Synthesis and photochromic properties of novel yellow developing photochromic compounds

Article abstract of DOI:10.1016/j.tet.2004.05.029

Two 1-thiazolyl-2-thienylcyclopentene derivatives, 1a and 2a, and a 1-thiazolyl-2-vinylcyclopentene derivative 3a have been synthesized in an attempt to obtain photochromic compounds which change the color from colorless to yellow, and have low photocycloreversion quantum yields and high absorption coefficients of the colored isomers. All of these compounds underwent reversible photochromic reactions. Compounds 1a and 2a in toluene solutions changed the color upon 313 nm light irradiation from colorless to orange and pink, in which absorption maxima were observed at 494 nm (ε=10,000 M^-1cm ^-1) and 525 nm (ε=8500 M^-1cm^-1), respectively. On the other hand, the colorless toluene solution of 3a turned yellow upon irradiation with 313 nm light, in which the absorption maximum was observed at 416 nm (ε=17,100 M^-1cm^-1). The photocyclization/cycloreversion quantum yields of 3 were 0.19 and 0.0014, respectively. The conversion from the open- to the closed-ring isomer of 3 in the photostationary state under irradiation with 313 nm light was close to 100%.

Full text of DOI:10.1016/j.tet.2004.05.029

Tetrahedron 60 (2004) 6155–6161
Synthesis and photochromic properties of novel yellow developing
photochromic compounds
*
Shizuka Takami and Masahiro Irie
*
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University,
and ‘Nanotechnology Support Project’ of the Ministry of Education, Culture, Sports, Science and Technology (MEXT),
Japan, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
Received 15 March 2004; revised 16 April 2004; accepted 14 May 2004
Available online 11 June 2004
Abstract—Two 1-thiazolyl-2-thienylcyclopentene derivatives, 1a and 2a, and a 1-thiazolyl-2-vinylcyclopentene derivative 3a have been
synthesized in an attempt to obtain photochromic compounds which change the color from colorless to yellow, and have low
photocycloreversion quantum yields and high absorption coefficients of the colored isomers. All of these compounds underwent reversible
photochromic reactions. Compounds 1a and 2a in toluene solutions changed the color upon 313 nm light irradiation from colorless to orange
and pink, in which absorption maxima were observed at 494 nm (1¼10,000 M21 cm21) and 525 nm (1¼8500 M21 cm21), respectively. On
the other hand, the colorless toluene solution of 3a turned yellow upon irradiation with 313 nm light, in which the absorption maximum was
observed at 416 nm (1¼17,100 M21 cm21). The photocyclization/cycloreversion quantum yields of 3 were 0.19 and 0.0014, respectively.
The conversion from the open- to the closed-ring isomer of 3 in the photostationary state under irradiation with 313 nm light was close to
100%.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
reported as yellow photochromic dyes.16,17 These colored
isomers are, however, photochemically unstable and the
photocycloreversion quantum yields are rather high. For a
full color display it is strongly desired to develop yellow
photochromic compounds which have low photocyclo-
reversion quantum yields and thermal stability at room
temperature. In previous papers, we showed that introduc-
tion of alkoxy groups at the reactive carbons of diarylethene
derivatives remarkably suppresses the photocycloreversion
quantum yields.6,12,18 Furthermore, the rational correlations
between the substitution and the photocycloreversion
quantum yields have been demonstrated based on an ab
initio MO calculation.19 In this study, we have synthesized
two 1-thiazolyl-2-thienylcyclopentene derivatives 1a and
2a, and a 1-thiazolyl-2-vinylcyclopentene derivative 3a
having methoxy substituents to obtain yellow photochromic
compounds having a low photocycloreversion quantum
yield (Scheme 1).
