Synthesis and properties of N-arylcarbazolophane-paracyclophane combined with carbazoles

Article abstract of DOI:10.1055/s-2004-834859

The intramolecular etherification of precursor tetrol 7 afforded N-arylcarbazolophane 5 as a single isomer. Carbazolophane 5 is considered to be a paracyclophane combined with a carbazole, and possesses excimer-like fluorescence properties with λ_max<

Full text of DOI:10.1055/s-2004-834859

SPECIAL TOPIC
2743
Synthesis and Properties of N-Arylcarbazolophane–Paracyclophane
Combined with Carbazoles
S
Y
ynthesis and Prop
o
erties of
N
-A
s
r
ylcarbaz
u
olophane–Pa
k
racyclopha
n
e
e
C
ombine
d
with
N
Carbazole
s
akamura, Takuzo Yamazaki, Yasuhiko Kakinoya, Hideyuki Shimizu, Jun Nishimura*
Department of Nano-Material Systems, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
Fax +81(277)301314; E-mail: nisimura@chem.gunma-u.ac.jp
Received 12 July 2004
Abstract: The intramolecular etherification of precursor tetrol 7 af-
forded N-arylcarbazolophane 5 as a single isomer. Carbazolophane
2
1
3
4
5
is considered to be a paracyclophane combined with a carbazole,
and possesses excimer-like fluorescence properties with lmax = 423
nm.
2 n N
(CH )
N
(CH2)n
N
8
N
N
N
(
CH2)n
5
Key words: paracyclophane, carbazole, fluorescence, excimer
6
7
syn isomer
anti isomer
Carbazole is the constituent of poly(N-vinylcarbazole)
1
1
a (n = 4)
b (n = 5)
2a (n = 4)
2b (n = 5)
3a (n = 4)
3b (n = 5)
which is well-known as a photoconductor, and the photo-
1
physical properties of its dimer model compounds and
Figure 1 Carbazolophanes prepared.
2
polymers have been extensively investigated. A cyclo-
phane composed of carbazoles, namely carbazolophane,
in which the relative arrangement of two carbazole chro- isomers based on the configuration of cyclobutane rings
mophores is fixed more rigidly, is desirable for the eluci- and their separation was extremely difficult.
dation of the relationship between the chromophore
Introduction of aromatic rings at the N-position of the car-
arrangement and fluorescence properties. Di-
oxa[3.3](3,6)carbazolophane, the first carbazolophane to
be synthesized by Tani et al., was found to adopt an anti-
conformation, leading to small overlap between the carba-
bazole is expected to extend the carbazole-based p-conju-
gated system, leading to a red shift in both absorption and
fluorescence spectra. Thus, we were stimulated to prepare
novel triply-bridged N-arylcarbazolophane 4 by incorpo-
rating benzene rings into 3. This carbazolophane 4 is also
regarded as a kind of paracyclophane that incorporates
zole rings and therefore, the absence of excimer fluores-
3
cence.
We have synthesized cyclobutane-fused [2.n]cyclophanes carbazole chromophores. Since it was likely that 4 would
that contain various aromatic hydrocarbons by the in- be obtained as a troublesome isomer mixture similar to 3,
tramolecular [2+2] photocycloadditions of bis(vinylar- the synthesis of 5 was also undertaken, in which cyclobu-
4
yl)alkanes. This synthetic method is usually suitable for tane rings were replaced by -CH OCH - units. The latter
2
2
the preparation of syn-isomers; in some cases, syn-iso- bridging units were expected to rule out the formation of
mers are exclusively obtained. By using this method, stereoisomers.
[
2.n](3,9)carbazolophanes 1 and 2 (n = 4, 5) were success-
The synthetic sequence leading to tetravinyl compound 6
and tetrol 7, the precursors of 4 and 5, respectively, is il-
lustrated in Scheme 1. The palladium-catalyzed coupling
fully prepared from the corresponding vinyl compounds
5
(Figure 1). These carbazolophanes displayed fluores-
cence spectra different from one another, depending on
their structures: for instance, 1a produced broad emission
assigned as sandwich excimer fluorescence, whereas 2a
gave monomer fluorescence with vibrational structures.
