Fluorescence properties of indolenine semi-squarylium dyes

Article abstract of DOI:10.1016/j.tet.2012.09.089

3-Butoxy-4-(1-butyl-3,3-dimethyl-3H-indol-2-ylidenemethyl)-3-cyclobut-1, 2-dione exhibited the most intense florescence at fluorescence maxima 536 and 563 nm with fluorescence quantum yield 0.21 among any indolenine semi-squarylium dyes in the crystalline form due to the isolated dimer-type molecular packing and its suitable melting point. This compound showed aggregation-induced emission enhancement.

Full text of DOI:10.1016/j.tet.2012.09.089

Tetrahedron 68 (2012) 9936e9941
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Fluorescence properties of indolenine semi-squarylium dyes
*
Masaki Matsui , Toshihiro Shibata, Masato Fukushima, Yasuhiro Kubota, Kazumasa Funabiki
Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 August 2012
Received in revised form 18 September 2012
Accepted 20 September 2012
Available online 26 September 2012
3-Butoxy-4-(1-butyl-3,3-dimethyl-3H-indol-2-ylidenemethyl)-3-cyclobut-1,2-dione exhibited the most
intense florescence at fluorescence maxima 536 and 563 nm with fluorescence quantum yield 0.21
among any indolenine semi-squarylium dyes in the crystalline form due to the isolated dimer-type
molecular packing and its suitable melting point. This compound showed aggregation-induced emis-
sion enhancement.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Fluorescence
Indolenine semi-squarylium dye
Solid-state fluorescence
Single X-ray crystallography
Aggregation-induced emission
enhancement
1. Introduction
SQ dye 13 was hydrolyzed to give 16. Semi-SQ dyes 11, 13, and 16
are known compounds.
Survey of solid-state fluorescent organic compounds is one of the
mostexciting subjects in connectionwith developmentof emitters in
ii) OR2
1
2
3
O
O
Me Me
OR2
OLED, solid dye laser, and probes. Though many compounds show
fluorescence in solution, less compounds exhibit fluorescence in the
solid state. Semi-squarylium (semi-SQ) dyes are known as the in-
1
Me Me
i)
R I
O
O
Me Me
Me
OR2
8-10
2
-4
Me
N
N
N
4
5
R1
1
termediates for the preparation of unsymmetrical SQ, cationic SQ,
and bisSQ dyes. The potential applications of semi-SQ dyes for
sensors and sensitizers have been also reported. On the other hand,
recently, survey of new materials, such as siloles, tetraaryl-
I
R
11-15
5
-7
6
1
7
8
O
O
O
O
Me Me
9
Me Me
iii)
OBu
ethylenes,10 and triarylethylenes showing aggregation-induced
emission enhancement (AIEE) has been attracted large attention.
AIEE has been usually reported to come from the inhibition of free
rotation of CeAr bonds in the aggregated form. We consider that
other flexible linkage, such as CeO bonds can also cause AIEE. We
reporthereinthefluorescencepropertiesofindoleninesemi-SQdyes.
11
N
OH
N
Bu
Bu
13
16
R1
R2
Compd R1 R2
Compd
, 5
Compd
2
Me
Bu
Oct
8
Me
Bu
Oct
11
12
13
Me Bu
Bu Et
Bu Bu
Bu Oct
Oct Bu
3, 6
, 7
9
4
10
14
2
2
. Results and discussion
15
.1. Synthesis
Scheme 1. Reagents and conditions: i) 1 (1.0 equiv), 2e4 (3.3 equiv), reflux, MeCN, 1
ꢀ
day, ii) 5e7 (1.0 equiv), 8e10 (1.0 equiv), TEA, alcohol, 75 C, 0.3e2 h, iii) 13 (1.0 equiv),
aq NaOH, reflux, 5 min, then 2 N HCl.
Indolenine semi-SQ dyes 11e16 were synthesized as shown in
Scheme 1. 2,3,3-Trimethylindolenine (1) was allowed to react with
alkyl iodides 2e4 to give N-alkylindolenium iodides 5e7, followed
by the reaction with dialkyl squarates 8e10 to afford 11e15. Semi-
2.2. UVevis absorption and fluorescence spectra
The UVevis absorption and fluorescence spectra of 13 in various
solvents are shown in Fig S7. Compound 13 showed the most in-
tense fluorescence in ethanol. Fig. 1 depicts the UVevis absorption
*
Corresponding author. Tel.: þ81 58 293 2601; fax: þ81 58 293 2794; e-mail
address: matsuim@gifu-u.ac.jp (M. Matsui).
0
040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.09.089

M. Matsui et al. / Tetrahedron 68 (2012) 9936e9941
9937
1
.8
.6
.4
.2
0
100
80
1
1
1
1 12
3 14
5
0
0
0
0
1
1
1
1
5
6
3
2
16
60
0%
30%
60%
70%
80%
90%
95%
14
40
20
0
hexane content
11
5
00
Hexane content
6
0
0
0%
400
3
0%
4
00
500
600
60%
70%
80%
300
4
Wavelength / nm
90%
5%
9
200
100
0
ꢁ
5
ꢁ3
Fig. 1. UVevis absorption spectra of 11e16 in ethanol. Measured on 1ꢂ10 mol dm
20
ꢀ
of substrate at 25 C. Solid and dotted lines represent UVevis absorption and fluo-
rescence spectra, respectively.
0
400
500
600
700
20
40
60
80
100
Wavelength / nm
Hexane content / %
ꢁ
5
ꢁ3
and fluorescence spectra of 11e16 in ethanol. The results are also
Fig. 3. AIEE test for 16. Measured on 1ꢂ10 mol dm of 16 in ethyl acetateehexane
ꢀ
summarized in Table 1. The absorption maximum (lmax) was ob-
mixed solvent at 25 C.
served at around 425 nm. The molar absorption coefficient (ε) was
3
ꢁ1
ꢁ1
observed at around 460 nm in 0 and 30% water content. The mixed
solvent was almost transparent when the water content is less than
calculated to be ca. 70,000 dm mol cm except for 16 (44,100).
The fluorescence maximum (Fmax) was observed at around 460 nm.
The Stokes shift was small, there being ca. 36 nm. They showed
similar fluorescence spectra with low fluorescence quantum yield
(F , <0.01). Thus, no remarkable differences in the UVevis ab-
f
sorption and fluorescence spectra were observed among 11e16 in
60%. In 70% water content, apparent Tyndall scattering was ob-
served. Then, as higher was the water content, the solvent became
opaque. At the same time, the fluorescence peaks at around 535
and 560 nm comes from the aggregated form drastically increased.
The intensity is much stronger than that in 0% water content. Thus,
semi-SQ dye 13 showed clear AIEE.
As semi-SQ dye 16 is soluble in water, the AIEE test was per-
formed in ethyl acetateehexane mixed solvent. In 0, 30, and 60%
hexane content, weak fluorescence peak was observed at 480 nm.
This peak gradually decreased with increasing hexane content.
Tyndall scattering was observed in 80% hexane content and new
emission from the aggregated form was observed at around
560 nm. Then, this emission decreased by adding hexane. Thus,
though semi-SQ dye 16 showed very weak fluorescence in the ag-
gregated form, no clear AIEE was observed.
ethanol.
Table 1
UVevis absorption and fluorescence spectra of 11e16
Compd In ethanola
Solid state
b
SSc nm
d
b
lmax (εmax) nm
Fmax nm
F
f
l
ex nm
Fmax nm
F
f
11
12
13
14
15
16
422 (71,900)
424 (71,400)
425 (69,200)
424 (69,700)
425 (69,800)
423 (44,100)
460
461
461
460
461
459
<0.01 38
<0.01 36
<0.01 36
<0.01 36
<0.01 35
<0.01 36
427
425
435
425
425
425
511, 546 <0.01
526, 545 <0.01
536, 563 0.21
502
522
<0.01
0.02
d
e
e
d
To understand why dye 13 shows AIEE, the effects of solvent and
temperature on the UVevis absorption and fluorescence spectra of
13 and 16 were examined. The results are indicated in Figs. 4 and 5.
Fig. 4(a) depicts that though no significant differences in the
a
b
c
ꢁ5
ꢁ3
ꢀ
Measured at the concentration of 1ꢂ10 mol dm at 25 C.
Determined by absolute PL quantum yield measurement system C9920-02.
Stokes shift.
Excitation wavelength determined by diffuse reflection spectra given by
d
KubelkaeMunk units.
UVevis absorption spectra of 13 are observed in diethylene glycol
e
Too weak.
ꢀ
(
2
DEG, velocity (
h
): 30 cp at 25 C) and in ethanol (
h
: 1.06 cp at
ꢀ
5 C), the fluorescence intensity of 13 in DEG is 4.8-times stronger
2
.3. AIEE test
The AIEE test was performed for 13 and 16. The results are
shown in Figs. 2 and 3. In the case of 13, the test was performed in
ethanolewater mixed solvent. Weak fluorescence peak was
0
.8
300
0.8
0.6
0.4
300
200
100
0
(a)
DEG
(b)
DGE
EtOH
EtOH
0.6
FI (DEG)
FI (EtOH)
=
4.8 200
FI (DEG)
FI (EtOH)
= 2.4
0
.4
.2
0
100
0.2
0
0
0
400
500
Wavelength / nm
600
400
500
Wavelength / nm
600
Fig. 4. UVevis absorption and fluorescence spectra of (a) 13 and (b) 16 in diethylene
glycol (DEG) and ethanol at 25 C. Measured on 1ꢂ10 mol dm of substrate.
0
%
30%
60%
70%
water content
80%
90%
95%
ꢀ
ꢁ5
ꢁ3
5
00
Water content
1
.8
.6
100
80
60
40
20
0
1
0.8
0.6
0.4
0.2
0
100
80
60
40
20
0
4
00
00
00
00
0
Temperature / o
Temperature / o
(a)
C
(b)
C
0
%
400
300
200
0
0
3
0%
5
5
3
60%
15
25
35
15
7
0%
0%
25
8
35
2
1
90%
o
FI (5oC)
95%
0.4
0.2
0
FI (5 C)
=
1.2
o
= 1.6
FI (35oC)
FI (35 C)
100
0
400
500
600
700
20
40
60
80
100
400
500
600
400
500
600
Wavelength / nm
Water content / %
Wavelength / nm
Wavelength / nm
ꢁ
4
ꢁ3
Fig. 2. AIEE test for 13. Measured on 1ꢂ10 mol dm of 13 in ethanolewater mixed
Fig. 5. UVevis absorption and fluorescence spectra of (a) 13 and (b) 16 at 5, 15, 25, and
35 C in ethanol. Measured on 1ꢂ10 mol dm of substrate.
ꢀ
ꢀ
ꢁ5
ꢁ3
solvent at 25 C.

9938
M. Matsui et al. / Tetrahedron 68 (2012) 9936e9941
than that in ethanol. Meanwhile, in the case 16, only 2.4-times as
shown in Fig. 4(b).
Fig. 8 indicates the single X-ray crystallography of 12. Molecules
are arranged as a ‘herring-bone’ fashion with forming a pair of di-
mers. CH/O interactions are observed between B and J with the tilt
angle 102.6 as shown in side view (2). Side view (1) and top view
(1) show that molecules A and B form a pair of head-to-tail dimer.
Fig. 5(a) shows that though the UVevis absorption spectra of 13
ꢀ
ꢀ
ꢀ
at 5 and 35 C are identical, the fluorescence of 13 at 5 C is 1.6-times
ꢀ
more intense than that at 35 C. Fig. 5(b) indicates that the fluores-
cence intensity of 16 at 5 C is only 1.2-times stronger than that at
ꢀ
p/p-interactions are observed between A and B with interplanar
ꢀ
ꢀ
3
5
C. These results suggest that the free rotation of flexible CeO
distance 3.72 A as shown in side view (3). Molecule F is located on
the same plane to B with CH/O interactions. Side view (3) and top
bonds of 13 were inhibited in the aggregated form to exhibit AIEE.
view (2) indicate that p/p-interactions are also observed between B
ꢀ
and C at the squarate moiety with interplanar distance 3.40 A. The
same interactions are observed among C, D, and G as shown in top
2
.4. Solid-state fluorescence
view (3). Thus, dye 12 has consecutive
side view (3).
p/p stacking as shown in
The solid-state fluorescence spectra of 11e16 recrystallized from
hexane are shown in Fig. 6. No clear fluorescence spectrum was
observed for 16. Compounds 11, 12, 14, and 15 showed weak fluo-
rescence. Interestingly, semi-SQ dye 13 significantly exhibited in-
tense florescence. The
solution (<0.01). The Fmax at 536 and 563 nm could come from S
transition and the vibration level, respectively. The Fmax are more
F
f
0.21 is remarkably greater than that in
1
to
S
0
bathochromic compared with that in ethanol (461 nm), showing
intermolecular interactions in the solid state.
2500
2000
1500
1000
13
1
5
1
1 12
14 16
500
16
0
400
500
600
700
Wavelength / nm
Fig. 6. Solid-state fluorescence spectra of 11e16.
2
.5. Single X-ray crystallography
To understand why 13 exhibited intense fluorescence in the
crystalline form, the single X-ray crystallographic analysis of 11, 12,
3, 14, and 15 was performed.
1
The single X-ray crystallography of 11 is shown in Fig. 7. Side
view (1) depicts that molecules are arranged as a ‘bricks-in-a-wall’
fashion. Side view (1), (2) and top view (1), (2) indicate that mol-
ecules A, B, and C are located on the same plane and are aligned
toward the same direction. CH/O interactions are observed among
A, B, and C. p/p-interactions are observed between B and D at the
squarate moiety, there being the interplanar distance 3.51 A. The
Fig. 8. Single X-ray crystallography of 12.
ꢀ
same interactions are observed between B and G. Thus, dye 11 has
The single X-ray crystallography of 13 is depicted in Fig. 9. A pair
of dimers is arranged in a ‘sandwich’ fashion as shown in overview
and side view (1). Side view (1) also indicates that the tilt angle
consecutive
p
/p
stacking as shown in side view (1).
ꢀ
between the dimers is 67.4 . No intermolecular interactions are
observed between B and I. Side view (2) depicts that molecules A
and B form a pair of head-to-tail dimers with two CH/
p in-
teractions. No interactions are observed between A and B as
p/p
shown in top view (2). Top view (1) and side view (3) depict that
molecules A, C, D, and E are located almost on the same plain with
CH/O interactions. Molecules F, G, B, and H are also arranged in
ꢀ
parallel for C, D, A, and E with interplanar distance 3.27 A
p/p
in-
teractions are observed between the carbonyl groups of A and G.
The same interactions are observed between B and E. Thus, dye 13
has isolated dimer-type packing.
Fig. 10 shows the single X-ray crystallography of 14. Side view
and top view (1) depict that molecules A, B, and C are located on the
same plane and are aligned toward the same direction with CH/O
interactions. Molecules B and E form a pair of head-to-tail dimer.
Fig. 7. Single X-ray crystallography of 11.

M. Matsui et al. / Tetrahedron 68 (2012) 9936e9941
9939
Fig. 11. Single X-ray crystallography of 15.
overlapping is observed between them as shown in top view (2).
Side view (2) and top view (3) indicate that molecules E and F are
located almost on the same plane to A with CH/O interactions. Thus,
dye 15 has isolated dimer-type packing.
Fig. 9. Single X-ray crystallography of 13.
The solid-state fluorescence intensity depends on the packing
motif and melting point of the fluorophores. Consecutive
p/p-in-
teractions and hydrogen bonding can reduce the solid-state fluo-
12
rescence intensity. Furthermore, when the melting point is low,
the internal conversion process comes from stretching, vibration,
and rotation modes of the flexible linkages could be accelerated to
13
decrease the solid-state fluorescence intensity. As dyes 11 and 12
have consecutive stacking, it is reasonable that their solid-state
p/p
fluorescence intensityis low. Dyes 13,14, and 15 have isolated dimer-
type packing. No emission from the eximers was observed for 13,14,
and 15. From only the view point of packing motif, dyes 13,14, and 15
could show solid-state fluorescence. However, as the melting point
ꢀ
of 14 (76.7 C) and 15 (91.1) is significantly lowcompared with thatof
13 (126.0), dye 13 could show strong solid-state fluorescence in-
tensity. The intermolecular interactions of 13 in the aggregated form
are supposed to be similar tothose in the crystalline form. Therefore,
semi-SQ dye 13 could showAIEE due tothe freerotation inhibition of
flexible CeO bonds in the aggregated form.
3. Conclusions
We have serendipitously found that 3-butoxy-4-(1-butyl-3,3-
dimethyl-3H-indol-2-ylidenemethyl)-3-cyclobut-1,2-dione exhibi-
ted intense solid-state fluorescence (
¼0.21) at Fmax 536 and
63 nm in the crystalline form, whereas the other any derivatives
showed very weak ( <0.02) or no fluorescence. This result is at-
F
f
5
Fig. 10. Single X-ray crystallography of 14.
F
f
tributed to the isolated dimer-type packing and suitable melting
point. This compound showed AIEE due to this packing motif and
prevention of flexible CeO bond free rotation in the aggregated
form.
Side view indicates that molecules D, E, and F are arranged in
parallel for A, B, and C. However, no
between B and E as well as between B and F as depicted in top view
2). Molecules G, H, and I are also arranged in parallel for A, B, and C
p/p overlapping is observed
(
ꢀ
with interplanar distance 5.01 A, being too long to have in-
teractions. Thus, dye 14 has isolated dimer-type packing.
Fig. 11 depicts the single X-ray crystallography of 15. Molecules
4. Experimental
4.1. General
A and B form a pair of head-to-tail dimer with
p
/
p
interactions, the
interplanar distance being 3.55 A as shown in side view (1) and top
view (1). Though molecule C is arranged in parallel for A, no
ꢀ
Melting points were measured with a Yanagimoto MP-S2 micro-
melting-point apparatus. Those of 11e15 were measured by SII
p
/p

9940
M. Matsui et al. / Tetrahedron 68 (2012) 9936e9941
Technology Co., EXSTAR-6000 instrument. NMR spectra were ob-
tained by a JEOL ECX 400P spectrometer. MS spectra were mea-
sured with a JEOL MStation 700 spectrometer. UVevis absorption,
reflection, and fluorescence spectra were taken on Hitachi U-3500,
U-4000, and F-4500 spectrophotometers, respectively. Fluores-
cence quantum yields were measured by a Hamamatsu Photonics
Absolute PL Quantum Yield Measurement System C9920-02. 2,3,3-
Trimethylindolenine (1), 1-butyl iodide (3), 1-octyl iodide (4), 3,4-
dibutoxy-3-cyclobutene-1,2-dione (9), and 3,4-dihydroxy-3-
cyclobutene-1,2-dione were purchased from Tokyo Kasei Co., Ltd.
Methyl iodide (2) was purchased from Nacalai Tesque Co., Ltd.
(48) 212 (64), 149 (32). Anal. Found: C, 75.36, H, 8.00; N, 3.85. Calcd
for C23 : C, 75.17, H, 7.95; N, 3.81.
H29NO
3
4.2.4. 4-(1-Butyl-3,3-dimethyl-3H-indol-2-ylidenemethyl)-3-
ꢀ
octyloxy-3-cyclobut-1,2-dione (14). Yield 0.17 g (5%); mp 76.7 C; IR
ꢁ1 1
(KBr):
n
1769 cm ; H NMR (CDCl
3
)
d
¼0.89 (t, J¼7.1 Hz, 3H), 1.00 (t,
J¼7.6 Hz, 3H), 1.23e1.41 (m, 10H), 1.46 (quin, J¼7.1 Hz, 2H), 1.62 (s,
6H), 1.74 (quin, J¼7.6 Hz, 2H), 1.87 (quin, J¼7.1 Hz, 2H), 3.82 (t,
J¼7.6 Hz, 2H), 4.85 (t, J¼7.1 Hz, 2H), 5.42 (s, 1H), 6.88 (d, J¼7.4 Hz,
1H), 7.07 (t, J¼7.4 Hz, 1H), 7.27 (t, J¼7.4 Hz, 1H), 7.28 (d, J¼7.4 Hz,
13
1H); C NMR (CDCl
3
)
d
¼13.9, 14.2, 20.4, 22.7, 25.5, 27.0 (2C), 27.8,
2
,3,3-Trimethyl-3H-indolium iodides 5e7 were synthesized as de-
28.6, 29.2, 30.2, 31.8, 42.8, 48.0, 74.1, 81.3, 108.5, 122.1, 122.7, 127.8,
8
scribed in our previous paper. 3,4-Dialkoxy-3-cyclobutene-1,2-
141.0, 142.8, 168.4, 173.6, 187.6, 187.7, 192.8; EIMS (70 eV) m/z (rel
þ
diones 8 and 10 were prepared by the reaction of 3,4-dihydroxy-
intensity) 423 (M , 79), 254 (100). Anal. Found: C, 76.22, H, 8.95; N,
3
-cyclobutene-1,2-dione with an alcohol followed by purification
3
3.34. Calcd for C27H37NO : C, 76.56, H, 8.80; N, 3.31.
by column chromatography (SiO , CH Cl
2
2
2
/AcOEt¼20:1).
4
.2.5. 3-Butoxy-4-(1-octyl-3,3-dimethyl-3H-indol-2-ylidenemethyl)-
ꢀ
4
.2. Synthesis of 3-alkoxy-4-(3,3-trimethyl-3H-indol-2-
3-cyclobut-1,2-dione (15). Yield 1.3 g (39%); mp 91.1 C; IR (KBr):
1769 cm
n
ꢁ1
13
ylidenemethyl)-3-cyclobut-1,2-diones 11e15
;
H NMR (CDCl
3
)
d
¼0.88 (t, J¼7.5 Hz, 3H), 1.01 (t,
J¼7.3 Hz, 3H), 1.20e1.45 (m, 10H), 1.51 (sex, J¼7.3 Hz, 2H), 1.62 (s,
6H), 1.74 (quin, J¼7.5 Hz, 2H), 1.86 (quin, J¼7.3 Hz, 2H), 3.81 (t,
J¼7.5 Hz, 2H), 4.86 (t, J¼7.3 Hz, 2H), 5.41 (s, 1H), 6.87 (d, J¼7.8 Hz,
An alcohol solution (11, 13, 15: BuOH; 12, 14: EtOH, 12 mL) of
a
2,3,3-trimethyl-3H-indolium iodide 5e7 (8 mmol), a 3,4-
dialkoxycyclobut-3-ene-1,2-dione 8e10 (8 mmol), and triethyl-
1H), 7.07 (t, J¼7.8 Hz, 1H), 7.27 (t, J¼7.8 Hz, 1H), 7.28 (d, J¼7.8 Hz,
ꢀ
13
amine (1.6 mL) was heated at 75 C (11: 0.3 h; 12, 14: 2 h; 13, 15:
1H); C NMR (CDCl
3
)
d
¼13.8, 14.1, 18.8, 22.7, 26.4, 27.0 (2C), 27.1,
1
h). After the reaction was completed, to the mixture were added
29.2, 29.3, 31.8, 32.2, 43.1, 48.0, 73.8, 81.3, 108.5, 122.1, 122.7,
water (20 mL) and dichloromethane (50 mL). The dichloromethane
layer was separated, washed with water (50 mLꢂ3), and dried over
anhydrous sodium sulfate. The solvent was removed in vacuo. The
127.8, 141.0, 142.8, 168.4, 173.6, 187.6 (2C), 192.8; EIMS (70 eV) m/z
(rel intensity) 423 (M , 91), 330 (100), 212 (72). Anal. Found:
þ
C, 76.46, H, 8.86; N, 3.38. Calcd for C27
N, 3.31.
3
H37NO : C, 76.56, H, 8.80;
product was purified by silica gel column chromatography (CH
2 2
Cl
then CH Cl
2
2
/AcOEt¼20:1) and recrystallized from hexane.
4.3. Synthesis of 4-(1-butyl-3,3-dimethyl-3H-indol-2-
4
.2.1. 3-Butoxy-4-(1,3,3-trimethyl-3H-indol-2-ylidenemethyl)-3-
ylidenemethyl)-3-hydroxy-3-cyclobut-1,2-dione (16)
ꢀ
8
cyclobut-1,2-dione (11). Yield 1.6 g (60%); mp 125.3 C (lit.
ꢀ
ꢁ1
1
126e128 C); IR (KBr)
n
1769 cm
;
H NMR (CDCl
3
)
d¼1.00 (t,
To 40% aqueous sodium hydroxide (0.12 mL, 0.85 mmol) was
added an ethanol solution (4 mL) of 13 (0.367 g, 1 mmol). The
mixture was refluxed for 5 min. After the reaction was completed,
to the mixture was added 2 N hydrochloric acid (1.2 mL). Then, the
solvent was evaporated in vacuo. The product was purified by silica
J¼7.1 Hz, 3H), 1.51 (sex, J¼7.1 Hz, 2H), 1.63 (s, 6H), 1.87 (quin,
J¼7.1 Hz, 2H), 3.37 (s, 3H), 4.86 (t, J¼7.1 Hz, 2H), 5.37 (s, 1H), 6.90 (d,
J¼7.5 Hz, 1H), 7.07 (t, J¼7.5 Hz, 1H), 7.26 (d, J¼7.5 Hz, 1H), 7.28 (t,
13
J¼7.5 Hz, 1H); C NMR (CDCl
3
)
d
¼13.8, 18.8, 27.0 (2C), 30.0, 32.2,
47.9, 73.9, 81.6, 108.2, 122.0, 122.8, 127.9, 140.9, 143.2, 169.1, 173.6,
gel column chromatography (CH
(28%); mp 102e103 C (lit. 102e103 C); IR (KBr):
2
Cl
2
/MeOH¼10:1). Yield 0.087 g
þ
ꢀ
8
ꢀ
1
2
87.9, 187.9, 192.7; EIMS (70 eV) m/z (rel intensity) 325 (M , 72),
12 (100). Anal. Found: C, 74.01, H, 7.24; N, 4.19%. Calcd for
: C, 73.82, H, 7.12; N, 4.30%.
n
3443,
ꢁ
1
1
1763 cm
J¼7.4 Hz, 2H), 1.61 (s, 6H), 1.70 (quin, J¼7.4 Hz, 2H), 3.84 (t, J¼7.4 Hz,
H), 5.70 (s, 1H), 6.93 (d, J¼7.8 Hz, 1H), 6.96 (t, J¼7.8 Hz, 1H), 7.21 (t,
;
H NMR (CDCl
3
)
d
¼0.97 (t, J¼7.4 Hz, 3H), 1.44 (sex,
20 3
C H23NO
2
1
3
4
3
.2.2. 4-(1-Butyl-3,3-dimethyl-3H-indol-2-ylidenemethyl)-3-ethoxy-
-cyclobut-1,2-dione (12). Yield 1.0 g (37%); mp 120.6 C; IR (KBr):
J¼7.8 Hz, 1H), 7.25 (d, J¼7.8 Hz, 1H); C NMR (CDCl
3
)
d
¼13.6, 22.0,
ꢀ
n
26.8 (2C), 28.3, 41.9, 46.1, 82.7, 107.3, 120.9, 121.4, 127.3, 140.6, 143.5,
ꢁ1
1
þ
1769 cm
;
H NMR (CDCl
3
)
d
¼1.00 (t, J¼7.5 Hz, 3H), 1.45 (sex,
163.6, 180.3 (2C), 196.2, 203.1; FABMS (NBA) m/z 312 (MH ). Anal.
J¼7.5 Hz, 2H), 1.54 (t, J¼7.1 Hz, 3H), 1.62 (s, 6H), 1.74 (quin, J¼7.5 Hz,
Found: C, 73.45, H, 6.58; N, 4.30. Calcd for C19
6.80; N, 4.50.
3
H21NO : C, 73.29, H,
2
H), 3.82 (t, J¼7.5 Hz, 2H), 4.90 (q, J¼7.1 Hz, 2H), 5.41 (s,1H), 6.88 (d,
J¼7.8 Hz, 1H), 7.07 (t, J¼7.8 Hz, 1H), 7.27 (t, J¼7.8 Hz, 1H), 7.27 (d,
1
3
J¼7.8 Hz, 1H); C NMR (CDCl
3
)
d
¼13.9, 16.0, 20.4, 27.0 (2C), 28.6,
4.4. Single X-ray crystallographic analysis
4
2.9, 48.0, 70.0, 81.4, 108.5, 122.1, 122.7, 122.8, 141.0, 142.8, 168.5,
þ
173.8,187.5,187.5,192.6; FABMS (NBA) m/z 340 (MH ). Anal. Found:
Single crystals were obtained by diffusion method using
C, 74.73, H, 7.61; N, 4.19. Calcd for C21 : C, 74.31, H, 7.42; N,
H
25NO
3
dichloromethane and hexane. The diffraction data were collected
ꢀ
4
.13.
by using graphite monochromated Mo-K
a
radiation (l¼0.71069 A).
The structure was solved by direct methods SIR97 and refined by
fill-matrix least-squares calculations.
4
. 2. 3. 3-Butoxy-4-(1-butyl-3, 3-dimethyl-3H-indol-2-
ylidenemethyl)-3-cyclobut-1,2-dione (13). Yield 1.6 g (56%); mp
Crystal data for 11: C20
H
23NO
3
, M
w
¼325.39, monoclinic, C2/m,
ꢀ
14
ꢀ
ꢁ1
1
ꢀ
126.0 C (lit. 128e129 C); IR (KBr):
n
1772 cm ; H NMR (CDCl
3
)
Z¼4, a¼23.826(16), b¼7.023(5), c¼11.065(8) A,
a¼90,
b
¼112.071(8),
ꢀ
ꢁ3
d
¼1.00 (t, J¼7.6 Hz, 3H), 1.01 (t, J¼7.2 Hz, 3H), 1.45 (sex, J¼7.6 Hz,
g
¼90 ,
D
calcd¼1.260
g
cm ,
T¼123(2) K, F(000)¼696,
ꢁ
1
2
1
5
H), 1.52 (sex, J¼7.2 Hz, 2H), 1.62 (s, 6H), 1.74 (quin, J¼7.6 Hz, 2H),
m
¼0.084 mm , 6875 reflections were corrected, 2094 unique
.87 (quin, J¼7.2 Hz, 2H) 3.82 (t, J¼7.6 Hz, 2H), 4.86 (t, J¼7.2 Hz, 2H),
(Rint¼0.0327). 2094 observed (I>2
wR
¼0.1229.
Crystal data for 12: C21H25NO
3
s
(I)), 162 parameters, R
1
¼0.0623,
.42 (s, 1H), 6.89 (d, J¼7.3 Hz, 1H), 7.07 (t, J¼7.3 Hz, 1H), 7.27 (t,
2
13
J¼7.3 Hz, 1H), 7.28 (d, J¼7.3 Hz, 1H); C NMR (CDCl
8.8, 20.4, 27.0 (2C), 28.6, 32.2, 42.8, 48.0, 73.8, 81.3, 108.5, 122.1,
22.7, 127.8, 141.0, 142.8, 168.4, 173.6, 187.6, 187.6, 192.8; EIMS
3
)
d
¼13.8, 13.9,
, Mw¼339.42, monoclinic, P21/n,
ꢀ
1
1
Z¼4, a¼9.389(4), b¼20.255(8), c¼10.201(4) A,
a¼90,
b
¼105.020(6),
ꢀ
ꢁ3
g
¼90 ,
D
calcd¼1.203
g
cm
,
T¼123(2) K, F(000)¼728,
þ
ꢁ1
(
70 eV) m/z (rel intensity) 367 (M , 98), 254 (100), 242 (54), 226
m
¼0.080 mm , 15,160 reflections were corrected, 4285 unique

M. Matsui et al. / Tetrahedron 68 (2012) 9936e9941
9941
(
R
R
int¼0.0375). 4285 observed (I>2
¼0.0667, wR ¼0.1162.
Crystal data for 13: C23
s
(I)), 298 parameters,
References and notes
1
2
1. (a) Lee, M.-T.; Yen, C.-K.; Yang, W.-P.; Chen, H.-H.; Liao, C.-H.; Tsai, C.-H. Org. Lett.
H29NO
3
, Mw¼367.47, monoclinic, P21/n,
2004, 6, 1241; (b) Swanson, S. A.; Wallraff, G. M.; Chen, J. P.; Zhang, W.; Bozano,
ꢀ
Z¼4, a¼10.849(4), b¼10.654(4), c¼19.083(7) A,
a
¼90,
b
¼106.919(4),
L. D.; Carter, K. R.; Salem, J. R.; Villa, R.; Scott, J. C. Chem. Mater. 2003, 15, 2305;
(c) Chen, C.-T.; Chiang, C.-L.; Lin, Y.-C.; Chan, L.-H.; Huang, C.-H.; Tsai, Z.-W.;
Chen, C.-T. Org. Lett. 2003, 5, 1261.
ꢀ
ꢁ3
ꢁ1
g
¼90 , Dcalcd¼1.157 g cm , T¼123(2) K, F(000)¼792,
m
¼0.076mm
,
1
6,641 reflections were corrected, 4817 unique (Rint¼0.0358). 4817
observed (I>2 (I)), 317 parameters, R ¼0.1342.
¼0.0663, wR
Crystal data for 14: C27
2. (a) Zhang, D.; Zhang, S.; Ma, D.; Gulimina; Li, X. Appl. Phys. Lett. 2006, 89,
s
1
2
231112; (b) Jones, G., II; Rahman, M. A. J. Phys. Chem. 1994, 98, 13028.
H37NO
3
, Mw¼423.58, triclinic, P-1, Z¼4,
3. (a) Wang, X.; Morales, A. R.; Urakami, T.; Zhang, L.; Bondar, M. V.; Komatsu, M.;
Belfield, K. D. Bioconjugate Chem. 2011, 22, 1438; (b) Xu, J.-P.; Fang, Y.; Song,
Z.-G.; Mei, J.; Jia, L.; Qin, A. J.; Sun, J. Z.; Ji, J.; Tang, B. Z. Analyst 2011, 136, 2315;
ꢀ
a¼13.011(4), b¼13.775(4), c¼14.943(5) A,
a¼74.868(10),
ꢀ
ꢁ3
b
¼88.342(13),
g
¼69.521(10) , Dcalcd¼1.164 g cm , T¼123(2) K,
(c) Song, P.; Chen, X.; Xiang, Y.; Huang, L.; Zhou, Z.; Wei, R.; Tong, A. J. Mater.
