Reaction of (diacetoxyiodo)benzene with excess of trifluoromethanesulfonic acid. A convenient route to para-phenylene type hypervalent iodine oligomers

Article abstract of DOI:10.1016/j.tet.2004.07.026

Reaction of (diacetoxyiodo)benzene [PhI(OAc)₂] in trifluoromethanesulfonic acid (TfOH) resulted in oligomerization of PhI(OAc)₂. Quenching with NaBr gave the bromide salts of hypervalent iodine oligomers that were determined by therm

Full text of DOI:10.1016/j.tet.2004.07.026

Tetrahedron 60 (2004) 8855–8860
Reaction of (diacetoxyiodo)benzene with excess of
trifluoromethanesulfonic acid. A convenient route to
para-phenylene type hypervalent iodine oligomers
a
b
b
b
Tsugio Kitamura,a, Daisuke Inoue, Ichiro Wakimoto, Tetsu Nakamura, Ryoji Katsuno
*
and Yuzo Fujiwarab
aDepartment of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Honjo-machi,
Saga 840-8502, Japan
bDepartment of Applied Chemistry, Faculty of Engineering, Kyushu University, Hakozaki, Fukuoka 812-8581, Japan
Received 2 June 2004; accepted 9 July 2004
Available online 21 August 2004
Abstract—Reaction of (diacetoxyiodo)benzene [PhI(OAc)2] in trifluoromethanesulfonic acid (TfOH) resulted in oligomerization of
PhI(OAc)2. Quenching with NaBr gave the bromide salts of hypervalent iodine oligomers that were determined by thermolysis with KI to be
a para phenylene type of oligomers. Neutralization of the reaction mixture of PhI(OAc)2 and TfOH with aqueous NaHCO3 yielded the triflate
salts of iodine oligomers. Furthermore, quenching the reaction mixture with aromatic substrates afforded arylated iodine oligomers. These
iodine oligomers were found to be 3–4 of the number average degree of polymerization (Pn) by GC analysis of the thermolysis products and
1H NMR analysis. The major products, trimer and tetramer, were synthesized independently.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
Applications of hypervalent iodine compounds to organic
chemistry have recently attracted a great deal of attention
because they show high reactivity and have come into wide
use in organic synthesis.1 Since Hartmann and Meyer2
reported the formation of (p-iodophenyl)(phenyl)iodonium
salt (1) in Figure 1 as a stable hypervalent iodine compound,
many diaryliodonium salts have been prepared. The
preparation and chemistry of diaryliodonium salts have
been summarized in early reviews.3 An extended type of the
salts, p-phenylenebis(aryliodonium) salts (2), has been
prepared recently by arylation of 1,4-bis(trifluoroacetoxy-
iodo)benzene.4 Okawara and his coworkers studied the
Figure 1.
synthesis of the tetramers of iodonium salts5 and suggested
sulfonyloxy)iodo]-4-[(phenyl)(trifluoromethylsulfonyl-
oxy)iodo]benzene (4),6 as shown in Scheme 1. This reagent
4 showed high reactivity to aromatic substrates and afforded
that the structure of the tetramers was composed of a meta-
phenylene skeleton. However, no further extended poly-
meric iodonium salts (3) have been prepared.
On the other hand, we found that the self-condensation of
PhIO takes place in the presence of 2 equiv. of TfOH to give
a bisiodine(III) reagent, 1-[(hydroxy)(trifluoromethyl-
Keywords: Hypervalent iodine oligomer; (Diacetoxyiodo)benzene; Tri-
fluoromethanesulfonic acid; para-Phenylene structure.
* Corresponding author. Tel.: C81-952-28-8550; fax: C81-952-28-8548;
e-mail: kitamura@cc.saga-u.ac.jp
Scheme 1.
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.07.026

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T. Kitamura et al. / Tetrahedron 60 (2004) 8855–8860
(p-phenylene)bis(phenyliodonium) ditriflate (5) in the
reaction with benzene. Furthermore, the reaction of 4 with
diphenyl ether also gave oxygen-bridged tetraiodonium salt
(6).6a On the basis of the self-condensation of PhIO, the
mechanism on the transformation of PhIO into 1 was
elucidated.7
bromide 7 did not dissolve even in a polar organic solvent
such as DMF, DMSO, or MeOH. To elucidate the structure
of the solid, we conducted thermolysis with KI affording
the corresponding organic iodides according to the con-
ventional method11 and analyzed the iodides with a
capillary GC.
