Synthesis and sequential photochromism of thiophene-linked bis-pyrans

Article abstract of DOI:10.1016/j.tet.2015.04.068

Novel bis[3H]-naphtho[2,1-b]pyrans 1a-1g and bis[2H]-naphtho[1,2-b]pyrans 2a-2g were prepared efficiently. Such thiophene-linked bispyrans display distinct color change under continuous UV irradiation with up to 110 nm of bathochromic shift between the fi

Full text of DOI:10.1016/j.tet.2015.04.068

Tetrahedron 71 (2015) 4061e4069
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Tetrahedron
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Synthesis and sequential photochromism of thiophene-linked
bis-pyrans
Xiuhong Lu , Qian Dong a , Xiaochun Dong , Weili Zhao a
a
,
y
,
y
a
,b,
*
a
School of Pharmacy, Fudan University, Shanghai 201203, PR China
Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 March 2015
Received in revised form 16 April 2015
Accepted 20 April 2015
Available online 24 April 2015
Novel bis[3H]-naphtho[2,1-b]pyrans 1ae1g and bis[2H]-naphtho[1,2-b]pyrans 2ae2g were prepared
efficiently. Such thiophene-linked bispyrans display distinct color change under continuous UV irradi-
ation with up to 110 nm of bathochromic shift between the finally generated colored forms and initially
generated forms. They also show high colorability, as well as good fatigue-resistance.
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Photochromic
Sequential photochromism
Bis-pyrans
Bathochromic
Biphotochromic
1. Introduction
absorption maxima between the final colored forms and that ini-
tially generated species upon UV irradiation exceeded 100 nm.
9
Over the last number of decades, studies on photochromic
molecules have become intense areas of research because of their
potential applications in information storage, smart windows, op-
tical lenses, optical switches, logic gates, as well as fluorescence
modulators.1 There has been recent particular interest in the de-
sign, synthesis, and study of novel photochromic dyes containing
more than one photochromic unit in a molecule, especially
However, the diarylethene unit is only photochemically reversible
while the pyran system easily undergoes thermal bleaching.
We have documented bisnaphthopyrans displaying sequential
and/or temperature-dependent photochromism, as noted by
,2
8
a change in hue with time/temperature under UV irradiation.
Bispyrans incorporating a bithiophene linker lead to up to
a 62 nm of bathochromic shift between bisopen colored forms and
3
4
8b
bisphotochromophores in diarylethene, benzodihydropyrene,
monoopen colored forms generated under UV irradiation. 1,4-
5
6
7,8
spiropyran, spirooxazine, diarylpyran, as well as hybrid sys-
tems.9 Among the reported bisphotochromic systems, only a few
examples existed wherein both photochromic subunits operate
synergistically. In the documented bisdiarylethenes, the difference
in absorption between the monomeric and dimeric systems is
Phenyl linked bispyrans display much shorter absorption (around
430 nm) of the colored forms, however, afford large difference of
absorption (up to 60 nm) in temperature-dependent photo-
8
c
chromism. In contrast, 1,3-pheny linked bispyrans provide less
8
c
distinguishable color change under irradiation. These results
imply that both electronic nature and co-planarity of the bispyrans
are crucial to the color change under continuous irradiation. In our
continuing interest in the discovery of bisphotochromophores
displaying novel properties, on the basis of our earlier observations,
we speculate that electron-rich thiophene would be an ideal linker
to provide in one hand enough long absorption maxima, in another
hand with appropriate distance and co-planarity to allow effective
communication between the two open forms, leading to enhanced
sequential photochromism. Consequently thiophene-linked bis-
pyrans 1 and 2 were designed and synthesized. For the clear ob-
servation of sequential photochromism, the phenyl moieties were
substituted with various substituents and furnishes novel systems
3
ceg
typically less than 20 nm.
In unsymmetric bis-
dimethyldihydropyrene system, 80 nm difference between biscol-
ored and monocolored forms could be reached, however, the col-
orability was very low and biscolored forms were generated under
laser flash irradiation, and exhibited very fast thermal fading (half-
ꢀ
4
life of 0.1 s at 20 C). Recently, in hybrid bisphotochromic system
involving naphthopyran and diarylethene, the difference of
*
Corresponding author. Tel./fax: þ86 21 51980111; e-mail address: zhaoweili@
fudan.edu.cn (W. Zhao).
y
These authors contribute equally to this work.
http://dx.doi.org/10.1016/j.tet.2015.04.068
0
040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

4062
X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
wherein covalently coupled photochromophores work synergisti-
cally leading to clear sequential photochromism in both 1 and 2
with greater bathochromic shift (Scheme 1).
afforded 4b in excellent yield. Further optimization resulted in
a general and synthetic friendly one-pot procedure by adding
methanol to the reaction mixture of lithiated TMSeacetylene and
bisketone to allow in situ deprotection of TMS group. Excellent
yields were obtained for both symmetric and non-symmetric bis-
propargyl alcohols 4ce4g. Our elegant synthetic procedure with
catalytic PPTS and 4 equiv trimethyl orthoformate was adopted for
8
c,11
the preparation of the desired bispyrans.
Good to excellent
yields of thiophene-linked non-symmetric and symmetric bispyr-
ans were obtained.
2.2. Sequential photochromism of compounds 1 and 2
Scheme 1. Molecular structures of photochromic bispyrans 1 and 2.
The photochromic properties were typically evaluated by ab-
sorption maximum (
form), colorability (A
absorption maximum under white light irradiation), thermal fading
l
max, maximum wavelength of the colored
0
, the absorbance at photostationary state at
2
2
. Results and discussion
ꢁ
1
rate (k , the bleaching rate of the colored form in the dark), and
fatigue-resistance (T1/2, time required to decrease to the half of the
.1. Materials
1
colorability under white light irradiation).
The syntheses of thiophene-linked bispyrans were shown in
For the evaluation of photochromic properties of bispyrans 1
and 2, the photochromic 3,3-diphenyl-[3H]-naphtho-[2,1-b]pyran
(ref 1), 3-phenyl-3-thienyl-[3H]naphtha [2,1-b]pyran (ref 2), and
2,6-diphenyl-5-ethoxycarbonyl-2-(thiophene-2-yl)-[2H]naphtha
Scheme 2. Our synthesis started with easily available aryl thienyl
ketone 3.8b For 2,5-diacylthiophene, attempted synthesis following
the reported FriedeleCrafts acylation afforded very low yield of the
required product.10 We discovered that by using aroyl chloride as
12
[1,2-b]pyran (ref 3) were used as reference dyes (Scheme 3).
4
acylating reagent, SnCl as Lewis acid and 1,2-dichloroethane as
solvent, good yield of diacylthiophene ranging from 43.7% to 84.7%
could be obtained. Such a method is also applicable to symmetric
bisketone via direct FriedeleCrafts diacylation on thiophene.
Scheme 3. Molecular structures of reference dyes.
The mechanistic details of the photochromism of the naph-
thopyrans (e.g., ref 2) are shown in Scheme 4. It is well-known that
the original state of ref 2 is the closed pyran form (closed). Upon
exposure to UV irradiation, the colored species generated are the
more abundant and fast-fading trans-cis (TC) and the trans-trans
13
(TT), which is present as a minor component and is most stable.
The TC form has been shown to be generated preferentially in the
14
early stages of the photocoloration process. These (TC and TT) can
undergo fast thermal fading, and the bleaching process can be
enhanced photochemically with visible light.
Scheme 2. Synthesis of photochromic bispyrans 1 and 2.
Scheme 4. Photochromic reaction of ref 2.
For bispropargylic alcohol, our modified procedure with sodium
acetylide/DMSO/acetylene gas combination, which could reduce
the amount of side product significantly was applied successfully
for compound 4a in 73% yield. Compound 4b, however, suffered
from low yielding and difficult work-up under identical conditions.
Thus, alternative way by using lithiated TMSeacetylene in THF,
followed by deprotection of TMS with TBAF was developed, which
All the synthesized bispyrans 1ae1g and 2ae2g display se-
quential and/or temperature-dependent photochromism as ex-
pected. As typical examples, the color and absorption spectra of 1c
and 2c prior to and after UV irradiation are shown in Fig. 1. The
colorless solution of 1c in toluene displays four distinct absorption
8
c

X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
4063
peaks located in the region 300e400 nm, which are 304, 317, 347,
and 361 nm, respectively. Upon UV irradiation, a yellow color was
generated quickly. Under prolonged exposure to UV irradiation, the
color hue started change from yellow to red and finally to purple.
For bispyran 2c, the slightly pale pink solution turned red
We proceeded to identify the colored species generated with 1a
after short time UV irradiation for monocolored Closed-TC and
Closed-TT forms by taking advantage the relatively long lifetime of
the colored forms at low temperature. The implementation of low-
temperature chromatography technique allows us to isolate pure
8
b
(lmax¼494 nm), then purple, and finally blue (lmax¼606 nm) upon
and Closed-TT of 1a (Fig. 2). Once warmed up to room tempera-
ture, the colored form(s) converted to the colorless closedeclosed
UV (366 nm) irradiation. In both cases, greater than 100 nm of
bathochromic shift between final generated colored forms and
initial colored forms were observed, and the absorption spectra of
those colored forms was found to cover the entire visible region.
