Synthesis, structure, and electronic properties of syn-[2.2]phenanthrenophanes: First observation of their excimer fluorescence at high temperature

Article abstract of DOI:10.1021/ja951762a

Two syn-[2.2](1,6)- and -(3,6)phenanthrenophanes, 1a,b, were synthesized for the first time by means of intermolecular [2 + 2] photocycloaddition of the corresponding divinylphenanthrenes. Phenanthrenophanes 1a,b were obtained as mixtures of two (exo,exo and exo,endo) and three (exo,exo, exo,endo, and endo,endo) structural isomers, respectively, which were isolated by reversed-phase HPLC and gel permeation chromatography. All of the isomers, whose structures were characterized mainly on the basis of ¹H NMR spectroscopy, were in a syn conformation. X-ray crystallographic analysis of exσ,endo-1a was successful, also in agreement with the results of ¹H NMR. Birch reduction of 1b, followed by DDQ oxidation, afforded [4.4](3,6)phenanthrenophane 5b in an anti conformation, due to opening of the cyclobutane rings. The absorption spectra of 1b were relatively similar to that of phenanthrene itself, while those of 1a were rather broadened and red-shifted compared to those of phenanthrene and 1b. In both cases, the spectra were independent of the configuration of the cyclobutane rings. The fluorescence spectra of 1b exhibited sharp vibrational structures, as in phenanthrene, suggesting fluorescence from the locally excited state. On the other hand, 1a afforded a broad and structureless emission due to the excimer fluorescence, even at room temperature. This is the first observation of the excimer emission almost free from the monomer-like emission for phenanthrene derivatives at rather high temperature. Such differences in the absorption and fluorescence spectra between 1a,b can be explained reasonably in terms of differences in the arrangement of the two phenanthrene rings; they are tightly held almost in parallel for 1a, according to the X-ray structural analysis, while tilted by the dihedral angle of ca. 30° for 1b on the basis of MM2 calculations.

Full text of DOI:10.1021/ja951762a

1006
J. Am. Chem. Soc. 1996, 118, 1006-1012
Synthesis, Structure, and Electronic Properties of
syn-[2.2]Phenanthrenophanes: First Observation of Their
Excimer Fluorescence at High Temperature
Yosuke Nakamura, Takeshi Tsuihiji, Tadahiro Mita, Toshiyuki Minowa,
Seiji Tobita, Haruo Shizuka, and Jun Nishimura*
Contribution from the Department of Chemistry, Gunma UniVersity,
Tenjin-cho, Kiryu, Gunma 376, Japan
ReceiVed May 30, 1995X
Abstract: Two syn-[2.2](1,6)- and -(3,6)phenanthrenophanes, 1a,b, were synthesized for the first time by means of
intermolecular [2 + 2] photocycloaddition of the corresponding divinylphenanthrenes. Phenanthrenophanes 1a,b
were obtained as mixtures of two (exo,exo and exo,endo) and three (exo,exo, exo,endo, and endo,endo) structural
isomers, respectively, which were isolated by reversed-phase HPLC and gel permeation chromatography. All of the
isomers, whose structures were characterized mainly on the basis of 1H NMR spectroscopy, were in a syn conformation.
X-ray crystallographic analysis of exo,endo-1a was successful, also in agreement with the results of 1H NMR. Birch
reduction of 1b, followed by DDQ oxidation, afforded [4.4](3,6)phenanthrenophane 5b in an anti conformation, due
to opening of the cyclobutane rings. The absorption spectra of 1b were relatively similar to that of phenanthrene
itself, while those of 1a were rather broadened and red-shifted compared to those of phenanthrene and 1b. In both
cases, the spectra were independent of the configuration of the cyclobutane rings. The fluorescence spectra of 1b
exhibited sharp vibrational structures, as in phenanthrene, suggesting fluorescence from the locally excited state.
On the other hand, 1a afforded a broad and structureless emission due to the excimer fluorescence, even at room
temperature. This is the first observation of the excimer emission almost free from the monomer-like emission for
phenanthrene derivatives at rather high temperature. Such differences in the absorption and fluorescence spectra
between 1a,b can be explained reasonably in terms of differences in the arrangement of the two phenanthrene rings;
they are tightly held almost in parallel for 1a, according to the X-ray structural analysis, while tilted by the dihedral
angle of ca. 30° for 1b on the basis of MM2 calculations.
