A Simple and Versatile Strategy for Rapid Color Fading and Intense Coloration of Photochromic Naphthopyran Families

Article abstract of DOI:10.1021/jacs.7b06293

Benzo-annulated chromenes, i.e., naphthopyrans, are well-known photochromic molecules that undergo photochemical ring-opening reactions to form two colored open-ring isomers, the transoid-cis and transoid-trans forms, upon light irradiation. Though the transoid-cis form returns thermally to the uncolored closed form, the fading rate of the transoid-trans form is extremely slow because of its higher thermal stability. This slow fading behavior of the transoid-trans form is responsible for the persistence of residual color for several minutes to hours, and prevents the application of such molecules to fast photoswitching materials. We have found a new simple and versatile strategy to substantially reduce the amount of the undesirable long-lived colored transoid-trans form by introducing an alkoxy group at the 1-position of azino-fused chromenes, i.e., 8H-pyranoquinazolines. The alkoxy group effectively reduces the formation of the transoid-trans form due to C-H···O intramolecular hydrogen bonding in the transoid-cis form. Moreover, the introduction of a condensed aromatic ring at the 3-position was found to be effective to increase the photosensitivity of the ring-opening reaction. This strategy can also be applied for naphthopyran derivatives and is useful for the development of fast photoresponsive photochromic lenses and fast photoswitching applications such as dynamic holographic materials and molecular actuators.

Full text of DOI:10.1021/jacs.7b06293

Article
pubs.acs.org/JACS
A Simple and Versatile Strategy for Rapid Color Fading and Intense
Coloration of Photochromic Naphthopyran Families
Yuki Inagaki,† Yoichi Kobayashi,‡ Katsuya Mutoh,† and Jiro Abe*,†
†Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara,
Kanagawa 252-5258, Japan
‡Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577,
Japan
S
* Supporting Information
ABSTRACT: Benzo-annulated chromenes, i.e., naphtho-
pyrans, are well-known photochromic molecules that undergo
photochemical ring-opening reactions to form two colored
open-ring isomers, the transoid-cis and transoid-trans forms,
upon light irradiation. Though the transoid-cis form returns
thermally to the uncolored closed form, the fading rate of the
transoid-trans form is extremely slow because of its higher
thermal stability. This slow fading behavior of the transoid-
trans form is responsible for the persistence of residual color
for several minutes to hours, and prevents the application of
such molecules to fast photoswitching materials. We have
found a new simple and versatile strategy to substantially reduce the amount of the undesirable long-lived colored transoid-trans
form by introducing an alkoxy group at the 1-position of azino-fused chromenes, i.e., 8H-pyranoquinazolines. The alkoxy group
effectively reduces the formation of the transoid-trans form due to C−H···O intramolecular hydrogen bonding in the transoid-cis
form. Moreover, the introduction of a condensed aromatic ring at the 3-position was found to be effective to increase the
photosensitivity of the ring-opening reaction. This strategy can also be applied for naphthopyran derivatives and is useful for the
development of fast photoresponsive photochromic lenses and fast photoswitching applications such as dynamic holographic
materials and molecular actuators.
Scheme 1. Photochromic Reactions of 3,3-Diphenyl-3H-
naphtho[2,1-b]pyran and 8,8-Diphenyl-8H-pyrano[3,2-
f ]quinazoline
1. INTRODUCTION
Switching of the physical and chemical properties of materials
by light irradiation has been the subject of considerable
research. There is an increasing interest in the use of organic
photochromic compounds to modulate conductivity, fluores-
cence, magnetism, and shape at the bulk level.1−4 Photo-
chromism of chromenes was first reported by Becker and Michl
in 1966.5 Among the chromene families, 3,3-diaryl-3H-
naphtho[2,1-b]pyran derivatives (3H-naphthopyrans, Scheme
1) have been widely studied for fundamental science and
applied to industrial photochromic lenses.6−21 UV light
irradiation on the closed form (CF) of naphthopyrans
promotes the cleavage of the C(sp3)−O bond of the pyran
ring to afford the transoid-cis (TC) and transoid-trans (TT)
forms through the short-lived cisoid-cis (CC) form. The TC
form photochemically isomerizes to the TT form (and vice
versa) through the CC bond rotation. The TC form
thermally reverts to the CF in a few seconds/minutes, whereas
the thermal back reaction from the TT form to the CF is much
slower (minutes/hours) because the TT form is thermally
stable and must overcome a relatively large activation energy
barrier to isomerize to the TC form. The residual color by the
TT form and the slow thermal back reaction of the TC form
have been considered as one of the inconvenient problems to
a
a
The atomic label for 8H-pyranoquinazoline is shown in parentheses.
be solved for photochromic lenses and fast photoswitching
applications such as dynamic holographic materials22−24 and
molecular actuators.25−29 Sousa and co-workers reported that
the formation of the TT form of 2,2-diaryl-2H-naphtho[1,2-
b]pyrans (2H-naphthopyrans) can be suppressed by bridging
between the pyran ring and the naphthalenic core by a fused
Received: June 16, 2017
© XXXX American Chemical Society
A
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alkyl chain.30−33 Though this technique effectively suppressed
the formation of the TT form, lots of labor and time were
required to prepare these compounds. In the meantime, we
reported that the substitution on the 2-position of the 3H-
naphthopyrans suppresses the formation of the TT form and
drastically accelerates the thermal back reaction from the TC
form to the CF from tens of minutes to μs time regions.34,35
However, the thermal back reaction rate is too fast for the
human eye to recognize the color change. In this study, we
report a simple strategy to reduce the formation of the TT form
that is applicable to a wide variety of naphthopyran families.
The photochromism of 8,8-diphenyl-8H-pyrano[3,2-f ]-
quinazoline (8H-pyranoquinazoline, Scheme 1) was first
reported by Pozzo and co-workers in 1994.36 The significant
acceleration of the thermal back reaction and the marked
improvement of fatigue resistance of 8H-pyranoquinazoline
derivatives were also reported.37−40 Actually, the thermal
bleaching rate constants of 8H-pyranoquinazoline and 3H-
naphthopyran are 0.48 and 0.09 s−1 in toluene at 298 K,
respectively.37 Though the heterocyclic effect and the role of
substituents in the pyran moiety of azino-fused chromenes on
their photochromic properties were studied intensively, little
attention has been paid to the suppression of the formation of
the TT form. This study emerged from the basic idea to
destabilize the TT form by steric repulsion of the bulky
substituent at the 1-position of 8H-pyranoquinazoline, which
would be expected to reduce the formation of the undesirable
long-lived colored TT form and to accelerate the thermal back
reaction to recover the CF.
3H-naphthopyran derivatives were prepared from a 2-naphthol
derivative and 1,1-diphenyl-2-propyn-1-ol (see Scheme 10).
Figure 1 shows the absorption spectra for the CFs of the 8H-
pyranoquinazoline derivatives and the 3H-naphthopyran
2. RESULTS AND DISCUSSION
We have investigated the substituent effect for the photo-
chromic properties of the 8H-pyranoquinazoline derivatives,
PQ1−PQ9, and the 3H-naphthopyran derivatives, NP1−NP3,
listed in Scheme 2. The syntheses of 8H-pyranoquinazoline
Scheme 2. Chemical Structures of the 8H-Pyranoquinazoline
Derivatives, PQ1−PQ9, and the 3H-Naphthopyran
Derivatives, NP1−NP3
Figure 1. UV−vis absorption spectra of the CFs of (a) PQ1−PQ9 and
(b) NP1−NP3 in toluene at 298 K.
derivatives in toluene. By comparing the absorption spectra
of PQ1, PQ4, PQ7, and PQ9, it was found that an alkoxy
group at the 1-position results in a hypsochromic shift of the
absorption tails of PQ4 and PQ7 by ca. 14 and 7 nm,
respectively, without significant changes in the absorption
coefficient, although a thiomethyl group at the same position
leads to the increase in the absorption coefficient without any
spectral shift. On the other hand, a bathochromic shift of about
10 nm is observed for NP3 compared with NP1. As can be
found from the UV−vis absorption spectra of the CFs of PQ5,
PQ6, and PQ8, the introduction of a pyrenyl group or a
dithienothienyl group on the 3-position induces an intense
absorption band in the UVA light region. The absorption
spectrum of PQ5 is almost identical with that of PQ8 and
overlapped with each other in Figure 1a. The absorption tails of
these compounds are fairly long and extend to 420 nm.
derivatives were accomplished by the Claisen rearrangement
protocol, in which a 1,1-diaryl-2-propyn-1-ol with a 6-
quinazolinol derivative in toluene containing an acidic catalyst
promotes the formation of the corresponding 8H-pyranoquin-
azoline (see Schemes 3−9).14,18 In this study, we used a
commercially available 1-phenyl-1-[4-(1-piperidinyl)phenyl]-2-
propyn-1-ol due to the improved reaction yields, whereas the
Steady-state UV light (365 nm, 440 mW/cm2) irradiation on
the toluene solutions of PQ1−PQ9 led to purple coloration at
298 K. The solutions return to the original colorless state after
the removal of the light source. In Figure 2 are shown the
absorption spectra of the toluene solutions at the photosta-
tionary state (PSS) under UV light irradiation with the same
B
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pyrene unit of PQ5 and PQ8 by the 8H-pyranoquinazoline
framework seems to result in the photosensitization effect for
the ring-opening reaction by the pyrene unit, because the
fluorescence quantum yield of pyrene was reported to be 0.65
at 293 K in ethanol and cyclohexane.41
Although the maximum absorption peak wavelength (λmax
)
for the colored form generally depends on the degree of π-
conjugation of molecules, the λmax of the colored forms of PQ5,
PQ6, and PQ8 are almost identical with that of PQ1.
