Chemoselective and scalable preparation of alkyl tosylates under solvent-free conditions

Article abstract of DOI:10.1016/j.tet.2007.03.083

The improved method for the efficient tosylation of alcohols has been reported using two procedures (A and B). Procedure A: methanol, ethanol, benzyl alcohols, and valuable ethylene glycols can be converted into their corresponding alkyl tosylates in very fast, simple, and efficient grinding method using potassium carbonate as solid base. Other primary and secondary alcohols need to add potassium hydroxide to reaction mixture (procedure B). High selectivity of tosylation was observed for these two procedures. Scale up ability was found in this method even in 100 mmol of substrate. The present method is the example of solid-state tosylation using tosyl chloride, and is a green chemical process due to solvent-free conditions.

Full text of DOI:10.1016/j.tet.2007.03.083

Tetrahedron 63 (2007) 5083–5087
Chemoselective and scalable preparation of alkyl tosylates under
solvent-free conditions
a,*
b
Foad Kazemi, Ahmad R. Massah and Mohammad Javaherian
c
a
Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Gava Zang, Zanjan 45195-1159, Iran
b
Department of Chemistry, Islamic Azad University, Shahreza Branch, Shahreza, Isfahan, Iran
c
Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz, Iran
Received 4 February 2007; revised 14 March 2007; accepted 15 March 2007
Available online 18 March 2007
Abstract—The improved method for the efficient tosylation of alcohols has been reported using two procedures (A and B). Procedure A:
methanol, ethanol, benzyl alcohols, and valuable ethylene glycols can be converted into their corresponding alkyl tosylates in very fast,
simple, and efficient grinding method using potassium carbonate as solid base. Other primary and secondary alcohols need to add potassium
hydroxide to reaction mixture (procedure B). High selectivity of tosylation was observed for these two procedures. Scale up ability was found
in this method even in 100 mmol of substrate. The present method is the example of solid-state tosylation using tosyl chloride, and is a green
chemical process due to solvent-free conditions.
Ó 2007 Elsevier Ltd. All rights reserved.
3
3b
1
. Introduction
p-toluenesulfonic acid in the presence of silica chloride
3
c
or Lewis acids such as CoCl2. The first method is used fre-
quently due to its simplicity and generality. In this method,
using triethylamine or especially pyridine, as a base, is often
Sulfonate derivatives, which are precursors of cyclic crown
ethers, azacrown ethers, and lariat ethers, are widely used
in polyether chemistry and many other organic transforma-
1
common. The use of an equimolar amount of wasted organic
1
tions as the tosylate anion makes a good leaving group.
amine reagent necessitates a large amount of BOD and COD
(biological and chemical oxygen demands). In order to avoid
using toxic material, application of aqueous sodium or potas-
Among the sulfonates, tosylate is selected for its physical
properties, availability of its reagent, and appropriate reactiv-
ity. Tosylate derivatives have three clear advantages. First,
crystallinity (they are often crystalline and have low vapor
pressure), therefore, can be obtained in high purity. Second,
significant addition to the mass of parent compound (a
mole of diethylene glycol weighs 106.1 g, its ditosylate de-
rivatives, 414.5 g) causes more accuracy in handling. Finally,
the tosylate salts form as insoluble precipitates upon reaction
with the nucleophilic salts such as alkali metal salts of alco-
hols and phenols in non-aqueous solvents. As a result, simple
filtration followed by solvent removal is often all that is
necessary to isolate the product. Also, in comparison with
alkyl halides, tosylate is often the leaving group of choice
as its preparation from the corresponding alcohol takes
place under mild conditions, which avoids the stereochem-
ical uncertainties and skeletal rearrangements associated
4
5a
5b
sium hydroxide, Me N$HCl, and Me N(CH ) NMe
2
3
2
2 n
was also reported. Also, Tanabe et al. reported the water–sol-
vent method for tosylation of alcohols promoted by KOH and
catalytic amines such as N,N-dimethyl aniline. Their
method only works efficiently for primary alcohols, for ex-
ample, tosylation of 2-octanol provides its product in 27%
yield. The control of pH is necessary to avoid hydrolysis of
5
c
sulfonyl chloride. TsCl/NEt in the presence of catalytic
3
6
amounts of Bu SnO , ring opening of dibutylstannylene
4
2
7
8
acetal with sulfonyl chloride, Ag O/KI/sulfonyl chloride,
2
1
d
9
and zinc tosylate in a Mitsunobu type reaction are the other
modifications. Difficulties such as tedious procedure to
remove hazardous materials (e.g., pyridine), unavailability
of reagents, side reactions, necessary of control of pH and
temperature, long reaction times encourages development
of this transformation.
