), 7.79 (2H, d, o-H, J = 8.8 Hz). 13C NMR (200 MHz,
CDCl3) δ: 143.99, 134.32, 129.38, 127.11 (Ar carbons),
81.12 (CHO), 31.90, 24.46, 22.92, 21.11 (alkane). MS (EI)
m/z: 254 (M+, 2), 173 (100), 155 (46), 91 (31), 82 (31), 67
(22), 65 (7).
Results and discussion
Experimental
At first, to investigate the catalytic ability of hetero-
polyacids (H3PW12O40, H3PMo12O40, AlPW12O40, AlPMo12O40)
to act as catalysts on the tosylation of alcohols and phenols,
different alcohols and phenols were mixed with p-TsCl in
the presence of POMs to form the tosylates under solvent-
free conditions. The results showed that AlPW12O40 and
AlPMo12O40 show higher catalytic activity than the acid forms
in our experimental conditions (Tables 1 and 2). The cata-
Tungstophosphoric acid and dodecamolybdophosphoric
acid (HTP and HMP), which are cheap, reusable, heteroge-
neous, and easily available catalysts, were purchased from
Merck and were purified by extraction with Et2O from the
aqueous solution of the acids. After evacuation at 150–
300 °C for 1 to 2 h under reduced pressure, pure HTP and
HMP were obtained (24). AlTP can be prepared from cheap
and commercially available chemicals in a quantitative yield
in aqueous media. In contrast to many other Lewis acids,
storage of this compound does not need special precautions,
e.g., it can be stored on a bench top for months without los-
ing its catalytic activity. In addition, as a nonhygroscopic,
noncorrosive, and water stable compound, handling of AlTP
is easy, which makes it a suitable catalyst for large-scale op-
erations.
lytic activities are as follows: AlPW12O40 ~ AlPMo12O40
≥
H3PW12O40 > H3PMo12O40. The blank experiments, in the
absence of catalysts, showed that p-TsCl is much less effi-
cient in producing the tosylated products.
As shown in Tables 1 and 2, by using AlPW12O40 or
AlPMo12O40 as catalyst, primary, secondary, benzylic, and
allylic alcohols gave tosylated products in good yields.
Benzylic alcohols, such as benzyl, 2-nitrobenzyl, 4-
© 2006 NRC Canada

814
Can. J. Chem. Vol. 84, 2006
Table 1. Results on the tosylation of different alcohols using some heteropoly acids.
Time
(min)
20
Yield
(%)a,b,c
45
Type of POM
HTP
Entry
a
Substrate
HO
Product
TsO
HMP
27
50
AlTP
AlMP
7
9
100
95
N
N
OH
OTs
b
c
d
e
f
HTP
25
31
8
50
55
100
98
HMP
AlTP
AlMP
C
H
CH3
C
H
CH3
8
HTP
20
25
15
18
60
45
98
78
OTs
NO2
OH
NO2
HMP
AlTP
AlMP
HTP
20
25
10
14
50
55
90
95
OH
OTs
HMP
AlTP
AlMP
O2N
O2N
HTP
21
28
5
60
60
92
95
OH
OTs
CH3
HMP
AlTP
AlMP
CH3
O
O
7
HTP
20
35
7
55
60
98
92
OH
OTs
HMP
AlTP
AlMP
H3C
O
H3C
O
7
g
h
HTP
20
30
10
10
60
55
98
98
OTs
OH
HMP
AlTP
AlMP
OH
OTs
HTP
20
20
10
11
60
55
98
93
HMP
AlTP
AlMP
CH2OH
i
HTP
20
30
14
17
60
55
98
98
CH2OTs
HMP
AlTP
AlMP
j
HTP
20
25
10
10
65
65
90
95
HMP
AlTP
AlMP
CH2OH
CH2OTs
OH
k
HTP
25
25
7
60
50
98
89
OTs
HMP
AlTP
AlMP
13
nitrobenzyl, 3-methoxybenzyl, 4-methoxybenzyl, and 1-
phenylpropyl alcohol, were converted to the corresponding
tosylates in 78%–100% yields (Table 1, entries b–h). Simi-
larly, allylic alcohols, such as cinnamyl and geraniol alco-
hol, underwent tosylation to afford the corresponding
tosylates in 90%–98% yields (Table 1, entries i and j).
