Photoinduced pitch changes in chiral nematic liquid crystals formed by doping with chiral diarylethene

Article abstract of DOI:10.1039/b103925n

Chiral binaphthyl derivatives having two photochromic diarylethene units were synthesized in an attempt to use them as dopants for photoresponsive liquid crystals. These compounds showed thermally irreversible photochromic reactions. The circular dichrois

Full text of DOI:10.1039/b103925n

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Photoinduced pitch changes in chiral nematic liquid crystals formed
by doping with chiral diarylethene
Tadatsugu Yamaguchi,* Takatoshi Inagawa, Hiroyuki Nakazumi, Setsuko Irie{ and
Masahiro Irie*{
Department of Applied Materials Science, Graduate School of Engineering, Osaka Prefecture
University, Gakuen-cho 1-1, Sakai, Osaka 599-8531, Japan.
E-mail: tyama@ams.osakafu-u.ac.jp
Received 2nd May 2001, Accepted 12th July 2001
First published as an Advance Article on the web 24th August 2001
Chiral binaphthyl derivatives having two photochromic diarylethene units were synthesized in an attempt to use
them as dopants for photoresponsive liquid crystals. These compounds showed thermally irreversible
photochromic reactions. The circular dichroism (CD) spectra and the optical rotation values of the derivatives
reversibly changed in methanol upon alternate irradiation with ultraviolet and visible light. Large
photostimulated pitch changes of chiral nematic K-15 liquid crystals were observed on addition of the
derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.
Introduction
Various types of photochromic compounds such as azoben-
zenes, spiropyrans, furylfulgides and diarylethenes have been
so far reported.1–5 These photochromic compounds have
potential for applications to optical memories and photo-
optical switches. Among the compounds diarylethene deriva-
tives are the most promising photochromic compounds for the
applications because of their fatigue-resistant and thermally
irreversible properties.6,7 The photochromic diarylethenes can
be used as dopants for photoresponsive liquid crystals.
Photochromic dopants can induce optical rotation and
refractive index changes as well as reflection band shifts in
liquid crystals along with the photochromic reactions.8–14 In
previous papers,15–17 we have reported that upon photoirra-
diation doped chiral cyclohexanes having two photochromic
diarylethene units can switch the nematic liquid crystals from
apparently nematic to chiral nematic (induced cholesteric)
phases. The cyclohexane derivatives were an efficient trigger for
the pitch change. In the present work, we have prepared
chiral 3,3’-binaphthyl derivatives having two diarylethene
units. We adopted the derivatives as dopants, which induce a
photoinduced pitch change in the chiral nematic phase.
Results and discussion
Synthesis of dopants 1–4
Binaphthyl derivatives 3, 4 were also synthesized as reference
Binaphthyl derivative 1 was prepared as shown in Scheme 1.
(R)-(z)-1,1’-Binaphthyl-2,2’-diamine (1 equiv.) was reacted
with the aldehyde derivative of the diarylethene (2 equiv.)18
to produce compound 1.
Binaphthyl derivative 2 was synthesized as shown in
Scheme 2. Starting material 6 was prepared from (R)-(z)-1,1’-
bi-2-naphthol.19 Compound 6 was reacted with a hydroborated
thiophene20 to give compound 7. The coupling reaction of
compound 7 with compound 8 gave the diarylethene 2.
compounds as shown in Scheme 3. The synthetic route was
similar to compound 2. Conc. hydrochloric acid was used in the
deprotection process. The purity of the chiral binaphthyl
derivatives was confirmed to be w99% by HPLC measure-
ment using a chiral column (Chiralcel OD, eluent: hexane–
propanol ~ 95 : 5).
Photochromic reactions of compounds 1 and 2
Fig. 1 shows the absorption spectral change of 1 in methanol.