However, bisiodine(III) reagent 4 did not undergo
polymerization to afford polymeric iodonium salts 3
although 4 had a reactive hypervalent iodonio group. The
failure in polymerization was considered to be due to the
reduced reactivity of the phenyl ring by the electron-
withdrawing hypervalent iodine8 and to the insolubility of 4
in the organic solvent employed. Thus, we conducted the
reaction of PhI(OAc)2 using excess of TfOH and found that
PhI(OAc)2 underwent polymerization to give the
oligomers.9 In this paper, we report in detail our findings
on the formation and structure of the hypervalent iodine
oligomers, and the independent synthesis of the hypervalent
iodine trimer and tetramer to confirm the structure of the
oligomers obtained by the reaction of PhI(OAc)2.
When the solid bromide 7 were reacted with KI in DMF
under reflux conditions, iodobenzene and 1,4-diiodo-
benzene were formed. No isomers other than 1,4-diiodo-
benzene were detected. Therefore, the formation of 1,4-
diiodobenzene strongly indicates that the structure of
bromide 7 is composed of a para-phenylene unit. On the
basis of the quantitative GC analysis of iodobenzene
and 1,4-diiodobenzene, the number average degree of
polymerization (Pn) was calculated to be 3–4 as shown in
Table 1. Therefore, the solid bromides were determined to
be hypervalent iodine oligomers bearing a p-phenylene
structure.
This result is different from Okawara’s report5 that iodine
oligomers (tetramers) have meta-phenylene units. However,
our previous study6 on the dimerization of PhIO with TfOH
supports this para orientation. It is, therefore, considered
that the lone pairs on the iodine(III) atom govern the
orientation of the oligomerization in the same way as the
effect of halogen on electrophilic aromatic substitution of
halobenzenes.
2. Results and discussion
2.1. Oligomerization of PhI(OAc)2 with TfOH. Isolation
of hypervalent iodine oligomers as the bromide salts
PhI(OAc)2 was treated with excess of TfOH and then the
reaction was quenched with ice-water. However, no
precipitates were formed on standing. When NaBr was
added to the reaction mixture according to an early
procedure10 to isolate diaryliodonium salts, pale yellow
precipitates were formed. For example, the reaction of
PhI(OAc)2 (2.5 mmol) with TfOH (50 mmol) followed by
treatment with aqueous NaBr gave 0.5–0.7 g of a pale
yellow solid of the bromide (7), mp 149–157 8C (dec), as
shown in Table 1 and Scheme 2. However, the solid
2.2. Isolation of hypervalent iodine oligomers as triflate
salts
The bromide salt 7 of hypervalent iodine oligomers could
not be analyzed by NMR since the solubility of 7 in organic
solvents was extremely low. Then, we tried to isolate the
hypervalent iodine oligomers as triflate salts and found that
the neutralization of the reaction mixture with NaHCO3
resulted in the formation of the precipitates of triflate (8), as
shown in Scheme 3.
Table 1. Reaction of PhI(OAc)2 with TfOH followed by treatment with
NaBra
b
Pn
Entry
Reaction time
(h)
Yield of
7 (g)
1
2
3
4
5
6
7
8
1
2
8
24
48
64
96
168
0.55
0.64
0.66
0.68
0.65
0.72
0.58
0.62
3.0
3.1
3.2
3.4
3.6
3.9
3.2
3.1
Scheme 3.
For example, the reaction of PhI(OAc)2 (2.5 mmol) with
TfOH (50 mmol) for 8–48 h followed by neutralization with
aqueous NaHCO3 afforded white solids (0.5–0.6 g) of
hypervalent iodine oligomers as shown in Table 2. The
triflate salt 8 of oligomers dissolved in polar solvents such as
DMSO and MeOH and this enabled the analysis by NMR.
The 1H NMR spectrum of 8 showed characteristic chemical
shifts of hypervalent iodine compounds bearing a p-phenyl-
ene structure, indicating that the aromatic protons between
the hypervalent iodines in the p-phenylene ring were
observed around 8.32 ppm as a singlet. The terminal
p-iodophenyl group showed a typical A2B2 pattern at 7.9–
8.0 ppm and the ortho protons of the phenyl group appeared
around 8.26 ppm as a doublet. The number average degree
of polymerization Pn was determined to be 3.5–3.8 (entries
a
Reaction conditions: PhI(OAc)2 (0.80 g, 2.5 mmol), TfOH (4.5 mL,
50 mmol) at room temperature.
