Synthesis of partially and fully fused polyaromatics by annulative chlorophenylene dimerization

Article abstract of DOI:10.1126/science.aap9801

Since the discovery by Ullmann and Bielecki in 1901, reductive dimerization (or homocoupling) of aryl halides has been extensively exploited for the generation of a range of biaryl-based functional molecules. In contrast to the single-point connection in these products, edge-sharing fused aromatic systems have not generally been accessible from simple aryl halides via annulation cascades. Here we report a single-step synthesis of fused aromatics with a triphenylene core by the palladium-catalyzed annulative dimerization of structurally and functionally diverse chlorophenylenes through double carbon-hydrogen bond activation. The partially fused polyaromatics can be transformed into fully fused, small graphene nanoribbons, which are otherwise difficult to synthesize. This simple, yet powerful, method allows access to functional p-systems of interest in optoelectronics research.

Full text of DOI:10.1126/science.aap9801

RESEARCH
◥
atom precision is in high demand (3–7). In
particular, methods that involve C–H function-
alization (8, 9), a direct molecular activation-
transformation technology, are attractive not only
to streamline overall synthesis but also to un-
lock opportunities for markedly different reactivity
and selectivity. On the basis of our single-step
p-extension strategy for making new nanocarbon
molecules by C–H functionalization (10, 11), we
envisioned that ortho-C–H bonds of aryl halides
might be activated for annulative dimerization
processes to access p-extended, fused polyaromat-
ic systems (Fig. 1A).
Here we report a single-step synthesis of
triphenylene-cored, fused aromatics by the
palladium-catalyzed annulative dimerization of
structurally and functionally diverse chlorophenyl-
enes (12, 13) through double C–H activation
(Fig. 1B). The overall reaction is redox-neutral,
such that stoichiometric reductant is not required.
Chlorinated aromatic reagents are readily avail-
able. This simple, yet powerful, dimerization allows
for the fusion of two functional aromatic nuclei
to directly access triphenylene-cored p-systems
that are known as privileged structures for ma-
terials in organic light-emitting diodes (OLEDs)
(14–17). Moreover, the thus-generated partially
fused aromatics can be transformed into fully
fused, small graphene nanoribbons, which are
otherwise difficult to synthesize.
REPORT
ORGANIC CHEMISTRY
Synthesis of partially and fully fused
polyaromatics by annulative
chlorophenylene dimerization
Yoshito Koga,1 Takeshi Kaneda,1 Yutaro Saito,1 Kei Murakami,1,2* Kenichiro Itami1,2,3
*
Since the discovery by Ullmann and Bielecki in 1901, reductive dimerization (or
homocoupling) of aryl halides has been extensively exploited for the generation of a range of
biaryl-based functional molecules. In contrast to the single-point connection in these
products, edge-sharing fused aromatic systems have not generally been accessible from
simple aryl halides via annulation cascades. Here we report a single-step synthesis of fused
aromatics with a triphenylene core by the palladium-catalyzed annulative dimerization of
structurally and functionally diverse chlorophenylenes through double carbon-hydrogen
bond activation. The partially fused polyaromatics can be transformed into fully fused, small
graphene nanoribbons, which are otherwise difficult to synthesize. This simple, yet powerful,
method allows access to functional p-systems of interest in optoelectronics research.
he reductive dimerization (or homocou-
pling) of aryl halides (1) has been exten-
sively exploited in organic synthesis since
Ullmann and Bielecki’s discovery of the
copper-mediated dimerization of aryl halides
two aromatic nuclei, methods to access fused
aromatic systems from simple aryl halides, via
annulation cascades, have not been developed
(Fig. 1A). Such fused polycyclic aromatics repre-
sent an emerging class of p-conjugated molecules
in optoelectronic devices, nanographene materials
(3), ultrashort carbon nanotubes (4), and carbon
nanobelts (5). Their optoelectronic properties are
susceptible to structural perturbations based
on shape, width, edge topology, and degree of
p-extension. Thus, a method to synthesize fused
aromatics in a bottom-up fashion with atom-by-
T
1Graduate School of Science, Nagoya University, Chikusa,
Nagoya 464-8602, Japan. 2Institute of Transformative
Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa,
Nagoya 464-8602, Japan. 3Japan Science and Technology
Agency–Exploratory Research for Advanced Technology
(JST-ERATO), Itami Molecular Nanocarbon Project, Nagoya
University, Chikusa, Nagoya 464-8602, Japan.
in 1901 (2) (Fig. 1A). This reaction has proved to
be particularly useful in the synthesis of biaryl-
based functional molecules, including pharma-
ceuticals, biologically active natural products,
optoelectronic p-conjugated materials, and poly-
mers. Although this textbook reaction is a pow-
erful technique for the single-point connection of
*Corresponding author. Email: itami@chem.nagoya-u.ac.jp (K.I.);
murakami@chem.nagoya-u.ac.jp (K.M.)
