Short Synthesis of [5]- and [7]Phenacenes with Silyl Groups at the Axis Positions

Article abstract of DOI:10.1002/asia.201500700

[5]Phenacene with trimethylsilyl groups at the axis positions was synthesized by the ruthenium-catalyzed direct C-H arylation of a 1-formyl-7-phenanthrene-derived aldimine, followed by sequential Wittig olefination and bismuth-catalyzed cyclization of the resulting vinyl ethers. By using the same synthetic building blocks and sequential Wittig olefination and photocyclization, the number of fused benzene rings was readily increased to seven to afford 3,12-disilyl[7]phenacene. The introduction of silyl groups endowed the [n]phenacene frameworks with good solubility, as well as enabling further functionalization. The electronic structure of these new [n]phenacenes was determined by photophysical measurements and by density functional theory calculations, which clearly implied effective conjugation throughout the entire πframework. End game: [5]- and [7]Phenacenes with two silyl groups at the axis positions were synthesized through repeated ruthenium-catalyzed direct C-H arylation/Wittig olefination/bismuth-catalyzed cyclization steps. The incorporation of silyl functionalities endowed these polycyclic aromatic hydrocarbons with solubility without significantly affecting their photophysical properties.

Full text of DOI:10.1002/asia.201500700

DOI: 10.1002/asia.201500700
Full Paper
Synthetic Methods
Short Synthesis of [5]- and [7]Phenacenes with Silyl Groups at the
Axis Positions
David Roy,[a] Hiroyuki Maekawa,[a] Masahito Murai,*[a] and Kazuhiko Takai*[a, b]
Abstract: [5]Phenacene with trimethylsilyl groups at the axis
positions was synthesized by the ruthenium-catalyzed direct
CÀH arylation of a 1-formyl-7-phenanthrene-derived aldi-
mine, followed by sequential Wittig olefination and bismuth-
catalyzed cyclization of the resulting vinyl ethers. By using
the same synthetic building blocks and sequential Wittig
olefination and photocyclization, the number of fused ben-
zene rings was readily increased to seven to afford 3,12-disi-
lyl[7]phenacene. The introduction of silyl groups endowed
the [n]phenacene frameworks with good solubility, as well
as enabling further functionalization. The electronic structure
of these new [n]phenacenes was determined by photophysi-
cal measurements and by density functional theory calcula-
tions, which clearly implied effective conjugation throughout
the entire p framework.
Introduction
more, [5]phenacene (picene) is the first hydrocarbon to show
unique superconductivity through intercalation with an alkali
metal.[5] The importance of [n]phenacenes means that an effi-
cient route is required for the direct synthesis of suitably func-
tionalized [n]phenacenes from simple building blocks in fewer
steps. However, although numerous studies have investigated
the transition-metal-catalyzed synthesis of fused polyaromatic
hydrocarbons,[6] their application to the short and efficient syn-
thesis of functionalized [n]phenacenes has so far been limit-
ed.[7]
The synthesis of fused polycyclic aromatic hydrocarbons for
optoelectronic applications has received considerable atten-
tion, owing to their potential utility in organic photovoltaics
(OPVs), organic light-emitting diodes (OLEDs), and organic
field-effect transistors (OFETs).[1] Among many promising small
molecules, pentacene and rubrene are known to be key com-
ponents of high-performance OFETs.[2] Such OFETs are lighter,
more flexible, and more-easily shaped than transistors based
on silicon or other inorganic materials, and they have attracted
interest owing to their potential use in flexible displays, elec-
tronic paper, and large-area chemical sensors. Although these
acene-type organic semiconductors show excellent per-
formance,[2] their major drawback is instability in air, owing to
their high HOMO energy levels. Therefore, the development of
new molecules with superior device performance, better stabil-
ity, and solubility remains a challenge. Recently, [n]phenacenes
that contains fused benzene rings in a “W-shape” have attract-
ed interest as a new and promising class of organic OFETs.[3,4]
Because of their low HOMO energies, these compounds exhibit
improved chemical stability under ambient conditions com-
pared with their isostructural analogues, [n]acenes. Further-
To further develop the unique properties of [n]phenacenes,
we investigated short transition-metal-catalyzed syntheses of
[n]phenacenes that contained appropriate functional groups at
the axis positions. This design was inspired by a recent mobili-
ty study of 3,10-di(tetradecyl)[5]phenacene (1a) by Kubozono
and co-workers (Scheme 1).[4e] The hole mobility of compound
1a reached 20 cm2 VÀ1 sÀ1 (average value: 14 cm2 VÀ1 sÀ1), the
second-highest among p-channel organic thin-film FETs. In
view of the fact that the mobility of picene without any sub-
stituents was less than 5 cm2 VÀ1 sÀ1, it was concluded that the
[a] Dr. D. Roy, H. Maekawa, Dr. M. Murai, Prof. Dr. K. Takai
Division of Applied Chemistry
Graduate School of Natural Science and Technology
Okayama University
3-1-1 Tsushimanaka, Kita-ku, Okayama 700-8530 (Japan)
E-mail: masahito.murai@okayama-u.ac.jp
[b] Prof. Dr. K. Takai
ACT-C (Japan) Science and Technology Agency
4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
E-mail: ktakai@cc.okayama-u.ac.jp
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/asia.201500700.
