Synthesis and photochromic properties of new naphthopyrans

Article abstract of DOI:10.1007/s10593-018-2366-z

[Figure not available: see fulltext.] Two novel isomeric naphthopyrans substituted with phenyl (13-butyl-6,7-dimethoxy-3,3-bis(6-methoxybiphenyl-3-yl)-3,13-dihydrobenzo[h]indeno[2,1-f]chromen-13-ol) and 4-(naphthalen-1-yl)phenyl (13-butyl-6,7-dimethoxy-3,3-bis[6-methoxy-4'-(naphthalenyl)-biphenyl-3-yl]-3,13-dihydrobenzo[h]indeno[2,1-f]chromen-13-ol) moieties were synthesized. Their photochromism, electrochemical and fluorescent properties were investigated. They displayed faster color fading rate and larger fluorescence quantum yield than 13-butyl-6,7-dimethoxy-3,3-bis(4-methoxyphenyl)-3,13-dihydrobenzo[h]indeno[2,1-f]chromen-13-ol. Moreover, they showed excellent photochromic and fluorescent properties both in solution and in polymethylmethacrylate film. In addition, cyclic voltammetry tests showed that the aromatic substituents had a significant effect on the electrochemical behavior of the naphthopyran derivatives.

Full text of DOI:10.1007/s10593-018-2366-z

DOI 10.1007/s10593-018-2366-z
Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
Synthesis and photochromic properties of new naphthopyrans
1
1
1
2
1
Qian Zhao , Yanhua Yang , Yingxiang Duan , Xian Tao , YingZhong Shen *
1
Ying-Zhong Shen, Applied Chemistry Department, College of Material Science and Technology,
Nanjing University of Aeronautics and Astronautics,
2
9 Yudao St., Nanjing 210016, P. R. China; e-mail: yz_shen@nuaa.edu.cn
2
Jiangsu MO Opto-Electronic Material Co. Ltd.
Qinglongshan Branch Road, Zhenjiang New District, Zhenjiang 212132, P. R. China;
e-mail: 18651656012@163.com
1
Published in Khimiya Geterotsiklicheskikh Soedinenii,
018, 54(9), 840–847
Submitted January 19, 2018
Accepted after revision April 4, 2018
2
Two novel isomeric naphthopyrans substituted with phenyl (13-butyl-6,7-dimethoxy-3,3-bis(6-methoxybiphenyl-3-yl)-3,13-dihydro-
benzo[h]indeno[2,1-f]chromen-13-ol) and 4-(naphthalen-1-yl)phenyl (13-butyl-6,7-dimethoxy-3,3-bis[6-methoxy-4'-(naphthalenyl)-
biphenyl-3-yl]-3,13-dihydrobenzo[h]indeno[2,1-f]chromen-13-ol) moieties were synthesized. Their photochromism, electrochemical and
fluorescent properties were investigated. They displayed faster color fading rate and larger fluorescence quantum yield than 13-butyl-
6
,7-dimethoxy-3,3-bis(4-methoxyphenyl)-3,13-dihydrobenzo[h]indeno[2,1-f]chromen-13-ol. Moreover, they showed excellent photo-
chromic and fluorescent properties both in solution and in polymethylmethacrylate film. In addition, cyclic voltammetry tests showed
that the aromatic substituents had a significant effect on the electrochemical behavior of the naphthopyran derivatives.
Keywords: naphthopyran, electrochemistry, fluorescence, photochromism, wavelength.
Photochromic materials find application in various
photonic devices, such as erasable memory media, photo-
back reaction of the TC form have been considered as one
of the inconvenient problems to solve for the photo-
switching applications. This can be solved by incorporating
some alkyl or phenyl groups to the pyran or naphthalene
ring of the naphthopyran ring system.12 Recently, Liwen
Song and coworkers explored new excellent fluorescent
switching with naphthopyran as photochromic group;13
they studied different N-substituted imide groups at the
naphthopyran moiety, indicating that the photochromic
properties can be affected by the different functional
groups of the naphthopyran unit. It has been revealed that
the aryl moieties and functional substituents imposed
significant influence on its photochromic properties.
1
,2
optical switch components, and displays. Among various
photochromic systems, naphthopyran plays a great role
because of the excellent photochromic response, good
3
colorability, and rapid color fading rate. UV light
irradiation of the closed form of naphthopyran (NOP)
3
promotes the cleavage of the C(sp )–O bond of the pyran
ring to afford the transoid-cis (TC) form and transoid-trans
(
TT) form. The TC form thermally reverts to the NOP form
in a few seconds/minutes, whereas the TT form reverts to
4
the NOP form much slower (minutes/hours). Although
hundreds of naphthopyrans have been prepared over the
past two decades, there are still problems with these
molecules. Most of the coloration disappears rapidly in few
seconds, but 10–20% slowly fades (minutes/hour) because
Based on the previous research, we introduced the
methoxy, phenyl, and 4-(naphthalen-1-yl)phenyl substi-
tuents into naphthopyran ring system. The molecular
structures and synthetic routes are shown in Scheme 1.