PdCl2 (5.0 mol%)
PBu(Ad)2 (10 mol%)
Cs2CO3 (3.0 equiv)
Classical dimerization
Annulative dimerization
(widely used since 1901)
(virtually unknown)
CPME
140 °C, 18 h
H
Ar
Cl
2
Ar
Ar
Ar
Ar
– 2 X
– 2 HX
X
biaryls
fused aromatics
X = halogen
Ar = aromatic
1a
2a
82% NMR yield
81% isolated yield
Annulative dimerization
Pd catalyst
phosphine ligand
base
Cl
Bu
Bu
P
P
P
P
+
Bu
Cl
(this work)
PCy3
(77%)
PBu(Ad)2
(82%)
chlorophenylenes
triphenylene-based
fused aromatics
PBu3
(3%)
PtBu3
(0%)
Fig. 1. Potential of annulative dimerization of aryl halides. (A) Classical reductive dimerization and annulative dimerization. (B) Pd-catalyzed
annulative dimerization of chlorophenylenes to give triphenylene-based fused aromatics. (C) Optimized reaction conditions: 1a (1.0 equivalent), PdCl2
(5.0 mol %), PBu(Ad)2 (10 mol %), Cs2CO3 (3.0 equivalents), CPME, 140°C, 18 hours. (D) Effect of phosphine ligands. Conditions: 1a (1.0 equivalent),
PdCl2 (5.0 mol %), ligand (10 mol %), Cs2CO3 (3.0 equivalents), CPME, 140°C, 18 hours. 1H NMR yields of 2a are given in parentheses. Red bonds indicates
those that are newly formed.
Koga et al., Science 359, 435–439 (2018)
26 January 2018
1 of 5

RESEARCH
| REPORT
We began our campaign by establishing the
conditions for the annulative dimerization reac-
tion using 2′-chloro-1, 1′:4′, 1″-terphenyl (1a) as a
representative chlorinated oligophenylene. Through
extensive screening of various catalysts and ad-
ditives, we identified the optimized reaction con-
ditions: Treatment of 1a (1.0 equivalent) with
PdCl2 [5.0 mole % (mol %)], PBu(Ad)2 (10 mol %;
Bu, n-butyl; Ad, 1-adamantyl), and cesium carbon-
ate (3.0 equivalents) in cyclopentyl methyl ether
(CPME) at 140°C for 18 hours afforded the annu-
lative dimerization product 2a in 81% isolated
yield (Fig. 1C). The structure of 2a was unambig-
uously confirmed by x-ray crystallographic anal-
ysis. The ligand had a critical effect on the reaction
efficiency; representative results are shown in
Fig. 1D. The use of less bulky PBu3 hindered the
reaction. Moderately large trialkylphosphines PCy3
(Cy, cyclohexyl) and PBu(Ad)2 afforded the best
results (77 and 82%), whereas much bulkier PtBu3
(tBu, tert-butyl) did not facilitate the dimerization.
Other phosphine ligands P(o-tol)3 (o-tol, o-CH3C6H4)
and 1,2-bis(dicyclohexylphosphino)ethane, as well
as N-heterocyclic carbene ligands, were not effec-
tive for the reaction.
