Syntheses of Diverse Donor-Substituted Bisbenzofuro[2,3- b:3′,2′- e]pyridines (BBZFPys) via Pd Catalysis, and Their Photophysical Properties

Article abstract of DOI:10.1021/acs.joc.8b01451

A series of bisbenzofuro[2,3-b:3′,2′-e]pyridines (BBZFPys) bearing a chlorine functionality have been efficiently synthesized through a Pd-catalyzed double oxidative intramolecular C-H/C-H coupling of monochlorinated 2,6-diaryloxypyridines. The subsequent

Full text of DOI:10.1021/acs.joc.8b01451

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Article
Syntheses of Diverse Donor-Substituted Bisbenzofuro[2,3-b:3’,2’-
e]pyridines (BBZFPys) via Pd Catalysis, and Their Photophysical Properties
Yuhei Itai, Yuji Nishii, Patrycja Stachelek, Przemyslaw Data,
Youhei Takeda, Satoshi Minakata, and Masahiro Miura
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01451 • Publication Date (Web): 13 Aug 2018
Downloaded from http://pubs.acs.org on August 13, 2018
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Syntheses of Diverse Donor-Substituted
Bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys) via Pd Catalysis, and
Their Photophysical Properties
†
†,‡
§
,§, ,
,†
∥
⊥
Yuhei Itai, Yuji Nishii, Patrycja Stachelek, Przemyslaw Data,*
Youhei Takeda,* Satoshi
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,†
Minakata, and Masahiro Miura*
†
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita,
Osaka 565-0871, Japan
‡
Frontier Research Base for Global Young Researchers, Graduate School of Engineering, Osaka University,
Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
§
Durham University, Physics Department, South Road, Durham DH1 3LE, United Kingdom
∥Faculty of Chemistry, Silesian University of Technology, M. Strzody 9, 44-100 Gliwice, Poland
⊥Center of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, 41-819 Zabrze,
Poland
przemyslaw.data@durham.ac.uk; takeda@chem.eng.osakaꢀu.ac.jp; miura@chem.eng.osakaꢀu.ac.jp
Table of Contents
Abstract
A series of bisbenzofuro[2,3ꢀb:3’,2’ꢀe]pyridines (BBZFPys) bearing a chlorine
functionality have been efficiently synthesized through a Pdꢀcatalyzed double oxidative
intramolecular C–H/C–H coupling of monoꢀchlorinated 2,6ꢀdiaryloxypyridines. The subsequent
BuchwaldꢀHartwig amination of the chlorinated BBZFPys allowed for the access to a new class of
donorꢀacceptor (DꢀA) πꢀconjugated compounds that comprise of BBZFPy as an electronꢀacceptor
(
A) and diarylamines as a donor (D) units. The investigation of the steadyꢀstate photophysical
properties of the prepared DꢀA compounds revealed that they are emissive in both of solution and
solid states in blueꢀtoꢀgreen color region. The singletꢀtriplet energy splitting (ꢀEST) was found
much smaller than that of substituentꢀfree BBZFPy (0.70 eV), ranging from 0.01 to 0.56 eV. The
timeꢀresolved spectroscopy revealed that the DꢀA compounds comprising of
a
bis(tertꢀbutyl)carbazole as the D and CF ꢀattached BBZFPy as the A showed delayed fluorescence
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®
�
(
DF) in nonꢀpolar matrix host material (Zeonex ), while in a polar matrix (DPEPO),
roomꢀtemperature phosphorescence (RTP) was faintly observed. Furthermore, organic
lightꢀemitting diodes (OLEDs) fabricated with the DꢀA compounds as a blueꢀemitter showed a
moderate external quantum efficiencies (EQEs) up to 1.5%.
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Introduction
Benzofuro[2,3ꢀb]pyridines (BZFPys) constitute an important scaffold in medicinal
chemistry and materials science. For example, 4ꢀamino or arylꢀsubstituted BZFPys serve as a class
1
of multiꢀkinase inhibitors, while BZFPys having an electronꢀdonating group at the 6ꢀposition serve
as promising bipolar host materials for blue phosphorescent organic lightꢀemitting diodes
2
(
PHOLEDs). Traditionally, BZFPYs are prepared through intramolecular S
N
Ar cyclization of the
diazonium salts derived from 3ꢀaminoꢀ2ꢀphenoxypyridines. Nevertheless, this method requires the
1
preparation of explosive diazonium compounds, and the product yields are typically low. Recent
progress mainly focuses on the utilization of transitionꢀmetal catalysis, allowing milder reaction
conditions.
ꢀ(2ꢀbromophenoxy)pyridine to give nonꢀsubstituted BZFPy, albeit in a low yield, while the Li
group developed a Pdꢀcatalyzed highꢀyielding protocol that comprises of the stannylation of
Ames and Opalko reported
a
Pdꢀcatalyzed Heckꢀtype cyclization of
3
a
2
3b
3
ꢀiodoꢀ2ꢀ(2ꢀiodophenoxy)pyridine and the subsequent intramolecular Stille crossꢀcoupling.
Another efficient route to BZFPys involves a CuTCꢀmediated intramolecular Ullmannꢀtype
3
c
Oꢀcyclization of 2ꢀ(2ꢀchloropyridinꢀ3ꢀyl)phenols.
A Rhꢀcatalyzed CNꢀcleaving cyclization of
2
ꢀ(2ꢀchlorophenoxy)nicotinonitrile developed by the Tobisu and Chatani group constitutes an
3d
intriguing route to BZFPy skeleton.
Nevertheless, these precedent methods use the
preꢀfunctionalized aryloxypyridine substrates, and therefore, multi steps are required from readily
available organic compounds.
Oxidative C–H/C–H coupling of heteroatomꢀlinked polyarenes would be one of the most
atomꢀeconomical, straightforward, and diverse approaches to polycondensed heteroacenes, because a
4
–6
large variety of the diaryl ethers, amines, and sulfides are readily available.
As a program of our
7
research on direct C–H functionalization of aromatic compounds via transitionꢀmetal catalysis, we
have contributed to the development of highly atomꢀ and stepꢀeconomical synthetic methods for
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a
5b
ladderꢀtype heteroacenes (e.g., thienobenzofurans and benzobisꢀ and benzotrisbenzofurans).
More recently, we have developed a Pdꢀcatalyzed oxidative intramolecular double C–H/C–H
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coupling of 2,6ꢀdiaryloxypyridines to give bisbenzofuro[2,3ꢀb:3’,2’ꢀe]pyridines (BBZFPys) (Eq. 1).
The preliminary investigation of the physicochemical properties of substituentꢀfree BBZFPy
revealed that its chloroform solution emits a violet fluorescence (
λ
em 360 nm) with a narrow Stokes
–1
shift (ꢀ
λ
1041 cm ) and a high photoluminescence quantum yield (PLQY) (
Φ
F
0.70). Other
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interesting physicochemical aspects involve a wide HOMO/LUMO gap (E 3.44 eV), a high triplet
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energy (E
T
2.88 eV), and a high electron affinity (EA: 2.67 eV), indicating that the BBZFPy can
serve as a unique electron accepting building block for organic functional materials.
Donorꢀacceptor (DꢀA) πꢀconjugated organic compounds have increasingly emerged as
8a
useful scaffolds for organic functional materials such as organic photovoltaics (OPVs), organic
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lightꢀemitting diodes (OLEDs),
and bioꢀimaging probes.
Specifically, twisted D–A
πꢀconjugated compounds that show charge transfer (CT) emissions have rapidly attracted much
attention as promising thermally activated delayed fluorescence (TADF) materials over the last
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several years.
To gain efficient TADF with DꢀA conjugated systems, the reverse intersystem
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crossing (RISC) from the triplet excited state (T
1
) to the singlet charge transfer state ( CT) should be
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promoted by modifying the D/A combinations and the D–A dihedral angles.
As one of the key
criteria for designing TADFꢀactive molecules, it is desirable to tune the singletꢀtriplet energy
splitting (ꢀEST) to be almost zero.
Based on these backgrounds, we decided to expand our oxidative intramolecular C–H/C–H
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coupling method to the preparation of diverse DꢀAꢀtype BBZFPys and to investigate the
photophysical properties of the resulting DꢀA compounds with the aim at applying to organic
emitters in OLED devices. Herein we disclose a highly atomꢀ and stepꢀeconomical synthetic
strategy for the preparation of DꢀAꢀtype BBZFPys through a sequential protocol comprising of a
Pdꢀcatalyze intramolecular C–H/C–H oxidative coupling of monochloro 2,6ꢀdiaryloxypyridines and
the subsequent BuchwaldꢀHartwig amination (Eq. 2). Photophysical properties of the DꢀA
compounds in solution and solid states also have been investigated. Furthermore, applications of
the DꢀA compounds as a blue emitter in OLED devices have been demonstrated.
Results and Discussion
Design and Syntheses
As an initial study, theoretical calculation of a DꢀA type BBZFPy in the gas phase was
conducted by the DFT method at the B3LYP/6ꢀ31G level (Figure 1; for the details, see the
Supporting Information). The optimized structure of the DꢀA compound in the ground state takes
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the twisted conformation around the C–N bond with the dihedral angle being 58.5 ° (Figure 1),
which would be the consequence of the balance between the steric repulsion of aromatic C–H groups
of the D and A units and weak πꢀsystem conjugation. This propensity of the DꢀA twisted structure
was rationalized by the potential energy surface (PES) scan of the grond state of this DꢀA compound
around the DꢀA dihedral angle (Figure S1). The ꢀEST of the simplest DꢀA BBZFPy compound was
estimated by the timeꢀdependent DFT (TDDFT) method at the same level using the optimized
structure of the ground state (for the details, see the Supporting Information). Although the TDDFT
calculation using the B3LYP functional often gives substantial errors for the charge transfer excited
states of DꢀA type molecules, it is still useful for a brief estimation of ꢀEST of designed molecules,
due to the low calculation cost. Owing to the twisted structure, the HOMO and LUMO are
distinctly separated (Figure 1), and thereby ꢀEST being substantially reduced to 0.26 eV, which is
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much narrower than that of BBZFPy (0.70 eV).
Figure 1. The illustrative summary of the theoretical calculation by the DFT method.
As starting substrates, unsymmetric 2,6ꢀdiaryloxypyridines 2 were readily prepared by the
sequential double substitution of the dihalo groups of 2,6ꢀdichloroꢀ and dibromopyridines with
phenol derivatives (Scheme 1). The treatment of dichloropyridines with about a half equivalent of
phenol derivatives under basic conditions (Conditions A, Scheme 1) selectively gave
monoꢀsubstituted products 1a–1d in high yields (88–93% based on the amount of phenol substrates),
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while in the case of dibromopyridine, Cuꢀcatalyzed Ullmannꢀtype Oꢀarylation gave the
corresponding monoaryloxy bromopyridine 1e and 1f in moderate yields (Conditions B, Scheme 1).
1
2
Using similar reaction conditions (Conditions C and D, Scheme 1), the remaining halogen group
was substituted with phenol derivatives to give a variety of unsymmetric diaryloxypyridines 2.
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Scheme 1. Preparation of unsymmetric chloroꢀbearing 2,6ꢀdiaryloxypyridines 2.
To synthesize precursors for DꢀAꢀtype BBZFPys and to verify the generality of the
previously developed oxidative C–H/C–H coupling, diaryloxypyridines 2 were subjected to the
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slightly modified coupling reaction conditions (Table 1). In the presence of Pd(TFA)
2
as a catalyst
and AgOAc as a stoichiometric oxidant, p-chlorinated diphenoxypyridine 2a smoothly underwent the
double C–H/C–H coupling to give monochlorinated BBZFPy product 3a in a good yield (80%).
