Synthesis of π-expanded O-chelated boron-dipyrromethene as an NIR dye

Article abstract of DOI:10.1016/j.tet.2011.03.016

A π-expanded BODIPY dye with an intramolecular boronate skeleton was synthesized by retro Diels-Alder reaction of the bicyclo[2.2.2]octadiene (BCOD)-fused BODIPY and the subsequent O-chelation. The photophysical and electrochemical properties were examined by UV-vis, fluorescence, CV measurements, and DFT calculation. This BODIPY exhibited the absorption and emission over a visible-NIR region at 600-850 nm. O-chelated BODIPY showed a bathocromic shift compared to F-BODIPYs. This dye showed a bright fluorescence emission at 733 nm with the high Φ value of 0.58.

Full text of DOI:10.1016/j.tet.2011.03.016

Tetrahedron 67 (2011) 3187e3193
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of
p
-expanded O-chelated boronedipyrromethene as an NIR dye
,
a
b
a
Yuya Tomimori a, Tetsuo Okujima a , Tomoko Yano , Shigeki Mori , Noboru Ono ,
*
Hiroko Yamada a c, Hidemitsu Uno a
,
a Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
b Department of Molecular Science, Integrated Center for Sciences, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
c CREST, Japan Science and Technology Agency, Chiyoda-ku 102-0085, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A p-expanded BODIPY dye with an intramolecular boronate skeletonwas synthesized by retro DielseAlder
Received 3 February 2011
Received in revised form 5 March 2011
Accepted 7 March 2011
reaction of the bicyclo[2.2.2]octadiene (BCOD)-fused BODIPY and the subsequent O-chelation. The pho-
tophysical and electrochemical properties were examined by UVevis, fluorescence, CV measurements, and
DFT calculation. This BODIPY exhibited the absorption and emission over a visibleeNIR region at
600e850 nm. O-chelated BODIPY showed a bathocromic shift compared to F-BODIPYs. This dye showed
Available online 12 March 2011
a bright fluorescence emission at 733 nm with the high
F
value of 0.58.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Dyesepigments
Boronedipyrromethene
[1,3,2]Oxazaborine
Fluorophore
Near-infrared absorbing dye
1. Introduction
region (ca. 750 nm).7d In their method, formation of BODIIs
according to literature procedure from methyl o-methox-
ybenzoate5a followed by intramolecular substitution afforded only
O-chelated BODIIs without a meso-substituent and the molecular
structures and emission properties have not been reported. We
have already reported the synthesis of BODIIs based on retro
DielseAlder conversion of bicyclo[2.2.2]octadiene (BCOD) to ben-
zene.1a,c,d In our method, substituted-BODIIs at meso-position,
where functional groups could be introduced, are easily obtained.1d
We herein report the synthesis of O-chelated meso-phenylBODIIs
with NIR absorption and emission.
Boronedipyrromethene (BODIPY) is a well-known stable fluo-
rescent dye with strong absorption and emission. This dye is gen-
erally composed of a dipyrromethene
difluoride core. Modification of the BODIPY structure has been
developed in order to tune the absorption and emission wave-
lengths. Introduction of substituents at pyrrole meso-position and
boron moieties has afforded a variety of BODIPYs, electronic
p-system and a boron-
structures of which are greatly influenced not only by the p-system
modification at the dipyrromethene moiety but by the substitution
of core fluorine atoms.1ꢀ4 In the latter case, substituents making
strong bonds with boron atom are employed. Therefore, many
BODIPYs with carbon (C-BODIPY)6 and oxygen (O-BODIPY)5,7 sub-
stituents on the core boron atom have been reported. The first O-
BODIPYs have been synthesized by intramolecular substitution of
fluorine atoms with phenoxyl groups appended to 3- and 5-posi-
tions of the dipyrromethene moiety.2a,7aꢀc The O-chelated BODIPY
showed a significant red-shift (80 nm) in the UV absorption spec-
trum and a sharper emission with ca. six-times higher quantum
yield than the corresponding precursor. Recently, Kubo et al. have
reported that the O-chelated boron-di(2H-isoindolyl)methenes
meso
8
7
5
1
3
6
2
N
N
N
N
4
B
B
F
F
F
F
F-BODIPY
F-BODII
(BODIIs) have strong absorptions (
e
¼8.3ꢁ104 Mꢀ1 cmꢀ1) in NIR
2. Results and discussion
Synthesis of BODIPYs and BODIIs (4, 9, and 5) is shown in
Scheme 1. N-Butoxycarbonyl BCOD-pyrrole-2-carboxylate 18a
* Corresponding author. Tel./fax: þ81 89 927 9615; e-mail address: okujima.
tetsuo.mu@ehime-u.ac.jp (T. Okujima).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.03.016

3188
Y. Tomimori et al. / Tetrahedron 67 (2011) 3187e3193
Boc
N
H
H
N
N
1. ArB(OH)2, Pd(PPh3)4
Na2CO3
1. TFA, C6H5CHO
2. DDQ
I
CO2Et
CO2Et
KOH
R
R
160 °C
2. conc. HCl
3. (i-Pr)2EtN, BF3·OEt2
1
2a
3a
3b
: R = H (67%)
(65%)
(72%)
2b
: R = OMe (72%)
210 °C
BBr3
N
N
N
R
N
N
N
R
R
R
B
B
B
F
F
F
F
O
O
4a
5a
(78%)
(52%)
(quant)
(quant)
10
(91%)
4b
5b
(from 5b)
H
N
H
N
H
N
1. TFA, C6H5CHO
2. DDQ
I
CO2Et
CO2Et
ArB(OH)2, Pd(PPh3)4
Na2CO3
KOH
OMe
OMe
160 °C
3. (i-Pr)2EtN
BF3·OEt2
6
7
8
(88%)
(60%)
BBr3
N
B
F
N
N
N
O
OMe
MeO
B
F
O
9 (42%)
11
(78%)
Scheme 1.
reacted with phenyl- and 2-methoxyphenylboronic acids by
SuzukieMiyaura coupling followed by deprotection of Boc groups
to give 2a and 2b in 67% and 72% yields, respectively. Removal of
0
the ester group of 2a and 2b with KOH gave a-free aryl pyrroles 3a
-5
and 3b in 65% and 72% yields, respectively. Condensation of 3a and
3b with benzaldehyde followed by oxidation with DDQ and com-
plexation gave BCOD-fused BODIPYs 4a and 4b in 78% and 52%
yields, respectively. Thermal treatment of 4a and 4b at 210 ꢂC
quantitatively gave the corresponding BODIIs 5a and 5b. Bicyclo
[2.2.2]octene-fused (BCO-fused) BODIPY 9 was prepared in the
similar manner starting from 6.8b Demethylation of 5b and 9 with
BBr3 and simultaneous cyclization afforded constrained com-
pounds 10 and 11 with a spirobi[1,3,2]oxazaborine skeleton in 91%
and 78% yields, respectively. When 4b was treated with BBr3,
however, the corresponding O-chelated and brominated product
was obtained in low yield.