Although the exact mechanism of the annula-
tive dimerization remains unclear, our current
assumption is shown in Fig. 2. An in situ–
generated, phosphine-bound Pd(0) species Pd0L
[L, PBu(Ad)2] undergoes the first oxidative addi-
tion with chloroterphenyl 1a to give arylpalladium
A. The resulting arylpalladium A can abstract
three hydrogen atoms via path 1, intramolecular
HA (red); path 2, intramolecular HB (blue); or
path 3, intermolecular HC (green). Path 1 initiates
from intramolecular ortho-C–H activation (18)
from A to give Pd-aryne B (19). Oxidative addi-
tion of 1a to B provides C, which undergoes an
insertion (carbopalladation) across the aryne moi-
ety to give arylpalladium D. Subsequent intramo-
lecular C–H palladation affords seven-membered
palladacycle E, which then undergoes reductive
elimination to provide triphenylene product 2a
and Pd0L, completing the catalytic cycle. As an
alternative to the Pd-aryne pathway (path 1), the
Pd(IV) pathway (path 2) might also be possible
(20). For example, intramolecular C–H activation
of A at the baylike region affords palladacycle
intermediate F. Subsequent oxidative addition of
1a generates Pd(IV) intermediate G, which then
undergoes biaryl-forming reductive elimination
to yield arylpalladium H. Intramolecular C–H
activation affords I, which finally gives 2a and
Pd0L. Path 3 involves intermolecular C–H acti-
vation of A with 1a, whereby the C–H bond ortho
to the chlorine atom is activated, to give inter-
mediate J, which then provides K. Subsequent
intramolecular C–H arylation of K affords 2a
through intermediates D and E.
With the optimal conditions for the annulative
dimerization in hand, the scope of the reaction
was investigated with a range of structurally and
functionally diverse chlorophenylenes (Fig. 3A).
Terphenyl 1b with a tBu group was converted into
the corresponding triphenylene derivative 2b in
77% isolated yield. Terphenyls with an electron-
donatingmethoxy,trifluoromethoxy,methylsulfanyl,
or electron-withdrawing trifluoromethyl group
(1c to 1f) were smoothly converted into 2c
to 2f in good to high yields (85, 68, 49, and
64%, respectively). The methylsulfanyl group can
be transformed through metal-catalyzed cross-
coupling reactions as a halogen equivalent. Silyl
groups, which can be used for further derivatiza-
tions, were also tolerated, and 2g was obtained
in 66% yield. In the reaction of 1h, the methoxy-
carbonyl group remained intact to give 2h. A
small amount of isomer 2h′ was also generated,
presumably because the ester group increased the
acidity of the C–H bond on the arene to induce an
unwanted palladium migration through the pal-
ladacycle intermediate (21). The reaction of 1i
afforded carbazole-containing triphenylene 2i
that could have potential as a hole-transporting
material. m-Methyl– or m-phenyl–substituted 1j
and 1k reacted smoothly to give 2j and 2k in 85
and 58% yields, respectively. Chlorobenzene deriv-
atives with two naphthalene rings (1l and 1m)
dimerized to give fused p-extended systems 2l
Ph
'ortho' C–H
activation
PdL
Path 1
Ph
– HAX
B
Cl
Ph
Ph
1a
'bay' C–H
activation
Path 2
HA
Cs2CO3
Pd0L
PdX(L)
HB
oxidative
addition
– HBX
PdL
L = PBu(Ad)2
A
F
X = Cl or CO3Cs
Ph
‘intermolecular’
C–H activation
L
Path 3
Pd
1a
– HCX
Ph
Cl
Ph
HC
Cl
J
Path 1 'ortho' C–H activation pathway
Ph
Ph
Ph
Ph
Ph
Ph
oxidative
L
addition
intramolecular
C–H activation
insertion
Pd
1a
B
X
Cs2CO3
Ph
Ph
Pd
Pd
L
L
X
C
E
D
Path 2 'bay' C–H activation pathway
Ph
Ph
Ph
oxidative
Ph
L
addition
reductive
elimination
intramolecular
C–H activation
L
Pd
Ph
1a
Ph
Pd
2a + Pd0L
F
X
Pd
Cs2CO3
X
L
Ph
Ph
Ph
H
D
I
G
Path 3 ‘intermolecular’ C–H activation pathway
Ph
intramolecular
C–H activation
oxidative
reductive
addition
elimination
Ph
J
E
Pd0L
Cl
K
Fig. 2. Possible reaction pathways. Three pathways are shown: path 1, ortho C–H activation
pathway; path 2, bay C–H activation pathway; and path 3, intermolecular C–H activation pathway.
Ph, phenyl; L, PBu(Ad)2; X, Cl or CO3Cs.
