Development of non-symmetric thiophene-fused BODIPYs

Article abstract of DOI:10.1016/j.tet.2012.09.011

A series of non-symmetric BODIPYs containing thieno[3,2-b]pyrrole moiety were synthesized in 21-63% yields. The absorption and emission maxima covered from the visible green to red region (λ_abs=532-647 nm; λ_em=547-664 nm; Φ_f

Full text of DOI:10.1016/j.tet.2012.09.011

Tetrahedron 68 (2012) 9795e9801
Contents lists available at SciVerse ScienceDirect
Tetrahedron
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Development of non-symmetric thiophene-fused BODIPYs
,
a
,
,
,b,
Xin-Dong Jiang a , Houjun Zhang y, Yuanlin Zhang a y, Weili Zhao a
*
*
a Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004, China
b School of Pharmacy, Fudan University, Shanghai 201203, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 April 2012
Received in revised form 27 August 2012
Accepted 4 September 2012
Available online 11 September 2012
A series of non-symmetric BODIPYs containing thieno[3,2-b]pyrrole moiety were synthesized in 21e63%
yields. The absorption and emission maxima covered from the visible green to red region
(
labs¼532e647 nm; lem¼547e664 nm; Ff¼0.19e0.45). X-ray analysis indicated that the SeC bond
ꢀ
lengths were shorter than those of thienopyrrole and thienohelicene by 0.03e0.05 A. The crystal packing
pattern suggested that strong interaction, intermolecular CeH/F interaction, and weak S/ in-
teraction existed. The tunable emission was achieved by structure modifications. Oxidation of BODIPY
lem¼547 nm) with m-CPBA generated thiophene-1,1-dioxide derived BODIPY lem¼528 nm).
Knoevenagel-type condensation of BODIPY with N,N-dimethylaminobenzaldehyde led to BODIPY
lem¼693 nm) with extended conjugation.
p
e
p
p
Keywords:
Fluorescent
BODIPY
Dye
X-ray
(
(
(
Ó 2012 Elsevier Ltd. All rights reserved.
Thiophene-fused
1. Introduction
many research studies in electro-optical devices.4 Our recent re-
search interest lies in the novel BODIPY family of fluorescent dyes.5
We are interested in thieno[3,2-b]pyrroles derived BODIPYs as
bright and tunable fluorescent dyes. During the preparation of this
manuscript, a thieno[3,2-b]pyrrole-containing symmetric BODIPY
2 carrying bromine atoms was reported by You et al. as a photo-
dynamic therapy reagent.6 Herein we communicate our studies on
thieno[3,2-b]pyrrole-containing non-symmetric BODIPYs as highly
fluorescent dyes.
4,40-Difluoro-4-bora-3a,4a-diaza-s-indacene (abbreviated as
BODIPY) dyes are well-known and widely used fluorescent dyes
with intense absorption, and high quantum yields. BODIPYs acted
as good candidates for biological labeling, photonic molecular
systems, laser dyes, organogelators, and light-emitting devices.1
Very recently, furo[3,2-b]pyrrole derived BODIPY 1 was declared
as a fluorescent dye with long absorption and high brightness,
which is insensitive to solvent polarity (Fig. 1).2 Thieno[3,2-b]pyr-
roles are useful scaffolds of biologically active compounds, photo-
chromic compounds, and organic field effect transistors.3 The
unique electronic properties of thiophene moiety have attracted
2. Result and discussion
The precursors thieno[3,2-b]pyrrole-5-carbaldehyde 6a and 6b
were synthesized in three steps from thiophene-2-carbaldehydes
3a and 3b, respectively, as outlined in Scheme 1. Non-symmetric
Fig. 1. Reported heterocycle fused [3,2-b]pyrroles derived BODIPYs.
* Corresponding authors. Tel./fax: þ86 (0)378 3881358 (X.-D.J); tel.: þ86 (0)378
3881358/(0)21 51980111; fax: þ86 (0)378 3881358/(0)21 51980111 (W.Z); e-mail
addresses: xdjiang@henu.edu.cn, jiangxindong@gmail.com (X.-D. Jiang), zhaow@
henu.edu.cn (W. Zhao).
Scheme 1. Synthetic route of thieno[3,2-b]pyrrole-5-carbaldehyde.
y
Tel./fax: þ86 (0)378 3881358.
