Facile synthesis of nitrogen-doped [(6.)M8]ncyclacene carbon nanobelts by a one-pot self-condensation reaction

Article abstract of DOI:10.1021/jacs.1c00409

Synthesis of fully conjugated carbon nanobelts (CNBs) remains one of the biggest challenges in organic chemistry. Herein, we report a facile synthesis of four nitrogen-doped [(6.)_m8]_ncyclacene CNBs (m = 1-3; n = 3,4) with different sizes by a one-pot self-condensation reaction of three bis(o-aminobenzophenone) precursors. The belt-shaped structure was confirmed by X-ray crystallographic analysis. The existence of eight-membered [1,5]diazocine rings releases the strain while maintaining weak πconjugation throughout the belt backbone, which is supported by electronic absorption spectra and frontier molecular orbital analysis. NMR measurements and magnetic shielding calculations suggest an alternating aromatic-nonaromatic ring structure, with a slightly more shielded chemical environment in the cavity. Our method opens the opportunities to access more sophisticated πconjugated 2D/3D belt-/cage-like molecules in a simple way.

Full text of DOI:10.1021/jacs.1c00409

pubs.acs.org/JACS
Communication
Facile Synthesis of Nitrogen-Doped [(6.)m8]nCyclacene Carbon
Nanobelts by a One-Pot Self-Condensation Reaction
Jun Zhu, Yi Han, Yong Ni, Guangwu Li, and Jishan Wu*
Cite This: J. Am. Chem. Soc. 2021, 143, 2716−2721
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Synthesis of fully conjugated carbon nanobelts (CNBs) remains one of the biggest challenges in organic chemistry.
Herein, we report a facile synthesis of four nitrogen-doped [(6.)m8]ncyclacene CNBs (m = 1−3; n = 3,4) with different sizes by a
one-pot self-condensation reaction of three bis(o-aminobenzophenone) precursors. The belt-shaped structure was confirmed by X-
ray crystallographic analysis. The existence of eight-membered [1,5]diazocine rings releases the strain while maintaining weak π-
conjugation throughout the belt backbone, which is supported by electronic absorption spectra and frontier molecular orbital
analysis. NMR measurements and magnetic shielding calculations suggest an alternating aromatic−nonaromatic ring structure, with
a slightly more shielded chemical environment in the cavity. Our method opens the opportunities to access more sophisticated π-
conjugated 2D/3D belt-/cage-like molecules in a simple way.
elt-shaped molecules consisting of fused, unsaturated
rings have gained extensive research attention not only
molecular design was reported by Chi et al.29 In addition, sp3-
carbon- or heteroatom-bridged nanobelts as cyclacene
analogues were reported.30−34 In another aspect, Gleiter has
successfully demonstrated a strategy to bypass the issue of
large strain by incorporating naturally convex, yet still weakly
conjugated cyclooctatetraene (COT) rings into the belt
structure. The tub-shaped COT units in [4.8]3cyclacene and
[6.8]3cyclacene35−37 (Figure 1a) circumvented both obstacles
of cyclacene synthesis.
In one of our experiments, we obtained 6,12-
diphenyldibenzo[1,5]diazocine by accident from a refluxed
toluene solution of 2-aminobenzophenone and diphenyl
phosphate (DPP) with more than 80% yield (Figure 1b).
This one-pot self-condensation cyclization can be dated back
to 1896,38 and it has been achieved under various reaction
conditions with excellent yields.39−44 The [1,5]diazocine can
be regarded as a 1,5-nitrogen-doped COT, and its X-ray
structure clearly reveals a tub-shaped structure with a bending
angle of about 75° (Figure 1b),43 which is desirable for the
formation of nanobelts containing eight-membered rings.
