Synthesis, optical properties, and crystal structure of 1,4-dipropyltetracene

Article abstract of DOI:10.1002/ejoc.201000112

We synthesized 1,4-dipropyltetracene on a 200-mg scale, the key step of which involved a Diels-Alder reaction between alkyl-substituted o-quinodimethane, generated in situ, and 1,4-naphthoquinone. The product was obtained as an orange solid, which was soluble in organic solvents including hexane. The optical properties of the product in solution showed no marked differences from those of other 1,4,7,10-tetraalkyltetracenes. Solid-state absorption and fluorescence spectra exhibited 20-30 nm blueshifts compared with those of 1,4,7,10-tetrapropyltetracene. X-ray analysis revealed that two propyl groups were coplanar with the tetracene ring, that there was no π overlap along the stacking direction, and that the molecules formed a herringbone structure. The peripheral alkyl chains were found to be important for controlling the molecular packing and optical properties in the solid state.

Full text of DOI:10.1002/ejoc.201000112

FULL PAPER
DOI: 10.1002/ejoc.201000112
Synthesis, Optical Properties, and Crystal Structure of 1,4-Dipropyltetracene
Chitoshi Kitamura,*[a] Chika Matsumoto,[a] Akio Yoneda,[a] Takashi Kobayashi,[b]
Hiroyoshi Naito,[b] and Toshiki Komatsu[c]
Keywords: Polycycles / Arenes / Cycloaddition / Structure elucidation / Optical properties
We synthesized 1,4-dipropyltetracene on a 200-mg scale, the
key step of which involved a Diels–Alder reaction between
alkyl-substituted o-quinodimethane, generated in situ, and
1,4-naphthoquinone. The product was obtained as an orange
exhibited 20–30 nm blueshifts compared with those of
1,4,7,10-tetrapropyltetracene. X-ray analysis revealed that
two propyl groups were coplanar with the tetracene ring,
that there was no π overlap along the stacking direction, and
solid, which was soluble in organic solvents including hex- that the molecules formed a herringbone structure. The pe-
ane. The optical properties of the product in solution showed ripheral alkyl chains were found to be important for con-
no marked differences from those of other 1,4,7,10-tetraalk- trolling the molecular packing and optical properties in the
yltetracenes. Solid-state absorption and fluorescence spectra
solid state.
tween the alkyl side chain and the solid-state optical prop-
erties. We believed that a reduction in the number of side
alkyl chains, which creates a low-symmetry structure, would
improve the solubility of the tetracene molecules and pro-
duce new molecular arrangements in the solid state.[5] We
believed the latter effect would bring about new solid-state
physical properties. We planned to synthesize tetracenes 2
having two alkyl side chains at the 1- and 4-positions (Fig-
ure 1). We expected that a propyl group would be the short-
est side-chain length that would achieve good solubility in
organic solvents. Here, we report on the synthesis, solid-
state optical properties, and crystal structure of 1,4-diprop-
yltetracene (2a).
Introduction
Recently, oligoacenes, especially tetracene and pentacene,
have attracted considerable interest for their excellent elec-
tronic performances as organic semiconductors in organic
field-effect transistors, organic light-emitting diodes, and
organic photovoltaic cells.[1] However, tetracene and pent-
acene are hardly soluble in organic solvents, which limits
their practical application. Therefore, to achieve low-cost
solution processability with high performance, soluble func-
tionalized oligoacenes have been prepared.[2,3]
Very recently, we developed a new method for the prepa-
ration of a series of 1,4,7,10-tetraalkyltetracenes 1 (alkyl =
methyl to hexyl) by using 2,5-dialkylfurans and 2,6-naptho-
diyne precursor.[4] The tetrasubstituted tetracenes had
unique side-chain conformations and molecular arrange-
ments in the solid state, which were found to give rise to a
wide range of interesting solid-state optical properties. One
of the most striking observations was that the isolated sol-
ids showed colors varying from yellow to red, which were
dependent upon the alkyl side-chain length. We recognized
that the alkyl side chain had the ability not only to increase
solubility in organic solvents but also to control both the
crystal packing and the solid-state physical properties.