5
−9
of the formation of a more stable TT isomer. In the dark
it fades very slowly, and does not disappear completely.1
The residual color of the TT form and the slow thermal
0,11
Benzophenone derivative
2
was synthesized by
bromination of compound 1, while biphenylmethanones
0
009-3122/18/54(9)-0840©2018 Springer Science+Business Media, LLC
840

Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
Scheme 1. Synthesis of compounds NOP2,3
3
a,b were synthesized using Suzuki reaction with phenyl-
previously. The NMR spectra, IR data, and the synthetic
route to compound NOP1 are given in the Supplementary
information file.
boronic acid and 4-(naphthalenyl)phenylboronic acid,
respectively. The synthesis of alkynols 4a,b was carried
out by reaction of compounds 3a,b with ethynyllithium at
low temperature. (3,4-Dimethoxyphenyl)(phenyl)methanone
Under UV light irradiation, naphthopyrans NOP1–
NOP3 underwent an electrocyclic pyran ring opening with
3
(
5) as a starting material was subjected to the Stobbe
cleavage of the C(sp )–O bond and a subsequent structural
condensation to get compound 6. Phenylbutenoic acid 6
underwent cyclodehydration by acetic anhydride and then
was hydrolyzed by sodium hydroxide to give compound 7,
which in reaction with polyphosphoric acid (PPA) afforded
fluorenone 8. Compound 8 and two alkynols 4a,b through
Claisen condensation reaction in the presence of pyridinium
p-toluenesulfonate (PPTS) gave chromenones 9a,b. These
reacted with n-butyllithium to give products NOP2 and
NOP3. They contain large conjugated moieties and
excellent electron-donating units and were obtained with
good yield. In order to better explain the effect of
introducing conjugated benzene ring on the photochromic
properties, we refer to a patent on the synthesis of
naphthopyran (NOP1) without a benzene moiety on the
pyran ring for comparison (see Supplementary information
reorganization allowing the photogenerated species to
adopt more planar structures (open form) with greater
conjugation, which is responsible for the increased
absorption in the visible part of the spectrum. Their
molecular structures are shown in Scheme 2.
Compound NOP1-I exhibited a small absorption peak at
350 nm, which arose from π–π* transition;15 after 365 nm
UV light irradiation, a new absorption band in the visible
region around 550 nm appeared belonging to the open form
NOP1-II (Fig. 1). The purple color of the solution could
fade to colorless in dark within 7 min. After UV irradiation,
it turned purple again. In a similar manner, the colorless
solution of NOP2-I and NOP3-I turned blue (NOP2-II)
and green (NOP3-II) by 365 nm UV irradiation (Fig. 2c).
In polymethylmethacrylate (PMMA) films, NOP1–3
also showed similar photochromic activity (Fig. 1). The
absorbance band of open form NOP1–3 in PMMA film
broaden at 410–660 nm, which was broader than in the
solution. The red shift values of the closed-ring isomers
14
1
file, Scheme SI). Compounds were characterized by H
and 13C NMR spectra, IR spectra, and elemental analysis.
To the best of our knowledge, this kind of naphthopyran photo-
switching in solution and film has never been reported
8
41

Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
Scheme 2. Structural reorganization of compounds NOP1-I–3-I under UV light irradiation
were consistent with those of reported for diarylethenes16,17
and may be attributed to the polar effect of the polymer
matrix in amorphous solid state. The absorbance bands of
the film were broadened, because the movement of the
molecules in solid medium is restricted rendering the speed
of photochromic switching significantly slower.
quantum yield and influence the fluorescence emission
intensity of naphthopyrans.
The colored forms TT and TC fade back to colorless
form NOP. The process TC→NOP (k ) is usually rapid,
1
while TT→NOP (k ) is slow. The thermal fading kinetics
2
which is determined from the absorption–time dataset is
analyzed to evaluate the photochromic fade rate using the
following biexponential equation:19
The fluorescence was also investigated at room
temperature (Fig. 2); the fluorescence quantum yields and
optical properties of three compounds are summarized in
Table 1. The emission wavelengths going from NOP1 to
NOP3 were red-shifted because of the extended π-
conjugation in the molecule. We calculated quantum yield
y = A
and A are the contributions to the initial optical
density, k and k are exponential decay rate constants of
1
exp(–t/k
1
) + A
2
exp(–t/k
2
0
) + y .
