Efficient synthesis of 9,10-bis(phenylethynyl)anthracene derivatives by integration of sonogashira coupling and double-elimination reactions

Article abstract of DOI:10.1055/s-0032-1316867

9,10-Bis(phenylethynyl)anthracene (BPEA) derivatives were synthesized from 10-bromo-9-anthracenecarbaldehyde by stepwise Sonogashira coupling with phenylethynes and the one-shot double-elimination reaction with benzyl phenyl sulfones. Those two reactions could be integrated in a one-pot process to give unsymmetrically substituted BPEA derivatives in good yields by simple operations. This integrated process was applied to the synthesis of an extended BPEA derivative having an extra phenylethynyl group. The photophysical properties of the BPEA derivatives were investigated by UV/Vis and fluorescence spectroscopy. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0032-1316867

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PAPER
paper
Efficient Synthesis of 9,10-Bis(phenylethynyl)anthracene Derivatives by
Integration of Sonogashira Coupling and Double-Elimination Reactions
9,10-Bis(phenylethynyl)anthracenes
Shinji Toyota,*a Daiki Mamiya,a Rie Yoshida,a Ryo Tanaka,a Tetsuo Iwanaga,a Akihiro Orita,b Junzo Oterab
a
Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1 Ridaicho, Kita-ku, Okayama 700-0005, Japan
Fax +81(86)2569457; E-mail: stoyo@chem.ous.ac.jp
b
Department of Applied Chemistry, Faculty of Engineering, Okayama University of Science, 1-1 Ridaicho, Kita-ku, Okayama 700-0005, Japan
Received: 13.01.2013; Accepted after revision: 18.02.2013
Abstract: 9,10-Bis(phenylethynyl)anthracene (BPEA) derivatives
1a: R = H
were synthesized from 10-bromo-9-anthracenecarbaldehyde by
stepwise Sonogashira coupling with phenylethynes and the one-
shot double-elimination reaction with benzyl phenyl sulfones.
Those two reactions could be integrated in a one-pot process to give
unsymmetrically substituted BPEA derivatives in good yields by
simple operations. This integrated process was applied to the syn-
thesis of an extended BPEA derivative having an extra phenylethy-
nyl group. The photophysical properties of the BPEA derivatives
were investigated by UV/Vis and fluorescence spectroscopy.
1b: R = Me
1c: R = NO2
1d: R = Br
R
2: R = C≡CPh
Figure 1 9,10-Bis(phenylethynyl)anthracene (BPEA) derivatives
aromatization,2 (3) the conversion of formyl groups in an-
thracenecarbaldehydes into ethynyl groups, and (4) the
elimination from 9,10-bis(phenylethenyl)anthracenes.15
Previously, unsymmetric BPEA derivatives were pre-
pared from symmetric starting materials by stepwise reac-
tions under statistical conditions. Therefore, the yields
were not always high because of the formation of unde-
sired products. For example, Sonogashira coupling (SC)18
of 9,10-dibromoanthracene (3) with phenylethynes gave a
singly coupled product in low to moderate yields [Scheme
1 (a)].7,13,16,19 To overcome this problem, Nesterov and co-
workers used 9-bromo-10-iodoanthracene (4), which was
prepared from 9,10-dibromoanthracene by monolithiation
and then iodination, for selective SC.8 This precursor is
now widely used for the synthesis of unsymmetric BPEA
derivatives.9,14 Another practical approach is the stepwise
alkynylation of 10-bromo-9-anthracenecarbaldehyde (5),
which is prepared from 9,10-dibromoanthracene by
monolithiation followed by formylation with N,N-dimeth-
ylformamide.20 The formyl and bromo groups in 5 are
converted into ethynyl groups by the Corey–Fuchs reac-
tion and SC, respectively [Scheme 1 (b)]. A 9,10-diethyn-
ylanthracene derivative with different terminal silyl
groups was prepared by this method. This product is an at-
tractive intermediate for the synthesis of unsymmetric
BPEA derivatives, even though the conversion via selec-
tive desilylation and SC requires several steps.
Key words: alkynes, anthracenes, Sonogashira coupling, double
elimination, one-pot process, reaction integration, fluorescence
9,10-Bis(phenylethynyl)anthracene (BPEA, 1a; Figure 1)
and its derivatives are strongly fluorescent π-conjugated
compounds that are employed as fluorophores or light
emitters in functional materials chemistry.1–3 This fluores-
cent property makes BPEA and its derivatives useful as
fluorescent dyes in chemical light sticks.4 Recently, these
compounds have received attention as light-emitting
diodes5 and nonlinear optical materials.6 Because the
chemical structure of BPEA enables extension of the π-
conjugation between the two terminal phenyl groups
across anthracene and acetylene moieties, this unit is oc-
casionally incorporated in arylene–ethynylene oligomers
and polymers.7–11 The electronic properties of the parent
compound are tunable by introducing substituents on the
phenyl and anthracene units.12–17 As for BPEA derivatives
with substituted phenyl groups, a large number of com-
pounds have been synthesized using similar methods and
the substituent effects on the electronic spectra have been
systematically investigated.2,15 Whereas most of the
known compounds have two identically substituted phe-
nyl groups, those with different substituents are less pop-
ular because of synthetic limitations. The development of
efficient methods for the synthesis of such unsymmetric
derivatives would widen the scope of their application as
functional materials.