The oxidative reactions using diaryloxypyridines that have a paraꢀtertꢀbutyl group on a benzene ring
and a pꢀ and mꢀCl substituent on the other aryl moiety (2b and 2c) gave 3b and 3d, respectively, in
good yields. On the other hand, the reactions of pyridines with metaꢀtertꢀbutyl and pꢀCl (2d) and
mꢀCl (2e) functionalities afforded the corresponding products 3d and 3e in low yields. From the
diaryloxypyridines with an orthoꢀtertꢀbutyl substituent (2f and 2g), cyclized products 3f and 3g,
respectively, in moderate yields (63% and 68%). To enhance the electronꢀaccepting ability of the
3
BBZFPy core, CF ꢀincorporated substrates 2h and 2i were subjected to the reaction conditions to
afford electronꢀdeficient BBZFPys 3h and 3i, respectively, in moderate yields. Under these
oxidative conditions, the chloro functionality of BBZFPy remains intact, which would be a merit of
using this atomꢀ and stepꢀeconomical synthetic method.
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Table 1. Scope of the Pdꢀcatalyzed intramolecular double C–H/C–H oxidative coupling of 2
Substrate
Product (Isolated yield)
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Reaction conditions: 2 (0.40 mmol), Pd(TFA)
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(40 ꢁmol, 10 mol%), and AgOAc
(1.60 mmol, 4.0 equiv) in PivOH (4.0 mL) in a 10 mL Schlenk tube at 150 °C for 16
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With a variety of BBZFPy building blocks in hand, a series of diarylamines were
incorporated into the acceptor core through the Pdꢀcatalyzed BuchwaldꢀHartwig amination (Table 2).
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MoPhos was found effective for executing the challenging C–Cl amination.
The amination of the
simplest BBZFPy 3a with carbazole and carbazolylcarbazole gave 4aa and 4ab in poor isolated
yields (17% and 3%, respectively), probably due to the low solubilities of the starting materials and
products in oꢀxylene. On the other hand, the amination of 3b, which has a stericallyꢀdemanding
alkyl group (tꢀBu) on the benzofuranyl unit, resulted in DꢀA compounds 4ba, 4bb, 4bc, and 4bd in
moderate to good yields (Table 2), probably due to the increased solubilities of the substrates and the
products. Amination of 3b with phenothiazine, acridone, and diphenylamine also successfully gave
the corresponding products 4be, 4bf, and 4bg, albeit in low yields. The versatility of this protocol
starting from 2,6ꢀdihalopyridine was demonstrated by preparing a variety of regio isomers of DꢀA
compounds (i.e., 4ba, 4ca, 4da, 4fa, and 4ga), which would allow for structureꢀproperties
relationship (SPR) studies. Furthermore, this method allows for the syntheses of D–A conjugated
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compounds whose electronꢀwithdrawing ability is enhanced with a CF group (4ha, 4hc, 4hd, 4hg,
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Table 2. Synthesis of donorꢀsubstituted BBZFPys through BuchwaldꢀHartwig amination of 3
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Reaction conditions: 3 (0.50 mmol), [(πꢀallyl)PdCl] (10 ꢁmol, 2 mol%), MoPhos (40 ꢁmol, 8 mol%),
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and NaOtꢀBu (0.60 mmol, 1.2 equiv) in oꢀxylene (2.0 mL) in a 10 mL Schlenk tube at 130 °C for 16 h
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Steady-State Photophysical Properties
To explore the possibilities of the DꢀAꢀtype BBZFPys as emissive materials for
optoelectronic devices, the steadyꢀstate photophysical properties in diluted solutions and solid states
were investigated.
photoluminescence (PL) spectra of 4aa, 4bc, 4bd, 4hc, and 4ic in solutions (Figure 2a, c, e, g, and i)
and in the solid state (Figure 2b, d, f, h, and j) (for other compounds, see the Figure S6 S8), and the
properties of all the DꢀA compounds are summarized in Table 3 and 4. Typically, in CHCl
Figure 2 illustrates representative UVꢀvis absorption and steadyꢀstate
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9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
–
3
solutions, almost all the compounds exhibited an absorption at around 290 nm and structured
absorptions ranging from 330 nm to 380 nm (Figure 2a, c, e, g, and i), which are very similar to that
6
of nonꢀsubstituted BBZFPy. Upon the irradiation of UV light, all the compounds are emissive in
solution in violetꢀtoꢀgreen region, with the PLQYs ranging from 0.01 to 0.71 (Table 3).
Steadyꢀstate photoluminescence (PL) spectra of the CHCl
3
/EtOH (1:4 v/v) solution of 4aa recorded
at room temperature showed a broad Gaussianꢀtype shape peaked at 448 nm (Figure 2a, green line).
6
–1
When compared with nonꢀsubstituted BBZFPy, the Stokes shift is much larger (6547 cm for 4aa,
–
1
1
041 cm for BBZFPy), which is typical to the emissions from the singlet chargeꢀtransfer excited
1
state ( CT) of DꢀA type conjugated compounds. In fact, distinct positiveꢀsolvatochromism of the
3
emissions were observed with a DꢀA compound 4hc, which has an electronꢀwithdrawing group (CF )
on the BBZFPy acceptor core (Figure S9, Table S12). In the cases of 4ab, 4ba, 4bb, 4bc, 4bg, 4da,
1
4fa, 4hc, along with the CT emissions, the remnant emissions from the local excited state of the
1
1
acceptor ( LE
A D
) or the donor ( LE ) were observed (Figure 2c, g; Figure S6a, c, e; Figure S7a, e, g),
which would reflect the slow electron transfer (EA) process within these molecules due to
9
g,f,10c
1
1
significantly twisted DꢀA geometries.
inverted in the cases of phenoxazineꢀ and phenothiazineꢀ, and acridoneꢀsubstituted BBZFPys (4bd,
be, and 4bf, Figure 2e, Figure S6g, and Figure S6i, respectively), implying their perpendicularly
The population of the LE and CT emissions is
4
twisted and rigid DꢀA geometries in solutions to suppress the ET process from the D to A units.
This was supported by the PES scans of a series of DꢀA compounds 4aa, 4bd, 4bd, 4bf, and 4bg
(
Figure S1–5): Compounds 4bd, 4be, and 4bf have the potential minima where the DꢀA interplanar
angles make a right angle, while 4aa and 4bg take less twisted angles (ca. 58° and 42 °, respectively)
at the potential minima. All the phosphorescence (PH) spectra recorded at 77 K in the CHCl /EtOH
1:4 v/v) solutions looked alike, featured with vibronic structures (e.g., blue lines in Figure 2a, c, e, g,
3
(
6
and i), and they are almost superimposed with the PH spectrum of nonꢀsubstituted BBZFPy. This
strongly suggests that the nature of the excited triplet states of the DꢀA compounds are almost
3
6
correlated with that of the local excited triple state of BBZFPy ( LE
A
). Owing to the stabilized
1
3
CT states and the dominant contribution of the LE
A
in their triplet excited states with a high energy
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level (at around 2.88 eV), the singletꢀtriplet energy splitting (ꢀE1CTꢀ3LE) in solution are narrower than
that of BBZFPy (0.70 eV) in all cases, ranging from 0.01 to 0.56 (Table 3). Overall, quantum
yields are very low except for 4bf and 4ca. Taken together with the facts that these DꢀA
compounds also have small ꢀE1CTꢀ3LE, it is speculated that either efficient intersystem crossing (ISC)
process followed by nonꢀradiative decays based on the molecular rotation and/or vibration or charge
recombination leading to the “dark” state are the possible reasons for such low quantum yields.
In the solid states, several compounds that contain carbazoles as the donor (e.g., 4aa, 4ba,
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9
0
1
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4
5
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9
0
1
4
4
bc, and 4da) showed aggregationꢀinduced enhanced emission (AIEE) properties, implying that
twisted geometries suppress intermolecular πꢀπ interactions in the solid states. Judged from the
similarity of the phosphorescence spectra between the solution and solid states, the triplet nature of
3
DꢀAꢀtype BBZFPys 4 can be correlated with the LE states of the acceptor. Interesting features
were observed with 4aa, 4ba, 4fa, and 4ga, where dual emissions were observed, one with structured
3
PH (
λ
em 450–700 nm) from the LE
A
as observed in solutions and the one overlapped with the PL
λem 350–450 nm).
1
from the LE of the donor or acceptor (
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Figure 2. (a), (c), (e), (g), and (i) Normalized UVꢀvis absorption (red, 50 ꢁM, CHCl ), fluorescence
(green, 50 ꢁM, EtOH/CHCl
3
4:1 v/v measured at room temperature), and phosphorescence (blue, 10
ꢁ
M, EtOH/CHCl 4:1 v/v measured at 77K) of diluted solutions of 4aa, 4bc, 4bd, 4hc, and 4ic. (b),
3
(d), (f), (h), and (j) Normalized absorption (red), fluorescence (green, measured at room temperature),
and phosphorescence (blue, measured at 77K) of 4aa, 4bc, 4bd, 4hc, and 4ic in the solid state.
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Table 3. Selected photophysical data of diluted solutions of DꢀA compounds
PL
PH
Compd
λabs
λem
ΦPL
a,c
λem
E
1CT
E
3LE
ꢀE1CTꢀ3LE
a
a,b
d
e
f
(
nm)
(nm)
(%)
(nm)
(eV)
(eV)
(eV)
4aa
294, 330, 340, 346
294, 354
448
489
446
446
444
491
0.074
0.027
0.076
0.150
0.044
0.057
0.016
0.391
0.083
0.714
0.075
0.072
0.704
0.074
0.058
0.055
0.099
0.065
426, 440, 459
426, 439, 457
429, 443, 459
429, 443, 461
428, 444, 462
454, 469, 490
495, 532
3.24
3.10
3.30
3.30
3.28
2.96
2.97
2.95
2.95
2.95
2.81
2.68
2.72
2.85
2.84
2.89
2.97
2.96
3.00
3.00
2.82
2.86
2.98
0.28
0.13
0.35
0.35
0.33
–
4
ab
4ba
bb
bc
bd
be
bf
bg
4ca
da
fa
ga
ha
hc
hd
4hg
ic
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
294, 335, 342, 348
334, 343, 348
4
4
298, 337, 342, 346
295, 334, 341, 347
g
4
–
g
4
295, 337, 342, 348 371, 524
375, 396 409, 431
263, 319, 339, 342 379, 465
–
–
4
476, 510
3.09
3.01
3.36
3.30
3.27
3.41
3.23
3.07
2.81
2.87
3.05
0.37
0.16
0.52
0.41
0.30
0.45
0.23
0.07
0.02
0.01
0.07
4
470
332, 340, 347
294, 336, 344, 350
293, 333, 342, 348
294, 355
396
417
419
397
438
450, 480
4
432, 446, 464
425, 439, 456
449, 480
4
4
4
292, 330, 339, 342
426, 440, 456
428, 460
4
297, 331, 338, 345 364, 460
4
289, 330, 343, 344
328, 338, 345
489
487
466
455, 469, 489
477
4
298, 333, 340, 346
429, 461
a
b PL
Measured at room temperature using CHCl
3
solutions (c ~ 50 ꢁM).
λem indicates the
c
lowestꢀenergy wavelength of the maximum emission. Absolute quantum yields were measured
d
with a spectrometer equipped with an integrated sphere. Measured at 77 K using EtOH/CHCl
3
=
e
4
:1 (c ~ 50 ꢁM). Determined from the following equation: E1CT = 1240/
λonset, 1CT, where
λ
onset, 1CT
f
indicates the onset wavelength (nm) of the CT emission observed at room temperature.
