Photochromic reaction behavior and thermal stability of thiophene-S,S-dioxidized diarylethenes having a benzofuryl group

Article abstract of DOI:10.1016/j.tet.2016.03.062

Diarylethenes having a benzofuryl group and their thiophene-S,S-dioxidized diarylethenes were synthesized and their optical properties and thermal stability were investigated. Upon oxidation of the thiophene ring, the optical properties such as absorption

Full text of DOI:10.1016/j.tet.2016.03.062

Accepted Manuscript
Photochromic reaction behavior and thermal stability of thiophene-S,S-dioxidized
diarylethenes having a benzofuryl group
Koki Tanaka, Daichi Kitagawa, Seiya Kobatake
PII:
S0040-4020(16)30191-0
10.1016/j.tet.2016.03.062
TET 27602
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 11 February 2016
Revised Date: 15 March 2016
Accepted Date: 17 March 2016
Please cite this article as: Tanaka K, Kitagawa D, Kobatake S, Photochromic reaction behavior and
thermal stability of thiophene-S,S-dioxidized diarylethenes having a benzofuryl group, Tetrahedron
(2016), doi: 10.1016/j.tet.2016.03.062.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
Photochromic reaction behavior and thermal
stability of thiophene-S,S-dioxidized
Leave this area blank for abstract info.
diarylethenes having a benzofuryl group
Koki Tanaka, Daichi Kitagawa, Seiya Kobatake*
Department of Applied Chemistry, Graduate School of Engineering, Osaka City University,
3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
UV
Vis.
+ SO2
+ SO2

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Photochromic reaction behavior and thermal stability of thiophene-S,S-dioxidized
diarylethenes having a benzofuryl group
Koki Tanaka, Daichi Kitagawa, Seiya Kobatake*
Department of Applied Chemistry, Graduate School of Engineering, Osaka City University,
3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
Corresponding author. Tel. & fax: +81-6-6605-2797; e-mail: kobatake@a-chem.eng.osaka-cu.ac.jp
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Diarylethenes having a benzofuryl group and their thiophene-S,S-dioxidized diarylethenes were
synthesized and their optical properties and thermal stability were investigated. Upon oxidation
of the thiophene ring, the optical properties such as absorption maxima, photocycloreversion
quantum yields, and conversion from the open-ring isomer to the closed-ring isomer have
changed. On the other hand, the thermal stability of the closed-ring isomers of the S,S-dioxidized
diarylethenes is significantly higher than those of thiophene-S,S-dioxidized diarylethenes having
a phenylthienyl group instead of a benzofuryl group. The high thermal stability of the closed-
ring isomer was quantitatively discussed based on ground state energies obtained by quantum
chemical calculations.
Available online
Keywords:
Photochromism
Diarylethene
Thermal reaction
DFT calculation
2009 Elsevier Ltd. All rights reserved
.
1. Introduction
thiophene-S,S-dioxidized diarylethenes with secondary alkyl
substituents at the reactive positions were found to undergo
thermal bleaching reactions to produce byproducts. The rate of
the thermal bleaching reactions can be controlled by the
bulkiness of the substituent at the reactive positions and the
introduction of methyl groups at the 4-position of the thiophene
rings. Such materials can be used in application such as light-
starting irreversible thermosensors. Thus, the investigation of
novel oxidized diarylethenes is of great interest for making new
functional photochromic materials.
A lot of photochromic compounds have been so far
synthesized and investigated because they have a potential for
use in application such as ophthalmic lenses,1 optical memories,2
photooptical switches,3 displays,4 nonlinear optics,5 and
photoresponsive actuators.6 Especially, diarylethene derivatives
are one of the representative photochromic compounds and can
modulate physicochemical properties such as conductivity,
dielectric constant, refractive index, and fluorescence according
to photochromic reactions.7,8 Furthermore, in recent studies,
thiophene oxidized diarylethenes have attracted much attention
because they have different properties from non-oxidized
diarylethenes. For example, Kim and Ahn and coworkers have
reported that while non-oxidized diarylethenes show no
fluorescence at room temperature, diarylethenes having
dioxidized benzothienyl groups as both aryl groups showed a
strong fluorescent property in the closed-ring isomer.9−11 Irie and
coworkers have reported that the oxidized diarylethenes
introducing ethyl groups at the reactive carbons showed much
larger fluorescence quantum yields (Φf = 0.6-0.9) in the closed-
ring isomer.12,13 Kawai and coworkers have also reported that
oxidized terarylenes showed relatively high fluorescence
properties (Φf = 0.34-0.36).14 These turn-on mode fluorescence
switching systems are expected for application to optical
recording media and biological systems.
