Synthesis and characterization of 1,3-diarylbenzo[c]selenophenes

Article abstract of DOI:10.1016/j.tet.2008.06.002

A series of 1,3-diarylbenzo[c]selenophenes (symmetrical/unsymmetrical) have been synthesized involving a selenium transfer reaction of keto-alcohol/benzo[c]furan using Woollins reagent. The optical and electrochemical studies of these diarylbenzo[c]selenophenes are correlated with their structures.

Full text of DOI:10.1016/j.tet.2008.06.002

Tetrahedron 64 (2008) 7992–7998
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Tetrahedron
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Synthesis and characterization of 1,3-diarylbenzo[c]selenophenes
*
P. Amaladass, Natarajan Senthil Kumar, Arasambattu K. Mohanakrishnan
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 1,3-diarylbenzo[c]selenophenes (symmetrical/unsymmetrical) have been synthesized in-
volving a selenium transfer reaction of keto-alcohol/benzo[c]furan using Woollins reagent. The optical
and electrochemical studies of these diarylbenzo[c]selenophenes are correlated with their structures.
Ó 2008 Elsevier Ltd. All rights reserved.
Received 21 March 2008
Received in revised form 30 May 2008
Accepted 2 June 2008
Available online 6 June 2008
Keywords:
Benzo[c]selenophene
Diarylbenzo[c]furan
Woollins reagent
1. Introduction
benzo[c]selenophene analogs using the procedure established for
naphtho[c]thiophenes6 is also achieved. Cava and co-workers have
Conjugated macromolecules attracted considerable interest in
the past two decades due to their unique electrical and optical
properties.1 Among the various conjugated systems developed,
poly(thiophene) derivatives have been paid much attention due to
their electronic properties, stability, and structural versatility.2 The
synthesis and electrochemical properties of benzo[c]thiophene an-
alogs have been well explored due to the low band-gap properties
associated with their polymer.3,4 However, the unstable benzo[c]-
selenophene 1 and its polymer have received only scant attention,
Scheme 1. Hence, the synthesis of stable 1,3-diarylbenzo[c]-
selenophene analogs will be highly useful for further understanding
of their physical properties.
reported 3,4-ethylenedioxyselenophene as a novel building block
for electron rich
p
-conjugated polymers.7 The same group also
reported the synthesis of benzo[c]selenophene via bromination–
dehydrobromination as well as oxidation of the 1,3-dihydro-
benzo[c]selenophene.8 Aqad and co-workers reported the synthesis
and electrochemical studies of seleno[3,4-b]quinoxalines.9 The
synthesis of methylthiocapped bi-isothianaphthalene and bi-iso-
selenophene derivatives10 was also achieved. Larock and
co-workers recently reported 2,3-disubstituted benzo[b]-
selenophenes.11
Satoshi Ogawa and co-workers outlined the synthesis and
electrochemical studies of 1,3-diferrocenyl benzo[c]seleno-
phene 4.12
2. Results and discussion
R1
R1
Se
Se
1 R1 = H
Fe
The incredible properties of conducting poly(benzo[c]-
thiophene) led us to explore the synthesis of the corresponding
selenium analog namely benzo[c]selenophenes, which will be
useful for further understanding of its optical properties. We
have recently communicated the synthesis of 1,3-diarylbenzo-
[c]thiophenes13 as well as benzo[c]selenophene14 analogs.
4
Fe
2 R1 = CN
3 R1 = 2-thienyl
Scheme 1.
The synthesis of dicyanobenzo[c]thiophene and dicyano-
benzo[c]selenophene 2 analogs starting from o-xylene dicyanide
using SOCl2 and SeOCl2 as sulfur and selenium transfer reagents
have been reported,5 Scheme 1. The synthesis of 1,3-disubstituted
A survey of the literature revealed that Woollins reagent
[PhP(Se)(m-Se)]2, a selenium analog of well-known sulfur transfer
Lawesson reagent, has been widely employed for the preparation of
selenoamides.15 The usual ring opening of the lactones 5a–d with
freshly prepared aryl/hetero-arylmagnesium bromides followed by
aqueous NH4Cl quenching and subsequent interaction of the
resulting keto-alcohols 6a–f with 0.25 equiv of Woollins reagent at
* Corresponding author. Tel.: þ91 44 24451108; fax: þ91 44 22300488.
E-mail address: mohan_67@hotmail.com (A.K. Mohanakrishnan).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.06.002

P. Amaladass et al. / Tetrahedron 64 (2008) 7992–7998
7993
room temperature furnished the expected benzo[c]selenophenes
7a–f. However, the yields of the various 1,3-disubstituted benzo-
[c]selenophenes 7a–f prepared using this procedure were only
around 10–30%, Scheme 2.
i) Ar2MgBr
ii) aq. HCl
Ar1
Ar1
Ar2
O
O
8a-f
O
5a-d
i) Ar2MgBr
Ar1
Ar2
Ar1
Woollins reagent
O
ii) aq. NH4Cl
O
5a-d
Ar1
OH O
6a-f
Ar2
Dry DCM
55-66%
Se
7a-f
Scheme 3.
Woollins reagent
Ar1
Ar2
Dry DCM
10-30%
Se
should be mentioned that the dithienylbenzo[c]furan on treatment
with Lawesson reagent led to the formation of the 1,3-dithieny-
benzo[c]thiophene16 in good yields. To our delight, the interaction
of known 1,3-dithienylbenzo[c]furan 8a with 0.25 equiv of Wool-
lins reagent at room temperature in dry DCM for 4 h followed
by mass spectral analysis of the crude product indicated the
absence of the Mþ ion peak at m/z 282 corresponding to the
dithienylbenzo[c]furan. The presence of Mþ ion peak at m/z 345
confirmed the complete transformation of 8a into the required
dithienylbenzo[c]selenophene 7a (67%).
7a-f
Scheme 2.
The formation of the selenophenes 7a–f can be visualized
through selenation of carbonyl group followed by intramolecular
cyclization analogous to that of benzo[c]thiophenes.4a The recovery
of keto-alcohols 6a–f confirmed that the selenation of keto group
was not facile as that of thionation. Hence, it was decided to explore
an alternative route to the preparation of benzo[c]selenophenes. It
Table 1
Synthesis of 1,3-diarylbenzo[c]selenophenes using keto-alcohol/benzo[c]furan
Entry
Phthalide
Grignard
Benzo[c]selenophene
Yield (%)a
10,b 67c
1
MgBr
S
Se
O
O
5a
S
S
S
7a
n-C6H13
n-C6H13
2
5a
5a
25,b 61c
Se
7b
MgBr
S
S
S
3
4
22,b 66c
MgBr
n-C6H13
S
Se
7c
S
S
C6H13
30,b 55c
R1
MgBr
O
S
S
Se
O
C6H13O
S
5b R1 = O-n-C6H13
7d
5
20,b 62c
Se
7e
O
O
MgBr
S
5c
6
15,b 58c
Se
7f
MgBr
n-C6H13
S
S
S
S
S
O
C6H13
O
5d
S
a
Isolated yield after column chromatography.
