Synthesis of Sulfur-Hybridized Pyracylene and the Unexpected Phenyl Shift Mediated Rearrangement of Scholl Reaction

Article abstract of DOI:10.1002/ejoc.201900344

We present herein a strategy towards the straightforward synthesis of a novel sulfur-hybridized pyracylene, tetraceno[5,6-bc:11,12-b'c']dithiophene (TDT) derivatives, via 2-fold FeCl₃-mediated Scholl reaction. Surprisingly, the substituents on the precursors will guide the synthetic route, when the substituents were bromo- or phenyl-, quantitatively debromination or phenyl ring shift mediated rearrangement were observed respectively, the rearrangement products were identified by the HR-Mass and 2D NMR analyses. Additionally, a retrosynthetic method was adopted to confirm the unexpected reaction results in rearrangement of Scholl reaction.

Full text of DOI:10.1002/ejoc.201900344

A Journal of
Accepted Article
Title: Synthesis of Sulfur-Hybridized Pyracylene and the Unexpected
Phenyl Shift Mediated Rearrangement of Scholl Reaction
Authors: Shuli Liu, Chengting Huang, Jing Zhang, Siyu Tian, Chang Li,
Nina Fu, Lianhui Wang, Baomin Zhao, and Wei Huang
This manuscript has been accepted after peer review and appears as an
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of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
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content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900344
Link to VoR: http://dx.doi.org/10.1002/ejoc.201900344
Supported by

10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
Synthesis of Sulfur-Hybridized Pyracylene and the Unexpected
Phenyl Shift Mediated Rearrangement of Scholl Reaction
†
†
Shuli Liu,[a] Chengting Huang, [a] Jing Zhang, [a] Siyu Tian, [a] Chang Li, [a] Nina Fu, [a] Lianhui
Wang,[a] Baomin Zhao,*[a] and Wei Huang*[a,b]
Abstract: We present here a strategy towards the straightforward
synthesis of a novel sulphur-hybridized pyracylene, tetraceno[5,6-
bc:11,12-b’c’]dithiophene (TDT) derivatives, via 2-fold FeCl3-
mediated Scholl reaction. Surprisingly, the substituents on the
precursors will guide the synthetic route where quantitatively
debromination vs phenyl ring shift mediated rearrangement were
observed and the rearrangement products were identified by the HR-
MALDI-TOF and 2D NMR analyses. Additionally, a retrosynthetic
method was adopted to confirm the unexpected reaction results in
rearrangement of Scholl reaction.
properties that might qualify them as new opto-electronic materials
for various applications.8
With very few exceptions, most reported tetracene derivatives to
date have been constructed by combining functional groups onto
tetracene motif to tune their energy levels and solubility.9 Many
innovative bottom-up synthetic strategies have been developed to
tetracene based PAHs.10 For example, the Scholl reaction, that is,
oxidized dehydrogeneration cyclization reaction conducted with
acidic oxidants such as FeCl3 or DDQ/MeSO3H is usually
preferred.11,12 Müllen and coworkers synthesize numbers of
excellent PAHs molecules by Scholl reaction and have made great
contributions to explore the mechanism of Scholl reaction.13 Very
recently, Murata et al. reported the synthesis of dithieno-fused PAH
and tetrabenzo-fused pyracylene with a pyracylene moiety starting
Introduction
with 5,11-dibromo-tetracene via
a
2-fold Scholl reaction.14
Whatever the global synthetic strategy were adopted, in most cases
the last step is similar, a highly conjugated but flexible molecules
has to be fused, that is, transformed into rigid, polycyclic, aromatic
plate by the formation of several C-C bonds between adjacent
aromatic rings.6d,15
The design and synthesis of fused ring aromatics have attracted
considerable interests owing to their potentials in organic electronics
applications,1 such as field-effect transistors,2 organic light-emitting
diodes,3 and solar cells.4 One efficient approach toward the
development of new oligomers and/or conjugated polymers for
particular properties and applications is to integrate the parent
structures of fused ring aromatics into conjugated systems.5 Works
are mainly focused on obtaining the end products; however, few
efforts have been devoted into the discovery of building-blocks with
widespread usages. As the field aims is to products the materials
with tunable properties, it is necessary to emphasize the design and
synthesis of novel fused ring aromatics. Over the past decade, the
synthetic methodologies mainly include cross-coupling reaction,
Diels-Alder reaction, alkyne cyclization, photo-cyclization that can
serve this purpose.5,6 Among the acene-based polycyclic aromatic
hydrocarbons (PAHs), tetracene and its derivatives which
containing heteroatoms such as N, S, O in their aromatic skeletons
exhibit unprecedented chemical and physical properties.7 They have
attracted increasing interests owing to their potentially interesting
On the other hand, by introducing heteroatoms into PAHs will
smartly tune their HOMO/LUMO levels, bandgaps, and the
crystalline phase via supramolecular interactions.16 It will be very
interesting to introduce heteroatoms into the antiaromatic
cyclopentafused PAHs so as to discover interesting physical and
chemical properties.17 Note that despite all of these attracting
properties and promising applications, the π-conjugation of
naphtho[1,2-b:5,6-b’ ]dithiophene (NDT)18 was seldom developed
to extend their π-delocalization skeletons deeply due to the lack of
suitable design principle and synthetic strategy. Herein, we report
the design and synthesis of novel tetraceno[5,6-bc:11,12-
b’c’]dithiophene (TDT) derivatives starting from several 3,3-
bisthiophene derivatives (shown in Scheme 1 and 2). Yet, only the
bilateral
ring
fused
2-bromotetraceno[5,6-bc:11,12-
b’c’]dithiophene (2-BrTDT, noted as 1) with debromination was
exclusively observed when we adopted the FeCl3-mediated Scholl
reaction
to
synthesize
2,8-dibromotetraceno[5,6-bc:11,12-
b’c’]dithiophene (2,8-DBrTDT, noted as 7) (Scheme 2). Furtherly,
compound 8 was developed by replacing two bromine atoms in
compound 6 with phenyl, 4-methyloxyl-phenyl and 4-methylphenyl
groups (Scheme 2). Surprisingly, instead of the bilateral ring fusion
products, very complicated reactions took place on 8 under the same
Scholl conditions. We are extremely intrigued with these unusual
observations associated with the synthesis of S-cyclopenta fused
tetracenes. We would like to report our preliminary investigations
on these reactions and the corresponding products including, 1) The
unexpected products obtained through the rearrangement of Scholl
reaction were confirmed with a designed retrosynthetic route, 2) The
possible reaction mechanisms were proposed.
[a]
Dr. S. Liu, Ms. C. Huang, Ms. J. Zhang, Ms. S. Tian, Mr. C. Li,
Prof. Dr. N. N. Fu, Prof. Dr. L. H. Wang, Dr. B. M. Zhao
Key Laboratory for Organic Electronics and Information Displays
& Jiangsu Key Laboratory for Biosensors, Institute of Advanced
Materials, National Jiangsu Synergetic Innovation Center for
Advanced Materials (SICAM), Nanjing University of Posts &
Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
E-mail: iambmzhao@njupt.edu.cn
[b]
Prof. Dr. W. Huang
Shaanxi Institute of Flexible Electronics (SIFE) Northwestern
Polytechnical University (NPU) Xi’an 710072 China
E-mail: iamdirector@fudan.edu.cn
† These authors contributed equally.