Here, we have synthesized diarylethenes having a benzofuryl
group (1a−3a) and their thiophene-S,S-dioxidized diarylethenes
(1b−3b) as shown in Scheme 1. The photochromic reaction
behavior and thermal stability of the closed-ring isomers are
discussed in this paper.
F
F
F F
F
F
F
F
F
F
F
F
UV
R1
R1
Vis.
S
O
S
O
R2
R2
1a(O): R1 = R2 = CH3
1a(C): R1 = R2 = CH3
2a(O): R1 = CH(CH3)2, R2 = CH3
3a(O): R1 = R2 = CH(CH3)2
2a(C): R1 = CH(CH3)2, R2 = CH3
3a(C): R1 = R2 = CH(CH3)2
F
F
F F
F
F
F
F
F
F
F
F
UV
R1
R1
Vis.
S
O
S
O O
O
R2
R2
O
O
1b(O): R1 = R2 = CH3
1b(C): R1 = R2 = CH3
2b(O): R1 = CH(CH3)2, R2 = CH3
3b(O): R1 = R2 = CH(CH3)2
2b(C): R1 = CH(CH3)2, R2 = CH3
3b(C): R1 = R2 = CH(CH3)2
On the other hand, we have reported the thermal irreversible
reaction in the closed-ring isomer of diarylethenes having a
dioxidized phenylthienyl group.15,16 The closed-ring isomers of
Scheme 1. Photochromic diarylethenes used in this work.

2
Tetrahedron
2. Results and Discussion
These results are similar to those of the thiophene-S,S-dioxidized
ACCEPTED MANUSCRIPT
diarylethenes having a phenylthienyl group.9
2.1. Photochromic reaction behavior
Table 1
Diarylethenes
1a−3a
and
thiophene-S,S-dioxidized
Optical properties of diarylethenes in n-hexane
diarylethenes 1b−3b showed reversible photochromic reactions
upon alternating irradiation with ultraviolet (UV) and visible
light. In their diarylethenes, the photocyclization and
photocycloreversion reactions can be repeated for several cycles.
Fig. 1 shows the absorption spectral changes of diarylethenes
1a−3a and thiophene-S,S-dioxidized diarylethenes 1b−3b in n-
hexane. The open-ring isomers 1a(O)−3a(O) have absorption
maxima around 250 nm. Upon irradiation with 313 nm light, the
colorless solution turned to red-purple, in which the visible
absorption maxima were observed at 525, 542, and 552 nm for
1a(C), 2a(C), and 3a(C), respectively. These spectral changes
are ascribed to the photoisomerization from the open-ring
isomers to the closed-ring isomers. The colored solution returned
to the initial colorless solution by irradiation with visible light (>
500 nm) and the absorption spectra returned to those of
1a(O)−3a(O). After the oxidation of the thiophene ring, the
open-ring isomers 1b(O)−3b(O) have absorption maxima around
340 nm. Upon irradiation with 313 nm light, the color of the
solution changed from colorless to yellow-orange, in which the
visible absorption maxima were observed at 470, 479, and 491
nm for 1b(C), 2b(C), and 3b(C), respectively. This is due to the
photochromic reaction from the open-ring isomer to the closed-
ring isomer. Upon irradiation with visible light (> 500 nm), the
solution colors and absorption spectra returned to the initial states.
open-ring isomer
λmax/nm ε/M−1cm−1 λmax/nm ε/M−1cm−1
closed-ring isomer
Conv./
%
Φo→c
Φc→o
1a
2a
3a
1b
2b
3b
257
256
255
341
337
339
29400
23400
27000
7200
525
542
552
470
479
491
18100
14000
14400
19000
20700
20300
0.39
0.52
0.51
0.088
0.20
0.14
89
84
84
96
98
0.39 0.0066
0.39 0.0028
8400
8500
0.30 0.0024 ~100
2.2. Thermal stability of the closed-ring isomer
The closed-ring isomers of diarylethenes having bulky
substituents at the reactive carbons, such as isopropyl or isobutyl
groups, show thermal cycloreversion reaction to the open-ring
isomers.17−23 On the other hand, the closed-ring isomers of the
thiophene-S,S-dioxidized diarylethenes having secondary alkyl
groups at the reactive positions undergo a thermally irreversible
reaction to produce byproducts. Byproducts are produced by
elimination of the sulfonyl group and rearrangement of the
secondary alkyl group from the closed-ring isomer upon heating
as shown in Scheme 2.15,16 The photogenerated closed-ring
isomer (4b(C)) of the oxidized diarylethene having isopropyl
groups at the reactive positions (4b(O)) formed three byproducts
upon heating.