Isolated yield from keto-alcohol.
Isolated yield from benzo[c]furan.
b
c

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P. Amaladass et al. / Tetrahedron 64 (2008) 7992–7998
Hence, following this procedure, the unsymmetrical benzo-
workup afforded the required diarylbenzo[c]furans 8a/10a–e in 45–
55% yields. As expected, these symmetrical diarylbenzo[c]furans on
reaction with 0.25 equiv of Woollins reagent led to the isolation of
the corresponding diarylbenzo[c]selenophene analogs 7a/7k–o in
40–61% yields, Scheme 5.
[c]furans 8b–f are smoothly converted into the corresponding
benzo[c]selenophenes 7b–f in 55–66% yields, Scheme 3. Obviously,
the interaction of the benzo[c]furans 8a–f with Woollins reagent
will lead to the formation of hetero Diels–Alder adduct between
furan and P¼Se. The unstable adduct on rearrangement will furnish
the selenophenes 7a–f. The yields of the various benzo[c]seleno-
phenes prepared via interaction of keto-alcohol/benzo[c]furan with
Woollins reagent are listed in Table 1.
Thus, the conversion of symmetrical/unsymmetrical benzo[c]-
furans 8a–f into the corresponding selenium analogs 7a–f could be
easily carried out via interaction with Woollins reagent. The ring
opening of the lactones 5a/5e with Grignards followed by acidic
workup led to the isolation of stable benzo[c]furan analogs 8g–j in
51–72% yields. As expected, the benzo[c]furans 8g–j on interaction
with Woollins reagent afforded respective benzo[c]selenophene
analogs 7g–j in 58–70% of yields, Scheme 4. The details of the aryl
Grignards used and the yield of the benzo[c]selenophene analogs
7g–j obtained from the respective benzo[c]furans 8g–j are pre-
sented in Table 2.
Ar1
O
1) 2 eq. Ar1MgBr
2) HCl
O
O
Ar1
8a, 10a-e
OCH3
9
Ar1
Se
0.25 eq.
Woollins reagent
Dry DCM
40–61%
Ar1
7a, 7k-o
No
Ar1
Yield (%)
7a
7k
7l
2-Thienyl
P-Anisyl
P-Tolyl
61
52
51
46
40
43
Ar2MgBr
dil. HCl
7m
7n
7o
o-Tolyl
Ar1
Phenyl
Ar1
Ar2
O
8g-j
O
O
5a/5e
1-Naphthyl
Scheme 5.
0.25 eq.
Woollins reagent
Finally, the bis-benz-annelated benzo[c]selenophenes 13/14
were synthesized via ring opening reaction of commercially avail-
able diphthalide 11 with thienylmagnesium bromide followed by
neutral workup and subsequent selenation of the resulting keto-
alcohol using 0.5 equiv of Woollins reagent in 30 and 25% yields,
respectively, Scheme 6. Since, the furan analogs of 13/14 were
found to be unstable, an alternative route for selenophenes 13/14
from the respective benzo[c]furan could not be explored.
Ar1
Ar2
Dry DCM
58–70%
Se
7g-j
Scheme 4.
The additional diarylbenzo[c]furans were prepared adopting the
published procedure.17 The interaction of 3-methoxyphthalide
with 2 equiv of aryl/hetero-aryl Grignards followed by acidic
Table 2
Synthesis of benzo[c]selenophene from benzo[c]furan
Entry
Phthalide
Grignard
Benzo[c]furan
Benzo[c]selenophene
Yield (%)a
MgBr
1
66
Se
O
O
S
Me
O
5a
S
S
8g
H3C
H3C
7g
MgBr
2
3
5a
62
58
O
Se
S
S
S
S
7h
8h
MgBr
MgBr
O
8i
Se
S
O
O
7i
5e
4
5a
70
O
8j
Se
7j
a
Isolated yield after column chromatography.

P. Amaladass et al. / Tetrahedron 64 (2008) 7992–7998
7995
Table 4
Redox behavior of some selected benzo[c]selenophene analogs
Compound 1Epa (V) 1Epcb (V) 1DEpc (mV) 2Epa (V) 2Epc (V) 2DEpc (mV)
a
a
b
O
S
O
O
þ0.71e
þ0.88e
þ0.80
þ0.86
þ0.63
þ0.77e
þ0.98e
þ0.86e
þ0.86e
O
7a
7c
7e
7i
7g
7k
7n
7j
11
þ0.47
þ0.40
330e
230e
R1
i)
MgBr
þ1.00
þ1.10
þ0.56
þ0.67
440e
430e
ii) aq.NH4Cl
iii) 0.5 eq.Woollins reagent/DCM
13
a
2
1Epa and Epa are the anodic peak potentials of the first and second redox pro-
Se
R1
Se
cesses, respectively.
R1
S
S
b
2
1Epc and Epc are the cathodic peak potentials of the first and second redox
13 R1 = H (30%)
processes, respectively.
14 R1 = C6H13 (25%)
c
1DEp and 2DEp are the differences between the cathodic and anodic peak po-
tentials of the first and second redox processes, respectively.
Scheme 6.
d
Quasireversible.
Irreversible.
e
f
3. Photo physical and electrochemical studies
Reversible.
The UV–vis spectra of the benzo[c]selenophenes exhibited strong
benzo[c]selenophene analogs, compound 13 exhibited lowest Eg
value (~2 eV). The increase of the number of benzo[c]selenophene
unit significantly increased the LUMO energy level. It should be
mentioned that the corresponding HOMO energy levels of 7a and
13 are almost identical (~5 eV). The higher HOMO energy levels of
benzo[c]selenophenes (~5.2 eV) greatly reduces energy barrier for
absorption in the region 410–447 nm corresponding to the
p–p
*
electron transfer of the entire conjugated backbone. The exact lmax
values of the benzo[c]selenophene are listed in Table 3. On com-
parison with 1,3-dithienylbenzo[c]thiophene
benzo[c]selenophene 7a exhibited lmax at 447 nm, which confirms
(
lmax¼432 nm),4d
the enhancement of conjugation. The introduction of alkyl sub-
hole injection from ITO (
Hence these benzo[c]selenophenes can be explored as hole trans-
port material for double-layer OLEDS.