Supporting information for this article is given via a link at the
end of the document.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
expected compound 9. The dehedrogeneration and success in ring-
fusion steps of 8A/8B to generate 2A/2B were identified by the HR-
MS and 2D NMR analyses. However, when the same Scholl
reactions were attempted upon 8Aa/8Ba/8Ab/8Bb, there was no
expected ring fusion products observed. Considering the strong
electron donating characteristics of 4-methoxylbenzene and 3,4-
dimethyloxylbenzene rings, this is common for 8Aa/8Ba/8Ab/8Bb
under the FeCl3-mediated Scholl reaction, because the mechanism
of Scholl reaction involved a cationic generation process.24 When
other Lewis acids, such as Scannium triflates and
DDQ/trifluoromethylsufuric acid, for Scholl reaction were used,
they either failed in generation of expected products.12,13,25
Results and Discussion
As shown in Scheme 1, starting from catechol, 4 was prepared
following the reported procedures with optimization in excellent
yields.19 The lithium exchange of 3-bromo-thiophene by addition of
n-butyl lithium in anhydrous tetrahedronfuran (THF) was followed
by a copper-catalyzed coupling reaction to give 3,3’-bisthiophene in
a yield of 60%.20 The bromination with 3,3’-bisthiophene using NBS
in THF furnished compound 3, quantitatively. 3,3’-Bisthiophene-
2,2’-bisphenyl (5) was obtained via Suzuki-Miyaura coupling
reaction starting from compound 3 and 4. Then, 5 was subjected to
NBS mediated bromination to afford the key intermediates of 6.
Interestingly, although very electron-rich, no bromination on the two
bisalkyloxylphenyl rings was observed, indicating the
electrophilicity of α-thiophene is superior to bisalkyloxylphenyl ring.
Br
R1
S
R2
RO
RO
RO
OR
OR
S
RO
S
Br
OR
S
2,8-DBrTDT
7A, 7B
9A, 9B
no observed
OR
R1
no observed
(a) n-BuLi
-78oC
Br
R2
(b) NBS
THF
RO
RO
S
R1
S
S
+
2
S
S
O
Scholl
Scholl
CuCl2
R2
rt
B
Br
Br
RO
RO
O
S
RO
RO
Br
S
3
4
Br
Suzuki-Miyaura
OR
S
S
S
OR
(f) NBS
THF
(e) Pd(PPh3)4
2 M K2CO3
RO
RO
OR
OR
RO
RO
OR
OR
OR
S
Br
8A, 8B:
R1=R2=H
OR
~81%
~92%
~88%
~86%
R2
6A, 6B
rt
8Aa, 8Ba: R1=H, R2=OCH3
8Ab: R1=R2=OC4H9
R1
100oC
S
S
Scholl
8Bb: R1=R2=OC8H17
Scholl
Br
R1
RO
6
5
A:R=C4H9, B:R=C8H17
Br
R2
RO
S
S
Scheme 1. Synthesis of the key intermediate of 6.
OR
OR
RO
RO
S
The FeCl3-mediated Scholl reaction has been successfully used for
the synthesis of various benzenoid PAHs,11 PAHs with a pyracylene
moiety and other π-extended systems. Given the electron-rich
characteristics of 6, we hypothesized that the 2,2’-alkyloxylphenyl
substituted 3,3’-bisthiophene compounds can undergo similar
oxidative cyclization reactions to form thiophene rings fused
tetracene along the peri-position. To test this idea, a series
derivatives of 8 were first prepared from 6 by using a standard
Suzuki-Miyaura protocol (Scheme 2). It was also expected that the
FeCl3-mediated oxidative cyclodehydrogeneration reaction on 6 can
afford compounds 7, which contains two bromine atoms will be
priority to be used as versatile building blocks to develop oligomers
or polymers. Surprisingly, the FeCl3 mediated Scholl reaction of 6
and 8 gave very different results. For example, upon 2-fold
cyclization of compound 6, the debrominated products of 1 were
isolated in high yields, and no compounds 7 were observed. As well
known, the loss of perssad phenomenon is common for the typical
Scholl reaction,21 however, it is rare to observe this kind of
quantitative debromination process. To confirm this result, we
lowered the ratio of FeCl3 to 6 from 2.2:1 to 1.1:1. Interestingly, only
compound 1 and 6 were collected, with no single fused intermediate
detected, indicating the FeCl3 mediated oxidization cyclization step
run in a cascade fashion leading to a bilateral fusion product.22
Considering the C-Br bond energy is lower than C-C band23 and the
cleavage of aromatic ring from a conjugated system is difficult,
Scholl reaction on compound 8 was conducted with the similar
conditions as those for 6. It was found that the electron-donating
property of benzene rings, 4-methoxylbenzene and 3,4-
dimethyloxylbenzene rings imparted significant influence on the
products of Scholl reaction upon 8. The FeCl3-mediated Scholl
reaction was performed on 8A/8B, which produced an unusual
double fused product of 2A/2B in yields around 90% instead of the
S
OR
RO
2-BrTDT
1A, 1B
~76%
R1
R2
2A, 2B:
R1=R2=H
2Aa, 2Ba: R1=H, R2=OCH3
2Ab: R1=R2=OC4H9
2Bb: R1=R2=OC8H17
~90%
no detected
no detected
no detected
A:
R=C4H9
B:R=C8H17
Scheme 2. The ring-fusion toward bithiophene-fused tetracene.
The chemical structure of 1 is unambiguously determined by NMR
and HR-MS measurements. As shown in Figure 1, the H NMR
1
spectra of 1A at low field display five distinct proton signals,
indicating the double-fold ring-fusion of compound 6A. Particularly,
when the concentrations of 1A in CDCl3 increase from 2.0 mg/mL
to 60.0 mg/mL, each of these peaks shift to high field, suggesting
the existing of strong π-π interaction. This result agrees well with its
theoretically simulated planar molecular structure. As seen in Figure
S1b, compound 1 displays a planar molecular configuration. In
contrast to compound 1, the 1H NMR spectra of 2A/2B exhibit very
complicated features (see ESI), which suggests the molecular
symmetricity of 2A/2B has been disrupted. This notion is consistent
with the chemical structure shown in Scheme 2. Fortunately, the
chemical structures of 2A/2B can be confirmed with the COSY and
1
NOESY analyses, and the integrations in H NMR spectrum agree
well with their chemical structures. As shown in Figure 2 (also see
Figure S2), the duplet peaks of Ha/Hd and multiplet peaks of Hb/Hc
can be assigned accordingly, thus, the left duplet peak (at 7.74 ppm)
is assigned to proton Hj according to the J values and the COSY
analysis deduced from the aromatic regime, proton Hi is also
confirmed. Other singlet peaks are assigned unambiguously
according to the NOESY spectrum shown in Figure 3. For instance,
Hf at 8.31 ppm is close to Hg at 8.51 ppm. Proton Hd at 8.57 ppm is
spatially close to proton He at 8.11 ppm. And the other protons in
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10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
RO
RO
RO
RO
RO
RO
RO
RO
compound 2A could be assigned accordingly. Thus, the assignment
of all protons in compound 2A can definitely define the chemical
structure of compound 2A/2B.
S
S
S
S
Br
Br
Br
-e-
Br
H
-2H
Br
OR
OR
Br
OR
OR
Br
OR
OR
Br
OR
OR
S
S
S
S
M1
6
M3
M2
S
RO
RO
RO
RO
RO
S
RO
S
Br
Br
Br
-e-
-HBr
H
Br
OR
OR
Br
OR
S
S
S
OR
OR
OR
M4
M5
1
Scheme 3. Possible mechanisms of the Scholl reaction to get
compound 2.
RO
RO
RO
RO
S
S
S
S
RO
RO
RO
RO
-e-
H
H
OR
OR
OR
OR
OR
OR
OR
OR
S
S
H
S
S
H
8
M6
M7
M7'
RO
RO
RO
RO
RO
RO
S
S
S
S
RO
RO
H
H
OR
OR
OR
OR
S
S
S
S
OR
OR
RO
RO
M8
M9
M8'
M10
RO
RO
RO
RO
RO
RO
RO
S
RO
S
S
S
-e-
-2H
-2H
H
2
1
H
S
Figure 1. H NMR spectra (400 MHz, CDCl3) of 1A at different
S
S
OR
S
OR
RO
OR
RO
OR
RO
RO
concentrations for aromatic regime.
M13
M11
M12'
M12
Scheme 4. Possible mechanisms of the Scholl reaction to get
compound 2.