Photochromic compounds have attracted much attention
because of their potential ability for optical memory, photo-
optical switching and display devices.1,2 Among them
diarylethenes with heterocyclic aryl groups, such
as thiophene or benzothiophene groups, are the most
promising candidates for the applications3–8 because of
their fatigue resistant and thermally irreversible photo-
chromic performance.9,10 For the application to a full color
display it is indispensable to prepare red and yellow
developing diarylethene derivatives. Several attempts have
been conducted to shift the absorption maximum of the
closed-ring isomer to shorter wavelengths by introduction of
thiazole rings as the aryl group. When the thiophene rings
of 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclo-
pentenes11 are replaced with thiazole rings, the absorption
maximum of the closed-ring isomer shifts from 575 nm
(blue) to 525 nm (red).12,13 Another approach to further shift
the absorption band to shorter wavelength (yellow) is to
attach the thiophene rings to the ethene moiety at the
2-position.13 – 15 Very recently, oxazolylfulgides and
2,3-bis(2,3,5-trimethyl-3-thienyl)maleic imidine have been
2. Results and discussion
2.1. Synthesis and photochromic properties of
1-thiazolyl-2-thienylcyclopentene derivatives
Keywords: Photochromic compound; Yellow color; Photochromism;
Quantum yields.
4-Thiazolyl12,13 and 2-thienyl14,15 chromophores were
chosen as the aryl groups of diarylethenes to shift the
absorption maxima of the closed-ring isomers to shorter
*
Corresponding authors. Tel.: þ81-92-642-4132; fax: þ81-92-642-3568;
e-mail addresses: takami@cstf.kyushu-u.ac.jp; irie@cstf.kyushu-u.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.05.029

6156
S. Takami, M. Irie / Tetrahedron 60 (2004) 6155–6161
Scheme 1.
wavelengths. In order to reduce the photocycloreversion
quantum yield, methoxy substituents were introduced at the
reactive carbons. According to the above molecular design
principle, compounds 1a and 2a were constructed.
Compound 1a was synthesized by the reaction of
4-bromo-5-methyl-2-phenylthiazole12 with 1-(3-methyl-2-
thienyl)octafluorocyclopentene (4) by bromine-lithium
exchange followed by nucleophilic displacement of fluor-
ide. A colorless solid was obtained in 14% yield. 2a was
synthesized by the reaction of 2-bromo-3-methoxythio-
phene20 with 1-(5-methoxy-2-phenyl-4-thiazolyl)octafluoro-
cyclopentene12 in dry ether as a colorless solid. Both
compounds were purified by column chromatography
(hexane/AcOEt) and characterized by 1H NMR spectroscopy,
MS, and elemental analysis. (Scheme 2).
(3.3£1025 M) in toluene by UV irradiation. Upon
irradiation with 313 nm light, the colorless solution turned
orange, in which a visible absorption band was observed at
494 nm (1¼10,000 M21 cm21). The orange color is due to
the closed-ring isomer 1b. When the orange solution was
irradiated with visible light (l.440 nm), the spectrum
readily returned back to the original one. The colored
isomer was stable in the dark at room temperature and could
be isolated by high performance liquid chromatography
(HPLC, ethyl acetate/hexane¼1/9 as the eluent). The
1
structure of 1b was analyzed with H NMR spectroscopy,
MS, and elemental analysis. All data agreed well with the
closed-ring isomer 1b. The conversion from 1a to 1b in the
photostationary state under irradiation with 313 nm light
was 69%.
Figure 1 shows the absorption spectral change of 1
Figure 1. Absorption spectra of compound 1 (3.3£1025 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.
Figure 2 shows the absorption spectral changes of 2
(2.4£1025 M) in toluene by UV irradiation. The absorption
maximum of the photogenerated closed-ring isomer 2b was
observed at 525 nm. The absorption maximum is 31 nm
longer than that of 1b (494 nm). The pink color is due to the
closed-ring form 2b and bleached by irradiation with visible
Scheme 2.

S. Takami, M. Irie / Tetrahedron 60 (2004) 6155–6161
6157
yellow color. Therefore, the 2-thiophene group14,15 was
replaced with an ethylene unit to further shift the absorption
band of the closed-ring isomer to shorter wavelengths.