Determined by GC after the decomposition with KI.
b
Scheme 2.

T. Kitamura et al. / Tetrahedron 60 (2004) 8855–8860
8857
Table 2. Reaction of PhI(OAc)2 with TfOH followed by treatment with
NaHCO3
Thus, PhI(OAc)2 was treated with excess of TfOH and
then allowed to react with benzene, toluene, chloro-
benzene, or bromobenzene, as shown in Scheme 4. The
quenching and neutralization of the reaction mixture
yielded the corresponding arylated hypervalent iodine
oligomers (10) in good yields. The fact that the reaction
with less reactive halobenzenes proceeds readily
suggests that the terminal hypervalent iodine of 9 has
a highly electrophilic character. The 1H NMR spectra,
however, showed that arylated iodine oligomers 10 were
contaminated by small amounts of unarylated iodine
oligomers 8.
a
b
Entry
TfOH
(mmol)
Reaction
time (h)
Yield of
8 (g)
Pn
1
2
3
4
5
6
12.5
25
50
75
50
50
24
24
24
24
8
0.26
0.48
0.64
0.55
0.53
0.62
2.3
3.3
3.7
3.7
3.5
3.8
48
a
Reaction conditions: PhI(OAc)2 (0.80 g, 2.5 mmol) at room tempera-
ture.
b
1
Determined by H NMR.
The thermolysis of phenylated iodine oligomers 10a with KI
similarly gave iodobenzene and 1,4-diiodobenzene. The
quantitative GC analysis of iodobenzene and 1,4-diiodo-
benzene indicated that the number average degree of
polymerization Pn was 3.5.
2.4. Independent synthesis of hypervalent iodine trimer
and tetramer
From the above results, it is found that the reaction of
PhI(OAc)2 with excess of TfOH gives hypervalent iodine
oligomers 7, 8, and 10 which are mostly composed of the
trimer and the tetramer. Thus, we conducted an independent
synthesis of the hypervalent iodine trimer, as illustrated in
Scheme 5, to confirm its existence in the iodine oligomers
10a.
Scheme 4.
3–6 in Table 2) by the calculation of the integrals of these
protons. This result is almost identical to that determined by
the GC analysis of the thermolysis of 7 with KI. Therefore,
the hypervalent iodine oligomers obtained in this study were
found to be mostly composed of a trimer and a tetramer
bearing a p-phenylene structure.
The self-condensation of PhIO with 2 equiv. of TfOH in
CH2Cl2 gave bisiodine(III) reagent 4 in 84% yield.
Arylation of 4 with 1,4-bis(tributylstannyl)benzene pro-
vided 4-(tributylstannyl)phenyl-substituted bisiodine(III)
compound (11) in 61% yield. Reaction of 11 with a PhIO/
TfOH reagent followed by repeated recrystallization
afforded hypervalent iodine trimer [10a (nZ2)] in 26%
yield. The 1H NMR spectrum of 10a (nZ2) is almost
identical with that of phenylated hypervalent iodine
oligomers 10a. The triplet signals at 7.53 and 7.70 ppm
are attributed to the meta and para protons of the terminal
phenyl rings, respectively, and the doublet signal at
8.25 ppm to the ortho protons. Specially, the single peak
observed at 8.34 ppm corresponds to all protons of the
p-phenylene units. The 13C NMR spectrum showed
characteristic high-field signals of ipso carbons bound to
iodine(III) at 116.7, 120.3, and 120.5 ppm.
2.3. Arylation of hypervalent iodine oligomers
In the reaction mixture of PhI(OAc)2 and TfOH, before
quenching with NaBr or H2O, it is presumed that there exists
an intermediate hypervalent iodine species (9) having a
reactive terminal site such as a bis(trifluoromethylsulfonyl-
oxy)iodanyl group.12 Since a PhI(OAc)2/2TfOH reagent
system shows high reactivity to aromatic substrates to give
diaryliodonium salts,13 it is expected that this terminal
iodine group can react with aromatic substrates to provide
arylated hypervalent iodine oligomers.
p-Phenylene-type hypervalent iodine tetramer [10a (nZ3)]
Scheme 5.