Scheme 1. Structures and average hole mobilities of high-performance thin-
film OFETs.
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effect of alkyl side-chains is important for the development of
high-performance organic FET devices.[4a–d] This hypothesis is
likely to be true, because [1]benzothieno[3,2-b][1]benzothio-
phene (1b), which contains two octyl groups at the axis posi-
tions, has been reported to possess the highest mobility value
(43 cm2 VÀ1 sÀ1) reported to date.[8c] In addition, thiophene-
fused polycyclic aromatic compounds with linear alkyl chains
at the axis positions, such as 2,7-dioctyl[1]benzothieno[3,2-b]
[1]benzothiophene (1c) and 2-tridecyldinaphtho[2,3-d:2’,3’-
d’]benzo[1,2-b:4,5-b’]dithiophene (1d), have been found to be
good candidates for application in organic transistors.[8b,d]
These side-chains are considered essential to high-performance
organic thin-film transistors because they result in the forma-
tion of well-defined layered crystal structures.[4e,8] Based on
these results, we chose [n]phenacenes with two trimethylsilyl
groups as targets for this study, because the trimethylsilyl
groups can be easily transformed into various functional
groups, including halogen, hydroxy, and aryl groups, by oxida-
tive halogenation, Tamao oxidation, and Hiyama cross-coupling
reactions (Scheme 2).[9–11]
benzene (Scheme 4b) did not proceed efficiently. Only a small
amount of the desired coupling products (4 and 5) were
formed and the corresponding monoarylated compounds (2-
formylbiaryl, Scheme 4a, and 2-arylphenanthrene, Scheme 4b,
respectively) were obtained in low yields. These monoarylated
compounds were obtained as mixtures of the corresponding
debrominated compounds and these mixtures were insepara-
ble. In view of these results, we decided to change the syn-
thetic route, as shown in Scheme 5. This new design has the
advantage of allowing the synthesis of both [5]- and [7]phena-
cenes from a common synthetic intermediate, 1-formyl-7-
phenanthrene (9), without the requirement for a two-fold
direct CÀH arylation reaction.
First, building block 9 was synthesized by direct CÀH bond
arylation, Wittig reaction, and cyclization of the resulting vinyl
ether (Scheme 6). Ruthenium-catalyzed direct arylation of the
CÀH bond of an aldimine derived from 2-tolualdehyde gave 2-
biarylcarbaldehyde 6 in 72% yield.[12] Next, the formyl group of
compound 6 was converted into a methoxyethenyl group by
Wittig reaction with chloromethoxymethyltriphenylphosphine
and potassium tert-butoxide. Treatment of the resulting regioi-
someric mixture of methyl vinyl ether 7 (E/Z=81:19) with a cat-
alytic amount of [Bi(OTf)3] furnished the corresponding 1-
methyl-7-silylphenanthrene (8) in 92% yield.[13] Subsequent
bromination, which led to dibromomethylphenanthrene, fol-
lowed by hydrolysis, provided the key synthetic building block
1-formyl-7-trimethylsilylphenanthrene (9) in 90% yield.
Aldehyde 5 was submitted to the same pattern of reactions
again to increase the number of benzene rings in [3]phena-
cene 9 (Scheme 7). The ruthenium-catalyzed direct CÀH bond
arylation of aldimine 9’ was slightly less efficient than that in
the synthesis of compound 6, although the subsequent Wittig
reaction afforded vinyl ether 11 in moderate yield with similar
stereoselectivity, which was observed in the formation of com-
pound 7. Finally, bismuth-catalyzed cyclization afforded the de-
sired 3,10-di(trimethylsilyl)[5]phe-
Results and Discussion
We recently reported a short synthesis of [6]phenacenes (fulmi-
nenes) that contained two long alkyl chains at the axis posi-
tions.[7d] This synthesis consisted of ruthenium-catalyzed direct
CÀH arylation,[12] followed by sequential Wittig olefination and
bismuth-catalyzed cyclization of the resulting vinyl ethers
(Scheme 3).[13] Based on this success, we initially attempted the
synthesis of 3,10-disilyl[5]phenacene (2) and 3,12-disilyl[7]phe-
nacene (3) through a similar three-step synthesis strategy.