Aliphatic alcohols were more easily tosylated than aromatic
alcohols. However, long-chain alcohols, in the presence of
AlPW12O40 or AlPW12O40 as catalyst, were converted to the
desired products in moderate yields (Table 1, entries q–t,
73%–80%). Cholesterol (Table 1, entry o), which is a more
complex secondary alcohol, produced the tosylated product
© 2006 NRC Canada

Fazaeli et al.
Table 1. (continued).
815
Time
(min)
Yield
(%)a,b,c
Entry
Substrate
Product
Type of POM
HTP
HMP
AlTP
AlMP
l
15
16
9
75
60
96
90
9
OTs
OH
OH
OTs
m
n
HTP
20
20
6
65
50
96
90
HMP
AlTP
AlMP
9
HTP
20
25
11
17
65
65
96
90
HMP
AlTP
AlMP
OTs
OH
o
HTP
20
20
6
65
50
96
90
HMP
AlTP
AlMP
9
HO
TsO
OTs
OH
n
n
n = 2
p
q
r
n = 2
n = 7
n = 11
n = 13
n = 15
HTP
55
55
30
38
60
45
80
75
HMP
AlTP
AlMP
n = 7
HTP
60
55
30
35
55
50
80
75
HMP
AlTP
AlMP
n = 11
n = 13
n = 15
HTP
50
50
40
48
50
50
80
75
HMP
AlTP
AlMP
s
t
HTP
20
20
11
13
40
40
75
73
HMP
AlTP
AlMP
HTP
55
60
29
48
45
40
83
75
HMP
AlTP
AlMP
H
H
u
HTP
60
20
7
65
55
95
95
HMP
AlTP
AlMP
H
H
OH
OTs
9
H
H
in high yield (90%–96%). Some phenols (Table 2) and ter-
tiary alcohols (Table 1, entries u and v) undergo tosylation
under the same experimental conditions. For aromatic alco-
hols, no rearranged or polymeric products were observed. In
the case of diols, under the same reaction conditions, no
tosylate product was detected in the reaction mixture and
both hydroxyl groups remained intact in the presence of p-
TsCl (Table 1, entries w–z).
© 2006 NRC Canada

816
Can. J. Chem. Vol. 84, 2006
Table 1 (concluded).
Time
(min)
Yield
(%)a,b,c
Entry
v
Product
Type of POM
Substrate
HTP
40
55
15
23
60
30
80
75
OTs
OH
HMP
AlTP
AlMP
OH OH
w
x
HTP
120
120
120
120
0
0
0
0
HMP
AlTP
AlMP
No product
CH2CH3
HTP
120
120
120
120
0
0
0
0
HMP
AlTP
AlMP
CH2OH
No product
No product
No product
OH
OH
y
z
HTP
120
120
120
120
0
0
0
0
HMP
AlTP
AlMP
OH
HTP
120
120
120
120
0
0
0
0
HMP
AlTP
AlMP
OH OH
aSubstrate (1 mmol), p-TsCl (1.2 mmol), and POM (3 mol%) were ground together in a mortar with a pestle at room tempera-
ture for the appropriate time to form the tosylates.
bIsolated yield.
cIdentification of the products was ascertained by NMR, IR, and mass spectrometric analysis.
Table 2. Results of the tosylation of different phenols using some heteropolyacids (polyoxometalates).
Time
(min)
20
Yield
(%)a,b,c
50
Entry
a
Substrate
Product
Type of POM
HTP
OTs
OH
HMP
35
50
AlTP
10
85
AlMP
10
85
OTs
b
c
d
HTP
38
40
5
51
44
90
85
OH
HMP
AlTP
AlMP
8
OH
HTP
25
30
5
50
35
98
91
OTs
HMP
AlTP
AlMP
CH3
OH
8
CH3
OTs
HTP
25
25
8
30
30
95
91
HMP
AlTP
AlMP
9
CH3
CH3
OTs
OH
e
HTP
22
40
10
10
50
45
90
83
HMP
AlTP
AlMP
H3C
H3C
aSubstrate (1 mmol), p-TsCl (1.2 mmol), and POM (3 mol%) were ground together in a mortar with a pestle at room temperature
for the appropriate time to form the tosylates.
bIsolated yield.
cIdentification of the products was ascertained by NMR, IR, and mass spectrometric analysis.
© 2006 NRC Canada

Fazaeli et al.
817
Scheme 2.
OTs
OH
trace
98%
1.2 mol% p-TsCl
+
+
3 mol % AlTP
Solvent-free, r.t.
(10 min)
OTs
OH
Table 3. Tosylation of cyclohexanol with p-TsCl in the presence of AlPW12O40 in various solvents.
