One-shot K-region-selective annulative π-extension for nanographene synthesis and functionalization

W2048606495 · 수집 2026-10-04 18:12:19

T10083 Graphene research and applications

CoT 라벨링

라벨링 전

PDF 파일

자동 다운로드한 PDF PDF 보기

기본 정보

DOI 제목 발행년도 저널 URL 페이지 열기 PDF URL PDF 열기 발행기관 피인용수 라이선스

추가 정보 초록

Abstract The optoelectronic nature of two-dimensional sheets of sp 2 -hydridized carbons (for example, graphenes and nanographenes) can be dramatically altered and tuned by altering the degree of π -extension, shape, width and edge topology. Among various approaches to synthesize nanographenes with atom-by-atom precision, one-shot annulative π -extension (APEX) reactions of polycyclic aromatic hydrocarbons hold significant potential not only to achieve a ‘growth from template’ synthesis of nanographenes, but also to fine-tune the properties of nanographenes. Here we describe one-shot APEX reactions that occur at the K-region (convex armchair edge) of polycyclic aromatic hydrocarbons by the Pd(CH 3 CN) 4 (SbF 6 ) 2 / o -chloranil catalytic system with silicon-bridged aromatics as π -extending agents. Density functional theory calculations suggest that the complete K-region selectivity stems from the olefinic (decreased aromatic) character of the K-region. The protocol is applicable to multiple APEX and sequential APEX reactions, to construct various nanographene structures in a rapid and programmable manner.

본문

### ARTICLE

Received 23 Oct 2014 | Accepted 9 Jan 2015 | Published 16 Feb 2015 DOI: 10.1038/ncomms7251 OPEN
## One-shot K-region-selective annulative p-extension for nanographene synthesis and functionalization

Kyohei Ozaki 1, Katsuaki Kawasumi 1, Mari Shibata 1, Hideto Ito 1 & Kenichiro Itami 1,2

The optoelectronic nature of two-dimensional sheets of sp 2 -hydridized carbons (for example,

graphenes and nanographenes) can be dramatically altered and tuned by altering the degree

of p-extension, shape, width and edge topology. Among various approaches to synthesize

nanographenes with atom-by-atom precision, one-shot annulative p-extension (APEX)

reactions of polycyclic aromatic hydrocarbons hold significant potential not only to achieve a

‘growth from template’ synthesis of nanographenes, but also to fine-tune the properties

of nanographenes. Here we describe one-shot APEX reactions that occur at the K-region

(convex armchair edge) of polycyclic aromatic hydrocarbons by the Pd(CH3CN)4(SbF6)2/

o-chloranil catalytic system with silicon-bridged aromatics as p-extending agents. Density

functional theory calculations suggest that the complete K-region selectivity stems from the

olefinic (decreased aromatic) character of the K-region. The protocol is applicable to multiple

APEX and sequential APEX reactions, to construct various nanographene structures in a rapid

and programmable manner.

1 Institute of Transformative Bio-Molecules (WPI-ITbM) and Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
2 JST-ERATO, Itami Molecular Nanocarbon Project, Nagoya University, Chikusa, Nagoya 464-8602, Japan. Correspondence and requests for materials should
be addressed to K.I. (email: [itami@chem.nagoya-u.ac.jp).](mailto:itami@chem.nagoya-u.ac.jp)

anographenes, which are nanometre-size subunits of
graphenes (single-layer two-dimensional sp 2 -hybridized
carbon sheets) 1–5 with a tunable bandgap, have become
# N
hot molecular entities in the field of nanocarbon materials
science 6 . As the properties of nanographenes depend heavily on
the degree of p-extension, shape, width and edge topology,
a novel bottom-up methodology for the precisely controlled
synthesis of structurally uniform nanographenes is highly
desirable 6 . Among various approaches to synthesize nanographenes with atom-by-atom precision 6, one-shot annulative
p-extension (APEX) reactions of polycyclic aromatic hydrocarbons (PAHs) hold significant potential not only to achieve a

‘growth from template’ synthesis of nanographenes, but also to
fine-tune the properties of nanographenes.

In the last two decades, various bottom-up organic synthesis
methods have been established for the controlled synthesis of
large p-extended PAHs and nanographenes, as exemplified by the
groundbreaking achievements of Mu¨llen and colleagues 7–10,
Scott and colleagues 11,12, Fasel and colleagues 13,14 and others 15
(Fig. 1a). In essence, most of the reported nanographene
syntheses rely on a two-step sequence of (i) component
assembly of small p-components, using reactions such as
Diels–Alder reactions, Suzuki–Miyaura couplings and C–H
activation reactions, to synthesize soluble nanographene

Small π-components Soluble precursors Nanographenes

R R R R

Component assembly

Diels–Alder
Suzuki–Miyaura

C–H activation

R R R R

R R

R R R R

R R

Stitching
cyclodehydrogenation
flash-vacuum pyrolysis

R R flash-vacuum pyrolysis R R

B(OH)2

photocyclization

R
R

Template PAH molecules

B ay-regio n

L-region

K-region

R R

One-shot,
region-selective,
annulative π-extension

(APEX)

"growth from template"
nanographene synthesis

late-stage fine tuning of
nanographene properties

R R

Nanographenes

Bay-region, concave armchair edge; K-region, convex armchair edge; L-region, zigzag edge

Bay-selective,
Diels–Alder APEX

NO2

or
(template growth)

K-selective,
C–H activation APEX

(template growth)

This work

Figure 1 | Organic synthesis approaches for structurally uniform nanographenes. (a) The well-established two-step synthesis of nanographenes through
p-component-assembling reaction and stitching (graphenization). (b) One-shot, region-selective APEX as alternative synthesis and functionalization
of nanographenes through ‘growth from template’. (c) One-shot, bay-region-selective APEX by Diels–Alder reaction. (d) One-shot, K-region-selective
APEX by double C–H activation (this work).