-10
-15
100
200
temperature/°C
300
Fig. 1. TG analysis of 4a (red) and 4b (blue line).
Thermogravimetric analysis of 4 was carried out in order to
determine the temperature of the retro DielseAlder reaction
(Fig. 1). The weight loss from 4a and 4b started at 160 and 140 ꢂC,
and finished at 240 and 220 ꢂC, respectively. The lost amounts from
4a and 4b are 11.1% and 10.1%, which are slightly larger than the
calculated ones of 9.7% and 8.8%, respectively.
UVevis absorption spectra of BODIPYs 4, 5, 9, 10, and 11 are
shown in Fig. 2. Their absorption bands are observed in a visi-
bleeNIR region. The BODIPYs 4 and 9 show broad absorption bands
around 550 nm similar to those of typical 3,5-diaryl-substituted
BODIPYs.2a Absorption spectra of BODII 5a and 5b are well in accord
with the reported value of other BODIIs.1a,9 The absorption maxima
of 4b and 5b with o-methoxyphenyl group are blue-shifted com-
pared with those of 4a and 5a due to insufficient conjugation of o-
methoxyphenyl groups by steric hindrance.9 An absorption band of
10 (711 nm) is red-shifted by 80e94 nm compared to those of 5a
and 5b. An absorption band of 11 is observed at 626 nm, which is
red-shifted by 76 nm compared to that of 9.
Absorption and emission maxima, absolute quantum yields (
F)
and fluorescence lifetime ( ) are summarized in Table 1, and the
s

Y. Tomimori et al. / Tetrahedron 67 (2011) 3187e3193
3189
(Table 2 and Fig. S1). All compounds show reversible reduction and
oxidation peaks. No obvious effect is observed in the potentials by
fusion of BCOD and BCO. The reduction and oxidation potentials of
4b and 9 are the almost same. Intramolecular spiro ring formation
results in the stabilization of LUMO and destabilization of HOMO by
effective conjugation of appended aryl groups (Table 2). The lowest
oxidation potential is recorded in 10 (0.19 V).
12
10
8
6
4
2
Table 2
Electrochemical dataa, and calculated HOMO and LUMO energy values
0
50
0
6
00
70
0
800
E1ox/V
E2ox/V
E
red/V
Eg/eVc
EHOMO/eVd
ELUMO/eVd
Eg/eVd
wavelength /n m
EHOMO/eVb
ELUMO/eVb
9
0.55
d
ꢀ1.76
ꢀ3.02
ꢀ1.70
ꢀ3.08
ꢀ1.58
e3.20
ꢀ1.63
ꢀ3.15
ꢀ1.64
ꢀ3.14
ꢀ1.54
ꢀ3.24
ꢀ1.48
ꢀ3.30
2.31
2.27
2.25
1.95
2.03
1.91
1.67
ꢀ4.96
ꢀ2.19
ꢀ5.04
ꢀ2.26
ꢀ5.11
e2.41
ꢀ4.81
ꢀ2.39
ꢀ4.82
ꢀ2.34
ꢀ4.80
ꢀ2.45
ꢀ4.65
ꢀ2.45
2.77
2.78
2.70
2.42
2.48
2.35
2.20
Fig. 2. UVevis absorption spectra of 9 (red), 4b (orange), 4a (yellow), 5b (light green),
11 (green), 5a (light blue), and 10 (blue line) in CH2Cl2.
ꢀ5.33
4b
4a
5b
11
5a
10
0.57
d
ꢀ5.35
0.67
d
Table 1
Photophysical properties
ꢀ5.45
0.32
(1.17)
(1.08)
(1.22)
(0.90)
a
b
labs/nm (log
e)
lem/nm (
F
)
s
/nsc
lex/nm
ꢀ5.10
0.39
9
550 (4.81)
556 (4.79)
558 (4.85)
617 (5.01)
626 (4.80)
631 (5.01)
711 (4.96)
583 (0.77)
587 (0.87)
588 (0.87)
652 (0.91)
645 (0.99)
664 (0.93)
733 (0.58)
4.5
5.1
6.1
5.8
9.6
5.2
7.0
517
517
510
617
571
583
651
ꢀ5.17
4b
4a
5b
11
5a
10
0.37
ꢀ5.15
0.19
ꢀ4.97
a
The redox potentials were measured by CV (V vs Fc/Fcþ, 0.1 M TBAPF6 in CH2Cl2
Pt electrode, scan rate¼0.1 V sꢀ1 Fc/Fcþ¼0.25 V vs Ag/Agþ). In the case of irreversible
a
In CH2Cl2 at 10ꢀ6 M.
In CH2Cl2 at 10ꢀ7 M.
Excited at 532 nm in CH2Cl2.
b
c
waves, which are shown in parentheses, E2ox are anodic peak potentials.
b
EHOMO(Fc)¼ꢀ4.78 eV10, EHOMO¼ꢀ4.78 eVꢀE1ox, ELUMO¼ꢀ4.78ꢀE1red
.
c
HOMOeLUMO energy gaps obtained by CV.
d
HOMO and LUMO energy values and gaps calculated by the B3LYP/6-31G(*)
emission spectra are shown in Fig. 3. The BODIPYs 4 and 9 show
strong and broad emission bands at 583e588 nm with high
density functional theory.
