Efficient and Practical Synthesis of Electron Transport Material and Its Key Intermediate

Article abstract of DOI:10.1021/acs.oprd.7b00280

An efficient and practical synthesis of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)triphenylene 4 from two cheap commodity chemicals in five steps with a total yield of 48.6% was developed. This process had been successfully applied in the synthesis of electron transport material (ETM) BPyTP-2 in the gram scale with a total yield of 47.2%. This practical development of the key intermediate 4 opens a door in its further application in the synthesis of other triphenylene-based ETMs and host materials in the materials field.

Full text of DOI:10.1021/acs.oprd.7b00280

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Full Paper
Efficient and Practical Synthesis of Electron
Transport Material and Its Key Intermediate
Xiangdong Zhao, Guijie Li, Zhi-Qiang Zhu, Kun Fang, Yuning Yang, Jian Li, and Yuanbin She
Org. Process Res. Dev., Just Accepted Manuscript • DOI: 10.1021/acs.oprd.7b00280 • Publication Date (Web): 15 Sep 2017
Downloaded from http://pubs.acs.org on September 15, 2017
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Efficient and Practical Synthesis of Electron Transport Material and Its Key Intermediate
†
†
‡
†
†
‡
†
Xiangdong Zhao , Guijie Li* , ZhiꢀQiang Zhu , Kun Fang , Yuning Yang , Jian Li , Yuanbin She*
†
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State Key Laboratory Breeding Base of Green ChemistryꢀSynthesis Technology, College of Chemical
Engineering, Zhejiang University of Technology, 18 Chaowang Road, Hangzhou, Zhejiang 310014, P. R.
China.
‡
Department of Materials Science and Engineering, Arizona State University, Tempe, AZ 85284, USA
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ABSTRACT:
An
efficient
and
practical
synthesis
of
2,7ꢀbis(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)triphenylene 4 from two cheap commodity
chemicals in five steps with a total yield of 48.6% was developed. And this process had been
successfully applied in the synthesis of electron transport material (ETM) BPyTP-2 in gram scale with a
total yield of 47.2%. This practical development of the key intermediate 4 open a door in its further
application in the synthesis of other triphenyleneꢀbased ETMs and host materials in material field.
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Keywords: electron transport material; host material; triphenylene; Scholl oxidation; SuzukiꢀMiyaura
coupling
■
INTRODUCTION
Since the first practical organic lightꢀemitting diode (OLED) was demonstrated by Tang and VanSlyke in
1
1987, OLEDs have been attracting more and more attention in both academic and industrial research
2
ꢀ5
for their great potential in commercial applications, such as fullꢀcolor displays and solidꢀstate lighting.
Both hole transport and electron transport layer (ETL) are critical for most multilayer advanced OLED
devices. However, the development of electron transport materials (ETMs) are more important because
the electron mobilities are usually one or two orders of magnitude lower than the hole mobilities in
OLEDs, which are unfavorable to the charge balance in the emitting layer and the operational lifetime of
the devices. In 2012, Adachi and his coworkers developed a series of triphenyleneꢀbased ETMs, like
6
6
7
7
BPyTP-1 , BPyTP-2 , 2,3'-BPyTP and 2,4'-BPyTP (Figure 1), which could lower driving voltage
significantly and also shown great electrochemical stability in green OLEDs, attributing to the high
7
horizontal molecular orientation to substrates . In 2013, triphenyleneꢀbased host materials, BDBF-TP
and BDBP-TP, were also developed by Adachi's group, which could lower driving voltages and
increase the external quantum efficiency (EQE) compared with that of host materials
8
4,4'ꢀbis(carbazolꢀ9ꢀyl)ꢀ1,1'ꢀbiphenyl (CBP) in red phosphorescent OLED. Recently, it was
demonstrated that BPyTP-2 could sever as efficient and stable ETM and widely utilized in
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10
11
platinum(II)ꢀbased phosphorescent red and blue OLEDs and also OLEDs incorporating fluorescence
1
2
or thermally activated delayed fluorescence (TADF) emitters . However, the synthetic route of the
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ETMs and its key triphenyleneꢀbased precursor was rare.