_t_ Bu

_t_ Bu F

_t_ Bu

_t_ Bu Cl

_t_ Bu

1a (R = _t_ Bu)
1b (R = H)

2a (established standard conditions) 3aa (R = _t_ Bu): 88%
1.5 equiv 3ba (R = H): 48%

Pd(CH3CN)4(SbF6)2 (5 mol%)

_t_ Bu

_t_ Bu CF3

_t_ Bu

3aj (47%)

OMe

Cl
Cl

~~Cl~~

~~O~~

_o_ -chloranil
(2.0 equiv)

Me
Si

ClCH2CH2Cl

80 °C, 2 h

3ab (89%) 3ac (93%) 3ad (88%) 3ae (70%)

Bpin

_t_ Bu _t_ Bu

_t_ Bu _t_ Bu _t_ Bu

_t_ Bu

Standard conditions: 48% yield for APEX reaction of 1b and 2a

(a) π-Extending agent (instead of 2a ) (c) oxidant (instead of _o_ -chloranil)

Me
Si

R 2

2b   - 2i

CuCl2

Trace

_t_ Bu

3af (25%) 3ag (63%) 3ah (74%)

R 1

_t_ Bu OMe

_t_ Bu

3ai (57%) 3ca (51%)

Me
Sn

SiMe3

Me
Ge

Me3Si

28% 21%

(b) Pd source (instead of Pd(CH3CN)4(SbF6)2)

Pd(CH3CN)4(BF4)2
PdCl2/AgX (X = SbF6, BF4, OSO2CF3)

Pd(OAc)2

0% 0%

43%

Me
Si

R 3

2b : R 1 = H, R 2 = CF3, R 3 = H
2c : R 1 = H, R 2 = F, R 3 = H Me
2d : R 1 = H, R 2 = Cl, R 3 = H Me Si
2e : R 1 = R 2 = Cl, R 3 = H
2f : R 1 = R 2 = Bpin, R 3 = H
2g : R 1 = R 2 = _t_ Bu, R 3 = H
2h : R 1 = H, R 2 = OMe, R 3 = H
2i : R 1 = R 2 = H, R 3 = OMe 2j

36–43%

Trace

Figure 2 | One-shot K-region-selective C–H activation APEX. (a) The established reaction conditions. (b) Deviation from standard conditions
(effect of reaction parameters) in the reaction of 1b and 2a. (c) Scope of one-shot, K-region-selective, C–H activation APEX. Reaction conditions: polycyclic
aromatic compounds 1 (0.2 mmol), silicon-bridged aromatics 2 (1.5 equiv), Pd(CH3CN)4(SbF6)2 (5 mol%), o-chloranil (2.0 equiv), 1,2-dichloroethane,
80 �C, 2 h. Bpin, pinacolatoboryl.

precursors, followed by (ii) stitching (graphenization 6 ) of soluble
polyphenylene precursors by cyclodehydrogenation, flashvacuum pyrolysis or photocyclization, to yield the target
nanographenes (Fig. 1a) 6,16 . Although this state-of-the-art
methodology has contributed significantly to the rapid progress
of nanographene materials science, it has been well documented
that the final and vital step of stitching (graphenization) is
usually problematic 16 . For example, intramolecular oxidative
cyclodehydrogenation by Lewis acids and oxidants (Scholl-type
reactions) often suffer from problems such as incomplete
stitching, lack of regioselectivity and undesirable rearrangements.

The continuing evolution of nanographene science is heavily
dependent on the discovery of new reactions and strategies that
allow rapid and predictable synthesis, and functionalization of
nanographenes. Here we illustrate the significant potential of
one-shot APEX reactions of template PAH molecules with
p-extending agents (Fig. 1b) as an enabling concept that is
complementary to the aforementioned two-step methodology. By
devising APEX reactions that are selective to the specific regions
of PAH structures (bay region, K-region and L-region, see
Fig. 1b) 17, the direction-controlled growth or polymerization of a
template PAH producing structurally uniform nanographenes
would become possible. These regions correspond to the concave
armchair edge (bay region), convex armchair edge (K-region)
and zigzag edge (L-region) in graphene nomenclature. APEX
technology should also be useful for the late-stage fine-tuning of
nanographene properties by subtly modifying their edge
structures. Moreover, as a result of significant recent progress
in surface-catalysed cyclodehydrogenation and subsequent
epitaxial elongation reactions of PAHs by the group of Fasel
and colleagues 18, a number of p-extended PAHs provided by the
APEX technology could also be converted into structurally
uniform carbon nanotubes 18,19 .