According to the study of rearrangements in the Scholl oxidation
reported by King and coworkers,12,26 the formation of 2 seems
reasonable. Scheme 4 depicts the first oxidization step to convert
precursor 8A/8B into radical cation M6. Radical cation M6 can
potentially undergo 1,4-shift of the 3,4-dimethyloxylbenzene group
to generate radical cation M8, through the radical cations M7 and
M7’ containing a six-member ring as the transition state. Then, M8
can potentially undergo1,2-shift of the 3,4-dimethyloxylbenzene
group to afford radical cation M9. After the oxidization
dehydrogenation step, M11 is formed. M11 can occur the same
protonation.Then, the thienyl ring in the radical cation M12 rotates
to M12’ as the transition state. Subsequently, compound 2 is formed
after the deproton step. Obviously, during the first Scholl oxidation
stage for compound 8A/8B, a phenyl migration occurs to convert
M8 into M8’. This mechanism speculated by us, which involves a
possible cleave of phenyl ring followed by intramolecular migration
to form a rearrangement ring-fusion product, has never been
reported before. Furthermore, we attempt to propose a retrosynthetic
strategy to confirm the chemical structure of compound 2A, instead
of the indirect evidences of the COSY and NOESY analyses.
Figure 2. 2D NMR / 1H NMR spectra (400 MHz, CDCl3) of 2A and
the assignment of the corresponding proton signals.
The reactivity and regioselectivity of intramolecular Scholl reactions
remain only partially predictable. Not every polyphenylene
configuration can be fused to produce PAHs with designed chemical
structures, mainly because of incomplete reactions or the unexpected
rearrangements.12,14b In addition, some experimentally determined
regioselectivity remains unexplained.14c In this study, both the
quantitative debromination in the 2-fold fusion step from 6 to 1 and
the aromatic system rearrangement in that from 8A/8B to 2 are
unexpected. Empirically, the debromination could be accounted for
the localization of cationic ion on the thiophene motif in compound
6, which underwent a process as the mechanism shown in Scheme
3. The Scholl reaction of compound 6 likely proceeds by oxidization
(M1), electrophilic attack (M2), deprotonation and subsequently
oxidized dehydrogenation to obtain M3.14c In the second ring-fusion
step, M5 is formed through the same protonation and electrophilic
attack process. But, the deprotonation and oxidation process involve
the split of HBr, which leads the debrominated products 1 in high
yields. We speculate that the split of HBr is caused by more electron
rich of the intermediate M5.
C4H9O
C4H9
O
OH
C4H9O
C4H9
C4H9
O
S
B
Br
S
Sn(Bu)3
C4H9O
S
C4H9
O
OH
Br
O
S
NBS
THF
2M K2CO3
Pd(PPh3
C4H9
O
S
Br
Pd(PPh3
)
4
)
4
S
S
Toluene
100oC
Toluene
100oC
Br
Br
11
12
13
Br
C4H9
C4H9
FeCl3 MeNO2
O
C4H9
O
C4H9
C4H9
O
OC4H9
THF
O
C4H9O
S
S
O
S
OC4H9
Sn
n-BuLi
15
S
S
Pd(PPh3
)
4
Cl
Sn
S
Toluene
OC4H9
OC4H9
100o
C
C4H9
O
C4H9
O
14
10
16
Scheme 5. Retrosynthesis of compound 10 for identification of its
chemical structure.
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10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
As shown in Scheme 5, compound 10 can be obtained starting from
11, where short alkyl chains were used for simplifying the NMR
spectrum. Obviously, the two key intermediates, 13 and 16, can be
obtained via common coupling reactions with designed building
blocks. Finally, compound 16 undergoes a two-fold Scholl reaction
to give compound 10.27 As shown in Figure S4, all intermediates
mentioned in this retrosynthetic route were unambiguously
identified. Since the only reactive site in compound 16 is designed.
the chemical structure of compound 10 can be deduced by the
conventional consideration of Scholl reaction. Excitingly, the proton
peaks shown in aromatic regime of compound 2A and compound 10
agree very well at the same molar concentration in CDCl3. In
addition, their 13C NMR spectra are also the same at the low field
(see ESI, Figure S3 and S4). As a result, we exclusively confirmed
the phenyl ring migration mediated rearrangement of the Scholl
reaction in converting 8A to 2A.
corresponding electrochemical energy gaps were then estimated to
be 2.00 (6A), 1.64 (1A) and 1.89 (8A) and 1.85 eV (2A). The
calculations on HOMO-LUMO energy levels for 1 and 2 also
predicted a significant decrease of band gaps, which is consistent
with the experiment data.
With 1 and 2 in hand, their absorption spectra and cyclic
voltammograms were measured to elucidate their electronic
properties, and the data were summarized in Table 1. Figure 3 shows
the UV-vis absorption spectra of 6A and 1A. After the ring fusion,
the absorption maximum of 1A (at 356 nm) shows a red shift in
comparison with that of 6A (at 310 nm). Similarly, as to 2A and 8A,
the absorption maximum of 2A red-shifted about 36 nm in
comparison with that of 8A, indicating 2A has a lower band-gap and
more extended π-conjugation system. The HOMO/LUMO energy
levels were determined to be -5.50/-3.50 eV for 6A, -5.12/-3.48 eV
for 1A. Meanwhile, -5.40/-3.51 eV for 8A and -5.38/-3.53 eV for 2A
from their onsets of the first oxidation/reduction waves. The
Figure 3. (a, b) UV-vis absorption spectra of 6A/1A and 8A/2A; (c,
d) cyclic voltammograms of 6A/1A and 8A/2A in dry
dichloromethane.
Table 1 Summary of Photophysical properties and Electrochemical Data of compound 6, 8, 1 and 2.
[d]
ꢃꢁꢄ
ꢆꢇꢈꢉꢊ
ꢅ
ꢋꢉꢌ
ꢆꢇꢈꢉꢊ [a]
[a]
ꢀ
ꢅ
HOMO [b]
LUMO [c]
HOMO [e]
LUMO [e]
ꢅꢍ
ꢆꢄ
ꢁꢂ
Compound
(eV)
(nm)
(V)
(V)
(eV)
(eV)
(eV)
(eV)
6A,6B
8A, 8B
1A,1B
2A,2B
310
263,339
263, 294,356
282,375
1.10
1.00
0.72
0.98
−0.90
−0.89
−0.92
−0.87
−5.50
−5.40
−5.12
−5.38
−3.50
−3.51
−3.48
−3.53
2.00
1.89
1.64
2.05
−4.74
−4.88
−4.83
−5.00
−1.17
−1.19
−1.43
−1.37
ꢏꢑꢒꢓꢔ
[a] ꢎ
is the onset potential of the first oxidation wave relative to Fcꢕ/Fc. Fcꢕ/Fc was used as internal reference for the measurements, ꢎꢖ/ꢗ = 0.40 V for Fcꢕ/Fc
ꢏꢐ
). [c] LUMO = − (4.40 + ꢅꢆꢋꢉꢇꢌꢈꢉꢊ) [d] ꢎꢘ = LUMO – HOMO [e] values obtained by theoretical simulation.
ꢏꢑꢒꢓꢔ
vs Ag/AgCl. [b] HOMO = − (4.40 + ꢎ
ꢏꢐ
received without any further treatment. Anhydrous DCM and N,N-
Conclusion
dimethylformaldehyde (DMF) were freshly distilled from CaH2.
Toluene and THF were distilled from sodium benzophenone
immediately prior to use. The 1H NMR and 13C NMR spectra were
recorded in CDCl3 solution on NMR spectrometer with
tetramethylsilane (TMS) as the standard. The chemical shift was
recorded in ppm, and the following abbreviations were used to
explain the multiplicities: s = singlet, d = doublet, t = triplet, m =
multiplet, br = broad. MALDI-TOF mass spectra were measured by
using trans-2-[3-(4-tert-Butylphenyl)-2-methyl-2-propenylidene]
In summary, we have synthesized a family of sulfur-hybridized
pyracylene (1A/1B) via 2-fold Scholl cyclization with quantitatively
single debromination. The same Scholl reaction conducted on
derivatives of 8 delivered very different results. An unusual phenyl-
shift mediated rearrangement Scholl reaction was observed and
1
afforded 2-fold fused product of 2. According to the H NMR, 13C
NMR, HR-MALDI-TOF, 2D NMR analyses and retrosynthetic
strategy, the chemical structures of 1A/1B and 2A/2B are
determined unambiguously.