Recently, we have succeeded in the preparation of triple-
bridged [2.2.n](3,6,9)carbazolophanes 3 (n = 4, 5) by the
photoreaction of a,w-bis(3,6-divinyl-N-carbazolyl)al-
7
reaction of carbazole with dibromide 8, prepared from
1
,3-dibromopropane and 4-bromophenol, was accom-
plished using Pd(dba) and (t-Bu) P to give 9 in a moder-
2
3
ate yield. The bromination of 9 with Br in CCl afforded
2
4
1
0, which was transformed into tetraldehyde 11 by lithia-
tion and subsequent treatment with DMF. The conven-
tional Wittig reaction of 11 afforded 6, while NaBH4
reduction of 11 in EtOH yielded 7.
6
kanes. These carbazolophanes 3 adopted exclusively a
syn-conformation and suffered from no isomerization into
anti-conformation, since two carbazole nuclei are fixed
more rigidly by two cyclobutane rings and an oligometh-
ylene linkage. Carbazolophanes 3 were composed of three
The intramolecular [2+2] photocycloaddition of 6 was at-
–3
tempted in toluene (ca. 1 × 10 M) with a 400 W high-
pressure mercury lamp through a Pyrex filter in a manner
4
similar to that reported previously. After irradiation for
one hour, insoluble polymeric materials were produced,
SYNTHESIS 2004, No. 16, pp 2743–2746
x
x.
x
x
.
2
0
0
4
while the formation of desired carbazolophane 4 was not
detected by H NMR spectroscopy. Prolonged irradiation
caused only an increase in insoluble products.
1
Advanced online publication: 07.10.2004
DOI: 10.1055/s-2004-834859; Art ID: C04804SS
Georg Thieme Verlag Stuttgart · New York
©

2
744
Y. Nakamura et al.
SPECIAL TOPIC
NH
Br
OH
Br (CH2)3 Br
Br
O (CH2)3 O
Br
NaOH,
CH3CN
Pd(dba)2,
8
(t-Bu) P,
3
68%
t-BuONa
6
2%
Br
Br
Br
Br2
N
O (CH2)3 O
N
N
O (CH2)3 O
N
CCl4
8
2%
Br
9
10
OHC
OHC
CHO
1
) n-BuLi
N
O (CH2)3 O
N
2
) DMF
8%
3
11
CHO
NaBH4,
EtOH
(
C6H5)3PCH3Br,
80%
33%
n-BuLi,
THF
HOH2C
HOH2C
CH2OH
N
O (CH2)3 O
N
N
O (CH2)3 O
N
7
6
CH2OH
Pyridinium
p-toluenesulfonate,
CH2Cl2, r.t.
hν (Pyrex),
toluene
16%
O
O
O
O
N
N
(CH2)3
O
O
N
N
(
CH2)3
5
4
Scheme 1
The intramolecular etherification of 7 to produce 5 was (three for the carbazoles and two for the benzene rings)
carried out in the presence of pyridinium p-toluene- are observed, and they are generally high-field shifted
sulfonate as acid catalyst under high dilution conditions compared to those of precursor 7, indicating that the two
–
4
(
ca. 1 × 10 M). The reaction carried out at reflux in 1,2- N-arylcarbazole chromophores are well overlapped with
dichloroethane resulted only in the formation of insoluble each other and subjected to their shielding effect. The ben-
polymeric products instead of the desired 5. In contrast, zyl protons were split into two broadened doublets, in
the reaction in CH Cl at room temperature for 10 days af- contrast with how they appeared as a sharp singlet in 7, in-
2
2
forded 5 in 16% yield. After purification by silica gel col- dicating the formation of cyclic structure and dynamic be-
umn chromatography and GPC, carbazolophane 5 was havior of -CH OCH - linkages. The number of signals in
2
2
1
3
isolated as a single product.
