Synthesis and characterization of naphth-annelated thiophene analogs

Article abstract of DOI:10.1016/j.tet.2010.01.111

Synthesis of symmetrical and unsymmetrical naphth-annelated thienyl heterocycles has been achieved via thionation of hydroxyketones/diketones using Lawesson's reagent. Photophysical studies of 1,3-disubstituted naphtho[c]thiophene analogs are presented. Electro-oxidative behavior of these naphtha-annelated thiophenes are investigated using cyclic voltammeter.

Full text of DOI:10.1016/j.tet.2010.01.111

Tetrahedron 66 (2010) 2340–2350
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and characterization of naphth-annelated thiophene analogs
*
J. Arul Clement, 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:
Synthesis of symmetrical and unsymmetrical naphth-annelated thienyl heterocycles has been achieved via
thionationofhydroxyketones/diketonesusingLawesson’s reagent.Photophysicalstudies of1,3-disubstituted
naphtho[c]thiophene analogs are presented. Electro-oxidative behavior of these naphtha-annelated thio-
phenes are investigated using cyclic voltammeter.
Received 25 November 2009
Received in revised form 27 January 2010
Accepted 29 January 2010
Available online 4 February 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Napthalides
Lawesson’s reagent
Naphtho[c]thiophene
Annelated thiophenes
Cyclic Voltamogram
Band gap
1. Introduction
and feature small optical gaps of 1–2 eV, by exploiting the high-
energy HOMO of the donating unit and the low-energy LUMO of
Synthesis and application of thienyl oligomers has been of
great interest for chemists and material scientists due to their
intrinsic electronic, optical, and redox-properties.1 Oligothio-
the accepting unit. The reduction of band gap (Eg) will enhance the
thermal population of the conducting band and thus increase
the number of intrinsic charge carriers. Theoretical investigation of
the lowering of Eg as a function of increasing quinonoid character of
polyaromatics led to the development new approaches to the
design of low-band gap materials.8 Hence, the synthesis and
characterization of new low-band gap oligomers is highly de-
manding due to their potentially superior conductivity and non-
linear optical properties Moreover, synthesis and investigation of
structurally well-defined thienyl oligomers are useful in gaining
insight into the structural and electronic peculiarities of the cor-
responding polymers. Indeed, saturation of electronic properties
after a particular chain length significantly reduces the vast dif-
ference between thienyl oligomers and their polymers.
phenes are one of the most frequently used
p-conjugated mate-
rials in organic electronic devices and molecular electronics.2 The
higher polarizability of the sulfur atom in thiophenes leads to
excellent charge transport-properties, which spurred their
growth. Additionally, the availability of plethora of methods to
modify the core thiophene unit led to the development higher
dimensionalities of oligothiophenes.3 Indeed, compared to their
polymeric counterparts, the structurally defined
p-conjugated
thienyl oligomers are synthetically demanding, since they can be
easily processed into defect-free layers and films using vacuum
evaporation techniques.
Thienyl oligomers have been widely used as components in
organic light-emitting diodes (OLEDs),4 organic solar cells (OSC),5
organic field-effect transistors (OFET),6 and photo refractive ho-
lography.7 In particular, thienyl oligomers that absorb both visible
and near-infrared light have been developed to increase the energy
conversion efficiency of solar cells by collecting a larger part of the
solar spectrum. These small band gap oligomers usually consist of
electron-rich and electron-poor units alternating along the chain
The use of terthienyl 1 as a precursor for electropolymerization
has been well explored.9 The insertion of tailored ring system into
the middle of this trimeric precursor presents several advantages,
such as the construction of alternate donor-acceptor moieties or
the stabilization of rather unstable fused ring systems. The com-
paratively smaller band gap of ITN (isothianapthene) based
terthienyl 2 over the thiophene-containing materials is a result of
the increased contribution of the quinoid resonance structure due
to the stabilization achieved by the aromatization of the benzene
ring.10 Over the years, the synthesis and characterization of 1,3-
dithienylbenzo[c]thiophene 2 and its analogs have been well
explored.11 In particular, benzo[c]thiophene analogs are used as
* Corresponding author. Tel.: þ91 44 22202813; fax: þ91 44 22300488.
E-mail address: mohan_67@hotmail.com (A.K. Mohanakrishnan).
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.01.111

J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
2341
fluorescent labels,12components in OLEDs13 as well as photovol-
taics.14 Kisselev and Thelakkat achieved the synthesis of polymer
containing ITN and triaryl amine groups, a new class of light-
harvesting dyes with band gap values below 1.8 eV.15 Recently,
Swager and co-workers reported the synthesis of push-pull-type
near-IR
fluorophores
containing
isobenzofuran
and
isothianaphthene subunits.16
Cava and co-workers reported the synthesis and electro-
polymerization of 1,3-dithienylnaphtho[c]thiophene 3.17 Even after
fifteen years of this first report, with the exception of parent
naphtho[c]thiophene18 till date any further derivative of
isothiaanthracene (ITA) is yet to be explored. This may be due to
either synthetic difficulty associated with the preparation of this
compound or its reduced stability. However, very recently, Lin and
Hsu reported19 synthesis of a series of benzo[c]heterocycle and
naphtho[c]heterocycle diesters and dinitriles involving iterative
elongation protocol.
The exciting photophysical properties along with the enormous
application potential of isothianaphthenes11–16 prompted us to
explore the synthesis of the corresponding naphth-annelated
thiophene analogs. Obviously, the easy availability of naph-
tho[c]thiophene analogs will provide us an opportunity to analyze
their photophysical and electrochemical properties to ascertain
their exact band gap values. As a continuation of our work on
synthesis and characterization of annelated thienyl heterocycles,20
we report herein our detailed study on synthesis and character-
ization of 1,3-disubstituted naphtho[c]thiophene analogs.
Scheme 1.
Using the procedure as mentioned above, various types of arenes
10 on Friedel–Crafts acetylation with chloro ester 5 followed by
condensation of the resulting keto-esters 11a–j with phthalaldehyde
7 led to the isolation of corresponding keto-acids 12a–j in 59–69%
yields. Reductive cyclization of these keto-acids yielded respective
lactones 13a–j (Scheme 2).
S
1
S
S
S
2
S
3
S
S
S
S
2. Results and discussion
Cava and co-workers achieved the synthesis of 1,3-dithie-
nylnaphtho[c]thiophene 3 via ring opening of 2-thienylnaphthalide
with 2-thienylmagnesium bromide followed by thionation.17 The
required 2-thienylnaphthalide was prepared using Friedel–Crafts
naphthoylation of thiophene with 2,3-naphthalic anhydride
followed by reductive cyclization. Due to the difficulty associated
with the ready availability 2,3-naphthalic anhydride,21 an alterna-
tive methodology was visualized for the synthesis of 2-thie-
nylnaphthalide and possibly other 2-arylnaphthalides as well.
Accordingly, substituted thiophenes 4 upon Friedel–Crafts acety-
lation with chloro ester 522 in the presence of anhydrous SnCl4 at
room temperature afforded crude keto-esters 6a–d. Condensation
of phthalaldehyde 7 with the keto-esters 6a–d using t-BuOK as
a base in ethanol at room temperature led to the isolation of
expected keto-acids 8a–d in 65–79% yields.
Scheme 2.
Next, ring opening of 2-thienylnaphthalide 9a with freshly pre-
pared 2-thienyl Grignard/aryl Grignards followed by aq NH4Cl
quenching and subsequent work up of the reaction mixture led to
the isolation of keto-alcohols 14a–e. Thionation of these crude keto-
alochols using Lawesson’s reagent (LR) in dry DCM at room tem-
perature for ten minutes followed by workup and careful column
chromatographic purification furnished naphtho[c]thiophenes 3/
15a–e as black solid in 35–42% yield, (Scheme 3).
Selective reduction of the ketone-carbonyl function of 8a–d using
NaBH4 in THF–EtOH (2:5) at reflux for 12 h, followed by acid cata-
lyzed cyclization furnished respective lactones 9a–d (Scheme 1). It
should be noted that the procedure adopted herein for the prepa-
ration of 2-thienylnaphthalides 9a is much simpler than the pre-
viously reported procedure.17

2342
J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
Finally, heteroarylnaphthalides 13h, 13i, and 13j could be
smoothly transformed into the respective naphtho[c]thiophenes
18, 19, and 20a,b in reasonable yields (Scheme 6).
i) 2-thienylMgBr
ii) aq. NH4Cl
13h
N
S
18
S
iii) LR/DCM
rt, 10 min
45%
i) 2-thienylMgBr
ii) aq. NH4Cl
13i
iii) LR/DCM
rt, 10 min
47%
S
19
S
S
i) ArMgBr
ii) aq. NH4Cl
Ar1
Me
S
Scheme 3.
13j
N
iii) LR/DCM
rt, 10 min
20a Ar1 = thiophen-2-yl (49%)
20b Ar1 = p-tolyl (52%)
Similarly, the interaction of 5-methyl-2-thienylnaphthalide 9c
with freshly prepared aryl Grignards followed by thionation of the
resulting keto-alcohols led to the isolation of naphtho[c]thiophenes
16a–c (Scheme 4).
Me
Scheme 6.
Alternatively, synthesis of symmetrical and unsymmetrical
naphtho[c]thiophenes are visualized via interaction of respective 2,3-
diaroylnapthalenewithLawesson’s reagent. Toward the realization of
this objective, preparation of required unsymmetrical diketones 21a–
c was achieved using NaCN catalyzed Stetter23 reaction of aryl alde-
hyde and Mannich base. Condensation of the resulting diketones
21a–c with phthalaldehyde 7 using t-BuOK as a base furnished un-
symmetrical 2,3-diaroylnapthalenes 22a–c in 72–82% yields.
Interaction of 2,3-diaroylnaphthalenes 22a–c with 1 equiv of
Lawesson’s reagent in dry benzene at 50 ꢀC for 15 min followed by
a careful column chromatographic purification afforded the naph-
tho[c]thiophenes 3/15b/23a (Scheme 7).
Scheme 4.
Under identical conditions, ring opening of the arylnaphthalides
13a–c with 2-thienyl Grignards followed by thionation and column
chromatographic purification afforded naphtho[c]thiophenes 15d/
17a,b (Scheme 5).
Scheme 5.
Scheme 7.

J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
2343
Similarly, the condensation of diketones 24a–c23 with phtha-
laldehyde 7 gave 2,3-diaroylnapthalenes 25a–c in 72–80% yields.
Upon interaction of diaroylnapthalenes 25a–c with Lawesson’s re-
agent in dry benzene at 50 ꢀC led to the isolation of 1,3-disubstituted
naphtho[c]thiophenes 26a–c as black solids (Scheme 8).
naphtho[c]thiophene 3 with benzene/toluene reduced the
p
-con-
jugation. However, a similar replacement of the thiophene unit with
p-anisyl group closely matched with its lmax value. Indeed, the re-
placement of the thiophene unit of 3 with 1-naphthalene caused
10 nm red shift of its lmax value. Substitution of thiophene ring with
electron rich aryl units significantly enhanced the p-conjugation of
3. Replacement of thiophene unit with benzo[b]thiophene, tri-
phenyl amine, and N-2-ethylcarbzaole produced red shift of lmax
value in the range of 10–18 nm.
The qualitative photoluminescence spectra of naphtho[c]thienyl
heterocycles exhibited emission in the region of 640–690 nm with
emission value being gradually red shifted with increase of
p-
conjugation. Naphth-annelation of terthiophene 1, red shifted
emission value w200 nm. Similar to benzo[c]thiophene analogs,
luminescence value of naphtho[c]thiophenes also red shifted with
respect to the increase of p-conjugation.
The oxidation potentials and also the onset oxidation values
of the naphtho[c]thiophenes are presented in Table 1. It is clear
that benz-annelation/naphth-annelation of parent terthienyl 1
has equally enhanced its electro-oxidation behavior. Exchange of
one of thiophene unit of 3 with aryl units has significantly in-
creased its oxidation potential values. Surprisingly, the in-
troduction of
a-alkyl substituents (methyl and n-hexyl) into 3
led to an increase in the oxidation potential value. Indeed, in-
corporation of methoxy group into naphtho[c]thiophene 15b
also increased the Epa value. Recently, Lin and Hsu observed19
a decrease in the Epa value when electron withdrawing ester
units are attached to the benzene portion of 3. Replacement of
thiophene unit of 3 with benzo[b]thiophene, triphenyl amine,
and N-2-ethylcarbzaole led to the decrease in their electro-
oxidation behavior.
The difference between Epa and oxidation onset (Eox) values of
benz-annelated thienyl heterocycle 2 is large compared to naphth-
annelated heterocycle 3. This clearly confirms that, relatively, the
oxidation rate of naphth-annelated heterocycle 3 is faster than the
benzo[c]thiophene 2. Indeed, most of the naptho[c]thienyl het-
erocycles showed only a small difference between the Epa and ox-
idation onset values.
Scheme 8.