2
with the conversion of an alcohol to a halide. There are
two general methods for tosylation according to tosylating
agent: (i) using reactive agent such as p-toluenesulfonyl
chloride (or anhydride) in the presence of a base; (ii) using
Recently considerable attention has been paid to solvent-free
reactions. These reactions are not only of interest from an
environmental point of view, but in many cases also offer
considerable synthetic advantages in terms of yield, selectiv-
1
0
ity, and simplicity of the reaction procedure. There are
a few reports about solvent-free tosylation of alcohols
such as using heteropolyacids.
1
1
*
0
Corresponding author. Tel.: +98 241 4153219; fax: +98 241 4153232;
e-mail: kazemi_f@iasbs.ac.ir
1
1a
040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.03.083

5084
F. Kazemi et al. / Tetrahedron 63 (2007) 5083–5087
2
. Results and discussion
Table 1. Tosylation of alcohols with p-toluenesulfonyl chloride (1.5 equiv)
on potassium carbonate at solid-state conditions
Tosyl chloride/potassium carbonate combination was used
successfully in anhydride and sulfonamide preparations at
Entry
Alcohol
Alkyl tosylate
Yield (%)
a
1
2
CH
3
OH
OH
CH
3
OTs
OTs
94
92
1
2
solvent-free conditions by us. Using potassium carbonate
as cheap, weak basic solid support has advantages such as
controlled promotion of reaction and simplicity. In order to
develop the applications of TsCl/K CO combination, we
a
C
2
H
5
C
2
H
5
a
3
CH OH
CH OTs
91
2
2
2
3
decided to try it for tosylation of alcohols. Methanol as vol-
atile and cheap alcohol was used as first starting material.
The well mixed K CO and tosyl chloride was wetted with
methanol and grinded (procedure A). Surprisingly, accord-
ing to TLC, the reaction was completed in about 5 min
and the corresponding tosylate was obtained very easily in
high yield without any other basic additive (Table 1, entry
CH OH
2
2
CH OTs
a
4
93
2
3
H3CO
H CO
H3CO
CH OH H CO
a
5
CH OTs 89
2
3
2
3
1
). Ethanol and benzyl alcohols are also quantitatively con-
verted into their corresponding tosylates using this method
Scheme 1, Table 1). In the case of benzyl alcohols, the
.5 equimolar of TsCl was used and the reaction was com-
pleted in about 5 min.
a
a
a
a
6
O N
CH OH
O N
CH OTs
87
95
94
90
2
2
2
2
(
1
O
O
O
O
O
O
7
HO
OH
TsO
OTs
TsCl
2
2
CH2OH
CH OTs
8
2
K2CO3
HO
HO
OH
TsO
TsO
OTs
93%
H3CO
3
H CO
3
3
9
Scheme 1.
OH
OTs
For removing the remaining TsCl, in addition to known
b
b
5
c
10
89
(
CH2)3OH
(CH2)3OTs
method, using N,N-dimethylethylenediamine, we found
that addition of KOH and grinding were very efficient. Inter-
estingly, up to 5 equimolar of KOH was examined success-
fully without considerable hydrolysis of tosylate. Also, we
found that wetting the reaction mixture with t-BuOH and
irradiation under microwave (900 W for 2 min) can be used
for removing the remaining TsCl without reducing the yield
of the product. It might be owing to tosylation of t-BuOH
followed by elimination reaction that produces volatile iso-
OH
OTs
1
1
93
b
b
1
1
2
3
OH
OTs 92
OH
OTs
CH3
90
H3C
CH3
H3C
ꢁ
butene (bp ꢀ6.9 C) and salt of tosylate, which do not cause
any problem in the work up process.