C NMR spectrum is also consistent with the structure of
5
.
The structure of carbazolophane 5 was definitively char-
1
13
1
acterized by H and C NMR spectroscopy. H NMR Figure 2 shows the absorption spectrum of 5 in cyclohex-
spectrum of 5 showed a very simple pattern consistent ane along with that of N-(4-methoxyphenyl)carbazole
with its symmetry. Five sets of aromatic proton signals (12) for comparison. The absorption spectrum of 5 exhib-
Synthesis 2004, No. 16, 2743–2746 © Thieme Stuttgart · New York

SPECIAL TOPIC Synthesis and Properties of N-Arylcarbazolophane–Paracyclophane Combined with Carbazoles
2745
Figure 2 Absorption spectra of (a) 5 and (b) 12 in cyclohexane at
room temperature.
Figure 3 Fluorescence spectra of (a) 5 and (b) 12 upon 280 nm ex-
citation in cyclohexane at room temperature.
its considerable broadening and a slight red shift relative
to 12. These features result from a transannular electronic
interaction between the carbazole rings overlapped with
each other.
Preparation of 10; Typical Procedure
To a solution of 9 (1.10 g, 1.97 mmol) in CCl (250 mL) was added
bromine (0.80 mL, 15.4 mmol) at 0 °C. After stirring at r.t. for 5 h,
4
5
% aq NaHSO solution (250 mL) was added to the mixture, which
Figure 3 shows the fluorescence spectra of 5 and 12 mea-
sured in cyclohexane at room temperature. The fluores-
3
8
was extracted with CHCl (3 ×). The combined organic phase was
3
successively washed with aq NaHCO solution (1 ×) and water
3
cence spectrum of 12 is composed of vibrational
structures characteristic of carbazole derivatives and ex-
hibits a mirror image of the longest absorption band. In
contrast, 2 afforded broad and structureless fluorescence
with a peak at 423 nm. This is reasonably assigned as ex-
cimer fluorescence. The peak maximum is further red-
shifted relative to the triply-bridged carbazolophane 3a
(
2 ×), dried over anhyd MgSO , and concentrated under reduced
4
pressure. The residue was recrystallized from toluene to give 10
(1.41 g, 1.61 mmol, 82%) as white crystals; mp 125–126 °C.
1
H NMR (500 MHz, CDCl ): d = 8.19 (s, 4 H), 7.48 (d, J = 8.2 Hz,
3
4
H), 7.39 (d, J = 8.6 Hz, 4 H), 7.17 (d, J = 8.2 Hz, 4 H), 7.15 (d,
J = 8.6 Hz, 4 H), 4.33 (t, J = 5.1 Hz, 4 H), 2.42 (m, 2 H).
13
C NMR (125 MHz, CDCl ): d = 158.48, 140.24, 129.37, 129.27,
3
6
reported previously. This red shift is partly ascribed to
1
28.41, 123.65, 123.15, 115.74, 112.80, 111.37, 64.58, 29.24.
the introduction of N-aryl groups.
Preparation of 11; Typical Procedure
To a three-necked flask containing 10 (1.72 g 1.97 mmol) was add-
In summary, we have prepared N-arylcarbazolophane 5, a
paracyclophane combined with carbazoles, by the in-
tramolecular etherification of precursor tetrol 7.
ed anhyd THF (200 mL) under a N atmosphere. After the solution
2
was stirred and cooled to –78 °C with a dry ice–acetone bath (1.58
M) n-BuLi hexane solution (7.6 mL, 12.0 mmol) was added to the
solution, and the mixture was stirred for 30 min at the temperature.