The electrochemical properties of benzo[c]selenophenes are
summarized in Table 4. The benzo[c]selenophene 7a showed a
irreversible anodic peak potential at þ0.71 V at scan rate of
100 mV Sꢀ1. The anodic peak potential for 7a and the corresponding
1,3-dithienylbenzo[c]thiophene (~0.71)4d was found to be the
4
¼4.8 eV) to emissive Alq3
(
4
¼5.8 eV).
stituent (n-C6H13) in the
length absorption to 422 nm. In general, the introduction of alkyl/
alkoxy groups into the benzo[c]selenophene system reduced the
a/b positions of 7a lowers the long-wave-
p-
conjugation, which was reflected through the bathochromic shift of
its lmax value. The bis-benzo[c]selenophenes 13 and 14 exhibited
lmax at 535 and 525 nm, respectively. Thus, the introduction of hexyl
substituents at both the ends of benzo[c]selenophene 13 has de-
creased the
p-conjugation. Increasing the ratio of benzo[c]seleno-
same. The introduction of alkyl side chain (n-C6H13) in the a/b po-
phene/thiophene (7a/13/14) led to the enhancement of
conjugation, which was reflected by an increased lmax value.
Qualitative fluorescence spectral data of the benzo[c]seleno-
phenes are recorded in DCM solution and the values are presented
in Table 3. Compounds 7a–k containing one benzo[c]selenophene
unit emitted light in the region 485–570 nm. As in the case of ab-
sorption, the emission value of benzo[c]selenophenes 13/14 also
sitions of 7a significantly diminished its electro-oxidation behavior.
Surprisingly, the increase of the number of benzo[c]selenophene
unit (7a/13) does not influence on its anodic peak potential value.
4. Conclusions
The synthesis of several 1,3-diarylbenzo[c]selenophenes
involving a selenium transfer reaction of keto-alcohol or diaryl-
benzo[c]furans using Woollins reagent was achieved. The bis-
annelated benzo[c]selenophenes were also prepared using this
procedure. The benzo[c]selenophenes were obtained in relatively
better yields from the respective benzo[c]furan rather than the
keto-alcohol. Results from the optical and electrochemical studies
of benzo[c]selenophenes are also presented.
red shifted with respect to the increase of p-conjugation.
The HOMO and LUMO energy levels of selected benzo[c]sele-
nophenes were calculated from the absorption onset and the onset
oxidation potential, and the values are presented in Table 3. All the
benzo[c]selenophene analogs exhibited Eg value in the range of
2–2.8 eV. Increasing the ratio of benzo[c]selenophene to thiophene
significantly reduced the Eg value (7a/13/14). Among the
Table 3
Summary of physical measurements for some selected benzo[c]selenophenes
5. Experimental
5.1. General
a
b
c
onset
Compound
lmax
lonset
llum
Eg
E
ox
HOMOd
(eV)
LUMOe
(eV)
(nm)
(nm)
(nm)
(eV)
(eV)
7a
7b
7c
7e
7j
7k
7m
7n
13
14
447
422
432
421
412
420
410
420
535
525
470
465
460
453
437
452
450
455
610
595
550
530
538
570
495
517
510
485
615
610
2.64
2.66
2.69
2.74
2.84
2.74
2.75
2.72
2.03
2.08
0.60
0.77
0.75
0.75
0.72
0.70
0.78
0.81
0.57
0.61
5.04
5.21
5.19
5.19
5.16
5.14
5.22
5.25
5.01
5.05
2.40
2.55
2.50
2.45
2.32
2.40
2.47
2.53
2.98
2.97
All melting points are uncorrected. IR spectra were recorded on
a SHIMADZU FT-IR 8300 instrument. 1H and 13C NMR spectra were
recorded in CDCl3 using TMS as an internal standard on a JEOL 400
and Bruker-300 spectrometers, respectively. Mass spectra were
recorded on a JEOL DX 303 HF spectrometer. Elemental analyses
were carried out on Perkin–Elmer (Layolla College, Chennai) and
Vario EL III (CDRI, Lucknow) equipments. All UV–vis spectra were
recorded in CH2Cl2 solution. The emission spectra were recorded on
Perkin–Elmer LS-45 spectrophotometer. The cyclic-voltammogram
of 10ꢀ3 M solution of diarylbenzo[c]selenophenes was carried out
on a CHI 600C electrochemical analyzer. All the measurements
were carried out under oxygen free condition using three-electrode
a
Measured in dilute dichloromethane solution.
Excited at the absorption maxima.
Estimated from the onset of absorption (Eg¼1240/lonset).
Calculated using empirical equation: HOMO¼(4.44þEoonxset).
Calculated from LUMO¼HOMOꢀEg.
b
c
d
e

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P. Amaladass et al. / Tetrahedron 64 (2008) 7992–7998
cell in which glassy carbon electrode was working electrode, sat-
urated Ag/AgCl electrode was reference electrode, and platinum
wire was used as an auxiliary electrode. Tetrabutylammo-
niumhexafluoro phosphate (TBAPF6) was used as supporting
electrolyte and its concentration was 10ꢀ1 M.
(1H, d, J 7.8 Hz, ArH), 2.53 (2H, t, J 7.8 Hz, CH2), 1.31–1.60 (8H, m,
CH2), 0.74 (3H, t, J 6.8 Hz, CH3); dc (75.6 MHz, CDCl3) 143.9, 132.1,
131.8, 131.4, 130.4, 130.2, 129.1, 127.3, 126.8, 126.5, 125.3, 124.9,
124.0, 122.7, 122.3, 120.3, 31.9, 31.8, 30.1, 29.0, 22.8, 14.3; m/z (EI)
430 (Mþ1, 100).
5.2. A representative procedure for the preparation of
benzo[c]selenophene from keto-alcohol (procedure A)
5.3.3. 2-Hexyl-5-(1-(thiophen-2-yl)benzo[c]selenophen-3-yl)-
thiophene (7c)
Following the above-mentioned procedure B, compound 7c was
obtained using the phthalide 5a (1 g, 4.63 mmol), 5-hexyl-2-thi-
enylmagnesium bromide [prepared from 2-bromo-5-hexylthio-
phene (1.37 g, 5.54 mmol) and Mg (0.14 g, 5.83 mmol)] and
Woollins reagent (0.61 g, 1.15 mmol) as a thick orange liquid (1.30 g,
66%). [Found: C, 61.32; H, 5.32; S, 15.15. C22H22S2Se requires: C,
61.52; H, 5.16; S, 14.93%.] Rf (hexane) 0.86; dH (400 MHz, CDCl3)
7.82–7.83 (2H, m, ArH), 7.27 (1H, d, J 1.2 Hz, ArH), 7.26 (1H, d, J
1.2 Hz, ArH), 7.10–7.13 (2H, m, ArH), 6.97–7.08 (2H, m, ArH), 6.78
(1H, d, J 3.6 Hz, ArH), 2.81 (2H, t, J 7.5 Hz, CH2), 1.72 (2H, quintet,
CH2), 1.25–1.34 (6H, m, CH2), 0.90 (3H, t, J 3.3 Hz, CH3); dc (100 MHz,
CDCl3) 147.0, 137.9, 137.8, 135.1, 129.0, 127.8, 127.5, 127.1, 125.9,
125.8, 125.6, 124.9, 124.4, 124.1, 122.3, 122.0; m/z (EI) 429 (Mþ, 05).