These results prompted us to explore further synthesis of
alkyl-substituted tetracenes to clarify the relationship be-
Figure 1. Chemical structures of alkyl-substituted tetracenes.
Results and Discussion
Synthesis
We developed a convenient and efficient synthetic
method for 1,4-dialkyltetracenes (Scheme 1). McOmie[6a]
and Kametani[6b] reported that 5,12-tetracenequinone was
easily obtained by treatment of 1,2-bis(bromomethyl)ben-
zene with 1,4-napthoquinone in the presence of NaI in
DMF, which generated o-quinodimethane in situ and then
underwent a Diels–Alder reaction. We believed that alkyl-
substituted 1,2-bis(bromomethyl)benzene was a key inter-
[a] Department of Materials Science and Chemistry, University of
Hyogo,
2167 Shosha, Himeji, Hyogo 671-2280, Japan
Fax: +81-79-267-4888
E-mail: kitamura@eng.u-hyogo.ac.jp
[b] Department of Physics and Electronics, Osaka Prefecture Uni-
versity,
1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
[c] Goi Research Center, Chisso Petrochemical Corporation,
5-1 Goikaigan, Ichihara, Chiba 290-8551, Japan
Eur. J. Org. Chem. 2010, 2571–2575
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2571

C. Kitamura et al.
FULL PAPER
mediate, as tetracene can be easily transformed from Absorption and Fluorescence Spectra
tetracene quinone. 1,2-Bis(bromomethyl)-3,6-dimethylbenzene
UV/Vis absorption and fluorescence spectra for 2a, both
in hexane and in the solid state, are shown in Figure 2. In
solution, both absorption and fluorescence spectra exhib-
ited vibrational structures (Figure 2a). Absorption peaks
based on 0–0, 0–1, and 0–2 transitions were observed at
477, 447, and 421 nm, respectively. The corresponding fluo-
rescence peaks were observed at 488, 516, and 552 nm,
respectively, and exhibited a small Stokes shift of 11 nm
with a fluorescence quantum yield (ΦF) of 0.09. These
wavelengths and quantum yield were similar to those for
1,4,7,10-tetraalkyltetracenes 1. Furthermore, there was no
marked difference in the spectral shape between 2a and
other tetraalkyltetracenes 1. These facts suggest not only
that molecules in dilute solution exist in a practically mono-
dispersed state, but also that the presence of two alkyl
groups at the 1- and 4-positions hardly affects the electronic
structure of tetracene ring.
was prepared in four steps from a Diels–Alder reaction be-
tween 2,5-dimethylfuran and maleic anhydride by Brick-
wood et al.,[7] and we adopted the same protocol with the
use of 2,5-dipropylfuran (3) in place of 2,5-dimethylfuran.
Scheme 1. Reagents and conditions: (a) Et2O, room temp., 3 h,
76%; (b) conc. H2SO4, –10 to 0 °C, 30 min, 65%; (c) LiAlH4, THF,
reflux, 62 h, 84%; (d) PBr3, Et2O, room temp., 15 h, 75%; (e) 1,4-
naphthoquinone, NaI, DMF, 110 °C, 19.5 h, 55%; (f) NaBH4,
MeOH/THF, room temp., 1 h; then 57% HI, THF, reflux, 3 h,
66%.