From these backgrounds, we intended to conduct double-
elimination (DE) reactions between arylaldehydes and
benzyl phenyl sulfones in the presence of a base, a method
which was developed by one of the author’s groups, for
the synthesis of unsymmetric BPEA derivatives.21,22 The
overall reaction involves the aldol reaction, the formation
of phosphate, the elimination of phosphoric acid, and the
elimination of sulfinic acid (Scheme 2). The DE protocol
is extensively utilized for the synthesis of various alkynes,
particularly in cases where other alkyne formation reac-
Typical synthetic approaches to BPEA derivatives in-
clude (1) the cross-coupling reactions of 9,10-dihalo-
anthracenes with phenylethynes, (2) the addition of
phenylacetylides to anthraquinone followed by reductive
SYNTHESIS 2013, 45, 1060–1068
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DOI: 10.1055/s-0032-1316867; Art ID: SS-2013-F0043-OP
© Georg Thieme Verlag Stuttgart · New York

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9,10-Bis(phenylethynyl)anthracenes
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(a)
Br
Sonogashira
Y
Sonogashira
Z
Z
Y
X
Br
Y
H
H
3 X = Br
4 X = I
(b)
Br
Corey–Fuchs
Sonogashira
Z
Z
Y
CHO
Br
Y
arylation or
silylation
H
5
Y, Z = aryl or trialkylsilyl
Scheme 1 Examples of synthetic approaches to unsymmetric 9,10-diethynylanthracene derivatives
tions are unsuccessful.23,24 Whereas the multistep conver- The isolated yields of the stepwise and one-pot syntheses
sion was originally carried out by the sequential addition are compiled in Table 1.
of reagents into a reaction flask (one-pot process), the pro-
cedure was further simplified by mixing all reagents in a
reaction flask at once (one-shot process).25 In terms of the
Synthesis by Stepwise Reactions
integration of chemical reactions, the one-pot process and
the one-shot process are classified as ‘time integration’ Compound 1a was synthesized from 5 by two routes con-
and ‘time and space integration’, respectively.26 We have sisting of SC and one-shot DE in a stepwise manner
successfully applied the one-shot protocol to the synthesis (Scheme 3). In route A, we first performed SC of 5 and
of anthrylethynes.27 We introduced one ethynyl group by phenylethyne (6a). The reaction in the presence of palla-
one-shot DE and another ethynyl group by conventional dium(II) catalyst and copper(I) iodide in tetrahydrofuran
SC into 10-bromo-9-anthracenecarbaldehyde (5). We also and triethylamine gave compound 8a in 96% yield. This
tried to integrate the two reactions by the one-pot process product was then subjected to DE with 7a (1.2 equiv) fol-
to achieve an efficient synthesis. We herein report the op- lowing the standard protocol reported in the literature;27
timization of the reaction conditions for the convenient namely, those two reactants were treated with diethyl
synthesis of unsymmetric BPEA derivatives by the inte- chlorophosphate (DECP, 1.2 equiv) and lithium hexa-
grated reactions, as well as the photophysical properties of methyldisilazide (LiHMDS, 5.0 equiv) in tetrahydrofu-
the new fluorescent compounds.
ran. The crude product was collected by filtration and then
recrystallized from hexane–chloroform to give pure
BPEA (1a) in 98% yield. The overall yield of the two-step
conversion was 94% based on 5. The same transformation
was achieved by the two reactions in the reverse order
(route B). One-shot DE with 5 and 7a gave 9-bromo-10-
(phenylethynyl)anthracene (9a) in 90% yield, and subse-
quent SC with 6a gave BPEA (1a) in 93% yield. The over-
all yield via route B was 84%. We were able to obtain
practically pure products by recrystallization, without ex-
traction and chromatography, in the DE step in both
routes.
LiHMDS
Ar1 CH2SO2Ph
Ar2 CHO
ClPO(OEt)2
+
+
Ar1
Ar2
PhSO2 OPO(OEt)2
Ar1 Ar2
Ar1
C
C
Ar2
C
C
C
C
PhSO2
H
H
H
Scheme 2 One-shot DE reaction for the synthesis of unsymmetric
diarylethynes
The starting material, 10-bromo-9-anthracenecarbalde-
hyde (5), was prepared from 9,10-dibromoanthracene (3)
by the literature method.20 Substituted benzyl phenyl sul-
fones 7b–d were prepared by conventional methods. We
optimized the conditions for the fundamental processes
for substituent-free BPEA (1a) and, if necessary, those
processes were further optimized for the unsymmetric de-
rivatives 1b–d which contain a 4-methyl, 4-nitro, or 4-
bromo group, respectively, at one phenylethynyl moiety.
In principle, for the synthesis of unsymmetric BPEA de-
rivatives, substituted phenyl groups can be introduced ei-
ther by DE with substituted benzyl phenyl sulfones or by
SC with substituted phenylethynes. We adopted the for-
mer approach in most cases because of the availability and
ease of handling of the starting materials. Compound 1b
could be synthesized by both routes with phenylethyne
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 1060–1068

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S. Toyota et al.