Introduction
anthrenophane (eq 1).4 The obtained phenanthrenophane,
however, was a mixture of the syn and anti isomers, whose
separation was not achieved. [2.2](3,6)Phenanthrenophanediene
was prepared by a sequence of Wittig reaction and aryl iodide
[2.2]Cyclophanes, including [2.2]naphthalenophanes and
phenanthrenophanes, have been of much interest from the
viewpoints of their synthesis, reactivities, and physical properties
resulting from the intramolecular interaction between the
π-electron systems of the two aromatic nuclei.1 Among them,
syn-cyclophanes, in which the two aromatic rings are aligned
face-to-face, are more attractive compounds, since they can bring
about larger electronic interaction than the corresponding anti
conformers. Various [2.2]naphthalenophanes2 have been syn-
thesized by various methods since the preparation of [2.2](2,7)-
naphthalenophane by Baker et al. in 1951,2a but the selective
synthesis of syn-[2.2]naphthalenophanes had not been attained
for a long time. Recently, we have successfully synthesized
[2.2]cyclophanes by means of intermolecular [2 + 2] photo-
cycloaddition of divinylarenes.3 This reaction also enabled the
selective and systematic synthesis of several syn-[2.2]naphtha-
lenophanes for the first time.3c
1
photolysis (eq 2).5 Its H NMR data suggested a relatively
The synthesis of [2.2]phenanthrenophanes has been much less
known because of its great difficulties. Staab and Haenel
reported the synthesis of [2.2](2,7)phenanthrenophane by the
pyrolysis of the disulfones derived from dithia[3.3]phen-
X Abstract published in AdVance ACS Abstracts, January 15, 1996.
(1) Vo¨gtle, F. Cyclophane Chemistry; Wiley: New York, 1993.
(2) (a) Baker, W.; Glockling, F.; McOmie, J. F. W. J. Chem. Soc. 1951,
1118. (b) Abell, J.; Cram, D. J. J. Am. Chem. Soc. 1954, 76, 4406. (c)
Brown, G. W.; Sondheimer, F. J. Am. Chem. Soc. 1967, 89, 4406. (d)
Haenel, M. W. Tetrahedron Lett. 1977, 4191.
(3) (a) Nishimura, J.; Horikoshi, Y.; Wada, Y.; Takahashi, H.; Sato, M.
J. Am. Chem. Soc. 1991, 113, 3485. (b) Wada, Y.; Ishimura, T.; Nishimura,
J. Chem. Ber. 1992, 125, 2155. (c) Takeuchi, M.; Tuihiji, T.; Nishimura, J.
J. Org. Chem. 1993, 58, 7388.
planar structure, while the UV spectrum indicated that the two
phenanthrene rings are almost perpendicular without significant
electronic interaction.5 According to the molecular mechanics
calculations, the aromatic nuclei were expected to form a
V-shape with an angle of 67°.6 As in the case of naphthale-
(4) Staab, H. A.; Haenel, M. Chem. Ber. 1973, 106, 2190.
(5) Thulin, B.; Wennerstro¨m, O. Acta Chem. Scand. 1976, B30, 369.
(6) Liljefors, T.; Wennerstro¨m, O. Tetrahedron 1977, 33, 2999.
0002-7863/96/1518-1006$12.00/0 © 1996 American Chemical Society

Synthesis of syn-[2.2]Phenanthrenophanes
J. Am. Chem. Soc., Vol. 118, No. 5, 1996 1007
nophanes, syn-[2.2]phenanthrenophanes have not been obtained
selectively. Therefore, we have been stimulated to apply the
intermolecular [2 + 2] photocycloaddition to two divinylphenan-
threnes for the synthesis of syn-[2.2]phenanthrenophanes. In
both cases, desired syn isomers were obtained efficiently and
selectively.