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.09.011

9796
X.-D. Jiang et al. / Tetrahedron 68 (2012) 9795e9801
thiophene-fused BODIPYs 8ae9d were obtained in 21e63% yields
by the reaction of pyrrole carbaldehyde 6 with another pyrrole
moiety 73e,5d (Scheme 2).7 It was found that the yields of the dyes
8ae8d from 6a were generally higher than those of the corre-
sponding dyes 9ae9d from 6b with a phenyl group.
similar to those found for the reported BODIPYs. The sp3 hybridized
boron center appears as slightly distorted tetrahedron geometry
with the angles N1eB1eN2 of 106.8ꢀ and F1eB1eF2 of 109.0ꢀ. The
side view (B) of 8a shows a flat plane. In the crystal packing of 8a,
the neighboring BODIPY molecules are assembled by in-
Scheme 2. Synthesis of non-symmetric thiophene-fused BODIPYs 8 and 9.
The structure of dye 8a is confirmed by single crystal X-ray
analysis (Fig. 2). The SeC distances (1.718(2) and 1.701(4) A) in 8a
termolecular CeH/F interaction to form a one-dimensional chain
along the c axis (top view (C), side view (D)). The average CeH/F
ꢀ
ꢀ
are found to be shorter than those of the thienopyrrole and thie-
distance (2.424 A) is less than the sum of the van der Waals radii for
8
9
ꢀ
ꢀ
ꢀ
nohelicene by 0.03e0.05 A. Other bond lengths of 8a are very
hydrogen and fluorine (2.62 A) by 0.2 A, indicating that there is
Fig. 2. Molecular structure and conformation for 8a. Carbon, bꢀoron, nitrogen, fluorine, and sulfur atoms are depicted with thermal ellipsoids set at the 30% probability level. Top
ꢀ
view (A). Side view (B). Selected bond lengths (A) and angles ( ) for 8a: N1eC1, 1.375(3); N1eC4, 1.356(4); N2eC7, 1.385(3); N2eC10, 1.337(3); N1eB1, 1.520(3); N2eB1, 1.539(3);
B1eF1, 1.373(3); B1eF2, 1.384(3); S1eC3, 1.718(2); S1eC6, 1.701(4); C3eC4, 1.386(3); C4eC5, 1.390(3); C5eC6, 1.347(4); N1eB1eN2, 106.80(19); F1eB1eF2, 109.0(2); C3eS1eC6,
ꢀ
90.41(13). A one-dimensional chain of 8a viewed along the c axis. Top view (C). Side view (D). Selected bond lengths (A) for 8a: CeH/F, 2.424; S/C, 3.715.

X.-D. Jiang et al. / Tetrahedron 68 (2012) 9795e9801
9797
a strong
p
e
p
interaction within the chain. In addition, a weak S/
p
the parent 9d, and clearly differentiated from BODIPY 9d in NMR
(see: Experiment section).11 When treated with 4,4-
dimethylaminobenzaldehyde in the presence of acetic acid, piper-
idine, and molecular sieves in toluene, 8a undertook a Knoevena-
gel-type condensation reaction and generated dye 12 in 20% yield
(Scheme 4).12
interaction could also be observed among a and b axes, for exam-
ple: the S/C distance is 3.715 A.
The absorption and emission spectra of 8ae9d were outlined in
Fig. 3 and Table 1 respectively. BODIPYs 8ae9d absorb and emit
from the visible green to red region
8
ꢀ
(labs¼532e647 nm;
lem¼547e664 nm). In the class of 8, 8b possesses large Stokes shift
(34 nm) and 8c has a high quantum yield (Ff¼0.45) compared with
2 (Ff¼0.37) (entries 2 and 3 of Table 1).6 For 9 carrying a phenyl
substituent on thiophene, about 40 nm of bathochromic shift was
noticed compared to 8, however, with lower fluorescent quantum
yield presumably due to the rotation of the phenyl group and the
increased internal conversion. Notably, 9c (lem¼662 nm) and 9d
The absorption and emission spectra of 8a, 10, and 12 as well as
spectroscopic data of 10e12 are shown and collected in Fig. 4 and
Table 2 respectively. As expected, oxidation of thiophene led to the
hypsochromic shift of the absorption and emission (Fig. 4, and
entries 1 and 2 of Table 2) because of the reduced electron donating
ability. Extension of conjugation led to a dramatic bathochromic
shift (146 nm), however, with decreased fluorescent quantum yield
(Fig. 4, and entry 3 of Table 2).