The binaphthyl having two open-form diarylethenes (1O-O),
where O means the open-ring form isomer, showed absorption
maxima at 318 nm (e: 5.0 6 104 M21 cm21) and 298 nm
(e: 5.1 6 104 M21 cm21). Upon irradiation with UV light
{Research Institute for Advanced Science and Technology, Osaka
Prefecture University, Gakuen-cho 1-2, Sakai, Osaka 599-8570, Japan.
{Department of Chemistry and Biochemistry, Graduate School of
Engineering, Kyushu University and CREST, Hakozaki 6-10-1,
Higashi-ku, Fukuoka, 812-8581, Japan.
DOI: 10.1039/b103925n
J. Mater. Chem., 2001, 11, 2453–2458
This journal is # The Royal Society of Chemistry 2001
2453

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Scheme 1
Fig. 1 Absorption spectra of three isomers of
1 in methanol
(c ~ 1.07 6 1025 M); solid line 1O-O; dotted line 1C-O; dashed line
1C-C.
Scheme 2
The CD spectrum of two open-form diarylethenes (1O-O)
showed maxima at 363 nm (De: 28.9 M21 cm21) and 317 nm
(De: z43.0 M21 cm21). The spectrum was an exciton type
spectrum, which has zero value at 340 nm. Upon irradiation
with UV light, a mixture of 1C-O and 1C-C was obtained. The
two isomers were isolated by HPLC and the CD spectra
were measured. 1C-O showed an induced type CD spec-
trum at 588 nm (De: 23.1 M21 cm21) and 298 nm (De:
z25.4 M21 cm21). 1C-C showed a spectrum at 579 nm
(De: 28.6 M21 cm21), 360 nm (De: z2.1 M21 cm21) and
292 nm (De: z24.3 M21 cm21). The De value of 1C-C
around 363 nm and 317 nm was much smaller than the
Scheme 3
(254 nm), the two open-ring isomers transformed into closed-
ring isomers independently, producing a mixture of 1C-O and
1C-C, where C and O mean the closed and open-ring form
isomers, respectively. Two isomers 1C-O and 1C-C were
isolated by HPLC (column: Wakosil 5C18; eluent: methanol)
and their electronic absorption and CD spectra were measured.
1C-O showed absorption maxima at 546 nm (e: 1.4 6
104 M21 cm21), 388 nm (e: 1.1 6 104 M21 cm21) and 298 nm
(e: 5.7 6 104 M21 cm21). 1C-C, which has two closed-ring
form isomers, also showed a maximum at 546 nm (e: 2.5 6
104 M21 cm21). The molar absorption coefficient of 1C-C at
546 nm was slightly less than twice of that of 1C-O. In the
photostationary state under irradiation with 254 nm light, the
main product was 1C-O (48%) and the rest was 1C-C (26%)
and 1O-O (26%). Upon irradiation with light of wavelength
longer than 420 nm, both 1C-C and 1C-O returned to 1O-O.
Fig. 2 shows the CD spectrum of 1 in methanol. The
binaphthyl chromophore is inherently optically active due to
the orientation of the two naphthyl groups. It gives a plus (or
minus) typical Cotton effect shape, which has a molecular
ellipticity of zero at the absorption maximum (exciton
coupling CD). The diarylethene units are inherently achiral.
They give an induced type CD spectrum in the chiral
environment. The induced CD spectral intensity is propor-
tional to the absorption coefficient and the maximum position
is the same as that of the absorption maximum.
Fig. 2 CD spectra of three isomers of 1 in methanol; solid line 1O-O;
dotted line 1C-O; dashed line 1C-C.
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Fig. 3 An HPLC chromatogram of 2 after irradiation with 254 nm
light in n-hexane monitored at 313 nm. Eluent hexane–ethyl acet-
ate ~ 94 : 6; flow rate 2.0 ml min21
.