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
0.8
0.6
0.4
0.2
0
(a)
(d)
F
F
F F
F
F
F F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
R
+
+
R
300
300
300
400
500
600
700
700
700
800
300
300
300
400
500
600
700
700
700
800
800
800
S
H
SO2
S
Wavelength/nm
Wavelength/nm
R
H
R
S
S
S
R
R
R
1
0.8
0.6
0.4
0.2
0
0.4
0.3
0.2
0.1
0
O
O
4b(C): R = CH(CH3
)
4b(BP): R = CH(CH3)
2
(b)
(e)
2
Scheme 2. Thermal byproducts formation of thiophene-S,S-dioxidized
diarylethene closed-ring isomer 4b(C).
Here, we investigated the thermal reaction behavior of the
closed-ring isomers 1a(C)−3a(C) and 1b(C)−3b(C). Fig. 2
shows the absorbance changes of the colored solutions of
1a(C)−3a(C) and 1b(C)−3b(C) in toluene at 110 °C. Before the
oxidation, 1a(C) and 2a(C) did not show any decoloration even
after 10 h. On the other hand, the absorbance of 3a(C) slightly
decreased. This is due to the introduction of bulky isopropyl
substituents at both reactive carbons. After the oxidation of a
thiophene ring, 1b(C)−3b(C) caused less thermal decoloration
reaction even after 10 h at 110 °C, regardless of the introduction
of bulky isopropyl substituents at the reactive carbons. These
results are different from those of the thiophene-S,S-dioxidized
diarylethenes having the phenylthienyl group. This is ascribed to
the introduction of a benzofuryl group instead of a phenylthienyl
group.
400
500
600
400
500
600
800
Wavelength/nm
Wavelength/nm
1.4
1.2
1
0.5
0.4
0.3
0.2
0.1
0
(c)
(f)
0.8
0.6
0.4
0.2
0
400
500
600
400
500
600
800
Wavelength/nm
Wavelength/nm
Fig. 1. Absorption spectra of 1a (a), 2a (b), 3a (c), 1b (d), 2b (e), and 3b (f)
in n-hexane: open-ring isomer (O) (- - -), closed-ring isomer (C) (‒), and the
photostationary solution upon irradiation with 313 nm light (‒ — ‒).
In order to compare the photoreactivity before and after the
oxidation of the thiophene ring, the molar absorption coefficient
(ε), the photocyclization quantum yield (Фo→c), the
photocycloreversion quantum yield (Фc→o), and the conversion
from the open-ring isomer to the closed-ring isomer were
determined as shown in Table 1. By the oxidation of the
thiophene ring, the absorption maxima of the closed-ring isomers
1b(C)−3b(C) were blue-shifted in comparison with those of
1a(C)−3a(C). Although the photocyclization quantum yields
scarcely changed, the photocycloreversion quantum yields
significantly decreased by a factor of 10−102 upon the oxidation.
Moreover, the conversion from the open-ring isomer to the
closed-ring isomer increased up to 96-100% upon the oxidation.

3
ACCEPTED MANUSCRIPT
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
(a)
(b)
(c)
(d)
(e)
(f)
Table 2
Energy gap (
ꢀ
H) calculated between the open- and closed-ring
H') calculated between the dioxidized
closed-ring isomer and the byproduct.
isomers and energy gap (
ꢀ
ꢀ
H/kJ mol−1
ꢀ
H'/kJ mol−1
0
0
0
2
2
2
4
4
4
6
8
8
8
10
10
10
0
2
4
4
4
6
8
8
8
10
10
10
1a
2a
3a
1b
2b
3b
4b
37.90
61.01
88.95
−25.89
6.48
Time/h
Time/h
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
148.22
179.51
198.94
214.56
38.82
57.31
6
0
2
6
Time/h
Time/h
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
2
0
(a)
0
2
6
6
Time/h
Time/h
-2
4b
Fig. 2. Absorbance change of 1a(C) (a), 2a(C) (b), 3a(C) (c), 1b(C) (d),
2b(C) (e), and 3b(C) (f) in toluene at 110 °C.
-4
3b
-6
2b
-8
In order to quantitatively discuss the thermal stability of the
closed-ring isomer of diarylethenes, the energy difference (ꢀH)
between the open- and closed-ring isomers in the ground states
and the energy difference (ꢀH') between the closed-ring isomer
and the total energy of byproduct and SO2 were calculated by
density functional theory (DFT) at the B3LYP/6-31G(d) level.
