Deep blue fluorescent material with a narrow FWHM based on indolo[3,2,1-jk]carbazol/pyrimidine hybrids

Article abstract of DOI:10.1016/j.tet.2021.132049

A series of blue fluorescent materials containing electron accepting pyrimidine and electron donating bis(biphenyl)amine, diphenylcarbazole, and diphenylindolo[3,2,1-jk]carbazole moieties were synthesized in moderate yields, and their optical and electroc

Full text of DOI:10.1016/j.tet.2021.132049

Tetrahedron 86 (2021) 132049
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Deep blue fluorescent material with a narrow FWHM based on indolo
[3,2,1-jk]carbazol/pyrimidine hybrids
, c, *
Yasuhide Hiraga a, Rempei Kuwahara a, Taizo Hatta b
a Hirata Corporation, 111, Hitotsugi, Ueki, Kita-ku, Kumamoto, 861-0198, Japan
b Department of Nanoscience, Faculty of Engineering, Sojo University, 4-22-1, Ikeda, Nishi-ku, Kumamoto, 860-0082, Japan
c Kumamoto Institute for Photo-Electro Organics (PHOENICS), 3-11-38 Higashi-machi, Higashi-ku, Kumamoto, 862-0901, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of blue fluorescent materials containing electron accepting pyrimidine and electron donating
bis(biphenyl)amine, diphenylcarbazole, and diphenylindolo[3,2,1-jk]carbazole moieties were synthe-
sized in moderate yields, and their optical and electrochemical properties were investigated. Dipheny-
lindolo[3,2,1-jk]carbazole was revealed to be a promising building block for deep blue fluorescent
materials with a very narrow full width at half maximum.
Received 21 October 2020
Received in revised form
17 February 2021
Accepted 19 February 2021
Available online 5 March 2021
© 2021 Elsevier Ltd. All rights reserved.
Keywords:
Blue fluorescent materials
Blue emitter
Indolocarbazole
Full width at half maximum
Organic light emitting diodes
1. Introduction
and hole transport materials for organic electronics devices [12].
Furthermore, the carbazole skeleton is used as a building block for
Small-molecule fluorescent dyes are widely utilized for various
applications such as fluorescent indicators [1], fluorescent probes
for bioimaging [2], fluorescent sensors for metal ions [3], solar cells
[4], organic laser dyes [5], and emitting materials of organic light
emitting diodes (OLEDs) [6]. Therefore, several research studies
have been actively conducted on the development of novel func-
tional building blocks and into the optimization of molecular
structures to create small-molecule materials with desired lumi-
nescent properties for application in various fields.
emitting materials that exhibit thermally activated delayed fluo-
rescence (TADF), where Adachi et al. developed TADF
polycarbazolyl-substituted dicyanobenzenes and successfully
realized highly efficient OLEDs [13].
Phosphorescent materials have recently become the dominant
emitting materials of OLEDs, while the development of TADF ma-
terials [14] and hyperfluorescence systems [15] has focused on
fluorescent materials, as TADF materials have already achieved
comparable external quantum efficiencies to those of phospho-
rescent materials. However, the development of deep blue emitting
materials for OLEDs, using either TADF materials or conventional
fluorescent materials, remains a challenge, and so the development
of blue OLEDs exhibiting higher color gamuts and improved color
rendering capabilities is desirable [6b,16]. Thus, the combination of
a compact conjugation system, a high fluorescent quantum yield,
and stability against a high excitation energy, which are required to
achieve deep blue emission, is difficult to achieve [16].
In the field of organic electronics,
p-conjugated N-containing
heteroaromatic compounds are essential as organic semiconductor
materials for OLEDs [7], organic field-effect transistors (OFETs) [8],
organic nonlinear optical devices (ONLOs) [9], and organic photo-
voltaics (OPVs) [10]. In particular, the carbazole skeleton, as rep-
resented
by
CBP
(4,40-di(9H-carbazol-9-yl)-1,10-biphenyl)
derivatives [11] and PVK (polyvinylcarbazole) has been most
extensively used as a functional building block of host materials
In this context, several reports have been published into the
development of deep blue emitters exhibiting high fluorescent
quantum yields through the combination of a small aromatic donor
and an acceptor [17]. This type of ambipolar architecture is suitable
for emitting dopants in OLEDs because it acts as a charge trapping
* Corresponding author. Department of Nanoscience, Faculty of Engineering, Sojo
University, 4-22-1, Ikeda, Nishi-ku, Kumamoto, 860-0082, Japan.
E-mail addresses: y_hiraga@hirata.co.jp (Y. Hiraga), r_kuwahara@hirata.co.jp
(R. Kuwahara), hatta@nano.sojo-u.ac.jp (T. Hatta).
https://doi.org/10.1016/j.tet.2021.132049
0040-4020/© 2021 Elsevier Ltd. All rights reserved.

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
1
2
2
3
PhICz-Pyr
PhCz-Pyr
BBA-Pyr
BBA-Pyr
Fig. 1. Molecular structures of BBA-Pyr, PhCz-Pyr, and PhICz-Pyr.
2
site in the emitting layer, and effective electron-hole recombination
at the dopant is achieved. In addition, the distinct donor/acceptor
architecture provides a small energy gap between S1 and T1, and so
TADF can be expected to occur [18].
5
4
However, the key structural feature of a typical TADF molecule is
usually a diphenylamine or 9H-carbazole/acceptor hybrid, and so
further investigation is required to find a more effective building
block. Recently, it was revealed that indolo[3,2,1-jk]carbazole not
only functions as an electron donor for ambipolar hosts [19], but
that it also acts as an electron acceptor for blue TADF emitters [20].
Therefore, indolo[3,2,1-jk]carbazole can be considered particularly
attractive and promising as a fully planar ambipolar building block;
however, the number of reports into its application as a blue
emitter for OLEDs are limited.
6
PhCz-Pyr
Scheme 1. Syntheses of BBA-Pyr and PhCz-Pyr.
Thus, we herein focus on indolo[3,2,1-jk]carbazole due to its
wide band gap and distinctive structure, and a novel emitter PhICz-
Pyr is developed through its combination with pyrimidine. Ana-
logues bearing the conventional amine and carbazole units instead
of indolo[3,2,1-jk]carbazole, i.e., BBA-Pyr and PhCz-Pyr, are also
synthesized, and the three compounds are compared to determine
the applicability of indolo[3,2,1-jk]carbazole as a building block for
an ambipolar deep blue emitter (Fig. 1).
7
8
9
10
2. Results and discussions
The only structural differences between the three molecules
presented in Fig. 1 are the presence of intramolecular CeC bonds
that neighbor the CeN bonds in the electron donating moiety. Thus,
a comparison of the properties of these materials provides pure
information relating to the effect of the ortho-linkage through the
application of increasingly planarized triarylamine donors to a
pyrimidine acceptor.
11
12
2
The synthetic routes to BBA-Pyr and PhCz-Pyr are shown in
Scheme 1.
