Photochromic performance of 1-thiazolyl-2-vinylcyclopentene derivatives having a phenyl-or 4-methoxyphenyl-substituted olefin

Article abstract of DOI:10.1246/bcsj.20130091

1-Thiazolyl-2-vinylcyclopentene derivatives, 1-(5-methoxy-2-phenyl-4- thiazolyl)-2-(2-methyl-1-phenyl-1-propenyl) perfluorocyclopentene (1a), 1-[5-methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2-(2-methyl-1-phenyl-1-propenyl) perfluorocyclopentene (2a), and 1-[5-methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2- [1-(4-methoxyphenyl)-2-methyl-1-propenyl] perfluorocyclopentene (3a) were synthesized in an attempt to obtain yellow photochromic compounds having low photocycloreversion quantum yields and large absorption coefficients of the closed-ring isomers. Their photochromic performance, thermal stability, and fatigue resistance were compared with 1-[5-methoxy-2-(4-methoxyphenyl)-4- thiazolyl]-2-(1,2-dimethyl-1-propenyl)perfluorocyclopentene (4a) having a methyl-substituted olefin. Upon irradiation with 313 nm light, compounds 1a, 2a, and 3a changed from colorless to various shades of yellow in toluene. The conversions from the open-ring (1a, 2a, and 3a) to the closed-ring (1b, 2b, and 3b) isomers in the photostationary state under irradiation with 313nm light were 93, 95, and 98%, respectively. Among the three derivatives 3b has the largest absorption coefficient (= 18900M^-1cm^-1) at 428nm and the lowest cycloreversion quantum yield of 1.8 10^-3.

Full text of DOI:10.1246/bcsj.20130091

© 2013 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 86, No. 9, 1059-1064 (2013) 1059
Photochromic Performance of 1-Thiazolyl-2-vinylcyclopentene
Derivatives Having a Phenyl- or 4-Methoxyphenyl-Substituted Olefin
Shizuka Takami,*1 Ayano Shimizu,1 Kazuyuki Shimizu,1 Ryota Miyoshi,1
Tadatsugu Yamaguchi,2 and Masahiro Irie3
1Department of Environmental Materials Engineering, Niihama National College of Technology,
7-1 Yagumo-cho, Niihama, Ehime 792-8580
2Hyogo University of Teacher Education, 942-1 Shimokume, Kato, Hyogo 673-1494
3Department of Chemistry and Research Center for Smart Molecules, Rikkyo University,
3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501
Received April 3, 2013; E-mail: takami@mat.niihama-nct.ac.jp
1-Thiazolyl-2-vinylcyclopentene derivatives, 1-(5-methoxy-2-phenyl-4-thiazolyl)-2-(2-methyl-1-phenyl-1-prope-
nyl)perfluorocyclopentene (1a), 1-[5-methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2-(2-methyl-1-phenyl-1-propenyl)per-
fluorocyclopentene (2a), and 1-[5-methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2-[1-(4-methoxyphenyl)-2-methyl-1-pro-
penyl]perfluorocyclopentene (3a) were synthesized in an attempt to obtain yellow photochromic compounds having
low photocycloreversion quantum yields and large absorption coefficients of the closed-ring isomers. Their photo-
chromic performance, thermal stability, and fatigue resistance were compared with 1-[5-methoxy-2-(4-methoxyphenyl)-4-
thiazolyl]-2-(1,2-dimethyl-1-propenyl)perfluorocyclopentene (4a) having a methyl-substituted olefin. Upon irradiation
with 313 nm light, compounds 1a, 2a, and 3a changed from colorless to various shades of yellow in toluene. The
conversions from the open-ring (1a, 2a, and 3a) to the closed-ring (1b, 2b, and 3b) isomers in the photostationary state
under irradiation with 313 nm light were 93, 95, and 98%, respectively. Among the three derivatives 3b has the largest
¹3
absorption coefficient (¾ = 18900 M¹1 cm¹1) at 428 nm and the lowest cycloreversion quantum yield of 1.8 © 10
.