(
lem¼664 nm) carrying conformationally restricted pyrrole moiety
have long absorption,10 large absorption coefficients, and maintain
relatively good fluorescence quantum yields.1b,c,6
For the clear view of the effect of structure modification, pic-
tures of the synthesized compounds in chloroform were taken
Fig. 3. (a) Normalized absorption; and (b) fluorescence spectra of 8ae9d in CHCl3 at 298 K.
Table 1
under a normal condition and irradiation as well (Fig. 5). All the
BODIPYs prepared exhibited relatively vivid bright fluorescence
emission. The relatively distinct colors for individual dyes are dif-
ferentiated by naked eye.
Spectroscopic data of 8 and 9 in CHCl3 at 298 K
Entry Dye labs (nm) lem (nm) Stokes
Ff
3
(Mꢁ1 cmꢁ1
)
Fwhm (nm)
shift (nm)
1
2
3
4
5
6
7
8
8a 532
8b 570
547
604
618
618
588
631
662
664
15
34
13
12
17
20
17
17
0.34 53,800
0.41 42,100
0.45 64,200
0.42 82,000
0.32 99,200
0.38 85,300
0.20 118,000
0.19 143,000
34
47
28
27
32
39
33
32
8c
605
3. Conclusion
8d 606
9a 571
9b 611
Utilizing the thieno[3,2-b]pyrrole, we successfully synthesized
a
series of non-symmetric thiophene-fused BODIPYs 8ae9d
9c
645
9d 647
in 21e63% yields
(
labs¼532e647 nm; lem¼547e664 nm;
Ff¼0.19e0.45). The structure of 8a was confirmed by X-ray analysis,
Stokes shift: the difference in wavelength between positions of the band maxima of
the emission and absorption spectra.
Fwhm: full width half maximum.
and the SeC distance was shorter than that of thienopyrrole and
ꢀ
thienohelicene by 0.03e0.05 A. The tunable emission wavelengths
were achieved by the modification of 8a. BODIPY 8a (lem¼547 nm)
reacted with m-CPBA to give the thiophene-1,1-dioxide derivative 10
Non-symmetric thiophene-fused BODIPYs are selected to be
modified, due to quantity amounts and reaction sites of non-
symmetric BODIPYs.1b,c,2,6 When 8a and 9d were treated with m-
CPBA, the thiophene-1,1-dioxide derivatives (10: 18%; 11: 100%)
were successfully obtained (Scheme 3).11 Unfortunately, dye 10 was
unstable to air, moisture, and solvent. BODIPY 11 is more polar than
(
lem¼528 nm), along with the blue shift (19 nm). BODIPY 8a un-
dertook a Knoevenagel-type condensation to give the NIR BODIPY 12
(
lem¼693 nm) and the remarkable redshift (146 nm) was achieved.
Importantly, the absorption and emission maxima of such
thiophene-fused BODIPYs covered the visibleenear-infrared region
(labs¼518e647 nm; lem¼528e693 nm); in crystal packing of 8a,
Scheme 3. Oxidation of thieno-containing BODIPY with m-CPBA.

9798
X.-D. Jiang et al. / Tetrahedron 68 (2012) 9795e9801
Scheme 4. Synthesis of BODIPY 12 by Knoevenagel-type condensation.
Fig. 4. The spectra of normalized absorption (a) and fluorescence (b) of 8a (black), 10 (blue), and 12 (red) in CHCl3 at 298 K.
Table 2
million downfield from Me4Si, determined by residual chloroform
(d
¼7.26 ppm). 13C NMR spectra were recorded on a VARIAN Mer-
Spectroscopic data of 10, 11, and 12 in CHCl3 at 298 K
Entry Dye labs (nm) lem (nm) Stokes Ff
3
(Mꢁ1 cmꢁ1
)
Fwhm (nm)
cury 100 MHz spectrometer in CDCl3, all signals are reported in
shift (nm)
10
23
51
parts per million with the internal chloroform signal at
d 77.0 ppm
1
2
3
10 518
11 630
12 642
528
653
693
da da
50
72
69
as standard. Mass spectrometric measurements were performed by
the mass spectrometry service of the ETHZ on a Bruker Reflex
MALDI as matrix (20 kV). All reactions were carried out under N2.
