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K. Ono et al. / Tetrahedron 63 (2007) 9699–9704
and 4 is of interest as an ecological technology for the fabri-
cation of solution-processed OFETs.
7.97 (dd, J¼6.2, 3.2 Hz, 2.52H), 8.20 (s, 1.48H), 8.54 (s,
2.52H).Dataforthemajorproductareasfollows:Orangecrys-
tals. Decomp. >190 ꢂC. IR (KBr): 3513, 3436, 3057, 1231,
1092, 988, 955, 828, 748, 698 cmꢁ1 1H NMR (CDCl3,
.
3. Conclusions
300 MHz): d 3.10 (s, 2H), 5.76 (dd, J¼3.7, 0.9 Hz, 2H), 6.21
(dd, J¼5.0, 3.7 Hz, 2H), 6.84 (dd, J¼5.0, 0.9 Hz, 2H), 7.59
(dd, J¼6.2, 3.3 Hz, 4H), 7.90 (dd, J¼6.2, 3.3 Hz, 4H), 8.40
(s, 4H). 13C NMR (acetone-d6, 50 MHz): d 73.2, 125.5,
126.1, 126.5, 127.1, 127.4, 128.9, 133.8, 140.8, 151.8.
MS m/z (%): 458 (100) [M+ꢁH2O]. Anal. Calcd for
C30H20O2S2: C, 75.60; H, 4.23. Found: C, 75.45; H, 4.22.
We synthesized pentacene derivatives substituted by aro-
matic groups at the 6,13-positions (1b–d). The absorption
bands based on the pentacene moieties were observed in
a similar wavelength region. The electron-donating ability
and the electron affinity depended on the aromatic groups.
Although these compounds were more stable in solution
than pentacene 1a, compounds 1b and 1c were highly reac-
tive with oxygen under irradiation and afforded their endo-
peroxides. Pentacene 1d was relatively stable in solution.
The thermolysis and photolysis of endoperoxide 4 in
solution afforded pentacene 1b with yields of 30 and 44%,
respectively. UV irradiation of the thin film of endoperoxide
4 indicated the reproduction of pentacene 1b. These deoxy-
genation reactions are of interest for the film formation tech-
nology, which is of use in OFETs because pentacene 1b was
reported as a good semiconductor in the thin films formed by
vacuum deposition. Further investigation on the photolysis
of endoperoxide 4 in film is under progress.
Similar reaction conditions were applied to the synthesis of
compounds 3c6,15 and 3d. These compounds were obtained
as a single isomer.
Compound 3c: Yield 50%. Decomp. >244 ꢂC. IR (KBr):
1
3526, 3434, 3056, 1493, 1096, 868, 694 cmꢁ1. H NMR
(CDCl3, 300 MHz): d 3.04 (s, 2H), 6.72–6.89 (m, 10H),
7.56 (dd, J¼6.3, 3.2 Hz, 4H), 7.94 (dd, J¼6.3, 3.2 Hz,
4H), 8.40 (s, 4H). MS m/z (%): 464 (6) [M+], 446 (42),
430 (45), 341 (100). Anal. Calcd for C34H24O2: C, 87.90;
H, 5.21. Found: C, 87.89; H, 5.21.
Compound 3d: Yield 48%. Decomp. >200 ꢂC. IR (KBr):
3301, 1526, 1487, 993, 951 cmꢁ1 1H NMR (CDCl3,
.
4. Experimental
4.1. General
300 MHz): d 3.55 (s, 2H), 7.52 (dd, J¼6.2, 3.3 Hz, 4H),
7.73 (s, 4H), 7.78 (dd, J¼6.2, 3.3 Hz, 4H). MS m/z (%):
644 (31) [M+], 627 (30), 610 (100), 460 (37), 309 (31).
Anal. Calcd for C34H14F10O2: C, 63.37; H, 2.19. Found: C,
63.60; H, 2.23.