To a solution of phthalide 5a (2 g, 9.25 mmol) in anhydrous THF
(25 mL), 2-thienylmagnesium bromide [prepared from 2-bromo-
thiophene (1.81 g, 11.10 mmol) and magnesium turnings (0.29 g,
12.08 mmol)] was added at 0 ꢁC under N2. The reaction mixture
was slowly raised to room temperature and stirred for 4 h. It was
then quenched with aqueous ammonium chloride solution,
extracted with DCM (2ꢂ20 mL), and dried (Na2SO4). The pale yel-
low solution of keto-alcohol in DCM was stirred with Woollins
reagent (1.23 g, 2.31 mmol) for 4 h. After removal of the solvent, the
residue was purified by column chromatography (neutral alumina,
hexane) to afford the benzo[c]selenophene 7a as an orange solid
(0.32 g, 10%).
5.2.1. 2-(1-(Thiophen-2-yl)benzo[c]selenophen-3-yl)thiophene (7a)
Mp 85 ꢁC. [Found: C, 55.81; H, 3.15; S, 18.81. C16H10S2Se requires:
C, 55.65; H, 2.92; S, 18.57%.] Rf (hexane) 0.82; dH (300 MHz, CDCl3)
7.82 (2H, dd, J 3.88, 2.96 Hz, ArH), 7.39–7.37 (2H, m, ArH), 7.30–7.28
(2H, m, ArH), 7.17–7.14 (2H, m, ArH), 7.01 (2H, dd, J 3.88, 3.2 Hz,
ArH); dc (75.6 MHz, CDCl3) 137.7, 127.9, 127.8, 126.1, 125.8, 124.4,
122.0, 119.8; m/z (EI) 345 (Mþ, 13).
5.3.4. 2-(1-(4-(Hexyloxy)phenyl)benzo[c]selenophen-3-yl)-
thiophene (7d)
Following the above-mentioned procedure B, compound 7d was
obtained using the phthalide 5b (1 g, 3.22 mmol), 2-thienylmagne-
sium bromide [prepared from 2-bromothiophene (0.63 g,
3.86 mmol) and Mg (0.10 g, 4.16 mmol)] and Woollins reagent
(0.43 g, 0.81 mmol) as yellow solid (0.78 g, 55%). Mp 63 ꢁC. [Found:
C, 65.81; H, 5.30; S, 7.41. C24H24OSSe requires: C, 65.59; H, 5.50; S,
7.30%.] Rf (hexane) 0.80; dH (400 MHz, CDCl3) 7.83 (1H, d, J 8.8 Hz,
ArH), 7.59 (1H, d, J 9.3 Hz, ArH), 7.51 (2H, d, J 8.8 Hz, ArH), 7.35 (1H,
dd, J 4.1, 0.9 Hz, ArH), 7.26 (1H, dd, J 2.9, 0.9 Hz, ArH), 7.12 (1H, dd, J
3.7, 1.4 Hz, ArH), 6.95–7.01 (4H, m, ArH), 4.01 (2H, t, J 6.6 Hz, OCH2),
1.81 (2H, quintet, J 7.1 Hz, CH2), 1.45–1.55 (4H, m, CH2), 1.34–1.38
(2H, m, CH2), 0.90 (3H, t, J 7.1 Hz, CH3); dc (100 MHz, CDCl3) 159.7,
141.4, 138.2, 137.1, 136.5, 135.2, 132.5, 130.0, 128.6, 125.2, 124.5,
122.7, 124.4, 121.9, 121.2, 115.2, 68.3, 31.6, 29.2, 25.8, 22.62, 14.11;
m/z (EI) 439 (Mþ, 54).
5.3. A representative procedure for the preparation of
benzo[c]selenophenes from benzo[c]furans (procedure B)
To a solution of phthalide 5a (1 g, 4.62 mmol) in anhydrous THF
(25 mL) was added 2-thienylmagnesium bromide [prepared from
2-bromothiophene (0.90 g, 5.55 mmol) and magnesium turnings
(0.14 g, 5.83 mmol)] at 0 ꢁC under N2. The reaction mixture was
slowly raised to room temperature and stirred for 4 h. It was then
quenched with crushed ice (5 g) containing HCl (10 mL), extracted
with DCM (2ꢂ20 mL), and dried (Na2SO4). The greenish-yellow
fluorescent solution of benzo[c]furan was then stirred with Wool-
lins reagent (0.62 g, 1.15 mmol) at room temperature for 4 h. After
removal of the solvent, the residue was purified by column chro-
matography (neutral alumina, hexane) to afford the benzo[c]sele-
nophene 7a as an orange solid (1.07 g, 67%).
5.3.5. 2-(1-(Anthracen-10-yl)benzo[c]selenophen-3-yl)thio-
phene (7e)
Following the above-mentioned procedure B, compound 7e
was obtained using the phthalide 5c (1 g, 3.22 mmol), 2-thi-
enylmagnesium bromide [prepared from 2-bromothiophene (0.63 g,
3.86 mmol) and Mg (0.10 g, 4.16 mmol)] and Woollins reagent
(0.43 g, 0.81 mmol) as orange solid (0.87 g, 62%). Mp 162 ꢁC.
[Found: C, 71.00; H, 3.50; S, 7.40. C26H16SSe requires: C, 71.06; H,
3.67; S, 7.30%.] Rf (hexane) 0.82; dH (400 MHz, CDCl3) 8.62 (1H, s,
ArH), 8.09 (2H, d, J 8.1 Hz, ArH), 7.88 (2H, t, J 9.1 Hz, ArH), 7.42–7.55
(6H, m), 7.35 (1H, d, J 4.5 Hz), 7.15–7.17 (1H, m, ArH), 7.08–7.10 (2H,
m, ArH), 6.91–6.93 (1H, m, ArH); dc (100 MHz, CDCl3) 147.0, 137.9,
137.8,135.1,129.0,127.8,127.5, 127.1,125.9,125.8,125.6,124.9,124.4,
124.1, 122.3, 122.0, 119.5; m/z (EI) 440 (Mþ, 35).