However, in the first reaction that we attempted, the rutheni-
um-catalyzed direct CÀH arylations of aldimines that were de-
rived from 3-silylbenzaldehyde with 1,4-dibromobenzene
(Scheme 4a) or 1,8-diformylphenanthrene with bromo-4-silyl-
nacene (2) in 77% yield.[9]
The number of benzene rings
could also be increased to seven
in three steps by using com-
pound 8 as a synthetic building
block (Scheme 8). First, phenan-
Scheme 2. Structures of the target [5]- and [7]phenacenes with silyl groups at the axis positions.
threne 8 was brominated by
using N-bromosuccinimide (NBS)
to yield the corresponding
benzyl bromide, which was used
in the subsequent Wittig reac-
tion directly without purification.
After heating at reflux in CH2Cl2
with triphenylphosphine, the re-
sulting phosphonium salts were
treated with aldehyde
9 and
K2CO3 to furnish diphenanthryl
ethylene 12 as a mixture of E
and Z stereoisomers. Photocycli-
zation under irradiation by
a UV lamp in the presence of
Scheme 3. Short transition-metal-catalyzed synthesis of 3,11-dialkyl[6]phenacenes.
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Scheme 4. Attempted synthesis of [5]- and [7]phenacenes with silyl groups at the axis positions.
iodine yielded 3,12-di(trimethyl-
silyl)[7]phenacene (3) in 46%
yield. This is a rare example of
the synthesis of functionalized
[n]phenacenes (n>6).[7c,d,14]
The photophysical properties
of 3,10-disilyl[5]phenacene (2)
and 3,12-disilyl[7]phenacene (3)
were investigated by UV/Vis ab-
sorption spectroscopy to obtain
insight into their electronic
Scheme 5. Modified synthetic route to [5]- and [7]phenacenes 2 and 3 from [3]phenacene.
structures (Figure 1). [5]Phenacene 2 showed a maximum peak
at 297 nm, along with two shoulder peaks at 308 and 330 nm.
The absorption peaks of [7]phenacene 3 shifted bathochromi-
cally by 14–16 nm with respect to those of compound 2, there-
by reflecting the effective expansion of p conjugation through
the phenacene backbone. These values are summarized in
Table 1, along with the HOMO–LUMO gaps (Egopt) that were cal-
culated from the onset of absorption. A clear shift in emissions
(11 nm) was also observed for [5]phenacene 2 and [7]phena-
cene 3.
To obtain further insight into the effects of the silyl substitu-
ents and the number of fused benzene rings on the conjugat-
ed p system, the molecular orbitals and energy levels of the
frontier orbitals were calculated by using density functional
theory (DFT) at the B3LYP/6-31G(d) level of theory (Figure 2).
The calculated band-gaps were higher than those obtained
Scheme 6. Preparation of the synthetic building blocks of [5]- and [7]phena-
cenes (Si=SiMe3).
opt
from the UV/Vis absorption onset study (see Eg in Table 1) by
about 1.0 eV. Although the distribution of the LUMO orbital of
[5]phenacene looked different to that of compound 2, the
Scheme 7. Synthesis of 3,10-disilyl[5]phenacene (2).
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Scheme 8. Synthesis of 3,12-disilyl[7]phenacene (3).
Figure 2. Molecular orbital plots and energy diagram of the frontier orbitals
(HOMO and LUMO) of picene, compound 2, and compound 3, as estimated
by using density functional theory at the B3LYP/6-31G(d) level of theory. The
values between each level are the energy gaps of the each frontier orbitals.
Figure 1. UV/Vis absorption (solid lines) and emission spectra (dashed lines)
of 3,10-disilyl[5]phenacene (2) and 3,12-disilyl[7]phenacene (3) in CH2Cl2 at
258C.
For example, treatment of [5]phenacene 2 with N-bromosucci-
nimide afforded 3-bromo-10-trimethylsilyl[5]phenacene (13) in
93% yield. The reaction occurred selectively at one of the tri-
methylsilyl groups without producing 3,10-dibromo[5]phena-
cene.