PhICz-Pyr
Initially, an aldol condensation between acetophenone and 4-
bromobenzaldehyde gave bromochalcone 1, and this was fol-
lowed by cyclization with benzamidine to afford the common
precursor 2 for BBA-Pyr, PhCz-Pyr, and PhICz-Pyr. BBA-Pyr was
synthesized by the Suzuki-Miyaura coupling reaction of 2 and
dibiphenylaminophenyboronic acid 3 in a moderate yield. The
same coupling reaction of 2 and 1,3,2-dioxaborinanylphenyl-9H-
carbazole 4 gave pyrimidinylbiphenyl-9H-carbazole 5, which was
followed by bromination and coupling with phenylboronic acid to
afford PhCz-Pyr in a similar yield as BBA-Pyr.
The synthesis of PhICz-Pyr was performed according to the
procedure outlined in Scheme 2. The nucleophilic aromatic sub-
stitution of 2-fluoronitrobenzene with potassium carbazolide
afforded 9-(2-nitrophenyl)-9H-carbazole (7). This was followed by
bromination, a Suzuki-Miyaura coupling reaction with phenyl-
boronic acid, and reduction using Pd/C-hydrazine to give 9-(2-
aminophenyl)-3,6-diphenyl-9H-carbazole (10). Diazotization and
13
Scheme 2. Synthesis of PhICz-Pyr.
subsequent pyrolysis of 10 afforded 2,11-diphenylindolo[3,2,1-jk]
carbazole (11), which was converted to 2,11-diphenyl-5-
dioxaborolanylindolo[3,2,1-jk]carbazole 13 by bromination and
reaction with bis(pinacolato)diboron using a Pd(II) catalyst. PhICz-
Pyr was synthesized by the Suzuki-Miyaura coupling reaction be-
tween 2 and 13 in a moderate yield.
These compounds were thermally stable and easily purified by
sublimation. Thus, all analyses were performed using sublimed
compounds. Glass transition temperature (Tg) of PhICz-Pyr
couldn’t be determined due to high crystallinity, while BBA-Pyr
and PhCz-Pyr were determined to 123 and 142 ꢀC respectively on
2

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
Table 1
Thermal and optical properties of BBA-Pyr, PhCz-Pyr, PhICz-Pyr and TBPe as a reference.
b
d
e
e
e
e
Compounds
Tm/oC a
Tg/oC a
Td/oC
D
E(S1eS0)/eV c
DE(T1-S0)/eV
4e
lem/nm
CIE1931x
CIE1931y
FWHM/meV (nm)
BBA-Pyr
PhCz-Pyr
PhICz-Pyr
TBPe
253
310
358
123
142
n.d.
447
459
478
2.64
2.95
2.95
2.68 [22]
2.55
2.70
2.83
1.53[22]
0.81
0.75
0.52
452
412
404
465
0.133
0.146
0.154
0.125
0.107
0.051
0.034
0.225
48.4 (60)
49.2 (61)
26.6 (33)
46.8 (58)
f
f
f
f
-
-
-
-
a
determined by DSC measurement.
b
c
d
e
f
5% weight loss on TG measurement under N2.
determined by onset wavelength on UV/Vis absorption spectrum.
determined by highest energy peak of phosphorescence spectrum.
measured in 1 ꢁ 10-8 M toluene solution.
- sign means not measured.
BBA-Pyr
PhCz-Pyr
PhICz-Pyr
BBA-Pyr
PhCz-Pyr
PhICz-Pyr
Fig. 2. Spatial distributions of the HOMO and LUMO molecular orbitals of BBA-Pyr,
PhCz-Pyr, and PhICz-Pyr determined by DFT calculations (structural optimization:
B3LYP/6-31G*; energy calculation: CAM-B3LYP/6e311þþG**).
DSC (Table 1, Figure S56). The thermal decomposition temperature
(Td) determined on TG were 447, 459, and 458 ꢀC for BBA-Pyr,
PhCz-Pyr, and PhICz-Pyr respectively (Table 1, Figure S57), and the
tendency corresponds to structural rigidity.
The spatial distributions of the HOMOs and LUMOs calculated by
the Gaussian 09 molecular simulation program are illustrated in
Fig. 2. The density functional theory (DFT) calculation was per-
formed using a new hybrid exchangeecorrelation functional using
the Coulomb-attenuating method (CAM-B3LYP/6e311þþG**).[21]
For all compounds, the HOMOs were localized on the electron
donating triarylamine and carbazole moieties, while the LUMOs
were localized on the electron accepting pyrimidine unit. PhCz-Pyr
showed the most localized and spatially separated molecular or-
bitals, and the tendency toward localization on PhICz-Pyr was the
weakest. The dihedral angle of optimized structure between donor
and acceptor units were 40ꢀ, 54ꢀ, and 0ꢀ respectively, and are in
good agreement with the tendency of molecular orbital (MO)
localization.
The ultraviolet/visible (UV/Vis) absorption spectral differences
of these compounds clearly reflect their structural features. More
specifically, the optical bandgaps (DE(S1eS0)) estimated from the
wavelengths of the absorption onsets were 2.64, 2.95, and 2.95 eV
for BBA-Pyr, PhCz-Pyr, and PhICz-Pyr, respectively (Fig. 3b and
Table 1). These values indicate that the HOMO level of the bis(bi-
phenyl)amino group is significantly shallower than those of the
diphenylcarbazole and diphenylindolo[3,2,1-jk]carbazole groups.
Fig. 3. a) UV/Vis absorption spectra of BBA-Pyr, PhCz-Pyr, and PhICz-Pyr, and b) an
enlarged view around the absorption onset (dichloromethane, 1 ꢁ 10ꢂ5 M, 10 mm
width cell).
2.73 eV for BBA-Pyr, PhCz-Pyr, and PhICz-Pyr respectively (Table 1,
Figure S58). Interestingly,
DE(T1-S0) of PhICz-Pyr was comparable
with PhCz-Pyr although its conjugated planar architecture.
The fluorescence spectra of diluted toluene solutions
(1.0 ꢁ 10ꢂ8 M) of these compounds and of 2,5,8,11-tetra-tert-
butylperylene (TBPe) for comparison are shown in Fig. 4. BBA-Pyr
exhibited its emission spectrum at the longest wavelength region
among the various compounds, with the exception of TBPe. This
result is reasonable since it also has the narrowest optical bandgap.