b,c
b
1
1
4
5
85
OH
OH
OH
OTs
OTs
OTs
More surprisingly, in extending this procedure to other
alcohols we found that valuable ethylene glycols that are
very important in macrocycle, rotaxane, and cryptand
syntheses as building block can be prepared as simple as
benzylic alcohols. The equimolar amount of them against
88
b,c
81
1
6
3
equimolar of TsCl can be converted into their correspond-
ing ditosylates in very short reaction times (Table 1, Scheme
). According to the literature, the ditosylate derivatives can
a
b
c
2
Reaction carried out without KOH (procedure A).
Reaction carried out in the presence of KOH (procedure B).
.5 equiv of TsCl was used.
1
3
be prepared with pyridine as base, or they are synthesized
more effectively in higher yield using aqueous sodium hy-
2
4
a
droxide and tetrahydrofuran. In this method, the excess
of sodium hydroxide is used, reaction temperature must be
controlled, and the yield of some ditosylates is not very high,
e.g., 79% for diethylene glycol ditosylate. Then, present
method has superiority to the current methods due to sim-
plicity, reaction time, solvent-free conditions, and free base
additive.
It was found that addition of KOH to K CO (TsCl/KOH/
2
3
K CO combination, procedure B) can increase the ability
2
3
of present method for tosylation of alcohols that were not
successful at tosylation reaction using TsCl/K CO com-
2
3
bination (procedure A). For example, citronellol, 1- and
2-octanol, and cyclohexanol quantitatively can be converted
into the corresponding tosylate, respectively, in high yields
and very short reaction times (Table 1, entries 11, 12, 14,
and 15).
TsCl
K2CO3
O
n
O
n
HO
OH
TsO
OTs
yield:90-94%
n:1-3
The necessity of using KOH in procedure B, and importance
of selectivity in organic chemistry encouraged us to consider
Scheme 2.

F. Kazemi et al. / Tetrahedron 63 (2007) 5083–5087
5085
Table 2. Consideration of selectivity in tosylation of alcohols in the absence
of KOH
were tosylated successfully without considerable limitation.
For example, 1-octanol, citronellol, and diethylene glycol
were converted into their tosylates at 100 mmol scale of sub-
strate. The scales in this table are optional and we have not
encountered with special limitation.
Entry
Mixture of
alcohols
Product(s)
Conversion
(%)
O
O
1
00
HO
OH
TsO
OTs
OTs
1
OH
OH
3. Conclusion
Trace
In conclusion, we have demonstrated that solvent-free tosy-
ꢁ ꢁ
lation of wide range of 1 and 2 alcohols on K CO is prac-
2 3
O
O
O
O
1
00
HO
HO
OH
OH
TsO
TsO
OTs
tical and very good alternative for previous reports. The
major advantages of this method are: (i) simplicity of proce-
dure; (ii) high yields and purity of products; (iii) it can be
2
3
OTs Trace
ꢁ
ꢁ
used for both 1 and 2 alcohols; (iv) solvent-free conditions,
therefore, good choice according to green chemistry point of
view; (v) short reaction times; (vi) scale up ability without
considerable limitation; (vii) high selectivity; (viii) very
simple and fast removing the excess of tosyl chloride at
the end of reaction.
1
0
00
00
OTs
OH
OTs
O
O
2
O
O
2
1
0
HO
HO
OH
TsO
TsO
OTs
4
5
4. Experimental
OH
OTs
4.1. General
3
3
1
0
00
OH
OTs
All chemicals were commercial products and distilled or re-
crystallized before use. All melting points were obtained by
a Buchi 510 and are uncorrected. IR spectra were recorded
on a BOMEM (MB102) spectrophotometer; and NMR spec-
tra were recorded on a Bruker Avance DPX instrument
OH
OTs
(400 MHz). Chemical shifts (d, ppm) were reported down-
field from tetramethylsilane (0 ppm) for H NMR and
1
the selectivity of tosylation of different alcohols. Several
reactions were carried out and surprisingly, the excellent
selectivity was found according to TLC and H NMR of
were reported in the scale relative to CDCl (77.00 ppm)
3
13
for C NMR.
