Desulfonyloxyiodination of arenesulfonic acids with mCPBA and molecular iodine

Article abstract of DOI:10.1016/j.tetlet.2010.09.034

Treatment of p-alkylbenzenesulfonic acids with mCPBA and molecular iodine gave p-alkyliodobenzenes in good to moderate yields via electrophilic ipso-substitution by the iodonium species (I⁺) formed. This desulfonyloxyiodination was promoted by the addition of a catalytic amount of iodoarenes, such as o-iodobenzoic acid. The same treatment of dimethylbenzenesulfonic acids and trimethylbenzenesulfonic acids with mCPBA and molecular iodine proceeded smoothly both in the absence and in the presence of o-iodobenzoic acid to provide the corresponding monoiodo-dimethylbenzene and diiodo-dimethylbenzene, and diiodo-trimethylbenzene and triiodo- trimethylbenzene, in good to moderate yields, respectively. On the other hand, the same desulfonyloxyiodination of benzenesulfonic acid and p-chlorobenzenesulfonic acid with mCPBA and molecular iodine proceeded only in the presence of o-iodobenzoic acid to generate iodobenzene and p-chloroiodobenzene, respectively, in moderate yields.

Full text of DOI:10.1016/j.tetlet.2010.09.034

Tetrahedron Letters 51 (2010) 5950–5953
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Desulfonyloxyiodination of arenesulfonic acids with mCPBA
and molecular iodine
⇑
Yuhsuke Suzuki, Yoshihide Ishiwata, Katsuhiko Moriyama, Hideo Togo
Graduate School of Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of p-alkylbenzenesulfonic acids with mCPBA and molecular iodine gave p-alkyliodobenzenes in
good to moderate yields via electrophilic ipso-substitution by the iodonium species (I+) formed. This
desulfonyloxyiodination was promoted by the addition of a catalytic amount of iodoarenes, such as
o-iodobenzoic acid. The same treatment of dimethylbenzenesulfonic acids and trimethylbenzenesulfonic
acids with mCPBA and molecular iodine proceeded smoothly both in the absence and in the presence of
o-iodobenzoic acid to provide the corresponding monoiodo-dimethylbenzene and diiodo-dimethylben-
zene, and diiodo-trimethylbenzene and triiodo-trimethylbenzene, in good to moderate yields, respectively.
On the other hand, the same desulfonyloxyiodination of benzenesulfonic acid and p-chlorobenzenesulfonic
acid with mCPBA and molecular iodine proceeded only in the presence of o-iodobenzoic acid to generate
iodobenzene and p-chloroiodobenzene, respectively, in moderate yields.
Received 6 August 2010
Revised 3 September 2010
Accepted 10 September 2010
Available online 16 September 2010
Ó 2010 Elsevier Ltd. All rights reserved.
The use of hypervalent iodines in organic synthesis has been
widely studied.1 (Diacetoxyiodo)benzene (DIB) and [(hydroxy)-
(tosyloxy)iodo]benzene (HTIB) are the most popular and useful tri-
valent iodine reagents for organic synthesis because they are good
alternatives to toxic heavy-metal oxidants.2 On the other hand, to-
day, the ArI-catalyzed oxidative conversion reactions of substrates,
such as ketones, hydroquinones, and alcohols, with m-chloroper-
benzoic acid (mCPBA) or OxoneÒ have become very popular3 be-
cause they are metal-free oxidative reactions and thus conform to
environmentally benign organic synthesis. Recently, we reported
an efficient method for the preparation of various [(hydroxy)(sulfo-
nyloxy)iodo]arenes directly from iodoarenes with mCPBA and
sulfonic acids at room temperature;4 the PhI-catalyzed, polymer-
and the reaction mixtures were stirred at 50 °C for 8 h, as shown