The energy of SO2 was calculated to be −1440317.2 kJ mol−1. For
comparison, the ꢀH and ꢀH' values of the thiophene-S,S-
dioxidized diarylethene having a phenylthienyl group (4b) were
also calculated. Table 2 shows ground state energies of the open-
ring isomer (O), the closed-ring isomer (C), the byproduct (BP),
and their energy differences (ꢀH and ꢀH'). In our previous work,
it was clarified that diarylethenes having ꢀH value over about 60
kJ mol−1 exhibit the thermal cycloreversion reaction at 100 °C.16
Before the oxidation, the ꢀH values of 1a−3a are 37.90, 61.01,
and 88.95 kJ mol−1, respectively. These values suggest that only
the closed-ring isomer 3a(C) shows the thermal cycloreversion
reaction at 100 °C, which is consistent with the experimental
results. After the oxidation, the ꢀH values of 1b−3b are much
smaller than 60 kJ mol−1, which means that the closed-ring
isomers of the thiophene-S,S-dioxidized diarylethenes
1b(C)−3b(C) cannot undergo thermal cycloreversion reactions at
100 °C. This is also consistent with the experimental results.
-10
170 180 190 200 210 220 230 240 250
ꢀH/kJ mol−1
180
(b)
160
140
120
100
80
2b
3b
4b
60
170 180 190 200 210 220 230 240 250
ꢀH'/kJ mol−1
Fig. 3. Relationship between ∆H' and the logarithm of k at 100 °C (a) and the
activation energy (b) for the thermal byproduct formation of the oxidized
diarylethenes.
From these relationships with the ∆H' values, the k values at
100 °C and the Ea values of 2b and 3b were calculated to be k =
1.3 × 10−11 s−1 and Ea = 186 kJ mol−1 for 1b, k = 4.6 × 10−8 s−1 and
Ea = 155 kJ mol−1 for 2b, and k = 7.6 × 10−6 s−1 and Ea = 136 kJ
mol−1 for 3b as shown in Table 3. Compared with the values for
4b (k = 1.2 × 10−3 s−1 and Ea = 121 kJ mol−1), the k value
decreased by a factor of 102−108 and the Ea value became
significantly large. This is due to the decrease in aromatic
stabilization energy by the introduction of the benzofuryl group
instead of the phenylthienyl group, which results in the
destabilization of the open-ring isomer and the byproduct in the
ground state as shown in Fig. 4. As a result, the closed-ring
isomer 1b(C)−3b(C) could not cause the thermal bleaching
reaction even at 110 °C. Thus, the thermal reaction behavior of
the closed-ring isomer could be explained by the quantum
chemical calculations.
Next, we discuss the ꢀH' values for the thiophene-S,S-
dioxidized diarylethenes. The ꢀH' values of 1b, 2b, and 3b were
estimated to be 148.22, 179.51, and 198.94 kJ mol−1, respectively,
by the DFT calculation. These values are smaller than 214.56 kJ
mol−1 for 4b that undergoes the thermal bleaching reaction to
produce byproducts.15,16 The relationships between the ꢀH'
values and the logarithm of the rate constant (k) at 100 °C and
activation energy (Ea) for the thermal byproduct formation of the
thiophene-S,S-dioxidized diarylethenes have been reported
previously as shown in Fig. 3.16 The relationships are expressed
as follows:
log(k/s−1) = 0.114 × (∆H'/kJ mol−1) – 27.8
(Ea/kJ mol−1) = –0.968 × (∆H'/kJ mol−1) + 329

4
Tetrahedron
ACCEPTED MANUSCRIPT
out using a constant temperature chamber ESPEC ST-110. The
Table 3
sample in an optical quartz cell was degassed and sealed off
under vacuum. High-performance liquid chromatography
(HPLC) was carried out using a HITACHI HPLC system
equipped with a Kanto Chemical Mightysil Si 60 column. The
difference in energy in the ground states was calculated using
Spartan’14 computational software. The molecular structures
were fully optimized at the B3LYP/6-31G(d) level of theory, and
vibrational frequencies for all optimized species were computed
at the same level to confirm each stationary point to be a
minimum.
The rate constant and activation energy of the thermal byproduct
formation for 2b(C), 3b(C), and 4b at 100 °C.
k/s−1 at 100 °C
Ea/kJ mol−1
1b(C)
2b(C)
3b(C)
4b(C)
1.3 × 10−11 a)
4.6 × 10−8 a)
7.6 × 10−6 a)
1.2 × 10−3 b)
186 a)
155 a)
136 a)
121 b)
a) Calculated values. b) Experimental values.
4.2. Materials.
Thermal cycloreversion
Byproduct formation
Diarylethenes
1a−3a
and
thiophene-S,S-dioxidized
diarylethenes 1b−3b were synthesized as shown in Scheme 3.