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route A
Ar1
H
Ar2 CH2SO2Ph
6
7
Ar1
Ar2
Br
CHO
Ar1
CHO
ClPO(OEt)2
LiHMDS, THF
[PdCl2(PPh3)2]
CuI, THF, Et3N
5
8
1
route B
Ar2 CH2SO2Ph
Ar1
H
7
6
Ar1
Ar2
Br
CHO
Br
Ar2
[PdCl2(PPh3)2]
CuI, THF, Et3N
ClPO(OEt)2
LiHMDS, THF
5
9
1
a: Ar1 = Ph
a: Ar2 = Ph
a: Ar1 = Ar2 = Ph
1
6 and 8
7 and 9
c: Ar1 = 4-O2NC6H4
b: Ar2 = 4-MeC6H4
c: Ar2 = 4-O2NC6H4
d: Ar2 = 4-BrC6H4
b: Ar1 = Ph, Ar2 = 4-MeC6H4
c: Ar1 = Ph, Ar2 = 4-O2NC6H4 or
Ar1 = 4-O2NC6H4, Ar2 = Ph
d: Ar1 = Ph, Ar2 = 4-BrC6H4
Scheme 3 Synthesis of BPEA derivatives 1 from 5 by SC and DE reactions
Table 1 Yields for Stepwise and One-Pot Synthesis of BPEA Derivatives 1 from 10-Bromo-9-anthracenecarbaldehyde (5) by Sonogashira
Coupling (SC) and Double-Elimination (DE) Reactionsa
Route A 1st reaction (SC)
2nd reaction (DE)
Sulfone Product
Stepwise
One-pot
Alkyne
Product
Yield (%)
Yield (%)
Overall yield (%)
Yield (%)
6a
6a
6a
6c
6a
8a
8a
8a
8c
8a
96
96
96
87c
96
7a
7b
7c
7a
7d
1a
1b
1c
1c
1d
98
94
90
95
91
90
<10b
94
low
–
82
72c
89
85
35 (91)d
Route B 1st reaction (DE)
2nd reaction (SC)
Alkyne Product
Stepwise
One-pot
Sulfone
7a
Product
9a
Yield (%)
Yield (%)
Overall yield (%)
Yield (%)
90
76
80
6a
6a
6a
1a
1b
1c
93
98
71
84
74
57
7b,e
–
7b
9b
7c
9c
–
a Isolated yields unless otherwise indicated. Typical conditions for SC: bromide (1.0 equiv), alkyne (1.2 equiv), [PdCl2(PPh3)2] (0.04 equiv),
CuI (0.08 equiv) in THF–Et3N at 70 °C for 2 h. Typical conditions for DE: aldehyde (1.0 equiv), sulfone (1.2 equiv), DECP (1.2 equiv),
LiHMDS (5.0 equiv) in THF at r.t. for 20 h.
b Estimated yields from 1H NMR spectra.
c Reaction time of 24 h for SC.
d LiHMDS (6.5 equiv) for DE.
e Reaction time of 16 h for SC.
Synthesis 2013, 45, 1060–1068
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9,10-Bis(phenylethynyl)anthracenes
1063
(6a) and 4-methylbenzyl phenyl sulfone (7b), and the reaction mixture was heated for as long as 16 hours. Un-
overall yields via routes A and B were 91% and 74%, re- fortunately, the product was a mixture of 1a and 9a in the
spectively. For the synthesis of 1c, DE of 8a and 4-nitro- ratio of 7:93 and thus we abandoned isolation of the de-
benzyl phenyl sulfone (7c) under the standard conditions sired product from the mixture. We also tried to integrate
gave a small amount of the desired product as an insepa- the two reactions by the one-shot process. The starting
rable mixture. Therefore, we introduced the 4-nitrophenyl materials and all reagents for the two reactions were put
group first by SC with 6c, even though this reaction re- into a reaction flask at once, and the whole was stirred for
quired a longer time than SC with 6a. The product, 10-[(4- 2 hours at room temperature and then heated at 70 °C for
nitrophenyl)ethynyl]-9-anthracenecarbaldehyde
(8c), 16 hours. The product was a mixture of 1a and 9a in the
smoothly formed 1c by DE with 7a (82% overall yield). ratio of 15:85. These unsuccessful results, the one-pot
Route B involving DE with 7c and SC with 6a produced process of route B and the one-shot process, indicated that
1c in 57% overall yield. For the synthesis of 1d, route B the reagents and products involving salts of the DE reac-
was far from practical because the bromophenyl unit is tion deactivated the catalytic system of SC. Thereafter, we
also reactive to SC. The only possible approach was route adopted the one-pot protocol following the reaction order
A with 6a and 4-bromobenzyl phenyl sulfone (7d). The of route A for the synthesis of unsymmetric BPEA deriv-
stepwise SC and DE worked well to give 1d in 85% over- atives.
all yield. Alternatively, 1d could be synthesized by SC
Methyl derivative 1b was synthesized by the one-pot pro-
with 9-ethynyl-10-(phenylethynyl)anthracene (10) and 1-
cess with 6a and then 7b in 90% yield. Nitro derivative 1c
bromo-4-iodobenzene, although the yield was not high
was similarly synthesized with 6c (reaction time: 24 h)
and then 7a in 72% yield. For bromo derivative 1d, the
standard procedure with 6a and 7d gave the final product
in only 35% yield with the recovery of a large amount of
8a. After several trials, the conversion efficiency of DE
was found to be improved by the use of an additional
(Scheme 4). In this reaction, we needed to carefully sepa-
rate the desired product from a small amount of the homo-
coupling product, the dimer of 10, as byproduct. The
above results showed that the stepwise approaches involv-
ing the two reactions gave unsymmetric BPEA deriva-
tives in good overall yields without formation of
amount of LiHMDS rather than long reaction times and
symmetric derivatives as byproducts.
high reaction temperatures. On treatment with 6.0 and 6.5
equivalents of LiHMDS (5.0 equiv for the standard proce-
dure), the isolated yields increased to 79% and 91%, re-
spectively. These one-pot procedures proved that
One-Pot Synthesis
unsymmetric BPEA derivatives can be effectively synthe-
We then integrated the two reactions to simplify the ex-
sized by simple operations. Both extraction and chromato-
perimental operations. We first synthesized BPEA (1a) by
graphic purification were not always essential even
the one-pot process based on the conditions for the step-
though the final reaction mixture contained several chem-
wise synthesis. For the integration of route A, SC of 5 with
ical species. Therefore, the overall process can be realized
with the least amount of solvents and other chemicals.
6a was carried out by the standard method and then 7a and
other reagents for DE were added to the reaction flask. Af-
ter the mixture was stirred for 20 hours at room tempera-
ture, we obtained practically pure BPEA in 90% yield,
even without extraction and chromatographic purifica-
Synthesis of an Extended Derivative
tion. Although the SC step formed one equivalent of tri-
ethylammonium bromide, the subsequent DE step
The introduction of an extra arylethynyl unit into the par-
ent BPEA structure can extend the π-conjugation and
required no extra amount of LiHMDS as base, a part of
yield candidates for photovoltaic and other functional ma-
which should be consumed by reaction with the ammoni-
terials.9,28 Bromo derivative 1d is a convenient precursor
to construct such structures by using cross-coupling reac-
tions. As an example of this application, we introduced an
extra phenylethynyl group into the BPEA core. SC of 1d
um salt. For the integration of route B, DE with 5 and 7a
was carried out by the standard method and then 6a, the
catalysts, and the base for SC were added to the reaction
flask. Because SC required a long time to complete, the
and 6a (2.0 equiv) was performed in triethylamine with-
I
Br
H
Br
[PdCl2(PPh3)2]
CuI, THF, Et3N
58%
10
1d
Scheme 4 An alternative synthesis of 1d by SC of 10 and 1-bromo-4-iodobenzene
© Georg Thieme Verlag Stuttgart · New York
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S. Toyota et al.
