Selective Synthesis, Characterization of Isomerically Pure Arylated Benzo[1,2- b:6,5- b ′]dithiophenes by Regioselective Suzuki-Miyaura Reaction and Evaluation of the Catalytic Properties of Nickel versus Palladium Complexes

Article abstract of DOI:10.1055/s-0035-1562538

Selective synthesis of isomerically pure, angular-shaped benzo[1,2-b:6,5-b′]dithiophenes and various aryl-substituted analogues via the regioselective Suzuki-Miyaura cross-coupling reaction is described. The structural assignments of symmetrical and unsymmetrical derivatives of benzodithiophenes and coumarin-type polyheterocycles are based on X-ray crystallography and spectroscopic studies. A comparative study of nickel versus palladium complexes demonstrated that the nickel complex NiCl₂(dppe) is more effective in terms of reactivity and yields than palladium catalysis in the Suzuki-Miyaura cross-coupling of hindered 3,6-dichlorobenzo[1,2-b:6,5-b′]dithiophenes with arylboronic acids.

Full text of DOI:10.1055/s-0035-1562538

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2016, 48, A–H
paper
A
Z. Hassan et al.
Paper
Synthesis
Selective Synthesis, Characterization of Isomerically Pure Arylated
Benzo[1,2-b:6,5-b′]dithiophenes by Regioselective Suzuki–Miyaura
Reaction and Evaluation of the Catalytic Properties of Nickel
versus Palladium Complexes
Zahid Hassan*a,b,c
Ahmed Al-Harrasi*a,b
Tania Rizvia
Javid Hussaina,b
Peter Langerc,d
Cl
S
Cl
Ar
earlier
studies
RO2C
CO2R
S
CO2H
S
Pd
S
CO2Bu
Cl
linear-shape, anti-, (0%)
BuO2C
X
6 examples, 72–87%
1) SOCl2
2) ROH
Ni vs Pd complexes
Cl
Cl
Ar
Ar
a Chair of Oman’s Medicinal Plants and Marine Natural Products,
University of Nizwa, PO Box 33, PC 616, Birkat Al-Mauz, Oman
zahidhassan@unizwa.edu.om
Ni
CO H
2
our
studies
S
S
CO2R
RO2C
S
S
CO2Bu
3 examples, 74–88%
Ar = phenyl, heteroaryl
angular-shape, syn- (100%)
R = Me, Et, Bu (57–65%)
BuO2C
aharrasi@unizwa.edu.om
b Department of Biological Sciences & Chemistry, University of
Nizwa, PO Box 33, PC 616, Birkat Al-Mauz, Oman
c Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a,
18059 Rostock, Germany
Isomeric Purity and Positional Isomerism?
Symmetry, Spectroscopy & Crystallography
d Leibniz-Institut für Katalyse e. V. an der Universität Rostock,
Albert-Einstein-Str. 29a, 18059 Rostock, Germany
Received: 09.06.2016
Accepted after revision: 21.07.2016
Published online: 01.09.2016
core structures of magnetic and electronic materials,3 such
as organic ferromagnets, conductors, transistors, photovol-
taic cells, and organic light-emitting diodes (OLEDs).4
DOI: 10.1055/s-0035-1562538; Art ID: ss-2016-z0423-op
S
Abstract Selective synthesis of isomerically pure, angular-shaped ben-
zo[1,2-b:6,5-b′]dithiophenes and various aryl-substituted analogues via
the regioselective Suzuki–Miyaura cross-coupling reaction is described.
The structural assignments of symmetrical and unsymmetrical deriva-
tives of benzodithiophenes and coumarin-type polyheterocycles are
based on X-ray crystallography and spectroscopic studies. A compara-
tive study of nickel versus palladium complexes demonstrated that the
nickel complex NiCl2(dppe) is more effective in terms of reactivity and
yields than palladium catalysis in the Suzuki–Miyaura cross-coupling of
hindered 3,6-dichlorobenzo[1,2-b:6,5-b′]dithiophenes with arylboronic
acids.
S
S
S
1
2
linear-shaped, anti-BDT
benzo[1,2-b:4,5-b']dithiophene
linear-shaped, syn-BDT
benzo[1,2-b:5,4-b']dithiophene
S
S
S
S
4
3
angular, syn-BDT
benzo[1,2-b:4,3-b']dithiophene
angular, syn-BDT
benzo[1,2-b:6,5-b']dithiophene
Figure 1 Isomeric fused benzodithiophenes
Key words isomeric purity, symmetry, spectroscopy, regioselectivity,
benzodithiophenes, Suzuki–Miyaura reaction
The synthesis and properties of rigid annulated thio-
phene-fused aromatic compounds that possess an extend-
ed conjugation have been extensively studied in recent
years.5 Their molecular structure, symmetry pattern, and
mechanism of formation are of substantial chemical and in-
dustrial importance. The symmetry pattern of the position-
al isomeric syn- and/or anti-fused compounds plays a criti-
cal role, altering the photophysical and electrochemical
properties, phase behaviors, and intrinsic charge carrier
mobility of the benzodithiophene products.6 Recent inves-
tigations on [1,2-b]dihydroindenofluorenes highlight the
role of the symmetry pattern and the remarkable effect of
positional isomerism on the resulting electronic proper-
ties.7 For instance, linear-shaped centrosymmetric naph-
tho[2,3-b:6,7-b′]dithiophene (NDTs), in comparison to
Benzodithiophenes (BDT), the simplest benzo-fused
thiophenes, which constitute a class of important heterocy-
clic cores that serve as precursors in constructing π-conju-
gated organic materials, contain two annulated thiophene
rings,1 with two linear-shaped [anti-benzo[1,2-b:4,5-
b′]dithiophene (1), syn-benzo[1,2-b:5,4-b′]dithiophene (2)]
and two angular-shaped [benzo[1,2-b:6,5-b′]dithiophene
(3), benzo[1,2-b:4,3-b′]dithiophene (4)] positional isomers
(Figure 1). Benzodithiophene is one of the often incorporat-
ed planar cores in polymers for thin-film transistors, high-
performance solar cells, and other organic semiconduc-
tors.2 More complex, annulated thiophene derivatives often
contain a low singlet–triplet energy gap and are important
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–H

B
Z. Hassan et al.
Paper
Synthesis
those of the angular-shaped NDTs, have been reported as
promising building blocks for the development of organic
semiconducting materials.8 However, selective synthesis
and structural discrimination among isomerically pure syn-
and/or anti-products, and their characterization, isomeric
purity, and structural features that govern the specific
properties of such compounds have only scarcely been
studied. Here, we report the selective synthesis and charac-
terization of various isomerically pure benzo[1,2-b:6,5-
b′]dithiophene derivatives and their subsequent transfor-
mation via the regioselective palladium-catalyzed Suzuki–
Miyaura reaction. After a screening and comparative study
employing different palladium-based complexes versus
nickel complexes, we also established that use of the nickel
complex NiCl2(dppe) is more effective than palladium catal-
ysis in the Suzuki–Miyaura reaction of hindered 3,6-dichlo-
robenzo[1,2-b:6,5-b′]dithiophenes with various boronic ac-
ids.