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T. Kitamura et al. / Tetrahedron 60 (2004) 8855–8860
Scheme 6.
was prepared by the reaction of 4 with excess of 1,4-
bis(tributylstannyl)benzene, as shown in Scheme 6. How-
ever, the procedure also provided mono-substituted
compound 11. Accordingly, tetramer 10a (nZ3) was
4. Experimental
4.1. General
1
Melting points are uncorrected. Analytical GC evaluations
of the product mixture were performed on a capillary gas
chromatography using 30 m!0.25 mm capillary column
(DB-5, J&J Scientific). Elemental analyses were performed
by the Service Center of the Elementary Analysis of
Organic Compounds, Faculty of Science, Kyushu
University.
isolated in 3% yield by repeated recrystallization. The H
NMR spectrum of tetramer 10a (nZ3) was almost the same
as that of trimer 10a (nZ2), giving signals at 7.54 (triplet),
7.69 (triplet), and 8.26 (doublet) ppm corresponding to the
meta, para, and ortho protons of the terminal phenyl
rings, and the single peak at 8.34 ppm due to the protons of
the para phenylene rings. The 13C NMR spectrum of 10a
(nZ3) indicated similarly high-field signals of the ipso
carbon bound to iodine(III) at 116.7, 120.3, 120.5, and
4.2. Oligomerization of PhI(OAc)2 with TfOH. Isolation
of hypervalent iodine oligomers 7 as bromide salts
1
120.6 ppm. The H NMR spectra of trimer 10a (nZ2) and
tetramer 10a (nZ3) are very similar except for higher
integration of the p-phenylene signal. Comparison of
these spectra with phenylated oligomers 10a indicates that
the 1H NMR spectrum of 10a is close to that of tetramer 10a
(nZ3).
(Diacetoxyiodo)benzene (0.80 g, 2.5 mmol) was added to
TfOH (4.5 mL, 50 mmol) at 0 8C and the mixture was
stirred at room temperature for the time given in Table 1.
The reaction mixture was poured onto ice (45 g) and NaBr
(7.72 g, 75 mmol) was added. The resulting precipitates
were collected by suction, washed with water and methanol,
and dried in vacuo. The oligomers 7 (0.55–0.72 g) were
obtained as a pale yellow solid as shown in Table 1. The
oligomers 7 decomposed in the range of 149–157 8C.
3. Conclusion
We have demonstrated that reaction of PhI(OAc)2 in excess
of TfOH gives hypervalent iodine oligomers comprising 3
or 4 units of –C6H4I(X)–. The structure of the oligomers
was characterized by GC analysis of the decomposition
products with KI and by NMR. The oligomers obtained in
this study have a para phenylene structure and 3–4 of Pn.
Functionalization of the iodine oligomers 9 with aromatic
substrates was readily performed to give aryl-substituted
oligomers 10. As the practical applications, it has been
reported that several types of diaryliodonium salts show
strong biological activity.1 Preliminarily, we examined the
biological activity of the hypervalent iodine oligomers.
Evaluation results of the biological activity indicate that
these iodine oligomers show toxicity toward fungi and
bacteria.14 Particularly, hypervalent iodine oligomers 10
exhibit in vitro toxicity against Aureobasidium pullulans
and Penicillium funiculosum at the 50 ppm level and strong
toxicity at the 25 ppm level against bacterial species such as
Bacillus subtilis, Enterobacter aerogenes, Escherichia coli,
Staphylococcus aureus, Klebsiella pneumoniae, Micro-
coccus luteus and Enterococcus faecalis. Independent
syntheses of trimer 10a (nZ2) and tetramer 10a (nZ3)
confirm the structure of the hypervalent iodine oligomers.
As a future subject of study on hypervalent iodine
oligomers, it will be very interesting to see the structure
and property of these new types of hypervalent iodine
oligomers because these oligomers contain many hyper-
valent iodines in the molecule.
4.3. Decomposition of the oligomers 7 with KI
A mixture of oligomers 7 (50 mg) and KI (1.5 g, 9.0 mmol)
in DMF (5 mL) was heated under reflux (163 8C) for 1 h.
Water was added to the mixture and the products were
extracted with ether. The organic layer was washed with
water and aqueous sodium thiosulfate, and dried over
anhydrous Na2SO4. The GC analysis of the products was
performed on a Shimadzu gas chromatograph equipped with
a capillary column (DB-5, J&W Scientific) using hexa-
methylbenzene as an internal standard. The products formed
were iodobenzene and 1,4-diiodobenzene. The number
average degree of polymerization (Pn) was calculated on
the basis of the concentration of these products. Since the
decomposition of 7 by KI affords a 1: n stoichiometric ratio
of iodobenzene and 1,4-diiodobenzene, the Pn value is
obtained by the following equation; PnZnK1, where nZ
[1,4-diiodobenzene]/[iodobenzene]. The results are given in
Table 1. Because of the insolubility of 7 in organic solvents
other methods for determination of Pn could not be applied.