Scheme 1. Preparation of 1,6- and 3,6-Divinylphenanthrenea
The photophysical properties of [2.2]phenanthrenophanes are
of great interest from the viewpoint of the intramolecular
excimer formation. A large number of aromatic hydrocarbons
in the excited states are known to form excimers whose
fluorescence has been observed in a concentrated solution or
crystalline states.7 Cyclophanes, including naphthalenophanes,
have proved to provide intramolecular excimer fluorescence,
even in a dilute solution.8 In contrast with such aromatic
hydrocarbons and cyclophanes, unambiguous excimer fluores-
cence of phenanthrene has hardly been observed under usual
experimental conditions in fluid media. The red-shifted, broad
spectra due to the excimer fluorescence were detected for the
evaporated films9 and the phenanthrene adlayers on Al2O3.10
Azumi and McGlynn reported the delayed excimer fluorescence
in a hydrocarbon matrix at 77 K.11 Its intensity increased with
increasing temperatures, reached the maximum, and then
decreased to zero at room temperature.11 On the other hand,
Chandross and Thomas suggested the failure of excimer
formation of phenanthrene, on the basis of the study on the
photolytic dissociation of the cis,syn dimer of 9-(hydroxy-
methyl)phenanthrene and others in a rigid matrix at 77 K.12
Stevens and Dubois found the extremely low self-quenching
constant for the fluorescence of phenanthrene, which was
attributed to the rapid excimer dissociation at room tempera-
ture.13 At any rate, the excimer formation of phenanthrene
seems to be more difficult than that of other aromatic hydro-
carbons such as pyrene. The fluorescence spectrum of a
phenanthrene derivative, 9-cyano-10-methoxyphenanthrene, in
a benzene solution at room temperature exhibited a red-shifted
component with an increase in the concentration, suggesting
excimer fluorescence, although the monomer fluorescence
considerably remained.14 Concerned with phenanthrenophanes,
Staab et al. could detect the excimer fluorescence of [2.2](2,7)-
phenanthrenophane, a mixture of the syn and anti isomers, in a
fluorene host crystal at 4.2 K, though no mention was made
about the spectrum at room temperature.15 In contrast to the
[2.2]phenanthrenophanes prepared so far,4,5 the obtained ones
in this study are kept exclusively in a syn conformation.
Therefore, they are considered to produce the intramolecular
excimer efficiently and facilitate the observation of its fluores-
cence.
a
(a) hυ, I2/benzene, (b) (n-Bu)3SnCHdCH2, (Ph3P)4Pd/toluene.
Scheme 2. Photoreaction of Divinylphenanthrene 2a,b
Results and Discussion
Preparation of Divinylphenanthrenes. The synthesis of
divinylphenanthrenes 2a,b is shown in Scheme 1. Vinylarenes
are generally prepared either by Stille reaction of the corre-
sponding bromides or triflates16 or by Wittig reaction of aryl
aldehydes. Thus, we synthesized 1,6-dibromophenanthrene (4a)
from 2,4′-dibromostilbene (3a)17 in a manner similar to that in
3,6-dibromophenanthrene (4b),18 which had been prepared from
4,4′-dibromostilbene (3b) by Blackburn et al.18 Vinylation of
dibromides 4a,b was carried out by palladium-catalyzed dis-
placement in good yield.16a,b
Preparation and Characterization of [2.2]Phenan-
threnophanes. Intermolecular [2 + 2] photocycloaddition of
divinylphenanthrenes (2a,b) was performed with a 400-W high-
pressure mercury lamp through a Pyrex filter in dry benzene
(100 mmol/L) under a nitrogen atmosphere (Scheme 2). After
appropriate periods, the reaction mixture was evaporated and
then treated with borane-THF complex in order to react with
the remaining olefins. The purification by column chromatog-
raphy on silica gel gave desired phenanthrenophanes 1a,b as
mixtures of structural isomers.
In this paper, the synthesis, structure, and electronic properties
of the first syn-[2.2](1,6)- and -(3,6)phenanthrenophanes, 1a,b,
are described in detail.
(7) Birks, J. B. Photophysics of Aromatic Molecules; Wiley: New York,
1970.
(8) (a) Froines, J. R.; Hagerman, P. J. Chem. Phys. Lett. 1969, 4, 135.
(b) Shizuka, H.; Ogiwara, T.; Morita, T. Bull. Chem. Soc. Jpn. 1975, 48,
3385. (c) Feguson, J.; Morita, M.; Puza, M. Chem. Phys. Lett. 1976, 42,
288. (d) Yanagidate, M.; Takayama, K.; Takeuchi, M.; Nishimura, J.;
Shizuka, H. J. Phys. Chem. 1993, 97, 8881.
(9) Arden, W.; Peter, L. M.; Vaubel, G. J. Luminescence 1974, 257, 9.
(10) Haynes, D. R.; Helwig, K. R.; Tro, N. J.; George, S. M. J. Chem.
Phys. 1990, 93, 2836.
The photocycloaddition of 2a,b afforded 1a as a mixture of
two isomers in 33% yield and 1b as a mixture of three isomers
in 46% yield, respectively. These isomers are derived from
the difference in the direction of the cyclobutane rings. The
(11) Azumi, T.; McGlynn, S. P. J. Chem. Phys. 1964, 41, 3131.