Table 1. Optical data for [n]phenacenes.
abs
abs
opt
em
Compound
lmax
[nm][a]
e [MÀ1 cmÀ1
]
lmax
[nm][a]
Eg
lmax
[nm][c]
[eV][b]
[5]phenancene[d]
285
292
293
308
94300
60800
–
384
388
389
412
3.23
3.20
3.19
3.01
378
383
385
394
2
Conclusion
[6]phenacene[e]
3
47300
We have demonstrated a short synthesis of [n]phenacenes
with silyl groups at the axis positions that proceeded through
sequential ruthenium-catalyzed direct CÀH arylation/Wittig ole-
fination/bismuth-catalyzed cyclization, and photocyclization re-
actions. UV/Vis absorption and fluorescence studies of the re-
sulting 3,10-disilyl[5]- and 3,12-dislyl[7]phenacenes indicated
that the silyl groups did not affect the energy levels of the
frontier orbitals. However, effective conjugation over the whole
p framework was observed for both [n]phenacenes. Therefore,
the incorporation of trimethylsilyl groups is an effective way of
endowing these polycyclic aromatic hydrocarbons with solubil-
ity without affecting their photophysical properties. The silyl
groups could be transformed into bromide groups, which sug-
gests that further tuning of the electronic properties of these
compounds is possible. These results exemplify that such
[n]phenacenes are p-conjugated systems with potential appli-
cations as optoelectronic devices.
[a] In CH2Cl2 (1”10À5 m); [b] Determined from the onset wavelength
(lonset) in the absorption spectrum (Egopt =1240/lonset); [c] Maximum fluo-
rescence emission in CH2Cl2 (5”10À6 m); [d] Ref. [7a]; [e] Ref. [7c]; the
molar absorption coefficient could not be determined, owing to the low
solubility of [6]phenacene.
energy levels of these compounds were almost identical. This
similarity was because the LUMO coefficient of picene in the 3-
position was relatively small and, therefore, the electronic
effect of functional groups at this position was not significant.
In contrast, the optical band-gap became slightly narrower as
the number of fused benzene rings increased (2 versus 3), thus
implying that there was effective conjugation over the whole
p framework of compound 3.
Finally, the resulting [n]phenacenes underwent further trans-
formations to demonstrate their synthetic utility (Scheme 9).
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08C. The resulting mixture was warmed to 258C and stirred for 1 h.
A solution of 2-(4-trimethylsilylphenyl)-6-tolualdehyde (6; 7.7 g,
29 mmol) in THF (30 mL) was added dropwise at 08C and the re-
sulting mixture was stirred at 258C for an additional 15 h. The mix-
ture was quenched with NH4Cl and extracted three times with
EtOAc (3”100 mL). The combined organic layer was dried over
MgSO4 and the organic solvent was removed under reduced pres-
sure. The residue was purified by flash column chromatography on
silica gel (n-hexane) to give (E)-3-(4-trimethylsilylphenyl)-2-(methox-
yethenyl)toluene (7) as a yellow oil (77% yield, 6.5 g, 22 mmol). An-
other fraction contained a mixture of two stereoisomers, (E)-7 and
(Z)-7, as a yellow oil (17% yield, 1.5 g, 4.9 mmol). (E)-7: 1H NMR
(400 MHz, CDCl3, 258C): d=7.56 (d, J=8.4 Hz, 2H), 7.37 (d, J=
8.4 Hz, 2H), 7.24–7.15 (m, 3H), 6.22 (d, J=13.2 Hz, 1H), 5.64 (d, J=
13.2 Hz, 1H), 3.51 (s, 3H), 2.44 (s, 3H), 0.34 ppm (s, 9H); 13C NMR
(100 MHz, CDCl3, 258C): d=151.7, 143.0, 141.4, 138.1, 136.5, 133.1,
132.8, 129.4, 129.2, 128.0, 125.8, 56.1, 21.5, À1.1 ppm; HRMS
(FAB+): m/z calcd for C19H24OSi: 296.1596[M]+; found: 296.1585.
Scheme 9. Bromination of 3,11-disilyl[5]phenacene (2).
Experimental Section
General Methods
All of the reactions were performed in dry solvent under an argon
atmosphere. Unless otherwise noted, all chemicals were purchased
from commercial suppliers and used without further purification.