These distinct color hue changes are attributed to the photo-
chemical opening of the second photochromic unit, which renders
extended conjugation and exhibits color hue change.
form and allowed the calculated absorption coefficients
3
ꢁ
3
ꢁ1
ꢁ1
(dm mol cm ) for Closed-TC as 304 (19,600), 318 (20,200),
8
b
337sh (14,100), and 478 (22,200). For Closed-TT, the absorption
coefficients are 303 (17,800), 317 (17,800), 337sh (12,700), and 479
8
b
(19,500).
ꢁ
5
Fig. 1. UVevisible spectra of 2.5ꢂ10 M solution of bispyran 1c (top) and 2c (bottom)
prior to and after UV (366 nm) irradiation at room temperature, respectively.
2
.3. Photocoloration and quantum yield measurements
Fig. 2. Absorption spectra of the colored species of 1a isolated by low-temperature
chromatography on silica gel at ꢁ78 ꢀC in dichloromethane.
We believe such TC and TT isomers are generated during the
sequential photochromism of 1 and 2 as well.
Similarly, the Closed-TC of the colored species of 2a was isolated
ꢁ3
ꢁ1
ꢁ1
as well and the absorption coefficients
3
(dm mol cm ) were
The photochromic process involving bispyran 1 is shown in
Scheme 4. The original state of 1 is the closedeclosed form (Closed-
Closed); upon UV irradiation, one pyran unit opens to generate
closed-open forms, which constitute the fast-fading closed-trans-
cis isomer (Closed-TC) and slow fading closed-trans-trans isomer
calculated to be 313 (21,200), 333 (15,300), 348 (13,700), 365
10,500), and 509 (15,800).
(
Due to the co-existence of various colored species under pro-
longed irradiation and relatively fast fading of the openeopen
isomers, the attempted isolation of the long wavelength close-
declosed isomers as clean species was unsuccessful.
Photocoloration kinetic measurements were carried out in
thermostated cuvette irradiated with UV (366 nm) using
(
Closed TT), which display yellow color accordingly. Under ex-
tended UV irradiation, the second pyran unit undergoes opening to
generate openeopen forms (Open-Open, only one isomer is shown
in Scheme 5), which display purple color.
ꢁ
5
5
.0ꢂ10 M solution of photochromic compound in CH
2 2
Cl . Irra-
ꢀ
diation beam of UV is at 90 angle to the monitoring beam and the
absorbance was monitored at the absorption maximum of the
colored form with Cary 50 UVevis spectrometer. The light intensity
was measured with potassium ferrioxalate actinometer following
ꢁ
6
ꢁ1
ꢁ3 15
.
standard procedure to be 7.98ꢂ10 E s dm
In general biexponential fading processes are involved for pho-
tochromic pyrans. Upon short period time of irradiation (tꢃ6 s), due
to the low content of slow fading Closed-TT, the fading process is
dominated by Closed-TC and could be simplified as monoexponential
1
4
process. Thus the photochromic reaction is simplified as:
The following equation could be obtained from the literature:16
dAClosedꢁTC=dt ¼
3
F
I0½1 ꢁ expðꢁ2:3AClosedeClosedÞꢄ
ClosedꢁTC
Scheme 5. Photochromic reactions of bispyran 1.
ꢁ
1AClosedꢁTC
ꢁ
k

4064
X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
The quantum efficiency
following equation:
ClosedeClosed)]}. Wherein AClosed-TC is the absorbance of Closed-TC at
absorption maximum. Closed-TC is the absorption coefficient of
Closed-TC; I is the intensity of the light. AClosedeClosed is the ab-
sorbance of ClosedeClosed at the irradiation wavelength (366 nm).
F
could be calculated by the
F
¼(dAClosed-TC/dt)t/0/{
Closed-TC 0
3 I
[1ꢁexp(ꢁ2.3
A
3
0
(
dAClosed-TC/dt)t/0 could be obtained from linear fitting of photo-
8b
coloration curve.
By applying the obtained data from Fig. 3, the photocoloration
quantum yields were calculated. Repetition of three parallel mea-
surements allowed the determination of
F
as 0.74ꢅ0.01 for 1a and
0
.98ꢅ0.01 for 2a, respectively (see Supplementary data for details).
ꢁ
5
Fig. 4. Thermodecoloration of Closed-TC of compound 1a in toluene (5ꢂ10 M) at
98.4 K monitored at 478 nm. Inset: linear fit.
The reference dye ref 1 possesses the quantum yield of 0.92. Thus
very efficient process of coloration took place among the bispyrans.
2
Fig. 5. Normalized absorbance of photochromic compound under continuous irradi-
ation with xenon lamp.
Other photochromic compounds were measured as well. The
summary of the photochromic properties was collected in Table 1.
The half-life of the bispyrans well collected in Table 1. The colo-
rability, thermal fading rate were included as well.
Table 1
Colorability (A
0
), absorption maxima, thermal fading rate (kꢁ1), and fatigue-
resistance (T1/2) of bispyrans at 298.4 K in toluene
ꢁ
5
Fig. 3. Photocoloration of compound 1a (a) and 2a (b) in CH
2
Cl
2
(5ꢂ10 M) at 300 K
0
ꢁ1 ꢁ1
(s )
upon UV irradiation (monitored at 478 nm for 1a and 509 nm for 2a, respectively).
Inset: linear fit of the coloring kinetics.
Compd
Ar
Ar
A
0
/lmax (nm)
k
T1/2 (min)
1
1
1
a
b
c
Ph
Ph
p-Fph
o-Fph
o-Fph
p-Meph
p-MeOph
p-MeOph
Ph
p-Fph
o-Fph
0.391/468
0.308/466
0.536/460
0.529/455
0.315/476
0.243/487
0.295/483
0.681/494
0.686/494
0.699/494
0.694/494
0.692/494
0.672/494
0.707/495
0.390/432
0.275/478
0.542/505
0.107
0.163
0.025
0.084
0.149
0.252
0.179
0.015
0.019
0.004
0.012
0.020
0.035
0.025
0.101
0.126
0.023
108
113
73
p-Fph
o-Fph
p-Fph
p-Meph
p-MeOph
Ph
2
.4. Colorability of compounds 1 and 2 and thermal fading of
1d
94
1
1
1
2
e
f
g
a
120
the colored forms
155a
122
Due to the complication involved in bisphotochromic processes,
we only studied the thermal fading of one of the initial formed
monocolored forms. Once the light source was removed, the ab-
sorbance at the absorption maximum of the colored form was
monitored with Cary 50. The temperature was controlled with
thermo-cryostat to be 287.4 K.
Mathematic manipulation of the curve in Fig. 4 by plotting dA/dt
versus time leads to good linearity (correlation coefficient better
than 0.99) and the rate of thermal fading for Closed-TC was cal-
218a
Ph
2b
2c
p-Fph
o-Fph
p-Fph
p-Meph
p-MeOph
Ph
234
161
2
2
2
2
d
e
f
o-Fph
179
p-Meph
p-MeOph
p-MeOph
223a
a
237
216a
g
ref 1
ref 2
ref 3
85
a
137
342a
ꢁ
1
a
culated to be 0.107 s at 298.4 K.
Estimated from 1 h experimental result.
2
.5. Fatigue-resistance measurements
From Table 1, it could be concluded that all the bispyrans possess
very high colorability. The bispyrans display greater colorability,
higher fading rate, however diminished fatigue-resistance than cor-
responding pyran precursors (compare 1a with ref 2, 2a with ref 3).
The substituent in the phenyl ring of the bispyran dye has sig-
nificant effects on the photochromic properties, which follows the
The fatigue-resistance of photochromic compound was mea-
sured by monitoring the absorbance of a continuous irradiated
solution of photochromic compound in toluene with white light
with UVevis spectrometer (see Supplementary data for details).
Examples were shown in Fig. 5 for compounds 1a and 2a in com-
parison with ref 1 dye.
1
same trend as the monophotochromic pyran system. Moreover,

X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
4065
2
3
3
the pattern of the substitution affects the sequential photochro-
mism significantly in the bispyrans. Fluorine substitution on the 3-
phenyl group has little effect on the absorption maxima of the
colored form, however, it affects thermal fading rate. para-Fluoro
substitution led to increased fading rate and enhanced fatigue-
resistance (1b, 2b in comparison with 1a, 2a). ortho-Fluoro sub-
stitution, however, resulted in significantly decreased thermal
fading rate, diminished fatigue-resistance (1c, 1d, 2c, 2d). Electron
donating substituent decreases colorability and concurrently in-
creases the fading rate, as well as fatigue-resistance (1ee1g,
134.1 ( J¼3.1 Hz), 133.46 ( J¼8.5 Hz), 133.43 ( J¼8.5 Hz), 130.3
3
3
2
( J¼2.4 Hz), 130.2 ( J¼2.4 Hz), 126.7 ( J¼14.7 Hz), 126.1
2
4
4
2
( J¼14.7 Hz),124.4 ( J¼3.7 Hz),124.3 ( J¼3.7 Hz),116.5 ( J¼21.4 Hz),
2
116.4 ppm ( J¼21.4 Hz).