PAPER
H
6a
Br
[PdCl2(PPh3)2]
CuI, Et3N
80%
1d
2
H
Br
CH2SO2Ph
H
6a
7d
6a
Br
CHO
2
[PdCl2(PPh3)2] *
ClPO(OEt)2
LiHMDS
[PdCl2(PPh3)2]
CuI, THF, Et3N
58%
35% (without *)
5
Scheme 5 Synthesis of BPEA derivative 2 with extended π-conjugation
out tetrahydrofuran for 16 hours at 100 °C to give the de-
Electronic Spectra
sired product 2 in 80% yield (Scheme 5). We also
attempted to integrate this step with the one-pot process The UV/Vis and fluorescence spectra of the BPEA deriv-
from 5. After the one-pot process for the synthesis of 1d, atives were measured in chloroform. The spectral data are
phenylethyne (6a) was charged into the reaction flask. compiled in Table 2. In the UV/Vis spectra, all com-
The whole mixture was heated at 70 °C for 16 hours to pounds show structured absorption bands at around 450
give 2 in 35% yield along with the recovery of 1d (50%). nm in the p-band region. The peak at the longest wave-
When the palladium catalyst was also charged in addition length was observed at 464 nm for BPEA (1a) and its
to 6a, the yield of the desired product was increased to methyl and bromo derivatives 1b and 1d. The correspond-
58%. Accordingly, although the palladium catalyst ing peak was shifted to longer wavelength by ca. 15 nm by
charged in the first step was still active in the last step, the the substitution of nitro and phenylethynyl groups (1c and
use of additional catalyst improved the result. This highly 2, respectively). In the fluorescence (FL) spectra, intense
integrated process consisting of two SC steps and one emission peaks were observed at ca. 480 nm, except for
one-shot DE step gave the final product in moderate yield, the nitro derivative 1c that showed no emission. The fluo-
thereby proving the flexibility of the integration of multi- rescence quantum yields (ca. 0.80) were not affected by
ple alkynylations.
the substitution of the methyl, bromo, or phenylethynyl
group. The effective quenching by the nitro group is at-
tributed to intramolecular charge transfer, which facili-
tates nonradiative decay.29 Compound 1a has the longest
fluorescence lifetime (2.5 ns) among the four compounds,
and the substituents tend to shorten the lifetime.
Table 2 Electronic Spectral Data of BPEA Derivatives 1a–d and 2 in Chloroform
Compound
UV
FL
Stokes shift
(nm)
λ
max (nm)a
εa
λem (nm)
Φfb
τf (ns)c
1a
1b
1c
1d
2
464
463
480
464
479
41000
53100
52000
60500
41200
475, 506
478, 509
0.81
0.83
–
2.5
2.3
–
11
15
–
d
–
478, 509
487, 519
0.80
0.75
2.2
1.8
14
8
a Wavelength and molar extinction coefficient of the peak at the longest wavelength in the p-band region.
b Absolute fluorescence quantum yield.
c Fluorescence lifetime.
d No emission peak was observed.
Synthesis 2013, 45, 1060–1068
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9,10-Bis(phenylethynyl)anthracenes
1065
1H NMR (400 MHz, CDCl3): δ = 7.50 (m, 2 H), 7.65–7.74 (m, 4 H),
7.81 (m, 2 H), 8.79 (d, J = 8.7 Hz, 2 H), 8.97 (d, J = 8.7 Hz, 2 H),
11.53 (s, 1 H).
13C NMR (100 MHz, CDCl3): δ = 90.9, 101.7, 123.8, 123.9, 124.1,
127.2, 127.3, 129.1, 131.0, 132.2, 132.6, 133.4, 134.1, 147.6, 193.2.
HRMS–FAB: m/z [M]+ calcd for C23H13NO3: 351.0895; found:
351.0993.
In conclusion, the combination of DE and SC starting
from 10-bromo-9-anthracenecarbaldehyde offers an effi-
cient approach toward BPEA derivatives by both the step-
wise and one-pot processes in good overall yields. In
particular, unsymmetric BPEA derivatives can be synthe-
sized by simple operations without the formation of sym-
metric analogues as byproducts. Because a large number
of substituted phenylethynes and substituted benzyl phe-
nyl sulfones are commercially available or readily pre-
pared from ordinary compounds, these protocols are
efficient for the synthesis of various BPEA derivatives in-
volving oligomers, dendrimers, and functional materials.
Anal. Calcd for C23H13NO3: C, 78.62; H, 3.73; N, 3.99. Found: C,
78.44; H, 3.34; N, 4.15.
9-Bromo-10-(phenylethynyl)anthracene (9a); Typical Proce-
dure for One-Shot DE
To a soln of 5 (114 mg, 0.40 mmol), benzyl phenyl sulfone (7a)
(112 mg, 0.48 mmol), and DECP (70 μL, 0.48 mmol) in anhyd THF
(12 mL) was slowly added the LiHMDS soln (2.0 mL, 2.0 mmol)
with a syringe at 0 °C under argon. This solution was stirred at 0 °C
for 10 min, and then at r.t. for 20 h (reaction mixture B). The reac-
tion was quenched with aq NH4Cl (12 mL), and the organic materi-
als were extracted with CHCl3 (3 × 20 mL). The combined organic
solution was dried over MgSO4 and concentrated. The residue was
recrystallized (hexane–CHCl3) to give the pure product as yellow
crystals.