Compounds 5-12 were prepared by similar methods according
to the procedures described in the literature.24-26
Ea
Ea
∆H
1b(O)−3b(O)
∆H'
+ SO2
9: R2 = CH3
10: R2 = CH(CH3)2
7: R2 = CH3
8: R2 = CH(CH3)2
(closed)
11: R2 = CH3
12: R2 = CH(CH3)2
1b(BP)−3b(BP)
F
F
F
F
F
F
F
F
Br
F
F
F
F
4b(O)
mꢀCPBA
nꢀBuLi / 11 or 12
R1
R1
R1
S
CH2Cl2
THF
+ SO2
S
O
S
O
R2
R2
O
O
5: R1 = CH3
6: R1 = CH(CH3)2
4b(BP)
1a: R1 = R2 = CH3
1b: R1 = R2 = CH3
2a: R1 = CH(CH3)2, R2 = CH3
3a: R1 = R2 = CH(CH3)2
2b: R1 = CH(CH3)2, R2 = CH3
3b: R1 = R2 = CH(CH3)2
Fig. 4. Schematic energy diagram of the oxidized diarylethene system in the
Scheme 3. Synthetic routes of diarylethenes and thiophene-S,S-dioxidized
ground state.
diarylethenes.
3. Conclusion
4.2.1. 1-(2-Methyl-3-benzofuryl)-2-(2-methyl-5-
phenyl-3-thienyl)perfluorocyclopentene (1a)
We have synthesized diarylethenes having a benzofuryl group
(1a−3a) and their thiophene-S,S-dioxidized diarylethenes
(1b−3b) and investigated their optical properties and the thermal
stability of the closed-ring isomers. Upon oxidation of the
thiophene ring, the absorption maxima of the closed-ring isomers
were blue-shifted. The photocycloreversion quantum yields
decreased by a factor of 10−102, whereas the photocyclization
quantum yields scarcely changed. Moreover, the conversion from
the open-ring isomer to the closed-ring isomer increased up to
96-100%. The diarylethene closed-ring isomers 1b(C)−3b(C)
have high thermal stability, which is predicted from the ꢀH and
ꢀH' values obtained from the DFT calculations. These results
provide new knowledge for molecular design of diarylethenes
with a desired thermal stability.
n-BuLi (1.6 M solution in n-hexane) (0.32 mL, 0.51 mmol) was
slowly added to a stirred dry THF solution (5.0 mL) containing
compound 5 (120 mg, 0.46 mmol) at −78 °C under argon
atmosphere. After the mixture has been stirred for 2 h, compound
11 (150 mg, 0.46 mmol) in dry THF was added to the mixture.
The reaction was further stirred at −78 °C for 2 h, and the
reaction was allowed to slowly warm up to room temperature.
The reaction was quenched by the addition of water. The product
was extracted with diethyl ether. The organic layer was dried
over MgSO4, filtered, and concentrated. The crude product was
purified by column chromatography on silica gel (n-hexane/ethyl
acetate = 9:1) and by HPLC (n-hexane/ethyl acetate = 98:2) to
give 68 mg of 1a in 47% yield as a colorless crystal. mp 155-
156 °C. 1H NMR (300 MHz, CDCl3, TMS) δ = 1.88 (s, 3H, CH3),
2.13 (s, 3H, CH3), 7.1-7.6 (m, 10H, Aromatic H). 13C NMR (75
MHz, CDCl3) δ = 13.5, 14.9, 105.7, 111.2, 120.2, 122.5, 123.8,
124.7, 125.8, 126.4, 128.1, 129.2, 133.4, 141.5, 142.5, 154.3,
156.3. IR (v, KBr, cm−1): 432, 474, 544, 575, 694, 756, 798, 841,
891, 926, 987, 1065, 1126, 1192, 1273, 1338, 1435, 1458, 1597,
1635, 2854, 2920, 2958, 3024, 3070. HRMS (MALDI) m/z =
478.0819 (M+). Calcd for C25H16F6OS = 478.0821.
4. Experimental Section
4.1. General.
Solvents used were spectroscopic grade and purified by
1
distillation before use. H NMR (300 MHz) and 13C NMR (75
MHz) spectra were recorded on a Bruker AV-300N spectrometer
with tetramethylsilane as the internal standard. Infrared spectra
(IR) were recorded on a JASCO FT/IR-410 spectrometer. High-
resolution mass spectra (HRMS) were obtained on a Bruker FT-
ICR/solariX mass spectrometer. UV-vis absorption spectra were
4.2.2. 1-(2-Methyl-3-benzofuryl)-2-(2-isopropyl-5-
phenyl-3-thienyl)perfluorocyclopentene (2a)
n-BuLi (1.6 M solution in n-hexane) (0.73 mL, 1.2 mmol) was
slowly added to a stirred dry THF solution (5.0 mL) containing
compound 6 (300 mg, 1.1 mmol) at −78 °C under argon
atmosphere. After the mixture has been stirred for 2 h, compound
11 (350 mg, 1.1 mmol) in dry THF was added to the mixture.