4.1.4. 2-(o-Fluorobenzoyl)-5-(p-fluorobenzoyl)thiophene (3d). The
general procedure was followed except that the refluxing time was
26.5 h and pale-yellow solid was obtained in yield of 43.7%. Mp
ꢀ
1
136.2e137.7 C; H NMR (300 MHz, CDCl
3
):
d
¼8.24 (t, J¼1.6 Hz,
0.5H), 8.04 (t, J¼1.0 Hz, 0.5H), 7.98e7.91 (m, 2H), 7.66e7.50 (m, 3H),
13
2
ee2g). Bispyran substituted with para-methoxyphenyl shows
7.33e7.14 ppm (m, 4H); C NMR (75 MHz, CDCl ):
3
d¼186.2, 186.2,
1
1
temperature-dependent photochromism and affords the highest
fading rate, the best fatigue-resistance, however, with the poorest
colorability (1f, 2f).
185.9, 165.9 ( J¼254.5 Hz), 159.6 ( J¼247.0 Hz), 148.8, 144.1, 142.1,
5 5
141.2 ( J¼2.4 Hz), 134.0 ( J¼2.9 Hz), 133.8, 133.6, 133.6, 133.5, 133.5,
2
2
133.5, 133.3 ( J¼8.7 Hz), 133.2 ( J¼8.7 Hz), 132.0, 131.8, 131.7, 130.31
3
3
4
(
J¼2.5 Hz), 133.2 ( J¼2.5 Hz), 126.8, 126.6, 126.3, 124.4 ( J¼3.7 Hz),
4 2 2
3
. Conclusion
124.3 ( J¼3.7 Hz), 116.6 ( J¼21.4 Hz), 116.4 ( J¼21.4 Hz), 115.9 ppm
2
(
J¼22.0 Hz); IR (CHCl
3
):
n
max¼3022, 1647, 1612, 1601, 1519, 1507,
1
ꢁ
In conclusion, bis[3H]-naphtho[2,1-b]pyran 1 and bis[2H]-
1486, 1454, 1300, 1280, 1242, 1218, 1097, 890, 874, 850 cm
.
naphtho[1,2-b]pyran 2 represent unique dimeric systems possess-
ing sequential photochromic properties. Compounds 1 and 2 pos-
sess high colorability and good fatigue-resistance. More
interestingly, bathochromic shifts greater than 100 nm were ob-
served in the studied sequential photochromic process. The high
colorability, good fatigue-resistance, broad absorption, and tunable
color change upon UV irradiation may render the bispyrans as
novel photochromic dyes for the preparation of materials with
applications in display, filter, and modulation of fluorescence.
4.1.5. 2,5-Di(p-methylbenzoyl)thiophene (3e). The general pro-
cedure was followed and pale-yellow solid was obtained in yield of
ꢀ
1
61.2%. Mp 143e144 C; H NMR (300 MHz, CDCl
4H), 7.67 (s, 2H), 7.36e7.29 (m, 4H), 2.46 ppm (s, 6H); C NMR
(75 MHz, CDCl ):
¼187.7, 148.4, 143.9, 134.6, 133.4, 129.6, 129.3,
21.7 ppm. IR (CHCl ):
max¼3027, 3020, 3013, 2925, 1640, 1607,
1570, 1517, 1443, 1408, 1340, 1312, 1278, 1261, 1182, 1125, 1020, 911,
3
):
d
¼7.89e7.80 (m,
13
3
d
3
n
ꢁ1
886, 835 cm
.
4
4
. Experimental section
4.1.6. 2,5-Di(p-methoxybenzoyl)thiophene (3f). The general pro-
cedure was followed and yellow solid was obtained in yield of
ꢀ
1
.1. General procedure for preparation of diacyl-thiophenes (3)
Aroyl chloride (10.5 mmol), thiophene-2-yl aryl ketone
84.7%. Mp 192.5e193.5 C;
3
H NMR (300 MHz, CDCl ):
d
¼7.99e7.91 (m, 4H), 7.66 (s, 2H), 7.06e6.94 (m, 4H), 3.91 ppm (s,
13
6H); C NMR (75 MHz, CDCl
129.8, 113.8, 55.6 ppm. IR (CHCl
1601, 1574, 1509, 1463, 1442, 1420, 1310, 1282, 1257, 1172, 1030,
3
):
d
¼186.3, 163.4, 148.1, 132.8, 131.7,
(
10 mmol), and tin chloride (10.5 mmol) were refluxed in 1,2-
3
):
n
max¼3020, 2938, 2843, 1636,
dichloroethane for 24 h. The cooled reaction mixture was poured
into a mixture of ice (50 g) and 5 M HCl (5 ml) with vigorous stir-
ring. Extracted with methylene chloride, filtrated through a pad of
silica gel, wash with methylene chloride, and decolored with
charcoal. Solvent was removed, the residue was recrystallized from
methylene chloride/ethanol. Solid was collected by filtration. The
mother liquid was concentrated to dryness, purified by chroma-
tography (silica gel, methylene chloride/hexane¼2:3 as eluant) and
recrystallization from ethanol.
ꢁ
1
896, 845 cm
.
4.1.7. 2-Benzoyl-5-(p-methoxylbenzoyl)thiophene (3g). The general
procedure was followed and pale-yellow solid was obtained in
ꢀ
1
yield of 71.0%. Mp 151e152 C; H NMR (300 MHz, CDCl
3
):
d
¼7.99e7.93 (m, 2H), 7.93e7.88 (m, 2H), 7.70e7.60 (m, 3H),
13
7.58e7.49 (m, 2H), 7.05e6.98 (m, 2H), 3.91 ppm (s, 3H); C NMR
(75 MHz, CDCl ):
¼187.9, 186.3, 163.5, 148.8, 147.6, 137.2, 133.6,
32.9, 132.8, 131.9, 131.8, 129.7, 129.2, 128.5, 113.8, 55.6 ppm; IR
(CHCl ):
max¼3022, 2938, 2842, 1640, 1574, 1510, 1461, 1442, 1420,
1340, 1311, 1278, 1258, 1174, 1127, 1029, 910, 884, 845 cm
3
d
1
4.1.1. 2,5-Dibenzoyl-thiophene (3a). The general procedure was
3
n
ꢁ
1
followed and pale-yellow-gray solid was obtained in yield of 71.9%.
.
ꢀ
1
Mp 112e113 C; H NMR (300 MHz, CDCl
.68 (2H, s), 7.68e7.60 (m, 2H), 7.58e7.48 ppm (m, 4H); C NMR
75 MHz, CDCl ):
¼188.3, 148.6, 137.4, 133.8, 133.1, 129.4,
28.7 ppm; IR (CHCl ):
max¼3012, 1644, 1600, 1579, 1516, 1448,
3
):
d
¼7.95e7.85 (4H, m),
13
7
(
1
4.2. Direct bisacylation for the synthesis of bisketone 3b
3
d
3
n
Tin chloride (17 mmol) was added dropwise with stirring to
ꢁ
1
1340, 1318, 1276, 1258, 1220, 1180, 1127, 880 cm
.
a mixture of p-fluorobenzoyl chloride (17 mmol) and thiophene
ꢀ
(
8 mmol) in dry 1,2-dichloroethane at 0e5 C over 10 min, stirred
4
.1.2. 2,5-Di(p-fluorobenzoyl)thiophene (3b). The general pro-
for 2 h. Then the mixture was refluxed for 48 h, cooled down,
poured into a mixture of ice (50 g) and 5 M HCl (5 ml) under vig-
orous stirring. The mixture was extracted with dichloromethane,
filtrated through a pad of silica gel, and washed with dichloro-
methane. Most of the solvents were removed in vacuo, the resulted
solid was filtered, recrystallized from dichloromethane/hexane.
Solid was collected by filtration. The mother liquid was concen-
trated to dryness, digested with dichloromethane/hexane, and then
recrystallized from dichloromethane/hexane. 3b was obtained in
yield of 68.5%.
cedure was followed and pale-yellow solid was obtained in yield of
6
ꢀ
1
7.8%. Mp 184.8e186.2 C; H NMR (300 MHz, CDCl
3
):
d
¼8.00e7.92
13
(
m, 4H), 7.67 (s, 2H), 7.28e7.17 ppm (m, 4H); C NMR (75 MHz,
1
4
CDCl
3
):
d
¼186.4,165.6 ( J¼255.1 Hz),148.2, 133.5, 133.4 ( J¼2.4 Hz),
3
2
1
31.9 ( J¼7.6 Hz), 115.8 ppm ( J¼22.0 Hz); IR (CHCl
3
):
n
max¼3022,
1
ꢁ
1645, 1600, 1506, 1409, 1339, 1276, 1242, 1156, 887, 850 cm
.
4.1.3. 2,5-Di(o-fluorobenzoyl)thiophene (3c). The general procedure
was followed and pale-yellow solid was obtained in yield of 52.1%.