N
N
N
N
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,2'-BPyTP (BPyTP-2)
BPyTP-1
BDBF-TP
BDBT-TP
O
S
O
S
N
N
2,3'-BPyTP
N
N
2,4'-BPyTP
Figure 1. Triphenyleneꢀbased electron transport materials and host materials
A
fourꢀstep
strategy
for
the
synthesis
of
the
key
intermediate
2
2
,7ꢀbis(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)triphenylene 4 was developed by Adachi's Group in
6
,13
012 (Scheme 1).
1,2ꢀDiiodobenzene ($461/25g, TCI) and 3ꢀ(trimethylsilyl)phenylboronic acid
($257/5g, TCI) were employed as starting materials to afford 1,2ꢀbis(3ꢀ(trimethylsilyl)phenyl)benzene 1
through Pd(0)ꢀcatalyzed SuzukiꢀMiyaura coupling reaction. Then bromination, MoCl ꢀpromoted Scholl
5
oxidation and Pd(II)ꢀcatalyzed Miyaura boration were involved via intermediates 2 and 3 to give 4 in a
total yield of 17.6%. And a series of ETMs, like BPyTP-2, could be obtained by the SuzukiꢀMiyaura
6
,7
coulping reaction between 4 and corresponding bromide compounds. The Adachi's synthesis route was
relative concise and could be applied in gramꢀscale synthesis of the ETMs. Nevertheless, both the
starting materials were very expensive, and the yields for the bromination and Scholl oxidation were
unsatisfied, which resulted in low total yields for both the key intermediate 4 and BPyTP-2 (Scheme 1).
In 2008ꢀ2012, the synthesis of 2,7ꢀdi(trifluoromethylsulfonyloxy)triphenylene (8), which could sever as
a potential precursor for the preparation of the key intermediate 4, was independently developed through
SuzukiꢀMiyaura coupling, Scholl oxidation, demethylation and trifluoromethylsulfonylation using
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1,2ꢀdibromobenzene and 3ꢀmethoxyphenylboronic acid as starting materials by Iida , Minakami ,
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Kim , Brown and their coꢀworkers respectively. However, limitations still remain, like the low yields
(45ꢀ48%) of Scholl oxidation promoted by FeCl or 2,3ꢀdichloroꢀ5,6ꢀdicyanoꢀ1,4ꢀbenzoquinone (DDQ)
3
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in Iida , Minakami and Brown's work, or the high reaction temperature (220 C) of the
1
6
demethylation in Kim's work (Figure 2). Inspired by Adachi's synthetic strategy and the previous work,
herein, we report an improved practical synthetic route for the key intermediate
2,7ꢀbis(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)triphenylene 4 and BPyTP-2 starting from
inexpensive commodity chemicals 1,2ꢀdibromobenzene ($260/500g, Energy Chemical) and
3ꢀmethoxyphenylboronic acid ($100/100g, Energy Chemical) with high total yields of 48.6% and 47.2%
respectively.