Although the full potential of APEX reactions in nanographene
chemistry is yet to be realized partly because the concept had not
been formulated, significant experimental 20–25 and theoretical 26
advances have appeared, describing methods for bay-regionspecific p-extension in PAHs. For example, Scott has revisited the
finding of the Diels–Alder reactivity at the PAH bay regions
by Clar et al. 27 and proposed its use for metal-free growth of

single-chirality carbon nanotubes 20–26 (Fig. 1c). This represents a
bay-region-selective APEX reaction in our definition. However,
no APEX reactions at other PAH regions (L-region and K-region)
have been developed up until now. Although the dimerization of
perylene under Scholl-type coupling to furnish quaterrylene
represents the closest example of an L-region-selective APEX
reaction, this can be categorized as the two-step method having a
serious problem at the stitching (cyclodehydrogenation) stage 28 .
The reactions at K-regions (convex armchair edges) are
considered to be particularly difficult, as K-region bonds tend
to have relatively high bond orders, and most aromatic
substitution reactions occur preferentially at other aromatic
C–H bonds 17 .

Our APEX campaign 29–34 began when we serendipitously
discovered Pd(OAc)2/o-chloranil as the first-generation C–H
activation catalyst for PAHs in 2011 (ref. 35). This catalyst
uniquely and effectively promotes the C–H arylation of
non-functionalized PAHs with arylboroxines, with complete
K-region selectivity. When coupled with the Scholl-type
cyclodehydrogenation of the thus-formed arylated PAHs, a
number of structurally intriguing nanographenes such as
warped nanographenes 34 (Fig. 1a) have been synthesized.
Although this was a two-step nanographene synthesis at the
time, we felt that the observed C–H activation reactivity and
selectivity might be translated into an APEX reaction when
the K-region is activated and annulated with properly arranged
1,4-dimetal p-units in a [2 þ 4] annulation manner. Here, in we
describe a one-shot APEX reaction that occurs selectively at the
K-region of PAHs via double C–H activation 36–39 (Fig. 1d). This
protocol is applicable to multiple APEX and sequential APEX
reactions to construct various nanographene structures in a rapid
and programmable manner.

Results
Development of catalyst. We began our study by examining
various palladium salts, ligands, oxidants and p-extending agents
for the APEX reaction of phenanthrenes 1a and 1b. After
extensive screening, we determined that Pd(CH3CN)4(SbF6)2 and
o-chloranil serve as an efficient pre-catalyst and oxidant

2a Transmetalation

Pd 2+

Pd oxidation

π-Complexation

Pd +

Insertion

Transmetalation

Reductive elimination
oxidative aromatization

Pd 0

Pd +

+ 3ab

Pd +

_9_

Insertion

_2_

_10_

_9_

_10_ _3_ Pd +

_1_

_3_

_4_

C9–Pd complex

( 9Pd-10Ph )

2Pd-3Ph

3Pd-2Ph

2Pd-1Ph

3Pd-4Ph

9Pd-10Ph

–10

–15

–20

–25

–30

–35

–40

–45

C9–C10 π-complex

( 9,10Pd )

C2–C3

C3–C4
C1–C2

C9–C10

Figure 3 | Mechanistic considerations. (a) A possible mechanism of K-region-selective C–H activation APEX. (b) Theoretical calculations of
p-complexation and insertion steps. Structures were optimized by the density functional theory (DFT 44 ) calculations using B3PW91 hybrid
functional 45,46 (hydrogen atoms are omitted for clarity). Reaction pathways were followed by intrinsic reaction coordinate (IRC 47,48 ) computations,
and high-accuracy, single-point energy calculations of DFT-optimized structures were performed with Møller–Plesset perturbation theory (MP2) (ref. 49).
Energies are relative to that of o-chloranil-bound cationic phenylpalladium species.

respectively, while silicon-bridged aromatics 2 are optimal
p-extending agents (Fig. 2a). For example, when 2,7-di-tertbutyl-phenanthrene (1a: 1.0 equiv) was treated with dimethyldibenzosilole 40 (2a: 1.5 equiv) in 1,2-dichloroethane at 80 �C for 2 h
in the presence of Pd(CH3CN)4(SbF6)2 (5 mol%) and o-chloranil
(2.0 equiv), the corresponding K-region-annulated APEX
product 3aa was obtained in 88% isolated yield, representing
our standard APEX conditions. Unfunctionalized phenanthrene
(1b) also underwent an APEX reaction with 2a to yield
dibenzo[g,p]chrysene (3ba). It should be noted that under these
conditions, we observed the annulation exclusively at the
K-region of phenanthrene 1a or 1b.