in Table 1 (entries 1, 3, and 4). However, p-iodotoluene was not
formed at all. When the same reaction was carried out with molec-
ular iodine/OxoneÒ, p-iodotoluene was obtained in 23% yield (en-
try 2). Moreover, when p-toluenesulfonic acid monohydrate was
treated with NIS (N-iodosuccinimide) or molecular iodine/mCPBA
in acetonitrile, p-iodotoluene was obtained in moderate yields, as
shown in entries 5–8. When o-iodobenzoic acid (0.1 equiv or
1.1 equiv) was added to the solution, the yield of p-iodotoluene
was increased to 75% (entries 9 and 10).6 On the other hand,
Table 1
Desulfonyloxyiodination of p-toluenesulfonic acid
supported PhI-catalyzed, and ion-supported PhI-catalyzed a-tosyl-
oxylation of ketones with mCPBA and p-toluenesulfonic acid mono-
hydrate;5a–c the PhI-catalyzed and ion-supported PhI-catalyzed
preparation of 3,4-dihydro-1H-2,1-benzothiazine 2,2-dioxides from
N-methoxy-2-arylethanesulfonamides with mCPBA;5d,5e and the
ArI-catalyzed oxazole preparation from ketones and nitriles with
mCPBA5f or OxoneÒ.5g
CH3
CH3
Additives
CH3CN (3 mL), dark
50 oC, 8 h
I
SO3H•H2O
2a
1a
Entry
Additives (equiv)
Yield (%)
Herein, as part of our study on the catalytic use of organoio-
dines (I) in organic synthesis, we would like to report the
desulfonyloxyiodination of arenesulfonic acids with mCPBA and
molecular iodine both in the presence and in the absence of o-iod-
obenzoic acid. First, to an acetonitrile solution of p-toluenesulfonic
acid monohydrate (1 mmol) were added molecular iodine, molec-
ular iodine/tert-BuOOH (ꢀ70%), and molecular iodine/H2O2–urea,
1
2
3
4
5
6
7
8
9
10
I2 (1.2)
0
23
0
0
I2 (1.2), Oxone (1.1)
I2 (1.2), tBuOOH (1.1)
I2 (1.2), H2O2ꢁurea (1.1)
NIS (1.1)
58 (33:20a:5b)
NIS (1.1), BF3ꢁEt2O (2.2)
I2 (1.5), mCPBA (1.4)
I2 (2.0), mCPBA (1.1)
I2 (1.2), mCPBA (1.1), o-HO2CC6H4I (0.1)
I2 (1.2), mCPBA (1.1), o-HO2CC6H4I (1.1)
21
49
45
61
75 (46:22a:7b)
a
⇑
Corresponding author.
E-mail address: togo@faculty.chiba-u.jp (H. Togo).
Yield of 1,5-diiodo-2-methylbenzene.
Yield of 1,2-diiodo-4-methylbenzene.
b
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.034

Y. Suzuki et al. / Tetrahedron Letters 51 (2010) 5950–5953
5951
Table 3
p-bromotoluene was not formed at all, when a solution of p-tolu-
enesulfonic acid monohydrate with Br2 (1.2 equiv)/OxoneÒ
(1.1 equiv), NBS (1.1 equiv), or Br2 (1.2 equiv)/mCPBA (1.1 equiv)/
o-iodobenzoic acid (1.1 equiv) in acetonitrile was warmed at
50 °C. Thus, the desulfonyloxyiodination of arenesulfonic acids
with an oxidant proceeds specifically in the presence of molecular
iodine or iodine analogs. In the present desulfonyloxyiodination of
p-toluenesulfonic acid monohydrate with mCPBA (1.1 equiv) and
molecular iodine (1.2 equiv) in acetonitrile, the effect of iodoare-
nes, such as iodobenzene, p-iodobenzoic acid, p-chloroiodoben-
zene, p-iodotoluene, and o-iodobenzoic acid was studied and the
results are shown in Table 2. The present desulfonyloxyiodination
proceeded smoothly without iodoarene to generate p-iodotoluene
in 51% yield at 50 °C (entry 1). The addition of iodobenzene
(1.1 equiv) promoted the reaction slightly to give p-iodotoluene
in 60% yield at 50 °C (entry 3), while the same reaction at room
temperature was rather slow (entry 2). Entries 5 and 9 indicate
that a catalytic amount of iodobenzene and o-iodobenzoic acid
promoted the present desulfonyloxyiodination. However, the reac-
tion with o-iodobenzoic acid is practically convenient, as o-iodo-
benzoic acid can be removed from the reaction mixture by
washing with basic aq Na2SO3 solution.