5.3.1. 2-(1-(Thiophen-2-yl)benzo[c]selenophen-3-yl)thiophene (7a)
Mp 85 ꢁC. [Found: C, 55.81; H, 3.15; S, 18.81. C16H10S2Se requires:
C, 55.65; H, 2.92; S, 18.57%.] Rf (hexane) 0.82; nmax (KBr) 1600, 1510,
785, 465 cmꢀ1
; dH (300 MHz, CDCl3) 7.82 (2H, dd, J 3.88, 2.96 Hz,
ArH), 7.39–7.37 (2H, m, ArH), 7.30–7.28 (2H, m, ArH), 7.17–7.14 (2H,
m, ArH), 7.01 (2H, dd, J 3.88, 3.2 Hz, ArH); dc (75.6 MHz, CDCl3) 137.7,
127.9, 127.8, 126.1, 125.8, 124.4, 122.0, 119.8; m/z (EI) 345 (Mþ, 13).
5.3.2. 3-Hexyl-2-(1-(thiophen-2-yl)benzo[c]selenophen-3-yl)-
thiophene (7b)
5.3.6. 2-Hexyl-5-(1-(5-(thiophen-2-yl)thiophen-2-yl)benzo[c]-
selenophen-3-yl)thiophene (7f)
Following the above-mentioned procedure B, compound 7b was
obtained using the phthalide 5a (1 g, 4.63 mmol), 3-hexyl-2-thi-
enylmagnesium bromide [prepared from 2-bromo-3-hexylthio-
phene (1.37 g, 5.55 mmol) and Mg (0.14 g, 5.83 mmol)] and
Woollins reagent (0.61 g, 1.15 mmol) as a thick orange liquid (1.20 g,
61%). [Found: C, 61.22; H, 5.36; S, 15.22. C22H22S2Se requires: C,
61.52; H, 5.16; S, 14.93%.] Rf (hexane) 0.84; nmax (KBr) 3010, 1596,
Following the above-mentioned procedure B, compound 7f was
obtained using the phthalide 5d (1 g, 3.35 mmol), 5-hexyl-2-thi-
enylmagnesium bromide [prepared from 2-bromo-5-hexylthio-
phene (0.99 g, 4.01 mmol) and Mg (0.10 g, 4.16 mmol)] and
Woollins reagent (0.44 g, 0.83 mmol) as a thick orange liquid
(0.99 g, 58%). [Found: C, 60.92; H, 4.61; S, 18.92. C26H24S3Se re-
quires: C, 61.04; H, 4.73; S, 18.80%.] Rf (hexane) 0.78; nmax (KBr)
1491, 1200, 908, 764, 740, 689 cmꢀ1
; dH (400 MHz, CDCl3) 7.76 (1H,
d, J 8.8 Hz, ArH), 7.30–7.26 (4H, m, ArH), 7.22 (1H, dd, J 2.4, 1.2 Hz,
ArH), 7.05 (1H, dd, J 3.6, 1.4 Hz, ArH), 6.97 (1H, d, J 5.3 Hz, ArH), 6.90
1596, 1509, 1263, 954, 787, 753, 635 cmꢀ1
7.81–7.90 (1H, m, ArH), 7.70–7.76 (1H, m, ArH), 7.61–7.67 (1H, m,
; dH (400 MHz, CDCl3)

P. Amaladass et al. / Tetrahedron 64 (2008) 7992–7998
7997
ArH), 7.00–7.08 (2H, m, ArH), 7.11–7.12 (1H, d, J 6.6 Hz, ArH), 7.27–
7.33 (5H, m, ArH), 2.80 (2H, t, J 7.6 Hz, CH2), 1.23–1.54 (8H, m, CH2),
0.83 (3H, t, J 6.6 Hz, CH3); dc (75.6 MHz, CDCl3) 145.0, 132.2, 131.8,
130.5,130.3,130.1,129.2,128.8,127.8,127.4,127.2,127.1,126.9,126.6,
125.4, 125.0, 124.2, 123.0, 122.8, 122.5, 32.1, 31.9, 30.2, 29.1, 23.0,
14.5; m/z (EI) 511 (Mþ, 21).
(hexane) 0.92; nmax (KBr) 1595, 1495, 735, 451 cmꢀ1
;
dH (300 MHz,
CDCl3) 8.22–8.21 (1H, m, ArH), 7. 81 (1H, d, J 7.1 Hz, ArH), 7.73–7.70
(1H, m, ArH), 7.59–7.52 (4H, m, ArH), 7.48–7.44 (3H, m, ArH), 7.40–
7.36 (3H, m, ArH), 7.34–7.32 (3H, m, ArH); dc (75.6 MHz, CDCl3)
141.0,140.5,137.3,135.2,133.6,133.1,132.8,131.4,130.9,130.8,130.4,
130.0, 129.5, 129.0, 128.3, 128.1, 127.7, 126.4, 125.7, 123.9; m/z (EI)
320 (Mþ, 70).
5.4. Preparation of unsymmetrical benzo[c]furans
(procedure C)
5.5. A representative procedure for the preparation of
unsymmetrical benzo[c]selenophene from corresponding
benzo[c]furan (procedure D)
5.4.1. 1-(Thiophen-2-yl)-3-p-tolylisobenzofuran (8g)
To a solution of phthalide 5a (2 g, 9.26 mmol) in anhydrous THF
(25 mL), p-tolylmagnesium bromide [prepared from p-bromo-
toluene (1.90 g, 11.11 mmol) and magnesium turnings (0.29 g,
12.08 mmol)] was added at 0 ꢁC under N2. The reaction mixture
was slowly raised to room temperature and stirred overnight. The
reaction mixture was hydrolyzed by adding dropwise a solution of
concd HCl (20 mL) and H2O (20 mL) at 0 ꢁC. The reaction mixture
turned to bright orange with green fluorescence. Stirring was
maintained under nitrogen atmosphere for 0.5 h. Then, Et2O
(50 mL) was added and the organic phase separated. The organic
phase was washed with brine (2ꢂ50 mL), satd NaHCO3 (50 mL),
and dried (Na2SO4). After removal of the solvent, the residue was
purified by column chromatography (silica gel, hexane) to afford
the benzo[c]furan 8g as yellow solid (1.92 g, 72%). Mp 98 ꢁC.