In view of the significance of benzodithiophenes con-
taining a π-conjugated system in material sciences, we pre-
viously studied the selective synthesis and particular cy-
clization pattern of strained BDT ring formation.9 Our work
allowed us to correct a published structure, an error which
was overlooked in several earlier reports.10,11 In our present
work, we wish to extend the scope of the reaction for the
formation of BDTs. Thus, BDT derivatives 3a–c bearing bu-
tyl, ethyl, and methyl functionalities were synthesized us-
ing n-BuOH, EtOH, and MeOH as nucleophiles, respectively
(Scheme 1,Table 1). Each product was easily separable via
column chromatography. The particular angular-shaped
positional isomerism [i.e., 3,6-dichlorobenzo[1,2-b:6,5-
b′]dithiophene (3) instead of the earlier reported linear-
shaped (anti) isomeric 3,7-dichlorobenzo[1,2-b:4,5-b′]di-
thiophene (1)] was unambiguously confirmed by X-ray
crystal structure analysis (Figure 2).12 In order to obtain the
crystal structure of 3b, layering techniques were applied
and a well-defined needle-shaped crystal was obtained
from CH2Cl2/EtOH, 2:1.
The newly synthesized dithiophene derivatives 3a, 3b,
and 3c were analyzed by 1H NMR, 13C NMR, 2D NMR, HMBC,
HMQC, and COSY experiments in order to assign the aro-
matic core protons and to correlate their chemical shifts to
the specific molecular structure. However, these observa-
tions based on NMR spectroscopy are compatible with both
symmetrical structures of the resulting products (linear-
shaped isomer anti-1 and angular-shaped isomer syn-3)
and structural elucidation by NMR spectroscopy, and mass
spectrometry, delivered no indication since no coupling be-
tween the two aromatic core protons is expected (the pro-
tons are equivalent). The spectroscopic data, including NMR
and IR spectroscopy, and mass spectrometry, as well as ele-
mental analysis of anti-BDT products, is closely correlated
to the syn-BDT products (see the Supporting Information).
The isomeric purity of such compounds and the structural
discrimination among such isomerically pure compounds
has rarely been reported. Hence, unambiguous structural
assignment of these positional isomers has only been possi-
ble by desymmetrization. Along this line, we envisaged the
resulting BDTs as a synthetic handle to decode the specific
symmetry through selective control of the metal-catalyzed
Suzuki–Miyaura reaction for the synthesis of unsymmetri-
cal benzo[1,2-b:6,5-b′]dithiophenes. Despite significant re-
cent advances in transition-metal-catalyzed processes,
many noteworthy challenges still remain.13 Among them
are the 1) couplings of hindered reaction partners, 2) con-
Cl
S
ClOC
COCl
ii) ROH
reflux
S
Cl
H
Cl
linear, anti- (0%)
S
RO2C
CO2R
CO2H
S
Cl
H
1
H
H
CO2H
Cl
Cl
S
S
CO2R
RO2C
ii) ROH
reflux
i) SOCl2
3
Cl
Cl
3a R = Bu
3b R = Et
3c R = Me
65–57%
S
S
COCl
ClOC
angular, syn- (100%)
Scheme 1 Synthesis of BDTs 3a–c. Reagents and conditions: (i) SOCl2,
pyridine, 140 °C, 5 h; (ii) ROH (R = Bu, Et, Me), reflux, 2 h.
Table 1 Synthesis of Isomerically Pure Angular-Shaped BDTs 3a–c
Entry
ROH
n-BuOH
Reagenta
Baseb
Temp (°C)
Yield (%)
3a
3b
3c
SOCl2
SOCl2
SOCl2
pyridine
pyridine
pyridine
140
140
140
65
51
57
EtOH
MeOH
Figure 2 ORTEP plot of 3b; carbon atoms are in black, oxygen atoms in
red, sulfur atoms in yellow, hydrogen atoms in grey and chlorine atoms
in green
a Excess SOCl2 (up to 6 mL) was used.
b Added in a catalytic amount (0.2 mL).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–H

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Z. Hassan et al.
Paper
Synthesis
trol of chemo- and/or regioselectivity using substrates with
multiple reaction centers, and 3) coupling of electron-rich
aryl chlorides.14 In the last two decades, enormous efforts
have been undertaken to activate aryl chlorides by the ap-
plication of electron-rich, sterically encumbered phosphine
ligands or N-heterocyclic carbene ligands, which allow for
efficient cross-coupling reactions.15
Ha
S
Hb
S
Ha
S
Ha
S
Ar
Cl
Cl
Cl
i)
CO2Bu
BuO2C
CO2Bu
BuO2C
3a
6a–f
72–87% yield
Scheme 2 Synthesis of unsymmetrical biaryls 6a–f. Reagents and con-
ditions: (i) 3a (1.0 equiv), ArB(OH)2 5 (1.2 equiv), Pd(PPh3)4 (5 mol%),
K3PO4 (2.0 equiv), 1,4-dioxane, 120 °C, 4 h.