After addition of DMF (1.86 mL, 24.0 mmol) in anhyd THF (20
mL), the reaction mixture was stirred at r.t. for 2 h. The reaction was
NMR spectra were recorded on a JEOL l-500 FT NMR spectro-
meter with tetramethylsilane as an internal standard. Absorption
spectra were recorded on a HITACHI U-3210 spectrophotometer.
Fluorescence spectra were measured on an F-4500 spectrophoto-
meter. These spectra were obtained in cyclohexane (spectroscopic
grade) with a quartz cell of 10 mm optical path. GPC was performed
with a JAI LC-918 R/U Recycling Preparative HPLC using JAI-
GEL-1H and 2H columns.
quenched by adding 5% aq NH Cl solution (100 mL). The organic
4
phase was separated, and the aqueous phase was extracted with tol-
uene (3 ×). The combined organic phase was washed with water
(
3 ×), dried over anhyd MgSO , and concentrated under reduced
4
pressure. The residue was purified by column chromatography (sil-
ica gel, toluene–EtOAc) to afford 11 (0.51 g, 0.76 mmol, 38%) as
white powder; mp 135–136 °C.
Synthesis 2004, No. 16, 2743–2746 © Thieme Stuttgart · New York

2
746
Y. Nakamura et al.
SPECIAL TOPIC
1
H NMR (500 MHz, CDCl ): d = 10.16 (s, 4 H), 8.73 (s, 4 H), 8.01 Acknowledgment
3
(
d, J = 8.2 Hz, 4 H), 7.47 (d, J = 8.6 Hz, 4 H), 7.41 (d, J = 8.2, 4 H),
This work was financially supported by grants from The Ministry of
Education, Science, Sports, and Culture, Japan. The authors would
like to thank Prof. Dr. Keita Tani, Osaka Kyoiku University, for the
helpful discussions.
7
.22 (d, J = 8.6 Hz, 4 H), 4.37 (t, J = 5.1 Hz, 4 H), 2.46 (m, 2 H).
1
3
C NMR (125 MHz, CDCl ): d = 191.51, 159.11, 145.71, 130.22,
3
1
2
28.56, 128.30, 127.98, 124.22, 123.22, 115.97, 110.77, 64.63,
9.19.
Preparation of 7; Typical Procedure
A mixture of 11 (0.30 g, 0.45 mmol) and NaBH (0.25 g, 6.6 mmol)
References
4
(1) (a) Johnson, G. E. J. Chem. Phys. 1974, 61, 3002.
in EtOH (70 mL) was stirred at 30 °C for 5 h. The mixture was di-
luted with water (70 mL), and neutralized by a small amount of
HOAc. After EtOAc was evaporated under reduced pressure, the
residue was extracted with EtOAc (3 ×). The combined organic
phase was washed with water (2 ×), dried over anhyd MgSO , and
concentrated under reduced pressure, to give 7 (0.24 g, 0.35 mmol,
(
b) Johnson, G. E. J. Chem. Phys. 1975, 63, 4047. (c) De
Schryver, F. C.; Vandendriessche, J.; Toppet, S.; Demeyer,
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4
C.; Vandendriessche, J. J. Am. Chem. Soc. 1983, 105, 7256.
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(
(
8
0%) as white powder. This compound was used for the following
(b) Sakai, H.; Itaya, A.; Masuhara, H.; Sasaki, K.; Kawata,
reaction without further purification; mp > 300 °C.
S. Polymer 1996, 37, 31.
1
H NMR (500 MHz, CDCl ): d = 8.13 (s, 4 H), 7.43 (d, J = 8.6 Hz,
3
3) (a) Tani, K.; Tohda, Y.; Hisada, K.; Yamamoto, M. Chem.
Lett. 1996, 145. (b) For a recent contribution of this group
on the synthesis of carbazolophanes, see: Tani, K.; Tohda,
Y.; Takemura, H.; Ohkita, H.; Ito, S.; Yamamoto, M. Chem.