[Found: C, 78.47; H, 4.92; S, 11.00. C19H14OS requires: C, 78.59; H,
4.86; S, 11.04%.] Rf (hexane) 0.96; nmax (KBr) 1605, 1500, 755,
Compound 8g (0.2 g, 0.69 mmol) in dry DCM (10 mL) along with
Woollins reagent (0.09 g, 0.17 mmol) was stirred for 4 h at room
temperature. After removal of the solvent, the residue was purified
by column chromatography (silica gel, hexane) to afford the
benzo[c]selenophene 7g as a thick yellow liquid (0.16 g, 66%).
5.5.1. 2-(1-p-Tolylbenzo[c]selenophen-3-yl)thiophene (7g)
Found: C, 64.30; H, 4.19; S, 9.20. C19H14SSe requires: C, 64.58; H,
3.99; S, 9.07%. Rf (hexane) 0.86; dH (400 MHz, CDCl3) 7.85 (1H, d, J
8.8 Hz, ArH), 7.63 (1H, d, J 8.8 Hz, ArH), 7.51 (2H, d, J 8.3 Hz, ArH),
7.36 (1H, d, J 4.8 Hz, ArH), 7.02–7.14 (3H, m, ArH), 6.94–7.00 (3H, m,
ArH), 2.42 (3H, s, CH3); dc (100 MHz, CDCl3) 146.5, 141.4, 138.0,
137.0, 136.4, 135.6, 130.4, 130.0, 129.2, 124.8, 124.6, 121.9, 121.1,
21.29; m/z (EI) 354 (Mþ, 21).
685 cmꢀ1
; dH (300 MHz, CDCl3) 7.78 (2H, d, J 8.2 Hz, ArH), 7.69–7.76
(2H, m, ArH), 7.47 (1H, d, J 3.58 Hz, ArH), 7.17–7.27 (3H, m, ArH),
7.11–7.13 (1H, m, ArH), 6.95–6.99 (2H, m, ArH), 2.39 (3H, s, CH3); dc
(75 MHz, CDCl3) 137.0, 133.9, 130.2, 129.8, 129.2, 128.9, 127.9, 125.3,
125.2, 124.8, 123.9, 122.1, 121.7, 121.5, 120.3, 120.1, 21.5; m/z (EI) 290
(Mþ, 100).
5.5.2. 2-(1-Phenylbenzo[c]selenophen-3-yl)thiophene (7h)
Following the above-mentioned procedure D, 7h was obtained
using benzo[c]furan 8h (0.2 g, 0.72 mmol) and Woollins reagent
(0.10 g, 0.18 mmol) as thick yellow liquid (0.15 g, 62%). [Found: C,
63.60; H, 3.50; S, 9.51. C18H12SSe requires: C, 63.71; H, 3.56; S,
9.45%.] Rf (hexane) 0.82; nmax (KBr) 1597, 1500, 1227, 735,
5.4.2. 1-Phenyl-3-(thiophene-2-yl)isobenzofuran (8h)
681 cmꢀ1
; dH (400 MHz, CDCl3) 7.84 (1H, d, J 8.8 Hz, ArH), 7.61–
Following the above-mentioned procedure C, 8h was obtained
using the phthalide 5a (2 g, 9.25 mmol) and phenylmagnesium
bromide [prepared from bromo benzene (1.74 g, 11.08 mmol) and
Mg (0.29 g, 12.08 mmol)] as a thick yellow liquid (1.30 g, 51%).
[Found: C, 78.13; H, 4.17; S, 11.72. C18H12OS requires: C, 78.23; H,
4.38; S, 11.60%.] Rf (hexane) 0.92; nmax (KBr) 1600, 1505, 741,
7.71 (2H, m, ArH), 7.45 (2H, t, J 7.32 Hz, ArH), 7.35–7.38 (2H, m,
ArH), 7.29–7.30 (1H, m, ArH), 7.13–7.15 (1H, m, ArH), 6.94–7.03
(3H, m, ArH); dc (100 MHz, CDCl3) 143.7, 137.2, 132.9, 131.6, 130.3,
129.8, 129.6, 128.8, 128.3, 126.8, 125.1, 124.7, 122.1, 120.1; m/z (EI)
340 (Mþ1, 100).
691 cmꢀ1
;
dH (300 MHz, CDCl3) 7.62–7.64 (3H, m, ArH), 7.55–7.58
5.5.3. 2-(1-(Naphthalen-1-yl)benzo[c]selenophen-3-yl)thio-
phene (7i)
(3H, m, ArH), 7.40–7.47 (3H, m, ArH), 7.28–7.30 (2H, m, ArH), 6.98
(1H, t, J 4.2 Hz, ArH); dc (75.6 MHz, CDCl3) 144.1, 139.8, 139.6, 137.2,
134.9, 134.8, 133.2, 132.4, 130.8, 130.4, 129.8, 129.7, 129.0, 128.8,
128.3; m/z (EI) 276 (Mþ, 100).
Following the above-mentioned procedure D, 7i was obtained
using benzo[c]furan 8i (0.2 g, 0.61 mmol) and Woollins reagent
(0.08 g, 0.15 mmol) as a yellow solid (0.14 g, 58%). Mp 92 ꢁC. [Found:
C, 67.70; H, 3.52; S, 8.33. C22H14SSe requires: C, 67.86; H, 3.62; S,
8.24%.] Rf (hexane) 0.82; dH (400 MHz, CDCl3) 7.93 (2H, d, J 8.2 Hz,
ArH), 7.88 (2H, m, ArH), 7.63 (1H, d, J 6.8 Hz, ArH), 7.56 (1H, d, J
7.8 Hz, ArH), 7.50–7.54 (1H, m, ArH), 7.41–7.45 (2H, m, ArH), 7.33–
7.39 (1H, m, ArH), 7.14–7.17 (1H, m, ArH), 7.02–7.04 (2H, m, ArH),
6.84–6.99 (1H, m, ArH); dc (100 MHz, CDCl3) 143.8, 141.0, 134.2,
133.8, 130.8, 128.6, 128.4, 128.1, 127.8, 127.2, 126.6, 126.1, 126.1,
125.78, 125.3, 125.2, 125.0, 123.9, 122.1, 120.2, 119.6; m/z (EI) 390
(Mþ).