Tetrahydrofuran (THF) was freshly distilled from sodium. Other
solvents were distilled over CaH2. Merck silica gel 60 was used for
the column chromatography.
0.14 130,00
0.09 103,000
a
Not measured due to the instability of 10.
Fluorescence spectra were recorded on FluoroSENS spectro-
photometer and are reported. UV/vis spectra were recorded on
PerkineElmer Lambda 35 UV/Vis spectrophotometer at room
temperature. The fluorescence quantum yields (Ff) of the BODIPY
systems were calculated using the following relationship:
Ff
¼
Fref FsamplAref ns2ampl=Fref Asamplnr2ef
Here, F denotes the integral of the corrected fluorescence
spectrum, A is the absorbance at the excitation wavelength, and n is
the refractive index of the medium, ref and sampl denote param-
eters from the reference and unknown experimental samples, re-
spectively. The reference systems used were Rhodamine 6G as
standard [Ff¼0.95, lex¼530 nm, in ethanol]14 for 8a, 8b, and 9a,
and Nile blue as standard [Ff¼0.27, lex¼625 nm, 0.5% (v/v) 0.1 M
HCl in ethanol]15 for the other compounds.
Fig. 5. Photoimages of 8ae9d, 10, 11, and 12 under normal room illumination (upper
row) and UV light (bottom row) in CHCl3 at 298 K (lex¼365 nm).
a strong
pep interaction, intermolecular CeH/F interaction along c
axis, andaweak S/
p
interactionalong a and b axesexited.Suchtypes
of compounds might be used as novel organic functional materials.13
Further modifications of these compounds and their applications in
imaging and photo-electronic device studies are in progress.
4.2. X-ray crystal structure determinations of compound 8a
4. Experiment section
A single crystal of compound 8a was obtained by accurately
controlling the sublimation temperature. The X-ray crystal struc-
4.1. General method
ture analyses were made on a Bruker SMART CCD diffractor, using
ꢀ
graphite-monochromated MoK
a
radiation (l) 0.7107 A. The data
1H NMR spectra were recorded on a VARIAN Mercury 400 MHz
were collected at 298 K and the structures were refined by full-
spectrometer. 1H NMR chemical shifts (
d) are given in parts per
matrix least-squares on F2. The computations were performed

X.-D. Jiang et al. / Tetrahedron 68 (2012) 9795e9801
9799
with SHELEX-97 program.16 CCDC 847774 (compound 8a) contains
the supplementary crystallographic data.
J¼4.2 Hz,1H), 7.17 (s, 1H), 7.01 (d, J¼4.2 Hz,1H); 13C NMR (100 MHz,
CDCl3)
d 180.1, 144.3, 137.0, 132.8, 125.5, 113.7, 111.4.
4.2.1. Crystallographic data for 8a. C13H11BF2N2S, M¼276.11,
4.3.6. 2-Phenyl
thieno[3,2-b]pyrrole-5-carbaldehyde
(6b).
¼90ꢀ,
Compound 5b (20.1 mg, 0.088 mmol) was used as the starting
ꢀ
monoclinic, a¼7.1072(1), b¼12.2978(2), c¼14.0570(1) A,
a
3
b
¼92.399(2)ꢀ,
g
¼90 , V¼1227.55(3) A , T¼298(2) K, space group
material, and 6b was obtained as a yellow solid (7.0 mg, 35%). 1H
ꢀ
ꢀ
P21/c, Z¼4, data/restraints/parameters¼2169/0/175, R1¼0.0431
NMR (400 MHz, CDCl3)
J¼7.2 Hz, 2H), 7.41 (t, J¼7.2 Hz, 2H), 7.36 (t, J¼7.2 Hz, 2H), 7.22 (s,
1H), 7.15 (s, 1H); 13C NMR (100 MHz, CDCl3)
179.4, 151.4, 144.1,
d 9.58 (s, 1H), 9.41 (br s, 1H), 7.64 (d,
(I>2
s
(I)), wR2 (all data)¼0.1396, GOF¼0.927.
d
136.5, 134.6, 129.1, 128.5, 126.0, 125.8, 113.5, 106.9.