Commun. 2001, 1914. (c) Ohkita, H.; Ito, S.; Yamamoto,
M.; Tohda, Y.; Tani, K. J. Phys. Chem. A 2002, 106, 2140.
4) (a) Nishimura, J.; Doi, H.; Ueda, E.; Ohbayashi, A.; Oku, A.
J. Am. Chem. Soc. 1987, 109, 5293. (b) Nishimura, J.;
Ohbayashi, A.; Doi, H.; Nishimura, K.; Oku, A. Chem. Ber.
1988, 121, 2019. (c) Nishimura, J.; Takeuchi, M.;
4
H), 7.39 (d, J = 8.2 Hz, 4 H), 7.29 (d, J = 8.2 Hz, 4 H), 7.16 (d,
J = 8.6 Hz, 4 H), 4.86 (s, 8 H), 4.35 (t, J = 5.1 Hz, 4 H), 2.41 (m, 2
H).
1
3
C NMR (125 MHz, CDCl ): d = 158.19, 141.31, 136.64, 132.50,
3
1
28.45, 125.79, 123.05, 119.35, 115.67, 109.89, 66.01, 29.71.
(
Preparation of Carbazolophane 5; Typical Procedure
To 7 (0.19 g, 0.28 mmol) suspended in CH Cl (300 mL) was added
2
2
pyridinium p-toluenesulfonate (0.72 g, 2.82 mmol). The mixture
was stirred at r.t. for 10 d. After the solution was concentrated under
reduced pressure, the residue was purified by column chromatogra-
phy (silica gel, toluene–CH Cl ) and GPC (polystyrene, CHCl ) to
Takahashi, H.; Ueda, E.; Matsuda, Y.; Oku, A. Bull. Chem.
Soc. Jpn. 1989, 62, 3161. (d) Takeuchi, M.; Nishimura, J.
Tetrahedron Lett. 1992, 33, 5563. (e) Nishimura, J.; Okada,
Y.; Inokuma, S.; Nakamura, Y.; Gao, S. R. Synlett 1994,
884. (f) Nishimura, J.; Nakamura, Y.; Hayashida, Y.; Kudo,
T. Acc. Chem. Res. 2000, 33, 679.
2
2
3
give 5 (0.03 g, 0.047 mmol, 16%) as a white powder; mp > 300 °C.
1
H NMR (500 MHz, CDCl ): d = 7.87 (s, 4 H), 6.95 (d, J = 8.2, 4
3
H), 6.89 (d, J = 8.2, 4 H), 6.83 (d, J = 8.6, 4 H), 6.65 (d, J = 8.6, 4
H), 5.00 (br d, 4 H), 4.77 (br d, 4 H), 4.27 (t, J = 5.1 Hz, 4 H), 2.17
(
(
(
5) Nakamura, Y.; Kaneko, M.; Yamanaka, N.; Tani, K.;
Nishimura, J. Tetrahedron Lett. 1999, 40, 4693.
6) Nakamura, Y.; Kaneko, M.; Tani, K.; Shinmyozu, T.;
Nishimura, J. J. Org. Chem. 2002, 67, 8706.
7) (a) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L.
Acc. Chem. Res. 1998, 31, 805. (b) Hartwig, J. F. Angew.
Chem. Int. Ed. 1998, 37, 2047. (c) Hartwig, J. F. Synlett
(
m, 2 H).
1
3
C NMR (125 MHz, CDCl ): d = 157.04, 139.53, 130.81, 127.33,
3
1
3
26.38, 125.70, 123.20, 121.69, 114.94, 108.93, 75.47, 62.48,
1.18.
HRMS: m/z calcd for C H N O : 642.2519; found: 642.2523.
4
3
34
2
4
1997, 329.
(8) The fluorescence excitation spectra were in good agreement
with the corresponding absorption spectra in all cases.
Synthesis 2004, No. 16, 2743–2746 © Thieme Stuttgart · New York