The optical properties of selected naphth-annelated thienyl
heterocycles are listed in Table 1. The photophysical data of parent
terthienyl 117 as well as 1,3-dithienylbenzo[c]thiophene 211e are also
included. The UV–vis spectra of naphtho[c]thiophenes exhibited
highly intense absorption band in the region of 560–595 nm due to
The HOMO and LUMO energy levels of selected naph-
tho[c]thiophenes were calculated from the absorption onset and
the onset oxidation potential values and the exact values are pre-
sented in Table 1. Almost all the naphtho[c]thiophenes exhibited
band gap (Eg) value in the range of 2.1–2.2 eV. In general annelation
of naphthalene ring to the terthiophene 1 reduced its Eg value from
3.5 to 2.17 (terthiophene/3). Compared to benzo[c]thiophene 2,
compound 3 has 0.5 eV less Eg value. Replacement of the thiophene
unit of 3 with aryl as well as heteroaryl units did not have any
significant influence on its band gap values. The HOMO and LUMO
energy levels of naphtho[c]thiophenes lie in the range of 5.1–5.6 eV
and 2.9–3.4 eV, respectively.
p–p* electron transfer of the conjugated backbone. Apparently,
naphth-annelation of terthienyl (1/3) red shifted lmax value more
than twice (w235 nm) that of benz-annelation (w100 nm). The
introduction of
a-alkyl substituents (methyl and n-hexyl) into 3
increased its lmax value. Exchange of one thiophene unit of
Table 1
Physical data for some selected naphtho[c]thiophenes
a
b
c
d
onset
Compound
lmax
llum
Eg
1Epa
(v)
E
ox
HOMOe
(eV)
LUMOf
(eV)
(nm)
(nm)
(eV)
(eV)
1
2
3
335
433
570
595
560
565
570
580
578
582
584
591
580
598
560
431
532
640
665
645
655
652
660
650
649
652
682
685
691
623
3.49
2.66
2.17
2.08
2.21
2.19
2.17
2.14
2.14
2.13
2.12
2.10
2.13
2.07
2.21
1.05
0.87
0.66
1.01
0.75
0.93
0.98
1.14
1.07
0.85
0.81
0.73
0.95
0.78
1.23
0.98
0.64
0.62
0.95
0.69
0.87
0.92
1.08
1.01
0.79
0.75
0.69
0.83
0.72
1.17
5.42
5.08
5.06
5.39
5.13
5.31
5.36
5.52
5.45
5.23
5.19
5.13
5.27
5.16
5.61
1.93
2.42
2.86
3.31
2.92
3.12
3.19
3.38
3.31
3.10
3.07
3.03
3.14
3.09
3.40
15a
15b
15c
15d
15e
16a
17a
17b
18
3. Conclusions
Preparation of various types of aryl/heteroaryl naphthalides
have been achieved in reasonable yields via condensation of the
keto-ester with phthalaldehyde followed by reductive cyclization.
Thionation of 2,3-disubstituted naphthalene based keto-alcohols
or diketones with LR reagent led to the isolation of aryl/hetero-
aryl substituted naphtho[c]thiophene analogs. These naph-
tho[c]thienyl heterocycles are dark solids, reasonably stable, and
can be stored in refrigerator under inert atmosphere in the solid
state. However, purple color solution of these heterocycles
undergoes slow decomposition when exposed white light. The
HOMO, LUMO, and band gap values of naphtho[c]thiophene
analogs are correlated with their electronic structures. The higher-
lying HOMO energy levels of these naphtho[c]thiophenes
19
20a
26a
a
Measured in dilute dichloromethane solution.
Excited at the absorption maxima.
b
c
d
e
f
Estimated from the absorption (Eg¼1240/lmax).
1Epa denotes the first anodic peak potential.
onset
Calculated using the empirical equation: HOMO¼(4.44þE
Calculated from LUMO¼HOMꢁEg.
).
ox

2344
J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
(>5.1 eV) may be suitable to explore them as pontential candidates
for application as hole-transporting materials in double-layer
OLEDs. Emission values of the naphtho[c]thiophenes clearly
indicated that they can be explored Far-IR fluorophore applica-
tions.16 Research is in progress to synthesize push-pull systems
involving naphtho[c]thiophene unit.
(3H, m, ArH), 7.34 (1H, d, J 3.9 Hz, ArH), 7.04 (1H, t, J 4.4 Hz, ArH); dC
(75.6 MHz, CDCl3) 189.2, 170.6, 144.8, 137.2, 134.7, 134.5, 134.2,
132.8, 132.7, 129.3, 129.2, 128.3, 128.2, 128.1, 128.0; MS (EI): m/z
(%)¼282 [M]þ.
4.2.3. 3-(5-Hexylthenoyl)-2-naphthoic acid (8b). Condensation of
keto-ester 6b (5.0 g, 16.89 mmol) and phthalaldehyde 7 (2.26 g,
16.89 mmol) using the above-mentioned procedure afforded
compound 8b (4.88 g, 79%) as a thick liquid; [Found: C, 72.3; H, 5.9;
S, 8.6C22H22O3S requires C, 72.10; H, 6.05; S, 8.75%]; Rf (30% EA/
4. Experimental
4.1. General
hexane) 0.61; nmax (KBr) 3559, 2965, 1695, 1656 cmꢁ1
; dH
All melting points are uncorrected. IR spectra were recorded on
a SHIMADZU FTIR 8300 instrument. 1H and 13C NMR spectra were
recorded in CDCl3 using TMS as an internal standard on a Bruker-
300 spectrometer. Mass spectra were recorded on a JEOL DX 303
HF spectrometer. Elemental analyses were carried out on a Perkin–
Elmer series II 2400 (IIT Madras) instrument. All UV–vis spectra
were recorded in CH2Cl2 solution. The emission spectra were
recorded on Perkin–Elmer LS-45 spectrophotometer. The cyclic-
voltammogram of 10ꢁ3 M solution of naphtho[c]thiophenes was
carried out on a CHI 600C electrochemical analyzer. All the mea-
surements were carried out under oxygen free condition using
three electrode cells in which glassy carbon electrode was working
electrode, saturated Ag/AgCl electrode was reference electrode, and
platinum wire was used as an auxiliary electrode. Tetrabuty-
lammonium hexafluoro phosphate (TBAPF6) was used as support-
ing electrolyte and its concentration was 10ꢁ1 M.
(300 MHz, CDCl3) 8.61 (1H, s, ArH), 8.01–7.98 (1H, m, ArH), 7.95
(1H, s, ArH), 7.85 (1H, d, J 7.5 Hz, ArH), 7.75–7.69 (2H, m, ArH), 7.19
(1H, d, J 4.5 Hz, ArH), 6.71–6.69 (1H, m, ArH), 2.69 (2H, t, J 6.9 Hz,
CH2), 1.51–1.49 (2H, m, CH2), 1.24–1.06 (6H, m, CH2), 0.81–0.76 (3H,
m, CH3); dC (75.6 MHz, CDCl3) 189.1, 170.3, 150.6, 142.1, 136.4, 135.1,
133.9, 133.2, 132.1, 129.6, 129.1, 127.9, 127.4, 126.5, 125.5, 31.9, 30.5,
28.9, 28.5, 22.6, 14.3; MS (EI): m/z (%)¼366 [M]þ.
4.2.4. 3-(5-Methylthenoyl)-2-naphthoic acid (8c). Condensation of
keto-ester 6c (5.0 g, 22.12 mmol) and phthalaldehyde 7 (2.96 g,
22.12 mmol) using the above-mentioned procedure afforded
compound 8c (4.97 g, 76%) as a colorless solid; mp 215 ꢀC; [Found:
C, 68.7; H, 4.0; S, 10.7. C17H12O3S requires C, 68.90; H, 4.08; S,
10.82%]; Rf (30% EA/hexane) 0.71; nmax (KBr) 3563, 2975, 1690,
1660 cmꢁ1
; dH (300 MHz, CDCl3) 8.63 (1H, s, ArH), 7.98 (1H, d, J
7.2 Hz, ArH), 7.93 (1H, s, ArH), 7.89 (1H, d, J 7.2 Hz, ArH), 7.66–7.62
(2H, m, ArH), 7.17 (1H, d, J 3.3 Hz, ArH), 6.74–6.73 (1H, m, ArH), 2.54
(3H, s, CH3); dC (75.6 MHz, CDCl3) 188.8, 170.6, 150.9, 142.4, 137.2,
135.6, 134.3, 133.0, 132.6, 129.4, 129.3, 128.3, 128.2, 128.1, 126.9,
125.9, 16.2; MS (EI): m/z (%)¼296 [M]þ.
4.1.1. Ethyl 3-(chlorocarbonyl)propanoate (5)22. A solution of suc-
cinic anhydride (65.0 g, 0.65 mol) in absolute ethanol (75 mL) was
heated in a steam bath until alcohol ceased to reflux for 2 h. Then,
excess of alcohol was removed by distillation under reduced
pressure. The residue was refluxed with 75 mL of thionyl chloride
for 2 h. Then excess of thionyl chloride was removed and purifi-
cation of the crude product using vacuum distillation (2 mmHg,
94 ꢀC) gave ethyl 3-(chlorocarbonyl)propanoate (87 g, 82%) as
a colorless liquid.
4.2.5. 3-(3-Methylthenoyl)-2-naphthoic acid (8d). Condensation of
keto-ester 6d (5.0 g, 22.12 mmol) and phthalaldehyde 7 (2.96 g,
22.12 mmol) using the above-mentioned procedure afforded
compound 8d (4.25 g, 65%) as a colorless solid; mp 158 ꢀC; [Found:
C, 68.7; H, 4.0; S, 10.7. C17H12O3S requires C, 68.90; H, 4.08; S,
10.82%]; Rf (30% EA/hexane) 0.71; nmax (KBr) 3524, 2920,1656,1695,
4.2. General procedure for preparation of keto-esters (6a–d)22
1545 cmꢁ1
; dH (300 MHz, CDCl3) 8.64 (1H, s, ArH), 7.98 (1H, d, J
7.5 Hz, ArH), 7.91–7.87 (2H, m, ArH), 7.66–7.62 (2H, m, ArH), 7.45
(1H, d, J 4.5 Hz, ArH), 6.96 (1H, d, J 4.8 Hz, ArH), 2.42 (3H, s, ArH); dC
(75.6 MHz, CDCl3) 189.7,170.7,145.8,139.1,136.9,134.5,133.1,132.6,
131.7, 129.5, 129.3, 128.3, 128.2, 128.1, 127.7, 125.4, 16.5; MS (EI): m/z
(%)¼296 [M]þ.
To a solution of chloro ester 5 (5.0 g, 30.4 mmol) in dry DCM
(100 mL) at 0 ꢀC, thiophene 4 (2.56 g, 30.4 mmol) was added. To
this, a solution of SnCl4 (8.71 g, 30.4 mmol) in dry DCM (10 mL) was
slowly added. After the addition of SnCl4 was completed, the re-
action mixture was stirred at room temperature for 3 h. Then it was
poured into ice water (200 mL) and extracted with chloroform
(2ꢂ30 mL) and dried (Na2SO4). Removal of solvent in vacuo affor-
ded 6a–d as a thick liquid. The crude keto-esters were used as such
for next step without any further purification.
4.2.6. 3-(Thiophen-2-yl)naphtho[2,3-c]furan-1(3H)-one
(9a). To
a solution of 8a (3.5 g, 12.41 mmol) in THF–EtOH (2:5), NaBH4
(1.83 g, 49.64 mmol) was carefully added in small portions at 0 ꢀC.
The reaction mixture was refluxed for 12 h and then poured into
ice water (200 mL). It was acidified using HCl (pH¼2–3) and then
stirred for 0.5 h at room temperature. The solid obtained was
filtered and washed with methanol to afford thienyl-2,3-
naphthalide 9a (2.77 g, 84%) as a colorless solid; mp 172 ꢀC (lit.17
172 ꢀC).
4.2.1. 3-Thenoyl-2-naphthoic acid (8a). The ethyl 4-oxo-4-(thio-
phen-2-yl)butanoate 6a (5.0 g, 23.58 mmol) and phthalaldehyde 7
(3.16 g, 23.58 mmol) were dissolved in ethanol (60 mL). The t-BuOK
(6.60 g, 58.96 mmol) was slowly added to the solution and the re-
action mixture was stirred for 10 h at room temperature. Then it
was poured into water and extracted with DCM (1ꢂ20 mL). The
aqueous layer was acidified using HCl (pH¼2–3), and it was stirred
for 0.5 h at room temperature. The solid was filtered and washed
with methanol to afford 3-thenoyl-2-naphthoic acid 8a (4.78 g,
72%) as a colorless solid.
4.2.7. 3-(5-Hexylthiophen-2-yl)naphtho[2,3-c]furan-1(3H)-one
(9b). Reductive cyclization of acid 8b (3.5 g, 9.56 mmol) using
NaBH4 (1.41 g, 38.25 mmol) adopting the procedure similar to
that of 9a afforded compound 9b (2.51 g, 75%) as a colorless solid;
mp 134 ꢀC; [Found: C, 75.2; H, 6.3; S, 9.0. C22H22O2S requires C,
75.39; H, 6.33; S, 9.15%]; Rf (10% EA/hexane) 0.61; nmax (KBr) 2890,
4.2.2. 3-Thenoyl-2-naphthoic acid (8a). Colorless solid. Mp 205 ꢀC.