1
alcohol mixtures (1:1) (Table 2). For example, triethylene
glycol and tetraethylene glycol quantitatively can be con-
verted into their ditosylates in the presence of cyclohexanol
and 2-octanol, respectively (Table 2, entries 4 and 5).
4
.2. Procedure A: tosylation of alcohols without KOH
A mortar was charged with dry K CO (5 g), alcohol
2
3
(
5
10 mmol), TsCl (15 mmol), and grinded vigorously for
min. After the completion of tosylation, remaining tosyl
chloride was removed by addition of powdered KOH
50 mmol) and vigorously grinded (2 min), addition of
To show another advantage of present tosylation method and
because of the importance of scale up ability for laboratory
and industrial purposes, several alcohols were tosylated in
large scale and as shown in Table 3 all of the alcohols
(
a few drops of t-BuOH accelerates the disappearance of
TsCl, or the removing of tosyl chloride can be carried out
by wetting the reaction mixture with t-BuOH and irradiating
(900 W) in domestic microwave oven for 2 min. The product
was extracted by addition of ether (50 ml), filtered, and
finally by the evaporation of organic solvent. Further purifi-
cation can be carried out on the crude solid tosylate by
recrystallization in n-hexane or by column chromatography
over silica gel (hexane/diethyl ether¼10:1) for oily tosy-
lates. The yields were 88–91%.
Table 3. Consideration of ability of the present tosylation method in large
scale
Entry
Alkyl tosylate
Scale
(
Yield
(%)
mmol)
1
2
3
3-Phenyl-1-propyl tosylate
1-Octyl tosylate
3,7-Dimethyl-6-octene-1-tosylate
30
100
100
89
92
92
(
citronellol tosylate)
Diethyleneglycol ditosylate
DEG ditosylate)
4.3. Procedure B: tosylation of alcohols using KOH
4
100
89
(
A mortar was charged with a finely powder potassium hy-
droxide (50 mmol) and corresponding alcohol (10 mmol),
grinded with a pestle for 5 min, then dry potassium carbonate
(5 g) was added, and mixed thoroughly. Tosyl chloride
5
6
7
8
9
Cyclohexyl tosylate
(ꢀ)-Menthyl tosylate
3-Methoxybenzyl tosylate
4-Nitrobenzyl tosylate
Benzyl tosylate
50
50
100
100
100
50
86
77
90
88
91
87
(15 ml) was added in one portion and grinded vigorously
10
Triethylene glycol
ditosylate (TEG ditosylate)
for 3 min (caution: a highly exothermic reaction was
happened). Reaction progress was monitored by TLC

5086
F. Kazemi et al. / Tetrahedron 63 (2007) 5083–5087
3
a
(
CCl /EtOAc). Remaining tosyl chloridewas removed by the
4
4.4.6. Isopropyl tosylate (10). Thick oil; IR (film) 1177,
1362 cm ; H NMR (400 MHz, CDCl ) d 1.14 (6H, d,
ꢀ
1 1
addition of powdered KOH (50 mmol) and vigorously
grinded (2 min), addition of a few drops of t-BuOH acceler-
ates the disappearance of TsCl. After completion of the reac-
tion, the reaction mixture was stirred and filtered with ether
3
J 4 Hz, CHMe ), 2.32 (3H, s, CH ), 4.60 (1H, h, J 4 Hz,
2
3
CHO–), 7.25 (2H, d, J 8 Hz, m-H), 7.67 (2H, d, J 8 Hz,
o-H); C NMR (400 MHz, CDCl ) d 21.43, 22.38, 22.59,
127.76, 130.02, 134.37, 144.46.
1
3
3
(
50 ml). The combined organic layer was collected by sin-
tered glass in vacuo and the resulting product was concen-
trated by evaporation of the ether using a rotary evaporator.
The obtained crude tosylate was sufficiently pure. If neces-
sary, more purification can be carried out by silica-gel
chromatography for oily tosylates or by recrystallization in
n-hexane on solid tosylates.