Comparative catalysis employing different metal com-
plexes and selective transformations of highly hindered
polyheterocycles have only scarcely been studied. Aryl
chlorides, one of the commonest electrophiles in coupling
reactions, are perhaps the most attractive family of the aryl
halide substrates due to their low cost and their ready avail-
ability, but they also have some drawbacks (for instance,
low reactivity and selectivity) which offer the opportunity
for improvement.16 We examined selected C–C bond forma-
tions of less reactive aryl chlorides and evaluated catalytic
activity by employing different metal complexes of palladi-
um and nickel. In our preliminary trial, reactions were car-
ried out under classical conditions [using Pd(PPh3)4 as cata-
lyst] by applying the regioselective Suzuki–Miyaura mono-
cross-coupling reaction for the synthesis of unsymmetrical
benzo[1,2-b:6,5-b′]dithiophenes 6a–f (Scheme 2). 2,7-
Bis(butoxycarbonyl)-3,6-dichlorobenzo[1,2-b:6,5-b′]dithio-
phene (3a) was employed as a platform (due to its high sol-
ubility in organic solvents relative to the methoxy and
ethoxy derivatives) for the Suzuki–Miyaura cross-coupling
reaction. After a careful optimization of reaction parame-
ters, including base (K3PO4), temperature (100–120 °C), and
solvent (1,4-dioxane), using a range of commercially avail-
able aryl- and heteroarylboronic acids 5 [with Pd(PPh3)4 ca-
talysis], a highly selective monocoupling reaction was
achieved (Scheme 2, Table 2). The boronic acids 5 were cho-
Table 2 Synthesis of Monofunctionalized Unsymmetrical BDTs 6a–f
Entry
5: Ar
2-MeO-5-FC6H3
Solvent
Catalyst
Yield (%)
1
2
3
4
5
6
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
6a, 82
6b, 87
6c, 80
6d, 74
6e, 82
6f, 72
2-MeO-5-ClC6H3
2-MeOC6H4
4-MeOC6H4
4-ClC6H4
5-formyl-2-thienyl
We have thus established that it is possible to carry out
highly selective monofunctionalizations of difunctionalized
BDT under palladium catalysis. A clear structural differenti-
ation of the corresponding diarylated benzo[1,2-b:6,5-
b′]dithiophenes, which are expected to again have a sym-
metrical core, by NMR spectroscopy will not be possible.
The aromatic protons Ha would appear as a singlet with an
integration of two protons, as noted for the parent BDT
core. However, these observations are compatible with both
parent BDT isomers 1 and 3, since no coupling between the
two (equivalent) aromatic protons is expected.
1
sen on the basis that their H NMR signals in the products
In a separate experiment, the monoarylated products
6a–f were applied in a sequential diarylation coupling reac-
tion, but these reactions failed and almost none of the de-
sired diarylated Suzuki–Miyaura cross-coupling products
were observed. Our optimal procedures for Suzuki–Miyaura
cross-coupling of 3a using Pd(PPh3)4 (5–30 mol%) as cata-
lyst were much less effective; yields of the cross-coupled
products were less than 5%, and homocoupling products
were obtained as the major products (Table 3, entry 1). We
sought to optimize the conditions by refluxing the reaction
mixture at high temperature, increasing the amount of cat-
alyst and ligand, and applying extended reaction times, but
no significant improvement in yield was observed. Howev-
er, higher activity for Suzuki–Miyaura cross-coupling reac-
tions of BDT chlorides was exhibited upon addition of the
biaryl monophosphine ligand SPhos (Table 3, entry 3). The
use of Pd(PPh3)2Cl2 was less effective in terms of the yield,
and an inseparable mixture was formed in this particular
application when Pd(OAc)2 in the presence of XPhos was
used (Table 3, entries 2 and 4). Notably, when changing
from a palladium- to a nickel-based complex as catalyst,
there was an improved yield of the cross-coupled products
would not disturb structure elucidation of the BDT aromat-
ic core structure.
The regioselective Suzuki–Miyaura reaction proceeded
with high yields of biaryls 6 (up to 87%, Table 2). Various ar-
ylboronic acids were applied, to prepare a variety of ap-
pealing polyheterobiaryls. Inspection of the 1H NMR spectra
of unsymmetrical biaryls 6a–f (i.e., broken symmetry)
clearly showed that the two aromatic protons Ha and Hb are,
as expected, chemically and magnetically different, and res-
onate as characteristic doublets at ca. δ = 7.74 and 7.36
ppm with a coupling constant of 8.8 Hz. These results are
only compatible with the structure of the 3-aryl-6-chloro-
benzo[1,2-b:6,5-b′]dithiophenes 6a–f, and not with the
corresponding isomeric 3-aryl-7-chlorobenzo[1,2-b:4,5-
b′]dithiophenes (anti-BDT derivatives 1). In the latter case,
no significant coupling is possible for the two aromatic pro-
tons Ha and Hb. The NMR experiments on 6a–f clearly also
confirm the parental structure of angular BDT 3a, as no
change in the aromatic core is expected during the coupling
reactions.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–H

D
Z. Hassan et al.
Paper
Synthesis
(Scheme 3, Table 3, entries 5–7). Higher yields were
achieved when using NiCl2(dppe) (5 mol%) rather than the
heavier palladium complex homologues.
using nickel-mediated procedures and employing a range of
electronically and sterically diverse alternative π-conjugat-
ed polyheterocycles are currently in progress to further ex-
pand applications to other carbon–carbon and carbon–het-
eroatom bond-forming reactions.
H
H
H
H
Ar
Ar
Cl
Cl
In conclusion, we have demonstrated the selective syn-
thesis and structural assignment of highly isomerically
pure (100% syn), angular-shaped benzo[1,2-b:6,5-b′]dithio-
phenes, and their subsequent transformation via a Suzuki–
Miyaura/lactonization tandem protocol. The structural as-
signments of symmetrical and unsymmetrical derivatives
of benzodithiophenes are based on X-ray crystallography
and detailed NMR spectroscopic studies. Such molecular
symmetry has long been realized to be a key factor in de-
signing molecular architecture and can thus impart drasti-
cally altered physical and chemical properties. The present
studies also demonstrated that the nickel complex
NiCl2(dppe) is more effective in terms of reactivity and
higher yields than catalysis by heavier palladium homo-
logues in the Suzuki–Miyaura cross-coupling reaction of
hindered 3,6-dichlorobenzo[1,2-b:6,5-b′]dithiophenes with
arylboronic acids. These findings are important for the fu-
ture design of functional materials.
i)
S
S
CO2Bu
S
BuO2C
S
CO2Bu
BuO2C
3a
7a–c
Scheme 3 Synthesis of symmetrical biaryls 7a–c. Reagents and condi-
tions: (i) 3a (1.0 equiv), ArB(OH)2 5 (2.5 equiv), NiCl2(dppe) (5 mol%),
K3PO4 (4.0 equiv), toluene, 120 °C, 4–6 h.