The reaction was further stirred at −78 °C for 2 h, and the
reaction was allowed to slowly warm up to room temperature.
measured with
a JASCO V-560 absorption spectrometer.
Photoirradiation in solution was conducted using a 200 W
mercury−xenon lamp (Moritex MUV-202) as a light source.
Monochromatic light was obtained by passing the light through a
monochromator (Jobin Yvon H10 UV) and glass filters. The
heating of the sample for the thermal cycloreversion was carried

5
4.2.5. 1-(2-Methyl-3-benzofuryl)-2-(2-isopropyl-5-
phenyl-1,1-dioxide-3-thienyl)perfluorocyclo-
pentene (2b)
The reaction was quenched by the addition of water. The product
was extracted with diethyl ether. The organic layer was dried
over MgSO4, filtered, and concentrated. The crude product was
purified by column chromatography on silica gel (n-hexane/ethyl
acetate = 9:1) and by HPLC (n-hexane/ethyl acetate = 98:2) to
give 120 mg of 2a in 23% yield as a colorless crystal. mp 103-
ACCEPTED MANUSCRIPT
mCPBA (68 mg, 0.40 mmol) was added to a stirred
dichloromethane solution (2.0 mL) containing 2a (50 mg, 0.10
mmol). The reaction mixture was stirred overnight in the dark at
room temperature. The reaction mixture was extracted with
dichloromethane. The organic phase was dried over MgSO4,
filtered, and evaporated. The crude product was purified by
column chromatography on silica gel (n-hexane/ethyl acetate =
85:15) and by HPLC (n-hexane/ethyl acetate = 95:5) to give 28
1
104 °C. H NMR (300 MHz, CDCl3, TMS) δ = 0.78 (d, J = 6.8
Hz, 6H, CH3), 2.13 (s, 3H, CH3), 2.71 (sept, J = 6.8 Hz, 1H, CH),
7.2-7.6 (m, 10H, Aromatic H). 13C NMR (75 MHz, CDCl3) δ =
13.4, 25.0, 29.3, 105.3, 111.2, 119.9, 121.9, 123.2, 123.8, 124.7,
125.8, 126.9, 128.0, 129.1, 129.2, 133.7, 142.5, 154.3, 155.3,
156.0. IR (v, KBr, cm−1): 432, 513, 552, 575, 690, 752, 798, 849,
922, 991, 1057, 1122, 1192, 1269, 1335, 1458, 1597, 1643, 2870,
2931, 2970, 3024, 3066. HRMS (MALDI) m/z = 506.1132 (M+).
Calcd for C27H20F6OS = 506.1134;
1
mg of 2b in 53% yield as a pale yellow amorphous solid. H
NMR (300 MHz, CDCl3, TMS) δ = 0.98 (d, J = 7.1 Hz, 6H, CH3),
2.35 (s, 3H, CH3), 2.68 (sept, J = 7.1 Hz, 1H, CH), 6.80 (s, 1H,
Aromatic H), 7.2-7.7 (m, 9H, Aromatic H). 13C NMR (75 MHz,
CDCl3) δ = 14.0, 19.7, 29.2, 104.8, 111.6, 119.2, 119.8, 122.8,
124.3, 125.5, 126.0, 126.3, 126.7, 129.5, 130.9, 142.1, 149.5,
154.3, 156.8. IR (v, KBr, cm−1): 422, 486, 561, 596, 646, 688,
750, 800, 837, 864, 904, 928, 991, 1074, 1136, 1198, 1278, 1309,
1340, 1456, 1493, 1579, 2852, 2877, 2937, 2978, 3039, 3066.
HRMS (MALDI) m/z = 538.1030 (M+). Calcd for C27H20F6O3S =
538.1032.
4.2.3. 1-(2-Isopropyl-3-benzofuryl)-2-(2-isopropyl-
5-phenyl-3-thienyl)perfluorocyclopentene (3a)
n-BuLi (1.6 M solution in n-hexane) (1.0 mL, 1.6 mmol) was
slowly added to a stirred dry THF solution (5.0 mL) containing
compound 6 (400 mg, 1.4 mmol) at −78 °C under argon
atmosphere. After the mixture has been stirred for 2 h, compound
12 (500 mg, 1.4 mmol) in dry THF was added to the mixture.
The reaction was further stirred at −78 °C for 2 h, and the
reaction was allowed to slowly warm up to room temperature.