A Diels–Alder reaction between maleic anhydride and
furan 3 produced corresponding adduct 4 in 76% yield. Be-
cause adduct 4 was apt to decompose into maleic anhydride
and 3 upon standing at room temperature for several hours
or when dissolved in organic solvents, 4 was dehydrated in
cold, concentrated sulfuric acid to afford oily phthalic anhy-
dride 5 as soon as possible. Phthalic anhydride 5 was re-
duced with LiAlH4 in refluxing THF to phthalyl alcohol 6
in 84% yield after a long reaction time (more than 2 d);
otherwise, a mixture of phthalide and phthalyl alcohol 6
was obtained. Phthalyl alcohol 6 was treated with PBr3 to
provide dibromide 7 in 75% yield. Because we encountered
difficulties in the purification of 6 and 7 as a result of their
unstable nature, we performed the above reactions without
further purification. Subsequently, the generation of tran-
Figure 2. (a) UV/Vis absorption and fluorescence spectra of 2a in
hexane and (b) Kubelka–Munk and fluorescence spectra of 2a in
powder form.
In the solid state, the fluorescence spectrum showed one
sient o-quinodimethane upon iodide-induced debromina- intense emission band at 557 nm with ΦF = 0.23, although
tion of 7 in the presence of 1,4-napthoquinone provided the absorption (Kubelka–Munk) spectrum in a diluted KBr
stable tetracenequinone 8, which was easily soluble in or- pellet showed a vibrational structure with peaks at 432, 460,
ganic solvents, in 55% yield. Two consecutive procedures of and 491 nm (Figure 2b). The absorption edge was observed
hydride reduction of 8 with NaBH4 in MeOH/THF and at 560 nm. The difference in photophysical properties be-
treatment of the reduction product with 57% HI in re- tween the solution and solid state should be ascribed to the
fluxing THF gave tetracene 2a as an orange solid in 66% difference in the intermolecular interactions between the
yield. Compound 2a is readily soluble in common organic tetracene rings. Also, the solid-state color of 1,4,7,10-tet-
solvents such as THF, dichloromethane, toluene, and even rapropyltetracene (1a) was orange.[4] However, the absorp-
hexane. Tetracene 2a was readily prepared on a scale of tion edge for 1a was 580 nm, indicating a non-negligible
several hundred milligrams and purified by column difference in the solid-state optical properties of 2a and 1a.
chromatography on silica gel by using hexane as an eluent. Moreover, the fluorescence emission band for 2a in the so-
Although the solution was unstable in the presence of both lid state was observed at 557 nm with ΦF = 0.23, although
light and air, compound 2a showed high air stability in the that for 1a was observed at 588 nm with ΦF = 0.22. In other
solid state.
words, both absorption and fluorescence spectra of 2a in
2572
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 2571–2575

Synthesis, Optical Properties, and Crystal Structure of 1,4-Dipropyltetracene
the solid state exhibited blueshifts compared to those of was rather close to that in the solid state (λmax = 491 nm).
1a. We expected that these subtle differences in solid-state This seemingly peculiar result suggested that the prediction
photophysical properties were derived from different indi- of photophysical properties was very difficult at the present
vidual crystal structures.
theoretical level and that some corrections based on inter-
molecular interactions, such as exciton coupling, were re-
quired to estimate the solid-state photophysical properties
precisely.
Crystal Structure
Next, the stacking pattern of two neighboring molecules
along the 1D stacking direction in the crystal was examined
(Figure 3b). As in the case of 1,4,7,10-tetraalkyltetracenes
and 1,4-dipropylanthracene, there was no π overlap be-
tween the two molecules. The tetracene rings along the col-
umn direction slipped relative to each other along the long
molecular axis by 0.65 Å and along the short molecular axis
by 4.48 Å. The former geometrical parameter was within
the standard values for 1,4,7,10-tetraalkyltetracenes (0.10–
1.49 Å) and 1,4-dipropylanthracene (1.12 Å). However, the
latter parameter was larger than those for 1,4,7,10-tetraalk-
yltetracenes (1.32–3.76 Å) and 1,4-dipropylanthracene
(3.89 Å). In addition, the interplanar distance between the
adjacent tetracene planes was 3.27 Å, which was shorter
than the same distances for 1,4,7,10-tetraalkyltetracenes
(3.43–3.53 Å) and 1,4-dipropylanthracene (3.63 Å). Under
these circumstances, different intermolecular interactions
probably occurred between tetracene molecules.