Photochromic compounds have attracted much attention
because of their potential applications to optical memory,
photooptical switching, and display devices.1 In particular,
diarylethenes with heterocyclic aryl groups, such as thiophene
or benzothiophene groups, are the most promising candidates
for the applications, because they undergo fatigue resistant and
thermally irreversible photochromic reactions.2 For the appli-
cation to a full color display preparation of yellow developing
photochromic compounds which have low photocycloreversion
quantum yields and thermal stability at room temperature is
indispensable. Although some photochromic compounds ex-
hibit yellow color, the colored isomers are photochemically
unstable and the photocycloreversion quantum yields are rather
high.3 Recently, 1-heteroaryl-2-vinylcyclopentene derivatives
having a thiophene ring and a 2-butene or styryl unit have been
reported by Peters et al.4 and Yokoyama et al.5 The colorless
solutions of these compounds turn yellow by irradiation with
UV light.
In a previous paper,6 we have also prepared 1-heteroaryl-
2-vinylcyclopentene derivative 4a with a thiazole ring. The
closed-ring isomer of 4a having two methoxy groups shows
the absorption maximum at 416 nm (¾ = 17100 M¹1 cm¹1) in
toluene and a photocycloreversion quantum yield of 0.0014.6
The methoxy substituents effectively decrease the photocyclo-
reversion quantum yield7 and induce the large absorption co-
efficient of the closed-ring isomer.8 The derivative is a useful
candidate as a yellow developing photochromic dye. Although
the photochromic performance of these 1-heteroaryl-2-vinyl-
cyclopentene derivatives is of great interest, their fatigue resist-
ance is limited because of the formation of by-products.4-6,9 In
this study, we have synthesized three 1-thiazolyl-2-vinylcyclo-
pentene derivatives 1a, 2a, and 3a by introducing a phenyl- or
4-methoxyphenyl-substituted olefin to know the relationship
between the structure and the photochromic performance, as
shown in Scheme 1. The absorption maxima of closed-ring
isomers 1b-3b are expected to show a bathochromic shift. In
other words, the closed-ring isomers 1b-3b are able to provide
various shades of yellow. Thermal stability of the closed-ring
isomers and the fatigue resistance have also been studied in
detail.
Results and Discussion
Synthesis of 1-Thiazolyl-2-vinylcyclopentene Derivatives.
Compounds 1a and 2a were synthesized by the reaction of 4-
bromo-5-methoxy-2-phenylthiazole (5)10 or 4-bromo-5-meth-
oxy-2-(4-methoxyphenyl)thiazole (6)6 with 1-(2-methyl-
1-phenyl-1-propenyl)perfluorocyclopentene,5a respectively, by
bromine-lithium exchange followed by the nucleophilic dis-
placement of fluoride (Scheme 2). Both compounds were
obtained in 22 and 18% yields, respectively. Compound 3a
was also synthesized by the reaction of 1-bromo-2-methyl-1-
(4-methoxyphenyl)propene (10) with 1-[5-methoxy-2-(4-meth-
oxyphenyl)]perfluorocyclopentene6 by bromine-lithium ex-
change followed by the nucleophilic displacement of fluoride
Published on the web September 15, 2013; doi:10.1246/bcsj.20130091

1060 Bull. Chem. Soc. Jpn. Vol. 86, No. 9 (2013)
Yellow-Colored Photochromic Compounds
F2
F2
F2
S
F2
F2
F2
S
UV
R2
R2
N
N
OMe
OMe
Me
Vis.
Me
Me Me
R1
R1
1b : R1 = H, R2 = Ph
1a : R1 = H, R2 = Ph
2b : R1 = OMe, R2 = Ph
1
2
2a
3a
: R = OMe, R = Ph
: R = OMe, R = (4-MeO)C6H4
: R1 = OMe, R2 = (4-MeO)C H
1
2
3b
6
4
4b: R1 = OMe, R2 = Me
4a: R1 = OMe, R2 = Me
Scheme 1.
F2
F2
F2
F2
Br
N
F
F2
F2
S
Me
n-BuLi
Me
1)
2)
MeO
S
N
OMe
Me
dry THF
R1
Me
R1
1
1
5
1a
2a
: R = H
: R = H
6 : R1 = OMe
1
: R = OMe
Scheme 2.
OMe
P(Ph)3I
H
2) OHC
OMe
1) t-BuOK
dry THF
Me
Me
Me
Me
8
7
OMe
OMe
Br
Br
Br2
NaH
t-BuOH
8
Br
CH2Cl2
Me
Me
Me
Me
10
9
F2
F2
F2
F2
OMe
F2
F2
N
F
MeO
N
OMe
Me
2)
dry ether
S
1) n-BuLi
OMe
10
S
Me
MeO
3a
Scheme 3.