Determined from the following equation: E3LE = 1240/
λ
onset, 3LE, where
λ
onset, 3LE indicates the onset
g
wavelength (nm) of the phosphorescence emission observed at 77 K. Due to the absence of CT
emission, E1CT value was not estimated.
Table 4. Selected photophysical data of DꢀA compounds in solid states
PL
PH
Compd
λabs
λem
ΦPL
a,c
λem
E
1CT
E
3LE
ꢀE1CTꢀ3LE
a
a,b
d
e
f
(
nm)
(nm)
387
(%)
0.216
(nm)
(eV)
3.37
(eV)
2.74
(eV)
4aa
316
464, 504
0.63
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4
ab
ba
–
388
0.040
0.210
–
3.82
3.16
–
–
4
286, 318, 345
410, 434
410, 438, 487,
2.64
0.52
5
03, 527, 548,
565, 597
483, 495
470
4bb
281, 319, 343
285, 318, 346
314, 348, 370
320, 377
416
450
464
493
0.126
0.185
0.067
–
3.21
3.22
3.02
2.88
3.02
3.01
3.01
3.26
3.37
2.86
2.92
2.68
2.48
–
0.35
0.30
0.34
0.40
–
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
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5
5
5
5
5
5
5
5
5
6
0
1
2
3
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9
0
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2
3
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9
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9
0
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2
3
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7
8
9
0
4bc
bd
be
bf
bg
ca
da
4fa
4
495, 544, 560
516, 556
–
4
4
318, 348, 376, 393 433, 458
0.097
0.066
0.304
0.221
0.073
4
284, 386
332, 340, 347
283, 318, 352
281, 324
460
396
426
401
470
2.85
2.64
2.81
2.85
0.16
0.37
0.45
0.52
4
507, 524
476, 512
410, 468, 487,
4
5
20
4
ga
ha
hc
286, 329
282, 320, 365
287, 322, 349
316, 364
415
419
414
383
456
0.218
0.094
0.071
0.061
0.132
0.063
416, 477, 517
438, 476, 501
476, 506
551, 568
532
3.02
3.24
2.68
2.81
2.75
2.44
2.58
2.77
0.34
0.43
–
4
g
4
–
g
4
hd
hg
–
–
4
287
2.99
2.92
0.41
0.15
4ic
286, 320, 349, 414
455
b PL
476
a
Measured at room temperature.
λem indicates the lowestꢀenergy wavelength of the maximum
c
emission. Absolute quantum yields were measured with a spectrometer equipped with an
d
e
integrated sphere. Measured at 77 K. Determined from the following equation: E1CT
=
1
240/
λ
onset, 1CT, where λonset, 1CT indicates the onset wavelength (nm) of the CT emission observed at
f
room temperature. Determined from the following equation: E3LE = 1240/
λ
onset, 3LE, where
λ
g
onset,
3
LE indicates the onset wavelength (nm) of the phosphorescence emission observed at 77 K. The
1
CT and LE emissions seem to be overlapped, and the CT emission is too weak. Therefore, the CT
energies cannot be determined.
Time-Resolved Photophysical Analysis
To investigate the dynamic behavior of the photoꢀexcited states of a promising DꢀA
compound 4hc that shows a small ꢀE1CTꢀ3LE, timeꢀresolved luminescence spectroscopy of 4hc was
®�
performed in both inert nonꢀpolar Zeonex host (Figure 3a and b) and DPEPO host (Figure 4a and
b), the latter of which was used to mimic the chemical environment within an OLED device. Also,
3
to explore the effect of the CF position of the BBZFPy core on photophysical properties, the
1
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photophysics of 4ic, which is a regioisomer of 4hc, was also investigated (Figure 3c, d; Figure 4c, d).
Both showed emissions within two distinct time regions. The first, decaying with a lifetime within
the nanosecond time regime in all the materials, is attributed to prompt emission from the singlet
excited state due to its temperature independence (Figure 3a, c; Figure 4a, c). The emission spectra
®�
acquired in both Zeonex and DPEPO at the time delay (TD) of 3 ns showed a Gaussianꢀlike peak
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(black and green lines in Figure 3b, d; Figure 4b, d) that decayed quite fast and then reappeared in
almost the same place (blue lines in Figure 3b, d) or in the lower energy region (blue line in Figure
4d) over longer times. The first species can be attributed to the emission from the charge transfer
1
(
CT) singlet excited state. The energy onset of this CT emission follows the same trend as
®
�
observed in solution (Figure 2): 3.38 eV for 4hc and 3.32 eV for 4ic in Zeonex ; 3.28 eV for 4hc
and 3.20 eV for 4ic in DPEPO host.
At the longer delay times, in the microsecond/millisecond delay time regions, delayed
®
�
emission (DE) was observed in Zeonex
(Figure 3a, c). Depending upon the experimental
temperature, both the singlet state DE and triplet state emission were observed on similar millisecond
timescales, and therefore the emission from each state is most easily elucidated upon spectral
inspection at different temperatures (Figure 3a, c). At ambient temperature, the DE was observed
with the same spectral shape and onset energy as the prompt CT spectra (Figure 3b, d). Therefore,
it can be identified as delayed fluorescence (DF), but the emission is so weak, it would be difficult to
15
distinguish between TADF and tripletꢀtriplet annihilation (TTA) process. With all the materials,
the emission from the triplet state was observed at a low temperature (80 K), with this triplet energy
®�
being found at 3.00 eV (4hc) and 2.98 (4ic) in Zeonex (Figure 3b, d) and 2.96 eV (4hc) and 2.96
(4ic) in DPEPO (Figure 4b, d). From the energetical point of view, ꢁEST of the materials are
®
�
estimated to be 0.38 eV (4hc) and 0.36 (4ic) in Zeonex (Figure 3b, d), and 0.32 eV (4hc) and 0.24
eV (4ic) in DPEPO (Figure 4b, d). These moderate values suggested a moderate exchange energy,
probably due to the moderate DꢀA twisted angles.
®�
As for the compounds in Zeonex
host, we can conclude that there is some DF
contribution, while in DPEPO host, their behavior is different. It seems that there is no DF
emission at all. Moreover, the delayed emission disappeared for compound 4hc at a higher
temperature (Figure 4b). What is interesting, in the film composed of compound 4ic with the
DPEPO host, there was a weak room temperature phosphorescence (RTP), which might be a
16
candidate for RTP materials for future organic electronic applicastions.
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®
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Figure 3. (a) Plot of 1% w/w 4hc in Zeonex emission intensity against delay time measured 80 K
(black), 130 K (red), 180 K (green), 230 K (blue), 280 K (cyan), 330 K (pink). (b) Normalized
®�
intensity spectra of 1% w/w 4hc in Zeonex at both 330 K and 80 K. (c) Plot of 1% w/w 4ic in
®
�
Zeonex emission intensity against delay time measured 80 K (black), 130 K (red), 180 K (green),
230 K (blue), 280 K (cyan), 330 K (pink). (d) Normalized intensity spectra of 1% w/w 4ic in
®
�
Zeonex at both 330 K and 80 K.
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Figure 4. (a) Plot of 10% w/w 4hc in DPEPO emission intensity against delay time measured 80 K
(black), 130 K (red), 180 K (green), 230 K (blue), 280 K (cyan), 330 K (pink). (b) Normalized
emission spectra of 10% w/w 4hc in DPEPO at varying delay times at 330 K and 80 K. (c) Plot of
10% w/w 4ic in DPEPO emission intensity against delay time measured 80 K (black), 130 K (red),
180 K (green), 230 K (blue), 280 K (cyan), 330 K (pink). (d) Normalized emission spectra of 10%
w/w 4ic in DPEPO at varying delay times at 330 K and 80 K.
OLED Applications
Before applying the compounds 4hc and 4ic as blue emitters in OLED devices, their
thermal stabilities were investigated with thermogravimetric analyses (TGA). The degradation
temperatures (defined at 5 wt% loss) T of 4hc and 4ic under air were found over 330 °C (Figure
d
S10), which are high enough for the purification and deposition of OLED devices with vacuum
thermal deposition method. As the final step of the analyses, the OLED devices were fabricated
(Figure 5). The device structures of [ITO/NPB (50 nm)/CzSi (10 nm)/10% 4hc (dev 1) or 4ic (dev
3) in mCP (20 nm)/TPBi (50 nm)/LiF (1 nm)/Al (100 nm)] and [ITO/NPB (40 nm)/CzSi (10
nm)/10% 4hc (dev 2) or 4ic (dev 4) in DPEPO (20 nm)/DPEPO (10 nm)/TPBi (50 nm)/LiF (1
nm)/Al (100 nm)] were chosen for comparison (Figure 5). The inspection of the characteristics of
the fabricated OLED revealed that the EL observed in all the devices are ascribed to the CT
emissions from the compounds 4hc and 4ic. The overall efficiency is moderate (around 1%), which
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should be caused by low delayed fluorescence contribution. The most efficient devices were the
ones fabricated with DPEPO host, which resulted an efficiency around 1.5% external quantum
2
efficiency (EQE) with the brightness up to 2000 cd/m (Figure 5). The turnꢀon voltage was between
2 V (dev 2) and 3 V (dev 1), while the OLED characteristic showed the rollꢀoff dependency,
especially for device 4.
1
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9
0
Figure 5. Device characteristic of dev 1–4.
Conclusion
In conclusion, we have established a highly atomꢀ and stepꢀeconomical synthetic
procedures for diverse DꢀAꢀstructured BBZFPys utilizing a Pdꢀcatalyzed intramolecular double C–
H/C–H oxidative coupling of chlorinated 2,6ꢀdiaryloxypyridines and the subsequent
BuchwaldꢀHartwig amination. With this protocol, a series of regioisomers of DꢀAꢀtype BBZFPys
are selectively accessible. The steadyꢀstate photophysical investigation of the DꢀA compounds has
showed that they are emissive in violetꢀtoꢀgreen region, with ꢁEST values being moderately narrow
in solution and solid states. Timeꢀresolved inspection has revealed the hostꢀdependent involvement
®
�
of delayed fluorescence from 4hc and 4ic in Zeonex host, while the 4ic in DPEPO shows RTP.
Furthermore, these compounds have been demonstrated to be utilized as blueꢀemitters in OLED
devices, with the EQE achieving 1.5 %.
Experimental Section
General Experimental Methods. Nuclear magnetic resonance spectra were measured operating at
1
13
19
1
4
00 MHz ( H NMR), at 100 MHz ( C NMR), and at 376 MHz ( F NMR). H NMR chemical
13
shifts were reported in ppm relative to the resonance in TMS at δ 0.00. C NMR chemical shifts
were reported in ppm relative to the residual solvent signals of CDCl at δ 77.16. High resolution
3
mass spectra (HRMS) were recorded with APCIꢀTOF. Melting points were measured with Mettler
Toledo MP90. GC analysis was carried out using a Shimadzu silicon OVꢀ17 column (2.6 mm × 1.5
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m). UVꢀvis spectra were acquired with Shimadzu UVꢀ2500 PC and JASCO Vꢀ750 spectrometers.
PL spectra and PLQY measurements were conducted with Shimadzu RFꢀ5300PC Spectro Fluoro
Photometer (fluorescence) and JASCO FPꢀ8500 Spectro Fluoro Photometer (phosphorescence).
17
The DFT calculations were performed by using the Gaussian 09 package.
Materials. DMSO, NMP, and oꢀxylene were dried over CaH
2
and distilled under reduced
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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1
2
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4
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8
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1
2
3
4
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
pressure before use. All the other reagents were purchased from commercial sources and used as
received without further purification.
