Synthesis of 1,2,3,4,8,9,10,11-octasubstituted pentacenequinone derivatives and their conversion into substituted pentacenes

Article abstract of DOI:10.1002/asia.200900754

A series of 1,2,3,4,8,9,10,11-octasubstituted pentacenequinone derivatives were prepared by the oxidation of 1,2,3,4,8,9,10,11-octasubstituted pentacenes, which were synthesized by the double homologation method. Oxidation of the pentacenes was carried out with H₅IO₆ or air and DDQ. These octasubstituted pentacenequinones were converted into 1,2,3,4,6,8,9,10,11, 13-decasubstituted or 2,3,6,9,10,13-hexasubstituted pentacene derivatives by the introduction of aryl or alkynyl groups at the carbonyl carbons. The photophysical properties of these new pentacenes have been measured in solution, and the substituent effects are discussed.

Full text of DOI:10.1002/asia.200900754

FULL PAPERS
DOI: 10.1002/asia.200900754
Synthesis of 1,2,3,4,8,9,10,11-Octasubstituted Pentacenequinone Derivatives
and their Conversion into Substituted Pentacenes
Shi Li,[a] Lishan Zhou,[a] Kiyohiko Nakajima,[b] Ken-ichiro Kanno,[a] and
Tamotsu Takahashi*[a]
Abstract: A series of 1,2,3,4,8,9,10,11-
octasubstituted pentacenequinone de-
rivatives were prepared by the oxida-
tion of 1,2,3,4,8,9,10,11-octasubstituted
pentacenes, which were synthesized by
the double homologation method. Oxi-
dation of the pentacenes was carried
out with H5IO6 or air and DDQ. These
octasubstituted
were
1,2,3,4,6,8,9,10,11,13-decasubstituted or
pentacenequinones
converted into
2,3,6,9,10,13-hexasubstituted pentacene
derivatives by the introduction of aryl
or alkynyl groups at the carbonyl car-
bons. The photophysical properties of
these new pentacenes have been mea-
sured in solution, and the substituent
effects are discussed.
Keywords: NMR spectroscopy
oxidation · pentacenes · polycycles ·
quinones
·
Introduction
Since pentacene film has shown high performance as an or-
ganic semiconductor,[1] substituted soluble pentacene deriva-
tives have gained importance because they can be used for
wet process.[2a] Since then we have developed several meth-
ods for the formation of substituted pentacene derivatives,
such as homologation method (Figure 1, [Eq. (1)]),[2a,3]
double homologation method (Figure 1, [Eq. (2)]),[4] cou-
pling method,[5] and others. After our first report in 2000,
several groups also reported the formation and performance
of the substituted pentacenes.[6,7]
One general and simple introduction of substituents at
6,13-positions is the reaction of pentacenequinone with
organo Grignard or lithium reagents (Figure 1, [Eq. (3)]).
This promoted us to combine our double homologation
method and this pentacenequinone method. Here, we would
like to report the combination of the double homologation
[a] Dr. S. Li, Dr. L. Zhou, Dr. K.-i. Kanno, Prof. Dr. T. Takahashi
Catalysis Research Center
Hokkaido University
Kita 21, Nishi 10, Kita-ku, Sapporo 001-0021 (Japan)
Fax : (+81)11-706-9150
E-mail: tamotsu@cat.hokudai.ac.jp
[b] Prof. Dr. K. Nakajima
Department of Chemistry
Aichi University of Education
Igaya, Kariya 448-8542, Aichi (Japan)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.200900754.
Figure 1. The concept of homologation and double homologation, qui-
none method.
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Chem. Asian J. 2010, 5, 1620 – 1626

and pentacenequinone methods for the formation of multi-
substituted pentacene derivatives. Octasubstituted penta-
cenes prepared by the double homologation method were
oxidized by H5IO6 or air and DDQ to give the correspond-
ing pentacenequinones. The organic substituents were intro-
duced at the 6,13-positions for the formation of decasubsti-
tuted or hexasubstituted pentacenes with tetra ester groups
(Figure 2).
Scheme 1. Synthesis of pentacenequinones 1 from pentacenes 2 by oxida-
tion.
6,13-Diarylpentacenes from Pentacenequinones
The formation of 6,13-diarylpentacene derivatives 6 from
pentacenequinone 1a is described below. The conditions of
the reaction of phenyllithium with pentacenequinone 1a
were optimized as shown in Table 1. Pentacenequinone 1a
Figure 2. New strategy for synthesis of substituted pentacene.
Table 1. Reaction of pentacenequinone 1a with arylmetals.
Results and Discussion
Preparation of Octasubstituted Pentacenequinones by
Oxidation
Octasubstituted 6,13-pentacenequinones 1 were prepared by
the oxidation of the corresponding pentacenes 2, which
were prepared by a zirconium-mediated double homologa-
tion method as reported previously (Scheme 1).[4] The blue
chloroform solution of pentacenes 2 was stirred in air under
sunlight. The solvent was evaporated in vacuo after the blue
color had disappeared completely. The resulting yellow resi-
due that mainly contained pentacene endoperoxides 3 was
treated with 1 equiv of DDQ in toluene at 1008C for 3 h to
afford pentacenequinones 1a,b as yellow solids in 54 and
42% yields, respectively (Path A). The yields of pentacene-
quinones 1 obtained by the oxidation of pentacenes 2 with
4 equiv of H5IO6 in DMF at 1008C were higher. The blue
colour of 2 had disappeared completely within 3 h. The
usual workup and silica gel chromatography gave pentace-
nequinones 1a,b in 75 and 69% yields, respectively
(Path B).