In contrast, PhICz-Pyr showed an extremely sharp emission spec-
trum with an FWHM of only 33 nm, which is approximately half
that of the other compounds, and the peak wavelength was
significantly shorter than that of PhCz-Pyr, although the optical
bandgaps of these compounds are identical (Fig. 4a, Table 1). This
result is presumably due to the effective suppression of vibrational
The triplet excitation energies (
DE(T1-S0)) determined by the
highest energy peak of phosphorescent spectra were 2.55, 2.70, and
3

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
Fig. 4. a) Normalized fluorescence spectra of BBA-Pyr, PhCz-Pyr, PhICz-Pyr, and TBPe
in toluene, and b) their CIE coordinates. (1 ꢁ 10ꢂ8 M, lex ¼ 365 nm).
relaxation by the rigid backbone of indolo[3,2,1-jk]carbazole. The
ꢀ
Commission Internationale de l’Eclairage (CIE) coordinates are
(0.133, 0.107), (0.146, 0.051), and (0.154, 0.034) for BBA-Pyr, PhCz-
Pyr, and PhICz-Pyr, respectively (Fig. 4b, Table 1). Notably, PhCz-
Pyr and PhICz-Pyr exhibited a small CIE(y) of <0.1, which is
required for emitting materials of high color gamut displays. In
addition, the fluorescence quantum yield (4) of PhICz-Pyr (0.52)
was significantly lower than those of BBA-Pyr (0.81) and PhCz-Pyr
(0.75) (Table 1), which suggests that the electronic structure of
indolo[3,2,1-jk]carbazole is radically different from those of the
amine and 9H-carbazole derivatives.
Fig. 5. Effect of oxygen on fluorescence spectra: a) BBA-Pyr; b) PhCz-Pyr c) PhICz-Pyr
(toluene, 1 ꢁ 10ꢂ8 M, lex ¼ 365 nm).
assumed to this behavior.
These results suggest that these compounds exhibit reverse
intersystem crossing (RISC), and it can be supported by small DE(S1-
T1) of these compounds (90, 250, and 120 meV for BBA-Pyr, PhCz-
Pyr, and PhICz-Pyr, Table 1). Thus, it was suggested that the small
E(S1-T1) of PhICz-Pyr resulted in a large KISC (intersystem
In order to discuss the influence of triplet exciton, the effect of
oxygen on fluorescence spectra was investigated. At first, the
fluorescence spectra of toluene solutions were recorded under air.
Then the solutions were deaired by bubbling of toluene-saturated
N2 gas for 5 min, and the measurements were performed imme-
diately. After that, the solutions were exposed to air for 10 min and
the spectra were recorded.
D
crossing) and a large KRISC and caused the low fluorescence
quantum yield of PhICz-Pyr.
The fluorescent spectra of these compounds demonstrated
solvatochromism, and the degrees of spectral dependence on the
polarity of the solvents were both significant and distinct (Fig. 6). In
order to discuss about spectral intensity, the excitation wavelength
was set to 365 nm which is the wavelength at which no solvent
absorption and the molar extinction coefficients of all compounds
are unaffected by the solvent (Figure S59). More specifically, PhCz-
Pyr exhibited the most remarkable spectral change, and emission
For all cases, the increasing of fluorescent intensity was
observed upon N2 bubbling, and no spectral difference was
confirmed in comparison with the first and last measurements
performed under air (Fig. 5). The increasing percentages of fluo-
rescent intensity were 10%, 5%, and 20% for BBA-Pyr (Fig. 5a), PhCz-
Pyr (Fig. 5b), and PhICz-Pyr (Fig. 5c) respectively, and PhICz-Pyr
exhibited the most significant change among them. Therefore, the
less fluorescence quantum yield (4) of PhICz-Pyr under air can be
4

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
BBA-Pyr
PhCz-Pyr
PhICz-Pyr
BBA-Pyr
PhCz-Pyr
PhICz-Pyr
Fig. 7. Electrochemical analyses of BBA-Pyr, PhCz-Pyr, and PhICz-Pyr: a) Normalized
cyclic voltammograms at a scan rate of 100 mV/s; b) normalized differential pulse
voltammograms (dichloromethane, 1 ꢁ 10ꢂ3 M for BBA-Pyr and PhICz-Pyr, 1 ꢁ 10ꢂ4
M
for PhICz-Pyr, 0.1 M TBA-PF6 supporting electrolyte, glassy carbon working electrode).
pulse voltammetry and were estimated to be 0.47/ꢂ2.30 V, 0.78/
ꢂ2.27 V, and 0.90/ꢂ2.27 V versus a ferrocene/ferrocenium refer-
ence for BBA-Pyr, PhCz-Pyr, and PhICz-Pyr, respectively (Fig. 7b).
The first oxidation potentials were reflected by the ionization en-
ergies of their electron donating moieties; bis(biphenyl)amine,
diphenylcarbazole, and diphenylindolo[3,2,1-jk]carbazole; while
the first reduction potentials were almost equal. These results
indicate that the HOMO energies of BBA-Pyr, PhCz-Pyr, and PhICz-
Pyr decrease in this order, and the functions of the donors and
acceptors are well-separated, as supported by the DFT calculation
results.
Fig. 6. Solvatochromism of fluorescence spectra of a) BBA-Pyr, b) PhCz-Pyr, and c)
PhICz-Pyr in toluene, dichloromethane, and DMF (1 ꢁ 10ꢂ8 M, lex ¼ 365 nm).
was almost suppressed even in dichloromethane (Fig. 6b). BBA-Pyr
showed a weaker emission spectrum at a longer wavelength region
in dichloromethane than in toluene, and emission was suppressed
in the polar DMF (Fig. 6a). In contrast, PhICz-Pyr exhibited emis-
sion even in DMF, and the spectra showed a bathochromic shift
with increasing solvent polarity (Fig. 6c). These results suggest that
the strength of electron donation by indolo[3,2,1-jk]carbazole is
weak, and the N-connected carbazole realizes clear separation of
the molecular orbitals due to its large dihedral angle between the
carbazole ring and the N-connected aromatic ring.
3. Conclusion
In conclusion, a series of fluorescent materials exhibiting a
ambipolar architecture composed of an electron accepting pyrim-
idine unit and an aromatic donor with a similar molecular geom-
etry was developed. The compound bearing an indolo[3,2,1-jk]
carbazole donor exhibited a distinct fluorescent behavior against
the well-known carbazole and amine based derivatives, and a deep
blue emission with a particularly small FWHM was achieved. These
distinctive properties were derived from the extremely deep
HOMO level of indolo[3,2,1-jk]carbazole, in addition to its struc-
tural rigidity. Therefore, the indolo[3,2,1-jk]carbazole-based ambi-
polar architecture can be considered promising in the quest for
future effective deep and pure blue emitters. Investigations to
These compounds exhibited perfectly reversible oxidation and
reduction waves by cyclic voltammetry, which is considered to be
evidence of electrochemical stability (Fig. 7a). The first oxidation
and reduction potentials were determined based on differential
5

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
modify the structure of PhICz-Pyr are in progress, in order to
improve the luminescent properties of the compound.
The solvent was removed under reduced pressure and the residue
was purified by a silica gel column chromatography (eluted with
dhchloromethane/hexane mixture (2:1 (v/v)) and recrystallized
from dichloromethane/ethanol to give 4-(4-bromophenyl)-2,6-
diphenylpyrimidine (2) in 68% yield (4.58 g, 11.84 mmol) as a
colorless powder.