Then, p-ethylbenzenesulfonic acid, p-octylbenzenesulfonic acid,
p-dodecylbenzenesulfonic acid, and p-(b-bromoethyl)benzenesulf-
onic acid were treated with mCPBA and molecular iodine both in
the presence and in the absence of a catalytic amount of o-iodoben-
zoic acid (0.1 equiv) in acetonitrile at 50 °C or refluxing conditions to
provide p-iodoethylbenzene, p-iodooctylbenzene, p-iododocecyl-
benzene, and 4-(20-bromoethyl)-1-iodobenzene, respectively, in
moderate to good yields (methods A or B6). In each reaction, the
addition of o-iodobenzoic acid increased the yield of the desul-
fonyloxyiodination product in the range of 10–35%, as shown in
Table 3 (entries 3–10). Then, under the same conditions, mesitylene-
sulfonic acid, 2,5-dimethylbenzenesulfonic acid, and 2,4-dimethyl-
benzenesulfonic acid were treated with mCPBA and molecular
iodine both in the presence and in the absence of o-iodobenzoic acid
to generate 1,3-diiodo-2,4,6-trimethylbenzene and 1,3,5-triiodo-
2,4,6-trimethylbenzene; 2,5-dimethyl-1-iodobenzene and 1,4-diio-
do-2,5-dimethylbenzene; and 2,4-dimethyl-1-iodobenzene and
1,5-diiodo-2,4-dimethylbenzene, respectively, in good yields
(entries 11–24). Under acetonitrile refluxing conditions, polyiodoa-
renes were obtained as major products (entries 14 and 19). The same
treatment of 2-iodo-5-methylbenzenesulfonic acid both in the pres-
ence and in the absence of o-iodobenzoic acid, furnished 1,2-diiodo-
4-methylbenzene in good to moderate yields, as shown in entries 25
and 26. In those reactions, o-iodobenzoic acid induced the desul-
fonyloxyiodination to provide iodoarenes in better yields than that
Desulfonyloxyiodination of arenesulfonic acids
o-HO2CC6H4I (0.1 equiv.)
mCPBA (1.1 equiv.), I2 (1.2 equiv.)
CH3CN (3 mL), dark, 50 oC, time
Ar SO3H
Ar
I
1
2
Entry
Ar–
Time
Method
Yield (%)
1
2
8 h
A
A
61
51
CH3
8 ha
3
4
8 h
A
A
63
43
C2H5
C8H17
C12H25
8 ha
5
6
8 h
B (reflux)
B (reflux)
81
59
8 ha
7
8
8 h
B (reflux)
B (reflux)
88
53
8 ha
9
10
8 h
B (reflux)
B (reflux)
69
62
BrH2CH2C
8 ha
11
12
13
14
8 h
A
A
A
76 (58b:18c)
CH3
63 hd
62 (53b:9c)
8 ha
8 h
55 (27b:28c)
72 (15b:57c)
CH3
CH3
A (reflux)
CH3
15
16
8 h
16 h
A
A
A
64e
49 (42:7e)
17
18
19
20
8 h
78e
63 hd
8 h
A
68 (53:12e)
94e
CH3
A (reflux)
A
8 ha
66e
21
22
23
24
8 h
8 h
A
86f
CH3
CH3
A (reflux)
A
A
96f
8 ha
76f
CH3
63 hd
70 (38:32f)
25
26
8 h
A (reflux)
A
80
51
8 ha
I
27
28
8 hg
8 ha
B (reflux)
B (reflux)
40
7
29
30
8 hg
B (reflux)
B (reflux)
45
5
Cl
8 ha
31
32
33
8 h
A (rt)
A (reflux)
A (rt)
67h
CH3O
8 ha
69 (47h:22i)
8 ha
67h
34
35
8 h
A
A
65
62
8 ha
36
37
8 h
A
A
0
0
8 ha
CH3
CH3
38
8 h
A
0
O
Methods A and B: see to experimental procedure (Ref. 6).
a
Without o-HO2CC6H4I.
Yield of 1,3-diiodo-2,4,6-trimethylbenzene.
Yield of 1,3,5-triiodo-2,4,6-trimethylbenzene.
Solvent (30 mL) was used.
Yield of 1,4-diiodo-2,5-dimethylbenzene.
Yield of 1,5-diiodo-2,4-dimethylbenzene.
o-HO2CC6H4I (1.1 equiv) was used.
Yield of 2,4-diiodo-1-methoxybenzene.
b
c
Table 2
d
Desulfonyloxyiodination of p-toluenesulfonic acid
e
f
ArI
CH3
g
CH3
mCPBA (1.1 equiv.),
h
I
2 (1.2 equiv.)
i
Yield of 2,4,6-triiodo-1-methoxybenzene.