1
5
4.4.7. Citronellol tosylate (12). Thick oil; IR (film) 1178,
1362 cm ; H NMR (400 MHz, CDCl ) d 0.78 (3H, d,
ꢀ
1 1
3
J 4 Hz, CH ), 0.84–1.87 (15H, m), 2.38 (3H, s, CH ), 4.01
3
(2H, t, J 4 Hz), 4.98 (1H, t, J 8 Hz), 7.28 (2H, d, J 8 Hz,
m-H), 7.74 (2H, d, J 8 Hz, o-H); C NMR (400 MHz,
3
1
3
CDCl ) d 17.52, 19.52, 21.47, 25.43, 25.50, 29.55, 36.62,
3
4
.4. Large scale synthesis of diethylene glycol ditosylate
37.19, 69.05, 124.78, 127.77, 129.78, 131.19, 133.21,
1
44.63.
A mortar was charged with dry K CO (50 g), diethylene
2
3
5
c
glycol (9.47 ml, 100 mmol), and TsCl (57.19 g,
00 mmol), and grinded vigorously for about 10 min. After
4.4.8. 1-Octyl tosylate (13). Thick oil; IR (film) 1178,
1364 cm ; H NMR (400 MHz, CDCl ) d 0.79 (3H, t,
ꢀ
1
1
3
3
the completion of tosylation, remaining tosyl chloride was
removed by the addition of powdered KOH (50 mmol) and
vigorously grinded (2 min), addition of a few drops of
t-BuOH accelerates the disappearance of TsCl. The product
was extracted by the addition of ether (50 ml), filtered, and
finally by the evaporation of organic solvent. Further purifi-
cation can be carried out on the crude solid tosylate by
recrystallization in n-hexane. The yields were 89%.
J 8 Hz, CH ), 1.12–1.55 (12H, m), 2.34 (3H, s, CH ), 3.92
3
3
(2H, t, J 8 Hz), 7.25 (2H, d, J 8 Hz, m-H), 7.68 (2H, d,
J 8 Hz, o-H); C NMR (400 MHz, CDCl ) d 13.98, 21.43,
1
3
3
22.59, 25.24, 26.17, 29.24, 28.7, 29.41, 29.74, 31.78,
70.79, 127.74, 129.76, 133.14, 144.59.
3
a
4.4.9. 2-Octyl tosylate (14). Thick oil; IR (film) 1178,
1362 cm ; H NMR (400 MHz, CDCl ) d 0.66 (3H, t,
ꢀ
1
1
3
J 7 Hz, CH ), 0.98–1.38 (13H, m), 2.23 (3H, s, CH ), 4.38
3
3
3
a
4
.4.1. Methyl tosylate (1). Thick oil; IR (film) 1178,
(1H, m, CHO–), 7.26 (2H, d, J 8 Hz, m-H), 7.62 (2H, d,
J 8 Hz, o-H); C NMR (400 MHz, CDCl ) d 13.94, 21.30,
ꢀ1
1
13
1
CH ), 3.59 (3H, s, OCH ), 7.24 (2H, d, J 8 Hz, m-H), 7.64
362 cm ; H NMR (400 MHz, CDCl ) d 2.46 (3H, s,
3
3
22.30, 22.47, 23.33, 24.63, 25.66, 31.37, 80.33, 127.49,
129.60, 136.28, 144.27.
3
3
1
3
(
2H, d, J 8 Hz, o-H); C NMR (400 MHz, CDCl3)
d 21.38, 56.25, 127.68, 130.16, 131.98, 144.98.