Melting points are uncorrected. Elemental analyses were performed
with a Perkin-Elmer 2400 series analyzer. 1H and 13C NMR spectra
were measured on a Jeol JNM-ECS400 spectrometer at 400 and 100
MHz, respectively. High-resolution FAB mass spectra were mea-
sured on a Jeol MStation-700 spectrometer. UV/Vis spectra were
measured on a Hitachi U-3000 spectrometer with a 10-mm cell. Flu-
orescence spectra were measured on a Jasco FP-6500 spectrofluo-
rometer with a 10-mm cell; samples were degassed with argon gas
immediately before measurements. The absolute fluorescence
quantum yields were recorded on a Hamamatsu Photonics C9920-
02 system. The fluorescence lifetimes were measured on a Spectra-
Physics time-resolved spectrofluorometer system (Tsunami
3960/50-M2S) with a Ti:Sapphire laser. Phenylethyne, 4-nitro-
phenylethyne, benzyl phenyl sulfone, and 1-bromo-4-iodobenzene
are commercially available. 10-Bromo-9-anthracenecarbaldehyde
was prepared from 9,10-dibromoanthracene according to the known
method.20 4-Methylbenzyl phenyl sulfone,23d 4-nitrobenzyl phenyl
sulfone,30 and 4-bromobenzyl phenyl sulfone23c were prepared from
sodium benzenesulfinate and the corresponding benzyl bromides by
a standard method. All reactions were carried out under atmosphere
of argon. LiHMDS soln (1.0 M in THF) and THF (super dehydrat-
ed) were purchased from Sigma-Aldrich and Wako Pure Chemical
Industries, respectively.
Yield: 129 mg (90%); mp 167–169 °C (Lit.7,8 170–171 °C).
1H NMR (400 MHz, CDCl3): δ = 7.44–7.49 (m, 3 H), 7.63–7.66 (m,
4 H), 7.78 (dd, J = 8.0, 1.6 Hz, 2 H), 8.57 (m, 2 H), 8.72 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 86.0, 101.8, 118.2, 123.4, 124.2,
126.8, 127.2, 127.4, 128.2, 128.6, 128.8, 130.2, 131.6, 133.0.
9,10-Bis(phenylethynyl)anthracene (1a)
This compound was synthesized by DE with 8a (123 mg, 0.40
mmol) and 7a (112 mg, 0.48 mmol) according to the typical proce-
dure. The formed solid was collected by filtration, washed with wa-
ter, and dried. Recrystallization (hexane–CHCl3) gave the desired
product.
Yield: 148 mg (98%); mp 242–248 °C (dec) (Lit.32 257–258 °C,
Lit.2d 253 °C, Lit.33 249–250 °C). This sample slowly decomposed
>240 °C and showed a sharp endothermic peak at 258 °C on DTA
measurement.
10-(Phenylethynyl)-9-anthracenecarbaldehyde (8a); Typical
Procedure for SC
Rf = 0.41 (hexane–CHCl3, 4:1).
To a soln of 10-bromo-9-anthracenecarbaldehyde (5) (114 mg, 0.40
mmol) and phenylethyne (6a) (49 mg, 0.48 mmol) in a degassed
mixture of anhyd THF (8 mL) and Et3N (8 mL) were added
[PdCl2(PPh3)2] (11 mg, 16 μmol) and CuI (6.1 mg, 32 μmol). The
reaction mixture was stirred at 70 °C for 2 h under argon (reaction
mixture A). The solvent was removed, and the crude product was
purified by chromatography on silica gel (hexane–CHCl3, 10:1) to
give the desired product as an orange solid.
Yield: 117 mg (96%); mp 198–200 °C (Lit.31 179–180 °C);
Rf = 0.26 (hexane–CHCl3, 4:1).
1H NMR (400 MHz, CDCl3): δ = 7.48–7.53 (m, 3 H), 7.65–7.74 (m,
4 H), 7.79–7.82 (m, 2 H), 8.79 (d, J = 8.7 Hz, 2 H), 8.97 (d, J = 8.7
Hz, 2 H), 11.53 (s, 1 H).
1H NMR (400 MHz, CDCl3): δ = 7.40–7.48 (m, 6 H), 7.66 (m, 4 H),
7.78 (dd, J = 1.6, 8.0 Hz, 4 H), 8.70 (m, 4 H).
13C NMR (100 MHz, CDCl3): δ = 86.4, 102.4, 118.5, 123.3, 126.8,
127.2, 128.6, 128.7, 131.7, 132.1.
UV/Vis (CHCl3): λmax (ε) = 275 (105000), 313 (43300), 439
(38900), 464 nm (41000).
FL (CHCl3): λmax = 475, 506 nm (λex 458 nm, Φf 0.81, τf 2.5 ns).
The same compound was also synthesized by SC with 9a (143 mg,
0.40 mmol) and 6a (49 mg, 0.48 mmol) by the typical procedure.
Chromatographic purification (hexane–CHCl3, 10:1) gave 1a;
yield: 141 mg (93%).
13C NMR (100 MHz, CDCl3): δ = 86.1, 104.6, 122.8, 123.8, 124.9,
125.5, 126.5, 127.6, 128.6, 128.9, 129.2, 131.1, 131.7, 131.8, 192.9.
9-Bromo-10-[(4-methylphenyl)ethynyl]anthracene (9b)
This compound was synthesized by DE with 5 (114 mg, 0.40 mmol)
and 4-methylbenzyl phenyl sulfone (7b) (118 mg, 0.48 mmol) ac-
cording to the typical procedure. Recrystallization (hexane) gave
the desired compound as yellow needles.