CH3CN (3 mL), dark
50 oC, Time
I
SO3H•H2O
2a
1a
in the absence of o-iodobenzoic acid. Moreover, when benzenesulf-
onic acid and p-chlorobenzenesulfonic acid were treated with
mCPBA and molecular iodine under the same conditions without
o-iodobenzoic acid, the yields of iodobenzene and p-chloroiodoben-
zene were low. However, when the reactions were carried out in the
presence of o-iodobenzoic acid, iodobenzene, and p-chloroiodoben-
zene were obtained in moderate yields, respectively (entries 27–30).
p-Methoxybenzenesulfonic acid, which has an electron-rich aro-
matic group, reacted with molecular iodine and mCPBA both in the
presence and in the absence of o-iodobenzoic acid at room
temperature to give 2,4-diiodo-1-methoxybenzene in good yields
Entry
Arl (equiv)
Time
Yield (%)
1
2
3
4
5
6
7
8
9
—
8 h
51
7
PhI (1.1)
PhI (1.1)
16 ha
16 h
8 h
60
36
60
38
44
36
61
p-HO2CC6H4I (1.1)
PhI (0.1)
p-HO2CC6H4I (0.1)
p-ClC6H4I (0.1)
p-H3CC6H4I (0.1)
o-HO2CC6H4I (0.1)
8 h
8 h
8 h
8 h
8 h
a
Reaction was carried out at rt.

5952
Y. Suzuki et al. / Tetrahedron Letters 51 (2010) 5950–5953
(entries 31 and 33). When the same reaction was carried out
under acetonitrile refluxing conditions, a mixture of 2,4-diiodo-
1-methoxybenzene and 2,4,6-triiodo-1-methoxybenzene was ob-
tained (entry 32). The same treatment of 1-naphthalenesulfonic acid
gave 1-iodonaphthalene in good yields both in the presence and in
the absence of o-iodobenzoic acid (entries 34 and 35), while 2-iodo-
naphthalene was not formed at all from the reaction with 2-naph-
thalenesulfonic acid (entries 36 and 37). This result is closely
relatedto that 1-naphthalenesulfonicacid whichis a kinetically con-
trolled product and is isomerized to 2-naphthalenesulfonic acid, a
thermodynamically stable product, at high temperature. The desul-
fonyoxyiodination of 3-nitrobenzenesulfonic acid and 2,4-dinitro-
benzenesulfonic acid with mCPBA and molecular iodine both in
the presence and in the absence of o-iodobenzoic acid did not occur
at all, as the electrophilic ipso-substitution of 3-nitrobenzenesulfon-
ic acid and 2,4-dinitrobenzenesulfonic acid (SEAr) did not proceed
due to their low electron density on the aromatics. Aliphatic sulfonic
acids, such as camphorsulfonic acid, also did not react with molecu-
lar iodine and mCPBA both in the presence and in the absence of
o-iodobenzoic acid (entry 38). Thus, the present desulfonyloxyio-
dination reaction with molecular iodine and mCPBA both in the
presence and in the absence of o-iodobenzoic acid occurs only in
arenesulfonic acids, particularly those bearing electron-rich
aromatic groups.
iodobenzoic acid (0.1 equiv) in acetonitrile at 50 °C for 8 h under
the same conditions, p-iodotoluene was recovered in high yield
and 1,2-diiodo-4-methylbenzene was not formed at all. Based on
these results and entries 25 and 26, we believe the present reaction
proceeds through the reaction mechanism, shown in Scheme 1.7 In
the absence of o-iodobenzoic acid, the desulfonyloxyiodination
proceeds through path 1. m-Chlorobenzoyl hypoiodite A reacts
with arenesulfonic acids 1 to generate iodoarenes via electrophilic
ipso-substitution by the iodonium species. On the other hand, the
desulfonyloxyiodination of arenesulfonic acids 1 with mCPBA and
molecular iodine in the presence of o-iodobenzoic acid proceeds
through both path 1 and path 2. Thus, both m-chlorobenzoyl
hypoiodite A and o-iodobenzoyl hypoiodite B react with arenesulf-
onic acids 1 to give iodoarenes, and further electrophilic iodination
of the formed iodoarenes with both m-chlorobenzoyl hypoiodite A
and o-iodobenzoyl hypoiodite B occurs to provide polyiodoarenes,
depending on the electron density of the iodoarenes formed.
In conclusion, treatment of p-alkylbenzenesulfonic acids with
mCPBA and molecular iodine gave p-alkyliodobenzenes in good
to moderate yields via electrophilic ipso-substitution by the iodo-
nium species. This desulfonyloxyiodination was promoted by the
addition of a catalytic amount of iodoarenes, such as o-iodobenzoic
acid. Further synthetic study of the present reaction is underway in
this laboratory.