[Found: C, 68.3; H, 3.5; S, 11.2. C16H10O3S requires C, 68.07; H, 3.57;
S, 11.36%]; Rf (40% EA/hexane) 0.42; nmax (KBr) 3565, 1691,
1756, 1528 cmꢁ1
; dH (300 MHz, CDCl3) 8.44 (1H, s, ArH), 7.99 (1H,
d, J 7.2 Hz, ArH), 7.86–7.82 (2H, m, ArH), 7.58–7.53 (2H, m, ArH),
6.94–6.93 (1H, m, ArH), 6.68–6.67 (1H, m, ArH), 6.61 (1H, s, ArH),
2.67 (2H, t, J 7.1 Hz, CH2), 1.53–1.50 (2H, m, CH2), 1.20–1.10 (6H, m,
CH2), 0.78–0.70 (3H, m, CH3); dC (75.6 MHz, CDCl3) 169.7, 148.9,
1642 cmꢁ1
;
dH (300 MHz, CDCl3) 8.61 (1H, s, ArH), 7.97 (1H, d, J
9.0 Hz, ArH), 7.94 (1H, s, ArH), 7.93 (1H, d, J 9.0 Hz, ArH), 7.68–7.59

J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
2345
142.6, 136.7, 136.3, 133.5, 129.9, 129.1, 128.5, 128.1, 127.3, 126.9,
123.9, 123.8, 122.4, 78.4, 31.5, 30.3, 28.7, 22.5, 14.0; MS (EI): m/z
(%)¼350 [M]þ.
148.6,137.5,133.4,132.1,130.9,130.3,128.8,128.7,127.9,127.6,127.3,
124.6, 110.4, 110.2, 55.9, 55.4; MS (EI): m/z (%)¼336 [M]þ.
4.3.3. 3-(3,5-Dimethoxybenzoyl)-2-naphthoic
acid
(12c). Con-
4.2.8. 3-(5-Methylthiophen-2-yl)naphtho[2,3-c]furan-1(3H)-one
(9c). Reductive cyclization of acid 8c (3.5 g, 11.82 mmol) using
NaBH4 (1.75 g, 47.29 mmol) adopting the procedure similar to that
of 9a afforded compound 9c (2.68 g, 81%) as a colorless solid; mp
146 ꢀC; [Found: C, 72.6; H, 4.3; S,11.3C17H12O2S requires C, 72.83; H,
4.31; S, 11.44%]; Rf (10% EA/hexane) 0.58; nmax (KBr) 2945, 1753,
densation of keto-ester 11c (5.0 g, 18.79 mmol) and phthalaldehyde
7 (2.51 g, 18.79 mmol) using the procedure similar to that of 8a
afforded compound 12c (3.72 g, 59%) as a colorless solid; mp
215 ꢀC; [Found: C, 71.2; H, 4.6. C20H16O5 requires C, 71.42; H, 4.79%];
Rf (30% EA/hexane) 0.51; nmax (KBr) 3540, 2825, 1635, 1680,
1565 cmꢁ1
; dH (300 MHz, CDCl3) 8.53 (1H, s, ArH), 8.04–8.01 (1H,
1590 cmꢁ1
;
dH (300 MHz, CDCl3) 8.52 (1H, s, ArH), 8.04 (1H, d, J
m, ArH), 7.96–7.95 (2H, m, ArH), 7.65–7.63 (2H, m, ArH), 7.48 (1H, s,
ArH), 7.11 (1H, d, J 8.1 Hz, ArH), 6.93 (1H, d, J 7.8 Hz, ArH), 3.82 (6H,
s, OCH3) dC (75.6 MHz, CDCl3) 194.5, 164.9, 161.3, 149.5, 134.5, 133.9,
132.2, 131.8, 129.1, 129.0, 127.5, 126.9, 125.7, 120.4, 111.2, 110.4, 55.9,
55.1; MS (EI): m/z (%)¼336 [M]þ.
7.8 Hz, ArH), 7.93–7.88 (2H, m, ArH), 7.68–7.59 (2H, m, ArH), 7.01
(1H, d, J 3.0 Hz, ArH), 6.74–6.73 (1H, m, ArH), 6.68 (1H, s, ArH), 2.44
(3H, s, CH3); dC (75.6 MHz, CDCl3) 169.9, 142.7, 142.6, 137.1, 136.3,
133.4, 129.9, 129.1, 128.4, 128.3, 127.3, 126.9, 125.1, 123.7, 122.3, 78.4,
15.5; MS (EI): m/z (%)¼280 [M]þ.
4.3.4. 3-(3,4,5-Trimethoxybenzoyl)-2-naphthoic acid (12d). Con-
densation of keto-ester 11d (5.0 g,16.89 mmol) and phthalaldehyde
7 (2.26 g, 16.89 mmol) using the procedure similar to that of 8a
afforded compound 12d (4.20 g, 68%) as a colorless solid; mp
208 ꢀC; [Found: C, 68.7; H, 4.8. C21H18O6 requires C, 68.85; H,
4.95%]; Rf (30% EA/hexane) 0.45; nmax (KBr) 3552, 2815, 1647, 1685,
4.2.9. 3-(3-Methylthiophen-2-yl)naphtho[2,3-c]furan-1(3H)-one
(9d). Reductive cyclization of acid 8d (3.5 g, 11.82 mmol) using
NaBH4 (1.75 g, 47.29 mmol) adopting the procedure similar to that
of 9a afforded compound 9d (2.58 g, 78%) as a colorless solid; mp
136 ꢀC; [Found: C, 72.7; H, 4.3; S,11.3C17H12O2S requires C, 72.83; H,
4.31; S, 11.44%]; Rf (10% EA/hexane) 0.58; nmax (KBr) 2953, 1759,
1549 cmꢁ1
; dH (300 MHz, DMSO-d6) 8.53 (1H, s, ArH), 8.15–8.13
1510 cmꢁ1
;
dH (300 MHz, CDCl3) 8.49 (1H, s, ArH), 8.05 (1H, d, J
(1H, m, ArH), 8.04–8.01 (1H, m, ArH), 7.86 (1H, s, ArH), 7.66–7.64
(2H, m, ArH), 7.44 (1H, d, J 9.0 Hz, ArH), 6.93 (1H, d, J 8.7 Hz, ArH),
3.86 (3H, s, OCH3), 3.69 (3H, s, OCH3), 3.31 (3H, s, OCH3); dC
(75.6 MHz, DMSO-d6) 193.7, 167.5, 157.4, 153.6, 141.7, 140.4, 133.4,
131.9, 130.4, 128.9, 128.6, 128.1, 127.9, 127.6, 126.4, 124.7, 107.4, 60.5,
60.3, 56.1; MS (EI): m/z (%)¼366 [M]þ.
7.8 Hz, ArH), 7.91–7.87 (2H, m, ArH), 7.67–7.59 (2H, m, ArH), 7.20
(1H, d, J 4.8 Hz, ArH), 6.91 (1H, d, J 4.8 Hz, ArH), 6.89 (1H, s, ArH),
2.39 (3H, s, CH3); dC (75.6 MHz, CDCl3) 169.9, 142.6, 139.1, 136.2,
133.5, 132.6, 130.7, 129.9, 129.1, 128.5, 127.3, 126.9, 125.8, 123.9,
122.4, 77.6, 14.1; MS (EI): m/z (%)¼280 [M]þ.
4.3.5. 3-(Benzo[d][1,3]dioxoyl)-2-naphthoic acid (12e). Conden-
sation of keto-ester 11e (3.0 g, 12.0 mmol) and phthalaldehyde 7
(1.60 g, 12.0 mmol) using the procedure similar to that of 8a
afforded compound 12e (2.64 g, 69%) as a colorless solid; mp
183 ꢀC; [Found: C, 71.0; H, 3.7. C19H12O5 requires C, 71.25; H, 3.78%];
Rf (30% EA/hexane) 0.55; nmax (KBr) 3572, 2850, 1635, 1689,
4.3. General procedure for preparation of keto-esters (11a–j)
To a solution of chloro ester 5 (5.0 g, 30.4 mmol) in dry DCM
(100 mL) at 0 ꢀC, ansiole 10a (3.29 g, 30.4 mmol) was added. To this,
a solution of SnCl4 (9.51 g, 30.4 mmol) in dry DCM (10 mL) was
slowly added. After the addition of SnCl4 was completed, the re-
action mixture was stirred at room temperature for 3 h. Then it was
poured into ice water (200 mL) and extracted with chloroform
(2ꢂ30 mL) and dried (Na2SO4). Removal of solvent in vacuo affor-
ded 11a–j as a thick liquid. The crude keto-esters 11a–j was used as
such for next step without any further purification.
1570 cmꢁ1
; dH (300 MHz, CDCl3) 8.66 (1H, s, ArH), 8.01 (1H, d, J
6.9 Hz, ArH), 7.89 (1H, d, J 7.2 Hz, ArH), 7.83 (1H, s, ArH), 7.66–7.55
(2H, m, ArH), 7.40 (1H, s, ArH), 7.26–7.22 (1H, m, ArH), 6.77 (1H, d, J
7.8 Hz, ArH), 6.05 (2H, s, OCH2); dC (75.6 MHz, CDCl3) 195.2, 170.3,
151.9, 148.2, 137.9, 134.5, 133.0, 132.5, 132.4, 129.5, 129.3, 128.2,
127.9, 126.7, 125.7, 108.9, 107.8, 101.9; MS (EI): m/z (%)¼320 [M]þ.
4.3.1. 3-(4-Methoxybenzoyl)-2-naphthoic acid (12a). Condensation
of keto-ester 11a (5.0 g, 21.18 mmol) and phthalaldehyde 7
(2.83 g, 21.18 mmol) using the procedure similar to that of 8a
afforded compound 12a (4.01 g, 62%) as a colorless solid; mp
218 ꢀC; [Found: C, 74.3; H, 4.5. C19H14O4 requires C, 74.50; H,
4.61%]; Rf (30% EA/hexane) 0.48; nmax (KBr) 3545, 2820, 1659,
4.3.6. 3-(2,3-Dihydrobenzo[b][1,4]dioxinoyl)-2-naphthoic
acid
(12f). Condensation of keto-ester 11f (3.0 g, 11.36 mmol) and
phthalaldehyde 7 (1.52 g, 11.36 mmol) using the procedure similar
to that of 8a afforded compound 12f (2.35 g, 62%) as a colorless
solid; mp 190 ꢀC; Rf (30% EA/hexane) 0.50; nmax (KBr) 3585, 2870,
1630, 1695, 1562 cmꢁ1
; dH (300 MHz, DMSO-d6) 8.55 (1H, s, ArH),
1685, 1545 cmꢁ1
;
dH (300 MHz, DMSO-d6) 8.60 (1H, s, ArH),
8.12–8.10 (1H, m, ArH), 7.99–7.95 (1H, m, ArH), 7.85 (1H, s, ArH),
7.66–7.60 (2H, m, ArH), 7.12–7.10 (2H, m, ArH), 6.90 (1H, d, J 7.8 Hz,
ArH), 6.78 (1H, s, ArH), 4.21–3.98 (4H, m, OCH2); dC (75.6 MHz,
DMSO-d6) 194.9, 167.1, 147.8, 142.9, 137.3, 133.4, 132.0, 131.0, 130.7,
129.2, 128.9, 128.1, 127.5, 127.2, 123.3, 117.8, 117.1, 64.5, 63.9; HRMS:
found 334.0818, C20H14O5 requires 334.0841.
8.03–8.01 (1H, m, ArH), 7.91–7.89 (1H, m, ArH), 7.83 (1H, s,
ArH), 7.78–7.66 (5H, m, ArH), 6.91 (2H, d, J 7.2 Hz, ArH), 3.86
(3H, s, OCH3); dC (75.6 MHz, DMSO-d6) 195.2, 162.8, 137.7, 133.5,
132.1, 131.3, 131.1, 130.3, 128.5, 127.6, 127.3, 127.0, 113.1, 55.1; MS
(EI): m/z (%)¼306 [M]þ.
4.3.2. 3-(3,4-Dimethoxybenzoyl)-2-naphthoic acid (12b). Con-
densation of keto-ester 11b (5.0 g,18.79 mmol) and phthalaldehyde
7 (2.51 g, 18.79 mmol) using the procedure similar to that of 8a
afforded compound 12b (4.10 g, 65%) as a colorless solid; mp
234 ꢀC; [Found: C, 71.2; H, 4.7. C20H16O5 requires C, 71.42; H, 4.79%];
Rf (30% EA/hexane) 0.51; nmax (KBr) 3528, 2830, 1645, 1692,
4.3.7. 3-(6-Methoxynaphthonyl)-2-naphthoic acid (12g). Conden-
sation of keto-ester 11g (3.0 g, 10.48 mmol) and phthalaldehyde 7
(1.41 g, 10.48 mmol) using the procedure similar to that of 8a
afforded compound 12g (2.39 g, 64%) as a colorless solid; mp
246 ꢀC; [Found: C, 77.3; H, 4.5. C23H16O4 requires C, 77.52; H,
4.53%]; Rf (30% EA/hexane) 0.35; nmax (KBr) 3558, 2849, 1645, 1689,
1555 cmꢁ1
;
dH (300 MHz, CDCl3) 8.58 (1H, s, ArH), 8.08–8.06 (1H,
1540 cmꢁ1
; dH (300 MHz, DMSO-d6) 8.67 (1H, s, ArH), 8.22 (2H, d, J
m, ArH), 7.98–7.95 (1H, m, ArH), 7.88 (1H, s, ArH), 7.70–7.65 (2H, m,
ArH), 7.49 (1H, s, ArH), 7.13 (1H, d, J 8.1 Hz, ArH), 6.9 (1H, d, J 7.8 Hz,
ArH), 3.85 (6H, s, OCH3); dC (75.6 MHz, CDCl3) 194.7, 167.1, 152.8,
7.5 Hz, ArH), 8.10–8.07 (3H, m, ArH), 7.93–7.90 (3H, m, ArH), 7.73–
7.70 (2H, m, ArH), 7.41 (1H, s, ArH), 7.19 (1H, d, J 9.0 Hz, ArH), 3.89
(3H, s, OCH3); dC (75.6 MHz, DMSO-d6) 195.9, 167.2, 159.4, 137.7,

2346
J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
136.8, 133.6, 132.8, 132.3, 131.2, 131.1, 129.1, 128.3, 128.0, 127.9, 127.7,
143.4, 136.4, 133.3, 129.9, 129.4, 129.1, 128.3, 127.1, 126.9, 123.5,
127.2, 127.1, 124.9, 119.4, 106.0, 55.4; MS (EI): m/z (%)¼356 [M]þ.