General procedure for the preparation of 2-chloro-6-aryloxypyridines 1a–1d
(
Conditions A in Scheme 1): To a flask (50 mL) equipped with a magnetic stirring bar,
,6ꢀdichloropyridine (2.20 g, 15 mmol), phenol derivative (7.5 mmol), and K CO (8.29 g, 60 mmol)
were added, and the atmosphere inside the flask was replaced with N gas. DMSO (20 mL) was
2
2
3
2
added to the flask with a syringe, and the resulting solution was stirred at 160 °C for 24 h. After the
reaction completed, AcOEt (20 mL) and water (20 mL) were added to the reaction mixture, and the
2 4
organic layer was extracted with AcOEt for 3 times, dried with Na SO , and filtered through
activated alumina. The filtrate was concentrated under reduced pressure to give oil residue, which
was then dissolved in an eluent and purified by column chromatography on silica gel. Further
purification was conducted with GPC.
2-Chloro-6-phenoxypyridine (1a) [CAS No. 23628-24-2]. Purified by column
3
chromatography (eluent nꢀhex/AcOEt 20:1) on silica gel followed by GPC (CHCl ). 2.01 g, 93%,
1
white solid; m.p. 83.8–85.8 °C; H NMR (400 MHz, CDCl
3
) δ 6.73 (dd, J = 8.1, 0.6 Hz, 1H), 7.03
(dd, J = 7.6, 0.6 Hz, 1H), 7.12–7.15 (m, 2H), 7.22 (tt, J = 7.5, 1.1 Hz, 1H), 7.38–7.43 (m, 2H), 7.61
1
3
(dd, J = 8.0, 8.1 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 109.2, 118.6, 121.1, 125.2, 129.9, 141.5,
ClNO: 206.0367, found: 206.0367.
+
1
49.2, 153.7, 163.2; HRMS (APCI) m/z (M+H) calcd for C11
H
9
1
8
All the spectroscopic data are in accordance with the literature.
-Chloro-6-(4-tert-butylphenoxy)pyridine (1b). Purified by column chromatography
2
3
(eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ). 2.59 g, 94%,white solid; m.p.
1
61.4–62.4 °C; H NMR (400 MHz, CDCl
3
) δ 1.34 (s, 9H), 6.71 (dd, J = 8.1, 0.5 Hz, 1H), 7.02 (dd, J
=
7.6, 0.6 Hz, 1H), 7.07 (dd, J = 6.7, 2.1 Hz, 2H), 7.40 (dd, J = 6.7, 2.1 Hz, 2H), 7.59 (dd, J = 8.1,
13
8.1 Hz, 1H); C NMR (100 MHz, CDCl
3
): δ 31.6, 34.6, 109.0, 118.4, 120.4, 126.8, 141.4, 148.0,
+
1
49.2, 151.3, 163.5; HRMS (APCI) m/z (M+H) calcd for C15
H
17ClNO: 262.0993, found: 262.1006.
2-Chloro-6-(3-tert-butylphenoxy)pyridine (1c). Prepared by following a general
procedure using 20 mmol of 2,6ꢀdichloropyridine, 14 mmol of 3ꢀtertꢀbutylphenol, 80 mmol of
K
2
CO
3
, and 20 mL of DMSO. Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on
1
silica gel followed by GPC (CHCl
3
). 3.43 g, 88%, colorless oil; H NMR (400 MHz, CDCl
3
) δ 1.32
(s, 9H), 6.70 (d, J = 8.0 Hz, 1H), 6.95 (ddd, J = 7.9, 2.4, 1.0 Hz, 1H), 7.03 (d, J = 7.6 Hz, 1H), 7.17
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(
dd, J = 2.1, 2.1 Hz, 1H), 7.24 (ddd, J = 7.7, 1.6, 1.1 Hz, 1H), 7.32 (dd, J = 7.9, 7.9 Hz, 1H), 7.60 (dd,
13
J = 7.9, 7.9 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 31.3, 34.8, 108.9, 117.8, 118.2, 118.4, 122.1,
+
1
29.3, 141.4, 149.1, 153.52, 153.56, 163.3; HRMS (APCI) m/z (M+H) calcd for C15
H17ClNO:
262.0993, found: 262.0992.
-Chloro-6-(2-tert-butylphenoxy)pyridine (1d). Prepared by following a general
procedure using 20 mmol of 2,6ꢀdichloropyridine, 14 mmol of 3ꢀtertꢀbutylphenol, 80 mmol of
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
K
2
CO
3
, and 20 mL of DMSO. Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on
1
silica gel followed by GPC (CHCl
MHz, CDCl
Hz, 1H), 7.13–7.23 (m, 2H), 7.44 (dd, J = 7.7, 1.7 Hz, 1H), 7.59 (dd, J = 7.8, 7.8 Hz, 1H); C NMR
3
). 3.37 g, 92%, white solid; m.p. 36.1–37.8 °C; H NMR (400
3
) δ 1.37 (s, 9H), 6.66 (d, J = 8.1 Hz, 1H), 6.95 (dd, J = 7.8, 1.4 Hz, 1H), 7.03 (d, J = 7.6
13
(100 MHz, CDCl
3
) δ 30.3, 34.7, 109.3, 118.3, 122.5, 125.0, 127.2, 127.6, 141.4, 141.6, 149.4, 152.6,
+
1
63.5; HRMS (APCI) m/z (M+H) calcd for C15
H17ClNO: 262.0993, found: 262.0998.
General procedure for the preparation of 2-bromo-6-aryloxypyridines 1e and 1f
11
(Conditions B in Scheme 1): These compounds were prepared by modifying a reported procedure.
To a flask (100 mL) equipped with a magnetic stirring bar, 2,6ꢀdibromopyridine (6.39 g, 27 mmol),
CuI (514.2 mg, 2.7 mmol, 10 mol%), picolinic acid (664.8 mg, 5.4 mmol, 20 mol%), and K PO
11.46 g, 54 mmol) were added, and the atmosphere inside the flask was replaced with N gas.
3
4
(
2
Phenol derivative (15 mmol) was dissolved into DMSO (50 mL), which then was added to the flask
with a syringe, and the resulting solution was stirred at 90 °C for 24 h. After the reaction
completed, AcOEt (80 mL), water (80 mL), and ethylenediamine (10 mL) were added to the reaction
2 4
mixture, and the organic layer was extracted with AcOEt for 3 times, dried with Na SO , and filtered
through activated alumina. The filtrate was concentrated under reduced pressure to give oil residue,
which was then dissolved in an eluent and purified by column chromatography on silica gel.
Further purification was conducted with GPC.
2-Bromo-6-[4-(trifluoromethyl)phenoxy]pyridine
(1e).
Purified
by
column
chromatography (eluent nꢀhex/AcOEt 5:1) on silica gel followed by GPC (CHCl
3
). 2.41g, 51%, pale
1
yellow oil; H NMR (400 MHz, CDCl
3
) δ 6.89 (dd, J = 8.1, 0.6 Hz, 1H), 7.24–7.27 (m, 3H), 7.58 (dd,
13
J = 7.7, 7.7 Hz, 1H), 7.66 (dd, J = 8.9, 0.4 Hz, 2H); C NMR (100 MHz, CDCl
3
) δ 110.5, 121.0,
123.4, 124.1 (q, J = 272.0 Hz), 127.0 (q, J = 33 Hz), 127.1 (q, J = 3.7 Hz), 139.2, 141.6, 156.5,
19
+
1
62.0; F NMR (376 MHz, CDCl
17.9736, found: 317.9735.
3 8 3
) δ –61.99; HRMS (APCI) m/z (M+H) calcd for C12H BrF NO:
3
2-Bromo-6-[3-(trifluoromethyl)phenoxy]pyridine
(1f).
Purified
by
column
chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
3
). 3.58 g, 75%,
1
pale yellow oil; H NMR (400 MHz, CDCl
3
) δ 6.87 (d, J = 8.0 Hz, 1H), 7.23–7.26 (m, 1H), 7.35 (dd,
13
J = 7.9, 1.7 Hz, 1H), 7.42 (s, br, 1H), 7.46–7.59 (m, 3H); C NMR (100 MHz, CDCl
3
) δ 110.2,
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1
18.2 (q, J =3.7 Hz), 121.7 (q, J = 4.0 Hz), 123.2, 123.7 (q, J = 273.1 Hz), 124.4, 130.3, 1321.29 (q,
19
3
J = 33.0 Hz), 139.27, 141.5, 153.9, 162.2; F NMR (376 MHz, CDCl ) δ –62.66; HRMS (APCI)
+
m/z (M+H) calcd for C12
H
8
BrF
3
NO: 317.9736, found: 317.9735.
General procedure for the preparation of 2a–2g (Conditions C in Scheme 1): To a flask
equipped with a magnetic stirring bar, 2ꢀhaloꢀ6ꢀaryloxypyridine 1 (9.81 mmol), phenol derivative
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(11.7 mmol), and K
2 3
CO (4.06 g, 29.4 mmol) were added, and the atmosphere inside the flask was
replaced with N gas. DMSO (13 mL) was added to the flask with a syringe, and the resulting
2
solution was stirred at 160 °C for 24 h. After the reaction completed, AcOEt and water were added
to the reaction mixture, and the organic layer was extracted with AcOEt for 3 times, dried with
Na
2
4
SO , and filtered through activated alumina. The filtrate was concentrated under reduced
pressure to give oil residue, which was then dissolved in CHCl
3
and purified by column
chromatography on silica gel. Further purification was conducted with GPC.
2-(4-Chlorophenoxy)-6-phenoxypyridine (2a). Purified by column chromatography
1
(eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
3
). 2.62 g, 80%, pale yellow oil; H
NMR (400 MHz, CDCl
3
) δ 6.52 (ddd, J = 8.0, 7.9, 0.5 Hz, 2H), 6.99–7.11 (m, 4H), 7.17 (tt, J = 7.4,
13
1.2 Hz, 1H), 7.23–7.28 (m, 2H), 7.30–7.35 (m, 2H), 7.64 (dd, J = 8.0, 8.0 Hz, 1H); C NMR (100
MHz, CDCl
3
) δ 104.4, 121.2, 121.3, 122.6, 122.7, 124.8, 129.4, 129.5, 142.3, 152.4, 153.8, 162.0,
+
162.5; HRMS (APCI) m/z (M+H) calcd for C17
H13ClNO
2
: 298.0629, found: 298.0628.
2
-(4-tert-Butylphenoxy)-6-(4-chlorophenoxy)pyridine (2b) [CAS No. 2085326-80-1].
Prepared by following a general procedure on a 6 mmol scale (1b). Purified by column
chromatography (eluent nꢀhex/AcOEt 20:1) on silica gel followed by GPC (CHCl ). 1.52 g, 72%,
colorless oil; Spectroscopy data were in good agreement with those reported previously. H NMR
3
6
1
(
(
(
3
400 MHz, CDCl ) δ 1.33 (s, 9H), 6.49 (dd, J = 8.0, 0.5 Hz, 1H), 6.51 (dd, J = 7.9, 0.5 Hz, 1H), 6.97
d, J = 8.9 Hz, 2H), 7.02 (d, J = 8.9 Hz, 2H), 7.23 (d, J = 8.9 Hz, 2H), 7.31 (d, J = 8.9 Hz, 2H), 7.62
+
dd, J = 7.9, 7.8 Hz, 1H); HRMS (APCI) m/z (M+H) calcd for C21
2
H21NO Cl: 354.1255, found:
6
354.1264. All the spectroscopic data are in accordance with the literature.
2-(4-tert-Butylphenoxy)-6-(3-chlorophenoxy)pyridine (2c) [CAS No. 2085326-82-3].