When viewed down the long molecular axis, 2a had a
herringbone structure, in which the interplanar tilt angle
between tetracene rings in two adjacent columns was 72.4°
(Figure 3c). This molecular arrangement was dramatically
different from that of 1a, which adopted a slipped-parallel
pattern without π overlap. However, the molecular packing
of 2a was similar to that of 1,4-dipropylanthracene. The
difference in molecular packing arises from the nonexist-
ence of alkyl side chains at the 7- and 10-positions in 2a.
Thus, the presence of aromatic hydrogen atoms at the 7-
and 10-positions leads to an edge-to-face arrangement in
the crystal because of CH–π interactions, which have been
observed in numerous studies on aromatic hydrocarbons.
In the crystal of 2a, a relatively short nonbonded distance
between C(16) and H(8) atoms in the two adjacent columns
(2.76 Å) was observed (Figure 3d). We recognized that the
alkyl side chains in the solid state not only served as a
spacer but also adjusted the mutual positional relationship
of the tetracene rings. Therefore, we demonstrated that the
peripheral alkyl side chains on the tetracene ring played an
important role in the control of the molecular packing and
optical properties in the solid state.
The crystal structure of 2a was determined (Figure 3) to
observe the effect of the alkyl side chains on molecular
packing. In the crystals of 1,4,7,10-tetraalkyltetracenes,[4]
the following facts were observed: (1) The alkyl chains took
a zigzag (all-trans) conformation within their zigzag plane.
(2) The zigzag planes tended to be either coplanar with or
perpendicular to the tetracene ring because of the torsion
degrees of freedom in the alkyl chain. (3) Because of the
high symmetry of 2a, the alkyl conformations at the 1- and
7-positions (namely, a pair of diagonal components) were
the same, and also those at the 4- and 10-positions (another
pair of diagonal components) were the same. Moreover, for
the crystal of 1a, a pair of two propyl groups at the 1- and
7-positions took a coplanar conformation with the tetra-
cene ring whereas another pair of two propyl groups at the
4- and 10-positions took a perpendicular conformation. In
contrast, in the crystal of 2a, the two propyl groups at the
1- and 4-positions took a coplanar conformation with the
tetracene ring (Figure 3a), whose structural feature was
rather similar to that of 1,4-dipropylanthracene.[5]
Figure 3. Crystal structure of 2a: (a) molecular structure, showing
top view (upper) and side view (lower); (b) stacking pattern of two
neighboring molecules; (c) packing diagram; (d) edge-to-face inter-
action between nearest molecules in two adjacent columns.
Conclusions
In summary, we have developed an efficient method for
The time-dependent density functional theory (TD- the synthesis of 1,4-dipropyltetracene, which is readily solu-
DFT) calculations with the B3LYP/6-31G* method with ble in organic solvents, including hexane, from a Diels–
the use of the geometry obtained by X-ray analysis showed Alder reaction between maleic anhydride and dipropylfuran
a lowest-energy absorption band at the single molecular in seven steps. There was no significant difference in the
level at 496.5 nm for 2a, which was far from the longest optical properties of the product in solution compared to
absorption maximum in solution (λmax = 477 nm) and it the optical properties of 1,4,7,10-tetraalkyltetracenes. The
Eur. J. Org. Chem. 2010, 2571–2575
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2573

C. Kitamura et al.
FULL PAPER
was cooled to room temperature and then cooled with an ice bath.