122.0, 120.2, 111.1, 110.1, 83.1, 55.9; MS (EI): m/z (%)¼320 [M]þ.
4.3.8. 3-(4-(Diphenylamino)benzoyl)-2-naphthoic acid (12h). Con-
densation of keto-ester 11h (3.0 g, 8.04 mmol) and phthalaldehyde
7 (1.07 g, 8.04 mmol) using the procedure similar to that of 8a
afforded compound 12h (2.05 g, 60%) as a colorless solid; mp
120 ꢀC; [Found: C, 81.1; H, 4.8; N, 3.0. C30H21NO3 requires C, 81.25;
H, 4.77; N, 3.16%]; Rf (30% EA/hexane) 0.55; nmax (KBr) 3559, 1635,
4.3.13. 3-(3,5-Dimethoxyphenyl)naphtho[2,3-c]furan-1(3H)-one
(13c). Reductive cyclization of acid 12c (3.5 g, 10.41 mmol) using
NaBH4 (1.54 g, 41.66 mmol) adopting the same procedure as that of
9a afforded compound 13c (2.36 g, 71%) as a colorless solid; mp
160 ꢀC; [Found: C, 74.8; H, 5.1. C20H16O4 requires C, 74.99; H, 5.03%];
Rf (10% EA/hexane) 0.69; nmax (KBr) 2840, 1756, 1545 cmꢁ1
; dH
1695, 1571 cmꢁ1
;
dH (300 MHz, CDCl3) 8.68 (1H, s, ArH), 7.94 (1H, d,
(300 MHz, CDCl3) 8.50 (1H, s, ArH), 8.04 (1H, d, J 7.5 Hz, ArH), 7.86
(1H, d, J 7.8 Hz, ArH), 7.78 (1H, s, ArH), 7.61–7.56 (2H, m, ArH), 7.01
(1H, d, J 8.4 Hz, ArH), 6.89 (1H, s, ArH), 6.52 (1H, s, ArH), 6.41 (1H, d,
J 8.4 Hz, ArH), 3.83 (3H, s, OCH3), 3.79 (3H, s, OCH3); dC (75.6 MHz,
CDCl3) 170.9, 161.7, 158.7, 144.1, 136.4, 133.1, 129.9, 128.8, 128.7,
128.3, 126.8, 126.6, 124.2, 121.6, 117.9, 104.5, 98.9, 78.6, 55.6, 55.4;
MS (EI): m/z (%)¼320 [M]þ.
J 7.2 Hz, ArH), 7.90–7.87 (2H, m, ArH), 7.68–7.60 (3H, m, ArH), 7.34–
7.28 (5H, m, ArH), 7.20–7.11 (7H, m, ArH), 6.96 (2H, d, J 8.4 Hz, ArH);
dC (75.6 MHz, CDCl3) 195.3, 170.8, 152.3, 146.4, 138.2, 134.4, 132.9,
132.4, 131.5, 129.6, 129.4, 129.3, 128.2, 128.0, 127.8, 126.2, 126.1,
124.8, 119.2; MS (EI): m/z (%)¼443 [M]þ.
4.3.9. 3-(Benzo[b]thenoyl)-2-naphthoic acid (12i). Condensation of
keto-ester 11i (3.0 g, 11.45 mmol) and phthalaldehyde 7 (1.53 g,
11.45 mmol) using the procedure similar to that of 8a afforded
compound 12i (2.54 g, 69%) as a colorless solid; mp 210 ꢀC; [Found:
C, 72.3; H, 3.7; S, 9.8. C20H12O3S requires C, 72.12; H, 3.64; S, 9.65%];
4.3.14. 3-(3,4,5-Trimethoxyphenyl)naphtho[2,3-c]furan-1(3H)-one
(13d). Reductive cyclization of acid 12d (3.5 g, 9.56 mmol) using
NaBH4 (1.41 g, 38.25 mmol) adopting the same procedure as that of
9a afforded compound 13d (2.54 g, 76%) as a colorless solid; mp
134 ꢀC; [Found: C, 71.7; H, 5.3. C21H18O5 requires C, 71.99; H, 5.18%];
Rf (30% EA/hexane) 0.55; nmax (KBr) 3547, 1641, 1692, 1561 cmꢁ1
; dH
(300 MHz, DMSO-d6) 8.61–8.57 (2H, m, ArH), 8.13 (1H, s, ArH),
8.03–7.98 (4H, m, ArH), 7.69–7.66 (2H, m, ArH), 7.55–7.46 (2H, m,
ArH); dC (75.6 MHz, DMSO-d6) 191.1, 167.4, 140.8, 139.7, 137.9, 136.3,
135.3,133.4,132.3, 131.1,129.1,128.9, 128.3, 128.2, 127.8, 127.6, 125.7,
125.6, 124.6, 122.8; MS (EI): m/z (%)¼332 [M]þ.
Rf (10% EA/hexane) 0.55; nmax (KBr) 2840, 1756, 1545 cmꢁ1
; dH
(300 MHz, CDCl3) 8.51 (1H, s, ArH), 8.06–8.03 (1H, m, ArH), 7.87–
7.85 (1H, m, ArH), 7.77–7.74 (1H, m, ArH), 7.63–7.57 (2H, m, ArH),
6.83–6.73 (2H, m, ArH), 6.62–6.59 (1H, m, ArH), 3.87–3.77 (9H, m,
OCH3); dC (75.6 MHz, CDCl3) 170.7, 159.4, 152.5, 143.9, 142.4, 136.3,
133.1, 129.9, 128.8, 128.3, 126.9, 126.6, 124.2, 123.0, 121.6, 107.1, 79.4,
61.3, 60.8, 56.0; MS (EI): m/z (%)¼350 [M]þ.
4.3.10. 3-(Carbazoyl)-2-naphthoic acid (12j). Condensation of keto-
ester 11j (3.0 g, 7.37 mmol) and phthalaldehyde
7 (0.99 g,
7.37 mmol) using the procedure similar to that of 8a afforded
compound 12j (2.17 g, 62%) as a thick liquid; [Found: C, 80.3; H, 6.4;
N, 2.8. C32H31NO3 requires C, 80.47; H, 6.54; N, 2.93%]; Rf (30% EA/
4.3.15. 3-(Benzo[d][1,3]dioxol-5-yl)naphtho[2,3-c]furan-1(3H)-one
(13e). Reductive cyclization of acid 12e (2.0 g, 6.25 mmol) using
NaBH4 (0.93 g, 25.0 mmol) adopting the same procedure as that of
9a afforded compound 13e (1.40 g, 74%) as a colorless solid; mp
188 ꢀC; [Found: C, 75.2; H, 4.1. C19H12O4 requires C, 74.99; H, 3.97%];
hexane) 0.45; nmax (KBr) 3549, 2910, 1640, 1689, 1581 cmꢁ1
; dH
(300 MHz, CDCl3) 8.57 (2H, d, J 11.1 Hz, ArH), 7.99–7.83 (5H, m,
ArH), 7.56–7.55 (2H, m, ArH), 7.43 (1H, d, J 6.6 Hz, ArH), 7.36–7.29
(2H, m, ArH), 7.21–7.19 (1H, m, ArH), 4.08–4.06 (2H, m, N–CH2),
2.02–2.0 (1H, m, CH), 1.28–1.23 (8H, m, CH2), 0.85–0.83 (6H, m,
CH3); dC (75.6 MHz, CDCl3) 196.7 170.7, 143.8, 141.6, 138.6, 134.4,
132.9, 132.5, 129.3, 128.7, 128.2, 128.1, 128.0, 127.7, 126.4, 123.5,
123.2, 122.6, 120.7, 119.9, 109.5, 108.6, 60.5, 47.6, 39.4, 30.9, 28.7,
24.3, 14.0, 10.9; MS (EI): m/z (%)¼477 [M]þ
Rf (10% EA/hexane) 0.61; nmax (KBr) 2840, 1756, 1545 cmꢁ1
; dH
(300 MHz, CDCl3) 8.51 (1H, s, ArH), 8.05 (1H, d, J 6.3 Hz, ArH), 7.87
(1H, d, J 6.9 Hz, ArH), 7.72 (1H, s, ArH), 7.61–7.59 (2H, m, ArH), 6.87–
6.79 (2H, m, ArH), 6.64–6.63 (1H, m, ArH), 6.47–6.46 (1H, s, ArH),
5.93 (2H, s, OCH2); dC (75.6 MHz, CDCl3) 170.3, 148.6, 148.3, 143.4,
136.4, 133.3, 130.0, 129.9, 129.1, 128.3, 127.2, 126.9, 123.6, 122.0,
121.6, 108.4, 107.4, 101.5, 82.8; MS (EI): m/z (%)¼304 [M]þ.
4.3.11. 3-(4-Methoxyphenyl)naphtho[2,3-c]furan-1(3H)-one
(13a). Reductive cyclization of acid 12a (3.5 g, 11.43 mmol) using
NaBH4 (1.69 g, 45.75 mmol) adopting the procedure similar to that
of 9a afforded compound 13a (2.62 g, 79%) as a colorless solid; mp
202 ꢀC; [Found: C, 78.4; H, 4.8. C19H14O3 requires C, 78.61; H,
4.3.16. 3-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)naphtho[2,3-c]furan-
1(3H)-one (13f). Reductive cyclization of acid 12f (2.0 g, 5.98 mmol)
using NaBH4 (0.88 g, 23.95 mmol) adopting the same procedure as
that of 9a afforded compound 13f (1.45 g, 76%) as a colorless solid;
mp 215 ꢀC; [Found: C, 75.2; H, 4.3. C20H14O4 requires C, 75.46; H,
4.86%]; Rf (10% EA/hexane) 0.61; nmax (KBr) 2840, 1759, 1565 cmꢁ1
;
4.43%]; Rf (10% EA/hexane) 0.58; nmax (KBr) 2860, 1759, 1565 cmꢁ1
;
dH (300 MHz, CDCl3) 8.53 (1H, s, ArH), 8.07 (1H, d, J 8.1 Hz, ArH),
7.87 (1H, d, J 7.5 Hz, ArH), 7.73 (1H, s, ArH), 7.63–7.59 (2H, m, ArH),
7.24 (2H, d, J 8.7 Hz, ArH), 6.90 (2H, d, J 8.4 Hz, ArH), 6.54 (1H, s,
ArH), 3.81 (3H, s, OCH3); dC (75.6 MHz, CDCl3) 170.6, 160.4, 143.6,
136.4, 133.3, 129.9, 129.1, 129.0, 128.9, 128.3, 127.1, 126.9, 123.8,
122.0, 114.3, 82.8, 55.4; MS (EI): m/z (%)¼290 [M]þ.
dH (300 MHz, DMSO-d6) 8.56 (1H, s, ArH), 8.17 (1H, d, J 7.5 Hz, ArH),
7.99 (1H, d, J 7.8 Hz, ArH), 7.87 (1H, s, ArH), 7.69–7.62 (2H, m, ArH),
6.87–6.79 (3H, m, ArH), 6.64 (1H, s, ArH), 4.23–4.21 (4H, m, OCH2);
dC (75.6 MHz, DMSO-d6) 169.5,143.9,143.4,143.3,135.9,132.7,130.1,
129.6, 128.7, 128.1, 126.8, 126.2, 122.9, 121.8, 119.9, 117.3, 115.9, 81.8,
63.9, 63.8; MS (EI): m/z (%)¼318 [M]þ.