When toluene was treated with I2 (1.2 equiv)/mCPBA
(1.1 equiv)/o-iodobenzoic acid (0.1 equiv) in acetonitrile at 50 °C
for 8 h under the same conditions, a mixture of p-iodotoluene
and o-iodotoluene was obtained only in 2% yield. Moreover, when
p-iodotoluene was treated with I2 (1.2 equiv)/mCPBA (1.1 equiv)/o-
Acknowledgments
The financial support of a Grant-in-Aid for Scientific Research
(No. 20550033) from the Ministry of Education, Science, Sports,
and Culture in Japan and Iodine Research Project in Chiba Univer-
sity is gratefully acknowledged.
I
Cl
(Path 1)
I
OOH
References and notes
R
R
O
(mCPBA)
1. Varvoglis, A. Hypervalent Iodine in Organic Synthesis; Academic Press: San Diego,
1997.
(-mCBA)
A
I2
(-HOI)
2. Reviews: (a) Moriarty, R. M.; Vaid, R. K. Synthesis 1990, 431; (b) Stang, P. J.
Angew. Chem. Int., Ed. Engl. 1992, 31, 274; (c) Prakash, O.; Saini, N.; Sharma, P. K.
Synlett 1994, 221; (d) Kitamura, T. Yuki Gosei Kagaku Kyokaishi 1995, 53, 893;
(e) Stang, P. J.; Zhdankin, V. V. Chem. Rev. 1996, 96, 1123; (f) Umemoto, T. Chem.
Rev. 1996, 96, 1757; (g) Kita, Y.; Takada, T.; Tohma, H. Pure Appl. Chem. 1996, 68,
627; (h) Togo, H.; Hoshina, Y.; Nogami, G.; Yokoyama, M. Yuki Gosei Kagaku
Kyokaishi 1997, 55, 90; (i) Varvoglis, A. Tetrahedron 1997, 53, 1179; (j)
Zhdankin, V. V. Rev. Heteroat. Chem. 1997, 17, 133; (k) Muraki, T.; Togo, H.;
Yokoyama, M. Rev. Heteroat. Chem. 1997, 17, 213; (l) Kitamura, T.; Fujiwara, Y.
Org. Prep. Proced. Int. 1997, 29, 409; (m) Varvoglis, A.; Spyroudis, S. Synlett 1998,
221; (n) Zhdankin, V. V.; Stang, P. J. Tetrahedron 1998, 54, 10927; (o) Moriarty,
R. M.; Prakash, O. Adv. Heterocycl. Chem. 1998, 69, 1; (p) Togo, H.; Katohgi, M.
Synlett 2001, 565; (q) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002, 102, 2523; (r)
Richardson, R. D.; Wirth, T. Angew. Chem., Int. Ed. 2006, 45, 4402; (s) Ladziata,
U.; Zhdankin, V. Synlett 2007, 527.
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Kita, Y. Chem. Commun. 2009, 2073; (c) Uyanik, M.; Ishihara, K. Chem. Commun.
2009, 2086; Papers: (d) Ochiai, M.; Takeuchi, Y.; Katayama, T.; Sueda, T.;
Miyamoto, K. J. Am. Chem. Soc. 2005, 127, 12244; (e) Dohi, T.; Maruyama, A.;
Yoshimura, M.; Morimoto, K.; Tohma, H.; Kita, Y. Angew. Chem., Int. Ed. 2005,
44, 6193; (f) Li, J.; Chan, P. W. H.; Che, C. Org. Lett. 2005, 7, 5801; (g)
Thottumkara, A. P.; Bowsher, M. S.; Vinod, T. K. Org. Lett. 2005, 7, 2933; (h)
Dohi, T.; Maruyama, A.; Minamitsuji, Y.; Takenaga, N.; Kita, Y. Chem. Commun.
2007, 1224; (i) Richardson, R. D.; Page, T. K.; Altermann, S.; Paradine, S. M.;
French, A. N.; Wirth, T. Synlett 2007, 538; (j) Yakura, T.; Konishi, T. Synlett 2007,
765; (k) Sheng, J.; Li, X.; Tang, M.; Gao, B.; Huang, G. Synthesis 2007, 1165; (l)
Chen, C.; Feng, X.; Zhang, G.; Zhao, Q.; Huang, G. Synthesis 2008, 3205; (m)
Uyanik, M.; Akakura, M.; Ishihara, K. J. Am. Chem. Soc. 2009, 131, 251; (n)
Miyamoto, K.; Sei, Y.; Yamaguchi, K.; Ochiai, M. J. Am. Chem. Soc. 2009, 131,
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Chem. Pharm. Bull. 2009, 57, 252.
I
Cl
OI
(-SO 3)
O
A
I
SEAr
+
SO3H
-
SO3
R
R
(-mCBA)
R
1
(Path 2)
I
I
OH
I
O
(-mCBA)
mCPBA
OH
I
B
O
O
I
I2
(-HO I)
R
I
OI
(-SO 3)
O
B
SEAr
I
SO3H
+
-
R
SO3
4. Yamamoto, Y.; Togo, H. Synlett 2005, 2486.
R
1
5. (a) Yamamoto, Y.; Togo, H. Synlett 2006, 798; (b) Yamamoto, Y.; Kawano, Y.;
Toy, P. H.; Togo, H. Tetrahedron 2007, 63, 4680; (c) Akiike, J.; Yamamoto, Y.;
Togo, H. Synlett 2007, 2168; (d) Moroda, A.; Togo, H. Synthesis 2008, 1257; (e)
Scheme 1. Plausible reaction mechanisms.

Y. Suzuki et al. / Tetrahedron Letters 51 (2010) 5950–5953
5953
Ishiwata, Y.; Togo, H. Tetrahedron Lett. 2009, 50, 5354; (f) Kawano, Y.; Togo, H.
Tetrahedron 2009, 65, 6251; (g) Ishiwata, Y.; Togo, H. Tetrahedron 2009, 65,
10720.
d, J = 8.0 Hz), 7.06 (1H, s), 7.66 (1H, d, J = 8.0 Hz); 13C NMR (100 MHz, CDCl3):
d = 20.83, 27.90, 96.98, 128.32, 130.75, 138.06, 138.61, 140.99; MS (APPI): m/z
[M+] calcd for C8H9I: 234.9743; found: 231.9747.
6. Typical procedure for desulfonyloxyiodonation of arenesulfonic acid: Method A: To
a solution of p-toluenesulfonic acid (1.0 mmol), o-iodobenzoic acid (0.1 mmol),
and mCPBA (65% purity, 1.1 mmol) in CH3CN (3 mL) was added I2 (1.2 mmol).
The mixture was stirred for 8 h under dark conditions at 50 °C. Then the
reaction mixture was poured into saturated aq Na2SO3 solution and extracted
with ethyl acetate (15 mL ꢂ 3). The organic layer was dried over Na2SO4. After
removal of the solvent under reduced pressure, the residue was
chromatographed on silica gel (eluent: hexane) to afford pure 4-iodotoluene
in 61% yield.
4-Iodo-1-chlorobenzene: mp 54–55 °C (commercial, mp 53–54 °C). IR (nujol):
2923, 1469, 1377, 1091, 1006, 809 cmꢃ1 1H NMR (400 MHz, CDCl3): d = 7.08
;
(2H, d, J = 8.6 Hz), 7.61 (2H, d, J = 8.6 Hz); 13C NMR (100 MHz, CDCl3): d = 91.13,
130.53, 134.19, 138.77.
1,2-Diiodo-4-methylbenzene: oil. IR (neat): 2916, 1449, 1001, 807 cmꢃ1 1H
;
NMR (400 MHz, CDCl3): d = 2.24 (3H, s), 6.84 (1H, dd, J = 1.4, 8.2 Hz), 7.71 (1H,
d, J = 8.2 Hz), 7.72 (1H, d, J = 1.4 Hz,); 13C NMR (100 MHz, CDCl3): d = 20.46,
103.55, 107.69, 130.34, 138.93, 139.52, 140.05; MS (APPI): m/z [M+] calcd for
C7H6I2: 343.8553; found: 343.8554.
Typical procedure for desulfonyloxyiodonation of arenesulfonic acid: Method B: A
solution of benzenesulfonic acid (1.0 mmol), o-iodobenzoic acid (1.1 mmol),
and mCPBA (65% purity, 1.1 mmol) in CH3CN (3 mL) was stirred for 1.5 h at
room temperature. Then, I2 (1.2 mmol) was added. The obtained mixture was
stirred for 8 h under dark conditions at refluxing conditions. Then the reaction
mixture was poured into saturated aq Na2SO3 solution and extracted with ethyl
acetate (15 mL ꢂ 3). The organic layer was dried over Na2SO4. After removal of
the solvent under reduced pressure, the residue was chromatographed on silica
gel (eluent: hexane) to afford pure iodobenzene in 40% yield.
4-Ethyl-1-iodobenzene: oil. IR (neat): 2964, 1484, 1006, 818 cmꢃ1 1H NMR
;
(400 MHz, CDCl3): d = 1.21 (3H, t, J = 7.7 Hz), 2.59 (2H, q, J = 7.7 Hz), 6.95 (2H, d,
J = 8.2 Hz), 7.59 (2H, d, J = 8.2 Hz); 13C NMR (100 MHz, CDCl3): d = 15.43, 28.39,
90.51, 130.01, 137.28, 143.80; MS (APPI): m/z [M+] calcd for C8H9I1: 231.9743;
found: 231.9743.
4-(20-Bromoethyl)-1-iodobenzene: oil. IR (neat): 2961, 1484, 1007, 803 cmꢃ1 1H
;
NMR (400 MHz, CDCl3): d = 3.10 (2H, t, J = 7.7 Hz), 3.53 (2H, t, J = 7.7 Hz), 6.97
(2H, d, J = 8.2 Hz), 7.64 (2H, d, J = 8.2 Hz); 13C NMR (100 MHz, CDCl3): d = 32.46,
38.67, 92.26, 130.68, 137.64, 138.38; MS (APPI): m/z [M+] calcd for C8H8BrI:
309.8849; found: 309.8848.
4-Iodotoluene: mp 34–35 °C (commercial, mp 33–35 °C). IR (nujol): 2928, 1479,
1012, 796 cmꢃ1
;
1H NMR (400 MHz, CDCl3): d = 2.29 (3H, s), 6.92 (2H, d,
1-Iodonaphthalene: oil (commercial, mp 9 °C). IR (neat): 3051, 1556, 1498
J = 8.2 Hz), 7.56 (2H, d, J = 8.2 Hz); 13C NMR (100 MHz, CDCl3): d = 20.99, 90.17,
cmꢃ1 1H NMR (400 MHz, CDCl3): d = 7.17 (1H, t, J = 7.7 Hz), 7.51 (1H, t,
;
131.17, 137.19, 137.42.
J = 8.2 Hz), 7.57 (1H, t, J = 8.2 Hz), 7.76 (1H, d, J = 7.7 Hz), 7.82 (1H, d, J = 8.2 Hz),
8.02–8.12 (2H, m); 13C NMR (100 MHz, CDCl3): d = 99.57, 126.66, 126.79,
127.65, 128.49, 128.93, 132.06, 134.05, 134.28, 137.36.
Iodobenzene: oil. IR (neat): 729, 684 cmꢃ1 1H NMR (400 MHz, CDCl3): d = 7.11
;
(t, J = 7.7 Hz, 2H), 7.32 (t, J = 7.7 Hz, 1H), 7.70 (d, J = 7.7 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d = 94.38, 127.45, 130.24, 137.47.
1-Iodo-4-octylbenzene: oil. IR (neat): 2925, 1483, 1006, 795 cmꢃ1 1H NMR
;
1,3-Diiodo-2,4,6-trimethylbenzene: mp 79–80 °C (lit.8 82 °C). IR (KBr): 2975,
(400 MHz, CDCl3): d = 7.56 (2H, d, J = 1.21 (3H, t, J = 7.70 Hz), 1.18–1.36 (m,
10H), 1.51–1.61 (m, 2H), 8.2 Hz), 2.52 (2H, t, J = 7.7 Hz), 6.99 (2H, d, J = 8.2 Hz);
13C NMR (100 MHz, CDCl3): d = 14.11, 22.65, 29.18, 29.22, 29.41, 31.28, 31.85,
35.42, 90.49, 130.52, 137.18, 142.46; MS (APPI): m/z [M+] calcd for C14H21I:
316.0682; found: 316.0682.
1440, 1375, 860 cmꢃ1 1H NMR (400 MHz, CDCl3): d = 2.42 (6H, s), 2.92 (3H, s),
.
7.00 (1H, s); 13C NMR (100 MHz, CDCl3): d = 29.88, 39.54, 101.16, 127.89,
141.83, 144.11; MS (APPI): m/z [M+] calcd for C9H10I2: 371.8866; found:
371.8869.
1,3,5-Triiodo-2,4,6-trimethylbenzene: mp 205–206 °C (lit.8 206–207 °C). IR
1-Iodo-4-dodecylbenzene (mixture): oil. IR (neat): 2925, 1483, 1464, 1006,
818 cmꢃ1; MS (APPI): m/z [M+] calcd for C18H29I: 372.1308; found: 372.1314.
1,5-Diiodo-2-methoxybenzene: mp 67.5–68.5 °C (lit.11 mp 68–69 °C); IR (KBr)
(nujol): 1328, 1514, 936, 605 cmꢃ1 1H NMR (400 MHz, CDCl3): d = 3.01 (9H,
.
s); 13C NMR (100 MHz, CDCl3): d = 39.54, 101.16, 144.11; MS (APPI): m/z [M+]
calcd for C9H9I3: 497.7833; found: 497.7837.
2930, 1565, 1470, 1280, 800 cmꢃ1 1H NMR (400 MHz, CDCl3) d = 3.85 (3H, s),
;
1,4-Diiodo-2,5-dimethylbenzene: mp 102–103 °C (lit.9 mp 103–104 °C). IR (KBr):
6.58 (1H, d, J = 8.7 Hz), 7.57 (1H, dd, J = 8.7, 2.0 Hz), 8.04 (1H, d, J = 2.0 Hz); 13
C
2980, 1470, 1330, 880 cmꢃ1
;
1H NMR (400 MHz, CDCl3): d = 2.34 (6H, s), 7.65
NMR (100 MHz, CDCl3): d = 56.41, 83.23, 87.36, 112.75, 138.17, 146.60, 158.14;
(2H, s); 13C NMR (100 MHz, CDCl3): d = 26.85, 100.60, 139.22, 140.61; MS
MS (APPI): m/z [M+] calcd for C7H6OI2: 359.8503; found: 359.8495.
(APPI): m/z [M+] calcd for C8H8I2:357.8710; found: 357.8712.
7.
A referee pointed out that the present reaction proceeds through the
1-Iodo-2,5-dimethylbenzene: oil (lit.8 oil). IR (neat): 2918, 1487, 1034, 808 cmꢃ1
;
desulfonation of arenesulfonic acids to form arenes, followed by iodination of
the arenes formed. However, when p-iodotoluene was treated with I2
(1.2 equiv)/mCPBA (1.1 equiv)/o-iodobenzoic acid (0.1 equiv) in acetonitrile at
50 °C for 8 h under the same conditions, p-iodotoluene was recovered in high
yield and 1,2-diiodo-4-methylbenzene was not formed at all. Based on these
results and entries 25 and 26, we believe the present reaction proceeds through
the reaction mechanism shown in Scheme 1.
1H NMR (400 MHz, CDCl3): d = 2.23 (3H, s), 2.38 (3H, s), 7.04 (1H, d, J = 8.0 Hz),
7.11 (1H, d, J = 8.0 Hz), 7.65 (1H, s); 13C NMR (100 MHz, CDCl3): d = 20.27,
27.48, 101.03, 128.94, 129.34, 137.17, 138.12, 139.29; MS (APPI): m/z [M+]
calcd for C8H9I: 231.9743; found: 231.9746.
1,5-Diiodo-2,4-dimethylbenzene: mp 70–71 °C (lit.10 mp 71–72 °C). IR (KBr)
2980, 1470, 1330, 880 cmꢃ1 1H NMR (400 MHz, CDCl3): d = 2.37 (6H, s), 7.09
;
(1H, s), 8.17 (1H, s); 13C NMR (100 MHz, CDCl3): d = 27.36, 97.79, 130.73,
141.42, 147.09; MS (APPI): m/z [M+] calcd for C8H8I2: 357.8710; found:
357.8713.
8. Kajigaeshi, S.; Kakinami, T.; Moriwaki, M.; Tanaka, T.; Fujisaki, S.; Okamoto, T.
Bull. Chem. Soc. Jpn. 1989, 62, 439.
9. Suzuki, H.; Goto, R. Bull. Chem. Soc. Jpn. 1963, 36, 389.
10. Ogata, Y.; Aoki, K. J. Am. Chem. Soc. 1968, 90, 6187.
11. Kitamura, T.; Abe, T.; Fujiwara, Y.; Yamaji, T. Synthesis 2003, 2, 213.
2,4-Dimethyl-1-iodobenzene: oil (lit.8 oil). IR (neat): 2917, 1490, 1034,
809 cmꢃ1 1H NMR (400 MHz, CDCl3): d = 2.26 (3H, s), 2.38 (3H, s), 6.69 (1H,
;