The reaction was quenched by the addition of water. The product
was extracted with diethyl ether. The organic layer was dried
over MgSO4, filtered, and concentrated. The crude product was
purified by column chromatography on silica gel (n-hexane/ethyl
acetate = 95:5), HPLC (hexane/ethyl acetate = 98:2) and by
recrystallization from hexane to give 220 mg of 3a in 31% yield
as a colorless crystal. mp 128-129 °C. 1H NMR (300 MHz,
CDCl3, TMS) δ = 0.73 (d, J = 5.6 Hz, 6H, CH3), 0.98 (d, J = 6.7
Hz, 6H, CH3), 2.73 (sept, J = 6.8 Hz, 2H, CH), 7.20 (t, J = 1.3 Hz,
1H, Aromatic H), 7.2-7.6 (m, 9H, Aromatic H). 13C NMR (75
MHz, CDCl3) δ = 20.6, 25.0, 27.5, 29.2, 102.8, 111.4, 120.1,
122.2, 123.0, 123.7, 124.6, 125.9, 127.2, 128.0, 129.1, 133.8,
142.5, 154.4, 155.5, 163.3. IR (v, KBr, cm−1): 420, 467, 505, 544,
567, 694, 752, 806, 856, 922, 995, 1053, 1076, 1119, 1265, 1342,
1458, 1566, 1635, 2877, 2939, 2974, 3028, 3066. HRMS
(MALDI) m/z = 534.1444 (M+). Calcd for C29H24F6OS =
534.1447.
4.2.6. 1-(2-Isopropyl-3-benzofuryl)-2-(2-isopropyl-
5-phenyl-1,1-dioxide-3-thienyl)perfluorocyclo-
pentene (3b)
mCPBA (62 mg, 0.36 mmol) was added to a stirred
dichloromethane solution (3.0 mL) containing 3a (55 mg, 0.10
mmol). The reaction mixture was stirred overnight in the dark at
room temperature. The reaction mixture was extracted with
dichloromethane. The organic phase was dried over MgSO4,
filtered, and evaporated. The crude product was purified by
column chromatography on silica gel (n-hexane/ethyl acetate =
85:15) and by HPLC (n-hexane/ethyl acetate = 95:5) to give 31
mg of 3b in 53% yield as a pale yellow crystal. mp 111-112 °C.
1H NMR (300 MHz, CDCl3, TMS) δ = 0.95 (d, J = 6.9 Hz, 6H,
CH3), 1.27 (d, J = 6.9 Hz, 6H, CH3), 2.6-2.9 (m, 2H, CH), 6.79 (s,
1H, Aromatic H), 7.3-7.7 (m, 9H, Aromatic H). 13C NMR (75
MHz, CDCl3) δ = 19.8, 20.9, 27.6, 29.2, 102.0, 111.8, 119.4,
119.7, 122.4, 124.2, 125.3, 126.4, 126.7, 129.5, 130.9, 142.1,
149.7, 154.4, 163.9. IR (v, KBr, cm−1): 420, 488, 559, 596, 648,
688, 752, 802, 827, 870, 904, 937, 993, 1053, 1068, 1142, 1198,
1277, 1311, 1338, 1456, 1601, 2877, 2937, 2978, 3039, 3066.
HRMS (MALDI) m/z = 566.1426 (M+). Calcd for C29H24F6O3S =
566.1423.
4.2.4. 1-(2-Methyl-3-benzofuryl)-2-(2-methyl-5-
phenyl-1,1-dioxide-3-thienyl)perfluorocyclo-
pentene (1b)
m-Chloroperbenzoic acid (mCPBA) (63 mg, 0.37 mmol) was
added to a stirred dichloromethane solution (3.0 mL) containing
1a (50 mg, 0.11 mmol). The reaction mixture was stirred
overnight in the dark at room temperature. The reaction mixture
was extracted with dichloromethane. The organic phase was
dried over MgSO4, filtered, and evaporated. The crude product
was purified by column chromatography on silica gel (n-
hexane/ethyl acetate = 9:1) and by HPLC (n-hexane/ethyl acetate
= 95:5) to give 34 mg of 1b in 64% yield as a pale yellow crystal.
Acknowledgments
This work was partly supported by a Matching Planner
Program (No. MP27115663071) from Japan Science and
Technology Agency (JST) and a Grant-in-Aid for Scientific
Research on Innovative Areas "Photosynergetics" (No.
26107013) from The Ministry of Education, Culture, Sports,
Science and Technology (MEXT), Japan. The authors also thank
Nippon Zeon Co., Ltd. for providing octafluorocyclopentene.