Entry
Reagent
Equiv
T [8C]
t [h]
Yield of
Yield of
4 [%][a]
5 [%][a]
1
2
3
4
5b
6
7
PhLi
PhLi
PhLi
PhLi
PhLi
PhMgBr
2-thienylLi
2
2
2
3
6
3
3
RT
50
6
75
62
11
–
–
–
–
12
12
6
6
6
trace
43
58
12
56
45
reflux
reflux
reflux
reflux
reflux
6
–
[a] NMR yield. [b] Unidentified polar compounds were formed.
was reacted with 2 equiv of phenyllithium in THF at room
temperature. After 6 h, the corresponding keto alcohol 4a
was formed in 75% NMR yield (entry 1). When the reaction
proceeded at 508C, only trace amounts of diol 5a was
formed after 12 h (entry 2). In refluxing THF for 12 h, diol
5a was formed as a major product with keto alcohol 4a by
using 2 equiv of phenyllithium (entry 3). The optimized con-
dition for the reaction is 3 equiv of phenyllithium in reflux-
ing THF for 6 h. Diol 5a was obtained in 58% yield from
1a (entry 4). On increasing the amount of phenyllithium to
6 equiv, the desired diol 5a was formed in a very low yield
because unidentified polar compounds were formed which
could be detected by TLC (entry 5). The reaction of penta-
cenequinone 1a with phenyl Grignard reagent gave a similar
yield of diol 5a under the same conditions (entry 6). Similar-
ly, diol 5b was also prepared from 1a by its reaction with 2-
thienyllithium (entry 7).
Abstract in Japanese:
Diols 5a,b were purified by silica gel column chromatog-
raphy and then treated with 4 equiv of tin(II) chloride in
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T. Takahashi et al.
FULL PAPERS
acetonitrile. The desired 6,13-diarylpentacene derivatives
6a,b were formed as blue solids in 82 and 79% yields, re-
spectively (Scheme 2).
Upon treatment with TBAF, trimethylsilyl groups were ef-
ficiently removed as shown in Scheme 3. Diol 5a with four
used instead of alkynylmagnesium bromides, the yield of the
diols 5c,d were significantly decreased. The reduction of the
diols 5c,d with SnCl2 in acetonitrile produced the corre-
sponding 6,13-dialkynylpentacenes 6c,d in 86 and 90%
yields, respectively.
Alkynyl groups with various bulky substituents such as
tBu, TMS, and TIPS could be introduced into the pentacene
skeleton by using pentacenequinone 1b (Scheme 5). Diols
Scheme 2. Synthesis of 6,13-diarylpentacene derivatives 6 from diols 5.
Scheme 5. 6,13-Dialkynylpentacene formation from pentacenequinone
1b.
Scheme 3. Synthesis of hexasubstituted pentacene 8a.
9d–f were obtained in reasonable yields by the reaction of
pentacenequinone 1b and the corresponding alkynyl
Grignard reagents in refluxing THF. The 6,13-dialkynylpen-
tacenes were afforded in excellent yields by the same aro-
matization method mentioned above.
The structure of pentacene 10 f was determined by X-ray
analysis as shown in Figure 3. Pentacene 10 f exhibited a
nearly planar p-conjugated framework, and the angles be-
tween the two adjacent six-membered rings were within
3.30–4.048. The dihedral angles between the carbonyl planes
and the pentacene plane were within the range of 48.9–
trimethylsilyl groups was treated with 4 equiv of TBAF in
THF. After 3 h at room temperature, the silyl groups were
removed to afford diol 7a in 76% yield. Finally, the hexa-
substituted pentacene 8a was prepared by treatment with
SnCl2 under the same conditions as mentioned above.
6,13-Dialkynylpentacenes from Pentacenequinones
The synthesis of 6,13-dialkynylpentacenes 6c,d was achieved
by using the corresponding pentacenequinone 1a
(Scheme 4). The reaction of pentacenequinone 1a with 1-al-
kynylmagnesium bromide gave the desired diols 5c,d. When
the corresponding alkynyllithium reagents, however, were
Scheme 4. Synthesis of 6,13-dialkynylpentacenes 6c,d.
Figure 3. Structure of 6,13-bis(trimethylsilylethynyl)pentacene 10 f.
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Synthesis of Pentacenequinone Derivatives and their Conversion into Pentacenes
59.28, which suggested that the four ester groups did not
strongly alter the electronic properties of the pentacene
skeleton.
The stability of all the obtained pentacenes 6a–d, 8a,
10d–f were similar to the other derivatives reported thus
far. Our pentacenes were also thermally stable both in solu-
tion and in solid state under nitrogen atmosphere, but grad-
ually oxidized upon exposure to light and air.
cenes, 6c,d, 10d–f (196–270 cmÀ1), were smaller than for the
diaryl ones, 6a,b, and 8a (386–452 cmÀ1).