Mp 111e112 C; H NMR (300 MHz, CDCl
ꢀ
1
3
):
d
¼8.24 (t, J¼1.6 Hz, 1H),
13
7.98e7.94 (m, 1H), 7.66e7.50 (m, 5H), 7.33e7.14 ppm (m, 5H);
C
4.2.1. 1,4-Di(1-hydroxy-1-phenyl-prop-2-ynyl)thiophene
(4a). Bisketone 3a (1.65 g, 5.65 mmol) was added in one portion to
a suspension of sodium acetylide (1.09 g, 22.67 mmol) in dry THF
1
NMR (75 MHz, CDCl
3
):
d
¼185.8, 184.8, 159.62 ( J¼252.1 Hz), 159.57
1
5 5
(
J¼252.1 Hz), 144.6, 142.3, 141.9 ( J¼2.4 Hz), 134.7 ( J¼2.4 Hz),

4066
X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
1
(
20 ml) with stirring while acetylene gas was bubbled. DMSO (5 ml)
(s, 1H); 13C NMR (75 MHz, CDCl
3
):
d
¼162.3 ( J¼246.6 Hz), 126.98
1
4
was added. The mixture was stirred at room temperature for 3 h
while keeping bubbling of acetylene. The mixture was allowed to
stir overnight, poured onto crush ice, and extracted with
dichloromethane. After removal of solvent, the residue was purified
by chromatography and by recrystallization from dichloromethane/
( J¼249.0 Hz), 149.7, 149.7, 148.3, 148.3, 138.99 ( J¼4.9 Hz), 138.94
4
3
3
( J¼4.9 Hz), 130.32 ( J¼8.6 Hz), 127.50 ( J¼7.9 Hz), 127.49
3
3
3
( J¼8.5 Hz), 126.96 ( J¼7.1 Hz), 126.93 ( J¼7.1 Hz), 125.0, 123.8
4
2
2
( J¼3.7 Hz), 116.3 ( J¼21.4 Hz), 115.0 ( J¼21.4 Hz), 85.1, 85.0, 83.8,
5
5
83.8, 75.3, 75.3, 74.72 ( J¼2.2 Hz), 74.67 ( J¼2.2 Hz), 71.2, 69.0,
1
19
hexane to afford 4a in yield of 73% as pale-yellow gel. H NMR
68.9 ppm; F NMR (300 MHz, CDCl
3
):
d
¼ꢁ110.6, ꢁ113.7 ppm; IR
(
1
300 MHz, CDCl
H), 6.85 (s, 1H), 2.93 (s, 2H), 2.87 ppm (s, 2H); C NMR (75 MHz,
CDCl ):
¼149.9, 143.2, 143.1, 128.3, 125.7, 125.6, 124.9, 124.9, 85.4,
5.1, 75.1, 71.7 ppm; IR (CHCl ):
max¼3582, 3306, 3066, 3013, 2927,
3
):
d
¼7.71e7.64 (m, 4H), 7.40e7.30 (m, 6H), 6.89 (s,
(CHCl
868, 813 cm
3
):
n
max¼3586, 3306, 3013, 1614, 1490, 1450, 1179, 1031, 974,
13
ꢁ1
.
3
d
7
1
3
n
4.3.5. 2,5-Di[1-hydroxy-1-(p-methylphenyl)-prop-2-ynyl]thiophene
(4e). The general procedure was followed and pale orange gel was
obtained in yield of 96.1%. H NMR (300 MHz, CDCl
(m, 4H), 7.20e7.12 (m, 4H), 6.89 (s, 1H), 6.84 (s, 1H), 2.89 (s, 2H),
2.85 (s, 2H), 2.35 ppm (s, 6H); C NMR (75 MHz, CDCl
40.3, 138.0, 128.9, 125.5, 125.5, 124.7, 85.5, 74.9, 71.6, 21.2 ppm; IR
(CHCl ):
max¼3581, 3306, 3022, 2925, 2871, 1511, 1454, 1408, 1375,
1330, 1250, 1182, 1034, 974, 873, 817 cm
ꢁ
1
490, 1450, 1179, 1031, 974, 868, 813 cm
.
1
3
):
d
¼7.59e7.51
4
.3. General procedure for preparation of bispropargylic al-
13
cohols (4)
3
):
d
¼149.8,
1
Butyl lithium (1.6 M in hexane, 11 mmol) was added over 1 min
3
n
ꢁ
1
to a solution of TMSeacetylene (1.55 ml, 11 mmol) in THF (15 ml)
atꢁ10 C with stirring, the mixture was stirred for 10 min, 2,5-di(o-
.
ꢀ
fluorobenzoyl)thiophene (1.65 g, 5 mmol) was added in one por-
tion, stirred for over 0.5 h, warmed up to room temperature, and
stirred over night. Methanol (8 ml) was added, stirred for 2 h before
water (20 ml) was added. The reaction mixture was neutralized
with 5 M HCl to pH about 6, extracted with ethyl acetate, dried with
anhydrous sodium sulfate, and filtered. After removal of solvent,
the resulted oil was purified by chromatography on silica gel (ethyl
acetate/hexane¼1:3 as eluant), dried in high vacuum. Bispropargyl
alcohol derivative was obtained as pale-yellow gel, which was used
directly into the next step without further purification.
4.3.6. 2-[1-Hydroxy-1-(p-methoxyphenyl)-prop-2-ynyl]-5-(1-
hydroxy-1-(p-methylphenyl)-prop-2-ynyl)thiophene (4g). The gen-
eral procedure was followed and pale orange gel was obtained in
1
yield of 91.8%. H NMR (300 MHz, CDCl
3
):
d
¼7.70e7.64 (m, 2H),
7.62e7.55 (m, 2H), 7.40e7.28 (m, 3H), 6.92e6.82 (m, 4H), 3.81 (s,
13
3H), 2.96 (s, 1H), 2.91 (s, 1H), 2.87 (s, 1H), 2.86 ppm (s, 2H); C NMR
(75 MHz, CDCl ):
¼159.2, 150.1, 149.6, 143.0, 135.3, 128.2, 128.1,
127.0, 126.9, 125.6, 125.5, 124.7, 124.6, 113.5, 85.6, 75.1, 75.0, 71.7,
71.4, 55.3 ppm; IR (CHCl ):
max¼3581, 3305, 3020,1608,1510,1450,
1252, 1177, 1035, 973, 870, 828 cm
3
d
3
n
ꢁ
1
.
4
.3.1. 2,5-Di(1-hydroxy-1-phenyl-prop-2-ynyl)thiophene (4a). The
4.3.7. 2,5-Di[1-hydroxy-1-(p-methoxyphenyl)-prop-2-ynyl]thio-
phene (4f). Butyl lithium (1.6 M in hexane, 6.7 mmol) was added
over 10 min to a solution of TMSeacetylene (0.94 ml, 6.6 mmol)
general procedure was followed. Compound 4a was obtained in
yield of 92.9% as pale-yellow gel, which solidified on standing in
a refrigerator.
ꢀ
in THF (10 ml) at ꢁ10 C with stirring, the mixture was stirred for
0
.5 h, then ketone was added in one portion, stirred for over
4
.3.2. 2,5-Di[1-hydroxy-1-(p-fluorophenyl)-prop-2-ynyl]thiophene
0.5 h, warmed up to room temperature, and stirred over night.
Aqueous ammonium chloride solution was used to quench the
reaction, and ethyl acetate was used to extract product. Removal
of solvent provided brown oil, which was used directly for the
next step.
(4b). The general procedure was followed and yellow-brown gel
1
3
was obtained in yield of 91.8%. H NMR (300 MHz, CDCl ):
d
2
(
¼7.69e7.59 (m, 4H), 7.08e6.98 (m, 4H), 6.89 (s, 1H), 6.86 (s, 1H),
1
3
.96 (s, 2H), 2.88 ppm (s, 2H); C NMR (75 MHz, CDCl
3
):
d
¼162.3
1
4
4
J¼247.2 Hz), 149.9, 149.8, 138.93 ( J¼4.9 Hz), 138.87 ( J¼4.9 Hz),
Such brown oil was dissolved in THF and was treated with TBAF
3
3
2
ꢀ
1
8
(
8
27.54 ( J¼8.6 Hz), 127.49 ( J¼8.4 Hz), 124.8, 115.0 ( J¼20.0 Hz),
5.1, 75.4, 71.2 ppm; 19F NMR (300 MHz, CDCl
):
¼ꢁ113.6 ppm; IR
CHCl ):
max¼3582, 3306, 3020, 1604, 1508, 1226, 1159, 1033, 975,
(1 M in THF, 8 ml) at 0e5 C, then stirred at room temperature for
3
d
1 h. The reaction mixture was quenched with water and extracted
with ethyl acetate, removal of solvent afforded fairly pure 4f as
3
n
ꢁ
1
1
35 cm
.
orange gel in yield of 81.3%. H NMR (300 MHz, CDCl
3
):
d
¼7.62e7.54
(
m, 4H), 6.91e6.82 (m, 4H), 6.88 (s, 1H), 6.84 (s, 1H), 3.81 (s, 6H),
13
4
.3.3. 2,5-Di[1-hydroxy-1-(o-fluorophenyl)-prop-2-ynyl]thiophene
2.92 (s, 2H), 2.86 ppm (s, 2H); C NMR (75 MHz, CDCl
149.9, 135.4, 127.0, 126.9, 124.6, 113.5, 85.5, 74.9, 71.4, 55.3 ppm; IR
(CHCl ):
max¼3581, 3305, 3018, 3012, 2960, 2840, 1608, 1510, 1460,
1176, 1036, 973, 830 cm
3
):
d¼159.3,
(4c). The general procedure was followed and pale-yellow gel was
1
obtained in yield of 95.9%. H NMR (300 MHz, CDCl
m, 2H), 7.39e7.29 (m, 2H), 7.17 (td, J¼7.6, 1.6 Hz, 1H), 7.15 (td, J¼7.6,
.6 Hz, 1H), 7.07 (td, J¼8.1, 1.2 Hz, 1H), 7.03 (td, J¼8.1, 1.2 Hz, 1H),
3
):
d
¼7.72e7.62
3
n
ꢁ
1
(
1
.