4.3. Synthesis
4.3.7. BODIPY (8a). Under N2, to a stirred solution of 6a (66.5 mg,
4.3.1. Ethyl thieno[3,2-b]pyrrole-5-carboxylate (4a).17 A solution of
sodium ethoxide (8.17 g, 120 mmol, 20 wt % in ethanol) was added
dropwise into a mixture of 3a (2.8 mL, 30 mmol) and ethyl azidoa-
cetate (15.4 g, 120 mmol) in anhydrous ethanol (50 mL) at ꢁ10 ꢀC
and stirred for 4 h at room temperature. Excess amount of saturated
aqueous NH4Cl solution was added. The mixture was extracted with
ethyl acetate (2ꢂ80 mL), the organic layer was washed with brine
(2ꢂ60 mL), and dried over anhydrous Na2SO4. After removing the
solvents by evaporation, the resulting residue was dissolved in tol-
uene (30 mL) and heated to reflux for 1 h. After cooling, the solvent
was evaporated. The residue was separated by column chromatog-
raphy (n-hexane/CH2Cl2¼2:1) to afford 4a as white solid (2.93 g,
0.44 mmol) and 2,4-dimethylpyrrole (45.0
mL, 0.44 mmol) in
CH2Cl2 (5 mL) was added POCl3 (40.0
m
L, 0.44 mmol) at 0 ꢀC. When
TLC analysis showed the reaction was over, Et3N (0.61 mL,
4.4 mmol) was added at 0 ꢀC and stirred for 10 min. BF3$OEt2
(0.56 mL, 4.4 mmol) was added to the mixture. The reaction mix-
ture was stirred for 12 h at room temperature, quenched with
saturated aqueous NaHCO3, extracted with CH2Cl2, washed with
brine, dried over Na2SO4, and purified by chromatography column
(CH2Cl2/n-hexane¼1:1) to afford BODIPY 8a as coppery solid
(69.9 mg, 58%). 1H NMR (400 MHz, CDCl3)
d
7.51 (d, J¼5.2 Hz, 1H),
7.20 (s, 1H), 7.14 (d, J¼5.2 Hz, 1H), 6.97 (s, 1H), 6.18 (s, 1H), 2.62 (s,
3H), 2.27 (s, 3H); 13C NMR (100 MHz, CDCl3)
162.3, 155.7, 145.4,
d
50%). 1H NMR (400 MHz, CDCl3)
d
9.26 (br s, 1H), 7.32 (d, J¼5.2 Hz,
137.7, 136.9, 124.6, 121.7, 116.7, 113.4, 46.8, 15.3, 11.4, 8.6; HRMS-
MALDI (m/z): [M]þ calcd for C13H11BF2N2S: 276.0710; found:
276.0709.
1H), 7.14 (d, J¼0.8 Hz, 1H), 6.96 (dd, J¼5.2, J¼0.8 Hz, 1H), 4.38 (q,
J¼7.6 Hz, 2H), 1.39 (t, J¼7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d
161.7, 141.3, 129.4, 127.1, 124.8, 111.1, 107.5, 60.7, 14.5.