A
1
2
1
2
18
values of naphthopyrans by reference to literature using
fast and slow components, respectively, and y is the
0
fluorescein as a standard (Φstd 0.55, quinine sulfate, 1 μg/ml,
residual coloration.20 Figure 2 shows y – t decay and two-
phase exponential decay curve for compound NOP1,
obtained using the Origin software (OriginLab Co.,
H
2
SO , 0.1 mol/l, see Supplementary information file). As
4
shown in Table 1, the fluorescence quantum yields of
NOP2 and NOP3 were higher than that of NOP1 for both
open- and closed-ring isomers. The possible explanation is
that benzene ring could notably enhance the fluorescence
Northampton, MA, USA). Convenient feature of the fading
speed is the T1/2 value,2
1–23
which is the time required to
reduce the optical density by half of the initial optical
Figure 1. Absorption spectra of compounds NOP1-I–NOP3-I and NOP1-II–NOP3-II fading in time after irradiation with 365 nm UV
–
5
light in a) CH
2
Cl
2
solution (2 × 10 mol/l), 0–7 min, and b) PMMA film (13%, w/w), 0–13 min, at 293 K.
8
42

Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
Figure 2. a) Emission spectra of compounds NOP1–3 before and after UV irradiation, b) The biexponential fading kinetics of compound
–5
NOP1 in CH
2
Cl
2
at 352 nm, and c) the color change in CH
2
Cl
2
(2×10 mol/l) and PMMA film (13%, w/w) at 293 K before (left) and
after (right) irradiation with 365 nm UV light.
density of the colored form, and the smaller T1/2, the faster
is fading. That was reflected by the fitting curve which was
successfully simulated with the above equation. As a result,
the discoloration process followed a biexponential attenua-
tion law, which included fast and slow components.24,25
As shown in Table 1, the fading rate constant of NOP3
Table 1. The UV absorption and fluorescence, biexponential
–5
decay values, and T1/2 data of NOP1–3 in CH
2
Cl
2
(2·10 mol/l)
and PMMA film (13%, w/w) at 293 K
em
λmaxabs, nm
CH Cl PMMA CH
352* 300
595
363* 356
NOP2-II 598 587
NOP3-I
378* 312
NOP3-II 600 600
Φ
λ
max
,
k1
PMMA CH
T1/2
Com-
pound
nm
Cl
2
2
2
Cl
2
CH
2
2
CH
2
Cl
2
2
Cl
2
PMMA
NOP1-I
NOP1-II 560
NOP2-I
0.43
408
418
455
459
477
475
(
k
1
617.48) was about six times larger as compared with the
142.18 23.98 187
503
0.31
0.52
0.44
0.57
0.46
value of NOP1 (k 142.18). The data of fading kinetics
1
confirmed that the colored form of naphthopyran with a
naphthyl group was more thermally stable than this without
it. It had been demonstrated that donating group at the
conjugative position of 3,3-diaryl-3H-naphtho[2,1-b]pyran
increased fading speed because of electronic effect.2 As
compared to NOP1 (T1/2 187 s), the fading speed of NOP3
4
6
24.68 66.92 103
17.48 120.33 100
499
492
6,27
* The fluorescence excitation wavelength for the respective compound.
(
T
1/2 100 s) was increased significantly under the same
conditions. Similar results were obtained with NOP2 (T1/2
03 s). It is worth noting that the fading speed is increased
93.4% compared to the NOP2 original value, showing that
the tested compounds have good fatigue resistance.
The electrochemical properties of naphthopyran deriva-
1
for compounds with the phenyl group attached to a longer
chain. The results suggest that the fading speed of colored
form is promoted by the electronic effect of the phenyl
group and the length of the attached phenyl group chain.
We also tested the fatigue resistance of naphthopyran
derivatives (Figure S1 in the Supplementary information
file shows the trend of photochromic switching on-off 10
tives have attracted a great attention for potential
application in molecular switches.2
8–32
Figure 3 shows the
CV curves of NOP1–3 with the scanning rate of 50 mV/s.
The onset potentials (Eonset) of oxidation and reduction for
NOP1-I were initiated at +1.89 and –0.51 V, and NOP1-II
at +1.86 and –0.48 V, respectively. According to the
reported method,3
3,34
the ionization potential (IP) and
cycles of NOP1–3 in CH
Cl
2 2
solution and in PMMA film.)
electron affinity (E
A
) of NOP1-I were calculated to be
When the compounds were excited by UV light of 365 nm
for 200 s and left in the dark for 5–30 min, the absorption
intensity decreased to 83–94% of its original value.
Absorption intensity of NOP1 decreased to 94% of the
NOP1 original value and that of NOP2 was decreased to
–6.23 and –3.77 eV, and those of NOP1-II were –6.02 and
–3.35 eV. Based on the highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital (LUMO)
energy level, the band gap E
g
(E
g
= ELUMO – EHOMO)
of NOP1-I and NOP1-II can be determined as +2.46 and
Figure 3. Cyclic voltammetry of NOP1–3 in MeCN with a scanning rate of 50 mV/s.