Fig. 4 Absorption spectra of three isomers of
2 in n-hexane
(c ~ 1.52 6 1025 M); solid line 2O-O; dotted line 2C-O; dashed line
2C-C.
values for 1O-O. The optical rotation also changed dramati-
cally on alternate irradiation with 254 nm and w420 nm
25
650
light. The optical rotation value of 1O-O ([a] ~ –237u
(c ~ 5, CH3CN) ) decreased to 2735u upon irradiation with
254 nm light. This difference is due to the change in the ratio of
the three isomers.
Just as for 1, compound 2 also changed the absorption and
CD spectra upon irradiation with ultraviolet (l ~ 313 nm) and
visible light (l w 480 nm). To assign the spectral change the
photoirradiated sample was passed through an HPLC silica gel
column (Wakosil 5SIL; eluent: hexane–ethyl acetate ~ 94 : 6)
and the chromatogram in the photostationary state was
measured as shown in Fig. 3.
The two peaks of 2C-O are explained as follows. The 2C-O
isomer has two diastereomeric isomers, (R,R),Ra and (S,S),Ra
isomers.21,22 The (R,R),Ra and (S,S),Ra means the chiral (Ra)-
naphthyl derivatives have two closed-ring isomers (R,R) and
(S,S), respectively. The 2C-C showed three diastereomeric
isomers: the mixture of (R,R),(S,S),Ra and (S,S),(R,R),Ra
isomers, the (R,R),(R,R),Ra isomer and the (S,S),(S,S),Ra
isomer. The enantiomer ratio of the closed-ring forms was
almost unity, which means that enantioselection did not take
place in the photocyclization process. Although similar
resolution of the closed-ring isomers is expected for compound
1, we failed to detect them.
Fig. 5 CD spectra of three isomers of 2 in n-hexane; solid line 2O-O;
dotted line 2C-O; dashed line 2C-C.
Fig. 4 shows the absorption spectral change of 2 in methanol.
The binaphthyl having two open-form diarylethenes (2O-O)
showed an absorption maximum (shoulder) at 298 nm
(e: 2.3 6 104 M21 cm21). 2C-O showed maxima at 537 nm
(e: 1.2 6 104 M21 cm21), 412 nm (e: 4.6 6 103 M21 cm21) and
266 nm (e: 4.4 6 104 M21 cm21). 2C-C, which has two closed-
ring forms, showed maxima at 538 nm (e: 2.0 6
104 M21 cm21), 411 nm (e: 7.6 6 103 M21 cm21) and 280 nm
(e: 3.6 6 104 M21 cm21). In the photostationary state under
irradiation with 313 nm light, the main product was 2C-O
(72%) and the rest was 2C-C (10%) and 2O-O (17%).
The CD spectrum and the optical rotation of compound 2
were also changed on alternate irradiation with ultraviolet
(l ~ 313 nm) and visible light (l w 480 nm). Fig. 5 shows the
CD spectra of 2 in methanol. 2O-O showed maxima at 347 nm
(De: 26.0 M21 cm21), 327 nm (De: z5.0 M21 cm21), 300 nm
(De: z1.2 M21 cm21), 283 nm (De: 210.7 M21 cm21) and
258 nm (De: z41.0 M21 cm21). Upon irradiation with 313 nm
light, a mixture of 2C-O and 2C-C was obtained. 2C-O showed
maxima at 346 nm (De: 23.8 M21 cm21), 317 nm (De:
z4.9 M21 cm21), 288 nm (De: 25.9 M21 cm21) and 263 nm
(De: z32.4 M21 cm21). 2C-C showed maxima at 550 nm (De:
21.8 M21 cm21) and 347 nm (De: 21.2 M21 cm21), 325 nm
(De: z2.9 M21 cm21), 292 nm (De: 23.8 M21 cm21) and
257 nm (De: z22.6 M21 cm21). The CD spectra of 2C-O and
2C-C in the visible region were much smaller than those of 1C-
O and 1C-C.