(12) Chandross, E. A.; Thomas, H. T. J. Am. Chem. Soc. 1972, 94, 2421.
(13) Stevens, B.; Dubois, J. T. Trans. Faraday Soc. 1966, 62, 1525.
(14) Bouas-Laurent, H.; Lapouyade, R.; Castellan, A.; Nourmamode, A.;
Chandross, E. A. Z. Phys. Chem. N. F. 1976, 101, 39.
(15) Schweitzer, D.; Colpa, J. P.; Behnke, J.; Hausser, K. H.; Haenel,
M.; Staab, H. A. Chem. Phys. 1975, 11, 373.
(16) (a) Kosugi, M.; Sasazawa, K.; Shimizu, Y.; Migita, T. Chem. Lett.
1977, 301. (b) McKean, D. R.; Parrinello, G.; Renaldo, A. F.; Stille, J. K.
J. Org. Chem. 1987, 52, 422. (c) Echavarren, A. M.; Stille, J. K. J. Am.
Chem. Soc. 1987, 109, 5478.
(17) Bance, S.; Barber, H. J.; Woolman, A. M. J. Chem. Soc. 1943, 1.
(18) Blackburn, E. V.; Loader, C. E.; Timmons, C. J. J. Chem. Soc. C
1968, 1576.

1008 J. Am. Chem. Soc., Vol. 118, No. 5, 1996
Nakamura et al.
1
Table 1. Comparison of H NMR Spectroscopic Data among 1a, 1b, 5b, and Phenanthrene
chemical shift, δ
position
δexo,endo-1a
δexo,exo-1a
δexo,exo-1b
δexo,endo-1b
δendo,endo-1b
δ5b
δphenanthrene
1
2
3
4
5
6
7
8
9
7.49
7.28
7.50
7.31 (exo side)
7.40
7.06
7.76
7.41
8.12
7.82
7.88
8.93
8.93
7.88
7.82
8.12
7.71
7.71
7.10
7.85
7.10
7.67
7.07
7.72
7.07
7.30
8.61
8.61
8.72
8.99
9.11
9.11
8.52
8.52
6.52
6.99
6.99
7.46
6.95
7.12
7.00
7.44
7.28
7.49
7.28
7.28
7.03 (endo side)
7.06
7.40
7.28
7.28
7.41
7.76
7.60
7.60
7.38
7.26
7.27
10
Scheme 3. Birch reduction of 1ba
two isomers of 1a were found to be of exo,exo and exo,endo
configurations, and the three of 1b exo,exo, exo,endo, and
endo,endo ones, as described below. The two isomers of 1a
were isolated by the reversed-phase HPLC. The three isomers
of 1b were separated into one (exo,exo) and two isomers
(exo,endo and endo,endo) by the reversed-phase HPLC, and
the latter two isomers were separated by gel permeation
chromatography. The structures of the isolated phenan-
threnophanes were mainly determined by NMR spectroscopy
including NOESY and COSY experiments. The isomer ratio
a (a) NH3Na/ButOH, -60 °C, 30 min. (b) DDQ/decalin, 170 °C, 1
h.
1
was determined on the basis of the peak areas of H NMR
spectra and HPLC charts: exo,exo-1a:exo,endo-1a ) 60:40;
exo,exo-1b:exo,endo-1b:endo,endo-1b ) 5:54:41.
the cyclobutane rings, while those of the exo,exo-1b resonate
at the highest field. Furthermore, NOE interaction was observed
between the aromatic protons (C4 and C5 hydrogens) and the
methine protons of cyclobutane rings in exo,exo-1b and between
the aromatic protons (C4 and C5 hydrogens) and the methylene
protons of the cyclobutane rings in endo,endo-1b.
The chemical shifts for the aromatic protons of 1a,b and
phenanthrene itself are summarized in Table 1 for comparison.
The aromatic protons of 1a,b generally resonate at higher fields
than those of phenanthrene itself because of the shielding effect
of the aromatic nuclei, though the high-field shifts are more
remarkable in 1a than in 1b. Both 1a and 1b are, therefore,
concluded to have a syn conformation. The observed syn
selectivity is explained as follows. When a cyclobutane ring
is formed by the first photocycloaddition, the two phenanthrene
rings can be in either syn or anti conformation. In the second
cycloaddition, however, the anti intermediate cannot yield
desired intramolecular photocycloadducts, but only byproducts
such as polymer, since the two vinyl groups are too far apart to
react with each other. On the other hand, the intramolecular
two vinyl groups in the syn intermediate can easily react within
a molecule due to their closeness, leading to the second
cycloaddition. The obtained syn-[2.2]phenanthrenophanes were
never found to bring about the interconversion into anti isomers
at room temperature.