Scheme 1. Adachi's Strategy for the Synthesis of BPyTP-2 and Its Key Intermediate 4
B(OH)2
5
mol % Pd(PPh3)4
I
I
3
.0 eqiv NaOH
3.9 equiv Br2
+
Me Si
SiMe3
3
diglym/H O
9
2
CHCl
-5 C, 3 h
3
SiMe3
1.9 equiv)
o
5 C, 15 h
o
1
(
8
4%
then, rt, 4 h
65%
O
O
O
O
2
.0 equiv MoCl5
B
B
Br
Br
Br
Br
+
2.2 equiv
CH Cl , rt, 19 h
2
2
2
46%
3
3
mol % Pd(dppf)Cl2
O
O
O
B
O
3
.0 equiv KOAc
B
+ 2.1 equiv Br
dioxane
N
N
o
8
0 C, 10 h
4
7
0%
Total yield: 17.6%
4
mol % Pd(PPh3)4
.1 eqivK CO3
3
2
toluene/EtOH/H O
2
N
N
N
N
reflux, 9 h
2,2'-BPyTP (BPyTP-2)
Total yield: 11.6%
6
6%
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Minakami's
Iida's work
ref. 14)
Kim's work
Brown's work
(ref. 17)
work
Our work
(
(ref. 16)
(ref. 15)
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% Pd(PPh3)4
6% Pd(PPh3)4 2% Pd(PPh3)4 0.8% Pd(PPh3)4
5% Pd(PPh3)4
6.6 Na CO3
6.6 Na CO
4.0 Na CO
8.0 Na CO
6.0 Na CO3
2
2
3
2
3
2
i
3
2
Step condition
toluene/EtOH/H O toluene/EtOH
toluene/H O
toluene/ PrOH toluene/EtOH/H O
2
2
2
1
reflux
60%
reflux
79%
reflux
70%
reflux
84%
reflux
96%
yield
excess DDQ
2.5 FeCl3
2.5 FeCl3
>
2.0 FeCl3
1.0 MeSO H
(1.0+1.0) MoCl5
2
H SO (con.)
H SO (con.)
2
4
2
4
Step condition
CH
Cl
2.0 Et
O:BF
CH Cl
2 2
2
2
2
3
CH Cl
CH Cl
2
2
2
2
2
rt
CH
2
Cl
2
rt
o
o
0 Cꢀrt
0 Cꢀrt
o
0
Cꢀrt
yield
48%
48%
70%
45%
82%
HBr/AcOH
reflux
2
.5 BBr3
2.5 BBr3
CH Cl
pyridine
4.7 BBr3
Step condition
CH
Cl
hydrochloride
CH
Cl
2
o
2
2
2
2
2
(
purification with
column free)
100%
o
o
o
3
0 C
0 C
220 C
0 Cꢀrt
yield
98%
98%
88%
99%
2
.5 Tf O
2
2.5 Tf O
2.0 Tf O
2
2
2
.7 Tf O
3.0 Tf O
8.0 pyridine
2
2
2
.2 pyridine
excess
pyridine
rt
o
Step condition
2.7 pyridine
rt
excess pyridine
rt
CH
Cl
, 0 Cꢀrt
2
2
CH Cl2
2
4
(purification with
column free)
87%
rt
yield
98%
93%
68%
94%
Total yield
12.4%
35.0%
29.3%
35.2%
68.5%
Figure 2. Comparison of our work with previous work for the preparation of 5ꢀ8
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■ RESULTS AND DISCUSSION
One of the key steps was the construction of the triphenylene molecular skeleton through the Scholl
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oxidation , and bromine atom was a weakly deactivating substituent which would result in low
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conversion. Nevertheless, it was demonstrated that the alkoxyarene substrates for the Scholl oxidation
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proceeded via arenium cation mechanisms. Therefore, o,pꢀdirecting methoxy group could stabilize the
arenium cation and lower the transitionꢀstate energy, facilitating the Scholl oxidation. Thus, our
synthetic strategy employed 1,2ꢀbis(3ꢀmethoxyphenyl)benzene 5 as the substrate for the Scholl
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oxidation, which could be efficiently synthesized through SuzukiꢀMiyaura coupling catalyzed by
Pd(PPh ) in 96% yield utilizing inexpensive commodity chemicals 1,2ꢀdibromobenzene and
3
4
3
ꢀmethoxyphenylboronic acid as starting materials. Similar reactions for the synthesis of 5 were also
1
4ꢀ17,20,21
reported by previous literatures in 60ꢀ80% yield.
It had been reported that 5 could be oxidized to give 2,7ꢀdimethoxytriphenylene 6 promoted by
1
4ꢀ16,22
17
FeCl3
or DDQ in unsatisfied yield. Thus, we next optimized the Scholl oxidation conditions. It
was found that one equiv MoCl could not oxidize 5 completely. And adding two equiv MoCl at once or
5
5
separately in a short time generated unsatisfied yields. However, good yield of 82% could be achieved if
the two equiv MoCl were added at intervals of 24 hours. It was noted that insoluble product precipitate
5
of 2,7ꢀdimethoxytriphenylene 6 from solution was observed, which could suppress the oligomerization
14
of product and facilitate the yield enhancement. Recently, this Scholl oxidation intermolecular
20,21
coupling reaction was improved under acid conditions
or utlizing fluoroalkoxy Mo(V) reagent as
2
3
oxidant .