5.4.3. 1-(Napthalen-8-yl)-3-(thiophen-2-yl)isobenzofuran (8i)
Following the above-mentioned procedure C, 8i was obtained
using the phthalide 5e (2 g, 7.69 mmol) and 2-thienyl magnesium
bromide [prepared from 2-bromothiophene (1.50 g, 9.20 mmol)
and Mg (0.24 g, 10.00 mmol)] as a yellow solid (1.55 g, 62%). Mp
87 ꢁC. [Found: C, 80.87; H, 4.23; S, 9.92. C22H14OS requires: C, 80.95;
H, 4.32; S, 9.82%.] Rf (hexane) 0.90; dH (300 MHz, CDCl3) 8.41 (1H,
m, ArH), 7.80–7.96 (4H, m, ArH), 7.55–7.62 (5H, m, ArH), 7.32 (1H, d,
J 4.89 Hz, ArH), 7.15–7.18 (1H, m, ArH), 6.97–7.09 (2H, m, ArH); dc
(75.6 MHz, CDCl3) 134.2, 133.9, 130.8, 128.7, 128.5, 128.1, 127.9,
127.3,126.6,126.2,126.1,125.4,125.3,125.1,123.9,123.7,122.1,121.0,
120.8, 119.7; m/z (EI) 326 (Mþ, 100).
5.5.4. 1-(Naphthalene-1-yl)-3-phenylbenzo[c]selenophene (7j)
Following the above-mentioned procedure D, 7j was obtained
using benzo[c]furan 8j (0.2 g, 0.62 mmol) and Woollins reagent
(0.08 g, 0.15 mmol) as a thick yellow liquid (0.17 g, 70%). [Found: C,
74.85; H, 4.35. C24H16Se requires: C, 75.20; H, 4.21%.] Rf (hexane)
0.80; dH (400 MHz, CDCl3) 8.57 (1H, dd, J 3.42, 2.92 Hz, ArH), 8.17
(2H, d, J 7.32 Hz, ArH), 8.08 (2H, d, J 8.08 Hz, ArH), 7.98 (1H, d, J
7.36 Hz, ArH), 7.61–7.90 (5H, m, ArH), 7.41–7.58 (2H, m, ArH), 7.11–
7.21 (3H, m, ArH); dc (100 MHz, CDCl3) 144.6, 144.4, 134.2, 131.8,
130.9, 129.6, 129.4, 128.9, 128.4, 128.3, 127.3, 126.81, 126.6, 126.1,
5.4.4. 1-(Naphthalen-1-yl)-3-phenylisobenzofuran (8j)
Following the above-mentioned procedure C, 8j was obtained
using phthalide 5e (2 g, 7.69 mmol) and phenylmagnesium bro-
mide [prepared from bromo benzene (1.45 g, 9.23 mmol) and Mg
(0.24 g, 10.00 mmol)] as a yellow solid (1.50 g, 61%). [Found: C,
89.87; H, 4.96. C24H16O requires: C, 89.97; H, 5.03; S, 9.82%.] Rf

7998
P. Amaladass et al. / Tetrahedron 64 (2008) 7992–7998
125.4, 125.3, 124.6, 124.6, 123.9, 121.5, 120.3, 119.8; m/z (EI) 384
bromide [prepared from 2-bromothiophene (0.67 g, 4.11 mmol)
and Mg (0.11 g, 4.58 mmol)] and Woollins reagent (0.50 g,
0.94 mmol) as red solid (0.29 g, 30%). [Found: C, 54.81; H, 2.75; S,
12.35. C24H14S2Se2 requires: C, 54.97; H, 2.69; S,12.23%.] Rf (hexane)
(Mþ, 20).
5.6. A representative procedure for the preparation of
symmetrical benzo[c]furans 10a–e
0.72; nmax (KBr) 1598, 1502, 1227, 753, 695 cmꢀ1
; dH (300 MHz,
CDCl3) 8.03 (2H, d, J 8.4 Hz, ArH), 7.87 (2H, d, J 8.1 Hz, ArH), 7.35–
7.42 (4H, m, ArH), 7.16–7.23 (6H, m, ArH); dc (75.6 MHz, CDCl3)
136.9, 135.5, 135.1, 128.5, 127.9, 125.7, 125.0, 124.8, 124.2, 121.8,
121.4; m/z (EI) 525 (Mþ, 11).
Symmetrical benzo[c]furans 8a/10a–e were prepared using the
published procedure.17
5.6.1. 1,3-Bis(4-methoxyphenyl)benzo[c]selenophene (7k)
Following the above-mentioned procedure D, compound 7k
was obtained using the benzo[c]furan 10a (0.2 g, 0..61 mmol) and
Woollins reagent (0.08 g, 0.15 mmol) as a thick yellow liquid (0.12 g,
50%). [Found: C, 67.25; H, 4.57. C22H18O2Se requires: C, 67.18; H,
4.61%.] Rf (hexane) 0.65; dH (400 MHz, CDCl3) 7.76 (4H, d, J 9.0 Hz,
ArH), 7.65 (2H, dd, J 2.7, 4.2 Hz, ArH), 6.91–6.95 (6H, m, ArH), 3.79
(6H, s, OCH3); dc (100 MHz, CDCl3) 137.3, 135.0, 134.0, 131.5, 129.2,
123.9, 121.4, 55.6; m/z (EI) 394 (Mþ, 33).
5.6.7. 2-Hexyl-5-(1-(1-(5-hexylthiophen-2-yl)benzo[c]selenophen-
3-yl)benzo[c]selenophen-3-yl)thiophene (14)
Following the above-mentioned procedure A, 14 was obtained
using diphthalide 11 (0.5 g, 1.87 mmol), 5-hexyl-2-thienylmagne-
sium bromide [prepared from 2-bromo-5-hexylthiophene (1.02 g,
4.12 mmol) and Mg (0.11 g, 4.58 mmol)] and Woollins reagent
(0.50 g, 0.94 mmol) as a thick orange liquid (0.32 g, 25%). [Found: C,
62.50; H, 5.43; S, 9.30. C36H38S2Se2requires: C, 62.42; H, 5.53; S,
9.26%.] Rf (hexane) 0.75; dH (300 MHz, CDCl3) 8.01–8.07 (2H, m,
ArH), 7.86 (2H, d, J 9.0 Hz, ArH), 7.15–7.20 (6H, m, ArH), 6.85 (2H, d, J
3.3 Hz, ArH), 1.77 (4H, t, J 7.35 Hz, CH2), 1.33–1.47 (12H, m, CH2),
0.90–0.95 (10H, m, CH2CH3); dc (75.6 MHz, CDCl3) 146.76, 136.83,
134.74, 129.11, 125.33, 124.92, 124.66, 123.69, 121.88, 121.62, 31.58,
30.27, 28.83, 22.58, 14.08; m/z (EI) 694 (Mþ, 15).