F
values of 0.77e0.87. The emission peaks of 5a and 5b are observed
at the similar region to the reported BODIIs (664 and 652 nm) with
The crystal structures of 4, 5, 9, 10, and 11 were determined by
X-ray diffraction analysis (Figs. 4e6 and Figs.S2e5).11 The crystal-
lographic data are summarized in Tables S2 and S3. In 5a, both
phenyl rings lie out of the mean plane of the BODIPY chromophore
with torsion angles of 56.45ꢂ and 58.66ꢂ. The BODIPY skeleton is
high
shows strong fluorescence emission at 645 nm. This band is red-
shifted by 62 nm compared to that of precursor 9. The value
F values of 0.93 and 0.91, respectively. O-Chelated BODIPY 11
F
(0.99) of 11 is quite high than those of other BODIPY dyes emitting
at the same region.7a This is probably due to BCO rings blocking the
fluorescence quenching by the BODIPY-chromophore stacking and
by the meso-phenyl-group rotation. The emission band of O-che-
lated BODII 10 appears at 733 nm, value of which is red-shifted by
ꢀ
slightly distorted, and the mean plane deviation is 0.0585 A with
respect to the BODIPY mean plane (12 member’s atom). The di-
hedral angle of pyrrole moieties is 8.00ꢂ. BODIPY 5b adopts almost
S1 symmetry. Both phenyl rings of 5b lie nearly perpendicularly to
the mean plane of BODIPY moiety (80.26ꢂ and 89.07ꢂ). The BODIPY
skeleton is slightly distorted, the dihedral angle of pyrrole moieties
81 nm compared to 5b, and the
F value is 0.58. O-Chelated 10 and
11 have longer fluorescence lifetimes of 7.0 and 9.6 ns than 4, 5, and
9. This is due to the lack of wagging of aryl groups.
ꢂ
ꢀ
is 4.86 , and the mean plane deviation is 0.0508 A with respect to
BODIPY moiety. FeBeF, NeBeN bond angles and FeB, NeB bond
lengths of BODIIs 5 are well comparable to the reported values of
other BODIIs.1a,d O-Chelated BODII 10, however, adopts a consider-
1.0
0.8
0.6
0.4
0.2
0
ꢀ
ably distorted structure, and the mean plane deviation is 0.0959 A.
The bond angle of NeBeN is widened to be 108.4(7)ꢂ, while that of
OeBeO is narrowed to be 106.5(7)ꢂ.
500
600
700
800
900
wavelength/nm
Fig. 3. Normalized fluorescence emission spectra of 9 (red), 4b (orange), 4a (yellow),
11 (green), 5b (light green), 5a (light blue), and 10 (blue line) in CH2Cl2.
Redox potentials of the BODIPYs were measured by CV in CH2Cl2
using 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6)
as a supporting electrolyte, glassy carbon as a working electrode, Pt
wire as a counter electrode, and Ag/Agþ as a reference electrode
Fig. 4. ORTEP drawing of 5a. Hydrogen atoms are omitted for clarity.

3190
Y. Tomimori et al. / Tetrahedron 67 (2011) 3187e3193
MeOH at 50 ꢂC, in MeOH/CHCl3 at 50 ꢂC, in MeOH in the presence of
HCl, or in THF with NaOMe/MeOH.
Table 3
Selected distance and angles
ꢀ
ꢀ
ꢀ
FeB/A or OeB/A
FeBeF or OeBeO
NeB/A
NeBeN
5a
5b
10
12
1.374(4),
1.378(4)
111.4(3)ꢂ
1.567(4),
1.568(5)
107.5(2)ꢂ
1.3681(16),
1.3761(17)
1.478(10),
1.497(10)
1.459(3),
1.468(3)
111.54(11)ꢂ
106.5(7)ꢂ
1.5737(17),
1.5784(17)
1.494(12),
1.506(12)
1.524(3),
1.526(3)
105.83(10)ꢂ
108.4(7)ꢂ
109.00(17)ꢂ
105.75(17)ꢂ
Fig. 5. ORTEP drawing of 5b. Hydrogen atoms are omitted for clarity.
1.0
0.8
0.6
0.4
0.2
0
300
400
500
600
700
800
wavelength/nm
Fig. 6. ORTEP drawing of 10. Hydrogen atoms are omitted for clarity.
Fig. 8. UVevis absorption spectrum of 12 in CH2Cl2.
Unexpectedly we obtained yellow crystals of 12 with green
crystals of 10 during the recrystallization of 10 from CHCl3/MeOH.
The structure of 12 is unambiguously determined to be a bis-
methoxide adduct at the 3- and 5-positions of BODII, although the
crystal contains mono-chlorinated compound of 12 in ca. 13% as
a disordered structure (Supplementary data and Fig. 7). The dihy-
dro BODIPY core of 12 is almost flat, and the heavy distortion ob-
served in 10 is greatly released.15 The dihedral angle of pyrrole
moieties is 4.04 . The mean plane deviation is 0.0541 A. In 12,
OeBeO angle is larger than that in 10 and NeBeN angle is smaller.
These values become close to those of 5a and 5b (Table 3). UVevis
absorption of 12 is shown in Fig. 8. Three absorption bands appear
at 282, 411, and 434 nm. No fluorescence is observed in 12. The
yellow crystals of 12 were not obtained by recrystallization of 10
from CHCl3/MeOH in the dark. The photo stability of 5b, 4b, 10, and
11 in CH2Cl2 at ca. 10ꢀ5 M was measured by continuous irradiation
at the wavelength of absorption maxima with a Xe lamp. After 1 h,
67%, 87%, 69%, and 88% of the initial absorbance were retained,
respectively. In O-chelated BODIPY, BODII 10 showed low photo
stability compared to BODIPY 11, which was consistent with
destabilized HOMO of 10. Thus, oxidative MeO-addition of 10
afforded 12 with release of ring-strain, although no formation of 12
from 10 was observed under various conditions: a solution of 10 in
3. Conclusion
We have successfully synthesized an O-chelated BODII 10 by our
methodology, which easily introduced a functional group at meso-
position. The BODIPYs 4, 5, and 9e11 exhibit the absorptions and the
fluorescence emissions in the visibleeNIR region between 580 and
730 nm. The molecular structures of all BODIPYs were fully char-
acterized by the X-raycrystallographic analysis. We haveshown that
fusion of rigid BCOD or BCO at the 1,2- and 6,7-positions enhances
the fluorescence emission by prevention of wagging of the meso-
phenyl group and stacking of the BODIPY chromophore. The BODIPY
chromophore can be effectively expanded not only by the benzo-
fusion at the 1,2- and 6,7-positions but also by intramolecular ring-
connection of the appended aryl groups at 3- and 5-positions to the
core boron atom. This dye 10 was stable and showed a bright fluo-
ꢂ
ꢀ
rescence emission at 733 nm with the
relatively high compared to the
F
value of 0.58, which was
F
value of other BODIPYs emitted in
NIR region.3 Further application for O-chelated BODIPYs with
a meso-functional group as NIR dyes are underway, since our
methodology has an advantage for the preparation of various O-
chelated p-expanded-BODIPYs.
4. Experimental section
4.1. General
Melting points were determined on a Yanaco micro melting
point apparatus MP500D and are uncorrected. DIeEI and FAB mass
spectra were measured on a JEOL JMS-700. MALDI-TOF mass
spectra were measured on an Applied Biosystems Voyager de Pro.