The two isomers of 1a are derived from the difference in the
direction of the cyclobutane ring at C6 (exo or endo). The
cyclobutane ring on C1 is considered to face only the exo
direction because of the steric hindrance with the C10 hydrogen
(peri-hydrogen), while that on C6 can be directed to the both
sides. The steric effect of the cyclobutane ring at C6 on the
C5 and C7 hydrogens is clearly represented by the chemical
shift of their 1H NMR signals as shown in Table 1; the C5 proton
in the exo,endo isomer whose cyclobutane ring at C6 faces to
the C5 side resonates at a lower field than that in the exo,exo-
isomer, while the C7 protons are in the reverse relationship.
These interactions, however, were not detected clearly by the
NOESY experiments.
Birch Reduction of [2.2]Phenanthrenophanes to [4.4]-
Phenanthrenophanes. Cyclobutane rings are known to be
opened regioselectively by electron-transfer reactions such as
Birch reduction.19 Especially, the cyclobutane rings at the
benzyl position are readily opened by this reaction to afford a
tetramethylene unit.20 Several [2.n]cyclophanes can be readily
converted into the corresponding [4.n]cyclophanes by Birch
reduction in more than 60% yield.21 The ring expansion reaction
of [2.n]-22 and [2.2]naphthalenophanes3c was also carried out
by Birch reduction and subsequent DDQ oxidation of the
overreduced aromatic rings.
Thus, this method was applied to the transformation of [2.2]-
phenanthrenophanes into [4.4]phenanthrenophanes. The two-
isomer mixture of 1a afforded no desired [4.4]phenan-
threnophane, probably because of the severe oxidation conditions
by DDQ. On the other hand, the three-isomer mixture of 1b
could be successfully converted into the desired [4.4](3,6)-
phenanthrenophane 5b (Scheme 3) in 36% yield.
[4.4](3,6)Phenanthrenophane 5b, characterized mainly by 1H
and 13C NMR spectroscopy, was found to be a single isomer
due to the cleavages of the cyclobutane rings, in contrast with
the three-isomer mixture of 1b. As shown in Table 1, the C4
and C5 protons of 5b resonate at higher fields than the
corresponding ones of 1b, while the other aromatic protons of
5b resonate at lower fields. These changes in the chemical shifts
are considered to be obviously brought about by changes in
the conformation of the phenanthrenophanes, probably from syn
to anti conformation. By such a change, the shielding effect
on the C4 and C5 protons should be increased, in contrast to
On the other hand, the two cyclobutane rings in 1b can be
directed to the both sides, giving the three isomers. Their
conformation could be determined on the basis of the signals
(19) (a) Birch, A. J.; Rao, G. S. AdV. Org. Chem. 1972, 8, 1. (b) Birch,
A. J.; Hinde, A. L.; Radom, L. J. Am. Chem. Soc. 1980, 102, 3370.
(20) Nozaki, H.; Noyori, R.; Kawanishi, K. Tetrahedron 1968, 24, 2183.
(21) Nishimura, J.; Ohbayashi, A.; Ueda, E.; Oku, A. Chem. Ber. 1988,
121, 1531.
(22) Nishimura, J.; Takeuchi, M.; Takahashi, H.; Ueda, E.; Matsuda,
Y.; Oku, A. Bull. Chem. Soc. Jpn. 1989, 62, 3161.
1
for the protons on C4 and C5 in the H NMR spectra. The
protons on C4 and C5 in the exo,endo-1b are not equivalent, in
contrast to those in the other two isomers with C2V symmetry.
The C4 and C5 protons of the endo,endo-1b resonate at the
lowest field among the three due to the greatest influence of

Synthesis of syn-[2.2]Phenanthrenophanes
J. Am. Chem. Soc., Vol. 118, No. 5, 1996 1009
Figure 2. Absorption spectra of (a) exo,exo-1a, (b) exo,exo-1b, (c)
5b, and (d) phenanthrene in cyclohexane at room temperature.
Figure 1. Side and top views of (a) exo,endo-1a (X-ray crystallographic
analysis) and (b) exo,exo-1b (MM2 calculations).