25
The optical rotation values ([a] (c ~ 5, ethyl acetate)) of
669
2O-O and the photostationary state sample by irradiation with
254 nm light in methanol were 0u and 228u, respectively. The
optical rotation can be detected with light of wavelengths
longer than the absorption band. Therefore, the property
change is useful for non-destructive readout.15 The optical
rotation change of compound 2 was also much smaller than the
change observed for compound 1. The photoinduced specific
25
650
rotation change of 1 (D[a] ~ 2498u) was comparable to that
J. Mater. Chem., 2001, 11, 2453–2458
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Table 1 Pitch values and helical twisting powers of K-15 liquid crystals
containing compounds 1, 2 (2.0 wt%), 3, 4, (R)-(z)-1,1’-bi-2-naphthol
(3.0 wt%) and 5 (2.0 wt%) at 26 uC as determined by the droplet method
Compound
Pitch/mm
bm/mm21b
1 (Open form)
1 (Photostationary state sample)a
2 (Open form)
28.5
24.4
w100
24.1
6.4
z9.1
z10.6
—
z9.4
28.9
z24
21.7
29.5
228.6
2 (Photostationary state sample)a
3
4
2.9
(R)-(z)-1,1’-Bi-2-naphthol
5 (Open form)
21.4
23.7
7.9
5 (Photostationary state sample)a
aThe sample was irradiated with 254 nm light. bA positive sign refers
to a right-handed helix and vice versa.
binaphthyl derivative, on the other hand, switched phase
from apparently nematic to chiral nematic upon UV irradia-
tion. The same tendency was observed for the chiral cyclo-
hexane 5 having two diarylethene units.17 Doping with the
chiral derivatives having two diarylethene units (open–open
isomer) formed a chiral nematic phase with a very large pitch.
Upon UV irradiation, the photogenerated closed-ring form
tightened the pitch and the chiral nematic phase became more
obvious. The complementary properties of the two systems
may be useful to control the liquid crystalline phase.
Compound 1 was not an effective trigger for switching
between nematic and chiral nematic phases. The pitch changes
were determined by the droplet method in nematic liquid
crystal K-15 and listed in Table 1 along with the values for the
cyclohexane derivatives. Although compound 1 showed a large
specific rotation change by UV/visible light irradiation, the
liquid crystalline pitch change was very small.
The twisting power force and the helical sense of the open-
and the closed-ring forms of 1 and 2 were also shown in
Table 1.
The twisting power force bM is calculated as follows10 [eqn
(1)]:
b
M ~ 1/Cp
(1)
Fig. 6 A single droplet of K-15 containing 2 (1 wt%) suspended in
glycerol viewed at 100 6 magnification between crossed polarizers at
26 uC; (a) before irradiation with 254 nm light; (b) after irradiation with
254 nm light; (c) after irradiation with w420 nm light.
where C and p represent the concentration of dopant (mol of
dopant/mol of solution) and pitch, respectively. The twisting
power force of the closed-ring isomer was at least 10 times
larger than that of 2O-O.
25
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DSC measurement of the K-15 samples doped with mixture
1 and 2 (2 wt%) from 0 uC to 50 uC (1 uC min21) revealed an
endothermic peak at 25.2 uC, which is due to the phase change
from a crystal to a chiral nematic phase. The samples also
showed endothermic peaks at 33.3 uC (for 1) and 33.8 uC (for
2), which are assigned to the phase changes from the chiral
nematic phase to an isotropic liquid phase. The K-15 without
dopants showed a nematic phase from 25.5 uC to 36.7 uC. As
the additive concentration was increased, the transition
temperature from a chiral nematic phase to an isotropic
liquid phase was shifted to lower temperatures.
In order to elucidate the detailed mechanism of the pitch
change between 2O-O and the closed-ring isomer, compound 3
and 4 were doped into K-15. When the liquid crystal was doped
with 3 wt% of 3, which has two phenyl moieties at the 3 and 3’
positions, the pitch sense was a left-handed helix (Table 1).