To the ice-cooled mixture was cautiously added water (3 mL) and
10% H2SO4 (40 mL). The reaction mixture was extracted with
CHCl3. The combined organic layer was washed with brine and
dried with Na2SO4. After removal of the solvents and drying under
vacuum, 6 was obtained as a yellow oil (880 mg, 84%) and used in
the next reaction without further purification. 1H NMR (500 MHz,
CDCl3): δ = 0.98 (t, J = 7.1 Hz, 6 H, CH2CH2CH3), 1.58–1.62 (m,
4 H, CH2CH2CH3), 2.68 (t, J = 7.7 Hz, 4 H, CH2CH2CH3), 4.82
(s, 4 H, CH2OH), 7.11 (s, 2 H, Ar-H) ppm. 13C NMR (126 MHz,
CDCl3): δ = 13.95, 25.05, 35.40, 58.43, 129.44, 137.66, 139.39 ppm.
color of 1,4-dipropyltetracene was orange, which resembled
the 1,4,7,10-tetrapropyltetracenes. However, the solid-state
absorption and fluorescence of 1,4-dipropyltetracene exhib-
ited 20–30 nm blueshifts compared to those of 1,4,7,10-tet-
rapropyltetracene. X-ray analysis revealed that the molecu-
lar structure was planar, that there was no π overlap be-
tween the two neighboring molecules along the stacking di-
rection, and that the molecules adopted a herringbone
structure; these features were all directly ascribed to the so-
lid-state optical properties.
1,2-Bis(bromomethyl)-3,6-dipropylbenzene (7): To a solution of 6
(772 mg, 3.48 mmol) in Et2O (10 mL) was dropwise added a solu-
tion of PBr3 (0.7 mL, 7.45 mmol) in Et2O (10 mL) at room tem-
perature. The mixture was stirred at room temperature for an ad-
ditional 15 h. Then, the reaction mixture was poured into ice water,
neutralized with aqueous NaHCO3, and extracted with Et2O. The
organic layer was washed with brine and dried with Na2SO4. After
removal of the solvent and drying under vacuum, 7 was obtained as
a yellowish-white solid (990 mg, 75%) and used in the next reaction
Experimental Section
General: All reagents were commercially available and used without
further purification. Solvents for syntheses were purified by stan-
dard methods. Column chromatography was performed on Wako
silica gel C-300 (45–75 µm). Melting points were measured with a
Yanaco melting point apparatus. 1H and 13C spectra were measured
with a Bruker-Biospin DRX500 FT spectrometer. Elemental analy-
ses were performed with a Yanaco MT-5 CHN recorder. Absorp-
tion and fluorescence spectra in solution were recorded with a Hit-
achi U3500 spectrophotometer and Hitachi F2500 spectrophotom-
eter, respectively. Fluorescence yields (ΦF) in solution were deter-
mined with 9,10-diphenylanthracene (ΦF = 0.86)[8] in cyclohexane
as the standard. Kubelka–Munk spectra were measured by using a
Hitachi U3010 spectrophotometer with a Φ60 integrating sphere
attachment. Fluorescence spectra in the solid state were recorded
by using a Hamamatsu Photonics PMA11 calibrated optical multi-
channel analyzer (λex = 325 nm), and the measurement of the abso-
lute quantum yield (ΦF) was performed by using a Labsphere IS-
040-SF integrating sphere. TD-DFT calculations were carried out
by using the B3LYP/6-31G* method with the Gaussian 03 program
package.[9]
1
without further purification. M.p. 62–64 °C. H NMR (500 MHz,
CDCl3): δ = 1.02 (t, J = 7.0 Hz, 6 H, CH2CH2CH3), 1.66–1.70 (m,
4 H, CH2CH2CH3), 2.68 (t, J = 7.6 Hz, 4 H, CH2CH2CH3), 4.73
(s, 4 H, CH2Br), 7.11 (s, 2 H, Ar-H) ppm. 13C NMR (126 MHz,
CDCl3): δ = 14.20, 24.03, 27.30, 34.70, 130.18, 134.51, 140.34 ppm.