Prepared by following a general procedure on a 11.5 mmol scale (1b). Purified by column
3
chromatography (eluent nꢀhex/AcOEt 20:1) on silica gel followed by GPC (CHCl ). 2.47 g, 61%,
1
colorless oil; H NMR (400 MHz, CDCl
3
) δ 1.31 (s, 9H), 6.53 (dd, J = 7.5, 7.4 Hz, 2H), 6.97–7.02
(m, 3H), 7.08–7.12 (m, 2H), 7.21 (dd, J = 8.3, 8.1 Hz, 1H), 7.32–7.34 (m, 2H), 7.64 (dd, J = 8.2, 7.9
1
3
Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 31.5, 34.5, 104.4, 104.6, 119.5, 120.7, 121.7, 124.7, 126.4,
+
130.1, 134.5, 142.3, 147.5, 151.3, 154.6, 161.82, 162.81; HRMS (APCI) m/z (M+H) calcd for
C
21
H
2
21ClNO : 354.1255, found: 354.1245. All the spectroscopic data are in accordance with the
6
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-(3-tert-Butylphenoxy)-6-(4-chlorophenoxy)pyridine (2d). Prepared by following a
general procedure on a 5.73 mmol scale (1c). Purified by column chromatography (eluent
1
nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
MHz, CDCl
.4, 1.1 Hz, 1H), 7.02–7.04 (m, 2H), 7.08 (dd, J = 2.1, 2.1 Hz, 1H), 7.18–7.27 (m, 4H), 7.63 (dd, J =
3
). 1.45 g, 72%, colorless oil; H NMR (400
3
) δ 1.27 (s, 9H), 6.48 (d, J = 7.8 Hz, 1H), 6.54 (d, J = 7.8 Hz, 1H), 6.88 (ddd, J = 7.8,
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
7.8, 7.8 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 31.3, 34.8, 104.2, 104.4, 118.3, 118.5, 121.8, 122.6,
+
1
29.1, 129.4, 129.6, 142.3, 152.4, 153.3, 153.7, 162.0, 162.8; HRMS (APCI) m/z (M+H) calcd for
C
21
H
21ClNO
2
: 354.1255, found: 354.1257.
2-(3-tert-Butylphenoxy)-6-(3-chlorophenoxy)pyridine (2e). Prepared by following a
general procedure on a 5.73 mmol scale (1c). Purified by column chromatography (eluent
1
nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
MHz, CDCl
3
). 1.27 g, 63%, yellow oil; H NMR (400
3
) δ 1.27 (s, 9H), 6.50 (dd, J = 8.0, 0.5 Hz, 1H), 6.56 (dd, J = 7.9, 0.5 Hz, 1H), 6.90 (ddd,
J = 8.0, 2.3, 1.1 Hz, 1H), 6.99 (ddd, J = 8.2, 2.3, 1.0 Hz, 1H), 7.08–7.11 (m, 3H), 7.17–7.28 (m, 3H),
13
7
.65 (dd, J = 7.9, 7.9 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 31.3, 34.8, 104.6, 104.7, 118.2, 118.4,
119.4, 121.6, 121.8, 124.6, 129.0, 130.1, 134.6, 142.3, 153.3, 153.7, 154.7, 161.7, 162.8; HRMS
+
(
APCI) m/z (M+H) calcd for C21
H21ClNO
2
: 354.1255, found: 354.1237.
2-(2-tert-Butylphenoxy)-6-(4-chlorophenoxy)pyridine (2f). Prepared by following a
general procedure on a 5.73 mmol scale (1d). Purified by column chromatography (eluent
1
nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
MHz, CDCl
m, 2H), 7.21–7.25 (m, 2H), 7.36–7.39 (m, 1H), 7.63 (dd, J = 7.9, 7.9 Hz, 1H); C NMR (100 MHz,
3
). 1.65 g, 82%, colorless oil; H NMR (400
3
) δ 1.33 (s, 9H), 6.48–6.51 (m, 2H), 6.89–6.92 (m, 1H), 7.00–7.04 (m, 2H), 7.08–7.15
13
(
CDCl
3
) δ 30.4, 34.7, 104.1, 105.0, 122.5, 123.2, 124.7, 126.9, 127.3, 129.4, 129.6, 141.5, 1421.2,
+
1
3
52.6, 152.7, 162.1, 162.9; HRMS (APCI) m/z (M+H) calcd for C21
H
21ClNO
2
: 354.1255, found:
54.1255.
2-(2-tert-Butylphenoxy)-6-(3-chlorophenoxy)pyridine (2g). Prepared by following a
general procedure on a 5.73 mmol scale (1d). Purified by column chromatography (eluent
1
nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
MHz, CDCl
J = 8.2, 2.1, 1.0 Hz, 1H), 7.06–7.16 (m, 4H), 7.17–7.22 (m, 1H), 7.37 (dd, J = 7.8, 1.9 Hz, 1H), 7.65
3
). 1.66 g, 82%, colorless oil; H NMR (400
3
) δ 1.33 (s, 9H), 6.53 (dd, J = 7.9, 7.9 Hz, 2H), 6.92 (dd, J = 7.8, 1.6 Hz, 1H), 6.96 (ddd,
1
3
(
dd, J = 7.9, 7.9 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 30.4, 34.7, 104.4, 105.4, 119.2, 121.5,
1
23.1, 124.6, 124.7, 126.9, 127.3, 130.1, 134.5, 141.5, 142.3, 152.7, 154.8, 161.8, 162.9; HRMS
+
(
2
APCI) m/z (M+H) calcd for C21H21ClNO : 354.1255, found: 354.1236.
General procedure for the preparation of 2h and 2i (Conditions D in Scheme 1): These
6
compounds were prepared by modifying a reported procedure. To a flask (20 mL) equipped with a
magnetic stirring bar, 2ꢀbromꢀ6ꢀaryloxypyridine 1e or 1f (5.00 mmol), phenol derivative (7.00
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mmol), CuI (95.2 mg, 0.50 mmol, 10 mol%), and Cs
2 3
CO (2.44 g, 7.5 mmol) were added, and the
atmosphere inside the flask was replaced with N gas. NMP (10 mL) was added to the flask with a
2
syringe, and the resulting solution was stirred at 160 °C for 24 h. After the reaction completed,
AcOEt and water were added to the reaction mixture, and the organic layer was extracted with
AcOEt for 3 times, dried with Na
concentrated under reduced pressure to give oil residue, which was then dissolved in CHCl
purified by column chromatography on silica gel. Further purification was conducted with GPC.
-(4-Chlorophenoxy)-6-(4-(trifluoromethyl)phenoxy)pyridine (2h). Purified by column
2
SO
4
, and filtered through activated alumina. The filtrate was
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
and
2
3
chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ). 1.65g, 90%,
1
pale yellow oil; H NMR (400 MHz, CDCl
3
) δ 6.58 (dd, J = 8.0, 0.5 Hz, 1H), 6.62 (dd, J = 7.9, 0.5
Hz, 1H), 6.96–7.00 (m, 2H), 7.15 (d, J = 8.3 Hz, 2H), 7.22–7.26 (m, 2H), 7.56 (d, J = 8.4 Hz, 2H),
13
7
.70 (dd, J = 8.0, 8.0 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 105.1, 121.4, 122.8, 124.2 (q, J =
270.7 Hz), 126.76 (q, J = 32.7 Hz), 126.78 (q, J = 3.7 Hz), 129.5, 130.1, 142.7, 152.2, 156.4, 161.4,
19
+
1
62.1; F NMR (376 MHz, CDCl
366.0503, found: 366.0507.
-(4-Chlorophenoxy)-6-(3-(trifluoromethyl)phenoxy)pyridine (2i). Purified by column
3 3 2
) δ –62.01; HRMS (APCI) m/z (M+H) calcd for C18H12ClF NO :
2
3
chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ). 1.65 g, 90%,
1
pale yellow oil; H NMR (400 MHz, CDCl
3
) δ 6.60 (dd, J = 8.0, 0.6 Hz, 1H), 6.61 (dd, J = 7.9, 0.5
Hz, 1H), 6.94–6.98 (m, 2H), 7.19–7.24 (m, 3H), 7.30–7.31 (m, 1H), 7.37–7.41 (m, 2H), 7.70 (dd, J =
1
3
8.0, 8.0 Hz, 1H); C NMR (100 MHz, CDCl
3
) δ 104.9, 105.1, 118.4 (q, J = 3.4 Hz), 121.4 (q, J =3.7
Hz), 122.7, 123.8 (q, J = 272.7 Hz), 124.8, 129.4, 130.00, 130.01, 131.9 (q, J = 33 Hz), 142.7, 152.2,
19
+
154.0, 161.6, 162.0; F NMR (376 MHz, CDCl
NO : 366.0503, found: 366.0503.
3
) δ –62.63; HRMS (APCI) m/z (M+H) calcd for
C
18
H
12ClF
3
2
General procedure for oxidative C–H/C–H coupling of 2: The reaction was conducted
6
with a slightly modified procedure from those previously reported by our group. To a Schlenk
tube (10 mL) equipped with a magnetic stirring bar, 2,6ꢀdiaryloxypyridine 2 (0.40 mmol), Pd(TFA)
2
(13.2 mg, 0.04 mmol, 10 mol%), AgOAc (267.0 mg, 1.60 mmol), and PivOH (4.0 mL) were added
under air, and the flask was capped with a septum. The mixture was stirred at 160 °C for 16 h.
After the reaction completed, CH
2
Cl
2
(5 mL) was added to the reaction mixture, and the resulting
Cl to remove the residue of silver.
suspension was filtered through a Celite pad with an eluent of CH
2
2
The filtrate was concentrated under reduced pressure to give. The solid was washed with hexane
and methanol and collected and dried with suction filtration to give doubly cyclized product 3. Any
further purifications were not conducted, and the product 3 was used for the successive amination
step.
2-Chlorobis(benzofuro)[2,3-b:3’,2’-e]pyridine (3a). The title compound was prepared
2
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under slightly modified conditions from a general procedure using Pd(TFA) (26.4 mg, 0.08 mmol,
3
20 mol%), AgOAc (400.5 mg, 2.40 mmol), and 3a was extracted with a Soxhlet extractor (CHCl ,
4.5 h) and purified by washing with hexane followed by drying with suction filter. 125.8 gm, 80%,
1
white solid; m.p. >300 °C; H NMR (400 MHz, CDCl
3
) δ 7.43–7.50 (m, 2H), 7.52–7.57 (m, 1H),
7.61 (dd, J = 8.7, 0.4 Hz, 1H), 7.69 (ddd, J = 8.3, 0.8, 0.8 Hz, 1H), 8.00 (dd, J = 2.1, 0.4 Hz, 1H),
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2
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3
3
3
3
4
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4
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4
4
4
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5
5
5
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5
6
0
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2
3
4
5
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
8.03 (ddd, J = 7.6, 1.3, 0.6 Hz, 1H), 8.77 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 109.0, 112.4, 112.5,
113.4, 120.6, 120.8, 122.9, 123.9, 124.3, 124.6, 127.71, 127.99, 129.3, 130.1, 137.4, 139.0, 154.9;
+
HRMS (APCI) m/z (M+H) calcd for C17
9 2
H ClNO : 294.0316, found: 294.0319.
2
-(tert-Butyl)-10-chlorobis(benzofuro)[2,3-
b
:3',2'-
e
]pyridine
(3b)
[CAS
No.
1
2
085326-57-2]. 92.7 mg, 75%, white solid; m.p. 202.0–204.0 °C; H NMR (400 MHz, CDCl
3
) δ 1.46
(s, 9H), 7.37 (dd, J = 8.7, 2.2 Hz, 1H), 7.47 (d, J = 8.6 Hz, 1H), 7.49 (d, J = 8.7 Hz, 1H), 7.53 (dd, J
=
8.6, 2.1 Hz, 1H), 7.97 (d, J = 2.1 Hz, 1H), 8.03 (d, J = 2.1 Hz, 1H), 8.63 (s, 1H); HRMS (APCI)
+
m/z (M+H) calcd for C21
H
2
17NO Cl: 350.0942, found: 350.0934. All the spectroscopic data are in
6
accordance with the literature.
2
-(tert-Butyl)-9-chlorobis(benzofuro)[2,3-
b
:3',2'-
e
]pyridine
(3c)
[CAS
No.
2
085326-59-4]. Prepared by following a general procedure using 1.6 mmol of 2c, Pd(TFA)
2
(0.16
mmol), AgOAc (6.4 mmol), and PivOH (16 mL) in a 50 mL Schlenk tube. 314.6 mg, 56%, white
1
solid; m.p. 269.6–271.6 °C; H NMR (400 MHz, CDCl
3
) δ 1.45 (s, 9H), 7.42 (dd, J = 8.3, 1.8 Hz,
1H), 7.59–7.60 (m, 2H), 7.69 (d, J =1.8 Hz, 1H), 7.92 (d, J = 8.3 Hz, 1H), 8.02–8.03 (m, 1H), 8.79 (s,
13
1H); C NMR (100 MHz, CDCl
3
) δ 31.9, 35.1, 111.7, 112.5, 113.0, 114.3, 117.1, 121.2, 121.7, 122.1,
+
1
22.4, 124.3, 125.6, 133.1, 134.4, 147.1, 153.0, 154.8, 162.0; HRMS (APCI) m/z (M+H) calcd for
C
21
H
2
17ClNO : 350.0942, found: 350.0947. All the spectroscopic data are in accordance with the
6
literature.
9-(tert-Butyl)-2-chlorobis(benzofuro)[2,3-b:3',2'-e]pyridine (3d). Prepared by following
a general procedure using 1.6 mmol of 2d, Pd(TFA)
2
(0.16 mmol), AgOAc (6.4 mmol), and PivOH
1
(
16 mL) in a 50 mL Schlenk tube. 110.9 mg, 19%,white solid; m.p. 249.6 °C (decomp.); H NMR
(400 MHz, CDCl
3
) δ 1.43 (s, 9H), 7.45–7.51 (m, 2H), 7.59 (d, J = 8.7 Hz, 1H), 7.70 (s, 1H), 7.93 (d,
13
J = 8.2 Hz, 1H), 7.97 (d, J = 1.7 Hz, 1H), 8.71 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.7, 35.5,
109.2, 112.3, 113.9, 114.1, 119.8, 120.2, 120.55, 120.56, 121.5, 122.46, 122.47, 124.4, 127.5, 129.2,
+
1
52.4, 152.9, 155.3; HRMS (APCI) m/z (M+H) calcd for C21
H
17ClNO
2
: 350.0942, found: 350.0942.
3-(tert-Butyl)-9-chlorobis(benzofuro)[2,3-b:3',2'-e]pyridine (3e). Prepared by following
a general procedure using 1.6 mmol of 2e, Pd(TFA)
2
(0.16 mmol), AgOAc (6.4 mmol), and PivOH
1
(
16 mL) in a 50 mL Schlenk tube. 38.0 mg, 7%, white solid; m.p. 233.7–235.7 °C; H NMR (400
MHz, CDCl
3
) δ 1.44 (s, 9H), 7.41 (dd, J = 8.3, 1.8 Hz, 1H), 7.50 (dd, J = 8.3, 1.7 Hz, 1H), 7.70 (ddd,
13
J = 4.2, 1.7, 0.4 Hz, 2H), 7.92 (ddd, J = 8.3, 4.5, 0.5 Hz, 2H), 8.73 (s, 1H); C NMR (100 MHz,
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2
2
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CDCl
3
) δ 31.7, 35.5, 108.0, 109.2, 112.5, 113.0, 114.1, 114.8, 118.3, 119.9, 120.2, 121.2, 121.4,
+
1
3
22.2, 124.3, 133.0, 135.9, 152.3, 155.3; HRMS (APCI) m/z (M+H) calcd for C21
H
17ClNO
2
:
50.0942, found: 350.0933.
8-(tert-Butyl)-2-chlorobis(benzofuro)[2,3-b:3',2'-e]pyridine (3f). Prepared by following
a general procedure using 1.6 mmol of 2f, Pd(TFA)
2
(0.16 mmol), AgOAc (6.4 mmol), and PivOH
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
(16 mL) in a 50 mL Schlenk tube. 353.6 mg, 63%, white solid; m.p. 179.8–181.5 °C; H NMR
3
(400 MHz, CDCl ) δ 1.60 (s, 9H), 7.36–7.40 (m, 1H), 7.45–7.49 (m, 2H), 7.61 (d, J = 8.8 Hz, 1H),
13
7
3
1
3
.89 (d, J = 7.0 Hz, 1H), 7.99 (d, J = 2.2 Hz, 1H), 8.75 (s, 1H); C NMR (100 MHz, CDCl ) δ 29.9,
4.6, 112.1, 113.2, 133.7, 118.4, 120.4, 122.4, 122.7, 123.7, 124.2, 124.7, 127.4, 129.1, 135.8, 152.8,
+
53.0, 161.4, 161.7; HRMS (APCI) m/z (M+H) calcd for C21
H
17ClNO
2
: 350.0942, found: 350.0940.
8-(tert-Butyl)-3-chlorobis(benzofuro)[2,3-b:3',2'-e]pyridine (3g). Prepared by following
a general procedure using 1.6 mmol of 2g, Pd(TFA)
2
(0.16 mmol), AgOAc (6.4 mmol), and PivOH
1
(16 mL) in a 50 mL Schlenk tube. 380.0 mg, 68%,white solid; m.p. 212.2–213.2 °C; H NMR (400
MHz, CDCl
1H), 7.93 (d, J = 8.3 Hz, 1H), 8.76 (s, 1H); C NMR (100 MHz, CDCl
13.8, 118.5, 121.2, 121.6, 122.3, 122.9, 123.7, 124.3, 124.8, 133.1, 135.9, 153.1, 154.8, 161.2,
3
) δ 1.60 (s, 9H), 7.36–7.47 (m, 3H), 7.70 (d, J = 1.6 Hz, 1H), 7.88 (dd, J = 7.6, 1.3 Hz,
13
3
) δ 29.9, 34.7, 112.5, 113.0,
1
+
1
61.7; HRMS (APCI) m/z (M+H) calcd for C21
-Chloro-10-(trifluoromethyl)bis(benzofuro)[2,3-
following a general procedure using 1.6 mmol of 2h, Pd(TFA)
H17ClNO
2
: 350.0942, found: 350.0933.
:3',2'- ]pyridine (3h). Prepared by
(0.16 mmol), AgOAc (6.4 mmol),
2
b
e
2
and PivOH (16 mL) in a 50 mL Schlenk tube. 399.4 mg, 69%, white solid; m.p. 257.9–259.9 °C;
1
3
H NMR (400 MHz, CDCl ) δ 7.50 (dd, J = 8.7, 2.0 Hz, 1H), 7.61 (d, J = 8.7 Hz, 1H), 7.76–7.82 (m,
13
2H), 7.99 (d, J = 2.0 Hz, 1H), 8.31 (s, 1H), 8.81 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 112.8, 112.9,
1
3
13.3, 113.5, 118.4 (q, J = 4.0 Hz), 120.7, 123.0, 123.3, 123.8, 124.3 (q, J = 273.1 Hz), 125.0 (q, J =
19
.7 Hz), 126.6 (q, J = 33.0 Hz), 128.2, 129.6, 153.1, 156.2, 162.31, 162.38; F NMR (376 MHz,
+
CDCl
3
) δ –61.11; HRMS (APCI) m/z (M+H) calcd for C18
H
8
ClF
3
NO
2
: 362.0190, found: 362.0206.
2-Chloro-9-(trifluoromethyl)bis(benzofuro)[2,3-
b
:3',2'-
e
]pyridine (3i). Prepared by
following a general procedure using 1.6 mmol of 2i, Pd(TFA)
2
(0.16 mmol), AgOAc (6.4 mmol), and
1
PivOH (16 mL) in a 50 mL Schlenk tube. 265.9 mg, 46%, white solid; m.p. 267.8–269.8 °C; H
NMR (400 MHz, CDCl
Hz, 1H), 7.94 (s, 1H), 7.99 (d, J = 2.2 Hz, 1H), 8.12 (d, J = 8.1 Hz, 1H), 8.81 (s, 1H); C NMR (100
MHz, CDCl ) δ 110.0 (q, J = 4.0 Hz), 112.7, 113.4, 113.6, 120.8, 120.9 (q, J = 3.7 Hz), 121.2, 123.7,
23.9, 124.1 (q, J = 272.0 Hz), 125.8, 128.2, 129.6, 130.0 (q, J = 33.0 Hz), 153.2, 154.0, 162.5,
3
) δ 7.50 (dd, J = 8.7, 2.1 Hz, 1H), 7.61 (d, J = 8.7 Hz, 1H), 7.72 (d, J = 8.1
13
3
1
1
19
+
3 8 3 2
62.6; F NMR (376 MHz, CDCl ) δ –61.57; HRMS (APCI) m/z (M+H) calcd for C18H ClF NO :
362.0190, found: 362.0203.
General Procedure for Pd-Catalyzed Buchwald-Hartwig Amination of Chlorinated
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BBZFPys: According to the literature, the BuchwaldꢀHartwig amination of chlorinated BBZFPys
were conducted by the following procedure: To the Schlenk tube (10 mL), chlorinated BBZFPy (e.g.,
3
d, 175 mg, 0.50 mmol), [(πꢀallyl)PdCl]
2
(3.6 mg, 10 ꢁmol, 2.0 mol%), MoPhos (14.0 mg, 40 ꢁmol,
8.0 mol%), NaOtꢀBu (57.6 mg, 0.6 mmol, 1.2 equiv) and oꢀxylene (2 mL) were added under the N
2
atmosphere. The resulting mixture was stirred at 130 °C for 16 h. After the reaction completed,
AcOEt (20 mL) and water (20 mL) were added to the reaction mixture, and the organic layer was
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0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2 4
extracted with AcOEt for 3 times, dried with Na SO , and filtered through activated alumina. The
filtrate was concentrated under reduced pressure to give solid. The resulting solid was dissolved in
chloroform and purified by column chromatography on silica gel. Further purification was
conducted with GPC (CHCl
3
).
2
-(9 -Carbazol-9-yl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4aa). Purified by column
H
3
chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ). 35.9 mg, 17%,
1
white solid; m.p. >300 °C; H NMR (400 MHz, CDCl
3
) δ 7.33 (ddd, J = 8.0, 6.1, 1.7 Hz, 2H), 7.41–
7
.47 (m, 5H), 7.55 (td, J = 8.2, 1.0 Hz, 1H), 7.70 (dd, J = 8.3, 2.2 Hz, 2H), 7.90 (d, J = 8.6 Hz, 1H),
13
8.01 (d, J = 7.6 Hz, 1H), 8.19–8.21 (m, 3H), 8.80 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 109.7,
1
12.4, 113.0, 113.6, 113.9, 119.8, 120.2, 120.5, 120.8, 122.6, 123.0, 123.4, 123.9, 124.4, 126.2, 127.0,
+
1
27.9, 133.6, 141.5, 153.5, 154.9, 162.0, 162.2; HRMS (APCI) m/z (M+H) calcd for C29
H
17
2
N O
2
:
425.1285, found: 425.1288.
2
-(9H-[3,9'-Bicarbazol]-9-yl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4ab). Purified by
3
column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ). 9.4
1
mg, 3%, white solid; m.p. 197.2–198.2 °C; H NMR (400 MHz, CDCl
3
) δ 7.27–7.62 (m, 13H), 7.71
(d, J = 8.2 Hz, 1H), 7.79 (dd, J = 8.6, 2.3 Hz, 1H), 7.96 (d, J = 8.6 Hz, 1H), 8.02 (d, J = 7.0 Hz, 1H),
13
8
.16–8.21 (m, 3H), 8.29 (d, J = 2.0 Hz, 1H), 8.34 (d, J = 1.2 Hz, 1H), 8.85 (s, 1H); C NMR (100
MHz, CDCl ) δ 109.9, 110.1, 110.8, 112.4, 112.9, 113.8, 114.0, 119.7, 119.8, 120.4, 120.86, 120.89,
22.6, 123.0, 123.1, 123.2, 123.9, 124.5, 124.6, 125.8, 126.0, 126.9, 128.0, 130.2, 133.3, 140.6,
3
1
1
+
41.6, 142.0, 142.2, 153.73, 153.78, 154.9, 162.1, 162.2; HRMS (APCI) m/z (M+H) calcd for
C
41
H
24
N
3
O
2
: 590.1863, found: 590.1863.
2
-(tert-Butyl)-10-(9 -carbazol-9-yl)bis(benzofuro)[2,3-
H
b
:3',2'-
e
]pyridine
(4ba).
Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC
1
(CHCl
3
). 173.5 mg, 72%, white solid; m.p. 190.5–192.5 °C; H NMR (400 MHz, CDCl
3
) δ 1.44 (s,
9
2
H), 7.33 (ddd, J = 8.0, 5.8, 2.1 Hz, 2H), 7.14–7.45 (m, 4H), 7.60–7.62 (m, 2H), 7.70 (dd, J = 8.7,
13
.2 Hz, 1H), 7.90 (d, J = 8.7 Hz, 1H), 8.02 (s, 1H), 8.19–8.21 (m, 3H), 8.83 (s, 1H); C NMR (100
) δ 31.9, 35.1, 107.3, 109.7, 111.7, 112.8, 113.6, 114.3, 117.2, 119.6, 120.2, 122.2, 122.8,
MHz, CDCl
3
123.4, 124.5, 125.7, 126.2, 126.8, 133.6, 141.5, 147.5, 153.1, 153.5, 162.0, 162.3; HRMS (APCI)
+
m/z (M+H) calcd for C33
H
25
N
2
O
2
: 481.1911, found: 481.1908.
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3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
-(9
H
-[3,9'-Bicarbazol]-9-yl)-10-(tert-butyl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4bb).
Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC
1
(
CHCl
3
). 175.7 mg, 55%, white solid; m.p. 257.2–258.9 °C; H NMR (400 MHz, CDCl
3
) δ 1.46 (s,
9H), 7.30–7.39 (m, 3H), 7.44 (d, J = 3.6 Hz, 4H), 7.50–7.52 (m, 2H), 7.57–7.64 (m, 4H), 7.77 (dd, J
8.6, 2.1 Hz, 1H), 7.93 (d, J = 8.6 Hz, 1H), 8.03 (s, 1H), 8.16–8.21 (m, 3H), 8.28 (d, J = 1.8 Hz,
=
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
1H), 8.34 (d, J = 1.5 Hz, 1H), 8.86 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.9, 35.1, 109.9, 110.1,
1
1
1
6
10.8, 111.7, 112.6, 113.8, 114.4, 117.2, 119.6, 119.72, 119.78, 120.4, 120.6, 120.8, 122.1, 122.8,
23.0, 123.2, 124.5, 124.6, 125.77, 125.79, 126.0, 126.7, 126.9, 130.1, 131.0, 133.2, 140.5, 141.9,
+
42.1, 147.2, 153.1, 153.6, 162.0, 162.4; HRMS (APCI) m/z (M+H) calcd for C45
H
32
3
N O
2
:
46.2489, found: 646.2492.
2-(tert-Butyl)-10-(3,6-di-tert-butyl-9H-carbazol-9-yl)bis(benzofuro)[2,3-b:3',2'-e]pyrid
ine (4bc). Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by
1
GPC (CHCl
3
). 265.7 mg, 89%, white solid; m.p. 210.2–212.2 °C; H NMR (400 MHz, CDCl
3
) δ
1
.44 (s, 9H), 1.49 (s, 18H), 7.36 (dd, J = 8.6, 0.5 Hz, 2H), 7.49 (dd, J = 8.6, 2.0 Hz, 2H), 7.60–7.60
(m, 2H), 7.68 (dd, J = 8.7, 2.0 Hz, 1H), 7.86 (d, J = 8.6 Hz, 1H), 8.01 (dd, J = 1.7, 0.7 Hz, 1H),
1
3
8
.17–8.19 (m, 3H), 8.81 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.9, 32.1, 34.9, 35.1, 109.1, 111.6,
1
12.8, 113.4, 114.2, 116.4, 117.2, 119.2, 122.2, 122.7, 123.5, 123.9, 124.3, 125.6, 126.5, 134.1, 139.9,
+
1
5
43.1, 147.16 153.0, 153.2, 162.0, 162.3; HRMS (APCI) m/z (M+H) calcd for C41
H
41
N
O
2 2
:
93.3163, found: 593.3166.
2-(tert-Butyl)-10-(10H-phenoxazin-10-yl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4bd).
Purified by column chromatography (eluent nꢀhex/AcOEt 20:1) on silica gel followed by GPC
1
(CHCl
3
). 121.1 mg, 49%, white solid; m.p. 163.1–165.2 °C; H NMR (400 MHz, CDCl
3
): 1.45 (s,
9
H), 5.96 (dd, J = 8.0, 1.5 Hz, 2H), 6.60 (ddd, J = 7.4, 7.4, 1.6 Hz, 2H), 6.68 (ddd, J = 7.4, 7.4, 1.6
Hz, 2H), 6.74 (dd, J = 7.8, 1.6 Hz, 2H), 7.49 (dd, J = 8.6, 2.1 Hz, 1H), 7.60–7.61 (m, 2H), 7.89 (d, J
13
=
8.6 Hz, 1H), 8.01–8.02 (m, 2H), 8.79 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.9, 35.1, 111.7,
1
12.7, 113.4, 114.4, 114.9, 115.6, 117.2, 121.6, 122.1, 122.8, 123.3, 123.4, 125.6, 125.7, 130.1, 134.7,
+
25 2 3
143.8, 144.0, 147.2, 153.1, 153.9, 161.9, 162.3; HRMS (APCI) m/z (M+H) calcd for C33H N O :
4
97.1860, found: 497.1851.
2-(tert-Butyl)-10-(10H-phenothiazin-10-yl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4be).
Purified by column chromatography (eluent nꢀhex/AcOEt 20:1) on silica gel followed by GPC
1
(CHCl
3
). 67.0 mg, 17%, green solid; m.p. >300 °C; H NMR (400 MHz, CDCl
3
) δ 1.45 (s, 9H),
6
.23–6.25 (m, 2H), 6.83–6.87 (m, 4H), 7.05–7.07 (m, 2H), 7.55 (dd, J = 8.6, 2.1 Hz, 1H), 7.60–7.61
13
(
3
m, 2H), 7.90 (d, J = 8.6 Hz, 1H), 8.01–8.07 (m, 2H), 8.79 (s, 1H); C NMR (100 MHz, CDCl ) δ
31.3, 35.1, 111.6, 112.7, 114.3, 114.4, 116.0, 117.2, 120.1, 122.1, 122.7, 122.8, 123.5, 125.3, 125.7,
+
1
26.9, 127.0, 130.5, 136.5, 144.6, 147.1, 153.0, 153.8, 161.9, 162.2; HRMS (APCI) m/z (M+H)
2
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8
9
calcd for C33
H
25
N
2
O
2
S: 513.1631, found: 513.1630.
:3',2'-e]pyridin-2-yl)acridin-9(10H)-one (4bf).
10-(10-(tert-Butyl)bis(benzofuro)[2,3-
b
Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC
1
(CHCl
3
). 18.5 mg, 7%, brown solid; m.p. >300 °C; H NMR (400 MHz, CDCl
3
) δ 1.43 (s, 9H),
6.82 (d, J = 8.6 Hz, 2H), 7.30–7.34 (m, 2H), 7.50–7.54 (m, 3H), 6.60–7.64 (m, 2H), 7.99–8.04 (m,
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
3H), 8.64 (dd, J = 8.1, 1.5 Hz, 2H), 8.81 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.9, 35.1, 111.7,
1
1
12.3, 114.7, 114.9, 116.9, 117.2, 121.9, 122.0, 122.1, 122.5, 123.0, 125.6, 125.9, 127.6, 129.0, 133.5,
+
34.7, 143.6, 147.3, 153.1, 154.5, 162.0, 162.5, 178.3; HRMS (APCI) m/z (M+H) calcd for
C
34
H
25
N
2
O
3
: 509.1860, found: 509.1860.
10-(tert-Butyl)-N,N-diphenylbis(benzofuro)[2,3-b:3',2'-e]pyridin-2-amine
(4bg).
Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC
1
(CHCl
3
). 60.6 mg, 25%, brown solid; m.p. 211.8–212.5 °C; H NMR (400 MHz, CD
2
Cl
2
) δ 1.42 (s,
9H), 7.03 (tt, J = 7.3, 1.1 Hz, 2H), 7.10–7.13 (m, 4H), 7.26–7.31 (m, 5H), 7.57–7.59 (m, 3H), 7.78 (d,
13
J = 2.3 Hz, 1H), 8.00 (s, 1H), 8.71 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.9, 35.0, 111.6, 113.0,
113.2, 113.8, 117.0, 117.1, 122.3, 122.6, 122.7, 123.7, 123.9, 125.3, 125.4, 129.4, 144.3, 146.9,
+
148.3, 151.0, 152.9, 162.01, 162.04; HRMS (APCI) m/z (M+H) calcd for C33
H
27
N
2
O
2
: 483.2067,
found: 483.2047.
-(tert-Butyl)-9-(9H-carbazol-9-yl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4ca). Purified
2
3
by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ).
1
120.7 mg, 50%, white solid; m.p. 190.5–192.5 °C; H NMR (400 MHz, CDCl
3
) 1.48 (s, 9H), 7.33
(dd, J = 7.5, 7.5 Hz, 2H), 7.45 (dd, J = 7.6, 7.2 Hz, 2H), 7.51 (d, J = 8.1 Hz, 2H), 7.62–7.67 (m, 3H),
13
3
7.91 (d, J = 1.5 Hz, 1H), 8.07 (s, 1H), 8.17–8.22 (m, 3H), 8.90 (s, 1H); C NMR (100 MHz, CDCl )
δ 31.9, 35.1, 109.8, 111.2, 111.7, 112.7, 114.3, 117.2, 120.4, 120.5, 121.5, 122.1, 122.2, 122.5, 122.7,
+
1
23.6, 125.6, 126.2, 137.0, 140.9, 147.1, 153.0, 155.2, 161.9, 162.0; HRMS (APCI) m/z (M+H)
calcd for C33 : 481.1911, found: 481.1917.
-(tert-Butyl)-2-(9 -carbazol-9-yl)bis(benzofuro)[2,3-
25 2 2
H N O
9
H
b
:3',2'-
e
]pyridine (4da). Purified
3
by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ).
1
197.3 mg, 82%, white solid; m.p. >300 °C; H NMR (400 MHz, CDCl
3
): δ 1.44 (s, 9H), 7.31–7.35
(m, 2H), 7.40–7.50 (m, 5H), 7.68 (dd, J = 8.6, 2.0 Hz, 1H), 7.72 (s, 1H), 7.87–7.92 (m, 2H), 8.17–
13
8.20 (m, 3H), 8.74 (s, 1H); C NMR (100 MHz, CDCl
3
) δ 31.6, 35.5, 109.1, 109.7, 112.7, 113.4,
114.0, 119.6, 119.8, 120.1, 120.2, 120.5, 121.4, 122.5, 123.4, 124.4, 126.1, 126.7, 133.4, 141.4,
+
1
52.3, 153.4, 155.3, 161.7, 162.1; HRMS (APCI) m/z (M+H) calcd for C33
found: 481.1912.
8-(tert-Butyl)-2-(9
by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl
25 2 2
H N O : 481.1911,
H
-carbazol-9-yl)bis(benzofuro)[2,3-
b
:3',2'-
e
]pyridine (4fa). Purified
).
3
2
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8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
1
7
56.8 mg, 65%, white solid; m.p. 284.5–285.8 °C; H NMR (400 MHz, CDCl
3
) δ 1.63 (s, 9H), 7.31–
.36 (m, 2H), 7.38 (d, J = 7.7 Hz, 1H), 7.41–7.48 (m, 5H), 7.69 (dd, J = 8.6, 2.1 Hz, 1H), 7.87 (dd, J
13
=
7.6, 1.3 Hz, 1H), 7.91 (d, J = 8.6 Hz, 1H), 8.19–8.21 (m, 3H), 8.79 (s, 1H); C NMR (100 MHz,
CDCl
3
) δ 29.9, 34.7, 109.7, 112.7, 113.6, 113.9, 118.5, 119.7, 120.2, 120.5, 122.8, 122.9, 123.4,
1
23.8, 124.4, 124.8, 126.2, 126.8, 133.5, 135.9, 141.5, 153.2, 153.5, 161.6, 162.1; HRMS (APCI)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
+
m/z (M+H) calcd for C33
H
25
N
2
O
2
: 481.1911, found: 481.1904.
8
-(tert-Butyl)-3-(9
H
-carbazol-9-yl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4ga). Purified
3
by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC (CHCl ).
1
2
03.5 mg, 85%, white solid; m.p. 244.4–247.1 °C; H NMR (400 MHz, CDCl
3
) δ 1.63 (s, 9H), 7.33
(
t, J = 7.0 Hz, 2H), 7.39–7.53 (m, 6H), 7.67 (dd, J = 8.1, 1.8 Hz, 1H), 7.93 (dd, J = 7.7, 1.6 Hz, 2H),
13
8
3
3
.18 (d, J = 7.7 Hz, 2H), 8.22 (d, J = 8.1 Hz, 1H), 8.87 (s, 1H); C NMR (100 MHz, CDCl ) δ 23.0,
4.7, 109.8, 111.2, 112.7, 113.9, 118.5, 120.4, 120.5, 121.6, 122.1, 122.4, 122.7, 123.0, 123.7, 123.8,
+
124.8, 126.2, 136.0, 137.0, 141.0, 153.2, 155.3, 161.3, 162.1; HRMS (APCI) m/z (M+H) calcd for
C
33
H
25
N
2
O
2
: 481.1911, found: 481.1908.
2
-(9 -Carbazol-9-yl)-10-(trifluoromethyl)bis(benzofuro)[2,3-b:3',2'-e]pyridine (4ha).
H
Purified by column chromatography (eluent nꢀhex/CHCl
3
5:1) on silica gel followed by GPC
1
(CHCl
3
). 190.5 mg, 77%, white solid; m.p. 289.2–290.5 °C; H NMR (400 MHz, CDCl
3
) δ 7.32–
7
8
.35 (m, 2H), 7.40–7.46 (m, 4H), 7.72–7.74 (m, 1H), 7.78–7.83 (m, 2H), 7.89–7.92 (m, 1H), 8.18–
13
.22 (m, 3H), 8.30 (s, 1H), 8.86–8.87 (m, 1H); C NMR (100 MHz, CDCl
3
) δ 109.6, 112.7, 113.7,
118.4, 119.6, 119.8, 120.3, 120.5, 123.0, 123.5, 123.9, 124.9, 125.7, 120.2, 126.4, 126.7, 127.2,
27.4, 133.9, 141.4, 153.5, 156.2, 162.2, 162.5 (*Note: some signals were observed as broad and
overlapped peaks, probably due to the presence of rotamers. Thus, it is difficult to identify the
1
19
19
3
signals that are coupled with F nuclei); F NMR (376 MHz, CDCl ) δ –61.13; HRMS (APCI) m/z
+
(M+H) calcd for C30
H F
16 3
N
2
O
2
: 493.1158, found: 493.1157.
-carbazol-9-yl)-10-(trifluoromethyl)bis(benzofuro)[2,3-
2
-(3,6-Di-tert-butyl-9
H
b
:3',2'-
e
]
pyridine (4hc). Purified by column chromatography (eluent nꢀhex/CHCl 5:1) on silica gel
3
1
followed by GPC (CHCl
3
). 229.8 mg, 76%, white solid; m.p. >300°C; H NMR (400 MHz, CDCl
3
)
δ 1.49 (s, 18H), 7.36 (d, J = 8.7 Hz, 2H), 7.50 (dd, J = 8.7, 1.9 Hz, 2H), 7.71 (dd, J = 8.7, 2.1 Hz, 1
13
H), 7.77–7.82 (m, 2H), 7.87 (d, J = 8.7 Hz, 1H), 8.19–20 (m, 3H), 8.29 (s, 1H), 8.85 (s, 1H); C
NMR (100 MHz, CDCl ) δ 32.1, 34.9, 109.0, 112.85, 112.89, 113.6, 113.9, 116.5, 118.4 (q, J = 4.2
Hz), 119.5, 123.1, 123.4, 123.5, 123.9, 124.3 (q, J = 270.5 Hz) 124.9 (q, J = 3.7 Hz), 125.7, 126.6 (q,
3
1
9
3
J = 32.3 Hz), 127.2, 134.5, 139.8, 143.3, 153.4, 156.3, 162.3, 162.6; F NMR (376 MHz, CDCl ) δ
+
–61.14; HRMS (APCI) m/z (M+H) calcd for C38
H
32
F
3
N
2
O
2
: 605.2410, found: 605.2416.
:3',2'- ]pyridine
5:1) on silica gel followed by GPC
2-(10
H
-phenoxazin-10-yl)-10-(trifluoromethyl)bis(benzofuro)[2,3-
b
e
(
4hd). Purified by column chromatography (eluent nꢀhex/CHCl
3
2
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1
(
CHCl
3
). 215.3 mg, 85%, yellow solid; m.p. 283.2–285.2 °C; H NMR (400 MHz, CDCl
3
) δ 5.95
(
dd, J = 7.8, 1.4 Hz, 2H), 6.60 (td, J = 7.8, 1.5 Hz, 2H), 6.68 (td, J = 7.8, 1.4 Hz, 2H), 6.74 (dd, J =
.8, 1.5 Hz, 2H), 7.53 (dd, J = 8.6, 2.1 Hz, 1H), 7.79–7.84 (m, 2H), 7.92 (d, J = 8.6 Hz, 1H), 8.05 (d,
7
13
J = 2.1 Hz, 1H), 8.31 (s, 1H), 8.84 (s, 1H); C NMR (100 MHz, CDCl
15.1, 115.7, 118.5 (q, J = 4.2 Hz), 121.7, 123.0, 123.4, 123.6, 123.7, 124.3 (q, J = 271.6 Hz), 125.0
(q, J = 3.3 Hz), 125.1, 126.6 (q, J = 33.0 Hz), 130.8, 134.7, 135.1, 144.1, 154.1, 156.3, 162.3, 162.0;
3
) δ 112.8, 113.0, 113.4, 113.8,
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
9
+
F NMR (376 MHz, CDCl
09.1108, found: 509.1118.
3 16 3 2 3
) δ –61.10; HRMS (APCI) m/z (M+H) calcd for C30H F N O :
5
N,N-Diphenyl-10-(trifluoromethyl)bisbenzofuro[2,3-b:3',2'-e]pyridin-2-amine (4hg).
Purified by column chromatography (eluent nꢀhex/AcOEt 10:1) on silica gel followed by GPC
1
(CHCl
3
). 191.0 mg, 77%, yellow solid; m.p. 261.9–263.3 °C; H NMR (400 MHz, CDCl
3
) δ 7.04 (t,
J = 7.2 Hz, 2H), 7.12–7.14 (m, 4H), 7.26–7.30 (m, 4H), 7.33 (dd, J = 8.8, 2.2 Hz, 1H), 7.58 (d, J =
13
8.8 Hz, 1H), 7.75–7.80 (m, 3H), 8.23 (s, 1H), 8.72 (s, 1H); C NMR (100 MHz, CDCl
12.6, 113.0, 114.2, 117.1, 118.2 (q, J = 3.9 Hz), 122.896, 122.898, 123.1, 123.4, 123.8, 124.3 (q, J =
271.4 Hz), 124.6 (q, J = 3.7 Hz), 125.8, 126.4 (q, J = 32.5 Hz), 129.5, 144.6, 148.2, 151.1, 156.0,
3
) δ 112.2,
1
19
+
1
61.9, 162.5; F NMR (376 MHz, CDCl
: 495.1315, found: 495.1295.
-(3,6-Di-tert-butyl-9 -carbazol-9-yl)-9-(trifluoromethyl)bis(benzofuro)[2,3-
pyridine (4ic). Purified by column chromatography (eluent nꢀhex/CHCl
by GPC (CHCl
CDCl
2H), 7.90 (dd, J = 8.6, 0.5 Hz, 1H), 7.98 (s, 1H), 8.12 (d, J = 8.1 Hz, 1H), 8.19–8.20 (m, 3H), 8.86 (s,
3
) δ –61.14; HRMS (APCI) m/z (M+H) calcd for
30 18 3 2 2
C H F N O
2
H
b:3',2'-e]
3
3:1) on silica gel followed
1
3
). 232.8 mg, 77%, white solid; m.p. 291.8 °C (decomp.); H NMR (400 MHz,
3
): δ 1.49 (s, 18H), 7.35 (dd, J = 8.6, 0.5 Hz, 2H), 7.49 (dd, J = 8.6, 2.0 Hz, 2H), 7.71–7.74 (m,
13
1
H); C NMR (100 MHz, CDCl
3
) δ 32.1, 34.9, 109.1, 109.8 (q, J = 4.0 Hz), 112.5, 113.6, 113.9,
1
1
16.5, 119.4, 120.8 (q, J = 3.7 Hz), 121.2, 123.5, 123.7, 123.8, 123.9, 124.3 (q, J = 272.5 Hz), 125.8,
19
27.1, 129.8 (q, J = 33.0 Hz), 134.5, 139.8, 143.3, 153.3, 154.0, 162.4, 162.7; F NMR (376 MHz,
+
CDCl
3
) δ –61.54; HRMS (APCI) m/z (M+H) calcd for C38
H
32
F
3
N
2
O
2
: 605.2410, found: 605.2405.
Photophysics. Photoluminescence spectra of thin films were recorded at room temperature
with Edinburgh Instruments FLS980 fluorescence spectrometer with Xeꢀlamp as an excitation source
and Rꢀ928 photomultiplier detector. Phosphorescence, prompt fluorescence (PF), and delayed
fluorescence (DF) spectra and decays were recorded using nanosecond gated luminescence and
lifetime measurements (from 400 ps to 1 s) using either third harmonics of a high energy pulsed
2
Nd:YAG laser emitting at 355 nm (EKSPLA) or a N laser emitting at 337 nm. Emission was
focused onto a spectrograph and detected on a sensitive gated iCCD camera (Stanford Computer
Optics) having a subꢀnanosecond resolution. PF/DF timeꢀresolved measurements were performed by
exponentially increasing gate and integration times. Temperatureꢀdependent experiments were
2
9
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