4.3.12. 3-(3,4-Dimethoxyphenyl)naphtho[2,3-c]furan-1(3H)-one
(13b). Reductive cyclization of acid 12b (3.5 g, 10.41 mmol) using
NaBH4 (1.54 g, 41.66 mmol) adopting the same procedure as that of
9a afforded compound 13b (2.49 g, 75%) as a colorless solid; mp
158 ꢀC; [Found: C, 74.8; H, 4.9. C20H16O4 requires C, 74.99; H,
4.3.17. 3-(2-Methoxynaphthalen-6-yl)naphtho[2,3-c]furan-1(3H)-
one (13g). Reductive cyclization of acid 12g (2.0 g, 5.61 mmol)
using NaBH4 (0.83 g, 22.47 mmol) adopting the same procedure
as that of 9a afforded compound 13g (1.43 g, 75%) as a colorless
solid; mp 180 ꢀC; [Found: C, 81.0; H, 4.8. C23H16O3 requires C,
81.16; H, 4.74%]; Rf (10% EA/hexane) 0.61; nmax (KBr) 2852, 1759,
5.03%]; Rf (10% EA/hexane) 0.69; nmax (KBr) 2845, 1758, 1548 cmꢁ1
;
dH (300 MHz, CDCl3) 8.35 (1H, s, ArH), 8.08–8.05 (1H, m, ArH), 7.89–
7.87 (1H, m, ArH), 7.75 (1H, s, ArH), 7.64–7.62 (2H, m, ArH), 6.95–
6.87 (2H, m, ArH), 6.74 (1H, s, ArH), 6.53 (1H, s, ArH), 3.87 (3H, s,
OCH3), 3.79 (3H, s, OCH3); dC (75.6 MHz, CDCl3) 170.6, 149.9, 149.4,
1549 cmꢁ1
; dH (300 MHz, CDCl3) 8.59 (1H, s, ArH), 8.09 (1H, d, J
8.7 Hz, ArH), 7.87–7.82 (2H, m, ArH), 7.77–7.70 (3H, m, ArH),
7.65–7.59 (2H, m, ArH), 7.27–7.12 (3H, m, ArH), 6.71 (1H, s, ArH),
3.93 (3H, s, OCH3); dC (75.6 MHz, CDCl3) 170.5, 158.4, 143.6, 136.4,

J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
2347
134.9, 133.3, 132.1, 129.9, 129.6, 129.0, 128.5, 128.3, 127.9, 127.1,
127.0, 126.8, 124.7, 123.6, 122.1, 119.5, 105.8, 83.2, 55.4; MS (EI):
m/z (%)¼340 [M]þ.
and Mg (0.32 g, 13.51 mmol)], and Lawesson’s reagent (0.76 g,
1.87 mmol) as a black solid; mp 75 ꢀC; [Found: C, 72.3; H, 5.5; S, 2.1.
C26H24S3 requires C, 72.18; H, 5.59; S, 22.23%]; Rf (Hexane) 0.95; dH
(300 MHz, CDCl3) 8.48 (2H, s, ArH), 7.71–7.67 (2H, m, ArH), 7.43
(1H, d, J 3.6 Hz, ArH), 7.38 (1H, d, J 5.1 Hz, ArH), 7.27–7.24 (1H, m,
ArH), 7.19–7.13 (3H, m, ArH), 6.85 (1H, d, J 3.0 Hz, ArH), 2.89 (2H, t, J
7.6 Hz, CH2), 1.78–1.73 (2H, m, CH2), 1.36–1.25 (6H, m, CH2), 0.89
(3H, t, J 7.6 Hz, CH3); dC (75.6 MHz, CDCl3) 146.6, 136.4, 134.7, 134.4,
133.6, 131.8, 131.6, 129.1, 128.9, 128.0, 125.8, 125.3, 125.2, 125.1,
124.6, 123.9, 119.4, 119.1, 31.6, 30.3, 29.7, 28.9, 22.6, 14.1; MS (EI): m/
z (%)¼432 [M]þ.
4.3.18. 3-(4-(Diphenylamino)phenyl)naphtho[2,3-c]furan-1(3H)-one
(13h). Reductive cyclization of acid 12h (2.0 g, 4.51 mmol) using
NaBH4 (0.67 g, 18.05 mmol) adopting the same procedure as that of
9a afforded compound 13h (1.50 g, 78%) as a colorless solid; mp
194 ꢀC; [Found: C, 84.1; H, 5.0; N, 3.2. C30H21NO2 requires C, 84.29; H,
4.95; N, 3.28%]; Rf (10% EA/hexane) 0.57; nmax (KBr) 1759, 1529,
1240 cmꢁ1
; dH (300 MHz, CDCl3) 8.53 (1H, s, ArH), 8.07 (1H, d, J 7.8 Hz,
ArH), 7.91 (1H, d, J 7.8 Hz, ArH), 7.80 (1H, s, ArH), 7.67–7.59 (2H, m,
ArH), 7.27–7.26 (1H, m, ArH), 7.22–7.21 (1H, m, ArH), 7.16–7.01 (12H,
m, ArH), 6.53 (1H, s, ArH); dC (75.6 MHz, CDCl3) 170.4, 148.9, 147.3,
143.4, 136.4, 133.3, 130.1, 129.9, 129.4, 129.0, 128.4, 128.3, 127.1, 126.9,
124.8, 123.8, 123.4, 122.9, 122.1, 82.9; MS (EI): m/z (%)¼427 [M]þ.
4.3.23. 1-Phenyl-3-(thiophen-2-yl)naptho[2,3-c]thiophene
(15b). Following the same procedure as that of 3 afforded com-
pound 15b (0.49 g, 38%) was obtained using the lactone 9a (1.0 g,
3.76 mmol), with phenylmagnesium chloride (1.53 g, 11.20 mmol)
and Lawesson’s reagent (0.76 g, 1.87 mmol) as a black solid; mp
110 ꢀC. [Found: C, 77.0; H, 4.2; S, 18.7. C22H14S2 requires C, 77.15; H,
4.12; S, 18.73%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3) 8.52 (1H, s,
ArH), 8.38 (1H, s, ArH), 7.79 (2H, d, J 7.5 Hz, ArH), 7.72–7.64 (2H, m,
ArH), 7.54 (2H, t, J 7.5 Hz, ArH), 7.47 (1H, d, J 3.3 Hz, ArH), 7.43–7.40
(2H, m, ArH), 7.24–7.13 (3H, m, ArH); dC (75.6 MHz, CDCl3) 136.5,
134.9, 134.8, 134.4, 132.0, 131.7, 131.6, 129.3, 129.2, 128.9, 128.8, 128.0,
127.5, 125.2, 125.1, 125.0, 118.9, 118.6; MS (EI): m/z (%)¼342 [M]þ.
4.3.19. 3-(Benzo[b]thiophen-3-yl)naphtho[2,3-c]furan-1(3H)-one
(13i). Reductive cyclization of acid 12i (2.0 g, 6.21 mmol) using
NaBH4 (0.92 g, 24.84 mmol) adopting the same procedure as that
of 9a afforded compound 13i (1.48 g, 78%) as a colorless solid;
mp 166 ꢀC; [Found: C, 75.7; H, 3.7; S, 10.2. C20H12O2S requires C,
75.93; H, 3.82; S, 10.14%]; Rf (10% EA/hexane) 0.61; nmax (KBr)
1758, 1560, 1210 cmꢁ1
; dH (300 MHz, CDCl3) 8.58 (1H, s, ArH),
8.08 (1H, d, J 9.0 Hz, ArH), 7.88–7.85 (3H, m, ArH), 7.73–7.70 (1H,
m, ArH), 7.65–7.60 (2H, m, ArH), 7.41 (1H, s, ArH,), 7.38–7.35 (2H,
m, ArH), 6.94 (1H, s, ArH); dC (75.6 MHz, CDCl3) 170.1, 141.8,
140.9, 137.2, 136.3, 133.4, 131.8, 129.9, 129.2, 128.4, 127.4, 127.3,
126.8, 125.1, 124.7, 123.9, 123.1, 122.1, 122.0, 77.80; MS (EI): m/z
(%)¼316 [M]þ.
4.3.24. 1-(Thiophen-2-yl)-3-p-tolylnaphtho[2,3-c]thiophene
(15c). Following the same procedure as that of 3 afforded com-
pound 15c (0.48 g, 36%) was obtained using the lactone 9a (1.0 g,
3.76 mmol), p-tolylmagnesium bromide [prepared from p-bromo-
toluene (1.92 g, 11.28 mmol) and Mg (0.32 g, 13.51 mmol)], and
Lawesson’s reagent (0.76 g, 1.87 mmol) as a black solid; mp 71 ꢀC,
[Found: C, 77.6; H, 4.5; S, 17.8. C23H16S2 requires C, 77.49; H, 4.52; S,
17.99%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3) 8.50 (1H, s, ArH),
8.34 (1H, s, ArH), 7.68–7.65 (3H, m, CH3), 7.44–7.23 (5H, m, ArH),
7.18–7.13 (3H, m, ArH), 2.45 (3H, s, CH3); dC (75.6 MHz, CDCl3) 137.6,
136.7, 134.9, 134.7, 131.7, 131.5, 131.4, 129.9 129.4, 129.2, 129.0, 128.9,
128.0, 126.8, 125.1, 124.9, 124.8, 118.9, 118.8, 21.3; MS (EI): m/z
(%)¼356 [M]þ.
4.3.20. 3-(9-(2-Ethylhexyl)-9H-carbazol-3-yl)naphtho[2,3-c]furan-
1(3H)-one (13j). Reductive cyclization of acid 12j (2.0 g, 6.21 mmol)
using NaBH4 (0.92 g, 24.84 mmol) adopting the same procedure as
that of 9a afforded compound 13j (1.41 g, 73%) as a colorless solid;
mp 80 ꢀC; [Found: C, 83.0; H, 6.8; N, 3.1. C32H31NO2 requires C,
83.26; H, 6.77; N, 3.03%]; Rf (10% EA/hexane) 0.65; nmax (KBr) 2863,
1758, 1549 cmꢁ1
; dH (300 MHz, CDCl3) 8.56 (1H, s, ArH), 8.07–8.01
(3H, m, ArH), 7.83–7.80 (1H, m, ArH), 7.75 (1H, s, ArH), 7.60–7.56
(2H, m, ArH), 7.45–7.43 (1H, m, ArH), 7.39–7.32 (3H, m, ArH), 7.24–
7.20 (1H, m, ArH), 6.75 (1H, s, ArH), 4.13–4.11 (2H, m, N–CH2), 2.03–
2.00 (1H, m, CH), 1.34–1.25 (8H, m, CH2), 0.90–0.84 (6H, m, CH3); dC
(75.6 MHz, CDCl3) 170.7, 144.2, 141.4, 136.5, 133.3, 129.9, 128.9,
128.4, 127.2, 127.0, 126.8, 126.4, 126.1, 125.0, 124.0, 122.9, 122.5,
122.2, 120.4, 119.8, 119.2, 109.5, 109.2, 84.1, 47.5, 39.4, 31.0, 28.8,
24.4, 23.0, 14.0, 10.9; MS (EI): m/z (%)¼461 [M]þ.
4.3.25. 1-(4-Methoxyphenyl)-3-(thiophen-2-yl)naphtho[2,3-c]thio-
phene (15d). Following the same procedure as that of 3 afforded
compound 15d (0.58 g, 42%) was obtained using the lactone 9a
(1.0 g, 3.76 mmol), p-anisyl magnesium bromide [prepared from p-
bromoanisole (2.11 g, 11.28 mmol) and Mg (0.32 g, 13.51 mmol)],
and Lawesson’s reagent (0.76 g, 1.87 mmol) as a black solid; mp
82 ꢀC; [Found: C, 74.0; H, 4.4; S, 17.3. C23H16OS2 requires C, 74.16; H,
4.33; S, 17.22%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3) 8.54 (1H, s,
ArH), 8.30 (1H, s, ArH), 7.69–7.65 (3H, m, ArH), 7.47–7.25 (5H, m,
ArH), 7.11–7.08 (3H, m, ArH), 3.85 (3H, s, OCH3); dC (75.6 MHz,
CDCl3) 148.6, 146.5, 136.5, 135.4, 134.8, 131.3, 130.1, 129.6, 129.1,
128.9, 128.6, 128.1, 126.3, 125.4, 124.6, 124.1, 118.6, 118.2, 55.2; MS
(EI): m/z (%)¼372 [M]þ.
4.3.21. 1,3-Di(thiophen-2-yl)naphtho[2,3-c]thiophene (3). To a solu-
tion of lactone 9a (1.0 g, 3.75 mmol) in anhydrous THF (30 mL) was
added 2-thienylmagnesium bromide [prepared from 2-bromo-
thiophene (1.83 g, 11.27 mmol) and magnesium turnings (0.32 g,
13.47 mmol)] at 0 ꢀC under N2. The reaction mixture was slowly
raised to room temperature and stirred for 2 h. It was then
quenched with aq NH4Cl solution (30 mL), extracted with DCM
(2ꢂ20 mL) and dried (Na2SO4). The DCM solution was then stirred
with Lawesson’s reagent (0.76 g, 1.87 mmol) at room temperature
for 10 min. Solvent was evaporated in vacuo to give the crude
product, which was purified by column chromatography (100%
Hexane) to give the title compound 3 (0.45 g, 35%) as an black solid;
mp 118 ꢀC (lit.17 120 ꢀC).