Therefore, the condensed aromatic rings at the 3-position of
8H-pyranoquinazolines were found to give little effect on the
λmax of the colored open-ring forms. On the other hand, a
methyl group or a tert-butyl group on the 1-position induces
the hypsochromic shift of the λmax probably due to the
deviation from the planar structure of the TC and TT forms
due to the steric effect.
On the other hand, the colored forms of the naphthopyran
systems, NP1−NP3, show the absorption band at the
wavelength between 400 and 500 nm due to the molecular
framework of the unsubstituted diphenyl naphthopyran. It is
known that electron donating groups in the phenyl rings at the
3-position of the 3H-naphthopyran system bring about a
bathochromic shift of the absorption band of the colored form
accompanied by an increase in the fading speed.18 Electron
withdrawing groups cause a hypsochromic shift and slow the
fading speed.
As shown in Figure 3, the thermal fading curves after ceasing
the light irradiation consist of an initial fast decay attributable to
the thermal isomerization of the TC form to the CF and a
following slow decay of the long-lived TT form. The
remarkable acceleration of the thermal back reaction of the
TC form of NP2 compared with NP1 or NP3 lower the value
of the Δabsorbance at the PSS by nearly half.34 As will be
discussed later, the degree of coloration is strongly related to
the half-life of the colored isomers. The half-lives (τ1/2 at 298
K) of the TC form were determined from the fitting curves of
the time variation of the absorbance using the following
biexponential equation:
Figure 2. UV−vis absorption spectra of (a) PQ1−PQ9 and (b) NP1−
NP3 under UV light irradiation (365 nm, 440 mW/cm2) in toluene
(5.5 × 10−5 M) at 298 K.
concentration (5.5 × 10−5 M) recorded while stirring the
solution at 298 K. Under the continuous light irradiation, the
compounds reach the PSS quickly. The transient colored
species formed upon UV light irradiation can be attributable to
the formation of the colored TC and TT forms. The differences
in the magnitude of the change in absorbance (Δabsorbance) at
the PSS reflect the differences in the molar extinction
coefficients at the excitation wavelength (365 nm), the
quantum yields for the ring-opening reaction, and the rate
constants for the thermal back reaction. The detailed
consideration for the degree of coloration will be discussed
later. Anyhow, the large molar extinction coefficients in the
UVA light region of the CFs of PQ5, PQ6, and PQ8 as shown
in Figure 1a, and the large values of Δabsorbance for the UV
light-irradiated toluene solutions of them compared with those
of PQ1 or PQ4 confirm the enhancement of the photo-
sensitivity of the CFs due to the presence of a condensed
aromatic ring at the 3-position of 8H-pyranoquinazoline. The
toluene solutions of these compounds actually show bright and
deep color changes under sunlight (Movie S1).
f(t) = A1 e−k t + A2 e−k t
1
2
(1)
where k1 is the rate constant for the thermal back reaction of
the TC form and k2 is that of the TT form (Table S1). The
formation ratios of the TT form were defined as A2/(A1 + A2)
by assuming the molar extinction coefficients of the TC and TT
forms are same. These results are summarized in Table 1.
The residual colors of PQ4−PQ6, PQ8, and NP3 are
significantly lower, whereas the Δabsorbance at the PSS of PQ1
is higher than those of the other compounds. A phenoxy group
and a thiomethyl group are not effective to decrease the
residual color as suggested by PQ7 and PQ9, respectively.
Thus, we have confirmed that an alkoxy group considerably
reduces the formation of the TT form. The same effect of a
methoxy group is also observed for a 3H-naphthopyran
derivative, NP3 (Figure 3b).
By considering the results that a methyl group and a tert-
butyl group cannot reduce the amount of the TT form, the
steric effect of an alkoxy group is excluded. A possible
explanation for the origin of the effect is a C−H···O
intramolecular hydrogen bond in the TC form as shown in
Figure 4. The DFT calculations (M06-2X/6-311++G(d,p))
were carried out to investigate the possibility for the C−H···O
hydrogen bonding42 between the oxygen atom of the alkoxy
group and the olefinic proton in the TC form. The calculated
The negative signs of the Δabsorbance around the
wavelength region of 430 nm observed for PQ5 and PQ8 are
responsible for the fluorescence from the CF. The effect of the
fluorescence from the CF is also observed in the spectrum of
PQ6. The fluorescence quantum yields (λex = 355 nm) of the
CFs of PQ5, PQ6, and PQ8 in toluene are 0.059, 0.009, and
0.065, respectively. The efficient fluorescence quenching of the
C
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Figure 4. Plausible C−H···O hydrogen bonding between the oxygen
atom of the alkoxy group and the olefinic proton in the TC form of the
8H-pyranoquinazoline systems.
The hydrogen bond formation between the oxygen atom of
the methoxy group and the olefinic proton of PQ4 was
1
experimentally confirmed by H NMR spectra recorded in
toluene-d8 at 200 K as shown in Figure 5c. The excitation UV
Figure 3. Time variation of the change in absorbance at λmax of (a)
PQ1−PQ9, and (b) NP1−NP3 in toluene (5.5 × 10−5 M) under
continuous UV irradiation (365 nm, 440 mW/cm2, 20 s) at 298 K, and
the subsequent thermal fading when the irradiation was ceased.
Table 1. λmax for the Colored Form at the PSS, Half-Lives
(τ1/2) of the TC Forms, and Formation Ratios of the TT
Form in Toluene (5.5 × 10−5 M) at 298 K
compound
λmax/nm
τ1/2/s
TT form/%
PQ1
PQ2
PQ3
PQ4
560
535
520
552
560
590
565
571
557
561
557
425
419
0.63
0.32
3.0
51
23
30
10
5
0.86
0.20
0.49
0.75
0.69
0.50
0.32
0.05
6.9
a
PQ4
b
PQ4
∼ 0
6
Figure 5. Theoretical 1H NMR spectra of the TTC and CTC forms of
(a) PQ1 and (b) PQ4 obtained by the GIAO method at the DFT
TPSS/6-311++G(d,p)//M06-2X/6-311++G(d,p) level of theory. (c)
1H NMR spectra of PQ1 and PQ4 recorded in toluene-d8 at 200 K
after irradiation with 365 nm light. A label of 1TTC indicates the NMR
peak for the proton H1 of the TTC form; the other labels follow the
same convention.
PQ5
PQ6
PQ7
PQ8
PQ9
NP1
NP2
NP3
7
17
7
43
16
17
3
0.36
9.5
450
LED light (365 nm, 4.1 mW) was guided with an optical fiber
into the NMR spectrometer and irradiated the NMR tube
(Figure S78) at 200 K. Upon UV light irradiation for 1 h, a
sufficient amount of the open-ring isomers was accumulated
because the thermal back reaction of the open-ring isomers can
be suppressed at 200 K. While the formation of four kinds of
open-ring isomers, TTC, CTC, CTT, and TTT (Figure 6), was
expected for PQ1 and PQ4 due to the dissymmetrical phenyl
a
b
Measured in acetonitrile. Measured in the mixed solvent of toluene
and ethanol (v/v = 1:1).
distance between the oxygen atom and the hydrogen atom is
2.04 Å for PQ4, which is shorter than the sum of van der Waals
radii, 2.70 Å for H···O.42 Thus, the short C−H···O contact is
likely to form a C−H···O hydrogen bond.
D
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Figure 6. Molecular structures of the TTC, CTC, CTT, and TTT
isomers of PQ1 and PQ4.
substituent, the yields of the CTT and TTT forms were
negligibly small. The protons of H1 and H2 were reported as
fingerprints for the open-ring isomers of naphthopyrans by
Delbaere and Vermeersch,43 and were assigned on the basis of
the two-dimensional NMR (H−H COSY) spectra (Figures S79
and S80) and the DFT calculations (TPSS/6-311++G(d,p)//
M06-2X/6-311++G(d,p)) by including the solvent effect
(Figure 5a,b).
1
Figure 7. Theoretical H NMR spectra of the TC forms of (a) NP1,
and (b) NP3 obtained by the GIAO method at the DFT TPSS/6-
311++G(d,p)//M06-2X/6-311++G(d,p) level of theory. (c) 1H NMR
spectra of NP1 and NP3 recorded in toluene-d8 at 200 K after
irradiation with 365 nm light. A label of 1TC indicates the NMR peak
for the proton H1 of the TC form. The other labels are the same as
well.
The two doublet signals at 9.80 and 9.31 ppm of PQ1 were
assigned to the proton H2 of the TTC and CTC forms,
respectively. By comparing the integrated area of these signals,
the existence ratio of the TTC form is found to be nearly equal
to that of the CTC form. The proton H1 would be deshielded
by the formation of the C−H···O hydrogen bond with the
oxygen atom of the methoxy group. This prediction was
evidenced by the large downfield shifts of the corresponding
protons. The two doublet signals at 7.97 and 7.72 ppm assigned
to the proton H1 of the CTC and TTC forms of PQ1 shift to
9.72 and 9.14 ppm, respectively, in PQ4. Thus, it is apparent
that the introduction of a methoxy group causes a significant
downfield shift in the proton H1, suggesting that the proton H1
is involved in the intramolecular C−H···O hydrogen bonding
in the TC form as shown in Figure 4. The hydrogen bond
formation between the oxygen atom of the methoxy group and
the olefinic proton of the TC form of NP3 was also confirmed
S81 and S82), a significant downfield shift in the proton H1 was
also confirmed for the TC form of NP3.