Inspired by this highly efficient self-condensation cyclization
reaction and Gleiter’s strategy, we expected that similar
reactions starting from precursors carrying bis(o-
aminobenzophenone)s could give [1,5]diazocine-containing
nanobelts in one pot. To our delight, this concept works very
well, and four belt-like molecules 1−4 with [6.8N2]3cyclacene,
[6.6.8N2 ]3 cyclacene, [6.6.6.8N2 ]3 cyclacene, and
[6.6.6.8N2]4cyclacene backbones were successfully synthesized
B
due to their unique structures, which could open the way to a
rational chemical preparation of carbon nanotubes (CNTs),1
but also due to their potential for novel optoelectronic
properties and applications in materials science and supra-
molecular chemistry.2−7 Cyclacenes, first appearing in 1954 as
hypothetical molecules,8 consist solely of linearly fused
benzene rings. Although several groups have targeted
cyclacenes, their attempts were not successful,9−15 despite a
reported detection of an [8]cyclacene derivative by mass
spectrometry.16 In contrast, cyclophenacenes with angularly
fused benzene rings were observed by mass spectrometry,17 or
synthesized as derivatives from C60,18 which implied cyclo-
phenacenes could be synthesized in a stable form. Itami and
Segewa’s group made a breakthrough in 2017 for the successful
synthesis of a carbon nanobelt (CNB) as an isomer of
[12]cyclophenacene via multiple Wittig reactions followed by
Yamamoto coupling.19 Later, this method was applied for the
synthesis of larger size [16] and [20]CNBs.20 Miao’s group
developed a different method and obtained sidewall segments
of an armchair (12,12) CNT and a chiral (18,12) CNT.21
Isobe’s lab reported a finite phenine nanotube with periodic
vacancy defects.22
The past attempts have revealed that the synthesis of
cyclacenes was hindered both by their high reactivity and
highly strained structures, which were in line with a small
singlet−triplet gap and large strain energy as predicted by
computations.23,24 In general, the current synthetic strategies
involve three main steps, which are macrocyclization, belt
formation, and strain induction. Each step can be challenging,
especially the final strain-inducing step.9−15,25−27 Itami and
Segewa’s group proposed benzannulated cyclacenes coping
with the high reactivity to prepare stable CNBs,15 and a
dodecabenzo[18]cyclacene was successfully synthesized.28
Meanwhile, an octabenzo[12]cyclacene based on the same
Received: January 12, 2021
Published: February 10, 2021
https://dx.doi.org/10.1021/jacs.1c00409
J. Am. Chem. Soc. 2021, 143, 2716−2721
© 2021 American Chemical Society
2716

Journal of the American Chemical Society
pubs.acs.org/JACS
Communication
reaction and hydrolysis47 to yield the precursors 9 and 14.
Heating the corresponding precursors with DPP in a diluted
toluene solution (o-dichlorobenzene was used for 14 due to its
poor solubility in toluene) yielded 1, 2, 3, and 4 in 24, 19, 15,
and 5% yield, respectively. For comparison, the all-carbon
[6.8]3cyclacene as an analogue of 1 was synthesized in eight
steps with an overall yield of about 0.04%.36 The reaction
yields increased with longer reaction time and remained almost
unchanged after 5 days, which suggests the self-condensation
reaction has reached a thermodynamic equilibrium after about
5 days. The formation of 3 and 4 in one reaction suggests both
molecules are thermodynamically favored. 1 and 2 are pale-
yellow solids, and 3 and 4 are yellow solids. 1−3 are soluble in
organic solvents including dichloromethane (DCM), chloro-
form, tetrahydrofuran (THF), toluene, and carbon disulfide
(CS2), while 4 is more soluble in CS2 and less soluble in
others. The lower solubility of 4 could be due to its higher
symmetry.48 Also, the structures of 1−4 remain intact even in
the presence of a strong acid like trifluoroacetic acid.
Single crystals of 1 and 2 suitable for X-ray crystallography
analysis were obtained by slow diffusion of MeOH into their
DCM solution. Single crystals of 3 (long-rod crystals, Figure
S16 in Supporting Information) show very weak diffraction
and cannot be solved. Crystals of 4 were not obtained after
many attempts. The chemical structures of 3 and 4 were
confirmed by both NMR and high-resolution mass spectrom-
etry. The backbones of 1−3 adapt a triangle shape with some
deviation from D3 symmetry, while the backbone of 4 is
square, slightly deviating from D4 symmetry (Figure 2a,d,g,h).