Koga et al., Science 359, 435–439 (2018)
26 January 2018
2 of 5

RESEARCH
| REPORT
Representative products:2 isolated yield
R
R
N
N
Me
Me
(R = tBu)
2b
2c
2d
2e
2f
77%
85%
68%
49%
64%
66%
65%
(R = OMe)
(R = OCF3)
(R = SMe)
(R = CF3)
(R = SiMe3)
Me
R
R
2g
N
N
Me
2h+2h’ (R = CO2Me)
2i 47%
2j 85%
2k 58%
S
S
S
S
S
S
2l 73%
2m 91%
2n 46%
2o 33%
Ph
Ar’
Ar’
+
Cl
Ar
Ar
Cl
PdX(L)
Ph
Ph
Ph
Ph
Ar’
Ar’
1p
2p (X-ray)
2p’ (X-ray)
2p+2p’ 72%
no ortho-Pd shift
(Fig. S17)
no ortho-Cl shift
(Fig. S17)
path 1
PdL
2p+2p’
oxidative
addition
Ar’
Ar’
Ph
M
Ar
Ar
Cl
PdX(L)
path 2
Ar’
Ar’
PdX(L)
2p+2p’
PdL
Ph
Ph
F
L
X = Cl or CO3Cs
no 1,4-Cl shift
(Fig. S18–19)
no 1,4-Pd shift
(Fig. S20–21)
L
path 3
Pd
2p only
Ar’
Ar’
Cl
Ph
Ar
Ar
Ar’
Cl
Ar’
PdX(L)
Ph
N
Fig. 3. Annulative dimerization with various substrates. Optimized
reaction conditions: 1 (1.0 equivalent), PdCl2 (5.0 mol %), PBu(Ad)2
(10 mol %), Cs2CO3 (3.0 equivalents), CPME, 140°C, 18 hours. (A) Scope to
examine functional group compatibility and structural diversity. *Ratio of 2h
to 2hʹ is 3:1. For the structure of 2hʹ, see supplementary materials. †CsF
(3.0 equivalents) was used instead of Cs2CO3. Me, methyl. (B) Reaction of
1p. ‡Ratio of 2p to 2pʹ is 3:1. (C) No chloride or palladium migration occur.
L, PBu(Ad)2; Ar, aromatic; X, Cl or CO3Cs.
Koga et al., Science 359, 435–439 (2018)
26 January 2018
3 of 5

RESEARCH
| REPORT
and 2m in 73 and 91% yields with virtually com-
plete regioselectivity. No further dehydrocyclization
was observed. Benzothiophene-substituted deriv-
ative 1n also reacted to give thiophene-benzene
fused system 2n. Chlorinated thiophene deriva-
tive 1o also underwent annulative dimerization
to give 2o in 33% yield.
By applying various chloroarene substrates to
the present annulative dimerization, mechanistic
insights were also obtained. An overview of pos-
sible reaction pathways and the mechanistic ex-
periments are provided in the supplementary
materials. For example, chloroterphenyl 1p is
useful as a mechanistic probe (Fig. 3B). The re-
action of 1p resulted in the formation of a mix-
ture of 2p and 2p′, structures of which were
confirmed by x-ray crystallographic analysis. This
shows that either path 1 or 2 was dominant and
that the mixture of 2p and 2p′ was generated
through Pd-aryne intermediate M or pallada-
cycle intermediate F (Fig. 3B). Intermediate M or
F then reacted with 1p to give two regioisomers.
On the other hand, if path 3 had been dominant,
the reaction would have resulted in the exclusive
formation of 2p via intermediate N. Importantly,
this discussion is based on the hypothesis that no
chloride or palladium migration occurs in the
substrate and/or intermediates (Fig. 3C). From
extensive experiments, we confirmed that such
chloride or palladium migration is not taking
place under the present reaction conditions (figs.
S17 to S21). Taken together, we conclude that the
intermolecular C–H activation pathway (path 3)
is unlikely. Because both possible pathways, paths
1 and 2, involve previously unappreciated elemen-
tary reactions [the formation of Pd-aryne via ortho-
C–H activation of arylpalladium or the oxidative
addition of an aryl chloride to a palladacycle (22)],
the mechanism of the present reaction is of great
interest in its own right.
The construction of polycyclic aromatics has
garnered considerable attention owing to their
applicability in a range of functional materials.