OH
OTs
3 mol % AlTP
p-TsCl
Solvent
Entry
Solvent
GC yield (%) after 6 min
GC yield (%) after 30 min
1
2
3
CHCl3
CH3CN
CH2Cl2
20
35
10
50
65
35
4
5
Acetone
EtOH
25
15
50
35
Note: Reaction conditions: cyclohexanol (1 mmol), p-TsCl (1.2 mmol), AlPW12O40 (3 mol%), and reflux.
Table 4. Tosylation of cyclohexanol with p-TsCl in the presence of AlPMo12O40 in various solvents.
OH
OTs
3 mol % AlMP
p-TsCl
Solvent
Entry
Solvent
GC yield (%) after 9 min
GC yield (%) after 30 min
1
2
3
CHCl3
CH3CN
CH2Cl2
20
35
10
30
50
35
4
5
Acetone
EtOH
15
20
35
35
Note: Reaction conditions: cyclohexanol (1 mmol), p-TsCl (1.2 mmol), AlPMo12O40 (3 mol%), and reflux.
In the case of the aliphatic alcohols, secondary alcohols
were tosylated much faster compared with primary hydroxyl
groups (Table 1, entries k–t). Thus, a secondary alcohol can
be tosylated chemoselectively in the presence of a primary
alcohol, as previously reported in the case of CoCl2·6H2O
(8) and silica chloride (9).
The difference in reaction rates between primary and sec-
ondary alcohols, which is observed in Table 1, prompted us
to examine the chemoselective tosylation of alcohols. For
example, when a mixture of n-hexanol and cyclohexanol was
allowed to react with 0.5 equiv. p-TsCl in the presence of
these catalysts for 10 min, cyclohexanol underwent
tosylation chemoselectively in 98% yield and only a trace
amount of n-hexyl tosylate was detected (Scheme 2). These
studies clearly reveal that this methodology can be applied
for the chemoselective direct tosylation of aliphatic second-
ary alcohols in the presence of primary hydroxyl groups.
Effect of solvent
The tosylation of cyclohexanol was also conducted in dif-
ferent solvents (chloroform, acetonitrile, dichloromethane,
acetone, and ethanol). The results show that the yield of the
reaction in solutions is much less than those observed under
solvent-free conditions (Tables 3 and 4).
Effect of the catalyst
Amongst the catalysts used (H3PW12O40, H3PMo12O40,
AlPW12O40, and AlPMo12O40) in the tosylation of alcohols
© 2006 NRC Canada

818
Can. J. Chem. Vol. 84, 2006
Epsztein. Synthesis, 706 (1977); (c) H. Kotsuki, T. Oshisi, and
and phenols, it was found that both AlPW12O40 and
AlPMo12O40 were effective catalysts for the tosylation of
alcohols and phenols. The results showed that in the absence
of the catalysts, the tosylation reaction did not proceed after
30 min at room temperature, but in the presence of two
heteropolyacids (AlPW12O40 and AlPMo12O40), the conver-
sion proceeded efficiently in a few minutes under similar re-
action conditions (Tables 1 and 2). Therefore, we chose
AlPW12O40 and AlPMo12O40 which are heterogeneous and
environmentally benign compounds, as catalysts for further
tosylation studies. Furthermore, the use of just 3 mol% POM
is sufficient to promote the reaction and no other additives
are required for this conversion. No improvements were ob-
served in the reaction yields by increasing the amount of
POM from 3 to 5 mol%.
M. Inoue. Synlett, 255 (1988).
3. (a) K. Kurita. Chem. Ind. (London), 345 (1974); (b) G.W.
Kabalka, M. Varma, R.S. Varma, P.C. Srivastava, and F.F.
Knapp, Jr. J. Org. Chem. 51, 2386 (1986); (c) Y. Yoshida, Y.
Sakakura, N. Aso, S. Okada, and Y. Tanabe. Tetrahedron, 55,
2183 (1999); (d) J. Hartung, S. Hunig, R. Kueuer, M. Schwarz,
and H. Wenner, Synthesis, 1433 (1997).
4. (a) V.C. Sekera and C.S. Marvel. J. Am. Chem. Soc. 55, 345
(1933); (b) R.S. Tipson. J. Org. Chem. 9, 235 (1944).
5. (a) Y. Nitta and Y. Arakawa. Chem. Pharm. Bull. 33, 1380
(1985); (b) R. Karaman, H. Leader, A. Goldblum, and E.