10-[(4-Nitrophenyl)ethynyl]-9-anthracenecarbaldehyde (8c)
To a soln of 5 (114 mg, 0.40 mmol) and 4-nitrophenylethyne (6c)
(70 mg, 0.48 mmol) in a degassed mixture of anhyd THF (8 mL)
and Et3N (8 mL) were added [PdCl2(PPh3)2] (11 mg, 16 μmol) and
CuI (6.1 mg, 32 μmol). The reaction mixture was stirred at 70 °C for
24 h under argon (reaction mixture A′). The solvent was removed,
and the crude product was purified by chromatography on silica gel
(hexane–CHCl3, 10:1) to give the desired product as a red solid.
Yield: 113 mg (76%); mp 160–161 °C; Rf = 0.71 (hexane–CHCl3,
4:1).
1H NMR (400 MHz, CDCl3): δ = 2.44 (s, 3 H), 7.27 (d, J = 7.8 Hz,
2 H), 7.62–7.69 (m, 6 H), 8.58 (m, 2 H), 8.72 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 21.6, 85.4, 102.1, 118.5, 120.2,
123.9, 126.7, 127.3, 127.4, 128.2, 129.3, 130.2, 131.5, 132.9, 139.0.
Yield: 122 mg (87%); mp 221–224 °C; Rf = 0.42 (hexane–CHCl3,
1:1).
© Georg Thieme Verlag Stuttgart · New York
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S. Toyota et al.
PAPER
HRMS–FAB: m/z [M]+ calcd for C23H1579Br: 370.0357; found:
370.0373.
9-[(4-Bromophenyl)ethynyl]-10-(phenylethynyl)anthracene
(1d)
The DE reaction was carried out with 8a (123 mg, 0.40 mmol) and
4-bromobenzyl phenyl sulfone (7d) (149 mg, 0.48 mmol). Chro-
matographic purification (hexane–CHCl3, 10:1) gave 1d as orange
crystals.
Anal. Calcd for C23H15Br: C, 74.60; H, 4.08. Found: C, 74.52; H,
7.24.
9-Bromo-10-[(4-nitrophenyl)ethynyl]anthracene (9c)
This compound was synthesized by DE with 5 (114 mg, 0.40 mmol)
and 4-nitrobenzyl phenyl sulfone (7c) (133 mg, 0.48 mmol) accord-
ing to the typical procedure. Recrystallization (hexane) gave the de-
sired compound as a red solid.
Yield: 163 mg (89%); mp 223–224 °C; Rf = 0.63 (hexane–CHCl3,
4:1).
1H NMR (400 MHz, CDCl3): δ = 7.43–7.49 (m, 3 H), 7.59 (d,
J = 8.7 Hz, 2 H), 7.63–7.68 (m, 6 H), 7.79 (dd, J = 1.6, 7.8 Hz, 2 H),
8.65 (m, 2 H), 8.74 (m, 2 H).
Yield: 129 mg (80%); mp 254–256 °C (Lit.17 255.0–255.5 °C).
1H NMR (400 MHz, CDCl3): δ = 7.27 (m, 4 H), 7.92 (d, J = 8.0 Hz,
2 H), 8.34 (d, J = 8.4 Hz, 2 H), 8.60–8.67 (m, 4 H).
13C NMR (100 MHz, CDCl3): δ = 86.4, 87.7, 101.2, 102.6, 117.9,
118.8, 122.4, 122.9, 123.4, 126.8, 126.9, 127.1, 127.3, 128.6, 128.8,
131.7, 131.8, 132.1, 132.1, 133.0.
HRMS–FAB: m/z [M]+ calcd for C30H1779Br: 456.0514; found:
456.0518.
9-[(4-Methylphenyl)ethynyl]-10-(phenylethynyl)anthracene
(1b)
This compound was synthesized by SC with 9b (149 mg, 0.40
mmol) and 6a (49 mg, 0.48 mmol). Chromatographic purification
(hexane–CHCl3, 10:1) gave 1b as orange crystals.
UV/Vis (CHCl3): λmax (ε) = 275 (147000), 317 (66600), 442
(58200), 464 nm (60500).
Yield: 154 mg (98%); mp 216–217 °C; Rf = 0.45 (hexane–CHCl3,
4:1).
1H NMR (400 MHz, CDCl3): δ = 2.43 (s, 3 H), 7.25 (d, J = 7.7 Hz,
2 H), 7.41–7.49 (m, 3 H), 7.60–7.68 (m, 6 H), 7.78 (dd, J = 1.6, 8.1
Hz, 2 H), 8.66–8.70 (m, 4 H).
FL (CHCl3): λmax = 478, 509 nm (λex 458 nm, Φf 0.80, τf 2.2 ns).
Anal. Calcd for C30H17Br: C, 78.78; H, 3.75. Found: C, 79.00; H,
3.87.
Alternative Synthesis of 1d
To a soln of 9-ethynyl-10-(phenylethynyl)anthracene8,16 (10) (121
mg, 0.40 mmol) and 1-bromo-4-iodobenzene (170 mg, 0.60 mmol)
in a degassed mixture of anhyd THF (6 mL) and Et3N (6 mL) were
added [PdCl2(PPh3)2] (11 mg, 16 μmol) and CuI (6.1 mg, 32 μmol).
After the reaction mixture was stirred at r.t. for 17 h under argon,
the solvent was removed. The crude product was purified by chro-
matography on silica gel (hexane–CHCl3, 10:1) to give the desired
product; yield: 106 mg (58%).
13C NMR (100 MHz, CDCl3): δ = 21.0, 85.9, 86.5, 102.3, 102.7,
118.1, 118.7, 120.3, 123.4, 126.7, 126.8, 127.2, 127.3, 128.6, 128.7,
129.3, 131.6, 131.7, 132.0, 132.1, 138.9.
HRMS–FAB: m/z [M]+ calcd for C31H20: 392.1565; found:
392.1550.
UV/Vis (CHCl3): λmax (ε) = 275 (123000), 314 (49100), 441
(50100), 463 nm (53100).