It is particularly important to synthesize these
materials in a controlled fashion, because their
structure profoundly affects their properties. In
this study, all triphenylene-cored, p-extended com-
pounds 2 display blue fluorescence with reason-
ably sharp spectral widths. The photophysical
properties (ultraviolet through visible absorption
spectra, fluorescence spectra, and fluorescence
quantum yields) of 2 are provided in figs. S30 to
S48. Coupled with their nonplanar molecular
structures, these new molecules should have con-
siderable potential as materials for OLEDs (14–17).
For example, as reported by Adachi, triphenylene-
based molecules with bipyridine substituents are
high–molecular orientation electron-transport
materials (15, 16) that have become one of the
standard materials for OLEDs (17).
Annulative
dimerization
Dehydrocyclization
1 step
1 step
o
Chlorophenylene
-
Partially fused polyaromatics
Fully fused polyaromatics
Annulative dimerization
Dehydrocyclization
(Scholl reaction)
PdCl2 (5.0 mol%)
PBu(Ad)2 (10 mol%)
Cs2CO3 (3.0 equiv)
FeCl3
CPME (1.0 M of 1a)
CH2Cl2
0 °C, 2.5 h
140 °C, 18 h
2a (81%)
3 (77%)
In addition to their potential use as optoelec-
tronic materials, the annulation products also
serve as partially fused polyaromatics and may
be useful soluble precursors for the synthesis of
fully fused, graphene nanoribbon substructures
via Scholl-type dehydrocyclizations (23) (Fig. 4A).
As a proof-of-concept, we used the annulative
dimerization-dehydrocyclization sequence for the
synthesis of fully fused nanographenes (Fig. 4B).
Triphenylene 2a was treated with FeCl3 in
CH2Cl2 at 0°C (standard conditions for the Scholl
reaction), and 3 was obtained in 77% yield (62%
two-step yield from 1a). The clean, high-yielding
formation of 3 without any optimization was
quite surprising. It is well known that unwanted
side reactions such as arene rearrangement (24)
and aromatic chlorination often take place with
polyaromatic compounds (23) in Scholl chemis-
try. For example, when polyphenylene 4, which
can be prepared by the nickel-catalyzed reductive
dimerization of 1a (25), was subjected to the stan-
dard Scholl conditions (FeCl3, CH2Cl2, 0°C), the
fully fused product 3 was not obtained; instead, a
complex mixture of various unidentified products
(most likely arene rearrangement products) was
obtained. Thus, there is a clear advantage of the
present reaction, accessing partially fused struc-
tures (triphenylene substructures in this case), to
ensure that subsequent dehydrocyclization occurs
successfully. This ring-fusing sequence, enabled
by the annulative dimerization reaction, facilitates
the synthesis of privileged fused p-conjugated
systems, which are otherwise difficult to synthesize.
Reductive dimerization
Cl
Dehydrocyclization
(Scholl reaction)
NiBr2 (10 mol%)
PPh3 (13 mol%)
Zn (1.5 equiv)
1a
Et4NI (1.0 equiv)
FeCl3
CH2Cl2
0 °C, 2.5 h
THF (0.70 M of 1a)
50 °C, 108 h
4 (90%)
Br
Annulative
Suzuki–Miyaura
Scholl
dimerization†
*
coupling
reaction‡
92%
Cl
64%
72%
Br
Cl
1q
2q
5
Fig. 4. Access to graphene nanoribbon substructures. (A) Rapid synthesis of partially and fully
fused polyaromatics enabled by annulative dimerization of chlorophenylenes. (B) Advantage of
annulative dimerization over classical reductive dimerization in the synthesis of fully fused phenylene 3.
THF, tetrahydrofuran; Et, ethyl. (C) Synthesis of graphene nanoribbon substructure 5. Reaction
conditions: *1,4-dibromo-2-chlorobenzene (1.0 equivalent), 4-biphenylboronic acid (2.4 equivalents),
PdCl2(PPh3)2 (2.0 mol %), K2CO3 (5.0 equivalents), toluene/H2O/ethanol, 80°C, 18 hours, 92%. †PdCl2
(5.0 mol %), PBu(Ad)2 (10 mol %), Cs2CO3 (3.0 equivalents), CPME (1.0 M of 1q), 140°C, 18 hours,
64%. ‡2q (0.010 mmol), FeCl3 (0.47 mmol), CH2Cl2 (2.0 ml), room temperature, 42 hours, 72%.