4. Experimental section
4.1. General information
m.p. 164e165 ꢀC.
All reagents (GR grade) were purchased from Tokyo Chemical
Industry Co., Ltd. All melting points were measured with a Yana-
gimoto Micro Melting Point apparatus MP-500P and are uncor-
rected. Infrared (IR) spectra were recorded on a PerkinElmer
Spectrum 100 FT-IR spectrophotometer. Nuclear magnetic reso-
nance (NMR) spectra were recorded on JEOL JNM-ECS400 spec-
trometers (1H: 400 MHz, 13C: 100.5 MHz) using tetramethylsilane
(TMS) as an internal standard, and with measurement being carried
out in chloroform-d unless otherwise indicated. Electron ionization
(EI-) and fast atom bombardment (FAB-) mass spectra were recor-
ded on a JEOL JMS-700 mass spectrometer at the Evaluation Center
of Materials Properties and Function in the Institute for Materials
Chemistry and Engineering attached to Kyushu University. UV-VIS
absorption spectra were recorded on JASCO V-670 spectropho-
tometer. Fluorescence (FL) and phosphorescence (PL) spectra were
recorded on a PerkinElmer LS55 Luminescence spectrophotometer.
Differential scanning calorimetry (DSC) and thermal gravimetry
(TG) were performed on Rigaku Thermo Plus 2 instrument. Cyclic
and differential pulse voltammograms were recorded on a BAS ALS
model 612D electrochemical analyzer. Absolute fluorescence
quantum yields were determined on a HAMAMATSU C9920-02
instrument. Elemental analyses were carried out using a Yanaco
CHN Corder MT-6 analyzer at the Sub micro element analysis
research center of A Rabbit Science Japan Co., Ltd. Column chro-
matography was carried out on silica gel (Fuji Silysia, BW-300).
Temperature gradient sublimation purification was performed us-
ing an ULVAC TRS-1S.
IR (ATR, cmꢂ1): 3032, 1588, 1567, 1523, 1487, 1456, 1445, 1408,
1389,1379, 1359,1312,1296,1237,1199, 1172,1109,1072,1023,1007,
932, 868, 832, 825, 807, 776, 749, 715, 686, 654.
1H NMR (400 MHz, CDCl3):
d 7.51e7.55 (m, 6H, 3,4,5-H in 2-ph
and 3,4,5-H in 6-ph), 7.66 (d, J ¼ 8.4 Hz, 2H, 3,5-H in 4-ph), 7.93
(s, 1H, 5-H), 8.13 (d, J ¼ 8.4 Hz, 2H, 2,6-H in 4-ph), 8.25 (d, J ¼ 7.5 Hz,
2H, 2,6-H in 6-ph), 8.68 (d, J ¼ 7.4 Hz, 2H, 2,6-H in 2-ph).
13C NMR (100.5 MHz, CDCl3):
d 109.87, 125.37, 127.25, 128.43,
128.74, 128.89, 130.72, 130.86, 132.06, 136.37, 137.30, 137.91,163.51,
164.54, 164.93.
MS (EI): m/z 386 (79Br), 388 (81Br) ([M]þ).
4.2.3. N,N-Di([1,10-biphenyl]-4-yl)-4’-(2,6-diphenylpyrimidin-4-
yl)-[1,10-biphenyl]-4-amine (BBA-Pyr)
Compound 2 (176 mg, 0.45 mmol) and (4-(di([1,10-biphenyl]-4-
yl)amino)phenyl)boronic acid (3) (200 mg, 0.45 mmol) were added
to the mixture of toluene (5 mL), ethanol (2 mL), and 2 M aq. so-
dium carbonate (5 mL). After the mixture was refluxed under ni-
trogen atmosphere for
5 min, tetrakis(triphenylphosphine)
palladium(0) (149 mg, 0.13 mmol) was added to the mixture and
further refluxed for 4 h. The reaction mixture was cooled to room
temperature and washed with water (20 mL). The organic phase
was dried over anhydrous sodium sulfate and poured into meth-
anol. The precipitates were collected by filtration. The obtained
solid was purified by silica gel column chromatography (eluted
with dichloromethane/hexane mixture (2 : 1 (v/v)) and recrystal-
lization from dichloromethane/ethanol to give N,N-di([1,10-
biphenyl]-4-yl)-4’-(2,6-diphenylpyrimidin-4-yl)-[1,10-biphenyl]-4-
amine (BBA-Pyr) in 63% yield (200 mg, 0.28 mmol) as pale yellow
powder.
4.2. Synthesis
4.2.1. (E)-3-(4-Bromophenyl)-1-phenylprop-2-en-1-one (1)
To a solution of acetophenone (3.25 g, 27.02 mmol) and 4-
bromobenzaldehyde (5.00 g, 27.02 mmol) in methanol (50 mL)
was added a solution of sodium hydroxide (216 mg, 5.40 mmol) in
water (5 mL). After the mixture was stirred at room temperature for
6 h, the precipitates were collected by filtration and washed with
methanol to give (E)-3-(4-bromophenyl)-1-phenylprop-2-en-1-
one (1) in 94% yield (7.29 g, 25.40 mmol) as faint yellow needles.
m.p. 97e98 ꢀC.
m.p. 246e247 ꢀC.
IR (ATR, cmꢂ1): 3030, 1598, 1588, 1567, 1516, 1482, 1447, 1395,
1362, 1320, 1292, 1278, 1263, 1177, 1111, 1074, 1026, 1005, 966, 922,
873, 820, 757, 744, 721, 689, 655.
1H NMR (400 MHz, CDCl3):
d 7.25e7.28 (m, 6H, ArH), 7.32 (t,
J ¼ 7.3 Hz, 2H, 40-H at biphenyl), 7.43 (t, J ¼ 7.5 Hz, 4H, 30,50-H in
biphenyl), 7.52e7.53 (m, 16H, ArH), 7.79 (d, J ¼ 8.4 Hz, 2H, 3,5-H in
4-ph at pyrimidine), 8.05 (s, 1H, 4-H in pyrimidine), 8.30 (dd, J ¼ 1.7,
7.6 Hz, 2H, 2,6-H in 6-ph at pyrimidine), 8.37 (d, J ¼ 8.4 Hz, 2H, 2,6-
H in 4-ph at pyrimidine), 8.74 (dd, J ¼ 1.7, 7.8 Hz, 2H, 2,6-H in 2-ph
at pyrimidine).
IR (ATR, cmꢂ1): 3057, 3028, 1656, 1600, 1583, 1575, 1560, 1496,
1481, 1449, 1396, 1364, 1334, 1289, 1276, 1216, 1179, 1159, 1106,
1069, 1035, 1006, 995, 982, 955, 892, 874, 826, 791, 760, 727, 691,
665.