Melting points were measured with a Yanaco micro melting
point apparatus and are uncorrected. IR and UV–vis absorp-
tion spectra were obtained with JASCO FT/IR-5300 and
Hitachi U-3500 spectrometers, respectively. Mass spectra
(EI) were determined with a Hitachi M-2000S mass spectro-
meter operating at 70 eV by a direct inlet system. Elemental
analyses were performed with a Perkin–Elmer 2400II ana-
4.1.2. Preparation of 6,13-diarylpentacene (1b–d).10
A
solution of compound 3b (a mixture of two isomers)
(0.60 g, 1.26 mmol), NaH2PO2$H2O (1.00 g, 9.43 mmol),
and NaI (1.00 g, 6.67 mmol) in acetic acid (7 mL) was re-
fluxed for 30 min. A deep blue solid was precipitated. After
cooling, the precipitate was filtered and washed with water
to give a deep blue solid (0.56 g), which was sublimed at
320 ꢂC under 10ꢁ3 Torr to afford pentacene 1b6,10 (0.26 g,
47%) as deep blue crystals. Mp >300 ꢂC. IR (KBr): 3048,
1
lyzer. H and 13C NMR spectra were recorded with Varian
GEMINI (300 and 50 MHz) and Bruker AVANCE600 (600
and 150 MHz) spectrometers with tetramethylsilane as an
internal standard.
1364, 1321, 1221, 874, 828, 735, 696 cmꢁ1 1H NMR
.
4.1.1. Preparation of 6,13-dihydroxy-6,13-diarylpentacene
(3b–d).10 nBuLi in hexane (1.60 M, 2.43 mL, 3.89 mmol)
was added dropwise to a solution of 2-bromothiophene
(0.38 mL, 3.89 mmol) in dry THF (15 mL) at ꢁ78 ꢂC under
nitrogen. The solution was stirred for 30 min. After addition
of 6,13-pentacenedione (0.40 g, 1.30 mmol), the reaction
mixture was stirred at ꢁ78 ꢂC for 1 h and at room temperature
for 2 h. The mixture was poured into water (20 mL) and ethyl
acetate (40 mL) was added. The organic layer was separated
and the aqueous layer was extracted with ethyl acetate
(40 mLꢀ2). The combined organic solutions were washed
with water and dried over Na2SO4. After removal of the sol-
vent, the residue was chromatographed on silica gel (hexane/
CH2Cl2¼4:6/2:8) to afford compound 3b6,10 (0.49 g, 80%)
as a mixture of two isomers (1.7:1). 1H NMR (CDCl3,
300 MHz): d 2.93 (s, 0.74H), 3.11 (s, 1.26H), 5.85 (dd,
J¼3.7, 1.0 Hz, 1.26H), 6.26 (dd, J¼5.1, 3.7 Hz, 1.26H),
6.78 (dd, J¼3.6, 1.2 Hz, 0.74H), 6.89 (dd, J¼5.1, 1.0 Hz,
1.26H), 6.97 (dd, J¼5.1, 3.6 Hz, 0.74H), 7.34 (dd, J¼5.1,
1.2 Hz, 0.74H), 7.51 (dd, J¼6.2, 3.3 Hz, 1.48H), 7.59 (dd,
J¼6.2, 3.2 Hz, 2.52H), 7.87 (dd, J¼6.2, 3.3 Hz, 1.48H),
(CDCl3, 600 MHz): d 7.28 (dd, J¼6.7, 3.1 Hz, 4H), 7.40
(dd, J¼3.3, 1.1 Hz, 2H), 7.46 (dd, J¼5.3, 3.3 Hz, 2H),
7.77 (dd, J¼5.3, 1.1 Hz, 2H), 7.80 (dd, J¼6.7, 3.1 Hz,
4H), 8.50 (s, 4H). 13C NMR (CDCl3, 150 MHz): d 125.4,
125.5, 127.2, 127.4, 128.6, 130.0, 130.0, 130.1, 131.4,
139.5. MS m/z (%): 442 (100) [M+]. Anal. Calcd for
C30H18S2: C, 81.41; H, 4.10. Found: C, 81.41; H, 3.93.
Similar reaction conditions were applied to the synthesis of
pentacenes 1c6,15 and 1d.
Compound 1c: Yield 73%. Deep violet crystals. Mp 292–
293 ꢂC. IR (KBr): 3056, 1441, 1383, 1101, 1026, 878,
750 cmꢁ1. MS m/z (%): 430 (100) [M+]. Anal. Calcd for
C34H22: C, 94.85; H, 5.15. Found: C, 94.79; H, 5.00.
Compound 1d: Yield 69%. Deep violet crystals. Mp
>300 ꢂC. IR (KBr): 1495, 1364, 1098, 990, 781, 735 cmꢁ1
.
1H NMR (CDCl3, 600 MHz): d 7.37 (dd, J¼6.7, 3.0 Hz,
4H), 7.85 (dd, J¼6.7, 3.0 Hz, 4H), 8.22 (s, 4H). 13C NMR
(CDCl3, 150 MHz): d 112.7 (t, J¼20.2 Hz), 122.6, 123.9,