Koga et al., Science 359, 435–439 (2018)
26 January 2018
4 of 5

RESEARCH
| REPORT
To further demonstrate the utility of the pre-
sent strategy, the rapid and convergent synthesis
of an armchair-edged graphene nanoribbon seg-
ment (3, 26–31) was carried out (Fig. 4C). 1,4-
Dibromo-2-chlorobenzene was treated with
p-biphenylylboronic acid in the presence of a pal-
ladium catalyst (Suzuki-Miyaura cross-coupling)
to give chloropentaphenyl 1q (92% yield). The
palladium-catalyzed annulative dimerization of
1q afforded partially fused product 2q (64%
yield). Finally, the Scholl reaction of 2q gave
small graphene nanoribbon segment C60H26 (5)
in 72% yield. Notably, this 60-carbon nanoribbon
5 was obtained from 1,4-dibromo-2-chlorobenzene
in three steps in 42% overall yield. The Raman
and Fourier transform infrared spectra of small
nanoribbon 5 were quite similar to the calcu-
lated spectra, supporting the formation of the
expected nanoribbon structure (see figs. S7, S12,
and S13 for details). This represents a very rare
example of access to fully fused planar nano-
graphenes without any solubilizing substituents
under solution-phase conditions (32–34). Over-
all, the annulative dimerization reaction sequence
reported here should drastically alter the execu-
tion of partially and fully fused polyaromatics, as
chlorine and ortho hydrogen atoms on aromatic
nuclei can now be considered ring-fusing handles.
3. L. Chen, Y. Hernandez, X. Feng, K. Müllen, Angew. Chem.
Int. Ed. 51, 7640–7654 (2012).
4. L. T. Scott et al., J. Am. Chem. Soc. 134, 107–110 (2012).
5. G. Povie, Y. Segawa, T. Nishihara, Y. Miyauchi, K. Itami, Science
356, 172–175 (2017).
6. M. G. Schwab et al., J. Am. Chem. Soc. 134, 18169–18172
(2012).
7. Y. Segawa, H. Ito, K. Itami, Nat. Rev. Mater. 1, 15002 (2016).
8. L. Ackermann, R. Vicente, A. R. Kapdi, Angew. Chem. Int. Ed.
48, 9792–9826 (2009).
9. Y. Segawa, T. Maekawa, K. Itami, Angew. Chem. Int. Ed. 54,
66–81 (2015).
10. H. Ito, K. Ozaki, K. Itami, Angew. Chem. Int. Ed. 56, 11144–11164
(2017).
11. K. Ozaki, K. Kawasumi, M. Shibata, H. Ito, K. Itami,
Nat. Commun. 6, 6251 (2015).
26. K. Müllen, ACS Nano 8, 6531–6541 (2014).
27. A. Narita et al., Nat. Chem. 6, 126–132 (2014).
28. L. T. Scott et al., Pure Appl. Chem. 71, 209–219 (1999).
29. V. M. Tsefrikas, L. T. Scott, Chem. Rev. 106, 4868–4884
(2006).
30. J. Cai et al., Nature 466, 470–473 (2010).
31. M. Treier et al., Nat. Chem. 3, 61–67 (2011).
32. C. D. Simpson et al., Chem. Eur. J. 8, 1424–1429 (2002).
33. B. Schuler et al., Angew. Chem. Int. Ed. 53, 9004–9006
(2014).
34. Z. Wang et al., J. Am. Chem. Soc. 126, 7794–7795 (2004).
ACKNOWLEDGMENTS
This work was supported by JST ERATO grant number
JPMJER1302 (K.I.) and JSPS KAKENHI grant numbers JP15K17821
and JP17H04868 (K.M.). We are grateful to Y. Segawa, H. Ito,
and T. Yoshidomi for assistance with x-ray crystal structure analysis
and fruitful discussions. We acknowledge Y. Miyauchi and
A. Takakura for assistance with Raman measurements, H. Sakamoto
and N. Ozaki for assistance with Fourier transform infrared
measurements, and K. Kuwata and K. Ito for assistance with high-
resolution mass spectrometry measurements. ITbM is supported by
the World Premier International Research Center Initiative (WPI).