4.3.8. BODIPY (8b). Compound 6a (66.5 mg, 0.44 mmol) and 2,4-
diphenylpyrrole (96.5 mg, 0.44 mmol) were used as the starting
materials, and BODIPY 8b was obtained as gold metallic color solid
4.3.2. Ethyl 2-phenyl-4H-thieno[3,2-b]pyrrole-5-carboxylate
(4b). Compound 3b (78.3 mg, 0.4 mmol) was used as the starting
material, and 4b was obtained as yellow solid (23.8 mg, 24%). 1H
(82.9 mg, 48%). 1H NMR (400 MHz, CDCl3)
d
8.04 (d, J¼8.0 Hz, 2H),
NMR (400 MHz, CDCl3)
d
9.18 (br s, 1H), 7.62 (d, J¼7.2 Hz, 2H), 7.39
7.60 (d, J¼5.2 Hz, 1H), 7.60e7.45 (m, 8H), 7.42 (s, 1H), 7.15 (d,
(t, J¼7.2 Hz, 2H), 7.30 (t, J¼7.2 Hz, 1H), 7.18 (d, J¼0.8 Hz, 1H), 7.13 (d,
J¼5.2 Hz, 1H), 7.07 (s, 1H), 6.79 (s, 1H); 13C NMR (100 MHz, CDCl3)
J¼0.8 Hz, 1H), 4.38 (q, J¼7.6 Hz, 2H), 1.40 (t, J¼7.6 Hz, 3H); 13C NMR
d
139.8, 132.9, 131.9, 130.3, 129.5, 129.1, 128.9, 128.3, 119.7, 118.7,
(100 MHz, CDCl3)
d
161.5, 148.1, 141.6, 135.1, 128.9, 128.0, 126.6,
113.6, 31.9, 29.6, 22.6, 14.1; HRMS-MALDI (m/z): [M]þ calcd for
125.8, 124.2, 107.8, 107.0, 60.7, 14.5; HRMS-MALDI (m/z): [M]þ calcd
C23H15BF2N2S: 400.1053; found: 400.1043.
for C15H13NO2S: 271.0667; found: 271.0656.
4.3.9. BODIPY (8c). Compound 6a (33.3 mg, 0.22 mmol) and 4,5-
dihydro-7-methoxylbenzo[g]indole (43.8 mg, 0.22 mmol) were
used as the starting materials, and BODIPY 8c was obtained as blue
4.3.3. (4H-Thieno[3,2-b]pyrrol-5-yl)methanol (5a). To a stirred so-
lution of 4a (78.1 mg, 0.4 mmol) in anhydrous THF (10 mL) was
added LiAlH4 (30.4 mg, 0.8 mmol) slowly at 0 ꢀC. The mixture was
stirred at room temperature for 3 h and then cooled to 0 ꢀC. The
mixture was diluted with Et2O (5 mL), quenched with 15% aqueous
sodium hydroxide (0.03 mL). The organic layer was washed with
brine (2ꢂ10 mL), and dried over anhydrous Na2SO4. After removing
the solvents by evaporation, the resulting residue 5a was obtained
as a gray solid (61.3 mg, 100%), which was used for next step
metallic color solid (52.1 mg, 63%). 1H NMR (400 MHz, CDCl3)
d 8.78
(d, J¼8.8 Hz, 1H), 7.50 (d, J¼5.2 Hz, 1H), 7.20 (d, J¼5.2 Hz, 1H), 7.10
(s, 1H), 7.00 (dd, J¼8.8, 2.8 Hz, 1H), 6.94 (s, 1H), 6.87 (s, 1H), 6.83 (d,
J¼2.8 Hz, 1H); 13C NMR (100 MHz, CDCl3),
d 162.2, 157.3, 144.4,
139.3, 136.0, 131.7, 127.4, 124.7, 120.1, 115.3, 114.5, 113.6, 112.9, 55.4,
31.9, 30.5, 29.7, 29.4, 22.7, 22.4, 14.1; HRMS-MALDI (m/z): [M]þ
calcd for C20H15BF2N2OS: 380.0962; found: 380.0961.
without further purification. 1H NMR (400 MHz, CDCl3)
1H), 7.07 (d, J¼5.2 Hz, 1H), 6.88 (d, J¼5.2 Hz, 1H), 6.43 (s, 1H), 4.67
d 8.58 (br s,
4.3.10. BODIPY (8d). Compound 6a (33.3 mg, 0.22 mmol) and 4,5-
dihydro-7-methoxy-3-phenylbenzo[g]indole (60.6 mg, 0.22 mmol)
were used as the starting materials, and BODIPY 8d was obtained as
green metallic color solid (54.3 mg, 55%). 1H NMR (400 MHz, CDCl3)
(s, 1H); 13C NMR (100 MHz, CDCl3)
d 139.1, 136.3, 123.7, 111.1, 100.1,
58.7, 29.6; HRMS-MALDI (m/z): [MþH]þ calcd for C7H7NOS:
154.0327; found: 154.0320.
d
8.86 (d, J¼8.8 Hz, 1H), 7.53 (t, J¼6.8 Hz, 2H), 7.50 (d, J¼5.2 Hz, 1H),
4.3.4. (2-Phenyl-4H-thieno[3,2-b]pyrrol-5-yl)methanol
(5b).