43
8

Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
Table 2. Electrochemical properties of naphthopyrans NOP1–3
electrolyte was tetrabutylammonium perchlorate (0.1 mol/l)
in MeCN (20 ml), platinum electrode, Hg/Hg Cl as the
reference electrode. The working electrode preparation
Oxidation
Reduction
Band gap
Eg, eV
Com-
pound
2
2
Eonset, V
IP, eV
–6.23
–6.02
–6.45
–6.36
–6.12
–6.24
Eonset, V
EA, eV
–3.77
–3.35
–4.27
–3.99
–4.06
–4.13
5
method: the naphthopyrans in CH
2
Cl
2
(2·10– mol/l)
NOP1-I
NOP1-II
NOP2-I
NOP2-II
NOP3-I
NOP3-II
1.89
1.86
1.92
1.90
1.87
1.86
–0.51
–0.48
–0.52
–0.43
–0.64
–0.65
2.46
2.67
2.18
2.37
2.06
2.11
solution were dropped on a polished glassy carbon electrode
and dried in air. Open-ring isomers were obtained by
irradiation of a coated glassy carbon electrode by UV light
for testing.
The PMMA films were prepared by the following
procedure: PMMA (2 g) and CHCl (15 ml) were stirred
3
for 30 min, the solution of NOP1–3 (5 mg) in CHCl
3
+
2.67 eV. The corresponding values for NOP1–3 are
summarized in Table 2.
(2 ml) was added. The resulting solution was dripped onto
the glass slide to form the film by spin-coating at 100 rpm
for 30 s. The film was put in a dark place to dry in air.
THF was distilled from sodium and benzophenone under
pure nitrogen. All the other solvents and reagents of analy-
tical grade were used as purchased without further purifi-
cation.
From the Table 2, it can be clearly seen that the electro-
chemical parameters of the compounds are remarkably
dependent on the substituent effects. The oxidation process
for the open-ring isomers NOP1-II–3-II occurs at lower
potentials than the corresponding closed-ring isomers
NOP1-I–3-I. This is because the longer conjugation length
of the open-ring isomers generally leads to a less positive
potential.35 For the band gap of three compounds, the
Bis(3-bromo-4-methoxyphenyl)methanone (2). Bis-
(4-methoxyphenyl)methanone (1) (5.00 g, 0.02 mol),
methanesulfonic acid (50 ml), and NBS (7.75 g, 0.04 mol)
were stirred for 6 h at 60°C. When the reaction was
completed, ice water (60 ml) was added and precipitate
collected by filtration. The solid was washed with aqueous
solution of NaOH (4.5 mol/l, 3 × 50 ml), compound 2 was
obtained by recrystallization from n-hexane–EtOAc, 5:1.
values of E
of the closed-ring isomers. Among these compounds, the
of NOP3-I is the smallest, which implies that the charge
g
of the open-ring isomers are higher than those
E
g
3
6
transfer in NOP3 is the fastest. The results of electro-
chemical calculations generally correspond to the band gap
which is determined from the UV-visible spectrum. These
data indicate that the effect of the substituent on the
electron-conjugated structure has an influence on the
photochromic properties of naphthopyrans.
In conclusion, two naphthopyrans bearing conjugated
substituents were synthesized using a (3,4-dimethoxyphenyl)-
phenyl)methanone as starting material. The experimental
results indicate that that there is a correlation between
electronic nature of substituents and fatigue, fading rate,
and electrochemical behavior of naphthopyran photo-
chromes. These findings may lead to fast light-responsive
photochromic lenses, smart windows, and fast optical
switching applications and molecular actuators.
1
Yield 7.20 g (86%), yellow solid, mp 174–178°C. H NMR
spectrum, δ, ppm (J, Hz): 3.97 (6H, s, OCH ); 7.25–7.30
3
(2H, m, H Ar); 7.71–7.78 (2H, m, H Ar); 7.92 (2H, d,
13
J = 2.1, H Ar). C NMR spectrum, δ, ppm: 57.3; 111.3;
112.7; 131.2; 131.9; 134.6; 159.3; 191.4. Found, %: C 45.01;
H 3.01. C H Br O . Calculated, %: C 45.03; H 3.02.
15
12
2
3
(
Synthesis of biphenylmethanones 3a,b (General
method). A solution of bis(3-bromo-4-methoxyphenyl)-
methanone (2) (2.00 g, 0.005 mol), phenylboronic acid
(1.34 g, 0.01 mol) or [4-(naphthalen-1-yl)phenyl]boronic
acid (2.73 g, 0.01 mol), Pd[P(C H ) ] (0.17 g, 0.015 mmol),
6
5 3 4
and Na CO (2.12 g, 0.02 mol) in water (10 ml) and toluene
2
3
(20 ml) was stirred at 110°C for 7 h. After TLC exami-
nation indicated that no starting material remained, the
aqueous phase was extracted with EtOAc (3×35 ml). The
organic phase was dried over anhydrous Na SO , concen-
Experimental
Fourier transform infrared spectra were obtained on a
2
4
1
Nicolet NEXUS-470 FT-IR spectrometer in KBr pellets. H
trated under reduced pressure, the product was recrystal-
lized from appropriate solvent mixture.