Table 3 Optimization and Synthesis of Diarylated Symmetrical BDTs
7a–c
Entry 5: Ar
Solvent
Catalyst
Yield (%)
1
2
3
4
5
6
7
4-MeOC6H4
1,4-dioxane
THF
Pd(PPh3)4
<5
<5
22
20
88
74
78
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
2-MeO-5-ClC6H3
2-MeOC6H4
Pd(PPh3)2Cl2
Pd(O2CCF3)2/SPhos
Pd(OAc)2/XPhos
NiCl2(dppe)
toluene
toluene
toluene
toluene
toluene
NiCl2(dppe)
NiCl2(dppe)
All starting materials and anhydrous solvents were purchased com-
mercially and used without further purification. IR spectra were re-
corded on Nicolet 205 and Nicolet Protege 460 FT-IR spectrophotom-
eters. Peaks are given the following assignments: w = weak, m = me-
dium, s = strong, br = broad. 1H NMR spectra were recorded on Bruker
Avance 300 and 600 MHz instruments. Chemical shifts given in ppm
and coupling constants J in Hz are referenced to signals of the deuter-
ated solvent. Purification by column chromatography was performed
using a flash silica gel 60 chromatography system. TLC was performed
using silica gel 60 F254 and visualized with a UV lamp. All reactions
were carried out in oven-dried reaction pressure tubes under argon
atmosphere (purged with argon before use). GC-MS analysis was car-
ried out on an Agilent HP-5890 instrument with an Agilent HP-5973
Mass Selective Detector (EI). Crystal data for compound 3b were mea-
sured at the Research Facility of the Pohang University of Science and
Technology (POSTECH). Structures were solved and refined using
SHELX programs. Melting points were determined on a Micro heating
table HMK 67/1825 Kuestner (Buchi apparatus) and a Leitz Labolux
12 Pol with a Mettler FP 90 heating table and are uncorrected.
The resulting diarylated BDT fragment is an important
synthon that can be further transformed into various inter-
esting architectures. We demonstrated the synthetic utility
of BDTs for a rapid synthesis of coumarin-type polyhetero-
cycles, namely benzo-fused dilactones (Scheme 4). Due to
the wide range of their biological activities, lactones have
attracted the attention of the medicinal chemistry commu-
nity. An arylboronic acid with the useful functionality of a
2-OH group gave the condensed fused dilactone 8 via a
Suzuki–Miyaura/lactonization tandem protocol in a single
operation, providing a method for the rapid preparation of
highly conjugated frameworks.
H
H
H
H
Cl
Cl
i)
O
O
S
S
3,6-Dichlorobenzo[1,2-b:6,5-b′]dithiophenes 3a–c; General Proce-
dure A
S
S
CO2Bu
BuO2C
3a
8
O
O
Thionyl chloride (6 mL, 80 mmol) was added portionwise to a mix-
ture of 1,4-phenylenediacrylic acid (2.00 g, 9.16 mmol) and a catalytic
amount of pyridine (0.2 mL). The reaction mixture was heated for 5 h
at 140 °C. Upon cooling, the product solidified and the excess thionyl
chloride was removed under reduced pressure to give 3,6-dichloro-
2,7-bis(chlorocarbonyl)benzo[1,2-b:6,5-b′]dithiophene as a greenish
solid. This solid was dissolved in benzene (50 mL), and to the solution
ROH (10 mL) was added (under inert conditions). The mixture was re-
fluxed for 2 h to give crude ester product 3 as a crystalline solid. The
product was purified by flash column chromatography (silica gel;
heptanes/EtOAc, 9:1).
Scheme 4 Synthesis of the coumarin-type benzo-fused dilactone 8.
Reagents and conditions: (i) 3a (1.0 equiv), 2-HOC6H4B(OH)2 (2.5 equiv),
NiCl2(dppe) (5 mol%), K3PO4 (4.0 equiv), toluene, 120 °C, 6 h.
The higher reactivity and increased yields of the nickel-
mediated procedure suggest that it might serve as an effi-
cient tool for carbon–carbon and carbon–heteroatom bond-
forming reactions, where generally expensive bulky phos-
phine ligands, high catalyst loading, and long reaction times
under elevated temperature were required.17 Experiments
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Z. Hassan et al.
Paper
Synthesis
2,7-Bis(butoxycarbonyl)-3,6-dichlorobenzo[1,2-b:6,5-b′]dithio-
Unsymmetrical Biaryls 6a–f by the Suzuki–Miyaura Cross-
phene (3a)
Coupling Reaction; General Procedure B
Following general procedure A, 1,4-phenylenediacrylic acid (2.00 g,
9.16 mmol), SOCl2 (6 mL, 80 mmol), and pyridine (0.2 mL) were used.
n-BuOH (10 mL) was added to the benzene solution (under inert con-
ditions), which after reflux for 2 h gave crude butyl ester 3a as a white
crystalline solid (2.73 g, 65%); mp 95–97 °C.
A 1,4-dioxane (5 mL per 1 mmol) solution of K3PO4 (2.0 equiv per
cross-coupling step), Pd(PPh3)4 (5 mol%), 3a (200 mg, 0.43 mmol), and
an arylboronic acid 5a–f (1.0–1.2 equiv per cross-coupling step) was
transferred into a pressure tube. The reaction mixture in the pressure
tube was purged with argon for 10 min and sealed with a cap con-
taining a septum, then stirred at 110–120 °C for 4–6 h. After the mix-
ture was cooled to 20 °C, H2O was added. The organic and aqueous
layers were separated, and the latter was extracted with CH2Cl2
(15 × 3 mL). The combined organic layers were dried (Na2SO4) and the
filtrate was concentrated in vacuo. The residue was purified by flash
column chromatography (silica gel; hexane/EtOAc, 9:1) to obtain the
desired product.
IR (KBr): 3418, 2956, 2931, 2872 (s), 2736 (w), 1726, 1708, 1510,
1494 (s), 1476, 1406, 1380, 1301 (m), 1235, 1211, 1095, 1082, 1060,
1045, 1017, 964 (s), 932, 850, 804, 756 (m), 756, 734, 715 (s) cm–1
.
1H NMR (300 MHz, CDCl3): δ = 0.94 (t, J = 7.3 Hz, 6 H, CH3), 1.39–1.46
(m, 4 H, CH2), 1.68–1.77 (m, 4 H, CH2), 4.34 (t, J = 6.5 Hz, 4 H, OCH2),
7.91 (s, 2 H, Ar).
13C NMR (75.5 MHz, CDCl3): δ = 13.7 (CH3), 19.2, 30.6 (CH2), 65.9
(OCH2), 121.2 (CH), 126.2, 128.2, 132.9, 137.1, 160.8 (C).
GC-MS (EI, 70 eV): m/z (%) = 458 (100) ([M]+, 2 × 35Cl), 346 (78), 329
2,7-Bis(butoxycarbonyl)-3-chloro-6-(5-fluoro-2-methoxyphe-
nyl)benzo[1,2-b:6,5-b′]dithiophene (6a)
(41), 257 (33).
Starting with 3a (200 mg, 0.43 mmol), 5-fluoro-2-methoxyphenylbo-
ronic acid (5a) (1.2 equiv, 88 mg, 0.53 mmol), Pd(PPh3)4 (25 mg, 5
mol%), K3PO4 (2.0 equiv, 185 mg, 0.85 mmol), and 1,4-dioxane (5 mL),
following general procedure B, 6a was isolated as a white solid (194
mg, 82%); mp 108–110 °C.