A
possible mechanism for
malononitrile (DCTB) as
a matrix. UV-vis absorption and
debromination and phenyl-migration mediated rearrangement both
were proposed. For the first time, the retrosynthesis of PAHs was
realized and used to confirm an unusual rearrangement. Further
studies on sulfur hybridized pyracylene for applications in low-band
gap materials or other organic electronic applications are currently
in progress in our laboratory and will be reported in due course.
fluorescence spectra were recorded in HPLC pure solvents. The
electrochemical measurements were carried out in anhydrous DCM
with 0.1 M tetrabutylammonium hexafluorophosphate (Bu4NPF6) as
the supporting electrolyte at a scan rate of 0.02 V/s at room
temperature under the protection of nitrogen. A gold disk was used
as working electrode, platinum wire was used as counting electrode,
and Ag/AgCl (3 M KCl solution) was used as reference electrode.
Atmospheric Pressure Chemical Ionization Mass Spectrometry
(APCI MS) measurements were performed on a Finnigan TSQ 7000
triple stage quadrupole mass spectrometer.
Experimental Section
General: All reagents were commercially supplied and used as
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10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
2-(3,4-dibutoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(4A). To a 50 mL dry two-necked flask containing 4-bromo-1,2-
dibutoxybenzene (4.21 g, 13.99 mmol), 40 mL of THF was added
dropwise 9.62 mL (15.39 mmol) of 1.6 M n-BuLi at -78oC under N2.
After stirring at -78oC for 3 hr, then isopropoxyboronic acid pinacol
ester (2.86 g, 15.39 mmol) was added. The resulting solution was
allowed to warm up to room temperature and stirred overnight. The
resulting was poured into water and the product was extracted with
ethyl acetate (3×100 mL). The organic layer was washed with
saturated brine and dried over anhydrous Na2SO4. The solvent was
removed under vacuum, and the residue was purified by column
chromatography (silica gel, ethyl acetate/petroleum ether, 1:10) to
give a canary yellow oily liquid (4.23 g, 87%). 1H NMR (400 MHz,
CDCl3) δ(ppm): 7.39 (m, J = 8.0 Hz, 1H), 7.30 (d, J = 1.4 Hz, 1H),
6.88 (d, J = 8.0 Hz, 1H), 4.03 (m, J = 6.6 Hz, 4H), 1.84 – 1.77 (m,
4H), 1.51 (m, J = 7.5 Hz, 4H), 1.33 (s, 12H), 0.98 (m, J = 7.4 Hz,
6H). 13C NMR (100 MHz, CDCl3) δ(ppm): 152.07, 148.59, 128.72,
119.67, 112.84, 83.51, 68.99, 68.58, 31.52, 31.29, 24.86, 19.28,
19.23, 13.90, 13.85.
5,5'-dibromo-2,2'-bis(3,4-dibutoxyphenyl)-3,3'-bithiophene
(6A). 5 (133 mg, 0.22 mmol), N-bromosuccinimid (78 mg, 0.44
mmol) were dissolved in THF (10 ml). The mixture was stirred in
the dark for 3 h. The resulting was poured into water and the product
was extracted with dichloromethane (3×10 mL). The organic layer
was washed with saturated brine and dried over anhydrous Na2SO4.
The product was collected by filtration and rinsed with methanol,
and recrystallization from 1:1 dichloroethane/methanol affording
the title product as a white solid (151 mg, 90%). 1H NMR (400 MHz,
CDCl3) δ(ppm): 6.82 (s, 2H), 6.70 (d, J = 8.3 Hz, 2H), 6.68 – 6.64
(m, 2H), 6.62 (d, J = 2.0 Hz, 2H), 3.96 (t, J = 6.7 Hz, 4H), 3.73 (t,
J = 6.7 Hz, 4H), 1.82 – 1.75 (m, 4H), 1.74 – 1.66 (m, 4H), 1.54 –
1.40 (m, 8H), 0.96 (dt, J = 10.2, 7.4 Hz, 12H). 13C NMR (100 MHz,
CDCl3) δ(ppm):148.91, 148.79, 142.26, 132.76, 131.32, 125.69,
120.70, 113.47, 113.20, 109.74, 68.91, 68.70, 31.27, 31.14, 19.22,
13.88. MS (Maldi-TOF, positive mode, DCTB in chloroform) Calcd
for C36H44Br2O4S2: 762.10; found: 762.66.
(6B). Apart from the formation of 6A using the conditions
1
mentioned above, 6B can be separated as a white solid. H NMR
(4B) Apart from the formation of 4A using the conditions mentioned
above, 4B can be separated as a canary yellow oily liquid. 1H NMR
(400 MHz, CDCl3) δ(ppm): 7.41 (dd, J = 8.0, 1.4 Hz, 1H), 7.32 (d,
J = 1.4 Hz, 1H), 6.88 (d, J = 8.0 Hz, 1H), 4.03 (dt, J = 10.9, 6.6 Hz,
4H), 1.87 – 1.80 (m, 4H), 1.48 (br, 4H), 1.38 – 1.27 (m, 28H), 0.90
(m, 7H). 13C NMR (100 MHz, CDCl3) δ(ppm): 151.99, 148.52,
128.69, 119.45, 112.66, 83.50, 69.21, 68.82, 31.88, 31.86, 29.44,
29.41, 29.34, 29.32, 29.24, 26.11, 26.05, 24.86, 22.72, 22.71, 14.13.
2,2'-bis(3,4-dibutoxyphenyl)-3,3'-bithiophene (5A). To a 50 mL
flask was added 2-(3,4-dibutoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (0.77 g, 2.23 mmol), 2,2'-dibromo-3,3'-bithiophene
(0.30 g, 0.93 mmol), Pd(PPh3)4 (15 mg), toluene (15 mL) and 2 M
K2CO3 (6.0 mL). The solution mixture was heated to 110oC
overnight under N2 in the dark. After cooling to room temperature,
the reaction mixture was poured into water and extracted with
dichloromethane (3 × 20 mL). The organic layer was washed with
saturated brine and dried over anhydrous Na2SO4. The solvent was
removed under vacuum, and the residue was purified by column
chromatography (silica gel, DCM/petroleum ether, 1:4) to give a
white solid (0.42 g, 75%). 1H NMR (400 MHz, CDCl3) δ(ppm): 7.16
(d, J = 5.2 Hz, 2H), 6.87 (d, J = 5.2 Hz, 2H), 6.76 (m, 2H), 6.70 (m,
4H), 3.96 (t, J = 6.7 Hz, 4H), 3.70 (t, J = 6.7 Hz, 4H), 1.82 – 1.75
(m, 4H), 1.70 – 1.63 (m, 4H), 1.52 – 1.45 (m, 4H), 1.45 – 1.37 (m,
4H), 0.95 (m, 12H). 13C NMR (100 MHz, CDCl3) δ(ppm): 148.65,
148.36, 140.10, 132.36, 130.78, 127.11, 122.89, 120.78, 113.53,
113.48, 68.93, 68.50, 31.33, 31.14, 19.23, 19.17, 13.89, 13.85. MS
(Maldi-TOF, positive mode, DCTB in chloroform) Calcd for
(400 MHz, CDCl3) δ(ppm): 6.81 (s, 2H), 6.70 (t, J = 8.3 Hz, 2H),
6.67 – 6.61 (m, 4H), 3.95 (t, J = 6.7 Hz, 4H), 3.71 (t, J = 6.8 Hz, 4H),
1.79 (m, 4H), 1.70 (m, 4H), 1.42 (m, 8H), 1.28 (m, 32H), 0.88 (t, J
= 6.9 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ(ppm) 148.88, 148.78,
142.26, 132.76, 131.32, 125.66, 120.66, 113.42, 113.14, 109.71,
69.20, 68.97, 31.85, 31.84, 29.41, 29.38, 29.33, 29.29, 29.25, 26.03,
25.99, 22.71, 22.68, 14.13, 14.11. MS (Maldi-TOF, positive mode,
DCTB in chloroform) Calcd for C64H76Br2O4S2: 986.36; found:
986.65.