The temperature dependence of the photochromic reaction
was also performed to investigate the effect of the hydrogen
bonding. Although the amount of the TT form was not altered
in toluene over the temperature range 298−333 K, the
significant increase in the component of the TT form was
confirmed over the same temperature range in acetone (Figure
S77). That is, the hydrogen bond is thermally broken in
acetone, resulting in the formation of the TT form from the TC
form upon light irradiation.
Lewis and co-workers reported that the hydrogen-bonded
conformer of the Z isomer of 2-(2-(2-pyridyl)ethenyl)indole
does not undergo Z→E photoisomerization due to either the
occurrence of rapid nonradiative decay or a hydrogen-bonding-
dependent barrier for twisting the corresponding CC bond.44
Therefore, the C−H···O hydrogen bonding in the TC form of
8H-pyranoquinazoline is also considered to disturb the CC
bond twisting and reduces the formation of the TT form.
Although the detailed mechanism of the photoisomerization
process has not been cleared at the present time, the strategy
for the molecular design to reduce the formation of the
1
1
by the H NMR measurements. In contrast to the H NMR
spectra of PQ1 and PQ4, the diphenyl-substituted naphtho-
pyrans, NP1 and NP3, give only the TC and TT forms and
show simple spectra as shown in Figure 7c. The weak signals
attributable to the TT form were observed at 8.25 and 8.43
ppm in the spectrum of NP1. The formation ratio of the TT
form of NP1 was 15% calculated from the integrated intensity
ratio in the spectrum. The weak signals at 7.66 and 8.42 ppm in
the spectrum of NP3 are due to the CF. Based on the DFT
calculations (Figure 7a,b) and the H−H COSY spectra (Figures
E
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undesirable long-lived colored TT form is applicable to a wide
variety of naphthopyran families.
with that of NP1 (6.9 s) and the larger amount of the TT form
at the PSS of NP1 (16%) compared with that of NP3 (3%)
explain the less durable behavior of the TT form. On the other
hand, the electron-donating piperidinyl group reduces the
performance of the durability.
Moreover, we investigated the solvent dependence on the
formation ratio of the TT form at room temperature. The
photochromic responses of PQ4 (5.5 × 10−5 M) in acetonitrile
and binary mixed solvent of toluene and ethanol (v/v = 1:1)
were measured in a similar manner as above (Figures S75 and
S76). As shown in Table 1, the fading speed of the TC form
slightly accelerates and the formation ratio of the TT form
decreases in polar solvent. It is worth noting that the formation
of the TT form is completely suppressed in the mixed solvent
of toluene and ethanol.
The fatigue resistance against the repeated photochromic
reactions is an important issue for the practical applications
such as photochromic lenses, and smart windows. We
investigated the effect of the methoxy group on the fatigue
resistance of the 8H-pyranoquinazoline and the 3H-naphtho-
pyran frameworks. The durability test for the non-degassed
toluene solutions of PQ1, PQ4, NP1, and NP3 was conducted
by continuous recording of the Δabsorbance at the PSS under
continuous irradiation of UV light maintained at 298 K. A 355
nm continuous wave UV light from an optically pumped
semiconductor laser was used for the excitation light source.
The laser beam was diverged through a plano concave lens to
illuminate a circular area with the radius of 5 mm. To 1.6 mL of
the stirred solution in a quartz cell (10 × 10 mm), 26 mW of
355 nm light was irradiated continuously. The concentration of
the toluene solution of PQ1, PQ4, NP1, and NP3 were
adjusted to 1.4 × 10−5, 8.9 × 10−6, 1.0 × 10−5, and 7.4 × 10−6
M, respectively, so as to be the same value (0.046) of the
absorbance at 355 nm. Figure 8 shows the time courses of the
Furthermore, we investigated the photochromic behavior of
the polymer-doped film. We reported that the rapid photo-
switching properties of fast photochromic molecules can be
achieved in a commercially available block copolymer
(KURARITY LA2330, Kuraray Co., Ltd.), that is a triblock
acrylic-based polymer composed of poly(methyl methacrylate)
(PMMA) and poly(butyl acrylate) (PBA).45 The film of
LA2330 doped with PQ5 (3 wt%) was prepared on a glass
substrate by spin coating method (800 rpm, 5 s → 1500 rpm, 5
s). The film thickness is 16.5 μm measured by spectral
interferometry. Although the polymer film has absorption tail at
the wavelength longer than 400 nm as well as in solution
(Figure S83), the film is colorless for the human eye as shown
in Figure 9a. The clear and colorless film turns light blue by
Figure 9. Photographs taken (a) under room light and (b) under
irradiation with a solar simulator of a polymer film doped with PQ5.
shining with a solar simulator (AM 1.5 G) with a xenon 300 W
lamp (Figure 9b, Movie S2). The temperature dependence on
the coloration and the fading behavior after turning off the UV
light irradiation are shown in Figure 10b. The increase in the
fading speed at higher temperature results in the decrease in the
coloration as was observed for conventional T-type photo-
chromic molecules. It is noteworthy that the amount of the
formation of the long-lived TT form is also reduced in the
block copolymer as well as in solution. Therefore, the colorless
feature under room light and the fast response to sunlight of
the polymer film guarantees the applications in smart windows
and ophthalmic glasses.
It is known that there is a trade-off between the decoloration
speed and the absorbance of a photogenerated isomer in T-type
photochromic compounds. That is, when the thermal back
reaction of the photochromic reaction becomes faster, the
absorbance of the photogenerated open-ring isomer at the PSS
usually decreases. This relationship can be analyzed by solving
the rate equations of the photochromic reaction. Since the
synthesized compounds in this study generate few TT forms
upon UV light irradiation, we regard these systems as two-state
AB systems for simplicity, where the initial state A (CF) is
converted to the state B (TC form) by light irradiation with the
quantum yield of ϕAB and the back reaction from the B to A
occurs thermally with the rate constant of kBA (= 1/τ1/2).46
Since the lifetime of the excited state of A (A*) is usually
nanosecond time scales or faster, the concentration of the A*
remains low and changes little (d[A*]/dt ≈ 0). In this case, the
rate equation can be written as follows:
Figure 8. Time courses of the normalized Δabsorbance monitored at
λmax under the continuous irradiation of UV light (355 nm, 26 mW)
on the toluene solutions of PQ1, PQ4, NP1, and NP3 at 298 K.
normalized Δabsorbance monitored at λmax under the
continuous irradiation of UV light. The values of Δabsorbance
gradually decreased with time due to a photodecomposition of
the dyes. The methoxy-substituted derivatives, PQ4 and NP3,
shows higher durability compared with their parent molecules,
PQ1 and NP1. These results are suggestive in regard to
thinking about the degradation process of naphthopyran
families. The reduction of the amount of the TT form of
PQ4 and NP3 at the PSS is presumably concerned with the
higher fatigue resistance against the repeated coloration cycles.
The longer half-life of the TC form of NP3 (9.5 s) compared
d[A]
dt
−
= (kBA + ϕ εAI0F)[A] − kBA[A]0
AB
(2)
F
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cm−1, εB′ = 2.2 × 104 M−1 cm−1, I0 = 440 mW cm−2 (wavelength
is set to 365 nm), ϕAB = 0.8.
Figure 11 shows the absorbance at the PSS as a function of
τ1/2 obtained by the kinetic analyses. εA = 5.0 × 103 M−1 cm−1
Figure 11. Simulated absorbance of the photogenerated open-ring
isomer at the PSS as a function of τ1/2. We assume a condition for a
photochromic film dispersed in the polymer matrix and the parameters
are set as follows: l = 20 μm, c = 1.0 wt % (Mw = 500), I0 = 440 mW
cm−2, εB = 1.0 × 104 M−1 cm−1, εB′ = 2.2 × 104 M−1 cm−1, and ϕAB
0.8.
=
approximately corresponds to PQ1−PQ4, PQ7, and PQ9
(black curve), while εA = 4.0 × 104 M−1 cm−1 corresponds to
PQ5, PQ6, and PQ8 (red curve). It shows that the absorbance
at the PSS gradually saturates at τ1/2 ≈ 0.2−0.3 s with the
increase in τ1/2 and the absorbance at the PSS becomes
insensitive to τ1/2 for larger τ1/2. In general, commercially
applicable photochromic films require the transmittance less
than ∼10% upon UV light irradiation, that is, the absorbance
>1. The figure suggests that the absorbance over 1 can be
realized when the τ1/2 is slower than 0.15 s for large εA
compounds (red curve) or the τ1/2 is slower than 0.36 s for
small εA compounds (black curve). Since τ1/2 of PQ4−PQ6
and PQ8 are 0.85, 0.76, 0.66, and 0.31 s, respectively, the
kinetic analyses suggest that these compounds are promising
for photochromic devices which realize dense coloration and
fast color fading. Moreover, the figure also suggests that the
increase in εA increases the absorbance at the PSS about 10−
20%. This effect of the large εA is remarkable in the fast τ1/2
region (<200 ms). Therefore, the increase in the photo-
sensitivity is one of the effective methods for the application of
the photochromic films to holographic movies because tens of
milliseconds to ∼100 ms are important time scales for these
applications.