Listed in Fig. 2b are the effects of variations from the standard
APEX conditions (1b þ 2a-3ba: 48% yield). For full lists of the
effects of reaction parameters, see Supplementary Tables 2–4. As

for the p-extension agents, we found that other dimetallobiphenyl
derivatives such as 2,2 0 -bis(trimethylsilyl)-1,1 0 -biphenyl and
dimethyldibenzogermole also reacted but led to the desired
product in much lower yield. Dimethyldibenzostannole did not
yield the product but generated a considerable amount
of tetraphenylene and quaterphenyl by homodimerization.
Changing the methyl groups of 2a only had detrimental effect
on reaction efficiency. The commercially available cationic
palladium complex Pd(CH3CN)4(BF4)2 showed APEX activity
comparable to Pd(CH3CN)4(SbF6)2. Similar catalytic activities
were also observed with the combined use of PdCl2 and silver
salts such as AgOSO2CF3, AgBF4 and AgSbF6. On the other hand,
neutral Pd(OAc)2 (our previous palladium pre-catalyst) 29 did not
promote the APEX reaction at all. These results clearly indicate
the importance of a cationic palladium species for the APEX

2:1 APEX
condition A
(53% yield)

2:1 APEX

1:2 APEX

(gram scale)

_t_ Bu

5 (69%)

_t_ Bu

7 (83%)
(2.6 g)

_t_ Bu

Me Me

Si Si

_t_ Bu

_t_ Bu _t_ Bu

1a 4

_t_ Bu

_t_ Bu _t_ Bu

_t_ Bu 11 _t_ Bu

1:2 APEX
condition B

(17% yield) Me Me

_t_ Bu _t_ Bu

_t_ Bu 12 _t_ Bu

Si
Me

2a
(3.2 g)

6
(1.6 g)

_t_ Bu _t_ Bu

Si
Me

1:4 APEX

Si
Me

_t_ Bu _t_ Bu

2a 8 9 (31%)

Figure 4 | Multiple APEX and sequential APEX. Multiple APEX (a–c). (a) 2:1 APEX. Reaction conditions: 4 (1 equiv), 1a (5 equiv), Pd(CH3CN)4(SbF6)2
(5 mol%), o-chloranil (4 equiv), 1,2-dichloroethane, 80 �C, 2 h. (b) 1:2 APEX. Reaction conditions: 6 (1 equiv), 2a (3 equiv), Pd(CH3CN)4(SbF6)2 (5 mol%),
o-chloranil (4 equiv), 1,2-dichloroethane, 80 �C, 8 h. (c) Reaction conditions: 8 (1 equiv), 2a (10 equiv), Pd(CH3CN)4(SbF6)2 (15 mol%), o-chloranil
(10 equiv), 1,2-dichloroethane, 80 �C, 1 h. (d) Sequential APEX. 2:1 APEX conditions (A): 6 (3 equiv), 10 (1 equiv), Pd(CH3CN)4(SbF6)2 (5 mol%),
o-chloranil (4 equiv), 1,2-dichloroethane, 80 �C, 6 h. 1:2 APEX conditions (B): 11 (1 equiv), 2a (4 equiv), Pd(CH3CN)4(SbF6)2 (15 mol%), o-chloranil
(5 equiv), 1,2-dichloroethane, 80 �C, 4 h.

reaction to occur. In the investigation of oxidants, commonly
used oxidants such as benzoquinone, p-chloranil, DDQ and
CuCl2 (ref. 35) displayed virtually no APEX-type activity. We
assume that the high reactivity of o-chloranil stems not only from
its high oxidation aptitude but also from its unique o-quinone
structure, which can bind to palladium in a bidentate manner
and modulate the redox property effectively 41,42 . Our preferred
solvent is 1,2-dichloroethane, but aromatic solvents such as
toluene, chlorobenzene, 1,2-dichlorobenzene, fluorobenzene and
trifluoromethylbenzene can also be used for the present APEX
reactions.

Scope of K-region-selective APEX. As shown in Fig. 2c, various
structurally and electronically diverse silicon-bridged aromatics 2
were found to react with 2,7-di-tert-butylphenanthrene (1a),
providing the corresponding dibenzo[g,p]chrysenes (3ab–3aj)
in good-to-excellent yield with virtually complete K-region
selectivity. In particular, dibenzosiloles having electron-deficient
substituents (2b–2e) 40,43 showed excellent reactivity. The
tribenzo[a,c,f]tetraphene framework (3aj) can be readily
constructed by the APEX reaction of 1a and benzonaphthosilole 2j 43 . Notably, dichloro- and diboryl-substituted
dibenzosiloles underwent the APEX reaction smoothly, leaving
C–Cl and C–B bonds intact (3ad, 3ae and 3af). The tolerance
of the reaction for these bonds makes it attractive for further

p-extension and functionalization, using well-established
cross-coupling chemistry. Furthermore, methylene-bridged
phenanthrene 1c reacted with 2a to afford benzoindenochrysene 3ca, which can potentially lead to soluble
nanographenes by facile substitution at the methylene moiety.
Ease of post-functionalization is particularly advantageous for
controlled surface alignment of nanographenes for device
applications.

Mechanistic considerations of K-region-selective APEX.
Although the exact mechanism of the present APEX reaction
remains unclear, our current assumption is shown in Fig. 3a. A
palladium(II) species undergoes the first transmetalation with
silicon-bridged aromatic 2a, followed by coordination of phenanthrene (1b) to arylpalladium intermediate A at the K-region,
yielding p-complex B. Coordination-induced insertion at the
K-region C ¼ C bond, followed by a second transmetalation
forms palladacycle intermediate D. Reductive elimination and
oxidative aromatization yields APEX product 3ab and palladium(0), the latter of which is oxidized to the active palladium(II)
species by the action of o-chloranil.