Water was degassed with argon for 20 min before use. 1,2-Di-
chloroethane was purchased from Wako Pure Chemical Industries
and dried by using the usual methods, distilled, and degassed with
argon for 20 min before use. [{RuCl2(p-cymene)}2] was purchased
from Kanto Chemical Co., Inc. [Bi(OTf)3] was purchased from
Sigma–Aldrich. 4-Trimethylsilyl-1-bromobenzene was prepared ac-
cording to a literature procedure.[15] Column chromatography was
performed on neutral silica gel 60N (40–50 mm) that was pur-
1-Methyl-7-(trimethylsilyl)phenanthrene (8)
A solution of a mixture of (E)- and (Z)-3-(4-trimethylsilylphenyl)-2-
(methoxyethenyl)toluene (7; 6.4 g, 22 mmol) in 1,2-dichloroethane
(130 mL) was treated with [Bi(OTf)3] (709 mg, 1.1 mmol) and the
mixture was stirred at 258C for 1 h. The solvent was removed in va-
cuo and the residue was purified by flash column chromatography
on silica gel (n-hexane) to afford 1-methyl-7-(trimethylsilyl)phenan-
threne (8) as a white solid (92% yield, 5.3 g, 20 mmol). 1H NMR
(400 MHz, CDCl3, 258C): d=8.70 (d, J=8.4 Hz, 1H), 8.62 (d, J=
8.4 Hz, 1H), 8.09 (s, 1H), 7.99 (d, J=8.8 Hz, 1H), 7.83 (d, J=8.4 Hz,
1H), 7.82 (dd, J=1.2, 8.4 Hz, 1H), 7.58 (t, J=8.8 Hz, 1H), 7.48 (d,
J=7.6 Hz, 1H), 2.79 (s, 3H), 0.43 ppm (s, 9H); 13C NMR (100 MHz,
CDCl3, 258C): d=138.1, 134.5, 133.8, 130.7 (overlapped), 130.6,
130.0, 127.5, 126.5, 125.8, 122.5, 121.7, 120.6, 19.6, À1.1 ppm.
HRMS (FAB+): m/z calcd for C18H20Si: 264.1334 [M]+; found:
264.1335.
1
chased from Kanto Chemical Co., Inc. H NMR (400 and 600 MHz)
and 13C NMR spectra (100 and 150 MHz) were recorded on Varian
1
400 and 600 MR spectrometers, respectively. H chemical shifts are
reported in ppm, relative to the solvent resonance resulting from
incomplete deuteration (CDCl3, d=7.26 ppm) as an internal stan-
dard. 13C NMR spectra were recorded with complete proton decou-
pling and the chemical shifts are reported relative to CDCl3 (d=
77.0 ppm). The following abbreviations are used: s=singlet, d=
doublet, t=triplet, m=multiplet. High-resolution mass spectrosco-
py (HRMS) was performed on a JEOL JMS-700 MStation FAB-MS.
Melting points were recorded on a Yanako MP-J3 melting-point ap-
paratus and are uncorrected.
2-(4-Trimethylsilylphenyl)-6-tolualdehyde (6)
A mixture of 2-tolualdehyde (4.6 mL, 40 mmol) and toluidine (4.3 g,
40 mmol) was stirred at 258C for 1 h before 4-bromo(trimethylsi-
lyl)benzene (13.8 g, 60 mmol), potassium carbonate (16.6 g,
120 mmol), triphenylphosphine (2.1 g, 8.0 mmol), potassium ace-
tate (1.6 g, 16 mmol), dichloro(p-cymene)ruthenium dimer (2.45 g,
4.0 mmol), and water (80 mL) were added. The resulting mixture
was stirred at 1308C for 36 h, and then a concentrated aqueous so-
lution of HCl (20 mL) was added dropwise at 08C. After stirring at
258C for 4 h, the mixture was quenched with brine and extracted
three times with EtOAc (3”100 mL). The combined organic layer
was dried over MgSO4 and the organic solvent was removed under
reduced pressure. The residue was purified by flash column chro-
matography on silica gel (n-hexane) to give 2-(4-trimethylsilylphen-
yl)-6-tolualdehyde (6) as a yellow oil (72% yield, 7.7 g, 29 mmol).
1H NMR (400 MHz, CDCl3, 258C): d=9.97 (s, 1H), 7.60 (d, J=7.6 Hz,
2H), 7.46 (t, J=7.2 Hz, 1H), 7.34 (d, J=7.8 Hz, 2H), 7.27 (d, J=
7.8 Hz, 2H), 2.66 (s, 3H), 0.32 ppm (s, 9H); 13C NMR (100 MHz,
CDCl3, 258C): d=194.5, 147.1, 140.2, 139.9, 139.2, 133.3, 132.6,
132.1, 131.1, 129.4, 128.5, 21.5, À1.1 ppm; HRMS (FAB+): m/z calcd
for C17H20OSi: 268.1283 [M]+; found: 268.1288.