1
4,15,17,24,25
16
It has been demonstrated that both BBr3
and pyridine hydrochloride could be employed
1
6
for the demethylation of 6, which suffered from complicated workup or high reaction temperature .
2
6
Thus, demethylation of 6 using concentrated hydrobromic acid
in acetic acid gave
2,7ꢀdihydroxyltriphenylene 7 in quantitative yield, which further reacted with Tf O to afford
2
ditrifluoromethanesulfonate in 87% yield. It was encouraging to find that pure products of both 6 and 7
could be separated easily with column chromatography free. Then, key intermediate 4 could be obtained
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through the Miyaura boration in a total yield of 48.6% for the five steps, which was much higher than
that of the Adachi's synthetic route. Finally, the synthesis of BPyTP-2 could be completed through
Pd(0)ꢀcatalyzed SuzukiꢀMiyaura coupling reaction between 4 and 2ꢀ(5ꢀbromopyridinꢀ2ꢀyl)pyridine in
gram scale in 47.2% total yield. It was worth mentioning that prolonging reaction time could increase
the yield of the last step.
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Scheme 2. Improved Strategy for the Synthesis of 4 and BPyTP-2
Importantly, 2,7ꢀbis(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)triphenylene 4 was also a key
6
7
7
precursor for the synthesis of other ETMs, such as BPyTP-2 , 2,3'-BPyTP and 2,4'-BPyTP (Scheme
3
), all of which exhibited good device performance. Furthermore, precursor 4 could be also utilized for
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the synthesis of the triphenyleneꢀbased host materials BDBF-TP and BDBT-TP, which were
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incorporated in red phosphorescent OLEDs to improve the device performance significantly.
Scheme 3. Other Electron Transport Materials and Host Materials' Synthesis Using 4 as Key
Precursor
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■
CONCLUSION
In
summary,
an
efficient
and
practical
synthetic
method
of
precursor
2
,7ꢀbis(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)triphenylene 4, which was a key intermediate for the
synthesis of ETMs and host materials, was developed in five steps with a total yield of 48.6%. Moreover,
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two cheap commodity chemicals could be employed as the starting materials. Importantly, an improved
MoCl ꢀpromoted Scholl oxidation successfully construct the key triphenylene skeleton in high yield.
5
Furthermore, this process could be successfully applied in the synthesis of ETM BPyTP-2 in gram scale
in a total yield of 47.2%. And it is believed that this practical synthetic route can be also applied in the
synthesis of other triphenyleneꢀbased ETMs and host materials in the future in material field.
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■
EXPERIMENTAL SECTION
General. All commercial reagents were purchased and used without further purification unless
otherwise noted. The CH Cl was dried over anhydrous Na SO prior to use. Pd(PPh ) was purchased
2
2
2
4
3 4
1
13
from SigmaꢀAldrich. H spectra were recorded at 400 or 500 MHz, and C NMR spectra were recorded
at 100 or 125 MHz on Varian LiquidꢀState NMR instruments DMSOꢀd solutions and chemical shifts
6
1
were referenced to a residual protiated solvent. H NMR spectra were recorded with the residual
1
3
DMSOꢀd (δ = 2.50 ppm) as the internal reference; and C NMR spectra were recorded with DMSOꢀd
6
6
(δ = 39.52 ppm) as the internal reference. The following abbreviations (or combinations thereof) were
1
used to explain H NMR multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, p = quintet, m =
multiplet. High Resolution Mass spectra were recorded on LTC FTICR mass spectrometer using DART
positive ion mode.
Synthesis of 1,2-bis(3-methoxyphenyl)benzene (5) 3ꢀMethoxyphenylboronic acid (28.80 g, 189.00
mmol, 3.00 equiv) and Na CO (40.10 g, 378.00 mmol, 6.00 equiv) were added to a threeꢀnecked flask
2
3
equipped with a magnetic stir bar and a condenser. The flask was then evacuated and backfilled with
nitrogen, this evacuation and backfill procedure was repeated twice. Then toluene (150 mL), EtOH (150
mL), H O (150 mL), 1,2ꢀdibromobenzene (7.50 mL, 63.00 mmol, 1.00 eq) and Pd(PPh ) (2.91 g, 2.52
2
3 4
mmol, 0.05 eq) were added under nitrogen. The mixture was then bubbled with nitrogen for 30 min and
stirred at refluxed temperature for 2 days until the starting material was consumed completely monitored
by TLC. Then the mixture was cooled down to ambient temperature, filtered and washed with plenty of
ethyl acetate (100 mL×3). The filtrate was concentrate and the residue was diluted with plenty of ethyl
acetate (200 mL), washed with 3M hydrochloric acid and NaHCO solution until there was no bubble to
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generate. The organic layer was separated and dried over anhydrous Na SO , filtered, concentrated and
2 4
residue was purified through column chromatography on silica gel using petroleum ether/ethyl acetate
(20:1—10:1) as eluent to obtain the desired product as a white solid 12.97 g, and some impure product,
which could be further purified by a slurry in hexane/ethyl acetate (10 ml, 5:1) to give another 4.66 g
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product, thus desired product 5 was obtained in a total of 17.63 g in 96% yield. H NMR (500 MHz,
DMSOꢀd ): δ 3.59 (s, 6H), 6.65 (dd, J = 2.5, 1.5 Hz, 2H), 6.70 (ddd, J = 7.5, 1.5, 1.0 Hz, 2H), 6.78 (ddd,
6
1
3
J = 8.0, 2.5, 1.0 Hz, 2H), 7.16 (t, J = 8.0 Hz, 2H), 7.40ꢀ7.46 (m, 4H). C NMR (126 MHz, DMSOꢀd ): δ
6
54.8, 112.4, 115.0, 121.7, 127.7, 129.0, 130.2, 139.8, 142.4, 158.7. HRMS (TOF MS EI+) for C H O
2
2
0
18
+
[M] : calcd 290.1307, found 290.1303 .
Synthesis of 2,7-dimethoxytriphenylene (6) MoCl (7.82 g, 28.60 mmol, 1.00 equiv) was added
5
quickly to a solution of 1,2ꢀbis(3ꢀmethoxyphenyl)benzene 5 (8.31 g, 28.60 mmol, 1.00 equiv) in CH Cl
2
2
(500 mL) under nitrogen. The mixture was stirred at room temperature for 24 hours, then the other one
equiv MoCl (7.82 g, 28.60 mmol, 1.00 equiv) was added quickly to the mixture again. After being
5
stirred for 24 hours, the mixture was quenched by methanol (100 mL) and stirred for another 1 hour,
filtered and washed with CH Cl (500 mL). The filtrate was concentrated and residue was purified
2
2
through column chromatography on silica gel using petroleum ether/ethyl acetate (20:1ꢀ10:1ꢀ5:1ꢀ3:1) as
eluent to afford white solid 7.52 g, which was further purified to be slurried in hexane/ethyl acetate (22
1
mL, 10:1) to afford white solid 6.82 g in 82% yield. H NMR (500 MHz, DMSOꢀd ): δ 3.99 (s, 6H),
6
7
8
1
.28 (dd, J = 9.0, 2.5 Hz, 2H), 7.69ꢀ7.72 (m, 2H), 8.17 (d, J = 2.5 Hz, 2H), 8.59 (d, J = 9.5 Hz, 2H),
1
3
.79ꢀ8.82 (m, 2H). C NMR (126 MHz, DMSOꢀd ): δ 55.4, 105.7, 116.5, 123.3, 123.9, 124.7, 127.5,
6
+
29.3, 129.6, 158.1. HRMS (TOF MS EI+) for C H O [M] : calcd, 288.1150, found 288.1154.
2
0
16
2
Synthesis of 2,7-dihydroxytriphenylene (7) A solution of 2,7ꢀdimethoxytriphenylene 6 (4.30 g,
o
1
4.90 mmol) in hydrogen bromide acid (30 mL, 48%) and acetic acid (220 mL) refluxed (120 C) for 2
days under a nitrogen atmosphere. Then the mixture was cooled down to room temperature and the
solvent was removed under reduced pressure. The residue was diluted with water (30 mL) and
neutralized with a solution of K CO until there was no gas to generate. Then the precipitate was filtered
2
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off and washed with water for three times (50 mL×3). The collected solid was dried in under reduced
1
pressure to afford the product as a brown solid in quantitative yield. H NMR (500 MHz, DMSOꢀd ): δ
6
7.14 (dd, J = 9.0, 2.5 Hz, 2H), 7.64ꢀ7.67 (m, 2H), 7.97 (d, J = 2.0 Hz, 2H), 8.46 (d, J = 9.0 Hz, 2H),
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8.53ꢀ8.55 (m, 2H), 9.76 (s, 2H). C NMR (126 MHz, DMSOꢀd ): δ 107.6, 117.2, 122.4, 123.4, 124.4,
6
+
127.3, 129.2, 129.3, 156.0. HRMS (DART Positive Ion Mode) for C H O [M+H] : calcd 261.0910,
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8
13
2
found 261.0909 .
Synthesis of triphenylene-2,7-diol bistrifluoromethanesulfonate (8)
A
solution of
o
2
,7ꢀdihydroxytriphenylene 7 (3.94 g, 14.90 mmol, 1.00 equiv) in CH Cl (250 mL) was cooled to 0ꢀ5 C.
2
2
After adding pyridine (9.60 mL, 119.16 mmol, 8.00 equiv), Tf O (6.60 mL, 39.25 mmol, 2.60 equiv)
2
was added dropwise. Then the mixture was stirred at that temperature for 2 hours, quenched by water
(
25 mL). The mixture was diluted with CH Cl until the precipitate was dissolved. The organic layer was
2 2
separated and dried over anhydrous Na SO , filtered. The filtrate was concentrated until there was about
2
4
4
0 mL solvent was left, diluted with hexane (200 mL). The precipitate was filtered off and washed with
1
hexane (100 mL), dried. And white solid 6.77 g was obtained in 87% yield. H NMR (500 MHz,
DMSOꢀd ): δ 7.83ꢀ7.86 (m, 4H), 8.90ꢀ8.93 (m, 2H), 8.99 (d, J = 2.5 Hz, 2H), 9.03 (d, J = 9.5 Hz, 2H).
6
1
3
C NMR (126 MHz, DMSOꢀd ): δ 116.70, 118.35 (q, J = 320 Hz), 120.7, 124.4, 127.3, 128.1, 128.6,
6
+
1
29.1, 131.5, 149.2. HRMS (DART Positive Ion Mode) for C H F O S [M] : calcd for 523.9818,
2
0
10
6
6 2
found 523.9814.
Synthesis
of
2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)triphenylene
(4)
Triphenyleneꢀ2,7ꢀdiol bistrifluoromethanesulfonate
8
(9.00 g, 17.16 mmol, 1.00 equiv),
bis(pinacolato)diboron (17.43 g, 68.65 mmol, 4.00 equiv), KOAc (10.10 g, 102.96 mmol, 6.00 equiv)
and Pd(dppf)Cl (0.84 g, 1.03 mmol, 0.06 equiv) were added to a threeꢀnecked flask equipped with a
2
magnetic stir bar and a condenser. The flask was then evacuated and backfilled with nitrogen, this
evacuation and backfill procedure was repeated twice. Then dioxane (136 mL) was added under nitrogen.
o
The mixture was then bubbled with nitrogen for 20 minutes and stirred at 80 C for 2 days. Then the
mixture was cooled down to ambient temperature. The solvent was removed and the residue was
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purified through column chromatography on silica gel using petroleum ether/ethyl acetate (60:1ꢀ40:1) as
eluent to obtain the desired product containing some bis(pinacolato)diboron, The obtained solid was
further purified by a slurry in hexane/ethyl acetate (20:1) at room temperature for 4ꢀ6 hours to give pure
1
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white solid 5.86 g in 71% yield. H NMR (500 MHz, DMSOꢀd ): δ 1.39 (s, 24H), 7.75ꢀ7.78 (m, 2H),
6
1
3
7.98 (dd, J = 8.0, 1.0 Hz, 2H), 8.76ꢀ8.79 (m, 2H), 8.84 (d, J = 8.0 Hz, 2H), 9.03 (s, 2H). C NMR (126
MHz, DMSOꢀd ): δ 24.7, 84.0, 123.33, 123.4, 128.0, 128.8, 128.9, 129.7, 131.1, 132.8. HRMS (DART
6
10
34
+
Positive Ion Mode) for C H B O [M] : calcd 478.2710, found 478.2710.
3
0
2
4
Synthesis
of
2,7-bis(6-(pyridin-2-yl)pyridin-3-yl)triphenylene
(BPyTP-2)
2
,7ꢀBis(4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolanꢀ2ꢀyl)triphenylene 4 (5.16 g, 10.80 mmol, 1.00 equiv),
2
ꢀ(5ꢀbromopyridinꢀ2ꢀyl)pyridine (5.60 g, 23.76 mmol, 2.20 equiv, synthesized according reported
2
7
literature ) and Pd(PPh ) (0.62 g, 0.54 mmol, 0.05 equiv) were added to a threeꢀnecked flask equipped
3
4
with a magnetic stir bar and a condenser. The flask was then evacuated and backfilled with nitrogen, this
evacuation and backfill procedure was repeated twice. Then toluene (90 mL), EtOH (22 mL) and a
solution of K CO (4.50 g in 18 mL H O, 32.40 mmol, 3.00 equiv) were added under nitrogen through
2
3
2
syringe. The mixture was then bubbled with nitrogen for 20 minutes and stirred at refluxed temperature
for 2.5 days. Then the mixture was cooled down to ambient temperature. The precipitate was filtered off
and washed with water (100 mL), acetone (100 mL), ethyl acetate (100 mL), ether (150 mL) and then
1
dried under reduced pressure to afford a slight yellow solid 5.67 g in 97% yield. H NMR (500 MHz,
DMSOꢀd ): δ 7.51 (ddd, J = 7.5, 4.5, 1.0 Hz, 2H), 7.80ꢀ7.82 (m, 2H), 8.01 (td, J = 8.0, 1.5 Hz, 2H),
6
8
8
.21ꢀ8.23 (m, 2H), 8.51 (d, J = 8.0 Hz, 2H), 8.57 (d, J = 8.0 Hz, 2H), 8.62 (dd, J = 8.0, 2.0 Hz, 2H),
.75ꢀ8.76 (m, 2H), 9.04 (d, J = 9.0 Hz, 2H), 9.15 (dd, J = 6.5, 3.5 Hz, 2H), 9.25 (s, 2H ), 9.37 (d, J = 1.5
+
Hz, 2H). MS(+ESI) for C H N [M] : calcd 536.2, found 536.2.
3
8
24
4
■
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: xxx
xxx.
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NMR and MS data of compounds 4ꢀ8 and 2,2'-BPyTP (PDF)
■
AUTHOR INFORMATION
Corresponding Authors
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*
*
Eꢀmail: guijieli@zjut.edu.cn
Eꢀmail: sheyb@zjut.edu.cn
ORCID
Guijie Li: 0000ꢀ0002ꢀ0740ꢀ2235
Jian Li: 0000ꢀ0003ꢀ3300ꢀ0990
Notes
The authors declare no competing financial interest.
■ACKNOWLEDGEMENTS
The authors gratefully acknowledge the National Natural Science Foundation of China (Grant No.
1602198, 21776259 and 21476270), "Qianjiang Talents Plan" (Grant No. QJD1602017), National
2
Science Foundation of United State (CHEꢀ0748867) and Department of Energy (Contract No.
EE0007090) for partial support of this work.
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5754.
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