Breuer. Chem. Ind. (London), 857 (1987); (c) D. Klamann,
and P. Weyerstahl. Chem. Ber. 98, 2070 (1965); (d) T.
Mukaiyama and K. Hojo. Chem. Lett. 893 (1976).
6. (a) J.F. O’Connell and H.J. Rapoport. J. Org. Chem. 57, 4775
(1992); (b) A.R. Katritzky, G. Zhang, and J. Wu. Synth.
Commun. 24, 205 (1994).
7. B.M. Choudary, N.S. Chowdari, and M.L. Kantam. Tetrahe-
Conclusions
dron, 56, 7291 (2000).
In this study, we have introduced aluminum dodecatung-
stophosphate (AlPW12O40) and aluminium dodecamolybdo-
phosphate (AlPMo12O40) as new, highly effective,
nonhygroscopic, noncorrosive, heterogeneous, and environ-
mentally benign catalysts for the efficient tosylation of a va-
riety of alcohols and phenols in high yields. Phenols and
primary, secondary, benzylic, and allylic alcohols gave
tosylated products in good yields. In the case of aliphatic al-
cohols, secondary alcohols are transformed to the corre-
sponding tosylates chemoselectively in the presence of the
primaryhydroxy groups. The advantages of the present meth-
ods may be summarized as: high stereoselectivities, good
yields of the desired products, short reaction times, mild and
solvent-free conditions, and simple experimental procedure
and product isolation. The only disadvantage of this system
is the release of HCl as a by-product. We feel our protocol is
an attractive alternative to the existing procedures for
tosylation of alcohols and phenols.
8. S. Velusamy, J.S.K. Kumar, and T. Punniyamurthy. Tetrahe-
dron Lett. 45, 203 (2004).
9. B. Das, V.S. Reddy, and R. Reddy. Tetrahedron Lett. 45, 6717
(2004).
10. B. Das and V.S. Reddy. Chem. Lett. 33, 11 (2004).
11. (a) J.G. Smith. Synthesis, 629 (1984); (b) R. Oi and K.B.
Sharpless. Tetrahedron Lett. 33, 2095 (1992).
12. I. Kozhevnikov. Catalysts for fine chemical synthesis. Cataly-
sis by polyoxometalates. Vol. 2. Wiley, NewYork. 2002.
13. C.S.Turchi and D.F. Ollis. J. Catal. 122, 178 (1990).
14. A. Mylonas and E. Papaconstantantinou. J. Mol. Catal. 92, 261
(1994).
15. U. Stafford, K.A. Gray, and P.V. Kamat. J. Catal. 167, 25
(1997).
16. C. Hu, B. Yue, and T. Yamase. Appl. Catal. A, 194, 99 (2000).
17. T. Okuhara, H. Watanabe, T. Nishimura, K. Lnumaru, and M.
Misono. Chem. Mater. 12, 2230 (2000).
18. M. Misono. Chem. Commun. (Cambridge), 13, 1141 (2001).
19. T. Okuhara. Chem. Rev. 102, 3641 (2002).
20. H. Hayashi and J.B. Moffat. Talanta, 29, 943 (1982).
21. (a) T. Baba, J. Sakai, and Y. Ono. Bull. Chem. Soc. Jpn. 55,
2657 (1982); (b) T. Baba, H. Watanabe, and Y. Ono. J. Phys.
Chem. 87, 2406 (1983).
22. (a) H. Firouzabadi, N. Iranpoor, and K. Amani. Green Chem.
3, 131 (2000); (b) H. Firouzabadi, N. Iranpoor, and K. Amani.
Synthesis, 59 (2002); (c) H. Firouzabadi, N. Iranpoor, K.
Amani, and F. Nowrouzi. J. Chem. Soc. Perkin Trans. 1, 2601
(2002); (d) H. Firouzabadi, N. Iranpoor, and K. Amani. Syn-
thesis, 408 (2003).
Acknowledgment
We gratefully thank Isfahan University, Isfahan, Iran, for
financial support.
References
1. T.W. Green and P.G.M. Wuts. Protective groups in organic
synthesis. 3rd ed. Wiley, New York. 1999.
2. (a) R.A. Adlington, A.G.M. Barrett, P. Quayle, and A. Walker.
J. Chem. Commun. 404 (1981); (b) S. Holand, and R.
23. H. Firouzabadi, N. Iranpoor, F. Nowrouzi, and K. Amani.
Chem. Commun. (Cambridge), 764 (2003).
24. T.H. Chang. J. Chem. Soc. Faraday Trans. 91, 375 (1995).
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