1-Formyl-7-(trimethylsilyl)phenanthrene (9)
N-bromosuccinimide (1.78 g, 10 mmol) and benzoyl peroxide
(20 mg) were added to a stirring solution of 1-methyl-7-(trimethyl-
silyl)phenanthrene (8; 1.32 g, 5.0 mmol) in CCl4 (20 mL). The result-
ing mixture was heated at reflux for 16 h. The mixture was washed
with brine and extracted three times with EtOAc (3”40 mL). The
combined organic layer was dried over MgSO4 and the organic sol-
vent was removed under reduced pressure. To the resulting mix-
ture dissolved in DMSO (40 mL) was added NaHCO3 (840 mg,
10 mmol), and the solution was heated at 908C for 3 h. The mix-
ture was quenched with brine and extracted three times with
EtOAc (3”40 mL). The combined organic layer was dried over
MgSO4 and the organic solvent was removed under reduced pres-
sure. The residue was purified by flash column chromatography on
silica gel (n-hexane/EtOAc, 25:1 v/v) to give 1-formyl-7-(trimethylsi-
lyl)phenanthrene (9) as a yellow solid (90% yield, 1.3 g, 4.5 mmol).
1H NMR (400 MHz, CDCl3, 258C): d=10.5 (s, 1H), 9.14 (d, J=8.8 Hz,
1H), 8.97 (d, J=8.8 Hz, 1H), 8.65 (d, J=7.6 Hz, 1H), 8.10 (s, 1H),
8.08 (dd, J=1.2, 8.0 Hz, 1H), 7.97 (d, J=8.8 Hz, 1H), 7.84 (dd, J=
1.2, 9.6 Hz, 1H), 7.79 (t, J=8.0 Hz, 1H), 0.41 ppm (s, 9H); 13C NMR
(100 MHz, CDCl3, 258C): d=193.2, 139.4, 134.9, 133.9, 131.2, 131.2,
130.7, 130.5, 130.2, 130.1, 129.7, 128.7, 125.3, 121.8, 121.5,
À1.4 ppm; HRMS (FAB+): m/z calcd for C18H18OSi: 278.1127 [M]+;
found: 278.1137.
3-(4-Trimethylsilylphenyl)-2-(methoxyethenyl)toluene (7)
A solution of potassium tert-butoxide (4.5 g, 40 mmol) in THF
(50 mL) was added to a stirring solution of (methoxymethyl)triphe-
nylphosphonium chloride (13.1 g, 40 mmol) in THF (120 mL) at
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precipitate was filtered and dried under reduced pressure to yield
1,2-(8-trimethylsilyl-4-phenanthryl)ethene (12) as a mixture of two
stereoisomers (71% yield, 0.62 mmol, 332 mg). (E)-12: m.p.>
1-Formyl-2-(4-(trimethylsilyl)phenyl)-7-(trimethylsilyl)phenan-
threne (10)
1
According to a similar procedure for the synthesis of biphenyl 6,
the reaction of an aldimine derived from compound 9 (268 mg,
0.96 mmol) afforded 1-formyl-2-(4-(trimethylsilyl)phenyl)-7-(trime-
thylsilyl)phenanthrene (10) as a yellow solid (49% yield, 201 mg,
3008C; H NMR (600 MHz, CDCl3, 608C): d=8.74 (d, J=8.4 Hz, 2H),
8.71 (d, J=8.4 Hz, 2H), 8.22 (d, J=9.0 Hz, 2H), 8.07 (s, 2H), 8.00 (d,
J=7.2 Hz, 2H), 7.99 (s, 2H), 7.82 (d, J=8.4 Hz, 2H), 7.81 (d, J=
9.0 Hz, 2H), 7.72 (t, J=7.2 Hz, 2H), 0.40 ppm (s, 18H); 13C NMR
(150 MHz, CDCl3, 608C): d=139.0, 136.1, 134.2, 131.3, 131.2, 131.0,
130.8, 130.2, 130.0, 127.4, 126.3, 125.1, 122.7, 122.6, 122.1,
À1.0 ppm; HRMS (FAB+): m/z calcd for C36H36Si2: 524.2356 [M]+;
found: 524.2337.