HRMS (EI, 70 eV): m/z [M]+ calcd for C20H2035Cl2O4S2: 458.0180;
found: 458.0171.
3,6-Dichloro-2,7-bis(ethoxycarbonyl)benzo[1,2-b:6,5-b′]dithio-
phene (3b)
IR (KBr): 2958, 2932, 1872, 1836, 1718, 1697 (s), 1493, 1463, 1414,
1334, 1311 (m), 1273, 1255, 1227, 1206, 1180, 1155, 1125, 1085,
Following general procedure A, 1,4-phenylenediacrylic acid (2.00 g,
9.16 mmol), SOCl2 (6 mL, 80 mmol), and pyridine (0.2 mL) were used.
EtOH (10 mL) was added to the benzene solution (under inert condi-
tions), which after reflux for 2 h gave crude ethyl ester 3b as a yellow
crystalline solid (1.8 g, 51%); mp 105–107 °C.
1H NMR (600 MHz, CDCl3): δ = 0.92 (t, J = 7.3 Hz, 6 H, CH3), 4.32 (q,
J = 7.1 Hz, 4 H, OCH2), 7.91 (s, 2 H, Ar).
1069, 1029 (s), 992, 940, 907, 877 (m), 807, 757, 729 (s) cm–1
.
1H NMR (300 MHz, CDCl3): δ = 0.79 (t, J = 7.3 Hz, 3 H, CH3), 0.92 (t, J =
7.3 Hz, 3 H, CH3), 1.11–1.38 (m, 2 H), 1.40–1.48 (m, 4 H), 1.66–1.74
(m, 2 H), 3.61 (s, 3 H, OCH3), 4.10 (t, J = 6.3 Hz, 2 H), 4.31 (t, J = 6.3 Hz,
2 H), 6.86–6.95 (m, 2 H), 7.04–7.10 (td, J = 8.1, 3.1 Hz, 1 H), 7.36 (d, J =
8.8 Hz, 1 H), 7.74 (d, J = 8.8 Hz, 1 H).
13C NMR (75.5 MHz, CDCl3): δ = 13.3, 13.7 (CH3), 19.0, 19.2 (CH2),
30.5, 30.6 (CH2), 56.1 (OCH3), 65.4, 65.7 (OCH2), 111.9 (d, JF,C = 8.3 Hz,
CH), 115.9 (d, JF,C = 22.5 Hz, CH), 117.9 (d, JF,C = 23.6 Hz, CH), 120.5,
122.5 (CH), 124.6 (d, JF,C = 8.2 Hz, CH), 128.2, 130.5, 133.0, 134.2,
136.3, 139.2, 139.8, 153.5 (C), 156.1 (d, JF,C = 237.7 Hz, CF), 161.0,
162.0.
13C NMR (150 MHz, CDCl3): δ = 13.5 (CH3), 65.7 (OCH2), 121.2 (CH),
126.2, 128.2, 132.9, 137.1, 160.8 (C).
GC-MS (EI, 70 eV): m/z (%) = 402 (100) ([M]+, 2 × 35Cl), 254 (78).
HRMS (EI, 70 eV): m/z [M]+ calcd for C16H1235Cl2O4S2: 402.0228;
found: 402.0224.
19F NMR (282.4 MHz, CDCl3): δ = –124.0.
GC-MS (EI, 70 eV): m/z (%) = 548 (100) ([M]+, 35Cl), 475 (48), 461 (41),
447 (13), 405 (32), 391 (22), 381 (34), 359 (31), 325 (21).
HRMS (EI, 70 eV): m/z [M]+ calcd for C27H2635ClFO5S2: 548.0889;
3,6-Dichloro-2,7-bis(methoxycarbonyl)benzo[1,2-b:6,5-b′]dithio-
phene (3c)
Following general procedure A, 1,4-phenylenediacrylic acid (2.00 g,
9.16 mmol), SOCl2 (6 mL, 80 mmol), and pyridine (0.2 mL) were used.
MeOH (10 mL) was added to the benzene solution (under inert condi-
tions), which after reflux for 2 h gave crude methyl ester 3c as a yel-
low crystalline solid (1.9 g, 57%); mp 147–149 °C.
found: 548.0890.
2,7-Bis(butoxycarbonyl)-3-chloro-6-(5-chloro-2-methoxyphe-
nyl)benzo[1,2-b:6,5-b′]dithiophene (6b)
IR (KBr): 3434, 2960, 2842, 1727 (s), 1650, 1643, 1633, 6113, 1509,
1434 (m), 1322, 1306, 1250, 1238, 1110, 1090, 1038 (s), 973, 940,
Starting with 3a (200 mg, 0.43 mmol), 5-chloro-2-methoxyphenylbo-
ronic acid (5b) (1.2 equiv, 96 mg, 0.51 mmol), Pd(PPh3)4 (25 mg, 5
mol%), K3PO4 (2.0 equiv, 185 mg, 0.85 mmol), and 1,4-dioxane (5 mL),
following general procedure B, 6b was isolated as a light green solid
(211 mg, 87%); mp 77–99 °C.
910, 817, 759, 736, 611 (m) cm–1
.
1H NMR (300 MHz, CDCl3): δ = 3.93 (s, 6 H, OCH3), 7.95 (s, 2 H, Ar).
13C NMR (75.5 MHz, CDCl3): δ = 52.7 (OCH3), 121.3 (CH), 126.2, 128.5,
133.1, 137.0, 160.7 (C).
GC-MS (EI, 70 eV): m/z (%) = 374 (100) ([M]+, 2 × 35Cl), 343 (89), 315
IR (KBr): 2974, 2961, 2930, 2911, 2825, 1721, 1686 (s), 1675, 1663,
1582, 1561 (w), 1481, 1479, 1461, 1411, 1403, 1338, 1334 (m), 1289,
1261, 1251, 1182, 1134, 1127, 1025 (s), 802, 769, 684, 667 (s) cm–1
.
(43), 256 (29).
HRMS (EI, 70 eV): m/z [M]+ calcd for C14H835Cl2O4S2: 373.9276; found:
373.9274.
1H NMR (300 MHz, CDCl3): δ = 0.81 (t, J = 7.3 Hz, 3 H, CH3), 0.93 (t, J =
7.3 Hz, 3 H, CH3), 1.14–1.21 (m, 2 H), 1.38–1.42 (m, 4 H), 1.44–1.48
(m, 2 H), 3.60 (s, 3 H, OCH3), 4.13 (t, J = 6.5 Hz, 2 H), 4.32 (t, J = 6.5 Hz,
2 H), 6.88 (d, J = 8.8 Hz, 1 H), 7.16 (d, J = 2.6 Hz, 1 H), 7.30–7.36 (m, 2
H), 7.73 (d, J = 8.8 Hz, 1 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–H

F
Z. Hassan et al.
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Synthesis
13C NMR (75.5 MHz, CDCl3): δ = 13.7, 13.8 (CH3), 19.1, 19.2 (CH2),
30.5, 30.6 (CH2), 55.8 (OCH3), 65.5, 65.7 (OCH2), 112.1, 120.5, 122.5
(CH), 124.9, 125.3, 125.4, 128.2 (C), 129.6, 130.6 (CH), 130.7, 133.0,
134.2, 136.3, 138.9, 139.8, 155.9, 161.0, 162.0 (C).
GC-MS (EI, 70 eV): m/z (%) = 564 (100) ([M]+, 2 × 35Cl), 491 (24), 477
(36), 463 (11), 421 (31), 381 (37), 325 (24).
2,7-Bis(butoxycarbonyl)-3-chloro-6-(4-chlorophenyl)benzo[1,2-
b:6,5-b′]dithiophene (6e)
Starting with 3a (200 mg, 0.43 mmol), 4-chlorophenylboronic acid
(5e) (1.2 equiv, 78 mg, 0.52 mmol), Pd(PPh3)4 (25 mg, 5 mol%), K3PO4
(2.0 equiv, 185 mg, 0.85 mmol), and 1,4-dioxane (5 mL), following
general procedure B, 6e was isolated as a light green viscous oil (220
mg, 82%).
1H NMR (600 MHz, CDCl3): δ = 0.88 (t, J = 7. 3 Hz, 3 H, CH3), 0.99 (t, J =
7.2 Hz, 3 H, CH3), 1.29–1.49 (m, 2 H), 1.50–1.54 (m, 2 H), 1.55–1.64
(m, 2 H, CH2), 1.75–1.80 (m, 2 H, CH2), 4.19 (t, 2 H, OCH2), 4.37 (t, 2 H,
OCH2), 7.34 (d, J = 8.2 Hz, 2 H), 7.87 (d, J = 8.3 Hz, 2 H), 7.51 (d, J = 8.8
Hz, 1 H), 7.81 (d, J = 8.7 Hz, 1 H).
13C NMR (150 MHz, CDCl3): δ = 13.7, 13.8 (CH3), 19.1, 19.3 (CH2), 31.1,
31.3 (CH2), 65.2, 65.5 (OCH2), 112.8, 120.1, 122.1 (C), 125.1, 125.8
(CH), 127.0, 127.9 (C), 131.3 (CH), 133.1 (C), 134.0 (CH), 135.4, 140.2,
143.6, 148.6, 161.0, 162.2.
HRMS (EI, 70 eV): m/z [M]+ calcd for C27H2635Cl2O5S2: 564.0593;
found: 564.0594.
2,7-Bis(butoxycarbonyl)-3-chloro-6-(2-methoxyphenyl)ben-
zo[1,2-b:6,5-b′]dithiophene (6c)
Starting with 3a (200 mg, 0.43 mmol), 2-methoxyphenylboronic acid
(5c) (1.2 equiv, 78 mg, 0.52 mmol), Pd(PPh3)4 (25 mg, 5 mol%), K3PO4
(2.0 equiv, 185 mg, 0.85 mmol), and 1,4-dioxane (5 mL), following
general procedure B, 6c was isolated as a light green, highly viscous
oil (180 mg, 80%).
IR (KBr): 2957, 2930, 2872, 1716, 1698 (s), 1547, 1531, 1501, 1486,
1462, 1413, 1337, 1311 (m), 1274, 1228, 1175, 1123, 1114, 1071 (s),
2,7-Bis(butoxycarbonyl)-3-chloro-6-(5-formyl-2-thienyl)ben-
zo[1,2-b:6,5-b′]dithiophene (6f)
906, 875, 727 (s) cm–1
.
Starting with 3a (200 mg, 0.43 mmol), 5-formyl-2-thienylboronic
acid (5f) (1.2 equiv, 80 mg, 0.51 mmol), Pd(PPh3)4 (25 mg, 5 mol%),
K3PO4 (2.0 equiv, 185 mg, 0.85 mmol), and 1,4-dioxane (5 mL), follow-
ing general procedure B, 6f was isolated as a yellowish oil (170 mg,
72%).
1H NMR (600 MHz, CDCl3): δ = 0.90 (t, J = 7.4 Hz, 3 H), 0.99 (t, J = 7.3
Hz, 3 H), 1.31–1.34 (m, 2 H), 1.49–1.53 (m, 2 H), 1.58–1.63 (m, 2 H),
1.76–1.81 (m, 2 H), 4.25 (t, J = 6.5 Hz, 2 H), 4.39 (t, J = 6.7 Hz, 2 H), 7.29
(d, J = 3.8 Hz, 1 H), 7.66 (d, J = 8.8 Hz, 1 H), 7.86 (d, J = 3.8 Hz, 1 H), 7.90
(d, J = 8.8 Hz, 1 H), 9.98 (s, 1 H).
13C NMR (150 MHz, CDCl3): δ = 13.6, 13.7 (CH3), 19.1, 19.2 (CH2), 30.4,
30.6 (CH2), 65.8, 65.9 (OCH2), 121.2, 122.1, 126.1, 128.2 (C), 130.3
(CH), 131.8, 132.9, 134.1, 134.6 (C), 135.9 (CH), 136.7, 139.6, 143.7,
145.0, 160.8, 161.3 (C), 182.8 (CH).
1H NMR (300 MHz, CDCl3): δ = 0.79 (t, J = 7.3 Hz, 3 H, CH3), 0.92 (t, J =
7.3 Hz, 3 H, CH3), 1.11–1.20 (m, 2 H), 1.40–1.46 (m, 4 H), 1.66–1.74
(m, 2 H), 3.61 (s, 3 H, OCH3), 4.10 (t, J = 6.3 Hz, 2 H), 4.31 (t, J = 6.5 Hz,
2 H), 6.95 (d, J = 8.3 Hz, 1 H), 7.01 (td, J = 7.4, 1.2 Hz, 1 H), 7.17 (dd, J =
7.4, 1.7 Hz, 1 H), 7.34–7.39 (m, 2 H), 7.71 (d, J = 8.8 Hz, 1 H).
13C NMR (75.5 MHz, CDCl3): δ = 13.7, 13.8 (CH3), 19.1, 19.2 (CH2),
30.5, 30.6 (CH2), 55.8 (OCH3), 65.5, 65.7 (OCH2), 110.9, 120.2, 120.5
(CH), 123.2, 125.2 (CH), 128.2 (C), 129.9 (CH), 130.1 (C), 130.9 (CH),
133.0, 134.1, 136.1, 140.2, 140.7, 157.1, 161.0, 162.2.
GC-MS (EI, 70 eV): m/z (%) = 530 (100) ([M]+, 35Cl), 457 (49), 443 (33),
381 (37), 325 (21).
HRMS (EI, 70 eV): m/z [M]+ calcd for C27H2735ClO5S2: 530.0982; found:
530.0981.
2,7-Bis(butoxycarbonyl)-3-chloro-6-(4-methoxyphenyl)ben-
zo[1,2-b:6,5-b′]dithiophene (6d)
2,7-Bis(butoxycarbonyl)-3,6-bis(4-methoxyphenyl)benzo[1,2-
b:6,5-b′]dithiophene (7a)
Starting with 3a (200 mg, 0.43 mmol), 4-methoxyphenylboronic acid
(5d) (1.2 equiv, 78 mg, 0.52 mmol), Pd(PPh3)4 (25 mg, 5 mol%), K3PO4
(2.0 equiv, 185 mg, 0.85 mmol), and 1,4-dioxane (5 mL), following
general procedure B, 6d was isolated as a light greenish oil (170 mg,
74%).
Starting with 3a (100 mg, 0.21 mmol), 4-methoxyphenylboronic acid
(5d) (2.5 equiv, 80 mg, 0.53 mmol), NiCl2(dppe) (6.0 mg, 5 mol%), K3-
PO4 (4.0 equiv, 185 mg, 0.87 mmol), and toluene (5 mL), following the
general procedure B, 7a was isolated as a yellowish viscous solid (115
mg, 88%).
IR (KBr): 2930, 2872, 1716 (s), 1531, 1501, 1486, 1413, 1337, 1311
1H NMR (600 MHz, CDCl3): δ = 0.89 (t, J = 7.4 Hz, 6 H, CH3), 1.26–1.32
(m, 4 H), 1.56–1.60 (m, 4 H), 3.86 (s, 6 H, OCH3), 4.20 (t, J = 6.5 Hz, 4 H,
OCH2), 7.01 (d, J = 8.4 Hz, 4 H), 7.32 (d, J = 8.4 Hz, 4 H), 7.41 (s, 2 H).
13C NMR (150 MHz, CDCl3): δ = 13.7 (CH3), 19.1 (CH2), 30.5 (CH2), 55.2
(OCH3), 65.3 (OCH2), 113.5, 122.1, 126.5 (CH), 128.0, 131.0, 134.3,
139.5, 144.5, 159.6, 162.4 (C).
(m), 1274, 1175, 1114, 1071 (s), 906, 875 (s) cm–1
.
1H NMR (600 MHz, CDCl3): δ = 0.88 (t, J = 7.3 Hz, 3 H), 0.99 (t, J = 7.1
Hz, 3 H), 1.50–1.54 (m, 2 H), 1.50–1.54 (m, 2 H), 1.55–1.64 (m, 2 H),
1.75–1.80 (m, 2 H), 3.87 (s, 3 H, OCH3), 4.19 (t, J = 6.3 Hz, 2 H), 4.37 (t,
J = 6.2 Hz, 2 H), 7.02 (d, J = 8.5 Hz, 2 H), 7.33 (d, J = 8.5 Hz, 2 H), 7.53 (d,
J = 8.8 Hz, 1 H), 7.77 (d, J = 8.8 Hz, 1 H).
13C NMR (150 MHz, CDCl3): δ = 13.6, 13.7 (CH3), 19.1, 19.2 (CH2), 30.4,
30.5 (CH2), 55.2 (OCH3), 65.3, 65.6 (OCH2), 113.5, 120.3, 122.8 (C),
125.3, 126.1 (CH), 128.1, 128.6 (C), 130.9 (CH), 132.8 (C), 134.1 (CH),
136.2, 140.2, 144.3, 159.6, 160.9, 162.1.
HRMS (EI, 70 eV): m/z [M]+ calcd for C34H34O6S2: 602.1764; found:
602.1764.
2,7-Bis(butoxycarbonyl)-3,6-bis(5-chloro-2-methoxyphenyl)ben-
zo[1,2-b:6,5-b′]dithiophene (7b)
Starting with 3a (100 mg, 0.21 mmol), 5-chloro-2-methoxyphenylbo-
ronic acid (2.5 equiv, 99 mg, 0.53 mmol), NiCl2(dppe) (6.0 mg, 5
mol%), K3PO4 (4.0 equiv, 185 mg, 0.87 mmol), and toluene (5 mL), fol-
lowing the general procedure B, 7b was isolated as a light greenish
solid (107 mg, 74%).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–H

G
Z. Hassan et al.
Paper
Synthesis
1H NMR (600 MHz, CDCl3): δ = 0.82 (t, J = 7.3 Hz, 6 H, CH3), 1.14–1.49
(m, 4 H), 1.38–1.42 (m, 4 H), 3.58 (s, 6 H, OCH3), 4.12 (t, J = 6.4 Hz, 4
H), 6.85 (dd, J = 8.8, 2.8 Hz, 2 H), 7.13 (d, J = 2.5 Hz, 2 H), 7.21 (s, 2 H),
7.27–7.31 (m, 2 H).
13C NMR (150 MHz, CDCl3): δ = 13.7 (CH3), 19.1 (CH2), 28.7 (CH2), 55.8
(OCH3), 65.4 (OCH2), 112.1, 121.7, 129.4 (CH), 125.4, 128.2, 130.7(C),
130.8 (CH), 133.0, 134.4, 139.1, 155.9, 162.2 (C).
(2) (a) Takimiya, K.; Shinamura, S.; Osaka, I.; Miyazaki, E. Adv.
Mater. 2011, 23, 4347. (b) Sista, P.; Biewer, M. C.; Stefan, M. C.
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(3) (a) Shinamura, S.; Osaka, I.; Miyazaki, E.; Takimiya, K. Heterocy-
cles 2011, 83, 1187. (b) Takimiya, K.; Kunugi, Y.; Konda, Y.;
Niihara, N.; Otsubo, T. J. Am. Chem. Soc. 2004, 126, 5084.
(c) Takimiya, K.; Konda, Y.; Ebata, H.; Niihara, N.; Otsubo, T.
J. Org. Chem. 2005, 70, 10569. (d) Takimiya, K.; Kunugi, Y.;
Toyoshima, Y.; Otsubo, T. J. Am. Chem. Soc. 2005, 127, 3605.