13C NMR (100.5 MHz, CDCl3):
d 110.00, 124.11, 124.64, 126.70,
126.95, 127.28, 127.72, 127.91, 127.96, 128.42, 128.49, 128.77, 128.88,
130.59, 130.71, 134.33, 135.88, 135.91, 137.61, 138.23, 140.53, 142.90,
146.68, 147.43, 164.27, 164.50, 164.68.
1H NMR (400 MHz, CDCl3):
d 7.39e7.42 (m, 3H, 3,4,5-H in 3-ph),
7.46 (d, J ¼ 15.6 Hz, 1H, 2-H), 7.61e7.64 (m, 4H, 3,5-H in 1-ph and
2,6-H in 3-ph), 7.80 (d, J ¼ 15.6 Hz, 1H, 3-H), 7.87 (d, J ¼ 7.9 Hz, 2H,
2,6-H in 1-ph).
HRMS (FAB, PEG1000 as external standard): m/z calcd for
C
52H37N3 [M]þ: 703.2987; found: 703.2986.
13C NMR (100.5 MHz, CDCl3):
d 121.43, 127.84, 128.47, 128.95,
129.97, 130.70, 131.88, 134.64, 136.88, 145.33, 189.25.
MS (FAB): m/z 287 (79Br), 289 (81Br) ([Mþ1]þ).
4.2.4. 9-(4’-(2,6-Diphenylpyrimidin-4-yl)-[1,10-biphenyl]-4-yl)-9H-
carbazole (5)
4.2.2. 4-(4-Bromophenyl)-2,6-diphenylpyrimidine (2)
Compound 2 (1.00 g, 2.58 mmol) and 9-(4-(5,5-dimethyl-1,3,2-
dioxaborinan-2-yl)phenyl)-9H-carbazole (4) (917 mg, 2.58 mmol)
were dissolved in toluene (10 mL). Ethanol (5 mL) and 2 M aq.
sodium carbonate (10 mL) were added to this solution, and the
mixture was refluxed under nitrogen atmosphere for 5 min. Tet-
rakis(triphenylphosphine)palladium(0) (149 mg, 0.13 mmol) was
added to this mixture and further refluxed for 4 h. Following this,
To a solution of 1 (5.00 g,17.41 mmol) in DMF (30 mL) was added
sodium carbonate (9.62 g, 69.64 mmol) and benzamidine hydro-
chloride (2.73 g, 17.41 mmol). The mixture was stirred at 70 ꢀC for
24 h and then poured into water (100 mL) and extracted with
dichloromethane (50 mL). The organic phase was washed with
water (50 mL x 2) and dried over anhydrous magnesium sulfate.
6

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
the reaction mixture was cooled to room temperature and washed
with water (30 mL). The organic phase was dried over anhydrous
magnesium sulfate, and the solvent was removed under reduced
pressure. The residue was purified by a silica gel column chroma-
tography (eluted with dichloromethane/hexane mixture (2:1 (v/v))
and recrystallized from dichloromethane/ethanol to give 9-(4’-(2,6-
diphenylpyrimidin-4-yl)-[1,10-biphenyl]-4-yl)-9H-carbazole (5) in
82% yield (1.16 g, 2.12 mmol) as a colorless powder.
room temperature, it was poured into water (100 mL) and extracted
with chloroform (50 mL). The organic phase was dried over anhy-
drous magnesium sulfate and the solvent was removed under
reduced pressure. The residue was purified by a silica gel column
chromatography (eluted with chloroform/hexane mixture (2:1 (v/
v)) to give 9-(4’-(2,6-diphenylpyrimidin-4-yl)-[1,10-biphenyl]-4-
yl)-3,6-diphenyl-9H-carbazole (PhCz-Pyr) in 76% yield (752 mg,
1.07 mmol) as a pale yellow powder.
m.p. 187e188 ꢀC.
m.p. 310e311 ꢀC.
IR (ATR, cmꢂ1): 3039, 1588, 1568, 1522, 1496, 1478, 1450, 1424,
1395, 1381, 1361, 1335, 1319, 1301, 1226, 1171, 1118, 1074, 1027, 1004,
969, 932, 914, 871, 844, 823, 775, 741, 722, 689, 666.
IR (ATR, cmꢂ1): 3035, 1600, 1588, 1568, 1521, 1495, 1474, 1458,
1423, 1363, 1312, 1296, 1280, 1267, 1232, 1172, 1135,1121, 1074, 1027,
1004, 970, 944, 930, 916, 879, 852, 843, 817, 805, 763, 745, 734, 688.
1H NMR (400 MHz, CDCl3):
d
7.31 (t, J ¼ 7.4 Hz, 2H, 3,6-H in
1H NMR (400 MHz, CDCl3):
d
7.36 (t, J ¼ 7.5 Hz, 2H, 4-H in 3,6-ph
carbazole), 7.44 (t, J ¼ 7.4 Hz, 2H, 2,7-H in carbazole), 7.49e7.58 (m,
8H, ArH), 7.68 (d, J ¼ 8.4 Hz, 2H, 3,5-H in 4-ph at pyrimidine), 7.87
(d, J ¼ 8.2 Hz, 2H, 3,5-H in biphenyl), 7.89 (d, J ¼ 8.4 Hz, 2H, 20,60-H
in biphenyl), 8.07 (s, 1H, 5-H in pyrimidine), 8.16 (d, J ¼ 7.4 Hz, 2H,
4,5-H in carbazole), 8.32 (dd, J ¼ 1.8, 7.5 Hz, 2H, 2,6-H in 6-ph at
pyrimidine), 8.42 (d, J ¼ 8.2 Hz, 2H, 2,6-H in biphenyl), 8.76 (dd,
J ¼ 1.8, 7.8 Hz, 2H, 2,6-H in 2-ph at pyrimidine).
at carbazole), 7.49 (t, J ¼ 7.5 Hz, 4H, 3,5-H in 3,6-ph at carbazole),
7.53e7.58 (m, 8H, ArH), 7.69e7.75 (m, 8H, ArH), 7.90 (d, J ¼ 8.2 Hz,
2H, 3,5-H in biphenyl), 7.94 (d, J ¼ 8.2 Hz, 2H, 20,60-H in biphenyl),
8.09 (s, 1H, 4-H in pyrimidine), 8.33 (d, J ¼ 7.8 Hz, 2H, 2,6-H in 6-ph
at pyrimidine), 8.42 (s, 2H, 4,5-H in carbazole), 8.45 (d, J ¼ 8.2 Hz,
2H, 2,6-H in biphenyl), 8.77 (d, J ¼ 7.8 Hz, 2H, 2,6-H in 2-ph at
pyrimidine).
13C NMR (100.5 MHz, CDCl3):
d
109.79, 110.11, 120.05, 120.33,
13C NMR (100.5 MHz, CDCl3):
d 110.13, 110.21, 118.90, 124.18,
123.47, 125.97, 127.27, 127.35, 127.47, 127.84, 128.44, 128.48, 128.89,
130.65, 130.77, 136.66, 137.38, 137.49, 138.12, 139.22, 140.74, 142.45,
164.09, 164.52, 164.75.