Figure 10. (a) Transient UV−vis absorption spectra of the polymer
film doped with PQ5 (3 wt %) at 298 K. (b) Time variation of the
absorbance at λmax of the polymer film under continuous UV light
irradiation (365 nm, 440 mW/cm2), and the subsequent thermal
fading when the irradiation was turned off. The durations of the UV
light irradiation are 3, 1, and 0.5 s for 278, 298, and 313 K,
respectively.
(1 − 10Abs′
)
F =
(3)
(4)
Abs′
Abs′ = (εA[A] + εB[B])l
where εA and εB are the absorption coefficients of A and B at
the excitation wavelength, respectively, I0 is the total amount of
light absorbed by the reaction medium, F is the photokinetic
factor depending on the total absorbance at the excitation
wavelength,46 [A]0 is the initial concentration of the A species,
and l is the thickness of the sample. At the PSS, we can assume
d[A]/dt = 0, and therefore, the absorbance of B at the PSS
([B]PSS) can be derived by using [B]PSS = [A] − [A]PSS as
follows:
3. CONCLUSION
We have found a novel method to reduce the amount of the
long-lived TT form of 8H-pyranoquinazoline and 3H-naphtho-
pyran derivatives. The suppression of the TT form, which is
responsible for the persistent residual color, for several minutes
or hours has been a long-standing problem in photochromic
naphthopyran derivatives. The introduction of an alkoxy group
at the 1-position of 8H-pyranoquinazoline was found to make a
significant contribution to decrease the formation of the TT
form, whereas a bulky tert-butyl group and a methyl group did
not work well. An alkoxy group on the 1-position of 8H-
ϕ εAI0F
AB
′
[A]0εBl
[B]PSS
=
kBA + ϕ εAI0F
(5)
AB
where εB′ is the absorption coefficient of B at the probe
wavelength. Assuming a film sample, parameters are set as
follows based on several quantitative studies:47−49 the
concentration of the photochromic molecule (c = 1 wt%,
molecular weight, Mw = 500), l = 20 μm, εB = 1.0 × 104 M−1
G
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Journal of the American Chemical Society
Article
Inc., Acros Organics, Alfa Aesar, and Namiki Shoji Co., Ltd., and were
used without further purification. All reaction solvents were distilled
on the appropriate drying reagents prior to use.
pyranoquinazolines and one on the 10-position of 3H-
naphthopyrans effectively reduce the formation of the TT
form due to the C−H···O intramolecular hydrogen bonding
between the oxygen atom of the alkoxy group and the olefinic
proton in the TC form. The fast thermal back reaction and the
reduction of the formation of the TT form are also observed in
a PMMA-b-PBA block copolymer. Moreover, we found that the
introduction of a condensed aromatic ring at the 3-position of
8H-pyranoquinazoline is effective to increase the photo-
sensitivity of the CF in the UVA light region. Our new simple
strategy can be applied not only for 8H-pyranoquinazoline
derivatives but also for 3H-naphthopyran derivatives. These
findings will lead to the development of fast photoresponsive
photochromic lenses, smart windows, and fast photoswitching
applications such as dynamic holographic materials and
molecular actuators.
2-Phenylquinazolin-6-ol. A mixture of 2-bromo-5-hydroxyben-
zaldehyde (301 mg, 1.50 mmol), benzamidine hydrochloride (389 mg,
2.48 mmol), CuI (66 mg, 0.35 mmol), L-proline (75 mg, 0.65 mmol)
and Cs2CO3 (1353 mg, 4.15 mmol) in dry DMSO (3.8 mL) was
stirred at 70 °C for 1.5 h. The reaction was quenched with water. The
aqueous layer was extracted with ethyl acetate. The combined organic
layer was washed with water and passed through a phase separator
paper. After the evaporation of the solvent, the crude mixture was
purified by silica gel column chromatography (methanol:ethyl
acetate:hexane = 1:4:40), to give desired product as a yellow solid
1
(57 mg, yield: 17%). H NMR (400 MHz, DMSO-d6): δ 10.53 (s,
1H), 9.51 (s, 1H), 8.52−8.50 (m, 2H), 7.95 (d, J = 9.1 Hz, 1H), 7.59−
7.51 (m, 4H), 7.32 (d, J = 2.7 Hz, 1H); HRMS (ESI-TOF) calcd for
C14H10N2O [M + H]+, 223.0866; found, 223.0856.
3,8-Diphenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]-
quinazoline (PQ1). A solution of 2-phenylquinazolin-6-ol (21 mg,
0.094 mmol), 1-phenyl-1-[4-(1-piperidinyl)phenyl]-2-propyn-1-ol (53
mg, 0.18 mmol) and 2,4,6-triphenylboroxin (33 mg, 0.11 mmol) in
1,2-dichloroethane (3.6 mL) was stirred for 21.5 h at 80 °C (Scheme
3). After cooling to room temperature, the reaction mixture was
4. EXPERIMENTAL SECTION
Physical Measurements and Instrumentation. UV−vis
absorption spectra were measured with a UV-3600 Plus UV−vis−
NIR spectrophotometer equipped with a temperature-controlled cell
holder (Shimadzu Corp.). An absolute photoluminescence quantum
yield spectrometer (Quantaurus QY C11347-01, Hamamatsu
Photonics Co.) was used to measure the fluorescence quantum yields
(λex = 355 nm) at room temperature. The Optical NanoGauge
Thickness measurement system (C13027, Hamamatsu Photonics Co.)
based on spectral interferometry was used to measure the film
thickness of the polymer film. Light irradiation was carried out using a
solar simulator with a xenon 300 W lamp, 350−1100 nm, AM 1.5 G
(HAL-320, Asahi Spectra Inc.) or a UV-LED (UV-400, Keyence),
equipped with a UV-L6 lens unit (365 nm, 440 mW/cm2). A fiber
coupled UV-LED (365 nm, 4.1 mW, M365F1, Thorlabs, Inc.) was
used for the NMR experiment. The durability test under the
continuous UV light irradiation (355 nm) were conducted using an
optically pumped semiconductor laser (OPSL) Genesis CX 355-100
Scheme 3. Synthesis of PQ1
extracted with ethyl acetate. The combined organic layer was washed
with water and passed through a phase separator paper. After the
evaporation of the solvent, the crude mixture was purified by alumina
gel column chromatography (dichloromethane:hexane = 2:3), and
washed with hexane to give desired product as a yellow solid (20 mg,
1
1
SLM AO (Coherent Inc.). H NMR spectra were recorded at 400
yield: 43%). H NMR (400 MHz, DMSO-d6): δ 9.95 (s, 1H), 8.53−
MHz on an AVANCE III 400 NanoBay (Bruker). ESI-TOF-MS
spectra were recorded on a micrOTOF II-AGA1 (Bruker).
8.50 (m, 2H), 7.92 (d, J = 9.2 Hz, 1H), 7.76 (d, J = 9.0 Hz, 1H), 7.67
(d, J = 9.8 Hz, 1H), 7.56−7.48 (m, 5H), 7.38 (t, J = 7.6 Hz, 2H),
7.31−7.25 (m, 3H), 6.89 (d, J = 9.0 Hz, 2H), 6.71 (d, J = 10.1 Hz,
1H), 3.12−3.10 (m, 4H), 1.59−1.50 (m, 6H). 13C NMR (100 MHz,
CDCl3): δ 159.20, 154.72, 151.53, 150.86, 146.91, 144.61, 138.13,
133.83, 130.31, 130.16, 129.95, 128.58, 128.18, 128.17, 128.09, 127.65,
126.85, 126.48, 119.52, 116.81, 115.38, 113.72, 83.55, 49.96, 25.74,
24.25; HRMS (ESI-TOF) calcd for C34H29N3O [M + H]+, 496.2383;
found, 496.2375.
Transient Absorption Spectroscopy. Continuous UV light (365
nm, 440 mW/cm2) was irradiated to the solution of the compounds in
a quartz optical cuvette (optical path length = 10 mm) using a UV-
LED (UV-400, Keyence). The transient absorption spectra and the
time variation were recorded on a USB 4000 multichannel detector
(Ocean Optics, Inc.). The power of the excitation light was measured
using a Nova laser power meter equipped with a power thermal sensor
30A-P-17 (Ophir Optronics Solutions Ltd.). A CUV-qpod (Ocean
Optics, Inc.) equipped with a TC 125 temperature controller
(Quantum Northwest Inc.) was used as a cuvette holder. The probe
beam from a deuterium and a halogen lamps, a DH-2000-BAL (Ocean
Optics, Inc.), were guided with a QP-600-1-SR optical fiber (Ocean
Optics, Inc.).
1,3-Dichloro-8-phenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline. A solution of 2,4-dichloroquinazolin-6-
ol51 (344 mg, 1.60 mmol), 1-phenyl-1-[4-(1-piperidinyl)phenyl]-2-
propyn-1-ol (891 mg, 3.06 mmol) and 2,4,6-triphenylboroxin (506
mg, 1.62 mmol) in toluene (28 mL) was stirred for 3 days at 100 °C.