7
2
(
.00 (s, 1H), 6.95 (s, 1H), 3.24 (d, J¼2.2 Hz, 1H), 3.23 (J¼2.2 Hz, 1H),
4.4. General procedure for preparation of bispyrans (1 and 2)
1
3
.85 (s, 1H), 2.85 ppm (s, 1H); C NMR (75 MHz, CDCl
3
):
d
¼159.72
1
1
3
J¼249.0 Hz), 159.68 ( J¼249.0 Hz), 148.2, 148.4, 130.2 ( J¼7.9 Hz),
Bispropargyl alcohol (0.5 mmol), 2-naphthol (1.05 mmol), PPTS
(13.4 mg, 0.05 mmol), and trimethyl orthoformate (0.21 ml,
2.0 mmol) in 1,2-dichloroethane (2 ml) were refluxed for 2e3 h,
filtered through a pad of alumina while it was hot, and washed with
1,2-dichloroethane. The filtrate was concentrated, recrystallized
from dichloromethane/hexane. The solid was collected by filtration.
The mother liquid was concentrated and purified by chromatog-
raphy (silica gel). Recrystallization (dichloromethane/hexane)
afforded bispyran.
3
3
4
1
26.98 ( J¼8.8 Hz), 126.94 ( J¼8.8 Hz), 125.0, 123.8 ( J¼3.7 Hz),
2 5 5
1
16.2 ( J¼22.0 Hz), 83.8, 83.8, 74.64 ( J¼2.2 Hz), 74.58 ( J¼2.3 Hz),
8.9, 68.9 ppm; 19F NMR (300 MHz, CDCl
):
¼ꢁ110.6 ppm; IR
CHCl ):
max¼3586, 3306, 3013, 1614, 1490, 1450, 1179, 1031, 974,
68, 813 cm
6
(
8
3
d
3
n
ꢁ
1
.
4
1
.3.4. 2-[1-Hydroxy-1-(o-fluorophenyl)-prop-2-ynyl]-5-[1-hydroxy-
-(p-fluorophenyl)-prop-2-ynyl] thiophene (4d). The general pro-
cedure was followed and pale-yellow gel was obtained in yield of
1
9
(
3
7.5%. H NMR (300 MHz, CDCl
m, 1H), 7.20e7.12 (m, 1H), 7.10e6.97 (m, 3H), 6.91e6.87 (m, 2H),
.22 (t, J¼3.2 Hz, 1H), 2.97 (s, 1H), 2.88 (d, J¼0.9 Hz, 1H), 2.85 ppm
3
):
d
¼7.74e7.59 (m, 3H), 7.39e7.29
4.4.1. 2,5-Di-(3-phenyl-[3H]-naphtho[2,1-b]pyran-3-yl)-thiophene
(1a). The general procedure was followed and pale pink solid was
ꢀ
1
obtained in yield of 79.7%. Mp 213e214 C; H NMR (300 MHz,

X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
4067
CDCl
3
):
d
¼7.93 (d, J¼8.1 Hz, 2H), 7.73 (d, J¼8.1 Hz, 2H), 7.65 (dd,
(75 MHz, CDCl
3
):
d
¼150.2, 150.1, 140.9, 137.4, 129.7, 129.6, 129.3,
J¼9.0, 2.2 Hz, 2H), 7.64e7.55 (m, 4H), 7.53e7.43 (m, 2H), 7.40e7.18
128.6, 128.4, 127.0, 126.5, 126.2, 125.4, 125.3, 123.5, 121.2, 119.3,
118.2, 113.6, 80.4, 80.3, 21.2 ppm. IR (KBr):
13
(
m, 12H), 6.73 (d, J¼2.5 Hz, 2H), 6.27 ppm (d, J¼10.0 Hz, 2H);
NMR (75 MHz, CDCl ):
¼150.2, 150.2, 143.9, 129.9, 129.7, 129.4,
28.5, 128.0, 127.8, 126.9, 126.6, 126.3, 125.6, 125.5, 123.6, 121.3,
19.6, 118.2, 113.6, 80.4, 80.3 ppm. IR (KBr):
max¼3059, 1633, 1589,
515, 1460, 1384, 1245, 1204, 1090, 1006, 812, 740 cm . HRMS
C
n
max¼3055, 3024, 2918,
3
d
1633,1588,1509,1460,1384,1268, 1240,1223,1171,1084,1002, 942,
ꢁ1
1
1
1
805, 745 cm . HRMS (MALDI) calcd for C44
H
32
O
2
S: m/z (%):
þ
n
647.2015 [MþNa] . Found: 647.2018 (61.3%).
ꢁ1
þ
(
MALDI) calcd for C42
H
28
O
2
S: m/z (%): 619.1702 [MþNa] . Found:
4.4.6. 2,5-Di-[3-(p-methoxyphenyl)-[3H]-naphtho[2,1-b]pyran-3-
yl]-thiophene (1f). The general procedure was followed and pale
pink solid was obtained in yield of 72.8%. Mp 245.6e246.8 C; H
NMR (300 MHz, CDCl ):
619.1709 (32.4%).
ꢀ
1
4
.4.2. 2,5-Di-[3-(p-fluorophenyl)-[3H]-naphtho[2,1-b]pyran-3-yl]-
3
d
¼7.93 (d, J¼8.4 Hz, 2H), 7.71 (d, J¼8.1 Hz,
thiophene (1b). The general procedure was followed and pale pink
2H), 7.64 (d, J¼9.0 Hz, 2H), 7.50e7.40 (m, 6H), 7.36e7.28 (m, 2H),
ꢀ
1
solid was obtained in yield of 82.8%. Mp 198.5e200 C; H NMR
300 MHz, CDCl ):
¼7.94 (d, J¼8.7 Hz, 2H), 7.72 (d, J¼8.1 Hz, 2H),
.66 (dd, J¼9.0, 1.9 Hz, 2H), 7.56e7.43 (m, 6H), 7.38e7.27 (m, 3H),
7.24 (d, J¼10.0 Hz, 2H), 7.15 (dd, J¼8.7, 2.2 Hz, 2H), 6.86e6.77 (m,
13
(
7
3
d
4H), 6.68 (d, J¼3.1 Hz, 2H), 6.22 ppm (d, J¼10.0 Hz, 2H); C NMR
(75 MHz, CDCl
128.4,127.7,127.0,126.5,125.3,125.2,123.5,121.2,119.3,118.2,113.6,
113.3, 80.2, 80.3, 55.2 ppm. IR (KBr):
3
):
d
¼158.9, 150.3, 150.1, 135.9, 129.7, 129.6, 129.3,
7
6
(
.15 (dd, J¼8.7, 3.7 Hz, 2H), 7.03e6.93 (m, 4H), 6.68 (d, J¼1.2 Hz, 2H),
13
.20 ppm (d, J¼9.7 Hz, 2H); C NMR (75 MHz, CDCl
3
):
d
¼162.2
nmax¼3059, 3001, 2931, 2832,
1
4
J¼246.6 Hz), 150.0, 149.9, 139.5 ( J¼2.4 Hz), 130.0, 129.6, 129.3,
1630, 16,089, 1587, 1508, 1459, 1382, 1305, 1248, 1230, 1174, 1082,
1034, 993, 948, 822, 812 cm . HRMS (MALDI) calcd for C44
m/z (%): 679.1914 [MþNa] . Found: 679.1917 (30.4%).
3
3
ꢁ1
1
28.4, 128.18 ( J¼8.4 Hz), 128.15 ( J¼8.4 Hz), 126.7, 126.5, 125.5,
H
32
O
4
S:
2
þ
125.4, 123.7, 121.2, 119.8, 118.1, 114.8 ( J¼21.4 Hz), 113.6, 80.0,
8
0.0 ppm. IR (KBr):
n
max¼3061, 1634, 1601, 1586, 1506, 1460, 1384,
ꢁ1
1229, 1205, 1157, 1084, 996, 952, 828, 816, 749 cm . HRMS (MALDI)
4.4.7. 2-[3-(p-Methoxyphenyl)-[3H]-naphtho[2,1-b]pyran-3-yl]-5-
(3-phenyl-[3H]-naphtho[2,1-b]pyran-3-yl)-thiophene (1g). The
general procedure was followed and pale pink solid was obtained
þ
calcd for C42
H F
26 2
O
2
S: m/z (%): 655.1514 [MþNa] . Found: 655.1509
(
58.1%).