We assume that the K-region selectivity in the present APEX
reaction stems from the preferential palladium p-complexation at
the K-region of PAHs before the insertion step, as depicted in
Fig. 3a. To prove this hypothesis, we conducted density functional

theory 44 calculations (using B3PW91 hybrid functional 45,46 ) for
the p-complexation and insertion steps on a model reaction
of o-chloranil-bound cationic phenylpalladium species with
phenanthrene yielding the alkylpalladium species shown in
Fig. 3b (a model reaction relevant to A-B-C in Fig. 3a).
Reaction pathways were followed by intrinsic reaction
coordinate 47,48 computations, and high-accuracy, single-point
energy calculations of density functional theory-optimized
structures were performed with Møller–Plesset perturbation
theory 49 . Among possible p-coordination complexes at C1–C2,
C2–C3, C3–C4 and C9–C10 bonds, the p-complex at C9–C10
(K-region) was found to be most stable (9,10Pd). This may be
due to the tendency of this bond to have the most olefinic (less
aromatic) character 17,50 . We also calculated all possible transition
states of insertion from these p-complexes to give alkylpalladium
complexes (Fig. 3b). The formation of C9–Pd complex
(9Pd–10Ph), which leads to APEX at the K-region, was found
to be most favourable both kinetically and thermodynamically.
Thus, the basis of K-region selectivity in our new APEX
reaction has been supported by computational theory.
Detailed computational studies of Pd/o-chloranil-catalysed C–H
activation, including the present APEX reactions, will be reported
in due course. Based on these calculations, we predict the most
olefinic (least aromatic) K-region p-bond to be the first APEX
reaction site in future functionalizations of related p-extended
PAHs and nanographenes.

Multiple APEX and sequential APEX. To showcase the utility of
our APEX methodology in accessing a variety of nanographene
(p-extended PAH) structures in a rapid and programmable
manner, we examined several types of multiple APEX reactions
(Fig. 4a–c). For example, a 2:1 APEX reaction occurs when
treating ladder-type bis-silicon-bridged p-terphenyl 4 (ref. 51)
with an excess of 2,7-di-tert-butylphenanthrene (1a) in the
presence of Pd(CH3CN)4(SbF6)2/o-chloranil, to construct the
dibenzodiphenanthroanthracene framework 5 in 69% yield
(Fig. 4a). Other isomers were not observed in the reaction,
highlighting the fidelity of the present method to specific reaction
sites. An alternative mode of the double APEX reaction
(1:2 APEX) was also possible by the reaction of 2,7-di-tertbutylpyrene 6 (1.6 g, 1.0 equiv) and dibenzosilole 2a (3.2 g, 3.0
equiv) in the presence of Pd(CH3CN)4(SbF6)2 (5 mol%) and
o-chloranil (4.0 equiv) (Fig. 4b). It is noteworthy that the reaction
could be conducted on a gram scale to yield di-tert-butylhexabenzotetracene 7 in 2.6 g (83% yield). The gram-scale synthesis
clearly underscores the high capability of the present reaction
conditions for multiple APEX reactions. Furthermore, the
Pd(CH3CN)4(SbF6)2/o-chloranil system effectively promoted
the one-shot fourfold APEX reaction of 7,7 0 -di-tert-butyl-2,2 0 bipyrene 8 (1.0 equiv) with dibenzosilole 2a (10 equiv), to provide
bihexabenzotetracene 9 in 31% yield (Fig. 4c).

To further examine the applicability of APEX technology for
the construction of larger molecules, sequential APEX reactions
were investigated (Fig. 4d). Pleasingly, the 2:1 APEX reaction of
2,7-di-tert-butylpyrene 6 (3.0 equiv) with bis-silicon bridged
biphenyl 10 (ref. 51) (1.0 equiv) under Pd(CH3CN)4(SbF6)2/
o-chloranil conditions afforded tetra-tert-butylhexabenzohexacene
11 in 53% yield. The follow-up 1:2 APEX reaction of 11
(1.0 equiv) with dibenzosilole 2a (4.0 equiv) also took place to
furnish the target decabenzooctacene framework 12 in 17% yield.
In this particular reaction, we recovered a considerable amount of
starting material likely to be attributed to poor solubility in the
reaction media. Despite being relatively small in molecular size,
the electronic structures of these nanographenes can be
systematically altered. With the increase in molecular length,

the HOMO-LUMO gap becomes smaller. In line with this trend,
we observed decent red shift in both absorption and fluorescence
(see Supplementary Fig. 41 for details).

Discussion
It should also be mentioned that we observed the first sign of the
possibility of employing APEX in an oligomerization/polymerization manifold when we detected oligomers by matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry
analysis in the first 2:1 APEX reaction shown in Fig. 4d. Although
we have not yet investigated this possible mode of reaction
extensively, we envisage that the present APEX reaction could be
applied to even larger molecules through judicious choice of
solubilizing substituents on the substrates. Thus, the present
result bodes well for the potential application of our APEX
methodology to the bottom-up synthesis of graphene nanoribbons with controlled edge structures.