Crystallographic data for compounds 2a, 2p, and 2p′ are available
free of charge from the Cambridge Crystallographic Data Centre
under CCDC identifiers 1518668, 1518669, and 1518670, respectively
(www.ccdc.cam.ac.uk/structures/). All authors are inventors on a
patent application (PCT/JP2017/020703) submitted by Nagoya
University that covers the synthetic methods and molecules included
in this paper.
12. C.-W. Li, C.-I. Wang, H.-Y. Liao, R. Chaudhuri, R.-S. Liu,
J. Org. Chem. 72, 9203–9207 (2007).
13. R. K. Mohamed et al., Angew. Chem. Int. Ed. 55, 12054–12058
(2016).
14. P.-Y. Chou et al., Chem. Commun. (Camb.) 50, 6869–6871
(2014).
15. K. Togashi, S. Nomura, N. Yokoyama, T. Yasuda, C. Adachi,
J. Mater. Chem. 22, 20689–20695 (2012).
16. K. Togashi, Y. Sagara, T. Yasuda, C. Adachi, Chem. Lett. 42,
651–653 (2013).
17. C. Adachi, K. Togashi, N. Yokoyama, S. Nomura, Patent WO
2012/114745 (2012).
18. S. L. Buchwald, B. T. Watson, J. C. Huffman, J. Am. Chem. Soc.
108, 7411–7414 (1986).
19. D. A. Watson et al., Science 325, 1661–1664 (2009).
20. H. Jiang, Y. Zhang, D. Chen, B. Zhou, Y. Zhang, Org. Lett. 18,
2032–2035 (2016).
21. M. A. Campo et al., J. Am. Chem. Soc. 129, 6298–6307 (2007).
22. L.-M. Xu, B.-J. Li, Z. Yang, Z.-J. Shi, Chem. Soc. Rev. 39,
712–733 (2010).
23. M. Grzybowski, K. Skonieczny, H. Butenschön, D. T. Gryko,
Angew. Chem. Int. Ed. 52, 9900–9930 (2013).
24. J. He et al., Chem. Commun. (Camb.) 51, 7245–7248 (2015).
25. M. F. Semmelhack, P. M. Helquist, L. D. Jones, J. Am.
Chem. Soc. 93, 5908–5910 (1971).
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/359/6374/435/suppl/DC1
Materials and Methods
Figs. S1 to S188
Table S1
REFERENCES AND NOTES
References (35–47)
1. J. Hassan, M. Sévignon, C. Gozzi, E. Schulz, M. Lemaire,
Chem. Rev. 102, 1359–1470 (2002).
2. F. Ullmann, J. Bielecki, Chem. Ber. 34, 2174–2185 (1901).
16 September 2017; accepted 13 December 2017
10.1126/science.aap9801
Koga et al., Science 359, 435–439 (2018)
26 January 2018
5 of 5

Synthesis of partially and fully fused polyaromatics by annulative chlorophenylene
dimerization
Yoshito Koga, Takeshi Kaneda, Yutaro Saito, Kei Murakami and Kenichiro Itami
Science 359 (6374), 435-439.
DOI: 10.1126/science.aap9801
How to get two bonds for the price of one
For more than a century, we have known how to couple aryl chlorides at the sites of their C-Cl bonds to form a
single C-C bond. Koga et al. found that palladium catalysis can instead activate these C-Cl bonds to attack nearby
aromatic C-H bonds in a terphenyl molecular framework. The reaction thereby produces a new ring, fused to the original
rings on either side. Polycyclic compounds of this sort are of particular interest in optoelectronics research because of
their expansive electron delocalization.
Science, this issue p. 435
ARTICLE TOOLS
http://science.sciencemag.org/content/359/6374/435
SUPPLEMENTARY
MATERIALS
http://science.sciencemag.org/content/suppl/2018/01/24/359.6374.435.DC1
REFERENCES
This article cites 45 articles, 2 of which you can access for free
http://science.sciencemag.org/content/359/6374/435#BIBL
PERMISSIONS
http://www.sciencemag.org/help/reprints-and-permissions
Use of this article is subject to the Terms of Service
Science (print ISSN 0036-8075; online ISSN 1095-9203) is published by the American Association for the Advancement of
Science, 1200 New York Avenue NW, Washington, DC 20005. 2017 © The Authors, some rights reserved; exclusive
licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. The title
Science is a registered trademark of AAAS.