Comparison of HOMO–LUMO energy differences
(Eg,optical) of 6a–d to that of 1a showed that substitution of
diaryl groups at the 6,13-positions reduced the gap by
0.07 eV. This effect is much smaller than that for the dia-
lkynyl substitution in 6c,d (0.18–0.21 eV), which indicates
small effects of the conjugation between the aryl groups and
the pentacene backbone. When the gap values of 6a–c, 8a,
and 10e,f were compared with the reported data of 6,13-di-
phenylpentacene (1.94 eV),[6t] 6,13-bis(2-thienyl)pentacene
Photophysical Properties of 6,13-Disubstituted Pentacene-
2,3,9,10-tetraester Derivatives
(1.97 eV),[6x]
6,13-bis(triisopropylsilylethynyl)pentacene
The photophysical properties of pentacene-2,3,9,10-tetraest-
er derivatives were investigated in chloroform as shown in
Table 2. Compared with the wavelength of the absorption
(1.81 eV),[6t] 6,13-bis(phenylethynyl)pentacene (1.88 eV),[6u]
and 6,13-bis(trimethylsilylethynyl)pentacene (1.93 eV),[6u] it
was found that the effects of the introduction of four me-
thoxycarbonyl groups at the
2,3,9,10-positions were small.
The differences were within
Table 2. Photophysical properties of 6,13-disubstituted pentacene derivatives.[a]
only 0.03–0.11 eV. The results
would reflect the conformation
of these ester groups in the
solid state as mentioned in the
structure of 10 f. The substitu-
compound
2a[b]
6a
6b
8a
6c
6d
10d
10e
10 f
R1
R2
lmax
G
lmax(em) [nm]
Stokes shift [cmÀ1
]
E
g,optical [eV][c]
ents at 6,13-positions of the
pentacene derivatives also pro-
vided insight into the preven-
tion of dimerization.[4b]
TMS
TMS
TMS
H
TMS
TMS
Bu
H
Ph
2-thienyl
Ph
PhCC-
tBuCC-
tBuCC-
TIPSCC-
TMSCC-
602
622
622
616
673
660
648
655
652
625
638
640
631
682
672
658
666
661
611
403
425
386
196
270
235
252
209
1.98
1.91
1.91
1.93
1.77
1.80
1.85
1.83
1.84
Conclusions
Bu
Bu
A new method for the synthesis
of substituted pentacenes was
developed by the combination
of the quinone method and
double homologation method.
[a] Measured in CHCl3 at room temperature. [b] Ref. [4c]. [c] Optical HOMO–LUMO gaps determined from
the onset of lowest-energy visible absorption band. The onset is defined as the intersection between the base-
line and a tangent line that touches the point of inflection.
maximum of 6,13-nonsubstituted pentacene 2a, those of
6,13-diphenyl- and di-(2-thienyl)pentacene, 6a and 6b, were
red-shifted by 20 nm. Only small differences were observed
between 6a and 6b, although these have different aryl
groups at 6,13-positions. This can be ascribed to their pre-
ferred conformation perpendicular to the pentacene plane,
and the effect of p-conjugation between the pentacene skel-
eton and the aryl groups is small. Compared with the ab-
sorption maximum of 6,13-diphenylpentacene (lmax =595 nm
in CH2Cl2),[6k] that of 8a (lmax =616 nm) was red-shifted by
21 nm. This is a consequence of extending the p-system
through four ester groups on the terminal aromatic rings of
pentacene. Substitution of trimethylsilyl groups at 1,4,8,11-
positions causes a slight red-shift as can be seen in the com-
parison of 6a and 8a. In contrast to 6,13-diarylpentacenes
6a,b, 6,13-dialkynylsubstituted 6c,d and 10d–f exhibited the
absorption and emission maxima at much longer wavelength
regions. This illustrates that alkynyl groups effectively
extend the p-conjugation system of the pentacene moiety in
contrast to aryl groups. Stokes shifts of 6,13-dialkynylpenta-
6,13-Nonsubstituted pentacenes prepared by the double ho-
mologation method were converted to the corresponding
pentacenequinones by oxidation with H5IO6 or air and
DDQ. Aryl and alkynyl groups were introduced by the reac-
tion of the pentacenequinones with aryllithiums or alkynyl
Grignard reagents, and the resulting diols were aromatized
by tin(II) chloride to afford 6,13-diaryl- or dialkynylpenta-
cenes having four ester groups. The UV absorption spectra
illustrated that the alkynyl groups efficiently extended the
p-conjugation system of the pentacene moiety in contrast to
aryl groups.
Experimental Section
General
All reactions were carried out under a nitrogen atmosphere using stan-
dard Schlenk techniques. Tetrahydrofuran (THF) and toluene were dis-
tilled over sodium and benzophenone under a nitrogen atmosphere. All
the reagents were commercially available and used as received unless
otherwise mentioned. Compounds 2a,b were prepared according to the
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T. Takahashi et al.
FULL PAPERS
literature.[4b] 1H and 13C NMR spectra were measured in CDCl3 (contain-
ing 0.03% TMS) solutions.
5.1 Hz, 3.6 Hz, 2H, thienyl), 7.02 (dd, J=5.1 Hz, 1.8 Hz„ 2H, thienyl),
9.02 ppm (s, 4H, aromatic CH); 13C NMR (100 MHz, CDCl3, Me4Si): d=
2.0, 52.6, 73.3, 126.3, 126.6, 127.3, 127.5, 136.2, 136.5, 138.4, 139.0, 148.3,
170.5 ppm. HRMS m/z (FAB) calcd for C50H60O10Si4S2Na: 1019.2603
[M+Na+]; found: 1019.2598.
Syntheses
1,4,8,11-Tetrakis(trimethylsilyl)-6,13-pentacenequinone-2,3,9,10-tetracar-
boxylic acid tetramethyl ester (1a): Path A: The blue chloroform solution
of pentacene 2a (800 mg, 1.0 mmol) was kept in air under sunlight. After
several hours, the blue color disappeared completely. The solvent was
evaporated in vacuo, and the resulting yellow residue was treated with
DDQ (227 mg. 1.0 mmol) in toluene (15 mL) at 1008C for 3 h. Then the
reaction mixture was cooled to room temperature and purified by flash
chromatography (silica gel, CHCl3 as eluent) to afford the title com-
pound as a yellow solid (447 mg, 54% yield).
6,13-Bis(2-thienyl)-1,4,8,11-tetrakis(trimethylsilyl)pentacene-2,3,9,10-tet-
racarboxylic acid tetramethyl ester (6b): The title compound (76 mg) was
prepared as a purple–blue solid by the same way as described for 6a in
79% yield from 5b (100 mg, 0.10 mmol).
6b: purple–blue solid; m.p.:>3008C (dec); 1H NMR (400 MHz, CDCl3,
Me4Si): d=0.28 (s, 36H, SiACHTNUGTRNEUNG(CH3)3), 3.86 (s, 12H, CO2CH3), 7.40–7.41 (m,
2H, thienyl), 7.43–7.46 (m, 2H, thienyl), 7.75 (dd, J=5.0 Hz, 1.2 Hz, 2H,
thienyl), 8.91 ppm (s, 4H, aromatic CH); 13C NMR (100 MHz, CDCl3,
Me4Si): d=1.6, 52.5, 127.4, 127.5, 129.1, 129.6, 130.3, 130.4, 132.8, 136.0,
138.3, 139.8, 170.4 ppm. HRMS m/z (EI) calcd for C50H58O8Si4S2:
962.2650 [M]+; found: 962.2619. elemental analysis: calcd (%) for
C50H58O8Si4S2: C 62.33, H 6.07; found: C 62.42, H 5.95.
Path B: To a degassed solution of pentacene 2a (160 mg, 0.2 mmol) in
DMF (10 mL) was added H5IO6 (182 mg, 0.8 mmol). On heating to
1008C, the blue color disappeared completely. After the mixture was
heated at 1008C for 3 h, it was cooled to room temperature. The solvent
was evaporated in vacuo, and the resulting yellow residue was purified
by flash chromatography (silica gel, CHCl3 as eluent) to afford the title
compound as a yellow solid (124 mg, 75% yield).
6,13-Dihydroxy-6,13-diphenyl-6,13-dihydropentacene-2,3,9,10-tetracar-
boxylic acid tetramethyl ester (7a): To an oven dried 50 mL flask cooled
under N2 was added diol 5a (197 mg, 0.20 mmol) and dry THF (5 mL).
Tetrabutylammonium fluoride (1.0m in THF, 0.8 mL, 0.8 mmol) was
added dropwise at 08C and the mixture was stirred at room temperature
for 3 h. The mixture was quenched with 3m HCl at 08C and extracted
with ethyl acetate. The combined organic phase was washed with water,
saturated aqueous NaHCO3 solution, and brine. The solution was dried
over anhydrous Na2SO4. The solvent was evaporated, and the resulting
black viscous oil was purified by flash chromatography (silica gel,
hexane/ethyl acetate=3:1 as eluent) to afford the title compound as
yellow oil (105 mg, 76% yield).
7a: 1H NMR (400 MHz, [D6]DMSO, Me4Si): d=3.90 (s, 12H; CO2CH3),
6.50–6.52 (m, 4H; Ph), 6.63–6.65 (m, 4H; Ph), 6.77–6.79 (m, 2H; Ph),
6.93 (s, 2H; OH), 8.56 (s, 4H; aromatic CH), 8.80 ppm (s, 4H; aromatic
CH); 13C NMR (400 MHz, [D6]DMSO, Me4Si) d=52.7, 74.9, 126.18,
126.23, 126.9, 127.4, 128.3, 130.0, 132.0, 142.9, 143.0, 167.5 ppm; HRMS
m/z (EI) calcd for C42H32O10: 696.1996 [M]+; found: 696.2010.
1a: M.p.:>3008C; 1H NMR (400 MHz, CDCl3, Me4Si): d=0.57 (s, 36H;
SiACHTUNGTRENNUNG(CH3)3), 3.92 (s, 12H; CO2CH3), 9.39 ppm (s, 4H; aromatic CH);
13C NMR (100 MHz, CDCl3, Me4Si): d=2.0, 52.8, 129.7, 131.2, 138.8,
139.1, 141.8, 169.8, 182.3 ppm; HRMS (FAB): m/z (%) calcd for
C42H53O10Si4: 829.2716 [M+H]+; found: 829.2719; elemental analysis:
calcd (%) for C42H52O10Si4: C 60.84, H 6.32; found: C 60.69, H 6.35.
6,13-Dihydroxy-6,13-diphenyl-1,4,8,11-tetrakis(trimethylsilyl)-6,13-dihy-
dropentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester (5a): To an
oven dried 50 mL flask cooled under N2 was added pentacenequinone 1a
(415 mg, 0.5 mmol) and dry THF (15 mL). Then phenyllithium (0.98m in
cyclohexane-diethyl ether, 1.53 mL, 1.50 mmol) was added dropwise at
08C and the mixture was refluxed for 6 h. The mixture was quenched
with aqueous saturated NH4Cl at 08C and extracted with ethyl acetate.
The combined organic phase was washed with water, saturated aqueous
NaHCO3 solution, and brine. The solution was dried over anhydrous
Na2SO4. The solvent was evaporated, and the resulting black viscous oil
was purified by flash chromatography (silica gel, hexane/ethyl acetate=
3:1 as eluent) to afford the title compound as a yellow solid (285 mg,
58% yield).
6,13-Diphenylpentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester
(8a): The title compound (61 mg) was prepared as a blue solid by the
same way as described for 6a in 92% yield from 7a (70 mg, 0.10 mmol).
8a: Blue solid; m.p.>3008C (dec); 1H NMR (400 MHz, CDCl3, Me4Si):
d=3.92 (s, 12H; CO2CH3), 7.58–7.61 (m, 4H; Ph), 7.68–7.76 (m, 6H;
Ph), 8.22 (s, 4H; aromatic CH), 8.46 ppm (s, 4H; aromatic CH);
13C NMR (100 MHz, CDCl3, Me4Si): d=52.6, 127.6, 128.40, 128.44, 128.9,
129.6, 129.8, 131.5, 132.2, 138.2, 138.9, 167.8 ppm; HRMS m/z (EI) calcd
for C42H30O8: 662.1941 [M]+; found: 662.1944; elemental analysis: calcd
(%) for C42H30O8: C 76.12, H 4.56; found: C 76.10, H 4.61.
5a: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.13 (s, 36H, Si
ACTHNUGTRNEUGN(CH3)3), 3.80
(s, 12 CO2CH3), 7.39–7.49 (m, 6H, Ph), 7.57–7.64 (m, 4H, Ph), 8.06 ppm
(s, 4H, aromatic CH); 13C NMR (100 MHz, CDCl3, Me4Si): d=1.6, 52.4,
77.2, 127.7, 128.3, 128.4, 130.4, 135.8, 136.3, 138.8, 140.3, 143.5,
170.4 ppm; HRMS m/z (FAB) calcd for C54H54O10Si4Na: 1007.3474
[M+Na+]; found: 1007.3477.
6,13-Diphenyl-1,4,8,11-tetrakis(trimethylsilyl)pentacene-2,3,9,10-tetracar-
boxylic acid tetramethyl ester (6a): Diol 5a (99 mg, 0.1 mmol) was dis-
solved in degassed CH3CN (5 mL) and anhydrous SnCl2 (76 mg,
0.40 mmol) was then added. The mixture was stirred at room tempera-
ture under N2. After 2 h, the blue precipitate was collected by filtration,
and dissolved in degassed CH2Cl2, and filtered again to remove the inor-
ganic tin residue. The filtrate was concentrated in vacuo to yield the title
compound as a blue solid, which was further purified by re-precipitation
from dichloromethane and hexane (78 mg, 82% yield).
6,13-Dihydroxy-6,13-bis(phenylethynyl)-1,4,8,11-tetrakis(trimethylsilyl)-
6,13-dihydropentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester
(5c): To an oven dried 50 mL flask cooled under N2 was added phenyla-
cetylene (0.55 mL, 5.0 mmol), and dry THF (15 mL). EtMgBr (0.96m in
THF, 3.15 mL, 3.0 mmol) was added dropwise at 08C and the mixture
was stirred at 408C for 1 h. Pentacenequinone 1a (829 mg, 1.0 mmol) was
added and the mixture was refluxed for 6 h. The mixture was quenched
with aqueous saturated NH4Cl at 08C and extracted with ethyl acetate.
The combined organic phase was washed with water, saturated aqueous
NaHCO3 solution, and brine. The solution was dried over anhydrous
Na2SO4. The solvent was evaporated, and the resulting yellow viscous oil
was purified by flash chromatography (silica gel, hexane/ethyl acetate=
3:1 as eluent) afford the title compound as a yellow solid (352 mg, 68%
yield).
6a: M.p.:>3008C (dec); 1H NMR (400 MHz, CDCl3, Me4Si): d=0.17 (s,
36H, SiACHTUNGTRENNUNG(CH3)3), 3.84 (s, 12H, CO2CH3), 7.60–7.77 (m, 10H, Ph),
8.73 ppm (s, 4H, aromatic CH). 13C NMR (100 MHz, CDCl3, Me4Si): d=
1.4, 52.4, 128.1, 128.2, 128.9, 129.4, 131.5, 132.3, 135.6, 137.2, 138.8, 139.7,
170.5 ppm; HRMS m/z (ESI) calcd C54H62O8Si4: 950.3522 [M]+; found:
950.3516; elemental analysis: calcd (%) for C54H62O8Si4: C 68.17, H 6.57;
found: C 68.10, H 6.65.
5c: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.41 (s, 36H, Si
ACTHNUGTRNEUGN(CH3)3), 3.86
(s, 12H, CO2CH3), 7.43–7.49 (m, 6H, Ph), 7.69–7.72 (m, 4H, Ph),
9.22 ppm (s, 4H, aromatic CH); 13C NMR (100 MHz, CDCl3, Me4Si): d=
1.8, 52.6, 72.5, 87.6, 91.3, 121.5, 128.5, 129.3, 129.5, 132.1, 135.7, 136.5,
136.9, 139.3, 170.4 ppm; HRMS m/z (FAB) calcd for C58H64O10Si4Na:
1055.3474 [M+Na]+; found: 1055.3459.
6,13-Dihydroxy-6,13-bis(2-thienyl)-1,4,8,11-tetrakis(trimethylsilyl)-6,13-di-
hydropentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester (5b): The
title compound (45 mg) was prepared by the same way as described for
5a in 45% yield from 1a (83 mg, 0.10 mmol).
5b: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.51 (s, 36H, Si
C
6,13-Bis(phenylethynyl)-1,4,8,11-tetrakis(trimethylsilyl)pentacene-
(s, 12H, CO2CH3), 6.08 (dd, J=3.6 Hz, 1.8 Hz, 2H, thienyl), 6.46 (dd, J=
2,3,9,10-tetracarboxylic acid tetramethyl ester (6c): The title compound
1624
www.chemasianj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1620 – 1626

Synthesis of Pentacenequinone Derivatives and their Conversion into Pentacenes
(43 mg) was prepared as a dark green solid by the same way as described
1,4,8,11-Tetrabutyl-6,13-dihydroxy-6,13-bis(triisopropylsilylethynyl)-6,13-
for 6a in 86% yield from 5c (52 mg, 0.05 mmol).
6c: Dark green solid; m.p.:>3008C (dec); 1H NMR (400 MHz, CDCl3,
Me4Si): d=0.62 (s, 36H, SiACHTNUGTRNEUNG(CH3)3), 3.91 (s, 12H, CO2CH3), 7.47–7.55 (m,
6H, Ph), 7.82–7.86 (m, 4H, Ph), 9.81 ppm (s, 4H, aromatic CH);
13C NMR (100 MHz, CDCl3, Me4Si): d=2.1, 52.4, 87.5, 104.7, 118.5,
123.0, 128.7, 129.1, 129.6, 130.2, 131.8, 134.0, 136.7, 140.0, 170.3 ppm;
HRMS m/z (FAB) calcd for C58H63O8Si4: 999.3600 [M+H]+; found:
999.3580; elemental analysis: calcd (%) for C58H62O8Si4: C 69.70, H 6.25;
found: C 69.55, H 6.17.
dihydropentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester (9e):
The title compound (70 mg) was prepared by the same way as described
for 5c in 62% yield from 1b (76 mg, 0.1 mmol).
9e: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.94 (t, 3JH,H =7.2 Hz, 12H;
-CH2CH2CH2CH3), 1.05 (brs, 6H; -CH
ACHTUGNTRENUN(GN CH3)2), 1.06 (brs, 36H; -CH-
AHCTUNGTRENNUNG
3
-CH2CH2CH2CH3), 3.17 (t, JH,H =7.2 Hz, 8H; -CH2CH2CH2CH3), 3.43 (s,
2H; OH), 3.88 (s, 12H; CO2CH3), 8.96 ppm (s, 4H; aromatic CH);
13C NMR (100 MHz, CDCl3, Me4Si): d=11.2, 14.0, 18.6, 23.0, 29.6, 33.7,
52.4, 69.4, 90.3, 108.8, 124.0, 129.0, 132.5, 137.3, 137.4, 169.5 ppm; HRMS
m/z (FAB) calcd for C68H96O10Si2Na: 1151.6440 [M+Na]+; found:
1151.6455.
1,4,8,11-Tetrakis(trimethylsilyl)-6,13-dihydroxy-6,13-bis(3,3-dimethyl-but-
1-ynyl)-6,13-dihydropentacene-2,3,9,10-tetracarboxylic acid tetramethyl
ester (5d): The title compound (45 mg) was prepared by the same way as
described for 5c in 45% yield from 1a (83 mg, 0.10 mmol).
1,4,8,11-Tetrabutyl-6,13-bis(triisopropylsilylethynyl)pentacene-2,3,9,10-
tetracarboxylic acid tetramethyl ester (10e): The title compound (48 mg)
was prepared as a blue solid by the same way as described for 6a in 88%
yield from 9e (57 mg, 0.05 mmol).
5d: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.55 (s, 36H, Si
ACTHNUGTRNEUGN(CH3)3), 1.29
(s, 18H, tBu), 3.88 (s, 12H, CO2CH3), 9.02 ppm (s, 4H, aromatic CH);
13C NMR (100 MHz, CDCl3, Me4Si): d=2.1, 27.7, 30.9, 52.5, 69.1, 80.0,
98.0, 128.0, 136.3, 136.4, 136.6, 139.1, 170.4 ppm; HRMS m/z (FAB) calcd
for C54H72O10Si4Na: 1015.4100 [M+Na+]; found: 1015.4117.
1
10e: Blue solid; m.p.:>3008C (dec); H NMR (400 MHz, CDCl3, Me4Si):
d=0.90 (t, 3JH,H =7.2 Hz, 12H; -CH2CH2CH2CH3), 1.32 (brs, 6H; -CH-
A
ACHTUGNTRENUN(GN CH3)2), 1.38–1.50 (m, 8H;
1,4,8,11-tetrakis(trimethylsilyl)-6,13-bis(3,3-dimethyl-but-1-ynyl)penta-
cene-2,3,9,10-tetracarboxylic acid tetramethyl ester (6d): The title com-
pound (86 mg) was prepared as a purple–blue solid by the same way as
described for 6a in 90% yield from 5d (99 mg, 0.10 mmol).
6d: Purple–blue solid; m.p.:>3008C (dec); 1H NMR (400 MHz, CDCl3,
Me4Si): d=0.64 (s, 36H, SiACHTNUTRGNEG(UN CH3)3), 1.63 (s, 18H, tBu), 3.92 (s, 12H,
3
=
7.2 Hz, 8H; -CH2CH2CH2CH3), 3.94 (s, 12H; CO2CH3), 9.64 ppm (s, 4H;
aromatic CH); 13C NMR (100 MHz, CDCl3, Me4Si): d=11.7, 14.2, 19.0,
23.1, 29.7, 33.6, 52.4, 103.9, 108.6, 119.4, 125.5, 127.9, 130.9, 131.2, 138.1,
169.5 ppm; HRMS m/z (EI) calcd for C68H94O8Si2: 1094.6487 [M]+;
found: 1094.6504; elemental analysis: calcd (%) for C68H94O8Si2: C 74.54,
H 8.65; found: C 74.39, H 8.66.
CO2CH3), 9.64 ppm (s, 4H, aromatic CH); 13C NMR (100 MHz, CDCl3,
Me4Si): d=2.3, 29.3, 31.8, 52.5, 77.5, 113.7, 118.6, 129.5, 130.1, 133.5,
136.2, 139.9, 170.5 ppm; HRMS m/z (EI) calcd for C54H70O8Si4: 958.4148
[M]+; found: 958.4129; elemental analysis: calcd (%) for C54H70O8Si4:
C 67.60, H 7.35; found: C 67.41, H 7.34.
1,4,8,11-Tetrabutyl-6,13-dihydroxy-6,13-bis(trimethylsilylethynyl)-6,13-di-
hydropentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester (9 f): The
title compound (380 mg) was prepared by the same way as described for
5c in 79% yield from 1b (382 mg, 0.50 mmol).
1,4,8,11-Tetrabutyl-6,13-pentacenequinone-2,3,9,10-tetracarboxylic
acid
9 f: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.22 (s, 18H; Si
ACTHNUGTRNEUGN(CH3)3), 0.97
tetramethyl ester (1b): The title compound (528 mg) was prepared as a
yellow solid by the same way as described for 1a in 69% yield from 2b
(path B, 740 mg, 1.0 mmol).
(t, 3JH,H =7.2 Hz, 12H; -CH2CH2CH2CH3), 1.45–1.52 (m, 8H;
-CH2CH2CH2CH3), 1.70–1.80 (m, 8H; -CH2CH2CH2CH3), 3.06–3.16 (m,
8H; -CH2CH2CH2CH3), 3.82 (s, 12H; CO2CH3), 8.92 ppm (s, 4H; aro-
matic CH); 13C NMR (100 MHz, CDCl3, Me4Si): d=0.3, 14.0, 23.1, 29.8,
33.6, 52.4, 69.5, 94.0, 106.2, 123.8, 129.1, 132.4, 137.2, 137.3, 169.4 ppm;
HRMS m/z (EI) calcd for C56H72O10Si2: 960.4664 [M]+; found: 960.4675.
1b: Yellow solid; m.p.:>3008C; 1H NMR (300 MHz, CDCl3, Me4Si): d=
1.03 (t, 3JH,H =7.2 Hz, 12H, -CH2CH2CH2CH3), 1.50–1.62 (m, 8H,
-CH2CH2CH2CH3), 1.73–1.85 (m, 8H, -CH2CH2CH2CH3), 3.21–3.26 (m,
8H, -CH2CH2CH2CH3), 3.96 (s, 12H, CO2CH3), 9.22 ppm (s, 4H, aromat-
ic CH);. 13C NMR (100 MHz, CDCl3, Me4Si): d=13.9, 23.1, 30.1, 34.0,
52.7, 127.3, 130.9, 131.6, 134.9, 139.3, 168.7, 182.4 ppm; HRMS m/z (EI)
calcd for C46H52O10: 764.3560 [M]+; found: 764.3568; elemental analysis:
calcd (%) for C46H52O10: C 72.23, H 6.85; found: C 72.03, H 6.85.
1,4,8,11-Tetrabutyl-6,13-bis(trimethylsilylethynyl)pentacene-2,3,9,10-tetra-
carboxylic acid tetramethyl ester (10 f): The title compound (41 mg) was
prepared as a blue solid by the same way as described for 6a in 90%
yield from 9 f (48 mg, 0.05 mmol).
10 f: Blue solid; m.p.: 208–2108C (dec); 1H NMR (400 MHz, CDCl3,
1,4,8,11-Tetrabutyl-6,13-dihydroxy-6,13-bis(3,3-dimethyl-but-1-ynyl)-6,13-
dihydropentacene-2,3,9,10-tetracarboxylic acid tetramethyl ester (9d):
The title compound (67 mg) was prepared by the same way as described
for 5c in 72% yield from 1b (76 mg, 0.10 mmol).
9d: 1H NMR (400 MHz, CDCl3, Me4Si): d=0.97 (t, 3JH,H =7.2 Hz, 12H;
-CH2CH2CH2CH3), 1.29 (s, 18H; t-Bu), 1.46–1.52 (m, 8H;
-CH2CH2CH2CH3), 1.70–1.80 (m, 8H; -CH2CH2CH2CH3), 3.07–3.19 (m,
8H; -CH2CH2CH2CH3), 3.83 (s, 2H; CO2CH3), 8.89 ppm (s, 4H; aromatic
CH); 13C NMR (100 MHz, CDCl3, Me4Si): d=13.9, 23.1, 27.7, 29.9, 30.7,
33.6, 52.4, 69.2, 80.6, 98.1, 123.5, 128.9, 132.3, 137.3, 138.0, 169.4 ppm;
HRMS m/z (FAB) calcd for C58H72O10Na: 951.5023 ([M+Na]+); found:
951.5009.
Me4Si): d=0.52 (s, 18H; SiACHTNUGRTNEUNG
(CH3)3), 1.02 (t, 3JH,H =7.2 Hz, 12H;
-CH2CH2CH2CH3), 1.57–1.64 (m, 8H; -CH2CH2CH2CH3), 1.88–1.93 (m,
8H; -CH2CH2CH2CH3), 3.32–3.35 (m, 8H; -CH2CH2CH2CH3), 3.95 (s,
12H; CO2CH3), 9.58 ppm (s, 4H; aromatic CH); 13C NMR (100 MHz,
CDCl3, Me4Si): d=0.2, 14.1, 23.5, 30.3, 33.5, 52.4, 102.0, 111.6, 119.2,
125.5, 127.8, 130.86, 130.92, 138.2, 169.4 ppm; HRMS m/z (FAB) calcd
for C56H70O8Si2: 926.4609 [M]+; found: 926.4619; elemental analysis:
calcd (%) for C56H70O8Si2: C 72.53, H 7.61; found: C 72.78, H 7.62.
1,4,8,11-Tetrabutyl-6,13-bis(3,3-dimethyl-but-1-ynyl)pentacene-2,3,9,10-
tetracarboxylic acid tetramethyl ester (10d): The title compound (33 mg)
was prepared as a blue solid by the same way as described for 6a in 93%
yield from 9d (46 mg, 0.05 mmol).
[1] a) D. J. Gundlach, Y.-Y. Lin, T. N. Jackson, S. F. Nelson, D. G.
Schlom, IEEE Electron Device Lett. 1997, 18, 87; b) Y.-Y. Lin, D. J.
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IEEE Trans. Electron Devices 1997, 44, 1325; d) S. F. Nelson, Y.-Y.
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[2] For the first report on substituted soluble pentacene preparation
after the report of pentaceneꢁs high performance, see a) T. Takahashi,
M. Kitamura, B. Shen, K. Nakajima, J. Am. Chem. Soc. 2000, 122,
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10d: Blue solid; m.p.: 220–2218C (dec); 1H NMR (400 MHz, C6D6,
Me4Si): d=1.02 (t, 3JH,H =7.2 Hz, 12H; -CH2CH2CH2CH3), 1.55 (s, 18H;
t-Bu), 1.65–1.72 (m, 8H; -CH2CH2CH2CH3), 2.07–2.12 (m, 8H;
3
-CH2CH2CH2CH3), 3.50 (t, JH,H =7.2 Hz, 8H; -CH2CH2CH2CH3), 3.66 (s,
12H; CO2CH3), 9.76 ppm (s, 4H; aromatic CH); 13C NMR (100 MHz,
CDCl3, Me4Si): d=14.1, 23.5, 29.2, 30.4, 31.3, 33.5, 52.3, 114.6, 119.1,
125.4 (2C), 127.4, 130.5, 130.6, 138.2, 169.4 ppm; HRMS m/z (EI) calcd
for C59H74O8: 910.5384 [M]+; found: 910.5388; elemental analysis: calcd
(%) for C59H74O8: C 77.77, H 8.19; found: C 77.76, H 8.16.
Chem. Asian J. 2010, 5, 1620 – 1626
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1625

T. Takahashi et al.
FULL PAPERS
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Received: December 25, 2009
Published online: May 7, 2010
1626
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ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 1620 – 1626