The present APEX methodology is complementary to the stateof-the-art two-step nanographene synthetic methods, thereby
finding significant use in the ‘growth from template’ nanographene synthesis and in the late-stage fine-tuning of nanographene
properties. Moreover, our APEX technology is not limited to the
synthesis and functionalization of p-extended PAHs and
nanographenes. One of the most significant features of the
present APEX reaction is that unfunctionalized PAHs can be
directly used for p-component assembly and p-extension without
any pre-functionalization. Thus, various p-conjugated molecules
made by many research groups (for many different purposes) will
be suitable substrates for our APEX reaction, furnishing even
more exciting classes of p-conjugated systems. The realization of
APEX polymerization, the development of new APEX reactions
for other PAH regions and acquisition of the first structure–
property relationships for various nanographene structures are
now ongoing in our laboratory.

Methods
Materials and characterization data. For the synthesis of all starting materials,
siloles and p-extended PAHs, and their characterization, see Supplementary
Methods. 1 H, 13 C and 19 F NMR spectra were obtained for all compounds, see
Supplementary Fig. 1–40. Ultraviolet–visible absorption and fluorescence spectra of
6, 11 and 12 are provided in Supplementary Fig. 41. Calculated energy surface of
p-complexation and insertion are provided in Supplementary Fig. 42. Calculated
energies of stationary points and their Cartesian coordinates are summarized
in Supplementary Table 1. Effects of reaction parameters are provided in
Supplementary Tables 2–4.

Typical procedure of K-region-selective APEX reaction. 2,7-Di-tert-butylphenanthrene (1a: 58 mg, 0.2 mmol, 1.0 equiv), dimethyldibenzosilole (2a: 63 mg,
0.3 mmol, 1.5 equiv), Pd(CH3CN)4(SbF6)2 (7.4 mg, 10 mmol, 5 mol%), o-chloranil
(98 mg, 0.4 mmol, 2.0 equiv) and a stirring bar were placed in a screw cap test tube.
The tube was sealed with a perforated plastic cap and air was removed though a
needle under reduced pressure. After back filling with nitrogen or argon,
1,2-dichloroethane (2 ml) was added and the needle was removed to seal up the test
tube. The tube was fixed in an aluminum heating block and the mixture was stirred
at 80 �C. After 2 h, the reaction mixture was cooled to room temperature and then
passed through a short pad of silica gel (eluent: CH2Cl2). After the organic solvents
were removed under reduced pressure, the residue was purified by silica-gel
chromatography (eluent: hexane) to afford 3,14-di-tert-butyldibenzo[g,p]chrysene
(3aa) in 88% yield (77.0 mg) as a white powder.

References
1. Novoselov, K. S. et al. Electric field effect in atomically thin carbon films.
Science 306, 666–669 (2004).
2. Allen, M. J., Tung, V. C. & Kaner, R. B. Honeycomb carbon: a review of
graphene. Chem. Rev. 110, 132–145 (2010).
3. Geim, A. K. Graphene: status and prospects. Science 324, 1530–1534 (2009).
4. Wu, J., Psula, W. & Mu¨llen, K. Graphenes as potential material for electronics.
Chem. Rev. 107, 718–747 (2007).
5. Dreyer, D. R., Ruoff, R. S. & Bielawski, C. W. From conception to realization:
an historical account of graphene and some perspectives for its future. Angew.
Chem. Int. Ed. 49, 9336–9344 (2010).