(Scheme 3). A colorless solid was obtained in 36% yield. The
synthesis of compound 8 was carried out by the Wittig reaction
from isopropyltriphenylphosphonium iodide (7) and p-anisal-
dehyde in 85% yields. Compounds 1a, 2a, and 3a were purified
by column chromatography (hexane/AcOEt) and characterized
in toluene by irradiation with UV light. The spectrum of the
isolated closed-ring isomer is also shown in Figure 1. Upon
irradiation with 313 nm light the colorless toluene solution of
1a slowly turned pale yellow, in which the absorption maxi-
mum was observed at 419 nm (¾ = 12500 M¹1 cm¹1). When
the pale yellow solution was irradiated with visible light (- >
440 nm), the spectrum readily returned back to colorless one.
The pale yellow color is due to the closed-ring isomer 1b. In a
1
by H NMR spectroscopy, MS, and elemental analysis.
Absorption Spectra and Quantum Yields.
Figure 1
shows the absorption spectral change of 1 (2.95 © 10¹5 M)

S. Takami et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 9 (2013) 1061
0.6
0.5
0.4
0.3
0.2
0.1
0
0.6
0.5
0.4
0.3
0.2
0.1
0
300 350 400 450 500 550 600
300 350 400 450 500 550 600
Wavelength / nm
Wavelength / nm
Figure 3. Absorption spectra of compound 3 (2.52 ©
10¹5 M) in toluene: (dashed line) open-ring isomer 3a,
(solid line) closed-ring isomer 3b, and (dotted line) in the
photostationary state under irradiation with 313 nm light.
Figure 1. Absorption spectra of compound 1 (2.95 ©
10¹5 M) in toluene: (dashed line) open-ring isomer 1a,
(solid line) closed-ring isomer 1b, and (dotted line) in the
photostationary state under irradiation with 313 nm light.
0.6
0.5
0.4
0.3
0.2
0.1
measured by irradiation with 313 nm light, while the photo-
cycloreversion quantum yields were measured by irradiation
with 416 nm light. The photocyclization quantum yields of
1a and 2a were 0.15 and 0.20, respectively. The photocyclo-
¹3
reversion quantum yields of 1b and 2b were 7.8 © 10 and
4.2 © 10¹3, respectively. The photocycloreversion quantum
yield of 2b was a half of that of 1b. The decrease is ascribed to
the introduction of the methoxy substituent at the para-position
of the phenyl ring.8
Figure 3 shows the absorption spectral changes of 3 (2.52 ©
10¹5 M) in toluene by UV irradiation. Similar color and spec-
tral changes were observed. The absorption maximum (428 nm)
is 9 nm longer than that of 1b (419 nm) in toluene and the
solution shows a slightly deep yellow color. The yellow color
was bleached by irradiation with visible light (- > 440 nm).
The photobleaching rate of 3b was slower than that of 1b and
2b. The conversion from the open-ring to the closed-ring
isomers by irradiation with 313 nm was 98%. The absorption
coefficient of the closed-ring isomer 3b, (18900 M¹1 cm¹1),
is 1.5 times larger than that of 1b. Introduction of a 4-meth-
oxyphenyl-substituted olefin is effective in increasing the
¾ value of the closed-ring isomer.
Table 1 summarizes the photocyclization and photocyclo-
reversion quantum yields of 1-4. The photocyclization quan-
tum yields of these four derivatives 1-4 are similar in the range
from 0.15 to 0.19. On the other hand, the photocycloreversion
quantum yield was found to increase by replacing the methyl
group at R2 with phenyl substituents. The cycloreversion
quantum yield of 1b (7.8 © 10¹3) is 5 times larger than that
of 4b (1.4 © 10¹3). The cycloreversion quantum yields of 3b
(1.8 © 10¹3) and 4b are almost the same. Figure 4 shows the
photos of the color changes of four derivatives 1-4 upon UV
irradiation. When the toluene solutions of the derivatives 1a-4a
are irradiated with UV light, these colorless solutions turn to
various shade of yellow. As can be seen in Figure 4, the four
derivatives exhibit yellow colors from pale to golden deep
yellow.