When 3 wt% of 4, which has two naphthyl moieties at the 3 and
3’ positions, was added to the liquid crystal, the pitch sense was
a right-handed helix. The bulkiness of the substituents at the 3
and 3’ positions of binaphthol controlled the sense in the chiral
nematic phase. The twisting power force and the pitch sense of
3, 4, 2O-O and the photostationary state of 2 are summarized
in Fig. 7. The centerline represents a nematic phase. If the
compound is far from the line, the helix of the chiral nematic
of a chiral bis(diarylethenyl)cyclohexane derivative (D[a]
2490u).16
~
Photoswitching of the dopants in nematic liquid crystal
Compounds 1 and 2 were doped into the nematic liquid crystal,
K-15 and the phase change of the liquid crystals was followed
upon alternate irradiation with ultraviolet (l ~ 313 nm) and
visible light (l w 480 nm) at 26 uC. Compound 2 was an
effective trigger for the switching between nematic and
cholesteric phases. Fig. 6(a) shows a droplet of K-15 containing
1.0 wt% 2O-O viewed microscopically in glycerol between
crossed polarizers.23,24 The phase is typical nematic. When
the nematic liquid crystal was irradiated with 254 nm light
for 1 min, the spiral texture (cholesteric phase) appeared
(Fig. 6(b)). Irradiation of the sample with visible light
(w420 nm) for 3 min regenerated the schlieren texture
(Fig. 6(c)). The switching cycle was performed more than 10
times without deterioration of the liquid crystalline phase.
Bisimine-modified diarylethenes have been used as dopants
for photoresponsive liquid crystals.11 The addition of small
amounts of bisimine-modified diarylethenes formed a chiral
nematic phase. Upon irradiation with UV light, the pattern
changed to an apparently nematic phase. The present
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Fig. 7 Helical sense and helical twisting powers between 3,3’-bis-substituted chiral binaphthyl derivatives.
phase is strong, in other words, the twisting power force
becomes large. The compounds are aligned in their order of the
twisting power force. Diarylethene 2O-O did not effectively
affect the phase, therefore the phase was apparently nematic.
The closed-ring isomer induced a left handed helix. The
extended aryl moiety in 2 switched the phase between the
nematic and chiral nematic ones.
was measured with a JASCO J-720WI spectrometer. Optical
rotations were measured using a Union GIKEN PM-101 and
are given in units of 1021 deg cm2 g21. HPLC was carried out
on a Shimadzu LC-10AD liquid chromatography coupled with
a Shimadzu SPD-10AV spectrophotomeric detector. Optical
purity of the compounds was measured with HPLC using a
chiral column (Daicel Chiralcel OD). Silica gel columns (Wakosil
5SIL and Wakosil 5C18, Wako) were used for the analysis
of diastereomers. Differential scanning calorimetry (DSC)
measurement was carried out with a RIGAKU TAS-200. The
sample was heated from 0 uC to 50 uC (the temperature scan
rate: 1 uC min21). The pitch changes were monitored using a
polarization microscope (Nikon OPTIPHOT2-POL). Irradia-
tion for the pitch measurement was carried out with a mercury
lamp (254 nm, 10 W), and a halogen lamp (100 W). The cell
was constructed according to the previous paper.17
Conclusions
We have demonstrated that
a small amount of chiral
binaphthyl 2 having two photochromic diarylethenes in
nematic liquid crystalline K-15 can induce a stable photo-
switching between the apparently nematic and chiral nematic
phases. The present system can alter the wavelength of selective
reflection of light by photoirradiation. The wavelength change
can be potentially used for non-destructive readout of
rewriteable photochromic memory media.