6. Chen, L., Hernandez, Y., Feng, X. & Mu¨llen, K. From nanographene and
graphene nanoribbons to graphene sheets: chemical synthesis. Angew. Chem.
Int. Ed. 51, 7640–7654 (2012).
7. Mu¨llen, K. Evolution of graphene molecules: structural and functional
complexity as driving forces behind nanoscience. ACS Nano 8, 6531–6541
(2014).
8. Watson, M. D., Fechtenkoetter, A. & Mu¨llen, K. Big is beautiful – ‘‘aromaticity’’
revisited from the viewpoint of macromolecular and supramolecular benzene
chemistry. Chem. Rev. 101, 1267–1300 (2001).
9. Narita, A. et al. Synthesis of structurally well-defined and liquid-phaseprocessable graphene nanoribbons. Nat. Chem. 6, 126–132 (2014).
10. Schwab, M. G. et al. Structurally defined graphene nanoribbons with high
lateral extension. J. Am. Chem. Soc. 134, 18169–18172 (2012).
11. Scott, L. T. et al. Geodesic polyarenes with exposed concave surfaces. Pure Appl.
Chem. 71, 209–219 (1999).
12. Tsefrikas, V. M. & Scott, L. T. Geodesic polyarenes by flash vacuum pyrolysis.
Chem. Rev. 106, 4868–4884 (2006).
13. Cai, J. M. et al. Atomically precise bottom-up fabrication of graphene
nanoribbons. Nature 466, 470–473 (2010).
14. Treier, M. et al. Surface-assisted cyclodehydrogenation provides a synthetic
route towards easily processable and chemically tailored nanographenes. Nat.
Chem. 3, 61–67 (2011).
15. Vo, T. H. et al. Large-scale solution synthesis of narrow graphene nanoribbons.
Nat. Commun. 5, 3189 (2014).
16. Feng, X., Pisula, W. & Mu¨llen, K. Large polycyclic aromatic hydrocarbons:
synthesis and discotic organization. Pure Appl. Chem. 81, 2203–2224 (2009).
17. Harvey, R. G. Polycyclic Aromatic Hydrocarbons (Wiley-VCH, 1997).
18. Sanchez-Valencia, J. R. et al. Controlled synthesis of single-chirality carbon
nanotubes. Nature 512, 61–64 (2014).
19. Omachi, H., Nakayama, T., Takahashi, E., Segawa, Y. & Itami, K. Initiation
of carbon nanotube growth by well-defined carbon nanorings. Nat. Chem. 5,
572–576 (2013).
20. Fort, E. H., Donovan, P. M. & Scott, L. T. Diels–Alder reactivity of polycyclic
aromatic hydrocarbon bay regions: implications for metal-free growth of
single-chirality carbon nanotubes. J. Am. Chem. Soc. 131, 16006–16007
(2009).
21. Fort, E. H. & Scott, L. T. One-step conversion of aromatic hydrocarbon bay
regions into new unsubstituted benzene rings. A reagent for the lowtemperature, metal-free growth of single-chirality carbon nanotubes. Angew.
Chem. Int. Ed. 49, 6626–6628 (2010).
22. Fort, E. H. & Scott, L. T. Gas-phase Diels–Alder cycloaddition of benzyne
to an aromatic hydrocarbon bay region. Groundwork for the selective
solvent-free growth of armchair carbon nanotubes. Tetrahedron Lett. 52,
2051–2053 (2011).
23. Li, J., Jiao, C., Huang, K. W. & Wu, J. Lateral extension of p conjugation along
the bay regions of bisanthene through a Diels–Alder cycloaddition reaction.
Chem. Eur. J. 17, 14672–14680 (2011).
24. Konishi, A., Hirano, Y., Matsumoto, K., Kurata, H. & Kubo, T. Facile
synthesis and lateral p-expansion of bisanthenes. Chem. Lett. 42, 592–594
(2013).
25. Schuler, B. et al. From perylene to a 22-ring aromatic hydrocarbon in one-pot.
Angew. Chem. Int. Ed. 53, 9004–9006 (2014).
26. Fort, E. H. & Scott, L. T. Carbon nanotubes from short hydrocarbon templates.
Energy analysis of the Diels–Alder cycloaddition/rearomatization growth
strategy. J. Mater. Chem. 21, 1373–1381 (2011).
27. Clar, E. & Zander, M. Syntheses of coronene and 1: 2-7: 8-dibenzocoronene.
J. Chem. Soc. 4616–4625 (1957).
28. Thamatam, R., Skraba, S. L. & Johnson, R. P. Scalable synthesis of quaterrylene:
solution-phase 1 H NMR spectroscopy of its oxidative dication. Chem.
Commun. 49, 9122–9124 (2013).
29. Mochida, K., Kawasumi, K., Segawa, Y. & Itami, K. Direct arylation of
polycyclic aromatic hydrocarbons through palladium catalysis. J. Am. Chem.
Soc. 133, 10716–10719 (2011).
30. Kawasumi, K., Mochida, K., Kajino, T., Segawa, Y. & Itami, K. Pd(OAc)2/
o-chloranil/M(OTf)n: a catalyst for the direct C–H arylation of polycyclic
aromatic hydrocarbons with boryl-, silyl-, and unfunctionalized arenes. Org.
Lett. 14, 418–421 (2012).
31. Zhang, Q., Kawasumi, K., Segawa, Y., Itami, K. & Scott, L. T.
Palladium-catalyzed C–H activation taken to the limit. Flattening an
aromatic bowl by total arylation. J. Am. Chem. Soc. 134, 15664–15667
(2012).
32. Kawasumi, K., Mochida, K., Segawa, Y. & Itami, K. Palladium-catalyzed
direct phenylation of perylene: structural and optical properties of
3,4,9-triphenylperylene and 3,4,9,10-tetraphenylperylene. Tetrahedron 69,
4371–4374 (2013).
33. Ozaki, K., Zhang, H., Ito, H., Lei, A. & Itami, K. One-shot indole-to-carbazole
p-extension by Pd-Cu-Ag trimetallic system. Chem. Sci. 4, 3416–3420 (2013).