4.3.26. 1-(Naphthalen-1-yl)-3-(thiophen-2-yl)naphtho[2,3-c]thio-
phene (15e). Following the same procedure as that of 3 afforded
compound 15e (0.57 g, 39%) was obtained using the lactone 9a
(1.0 g, 3.76 mmol), 1-napthylmagnesium bromide [prepared from
1-bromonaphthalene (2.33 g, 11.28 mmol) and Mg (0.32 g,
13.51 mmol)], and Lawesson’s reagent (0.76 g,1.87 mmol) as a black
solid; mp 68 ꢀC; [Found: C, 79.4; H, 4.1; S, 16.4. C26H16S2 requires C,
79.55; H, 4.11; S, 16.34%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3)
8.56 (1H, s, ArH), 7.89 (3H, t, J 8.1 Hz, ArH), 7.79–7.77 (2H, m, ArH),
7.68–7.62 (2H, m, ArH), 7.52 (2H, t, J 7.6 Hz, ArH), 7.46–7.40 (2H, m,
ArH), 7.32–7.30 (1H, m, ArH), 7.13 (1H, t, J 4.2 Hz, ArH), 7.09–7.04
(1H, m, ArH), 7.01–6.98 (1H, m, ArH); dC (75.6 MHz, CDCl3) 138.6,
137.1, 136.6, 134.3, 134.1, 132.9, 131.8, 131.3, 131.1, 130.3, 129.6, 129.1,
4.3.22. 1-(5-Hexylthiophen-2-yl)-3-(thiophen-2-yl)naphtho[2,3-
c]thiophene (15a). Following the similar procedure as that of 3
afforded compound 15a (0.68 g, 42%) was obtained using the lac-
tone 9a (1.0 g, 3.76 mmol), 5-hexyl-2-thienyl magnesium bromide
[prepared from 2-bromo-5-hexylthiophene (2.77 g, 11.28 mmol)

2348
J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
129.0, 128.9, 128.5, 128.2, 128.0, 127.9, 126.7, 126.4, 126.1, 125.9,
afforded compound 17b (0.61 g, 49%) was obtained using the
lactone 13b (1.0 g, 3.12 mmol), 2-thienylmagnesium bromide
[prepared from 2-bromothiophene (1.52 g, 9.37 mmol) and Mg
(0.27 g, 11.19 mmol)], and Lawesson’s reagent (0.63 g, 1.56 mmol)
as a thick liquid; [Found: C, 71.5; H, 4.4; S, 15.8. C24H18O2S2 re-
quires C, 71.61; H, 4.51; S, 15.93%]; Rf (Hexane) 0.95; dH (300 MHz,
CDCl3) 8.51 (1H, s, ArH), 8.11 (1H, s, ArH), 7.72–7.69 (2H, m, ArH),
7.60 (2H, t, J 7.2 Hz, ArH), 7.54–7.51 (1H, m, ArH), 7.45 (1H, d, J
3.6 Hz, ArH), 7.38 (1H, d, J 5.4 Hz, ArH), 7.20–7.17 (1H, m, ArH),
7.13–7.10 (1H, m, ArH), 6.67 (1H, s, ArH), 3.91 (3H, s, OCH3), 3.85
(3H, s, OCH3); dC (75.6 MHz, CDCl3) 160.9, 157.8, 136.9, 136.1, 134.0,
132.9, 132.5, 131.5, 130.9, 128.9, 128.8, 127.9, 124.8, 124.7, 124.6,
124.6, 119.4, 118.5, 115.5, 104.9, 99.3, 55.7, 55.5; MS (EI): m/z
(%)¼402 [M]þ.
125.6, 125.3, 125.2, 125.0; MS (EI): m/z (%)¼392 [M]þ
4.3.27. 1-(5-Methylthiophen-2-yl)-3-(thiophen-2-yl)naphtho[2,3-
c]thiophene (16a). Following the same procedure as that of 3
afforded compound 16a (0.49 g, 38%) was obtained using the lac-
tone 9c (1.0 g, 3.57 mmol), 2-thienylmagnesium bromide [prepared
from 2-bromothiophene (1.75 g, 10.71 mmol) and Mg (0.31 g,
12.88 mmol)], and Lawesson’s reagent (0.72 g,1.78 mmol) as a black
solid; mp 98 ꢀC; [Found: C, 69.7; H, 3.8; S, 26.4. C21H14S3 requires C,
69.57; H, 3.89; S, 26.53%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3)
8.42 (2H, s, ArH), 7.63–7.60 (2H, m, ArH), 7.39–7.34 (2H, m, ArH),
7.20–7.10 (4H, m, ArH), 6.80–6.79 (1H, m, ArH), 2.55 (3H, s, CH3); dC
(75.6 MHz, CDCl3) 140.3,136.4,134.6,134.4,133.9,131.7,131.6,129.0,
128.9, 128.0, 126.3, 125.6, 125.3, 125.2, 125.1, 125.0, 124.9, 123.9,
119.4, 119.1, 15.5; MS (EI): m/z (%)¼362 [M]þ.
4.3.32. N,N-Diphenyl-4-(1-(thiophen-2-yl)naphtho[2,3-c]thiophen-
3-yl)benzenamine (18). Following the same procedure as that of 3
afforded compound 18 (0.54 g, 45%) was obtained using the lac-
tone 13h (1.0 g, 2.34 mmol), 2-thienylmagnesium bromide [pre-
pared from 2-bromothiophene (1.14 g, 7.03 mmol) and Mg (0.20 g,
8.39 mmol)], and Lawesson’s reagent (0.47 g, 1.17 mmol) as a black
solid; mp 131 ꢀC; [Found: C, 80.3; H, 4.5; N, 2.6; S, 12.6. C34H23NS2
requires C, 80.12; H, 4.55; N, 2.75; S, 12.58%]; Rf (Hexane) 0.95; dH
(300 MHz, CDCl3) 8.50 (1H, s, ArH), 8.38 (1H, s, ArH), 7.70–7.63
(3H, m, ArH), 7.44–7.37 (3H, m, ArH), 7.31–7.29 (1H, m, ArH), 7.24–
7.19 (3H, m, ArH), 7.13–7.02 (8H, m, ArH), 7.01–6.99 (3H, m, ArH);
dC (75.6 MHz, CDCl3) 147.6, 147.4, 147.1, 136.7, 134.9, 134.5, 132.4,
131.6, 131.4, 129.9, 129.8, 129.4, 129.3, 128.9, 128.7, 128.1, 128.0,
125.1, 124.8, 124.7, 124.5, 123.6, 123.4, 122.9, 118.9; MS (EI): m/z
(%)¼509 [M]þ.
4.3.28. 1-(5-Methylthiophen-2-yl)-3-p-tolylnaphtho[2,3-c]thiophene
(16b). Following the same procedure as that of 3 afforded com-
pound 16b (0.59 g, 45%) was obtained using the lactone 9c (1.0 g,
3.57 mmol), p-tolylmagnesium bromide [prepared from p-bro-
motoluene (1.83 g, 10.71 mmol) and Mg (0.31 g, 12.88 mmol)], and
Lawesson’s reagent (0.72 g, 1.78 mmol) as a black solid; mp 96 ꢀC;
[Found: C, 77.9; H, 4.8; S,17.2. C24H18S2 requires C, 77.80; H, 4.90; S,
17.31%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3) 8.47 (1H, s, ArH),
8.33 (1H, s, ArH), 7.67–7.65 (4H, m, ArH), 7.47 (1H, d, J 7.5 Hz, ArH),
7.33 (2H, d, J 7.2 Hz, ArH), 7.23–7.10 (2H, m, ArH), 6.83–6.82 (1H, m,
ArH), 2.57 (3H, s, CH3), 2.44 (3H, s, CH3); dC (75.6 MHz, CDCl3) 139.9,
138.3, 137.4, 136.7, 134.7, 134.6, 134.3, 131.6, 131.5, 129.9, 129.4,
129.1, 129.0, 128.9, 126.8, 126.2, 124.9, 124.8, 119.1, 118.7, 21.3, 15.5;
MS (EI): m/z (%)¼370 [M]þ.
4.3.33. 1-(Benzo[b]thiophen-3-yl)-3-(thiophen-2-yl)naphtho[2,3-
c]thiophene (19). Following the same procedure as that of 3 affor-
ded compound 19 (0.59 g, 47%) was obtained using the lactone 13i
(1.0 g, 3.16 mmol), 2-thienylmagnesium bromide [prepared from 2-
bromothiophene (1.55 g, 9.49 mmol) and Mg (0.27 g, 11.41 mmol)],
and Lawesson’s reagent (0.63 g, 1.56 mmol) as a black solid; mp
98 ꢀC; [Found: C, 72.5; H, 3.5; S, 24.0. C24H14S3 requires C, 72.32; H,
3.54; S, 24.14%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3) 8.56 (1H, s,
ArH), 8.37–8.32 (2H, m ArH,), 8.14–7.99 (2H, m, ArH), 7.72–7.43 (5H,
m, ArH), 7.21–7.15 (4H, m, ArH); dC (75.6 MHz, CDCl3) 138.9, 136.8,
135.0, 134.9, 132.8, 130.3, 129.8, 127.9, 127.5, 127.4, 126.6, 124.9,
124.1, 123.8, 123.7, 123.6, 123.5, 123.3, 122.9, 121.8, 121.5, 117.7, 117.5;
MS (EI): m/z (%)¼398 [M]þ.
4.3.29. 1-(4-Methoxyphenyl)-3-(5-methylthiophen-2-yl)naph-
tho[2,3-c]thiophene (16c). Following the same procedure as that of
3 afforded compound 16c (0.66 g, 48%) was obtained using the
lactone 9c (1.0 g, 3.57 mmol), p-anisyl magnesium bromide [pre-
pared from p-bromoanisole (1.83 g, 10.71 mmol) and Mg (0.31 g,
12.88 mmol)], and Lawesson’s reagent (0.72 g, 1.78 mmol) as
a black solid; mp 124 ꢀC; [Found: C, 74.4; H, 4.7; S, 16.5. C24H18OS2
requires C, 74.58; H, 4.69; S,16.59%]; Rf (Hexane) 0.95; dH (300 MHz,
CDCl3) 8.47 (1H, s, ArH), 8.28 (1H, s, ArH), 7.69–7.65 (3H, m, ArH),
7.47–7.42 (2H, m, ArH), 7.11–7.05 (3H, m, ArH), 6.95–6.90 (2H, m,
ArH), 3.88 (3H, s, OCH3), 2.57 (3H, s, CH3); dH (300 MHz, CDCl3)
159.3, 158.7, 139.8, 134.6, 134.4, 133.5, 131.5, 131.4, 130.5, 129.0,
128.9, 127.7, 126.2, 124.9, 124.8, 119.0, 118.6, 114.7, 114.2, 55.3, 15.5;
MS (EI): m/z (%)¼386 [M]þ
4.3.34. 9-(2-Ethylhexyl)-3-(1-(thiophen-2-yl)naphtho[2,3-c]thio-
phen-3-yl)-9H-carbazole (20a). Following the same procedure as
that of 3 afforded compound 20a (0.58 g, 49%) was obtained using
the lactone 13j (1.0 g, 2.17 mmol), 2-thienylmagnesium bromide
[prepared from 2-bromothiophene (1.06 g, 6.50 mmol) and Mg
(0.19 g, 7.80 mmol)], and Lawesson’s reagent (0.44 g, 1.08 mmol)
as a thick liquid; [Found: C, 79.7; H, 6.1; N, 2.6; S, 11.9. C36H33NS2
requires C, 79.51; H, 6.12; N, 2.58; S, 11.79%]; Rf (Hexane) 0.95; dH
(300 MHz, CDCl3) 8.54 (1H, s, ArH), 8.46 (2H, s, ArH), 8.18 (1H, d, J
7.5 Hz, ArH), 8.10 (1H, d, J 7.8 Hz, ArH), 7.88 (1H, d, J 8.4 Hz, ArH),
7.73–7.65 (2H, m, ArH), 7.51–7.45 (3H, m, ArH), 7.43–7.39 (1H, m,
ArH), 7.21–7.19 (2H, m, ArH), 7.16–7.14 (2H, m, ArH), 4.23–4.21
(2H, m, N–CH2), 2.15 (1H, m, CH), 1.41–1.25 (8H, m, CH2), 0.96–
0.86 (6H, m, CH3); dC (75.6 MHz, CDCl3) 141.5, 140.9, 140.6, 136.9,
134.9, 134.7, 134.1, 131.7, 131.4, 129.0, 127.9, 127.4, 126.1, 125.5,
125.1, 124.7, 121.2, 120.6, 120.3, 119.2, 119.1, 118.8, 118.6, 109.6,
109.3, 108.9, 47.6, 39.5, 31.1, 28.9, 24.5, 23.1, 14.1, 10.9; MS (EI): m/z
(%)¼543 [M]þ.