3
a
4.4.10. Cyclohexyl tosylate (15). Thick oil; IR (film)
1177, 1360 cm ; H NMR (400 MHz, CDCl ) d 1.20–
1
4
ꢀ1
1
4
.4.2. 3-Methoxybenzyl tosylate (4). Pale yellow crystal;
IR (film) 1178, 1364 cm ; H NMR (400 MHz, CDCl )
3
ꢀ
1 1
1.74 (10H, m, –(CH ) ), 2.40 (3H, s, CH ), 4.48 (1H, m,
2 5
3
3
d 2.45 (3H, s, CH ), 3.70 (3H, s, OCH ), 5.04 (2H, s,
3
OCH ), 7.21–7.82 (8H, m); C NMR (400 MHz, CDCl3)
2
CHO–), 7.28 (2H, d, J 8 Hz, m-H), 7.74 (2H, d, J 8 Hz,
o-H); C NMR (400 MHz, CDCl ) d 21.58, 23.32, 24.10,
24.97, 32.10, 32.26, 81.58, 127.79, 129.74, 134.70, 144.35.
3
1
3
13
3
d 21.60, 55.24, 71.80, 113.73, 114.75, 120.65, 127.96,
1
29.71, 133.30, 134.75, 144.84, 159.76.
5
b
4.4.11. Menthyl tosylate (16). Colorless crystals: mp 92–
93 C; IR (film) 1178, 1366 cm ; H NMR (400 MHz,
1
3
ꢁ
CDCl ) d 0.52 (3H, d, J 6.4 Hz), 0.70–2.25 (15H, m), 2.37
ꢀ1
1
4
mp 87–89 C; IR (film) 1165, 1352 cm
.4.3. Diethyleneglycol ditosylate (7). Colorless crystal;
;
ꢁ
400 MHz, CDCl ) d 2.45 (6H, s, CH ), 3.62 (4H, t,
ꢀ1
1
H NMR
3
(
J 4 Hz, OCH ), 4.09 (4H, t, J 4 Hz, OCH ), 7.34 (4H, d,
(3H, s, CH ), 4.32 (1H, m, OCH–), 7.26 (2H, d, J 8 Hz,
3
3
3
1
3
m-H), 7.73 (2H, d, J 8 Hz, o-H); C NMR (400 MHz,
CDCl ) d 15.21, 21.52, 22.21, 22.91, 23.13, 25.42, 31.57,
33.72, 41.91, 50.0, 83.50, 127.87, 129.64, 134.74, 144.31.
2
2
1
3
J 8 Hz, m-H), 7.77 (4H, d, J 8 Hz, o-H); C NMR
400 MHz, CDCl ) d 21.67, 68.71, 69.04, 127.94, 128.34,
3
(
3
1
29.91, 132.75, 145.
1
e
4
mp 78–81 C; IR (film) 1177, 1354 cm
.4.4. Triethyleneglycol ditosylate (8). Colorless crystal:
;
Acknowledgements
ꢁ
400 MHz, CDCl ) d 2.34 (6H, s, CH ), 3.47 (4H, s), 3.54
4H, t, J 4 Hz, OCH ), 4.01 (4H, t, J 4 Hz, OCH ), 7.25
2
4H, d, J 8 Hz, m-H), 7.67 (4H, d, J 8 Hz, o-H); C NMR
400 MHz, CDCl ) d 21.56, 70.34, 70.47, 71.20, 127.82,
ꢀ1
1
H NMR
(
(
(
(
We gratefully acknowledge the support of this work by the
Shahid Chamran University Research Council. The primar-
ily tests of this work were carried out in Prof. Hashem Shar-
ghi laboratory (Shiraz university) and we thank his help.
3
3
2
1
3
3
1
29.87, 132.72, 144.92.
1
e
4
.4.5. Tetraethylene glycol ditosylate (9). Thick oil; IR
References and notes
ꢀ1
1
(
film) 1178, 1358 cm
;
H NMR (400 MHz, CDCl3)
d 2.22 (6H, s, CH ), 3.35 (8H, m, J 12 Hz), 3.44 (4H, t,
1. (a) Larock, R. C. Comprehensive of Organic Transformation;
VCH: Weinheim, 1989; (b) Wagner, R. B.; Zokk, H. D.
Synthetic Organic Chemistry; Horning, E. C., Ed.; John
Wiley and Sons: New York, NY, 1955; Vol. 3; (c) Sandler,
S. R.; Karo, W. Organic Functional Group Preparations;
3
J 8 Hz, OCH ), 3.94 (4H, t, J 8 Hz, OCH ), 7.145 (4H, d,
2
2
1
3
J 8 Hz, m-H), 7.56 (4H, d, J 8 Hz, o-H); C NMR
400 MHz, CDCl ) d 21.40, 68.36, 69.44, 70.23, 70.62,
(
1
3
28.16, 129.83, 132.78, 144.8.