1
0.47 mmol). H NMR (400 MHz, CDCl3, 258C) : d=10.2 (s, 1H), 9.13
(d, J=10.0 Hz, 1H), 8.92 (d, J=8.8 Hz, 1H), 8.65 (d, J=8.8 Hz, 1H),
8.12 (s, 1H), 7.97 (d, J=8.8 Hz, 1H), 7.84 (d, J=8.4 Hz, 1H), 7.68 (d,
J=8.4 Hz, 1H), 7.67 (d, J=8.0 Hz, 2H), 7.46 (d, J=8.0 Hz, 2H), 0.42
(s, 9H), 0.38 ppm (s, 9H); 13C NMR (100 MHz, CDCl3, 258C): d=
195.0, 146.9, 140.7, 139.5, 138.8, 134.1, 133.3, 131.4, 131.0, 130.3,
129.9, 129.88, 129.85, 129.83, 129.6, 128.5, 127.6, 123.2, 121.7, À1.1,
À1.0 ppm; HRMS (FAB+): m/z calcd for C27H30OSi2: 426.1835 [M]+;
found: 426.1855.
3,12-Di(trimethylsilyl)[7]phenacene (3)
Iodine (17 mg, 0.067 mmol) and THF (91 mL, 1.1 mmol) were added
to a solution of diphenanthryl ethylene 12 (30 mg, 0.056 mmol) in
toluene (43 mL) and the solution was irradiated with a UV lamp
(125 W) at 258C for 24 h. The resulting precipitate was filtered and
dried under reduced pressure to give 3,12-di(trimethylsilyl)[7]phe-
nacene (3) as a white solid (46% yield, 14 mg, 0.026 mmol). M.p.>
3-(4-(Trimethylsilyl)phenyl)-4-methoxyethenyl-8-(trimethylsi-
lyl)phenanthrene (11)
1
3008C; H NMR (600 MHz, CDCl3, 608C): d=9.10 (d, J=9.0 Hz, 2H),
According to a similar procedure for the synthesis of methyl vinyl
ether 7, the reaction of 1-formyl-2-(4-(trimethylsilyl)phenyl)-7-(tri-
methylsilyl)phenanthrene (10; 200 mg, 0.47 mmol) afforded 1-(me-
thoxyethenyl)-2-(4-(trimethylsilyl)phenyl)-7-(trimethylsilyl)phenan-
threne (11) as a yellow solid (71% yield, 147 mg, 0.33 mmol).
1H NMR (400 MHz, CDCl3, 258C): d=8.69 (d, J=8.4 Hz, 1H), 8.66 (d,
J=8.8 Hz, 1H), 8.26 (d, J=8.8 Hz, 1H), 8.07 (s, 1H), 7.81 (d, J=
7.6 Hz, 1H), 7.79 (d, J=8.8 Hz, 1H), 7.60 (d, J=7.6 Hz, 1H), 7.62 (d,
J=8.0 Hz, 2H), 7.47 (d, J=8.0 Hz, 2H), 6.41 (d, J=12.8 Hz, 1H),
6.02 (d, J=12.8 Hz, 1H), 3.64, (s, 3H), 0.41 (s, 9H), 0.35 ppm (s, 9H);
13C NMR (100 MHz, CDCl3, 258C): d=152.8, 142.9, 139.5, 138.6,
138.4, 134.0, 133.0, 131.6, 131.2, 131.0, 130.9, 130.7, 129.8, 129.5,
128.5, 126.9, 124.6, 122.0, 121.1, 101.1, 56.4, À1.0 ppm; HRMS
(FAB+): m/z calcd for C29H34OSi2: 454.2148 [M]+; found: 454.2161.
9.05 (s, 2H), 9.02 (d, J=9.0 Hz, 2H), 8.88 (d, J=9.6 Hz, 2H), 8.86 (d,
J=9.6 Hz, 2H), 8.19 (s, 2H), 8.09 (d, J=9.6 Hz, 2H), 7.90 (d, J=
8.4 Hz, 2H), 0.44 ppm (s, 18H); 13C NMR spectra were not recorded,
owing to the low solubility of the product; HRMS (FAB+): m/z calcd
for C36H34Si2: 522.2199 [M]+; found: 522.2203.