1
mp 99-100 °C. H NMR (300 MHz, CDCl3, TMS) δ = 1.83 (s,
3H, CH3), 2.30 (s, 3H, CH3), 6.80 (s, 1H, Aromatic H), 7.2-7.7
(m, 9H, Aromatic H). 13C NMR (75 MHz, CDCl3) δ = 9.3, 13.9,
105.3, 111.6, 119.7, 120.2, 124.4, 125.6, 126.4, 126.7, 129.5,
131.0, 141.9, 154.4. IR (v, KBr, cm−1): 424, 463, 540, 687, 748,
795, 833, 876, 930, 991, 1057, 1084, 1138, 1192, 1277, 1311,
1342, 1431, 1585, 1624, 2854, 2920, 2989, 3032, 3070, 3093.
HRMS (MALDI) m/z = 510.0718 (M+). Calcd for C25H16F6O3S =
510.0719.
References
1.
2.
3.
Crano, J. C.; Flood, T.; Knowles, D.; Kumar, A.; Van Gemert, B. Pure
Appl. Chem. 1996, 68, 1395–1398.
Irie, M.; Matsuda, K. In Electron Transfer in Chemistry; Balzani, V.
Ed.; Wiley-VCH, Weinheim, 2001; pp. 215–242.
Irie, M. In Molecular Switchings; Feringa, B. L. Ed.; Wiley-VCH,
Weinheim, 2001; pp. 37–62.
4.
5.
Delaire, J. A.; Nakatani, K. Chem. Rev. 2000, 100, 1817–1846.
Bechinger, C.; Ferrere, S.; Zaban, A.; Sprague, J.; Gregg, B. A. Nature
1996, 383, 608–610.

6
Tetrahedron
ACCEPTED MANUSCRIPT
6. Kobatake, S.; Takami, S.; Muto, H.; Ishikawa, T.; Irie, M. Nature
17. Chen, D. Z.; Wang, Z.; Zhang, H. H. J. Mol. Struct. (Theochem) 2008,
2007, 446, 778–781.
859, 11–17.
7.
8.
Irie, M. Chem. Rev. 2000, 100, 1685–1716.
Irie, M.; Fukaminato, T.; Matsuda, K.; Kobatake, S. Chem. Rev. 2014,
114, 12174–12277.
18. Kobatake, S.; Irie, M. Chem. Lett. 2003, 32, 1078–1079.
19. Morimitsu, K.; Shibata, K.; Kobatake, S.; Irie, M. Chem. Lett. 2002,
572–573.
9.
Jeong, Y. C.; Han, J. P.; Kim, Y.; Kim, E.; Yang, S. I.; Ahn, K. H.
Tetrahedron 2007, 63, 3173–3182.
20. Morimitsu, K.; Shibata, K.; Kobatake, S.; Irie, M. J. Org. Chem. 2002,
67, 4574–4578.
10. Jeong, Y. C.; Yang, S. I.; Ahn, K. H.; Kim, E. Chem. Commun. 2005,
2503–2505.
21. Kobatake, S.; Uchida, K.; Tsuchida, E.; Irie, M. Chem. Lett. 2000,
1340–1341.
11. Jeong, Y. C.; Yang, S. I.; Kim, E.; Ahn, K. H. Tetrahedron 2006, 62,
5855–5861.
22. Kitagawa, D.; Sasaki, K.; Kobatake, S. Bull. Chem. Soc. Jpn. 2011, 84,
141−147.
12. Uno, K.; Niikura, H.; Morimoto, M.; Ishibashi, Y.; Miyasaka, H.; Irie,
M. J. Am. Chem. Soc. 2011, 133, 13558–13564.
13. Sumi, T.; Kaburagi, T.; Morimoto, M.; Une, K.; Sotome, H.; Ito, S.;
Miyasaka, H.; Irie, M. Org. Lett. 2015, 17, 4802–4805.
14. Taguchi, M.; Nakagawa, T.; Nakashima, T.; Kawai, T. J. Mater. Chem.
2011, 21, 17425–17432.
15. Shoji, H.; Kobatake, S. Chem. Commun. 2013, 49, 2362–2364.
16. Shoji, H.; Kitagawa, D.; Kobatake, S. New J. Chem. 2014, 38, 933–
941.
23. Shoji, H.; Kitagawa, D.; Kobatake, S. Res.Chem. Intermed. 2013, 39,
279−289.
24. Ortega, N.; Urban, S.; Beiring, B.; Glorius, F. Angew. Chem. Int. Ed.
2012, 51, 1710−1713.
25. Yamaguchi, T.; Irie, M. J. Org. Chem. 2005, 70, 10323−10328.
26. Ren, P.; Wang, R.; Pu, S.; Liu, G.; Fan, C. J. Phys. Org. Chem. 2014,
27, 183−190.