UVevis spectra were measured on a JASCO V-570 spectrophotom-
eter. 1H NMR spectra were recorded on a JEOL AL-400 at 400 MHz
or JEOL JNM-GSX 270 at 270 MHz. The fluorescence emission
spectra and the
F values were measured on a Hamamatsu Pho-
Fig. 7. ORTEP drawing of 12. Hydrogen atoms are omitted for clarity.
tonics K.K. absolute PL quantum yield measurement system C9920-

Y. Tomimori et al. / Tetrahedron 67 (2011) 3187e3193
3191
03. The fluorescence decay was measured, using a C7990-01 NIR
fluorescence lifetime measurements system, consisting of a Hama-
matsu Photonics K.K. using a 1 ns (FWHM) pulse laser light at
532 nm (45 mW, 14 kHz) from a CrsLas FTSS355-Q YAG laser and
a NIR region R5509-43 PMT. Elemental analyses were performed at
Integrated Center for Sciences, Ehime University. Pyrrole 1 was
prepared according to the literature.8a Dried solvents were pur-
chased from Kanto Chemical Co. All solvents used for chromatog-
raphy were simply distilled prior to use. Ethylene glycol was
distilled and stored under an Ar atmosphere. Other chemicals were
used as purchased.
295 [MꢀC2H4]þ. Anal. Calcd for C20H21NO3: C, 74.28; H, 6.55; N,
4.33. Found: C, 74.22; H, 6.61; N, 4.30.
4.2.3. Pyrrole 7. To a degassed solution of 6 (618 mg,1.79 mmol), 2-
methoxyphenylboronic acid (431 mg, 2.83 mmol) and Pd(PPh3)4
(9 mg, 0.008 mmol) in dry DMF (14 ml) was added a degassed
aqueous Na2CO3 (569 mg/5 ml) under an Ar atmosphere. The mix-
ture was refluxed for 5 h. The reaction was quenched by addition of
1 M HCl (10 ml), brine (10 ml), and CHCl3 (10 ml). The organic extract
was separated and concentrated under a reduced pressure. The
residue was purified by column chromatography on silica gel with
CHCl3 followed by recrystallization from CHCl3ehexane to give 7
(513 mg, 88%): colorless crystals; mp 141.6e142.1 ꢂC; 1H NMR
4.2. Synthesis
(400 MHz, CDCl3)
d
¼9.53 (br s, 1H), 7.57 (dd, J¼7.7 and 1.8 Hz, 1H),
4.2.1. Pyrrole 2a. To a degassed solution of 1 (4.56 g, 10.3 mmol),
phenylboronic acid (1.92 g, 15.8 mmol) and Pd(PPh3)4 (596 mg,
0.516 mmol) in dry DMF (100 ml) was added degassed aqueous
Na2CO3 (3.36 g/30 ml) under an Ar atmosphere. The mixture was
refluxed for 17 h. The reaction mixture was filtered through a Celite
pad and concentrated under a reduced pressure. The residue was
diluted with CHCl3. The organic extract was washed successively
with water and brine, dried over Na2SO4, and concentrated under
a reduced pressure. The residue was purified by column chroma-
tography on silica gel with CHCl3. After addition of concd HCl
(30 ml) to the crude product in EtOAc (30 ml), the mixture was
stirred at room temperature overnight. The mixture was extracted
with EtOAc. The organic extract was washed successively with
saturated aqueous NaHCO3, water, and brine; dried over Na2SO4;
and concentrated under a reduced pressure. The residue was pu-
rified by column chromatography on silica gel with CHCl3 followed
by recrystallization from CHCl3ehexane to give 2a (2.01 g, 67%):
7.28e7.23 (m, 1H), 7.03e6.97 (m, 2H), 4.33 (q, J¼7.1 Hz, 2H), 3.93 (s,
3H), 3.58 (m,1H), 3.35 (m,1H),1.82e1.76 (m, 4H),1.46e1.20 (m, 4H),
and 1.37 (t, J¼7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3)
¼161.87,
d
155.60, 135.71, 129.01, 127.97, 127.73, 124.94, 120.94, 120.80, 113.64,
111.26, 59.68, 55.58, 28.08, 27.64, 26.96 (2C), 26.54 (2C), and 14.64;IR
(KBr disk) nmax 3305 (NH), 3047, 2972, 2945, 2860, and 1670 cmꢀ1
;
MS (FAB) m/z 325 [M]þ. Anal. Calcd for C20H23NO3: C, 73.82; H, 7.12;
N, 4.30. Found: C, 73.82; H, 7.07; N, 4.30.
4.2.4. Pyrrole 3a. A suspension of 2a (1.57 g, 5.36 mmol) and KOH
(2.65 g, 47.3 mmol) in ethylene glycol (48 ml) was heated at 175 ꢂC
for 2 h underan Aratmosphere in the dark. The reaction mixturewas
cooled to room temperature. After addition of water, the mixture
was extracted with CHCl3. The organic extract was washed succes-
sively with water and brine, dried over Na2SO4, and concentrated
under a reduced pressure. The residue was purified by column
chromatography on silica gel with CHCl3 followed by re-
crystallization from CHCl3ehexane to give 3a (775 mg, 65%): pale
colorless crystals; mp 160.5 ꢂC; 1H NMR (270 MHz, CDCl3)
d¼8.53
(br s, 1H), 7.55e7.51 (m, 2H), 7.45e7.40 (m, 2H), 7.33e7.27 (m, 1H),
6.56e6.51 (m, 2H), 4.35 (m, 1H), 4.34 (q, J¼7.3 Hz, 2H), 4.21 (m, 1H),
1.63e1.53 (m, 4H), and 1.39 (t, J¼7.3 Hz, 3H); 13C NMR (67.8 MHz,
pink crystals; mp 200.0e201.3 ꢂC; 1H NMR (400 MHz, CDCl3)
(br s, 1H), 7.44 (m, 2H), 7.37 (m, 2H), 7.19 (m, 1H), 6.54 (m, 2H), 6.49
d
¼7.61
(d, J¼2.2 Hz, 1H), 4.19 (m, 1H), 3.86 (m, 1H), and 1.64e1.51 (m, 4H);
CDCl3)
d
¼161.90, 138.03, 135.89, 135.34, 132.24, 128.85, 128.66,
13C NMR (100 MHz, CDCl3)
d
¼136.11, 135.79, 133.60, 131.15, 128.72,
127.22, 127.13, 126.17, 113.86, 59.96, 33.75, 33.33, 26.68, 26.17, and
14.52; IR (KBr disk) nmax 3317 (NH), 3051, 2981, 2931, 2863, and
1684 cmꢀ1; MS (FAB) m/z 294 [MþH]þ and 265 [MꢀC2H4]þ. Anal.
Calcd for C19H19NO2: C, 77.79; H, 6.53; N, 4.77. Found: C, 77.76; H,
6.58; N, 4.69.
126.65,125.55,125.08,122.75,108.35, 33.34, 33.32, 27.35, and 27.13;
IR (KBr disk) nmax 3359 (NH), 3039, 2962, 2931, and 2858 cmꢀ1; MS
(FAB) m/z 221 [M]þ and 193[MꢀC2H4]þ. Anal. Calcd for C16H15N$1/
16H2O: C, 86.40; H, 6.83; N, 6.33. Found: C, 86.28; H, 6.88; N, 6.37.