125.73, 126.63, 127.21, 127.30, 127.51, 127.89, 128.45, 128.50, 128.60,
128.79, 128.91, 130.67, 130.80, 133.81, 136.77, 137.31, 137.53, 138.15,
139.38, 140.66, 141.83, 142.41, 164.12, 164.57, 164.81.
HRMS (FAB): m/z calcd for C52H35N3 [M]þ: 701.2831; found:
701.2829.
HRMS (FAB): m/z calcd for C40H27N3 [M]þ: 549.2205; found:
549.2206.
4.2.5. 3,6-Dibromo-9-(4’-(2,6-diphenylpyrimidin-4-yl)-[1,10-
biphenyl]-4-yl)-9H-carbazole (6)
4.2.7. 9-(2-Nitrophenyl)-9H-carbazole (7)
To a solution of 9H-carbazole (20.00 g, 119.61 mmol) in DMF
(150 mL) was added potassium carbonate (33.06 g, 239.22 mmol)
and 2-nitrofluorobenzene (18.56 g, 131.57 mmol) under a nitrogen
atmosphere. The mixture was stirred at 70 ꢀC for 12 h and poured
into water (300 mL). The precipitates were collected by filtration.
The obtained solid was washed with water (200 mL) and methanol
(200 mL) to give 9-(2-nitrophenyl)-9H-carbazole (7) in 94% yield
(32.41 g, 112.43 mmol) as yellow needles.
To a solution of 5 (1.00 g, 1.82 mmol) in DMF (20 mL) was added
dropwise
a solution of N-bromosuccinimide (NBS, 648 mg,
3.64 mmol) in DMF (10 mL) over a period of 5 min at room tem-
perature. The reaction mixture was poured into methanol (50 mL)
and allowed to stand for 8 h. The precipitates were collected by
filtration and washed with methanol (100 mL) to give 3,6-dibromo-
9-(4’-(2,6-diphenylpyrimidin-4-yl)-[1,10-biphenyl]-4-yl)-9H-carba-
zole (6) in 91% yield (1.17 g, 1.66 mmol) as a colorless powder.
m.p. 253e255 ꢀC.
m.p. 154e155 ꢀC.
IR (ATR, cmꢂ1): 3051, 1604, 1573, 1523, 1497, 1477, 1453, 1443,
1369, 1350, 1334, 1316, 1300, 1228, 1184, 1150, 1122, 1108, 1086,
1039, 1019, 1002, 994, 957, 942, 917, 872, 849, 782, 748, 725, 704,
667.
IR (ATR, cmꢂ1): 3038, 1676, 1604, 1588, 1566, 1520, 1495, 1467,
1435, 1397, 1361, 1316, 1277, 1226, 1172, 1120, 1057, 1021, 1004, 939,
854, 822, 795, 775, 755, 740, 710, 685, 669.
1H NMR (400 MHz, CDCl3):
d
7.31 (d, J ¼ 8.7 Hz, 1,8-H in
1H NMR (400 MHz, CDCl3):
d
7.09 (d, J ¼ 8.0 Hz, 2H, 1,8-H), 7.28
carbazole), 7.51 (dd, J ¼ 1.9, 8.8 Hz, 2H, 2,7-H in carbazole),
7.51e7.58 (m, 8H, ArH), 7.83 (d, J ¼ 8.3 Hz, 2H, 3,5-H in biphenyl),
7.87 (d, J ¼ 8.4 Hz, 2H, 20, 60-H in biphenyl), 8.05 (s, 1H, 5-H in
pyrimidine), 8.18 (d, J ¼ 1.9 Hz, 2H, 4,5-H in carbazole), 8.30 (dd,
J ¼ 1.9, 7.5 Hz, 2H, 3,5-H in 6-ph at pyrimidine), 8.41 (d, J ¼ 8.3 Hz,
2H, 2,6-H in biphenyl), 8.75 (dd, J ¼ 1.9, 7.8 Hz, 2H, 2,6-H in 2-ph at
pyrimidine).
(t, J ¼ 7.2 Hz, 2H, 3,6-H), 7.36 (dd, J ¼ 7.2, 7.7 Hz, 2H, 2,7-H),
7.59e7.63 (m, 2H, 4,6-H in 2-ph), 7.77 (dd, J ¼ 7.6, 7.8 Hz, 1H, 5-H in
ph), 8.09e8.14 (m, 3H, 4,5-H and 3-H in ph).
13C NMR (100.5 MHz, CDCl3):
d 109.03, 120.53, 120.63, 123.81,
125.88, 126.28, 129.10, 131.21, 131.35, 134.19, 140.74, 147.35.
MALDI-TOF-MS (positive, dithranol): m/z calcd for C18H12N2O2:
288; found: 288 [Mþ].
13C NMR (100.5 MHz, CDCl3):
d 110.08, 111.50, 113.23, 123.27,
124.06, 127.21, 127.29, 127.50, 127.91, 128.46, 128.50, 128.72, 128.92,
129.45, 130.69, 130.83, 136.39, 136.92, 137.47, 138.11, 139.73, 139.97,
142.13, 163.99, 164.55, 164.80.
4.2.8. 3,6-Dibromo-9-(2-nitrophenyl)-9H-carbazole (8)
To a solution of 7 (25.00 g, 86.72 mmol) in DMF (150 mL) was
added dropwise a solution of NBS in DMF (33.96 g, 190.78 mmol/
150 mL) over a period of 20 min. The mixture was stirred at room
temperature for 4 h and poured into water (500 mL). The pre-
cipitates were collected by filtration and washed with methanol
(200 mL) to give 3,6-dibromo-9-(2-nitrophenyl)-9H-carbazole (8)
in 76% yield (29.40 g, 65.91 mmol) as yellow needles.
HRMS (FAB): m/z calcd for C40H25Br2N3 [M]þ: 705.0415; found:
705.0415.
4.2.6. 9-(4’-(2,6-Diphenylpyrimidin-4-yl)-[1,10-biphenyl]-4-yl)-3,6-
diphenyl-9H-carbazole (PhCz-Pyr)
Compound 6 (1.00 g, 1.41 mmol) and phenylboronic acid
(366 mg, 3.00 mmol) were dissolved in toluene (10 mL). Ethanol
(5 mL) and 2 M aq.sodium carbonate aq. (10 mL) and refluxed under
m.p. 202e203 ꢀC.