The phenyl or 4-tert-butylphenyl substituents on the eight-
membered rings tilt away from the belts, while the 4-n-
butylphenyl groups in the optimized geometries of 3 and 4 are
almost perpendicular to the anthracene units. The average
dihedral angles at the eight-membered rings are 70, 70, 74, and
83°, respectively, which are close to those of most reported
structures containing [1,5]diazocines (about 72−75°),39−44
implying a slightly strained structure in these belts. The
benzene, naphthalene, and anthracene units in 1−3 are slightly
bent outward, while the anthracene moiety in 4 is slightly bent
inward. Axial chirality43 is found in the crystallographic
structures of 1 and 2 at a 1:1 racemic ratio (Figure 2b,e),
and the respective R and S isomers pack into 1D channels49−51
by intermolecular [C−H···π] and van der Waals interactions
(Figure 2c,f). The radii of the inner cavities are determined to
be 2.32, 3.15, 4.14, and 5.86 Å, respectively (Figure 2i). Bond
length analysis revealed localized aromatic character of the
bridging benzene, naphthalene, and anthracene rings and
nonaromatic character of the [1,5]diazocine units (Figure S1
in the Supporting Information).
Figure 1. (a) Reported [4.8]3cyclacene and [6.8]3cyclacene CNBs;
(b) self-condensation of 2-aminobenzophenone to give dibenzo[1,5]-
diazocine with a tub-like conformation and the synthesis of four
nitrogen-doped [(6.)m8]ncyclacenes (m = 1,2,3; n = 3,4) CNBs by this
method in this work.
in one step starting from the precursors 5, 9, and 14 with one
amino and one phenone group at each end of the benzene,
naphthalene, and anthracene rings (Figure 1b and Scheme 1).
Compound 5 was prepared according to a reported
procedure.45 By following our previously reported methods
with some modifications,46 the intermediates 8 and 13 were
synthesized, which underwent a Buchwald−Hartwig coupling
Scheme 1. Synthetic Routes of Compounds 1 (a), 2 (b), and
3 & 4 (c)
1
The H NMR spectrum of 1 in CD2Cl2 shows that protons
a1 from the backbone are located at 6.48 ppm (Figure 3). 2D
and 3D isochemical shielding surface (ICSS) calcualtions52,53
were conducted to elaborate the magnetic response (Figure 4).
The isotropic nuclear magnetic shielding tensor σiso and its
different components (σxx, σyy, σzz) as a response to an applied
magnetic field along the x-, y-, and z-axes were evaluated
(Figure 4a). Shielding cones are observed for each benzene
ring, indicating their local aromatic character. There is slight
overlap between the shielding cones of the three benzene rings
toward the center, leading to a slightly more shielded chemical
environment in the cavity, which is also evidenced from the 3D
ICSSiso map (Figure 4b). On the other hand, the σzz
component reveals a deshielding region, denoting a weak
2717
https://dx.doi.org/10.1021/jacs.1c00409
J. Am. Chem. Soc. 2021, 143, 2716−2721

Journal of the American Chemical Society
pubs.acs.org/JACS
Communication
Figure 2. (a,d) X-ray crystallographic structures of 1 and 2 (tilted view); (b,e) racemic ratio of R and S isomers identified for 1 and 2; (c,f) 3D
packing structures of 1 and 2 showing 1D channels; all hydrogen atoms are omitted for clarity; (g,h) optimized structures of 3 and 4 (top view); (i)
cavity sizes of 1 and 2 from crystallographic results and 3 and 4 from optimized structures.
1
Figure 3. H NMR spectra (aromatic region, 500 MHz) of 1−3 in
CD2Cl2 and 4 in CD2Cl2 + CS2 with labeling.
antiaromatic character of the [1,5]diazocine unit. Due to the
interaction with the neighboring [1,5]diazocine moiety, the
protons a1 on the benzene unit are less deshielded compared
with the normal benzene ring and are shifted to high field. This
analysis is consistent with the previous analysis on the all-
carbon [6.8]3cyclacene.54 Similar magnetic response maps
Figure 4. (a) Map presentation of calculated σij of 1 denoting the
isotropic and the responses to an applied field contained in the x-, y-,
and z-axes; (b) calculated 3D ICSSiso maps of 1−4 (isovalue: 6.5 for 1
& 2 and 5.5 for 3 & 4). The substituents are replaced by hydrogen
were calculated for 2−4 (Figures S7, S10, S13 in the
Supporting Information), and the protons on the naphtha-
lene/anthracene units appeared at a relative higher field
compared to parent naphthalene/anthracene rings (Figure 3).