(e) Takimiya, K.; Kunugi, Y.; Konda, Y.; Ebata, H.; Toyoshima, Y.;
Otsubo, T. J. Am. Chem. Soc. 2006, 128, 3044. (f) Yamamoto, T.;
Takimiya, K. J. Am. Chem. Soc. 2007, 129, 2224.
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2001, 34, 359. (b) Takimiya, K.; Kunugi, Y.; Otsubo, T. Chem. Lett.
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107, 1066. (d) Ong, B. S.; Wu, Y.; Li, Y.; Liu, P.; Pan, H. Chem. Eur.
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H.; Scherf, U. Angew. Chem. 2008, 120, 4138. (f) Chen, J.; Cao, Y.
Acc. Chem. Res. 2009, 42, 1709.
HRMS (EI, 70 eV): m/z [M]+ calcd for C34H3235Cl2O6S2: 670.6513;
found: 670.6509.
2,7-Bis(butoxycarbonyl)-3,6-bis(2-methoxyphenyl)benzo[1,2-
b:6,5-b′]dithiophene (7c)
Starting with 3a (100 mg, 0.21 mmol), 2-methoxyphenylboronic acid
(2.5 equiv, 80 mg, 0.53 mmol), NiCl2(dppe) (6.0 mg, 5 mol%), K3PO4
(4.0 equiv, 185 mg, 0.87 mmol), and toluene (5 mL), following the
general procedure B, 7c was isolated as a white solid (102 mg, 78%).
1H NMR (300 MHz, CDCl3): δ = 0.82 (t, J = 7.4 Hz, 6 H, CH3), 1.14–1.51
(m, 4 H), 1.38–1.42 (m, 4 H), 3.55 (s, 6 H, OCH3), 4.13 (t, J = 6.5 Hz, 4
H), 6.63–6.67 (m, 6 H), 7.12 (dd, J = 8.4, 2.5 Hz, 2 H), 7.29 (s, 2 H).
13C NMR (75.5 MHz, CDCl3): δ = 13.7 (CH3), 19.1 (CH2), 28.7 (CH2), 55.8
(OCH3), 65.4 (OCH2), 112.1, 121.7, 128.6, 129.4 (CH), 125.4 (C), 130.7
(CH), 131.0 133.0, 134.4, 139.1, 155.1, 162.3 (C).
(5) (a) Cinar, M. E.; Ozturk, T. Chem. Rev. 2015, 115, 3036.
(b) Sotzing, G. A.; Invernale, M. A.; Ding, Y. US Patent 0235323,
2013.
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Matsuda, W.; Kato, K.; Takata, M.; Miura, M.; Seki, S. Phys. Chem.
Chem. Phys. 2015, 17, 9624. (b) Minami, S.; Ide, M.; Hirano, K.;
Satoh, K.; Sakurai, T.; Kato, K.; Takata, M.; Seki, S.; Miura, M.
Phys. Chem. Chem. Phys. 2014, 16, 18805. (c) Ota, S.; Minami, S.;
Hirano, K.; Satoh, T.; Ie, Y.; Seki, S.; Aso, Y.; Miura, M. RSC Adv.
2013, 3, 12356. (d) Miura, M.; Ota, S.; Hirano, K.; Satoh, T.; Ueda,
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(7) (a) Romain, M.; Thiery, S.; Shirinskaya, A.; Declairieux, C.;
Tondelier, D.; Geffroy, B.; Jeannin, O.; Rault-Berthelot, J.;
Métivier, R.; Poriel, C. Angew. Chem. 2015, 127, 1192.
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O.; Rault-Berthelot, J.; Métivier, R.; Poriel, C. Angew. Chem. Int.
Ed. 2013, 52, 14147.
HRMS (EI, 70 eV): m/z [M]+ calcd for C34H34O6S2: 602.1764; found:
602.1764.
Benzo[1,2-b:6,5-b′]dithienobis[2,3-c]chromen-6-one (8)
Starting with 3a (100 mg, 0.21 mmol), 2-hydroxyphenylboronic acid
(2.5 equiv, 73 mg, 0.53 mmol), NiCl2(dppe) (6.0 mg, 5 mol%), K3PO4
(4.0 equiv, 185 mg, 0.87 mmol), and toluene (5 mL), following the
general procedure B, 8 was isolated as a white solid (50 mg, 54%).
1H NMR (600 MHz, CDCl3): δ = 6.85–6.88 (m, 4 H) 7.34–7.37 (m, 2 H),
7.59 (dd, J = 8.4, 1.6 Hz, 2 H), 7.81 (s, 2 H).
13C NMR (150 MHz, CDCl3): δ = 115.3, 115.4, 119.5 (CH), 120.5 (C),
129.6, 133.8, 135.7 (CH), 163.5 (C).
(8) Shinamura, S.; Osaka, I.; Miyazaki, E.; Nakao, A.; Yamagishi, M.;
Takeya, J.; Takimiya, K. J. Am. Chem. Soc. 2011, 133, 5024.
(9) Hassan, Z.; Reimann, S.; Wittler, K.; Ludwig, R.; Villinger, A.;
Langer, P. Adv. Synth. Catal. 2012, 354, 731.
(10) (a) Ried, W.; Oremek, G.; Ocakcioglu, B. Liebigs Ann. Chem. 1980,
1424. (b) Ried, W.; Oremek, G. Liebigs Ann. Chem. 1980, 1172.
(c) Malesevic, M.; Karminski-Zamola, G.; Bajic, M.; Boykin, D.
W. Heterocycles 1995, 41, 2691.
(11) (a) Miyasaka, M.; Hirano, K.; Satoh, T.; Miura, M. Adv. Synth.
Catal. 2009, 351, 2683. (b) Kumagai, J.; Hirano, K.; Satoh, T.;
Seki, S.; Miura, M. J. Phys. Chem. B 2011, 115, 8446. (c) Kumagai,
J.; Hirano, K.; Satoh, T.; Seki, S.; Miura, M. J. Phys. Chem. B 2012,
116, 4115. (d) Miyasaka, M.; Hirano, K.; Satoh, T.; Miura, M. Adv.
Synth. Catal. 2012, 354, 957.
(12) CCDC 852980 contains the supplementary crystallographic data
for compound 3b in this paper. The data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/getstructures.
Acknowledgment
Financial support from the Faculty Mentored Undergraduate Re-
search Program (FURAP), Oman Research Council (TRC) is gratefully
acknowledged. We gratefully acknowledge Dr. Yonghwi Kim and Prof.
Kimoon Kim, POSTECH for single crystal X-ray structures.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0035-1562538.
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