After cooling to room temperature, the reaction mixture was extracted
with diethyl ether. The combined organic layer was washed with water
and passed through a phase separator paper. After the evaporation of
the solvent, the crude mixture was purified by silica gel column
chromatography (ethyl acetate:dichloromethane:hexane = 1:28:12), to
give desired product as a yellow solid (314 mg, yield: 40%): 1H NMR
(400 MHz, acetone-d6) δ: 7.99 (d, J = 10.2 Hz, 1H), 7.86 (s, 2H),
7.54−7.52 (m, 2H), 7.39−7.29 (m, 5H), 6.89 (d, J = 8.9 Hz, 2H), 6.48
(d, J = 10.2 Hz, 1H), 3.16−3.13 (m, 4H), 1.65−1.53 (m, 6H); HRMS
(ESI-TOF) calcd for C28H23Cl2N3O [M + H]+, 488.1291; found,
488.1269.
DFT Computational Calculations. All calculations were carried
out using Gaussian09 program (Revision D.01).50 The bulk solvent
effect was included by the polarized continuum model (SCRF = PCM,
solvent = toluene). The molecular geometries of the CTC and TTC
forms of PQ1 and PQ4, the TC forms of NP1 and NP3, and
tetramethylsilane were fully optimized at the M06-2X/6-311++G(d,p)
1
level of theory. The calculated chemical shifts (δ) of H NMR were
obtained by the GIAO method at the DFT TPSS/6-311++G(d,p)//
M06-2X/6-311++G(d,p) level of theory and using tetramethylsilane
(TMS) as reference (δ = δTMS − δOUT; δTMS = 32.075 ppm).
Materials and Reagents. All reactions were monitored by thin-
layer chromatography carried out on 0.2 mm E. Merck silica gel plates
(60 F-254 or 60 RP-18 F-254s). Column chromatography was
performed on silica gel (Silica gel 60N, Kanto Chemical) or alumina
gel (Wako). Unless otherwise noted, all reagents and reaction solvents
were purchased-from Tokyo Chemical Industry Co., Ltd., Wako Pure
Chemical Industries, Ltd., Sigma-Aldrich Inc., Kanto Chemical Co.,
3-Chloro-1-methyl-8-phenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline. A mixture of 1,3-dichloro-8-phenyl-8-(4-
(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (48 mg, 0.098
mmol), CuI (10 mg, 0.053 mmol) in dry THF (0.4 mL) was cooled
to 0 °C. To the resulting solution, MeMgBr in THF (0.91 M, 0.15 mL,
0.14 mmol) was added dropwise and the solution was stirred for 5 h at
0 °C. The reaction was quenched by saturated ammonium chloride
H
DOI: 10.1021/jacs.7b06293
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Journal of the American Chemical Society
Article
solution. The mixture was extracted with ethyl acetate. The combined
organic layer was washed with water and passed through a phase
separator paper. After the evaporation of the solvent, the crude mixture
was purified by silica gel column chromatography (acetone:ethyl
acetate:dichloromethane = 1:10:200), to give desired product as a
= 8:1). This mixture was used in the next step without further
purification.
The mixture of 1-(tert-butyl)-3-chloro-8-phenyl-8-(4-(1-
piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline and 1,3-dichloro-8-
phenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (8:1,
14 mg) and phenylboronic acid (21 mg, 0.17 mmol) were dissolved in
the mixture of 1,4-dioxane (1.1 mL) and 1.0 M Cs2CO3 (aq) (0.081
mL). The reaction mixture was degassed with N2 bubbling and
Pd(PPh3)4 (12 mg, 0.010 mmol) was added to the solution. The
mixture was stirred for 16 h at 80 °C. After the removal of palladium
by Celite filtration, the filtrate was extracted with ethyl acetate, washed
with water and the organic layer was passed through the phase
separator paper. After the evaporation of the solvent, the crude mixture
was purified by silica gel column chromatography (ethyl acetate:di-
chloromethane:hexane = 1:24:16) and HPLC (acetonitrile), to give
1
brown solid (21 mg, yield: 46%): H NMR (400 MHz, DMSO-d6) δ:
7.81 (d, J = 8.7 Hz, 1H), 7.78 (d, J = 9.0 Hz, 1H), 7.52−7.47 (m, 3H),
7.38−7.34 (m, 2H), 7.29−7.25 (m, 3H), 6.87 (d, J = 8.4 Hz, 2H), 6.53
(d, J = 10.0 Hz, 1H), 3.11−3.08 (m, 4H), 2.97 (s, 3H), 1.56−1.49 (m,
6H); HRMS (ESI-TOF) calcd for C29H26ClN3O [M + H]+, 468.1837;
found, 468.1825.
1-Methyl-3,8-diphenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline (PQ2). 3-Chloro-1-methyl-8-phenyl-8-(4-
(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (20 mg, 0.043
mmol) and phenylboronic acid (14 mg, 0.11 mmol) were dissolved
in the mixture of 1,4-dioxane (1.4 mL) and 1.0 M Cs2CO3 (aq) (0.13
mL) (Scheme 4). The mixture was degassed by freeze−pump−thaw
1
desired product as a pink solid (4 mg, yield: 7% over two step): H
NMR (400 MHz, acetone-d6) δ: 8.59−8.57 (m, 2H) 7.95 (d, J = 9.0
Hz, 1H), 7.69 (d, J = 9.0 Hz, 1H), 7.58−7.49 (m, 5H), 7.39−7.25 (m,
6H), 6.92−6.88 (m, 1H), 6.90 (d, J = 8.9 Hz, 1H), 6.36 (d, J = 9.7 Hz,
1H), 3.16−3.13 (m, 4H), 1.66−1.53 (m, 6H), 1.57 (s, 9H). 13C NMR
(100 MHz, CDCl3): δ 174.91, 155.87, 151.78, 151.50, 149.49, 144.36,
138.03, 133.87, 131.95, 129.94, 129.04, 128.43, 128.23, 128.17, 128.12,
127.94, 127.45, 126.94, 126.46, 125.3, 124.87, 123.93, 120.72, 115.38,
114.92, 82.14, 50.10, 41.19, 31.37, 25.76, 24.26, 21.46; HRMS (ESI-
TOF) calcd for C38H37N3O [M + H]+, 552.3009; found, 552.2984.
2-Chloro-4-methoxyquinazolin-6-ol. A solution of 2,4-dichlor-
oquinazolin-6-ol (496 mg, 2.31 mmol) in methanol (10 mL) was
stirred for 14.5 h at 15 °C. After the reaction was complete, a large
excess of ethyl acetate was added to the precipitate 2,4-dimethox-
iquinazolin-6-ol. After Celite filtration, the filtrate was washed with
water and passed through a phase separator paper. After the solvent
was removed, the crude mixture was purified by silica gel column
chromatography (THF:dichloromethane = 1:20) to give desired
Scheme 4. Synthesis of PQ2
cycles and Pd(PPh3)4 (28 mg, 0.024 mmol) was added. The mixture
was stirred for 17.5 h at 80 °C. After the removal of palladium by
Celite filtration, the filtrate was extracted with ethyl acetate, washed
with water and the organic layer was passed through a phase separator
paper. After the evaporation of the solvent, the crude mixture was
purified by silica gel column chromatography (ethyl acetate:dichlor-
omethane:hexane = 1:28:12), to give desired product as a white solid
1
product as a yellow solid (131 mg, yield: 27%): H NMR (400 MHz,
DMSO-d6) δ: 10.47 (s, 1H), 7.73 (d, J = 9.0 Hz, 1H), 7.68 (dd, J = 9.0
Hz, J = 2.8 Hz, 1H), 7.31 (d, J = 2.7 Hz, 1H), 4.12 (s, 3H); HRMS
(ESI-TOF) calcd for C9H7ClN2O2 [M + H]+, 211.0269; found,
211.0271.
1
(2 mg, yield: 9%): H NMR (400 MHz, CD3CN) δ: 8.55−8.53 (m,
3-Chloro-1-methoxy-8-phenyl-8-(4-(1-piperidinyl)phenyl)-
8H-pyrano[3,2-f ]quinazoline. A solution of 2-chloro-4-methox-
yquinazolin-6-ol (151 mg, 0.717 mmol), 1-phenyl-1-[4-(1-
piperidinyl)phenyl]-2-propyn-1-ol (321 mg, 1.10 mmol) and 2,4,6-
triphenylboroxin (147 mg, 0.472 mmol) in 1,2-dichloroethane (31
mL) was stirred for 11 h at 80 °C. After cooling to room temperature,
the reaction mixture was extracted with diethyl ether. The organic
layer was washed with water and passed through a phase separator
paper. After the solvent was removed, the crude mixture was purified
by silica gel column chromatography (ethyl acetate:dichloromethane:-
hexane = 1:8:12) and alumina gel column chromatography
(dichloromethane:hexane = 2:3), to give desired product as a yellow
solid (183 mg, yield: 53%): 1H NMR (400 MHz, DMSO-d6) δ: 7.73−
7.67 (m, 3H), 7.46−7.44 (m, 2H), 7.35 (t, J = 7.6 Hz, 2H), 7.29−7.25
(m, 1H), 7.22 (d, J = 8.8 Hz, 2H), 6.87 (d, J = 9.0 Hz, 2H), 6.60 (d, J
= 10.3 Hz, 1H), 4.14 (S, 3H), 3.11−3.08 (m, 4H), 1.56−1.50 (m,
6H); HRMS (ESI-TOF) calcd for C29H26ClN3O2 [M + H]+,
484.1786; found, 484.1775.