2-bromo-4,5,10,11-tetrabutoxytetraceno[5,6-bc:11,12-
b'c']dithiophene (1A). To a solution of 6A (114 mg, 0.15 mmol) in
50 mL dry dichloroethane was added dropwise a solution of iron(III)
chloride (96 mg, 0.60 mmol) in 2 mL of nitromethane. After
complete addition, the reaction mixture was allowed to stir for 5min.
Methanol (50 mL) was added and then the reaction mixture was
stirred for 10 min. the reaction mixture was poured into water and
extracted with dichlorome. The organic layer was washed with
saturated brine and dried over anhydrous Na2SO4. The solvent was
removed under vacuum, and the residue was purified by column
chromatography (silica gel, DCM/petroleum ether, 1:3) to give a
brick-red solid (78 mg, 76%). 1H NMR (400 MHz, CDCl3) δ(ppm):
7.67 (s, 1H), 7.62 (s, 1H), 7.28 (s, 1H), 7.00 (s, 1H), 6.95 (s, 1H),
4.19 – 4.07 (m, 8H), 1.89 (d, J = 6.3 Hz, 8H), 1.59 (dd, J = 9.8, 5.2
Hz, 8H), 1.08 – 1.02 (m, 12H). 13C NMR (100 MHz, CDCl3)
δ(ppm):148.69, 148.58, 148.40, 147.69, 135.75, 132.49, 130.19,
124.40, 122.01, 111.87, 109.93, 108.22, 105.19, 104.61, 87.81,
69.46, 68.89, 68.37, 68.29, 31.70, 31.58, 31.34, 19.42, 19.41, 14.12,
C36H46O4S2: 606.28; found: 606.33. Elemental Analysis: calcd for C, 14.09. HR-Mass (APCI) (m/z): [M+H]+ Calcd for C36H42BrO4S2,
71.25; H, 7.64. Found C, 71.28; H, 7.62.
681.1715; Found C36H42BrO4S2, 681.1702.
(5B). Apart from the formation of 5A using the conditions
mentioned above, 5B can be separated as a white solid. H NMR
(1B). Apart from the formation of 1A using the conditions
mentioned above, 1B can be separated as a brick-red solid. 1H NMR
(400 MHz, CDCl3) δ(ppm): 7.88 (s, 1H), 7.78 (s, 1H), 7.47 (s, 1H),
7.17 (s, 1H), 7.07 (s, 1H), 4.22 – 4.08 (m, 8H), 1.99 – 1.87 (m, 8H),
1.55 (m, 8H), 1.30 (m, 32H), 0.91 – 0.85 (m, 12H). 13C NMR (100
MHz, CDCl3) δ(ppm): 148.81, 148.68, 148.49, 147.72, 135.82,
132.58, 130.14, 128.33, 124.74, 124.49, 124.43, 123.01, 122.09,
112.01, 109.87, 108.41, 105.26, 104.73, 87.83, 69.74, 69.29, 68.73,
1
(400 MHz, CDCl3) δ(ppm): 7.15 (d, J = 5.2 Hz, 2H), 6.86 (d, J = 5.2
Hz, 2H), 6.75 (dd, J = 8.3, 2.0 Hz, 2H), 6.69 (dd, J = 5.2, 3.1 Hz,
4H), 3.94 (t, J = 6.7 Hz, 4H), 3.68 (t, J = 6.7 Hz, 4H), 1.83 – 1.74
(m, 4H), 1.67 (m, 4H), 1.43 (m, 4H), 1.33 – 1.23 (br, 36H), 0.88 (t,
J = 6.9 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ(ppm): 148.89,
148.78, 142.26, 132.76, 131.33, 125.67, 120.66, 113.43, 113.15,
109.71, 69.21, 68.98, 31.85, 31.83, 29.40, 29.38, 29.33, 29.28, 29.25, 68.63, 32.00, 31.96, 31.95, 29.70, 29.49, 29.44, 29.42, 26.23, 22.78,
26.02, 25.99, 22.70, 22.68, 14.12, 14.10. MS (Maldi-TOF, positive
mode, DCTB in chloroform) Calcd for C52H78O4S2: 830.53. found:
830.25. Elemental Analysis: calcd for C, 75.13; H, 9.46; found C,
75.15; H, 9.43.
14.48, 14.17, 14.16. HR-Mass (APCI) (m/z): [M+H]+ Calcd for
C52H74BrO4S2, 905.4223; Found C52H74BrO4S2, 905.4206.
(8A). To a 25 mL two-neck round-bottom flask was added 6A (0.30
g, 0.39 mmol), phenylboronic acid (0.11 g, 0.94 mmol), Pd(PPh3)4
(15 mg), THF (10 mL) and 2 M K2CO3 (5.0 mL). The solution
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
mixture was heated to 70oC overnight under N2 in the dark. After
cooling to room temperature, the reaction mixture was poured into
water and extracted with dichloromethane (3 × 20 mL). The organic
layer was washed with saturated brine and dried over anhydrous
Na2SO4. The solvent was removed under vacuum, and the residue
was purified by column chromatography (silica gel,
DCM/Petroleum ether, 1:2) to give a yellow solid (0.24 g, 81%). 1H
NMR (400 MHz, CDCl3) δ(ppm): 7.56 (d, J = 7.5 Hz, 4H), 7.36 (t,
J = 7.6 Hz, 4H), 7.28 (d, J = 7.4 Hz, 2H), 7.25 (s, 1H), 7.19 (s, 2H),
6.88 – 6.82 (m, 4H), 6.72 (d, J = 8.2 Hz, 2H), 3.96 (t, J = 6.7 Hz,
4H), 3.70 (t, J = 6.7 Hz, 4H), 1.78 (s, 4H), 1.63 (s, 4H), 1.47 (d, J =
7.5 Hz, 4H), 1.32 (d, J = 7.5 Hz, 4H), 0.96 (t, J = 7.4 Hz, 6H), 0.84
(t, J = 7.4 Hz, 6H). 13C NMR (100MHz, CDCl3) δ(ppm):148.73,
148.46, 141.31, 139.72, 134.10, 133.24, 128.92, 127.49, 126.92,
125.42, 120.47, 113.54, 113.07, 69.26, 68.85, 31.86, 31.84, 29.43,
29.36, 29.31, 29.29, 29.13, 26.04, 25.91, 22.72, 22.70, 14.15, 14.12.
MS (Maldi-TOF, positive mode, DCTB in chloroform) Calcd for
7.6 Hz, 2H), 7.33 (t, J = 7.3 Hz, 1H), 4.33 – 4.20 (m, 6H), 4.02 (t, J
= 6.8 Hz, 2H), 2.00 (m, J = 14.7, 7.4 Hz, 6H), 1.70 (br, 2H), 1.58
(br, 6H), 1.27 (m, 34H), 0.95 – 0.85 (m, 12H). 13C NMR (100 MHz,
CDCl3) δ(ppm): 149.83, 149.54, 148.24, 148.07, 140.05, 135.73,
134.97, 134.48, 134.31, 132.40, 130.72, 129.08, 129.01, 128.38,
127.80, 127.38, 126.19, 126.07, 125.75, 124.62, 124.39, 123.97,
122.87, 122.31, 122.20, 121.56, 109.62, 106.65, 105.94, 105.35,
69.28, 69.17, 69.13, 31.97, 31.96, 31.82, 29.76, 29.60, 29.57, 29.47,
29.44, 29.43, 29.36, 29.30, 29.25, 26.26, 26.20, 26.19, 25.80, 22.80,
22.79, 22.78, 22.74, 14.21, 14.18. HR-Mass (APCI) (m/z): [M+H]+
Calcd for C64H83O4S2, 979.5720; Found C64H83O4S2, 979.5727.
(8Aa). To a 25 mL two-neck round-bottom flask was added 6A (0.30
g, 0.39 mmol), 2-(4-methoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (0.22 g, 0.94 mmol), Pd(PPh3)4 (15 mg),THF (10 mL)
and 2 M K2CO3 (5.0 mL). The solution mixture was heated to 70oC
overnight under N2 in the dark. After cooling to room temperature,
the reaction mixture was poured into water and extracted with
C48H54O4S2: 758.35; found: 758.09. Elemental Analysis: calcd for C, dichloromethane (3 × 20 mL). The organic layer was washed with
75.95; H, 7.17. found C, 75.98; H, 7.16.
(8B). Apart from the formation of 8A using the conditions
mentioned above, 8B can be separated as a yellow solid solid. H
saturated brine and dried over anhydrous Na2SO4. The solvent was
removed under vacuum, and the residue was purified by column
chromatography (silica gel, DCM/Petroleum ether, 2:3) to give a
1
1
NMR (400 MHz, CDCl3) δ(ppm): 7.58 – 7.54 (m, 4H), 7.36 (t, J =
7.6 Hz, 4H), 7.28 – 7.25 (m, 2H), 7.18 (s, 2H), 6.85 (m, 4H), 6.71
(d, J = 8.2 Hz, 2H), 3.94 (t, J = 6.7 Hz, 4H), 3.68 (t, J = 6.8 Hz, 4H),
1.83 – 1.74 (m, 4H), 1.67 – 1.59 (m, 4H), 1.47 – 1.38 (m, 4H), 1.32
– 1.17 (m, 36H), 0.88 (t, J = 7.0 Hz, 12H). 13C NMR (100 MHz,
CDCl3) δ(ppm): 148.73, 148.46, 141.31, 139.72, 134.10, 133.24,
128.92, 127.49, 126.92, 126.65, 125.42, 120.47, 113.54, 113.07,
69.26, 68.85, 31.86, 31.84, 29.43, 29.36, 29.31, 29.29, 29.13, 26.04,
25.91, 22.72, 22.70, 14.15, 14.12. MS (Maldi-TOF, positive mode,
DCTB in chloroform) MS (Maldi-TOF, positive mode, DCTB in
chloroform) Calcd for C64H86O4S2: 982.60, found: 982.87.
Elemental Analysis: calcd for C, 78.16; H, 8.81. found C, 78.20; H,
8.77.
yellow solid (0.30 g, 92%). H NMR (400 MHz, CDCl3) δ(ppm):
7.50 – 7.46 (m, 4H), 7.06 (s, 2H), 6.91 – 6.84 (m, 8H), 6.71 (d, J =
8.7 Hz, 2H), 3.95 (t, J = 6.7 Hz, 4H), 3.83 (s, 6H), 3.70 (t, J = 6.7
Hz, 4H), 1.80 – 1.74 (m, 4H), 1.65 – 1.59 (m, 4H), 1.47 (d, J = 7.5
Hz, 4H), 1.32 (d, J = 7.5 Hz, 4H), 0.95 (d, J = 7.4 Hz, 6H), 0.84 (t,
J = 7.4 Hz, 6H). 13C NMR (100MHz, CDCl3) δ(ppm): 159.21,
148.67, 148.28, 141.21, 138.54, 133.26, 127.09, 126.70, 125.63,
120.36, 114.30, 113.51, 113.01, 68.93, 68.49, 55.39, 31.30, 31.11,
19.23, 19.10, 13.91, 13.82. MS (Maldi-TOF, positive mode, DCTB
in chloroform) Calcd for C50H58O6S2: 818.37; found: 817.90.
Elemental Analysis: calcd for C, 73.32; H, 7.14. found C, 73.33; H,
7.12.
(8Ba). Apart from the formation of 8Aa using the conditions
mentioned above, 8Ba can be separated as a yellow solid solid. 1H
NMR (400 MHz, CDCl3) δ(ppm) 7.50 – 7.46 (m, 4H), 7.06 (s, 2H),
6.92 – 6.87 (m, 4H), 6.87 – 6.82 (m, 4H), 6.70 (d, J = 8.0 Hz, 2H),
3.94 (t, J = 6.7 Hz, 4H), 3.83 (s, 6H), 3.68 (t, J = 6.8 Hz, 4H), 1.82
– 1.74 (m, 4H), 1.62 (m, 4H), 1.43 (m, 4H), 1.27 (m, 32H), 0.88 (t,
J = 7.0 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ(ppm): 159.20,
148.60, 148.21, 141.20, 138.54, 133.27, 127.04, 126.97, 126.70,
125.62, 120.29, 114.29, 113.39, 112.85, 77.38, 77.07, 76.75, 69.20,
68.75, 55.36, 31.86, 29.44, 29.38, 29.35, 29.32, 26.04, 25.92, 22.74,
22.71, 14.17, 14.15. MS (Maldi-TOF, positive mode, DCTB in
chloroform) Calcd for C66H90O6S2: 1142.62; found: 1042.83.
Elemental Analysis: calcd for C, 75.96; H, 8.69. found C, 75.97; H,
8.67.
(2A). To a solution of 8A (103 mg, 0.13 mmol) in 50 mL dry
dichloroethane was added dropwise a solution of iron(III) chloride
(96 mg, 0.60 mmol) in 2 mL of nitromethane. After complete
addition, the reaction mixture was allowed to stir for 5min. Methanol
(50 mL) was added and then the reaction mixture was stirred for 10
min. the reaction mixture was poured into water and extracted with
dichlorome. The organic layer was washed with saturated brine and
dried over anhydrous Na2SO4. The solvent was removed under
vacuum, and the residue was purified by column chromatography
(silica gel, DCM/Petroleum ether, 1:1) to give a yellow solid (91 mg,
1
90%). H NMR (400 MHz, CDCl3) δ(ppm): 7.50 – 7.46 (m, 4H),
7.06 (s, 2H), 6.91 – 6.84 (m, 8H), 6.71 (d, J = 8.7 Hz, 2H), 3.95 (t,
J = 6.7 Hz, 4H), 3.83 (s, 6H), 3.70 (t, J = 6.7 Hz, 4H), 1.80 – 1.74
(m, 4H), 1.65 – 1.59 (m, 4H), 1.47 (d, J = 7.5 Hz, 4H), 1.32 (d, J =
(8Ab). To a 25 mL two-neck round-bottom flask was added 6A
(0.30 g, 0.39 mmol), 2-(3,4-dibutoxyphenyl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane(0.33 g, 0.94 mmol), Pd(PPh3)4 (15 mg), THF
(10 mL) and 2 M K2CO3 (5.0 mL). The solution mixture was heated
to 70oC overnight under N2 in the dark. After cooling to room
temperature, the reaction mixture was poured into water and
extracted with dichloromethane (3 × 20 mL). The organic layer was
washed with saturated brine and dried over anhydrous Na2SO4. The
solvent was removed under vacuum, and the residue was purified by
column chromatography (silica gel, DCM/Petroleum ether, 1:4) to
7.5 Hz, 4H), 0.95 (d, J = 7.4 Hz, 6H), 0.84 (t, J = 7.4 Hz, 6H). 13
C
NMR (100MHz, CDCl3) δ(ppm): 149.91, 149.61, 148.30, 148.14,
140.21, 135.77,134.99, 134.53, 134.31, 132.49, 130.75, 129.11,
129.02, 127.84, 127.40, 126.26, 126.15, 125.81, 124.64,124.43,
124.01, 122.90, 122.33, 122.28, 121.60, 109.64, 106.03, 69.02,
68.83, 31.50, 31.30, 31.27, 31.20, 19.44, 19.41, 19.01, 14.08, 14.06,
13.75. MS (Maldi-TOF, positive mode, DCTB in chloroform) Calcd
for C48H50O4S2: 754.32; found: 753.84. Elemental Analysis: calcd
for C, 76.36; H, 6.68. found C, 76.39; H, 6.66.
(2B). Apart from the formation of 8A using the conditions
mentioned above, 8B can be separated as a yellow solid solid. H
NMR (400 MHz, CDCl3) δ(ppm): 8.57 (d, J = 7.5 Hz, 1H), 8.52 (s,
1H), 8.31 (s, 1H), 8.22 – 8.18 (m, 1H), 8.12 (s, 1H), 7.76 (d, J = 7.4
Hz, 2H), 7.67 – 7.58 (m, 2H), 7.51 (s, 1H), 7.47 (s, 1H), 7.42 (t, J =
1
give a yellow solid (0.35 g, 86%). H NMR (400 MHz, CDCl3)
1
δ(ppm): 7.12 – 7.05 (m, 6H), 6.88 – 6.80 (m, 6H), 6.70 (d, J = 8.5
Hz, 2H), 4.03 (td, J = 6.6, 2.7 Hz, 8H), 3.94 (t, J = 6.7 Hz, 4H), 3.69
(t, J = 6.7 Hz, 4H), 1.91 – 1.68 (m, 12H), 1.66 – 1.39 (m, 4H), 1.35
– 1.06 (m, 16H), 1.07 – 0.78 (m, 24H). 13C NMR (100 MHz, CDCl3)
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
δ(ppm):149.36, 149.00, 148.66, 148.26, 141.49, 138.58, 133.24,
127.30, 125.71, 120.29, 118.24, 114.07, 113.47, 112.90, 111.35,
69.10, 68.92, 68.46, 31.38, 31.33, 31.30, 31.13, 19.27, 19.25, 19.22,
19.11, 13.93, 13.01. MS (Maldi-TOF, positive mode, DCTB in
chloroform) Calcd for C64H86O8S2: 1046.58; found: 1046.10.
Elemental Analysis: calcd for C, 73.38; H, 8.28. found C, 73.40; H,
8.27.
g, 31%). 1H NMR (400 MHz, CDCl3) δ(ppm): 7.59 – 7.56 (m, 2H),
7.36 (t, J = 7.6 Hz, 2H), 7.28 (s, 1H), 7.24 (s, 1H), 7.17 (d, J = 3.7
Hz, 1H), 7.01 (s, 1H), 6.93 (s, 1H), 6.90 (d, J = 3.8 Hz, 1H), 6.80 (d,
J = 3.7 Hz, 1H), 6.66 (d, J = 3.8 Hz, 1H), 4.05 (dd, J = 12.3, 6.5 Hz,
4H), 1.87 – 1.80 (m, 4H), 1.52 (m, 4H), 0.99 (t, J = 7.4 Hz, 6H). 13
C
NMR (100 MHz, CDCl3) δ(ppm): 149.02, 148.76, 144.51, 144.37,
141.79, 134.32, 129.81, 129.80, 128.90, 127.97, 127.43, 126.99,
126.24, 125.63, 125.31, 123.10, 115.97, 111.80, 69.16, 69.10, 31.28,
19.27, 13.92.
(8Bb). Apart from the formation of 8Ab using the conditions
mentioned above, 8Bb can be separated as a yellow solid solid. 1H
NMR (400 MHz, CDCl3) δ(ppm): 7.08 (dt, J = 7.3, 2.7 Hz, 6H), 6.87
– 6.80 (m, 6H), 6.69 (d, J = 8.1 Hz, 2H), 4.01 (td, J = 6.6, 3.7 Hz,
8H), 3.93 (t, J = 6.7 Hz, 4H), 3.67 (t, J = 6.7 Hz, 4H), 1.85 – 1.63
(5-(4,5-dibutoxy-2-(5-phenylthiophen-2-yl)phenyl)thiophen-2-
yl)trimethylstannane (14) To a solution of compound 13 (0.40 g,
0.74 mmol) in dry THF (10 mL), n-BuLi (0.50 mL, 1.6 M in
hexanes) was added via syringe at -78oC under N2. The mixture was
kept at -78oC for 2 hr before trimethyltin chloride (0.75 mL, 1 M in
THF) was added. The reaction mixture was extracted with PE (3 ×
20 mL) and the combined organic phase was dried over Na2SO4. The
solwent was removed under vacuum to give compound 14
quantitatively (0.46 g) as a yellow solid. 1H NMR (400 MHz,
CDCl3) δ(ppm): 7.58 (d, J = 7.2 Hz, 2H), 7.37 (t, J = 7.6 Hz, 2H),
7.26 (d, J = 7.5 Hz, 1H), 7.16 (d, J = 3.7 Hz, 1H), 7.06 (s, 1H), 7.05
(d, J = 3.3 Hz, 1H), 7.03 (s, 1H), 6.99 (d, J = 3.3 Hz, 1H), 6.78 (d,
J = 3.7 Hz, 1H), 4.11 – 4.06 (m, 4H), 1.88 – 1.82 (m, 4H), 1.57 –
1.50 (m, 4H), 1.01 (m, 6H), 0.37 (s, 9H). 13C NMR (100 MHz,
CDCl3) δ(ppm): 148.63, 148.56, 148.48, 143.86, 142.63, 137.70,
135.24, 134.54, 128.82, 128.15, 127.56, 127.22, 126.54, 125.90,
125.58, 122.98, 116.18, 115.93, 69.14, 69.04, 31.33, 31.30, 19.26,
13.91, 13.90.
(m, 16H), 1.52 – 1.38 (m, 16H), 1.25 (m, 64H), 0.87 (m, 24H). 13
C
NMR (100 MHz, CDCl3) δ(ppm): 149.36, 148.99, 148.63, 148.22,
125.69, 120.24, 118.22, 113.99, 113.43, 112.84, 111.29, 69.38,
69.23, 68.76, 31.85, 29.43, 29.39, 29.35, 29.32, 29.28, 29.12, 26.08,
26.05, 26.03, 25.94, 22.70, 14.13. MS (Maldi-TOF, positive mode,
DCTB in chloroform) Calcd for C96H150O8S2: 1495.08; found:
1495.23. Elemental Analysis: calcd for C, 77.06; H, 10.10. found C,
77.08; H, 10.09.
2,2'-(4,5-dibutoxy-1,2-phenylene)dithiophene (11) To a 25 mL
two-neck round-bottom flask was added 1,2-dibromo-4,5-
dibutoxybenzene (2.00 g, 5.26 mmol), 2-(tributylstannyl)thiophene
(4.32 g, 11.58 mmol), Pd(PPh3)4 (15 mg), toluene (20 mL). The
solution mixture was heated to 100oC overnight under N2 in the dark.
After cooling to room temperature, the reaction mixture was poured
into water and extracted with dichloromethane (3 × 20 mL). The
organic layer was washed with saturated brine and dried over
anhydrous Na2SO4. The solvent was removed under vacuum, and
the residue was purified by column chromatography (silica gel,
DCM/Petroleum ether, 1:8) to give a yellow solid (1.72 g, 85%). 1H
NMR (400 MHz, CDCl3) δ(ppm): 7.23 (dd, J = 5.1, 1.1 Hz, 2H),
7.00 (s, 2H), 6.94 (dd, J = 5.1, 3.5 Hz, 2H), 6.84 (dd, J = 3.5, 0.7
Hz, 2H), 4.05 (t, J = 6.6 Hz, 4H), 1.86 – 1.79 (m, 4H), 1.52 (m, 4H),
0.99 (t, J = 7.4 Hz, 6H). 13C NMR (100 MHz, CDCl3) δ(ppm):
148.67, 142.96, 126.84, 126.73, 126.38, 125.47, 116.24, 69.13,
31.33, 19.28, 13.93.
5,5'-(4,5-dibutoxy-1,2-phenylene)bis(2-bromothiophene) (12)
Compound 11 (1.50 g, 3.89 mmol), N-bromosuccinimid (1.38 g,
7.77 mmol) were dissolved in THF (15 ml). The mixture was stirred
in the dark for 3 h. The resulting was poured into water and the
product was extracted with dichloromethane (3×10 mL). The
organic layer was washed with saturated brine and dried over
anhydrous Na2SO4. The product was collected by filtration and
rinsed with methanol, and recrystallization from 1:1
dichloroethane/methanol affording the title product as a white solid
(2.07 g, 98%). 1H NMR (400 MHz, CDCl3) δ(ppm): 6.91 (d, J = 3.9
Hz, 4H), 6.61 (d, J = 3.8 Hz, 2H), 4.03 (t, J = 6.6 Hz, 4H), 1.86 –
1.79 (m, 4H), 1.51 (m, 4H), 0.98 (t, J = 7.4 Hz, 6H). 13C NMR (100
MHz, CDCl3) δ(ppm): 149.01, 144.03, 129.84, 127.14, 125.38,
115.84, 112.03, 69.12, 31.24, 19.24, 13.90.
2-(4,5-dibutoxy-2-(5-(3',4'-dibutoxy-[1,1'-biphenyl]-2-
yl)thiophen-2-yl)phenyl)-5-phenylthiophene (16) To a 25 mL
two-neck round-bottom flask was added compound 14 (0.40 g, 0.64
mmol), compound 15 (0.27 g, 0.70 mmol), Pd(PPh3)4 (10 mg), dry
toluene (10 mL). The reaction mixture was heated to 100oC
overnight under N2 in the dark. After cooling to room temperature,
the reaction mixture was poured into water and extracted with
dichloromethane (3 × 20 mL). The organic layer was washed with
saturated brine and dried over anhydrous Na2SO4. The solvent was
removed under vacuum, and the residue was purified by column
chromatography (silica gel, DCM/Petroleum ether, 1:4) to give a
1
yellow solid (0.36 g, 75%). H NMR (400 MHz, CDCl3) δ(ppm):
7.60 (d, J = 7.2 Hz, 2H), 7.54 – 7.51 (m, 1H), 7.39 – 7.33 (m, 5H),
7.27 (s, 1H), 7.18 (d, J = 3.7 Hz, 1H), 7.03 (s, 1H), 6.96 (s, 1H), 6.82
– 6.79 (m, 2H), 6.78 – 6.74 (m, 2H), 6.66 (d, J = 3.7 Hz, 1H), 6.54
(d, J = 3.7 Hz, 1H), 4.10 – 4.04 (m, 4H), 3.95 (t, J = 6.6 Hz, 2H),
3.89 (t, J = 6.6 Hz, 2H), 1.87 – 1.72 (m, 8H), 1.53 (m, 8H), 1.03 –
0.92 (m, 12H). 13C NMR (100 MHz, CDCl3) δ(ppm): 148.66, 148.57,
148.37, 143.92, 143.29, 142.60, 142.37, 140.63, 134.51, 134.17,
133.22, 130.77, 130.29, 128.87, 127.74, 127.55, 127.29, 127.21,
126.99, 126.91, 126.21, 126.11, 125.57, 123.05, 122.11, 116.12,
116.06, 115.72, 113.30, 69.16, 69.11, 68.92, 68.86, 31.46, 31.34,
31.32, 19.31, 19.28, 13.97, 13.91. MS (Maldi-TOF, positive mode,
DCTB in chloroform) Calcd for C48H54O4S2: 758.35; found: 758.20.
Elemental Analysis: calcd for C, 75.95; H, 7.17. found C, 75.97; H,
7.15.
(10) To a solution of 16 (100 mg, 0.13 mmol) in 50 mL dry
dichloroethane was added dropwise a solution of iron(III) chloride
(96 mg, 0.60 mmol) in 2 mL of nitromethane. After complete
addition, the reaction mixture was allowed to stir for 5min. Methanol
(50 mL) was added and then the reaction mixture was stirred for 10
min. the reaction mixture was poured into water and extracted with
dichlorome. The organic layer was washed with saturated brine and
dried over anhydrous Na2SO4. The solvent was removed under
vacuum, and the residue was purified by column chromatography
2-bromo-5-(4,5-dibutoxy-2-(5-phenylthiophen-2-
yl)phenyl)thiophene (13) To a 25 mL two-neck round-bottom flask
was added compound 12 (1.50 g, 2.76 mmol), phenylboronic acid
(0.36 g, 2.76 mmol), Pd(PPh3)4 (15 mg), THF (10 mL) and 2 M
K2CO3 (5.0 mL). The solution mixture was heated to 70oC overnight
under N2 in the dark. After cooling to room temperature, the reaction
mixture was poured into water and extracted with dichloromethane
(3 × 20 mL). The organic layer was washed with saturated brine and
dried over anhydrous Na2SO4. The solvent was removed under
vacuum, and the residue was purified by column chromatography
(silica gel, DCM/Petroleum ether, 1:8) to give a yellow solid (0.46
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10.1002/ejoc.201900344
European Journal of Organic Chemistry
FULL PAPER
(silica gel, DCM/Petroleum ether, 1:1) to give a yellow solid (75 mg,
76%). 1H NMR (400 MHz, CDCl3) δ(ppm): 8.59 (d, J = 7.9 Hz, 1H),
8.54 (s, 1H), 8.34 (s, 1H), 8.22 (d, J = 7.3 Hz, 1H), 8.15 (s, 1H), 7.78
(d, J = 7.4 Hz, 2H), 7.68 – 7.61 (m, 2H), 7.55 (s, 1H), 7.50 (s, 1H),
7.45 (t, J = 7.5 Hz, 2H), 7.36 (t, J = 7.4 Hz, 1H), 4.35 – 4.26 (m,
6H), 4.05 (t, J = 6.7 Hz, 2H), 2.01 (m, 6H), 1.67 (m, 8H), 1.25 (m,
2H), 1.10 (m, 9H), 0.80 (m, 3H). 13C NMR (100 MHz, CDCl3)
δ(ppm): 149.93, 149.64, 148.32, 148.16, 140.24, 135.78, 135.00,
134.54, 134.31, 132.51, 130.77, 129.02, 128.48, 127.86, 127.41,
126.28, 126.17, 125.83, 124.66, 124.45, 124.02, 122.91, 122.33,
121.62, 109.67, 106.78, 106.07, 105.47, 69.04, 68.93, 31.50, 31.28,
31.21, 19.41, 19.02, 14.06, 13.75. MS (Maldi-TOF, positive mode,
DCTB in chloroform) Calcd for C48H50O4S2: 754.32, found: 754.92.
Elemental Analysis: calcd for C, 76.36; H, 6.68. found C, 76.38; H,
6.66.
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was financially supported by the Key Research Program of National
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Synergistic Innovation Center for Advanced Materials (SICAM),
the Sci-tech Support Plan of Jiangsu Province (BE2014719), the
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Keywords: fused ring aromatics • sulfur-hybridized Pyracylene •
Scholl reaction • debromination of Scholl • rearrangement of
Scholl •
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Entry for the Table of Contents (Please choose one layout)
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Polycyclic Aromatics: The synthesis
Shuli Liu,[a]† Chengting Huang, [a]† Jing
Zhang, [a] Siyu Tian, [a] Chang Li, [a] Nina
Fu, [a] Lianhui Wang, [a] Baomin Zhao,* [a]
and Wei Huang*[a,b]
of
sulphur-hybridized
pyracylenes
(SHPs) was reported. Quantitatively
debromination vs phenyl ring-shift-
mediated rearrangement induced by the
Page No. – Page No.
substituents
were
observed.
A
Synthesis of Sulfur-Hybridized
Pyracylene and the Unexpected
Phenyl Shift Mediated Rearrangement
of Scholl Reaction
retrosynthetic method was successfully
adopted to confirm the unexpected
reaction results in rearrangement of
Scholl reaction.
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