ꢁ1
F(000)¼920,
0,963 unique (Rint¼0.0438). 10,963 observed (I>2
rameters, R ¼0.1420.
¼0.0767, wR
Crystal data for 15: C27
m
¼0.075 mm , 19,866 reflections were corrected,
Chem. 2011, 21, 13470; (d) Shundo, A.; Okada, Y.; Ito, F.; Tanaka, K. Macromol-
ecules 2012, 45, 329; (e) Fujishima, S.-H.; Nonaka, H.; Uchinomiya, S.-H.; Ka-
wase, Y. A.; Ojida, A.; Hamachi, I. Chem. Commun. 2012, 594.
. For example Law, K.-Y.; Bailey, F. C. J. Org. Chem 1992, 57, 3278.
. Nakazumi, H.; Natsukawa, K.; Nakai, K.; Isagawa, K. Angew. Chem., Int. Ed. Engl.
1994, 33, 1001.
1
s
(I)), 855 pa-
1
2
4
5
H37NO
3
, Mw¼423.58, triclinic, P-1, Z¼4,
ꢀ
a¼9.093(3), b¼10.930(4), c¼25.485(10) A,
a¼89.034(12),
ꢀ
ꢁ3
6. (a) Yagi, S.; Nakai, K.; Hyodo, Y.; Nakazumi, H. Synthesis 2002, 413; (b) Yagi, S.;
Fujie, Y.; Hyodo, Y.; Nakazumi, H. Dyes Pigm. 2002, 52, 245.
b
¼84.089(11),
g
¼72.177(9) , Dcalcd¼1.173 g cm , T¼123(2) K,
ꢁ
1
F(000)¼920,
0,829 unique (Rint¼0.0359). 10,829 observed (I>2
rameters, R
m
¼0.075 mm , 19,595 reflections were corrected,
7. (a) Avirah, R. R.; Jyothish, K.; Ramaiah, D. Org. Lett. 2007, 9, 121; (b) Bae, J. S.;
1
s
(I)), 775 pa-
Gwon, S. Y.; Son, Y. A.; Kim, S. H. Dyes Pigm. 2009, 83, 324.
8. Matsui, M.; Mase, H.; Jin, J.; Funabiki, K.; Yoshida, T.; Minoura, H. Dyes Pigm.
1
¼0.0812, wR ¼0.1570.
2
2006, 70, 48.
Crystallographic data (11 (CCDC 696948), 12 (CCDC 696951), 13
CCDC 696949), 14 (CCDC 696952), and 15 (CCDC 696950)) have
9
. (a) Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Chem. Commun. 2009, 4332 and references
cited therein; (b) Yuan, W. Z.; Lu, P.; Chen, S.; Lam, J. W. Y.; Wang, Z.; Liu, Y.;
Kwok, H. S.; Ma, Y.; Tang, B. Z. Adv. Mater. (Weinheim, Ger.) 2010, 22, 2159; (c)
Luo, J.; Xie, Z.; Lam, J. W. Y.; Cheng, L.; Chen, H.; Qiu, C.; Kwok, H. S.; Zhan, X.;
Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun. 2001, 1740.
(
been deposited at the CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK.
10. Zhao, Z.; Chen, S.; Lam, J. W. Y.; Jim, C. K. W.; Chan, C. Y. K.; Wang, Z.; Lu, P.;
Deng, C.; Kwok, H. S.; Ma, Y.; Tang, B. Z. J. Phys. Chem. C 2010, 114, 7963.
11. (a) Itami, K.; Ohashi, Y.; Yoshida, J. J. Org. Chem 2005, 70, 2778; (b) Ning, Z.; Chen,
Z.; Zhang, Q.; Yan, Y.; Qian, S.; Cao, Y.; Tian, H. Adv. Funct. Mater. 2007, 17, 3799.
Supplementary data
1
2. For example, (a) Shimizu, M.; Asai, Y.; Takeda, Y.; Yamatani, A.; Hiyama, T.
Tetrahedron Lett. 2011, 52, 4084; (b) Imoto, M.; Ikeda, H.; Ohashi, M.; Takeda,
M.; Tamaki, A.; Taniguchi, H.; Mizuno, K. Tetrahedron Lett. 2010, 51, 5877; (c)
Zhao, C.-H.; Zhao, Y.-H.; Pan, H.; Fu, G.-L. Chem. Commun. 2011, 5518; (d) Matsui,
M.; Ikeda, R.; Kubota, Y.; Funabiki, K. Tetrahedron Lett. 2009, 50, 5047; (e)
Ooyama, Y.; Nabeshima, S.; Mamura, T.; Ooyama, H. E.; Yoshida, K. Tetrahedron
2010, 66, 7954.
1
These data include H NMR spectra of 11, 12, 13, 14, 15, and 16,
UVevis absorption and fluorescence spectra of 13 in various sol-
vents, and single X-ray crystallographic data for 11, 12, 13, 14, and
15. Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2012.09.089.
13. An, P.; Shi, Z.-F.; Dou, W.; Cao, X.-P.; Zhang, H. L. Org. Lett. 2010, 12, 4364.