FL (CHCl3): λmax = 478, 509 nm (λex 458 nm, Φf 0.83, τf 2.3 ns).
One-Pot Synthesis of 1a; Typical Procedure
After reaction mixture A was cooled to r.t., 7a (112 mg, 0.48 mmol)
and DECP (70 μL, 0.48 mmol) were added to the mixture. To the
solution was slowly added the LiHMDS soln (2.0 mL, 2.0 mmol)
with a syringe at 0 °C. This solution was stirred at 0 °C for 10 min,
and then at r.t. for 20 h. The reaction was quenched with aq NH4Cl
(12 mL). The formed solid was collected by filtration, washed with
water, and dried. Recrystallization (hexane–CHCl3) gave the pure
product as yellow crystals; yield: 136 mg (90%).
Anal. Calcd for C31H20: C, 94.86; H, 5.14. Found: C, 94.48; H, 5.19.
This compound was also synthesized by DE with 8a (123 mg, 0.40
mmol) and 7b (118 mg, 0.48 mmol). The product was purified by
recrystallization (CH2Cl2) to give pure material 1b; yield: 149 mg
(95%).
9-[(4-Nitrophenyl)ethynyl]-10-(phenylethynyl)anthracene (1c)
This compound was synthesized by SC with 9c (161 mg, 0.40
mmol) and 6a (49 mg, 0.48 mmol). Chromatographic purification
(hexane–CHCl3, 10:1) gave 1c as a red solid.
One-Pot Synthesis of 1a (Reverse Order)
To reaction mixture B were added 6a (49 mg, 0.48 mmol),
[PdCl2(PPh3)2] (11 mg, 16 μmol), CuI (6.1 mg, 32 μmol), and Et3N
(8 mL). The mixture was stirred at 70 °C for 16 h and the reaction
was quenched with aq NH4Cl (12 mL). The organic materials were
extracted with CHCl3 (3 × 20 mL). The combined organic solution
was dried over MgSO4, and concentrated. 1H NMR spectra revealed
that the crude product was a mixture of 1a and 9a in 7:93 ratio.
Yield: 120 mg (71%); mp 256–258 °C; Rf = 0.61 (hexane–CHCl3,
2:1).
1H NMR (400 MHz, CDCl3): δ = 7.44–7.49 (m, 3 H), 7.66–7.71 (m,
4 H), 7.79 (dd, J = 1.6, 8.0 Hz, 2 H), 7.92 (d, J = 9.2 Hz, 2 H), 8.33
(d, J = 9.2 Hz, 2 H), 8.65 (m, 2 H), 8.74 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 86.2, 91.9, 100.2, 103.2, 116.8,
120.1, 123.2, 123.9, 126.8, 127.0, 127.4, 127.5, 128.6, 129.0, 130.3,
131.8, 132.0, 132.3, 132.4, 147.1.
One-Shot Synthesis of 1a
To a soln of 5 (114 mg, 0.40 mmol) and 6a (49 mg, 0.48 mmol) in
a degassed mixture of anhyd THF (8 mL) and Et3N (8 mL) were
added 7a (112 mg, 0.48 mmol), DECP (70 μL, 0.48 mmol),
[PdCl2(PPh3)2] (11 mg, 16 μmol), and CuI (6.1 mg, 32 μmol). To the
solution was slowly added the LiHMDS soln (2.0 mL, 2.0 mmol)
with a syringe at 0 °C under argon. This mixture was stirred at 0 °C
for 10 min, at r.t. for 2 h, and then at 70 °C for 16 h. The reaction
was similarly quenched with aq NH4Cl. 1H NMR spectra revealed
that the crude product was a mixture of 1a and 9a in 15:85 ratio.
HRMS–FAB: m/z [M]+ calcd for C30H17NO2: 423.1216; found:
423.1259.
UV/Vis (CHCl3): λmax (ε) = 275 (91300), 309 (41700), 457 (52900),
480 nm (52000).
Anal. Calcd for C30H17NO2: C, 85.09; H, 4.05; N, 3.31. Found: C,
85.22; H, 4.04; N, 3.29.
This compound was also synthesized by DE with 8c (141 mg, 0.40
mmol) and 7a (112 mg, 0.48 mmol). The product was purified by
recrystallization (CH2Cl2) to give pure material 1c; yield: 159 mg
(94%). The reaction was also carried out with 8a (122 mg, 0.40
mmol) and 7c (133 mg, 0.48 mmol). Chromatographic separation of
the crude product (hexane–CHCl3, 10:1) gave 54 mg of a mixture
containing 1c (<10%) and other byproducts.
One-Pot Synthesis of 1b
This reaction was carried out with reaction mixture A and 7b (118
mg, 0.48 mmol). The crude product was purified by chromatogra-
phy on silica gel (hexane–CHCl3, 10:1) to give the pure product;
yield: 141 mg (90%).
Synthesis 2013, 45, 1060–1068
© Georg Thieme Verlag Stuttgart · New York

PAPER
9,10-Bis(phenylethynyl)anthracenes
1067
One-Pot Synthesis of 1c
(d) Lydon, D. P.; Porres, L.; Beeby, A.; Marder, T. B.; Low,
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J. Photochem. Photobiol., A 1992, 63, 59.
This reaction was carried out with reaction mixture A′ and 7a (112
mg, 0.48 mmol). The crude product was purified by chromatogra-
phy on silica gel (hexane–CHCl3, 10:1) to give the pure product;
yield: 121 mg (72%).
(4) For selected patents for the use in light sticks, see:
(a) Cranor, E. PCT Int. Appl. WO 2003042326, 2003; Chem.
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Huang, D.-F.; Chow, T. J. J. Am. Chem. Soc. 2008, 130,
17320. (b) Han, Y. S.; Jeong, S.; Ryu, S. C.; Park, E. J.; Lyu,
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Michelet, V.; Leray, I. Chem. Eur. J. 2006, 12, 9056.