2H), 7.84 (d, J = 9.0 Hz, 1H), 7.62 (d, J = 9.0 Hz, 1H), 7.55−7.49 (m,
6H), 7.37−7.25 (m, 5H), 6.86 (d, J = 8.8 Hz, 2H), 6.39 (d, J = 10.0
Hz, 1H), 3.12−3.09 (m, 4H), 3.05 (s, 3H), 1.63−1.52 (m, 6H). 13C
NMR (100 MHz, CDCl3): δ 192.57, 165.72, 157.97, 151.93, 151.46,
147.89, 144.55, 138.09, 133.68, 131.09, 129.96, 128.48, 128.14, 128.12,
128.06, 127.54, 126.94, 125.88, 122.76, 120.89, 115.33, 115.28, 82.00,
49.98, 28.50, 25.76, 24.25; HRMS (ESI-TOF) calcd for C35H31N3O
[M + H]+, 510.2540; found, 510.2560.
1-(tert-Butyl)-3,8-diphenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline (PQ3). A mixture of 1,3-dichloro-8-
phenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (50
mg, 0.10 mmol), CuI (22 mg, 0.12 mmol) in dry THF (1 mL) was
cooled to 0 °C (Scheme 5). To the resulting solution, tBuMgCl in
Scheme 5. Synthesis of PQ3
1-Methoxy-3,8-diphenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline (PQ4). 3-Chloro-1-methoxy-8-phenyl-8-
(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (14 mg, 0.029
mmol) and phenylboronic acid (16 mg, 0.13 mmol) were dissolved in
the mixture of 1,4-dioxane (1 mL) and 1.0 M Cs2CO3 (aq) (0.090
mL) (Scheme 6). The reaction mixture was degassed by freeze−
pump−thaw cycles and Pd(PPh3)4 (21 mg, 0.018 mmol) was added to
the solution. The solution was stirred for 8.5 h at 50 °C. After the
removal of palladium by Celite filtration, the filtrate was extracted with
ethyl acetate, washed with water and the organic layer was passed
through a phase separator paper. After the evaporation of the solvent,
the crude mixture was purified by silica gel column chromatography
(ethyl acetate:hexane = 1:10) to give desired product as a white solid
THF (0.97 M, 0.2 mL, 0.20 mmol) was added dropwise and the
solution was stirred for 5 min at 0 °C. The mixture was allowed to
warm to room temperature and stirred for 26 h. The reaction was
quenched by saturated ammonium chloride solution. The mixture was
extracted with ethyl acetate. The combined organic layer was washed
with water and passed through a phase separator paper. After the
solvent was removed, the crude mixture was purified by silica gel
(neutralized by the treatment with triethylamine) column chromatog-
raphy (ethyl acetate:dichloromethane:hexane = 1:80:120), to give
mixture of the desired product and reactant (14 mg, product:reactant
1
(10 mg, yield: 62%): H NMR (400 MHz, DMSO-d6) δ: 8.49−8.47
I
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Journal of the American Chemical Society
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Hz, 2H), 6.88 (d, J = 9.0 Hz, 2H), 6.59 (d, J = 10.2 Hz, 1H), 4.25 (s,
3H), 3.11−3.09 (m, 4H), 1.56−1.50 (m, 6H). 13C NMR (100 MHz,
CDCl3): δ 166.88, 154.26, 151.40, 151.25, 148.48, 144.86, 144.29,
142.53, 141.79, 134.18, 133.48, 131.27, 129.11, 129.10, 128.11, 128.03,
127.42, 126.90, 126.78, 125.39, 122.57, 121.66, 120.78, 115.37, 115.29,
111.54, 82.08, 54.03, 50.03, 25.75, 24.25; HRMS (ESI-TOF) calcd for
C37H29N3O2S3 [M + H]+, 644.1495; found, 644.1469.
Scheme 6. Syntheses of PQ4−PQ6
3-Chloro-1-phenoxy-8-phenyl-8-(4-(1-piperidinyl)phenyl)-
8H-pyrano[3,2-f ]quinazoline. A mixture of 1,3-dichloro-8-phenyl-
8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (100 mg,
0.20 mmol), K2CO3 (31 mg, 0.22 mmol), phenol (0.03 mL, 0.32
mmol) in DMF (0.6 mL) was stirred for 4 h at room temperature.52
The reaction was quenched by water and the mixture was extracted
with ethyl acetate. The combined organic layer was washed with water
and passed through a phase separator paper. After the evaporation of
the solvent, the crude mixture was purified by alumina gel column
chromatography (dichloromethane:hexane = 1:1), to give desired
1
product as a yellow solid (84 mg, yield: 77%): H NMR (400 MHz,
(m, 2H), 7.83 (d, J = 9.0 Hz, 1H), 7.78 (d, J = 10.3 Hz, 1H), 7.67 (d, J
= 9.0 Hz, 1H), 7.55−7.52 (m, 3H), 7.48−7.46 (m, 2H), 7.36 (t, J = 7.6
Hz, 2H), 7.29−7.24 (m, 3H), 6.87 (d, J = 9.0 Hz, 2H), 6.58 (d, J =
10.2 Hz, 1H), 4.26 (s, 3H), 3.11−3.08 (m, 4H), 1.56−1.49 (m, 6H).
13C NMR (100 MHz, CDCl3): δ 167.15, 157.57, 151.41, 151.31,
148.78, 144.96, 138.03, 134.30, 130.08, 129.58, 128.93, 128.37, 128.13,
128.09, 128.04, 127.42, 126.93, 125.21, 122.68, 115.40, 114.99, 111.68,
82.12, 53.88, 50.06, 25.78, 24.28; HRMS (ESI-TOF) calcd for
C35H31N3O2 [M + H]+, 526.2489; found, 526.2464.
DMSO-d6) δ: 7.83−7.76 (m, 3H), 7.54−7.46 (m, 4H), 7.40−7.35 (m,
5H), 7.30−7.23 (m, 3H), 6.88 (d, J = 8.9 Hz, 2H), 6.65 (d, J = 10.3
Hz, 1H), 3.12−3.10 (m, 4H), 1.57−1.55 (m, 6H); HRMS (ESI-TOF)
calcd for C34H28ClN3O2 [M + H]+, 546.1943; found, 546.1936.
1-Phenoxy-3,8-diphenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline (PQ7). 3-Chloro-1-phenoxy-8-phenyl-8-
(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (43 mg, 0.079
mmol) and phenylboronic acid (12 mg, 0.098 mmol) were dissolved
in the mixture of 1,4-dioxane (2.2 mL) and 1.0 M Cs2CO3(aq) (0.22
mL) (Scheme 7). The reaction mixture was degassed with N2 bubbling
1-Methoxy-8-phenyl-8-(4-(1-piperidinyl)phenyl)-3-(1-pyren-
yl)-8H-pyrano[3,2-f ]quinazoline (PQ5). 3-chloro-1-methoxy-8-
phenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (81
mg, 0.17 mmol) and 1-pyreneboronic acid (72 mg, 0.29 mmol)
were dissolved in the mixture of 1,4-dioxane (5.6 mL) and 1.0 M
Cs2CO3(aq) (0.49 mL) (Scheme 6). The reaction mixture was
degassed by with N2 bubbling and Pd(PPh3)4 (59 mg, 0.051) was
added to the mixture. The solution was stirred for 11 h at 50 °C. After
the removal of palladium by Celite filtration, the filtrate was extracted
with ethyl acetate, washed with water and the organic layer was passed
through a phase separator paper. After the solvent was removed, the
crude mixture was purified by silica gel column chromatography (ethyl
acetate:dichloromethane = 1:200), to give desired product as a yellow
solid (67 mg, yield: 61%): 1H NMR (400 MHz, DMSO-d6) δ: 9.24 (d,
J = 9.4 Hz, 1H), 8.73 (d, J = 8.1 Hz, 1H), 8.42 (d, J = 8.2 Hz, 1H),
8.36 (t, J = 8.0 Hz, 2H), 8.30−8.25 (m, 3H), 8.13 (t, J = 7.6 Hz, 1H),
7.96 (d, J = 9.0 Hz, 1H), 7.87 (d, J = 10.2 Hz, 1H), 7.76 (d, J = 9.1 Hz,
1H), 7.53−7.50 (m, 2H), 7.39 (t, J = 7.6 Hz, 2H), 7.31−7.28 (m, 3H),
6.90 (d, J = 8.9 Hz, 2H), 6.64 (d, J = 10.2 Hz, 1H), 4.28 (s, 3H), 3.13−
3.10 (m, 4H), 1.57−1.50 (m, 6H). 13C NMR (100 MHz, CDCl3): δ
167.07, 160.14, 151.65, 151.43, 148.73, 144.88, 134.18, 133.36, 132.11,
131.32, 130.85, 129.65, 129.41, 129.18, 128.56, 128.15, 128.12, 128.06,
127.91, 127.45, 126.94, 125.90, 125.74, 125.45, 125.34, 125.26, 125.11,
124.78, 124.72, 122.75, 115.39, 115.03, 111.19, 82.17, 54.22, 50.03,
29.70, 25.77, 24.26; HRMS (ESI-TOF) calcd for C45H35N3O2 [M +
H]+, 650.2802; found, 650.2798.
3-(4H-Cyclopenta[2,1-b:3,4-b′]dithiophen-2-yl)-1-methoxy-
8-phenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]-
quinazoline (PQ6). 3-Chloro-1-methoxy-8-phenyl-8-(4-(1-
piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (80 mg, 0.17
mmol) and dithieno[3,2-b:2′,3′-d]thiophene-2-boronic acid (82 mg,
0.34 mmol) were dissolved in the mixture of 1,4-dioxane (5.6 mL) and
1.0 M Cs2CO3(aq) (0.49 mL). The reaction mixture was degassed
with N2 bubbling and Pd(PPh3)4 (62 mg, 0.054 mmol) was added to
the solution (Scheme 6). The solution was stirred for 24 h at 50 °C.
After the removal of palladium by Celite filtration, the filtrate was
extracted with ethyl acetate, washed with water and the organic layer
was passed through a phase separator paper. After the evaporation of
the solvent, the crude mixture was purified by silica gel column
chromatography (dichloromethane), to give desired product as a
yellowish green solid (58 mg, yield: 55%): 1H NMR (400 MHz,
DMSO-d6) δ: 8.41 (s, 1H), 7.80 (d, J = 5.2 Hz, 1H), 7.77−7.73 (m,
2H), 7.66 (d, J = 9.0 Hz, 1H), 7.58 (d, J = 5.2 Hz, 1H), 7.48−7.46 (m,
2H), 7.36 (t, J = 7.6 Hz, 2H), 7.28 (d, J = 7.4 Hz 1H), 7.24 (d, J = 8.9
Scheme 7. Synthesis of PQ7
and Pd(PPh3)4 (34 mg, 0.029 mmol) was added to the solution. The
solution was stirred for 18.5 h at 70 °C. After the removal of palladium
by Celite filtration, the filtrate was extracted with ethyl acetate, washed
with water and the organic layer was passed through a phase separator
paper. After the evaporation of the solvent, the crude mixture was
purified by silica gel column chromatography (ethyl acetate:dichlor-
omethane:hexane = 1:24:6), to give desired product as a white solid
(13 mg, yield: 28%): 1H NMR (400 MHz, DMSO-d6) δ: 8.11 (dd, J =
7.7 Hz, J = 1.9 Hz, 2H), 7.89 (t, J = 10.4 Hz, 2H), 7.77 (d, J = 9.0 Hz,
1H), 7.58−7.36 (m, 12H), 7.31−7.26 (m, 3H), 6.89 (d, J = 9.0 Hz,
2H), 6.64 (d, J = 10.2 Hz, 1H), 3.12−3.10 (m, 4H), 1.57−1.50 (m,
6H). 13C NMR (100 MHz, CDCl3): δ 166.68, 157.35, 152.43, 151.62,
151.44, 149.70, 144.90, 137.45, 134.21, 130.12, 129.73, 129.43, 129.15,
128.30, 128.13, 128.08, 127.99, 127.48, 126.92, 125.84, 125.50, 122.39,
122.31, 115.38, 114.79, 111.47, 82.31, 50.02, 25.77, 24.26; HRMS
(ESI-TOF) calcd for C40H33N3O2 [M + H]+, 588.2646; found,
588.2667.
4-(Tetrahydro-2H-2-pyranyloxy)-1-butanol. A solution of 1,4-
butanediol (2 mL, 22.6 mmol), dihydropyran (2.1 mL, 22.6 mmol)
and PTSA (440 mg, 2.31 mmol) in dry CH2Cl2 (10 mL) was stirred at
0 °C for 6 h.53 The reaction mixture was diluted with CH2Cl2, and the
organic layer was washed with saturated aqueous NaHCO3 and water,
and passed through a phase separator paper. After the evaporation of
the solvent, the crude mixture was purified by silica gel column
chromatography (ethyl acetate:hexane = 2:3), to give desired product
1
as a colorless oil (910 mg, yield: 23%): H NMR (400 MHz, CDCl3)
δ: 4.61−4.60 (m, 1H), 3.88−3.77 (m, 2H), 3.69−3.64 (m, 2H), 3.53−
3.40 (m, 2H), 2.21−2.18 (m, 1H), 1.85−1.50 (m, 10H).
3-Chloro-8-phenyl-8-(4-(1-piperidinyl)phenyl)-1-(4-((tetra-
hydro-2H-pyran-2-yl)oxy)butoxy)-8H-pyrano[3,2-f ]-
quinazoline. A mixture of NaH (55% suspension in oil, 29 mg, 0.66
mmol) and 4-(tetrahydro-2H-2-pyranyloxy)-1-butanol (0.3 mL) was
stirred for 1 h at room temperature. Then a solution of 1,3-dichloro-8-
phenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (300
J
DOI: 10.1021/jacs.7b06293
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Article
mg, 0.61 mmol) in dry THF (4.5 mL) was added to the mixture.54
The mixture was stirred for 4 h at room temperature. The reaction was
quenched with water and the mixture was extracted with ethyl acetate.
The combined organic layer was washed with water and passed
through a phase separator paper. After the evaporation of the solvent,
the crude mixture was purified by silica gel column chromatography
(ethyl acetate:dichloromethane:hexane = 1:10:3), to give desired
NMR (400 MHz, DMSO-d6) δ: 9.21 (d, J = 9.4 Hz, 1H), 8.70 (d, J =
8.0 Hz, 1H), 8.42 (d, J = 8.2 Hz, 1H), 8.36 (t, J = 8.6 Hz, 2H), 8.31−
8.25 (m, 3H), 8.13 (t, J = 7.6 Hz, 1H), 7.95 (d, J = 8.9 Hz, 1H), 7.91
(d, J = 10.2 Hz, 1H), 7.75 (d, J = 9.0 Hz, 1H), 7.52 (d, J = 7.2 Hz,
2H), 7.39 (t, J = 7.6 Hz, 2H), 7.31 (t, J = 7.2 Hz, 1H), 7.29 (d, J = 8.9
Hz, 2H), 6.90 (d, J = 9.0 Hz, 2H), 6.65(d, J = 10.2 Hz, 1H), 4.73 (t, J
= 6.6 Hz, 2H), 4.53 (t, J = 5.2 Hz, 1H), 3.53 (q, J = 6.0 Hz, 2H),
3.13−3.10 (m, 4H), 2.04−2.00 (m, 2H), 1.72−1.65 (m, 2H), 1.57−
1.51 (m, 6H). 13C NMR (100 MHz, CDCl3): δ 166.76, 160.19,
151.68, 151.44, 148.81, 144.88, 134.18, 133.45, 132.10, 131.34, 130.86,
129.69, 129.37, 129.21, 128.50, 128.15, 128.08, 127.91, 127.46, 126.94,
125.92, 125.71, 125.48, 125.36, 125.26, 125.13, 124.79, 124.73, 122.61,
115.42, 115.10, 111.14, 82.19, 67.14, 62.51, 50.06, 29.51, 25.78, 25.36,
24.27; HRMS (ESI-TOF) calcd for C48H41N3O3 [M + H]+, 708.3221;
found, 708.3242.
3-Chloro-1-(methylthio)-8-phenyl-8-(4-(1-piperidinyl)-
phenyl)-8H-pyrano[3,2-f ]quinazoline. To a solution of 1,3-
dichloro-8-phenyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]-
quinazoline (100 mg, 0.20 mmol) in THF (2 mL) was added slowly
15 wt% aqueous sodium thiomethoxide (0.3 mL, 4.7 mmol) at 0 °C.55
The mixture was stirred for 2 days at 0 °C, and the reaction was
quenched with water. The mixture was extracted with ethyl acetate.
The combined organic layer was washed with water and brine and
passed through a phase separator paper. After the evaporation of the
solvent, the crude mixture was purified by silica gel column
chromatography (ethyl acetate:dichloromethane:hexane = 1:28:12),
to give desired product as a yellow solid (48 mg, 48%): 1H NMR (400
MHz, DMSO-d6) δ: 7.78−7.76 (m, 3H), 7.46 (d, J = 7.3 Hz, 2H), 7.36
(t, J = 7.6 Hz, 2H), 7.28 (d, J = 7.3 Hz, 1H), 7.24 (d, J = 8.9 Hz, 2H),
6.86 (d, J = 8.8 Hz, 2H), 6.59 (d, J = 10.0 Hz, 1H), 3.11−3.08 (m,
4H), 2.66 (s, 3H), 1.58−1.49 (m, 6H); MS (ESI-TOF): m/z 500 [M
+ H]+.
1
product as a yellow oil (302 mg, yield: 79%): H NMR (400 MHz,
DMSO-d6) δ: 7.72−6.69 (m, 3H), 7.44 (d, J = 7.4 Hz, 2H), 7.35 (t, J =
7.6 Hz, 2H), 7.28 (d, J = 7.2 Hz, 1H), 7.22 (d, J = 8.8 Hz, 2H), 6.86
(d, J = 8.9 Hz, 2H), 6.58 (d, J = 10.3 Hz, 1H), 4.60−4.54 (m, 3H),
3.75−3.70 (m, 2H), 3.47−3.37 (m, 1H, partly overlaps the H2O
signal), 3.11−3.08 (m, 4H), 1.96−1.91 (m, 2H), 1.77−1.40 (m, 15 H).