(R)-1,1’-Bis(4-{3-[1-(2-methyl-1-benzothiophen-3-
yl)hexafluorocyclopent-1-en-2-yl]-2,4-dimethylthiophen-5-
yl}benzylideneamino)naphthalene (1)
Experimental
4-{3-[1-(2-Methyl-1-benzothiophen-3-yl)hexafluorocyclopent-1-
en-2-yl]-2,4-dimethylthiophen-5-yl}benzaldehyde16 (0.51 g) in
35 ml methanol solution and excess magnesium sulfate were
added to (R)-(z)-1,1-binaphthyl-2,2’-diamine (0.135 g), and
the solution was stirred for 24 h. The magnesium sulfate was
filtered, and the solvent was removed to give 1 in quantitative
General
Solvents used were spectrograde and purified by distillation
before use. Absorption spectra were measured with a spectro-
photometer (Shimadzu, UV-3100PC). A mercury lamp (Ushio,
500 W) and a Xenon lamp (Ushio, 1kW) were used as the light
sources. Monochromic light was obtained by passing the light
through a Toshiba cut-off filter (L-42 and Y-48). 1H NMR
spectra were recorded on a JNM EX 270 (270 MHz) spectro-
meter. The signals were expressed as ppm downfield from
tetramethylsilane (d value). Mass spectra were taken with a
Finnigan MAT TSQ-70 mass spectrometer. Circular dichroism
1
yield: mp 154–155 uC; H NMR (270 MHz, CDCl3) d 1.86 (s,
2H), 2.16 (s, 6H), 2.38–2.45 (m, 10H), 7.09 (s, 2H), 7.58
(d, J ~ 7.3 Hz, 2H), 7.70–7.73 (m, 2H), 7.87–7.90 (m, 4H),
8.11–8.19 (m, 2H); FAB-MS (m/z, %): 1320 (Mz, 100%).
Anal. Calcd for C74H48F12N2S4: C, 67.26; H, 3.66; N, 2.12.
25
650
Found: C, 67.14; H, 3.68; N, 2.18%. 1O-O [a] ~ 2237u)
c ~ 5, CH3CN).
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(R)-2,2’-Bis(methoxymethoxy)-3,3’-bis(3-bromo-2,4-
dimethylthiophen-5-yl)-1,1’-binaphthalene (7)
NMR (270 MHz, CDCl3) d 5.36 (s, 2H), 7.21–7.52 (m, 12H),
7.73 (dd, J ~ 6.9, 3.0, 2H), 7.87–7.92 (d, J ~ 7.5 Hz, 2H), 8.02
(s, 2H); FAB-MS (m/z, %): 438 (Mz, 100%). Anal. Calcd for
C32H22O2: C, 87.65; H, 5.06. Found: C, 87.65; H, 5.04%.
(R)-2,2’-Bis(methoxymethoxy)-3,3’-diiodo-1,1’-binaphthalene
6
(1.68 g),19 tetrakis(triphenylphosphine)palladium(0) salt
25
[a] ~ z 35 (c ~ 5, ethyl acetate).
650
(0.278 g) and 1 M sodium carbonate solution (12 ml) in
80 ml THF solution were added to 3-bromo-2,4-thienylboronic
acid20 (0.51 g), and the solution was refluxed for 48 h. The
saturated sodium chloride aqueous solution was added to the
solution, the product was extracted with diethyl ether, and
dried over anhydrous sodium sulfate. The organic layer was
(R)-3,3’-Di(2-naphthyl)-1,1’-bi-2-naphthol (4)
The synthetic procedure was the same as that for 3 except that
2-naphthylboronic acid was used instead of phenylboronic
acid. For 4: mp 177–178 uC; 1H NMR (270 MHz, CDCl3) d
7.28–7.54 (m, 6H), 7.86–7.98 (m, 4H), 8.14 (s, 2H), 8.21 (s, 2H);
FAB-MS (m/z, %): 538 (Mz,100%). Anal. Calcd for C40H26O2:
evaporated. The residue was purified using
a column
chromatography (Wakogel C300; eluent: hexane–ethyl
acetate ~ 5 : 1) to give 7 in 82% yield: mp 155–156 uC; 1H
NMR (270 MHz, CDCl3) d 2.16 (s, 6H), 2.38–2.45 (m, 10H),
7.09 (s, 2H), 7.58 (d, J ~ 7.3 Hz, 2H), 7.70–7.73 (m, 2H), 7.87–
7.90 (m, 4H), 8.11–8.19 (m, 2H); FAB-MS (m/z, %): 750 (Mz,
66%), 752 (Mz z 2, 100%), 754 (Mz z 4, 66%). Anal. Calcd
for C36H32Br2O4S2: C, 57.45; H, 4.29. Found: C, 57.56; H,
4.30%.