4.3.30. 1-(3,4-Dimethoxyphenyl)-3-(thiophen-2-yl)naphtho[2,3-
c]thiophene (17a). Following the same procedure as that of 3
afforded compound 17a (0.68 g, 54%) was obtained using the lac-
tone 13b (1.0 g, 3.12 mmol), 2-thienylmagnesium bromide [pre-
pared from 2-bromothiophene (1.52 g, 9.37 mmol) and Mg (0.27 g,
11.19 mmol)], and Lawesson’s reagent (0.63 g,1.56 mmol) as a thick
liquid; [Found: C, 71.4; H, 4.4; S, 15.8. C24H18O2S2 requires C, 71.61;
H, 4.51; S, 15.93%]; Rf (Hexane) 0.95; dH (300 MHz, CDCl3) 8.49 (1H,
s, ArH), 8.32 (1H, s, ArH), 7.71–7.67 (1H, m, ArH), 7.64–7.61 (1H, m,
ArH), 7.44 (1H, d, J 3.6 Hz, ArH), 7.38 (1H, d, J 5.1 Hz, ArH), 7.33 (1H,
d, J 8.4 Hz, ArH), 7.26–7.25 (1H, m, ArH), 7.19 (1H, t, J 4.4 Hz, ArH),
7.12 (2H, d, J 4.0 Hz, ArH), 7.03 (1H, d, J 8.4 Hz, ArH), 3.97 (3H, s,
OCH3), 3.96 (3H, s, OCH3); dC (75.6 MHz, CDCl3) 149.5, 148.9, 136.6,
134.8,134.7,132.2,131.7,131.4,129.7,129.0,129.9,128.4,128.0,127.1,
125.1,124.9,124.8,121.9,118.9,118.8,112.6,111.9, 56.1, 56.0; MS (EI):
m/z (%)¼402 [M]þ.
4.3.31. 1-(3,5-Dimethoxyphenyl)-3-(thiophen-2-yl)naphtho[2,3-
4.3.35. 9-(2-Ethylhexyl)-3-(1-p-tolylnaphtho[2,3-c]thiophen-3-yl)-
c]thiophene (17b). Following the same procedure as that of 3
9H-carbazole (20b). Following the same procedure as that of 3

J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
2349
afforded compound 20b (0.62 g, 52%) was obtained using the
lactone 13j (1.0 g, 2.17 mmol), p-tolylmagnesium bromide [pre-
pared from p-bromotoluene (1.11 g, 6.50 mmol) and Mg (0.19 g,
7.80 mmol)], and Lawesson’s reagent (0.44 g, 1.08 mmol) as
a black solid; mp 85 ꢀC; [Found: C, 84.6; H, 6.7; N, 2.6; S, 5.9.
C39H37NS requires C, 84.89; H, 6.76; N, 2.54; S, 5.81%]; Rf (Hexane)
0.95; dH (300 MHz, CDCl3) 8.45 (2H, s, ArH), 8.40 (1H, s, ArH), 8.15
(1H, d, J 6.3 Hz, ArH), 7.85 (1H, d, J 7.2 Hz, ArH), 7.72–7.64 (4H, m,
ArH), 7.50–7.34 (6H, m, ArH), 7.08–7.07 (2H, m, ArH), 4.16–4.14
(2H, m, N–CH2), 2.43 (3H, s, CH3), 2.10 (1H, m, CH), 1.38–1.32 (8H,
m, CH2), 0.90–0.88 (6H, m, CH3); dC (75.6 MHz, CDCl3) 141.5, 140.4,
136.9, 134.8, 133.8, 132.2, 131.4, 131.3, 130.9, 129.9, 129.1, 127.8,
127.5, 126.1, 125.8, 125.4, 124.7, 124.5, 123.7, 122.8, 121.2, 120.6,
119.2,118.8, 118.4, 109.7,109.3, 47.6, 39.9, 31.1, 28.9, 24.5, 23.2, 21.3,
14.1, 11.0; MS (EI): m/z (%)¼551 [M]þ
130.2, 128.9, 128.8, 128.1, 126.1, 125.4, 125.3, 121.5, 119.2, 118.3; MS
(EI): m/z (%)¼376 [M]þ.
4.3.40. 1-Phenyl-3-(thiophen-2-yl)naptho[2,3-c]thiophene (15b). Follo-
wing the same procedure as that of 23a afforded compound 15b
(0.12 g, 42%) as a black solid; mp 110 ꢀC.
4.3.41. 1,3-Di(thiophen-2-yl)naphtho[2,3-c]thiophene (3). Following
the same procedure as that of 23a afforded compound 3 (0.15 g,
52%) as a black solid; mp 118 ꢀC.
4.3.42. Naphthalene-2,3-dibis(phenylmethanone) (25a). Following
the same procedure as that of 22a afforded compound 25a (1.01 g,
72%) as a colorless solid; mp 156 ꢀC; [Found: C, 85.8; H, 4.7.
C24H16O2 requires C, 85.69; H, 4.79%]; Rf (10% EA/hexane) 0.61; nmax
(KBr) 1643, 1590 cmꢁ1
; dH (300 MHz, CDCl3) 8.09 (2H, s, ArH), 7.94–
4.3.36. Naphthalene-2,3-diylbis(thiophen-2-yl)methanone (22a). The
1,4-di(thiophen-2-yl)butane-1,4-dione 21a (1 g, 4.0 mmol) and
phthaladehyde 7 (0.54 g, 4.0 mmol) were dissolved in hot ethanol
(25 mL). To this, t-BuOK (1.13 g, 10 mmol) was slowly added and the
reaction mixture was stirred for 3 h at room temperature. The solid
obtained was filtered and washed with methanol to afford
naphthalene-2,3-diylbis(thiophen-2-yl)methanone 22a (1.14 g,
82%) as a colorless solid; mp 118 ꢀC; [Found: C, 68.7; H, 3.5; S, 18.2.
C20H12O2S2 requires C, 68.94; H, 3.47; S,18.40%]; Rf (10% EA/hexane)
7.90 (2H, m, ArH), 7.80 (4H, d, J 7.5 Hz, ArH), 7.65–7.62 (2H, m, ArH),
7.53 (2H, t, J 7.2 Hz, ArH), 7.40 (4H, t, J 7.5 Hz, ArH); dC (75.6 MHz,
CDCl3) 196.3, 137.4, 137.0, 133.0, 132.9, 130.8, 129.9, 128.8, 128.7,
128.4; MS (EI): m/z (%)¼336 [M]þ.
4.3.43. (3-Benzoylnaphthalen-2-yl)(4-chlorophenyl)methanone
(25b). Following the same procedure as that of 22a afforded
compound 25b (1.06 g, 78%) as a colorless solid; mp 168 ꢀC; [Found:
C, 77.5; H, 4.1. C24H15ClO2 requires C, 77.73; H, 4.08%]; Rf (10% EA/
0.61; nmax (KBr) 1655, 1590 cmꢁ1
;
dH (300 MHz, CDCl3) 8.20 (2H, s,
hexane) 0.65; nmax (KBr) 1640,1592 cmꢁ1
; dH (300 MHz, CDCl3) 7.90
ArH), 7.95–7.92 (2H, m, ArH), 7.67–7.62 (4H, m, ArH), 7.58 (2H, d, J
3.6 Hz, ArH), 7.08 (2H, t, J 4.4 Hz, ArH); dC (75.6 MHz, CDCl3) 187.9,
144.1, 136.4, 135.0, 134.8, 133.0, 130.3, 128.8, 128; MS (EI): m/z
(%)¼348 [M]þ.
(1H, s, ArH), 7.85 (1H, s, ArH), 7.68–7.66 (2H, m, ArH), 7.51–7.41 (9H,
m, ArH), 6.81 (2H, d, J 8.7 Hz, ArH); dC (75.6 MHz, CDCl3) 190.3,
151.5, 150.1, 143.6, 142.2, 135.1, 135.0, 134.9, 134.6, 134.5, 133.6,
133.3, 133.2, 132.0, 131.9, 130.5, 129.1, 128.9, 128.6, 128.5, 128.2,
128.1, 127.9; MS (EI): m/z (%)¼370 [M]þ.
4.3.37. 3-(Benzoylnaphthalen-2-yl)
(thiophen-2-yl)methanone
(22b). Following the same procedure as that of 22a afforded
compound 22b (1.01 g, 72%) as a colorless solid; mp 154 ꢀC;
[Found: C, 77.0; H, 4.1; S, 9.4. C22H14O2S requires C, 77.17; H, 4.12;
S, 9.36%]; Rf (10% EA/hexane) 0.51; nmax (KBr) 1645, 1635,
4.3.44. 2,3-Bis(4-chlorobenzoyl)naphthalene (25c). Following the
same procedure as that of 22a afforded compound 25c (1.06 g,
80%) as a colorless solid; mp 180 ꢀC; [Found: C, 71.4; H, 4.5.
C24H14Cl2O2 requires C, 71.13; H, 3.48%]; Rf (10% EA/hexane) 0.61;
1595 cmꢁ1
;
dH (300 MHz, CDCl3) 8.25 (1H, s, ArH), 8.11 (1H, s,
nmax (KBr) 1642, 1588 cmꢁ1
; dH (300 MHz, CDCl3) 8.05 (2H, s, ArH),
ArH), 7.97–7.92 (2H, m, ArH), 7.86–7.83 (2H, m, ArH), 7.68–7.56
(5H m, ArH), 7.44–7.41 (2H, m, ArH), 7.12–7.10 (1H, m, ArH); dC
(75.6 MHz, CDCl3) 196.3, 188.1, 144.1, 137.4, 136.8, 136.5, 134.9,
134.7, 133.1, 130.9, 130.2, 130.1, 129.9, 128.8, 128.7, 128.4, 128.1; MS
(EI): m/z (%)¼342 [M]þ.
7.94–7.91 (2H, m, ArH), 7.75 (4H, d, J 8.4 Hz, ArH), 7.67–7.64 (2H, m,
ArH), 7.38 (4H, d, J 8.4 Hz, ArH); dC (75.6 MHz, CDCl3); 195.0, 139.5,
136.4, 135.6, 133.0, 131.3, 130.8, 129.0, 128.9, 128.8; MS (EI): m/z
(%)¼404 [M]þ.
4.3.45. 1,3-Diphenylnaptho[2,3-c]thiophene (26a). Following the
same procedure as that of 23a afforded compound 26a (0.15 g, 49%)
4.3.38. (3-(4-Chlorobenzoyl)naphthalen-2-yl) (thiophen-2-yl) meth-
anone (22c). Following the same procedure as that of 22a afforded
compound 22c (1.05 g, 78%) as a colorless solid; mp 180 ꢀC; [Found:
C, 70.3; H, 3.4; S, 8.3. C22H13ClO2S requires C, 70.12; H, 3.48; S,
as a black solid; mp 160 ꢀC; [Found: C, 85.9; H, 4.8; S, 9.4. C24H16
S
requires C, 85.68; H, 4.79; S, 9.53%]; Rf (Hexane) 0.95; dH (300 MHz,
CDCl3) 8.39 (2H, s, ArH), 7.78 (4H, d, J 7.8 Hz, ArH), 7.64–7.61 (2H, m,
ArH), 7.52 (4H, t, J 7.5 Hz, ArH), 7.39 (2H, d, J 7.2 Hz, ArH), 7.11–7.08
(2H, m, ArH); dC (75.6 MHz, CDCl3) 134.9, 134.7, 132.5, 131.5, 129.3,
129.2, 128.9, 127.4, 124.9, 118.5; MS (EI): m/z (%)¼336 [M]þ
8.51%]; Rf (10% EA/hexane) 0.55; nmax (KBr) 1640, 1597 cmꢁ1
; dH
(300 MHz, CDCl3) 8.24 (1H, s, ArH), 8.04 (1H, s, ArH), 7.98–7.91 (2H,
m, ArH), 7.76 (2H, d, J 8.4 Hz, ArH), 7.69–7.64 (3H, m, ArH), 7.61 (1H,
d, J 3.3 Hz, ArH), 7.37 (2H, d, J 8.7 Hz, ArH), 7.12–7.10 (1H, m, ArH); dC
(75.6 MHz, CDCl3) 195.1, 187.5, 143.9, 139.5, 136.6, 136.2, 135.8,
135.0, 134.9, 133.1, 133.0, 131.4, 130.6, 130.5, 128.9, 128.8, 128.7,
128.1; MS (EI): m/z (%)¼376 [M]þ.
4.3.46. 1-(4-Chlorophenyl)-3-phenylnaphtho[2,3-c]thiophene
(26b). Following the same procedure as that of 23a afforded
compound 26b (0.12 g, 42%) as a black solid; mp 162 ꢀC; [Found: C,
77.5; H, 4.2; S, 8.7. C24H15ClS requires C, 77.72; H, 4.08; S, 8.65%]; Rf
(Hexane) 0.95; dH (300 MHz, CDCl3) 8.40 (1H, s, ArH), 8.32 (1H, s,
ArH), 7.78 (2H, d, J 8.7 Hz, ArH), 7.71–7.64 (4H, m, ArH), 7.58–7.42
(5H, m, ArH), 7.15–7.12 (2H, m, ArH); dC (75.6 MHz, CDCl3) 134.9,
134.8, 134.5, 133.2, 133.1, 133.0, 131.6, 131.5, 130.7, 130.2, 129.4,
129.3, 129.2, 128.9, 128.8, 127.5, 125.1, 124.9, 118.7, 118.1; MS (EI): m/
z (%)¼370 [M]þ.
4.3.39. 1-(4-Chlorophenyl)-3-(thiophen-2-yl)naphtho[2,3-c]thio-
phene (23a). To the solution of ketone 22c (0.3 g, 0.877 mmol) in
dry benzene (15 mL), Lawesson’s reagent (0.35 g, 0.877 mmol) was
added in one portion and the reaction mixture was heated for
15 min at 50 ꢀC. Removal of solvent followed by column chro-
matographic purification (silica gel; hexane) gave 23a (0.13 g, 45%)
as a black solid; mp 170 ꢀC; [Found: C, 70.3; H, 3.5; S, 17.2.