2.2. Synthesis and photochromic properties of a 1-
thiazolyl-2-vinylcyclopentene derivative
Recently, novel photochromic compounds having a thio-
phene and a 2-butene or stryl unit have been reported by
21
Branda et al.
and Yokoyama et al.22,23 The colorless
solutions of these compounds turned to yellow by
irradiation with UV light. The absorption maximum of the
closed-ring isomer of 1-(1,2-dimethylpropenyl)-2-(2-
methyl-5-phenyl-3-thienyl)perfluorocyclopentene (8) is
reported to be 450 nm in dichloromethane.21 When the
thiophene ring is replaced with a thiazole ring, the
absorption maximum of the closed-ring isomer is expected
to shift to a wavelength shorter 450 nm. In other words, the
closed-ring isomer would not give yellow color. In order to
obtain yellow colored closed-ring isomer, it is required to
introduce substituents24,25 which shift the band to longer
wavelengths. Wedesignedaderivative3a, whichhasmethoxy
substituents at the para-position of the phenyl ring and
5-position of the thiazole ring. Both methoxy substituents
are effective to induce bathochromic shift.6,12,18,24 The
methoxy group at the 5-position is also known to decrease
the photocycloreversion quantum yield. The synthesis was
performed according to Scheme 3. 5-Methoxy-2-(4-
methoxyphenyl)thiazole 5 was obtained from N-(4-
methoxybenzoyl) glycine methyl ester as a yellow solid in
80% yield. Compound 3a was synthesized by the coupling
reaction of 7 and 2-bromo-3-methyl-2-butene,26 and was
purified by HPLC. The structures of all compounds were
Figure 2. Absorption spectra of compound 2 (2.4£1025 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.
light (l.440 nm). The structure of isolated colored product
was analyzed by 1H NMR spectroscopy, MS, and elemental
analysis. All data agreed well with the closed-ring isomer
2b. The photobleaching rate of 2b was slower than that of
1b. The absorption coefficient of 2b is 8500 M21 cm21
,
which is less than that of 1b. The conversion from the open-
ring to the closed-ring isomer by irradiation with 313 nm
was 89%.
The photocyclization/cycloreversion quantum yields were
measured in toluene at 25 8C. The photocyclization
quantum yields of 1a and 2a were determined to be 0.36
and 0.26, respectively. The methoxy substitution scarcely
affected the cyclization reaction. On the other hand, the
photocycloreversion quantum yield was strongly suppressed
by the methoxy substituents. The photocycloreversion
quantum yield of 2b (0.012) was decreased as much as 10
times in comparison with that of 1b (0.12). The hypso-
chromic shifts of 1b and 2b are not large enough to exhibit
1
confirmed by H NMR, mass spectroscopy, and elemental
analysis.
Figure 3 shows the absorption spectral change of 3
(2.5£1025 M) in toluene by irradiation with UV light. The
Scheme 3.

6158
S. Takami, M. Irie / Tetrahedron 60 (2004) 6155–6161
yellow colored solution slowly returned back to the initial
colorless solution upon prolonged irradiation with visible
light. The colored isomer was stable in the dark at room
temperature and could be isolated by HPLC (silica gel; ethyl
acetate/hexane¼2/8 as the eluent). The molecular charac-
1
teristics of the yellow colored isomer was examined by H
NMR, mass spectrum, and elemental analysis. All analysis
data agreed with that of the closed-ring isomer 3b.
The cyclization quantum yield (313 nm) was determined to
be 0.19. The quantum yield is slightly smaller than the
values of 1a and 2a. On the other hand, the cycloreversion
quantum yield was remarkably suppressed to 0.0014.
Although the photocyclization/cycloreversion quantum
yields of (8) are not reported, the conversion from the
open- to the closed-ring isomer with 365 nm light at the
photostationary state is reported to be 64%.21 The low
conversion suggests that the photocycloreversion quantum
yield is rather high in comparison with 3, in which the
conversion as high as 100% is observed. The photocycliza-
tion and photocycloreversion quantum yields of 1, 2 and 3
are summarized in Table 1. The photocycloreversion
quantum yield of 3b is 10 times smaller than that of 2b.
Figure 3. Absorption spectra of compound 3 (2.5£1025 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.
spectrum of the isolated colored isomer is also shown in
Figure 3. Upon irradiation with 313 nm light the colorless
toluene solution of 3a slowly turned yellow, in which
absorption maxima were observed at 330 and 416 nm. It
should be noted that any photochemical side product was
not observed by HPLC analysis. The photostationary
spectrum is almost the same as the colored isomer,
indicating a high conversion from the colorless to the
colored isomers by irradiation with 313 nm light. The
Figure 4 shows the colors of the closed-ring isomers 1b, 2b
and 3b in toluene. The absorption band of 3b (416 nm)
showed hypochromic shift in compared with those of 1b
Table 1. Absorption maxima and coefficients of the open- and closed-ring isomers of compounds 1, 2, and 3, and the quantum yields in toluene
l max/nm (1/M21 cm21
)
Fa!b
l max/nm (1/M21 cm21
)
Fb!a
Conversion (313 nm)
1a
2a
3a
302 (22300)
321 (23000)
320 (22500)
0.36 (300 nm)
0.26 (313 nm)
0.19 (313 nm)
1b
2b
3b
494 (10000)
525 (8500)
416 (17100)
1.2£1021(492 nm)
1.2£1022(525 nm)
1.4£1023(416 nm)
0.69
0.89
0.97
Figure 4. Toluene solutions of compounds 1, 2, and 3 under irradiation with 313 nm: orange (1b), pink (2b), and yellow colors (3b).

S. Takami, M. Irie / Tetrahedron 60 (2004) 6155–6161
6159
(494 nm) and 2b (525 nm). This is ascribed to shorter
p-conjugation length of 3b in comparison with 1b and 2b.
More interestingly, the absorption coefficient of 3b is
17,100 M21 cm21, which is much larger than that of 1b
(10,000 M21 cm21) and 2b (8500 M21 cm21). The value, is
also much larger than the absorption coefficients of the
closed-ring isomers of yellow developing diarylethenes,7
such as 1,2-bis(3-methyl-2-thienyl)perfluorocyclopentene
(6870 M21 cm21 at 432 nm in 3-methylpentane),27 1,2-
bis(3,5-dimethyl-2-thienyl)perfluorocyclopentene
(5800 M21 cm21 at 425 nm in hexane),14,28,29 1,2-bis(3-
methyl-5-phenyl-2-thienyl)perfluorocyclopentene
(5250 M21 cm21 at 438 nm in hexane),14,28,29 1,2-bis(2,4-
dimethyl-5-thiazolyl)perfluorocyclopentene (7000 M21 cm21
at 390 nm in hexane)13 and 1,2-bis(2-methyl-4-phenyl-5-
thiazolyl)perfluorocyclopentene (7000 M21 cm21 at 406 nm
inhexane)13. Thelargeabsorptioncoefficientof3b isduetothe
methoxy group at the para-position of the phenyl ring.24
argon atmosphere. After the mixture had been stirred for
15 min at 280 8C, compound 4 (540 mg, 1.90 mmol) in dry
THF (2 mL) was added. The reaction mixture was further
stirred at 280 8C 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/
hexane¼1/9) and HPLC (ethyl acetate/hexane¼1/9) to
afford to 130 mg (14%) of 1a as colorless needles: mp
107–108 8C. 1H NMR (CDCl3, 200 MHz): d¼1.80 (s, 3H),
1.98 (s, 3H), 6.86 (d, J¼5.0 Hz, 1H), 7.44 (m, 5H), 7.88 (m,
2H). MS (m/z) 445 (Mþ). Anal. Found: C, 53.96; H, 2.85; N,
3.00%. Calcd for C20H13F6NS2: C, 53.93; H, 2.94; N, 3.14%.
4.1.2. Closed-ring isomer for 1a (1b). Compound 1b was
isolated as an orange solid by passing a photostationary
solution containing 1a and 1b thorough HPLC (ethyl
acetate/hexane¼1/9): 1H NMR (CDCl3, 200 MHz):
d¼1.68 (s, 3H), 1.81 (s, 3H), 5.73 (d, J¼6.0 Hz, 1H), 6.24
(d, J¼6.0 Hz, 1H), 7.42–7.62 (m, 3H), 7.85–8.05 (m, 2H).
MS (m/z) 445 (Mþ). Anal. Found: C, 53.93; H, 2.95; N,
3.18%. Calcd for C20H13F6NS2: C, 53.93; H, 2.94; N,
3.14%.
3. Conclusion
New photochromic compounds 1a, 2a and 3a were
synthesized in an attempt to obtain yellow developing
photochromic compounds with low photocycloreversion
quantum yields and large absorption coefficients of the
closed-ring isomers. The toluene solution of 3a turned
yellow by irradiation with 313 nm, showing an absorption
maximum at 416 nm (1¼17,100 M21 cm21). The absorp-
tion coefficient of the closed-ring isomer 3b was much
larger than those of 1b and 2b. The photocyclization/
cycloreversion quantum yields of 3 were determined to be
0.19 and 0.0014, respectively. Compound 3 is a useful
candidate as a yellow photochromic dye.
4.1.3. 1-(5-Methoxy-2-phenyl-4-thiazolyl)-2-(3-methoxy-
2-thienyl)perfluorocyclopentene (2a). To
a stirring
solution of 2-bromo-3-methoxythiophene20 (500 mg,
2.6 mmol) in dry ether (25 mL) was slowly added 1.6 M
n-BuLi in hexane (1.6 mL, 2.7 mmol) at 280 8C under
argon atmosphere. After the mixture had been stirred for
15 min at 280 8C, 1-(5-methoxy-2-phenyl-4-thiazolyl)per-
fluorocyclopentene12 (1.0 g, 2.8 mmol) in dry ether (10 mL)
was added. The reaction mixture was further stirred at
280 8C for 1 h, and then distilled water was added. The
product was extracted with diethyl ether, dried with MgSO4,
and concentrated under reduced pressure. The residue
was purified by column chromatography (ethyl acetate/
hexane¼2/8) and HPLC (ethyl acetate/hexane¼2/8) to
afford to 50 mg (4%) of 2a as colorless plates: mp 133–
134 8C. 1H NMR (CDCl3, 200 MHz). d¼3.59 (s, 3H), 3.81
(s, 3H), 6.80 (d, J¼5.6 Hz, 2H), 7.35–7.50 (m, 5H), 7.70–
7.80 (m, 2H). MS (m/z) 447 (Mþ). Anal. Found: C, 50.58; H,
2.85; N, 3.10%. Calcd for C20H13F6NO2S2: C, 50.31; H,
2.74; N, 2.93%.
4. Experimental
HPLC was performed on a Hitachi L-7100 liquid chroma-
tography coupled with a Hitachi L-7400 spectrophoto-
meteric detector. 1H NMR spectra were recorded on a
Varian Gemini 200 instrument. Mass spectra were measured
with a Shimadzu GCMS-QP5050A gas chromatography-
mass spectrometer. Absorption spectra were measured on a
Hitachi U-3500 absorption spectrophotometer. Photoirra-
diation was carried out using an Ushio 500 W superhigh-
pressure mercury lamp or an Ushio 500 W xenon lamp.
Monochromatic light was isolated by passing the light
through a cut off filter (UV-27) and monochromator (Ritsu
MC-10N). The quantum yields were determined by
comparing the reaction rate of the photochromic compounds
in toluene against furyl fulgide in toluene.30,31 The samples
were not degassed. The quantum yield measurement was
carried out three times and average values were adopted as
the quantum yields.
4.1.4. Closed-ring isomer for 2a (2b). Compound 2b was
isolated as a red solid by passing a photostationary solution
containing 2a and 2b thorough HPLC (ethyl acetate/
hexane¼2/8): 1H NMR (CDCl3, 200 MHz): d¼1.67 (s,
3H), 1.75 (s, 3H), 2.39 (s, 3H), 7.34–7.16 (m, 5H), 7.42–
7.34 (m, 3H), 7.85–7.76 (m, 2H). MS (m/z) 447 (Mþ). Anal.
Found: C, 50.57; H, 2.76; N, 3.18%. Calcd for
C20H13F6NO2S2: C, 50.31; H, 2.74; N, 2.93%.
4.1.5. 1-[5-Methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2-
(1,2-dimethylpropenyl)perfluoro-cyclopentene (3a). To a
stirring solution of 2-bromo-3-methyl-2-butene26 (210 mg,
1.4 mmol) in a mixed solvent of anhydrous hexane (13 mL)
and THF (13 mL) was slowly added 1.5 M t-BuLi in
heptane (1.1 mL, 1.7 mmol) at 280 8C under argon
atmosphere. After the mixture had been stirred for 40 min
at 280 8C, compound 7 (250 mg, 0.61 mmol) in a mixed
solvent of anhydrous hexane (2.5 mL) and THF (2.5 mL)
4.1. Compound data
4.1.1. 1-(5-Methyl-2-phenyl-4-thiazolyl)-2-(3-methyl-2-
thienyl)perfluorocyclopentene (1a). To a stirring solution
of 4-bromo-5-methyl-2-methylthiazole12 (524 mg, 2.10
mmol) in dry THF (6 mL) was slowly added 1.6 M
n-BuLi in hexane (1.30 mL, 2.20 mmol) at 280 8C under

6160
S. Takami, M. Irie / Tetrahedron 60 (2004) 6155–6161
was added. The reaction mixture was further stirred at
280 8C for 1 h, and the reaction was allowed to slowly
warm to room temperature and stirred there for 1 h. The
reaction was quenched with distilled water. The product was
extracted with ether, dried with MgSO4, and concentrated
under reduced pressure. The residue was purified by column
chromatography (ethyl acetate/hexane¼3/7) and HPLC
(ethyl acetate/hexane¼2/8) to afford to 15 mg (5%) of 3a
as colorless needles: mp 93–94 8C. 1H NMR (CDCl3,
200 MHz): d¼1.49 (s, 3H), 1.75 (s, 3H), 1.93 (s, 3H), 3.86
(s, 3H), 4.01 (s, 3H), 6.93 (d, J¼9.0 Hz, 2H), 7.71 (d,
J¼9.0 Hz, 2H). MS (m/z) 463 (Mþ). Anal. Found: C, 54.30;
H, 4.20; N, 3.18%. Calcd for C21H19F6NO2S2: C, 54.42; H,
4.13; N, 3.02%.
(140 mL). The mixture was stirred at 280 8C for 1 h and
room temperature for 1 h and extracted with ethyl acetate.
The organic layer was dried over MgSO4 and concentrated
under reduced pressure. The residue was purified by column
chromatography (ethyl acetate/hexane¼3/7) to afford 7.5 g
(80%) of 6 as colorless crystals: mp 102–103 8C. 1H NMR
(200 MHz, CDCl3): d¼3.85 (s, 3H), 4.02 (s, 3H), 6.93 (d,
J¼9.0 Hz, 2H), 7.75 (d, J¼9.0 Hz, 2H). MS (m/z) 300 (Mþ).
Anal. Found: C, 44.21; H, 3.41; N, 4.63%. Calcd for
C11H10NO2SBr: C, 44.01; H, 3.36; N, 4.67%.
4.1.10. 1-[5-Methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-
perfluorocyclopentene (7). To a solution of 7 (1 g,
3.33 mmol) in dry THF (40 mL) was added slowly 1.6 M
n-BuLi in hexane (2.0 mL, 3.2 mmol) at 280 8C under
argon atmosphere. After the mixture was stirred for 15 min
at 278 8C, perfluorocyclopentene (0.50 mL, 2.34 mmol) in
dry THF (2 mL) was added. The reaction mixture was
further stirred at 278 8C for 1 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/hexane¼3/7) to afford 870 mg (67%) of 7 as
colorless needles: mp 77–78 8C. 1H NMR (200 MHz,
CDCl3): d¼3.86 (s, 3H), 4.10 (s, 3H), 6.95 (d, J¼8.8 Hz,
2H), 7.78 (d, J¼8.8 Hz, 2H). MS (m/z) 413 (Mþ). Anal.
Found: C, 46.27; H, 2.63; N, 3.65%. Calcd for
C16H10NO2SF7: C, 46.50; H, 2.44; N, 3.39%.
4.1.6. Closed-ring isomer for 3a (3b). Compound 3b was
isolated as a yellow solid by passing a photostationary
solution containing 3a and 3b thorough HPLC (ethyl
acetate/hexane¼3/7): 1H NMR (CDCl3, 200 MHz):
d¼1.20 (s, 3H), 1.44 (s, 3H), 2.04 (s, 3H), 3.16 (s, 3H),
3.90 (s, 3H), 6.97 (d, J¼9.0 Hz, 2H), 8.01 (d, J¼9.0 Hz,
2H). MS (m/z) 463 (Mþ). Anal. Found: C, 54.40; H, 4.10; N,
2.80%. Calcd for C21H19F6NO2S2: C, 54.42; H, 4.13; N,
3.02%.
4.1.7. 1-(3-Methyl-2-thienyl)perfluorocyclopentene (4).
To
a solution of 2-bromo-3-methylthiophene (5.0 g,
28 mmol) in dry ether (60 mL) was added slowly 1.6 M
n-BuLi in hexane (18 mL, 29 mmol) at 280 8C under argon
atmosphere. After the mixture was stirred for 30 min at
280 8C, perfluorocyclopentene (3.8 mL, 28 mmol) in dry
ether (2 mL) was added. The reaction mixture was further
stirred at 280 8C for 1 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 (hexane) to afford 5.8 g
Acknowledgements
This work was partially supported by the Ministry of
Education, Science, Sports and Culture, Nanotechnology
Support Project, Grant-in-Aid for Scientific Research (S)
(No. 15105006) and the 21 Century COE program.
1
(71%) of 4 as colorless oil: H NMR (200 MHz, CDCl3):
d¼2.29 (d, J¼3.4 Hz, 1H), 6.99 (d, J¼5.2 Hz, 1H), 7.53 (d,
J¼5.2 Hz, 1H). MS (m/z) 290 (Mþ). Anal. Found: C, 41.42;
H, 1.76%. Calcd for C10H5F7S: C, 41.39, H, 1.74%.
References and notes
4.1.8. 5-Methoxy-2-(4-methoxyphenyl)thiazole (5). N-(4-
methoxybenzoyl) glycine methyl ester32,33 (10.0 g,
52 mmol) and phosphorus pentasulfide (10 g, 52 mmol)
were rapidly added to dry chloroform (15 mL), and the
mixture solution was stirred at 80 8C under argon
atmosphere. After stirring for 1 h, white precipitate was
deposited in the mixture solution. Then the mixture was
refluxed for 24 h under argon atmosphere. The reaction
mixture was poured in aqueous NaOH water, and extracted
with dichloromethane. The organic layer was dried over
MgSO4 and concentrated under reduced pressure. The
residue was purified by column chromatography (ethyl
acetate/hexane¼3/7) to afford 8 g (80%) of 5 as a yellow
solid. 1H NMR (200 MHz, CDCl3): d¼3.84 (s, 3H), 3.94 (s,
3H), 6.92 (d, J¼9.0 Hz, 2H), 7.06 (s, 1H), 7.73 (d,
J¼9.0 Hz, 2H). MS (m/z) 221 (Mþ). Anal. Found: C,
59.91; H, 5.25; N, 6.41%. Calcd for C11H11NO2S: C, 59.71;
H, 5.01; N, 6.33%.
1. Brown, G. H. Photochromism; Wiley: New York, 1971.
2. Du¨rr, H.; Bouas-Laurent, H. Photochromism, Molecules and
Systems; Elsevier: Amsterdam, 1990.
3. Irie, M.; Fukaminato, T.; Sasaki, T.; Tamai, N.; Kawai, T.
Nature 2002, 420, 759–760.
4. Matsuda, K.; Irie, M. Chem. Eur. J. 2001, 7, 3466–3473.
5. Morimoto, M.; Kobatake, S.; Irie, M. J. Am. Chem. Soc. 2003,
125, 11080–11087.
6. Morimitsu, K.; Shibata, K.; Kobatake, S.; Irie, M. J. Org.
Chem. 2002, 67, 4574–4578.
7. Kawata, S.; Kawata, Y. Chem. Rev. 2000, 100, 1777–1788.
8. Nakatani, K.; Delaire, J. A. Chem. Mater. 1997, 9,
2682–2684.
9. Irie, M. Chem. Rev. 2000, 100, 1685–1716.
10. Irie, M.; Uchida, K. Bull. Chem. Soc. Jpn 1998, 71, 985–996.
11. Irie, M.; Lifka, T.; Kobatake, S.; Kato, N. J. Am. Chem. Soc.
2000, 122, 4871–4876.
12. Takami, S.; Kawai, T.; Irie, M. Eur. J. Org. Chem. 2002,
3796–3800.
4.1.9. 4-Bromo-5-methoxy-2-(4-methoxyphenyl)thiazole
(6). N-bromosuccinimide (5.5 g, 31 mmol) was added to a
stirred solution of 5 (6.9 g, 31.0 mmol) in dry chloroform
13. Uchida, K.; Ishikawa, T.; Takeshita, M.; Irie, M. Tetrahedron
1998, 54, 6627–6638.
14. Uchida, K.; Irie, M. Chem. Lett. 1995, 969–970.

S. Takami, M. Irie / Tetrahedron 60 (2004) 6155–6161
6161
15. Uchida, K.; Kido, Y.; Yamaguchi, T.; Irie, M. Bull. Chem. Soc.
Jpn 1998, 71, 1101–1108.
24. Irie, M.; Sakemura, K.; Okinaka, M.; Uchida, K. J. Org. Chem.
1995, 60, 8305–8309.
16. Matsushima, R.; Morikane, H.; Kohno, Y. Chem. Lett. 2003,
302–303.
25. Irie, M.; Miyatake, O.; Sumiya, R.; Hanazawa, M.; Horikawa,
Y.; Uchida, K. Mol. Cryst. Liq. Cryst. 1994, 246, 155.
26. Patel, B. A.; Kim, J.-I. I.; Bender, D. D.; Kao, L.-C.; Heck,
R. F. J. Org. Chem. 1981, 46, 1061–1067.
17. Luo, Q.; Li, X.; Jing, S.; Zhu, W.; Tian, H. Chem. Lett. 2003,
1116–1117.
18. Shibata, K.; Kobatake, S.; Irie, M. Chem. Lett. 2001, 618–619.
19. Guillaumont, D.; Kobayashi, T.; Kanda, K.; Miyasaka, H.;
Uchida, K.; Kobatake, S.; Shibata, K.; Nakamura, S.; Irie, M.
J. Phys. Chem. A 2002, 106, 7222–7227.
27. Fukaminato, T.; Kawai, T.; Kobatake, S.; Irie, M. J. Phys.
Chem. B 2003, 107, 8372–8377.
28. Uchida, K.; Irie, M. J. Inf. Recording 1998, 24, 101–104.
29. Uchida, K.; Matsuoka, T.; Kobatake, S.; Yamaguchi, T.; Irie,
M. Tetrahedron 2001, 57, 4559–4565.
20. Demanze, F.; Yassar, A.; Garnier, F. Macromolecules 1996,
29, 4267–4273.
30. Yokoyama, Y.; Kurita, Y. J. Synth. Org. Chem. Jpn 1991, 49,
364–372.
21. Peters, A.; Vitols, C.; Mcdonald, R.; Branda, N. R. Org. Lett.
2003, 5, 1183–1186.
31. Heller, H. G.; Langan, J. R. J. Chem. Soc., Perkin Trans. 2
1981, 341–343.
22. Yokoyama, Y.; Nagashima, H.; Shrestha, S.; Yokoyama, Y.;
Takada, K. Bull. Chem. Soc. Jpn 2003, 76, 355–361.
23. Shrestha, S.; Nagashima, H.; Yokoyama, Y.; Yokoyama, Y.
Bull. Chem. Soc. Jpn 2003, 76, 363–367.
32. Matsumura, E.; Shin, T.; Murao, S.; Kawano, T. Agric. Biol.
Chem. 1985, 49, 973–979.
33. Storer, A. C.; Carey, P. R. Biochemistry 1985, 24, 6808–6818.