3-Bromo-10-trimethylsilyl[5]phenacene (13)
N-bromosuccinimide (6.4 mg, 0.036 mmol) was added to a solution
of 3,10-di(trimethylsilyl)[5]phenacene (2; 12.5 mg, 0.030 mmol) in
MeCN (1.0 mL) and the mixture was heated at reflux for 24 h. DMF
(5 mL) was added and the mixture was washed three times with
brine (3”10 mL). The organic solvent was removed under reduced
pressure to afford 3-bromo-10-trimethylsilyl[5]phenacene (13) as
a
white solid (93% yield, 12 mg, 0.028 mmol). M.p.>3008C;
1H NMR (600 MHz, CDCl3, 608C): d=8.97 (d, J=9.0 Hz, 1H), 8.87 (d,
J=9.6 Hz, 1H), 8.82–8.72 (m, 3H), 8.70 (d, J=9.0 Hz, 1H), 8.16 (s,
1H), 8.15 (s, 1H), 8.04 (d, J=9.0 Hz, 1H), 7.93 (d, J=8.4 Hz, 1H),
7.88 (d, J=7.8 Hz, 1H), 7.81 (d, J=7.8 Hz, 1H), 0.43 ppm (s, 9H);
13C NMR spectra were not recorded, owing to the low solubility of
the product; HRMS (FAB+): m/z calcd for C25H21BrSi: 428.0596 [M]+;
found: 428.0568.
3,10-Di(trimethylsilyl)[5]phenacene (2)
According to a similar procedure for the synthesis of phenanthrene
8, the reaction of 3-(4-(trimethylsilyl)phenyl)-4-methoxyethenyl-8-
(trimethylsilyl)phenanthrene (11; 105 mg, 0.23 mmol) afforded
3,10-di(trimethylsilyl)[5]phenacene (2) as a white solid (77% yield,
1
75 mg, 0.18 mmol). M.p.>3008C; H NMR (400 MHz, CDCl3, 258C):
d=8.95 (s, 2H), 8.82 (d, J=8.8 Hz, 2H), 8.78 (d, J=8.8 Hz, 2H), 8.16
(s, 2H), 8.04 (d, J=8.8 Hz, 2H), 7.87 (d, J=9.6 Hz, 2H), 0.41 ppm (s,
18H); 13C NMR (100 MHz, CDCl3, 258C): d=138.7, 134.2, 131.2,
131.1, 130.7, 128.9, 128.8, 128.7, 127.6, 122.2, 121.6, À1.0 ppm;
HRMS (FAB+): m/z calcd for C28H31Si2: 422.1886 [M]+; found:
422.1893.
Acknowledgements
This work was financially supported by a Grant-in-Aid for
Young Scientists (B) (No. 26870389) from MEXT, Japan, the Ad-
vanced Catalytic Transformation program for Carbon utilization
(ACT-C) project of the Japan Science and Technology Agency
(JST), and the MEXT Program for Promoting the Enhancement
of Research Universities. M.M. is grateful for the ADEKA Award
in Synthetic Organic Chemistry, Japan, and thanks the Okaya-
ma Foundation for Science and Technology. The authors grate-
fully thank Mr. Takahisa Sakae (Okayama University) for per-
forming the HRMS measurements.
1,2-(8-Trimethylsilyl-4-phenanthryl)ethene (12)
N-bromosuccinimide (170 mg, 0.96 mmol) and benzoyl peroxide
(5.0 mg) were added to a mixture of phenanthrene 8 (396 mg,
0.87 mmol) in CCl4 (3 mL) and the resulting mixture was heated at
reflux for 16 h. The mixture was washed with brine and extracted
three times with EtOAc (3”10 mL). The combined organic layer
was dried over MgSO4 and the organic solvent was removed under
reduced pressure. The mixture was dissolved in CH2Cl2 (10 mL), tri-
phenylphosphine (228 mg, 0.87 mmol) and potassium carbonate
(240 mg, 1.7 mmol) were added, and the resulting mixture was
heated at reflux for 24 h. A solution of 1-formylphenanthrene 9
(242 mg, 0.87 mmol) in CH2Cl2 (10 mL) was added and the mixture
was heated at reflux for an additional 24 h. Water (10 mL) was
added and the mixture was stirred for 10 min at 258C. The white
Keywords: bismuth
transistors · phenacenes · polycycles
·
cyclization
·
organic field-effect
Chem. Asian J. 2015, 10, 2518 – 2524
www.chemasianj.org
2523
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
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Manuscript received: July 7, 2015
Accepted Article published: July 28, 2015
Final Article published: August 21, 2015
Chem. Asian J. 2015, 10, 2518 – 2524
www.chemasianj.org
2524
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim