Enhanced reactivity of [hydroxy(tosyloxy)iodo]benzene in fluoroalcohol media. Efficient direct synthesis of thienyl(aryl)iodonium salts

Article abstract of DOI:10.3390/molecules15031918

In this manuscript, we report clear evidence for the generation of aromatic cation radicals produced by using [hydroxy(tosyloxy)iodo]benzene (HTIB) in fluoroalcohol solvents such as 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). The single-electron-transfer (SET) oxidation ability of HTIB to give cation radicals was first established by ESR and UV measurements. The reaction was broadly applied to various thiophenes, and unique thienyliodonium salts were directly synthesized by this method in excellent yields without the production of any harmful byproducts.

Full text of DOI:10.3390/molecules15031918

Molecules 2010, 15, 1918-1931; doi:10.3390/molecules15031918
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Enhanced Reactivity of [Hydroxy(tosyloxy)iodo]benzene in
Fluoroalcohol Media. Efficient Direct Synthesis of
Thienyl(aryl)iodonium Salts
Motoki Ito 1, Chieko Ogawa 1, Nobutaka Yamaoka 2, Hiromichi Fujioka 1, Toshifumi Dohi 1,2
and Yasuyuki Kita 2,*
1
Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka,
Japan
2
College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga,
Japan
* Author to whom correspondence should be addressed; E-Mail: kita@ph.ritsumei.ac.jp;
Tel.: +81-77-561-5829; Fax: +81-77-561-5829.
Received: 3 February 2010; in revised form: 15 March 2010 / Accepted: 16 March 2010 /
Published: 17 March 2010
Abstract: In this manuscript, we report clear evidence for the generation of
aromatic cation radicals produced by using [hydroxy(tosyloxy)iodo]benzene (HTIB)
in fluoroalcohol solvents such as 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-
2-propanol (HFIP). The single-electron-transfer (SET) oxidation ability of HTIB to give
cation radicals was first established by ESR and UV measurements. The reaction was
broadly applied to various thiophenes, and unique thienyliodonium salts were directly
synthesized by this method in excellent yields without the production of any harmful
byproducts.
Keywords: [hydroxyl(tosyloxy)iodo]benzene; fluoroalcohol solvents; diaryliodonium
salts; thiophenes; single-electron-transfer
1. Introduction
In the last quarter of a century, the chemistry of hypervalent iodine has been extensively studied
due to the increasing importance of greener synthetic processes [1–9]. A number of iodine(III) and
iodine(V) reagents, e.g., phenyliodine(III) diacetate (PIDA), phenyliodine(III) bis(trifluoroacetate)

Molecules 2010, 15
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(PIFA), [hydroxyl(tosyloxy)iodo]benzene (HTIB, Koser’s reagent), iodosobenzene, Dess-Martin
periodinane (DMP), and 2-iodoxybenzoic acid (IBX), have become commercially available and are
routinely used in modern organic synthesis due to their useful oxidizing properties, high stability, and
low toxicity, by which they are recognized as environmentally benign alternatives to highly toxic
heavy metal oxidants including lead (IV), mercury (II), cadmium (IV) and thallium (III) elements.
In our continuing study in the field of hypervalent iodine chemistry [10–24], we have successfully
introduced highly polar, but low nucleophilic fluoroalcohol solvents, that is, CF3CH2OH or
(CF3)2CHOH, for the first time to the hypervalent iodine-mediated oxidative transformation as
stabilizing solvents of the reactive cationic intermediates [25–28]. The oxidations of phenols 1 using
PIDA or PIFA should take place via two-electron transfer processes that involve the initial ligand
exchange of the phenolic oxygens at the iodine centers (Scheme 1). During the successive reductive
elimination step, various functionalized cyclohexadienones 2 would be produced by attack of the
nucleophiles at the para- or ortho-positions of the phenol rings [10–16].
Scheme 1. Phenolic oxidations using hypervalent iodine(III) reagents.
Ph
I
OH
OCOR
O
O
OCOR
I
ligand exchange
OCOR
CF3CH2OH (TFE)
or
(CF3)2CHOH (HFIP)
R'
R'
R'
Nu
R = CH3 (PIDA)
R = CF3 (PIFA)
Nu
PhI
Nu
2
1
Nu = Nucleophiles
For the phenyl ethers, we also discovered the use of PIFA in fluoroalcohol solvents that permitted
novel aromatic substitution by nucleophiles (Scheme 2) [17–20]. Usually, the phenylethers 3 are inert
to the iodine(III) reagents in other typical solvents. We established the formation of aromatic cation
radicals as the key intermediates of the reactions, which were generated by the single-electron-transfer
(SET) oxidation through the charge-transfer (CT)-complex of phenyl ethers 3 and PIFA. This is the
first report that the iodine(III) reagents showed a SET oxidation ability for the oxidations [18]. As the
cation radical intermediates would be effectively stabilized by the fluoroalcohol solvents, the nature of
the solvent was crucial for the success of the reactions, and the use of CH2Cl2 instead of the
fluoroalcohol solvents diminished the yield of the aromatic substitution products 4.
Regarding the reagents for the SET oxidations, only a few iodine(III) reagents are known to date
except for PIFA, PIDA, and iodosobenzene (Figure 1). Based on the analogy with PIFA and HTIB,
Koser et al. proposed in 2006 a SET reaction mechanism for the nucleophilic substitution of certain
polyaromatic hydrocarbons using HTIB in CH2Cl2 [29]. However, there was no clear evidence and
spectroscopic determination of the reactive intermediates in the literature, and thus the SET oxidation
ability of HTIB has not been elucidated until now.

Molecules 2010, 15
Scheme 2. Generation of cation radical intermediates by alternative SET oxidations.
1920
OR
OR
OR
-OCOCF3
+
Nu-
Nu
SET
PIFA
Ph
OCOCF3
I
+
(CF3)2CHOH
(HFIP)
RO
R'
PhI
R'
R'
R'
3
cation radical
4
CT-complex
Nu = N3, OAc, SAr, SCN,
O
O
etc.
Figure 1. Representative hypervalent iodine(III) reagents.
I O
*
*
OCOR
I
OH
I
OCOR
OTs
R = CH3 (PIDA)
R = CF3 (PIFA)
Koser's reagent
(HTIB)
iodosobenzene
Recently, we found a remarkable rate-accelerating effect of the fluoroalcohol solvents for the direct
dehydrative condensation of HTIB with various aromatic compounds, forming the corresponding
diaryliodonium(III) salts as the products and water as waste (Scheme 3) [30]. We now report the
spectroscopic study of the intermediates in the fluoroalcohol solvents to establish the SET oxidation
ability of HTIB. Based on this study, our greener synthetic method of diaryliodonium salts was
successfully applied to the various thiophenes that are sensitive to the SET oxidations [21–24].
Scheme 3. Synthesis of diaryliodonium salts using HTIB in fluoroalcohol solvents.
R
PhI(OH)OTs (1 equiv.)
R
I+Ph
-OTs
H2O
CF3CH2OH
or
only co-product
(CF3)2CHOH
R = alkyl, alkoxy etc.
(62-99%)
r. t.
2. Results and Discussion
2.1. Generation of aromatic cation radicals of phenyl ethers by HTIB
We first examined the reaction of 1,4-dimethoxybenzene and HTIB in (CF3)2CHOH. The
transparent solution of 1,4-dimethoxybenzene immediately changed to a green color with the addition
of HTIB, and the disappearance of the starting material was confirmed by analytical TLC. We assumed
that this observation implied the generation of a cation radical intermediate [18], and thus attempted to

Molecules 2010, 15
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detect the intermediate by UV-VIS spectroscopic measurement. The spectrum showed a typical strong
absorption band in the visible region between 400 and 500 nm, which shows good agreement with the
reported value of the aromatic cation radical (A) (Figure 2, left) [18]. Furthermore, the radical species
was detected by the ESR spectroscopic measurement, supporting the SET oxidation processes
(Figure 2, right). Under the conditions, various diaryliodonium(III) salts were obtained from phenyl
ethers and HTIB [30].
Figure 2. UV-VIS and ESR spectrums for the mixture of 1,4-dimethoxybenzene and HTIB
in (CF3)2CHOH at room temperature.
MeO
OMe
g = 2.0035
(A)
cation radical
333 334 335 336 337 338 (mT)
300
400
wavelength
500
600
700
(nm)
2.2. Application to the synthesis of thienyliodonium(III) salts
We next intended to apply this SET oxidation process for the synthesis of various thienyliodonium
salts. The iodonium salts having thienyl moieties show a wide range of applicability as photoacid
generator (PAG) for cationic polymerization [31], active bacteriocide [32,33], organic non-linear optic
material [34], precursor of fluorinated aromatic compounds [35,36], etc. Very recently, we developed a
novel metal-free oxidative cross-biaryl-coupling method of heteroaromatic compounds, in which
thienyliodonium salts were involved as the key intermediates [37]. For their synthesis, the direct
syntheses of the salts from thiophenes and activated iodine(III) reagents or HTIB were typically
achieved for a limited number of substrates in moderate yields [38–42].
Therefore, we examined the reaction of 3-methylthiophene (5a) and HTIB in CF3CH2OH. The
reaction completely finished in a short time at room temperature and the thienyliodonium salt 6a was
isolated in an excellent yield after the purification by precipitation, while bithiophene was not found in
this system because of the absence of Lewis acids that cause biaryl coupling reactions, such as
BF3·Et2O and TMSOTf [22]. Other solvents, such as CH2Cl2, MeOH, and CH3CN, provided poorer
results under the same reaction conditions (16%, 46%, and 23% yields, respectively). In the UV/VIS
measurement, the spectrum of the reaction mixture between 500 and 600 nm of wavelength is in
accordance with the absorption band of cation radical species (B) from the thiophene (Figure 3) [43].

Molecules 2010, 15
Figure 3. UV-VIS spectrum of the reaction of 3-methylthiophene (5a) using HTIB in
1922
CF3CH2OH. (The reaction was performed using an equimolar amount of thiophene 5a and
HTIB in CF3CH2OH (0.20M) at room temperature.)
PhI(OH)OTs
(1 equiv.)
I+Ph
S
CF3CH2OH
r. t.
-OTs
S
5a
6a-OTs
98%
SET
S
(B)
cation radical
PhI(OH)OTs
300
400
500
600
700
(nm)
Wavelength
This activating protocol of HTIB provided a facile access to a wide range of thienyliodonium salts 6
as shown in Table 1. The condensation preferentially occurred at the -position of the sulfur atoms in
the thiophene rings 5a-d that are sensitive to the SET oxidations [21,22], among which the 2-positions
of the cation radicals are known to be more reactive than the 5-positions (Entries 1–4) [23,24]. 3-
Methoxythiophene (5e) was smoothly converted to the corresponding thienyliodonium salt 6e in
excellent yield (Entry 5). This is surprising because oxidative transformation of highly electron-rich
alkoxythiophenes is limited owing to difficulty in suppressing uncontrollable polymerizations [44].
Even the substrates 5f-h containing halogen, aryl, and ester groups, were converted to products in
good yields with complete regioselectivity (Entries 6–8). Furthermore, 3,4-ethylenedioxythiophene
(EDOT) (5j), which attracted attention due to its unique electronic characteristics, was readily
functionalized (Entries 10 and 11), and the obtained diaryliodonium salt 6j has significant prospects as
an organic non-linear optic material [34]. For the -disubstituted thiophene 5l, on the other hand, the
-thienyl iodonium salt 6l was obtained (Entry 12). A unique selectivity was observed for the
organosilicon compound 5m. For the competitive reaction of the C-H and C-Si bonds in 3-
trimethylsilylthiophene (5m), an ipso-substitution product at the silicon-bound carbon as a result of
electrophilic substitution via the Wheland type of -complex [38–40] was not obtained, but instead
produced a dehydrative condensation product 6m (Entry 13). No ipso-substitution product was
obtained for the -silyl substituted thiophene 5n, while the condensation product 6n and a small
amount of the regioisomer were obtained (Entry 14).
A significant number of Koser’s-type reagents are now readily available [45–48], and variation of
the reagents in the reactions could expand the structural diversity of the obtained product. Selected
examples are shown in Scheme 4. Thienyliodonium salts having different aryl rings and counterions, X,
were obtained in excellent yields from a single thiophene substrate 5a and the reagents, ArI(OH)X. As
mentioned above, the present direct and waste-free approach based on the cation radical strategy has a
broad range of versatility for the synthesis of various heteroaromatic diaryliodonium salts with a
unique selectivity not seen in other synthetic methods.

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Table 1. Scope of thiophene substrates.a
Entry
Thiophene
Thienyliodonium salt
Yield (%)b
R
R
I+Ph
S
S
-OTs
6a-OTs
6b-OTs
6c-OTs
6d-OTs
6e-OTs
6f-OTs
6g-OTs
6h-OTs
1
2
3
4
5
6
7
8
R = Me (5a)
R = Hexyl (5b)
R = i-Buyl (5c)
R = c-Hex (5d)
R = OMe (5e)
98
84
93
74
89
95
88
98
R = Br (5f)
R = Ph (5g)
R = 4-MeO2CC6H4 (5h)
I+Ph
S
S
-OTs
9
93
(5i)
(6i-OTs)
O
O
O
O
94
I+Ph
10
S
S
-OTs
(5j)
(6j-OTs)
O
O
O
O
88
62
I+Ph
11
MeO2C
MeO2C
S
S
-OTs
(5k)
(6k-OTs)
I+Ph
-OTs
S
12
13
S
(5l)
(6l-OTs)
TMS
TMS
I+Ph
-OTs
71
S
S
(5m)
(6m-OTs)
I+Ph
-OTs
TMS
91c
TMS
S
S
14
(5n)
(6n-OTs)
a
Reactions were performed using equimolar amounts of the thiophenes 5 and PhI(OH)OTs in
b
CF3CH2OH (0.20M) for 3 h at room temperature;
precipitation; c Small amount of regioisomer was included.
Isolated yield of pure products after

Molecules 2010, 15
Scheme 4. Use of several Koser’s-type reagents. (Reactions were performed using an
1924
equimolar amount of 3-methylthiophene (5a) and ArI(OH)X in CF3CH2OH (0.20M) at
room temperature. a) Ms = methanesulfonyl. b) Cs = (+)-10-camphorsulfonyl.)
Ar
X
mesityl
C6F5
7a-OTs (78%)
8a-OTs (70%)
6a-OMs (89%)
6a-OCs (92%)
OTs
ArI(OH)X
OTs
I+Ar
X-
S
S
CF3CH2OH
r. t. 3 h
Ph
Ph
OMsa)
OCsb)
5a
3. Conclusions
In conclusion, we performed a detailed study of the enhanced reactivity of [hydroxy(tosyloxy)iodo]
benzene (HTIB) in fluoroalcohol media, resulting in the first establishment of the SET oxidation
ability of HTIB by successive spectroscopic detection of the aromatic cation radicals. The use of the
activation protocol of HTIB by fluoroalcohol solvents led to the efficient synthesis of diaryliodonium
salts from electron-rich heteroaromatic compounds represented by the thiophenes. This facile and
clean preparative method of diaryliodonium salts would expand the possibility of heteroaromatic
compounds as a unique aryl source in the field of organic synthesis.
4. Experimental
Melting points (mp) are uncorrected. The 1H-NMR and 13C-NMR spectra were recorded by a JEOL
13
JMN-300 or JMN-400 spectrometers operating at 300 or 400 MHz (75.3 or 100.53 MHz for C-
NMR) in CDCl3 or CD3OD at 25 °C with tetramethylsilane as the internal standard. The data are
reported as follows: chemical shift in part par million (), multiplicity (s = singlet, d = doublet,
t = triplet, q = quartet, br = broad singlet, m = multiplet), integration, and coupling constant (Hz). The
infrared spectra (IR) were obtained using a Hitachi 270-50 spectrometer. The mass spectra were
obtained using a Shimadzu GCMS-QP 5000 instrument with ionization voltages of 70 eV. The high
resolution mass spectra and elemental analysis were performed by the Elemental Analysis Section of
Osaka University. ESR spectra were taken on JEOL JES-RE 1X spectrometer. PhI(OH)OTs (HTIB,
Koser’s reagent) is a commercially available compound and was used as received. Thiophene 5h was
prepared by Suzuki coupling of 3-thiophene-boronic acid with methyl 4-iodobenzoate [49]. Solvents
and all other starting materials were obtained from commercial suppliers and used without further
purification.
4.1. Measurement of UV-VIS absorption spectrum
To a stirred solution of 1,4-dimethoxybenzene (1.4 mg, 1.0 × 10-2 mmol) in (CF3)2CHOH (5 mL)
was added HTIB (3.9 mg, 1.0 × 10-2 mmol) in one portion at room temperature under air. The UV-VIS
absorption spectrum of the reaction mixture was measured on Shimadzu 2200 UV-VIS spectrometer.

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4.2. Measurement of electron spin resonance spectrum
Under air at room temperature, to a stirred solution of 6a (2.0 mg, 2.0 × 10-2 mmol) in CF3CH2OH
(2 mL) was added HTIB (7.8 mg, 2.0 × 10-2 mmol) in one portion, and the mixture was inserted into
the ESR cavity. The spectrum was recorded at room temperature on a JEOL JES-RE 1X spectrometer.
Instrument conditions were as follows: magnetic field, 336 ± 5 mT; modulation frequency, 0.05 mT;
modulation amplitude, 100 kHz; output power, 1.4 mW; time constant, 0.1 sec; sweep time, 1 min/10
mT; amplitude, 32.
4.3. General procedure for the preparation of diaryliodonium salts
To a stirred solution of 5a (98 mg, 1 mmol) in CF3CH2OH (5 mL), [hydroxyl(tosyloxy)iodo]
benzene (392 mg, 1 mmol) was added in one portion at room temperature under air, and it was stirred
for 3 h. MeOH was then added to the reaction mixture when the solvents were removed under vacuum.
The resulting oily crude product 6a-OTs was precipitated by adding Et2O with stirring. The precipitate
was collected and dried in vacuo to give 6a-OTs (396 mg, 84%) as a slightly gray powder.
(3-Methyl-2-thienyl)(phenyl)iodonium tosylate (6a-OTs) [30,39]. A slightly gray solid, mp 165 °C. IR
(KBr) cm-1: 3051, 1575, 1469, 1440, 1377, 1191, 1132, 1045, 1014, 991, 815, 746, 680. 1H-NMR (300
MHz, CD3OD)  2.33 (s, 3H), 2.49 (s, 3H), 7.03 (d, 1H, J = 5.1 Hz), 7.19 (d, 2H, J = 7.2 Hz), 7.46-
13
7.49 (m, 2H), 7.59-7.67(m, 3H), 7.83 (d, 1H, J = 5.1 Hz,), 8.05 (d, 2H, J = 7.8 Hz) ppm. C-NMR
(75.5 MHz, CD3OD) 17.5, 21.3, 98.4, 118.4, 126.9, 129.8, 131.0, 133.0, 133.1, 133.4, 135.4, 137.7,
141.6, 150.0 ppm.