4.3.1. Isolation of hypervalent iodine oligomers 8 as
triflate salts. (Diacetoxyiodo)benzene (0.80 g, 2.5 mmol)
was added to TfOH (the quantity described in Table 2) at
0 8C and the mixture was stirred at room temperature for the
time given in Table 2. The reaction mixture was poured onto
ice (50 g) and NaHCO3 was carefully added until the
solution was neutralized. The solution was kept standing for

T. Kitamura et al. / Tetrahedron 60 (2004) 8855–8860
8859
3 d. The resulting white precipitates were collected by
suction, washed with water, and dried in vacuo to give
oligomers 8 as a white solid as shown in Table 2. Mp 241–
248 8C; 1H NMR (300 MHz, DMSO-d6) d 7.54 (t, JZ
7.8 Hz, ArH), 7.68 (t, JZ7.5 Hz, ArH), 7.90 (d, JZ8.4 Hz,
ArH), 8.00 (d, JZ8.4 Hz, ArH), 8.26 (d, JZ7.8 Hz, ArH),
8.32 (s, ArH).
vacuo to give 0.683 g (64%) of 11: mp 238–242 8C (dec),
1HMR (300 MHz, DMSO-d6) d 0.80 (t, JZ7.2 Hz, 9H),
1.05 (t, JZ7.5 Hz, 6H), 1.24 (m, 6H), 1.46 (m, 6H), 7.50–
7.69 (m, 5H), 8.17 (d, JZ8.1 Hz, 2H), 8.26 (d, JZ7.8 Hz,
2H), 8.33 (s, 4H); 13C NMR (75 MHz, DMSO-d6) d 9.31,
13.47, 26.57, 28.43, 116.77, 117.02, 119.99, 120.24, 131.91,
132.38, 134.18, 135.38, 137.63, 137.71, 139.24, 148.58.
4.3.2. Arylation of hypervalent iodine oligomers. (Dia-
cetoxyiodo)benzene (0.80 g, 2.5 mmol) was added to TfOH
(4.5 mL, 50 mmol) at 0 8C and the mixture was stirred at
room temperature for 2 h. An aromatic substrate (10 mmol)
was added and the reaction mixture was stirred for 20 h at
room temperature. The reaction mixture was poured onto
ice (50 g) and NaHCO3 (4.41 g, 52.5 mmol) was added
carefully. The solution was kept standing for 3 d. The
resulting precipitates were collected by suction, washed
with water, and dried in vacuo to give white solids of
arylated oligomers 10. Phenylated oligomers 10a, 0.81 g,
1H NMR (300 MHz, DMSO-d6) d 7.54 (t, JZ8 Hz, ArH),
7.62–7.72 (m, ArH), 8.26 (d, JZ8 Hz, ArH), 8.33 (s, ArH).
4-Methylphenylated oligomers 10b, 0.64 g, 1H NMR
(300 MHz, DMSO-d6) d 2.35 (s, Me), 7.35 (d, JZ8 Hz,
ArH), 7.54 (t, JZ8 Hz, ArH), 7.68 (t, JZ8 Hz, ArH), 8.13
(d, JZ8 Hz, ArH), 8.26 (d, JZ8 Hz, ArH), 8.34 (s, ArH).
4-Chlorophenylated oligomers 10c, 0.85 g, 1H NMR
(300 MHz, DMSO-d6) d 7.51–7.56 (m, ArH), 7.62–7.72
(m, ArH), 8.26–8.29 (m, ArH), 8.33 (s, ArH). 4-Bromo-
phenylated oligomers 10d, 0.81 g, 1H NMR (300 MHz,
DMSO-d6) d 7.51–7.56 (m, ArH), 7.66–7.78 (m, ArH),
8.17–8.27 (m, ArH), 8.33 (s, ArH).
4.4.3. Preparation of hypervalent iodine trimer, bis[4-
[(phenyl)(trifluoromethylsulfonyloxy)iodo]phenyl](tri-
fluoromethylsulfonyloxy)iodine [10a (nZ2)]. To a sus-
pension of PhIO (0.33 g, 1.5 mmol) in CH2Cl2 (5 mL) was
added TfOH (0.13 mL, 1.5 mmol) dropwise at 0 8C and the
mixture was stirred for 2 h at room temperature. A solution
of 11 (0.536 g, 0.5 mmol) in MeCN (40 mL) was added to
the resulting solution of PhIO/TfOH reagent at 0 8C and
then the mixture was heated with stirring at 40 8C for 22 h.