IR (ATR, cmꢂ1): 3083, 1599, 1523, 1495, 1466, 1429, 1362, 1318,
1297, 1285, 1230, 1179, 1157, 1142, 1123, 1089, 1057, 1020, 992, 961,
942, 932, 891, 876, 849, 817, 795, 777, 748, 727, 712, 676, 665.
nitrogen atmosphere for
5 min. Tetrakis(triphenylphosphine)
palladium(0) (162 mg, 0.14 mmol) was added to the mixture and
further refluxed for 6 h. After the reaction mixture was cooled to
1H NMR (400 MHz, CDCl3):
carbazole), 7.49 (dd, J ¼ 1.9, 8.6 Hz, 2H, 2,7-H in carbazole), 7.62 (d,
d
6.96 (d, J ¼ 8.6 Hz, 2H, 1,8-H in
7

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
J ¼ 7.7 Hz, 1H, 6-H in ph), 7.73 (t, J ¼ 7.7 Hz, 1H, 4-H in ph), 7.86 (t,
J ¼ 7.7 Hz, 1H, 5-H in ph), 8.17e8.19 (m, 3H, 4,5-H in carbazole and
3-H in ph).
4.2.11. 2,11-Diphenylindolo[3,2,1-jk]carbazole (11)
Compound 10 (10.00 g, 24.36 mmol) was dissolved in acetic acid
(100 mL). Concentrated sulfuric acid (10 mL) was slowly added to
this solution and cooled to 10 ꢀC. To this mixture was added
dropwise a solution of aq. sodium nitrite (1.73 g, 25.07 mmol/mL)
over a period of 15 min and the mixture was further stirred for
5 min. The obtained dark red solution was immediately heated to
the refluxing temperature and refluxed for 2 h. The reaction
mixture was cooled to room temperature and poured into water
(200 mL). The precipitates were collected by filtration, washed with
methanol (100 mL), purified by silica gel column chromatography
(eluted with chloroform), and recrystallized from dichloro-
methane/ethanol to give 2,11-diphenylindolo[3,2,1-jk]carbazole
(11) in 60% yield (5.75 g, 14.62 mmol) as a pale yellow powder.
m.p. 193e194 ꢀC.
13C NMR (100.5 MHz, CDCl3):
d 110.76, 113.87, 123.54, 124.38,
126.13, 129.80, 129.89, 130.21, 131.26, 134.50, 139.82, 147.17.
HRMS (EI): m/z calcd for C18H10Br2N2O2 [M]þ: 443.9109; found:
443.9108.
4.2.9. 9-(2-Nitrophenyl)-3,6-diphenyl-9H-carbazole (9)
Compound 8 (25.00 g, 56.04 mmol) and phenylboronic acid
(15.03 g, 123.29 mmol) were dispersed into a toluene/ethanol
mixture (5:1 (v/v), 100 mL) and 2 M aq. sodium carbonate (100 mL)
was added to it. After the mixture was refluxed for 5 min under
nitrogen atmosphere, tetrakis(triphenylphosphine) palladium(0)
(324 mg, 0.28 mmol) was added to it and further refluxed for 2 h.
The reaction mixture was poured into water (200 mL) and extrac-
ted with toluene (50 mL). The organic phase was dried over
anhydrous magnesium sulfate and the solvent was removed under
reduced pressure. The residue was purified by silica gel column
chromatography (eluted with toluene) and recrystallized from
acetone/methanol to give 9-(2-nitrophenyl)-3,6-diphenyl-9H-
carbazole (9) in 93% yield (22.96 g, 52.12 mmol) as an orange
powder.
IR (ATR, cmꢂ1): 3028, 1656, 1593, 1565, 1513, 1489, 1459, 1489,
1429, 1367, 1339, 1321, 1296, 1257, 1234, 1120, 1185, 1165, 1156, 1134,
1104, 1090, 1077, 1035, 1014, 967, 928, 885, 866, 813, 776, 760, 741,
731, 698, 675, 660.
1H NMR (400 MHz, CDCl3):
d
7.30 (t, J ¼ 7.5 Hz, 1H, 11-H),
7.34e7.39 (m, 2H, 4-H in 2,5-ph), 7.45e7.51 (m, 5H, ArH), 7.67e7.77
(m, 7H, ArH), 8.06 (d, J ¼ 7.7 Hz, 1H, 12-H), 8.13 (s, 1H, 1- or 3-H),
8.16 (s, 1H, 1- or 3-H), 8.25 (d, J ¼ 1.8 Hz, 1H, 4-H).
m.p. 150e151 ꢀC.
13C NMR (100.5 MHz, CDCl3):
d 112.35, 118.68, 119.30, 119.43,
IR (ATR, cmꢂ1): 3026, 1598, 1571, 1533, 1492, 1475, 1457, 1437,
1369, 1357, 1337, 1297, 1283, 1269, 1223,1185, 1162, 1143, 1130, 1088,
1076, 1040, 1019, 1010, 996, 967, 937, 915, 886, 859, 846, 810, 778,
755, 138, 729, 695.
121.85, 121.89, 123.28, 126.12, 126.71, 126.95, 127.05, 127.38, 128.37,
128.91, 128.98, 130.15, 130.68, 135.19, 137.69, 138.37, 139.04, 141.52,
143.47, 143.99.
HRMS (EI): m/z calcd for C30H19N [Mþ]: 393.1517; found:
393.1518.
1H NMR (400 MHz, CDCl3):
d
7.17 (d, J ¼ 8.5 Hz, 2H, 1,8-H in
carbazole), 7.34 (t, J ¼ 7.4 Hz, 2H, 4-H in 3,6-ph), 7.47 (t, J ¼ 7.7 Hz,
4H, 3,5-H in 3,6-ph), 7.63 (dd, J ¼ 1.8, 8.4 Hz, 2H, 2,7-H in carbazole),
7.66e7.71 (m, 6H, ArH), 7.84 (dt, J ¼ 1.5, 7.7 Hz,1H, 6-H in 9-ph), 8.19
(dd, J ¼ 1.6, 8.1 Hz, 1H, 3-H in 9-ph), 8.37 (d, J ¼ 1.7 Hz, 2H, 4,5-H in
carbazole).
4.2.12. 5-Bromo-2,11-diphenylindolo[3,2,1-jk]carbazole (12)
Compound 11 (5.00 g, 12.71 mmol) was dissolved in chloroform
(50 mL). To this solution was added dropwise a solution of NBS
(2.26 g, 12.71 mmol) in DMF (20 mL) at room temperature over a
period of 10 min. After the mixture was stirred for 8 h, chloroform
was removed under reduced pressure, and methanol (100 mL) was
added to the residue. The precipitates were collected by filtration
and washed with methanol (100 mL) to give 5-bromo-2,11-
diphenylindolo[3,2,1-jk]carbazole (12) in 97% yield (5.82 g,
12.33 mmol) as a colorless powder.
13C NMR (100.5 MHz, CDCl3):
d 109.56, 119.34, 124.61, 126.21,
126.86, 127.49, 128.92, 129.39, 131.41, 134.50, 134.55, 140.76, 141.81.
HRMS (EI): m/z calcd for C30H20N2O2 [M]þ: 440.1525; found:
440.1526.
4.2.10. 9-(2-Aminophenyl)-3,6-diphenyl-9H-carbazole (10)
Compound 9 (20.00 g, 45.40 mmol) was dispersed into ethanol
(150 mL), and 5% palladium carbon (500 mg) was added. Hydrazine
monohydrate (12.52 g, 0.25 mol) was added to the mixture and
refluxed for 28 h under nitrogen atmosphere. The reaction mixture
was hot-filtered to remove palladium carbon and allowed to stand
for 2 h at room temperature. The precipitates were collected by
filtration and washed with methanol (100 mL) to give 9-(2-
aminophenyl)-3,6-diphenyl-9H-carbazole (10) in 80% yield
(14.91 g, 36.32 mmol) as colorless plates.
m.p. 233e235 ꢀC.
IR (ATR, cmꢂ1): 3058, 3031, 1659, 1594, 1557, 1482, 1461, 1440,
1420, 1371, 1332, 1318, 1293, 1263, 1229, 1200, 1164, 1139, 1105,
1077, 1051, 1039, 1016, 1007, 961, 946, 932, 911, 885, 867, 832, 815,
790, 754, 743, 688, 664.
1H NMR (400 MHz, CDCl3):
d 7.36e7.41 (m, 2H, 4-H in ph),
7.47e7.53 (m, 6H, ArH), 7.65e7.70 (m, 6H, ArH), 8.04 (d, J ¼ 0.9 Hz,
1H, 1- or 3-H), 8.11 (s, 1H, 12-H), 8.13 (d, J ¼ 0.9 Hz, 1H, 1- or 3-H),
8.22 (s, 1H, 4-H).
m.p. 123e124 ꢀC.
13C NMR (100.5 MHz, CDCl3):
d 112.13, 113.07, 114.60, 117.31,
IR (ATR, cmꢂ1): 3475, 3380, 3061, 1728, 1628, 1614, 1597, 1508,
1498,1474,1458,1436,1365,1310,1296,1267,1233,1189,1172,1159,
1137, 1095, 1077, 1042, 1028, 1009, 984, 945, 912, 880, 844, 825, 759,
744, 736, 696, 671.
118.65, 119.33, 119.77, 121.75, 125.95, 126.11, 126.71, 127.01, 127.21,
128.14, 128.82, 128.85, 129.28, 130.41, 131.46, 135.37, 137.26, 137.82,
137.91, 141.15, 142.94, 143.91.
HRMS (EI): m/z calcd for C30H18BrN [Mþ]: 471.0623; found:
471.0623.
1H NMR (400 MHz, CDCl3):
d
3.61 (s, 2H, NH2), 6.94 (t, J ¼ 7.5 Hz,
1H, 5-H in 9-ph), 6.98 (d, J ¼ 8.5 Hz, 1H, 3-H in 9-ph), 7.24e7.36 (m,
6H, 1,8-H in carbazole, 4- and 6-H in 9-ph, and 4-H in 3,6-ph), 7.47
(t, J ¼ 7.7 Hz, 4H, 3,5-H in 3,6-ph), 7.66 (dd, J ¼ 1.7, 8.5 Hz, 2H, 2,7-H
in carbazole), 7.72 (d, J ¼ 7.7 Hz, 4H, 2,6-H in 3,6-ph), 8.40 (s, 2H,
4,5-H in carbazole).
4.2.13. 2,11-Diphenyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)-indolo[3,2,1-jk]carbazole (13)
Compound 12 (5.00 g, 10.58 mmol), bis(pinacolato)diboron
(2.79 g, 11.00 mmol), and potassium acetate (4.00 g, 40.75 mmol)
were added to degassed dimethyl sulfoxide (50 mL) under ni-
trogen atmosphere, and the mixture was heated to 100 ꢀC. To this
mixture was added [1,10-bis(diphenylphosphino)ferrocene]
dichloropalladium(II) dichloromethane adduct (433 mg,
13C NMR (100.5 MHz, CDCl3):
d 110.52, 116.64, 118.94, 122.16,
123.98,125.78,126.59,127.34,128.78,129.52,129.74,133.63,140.56,
141.93, 143.95.
HRMS (EI): m/z calcd for C30H22N2 [Mþ]: 410.1783; found:
410.1782.
8

Y. Hiraga, R. Kuwahara and T. Hatta
Tetrahedron 86 (2021) 132049
0.53 mmol). The mixture was stirred for 4 h at 100 ꢀC under ni-
trogen atmosphere. The reaction mixture was poured into water
(100 mL) and extracted with chloroform (50 mL). The organic
phase was washed with water (50 mL x 2) and dried over anhy-
drous magnesium sulfate. The solvent was removed under
reduced pressure, and the residue was purified by silica gel col-
umn chromatography (eluted with chloroform) and recrystal-
lized from dichloromethane/hexane to give 2,11-diphenyl-5-
(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)indolo[3,2,1-jk]
carbazole (13) in 75% yield (4.12 g, 7.94 mmol) as a colorless
powder.
Declaration of competing interest
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Acknowledgements
This work was supported in part by Regional Innovation Strat-
egy Support Program from the Ministry of Education, Culture,
Sports, Science and Technology of Japan.
m.p. 162e164 ꢀC.
IR (ATR, cmꢂ1): 3054, 3032, 2976, 2926, 1658, 1599, 1571, 1484,
1455, 1438, 1425, 1378, 1350, 1331, 1315, 1304, 1294, 1262, 1216,
1202, 1167, 1147, 1107, 1067, 1016, 966, 951, 917, 913, 882, 862, 847,
799, 758, 750, 699, 680, 664.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2021.132049.
1H NMR (400 MHz, CDCl3):
d 1.44 (s,12H, CH3), 7.36e7.41 (m, 2H,
4-H in ph), 7.47e7.59 (m, 4H, 3,5-H in ph), 7.71e7.77 (m, 5H, 2,6-H
in ph and 6-H), 7.87e7.93 (m, 2H, 7- and 9-H), 8.03 (d, J ¼ 8.0 Hz,1H,
10-H), 8.23 (s, 1H, 3-H), 8.23 (s, 1H, 4-H), 8.33 (s, 1H, 1-H), 8.64 (s,
1H, 12-H).
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519.2370.
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1H NMR (400 MHz, CDCl3):
d 7.38e7.40 (m, 2H, 4-H in 2,6-ph at
ICz), 7.50e7.61 (m,10H, ArH), 7.77 (d, J ¼ 7.2 Hz, 2H, 2,6-H in 2- or 5-
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ICz), 8.03 (d, J ¼ 8.6 Hz, 1H, 7-H in ICz), 8.06 (d, J ¼ 8.3 Hz, 8-H in
ICz), 8.11 (s, 1H, 5-H in pyrimidine), 8.33e8.36 (m, 4H, ArH), 8.42 (d,
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7.9 Hz, 2H, 2,6-H in 2-ph at pyrimidine).
€
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13C NMR spectrum could not be recorded due to poor solubility
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MS (FAB): m/z 699 [M]þ, 700 ([Mþ1]þ.
Anal. Calcd for C52H33N3, %: C, 89.24; H, 4.75; N, 6.00. Found, %:
C, 89.47; H, 4.55; N, 5.79.
9