For 3 and 4, the protons on the 4-n-butylphenyl groups are
atoms during the calculations.
2718
https://dx.doi.org/10.1021/jacs.1c00409
J. Am. Chem. Soc. 2021, 143, 2716−2721

Journal of the American Chemical Society
pubs.acs.org/JACS
Communication
Figure 5. (a) UV−vis absorption spectra of 1−4 in DCM; (b) calculated (B3LYP/6-31G(d,p)) frontier molecular orbital profiles and energy
diagram of 1.
split into two set of signals because of the restricted rotation.
Due to a more shielded chemical environment inside the cavity
(Figure 4b), the protons (e3, f3/e4, f4) pointed to the center are
more shielded (Figure 3). On the other hand, the 4-tert-
butylphenyl groups tilt away from the belt and can rotate
freely, and thus, their protons remain in low field (Figure 3).
Belts 1−4 in DCM all show intense absorption in the UV−
vis region. 1 shows two major absorption bands with maxima
(λmax) at 321 and 265 nm (Figure 5a). The frontier molecular
orbitals of 1 are delocalized along the backbone, and some
degree of orbital overlap can be observed at the arene−eight-
membered ring junctions (Figure 5b), indicating a weakly
conjugated structure. The orbitals 219/218 and 221/222 are
degenerated due to the high symmetry of its backbone.
According to time-dependent (TD) DFT calculations (Table
S1 and Figure S4 in the Supporting Information), the low-
energy absorption band at 321 nm can be attributed to 219/
218 → 220 electronic transitions. 2 displays a similar
absorption spectrum, but it is slightly red-shifted due to
extended conjugation, with λmax at 356/277 nm. 3 and 4 share
a similar absorption spectrum; both are red-shifted compared
to 1 and 2. The spectrum of 4 is also red-shifted compared to 3
due to increased conjugation. The calculated frontier
molecular orbital profiles of 2−4 also indicate a delocalized
nature, and TD DFT results are in good agreement with the
observed absorption spectra (Supporting Information). The
optical energy gaps of 1−4 are determined to be 3.02, 2.95,
2.58, and 2.48 eV, respectively. Cyclic voltammetry measure-
ments of 1−4 revealed irreversible redox waves, with the onset
of the first reduction wave at −1.39, −1.23, −0.76, and −1.19
V (vs Fc/Fc+), respectively (Figure S2 in the Supporting
Information).
In summary, we have developed a simple approach to access
nitrogen-doped [(6.)m8]ncyclacene carbon nanobelts (m = 1−
3; n = 3,4) by a one-pot self-condensation reaction. This
method takes advantage of dynamic covalent character of the
C=N bonds and bypasses the obstacles of high reactivity and
large strain in cyclacene synthesis. The obtained molecules are
well characterized by X-ray analysis, NMR, and electronic
absorption measurements, assisted by TD DFT and 2D/3D
ICSS calculations. They are weakly conjugated with an
alternating aromatic−nonaromatic ring structure, and the
inner cavity shows a more shielded chemical environment
due to intramolecular interactions. Our method could be used
for the synthesis of more challenging π-conjugated 2D/3D
belt-/cage-like molecules55 in the future.
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/jacs.1c00409.
Synthetic procedures and characterization data, addi-
tional spectra, and computational details (PDF)
Accession Codes
CCDC 2053162−2053163 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
■
Corresponding Author
Jishan Wu − Department of Chemistry, National University of
Singapore, Singapore 117543; Joint School of National
University of Singapore and Tianjin University, International
Campus of Tianjin University, Fuzhou 350207, China;
orcid.org/0000-0002-8231-0437; Email: chmwuj@
nus.edu.sg
Authors
Jun Zhu − Department of Chemistry, National University of
Singapore, Singapore 117543
Yi Han − Department of Chemistry, National University of
Singapore, Singapore 117543
Yong Ni − Department of Chemistry, National University of
Singapore, Singapore 117543
Guangwu Li − Department of Chemistry, National University
of Singapore, Singapore 117543
Complete contact information is available at:
https://pubs.acs.org/10.1021/jacs.1c00409
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was financially supported by an NRF Investigator-
ship (NRF-NRFI05-2019-0005) and a MOE Tier 2 grant
(MOE2018-T2-2-094). J.Z. acknowledges the PhD schloarship
from the Applied Materials-NUS Advanced Materials Corpo-
rate Lab.
2719
https://dx.doi.org/10.1021/jacs.1c00409
J. Am. Chem. Soc. 2021, 143, 2716−2721

Journal of the American Chemical Society
pubs.acs.org/JACS
Communication
(22) Sun, Z.; Ikemoto, K.; Fukunaga, T. M.; Koretsune, T.; Arita, R.;
Sato, S.; Isobe, H. Finite Phenine Nanotubes with Periodic Vacancy
Defects. Science 2019, 363, 151−155.
REFERENCES
■
(1) Iijima, S. Helical Microtubules of Graphitic Carbon. Nature
1991, 354, 56−58.
(2) Tahara, K.; Tobe, Y. Molecular Loops and Belts. Chem. Rev.
2006, 106, 5274−5290.
(3) Kawase, T.; Kurata, H. Ball-, Bowl-, and Belt-Shaped Conjugated
Systems and Their Complexing Abilities: Exploration of the Con-
cave-Convex π-π Interaction. Chem. Rev. 2006, 106, 5250−5273.
(4) Eisenberg, D.; Shenhar, R.; Rabinovitz, M. Synthetic Approaches
to Aromatic Belts: Building Up Strain in Macrocyclic Polyarenes.
Chem. Soc. Rev. 2010, 39, 2879−2890.
(5) Segawa, Y.; Yagi, A.; Matsui, K.; Itami, K. Design and Synthesis
of Carbon Nanotube Segments. Angew. Chem., Int. Ed. 2016, 55,
5136−5158.
(6) Lu, X.; Wu, J. After 60 Years of Efforts: The Chemical Synthesis
of a Carbon Nanobelt. Chem. 2017, 2, 619−620.
(7) Shi, T.; Wang, M. Zigzag Hydrocarbon Belts. CCS Chem. 2020,
2, 916−931.
(8) Heilbronner, E. Molecular Orbitals in Homologen Reihen
Mehrkerniger Aromatischer Kohlenwasserstoffe: I. Die Eigenwerte
yon LCAO-MO’s in Homologen Reihen. Helv. Chim. Acta 1954, 37,
921−935.
(9) Kohnke, F. H.; Slawin, A. M. Z.; Stoddart, J. F.; Williams, D. J.
M o l ec u l a r B e lt s a n d C o l la r s i n t he M a k i n g:
(23) Choi, H. S.; Kim, K. S. Fully Conjugated Beltenes (Belt-Like
and Tubular Aromatics). Angew. Chem., Int. Ed. 1999, 38, 2256−2258.
(24) Chen, Z.; Jiang, D.; Lu, X.; Bettinger, H. F.; Dai, S.; Schleyer, P.
V. R.; Houk, K. N. Open-shell Singlet Character of Cyclacenes and
Short Zigzag Nanotubes. Org. Lett. 2007, 9, 5449−5452.
(25) Wang, J.; Miao, Q. A Tetraazapentacene-Pyrene Belt: Toward
Synthesis of N-Doped Zigzag Carbon Nanobelts. Org. Lett. 2019, 21,
10120−10124.
(26) Chen, H.; Gui, S.; Zhang, Y.; Liu, Z.; Miao, Q. Synthesis of a
Hydrogenated Zigzag Carbon Nanobelt. CCS Chem. 2021, 3, 613−
619.
(27) Han, Y.; Dong, S.; Liau, Y. C.; Chi, C. Synthesis of a
Tetraepoxy Nanobelt and Its Reductive Aromatization Attempts. Org.
Mater. 2020, 02, 330−335.
(28) Cheung, K. Y.; Watanabe, K.; Segawa, Y.; Itami, K. Synthesis of
a Zigzag Carbon Nanobelt. Nat. Chem. [Online early acces].
Published Online Jan 25, 2021. https://doi.org/10.1038/s41557-
020-00627-5.
(29) Han, Y.; Dong, S.; Shao, J.; Fan, W.; Chi, C. Synthesis of a
Sidewall Fragment of a (12,0) Carbon Nanotube. Angew. Chem., Int.
Ed. 2021, 60, 2658−2662.
(30) Shi, T.; Guo, Q.; Tong, S.; Wang, M. Toward the Synthesis of a
Highly Strained Hydrocarbon Belt. J. Am. Chem. Soc. 2020, 142,
4576−4580.
(31) Shi, T.; Tong, S.; Wang, M. Construction of Hydrocarbon
Nanobelts. Angew. Chem., Int. Ed. 2020, 59, 7700−7705.
(32) Zhang, Q.; Zhang, Y.; Tong, S.; Wang, M. Hydrocarbon Belts
with Truncated Cone Structures. J. Am. Chem. Soc. 2020, 142, 1196−
1199.
A
Hexaepoxyoctacosahydro[12]cyclacene Derivative. Angew. Chem.,
Int. Ed. Engl. 1987, 26, 892−894.
(10) Ashton, P. R.; Brown, G. R.; Isaacs, N. S.; Giuffrida, D.;
Kohnke, F. H.; Mathias, J. P.; Slawin, A. M. Z.; Smith, D. R.; Stoddart,
J. F.; Williams, D. J. Molecular LEGO. 1. Substrate-directed Synthesis
via Stereoregular Diels-Alder Oligomerizations. J. Am. Chem. Soc.
1992, 114, 6330−6353.
(11) Cory, R. M.; McPhail, C. L.; Dikmans, A. J.; Vittal, J. J.
Macrocyclic Cyclophane Belts via Double Diels-Alder Cycloadditions:
Macroannulation of Bisdienes by Bisdienophiles. Synthesis of a Key
Precursor to an [8]Cyclacene. Tetrahedron Lett. 1996, 37, 1983−
1986.
(33) Li, Y.; Segawa, Y.; Yagi, A.; Itami, K. A Nonalternant Aromatic
Belt: Methylene-Bridged [6]Cycloparaphenylene Synthesized from
Pillar[6]arene. J. Am. Chem. Soc. 2020, 142, 12850−12856.
(34) Tan, M.; Guo, Q.; Wang, X.; Shi, T.; Zhang, Q.; Hou, S.; Tong,
S.; You, J.; Wang, M. Oxygen- and Nitrogen-Embedded Zigzag
Hydrocarbon Belts. Angew. Chem., Int. Ed. 2020, 59, 23649−23658.
(35) Hellbach, B.; Rominger, F.; Gleiter, R. Synthesis of Beltenes by
Reactions of 5,6,11,12-Tetradehydrodibenzo[a, e]cyclooctene with
[CpCo(CO)2] Derivatives. Angew. Chem., Int. Ed. 2004, 43, 5846−
5849.
(12) Kintzel, O.; Luger, P.; Weber, M.; Schluter, A.-D. Ring-Chain
̈
Equilibrium between an [18]Cyclacene Derivative and a Ladder
Oligomer. Eur. J. Org. Chem. 1998, 1998, 99−105.
(13) Neudorff, W. D.; Lentz, D.; Anibarro, M.; Schluter, A.-D. The
̈
Carbon Skeleton of the Belt Region of Fullerene C84 (D2). Chem. -
Eur. J. 2003, 9, 2745−2757.
(36) Esser, B.; Rominger, F.; Gleiter, R. Synthesis of
[6.8]3Cyclacene: Conjugated Belt and Model for an Unusual Type
of Carbon Nanotube. J. Am. Chem. Soc. 2008, 130, 6716−6717.
(37) Esser, B.; Bandyopadhyay, A.; Rominger, F.; Gleiter, R. From
metacyclophanes to Cyclacenes: Synthesis and Properties of
[6.8]3Cyclacene. Chem. - Eur. J. 2009, 15, 3368−3379.
(14) Stuparu, M.; Gramlich, V.; Stanger, A.; Schluter, A.-D. Double-
̈
Stranded Cycles: Toward C84’s Belt Region. J. Org. Chem. 2007, 72,
424−430.
(15) Matsui, K.; Fushimi, M.; Segawa, Y.; Itami, K. Synthesis,
Structure, and Reactivity of a Cylinder-Shaped Cyclo[12]-
orthophenylene[6]ethynylene: Toward the Synthesis of Zigzag
Carbon Nanobelts. Org. Lett. 2016, 18, 5352−5355.
̈
(38) Sondheimer, A. Zur Kenntniss Eines Korpers mit Achtglie-
drigem Ringe. Ber. Dtsch. Chem. Ges. 1896, 29, 1272−1275.
(39) Jung, D.-I.; Song, J.-H.; Lee, E.-J.; Kim, Y.-Y.; Lee, D.-H.; Lee,
Y.-G.; Hahn, J.-T. Simple Synthesis of Quinolines and Dibenzo[b,
f][1,5]diazocines Under Microwave Irradiation. Tetrahedron Lett.
2009, 50, 5805−5807.
(16) Shi, T. H.; Guo, Q. H.; Tong, S.; Wang, M. X. Toward the
Synthesis of a Highly Strained Hydrocarbon Belt. J. Am. Chem. Soc.
2020, 142, 4576−4580.
(17) Iyoda, M.; Kuwatani, Y.; Nishinaga, T.; Takase, M.; Nishiuchi,
T. Conjugated Molecular Belts Based on 3D Benzannulene Systems.
Fragments of Fullerenes and Carbon Nanotubes 2011, 311−342.
(18) Matsuo, Y.; Tahara, K.; Sawamura, M.; Nakamura, E. Creation
of Hoop- and Bowl-Shaped Benzenoid Systems by Selective
Detraction of [60]Fullerene Conjugation. [10]Cyclophenacene and
Fused Corannulene Derivatives. J. Am. Chem. Soc. 2004, 126, 8725−
8734.
(40) Chanda, T.; Verma, R. K.; Singh, M. S. InCl3-driven
Regioselective Synthesis of Functionalized/Annulated Quinolines:
Scope and Limitations. Chem. - Asian J. 2012, 7, 778−87.
(41) Eisch, J. J.; Yu, K.; Rheingold, A. L. 6,12-Diphenyldibenzo[b,
f][1,5]diazocine as an Electron-Capture Agent: Efficient Mechanistic
Probe for SET Processes and Reagent for the Oxidative Dimerization
of Benzylic Organometallics. Eur. J. Org. Chem. 2012, 2012, 3165−
3171.
(42) Cho, S. K.; Song, J. H.; Lee, E. J.; Lee, D.-H.; Hahn, J.-T.; Jung,
D.-I. Quinolines Formation by Condensation of Heteroaromatic
Ketones and 2-Aminobenzophenones under MW Irradiation. Bull.
Korean Chem. Soc. 2015, 36, 2746−2749.
(43) Li, Z. Y.; Pan, Y.; Jin, L. L.; Yin, Y.; Yang, B. Z.; Sun, X. Q.
Chiral Exploration of 6,12-Diphenyldibenzo[b, f][1,5]diazocine with
Stable Conformation. Chirality 2017, 29, 134−139.
(19) Povie, G.; Segawa, Y.; Nishihara, T.; Miyauchi, Y.; Itami, K.
Synthesis of a Carbon Nanobelt. Science 2017, 356, 172.
(20) Povie, G.; Segawa, Y.; Nishihara, T.; Miyauchi, Y.; Itami, K.
Synthesis and Size-Dependent Properties of [12], [16], and [24]
Carbon Nanobelts. J. Am. Chem. Soc. 2018, 140, 10054−10059.
(21) Cheung, K. Y.; Gui, S.; Deng, C.; Liang, H.; Xia, Z.; Liu, Z.;
Chi, L.; Miao, Q. Synthesis of Armchair and Chiral Carbon
Nanobelts. Chem 2019, 5, 838−847.
2720
https://dx.doi.org/10.1021/jacs.1c00409
J. Am. Chem. Soc. 2021, 143, 2716−2721

Journal of the American Chemical Society
pubs.acs.org/JACS
Communication
(44) Yaragorla, S.; Pareek, A. Regioselective Intramolecular
Annulations of Ambident β-Enamino Esters: A Diversity-oriented
Synthesis of Nitrogen-containing Privileged Molecules. Tetrahedron
Lett. 2018, 59, 909−913.
(45) Liu, S.; Jiang, P.; Song, G.; Liu, R.; Zhu, H. Synthesis and
Optical Properties of a Series of Thermally Stable Diphenylanthrazo-
lines. Dyes Pigm. 2009, 81, 218−223.
(46) Huang, R.; Phan, H.; Herng, T. S.; Hu, P.; Zeng, W.; Dong, S.
Q.; Das, S.; Shen, Y.; Ding, J.; Casanova, D.; Wu, J. Higher Order)-
Conjugated Polycyclic Hydrocarbons with Open-Shell Singlet
Ground State: Nonazethrene versus Nonacene. J. Am. Chem. Soc.
2016, 138, 10323−30.
(47) Wolfe, J. P; Åhman, J.; Sadighi, J. P; Singer, R. A; Buchwald, S.
L An Ammonia Equivalent for the Palladium-Catalyzed Amination of
Aryl Halides and Triflates. Tetrahedron Lett. 1997, 38, 6367−6370.
(48) Pinal, R. Effect of Molecular Symmetry on Melting Temper-
ature and Solubility. Org. Biomol. Chem. 2004, 2, 2692−2699.
(49) Venkataraman, D.; Lee, S.; Zhang, J.; Moore, J. S. An organic
solid with wide channels based on hydrogen bonding between
macrocycles. Nature 1994, 371, 591−593.
(50) Rosselli, S.; Ramminger, A.-D.; Wagner, T.; Silier, B.; Wiegand,
S.; Haussler, W.; Lieser, G.; Scheumann, V.; Hoger, S. Coil-ring-coil
block copolymer as building blocks for supramolecular hollow
cylindrical brushes. Angew. Chem., Int. Ed. 2001, 40, 3138−3141.
(51) Gleiter, R.; Werz, D. B.; Rausch, B. J. A world beyond hydrogen
bonds? -Chalcogen-chalcogen interactions yielding tubular structures.
Chem. - Eur. J. 2003, 9, 2676−2683.
(52) Klod, S.; Kleinpeter, E. Ab Initio Calculation of the Anisotropy
Effect of Multiple Bonds and the Ring Current Effect of Arenes-
application in Conformational and Configurational Analysis. J. Chem.
Soc. Perkin Trans. 2. 2001, 1893−1898.
(53) Lu, T.; Chen, F. Multiwfn: A Multifunctional Wavefunction
Analyzer. J. Comput. Chem. 2012, 33, 580−592.
̌
(54) Camacho Gonzalez, J.; Munoz-Castro, A. Alternation of
Aromatic-nonaromatic Rings in Belt-like Structures. The Behavior
of [6.8]3Cyclacene in Magnetic Fields. Phys. Chem. Chem. Phys. 2015,
17, 17023−17026.
(55) Ni, Y.; Gopalakrishna, T. Y.; Phan, H.; Kim, T.; Herng, T. S.;
Han, Y.; Tao, T.; Ding, J.; Kim, D.; Wu, J. 3D Global Aromaticity in a
Fully Conjugated Diradicaloid Cage at Different Oxidation States.
Nat. Chem. 2020, 12, 242−248.
2721
https://dx.doi.org/10.1021/jacs.1c00409
J. Am. Chem. Soc. 2021, 143, 2716−2721