4.2.5. Pyrrole 3b. A suspension of 2b (646 mg, 2.00 mmol) and KOH
(0.800 g, 14.3 mmol) in ethylene glycol (20 ml) was heated to 160 ꢂC
for 2 h under an Ar atmosphere in the dark. The reaction mixture
was cooled to room temperature. After addition of water, the
mixture was extracted with CHCl3. The organic extract was washed
successively with water and brine, dried over Na2SO4, and con-
centrated under a reduced pressure. The residue was purified by
silica gel column chromatography with CHCl3 give 3b (363 mg,
72%): pale pink crystals; mp >135 ꢂC (decomp.); 1H NMR (400 MHz,
4.2.2. Pyrrole 2b. To a degassed solution of 1 (6.01 g, 13.6 mmol), 2-
methoxyphenylboronic acid (4.00 g, 20.4 mmol) and Pd(PPh3)4
(749 mg, 0.648 mmol) in dry DMF (130 ml) was added degassed
saturated aqueous Na2CO3 (4.31 g/40 ml) under an Ar atmosphere.
The mixture was refluxed for 21.5 h. The reaction mixture was fil-
tered through a Celite pad and concentrated under a reduced
pressure. The residue was diluted with CHCl3. The organic extract
was washed successively with water and brine, dried over Na2SO4,
and concentrated under a reduced pressure. After addition of concd
HCl (45 ml) to the residue in EtOAc (90 ml), the mixture was stirred
at room temperature overnight. The mixture was extracted with
EtOAc. The organic extract was washed successively with saturated
aqueous NaHCO3, water, and brine; dried over Na2SO4; and con-
centrated under a reduced pressure. The residue was purified by
column chromatography on silica gel with CHCl3. Recrystallization
from CHCl3ehexane to give 2b (3.13 g, 72%): colorless crystals; mp
CDCl3)
d
¼8.74 (br s, 1H), 7.61 (dd, J¼7.6 and 1.2 Hz, 1H), 7.16 (m, 1H),
7.01 (m, 1H), 6.95 (d, J¼8.3 Hz, 1H), 6.56e6.51 (m, 3H), 4.23 (m, 1H),
3.88 (s, 3H), 3.86 (m, 1H), and 1.64e1.55 (m, 4H); 13C NMR
(100 MHz, CDCl3)
d
¼154.95, 136.35, 135.88, 130.21, 127.95, 127.49,
126.29, 122.34, 121.07, 119.83, 111.36, 107.48, 55.57, 34.07, 33.40,
27.41, and 27.12; IR (KBr disk) nmax 3444 (NH), 3047, 2970, 2927,
2897, and 2862 cmꢀ1; MS (70 eV) m/z (relative intensity) 251 (Mþ,
36) and 223 (MþꢀC2H4, 100). Anal. Calcd for C17H17NO$1/8H2O: C,
74.71; H, 7.19; N, 3.96. Found: C, 74.67; H, 7.17; N, 3.91.
141.6e142.1 ꢂC; 1H NMR (270 MHz, CDCl3)
d¼9.33 (br s, 1H),
7.63e7.59 (m, 1H), 7.30e7.23 (m, 1H), 7.07e6.97 (m, 2H), 6.57e6.50
(m, 2H), 4.43 (m, 1H), 4.33 (q, J¼7.3 Hz, 2H), 4.22 (m, 1H), 3.91 (s,
3H), 1.63e1.54 (m, 4H) and 1.39 (t, J¼7.3 Hz, 3H); 13C NMR
4.2.6. Pyrrole 8. A suspension of 7 (811 mg, 2.49 mmol) and KOH
(1.10 g, 19.6 mmol) in ethylene glycol (25 ml) was heated to 160 ꢂC
for 2 h under an Ar atmosphere in the dark. The reaction mixture
was cooled to room temperature. After addition of water, the
mixture was extracted with CHCl3. The organic extract was washed
successively with saturated aqueous NaHCO3, water, and brine;
(67.8 MHz, CDCl3)
d
¼161.74, 155.71, 137.10, 135.92, 135.57, 129.52,
128.89, 128.15, 124.14, 121.02, 120.75, 113.00, 111.39, 59.75, 55.56,
34.03, 33.69, 26.60, 26.21, and 14.57; IR (KBr disk) nmax 3305 (NH),
3047, 2993, 2939, 2866, and 1676 cmꢀ1; MS (FAB) m/z 323[M]þ and

3192
Y. Tomimori et al. / Tetrahedron 67 (2011) 3187e3193
dried over Na2SO4; and concentrated under a reduced pressure. The
residue was purified by column chromatography on silica gel with
CHCl3 followed by recrystallization from CHCl3ehexane to give 8
(360 mg, 60%): purple crystals; mp 147.5e146.3 ꢂC; 1H NMR
from CH2Cl2eMeOH gave 4b (349 mg, 52%) as a mixture of rotamer:
red crystals; mp >170 ꢂC (decomp.); 1H NMR (400 MHz, CDCl3)
d
¼7.73 (m, 1H), 7.59e748 (m, 6H), 7.37e7.23 (m, 2H), 7.02e6.85 (m,
4H), 6.37e6.04 (m, 4H), 3.80e3.67 (m, 6H), 3.51 (m, 2H), 2.63 (m,
(400 MHz, CDCl3)
d
¼8.97 (br s, 1H), 7.57 (dd, J¼7.6 and 1.7 Hz, 1H),
2H), and 1.54e1.24 (m, 8H); 13C NMR (100 MHz, CDCl3, typical
7.17e7.13 (m, 1H), 6.97 (m, 2H), 6.58 (d, J¼2.2 Hz, 1H), 3.90 (s, 3H),
signals)
d
¼157.15, 157.07, 157.00, 156.98, 156.91, 149.80, 149.78,
3.40 (m,1H), 3.02 (m,1H),1.84e1.74 (m, 4H), and 1.50e1.41 (m, 4H);
149.62, 149.48, 149.47, 149.45, 149.15, 149.13, 146.07, 146.05, 145.88,
145.73, 145.71, 145.55, 140.93, 140.89, 140.74, 140.69, 140.38, 140.35,
140.32, 140.28, 140.04,139.86, 139.77,135.86, 135.79, 135.66,135.54,
135.16, 134.28, 134.00, 133.83, 132.62, 132.57, 132.36, 132.26, 131.88,
131.82, 131.65, 131.57, 129.94, 129.87, 129.58, 129.36, 129.01, 128.88,
128.84, 128.70,128.64,128.56,128.44,128.38, 128.03, 127.94,127.91,
127.80, 121.45, 121.36, 121.11, 120.18, 120.15, 120.10, 120.06, 111.01,
110.77, 110.46, 110.44, 110.22, 55.78, 55.76, 55.71, 55.55, 55.46,
55.43, 55.38, 55.25, 35.31, 35.28, 35.21, 34.06, 26.37, 26.27, 26.05,
13C NMR (100 MHz, CDCl3)
d
¼154.88,128.58, 128.06,126.09,125.94,
122.46, 121.04, 120.18, 111.24, 108.07, 55.50, 28.20, 27.61, 27.57, and
27.41; IR (KBr disk) nmax 3452 (NH), 3059, 3012, 2935, 2858 cmꢀ1
;
MS (70 eV) m/z (relative intensity) 253 (Mþ, 82) and 224(MþꢀC2H4,
100); HRMS calcd for C19H19NO, 253.1467; found 253.1467.