13
and C NMR spectra were recorded on a Bruker Avance
4
00 spectrometer (400 and 101 MHz, respectively) in
DMSO-d (compounds 2, 7, 8) or CDCl (compounds 3a,
b, 4a, 4b, 6, 9a, 9b, NOP2, NOP3) as solvents and TMS
Bis(6-methoxybiphenyl-3-yl)methanone (3a) was re-
crystallized from n-hexane–EtOAc, 4:1. Yield 1.74 g
6
3
1
3
(82%), yellow solid, mp 143–145°C. H NMR spectrum,
as internal standard. Elemental analysis was performed on
a PerkinElmer 240 C elemental analyzer. UV-Vis
absorption spectra were obtained on a Shimadzu UV-2550
UV-Vis spectrophotometer. Samples were irradiated with
δ, ppm (J, Hz): 3.90 (6H, s, OCH ); 7.04 (2H, d, J = 8.4,
3
H Ar); 7.33–7.36 (2H, m, H Ar); 7.42 (4H, t, J = 7.4, H Ar);
7.55 (4H, d, J = 8.4, H Ar); 7.82–7.87 (4H, m, H Ar).
1
3
C NMR spectrum, δ, ppm: 55.9; 110.5; 127.4; 128.1;
–
2
3
65 nm, 20 mW·cm UV light at a distance of 7 cm from
129.6; 130.6; 130.8; 131.5; 133.1; 137.6; 159.8; 194.5.
Found, %: C 82.21; H 5.61. C H O . Calculated, %:
C 82.21; H 5.62.
the Nitecore CU6 UV lamp for 200 s. Fluorescence spectra
were recorded by a Varian Cary Eclipse fluorescence
spectrophotometer in films. Films were prepared using a
Chemat Technology KW-4A spin coater. Melting points
27
22
3
Bis[6-methoxy-4'-(naphthalen-1-yl)biphenyl-3-yl]-
methanone (3b) was recrystallized from n-hexane–EtOAc,
5:1. Yield 2.80 g (84%), white solid, mp 145–146°C.
were obtained in open capillaries in H
not corrected. Cyclic voltammetry curves were measured
by a CH Instruments 660C electrochemical analyzer. Typical
2
SO bath and were
4
1
H NMR spectrum, δ, ppm (J, Hz): 3.95 (6H, s, OCH );
3
7.09 (2H, d, J = 8.6, H Ar); 7.48–7.51 (4H, m, H Ar); 7.68–
8
44

Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
7
.70 (4H, m, H Ar); 7.79–7.81 (6H, m, H Ar); 7.85–7.97
141.9; 148.7; 149.3; 152.8; 169.2; 170.2; 177.2. Found, %:
C 67.26; H 5.73. C H O . Calculated, %: C 67.41; H 5.66.
1
3
(
10H, m, H Ar); 8.09 (2H, s, H Ar). C NMR spectrum,
δ, ppm: 55.9; 110.6; 125.6; 125.8; 126.0; 126.3; 127.2;
27.7; 128.3; 128.5; 130.1; 130.9; 131.6; 132.7; 133.0; 133.1;
33.7; 136.7; 138.2; 140.1; 159.9; 194.5. Found, %: C 87.26;
2
0
20
6
4-Hydroxy-6,7-dimethoxy-1-phenyl-2-naphthoic acid
1
1
(7). Compound 6 (10.00 g, 0.03 mol) and Ac O (130 ml)
2
were stirred at 135°C for 4 h under a nitrogen atmosphere.
H 5.30. C47
H
34
O
3
. Calculated, %: C 87.28; H 5.30.
When the reaction was completed, the Ac O was evaporated
2
Synthesis of alkynols 4a,b (General method). Under a
under reduced pressure. When the temperature decreased to
nitrogen atmosphere, ethynyllithium (30 mmol) in dry THF
40°C, a solution of NaHCO (5.00 g, 0.060 mol) in water
3
(
30 ml) was slowly added (5 min) to a cold (–30°C)
(100 ml) was added to the residue, in order to neutralize the
remaining Ac O and adjust the pH to weakly basic. The
solution of compound 3a (5.0 g, 12.67 mmol) or compound
2
3
b (5.00 g, 7.73 mmol) in dry THF (15 ml). After being
product was dissolved in NaOH (5.00 g, 0.12 mol, 30 ml of
water) and EtOH (20 ml) solution. The mixture was stirred
at 85°C for 10 h. HCl (12 mol/l, 17 ml) was added, and the
aqueous phase was extracted with EtOAc (3×50 ml), The
combined organic phases were dried over anhydrous
stirred for 3 h, water (50 ml) was added, and the aqueous
phase was extracted with EtOAc (3×30 ml). The combined
organic phases were dried over anhydrous Na
2
SO ,
4
concentrated under reduced pressure. The crude product
was purified by recrystallization from n-hexane– EtOAc,
Na
2
SO , concentrated under reduced pressure. The purified
4
8
:1.