25
650
C, 89.19; H, 4.87. Found: C, 88.87; H, 4.92%. [a] ~ 244u
(c ~ 5, ethyl acetate).
Acknowledgements
This work was partly supported by CREST (Core Research for
Evolution Science and Technology) of the Japan Science and
Technology Corp.
(R)-1,1’-Bis{3-[1-(2-methyl-1-benzothiophen-3-
yl)hexafluorocyclopent-1-en-2-yl]-2,4-dimethylthiophen-5-yl}-bi-
2-naphthol (2)
References
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277 uC under nitrogen gas. A solution of 1.6 M n-butyllithium
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(10 ml) of 1-(2-methyl-1-benzothiophen-3-yl)heptafluorocyclo-
pent-1-ene 8 (0.851 g) was added dropwise to the above
solution, and the solution was stirred for 2 h at 277 uC. 30 ml
of sodium thiosulfate aqueous solution was added to the
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then the solvent was evaporated. Trimethysilyl iodide (0.70 g)
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stirring at room temperature, the organic layer was evaporated.
The residue was purified using a column chromatography
(Wakogel C300; eluent: hexane–ethyl acetate ~ 5 : 1) to give 2
1
2
3
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1
in 18% yield: mp 144–145 uC; H NMR (270 MHz, CDCl3) d
2.22 (s, 6H), 2.36 (s, 6H), 2.46 (s, 6H), 7.31 (d, J ~ 4.3 Hz, 4H),
7.40–7.46 (m, 2H), 7.86 (d, J ~ 7.9 Hz, 2H), 7.91 (s, 2H); FAB-
MS (m/z, %): 1146 (Mz, 100%). Anal. Calcd for
C60H38F12N2S4 z C2H5O: C, 62.94; H, 3.96. Found: C,
12 K. Uchida, Y. Kawai, Y. Shimizu, V. Vill and M. Irie, Chem. Lett.,
2000, 654.
25
669
62.77; H, 3.96%. 2O-O [a] ~ 0u (c ~ 5, ethyl acetate).
13 T. Sagisaka and Y. Yokoyama, Bull. Chem. Soc. Jpn., 2000, 73,
191.
(R)-3,3’-Diphenyl-1,1’-bi-2-naphthol (3)
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The (R)-2,2’-bis(methoxymethoxy)-3,3’-diiodo-1,1’-binaphthal-
ene 6 (0.63 g), tetrakis(triphenylphosphine)palladium(0) salt
(0.173 g) and 1 M sodium carbonate solution (7.5 ml) in 60 ml
THF solution were added to phenylboronic acid (0.61 g),15 and
the solution was refluxed for 48 h. Saturated aqueous sodium
chloride solution was added to the solution, and the product
was extracted with diethyl ether. The organic layer was dried
over anhydrous sodium sulfate, and then the solvent was
evaporated. Concentrated hydrochloric acid (10 ml) was added
to the residue in 40 ml of chloroform. The solution was refluxed
for 5 h and then 30 ml of water was added to the solution,
and the product was extracted with diethyl ether. The
organic layer was dried over anhydrous sodium sulfate, and
then the solvent was removed. The residue was purified using
column chromatography (Wakogel C300; eluent: hexane–ethyl
acetate ~ 5 : 1) to give 3 in 75%: yield: mp 204–205 uC; 1H
2458
J. Mater. Chem., 2001, 11, 2453–2458