ꢀ
1
3
in yield of 65.1%. Mp 148e150 C; H NMR (300 MHz, CDCl ):
4
.4.3. 2,5-Di-[3-(o-fluorophenyl)-[3H]-naphtho[2,1-b]pyran-3-yl]-
d
¼7.93 (d, J¼8.1 Hz, 2H), 7.71 (d, J¼8.1 Hz, 2H), 7.69e7.60 (m, 2H),
thiophene (1c). The general procedure was followed and pale pink
7.59e7.42 (m, 2H), 7.50e7.41 (m, 4H), 7.37e7.21 (m, 7H), 7.18 (dd,
J¼8.7, 2.4 Hz, 1H), 7.15 (dd, J¼9.0, 3.1 Hz, 1H), 6.86e6.77 (m, 2H),
6.69 (d, J¼3.1 Hz, 1H), 6.68 (d, J¼2.5 Hz, 1H), 6.26 (d, J¼10.0 Hz, 1H),
ꢀ
1
solid was obtained in yield of 59.9%. Mp 178e180.5 C; H NMR
300 MHz, CDCl ):
¼7.92 (d, J¼8.4 Hz, 2H), 7.72 (d, J¼7.8 Hz, 2H),
.70 (d, J¼8.1 Hz, 2H), 7.67 (d, J¼8.4 Hz, 2H), 7.50e7.42 (m, 2H),
(
7
3
d
13
6.22 (d, J¼9.7 Hz, 1H), 3.75 (s, 1.5H), 3.75 ppm (s, 1.5H); C NMR
7.37e7.28 (m, 2H), 7.28e7.19 (m, 6H), 7.11e6.96 (m, 4H), 6.74 (s,
(75 MHz, CDCl
3
):
d
¼159.1, 150.6, 150.2, 150.2, 150.1, 144.0, 136.0,
13
2
H), 6.46 (d, J¼10.0 Hz, 1H), 6.44 ppm (d, J¼10.0 Hz, 1H); C NMR
129.9, 129.9, 129.7, 129.4, 128.5, 128.0, 127.8, 127.1, 127.0, 126.6,
126.3, 125.6, 125.5, 125.4, 125.3, 123.7, 123.6, 121.1, 119.6, 119.4,
118.3, 113.7, 113.3, 80.4, 80.4, 80.3, 80.2, 55.2 ppm. IR (KBr):
1
(
(
(
75 MHz, CDCl
3
):
d
¼159.2 ( J¼248.4 Hz), 149.8, 148.9, 130.6
2
3
3
J¼11.0 Hz), 130.0, 129.8 ( J¼8.6 Hz), 129.7, 129.5, 128.5, 127.6
4
J¼2.4 Hz), 126.7, 125.6, 125.6, 125.3, 123.8, 123.7 ( J¼3.1 Hz), 121.4,
n
max¼3058, 2923, 2834, 1633, 1606, 1587, 1509, 1460, 1385, 1302,
2
ꢁ1
1
19.5, 118.1, 116.5 ( J¼22.6 Hz), 113.6, 78.5, 78.5 ppm. IR (KBr):
1249, 1227, 1205, 1173, 1085, 1003, 944, 812 cm . HRMS (MALDI)
þ
n
max¼3058, 1634, 1615, 1583, 1515, 1484, 1448, 1385, 1276, 1246,
calcd for C43
(31.4%).
H
30
O
3
S: m/z (%): 649.1808 [MþNa] . Found: 649.1801
ꢁ
1
1229, 1215, 1108, 1084, 1006, 913, 807, 748 cm . HRMS (MALDI)
þ
calcd for C42
H F
26 2
O
2
S: m/z (%): 655.1514 [MþNa] . Found: 655.1508
(
64.3%).
4.4.8. 2,5-Di-(2,6-diphenyl-5-ethoxycarbonyl-[2H]-naphtho[1,2-b]
pyran-2-yl)-thiophene (2a). The general procedure was followed
1
4
.4.4. 2-[3-(o-Fluorophenyl)-[3H]-naphtho[2,1-b]pyran-3-yl]-5-[3-
and pale pink solid was obtained in yield of 87.6%. H NMR
(
(
p-fluorophenyl)-[3H]-naphtho[2,1-b]pyran-3-yl]-thiophene
1d). The general procedure was followed and pale pink solid was
(300 MHz, CDCl
3
):
d
¼8.40 (dd, J¼9.0, Hz, 2H), 7.64e7.55 (m, 4H),
7.54e7.46 (m, 4H), 7.46e7.24 (m, 18H), 6.80 (s, 2H), 6.77 (d, J¼10.0
Hz, 2H), 6.22 (d, J¼10.0 Hz, 2H), 3.97 (q, J¼7.5 Hz, 4H), 0.86 ppm (t,
ꢀ
1
obtained in yield of 83.7%. Mp 166e169 C; H NMR (300 MHz,
CDCl ):
¼7.93 (d, J¼8.7 Hz, 2H), 7.78e7.60 (m, 5H), 7.57e7.42 (m,
H), 7.38e7.20 (m, 6H), 7.20e7.02 (m, 6H), 6.78e6.64 (m, 2H), 6.46
d, J¼10.0 Hz, 0.5H), 6.44 (d, J¼10.0 Hz, 0.5H), 6.24e6.17 ppm (m,
1
3
3
d
J¼7.5 Hz, 6H); C NMR (75 MHz, CDCl
3
):
d
¼168.1, 150.3, 147.0,
4
(
143.9, 138.0, 132.7, 131.0, 130.4, 130.3, 128.5, 128.1, 127.8, 127.3, 127.1,
126.9, 126.7, 126.5, 126.1, 125.5, 125.4, 124.9, 122.1, 121.0, 111.7, 81.1,
H); 13C NMR (75 MHz, CDCl
):
d
¼162.1 ( J¼246.0 Hz), 159.0
1
61.1, 13.7 ppm. IR (KBr):
1370, 1292, 1225, 1174, 1108, 1039, 759, 699 cm . HRMS (MALDI)
n
max¼3057, 2977, 1728, 1639, 1501, 1446,
1
3
1
4
ꢁ1
(
(
J¼248.4 Hz), 149.9, 149.9, 149.7, 148.9, 139.5 ( J¼2.4 Hz), 130.5
2
3
þ
J¼11.0 Hz), 129.9, 129.9, 129.7 ( J¼8.6 Hz), 129.6, 129.4, 129.3,
calcd for C60
(95.6%).
H
44
O
6
S: m/z (%): 915.2751 [MþNa] . Found: 915.2750
3
3
3
1
1
1
7
1
7
28.2 ( J¼8.4 Hz), 128.2 ( J¼8.4 Hz), 127.5 ( J¼1.9 Hz), 126.6, 126.6,
4
25.5, 125.4, 125.4, 125.2, 123.7 ( J¼4.9 Hz), 121.2, 121.2, 119.7, 119.5,
2 2
18.1, 118.0, 116.4 ( J¼22.0 Hz), 114.8 ( J¼22.0 Hz), 113.5, 80.0, 80.0,
8.4, 78.4 ppm. IR (KBr):
max¼3059, 1634, 1603, 1586, 1504, 1482,
459, 1384, 1270, 1232, 1203, 1156, 1083, 996, 953, 827, 817,
4.4.9. 2,5-Di-[2-(p-fluorophenyl)-6-phenyl-5-ethoxycarbonyl-[2H]-
naphtho[1,2-b]pyran-2-yl]-thiophene (2b). The general procedure
was followed and red solid was obtained in yield of 81.9%. H NMR
n
1
ꢁ
1
51 cm . HRMS (MALDI) calcd for C42
H F
26 2
O
2
S: m/z (%): 655.1514
(300 MHz, CDCl
7.46e7.28 (m, 12H), 7.06e6.95 (m, 4H), 6.80 (d, J¼9.7 Hz, 1H), 6.80
s, 2H), 6.79 (d, J¼10.0 Hz, 1H), 6.18 (d, J¼9.7 Hz, 1H), 6.17 (d,
J¼10.0 Hz, 1H), 3.97 (q, J¼7.2 Hz, 2H), 3.96 (q, J¼7.2 Hz, 2H), 0.86 (t,
3
):
d
¼8.39e8.32 (m, 2H), 7.60e7.46 (m, 8H),
þ
[MþNa] . Found: 655.1520 (53.9%).
(
4
.4.5. 2,5-Di-[3-(p-methylphenyl)-[3H]-naphtho[2,1-b]pyran-3-yl]-
13
thiophene (1e). The general procedure was followed and pale pink
J¼7.2 Hz, 3H), 0.86 ppm (J¼7.2 Hz, 3H); C NMR (75 MHz, CDCl
3
):
ꢀ
1
1
solid was obtained in yield of 86.8%. Mp 222e223 C; H NMR
300 MHz, CDCl ):
¼7.92 (d, J¼9.0 Hz, 2H), 7.71 (d, J¼8.1 Hz, 2H),
.64 (d, J¼8.7HZ, 2H), 7.49e7.39 (m, 6H), 7.36e7.27 (m, 2H), 7.24 (d,
J¼10.0 Hz, 2H), 7.16 (dd, J¼9.7, 3.1 Hz, 1H), 7.13e7.06 (m, 4H), 6.68
d
¼168.1, 162.1 ( J¼247.4 Hz), 150.2, 150.2, 146.8, 139.6, 137.9, 132.8,
3
(
7
3
d
131.3, 130.4, 130.3, 128.5, 128.1 ( J¼8.5 Hz), 127.9, 127.4, 127.1, 126.8,
2
126.6, 125.5, 125.4, 122.0, 122.0, 121.3, 115.0 ( J¼21.6 Hz), 111.7, 80.6,
80.6, 61.1, 13.7 ppm. IR (KBr):
n
max¼2980, 1720, 1601, 1506, 1445,
13
ꢁ1
(
d, J¼3.1 Hz, 2H), 6.23 (d, J¼10.0 Hz, 2H), 2.29 (s, 3H); C NMR
1371, 1292, 1228, 1158, 1041, 933, 833, 770, 702 cm . HRMS

4068
X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
þ
(
9
MALDI) calcd for C60
51.2552 (100%).