7,12-Dipropyl-5,12-tetracenequinone (8): A mixture of 7 (904 mg,
2.60 mmol), 1,4-naphthoquinone (616 mg, 3.90 mmol), and NaI
(1.95 g, 13.0 mmol) in DMF (8 mL) was stirred at 110 °C for
19.5 h. The reaction mixture was cooled to room temperature, then
poured into 5% Na2SO3, and extracted with CHCl3. The organic
layer was washed with brine and dried with Na2SO4. After removal
of the solvents, the residue was subjected to column chromatog-
raphy (CHCl3/hexane, 1:1) on silica gel to afford 8 as a yellow solid
(500 mg, 56%). M.p. 155–156 °C. 1H NMR (500 MHz, CDCl3):
δ = 1.07 (t, J = 7.2 Hz, 6 H, CH2CH2CH3), 1.81–1.85 (m, 4 H,
CH2CH2CH3), 3.17 (t, J = 7.7 Hz, 4 H, CH2CH2CH3), 7.45 (s, 2
H, 8-H, 9-H), 7.84 (dd, J = 3.2, 5.6 Hz, 2 H, 2-H, 3-H), 8.42 (dd,
J = 3.2, 5.6 Hz, 2 H, 1-H, 4-H), 9.09 (s, 2 H, 6-H, 11-H) ppm. 13C
NMR (126 MHz, CDCl3): δ = 14.20, 24.29, 35.00, 126.32, 127.43,
128.73, 129.33, 134.09, 134.49, 134.63, 139.74, 183.26 ppm.
C24H22O2 (342.43): calcd. C 84.18, H 6.48; found C 84.33, H 6.77.
Materials: The synthesis of 2,5-dipropylfuran (3) was previously
described.[10]
3,6-Dipropylphthalic Anhydride (5): A mixture of mortar-ground
maleic anhydride (5.21 g, 53.1 mmol) and furan
3 (8.09 g,
53.1 mmol) in Et2O (10 mL) was stirred at room temperature for
20 h. Hexane (60 mL) was added to the reaction mixture. A large
part of Diels–Alder adduct 4 (6.54 g) precipitated as a white solid.
The filtrate was evaporated under reduced pressure, and hexane
was added to the residue to give a small part of 4 (992 mg). The
combined crude product was obtained in a total yield of 57%. Be-
cause compound 4 was apt to decompose on standing at room
temperature, 4 was used in the next reaction as soon as possible. To
concentrated H2SO4 (50 mL) cooled to –10 °C was added 4 (5.74 g,
22.9 mmol) in small portions. The mixture was stirred at 0 °C for
30 min. The reaction mixture was poured onto crushed ice. The
resulting product was extracted with Et2O. The organic layer was
washed with brine and dried with Na2SO4. After removal of solvent
and drying under vacuum, 5 was obtained as an orange oil (2.28 g,
43%) and used in the next reaction without further purification.
1H NMR (500 MHz, CDCl3): δ = 0.99 (t, J = 7.4 Hz, 6 H,
CH2CH2CH3), 1.67–1.72 (m, 4 H, CH2CH2CH3), 3.04 (t, J =
7.2 Hz, 4 H, CH2CH2CH3), 7.54 (s, 2 H, Ar-H) ppm. 13C NMR
(126 MHz, CDCl3): δ = 13.51, 23.55, 32.65, 127.89, 136.90, 142.51,
162.82 ppm.