0
300 350 400 450 500 550 600
Wavelength / nm
Figure 2. Absorption spectra of compound 2 (2.43 ©
10¹5 M) in toluene: (dashed line) open-ring isomer 2a,
(solid line) closed-ring isomer 2b, and (dotted line) in the
photostationary state under irradiation with 313 nm light.
previous paper,9 it was reported that 1-thiazolyl-2-vinylcyclo-
pentene having a methyl group at 5-position of the thiazole ring
forms a by-product upon UV irradiation. When the methyl
group was substituted with a methoxy group, the by-product
formation was suppressed. This indicates that the methoxy
substituent at the 5-position is indispensable for the molecule
to undergo reversible photochromic reactions. The colored
closed-ring isomer was stable in the dark at room temperature
and could be isolated by high-performance liquid chromatog-
raphy (HPLC, silica gel column, hexane/ethyl acetate =
80:20). The conversion from 1a to 1b in the photostationary
state under irradiation with 313 nm light was 93%.
Figure 2 shows the absorption spectral changes of 2 (2.43 ©
10¹5 M) in toluene by UV irradiation. The colorless solution
turned yellow upon irradiation with 313 nm light and a new
absorption band appeared at 424 nm. The yellow color is due
to the closed-ring isomer 2b and bleached by irradiation with
visible light (- > 440 nm). The absorption coefficient of 2b
was determined to be 17400 M¹1 cm¹1, which is larger than
that of 1b. The conversion from the open-ring to the closed-
ring isomer by irradiation with 313 nm was 95%. The photo-
cyclization/cycloreversion quantum yields were determined in
toluene at 25 °C. The photocyclization quantum yields were
Thermal Stability and Fatigue Resistance. The thermal
stability of the closed-ring isomers and the fatigue resistance of
compounds 1-4 were measured, as shown in Figures 5 and 6.
Figure 5 shows the thermal stability of the closed-ring isomers

1062 Bull. Chem. Soc. Jpn. Vol. 86, No. 9 (2013)
Yellow-Colored Photochromic Compounds
Table 1. Absorption Maxima and Coefficients of the Open- and Closed-Ring Isomers of Compounds 1, 2, 3, and 4,
and the Quantum Yields in Toluene
-
-
max
/nm (¾/M¹1 cm
max
Φa¼b
Φb¼a
Conversion
/nm (¾/M¹1 cm
)
)
¹1
¹1
¹3
1a
2a
3a
4a
316 (20210)
322 (22100)
322 (23600)
320 (22100)
0.15 (313 nm) 1b 419 (12500)
0.20 (313 nm) 2b 424 (17400)
0.17 (313 nm) 3b 428 (18900)
0.19 (313 nm) 4b 416 (17100)
7.8 © 10 (416 nm)
0.93
0.95
0.98
0.97a)
¹3
4.2 © 10 (416 nm)
¹3
1.8 © 10 (416 nm)
¹3
1.4 © 10 (416 nm)
a) Ref. 6.
a)
1
1b, 2b, 3b, 4b
0.8
0.6
0.4
0.2
0
0
50
100
150
200
250
Time / h
Figure 5. Thermal stability of the closed-ring isomers 1b
(black circles), 2b (blue squares), 3b (green circles), and
4b (red squares) in toluene.
b)
1
4b
0.8
1b
3b
0.6
2b
0.4
0.2
0
5
10
15
20
Figure 4. Photographs of color changes of compounds 1, 2,
3, and 4 under irradiation with 313 nm in toluene: a) before
photoirradiation, b) after photoirradiation.
Cycle Number
Figure 6. Fatigue-resistance of compounds 1 (black cir-
cles), 2 (blue squares), 3 (green circles), and 4 (red squares)
in toluene. Absorbances of 1b-4b were plotted after
irradiation with UV light.
1b, 2b, 3b, and 4b in toluene at 80 °C in the dark. The value of
A/A0 was plotted against the storage time in the dark, where
A0 is the initial absorbance and A the absorbance after t hours
at 80 °C. As can be seen from Figure 5, the absorbances of the
photogenerated closed-ring isomers 1b, 2b, 3b, and 4b remain
constant for 100 h. Even after 240 h storage no appreciable
decrease of the absorbances was observed.
Fatigue resistance, the number of times that photocyclization
and cycloreversion reactions can be repeated without loss of
performance, is indispensable for practical applications. Ac-
cording to the method described in the reference,11 fatigue
resistance of compounds 1-4 was measured. Toluene solutions
of compounds 1, 2, 3, and 4 were irradiated at first with UV
light (300-400 nm) and then bleached with visible light (- >
440 nm). The absorption intensity changes at the wavelength
of -max of the closed-ring isomers was followed against the
coloration/decoloration cycles, as shown in Figure 6. The
toluene solution of 3a (absorbance was about 0.6 at -max = 322
nm) was irradiated with UV light (300-400 nm) for 13 s and
then with visible light for more than 12 min in the absence of
air. The absorbances of 1b-4b show gradual decrease in 30
cycles. Among the three compounds 3 showed superior fatigue
resistance and was comparable to that of 4.
The conversion of open-ring isomer 1a to closed-ring isomer
1
1b was also followed using H NMR spectroscopy, as shown
1
in Supplementary Figure 1. In the H NMR spectrum of 1a in
CDCl3, the signals of the methoxy group and the two methyl
groups were observed at ¤ = 4.05 and 1.77 and 1.65 ppm,
respectively. Upon irradiation with UV light (300-400 nm) for
10 min, these signals decreased in intensity, while new peaks

S. Takami et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 9 (2013) 1063
appeared at 3.30 and 1.47 and 1.16 ppm. These new peaks are
assigned to those of closed-ring isomer 1b. In addition to these,
several additional weak new peaks (such as ¤ = 4.02 and 3.40
and 1.68 ppm) also appeared. These additional signals did not
decrease upon irradiation with visible light (- > 440 nm) and
were assigned to by-products,4,5 though the chemical structures
were not specified. On the other hand, such additional signals
were not observed in the H NMR spectrum of 3a upon irra-
diation with UV light (300-400 nm) for 10 min. This result also
shows that compound 3 has superior fatigue resistance.
cyclopentene5a (900 mg, 2.78 mmol) in dry THF (1 mL) was
added. The reaction mixture was further stirred at ¹80 °C
for 2 h, and then distilled water was added. The product was
extracted with ether, dried with MgSO4, and concentrated under
reduced pressure. The residue was purified by column chro-
matography (ethyl acetate/hexane = 2/8) to afford to 202 mg
(22%) of 1a as solid: mp 95-96 °C; 1H NMR (400 MHz,
CDCl3): ¤ 7.76-7.74 (m, 2H), 7.40-7.22 (m, 8H), 4.05 (s, 3H),
1.77 (s, 3H), 1.65 (s, 3H); MS m/z 495 [M+]. Calcd for
C25H19F6NOS: C, 60.60; H, 3.87; N, 2.83%. Found: C, 60.49;
H, 3.88; N, 2.76%.
1
Conclusion
Synthesis of 1-[5-Methoxy-2-(4-methoxyphenyl)-4-thia-
zolyl]-2-(2-methyl-1-phenyl-1-propenyl)perfluorocyclopen-
tene (2a). To a stirring solution of 4-bromo-5-methoxy-2-(4-
methoxyphenyl)thiazole (6)6 (500 mg, 1.67 mmol) in dry THF
(10 mL) was slowly added 1.6 M n-BuLi in hexane (1.10
mL, 1.76 mmol) at ¹80 °C under argon atmosphere. After the
mixture had been stirred for 15 min at ¹95 °C, 1-(2-methyl-
1-phenyl-1-propenyl)perfluorocyclopentene5a (773 mg, 2.38
mmol) in dry THF (1 mL) was added. The reaction mixture
was further stirred at ¹80 °C for 2 h, and then distilled
water was added. The product was extracted with ether, dried
with MgSO4, and concentrated under reduced pressure. The
residue was purified by column chromatography (ethyl acetate/
hexane = 2/8) to afford to 158 mg (18%) of 2a as solid: mp
We have examined the photochromic performance of 1-
thiazolyl-2-vinylcyclopentene derivatives 1a-3a bearing a
phenyl- or 4-methoxyphenyl-substituted olefin. When the
methyl group at the 5-position of the thiazole ring was replaced
with a methoxy group, the by-product formation was sup-
pressed and reversible photochromic reactions were observed.
Upon irradiation with 313 nm light, the colorless toluene
solutions of 1a, 2a, and 3a turned to various tone of yellow.
The absorption maxima of 1b (419 nm), 2b (424 nm), and
3b (428 nm) showed bathochromic shift as much as 3-12 nm
relative to the maximum of 4b (416 nm). Among the three com-
pounds 3 has the highest absorption coefficient of the closed-
ring isomer 3b (18900 M¹1 cm¹1) and exhibits superior fatigue
resistance. The closed-ring isomers 1b-3b were found to be
thermally stable at 80 °C for more than 240 h.
1
129-130 °C; H NMR (400 MHz, CDCl3): ¤ 7.67 (d, J = 8.8
Hz, 2H), 7.35-7.22 (m, 5H), 6.88 (d, J = 8.8 Hz, 2H), 4.01
(s, 3H), 3.82 (s, 3H), 1.75 (s, 3H), 1.63 (s, 3H); MS m/z 525
[M+]. Calcd for C26H21F6NO2S: C, 59.42; H, 4.03; N, 2.67%.
Found: C, 59.72; H, 3.83; N, 2.37%.
General. 1H NMR spectra were recorded on a JEOL JMN-
ECP 400 (400 MHz) instrument. Mass spectra were measured
with a Perkin-Elmer Turbo Mass gas chromatography-mass
spectrometer and a Shimadzu GCMS-PARVUM2 gas chro-
matography-mass spectrometer. High-resolution mass spectra
(HRMS) were obtained with a JEOL MS-700. Absorption spec-
tra were recorded on a Shimadzu UV-1800 absorption spec-
trophotometer. Photoirradiation was carried out using an Ushio
500 W super high-pressure mercury lamp or an Ushio 500 W
xenon lamp. Monochromatic light was isolated by passing
the light through a cutoff filter (UV-27) and monochromator
(SPG-120S, Shimadzu). Elemental analyses were performed by
the Laboratory for Organic Elemental Microanalysis, Kyoto
University. The cyclization quantum yields were determined by
comparing the photocyclization rate of furyl flugide in toluene
with a standard procedure. The cycloreversion quantum yields
were measured using 4 in toluene as a reference.
Synthesis of Isopropyltriphenylphosphonium Iodide (7).
A solution of 2-iodopropane (35 g, 204 mmol) and triphenyl-
phosphine (53 g, 203 mmol) in acetonitrile (325 mL) was
refluxed for 5 days. The solution was allowed to cool to room
temperature. After evaporation of the solvent, the residue was
washed with ether three times to afford 75 g (85%) of 7 as
1
pale yellow powder: H NMR (400 MHz, CDCl3): ¤ 8.0-7.9
(m, 6H), 7.8-7.65 (m, 9H), 5.35-5.25 (m, 1H), 1.35 (d, J = 7.0
Hz, 3H), 1.30 (d, J = 7.0 Hz, 3H), Calcd for C21H22IP: C,
58.35; H, 5.13%. Found: C, 58.05; H, 5.13%.
Synthesis of 2-Methyl-1-(4-methoxyphenyl)-1-propene
(8). To a solution of 7 (25 g, 58 mmol) in dry THF (230
mL) was added slowly 1 M potassium tert-butoxide (58
mL, 58 mmol) in THF at room temperature under argon. After
the mixture was stirred for 30 min at room temperature, p-
anisaldehyde (3.30 g, 24 mmol) in dry THF (40 mL) was added.
The reaction mixture was further stirred for 12 h and then
distilled water was added. The product was extracted with
ether, dried over MgSO4, and concentrated under reduced
pressure. The residue was purified by column chromatography
(ethyl acetate/hexane = 1/9) to afford 3.57 g (95%) of 8 as
Materials.
Compounds 5,10 6,6 1-(2-methyl-1-phenyl-
1-propenyl)perfluorocyclopentene,5a and 1-[5-methoxy-2-(4-
methoxyphenyl)]perfluorocyclopentene6 were prepared accord-
ing to methods reported previously. Spectroscopic grade
solvents were purified by distillation before use. All reactions
were monitored by thin-layer chromatography carried out on
0.2 mm Merck silica gel plates (60F-254). Column chromatog-
raphy was performed on silica gel (Kanto Kagaku 63-201 ¯m).
Synthesis of 1-(5-Methoxy-2-phenyl-4-thiazolyl)-2-(2-
methyl-1-phenyl-1-propenyl)perfluorocyclopentene (1a).
To a stirring solution of 4-bromo-5-methoxy-2-phenylthiazole
(5)10 (500 mg, 1.85 mmol) in dry THF (10 mL) was slowly
added 1.6 M n-BuLi in hexane (1.21 mL, 1.94 mmol) at ¹80 °C
under argon atmosphere. After the mixture had been stirred for
15 min at ¹80 °C, 1-(2-methyl-1-phenyl-1-propenyl)perfluoro-
1
colorless oil: H NMR (400 MHz, CDCl3): ¤ 7.15 (d, J = 8.8
Hz, 2H), 6.85 (d, J = 8.8 Hz, 2H), 6.20 (s, 1H), 3.78 (s, 3H),
1.87 (s, 3H), 1.84 (s, 3H), MS (GC) m/z 163 ([M + 1]: 11%),
162 (M: 100%), 147 ([M ¹ CH3]: 92%). Calcd for C11H14O: C,
81.44; H, 8.70%. Found: C, 81.58; H, 8.99%.
Synthesis of 1-(1,2-Dibromo-2-methylpropyl)-4-methoxy-
benzene (9). To a solution of 8 (1.20 g, 7.4 mmol) in di-
chloromethane (40 mL) was added bromine (1.16 g, 7.3 mmol)

1064 Bull. Chem. Soc. Jpn. Vol. 86, No. 9 (2013)
Yellow-Colored Photochromic Compounds
in dichloromethane (8 mL) at ¹80 °C, and stirring was con-
tinued for 30 min at the same temperature. To the reaction
mixture was added aqueous sodium thiosulfate. The mixture
was extracted with dichloromethane, dried over MgSO4, and
concentrated under reduced pressure. The residue was puri-
fied by column chromatography (AcOEt/hexane = 1/9) to
afford 1.37 g (58%) of 9 as colorless oil (This compound 9 is
(s, 3H), 1.76 (s, 3H), 1.62 (s, 3H); MS m/z 555 [M+]. Calcd for
C27H23F6NO3S: C, 58.37; H, 4.17; N, 2.52%. Found: C, 58.63;
H, 4.32; N, 2.52%.
We thank Professor Yasushi Yokoyama at Yokohama
National University for helpful discussions on the synthesis
of compound 10. This work was supported by the Grant-in-Aid
for Scientific Research on Priority Area “New Frontiers in
Photochromism (No. 471)” from the Ministry of Education,
Culture, Sports, Science and Technology (MEXT), Japan.
1
unstable): H NMR (400 MHz, CDCl3): ¤ 7.43 (d, J = 8.8 Hz,
2H), 6.85 (d, J = 8.8 Hz, 2H), 5.25 (s, 1H), 3.82 (s, 3H), 2.00
(s, 3H), 1.99 (s, 3H); MS (GC): m/z 243 ([M ¹ 80Br]: 24%),
241 ([M ¹ 82Br]: 25%), 162 ([M ¹ 2Br]: 100%), 147 ([M ¹
2Br ¹ CH3]: 76%).
Supporting Information
1H NMR chart (Figure S1). This material is available free of
charge on the web at http://www.csj.jp/journals/bcsj/.
Synthesis of 1-Bromo-1-(4-methoxyphenyl)-2-methyl-1-
propene (10).
To a solution of 9 (1.37 g, 4.28 mmol) in
t-butyl alcohol (9 mL) was added sodium hydride (40% in
mineral oil, 154 mg, 6.42 mmol, 1.5 equiv) and the resulting
mixture was stirred for 20 h at 40 °C. After adding water,
the mixture was extracted with ether, dried over MgSO4, and
concentrated under reduced pressure. The residue was purified
by column chromatography (AcOEt/hexane = 1/9) to afford
760 mg (74%) of 10 as colorless oil: 1H NMR (400 MHz,
CDCl3): ¤ 7.22 (d, J = 8.8 Hz, 2H), 6.85 (d, J = 8.8 Hz, 2H),
3.82 (s, 3H), 2.03 (s, 3H), 1.99 (s, 3H). MS (GC): m/z 242
(M: 23%), 240 (M: 23%), 161 ([M ¹ Br]: 100%), 91 ([M ¹
Br ¹ CH3]: 29%). Calcd for C11H13BrO: C, 54.79; H, 5.43%.
Found: C, 54.94; H, 5.46%.
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1
solid: mp 103-104 °C, H NMR (400 MHz, CDCl3): ¤ 7.67 (d,
J = 8.8 Hz, 2H), 7.25 (d, J = 8.8 Hz, 2H), 6.89 (d, J = 8.8 Hz,
2H), 6.83 (d, J = 8.8 Hz, 2H), 4.01 (s, 3H), 3.83 (s, 3H), 3.80