F. Kazemi et al. / Tetrahedron 63 (2007) 5083–5087
5087
Academic: New York, NY, 1983; Vol. 1; (d) Kabalka, G. W.;
Varma, M.; Varma, R. S. J. Org. Chem. 1986, 51, 2386; (e)
Cragg, P. J. A Practical Guide to Supramolecular Chemistry;
John Wiley and Sons: New York, NY, 2005.
. House, H. O. Modern Synthetic Reactions, 2nd ed.; W.A.
Benjamin: London, 1973.
. (a) Choudary, B. M.; Chowdari, N. S.; Kantam, M. L.
Tetrahedron 2000, 56, 7291; (b) Das, B.; Reddy, V. S.;
Reddy, M. R. Tetrahedron Lett. 2004, 45, 6717; (c)
Velusamy, S.; Kiran Kumar, J. S.; Punniyamurthy, T.
Tetrahedron Lett. 2004, 45, 203; (d) Comagic, S.;
Schirrmacher, R. Synthesis 2004, 885.
6. Purdie, T.; Matinelli, M. J.; Nayyar, K. N.; Moher, E. D.;
Dhokt, U. P.; Pawlak, J. M.; Vaidanathan, R. Org. Lett. 1999,
1633.
7. Boons, G. J.; Castle, G. H.; Clase, J. A.; Grice, P.; Ley, S. V.;
Pinel, C. Synlett 1993, 913.
8. Bouzide, A.; LeBerre, N.; Sauv ꢀe , G. Tetrahedron Lett. 2001,
42, 8781.
9. Galynker, I.; Still, W. C. Tetrahedron Lett. 1982, 43, 4461.
10. Cave, G. W. V.; Raston, C. L.; Scott, J. L. Chem. Commun.
2001, 2159.
11. (a) Hajipour, A. R.; Mallakpour, S. E.; Mazlumi, G. Sulfur Lett.
2000, 24, 137; (b) Fazaeli, R.; Tangestaninejad, S.; Aliyan, H.
Can. J. Chem. 2006, 86, 812.
12. (a) Kazemi, F.; Sharghi, H.; Nasseri, M. A. Synthesis 2004,
205; (b) Massah, A. R.; Kazemi, F.; Azadi, D.; Farzaneh, S.;
Aliyan, H.; Javaherian Naghash, H.; Momeni, A. R. Lett.
Org. Chem. 2006, 3, 235.
2
3
4
5
. (a) Ouchi, M.; Inoue, Y.; Liu, Y.; Nagamune, S.; Nakamura, S.;
Wada, K.; Hakushi, T. Bull. Chem. Soc. Jpn. 1990, 63, 1260;
(
b) Fenton, D. E.; Parkin, D. J. Chem. Soc., Perkin Trans. 1
981, 449; (c) Cornforth, J. W.; Morgan, E. D.; Potts, K. T.;
Rees, R. J. W. Tetrahedron 1973, 29, 1659.
1
. (a) Yoshida, Y.; Sakakura, Y.; Aso, N.; Okada, S.; Tanabe, Y.
Tetrahedron 1999, 55, 2183; (b) Yoshida, Y.; Shimonishi, K.;
Sakakura, Y.; Okada, S.; Aso, N.; Tanabe, Y. Synthesis 1999,
1633; (c) Morita, J.; Nakatsuji, H.; Misaki, T.; Tanabe, Y.
Green Chem. 2005, 7, 711.
13. Daleand, J.; Kristiansen, P. O. Acta Chem. Scand. 1972, 26,
1471.
14. Kochi, J. K.; Hammond, G. S. Chem. Soc. 1953, 75, 3443.
15. Zarbin, P. H. G.; Cruz, W.; Ferreira, J. T. B. J. Braz. Chem. Soc.
1998, 9, 511.