The solvent was evaporated by a rotary evaporator and ether
was added to crystallize the residue. The crystals obtained
from ether were recrystallized repeatedly from MeCN and
ether to give 0.15 g (26%) of 10a (nZ2): mp 241–243 8C
(dec); 1H NMR (300 MHz, DMSO-d6) d 7.53 (t, JZ7.8 Hz,
4H), 7.70 (t, JZ7.2 Hz, 2H), 8.25 (d, JZ7.8 Hz, 4H), 8.34
(s, 8H); 13C NMR (75 MHz, DMSO-d6) d 116.67, 120.34,
120.48, 131.84, 132.34, 135.27, 137.70, 137.77. Anal. Calcd
for C27H18F9I3O9S3: C, 28.59; H, 1.60. Found: C, 28.59; H,
1.69.
4.4.4. Preparation of hypervalent iodine tetramer, 1,4-
bis[[4-[(phenyl)(trifluoromethylsulfonyloxy)iodo]phe-
nyl](trifluoromethylsulfonyloxy)iodo]benzene [10a (nZ
3)]. To a solution of 1,4-bis(tributylstannyl)benzene
(0.328 g, 0.5 mmol) in MeCN (100 mL) was added 4
(1.083 g, 1.5 mmol) at 0 8C and the mixture was stirred
for 3 d at room temperature. At the end of the reaction,
crystals were precipitated. The crystals were collected by
suction, washed with ether, and finally recrystallized
repeatedly from MeCN and ether to give 0.020 g (2.6%)
The phenylated iodine oligomers 10a were also character-
ized by decomposition with KI. A mixture of oligomers 10a
(50 mg) and KI (1.5 g, 9.0 mmol) in DMF (5 mL) was
refluxed for 1 h. After workup of the reaction mixture, the
products were analyzed by GC using hexamethylbenzene as
an internal standard. The products formed were iodo-
benzene and 1,4-diiodobenzene. The number average
degree of polymerization (Pn) was calculated to be 3.5.
1
of 10a (nZ3). Mp 235–238 8C (dec); H NMR (300 MHz,
DMSO-d6) d 7.54 (t, JZ7.8 Hz, 4H), 7.69 (t, JZ7.5 Hz,
2H), 8.26 (d, JZ7.8 Hz, 4H), 8.34 (s, 12H); 13C NMR
(75 MHz, DMSO-d6) d 116.69, 120.28, 120.48, 120.58,
131.87, 132.37, 135.30, 137.70, 137.80, 137.93. Anal. Calcd
for C34H22F12I4O12S4: C, 27.47; H, 1.49. Found: C, 27.64;
H, 1.65.
4.4. Preparation of hypervalent iodine trimer 10a (nZ2)
and tetramer 10a (nZ3)
4.4.1. Preparation of 1-[(hydroxy)(trifluoromethylsul-
fonyloxy)iodo]-4-[(phenyl)(trifluoromethylsulfonyl-
oxy)iodo]benzene (4). To a suspension of PhIO (1.1 g,
5.0 mmol) in CH2Cl2 (10 mL) was added TfOH (0.89 mL,
10 mmol) dropwise at 0 8C and the mixture was stirred for
4 h at room temperature. The solvent was removed by a
rotary evaporator and ether was added to the residue. The
resulting crystals were collected by suction, washed with
ether, and dried in vacuo to afford 1.5 g (84%) of 4,6 mp
126–129 8C (dec).
Acknowledgements
This work was supported in part by a Grant-in-Aid for
Scientific Research (B) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan. We also
thank the Agricultural Chemical Research Laboratory of
Sumitomo Chemical Co., Ltd., for biological evaluations of
some hypervalent iodine oligomers.
4.4.2. Preparation of 1-[(phenyl)(trifluoromethylsulfo-
nyloxy)iodo]-4-[(4-(tributylstannyl)phenyl)(trifluoro-
methylsulfonyloxy)]benzene (11). To a solution of 1,4-
bis(tributylstannyl)benzene15 (0.656 g, 1.0 mmol) in MeCN
(10 mL) was added 4 (0.722 g, 1.0 mmol) at 0 8C and the
mixture was stirred for 1 h at room temperature. The
evaporation of the solvent gave crystals, which were
collected by suction, washed with ether, and dried in
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