1
product was obtained by recrystallization from n-hexane–
,1-Bis(6-methoxybiphenyl-3-yl)prop-2-yn-1-ol (4a).
EtOAc, 5:1. Yield 7.41 g (82%), white solid, mp 242–243°C.
1
1
Yield 4.01 g (75%), white solid, mp 93–95°C. H NMR
H NMR spectrum, δ, ppm (J, Hz): 3.53 (3H, s, OCH );
3
spectrum, δ, ppm (J, Hz): 2.82 (1H, s, OH); 2.89 (1H, s,
3.90 (3H, s, OCH ); 6.68 (1H, s, H Ar); 7.13 (1H, s, H Ar);
3
≡
7
CH); 3.81 (6H, s, OCH
3
); 6.95 (2H, d, J = 8.6, H Ar);
7.22–7.24 (2H, m, H Ar); 7.38–7.44 (3H, m, H Ar); 7.49
(1H, s, H Ar); 10.29 (1H, s, OH); 12.32 (1H, s, COOH).
.31–7.33 (2H, m, H Ar); 7.39–7.43 (4H, m, H Ar); 7.52–
13
7
.54 (4H, m, H Ar); 7.56–7.58 (2H, m, H Ar); 7.62 (2H, d,
C NMR spectrum, δ, ppm: 55.9; 56.1; 101.3; 102.8;
13
J = 2.4, H Ar). C NMR spectrum, δ, ppm: 55.7; 73.8;
103.7; 122.5; 123.6; 124.8; 125.6; 127.7; 131.2; 131.8;
7
1
5.4; 86.7; 110.9; 126.3; 127.1; 128.0; 128.8; 129.6; 130.4;
37.1; 138.4; 156.1. Found, %: C 82.83; H 5.73. C29
134.4; 135.5; 145.6; 150.8; 151.8; 154.3; 164.3. Found, %:
H
24
O
3
.
C 70.29; H 5.02. C19
H
16
O . Calculated, %: C 70.36; H 4.97.
5
Calculated, %: C 82.83; H 5.75.
5-Hydroxy-2,3-dimethoxy-7H-benzo[c]fluoren-7-one (8).
Compound 7 (7.00 g, 0.02 mol) and polyphosphoric acid
(60 ml) were stirred at 50°C for 10 h, ice water (200 ml) was
added. The product was filtered off, washed with water three
times and then with aqueous solution of NaOH (4.5 mol/l,
3×100 ml) to adjust pH to alkaline. The purified product
was obtained by recrystallization from n-hexane–EtOAc,
1,1-Bis[6-methoxy-4'-(naphthalen-1-yl)biphenyl-3-yl]-
prop-2-yn-1-ol (4b). Yield 3.42 g (67%), white solid,
1
mp 94–96°C. H NMR spectrum, δ, ppm (J, Hz): 2.91 (1H,
s, ≡CH); 3.85 (3H, s, OCH
3
); 3.88 (3H, s, OCH ); 6.86
3
(
1H, d, J = 8.6, H Ar); 6.97 (1H, d, J = 8.8, H Ar); 7.49–
7
.51 (6H, m, H Ar); 7.63–7.78 (6H, m, H Ar); 7.80–7.84
(
6H, m, H Ar); 7.87 (1H, d, J = 8.0, H Ar); 7.90–7.93 (5H,
4:1. Yield 5.13 g (84%), red solid, mp 270–271°C.
1
3
1
m, H Ar); 8.08 (2H, s, H Ar). C NMR spectrum, δ, ppm:
H NMR spectrum, δ, ppm (J, Hz): 3.82 (3H, s, OCH );
3
5
1
1
5.0; 73.2; 74.5; 86.6; 109.6; 124.6; 124.8; 125.0; 125.4;
26.2; 126.7; 127.3; 127.5; 129.1; 130.0; 130.6; 131.7;
3.92 (3H, s, OCH ); 6.81 (1H, s, H Ar); 7.10–7.14 (1H, m,
3
H Ar); 7.37–7.39 (2H, m, H Ar); 7.41–7.43 (1H, m, H Ar);
7.47 (1H, s, H Ar); 7.84 (1H, d, J = 8.6, H Ar); 10.58 (1H,
s, OH). 13C NMR spectrum, δ, ppm: 55.9; 56.2; 101.4;
102.9; 103.7; 122.6; 123.7; 125.6; 127.7; 131.2; 135.5;
145.6; 150.7; 151.7; 154.2; 194.4. Found, %: C 74.86;
32.1; 132.8; 135.7; 137.2; 141.1; 158.4. Found, %: C 87.45;
H 5.37. C49
H
36
O
3
. Calculated, %: C 87.47; H 5.39.