4.2.7. BCOD-fused triphenyldipyrromethene. To a solution of 3a
(338 mg,1.53 mmol) and benzaldehyde (0.077 ml, 0.77 mmol) in dry
CH2Cl2 (10 ml) were added three drops of TFAunder a N2 atmosphere.
The mixture was refluxed overnight in the dark. After cooling to room
temperature, DDQ (360 mg, 1.63 mmol) was added, and the mixture
was stirred overnight. The reaction mixture was poured into water
and extracted with CHCl3. The organic extract was washed succes-
sively with saturated aqueous NaHCO3, water, and brine; dried over
Na2SO4; and concentrated under a reduced pressure. The residue was
purified by column chromatography on alumina with hexaneeEtOAc
to give the dipyrromethene (321 mg, 79%): red crystals: mp
25.89, and 25.57; UVevis (CH2Cl2) labs nm (log e) 395 (4.07) and
556 (4.79); MS (FAB) m/z 636 [M]þ, 617 [MꢀF]þ, and 580
[Mꢀ2C2H4]þ. Anal. Calcd for C41H35BF2N2O2: C, 77.36; H, 5.54; N,
4.40. Found: C, 77.61; H, 5.49; N, 4.41.
4.2.10. BODIPY 9. To a solution of 8 (196 mg, 0.775 mmol) and
benzaldehyde (0.040 ml, 0.40 mmol) in dry CH2Cl2 (5 ml) was added
a drop of TFA under an Ar atmosphere. The mixture was refluxed for
18 h in the dark. After cooling to room temperature, DDQ (186 mg,
0.820 mmol) was added, and the mixture was stirred for additional
2h. Afteraddition of(i-Pr)2EtN (0.185 ml) andBF3$OEt2 (0.30 ml), the
mixture was refluxed for 30 min. The reaction mixture was poured
into water and extracted with CHCl3. The organic extract was
washed successively with saturated aqueous NaHCO3, water, and
brine; dried over Na2SO4; and concentrated under a reduced pres-
sure. The residue was purified by column chromatography on silica
gel with CH2Cl2. Recrystallization from CH2Cl2eMeOH gave 9
(103 mg, 42%) as a rotamer (38:62): red crystals; mp >350 ꢂC
198.7e199.2 ꢂC;1H NMR (400 MHz, CDCl3)
d
¼13.30(brs,1H), 7.86 (m,
4H), 7.59e7.45 (m, 9H), 7.36 (m, 2H), 6.46e6.41 (m, 2H), 6.17e6.12 (m,
2H), 4.28e4.26 (m, 2H), 2.55e2.53 (m, 2H), 1.48e1.44 (m, 4H), and
1.24e1.20 (m, 4H); 13C NMR (100 MHz, CDCl3)
d¼149.35, 149.27,
145.87, 145.82, 137.82, 137.78, 137.27, 137.25, 136.90, 135.39, 135.33,
134.98, 134.28, 134.25, 133.91, 133.89, 129.94, 129.67, 129.34, 128.64,
128.44, 127.90, 127.88, 127.81, 127.70, 127.62, 126.96, 126.94, 35.37,
34.85, 26.60, 26.55, 25.94, and 25.90; MS (FAB) m/z 529 [MþH]þ and
500 [MþHꢀ2C2H4]þ. Anal. Calcd. For C39H32N2$H2O C, 85.68; H, 6.27;
N, 5.12. Found: C, 85.52; H, 6.00; N, 5.07.
(decomp.); 1H NMR (400 MHz, CDCl3)
d
¼7.77 (d, J¼7.6 Hz, 1H),
7.61e7.44 (m, 6H), 7.32e7.25 (m, 2H), 7.04e6.84 (m, 4H), 3.76 and
4.2.8. BODIPY 4a. A solution of BCOD-fused triphenyldipyrrome-
thene (89 mg, 0.17 mmol) and (i-Pr)2EtN (0.088 ml) in toluene (5 ml)
was stirred at room temperature for 30 min. After addition of
BF3$OEt2 (0.134ml), the mixturewas refluxed for 15 min. The mixture
was poured into water and extracted with CHCl3. The organic extract
was washed successively with water and brine, dried over Na2SO4,
and concentrated under a reduced pressure. The residue was purified
by column chromatography on silica gel with CHCl3 to give 4a (97 mg,
99%): red crystals; mp >180 ꢂC (decomp.); 1H NMR (400 MHz, CDCl3)
3.67 (s, 6H), 2.61 (m, 2H), 1.75 (m, 2H), and 1.76e1.05 (m, 16H); 13C
NMR (100 MHz, CDCl3, typical signals)
d
¼157.16, 157.11, 148.27,
148.09, 147.40, 147.05, 139.96, 138.08, 135.49, 135.46, 132.50, 132.45,
132.40, 131.77, 131.70, 130.33, 129.86, 129.83, 129.45, 129.24, 128.76,
128.72, 128.67, 128.63, 127.81, 127.77, 127.69, 126.83, 121.70, 121.40,
120.15,120.09, 110.65, 110.47, 55.57, 55.38, 29.37, 27.76, 26.57, 26.48,
26.44, 26.43, 26.34, 26.23, 26.15, and 26.03; UVevis (CH2Cl2) labs nm
(log e) 382 (4.09) and 550 (4.81); MS (70 eV) m/z (relative intensity)
641 (Mþ, 100). Anal. Calcd for C41H39BF2N2O2$1/4H2O: C, 76.34; H,
d
¼7.66e7.33 (m, 15H), 6.36 (m, 2H), 6.10 (m, 2H), 3.82 (m, 2H), 2.66
6.17; N, 4.34. Found: C, 76.08; H, 6.15; N, 4.26.
(m, 2H), 1.41 (m, 4H), and 1.25 (m, 4H); 13C NMR (100 MHz, CDCl3)
d
¼150.98,149.31,140.77,139.11,135.75,134.98,134.01,133.89,131.82,
4.2.11. BODIIs 5. BCOD-fused BODIPYs 4a and 4b (ca. 10 mg each)
were heated at 210 ꢂC under a reduced pressure for 2 h in a glass
tube to give 5a and 5b in quantitative yields.
129.58, 129.54, 129.50, 129.47, 129.20, 129.15, 128.91, 128.58, 128.11,
128.02, 127.96, 127.80, 35.35, 35.33, 33.55, 33.52, 26.39, 26.34, 26.00,
and 25.95; UVevis (CH2Cl2) labs nm (log e) 405 (4.05) and 558 (4.85);
MS (FAB) m/z 577 [MþH]þ, 558 [MþHꢀF]þ, 521 [MþHꢀ2C2H4]þ, and
502 [MþHeFe2C2H4]þ. Anal. Calcd. For C39H31BF2N2$3/4H2O: C,
79.39; H, 5.55; N, 4.75. Found: C, 79.43; H, 5.31; N, 5.05.
4.2.11.1. BODII 5a. Blue crystals; mp >350 ꢂC (decomp.); 1H
NMR (400 MHz, CDCl3)
d
¼7.80e7.78 (m, 4H), 7.74e7.68 (m, 3H),
7.64e7.62 (m, 2H), 7.52e7.43 (m, 8H), 7.11e7.02 (m, 4H), 6.23 (d,
J¼8.3 Hz, 2H); 13C NMR (100 MHz, CDCl3)
¼151.51, 136.27, 135.11,
d
4.2.9. BODIPY 4b. To a solution of 3b (531 mg, 2.11 mmol) and
benzaldehyde (0.110 ml, 1.10 mmol) in dry CH2Cl2 (10 ml) were
added three drops of TFA under an Ar atmosphere. The mixture was
refluxed for 20 h in the dark. After cooling to room temperature,
DDQ (345 mg, 1.56 mmol) was added, and the mixture was stirred
for additional 1 h. After addition of (i-Pr)2EtN (0.51 ml) and
BF3$OEt2 (0.80 ml), the mixture was refluxed for 30 min. The re-
action mixture was poured into water and extracted with CHCl3.
The organic extract was washed successively with saturated
aqueous NaHCO3, water, and brine; dried over Na2SO4; and con-
centrated under a reduced pressure. The residue was purified by
column chromatography on silica gel with CH2Cl2. Recrystallization
134.15, 130.99, 130.87, 130.12, 130.09, 130.06, 129.44, 129.29, 129.21,
128.89, 128.62, 127.97, 126.21, 124.51, 123.38, and 121.22; UVevis
(CH2Cl2) labs nm (log e) 338 (4.30), 351 (4.34), and 631 (5.01); MS
(MALDI-TOF) m/z 520 [M]þ. Anal. Calcd for C35H23BF2N2: C, 80.78;
H, 4.45; N, 5.38. Found: C, 80.56; H, 4.15; N, 5.64.
4.2.11.2. BODII 5b. Blue crystals (41:59 rotamer mixture); mp
187.7e188.0 ꢂC (decomp.); 1H NMR (400 MHz, CDCl3)
d
¼7.73e7.58
(m, 6H), 7.52 (m,1H), 7.40 (m, 2H), 7.28e7.23 (m, 2H), 7.08e6.96 (m,
8H), 6.26e6.19 (m, 2H), 3.75 and 3.68 (s, 6H); 13C NMR (100 MHz,
CDCl3, typical signals)
135.27, 135.24, 133.62, 132.43, 132.40, 132.36, 131.93, 131.87, 131.41,
d
¼157.56, 157.51, 149.19, 148.92, 136.06,

Y. Tomimori et al. / Tetrahedron 67 (2011) 3187e3193
3193
131.39, 131.32, 130.66, 130.64, 129.27, 129.25, 129.21, 129.10, 129.02,
128.96, 128.89, 128.18, 126.09, 123.82, 123.34, 123.26, 121.05, 121.03,
120.24, 120.17, 120.06, 120.01, 111.00, 110.85, 55.82, and 55.62;
Education, Culture, Sports, Science and Technology. The authors
thank Venture Business Laboratory, Ehime University, for permis-
sion in obtaining the MALDI-TOF mass spectra. We appreciate the
Nippon Synthetic Chem. Ind. (Osaka Japan) for a gift of ethyl iso-
cyanoacetate, which was used in preparation of the starting
pyrroles.
UVevis (CH2Cl2) labs nm (log e) 348 (4.33) and 617 (5.04); MS (FAB)
m/z 580 [M]þ and 561 [MꢀF]þ. Anal. Calcd for C37H27BF2N2O2: C,
76.56; H, 4.69; N, 4.83. Found: C, 76.59; H, 4.72; N, 4.79.
4.2.12. O-Chelated BODII 10. 1.0 M solution of BBr3 in CH2Cl2 (1.2 ml)
was added dropwise to 5b (53 mg, 0.092 mmol) over 1 min at 0 ꢂC.
The solution was allowed to warm to room temperature and stirred at
the same temperature for 4 h. After filtration with a Celite pad, the
filtrate was concentrated under a reduced pressure. The residue was
purified by column chromatography on silica gel with CH2Cl2. Re-
crystallization from CH2Cl2eMeOH gave 10 (43 mg, 91%): green
crystals; mp >350 ꢂC (decomp.); 1H NMR (400 MHz, CDCl3)
Supplementary data
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2011.03.016. These data include MOL files and
InChIKeys of the most important compounds described in this
article.
d
¼8.28e8.22 (m, 4H), 7.70e7.66 (m, 5H), 7.42e7.12 (m, 8H), 7.00 (d,
References and notes
J¼8.1 Hz, 2H), and 6.59 (d, J¼8.3 Hz, 2H); 13C NMR (100 MHz, CDCl3)
d
¼153.47, 142.30, 134.51, 134.33,131.92,129.36, 129.33,129.21, 128.81,
1. (a) Wada, M.; Ito, S.; Uno, H.; Murashima, T.; Ono, N.; Urano, T.; Urano, Y. Tet-
rahedron Lett. 2001, 42, 6711e6713; (b) Descalzo, A. B.; Xu, H.-J.; Xue, Z.-L.;
Hoffmann, K.; Shen, Z.; Weller, M. G.; You, X.-Z.; Rurack, K. Org. Lett. 2008, 10,
1581e1584; (c) Okujima, T.; Tomimori, Y.; Nakamura, J.; Yamada, H.; Uno, H.;
Ono, N. Tetrahedron 2010, 66, 6895e6900; (d) Shen, Z.; Rohr, H.; Rurack, K.;
Uno, H.; Spieles, M.; Schulz, B.; Reck, G.; Ono, N. Chem.dEur. J. 2004, 10,
128.25, 125.87, 125.12, 122.92, 121.37, 120.62, 120.33, and 119.64;
UVevis (CH2Cl2) labs nm (log e) 313 (4.49), 365 (4.44), 651 (4.31), and
711 (4.96); MS (FAB) m/z 512 [M]þ. Anal. Calcd for C35H21BN2O2$1/
4H2O$1/2CH2Cl2: C, 76.23; H, 4.05; N, 5.01. Found: C, 76.39; H, 4.13; N,
5.01. HRMS calcd for C35H22BN2O2, 513.1774; found 513.1781.
€
4853e4871.
2. (a) Burghart, A.; Kim, H.; Welch, B. M.; Thoresen, H. L.; Reibenspies, J.; Burgess,
K. J. Org. Chem. 1999, 64, 7813e7819; (b) Wakamiya, A.; Sugita, N.; Yamaguchi,
S. Chem. Lett. 2008, 37, 1094e1095.
3. (a) Umezawa, K.; Nakamura, Y.; Makino, H.; Citterio, D.; Suzuki, K. J. Am. Chem.
Soc. 2008, 130, 1550e1551; (b) Umezawa, K.; Matsui, A.; Nakamura, Y.; Citterio,
D.; Suzuki, K. Chem.dEur. J. 2009, 1096e1106.
4.2.13. O-Chelated BODIPY 11. BBr3 (1.0 M solution) in CH2Cl2(1.0 ml)
was added dropwise to 9 (49 mg, 0.077 mmol) over 1 min at 0 ꢂC.
The solution was allowed to warm to room temperature and stirred
at the same temperature for 3h. After filtration with a Celite pad, the
filtrate was concentrated under a reduced pressure. The residue was
purified by column chromatography on silica gel with CH2Cl2 fol-
lowed by recrystallization from CH2Cl2eMeOH to give 11 (34 mg,
78%): green crystals; mp >350 ꢂC (decomp.); 1H NMR (400 MHz,
4. Chen, J.; Burghart, A.; Derecskei-Kovacs, A.; Burgess, K. J. Org. Chem. 2000, 65,
2900e2906.
5. (a) Ulinch, G.; Goeb, S.; Nicola, A. D.; Retailleau, P.; Ziessel, R. Synlett 2007,
1517e1520; (b) Goeb, S.; Ziessel, R. Org. Lett. 2007, 9, 737e740; (c) Ziessel, R.; Goze,
ꢁ
C.; Ulrich, G.; Cesario, M.; Retailleau, P.; Harriman, A.; Rostron, J. P. Chem.dEur. J.
2005, 11, 7366e7378.
6. Tahtoui, C.; Thomas, C.; Rohmer, F.; Koltz, P.; Duportail, G.; Mely, Y.; Bonnet, D.;
Hibert, M. J. Org. Chem. 2007, 72, 269e272.
ꢁ
CDCl3)
d¼7.89e7.58 (dd, J¼7.8 Hz, 1.5 Hz, 2H), 7.54e7.44 (m, 5H),
7.30e7.26 (m, 2H), 7.03e6.99 (m, 2H), 6.92 (dd, J¼8.3 Hz, 1.0 Hz, 2H),
3.52 (m, 2H), 2.08 (m, 2H), 1.82e1.75 (m, 2H), 1.66e1.49 (m, 6H),
1.45e1.37 (m, 2H), 1.33e1.23 (m, 2H), 1.19e1.11 (m, 2H), and
7. a Kim, H.; Burghart, A.; Welch, B. M.; Reibenspies, J.; Burgess, K. Chem. Commun.
1999, 1889e1890; (b) Ikeda, C.; Maruyama, T.; Nabeshima, T. Tetrahedron Lett.
2009, 50, 3349e3351; (c) Parhi, K. A.; Kung, M.-P.; Ploessl, K.; Kung, F. K. Tet-
rahedron Lett. 2008, 49, 3395e3399; (d) Kubo, Y.; Minowa, Y.; Shoda, T.;
Takeshita, K. Tetrahedron Lett. 2010, 51, 1600e1602.
8. a Ono, N.; Kuroki, K.; Watanabe, E.; Ochi, N.; Uno, H. Heterocycles 2004, 62,
365e373; (b) Uno, H.; Ito, S.; Wada, M.; Watanabe, H.; Nagai, M.; Murashima,
T.; Ono, N. J. Chem. Soc., Perkin Trans. 1 2000, 4347e4355.
0.95e0.88 (m, 2H); 13C NMR (100 MHz, CDCl3)
d¼154.31, 148.72,
142.28, 135.74, 134.53, 134.47, 131.14, 129.09, 129.04, 128.82, 127.92,
126.08, 120.39, 119.91, 119.64, 28.96, 28.39, 26.82, 26.29, 26.18, and
25.90; UVevis (CH2Cl2) labs nm (log e) 316 (4.64), 416 (4.02), and 626
9. Nagai, A.; Chujo, Y. Macromolecules 2010, 43, 193e200.
10. Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877e910.
(4.80); MS (FAB) m/z 572 [M]þ. Anal. Calcd for C39H33BN2O2$H2O: C,
79.32; H, 5.97; N, 4.74. Found: C, 79.22; H, 5.72; N, 5.09. HRMS calcd
for C39H33BN2O2, 572.2635; found 572.2646.
11. The diffraction data were corrected for Lorentz, polarization, and absorption
effects. The structures were solved with SIR200412 and refined with SHELXL-
97.13 All calculations were performed by using the Crystal Structure crystallo-
graphic software package.14 The data (excluding structure factors) for the
structure in this paper have been deposited with the Cambridge Crystallo-
graphic Data Center. Copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: þ44 1223
336033 or e-mail: deposit@ccdc.cam.ac.uk]
12. SIR2004: an improved tool for crystal structure determination and refinement
Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; De Caro,
L.; Giacovazzo, C.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 2005, 38, 381e388.
13. SHELXL-97: Program for Solution and Refinement of Crystal Structures from
4.2.14. DimethoxydihydroBODII 12. Yellow crystals; UVevis
(CH2Cl2) labs nm 282, 411, and 434; MS (FAB) m/z 574 [M]þ, 543
[MꢀMeO]þ, and 512 [Mꢀ2MeO]þ; HRMS calcd for C37H28BN2O4,
575.2142; found 575.2139.
Acknowledgements
€
€
Diffraction Data, University of Gottingen, Gottingen, Germany; ‘A short history
of SHELX’ Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112e122.
14. Rigaku. Crystal Structure. Version 3.8.2 or 4.0.1; Rigaku Corporation: Tokyo,
Japan, 2010.
This work was partially supported by Grants-in-Aid for the
Scientific Researches on Innovative Areas (No 21108517,
p-Space to
H.U.) and C (No 20550047 to H.U.) from the Japanese Ministry of
15. Fukuda, T.; Ogi, Y.; Kobayashi, N. Chem. Commun. 2006, 159e161.