H
42
F
2
O
6
S: m/z (%): 951.2562 [MþNa] . Found:
NMR (75 MHz, CDCl
136.1, 136.1, 132.8, 131.1, 130.5, 130.5, 128.7, 128.7, 127.9, 127.7, 127.5,
27.4,127.0,126.8,126.5,125.4,125.3,122.3,120.9,113.7,113.5,111.8,
81.0, 80.9, 61.0, 22.6, 13.6 ppm. IR (KBr):
3
):
d
¼168.4, 159.2, 150.7, 150.6, 147.1, 138.2,
1
4
.4.10. 2,5-Di-[2-(o-fluorophenyl)-6-phenyl-5-ethoxycarbonyl-[2H]-
n
max¼2930, 2835, 1720,
naphtho[1,2-b]pyran-2-yl]-thiophene (2c). The general procedure
1608, 1509, 1463, 1443, 1371, 1292, 1253, 1226, 1175, 1040, 827, 770,
1
ꢁ1
þ
was followed and red solid was obtained in yield of 69.6%. H NMR
702 cm . HRMS (MALDI) calcd for C62
H
48
O
8
S: m/z (%): 975.2962
(
7
7
300 MHz, CDCl
.57e7.48 (m, 4H), 7.47e7.22 (m, 14H), 7.08 (td, J¼7.8, 1.2 Hz, 2H),
.06 (dd, J¼8.1, 0.9 Hz, 1H), 7.02 (dd, J¼8.1, 0.9 Hz, 1H), 6.86 (d,
3
):
d
¼7.85e7.38 (m, 2H), 7.68 (tt, J¼7.8, 1.2 Hz, 2H),
[MþNa] . Found: 975.2952 (70.5%).
4.4.14. 2-[2-(2,6-Diphenyl)-5-ethoxycarbonyl-[2H]-(naphtho[1,2-b]
pyran-2-yl)-5-[2-(p-methoxyphenyl)-5-ethoxycarbonyl-6-phenyl-
[2H]-(naphtho[1,2-b]pyran-2-yl)-thiophene (2g). The general pro-
J¼1.2 Hz, 2H), 6.76 (d, J¼10.0 Hz, 2H), 6.44 (d, J¼10.0 Hz, 1H), 6.43
(
(
d, J¼10.0 Hz, 1H), 3.97 (q, J¼7.2 Hz, 2H), 3.96 (q, J¼7.2 Hz, 2H), 0.86
13
1
t, J¼7.2 Hz, 3H), 0.86 ppm (J¼7.2 Hz, 3H); C NMR (75 MHz,
cedure was followed and red solid was obtained in yield of 82.7%. H
1
1
CDCl
3
):
d
¼168.2, 153.4 ( J¼246.6 Hz), 153.3 ( J¼246.6 Hz), 149.1,
NMR (300 MHz, CDCl
3
):
d
¼8.45e8.34 (m, 2H), 7.65e7.57 (m, 2H),
2
1
49.1, 146.7, 138.1, 132.9, 131.4, 130.5 ( J¼11.1 Hz), 130.5, 130.4, 129.9
7.56e7.28 (m, 19H), 6.88e6.74 (m, 8H), 6.25 (d, J¼10.0 Hz, 0.5H), 6.24
(d, J¼10.0 Hz, 0.5H), 6.21 (d, J¼10.0 Hz, 0.5H), 6.20 (d, J¼10.0 Hz,
0.5H), 3.99 (q, J¼7.2 Hz, 2H), 3.98 (q, J¼7.2 Hz, 2H), 3.77 (s, 3H), 0.88
3
(
J¼7.9 Hz), 128.6, 127.9, 127.4, 127.3, 127.1, 126.9, 126.7, 125.8, 125.8,
4 2
1
1
2
1
25.2, 125.1, 124.8, 123.9 ( J¼3.1 Hz), 122.1, 121.1, 116.5 ( J¼22.0 Hz),
1
3
11.6, 111.6, 79.3, 79.3, 79.2, 61.1, 13.5 ppm. IR (KBr):
n
max¼3059,
(t, J¼7.2 Hz, 3H), 0.87 ppm (J¼7.2 Hz, 3H); C NMR (75 MHz, CDCl
3
):
978, 1721, 1638, 1611, 1583, 1504, 1484, 1446, 1370, 1292, 1226,
d
¼168.2, 159.0, 150.7, 150.6, 150.2, 150.1, 147.0, 147.0, 143.9, 143.9,
ꢁ
1
169, 1041, 758 cm . HRMS (MALDI) calcd for C60
H
42
F
2
O
6
S: m/z
138.0, 135.9, 135.9, 132.7, 132.7, 131.0, 130.9, 130.4, 130.3, 128.6, 128.1,
127.8, 127.6, 127.6, 127.3, 127.2, 126.9, 126.9, 126.7, 126.5, 126.4, 126.1,
þ
(
%): 951.2562 [MþNa] . Found: 951.2544 (100%).
1
25.5, 125.4, 125.2, 125.1, 124.9, 122.1, 120.9, 120.8, 113.4, 111.7, 81.1,
81.0, 80.9, 80.9, 61.1, 22.7, 13.7 ppm. IR (KBr):
max¼3057, 2954, 2927,
1719, 1636, 1607, 1508, 1444, 1370, 1291, 1254, 1225, 1174, 1144, 1109,
4
.4.11. 2-[2-(o-Fluorophenyl)-6-phenyl-5-ethoxycarbonyl-[2H]-
naphtho[1,2-b]pyran-2-yl]-5-(2-(p-fluorophenyl)-6-phenyl-5-
ethoxycarbonyl-[2H]-naphtho[1,2-b]pyran-2-yl)-thiophene (2d). The
n
ꢁ
1
1040, 931, 810, 770, 700 cm . HRMS (MALDI) calcd for C61
46 7
H O S:
þ
general procedure was followed and red solid was obtained in yield
m/z (%): 945.2857 [MþNa] . Found: 945.2864 (100%).
1
of 87.4%. H NMR (300 MHz, CDCl
3
):
d
¼8.46e8.33 (m, 2H), 7.73 (td,
J¼7.8, 1.1 Hz, 1H), 7.64e7.24 (m, 19H), 7.16e6.95 (m, 4H), 6.89 (d,
Supplementary data
J¼3.7 Hz,1H), 6.86e6.75 (m, 3H), 6.47 (dd, J¼10.0,1.9 Hz, 0.5H), 6.45
(
0
3
1
1
1
1
1
1
1
(
1
dd, J¼10.0,1.9 Hz, 0.5H), 6.21 (d, J¼10.0 Hz, 0.5H), 6.20 (d, J¼10.0 Hz,
Synthesis of intermediates. Isolation of the colored forms,
measurement on kinetics of photocoloration and thermal fading, as
well as fatigue-resistance of photochromic compounds. Copies of
NMR spectra. Supplementary data associated with this article can
be found in the online version, at http://dx.doi.org/10.1016/
j.tet.2015.04.068. These data include MOL files and InChiKeys of the
most important compounds described in this article.
.5H), 3.99 (q, J¼7.2 Hz, 2H), 3.97 (q, J¼7.2 Hz, 2H), 0.88 (t, J¼7.2 Hz,
13
H), 0.87 ppm (J¼7.2 Hz, 3H); C NMR (75 MHz, CDCl
3
):
d
¼168.1,
1
1
1
68.0, 162.2 ( J¼246.6 Hz), 159.1 ( J¼248.7 Hz), 159.0 ( J¼248.7 Hz),
4
50.1, 150.0, 149.2, 149.1, 146.8, 146.6, 139.6 ( J¼2.8 Hz), 137.9, 137.9,
2 3
32.8, 131.3 ( J¼7.6 Hz), 130.5, 130.4, 130.3, 129.8 ( J¼7.9 Hz), 128.5,
3 3
28.2 ( J¼7.9 Hz), 128.2 ( J¼7.9 Hz), 127.8, 127.3, 127.1, 127.0, 126.8,
26.8,126.7,126.6,125.6,125.6,125.5,125.4,125.2,125.1,124.8,124.7,
4
2
2
23.9 ( J¼2.6 Hz), 122.0, 121.1, 116.5 ( J¼21.6 Hz), 116.5 ( J¼21.6 Hz),
2
References and notes
15.0 ( J¼21.5 Hz),111.6,111.6,111.6, 80.7, 80.7, 79.1, 61.1,13.7 ppm. IR
KBr):
158, 1040, 996, 815, 758 cm
n
max¼3058, 2956, 2927, 1720, 1636, 1601, 1505, 1370, 1226,
1
1. (a) Durr, H.; Bouas-Laurent, H. Photochromism: Molecules and Systems; Elsevier:
ꢁ
.