8-Phenyl-8-(4-(1-piperidinyl)phenyl)-3-(pyren-1-yl)-1-(4-
((tetrahydro-2H-pyran-2-yl)oxy)butoxy)-8H-pyrano[3,2-f ]-
quinazoline. 3-Chloro-8-phenyl-8-(4-(1-piperidinyl)phenyl)-1-(4-
((tetrahydro-2H-pyran-2-yl)oxy)butoxy)-8H-pyrano[3,2-f ]quinazoline
(300 mg, 0.48 mmol) and 1-pyreneboronic acid (202 mg, 0.82 mmol)
were dissolved in the mixture of 1,4-dioxane (10 mL) and 1.0 M
Cs2CO3 (aq) (1.4 mL). The reaction mixture was degassed with N2
bubbling and Pd(PPh3)4 (163 mg, 0.14 mmol) was added to the
mixture. The mixture was stirred for 7.5 h at 60 °C. After removal of
palladium by Celite filtration, the filtrate was extracted with ethyl
acetate, washed with water and brine and the organic layer was passed
through a phase separator paper. After the evaporation of the solvent
was removed, the crude mixture was purified by silica gel column
chromatography (ethyl acetate:dichloromethane:hexane = 3:50:15), to
give desired product as a yellow solid (261 mg, yield: 69%): 1H NMR
(400 MHz, DMSO-d6) δ: 9.20 (d, J = 9.4 Hz, 1H), 8.70 (d, J = 8.0 Hz,
1H), 8.42 (d, J = 8.2 Hz, 1H), 8.36 (t, J = 8.6 Hz, 2H), 8.31−8.25 (m,
3H), 8.13 (t, J = 7.6 Hz, 1H), 7.95 (d, J = 8.9 Hz, 1H), 7.91 (d, J =
10.2 Hz, 1H), 7.75 (d, J = 9.0 Hz, 1H), 7.52 (d, J = 7.2 Hz, 2H), 7.39
(t, J = 7.6 Hz, 2H), 7.31 (t, J = 7.2 Hz, 1H), 7.29 (d, J = 8.9 Hz, 2H),
6.90 (d, J = 9.0 Hz, 2H), 6.63 (d, J = 10.2 Hz, 1H), 4.78−4.75 (m,
2H), 4.54−4.53 (m, 1H), 3.77−3.67 (m, 2H), 3.51−3.45 (m, 1H),
3.13−3.11 (m, 4H), 2.06−2.02 (m. 2H), 1.83−1.77 (m, 2H), 1.65−
1.34 (m, 13H); HRMS (ESI-TOF) calcd for C53H49N3O4 [M + H]+,
792.3796; found, 792.3821.
1-(Methylthio)-3,8-diphenyl-8-(4-(1-piperidinyl)phenyl)-8H-
pyrano[3,2-f ]quinazoline (PQ9). 3-Chloro-1-(methylthio)-8-phe-
nyl-8-(4-(1-piperidinyl)phenyl)-8H-pyrano[3,2-f ]quinazoline (30 mg,
0.060 mmol) and phenylboronic acid (14 mg, 0.11 mmol) were
dissolved in the mixture of 1,4-dioxane (1.3 mL) and 1.0 M Cs2CO3
(aq) (0.18 mL) (Scheme 9). The mixture was degassed with N2
4-((8-Phenyl-8-(4-(1-piperidinyl)phenyl)-3-(pyren-1-yl)-8H-
pyrano[3,2-f ]quinazolin-1-yl)oxy)butan-1-ol (PQ8). The mixture
of 3-chloro-8-phenyl-8-(4-(1-piperidinyl)phenyl)-1-(4-((tetrahydro-
2H-pyran-2-yl)oxy)butoxy)-8H-pyrano[3,2-f ]quinazoline (200 mg,
0.25 mmol), pyridinium p-toluenesulfonate (PPTS 14 mg, 0.06
mmol) in ethanol (4 mL) was stirred for 12 h at 60 °C (Scheme 8).
Scheme 9. Synthesis of PQ9
Scheme 8. Synthesis of PQ8
bubbling and Pd(PPh3)4 (13 mg, 0.011 mmol) was added to the
mixture. The mixture was stirred for 22.5 h at 60 °C. After removal of
palladium by Celite filtration, the filtrate was extracted with ethyl
acetate, washed with water and brine, and the organic layer was passed
through a phase separator paper. After the evaporation of the solvent,
the crude mixture was purified by silica gel column chromatography
(ethyl acetate:dichloromethane:hexane = 1:24:16) and HPLC
(acetonitrile), to give desired product as a yellow solid (9 mg,
28%): 1H NMR (400 MHz, THF-d8) δ: 8.54 (d, J = 8.1 Hz, 1H), 8.53
(d, J = 7.6 Hz, 1H), 7.89 (d, J = 10.0 Hz, 1H), 7.75 (d, J = 9.0 Hz,
1H), 7.48−7.38 (m, 6H), 7.26−7.21 (m, 4H), 7.17−7.15 (m, 1H),
6.76 (d, J = 8.8 Hz, 2H), 6.22 (d, J = 10.0 Hz, 1H), 3.07−3.04 (m,
4H), 2.76 (s, 3H), 1.60−1.46 (m, 6H). 13C NMR (100 MHz, CDCl3):
δ 169.00, 156.43, 151.69, 151.39, 146.23, 144.51, 138.05, 133.64,
130.89, 130.10, 128.42, 128.27, 128.11, 128.02, 127.99, 127.46, 127.03,
125.40, 122.73, 120.32, 115.39, 115.35, 81.86, 50.01, 25.76, 24.25,
14.64; HRMS (ESI-TOF) calcd for C35H31N3OS [M + H]+, 542.2261;
found, 542.2283.
After concentration by the rotary evaporation, water was added to the
mixture and the aqueous layer was extracted with dichloromethane.
The combined organic layer was washed with water and brine, and
passed through a phase separator paper. After the evaporation of the
solvent, the crude mixture was purified by silica gel column
chromatography (ethyl acetate:dichloromethane:hexane = 1:10:1), to
give desired product as a yellow-green solid (86 mg, yield: 49%):1H
10-Bromo-3,3-diphenyl-3H-benzo[f ]chromene (NP2). A sol-
ution of 8-bromonaphthalen-2-ol (96 mg, 0.43 mmol), 1,1-diphenyl-2-
propyn-1-ol (114 mg, 0.55 mmol) and PTSA (26 mg, 0.14 mmol) in
CH2Cl2 (8 mL) was stirred for 18 h at r.t. (Scheme 10). The reaction
mixture was diluted with ethyl acetate, washed with water and passed
K
DOI: 10.1021/jacs.7b06293
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Article
Scheme 10. Syntheses of NP2 and NP3
ACKNOWLEDGMENTS
■
This work was supported in part by JSPS KAKENHI Grant
Number JP26107010 in Scientific Research on Innovative Areas
“Photosynergetics”. Financial assistance for this research was
also provided by the MEXT-Supported Program for the
Strategic Research Foundation at Private Universities, 2013−
2017.
REFERENCES
■
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product as a yellow solid (131 mg, yield: 74%): H NMR (400 MHz,
DMSO-d6) δ: 8.10 (d, J = 10.0 Hz, 1H), 7.89 (d, J = 8.9 Hz, 1H),
7.88−7.83 (m, 2H), 7.53−7.51 (m, 4H), 7.45 (d, J = 8.9 Hz, 1H), 7.34
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129.20, 128.77, 128.01, 127.48, 127.17, 124.36, 123.98, 123.23, 119.36,
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Bromo-3,3-diphenyl-3H-benzo[f ]chromene (30 mg, 0.073 mmol),
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(Scheme 10). The reaction mixture was degassed with N2 bubbling.
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mg, 49%): H NMR (400 MHz, DMSO-d6) δ: 7.98 (d, J = 10.3 Hz,
1H), 7.74 (d, J = 8.8 Hz, 1H), 7.51−7.49 (m, 4H), 7.38−7.32 (m,
6H), 7.28−7.22 (m, 3H), 6.98 (d, J = 7.6 Hz, 1H), 6.44 (d, J = 10.2
Hz, 1H), 3.92 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 156.97,
151.06, 145.04, 131.55, 129.91, 127.97, 127.32, 127.05, 125.62, 124.85,
123.49, 121.98, 121.52, 119.01, 114.94, 106.84, 81.24, 55.52; HRMS
(ESI-TOF) calcd for C26H20O2 [M + Na]+, 387.1356; found,
387.1349.
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ASSOCIATED CONTENT
■
S
* Supporting Information
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The Supporting Information is available free of charge on the
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2009, 125, 249−261.
1H NMR spectra, 13C NMR spectra, MS spectra, HPLC
chromatograms, transient UV−vis absorption spectra, 2D
1H NMR spectra, and DFT calculations, including
Figures S1−S83 and Tables S1−S13 (PDF)
Movie S1, showing photochromic reaction under sun-
light in toluene at room temperature (AVI)
(20) Mukhopadhyay, A.; Moorthy, J. N. J. Photochem. Photobiol., C
2016, 29, 73−106.
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AUTHOR INFORMATION
■
Corresponding Author
*jiro_abe@chem.aoyama.ac.jp
ORCID
Yoichi Kobayashi: 0000-0003-3339-3755
Jiro Abe: 0000-0002-0237-815X
Notes
The authors declare no competing financial interest.
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DOI: 10.1021/jacs.7b06293
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