(3-Hexyl-2-thienyl)(phenyl)iodonium tosylate (6b-OTs). A colorless solid, mp 145-146 °C. IR (KBr)
cm-1: 3047, 2931, 1525, 1454, 1437, 1381, 1192, 1132, 1045, 1014, 910, 815, 732, 696. 1H-NMR (300
MHz, CD3OD) 0.84 (t, 3H, J = 5,4 Hz), 1.16-1.24 (m, 6H), 1.42-1.46 (m, 2H), 2.32 (s, 3H), 2.72 (t,
2H, J = 6.3 Hz), 6.94 (d, 1H, J = 4.2 Hz), 7.07 (d, 2H, J = 8.4 Hz), 7.33 (t, 2H, J = 7.8 Hz), 7.47 (t, 1H,
J = 7.8 Hz), 7.56 (d, 2H, J = 7.8 Hz), 7.63 (d, 1H, J = 4.2 Hz), 7.87 (d, 2H, J = 8.4 Hz) ppm. 13C-NMR
(75.5 MHz, CD3OD) 14.0, 21.3, 22.4, 28.9, 30.3, 31.5, 31.9, 97.5, 118.6, 126.0, 128.5, 128.8, 131.3,
131.6, 133.3, 136.1, 139.6, 142.2, 153.4 ppm. HRMS (FAB): Calcd for C13H12IO [M-OTs]+: 371.0330,
found 371.0339.
(3-Isobutyl-2-thienyl)(phenyl)iodonium tosylate (6c-OTs). Colorless amorphous. IR (KBr) cm-1: 3045,
1
2951, 1464, 1438, 1384, 1190, 1132, 1045, 912, 815, 731, 696. H-NMR (400 MHz, CDCl3) 0.84
(d, 6H, J = 4.8 Hz), 1.86 (m, 1H), 2.33 (s, 3H), 2.62 (d, 2H, J = 4.8 Hz), 6.96 (d, 1H, J = 5.6 Hz), 7.11
(d, 2H, J = 8.4 Hz), 7.36 (t, 2H, J = 8.0 Hz), 7.49 (t, 1H, J = 8.0 Hz), 7.63 (d, 2H, J = 8.0 Hz), 7.68
13
(1H, J = 5.6 Hz), 7.89 (d, 2H, J = 8.4 Hz) ppm. C-NMR (100.53 MHz, CDCl3)  21.3, 22.2, 29.8,
40.6, 97.5, 118.6, 126.0, 128.7, 129.4, 131.6, 131.8, 133.2, 136.4, 140.0, 141.8, 152.8 ppm. HRMS
(FAB) Calcd for C14H16IS [M-OTs]+ 343.0017, found 343.0015.
(3-Cyclohexyl-2-thienyl)(phenyl)iodonium tosylate (6d-OTs). A colorless solid, mp 128–130 °C
(ether). IR (KBr) cm-1: 3053, 2926, 2850, 1564, 1469, 1440, 1190, 1132, 1045, 991, 914, 815, 732.

Molecules 2010, 15
1926
1H-NMR (400 MHz, CDCl3)  1.22-1.77 (m, 10H), 2.33 (s, 3H), 2.76 (m, 1H), 6.97 (d, 1H,
J = 5.6 Hz), 7.09 (d, 2H, J = 8.0 Hz), 7.35 (t, 2H, J = 8.0 Hz), 7.48 (t, 1H, J = 8.0 Hz), 7.61 (d, 2H,
J = 8.0 Hz), 7.68 (d, 1H, J = 5.6 Hz), 7.88 (d, 2H, J = 8.0 Hz) ppm. 13C-NMR (100.53 MHz, CDCl3)
21.3, 25.6, 26.1, 34.1, 42.0, 96.4, 118.9, 126.0, 127.0, 128.7, 131.5, 131.8, 133.3, 136.6, 139.9, 141.9,
158.4 ppm. HRMS (FAB): Calcd for C16H18IS [M-OTs]+: 369.0174, found 369.0165
(3-Methoxy-2-thienyl)(phenyl)iodonium tosylate (6e-OTs). A blue solid, mp 49 °C. IR (KBr) cm-1:
3014, 1554, 1471, 1379, 1217, 1132, 1070, 1043, 1014, 771, 694. 1H-NMR (300 MHz, CD3OD) 2.35
(s, 3H), 4.02 (s, 3H), 7.08 (d, 1H, J = 6.0 Hz), 7.21 (d, 2H, J = 7.8 Hz), 7.46-7.51 (m, 2H), 7.61-7.69
13
(m, 3H), 7.97 (d, 1H, J = 6.0 Hz), 8.03 (d, 2H, J = 7.8 Hz) ppm. C-NMR (75.5 MHz, CD3OD)
21.3, 60.4, 77.4, 116.5, 118.7, 126.9, 129.8, 133.0, 133.4, 135.5, 138.7, 141.6, 143.6, 165.1 ppm.
HRMS (FAB): Calcd for C11H10IOS [M-OTs]+: 316.9497, found 316.9504.
(3-Bromo-2-thienyl)(phenyl)iodonium tosylate (6f-OTs). A colorless solid, mp 49 °C. IR (KBr) cm-1:
3045, 1562, 1469, 1438, 1373, 1330, 1191, 1130, 1043, 1014, 860, 815, 740, 692. 1H-NMR (300 MHz,
CD3OD) 2.35 (s, 3H), 7.19-7.24 (m, 3H), 7.53 (t, 2H, J = 7.8 Hz), 7.67 (d, 3H, J = 7.8 Hz), 7.98
(d, 1H, J = 5.7 Hz), 8.16 (d, 2H, J = 7.8 Hz) ppm. 13C-NMR (75.5 MHz, CD3OD) 21.3, 119.2, 125.6,
126.9, 129.8, 132.1, 133.2, 133.9, 135.9, 139.8, 141.4, 141.7, 143.5 ppm. HRMS (FAB): Calcd for
C10H7BrIS [M-OTs]+: 364.8497, found 364.8501.
(3-Phenyl-2-thienyl)(phenyl)iodonium tosylate (6g-OTs) [30]. A colorless solid, mp 122–123 °C. IR
(KBr) cm-1: 3053, 1485, 1469, 1440, 1265, 1197, 1132, 1045, 1014, 991, 815, 748, 696. 1H-NMR (300
MHz, CD3OD):  2.31 (s, 3H), 7.12-7.24 (m, 3H), 7.31 (t, 2H, J = 7.5 Hz), 7.37-7.47 (m, 2H), 7.48-
7.62 (m, 6H), 7.65 (d, 2H, J = 7.8 Hz), 8.00 (d, 1H, J = 5.1 Hz) ppm. 13C-NMR (75.5 MHz, CD3OD)
21.3, 98.7, 118.7, 126.9, 129.8, 130.2, 130.4, 130.5, 132.7, 133.3, 135.2, 135.6, 138.5, 141.6, 143.3,
153.2 ppm. HRMS (FAB): Calcd for C16H12IS [M-OTs]+: 362.9704, found 362.9702.
[3-(4-Methoxycarbonyl)phenyl-2-thienyl](phenyl)iodonium tosylate (6h-OTs). A slightly yellow solid,
mp 126–128 °C (ether). IR (KBr) cm-1: 3051, 1722, 1608, 1438, 1280, 1188, 1116, 1045, 1016, 912,
1
734. H-NMR (400 MHz, CDCl3)  2.30 (s, 3H), 3.98 (s, 3H), 7.03 (d, 2H, J = 7.6 Hz), 7.09 (d, 1H,
J = 5.6 Hz), 7.18 (t, 2H, J = 7.6 Hz), 7.39 (t, 1H, J = 7.6 Hz), 7.49 (m, 6H), 7.72 (d, 1H, J = 5.6 Hz),
8.08 (d, 2H, J = 7.6 Hz) ppm. 13C-NMR (100.53 MHz, CDCl3) 21.3, 52.3, 99.7, 118.9, 120.1, 126.0,
128.6, 129.2, 130.2, 130.5, 131.3, 131.4, 133.9, 136.3, 138.7, 140.1, 141.4, 150.4, 166.5 ppm. HRMS
(FAB): Calcd for C18H14IO2S [M-OTs]+: 420.9759, found 420.9778.
(5-Methyl-2-thienyl)(phenyl)iodonium tosylate (6i-OTs). A brown solid, mp 89–92 °C (ether). IR
1
(KBr) cm-1: 3053, 1440, 1193, 1128, 1039, 1012, 817, 792, 738, 680 H-NMR (400 MHz, CDCl3)
 2.30 (s, 3H), 2.51 (s, 3H), 6.65 (d, 1H, J = 3.6 Hz), 7.05 (d, 2H, J = 8.4 Hz), 7.30 (t, 2H, J = 8.0 Hz),
7.46 (t, 1H, J = 8.0 Hz), 7.54 (d, 2H, J = 8.4 Hz), 7.64 (d, 1H, J = 3.6 Hz), 7.93 (d, 2H, J = 8.0 Hz)
13
ppm. C- NMR (100.53 MHz, CDCl3)  15.4, 21.3, 93.5, 118.3, 126.0, 128.1, 128.7, 131.5, 131.6,
134.0, 140.3, 140.9, 141.7, 152.2 ppm. HRMS (FAB): Calcd for C11H10S [M-OTs]+: 300.9548, found
300.9548.

Molecules 2010, 15
1927
(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)(phenyl)iodonium tosylate (6j-OTs). A blue solid,
1
mp 48–49 °C. IR (KBr) cm-1: 2943, 1485, 1359, 1188, 1132, 1062, 1045, 1014, 750, 694. H-NMR
(300 MHz, CDCl3)  2.33 (s, 3H), 4.18-4.22 (m, 2H), 4.27-4.32 (m, 2H), 6.77 (s, 1H), 7.09 (d, 2H,
J = 8.4Hz), 7.35 (t, 2H, J = 7.8 Hz), 7.49 (t, 1H, J = 7.8 Hz), 7.59 (d, 2H, J = 7.8 Hz), 7.96 (d, 2H,
13
J = 8.4 Hz) ppm. C-NMR (75.5 MHz, CD3OD) 21.3, 64.4, 65.6, 74.1, 111.4, 119.3, 126.0, 128.6,
131.4, 131.6, 133.7, 139.7, 141.3, 142.1, 148.0 ppm. HRMS (FAB): Calcd for C12H10IO2S [M-OTs]+:
344.9446, found 344.9450.
(7-Methoxycarbonyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)(phenyl)iodonium tosylate (6k-OTs).
A colorless solid, mp 169 °C (ether). IR (KBr) cm-1: 3520, 3051, 2949, 1712, 1573, 1487, 1444, 1359,
1
1274, 1193, 1089, 912, 740. H-NMR (400 MHz, CDCl3) 2.31 (s, 3H), 3.83 (s, 3H), 4.28-4.32 (m,
4H), 7.02 (d, 2H, J = 7.6 Hz), 7.32 (t, 2H, J = 7.6 Hz), 7.45 (m, 3H), 7.96 (d, 2H, J = 7.6 Hz) ppm.
13C- NMR (100.53 MHz, CDCl3) 21.2, 52.2, 65.0, 65.1, 83.8, 99.9, 116.0, 118.6, 125.8, 128.4, 131.4,
134.5, 139.7, 141.9, 144.1, 146.4, 160.2 ppm. HRMS (FAB): Calcd for C14H12IO4S [M-OTs]+:
402.9501, found 402.9508.
(2,5-Dimethyl-3-thienyl)(phenyl)iodonium tosylate (6l-OTs). A colorless solid, mp 111–112 °C (ether).
1
IR (KBr) cm-1: 3539, 3047, 2918, 1562, 1469, 1193, 1132, 1045, 912, 815, 740. H-NMR (400 MHz,
CDCl3)2.31 (s, 3H), 2.36 (s, 3H), 2.52 (s, 3H), 6.87 (s, 1H), 7.04 (d, 2H, J = 8.0 Hz), 7.31 (t, 2H,
J = 7.6 Hz), 7.44 (t, 1H, J = 7.6 Hz), 7.50 (d, 2H, J = 8.0 Hz), 7.84 (d, 2H, J = 7.6 Hz) ppm. 13C-NMR
(100.53 MHz, CDCl3) 15.2, 17.0, 21.2, 99.6, 115.9, 125.9, 128.4, 129.5, 131.0, 131.4, 133.9, 139.3,
141.2, 142.6, 145.5 ppm. HRMS (FAB): Calcd for C12H12IS [M-OTs]+: 314. 9704, found 314. 9703.
Phenyl(4-trimethylsilyl-2-thienyl)iodonium tolsylate (6m-OTs). A colorless solid, mp 121 °C. IR
(KBr) cm-1: 3051, 2954, 1566, 1469, 1440, 1253, 1199, 1132, 1103, 1043, 1014, 991, 883, 842, 750,
1
680. H-NMR (300 MHz, CDCl3) 0.32 (s, 9H), 2.40 (s, 3H), 7.26 (d, 2H, J = 7.8 Hz), 7.54 (t, 2H,
13
J = 7.5 Hz), 7.67-7.74 (m, 3H), 7.99 (s, 1H), 8.11 (s, 1H), 8.19 (d, 2H, J = 7.8 Hz) ppm. C-NMR
(75.5 MHz, CD3OD) -0.59, 21.6, 119.1, 127.2, 130.1, 133.4, 133.9, 136.1, 136.4, 141.9, 143.8,
144.4, 146.5, 147.0 ppm. HRMS (FAB): Calcd for C13H16ISSi [M+H]+: 358.9781, found 358.9792.
Phenyl(5-trimethylsilyl-2-thienyl)iodonium tolsylate (6n-OTs, including a small amount of
regioisomer). A colorless solid. IR (KBr) cm-1: 3055, 2955, 1494, 1469, 1440, 1392, 1195, 1120, 1045,
1
1008, 985, 842, 738, 680. H-NMR (300 MHz, CD3OD) 0.37 (s, 9H), 2.40 (s, 3H), 7.25 (d, 2H,
J = 7.8 Hz), 7.34 (d, 1H, J = 3.3 Hz), 7.56 (t, 2H, J = 7.5 Hz), 7.69-7.74 (m, 3H), 8.04 (d, 1H, J = 3.3
Hz), 8.20 (d, 2H, J = 7.8 Hz) ppm. 13C-NMR (75.5 MHz, CD3OD) 0.43, 22.1, 103.5, 119.9, 127.8,
130.7, 134.0, 134.6, 136.7, 138.3, 142.5, 143.7, 144.4, 156.5 ppm.
(3-Methyl-2-thienyl)(2,4,6-trimethylphenyl)iodonium tosylate (7a-OTs). A colorless solid, mp 145 °C
(ether). IR (KBr) cm-1: 3637, 3466, 3061, 2953, 1923, 1600, 1450, 1377, 1300, 1215, 1132, 1043, 815,
758. 1H-NMR (300 MHz, CDCl3) 2.27 (s, 3H), 2.30 (s, 3H), 2.47 (s, 3H), 2.67 (s, 6H), 6.84 (d, 1H,
J = 5.4 Hz), 6.93 (s, 2H), 7.00 (d, 2H, J = 7.8 Hz), 7.40 (d, 2H, J = 7.8 Hz), 7.48 (d, 1H, J = 5.4 Hz)
13
ppm. C-NMR (75.3 MHz, CDCl3) 17.7, 20.9, 21.2, 27.1, 96.9, 125.8, 126.4, 128.3, 129.6, 129.7,

Molecules 2010, 15
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134.3, 139.2, 141.2, 142.3, 143.1, 147.2 ppm. HRMS (FAB): Calcd for C14H16IS [M-OTs]+: 343.0017,
found 343.0026.
(3-Methyl-2-thienyl)(pentafluorophenyl)iodonium tosylate (8a-OTs). A colorless solid, mp
140–141 °C. (ether). IR (KBr) cm-1: 3091, 1633, 1487, 1390, 1195, 1078, 974, 908, 815, 756, 696. 1H-
NMR (300 MHz, CDCl3) 2.35 (s, 3H), 2.49 (s, 3H), 6.81 (d, 1H, J = 5.4 Hz), 7.08 (d, 2H, J = 7.8 Hz),
13
7.37 (d, 2H, J = 7.8 Hz), 7.46 (d, 1H, J = 5.4 Hz) ppm. C-NMR (75.3 MHz, CDCl3) 17.5, 21.2,
93.7, 100.0, 125.7, 128.6, 129.4, 135.5, 138.0, 140.4, 140.6, 144.3, 146.8, 149.1 ppm. HRMS (FAB):
Calcd for C11H5 F5IS [M-OTs]+: 390. 9077, found 390.9095.
(3-Methyl-2-thienyl)(phenyl)iodonium methanesulfonate (6a-OMs). A colorless solid, mp 144 °C
(ether). IR (KBr) cm-1: 3047, 1562, 1525, 1469, 1440, 1377, 1327, 1222, 1053, 991, 912, 825, 785, 742.
1H-NMR (300 MHz, CDCl3) 2.51 (s, 3H), 2.52 (s, 3H), 6.97 (d, 1H, J = 5.1 Hz), 7.40 (t, 2H,
J = 7.5 Hz), 7.51 (t, 1H, J = 7.5 Hz), 7.62 (d, 1H, J = 5.1 Hz), 7.94 (d, 2H, J = 7.5 Hz) ppm. 13C-NMR
(75.3 MHz, CDCl3)  17.5, 39.0, 98.3, 1178.0, 129.8, 131.3, 131.5, 133.6, 135.7, 148.4 ppm. HRMS
(FAB): Calcd for C11H10IS [M-OMs]+: 300.9548, found 300.9550.
(3-Methyl-2-thienyl)(pheny)iodonium (+)-10-camphorsulfonate (6a-OCs). A colorless solid, mp
1
145 °C (ether). IR (KBr) cm-1: 3458, 2956, 1732, 1562, 1469, 1373, 1192, 1051, 918, 732. H-NMR
(400 MHz, CDCl3) 0.77 (s, 3 H), 1.01 (s, 3H), 1.26-1.32 (m, 1H), 1.52-1.59 (m, 1H), 1.83 (d, 1H,
J = 18.4 Hz), 1.89-2.00 (m, 2H), 2.25-2.32 (m, 1H), 2.51 (s, 3H), 2.54-2.62 (m, 1H), 2.68 (d, 1H,
J = 14.8 Hz), 3.21 (d, 1H, J = 14.8 Hz), 6.98 (d, 1H, J = 5.2 Hz), 7.40 (t, 2H, J = 8.0 Hz), 7.50 (t, 1H,
J = 8.0 Hz), 7.63 (d, 1H, J = 5.2 Hz), 7.96 (d, 2H, J = 8.0 Hz) ppm. 13C-NMR (100.53 MHz, CDCl3)
17.5, 19.7, 19.9, 24.3, 27.0, 42.6, 42.8, 47.2, 47.7, 58.5, 98.3, 118.6, 130.0, 131.3, 131.6, 133.6, 135.7,
148.7, 217.0 ppm. HRMS (FAB): Calcd for C11H10IS [M-OCs]+: 300.9548, found 300.9570.
Acknowledgments
This work was partially supported by Grant-in-Aid for Scientific Research (A) from the Japan
Society for the Promotion of Science (JSPS), Young Scientists (B) from the Ministry of Education,
Culture, Sports, Science and Technology (MEXT), and Ritsumeikan Global Innovation Research
Organization (R-GIRO) project. T.D. also acknowledges support from the Industrial Technology
Research Grant Program from the New Energy and Industrial Technology Development Organization
(NEDO) of Japan. M.I. thanks the research fellowship of JSPS for Young Scientists.
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