1,4-Dipropyltetracene (2a): To a solution of 8 (342 mg, 1.00 mmol)
in MeOH (20 mL) and THF (20 mL) was added NaBH4 (189 mg,
5.00 mmol) in small portions at room temperature. The mixture
was stirred at room temperature for an additional hour. After neu-
tralization with 10% AcOH, the reduction product was extracted
with CHCl3. The combined organic layer was washed with brine
and dried with Na2SO4. After removal of solvents, a white solid
was obtained. The solid was dissolved in THF (10 mL) and heated
to reflux. Under reflux conditions, 57% HI (10 mL) was added
dropwise, and then, the mixture was heated at reflux for 3.5 h. The
reaction mixture was cooled to room temperature, then poured into
5% Na2SO3, and extracted with Et2O. The organic layer was
washed with brine and dried with Na2SO4. After removal of the
solvents, the residue was subjected to column chromatography
(hexane) on silica gel to afford 2a as an orange solid (207 mg,
1
66%). M.p. 126–127 °C. H NMR (500 MHz, CDCl3): δ = 1.12 (t,
J = 7.3 Hz, 6 H, CH2CH2CH3), 1.89–1.93 (m, 4 H, CH2CH2CH3),
3.18 (t, J = 7.7 Hz, 4 H, CH2CH2CH3), 7.17 (s, 2 H, 2-H, 3-H),
7.54 (dd, J = 3.2, 6.6 Hz, 2 H, 8-H, 9-H), 8.01 (dd, J = 3.2, 6.6 Hz,
2 H, 7-H, 10-H), 8.69 (s, 2 H, 6-H, 11-H), 8.84 (s, 2 H, 5-H, 12-H)
ppm. 13C NMR (126 MHz, CDCl3): δ = 14.47, 23.38, 35.47, 123.22,
1,2-Bis(hydroxymethyl)-3,6-dipropylbenzene (6): To a suspension of
LiAlH4 (1.44 g, 37.9 mmol) in THF (30 mL) was dropwise added
a solution of 5 (1.10 g, 4.74 mmol) in THF (35 mL) at room tem-
perature. The mixture was heated at reflux for 62 h. The mixture
2574
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 2571–2575

Synthesis, Optical Properties, and Crystal Structure of 1,4-Dipropyltetracene
Bakus I, Chem. Commun. 2007, 4746–4748; e) Q. Miao, X. Chi,
S. Xiao, R. Zeis, M. L. Lefenfeld, T. Siegrist, M. L. Steiger-
wald, C. Nuckolls, J. Am. Chem. Soc. 2006, 128, 1340–1345; f)
T. Takahashi, S. Li, W. Huang, F. Kong, K. Nakajima, B. Shen,
T. Ohe, K. Kanno, J. Org. Chem. 2006, 71, 7967–7977; g) K.
Kobayashi, R. Shimaoka, M. Kawahata, M. Yamanaka, K.
Yamaguchi, Org. Lett. 2006, 8, 2385–2388; h) J. Jiang, B. R.
Kaafarani, D. C. Neckers, J. Org. Chem. 2006, 71, 2155–2158;
i) M. A. Wolak, B.-B. Jang, L. C. Palilis, Z. H. Kafafi, J. Phys.
Chem. B 2004, 108, 5492–5499.
124.24, 124.98, 126.38, 128.29, 129.64, 131.02, 131.46, 136.58 ppm.
C24H24 (312.45): calcd. C 92.26, H 7.74; found C 92.46, H 7.96.
X-ray Crystallography: X-ray diffraction data were collected with a
Rigaku/Mercury CCD area detector diffractometer with graphite-
monochromated Mo-Kα (α = 0.71070 Å) radiation, φ and ω scans
to a maximum 2θ value of 55.0° at 223 K. The structures were
solved by direct methods by using SIR92.[11] All non-hydrogen
atoms were refined anisotropically by full-matrix least-squares on
F2 by using SHELXL97.[12] Hydrogen atoms were positioned geo-
[4] C. Kitamura, Y. Abe, T. Ohara, A. Yoneda, T. Kawase, T. Ko-
bayashi, H. Naito, T. Komatsu, Chem. Eur. J. 2010, 16, 890–
898.
[5] C. Kitamura, C. Matsumoto, A. Yoneda, T. Kobayashi, H.
Naito, Bull. Chem. Soc. Jpn. 2008, 81, 754–756.
[6] a) J. F. W. McOmie, D. H. Perry, Synthesis 1973, 416–417; b)
T. Kametani, T. Takahashi, M. Kajiwara, Y. Hirai, C. Ohtsuka,
F. Satoh, K. Fukumoto, Chem. Pharm. Bull. 1974, 22, 2159–
2163.
metrically and refined by using a riding model. All calculations
were performed by using the teXsan program package.[13] Crystal-
lographic data for 2a: 0.50ϫ0.05ϫ0.02 mm, C24H24, M = 312.45,
monoclinic, space group P21/n, a = 17.69(1) Å, b = 5.538(3) Å, c =
17.87(1) Å, β = 103.220(3)°, V = 1704.3(16) Å3, Z = 4, Dcalcd.