7.49 (t, J¼6.8 Hz, 1H), 7.40 (d, J¼6.8 Hz, 2H), 7.22 (d, J¼5.2 Hz, 1H),
7.12 (s,1H), 7.02 (dd, J¼8.8, 2.8 Hz,1H), 6.91 (s,1H), 6.84 (d, J¼2.8 Hz,
1H), 3.90 (s, 3H), 2.92 (t, J¼6.4 Hz, 2H), 2.78 (t, J¼6.4 Hz, 2H); 13C
Compound 4b (25.8 mg, 0.095 mmol) was used as the starting
material, and 5b was obtained as a gray solid (20.1 mg, 92%),
which was used for next step without further purification.
NMR (100 MHz, CDCl3) d 162.2156.4,155.0,144.4,141.5,138.7,136.0,
132.0, 129.7, 128.8, 128.6, 124.6, 120.2, 115.3, 114.4, 113.6, 112.9, 55.4,
31.9, 30.6, 29.7, 22.7, 21.1, 14.1; HRMS-MALDI (m/z): [M]þ calcd for
C26H19BF2N2OS: 456.1276; found: 456.1274.
4.3.5. Thieno[3,2-b]pyrrole-5-carbaldehyde (6a). To a stirred solu-
tion of 5a (61.3 mg, 0.4 mmol) in CH2Cl2 (10 mL) was added man-
ganese dioxide (600 mg, 4 mmol). The reaction mixture was stirred
overnight, diluted with CH2Cl2 (10 mL), and filtered over Celite. The
filtrate was concentrated, and purified by chromatography column
(CH2Cl2/n-hexane¼1:1) to afford 6a as white solid (30.2 mg, 50%).
4.3.11. BODIPY (9a). Compound 6b (50.0 mg, 0.22 mmol) and 2,4-
dimethylpyrrole (22.7
mL, 0.22 mmol) were used as the starting
1H NMR (400 MHz, CDCl3)
d 10.0 (br s, 1H), 9.61 (s, 1H), 7.46 (d,
materials, and BODIPY 9a was obtained as green metallic color solid

9800
X.-D. Jiang et al. / Tetrahedron 68 (2012) 9795e9801
(16.3 mg, 21%). 1H NMR (400 MHz, CDCl3)
d
7.79 (d, J¼7.2 Hz, 2H),
presence of a small amount of activated 4 A molecular sieves. The
mixture was cooled to room temperature, quenched with water,
extracted with CH2Cl2, washed with brine, dried over Na2SO4,
evaporated, and purified by TLC (n-hexane/CH2Cl2¼1:1) to afford
12 as dark green solid (8.0 mg, 20%); HRMS-MALDI (m/z): [M]þ
calcd for C22H20BF2N3S: 407.1435; found: 407.1434.
ꢀ
7.43 (s, 1H), 7.41 (t, J¼7.2 Hz, 2H), 7.35 (t, J¼7.2 Hz, 1H), 7.16 (s, 1H),
6.96 (s, 1H), 6.17 (s, 1H), 2.63 (s, 3H), 2.28 (s, 3H); 13C NMR
(100 MHz, CDCl3)
d 162.0 156.6, 155.8, 144.5, 134.5, 129.1, 126.2,
123.4, 121.3, 116.8, 109.1, 31.9, 29.7, 22.7, 15.2, 14.1, 11.5; HRMS-
MALDI (m/z): [M]þ calcd for C19H15BF2N2S: 352.1013; found:
352.1012.
Acknowledgements
4.3.12. BODIPY (9b). Compound 6b (50.0 mg, 0.22 mmol) and 2,4-
diphenylpyrrole (48.2 mg, 0.22 mmol) were used as the starting
materials, and BODIPY 9b was obtained as green metallic color solid
This work was supported by the National Natural Science
Foundation of China (20872026), the Hi-Tech Research and De-
velopment Program of China (863 Plan, 2009AA02Z308), Shanghai
Pujiang Talent Plan Project (09PJD008), and Sino Swiss Science and
Technology Cooperation (SSSTC, EG 30-032010).