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1995, 99, 4886.
One-Pot Synthesis of 1d
This reaction was carried out with reaction mixture A and 7d (149
mg, 0.48 mmol). The LiHMDS soln (2.6 mL, 2.6 mmol) was added
to the reaction mixture, which was stirred at r.t. for 12 h (reaction
mixture C). The crude product was purified by chromatography on
silica gel (hexane–CHCl3, 10:1) to give the pure product; yield: 166
mg (91%). When 2.0 mL (2.0 mmol) and 2.4 mL (2.4 mmol) of the
LiHMDS soln were used, the isolated yields were 35% and 79%, re-
spectively.
9-(Phenylethynyl)-10-{[4-(phenylethynyl)phenyl]ethynyl}an-
thracene (2)
To a soln of 1d (60 mg, 0.13 mmol) and 6a (27 mg, 0.26 mmol) in
degassed Et3N (8 mL) were added [PdCl2(PPh3)2] (3.6 mg, 5.2
μmol) and CuI (1.9 mg, 10 μmol). The reaction mixture was stirred
at 100 °C for 16 h under argon, and the solvent was removed. The
crude product was purified by chromatography on silica gel
(hexane–CHCl3, 5:1) to give the desired product as a yellow solid.
(8) Nesterov, E. E.; Zhu, Z.; Swager, T. M. J. Am. Chem. Soc.
2005, 127, 10083.
(9) (a) Marrocchi, A.; Silvestri, F.; Seri, M.; Facchetti, A.;
Taticchi, A.; Marks, T. J. Chem. Commun. 2009, 1380.
(b) Seri, M.; Marrocchi, A.; Bagnis, D.; Ponce, R.; Taticchi,
A.; Marks, T. J.; Facchetti, A. Adv. Mater. 2011, 23, 3827.
(c) Marrocchi, A.; Spalletti, A.; Ciorba, S.; Seri, M.; Elisei,
F.; Taticchi, A. J. Photochem. Photobiol., A 2010, 211, 162.
(10) Morisaki, Y.; Sawamura, T.; Murakami, T.; Chujo, Y. Org.
Lett. 2010, 12, 3188.
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288.
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(13) Giménez, R.; Piñol, M.; Serrano, J. L. Chem. Mater. 2004,
16, 1377.
Yield: 50 mg (80%); mp 250–252 °C (dec); Rf = 0.30 (hexane–
CH2Cl2, 5:1).
1H NMR (400 MHz, CDCl3): δ = 7.22–7.26 (m, 3 H), 7.47 (t,
J = 7.8 Hz, 3 H), 7.62–7.68 (m, 8 H), 7.78 (m, 4 H), 8.67–8.72 (m,
4 H).
13C NMR (100 MHz, CDCl3): δ = 86.5, 88.5, 89.2, 91.7, 102.2,
102.7, 118.2, 118.9, 123.1, 123.3, 123.5, 123.7, 126.9, 127.0, 127.2,
127.4, 128.4, 128.5, 128.6, 128.8, 131.6, 131.7, 131.8, 132.20,
132.23.
HRMS–FAB: m/z [M]+ calcd for C38H22: 478.1722; found:
478.1686.
(14) Imoto, M.; Takeda, M.; Tamaki, A.; Taniguchi, H.; Mizuno,
K. Res. Chem. Intermed. 2009, 35, 957.
UV/Vis (CHCl3): λmax (ε) = 284 (90000), 316 (30600), 336 (27200),
350 (31100), 457 (41400), 479 nm (41200).
(15) (a) Nakatsuji, S.; Matsuda, K.; Uesugi, Y.; Nakashima, K.;
Akiyama, S.; Fabian, W. J. Chem. Soc., Perkin Trans. 1
1992, 755. (b) Akiyama, S.; Nakatsuji, S.; Nomura, K.;
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Stepanova, I. A.; Shenkarev, Z. O.; Berlin, Y. A.; Korshun,
V. A. Eur. J. Org. Chem. 2004, 1298.
FL (CHCl3): λmax = 487, 519 nm (λex 457 nm, Φf 0.75, τf 1.8 ns).
One-Pot Synthesis of 2
To reaction mixture C were added 6a (123 mg, 1.20 mmol) and
[PdCl2(PPh3)2] (11.2 mg, 16 μmol) at r.t. The reaction mixture was
heated at 70 °C for 16 h, and then quenched with aq NH4Cl. The or-
ganic materials were extracted with CHCl3 (3 × 20 mL). The com-
bined organic solution was washed with water, dried over MgSO4,
and concentrated. The crude product was similarly purified to give
2 (111 mg, 58% based on 5) and 1d (22%). When only 6a was add-
ed, the reaction gave 2 and 1d in 35% and 50%, respectively.
(17) Beeby, A.; Findlay, K.; Goeta, A. E.; Porrès, L.; Rutter, S.
R.; Thompson, A. L. Photochem. Photobiol. Sci. 2007, 6,
982.
(18) (a) Sonogashira, K. In Handbook of Organopalladium
Chemistry for Organic Synthesis; Vol. 1; Negishi, E.; de
Meijere, A., Eds.; John Wiley & Sons, Inc: New York, 2002,
493. (b) Chinchilla, R.; Nájera, C. Chem. Rev. 2007, 107,
874.
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Acknowledgment
This work was partly supported by Grants-in-Aid for Scientific Re-
search on Innovative Areas (Integrated Organic Synthesis) Nos.
22106543 and 24106743 from MEXT (The Ministry of Education,
Culture, Sports, Science and Technology, Japan) and by MEXT-
Supported Program for the Strategic Research Foundation at Private
Universities, 2009–2013.
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Ed.; Thieme: Stuttgart, 2008, Chap. 43.8.1.5.
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Synthesis 2013, 45, 1060–1068
© Georg Thieme Verlag Stuttgart · New York