=
1.218 gcm–3, µ = 0.068 mm–1, 5706 reflections measured, 2532
unique, GOF = 0.94, R = 0.065 [IϾ2σ(I)], wR = 0.188 (all data).
CCDC-761527 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[7] D. J. Brickwood, W. D. Ollis, J. S. Stephannatou, J. F. Stoddart,
J. Chem. Soc. Perkin Trans. 1 1978, 1398–1414.
[8] J. V. Morris, M. A. Mahaney, J. R. Huber, J. Phys. Chem. 1976,
80, 969–974.
[9] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pom-
elli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P.
Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D.
Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui,
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Revision C.02,
Gaussian, Inc., Wallingford, CT, 2004.
Acknowledgments
This work was supported by a Grant-in-Aid from the Ministry of
Education, Culture, Sports, Science and Technology, Japan (No.
20550128). We also thank the Instrument Center of the Institute
for Molecular Science for X-ray structural analysis.
[1] a) M. Bendikov, F. Wudl, D. F. Perepichka, Chem. Rev. 2004,
104, 4891–4945; b) J. E. Anthony, Angew. Chem. Int. Ed. 2008,
47, 452–483.
[2] a) Shimon, G. Leitus, M. Bendikov, Chem. Eur. J. 2008, 14,
10639–10647; b) Z. Chen, P. Müller, T. M. Swager, Org. Lett.
2006, 8, 273–276; c) R. Schmidt, S. Göttling, D. Leusser, D.
Stalke, A.-M. Krause, F. Würthner, J. Mater. Chem. 2006, 16,
3708–3714; d) J. Reichwagen, H. Hopf, A. Del Guerzo, J.-P.
Desvergne, H. Bouas-Laurent, Org. Lett. 2005, 7, 971–974; e)
J. A. Merio, C. R. Newman, C. P. Gerlach, T. W. Kelley, D. V. [10] C. Kitamura, Y. Abe, N. Kawatsuki, A. Yoneda, K. Asada, T.
Muyres, S. E. Fritz, M. F. Toney, C. D. Frisbie, J. Am. Chem.
Soc. 2005, 127, 3997–4009; f) S. A. Odom, S. R. Parkin, J. E.
Anthony, Org. Lett. 2003, 5, 4245–4248.
Kobayashi, H. Naito, Mol. Cryst. Liq. Cryst. 2007, 474, 119–
135.
[11] A. Altomare, M. C. Burla, M. Camalli, M. Cascarano, C. Gia-
covazzo, A. Guagriardi, G. Polidor, J. Appl. Crystallogr. 1994,
27, 435.
[12] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[13] teXsan: Crystal Structure Analysis Package, Molecular Struc-
ture Corporation 1985 and 1999.
[3] a) I. Kaur, W. Jia, R. P. Kopreski, S. Selvarasah, M. R.
Dkmeci, C. Pramanik, N. E. McGruer, G. P. Miller, J. Am.
Chem. Soc. 2008, 130, 16274–16286; b) D. Lehnherr, R. Mc-
Donald, R. R. Tykwinski, Org. Lett. 2008, 10, 4163–4166; c)
Y.-M. Wang, N.-Y. Fu, S.-H. Chan, H.-K. Lee, H. N. C. Wong,
Tetrahedron 2007, 63, 8586–8597; d) J. E. Anthony, J. Gi-
ershner, C. A. Landis, S. R. Parkin, J. B. Sherman, R. C.
Received: January 27, 2010
Published Online: March 23, 2010
Eur. J. Org. Chem. 2010, 2571–2575
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2575