4
-(3,4-Dimethoxyphenyl)-3-(methoxycarbonyl)-4-phenyl-
but-3-enoic acid (6). Potassium (3.10 g, 0.08 mol) and
t-BuOH (110 ml) were stirred at 60°C for 3 h under
nitrogen until the potassium disappeared. t-BuOH was
evaporated under reduced pressure to obtain the white solid
H 4.87. C19
H
14
O . Calculated, %: C 74.50; H 4.61.
4
Synthesis of chromenones 9a,b (General method).
solution of 5-hydroxy-2,3-dimethoxy-7H-benzo[c]-
A
(
(
t-BuOK). Then (3,4-dimethoxyphenyl)(phenyl)methanone
5) (15.00 g, 0.06 mol), dimethyl succinate (11.50 g, 0.07 mol),
fluoren-7-one (8) (0.20 g, 0.67 mmol), PPTS (0.02 g,
0.24 mmol), and trimethoxymethane (1 ml, 0.07 mmol) in
toluene (20 ml) was stirred at 60°C. 1,1-Bis(6-methoxy-
biphenyl-3-yl)prop-2-yn-1-ol (4a) (0.31 g, 0.80 mmol,
1.2 equiv) or 1,1-bis[6-methoxy-4'-(naphthalen-1-yl)bi-
phenyl-3-yl]prop-2-yn-1-ol (4b) (0.50 g, 0.75 mmol,
1.2 equiv) was added after 30 min and the solution stirred
at 110°C for 8 h. After the reaction was complete, the
aqueous phase was extracted with EtOAc (3×30 ml) and
the combined organic phases were dried over anhydrous
and toluene (100 ml) were added and stirred at 110°C for
3
4 h. After completion of the reaction, water (100 ml) was
added, and the aqueous phase was extracted with toluene
3×50 ml). The combined organic phases were dried over
(
anhydrous Na
2
SO , concentrated under reduced pressure,
4
and product 6 was purified by recrystallization from
n-hexane–EtOAc, 4:1. Yield 18.86 g (85%), yellow solid,
1
mp 211–212°C. H NMR spectrum, δ, ppm (J, Hz): 3.48
(
3H, d, J = 2.4, OCH
3
); 3.59 (2H, s, CH
3
2
); 3.78 (3H, s,
Na
2
SO , concentrated under reduced pressure. The purified
4
OCH
3
); 3.89 (3H, s, OCH
); 6.68–6.73 (2H, m, H Ar); 6.83–
product was obtained by silica gel column chromatography
(n-hexane–EtOAc, 10:1).
6
.87 (1H, m, H Ar); 7.10–7.14 (2H, m, H Ar); 7.26–7.29 (3H,
13
m, H Ar). C NMR spectrum, δ, ppm: 27.4; 38.4; 51.7;
6,7-Dimethoxy-3,3-bis(6-methoxybiphenyl-3-yl)benzo-
[h]indeno[2,1-f]chromen-13(3H)-one (9a). Yield 0.37 g
5
5.9; 81.2; 110.9; 112.5; 122.2; 123.4; 127.9; 128.8; 133.8;
8
45

Chemistry of Heterocyclic Compounds 2018, 54(9), 840–847
(
78%), red solid, mp 222–224°C. 1H NMR spectrum,
δ, ppm (J, Hz): 3.77 (6H, s, OCH ); 3.97 (3H, s, OCH );
.09 (3H, s, OCH ); 6.34 (1H, d, J = 8.8, H-1(2)); 6.90
2H, d, J = 8.0, H Ar); 7.18–7.20 (1H, m, H Ar); 7.29–7.33
chromen-13-ol (NOP3). Yield 0.14 g (61%), white powder,
–1
mp 196–198°C. IR spectrum, cm : 3484 (–OH), 2955 (–CH
3
),
–), 1486 (δC–H), 812 (γ=C–H). H NMR
spectrum, δ, ppm (J, Hz): 0.32–0.46 (2H, m, CH ); 0.58
(3H, t, J = 9.6, CH ); 1.02–1.04 (2H, m, CH ); 2.22–2.26
(2H, m, CH ); 3.71 (3H, s, OCH ); 3.84–3.85 (6H, m,
OCH ); 4.06 (3H, s, OCH ); 5.35 (1H, br. s, OH); 6.29 (1H,
3
3
1
4
3
2933, (–CH
2
(
2
(
2H, m, H Ar); 7.35–7.37 (4H, m, H Ar); 7.42–7.44 (7H, m,
3
2
H Ar); 7.50 (2H, s, H Ar); 7.58–7.59 (2H, m, H Ar), 7.61 (1H,
2
3
s, H Ar); 7.72–7.73 (1H, m, H Ar); 7.88 (1H, d, J = 8.0, H Ar).