HRMS (MALDI) calcd for
Amsterdam, The Netherlands, 1990; (b) Crano, J. C.; Guglielmetti, R. J. Organic
Photochromic and Thermochromic Compounds; Plenum: New York, NY, 1999; (c)
Feringa, B. L. Molecular Switches; Wiley-VCH: Weinheim, Germany, 2001; (d)
Irie, M. Chem. Rev. 2000, 100, 1685; (e) Tian, H. Chem. Commun. 2007, 781; (f)
Russew, M. M.; Hecht, S. Adv. Mater. 2010, 22, 3282.
þ
C
H
60 42
F
2
O
6
S: m/z (%): 951.2562 [MþNa] . Found: 951.2551 (100%).
4
.4.12. 2,5-Di-[2-(p-methylphenyl)-6-phenyl-5-ethoxycarbonyl-
[
2H]-naphtho[1,2-b]pyran-2-yl]-thiophene (2e). The general pro-
2. For a review, see: Raymo, F. M.; Tomasulo, M. J. Phys. Chem. A 2005, 109, 7343.
3
. For diarylethene, see: (a) Areephong, J.; Logtenberg, H.; Browne, W. R.; Feringa,
B. L. Org. Lett. 2010, 12, 2132; (b) Areephong, J.; Hurenkamp, J. H.; Milder, M. T.
W.; Meetsma, A.; Herek, J. L.; Browne, W. R.; Feringa, B. L. Org. Lett. 2009, 11,
721; (c) Higashiguchi, K.; Matsuda, K.; Tanifuj, N.; Irie, M. J. Am. Chem. Soc. 2005,
cedure was followed and red solid was obtained in yield of 86.7%.
1
H NMR (300 MHz, CDCl
0H), 7.14 (dd, J¼8.1, 3.7 Hz, 4H), 6.81 (d, J¼1.2 Hz, 2H), 6.79 (d,
3
):
d
¼8.41 (d, J¼7.8 Hz, 2H), 7.56e7.28 (m,
2
127, 8922; (d) Higashiguchi, K.; Matsuda, K.; Irie, M. Angew. Chem., Int. Ed. 2003,
J¼10.0 Hz, 1H), 6.78 (d, J¼10.0 Hz, 1H), 6.24 (d, J¼10.0 Hz, 1H), 6.22
42, 3537; (e) Matsuda, K.; Irie, M. J. Am. Chem. Soc. 2001, 123, 9896; (f) Luo, Q.;
(
(
(
1
1
1
1
7
[
d, J¼10.0 Hz, 1H), 3.99 (q, J¼7.2 Hz, 2H), 3.98 (q, J¼7.2 Hz, 2H), 2.22
Chen, B.; Wang, M.; Tian, H. Adv. Funct. Mater. 2003, 13, 233; (g) Kaieda, T.;
Kobatake, S.; Miyasaka, H.; Murakami, M.; Iwai, N.; Nagata, Y.; Itaya, A.; Irie, M.
J. Am. Chem. Soc. 2002, 124, 2015.
13
s, 6H), 0.88 (t, J¼7.2 Hz, 3H), 0.88 ppm (J¼7.2 Hz, 3H); C NMR
75 MHz, CDCl ):
¼168.2, 150.4, 150.3, 147.0, 141.0, 140.9, 138.0,
37.8, 132.7, 130.9, 130.4, 130.3, 128.7, 128.5, 127.8, 127.3, 127.3,
26.9, 126.8, 126.7, 126.4, 126.1, 125.3, 125.2, 124.9, 122.2, 120.8,
11.7,111.7, 81.0, 81.0, 61.0, 21.2,13.7 ppm. IR (KBr):
max¼2921,1719,
3
d
4
5
6
. For benzodihydropyrene, see: (a) Mitchell, R. H.; Ward, T. R.; Chen, Y.; Wang, Y.;
Weerawarna, S. A.; Dibble, P. W.; Marsellam, M. J.; Almutair, A.; Wang, Z. J. Am.
Chem. Soc. 2003, 125, 2974; (b) Mitchell, R. H.; Ward, T. R.; Wang, Y.; Dibble, P.
W. J. Am. Chem. Soc. 1999, 121, 2601.
. For spiropyran, see: (a) Shao, N.; Jin, J.-Y.; Wang, H.; Zheng, J.; Yang, R.-H.; Chan,
W.-H.; Abliz, Z. J. Am. Chem. Soc. 2010, 132, 725; (b) Zhang, Q.; Ning, Z.; Yan, Y.;
Qian, S.; Tian, H. Macromol. Rapid Commun. 2008, 29, 193; (c) Wen, G.; Yan, J.;
Zhou, Y.; Zhang, D.; Mao, L.; Zhu, D. Chem. Commun. 2006, 3016.
. For spirooxazine, see: Kumar, S.; Watkins, D. L.; Fujiwara, T. Chem. Commun.
n
636, 1610, 1504, 1444, 1370, 1291, 1225, 1166, 1040, 931, 811, 769,
ꢁ
þ
1
01 cm . HRMS (MALDI) calcd for C62
H
48
O
6
S: m/z (%): 943.3064
MþNa] . Found: 943.3053 (100%).
2009, 4369.
4
.4.13. 2,5-Di-[2-(p-methoxyphenyl)-6-phenyl-5-ethoxycarbonyl-
7. For diarylpyran, see: (a) Kickova, A.; Donovalova, J.; Kasak, P.; Putala, M. New J.
Chem. 2010, 34, 1109; (b) Gabbutt, C. D.; Heron, B. M.; Instone, A. C.; Kolla, S. B.;
Mahajan, K.; Coelho, P. J.; Carvalho, L. M. Dyes Pigments 2008, 76, 24; (c)
Moorthy, J. N.; Venkatakrishnan, P.; Samanta, S. Org. Biomol. Chem. 2007, 5,
[
2H]-naphtho[1,2-b]pyran-2-yl]-thiophene (2f). The general pro-
cedure was followed and red solid was obtained in yield of 79.8%.
1
H NMR (300 MHz, CDCl
0H), 6.87e6.80 (m, 4H), 6.85 (d, J¼1.9 Hz, 2H), 6.77 (d, J¼10.0 Hz,
H), 6.76 (d, J¼10.0 Hz, 1H), 6.20 (d, J¼10.0 Hz, 1H), 6.19 (d,
3
):
d
¼8.41e8.34 (m, 2H), 7.56e7.27 (m,
1354; (d) Samat, A.; Lokshin, V.; Chamontin, K.; Levi, D.; Pepe, G.; Guglielmetti,
2
1
R. Tetrahedron 2001, 57, 7349.
8
. (a) Zhao, W.; Carreira, E. M. J. Am. Chem. Soc. 2002,124,1582; (b) Zhao, W.; Carreira,
E. M. Chem.dEur. J. 2007,13, 2671; (c) Zhao, W.; Carreira, E. M. Org. Lett. 2006, 8, 99.
. For hybrid systems, see: (a) Delbaere, S.; Vermeersch, G.; Frigoli, M.; Mehl, G. H.
Org. Lett. 2010, 12, 4090; (b) Delbaere, S.; Micheau, J.-C.; Frigoli, M.; Mehl, G. H.;
J¼10.0 Hz, 1H), 3.97 (q, J¼7.2 Hz, 2H), 3.96 (q, J¼7.2 Hz, 2H), 3.78 (s,
9
13
3
H), 3.77 (s, 3H), 0.86 (t, J¼7.2 Hz, 3H), 0.86 ppm (J¼7.2 Hz, 3H);
C

X. Lu et al. / Tetrahedron 71 (2015) 4061e4069
4069
Vermeersch, G. J. Phys. Org. Chem. 2007, 20, 929; (c) Delbaere, S.; Vermeersch,
G.; Frigoli, M.; Mehl, G. H. Org. Lett. 2006, 8, 4931; (d) Frigoli, M.; Mehl, G. H.
Angew. Chem., Int. Ed. 2005, 44, 5048.
0. The reported procedure only afforded low yield of diacylthiophene see: (a)
Hartough, H. D.; Kosak, A. I. J. Am. Chem. Soc. 1947, 69, 1012; (b) Hartough, H. D.;
Kosak, A. I. J. Am. Chem. Soc. 1947, 69, 3098.
13. Milstein, D.; Stille, J. K. J. Am. Chem. Soc. 1978, 100, 3636.
14. (a) Delbaere, S.; Buccioni-Houze, B.; Bochu, C.; Teral, Y.; Campredon, M.; Ver-
meersch, G. J. Chem. Soc., Perkin Trans. 2 1998, 1153; (b) Delbaere, S.; Micheau, J.
C.; Vermeersch, G. J. Org. Chem. 2003, 68, 8968.
1
15. Murov, S. L.; Carmichael, L.; Hug, G. L. Handbook of Photochemistry; Marcel
Dekker: New York, NY, 1993; pp 298e305.
1
1. Zhao, W.; Carreira, E. M. Org. Lett. 2003, 5, 4153.
16. Becker, R. S.; Pelliccioli, A. P.; Romani, A.; Favaro, G. J. Am. Chem. Soc. 1999, 121,
2104.
1
2. Gemert, B. V. Benzo and Naphthopyrans (Chromenes) In Organic Photochromic
and Thermochromic Compounds; Crano, J. C., Guglielmetti, R. J., Eds.; Plenum:
New York, NY, 1999.