(22.9 mg, 22%). 1H NMR (400 MHz, CDCl3)
d
8.04 (d, J¼8.0 Hz, 2H),
7.68 (d, J¼8.0 Hz, 2H), 7.57e7.42 (m, 11H), 7.45 (s, 1H), 7.37 (s, 1H),
7.04 (s, 1H), 6.87 (s, 1H); 13C NMR (100 MHz, CDCl3)
158.9, 146.5,
d
139.7, 136.3, 134.2, 133.2, 132.2, 130.1, 129.7, 129.5, 129.1, 129.0,
128.4, 127.4, 126.3, 119.3, 118.7, 109.2, 31.9, 29.7, 29.4, 22.7, 14.1;
HRMS-MALDI (m/z): [M]þ calcd for C29H19BF2N2S: 476.1328; found:
476.1325.
Supplementary data
1H and 13C NMR spectra, and a CIF file giving crystallographic
data for 8a. Supplementary data associated with this article can be
found in the online version, at http://dx.doi.org/10.1016/
j.tet.2012.09.011. These data include MOL files and InChiKeys of the
most important compounds described in this article.
4.3.13. BODIPY (9c). Compound 6b (55.0 mg, 0.22 mmol) and 4,5-
dihydro-7-methoxylbenzo[g]indole (43.8 mg, 0.22 mmol) were
used as the starting materials, and BODIPY 9c was obtained as
green metallic color solid (43.6 mg, 43%). 1H NMR (400 MHz, CDCl3)
d
8.78 (d, J¼8.8 Hz, 1H), 7.71 (d, J¼7.2 Hz, 2H), 7.51 (s, 1H), 7.41 (t,
References and notes
J¼7.2 Hz, 2H), 7.34 (t, J¼7.2 Hz, 1H), 7.06 (s, 1H), 7.00 (dd, J¼8.8,
2.8 Hz, 1H), 6.91 (s, 1H), 6.84 (s, 1H), 6.83(d, J¼2.8 Hz, 1H), 3.89 (s,
3H), 2.93 (t, J¼6.4 Hz, 2H), 2.77 (t, J¼6.4 Hz, 2H); 13C NMR
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(100 MHz, CDCl3) d: 162.1, 156.3, 156.1, 155.0, 144.2, 139.1, 138.4,
134.7,134.4, 131.4,131.3,129.0, 126.9, 126.1,123.6, 120.4, 115.5,114.4,
112.9, 109.3, 55.4, 30.6, 29.7, 22.4; HRMS-MALDI (m/z): [M]þ calcd
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7.53 (t, J¼7.6 Hz, 3H), 7.47 (t, J¼7.6 Hz, 1H), 7.42 (s, 1H), 7.41 (t,
J¼7.6 Hz, 3H), 7.35 (t, J¼7.6 Hz, 1H), 7.08 (s, 1H), 7.03 (dd, J¼8.8,
2.8 Hz, 1H), 6.89 (s, 1H), 6.85 (d, J¼2.8 Hz, 1H), 3.91 (s, 3H), 2.93 (t,
J¼6.8 Hz, 2H), 2.78 (t, J¼6.8 Hz, 2H); 13C NMR (100 MHz, CDCl3)
d
162.1, 155.8, 154.9, 144.2, 141.0, 138.6, 134.7, 132.2, 131.5, 129.7,
129.0, 128.8, 128.5, 126.1, 123.4, 120.4, 115.5, 114.3, 112.8, 109.3, 55.4,
31.9, 30.6, 29.7, 29.4, 22.7, 21.1, 14.1; HRMS-MALDI (m/z): [M]þ calcd
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a stirred solution of 8a (20.7 mg,
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0.375 mmol) and stirred for 4 h. The reaction mixture was evapo-
rated and purified by TLC (n-hexane/CH2Cl2¼1:1) to give 10 as
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d
8.81 (d, J¼8.8 Hz, 1H),
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(100 MHz, CDCl3)
d 163.4, 151.2, 145.6, 131.1, 130.5, 129.6, 129.2,
129.1, 127.9, 126.7, 123.0, 119.4, 115.9, 114.6, 113.4, 55.6, 37.1, 31.9,
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(0.15 mL) were stirred for 24 h at 95 ꢀC in dry toluene (3 mL) in the

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