C22H13ClS2 requires C, 70.10; H, 3.48; S, 17.01%]; Rf (Hexane) 0.95; dH
(300 MHz, CDCl3) 8.50 (1H, s, ArH), 8.29 (1H, s, ArH), 7.63–7.62 (6H,
m, ArH), 7.46–7.36 (2H, m, ArH), 7.20–7.14 (3H, m, ArH); dC
(75.6 MHz, CDCl3) 136.3, 134.8, 133.4, 132.4, 131.8, 131.6, 130.5,
4.3.47. 1,3-Bis(4-chlorophenyl)naphtho[2,3-c]thiophene (26c). Follo-
wing the same procedure as that of 23a afforded compound 26c
(0.13 g, 45%) as a black solid; mp 220 ꢀC; [Found: C, 71.3; H, 3.5; S,
7.8. C24H14Cl2S requires C, 71.11; H, 3.48; S, 7.91%]; Rf (Hexane) 0.95;

2350
J.A. Clement, A.K. Mohanakrishnan / Tetrahedron 66 (2010) 2340–2350
(c) Li, X. C.; Sirringhaus, H.; Garnier, F.; Holmes, A. B.; Moratti, S. C.; Feeder, N.;
Clegg, W.; Teat, S. J.; Friend, R. H. J. Am. Chem. Soc. 1998, 120, 2206–2207; (d)
Bao, Z.; Lovinger, A. J. Chem. Mater. 1999, 11, 2607–2612.
7. (a) Moerner, W. E.; Silence, S. M. Chem. Rev. 1994, 94, 127–155; (b) Volodin, B. L.;
Kippelen, B.; Meerholz, K.; Javidi, B.; Peyghambarian, N. Nature 1996, 383,
58–60; (c) Hofmann, U.; Schloter, S.; Schreiber, A.; Hoechstetter, K.; Bauml, G.;
Zilker, S. J.; Haarer, D.; Thelakkat, M.; Schmidt, H. W.; Ewert, K.; Eisenbach, C. D.
Proc. SPIE Int. Soc. Opt. Eng. 1998, 3417, 174–176.
dH (300 MHz, CDCl3) 8.35 (2H, s, ArH), 7.73 (4H, d, J 8.7 Hz, ArH),
7.68–7.65 (2H, m, ArH), 7.52 (4H, d, J 8.4 Hz, ArH), 7.17–7.14 (2H, m,
ArH); dC (75.6 MHz, CDCl3) 134.9, 133.4, 133.0, 131.7, 131.4, 130.3,
129.5, 128.8, 125.2, 118.3; MS (EI): m/z (%)¼404 [M]þ.
Acknowledgements
8. (a) Meng, H.; Wudl, F. Macromolecules 2001, 34, 1810–1816; (b) Usta, H.; Lu, G.;
Facchetti, A.; Marks, T. J. J. Am. Chem. Soc. 2006, 128, 9034–9035; (c) Radke, K.
R.; Ogawa, K.; Rasmussen, S. C. Org. Lett. 2005, 7, 5253–5256; (d) Taerum, T.;
Lukoyanova, O.; Wylie, R. G.; Perepichka, D. F. Org. Lett. 2009, 11, 3230–3233; (e)
Balaji, G.; Shim, W. L.; Parameswaran, M.; Valiyaveettil, S. Org. Lett. 2009, 11,
4450–4453; (f) Balaji, G.; Valiyaveettil, S. Org. Lett. 2009, 11, 3358–3361; (g)
Kiebooms, R. H. L.; Goto, H.; Akagi, K. Macromolecules 2001, 34, 7989–7998.
9. Roncali, J. Chem. Rev. 1992, 92, 711–738.
We thank the Department of Science and Technology (DST),
New Delhi (SR/S1/OC-37/2005) for financial support. J.A thanks
CSIR, New Delhi for SRF fellowship. The authors thank the De-
partment of Science and Technology (DST-FIST) for a 300-MHz
NMR spectrometer.
10. Hoogmartens, I.; Adriaensens, P.; Vanderzande, D.; Gelan, J.; Quattrocchi, C.;
Lazzaroni, R.; Bredas, J. L. Macromolecules 1992, 25, 7347–7356.
References and notes
11. (a) Lorcy, D.; Cava, M. P. Adv. Mater. 1992, 4, 562–564; (b) Bauerle, P.; Gotz, G.;
Emerle, P.; Port, H. Adv. Mater. 1992, 4, 564–568; (c) Musinanni, S.; Ferraris, J. P. J.
Chem. Soc., Chem. Commun. 1993, 172–174; (d) Kiebooms, R. H. L.; Adriaensens,
P. J. A.; Vanderzande, D. J. N.; Gelan, J. M. J. V. J. Org. Chem. 1997, 62, 1473–1480;
(e) Mohanakrishnan, A. K.; Lakshmikantham, M. V.; Mcdougal, C. D.; Cava, M. P.;
Baldwin, J. W.; Metzger, R. M. J. Org. Chem. 1998, 63, 3105–3112; (f) Tan, S.;
Bhowmik, A. K.; Thakur, M.; Lakshmikantham, M. V.; Cava, M. P. J. Chem. Phys.
2000, 112, 383–385; (g) Raimundo, J. M.; Blanchard, P.; Brisset, H.; Akoudad, S.;
Roncali, J. Chem. Commun. 2000, 939–940.
12. Strassler, C.; Davis, N. E.; Kool, E. T. Helv. Chim. Acta 1999, 82, 2160–2171.
13. Mitschke, U.; Bauerle, P. J. Chem. Soc., Perkin Trans. 1 2001, 740–753.
14. (a) Vangeneugden, D. L.; Vanderzande, D. J. M.; Salbeck, J.; van Hal, P. A.;
Janssen, R. A. J.; Hummelen, J. C.; Brabec, C. J.; Shaheen, S. E.; Sariciftci, N. S. J.
Phys. Chem. B 2001, 105, 11106–11113; (b) Hansel, H.; Zettl, H.; Krausch, G.;
Kisselev, R.; Thelakkat, M.; Schmidt, H. W. Adv. Mater. 2003, 15, 2056–2060.
15. Kisselev, R.; Thelakkat, M. Macromolecules 1998, 37, 8951–8958.
16. Meek, S. T.; Nesterov, E. E.; Swager, T. M. Org. Lett. 2008, 10, 2991–2993.
17. Lakshmikantham, M. V.; Lorcy, D.; Kelley, C. S.; Wu, X.-L.; Parakka, J. P.; Metzger,
R. M.; Cava, M. P. Adv. Mater. 1993, 5, 723–726.
1. (a) Garnier, F.; Horowitz, G.; Fichou, D. Synth. Met. 1989, 28, 705–714; (b) Gar-
nier, F.; Horowitz, G.; Peng, X.; Fichou, D. Adv. Mater. 1990, 2, 592–594; (c) Tour,
J. Acc. Chem. Res. 2000, 33, 791–804; (d) Gronowitz, S.; Hornfeldt, A.-B. Thio-
phenes; Elsevier Academic: San Diego, CA, 2004; (e) Hotta, S. Molecular con-
ductive materials: polythiophenes and oligothiophenes In. Handbook of Organic
Conductive Molecules and Polymers; Nalwa, H. S., Ed.; Wiley: Chichester, UK,
1997; Vol. 2; Chapter 8, pp 309–387; (f) Blanchard, P.; Leriche, P.; Frere, P.;
Roncali, J. Advanced functional polythiophenes based on tailored precursors In
Handbook of Conducting Polymers, 3rd ed.; Skotheim, T. A., Reynolds, J. R., Eds.;
CRC: New York, NY, 2007; (g) Bauerle, P. Sulfur-containing oligomers In Elec-
tronic Materials: The Oligomer Approach; Mullen, K., Wegner, G., Eds.; Wiley-
VCH: Weinheim, 1998.
2. (a) Handbook of Oligo-and Polythiophnes; Fichou, D., Ed.; Wiley-VCH: Weinheim,
1999; (b) Electronic Materials: The Oligomer Approach; Mullen, K., Wegner, G., Eds.;
Wiley-VCH: Weinheim, 1998; (c) Roncali, J.; Blanchard, P.; Frere, P. J. Mater. Chem.
2005, 15, 1589–1610; (d) Schwab, P. F. H.; Smith, J. R.; Michl, J. Chem. Rev. 2005,
105, 1197–1279; (e) Perepichka, I. F.; Perepichka, D. F.; Meng, H.; Wudl, F. Adv.
Mater. 2005, 17, 2281–2305; (g) Barbarella, G.; Melucci, M.; Sotgiu, G. Adv. Mater.
2005, 17, 1581–1593; (h) Sun, Y.; Liu, Y.; Zhu, D. B. J. Mater. Chem. 2005, 17, 53–65.
3. (a) Mishra, A.; Ma, C.-Q.; Ba¨uerle, P. Chem. Rev. 2009, 109,1141–1276; (b) Roncali, J.
Chem. Rev. 1997, 97, 173–205; (c) Kertesz, M.; Choi, C. H.; Yang, S. Chem. Rev. 2005,
105, 3448–3481; (d) Apperloo, J. J.; Janssen, R. A. J.; Malenfant, P. R. L.; Groenendal,
L.; Frechet, J. M. J. Am. Chem. Soc. 2004,126, 3378–3379; (e) Adronov, A.; Malenfant,
P. R. L.; Frechet, J. M. J. Chem. Mater. 2004, 12, 1463–1472; (f) Zhang, Y.; Zhao, C.;
Yang, J.; Kapiamba, M.; Haze, O.; Rothberg, L. J.; Ng, M. K. J. Org. Chem. 2006, 71,
9475–9483.
4. (a) Tang, C. W. Appl. Phys. Lett. 1986, 48, 183–185; (b) Burroughes, J. H.; Bradley,
D. D. C.; Brown, A. R.; Marks, R. N.; Mackay, K.; Friend, R. H.; Burns, P. L.;
Holmes, A. B. Nature 1990, 347, 539–541; (c) Fichou, D. J. Mater. Chem. 2000, 10,
571–588; (d) Mitschke, U.; Bauerle, P. J. Mater. Chem. 2000, 10, 1471–1507; (e)
Ong, B. S.; Wu, Y.; Liu, P.; Gardner, S. J. Am. Chem. Soc. 2004, 126, 3378–3379; (f)
Garnier, F.; Hajlaoui, R.; Yassar, A.; Srivastava, P. Science 1994, 265, 1684–1686.
5. (a) Yu, G.; Gao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Science 1995, 270,
1789–1791; (b) Halls, J. J. M.; Walsh, C. A.; Greenham, M. C.; Marseglia, E. A.;
Friend, R. H.; Moratti, S. C.; Holmes, A. B. Nature 1995, 376, 498–500.
6. (a) Bao, Z.; Dodabalapur, A.; Lovinger, A. J. Appl. Phys. Lett. 1996, 69, 4108–4110;
(b) Garnier, F.; Hajlaoui, R.; Kassmi, M. E. Appl. Phys. Lett. 1998, 73, 1721–1723;
18. Mohanakrishnan, A. K.; Lakshmikantham, M. V.; Cava, M. P.; Rogers, R. D.;
Rogers, L. M. Tetrahedron 1998, 54, 7075–7080.
19. Hsu, D.-T.; Lin, C.-H. J. Org. Chem. 2009, 74, 9180–9187.
20. (a) Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett. 2005, 46,
4225–4229; (b) Mohanakrishnan, A. K.; Amaladass, P.; Arul Clement, J. Tetra-
hedron Lett. 2007, 48, 779–784; (c) Mohanakrishnan, A. K.; Arul Clement, J.;
Amaladass, P.; Thirunavukkarasu, V. S. Tetrahedron Lett. 2007, 48, 8715–8720;
(d) Mohanakrishnan, A. K.; Senthil Kumar, N.; Amaladass, P. Tetrahedron Lett.
2008, 49, 4792–4795; (e) Amaladass, P.; Arul Clement, J.; Mohanakrishnan, A. K.
Eur. J. Org. Chem. 2008, 3798–3810; (f) Senthil Kumar, N.; Arul Clement, J.;
Mohanakrishnan, A. K. Tetrahedron 2009, 65, 822–830; (g) Arul Clement, J.;
Gunasekaran, P.; Mohanakrishnan, A. K. Tetrahedron 2009, 65, 4113–4123.
21. Carlson, R. G.; Srinivasachar, K.; Givens, R. S.; Matuszewski, B. K. J. Org. Chem.
1986, 51, 3978–3983.
22. Raposo, M. M.; Sampaio, M. B. A.; Kirsch, G. Synthesis 2005, 2, 199–209.
23. (a) Stetter, H. Angew. Chem., Int. Ed. Engl. 1976, 15, 639–647; (b) Wynberg, H.;
Metselaar, J. Synth. Commun. 1984, 14, 1–9; (c) Kozaki, M.; Parakka, J. P.; Cava,
M. P. Tetrahedron Lett. 1995, 36, 6835–6838; (d) Kozaki, M.; Parakka, J. P.; Cava,
M. P. J. Org. Chem. 1996, 61, 3657–3661.