5.6.2. 1,3-Di-p-tolylbenzo[c]selenophene (7l)
Following the above-mentioned procedure D, 7l was obtained
using the benzo[c]furan 10b (0.2 g, 0.67 mmol) and Woollins re-
agent (0.09 g, 0.17 mmol) as a thick yellow liquid (0.12 g, 51%).
[Found: C, 73.03; H, 5.10. C22H18Se requires: C, 73.13; H, 5.02%.] Rf
(hexane) 0.82; dH (400 MHz, CDCl3) 7.55–7.57 (2H, m, ArH), 7.40
(4H, d, J 7.6 Hz, ArH), 7.14 (4H, d, J 7.6 Hz, ArH), 6.86–6.88 (2H, m,
ArH), 2.30 (6H, s, CH3); dc (100 MHz, CDCl3) 137.2, 137.2, 136.6,
130.4, 129.1, 126.7, 123.5, 121.7, 21.2; m/z (EI) 362 (Mþ, 54).
Acknowledgements
The authors thank DST, New Delhi and UGC-Potential for
excellence (F. 12-140/2001 SR-1) for a financial support. P.A. thanks
CSIR for a CSIR–SRF fellowship and NS thanks DST for a fellowship.
Authors thank DST–FIST for 300 MHz NMR facility.
5.6.3. 1,3-Di-o-tolylbenzo[c]selenophene (7m)
Following the above-mentioned procedure D, 7m was obtained
using the benzo[c]furan 10c (0.2 g, 0.67 mmol) and Woollins re-
agent (0.09 g, 0.17 mmol) as thick yellow liquid (0.11 g, 46%).
[Found: C, 73.01; H, 5.10. C22H18Se requires: C, 73.13; H, 5.02%.] Rf
References and notes
(hexane) 0.86; nmax (KBr) 3060, 1595, 1500, 1230, 743, 695 cmꢀ1
; dH
(400 MHz, CDCl3) 7.78–7.68 (4H, m, ArH), 7.47–7.40 (6H, m, ArH),
7.11–7.09 (2H, m, ArH), 2.71 (6H, s, CH3); dc (75.6 MHz, CDCl3) 145.3,
136.5, 131.3, 130.6, 129.4, 128.0, 125.9, 124.5, 122.4, 120.0, 21.3; m/z
(EI) 362 (Mþ, 14).
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5. Amaresh, R. R.; Lakshmikantham, M. V.; Baldwin, J. W.; Cava, M. P.; Metzger, R.
M.; Rogers, R. D. J. Org. Chem. 2002, 67, 2453–2458.
6. Mohanakrishnan, A. K.; Lakshmikantham, M. V.; Cava, M. P.; Rogers, R. D.;
Rogers, L. M. Tetrahedron 1998, 54, 7075–7080.
7. Aqad, E.; Lakshmikantham, M. V.; Cava, M. P. Org. Lett. 2001, 3, 4283–4285.
8. Aqad, E.; Lakshmikantham, M. V.; Cava, M. P.; Broker, G. A.; Rogers, R. D. Org.
Lett. 2003, 5, 2519–2521.
9. Aqad, E.; Lakshmikantham, M. V.; Cava, M. P. Org. Lett. 2003, 5, 4089–4092.
10. Aqad, E.; Lakshmikantham, M. V.; Cava, M. P. Org. Lett. 2004, 6, 3039–3041.
11. Kesharwani, T.; Worlikar, S. A.; Larock, R. C. J. Org. Chem. 2006, 71, 2307–2312.
12. Ogawa, S.; Muraoka, H.; Kikuta, K.; Saito, F.; Sato, R. J. Organomet. Chem. 2007,
692, 60–69.
5.6.4. 1,3-Diphenylbenzo[c]selenophene (7n)
Following the above-mentioned procedure D, 7n was obtained
using the benzo[c]furan 10d (0.2 g, 0.74 mmol) and Woollins re-
agent (0.10 g, 0.19 mmol) as thick yellow liquid 0.096 g, (40%).
[Found: C, 72.00; H, 4.18. C20H14Se requires: C, 72.07; H, 4.23%.] Rf
(hexane) 0.80; dH (400 MHz, CDCl3) 7.97 (4H, d, J 7.8 Hz, ArH), 7.82
(2H, dd, J 3.92, 2.96 Hz, ArH), 7.48 (4H, t, J 7.8 Hz, ArH), 7.29 (2H, t, J
6.52 Hz, ArH), 7.02 (2H, dd, J 3.92, 2.98 Hz, ArH); dc (100 MHz,
CDCl3) 143.6, 131.6, 128.5, 127.0, 126.8, 124.7, 122.03, 120.0; m/z (EI)
334 (Mþ, 31).
5.6.5. 1,3-Di(naphthalene-1-yl)selenophene (7o)
Following the above-mentioned procedure D, compound 7o was
obtained using the benzo[c]furan 10e (0.2 g, 0.54 mmol) and
Woollins reagent (0.07 g, 0.13 mmol) as thick yellow liquid (0.10 g,
43%). [Found: C, 77.70; H, 4.11. C28H18Se requires: C, 77.60; H, 4.19%.]
Rf (hexane) 0.72; nmax (KBr) 1596, 1479, 762, 722 cmꢀ1
; dH
(400 MHz, CDCl3) 7.72–7.68 (6H, m, ArH), 7.48–7.33 (8H, m, ArH),
7.20–7.18 (2H, m, ArH), 6.86–6.84 (2H, m, ArH); dc (100 MHz, CDCl3)
143.1, 133.1, 129.8, 128.7, 128.3, 127.3, 126.4, 126.3, 125.3, 124.8,
123.6, 121.6, 120.1; m/z (EI) 434 (Mþ, 11).
13. (a) Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett. 2005, 46, 4225–4229;
(b) Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett. 2007, 48, 779–784.
14. Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett. 2005, 46, 7201–7204.
15. (a) Bhattacharyya, P.; Woollins, J. D. Tetrahedron Lett. 2001, 42, 5949–5952; (b)
Bethke, J.; Karaghiosoft, K.; Wessjohann, L. A. Tetrahedron Lett. 2003, 44, 6911–
6913.
16. Ba¨uerle, P.; Go¨tz, G.; Emerle, P.; Port, H. Adv. Mater 1992, 4, 564–568.
17. Bederradji, F.; Nechab, M.; Einhorn, C.; Einhorn, J. Synth. Lett. 2006, 13, 2035–
2038.
5.6.6. 2-(1-(1-(Thiophen-2-yl)benzo[c]selenophen-3-yl)benzo[c]-
selenophen-3-yl)thiophene (13)
Following the above-mentioned procedure A, 13 was obtained
using diphthalide 11 (0.5 g, 1.87 mmol), 2-thienylmagnesium