3
3
1
3
C NMR spectrum, δ, ppm: 55.6; 55.9; 83.4; 101.9; 103.5;
d, J = 9.8, H-1(2)); 6.82 (1H, d, J = 8.4, H Ar); 7.02–7.03
(1H, m, H Ar); 7.22–7.23 (1H, m, H Ar); 7.27–7.29 (1H,
m, H Ar); 7.47–7.67 (18H, m, H Ar); 7.70–7.78 (4H, m,
H Ar); 7.85–7.92 (7H, m, H Ar); 8.05 (2H, d, J = 8.0, H Ar).
1
10.5; 119.6; 121.6; 123.6; 127.1; 127.3; 127.4; 127.9;
1
29.5; 129.9; 130.4; 133.9; 134.1; 135.1; 137.0; 138.4; 145.0;
1
48.1; 151.1; 151.3; 155.9; 195.7. Found, %: C 81.26;
H 5.32. C48 . Calculated, %: C 81.34; H 5.12.
,7-Dimethoxy-3,3-bis[6-methoxy-4'-(naphthalen-1-yl)-
biphenyl-3-yl]benzo[h]indeno[2,1-f]chromen-13(3H)-one
9b). Yield 0.49 g (74%), red powder, mp 218–200°C.
13
H
36
O
6
C NMR spectrum, δ, ppm: 13.5; 22.8; 25.8; 39.1; 55.5;
6
55.7; 55.8; 82.6; 83.5; 101.9; 103.9; 110.1; 110.8; 113.3;
121.1; 122.7; 125.5; 125.7; 125.9; 126.3; 126.6; 126.9;
127.1; 127.6; 128.2; 128.4; 128.7; 129.8; 129.9; 130.1;
130.2; 132.6; 133.7; 136.5; 138.2; 139.7; 140.8; 147.8;
148.6; 148.7; 149.9; 155.9; 156.1. Found, %: C 84.91;
(
1
H NMR spectrum, δ, ppm (J, Hz): 3.83 (6H, s, OCH
3
);
4
.03 (3H, s, OCH
3
); 4.10 (3H, s, OCH
3
); 6.39 (1H, d, J = 8.6,
H-1(2)); 6.95 (2H, d, J = 8.4, H Ar); 7.47–7.50 (7H, m,
H 5.66. C72
H
58
O . Calculated, %: C 84.85; H 5.74.
6
H Ar); 7.56 (1H, s, H Ar); 7.57–7.59 (5H, m, H Ar); 7.67
1
(
1H, s, H Ar); 7.72–7.74 (6H, m, H Ar); 7.75–7.77 (2H, m,
Supplementary information file containing IR, H and
C NMR spectral data of all synthesized compounds,
1
3
H Ar); 7.84–7.93 (9H, m, H Ar); 8.05 (2H, s, H Ar).
1
3
C NMR spectrum, δ, ppm: 55.7; 56.0; 56.1; 83.4; 99.9;
02.0; 103.5; 110.6; 113.2; 119.7; 123.6; 124.4; 125.5;
25.7; 125.9; 126.2; 127.0; 127.4; 127.6; 128.2; 128.4;
29.8; 129.9; 130.0; 130.3; 132.6; 133.7; 134.1; 135.0;
35.1; 137.1; 137.5; 138.2; 139.8; 145.0; 148.1; 151.1;
synthetic procedure of compound NOP1, and optical
1
1
1
1
1
density change curves of compounds NOP1–3 in CH
Cl
2 2
and PMMA is available on the journal website at http://
link.springer.com/journal/10593.
51.3; 156.1; 195.7. Found, %: C 85.12; H 5.23. C68
H
48
O
6
.
The authors are grateful to the financial support from
industry (1006-KFA17783). A project funded by the
Priority Academic Program Development of Jiangsu
Higher Education Institutions (PAPD).
Calculated, %: C 84.98; H 5.03.
Synthesis of naphthopyrans NOP2,3 (General method).
n-Butyllithium (10 ml, 0.25 M in hexane) was slowly
added (3 min) to a cold (–30°C) solution of compound 9a
References
(
0.22 g, 0.31 mmol) or compound 9b (0.21 g, 0.22 mmol)
1
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1
h and warmed up gradually to room temperature in 2 h.
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2
SO , concentrated
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(
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2
3
6
6
.23–2.35 (4H, m, CH
.84 (6H, m, OCH
2
CH
2
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1
1
1
1
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03.1; 109.9; 113.2; 121.3; 122.7; 125.8; 126.1; 126.9;
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H
46
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O .
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