34. Kawasumi, K., Zhang, Q., Segawa, Y., Scott, L. T. & Itami, K. A grossly warped
nanographene and the consequences of multiple odd-membered-ring defects.
Nat. Chem. 5, 739–744 (2013).
35. Funaki, K., Kawai, H., Sato, T. & Oi, S. Palladium-catalyzed direct C–H bond
arylation of simple arenes with aryltrimethylsilanes. Chem. Lett. 40, 1050–1052
(2011).
36. Okamoto, K., Zhang, J., Housekeeper, J. B., Marder, S. R. & Luscombe, C. K.
C–H arylation reaction: atom efficient and greener syntheses of p-conjugated
small molecules and macromolecules for organic electronic materials.
Macromolecules 46, 8059–8078 (2013).
37. Segawa, Y., Maekawa, T. & Itami, K. Synthesis of extended p-systems through
C–H activation. Angew. Chem. Int. Ed. 54, 66–81 (2015).
38. Yamaguchi, J., Yamaguchi, A. D. & Itami, K. C–H bond functionalization:
emerging synthetic tools for natural products and pharmaceuticals. Angew.
Chem. Int. Ed. 51, 8960–9009 (2012).
39. Wencel-Delord, J. & Glorius, F. C–H bond activation enables the rapid
construction and late-stage diversification of functional molecules. Nat. Chem.
5, 369–375 (2013).
40. Neugebauer, W., Kos, A. J. & Schleyer, P. v. R. Regioselektive dimetallierung
von aromaten. Bequemer zugang zu 2,2 0 -disubstituierten biphenylderivaten.
J. Organomet. Chem. 228, 107–118 (1982).
41. Balch, A. L. Oxidation of o-quinone adducts of transition metal complexes.
J. Am. Chem. Soc. 95, 2723–2724 (1973).
42. Fox, G. A. & Pierpont, C. G. Periodic trends in charge distribution for
transition metal complexes containing catecholate and semiquinone ligands.
Metal-mediated spin coupling in the bis(3,5-di-tert-butyl-1,2-semiquinone)
complexes of palladium(II) and platinum(II) M(DBSQ)2 (M ¼ Pd, Pt). Inorg.
Chem. 31, 3718–3723 (1992).
43. Ureshino, T., Yoshida, T., Kuninobu, Y. & Takai, K. Rhodium-catalyzed
synthesis of silafluorene derivatives via cleavage of silicon � hydrogen and
carbon � hydrogen bonds. J. Am. Chem. Soc. 132, 14324–14326 (2010).
44. Frisch, M. J. Gaussian09, Revision E.01 (Gaussian, Inc., Wallingford CT, 2004).
45. Becke, A. D. Density functional thermochemistry. III. The role of exact
exchange. J. Chem. Phys. 98, 5648–5652 (1993).
46. Perdew, J. P. Unified Theory of Exchange and Correlation Beyond the Local
Density Approximation/Electronic Structure of Solids. (Eds Ziesche, P. &
Eschrig, H.) 11–20 (Akademie Verlag, 1991).
47. Dunning, Jr T. H. & Hay, P. J. Methods of Electronic Structure Theory/Modern
Theoretical Chemistry. (Ed Schaefer, III H. F.3, 1–27 (Springer, 1977).
48. Hay, P. J. & Wadt, W. R. Ab initio effective core potentials for molecular
calculations. Potentials for the transition metal atoms Sc to Hg. J. Chem. Phys.
82, 270–283 (1985).
49. Grimme, S. Improved second-order Møller–Plesset perturbation theory by
separate scaling of parallel- and antiparallel-spin pair correlation energies.
J. Chem. Phys. 118, 9095–9102 (2003).
50. Hasegawa, T., Sekine, M., Schaefer, W. P. & Taube, H. Preparation and
characterization of a bis(pentaammineosmium(II)) pyrene complex. Inorg.
Chem. 30, 449–452 (1991).
51. Shimizu, M., Tatsumi, H., Mochida, K., Oda, K. & Hiyama, T. Silicon-bridge
effects on photophysical properties of silafluorenes. Chem. Asian J. 3,
1238–1247 (2008).

Acknowledgements
This work was supported by the ERATO programme from JST (K.I.), the Funding
Program for Next Generation World-Leading Researchers from JSPS (220GR049 to K.I.)
and KAKENHI from MEXT (26810057 to H.I.). K.O. and K.K. thank the Japan Society
for the Promotion of Science (JSPS) for fellowships. We thank Dr Yasutomo Segawa
(Nagoya University), Professor Cathleen M. Crudden (Queen’s University) and
Dr Ayako Miyazaki (Nagoya University) for fruitful discussion and critical comments.
Dr Keiko Kuwata (Nagoya University) is acknowledged for assistance in mass spectroscopy. Calculations were performed using the resources of the Research Center for
Computational Science, Okazaki, Japan. ITbM is supported by the World Premier
International Research Center (WPI) Initiative, Japan.

Author contributions
K.I. conceived the concept. K.O., K.K. and H.I. conducted experiments. M.S. performed
theoretical calculations. K.I and H.I. prepared the manuscript, with feedback from other
authors.

Additional information
Supplementary Information accompanies this paper at [http://www.nature.com/](http://www.nature.com/naturecommunications)
[naturecommunications](http://www.nature.com/naturecommunications)

Competing financial interests: The authors declare no competing financial interests.

Reprints and permission information is available online at [http://npg.nature.com/](http://npg.nature.com/reprintsandpermissions/)
[reprintsandpermissions/](http://npg.nature.com/reprintsandpermissions/)

How to cite this article: Ozaki, K. et al. One-shot K-region-selective annulative
p-extension for nanographene synthesis and functionalization. Nat. Commun. 6:6251
doi: 10.1038/ncomms7251 (2015).

This work is licensed under a Creative Commons Attribution 4.0
International License. The images or other third party material in this
article are included in the article’s Creative Commons license, unless indicated otherwise
in the credit line; if the material is not included under the Creative Commons license,
users will need to obtain permission from the license holder to reproduce the material.
To view a copy of this license, visit [http://creativecommons.org/licenses/by/4.0/](http://creativecommons.org/licenses/by/4.0/)

본문 출처 PDF: PDF 보기 · 다른 PDF는 위 [PDF 업로드]로 올릴 수 있습니다.

활용가능성

이력 0건

아직 편집 이력이 없습니다. 저장할 때마다 이전 내용이 여기에 백업됩니다.