(C3-C6 side), are tilted by the dihedral angle of ca. 30°, as
shown in Figure 1b. The interplanar distance is ca. 3.0 Å on
the C3-C6 side and ca. 6.0 Å on the C9-C10 side. The
planarity of the phenanthrene rings is still maintained because
of much less strain than in 1a. The other isomers, exo,endo-
and endo,endo-1b, were found to have structures quite similar
to that of exo,exo-1b.
Thus, the structures of the two phenanthrenophanes 1a,b
exhibited a remarkable contrast to each other, though little
depending on the direction of their cyclobutane rings. The
greater high-field shift of the aromatic protons in 1a than in 1b
can be explained reasonably in terms of the difference in their
structures.
Absorption Spectra. The absorption spectra of [2.2]phenan-
threnophanes 1a,b and [4.4]phenanthrenophane 5b were mea-
sured in cyclohexane at room temperature, along with phenan-
threne itself as the reference. No distinct difference was
observed between the two isomers of 1a and among the three
of 1b; the absorption spectra were almost independent of the
direction of the cyclobutane rings, as expected from their
structures. Figures 2 a-d show the spectra of exo,exo-1a,b,
5b, and phenanthrene.
the decrease on the other protons. In the mass spectra, the
molecular ion peak of 5b was observed much more clearly than
that of 1b; the molecular ion peak (m/z ) 464) was the base
peak in 5b, while that of 1b (m/z ) 460) was with an intensity
of about 1% of the base ion peak (m/z ) 230). These results
indicate that 5b is more flexible, more stable, and less strained
than 1b, arising from the loss of the two cyclobutane rings with
much strain.
Structures of [2.2]Phenanthrenophanes. It is apparent that
both 1a and 1b are in a syn conformation, according to the
results of 1H NMR. Strictly speaking, however, the arrangement
of the two phenanthrene rings is expected to be different between
1a and 1b, since the aromatic protons of 1a resonate at quite
higher fields than those of 1b, as described above, suggesting
a larger shielding effect in 1a. It is necessary and interesting
to investigate the structure and electronic properties of 1a,b
closely.
X-ray crystallographic analysis of exo,endo-1a was successful
among all the synthesized phenanthrenophanes. The side and
top views are shown in Figure 1a. The optimal structures of
1b and exo,exo-1a, whose appropriate single crystals have not
been obtained, were determined by the MM2 calculations.
These calculations are sufficiently reliable because the calculated
structure of exo,endo-1a is in good agreement with that by X-ray
analysis. The structure of exo,exo-1b is shown in Figure 1b as
a representative of 1b.
The two phenanthrene rings in exo,endo-1a are held almost
in parallel by the two cyclobutane rings on the opposite sides
and fully overlap with each other. The average interplanar
distance is about 3.5 Å (nearest 2.88 Å (C1 position); farthest
4.07 Å (C4 position)). Each phenanthrene ring, however, is
slightly distorted for the release of the strain in the molecule.
According to the MM2 calculations, the arrangement of the two
phenanthrene rings in exo,exo-1a was virtually the same as that
in exo,endo-1a, in spite of the difference in the direction of the
cyclobutane ring at the C6 position.
The absorption bands of phenanthrene itself have been well
characterized so far.23 The extremely weak vibrational struc-
tures (ꢀ ∼ 200) in the region 300-350 nm are the S1(1Lb) r
S0(1A) band, and those around 270-300 nm are the S2(1La) r
S0(1A), whose 0-0 transition is located at 292 nm (ꢀ ∼ 14 000).
The strong band (ꢀ ∼ 60 000) at 250 nm is interpreted by the
S4(1Ba) r S0(1A) rather than the S3(1Bb) r S0(1A), which is
1
masked by the much stronger Ba band due to the closeness
1
1
between the Ba and Bb bands. Phenanthrenophanes 1b and
5b also exhibited vibrational structures, as in phenanthrene. It
is reasonable to assign the quite weak bands around 320-350
nm and the rather strong ones around 270-310 nm to the S1 r
S0 and S2 r S0 transitions, respectively, by the comparison of
(23) (a) Do¨rr, F.; Hohlneicher, G.; Schneider, S. Ber. Bunsen-Ges. Phys.
Chem. 1966, 70, 803. (b) Thulstrup, E. W.; Michl, J.; Eggers, J. H. J. Phys.
Chem. 1970, 74, 3868. (c) Vasa´k, M.; Whipple, M. R.; Michl, J. J. Am.
Chem. Soc. 1978, 100, 6867.
On the other hand, the two phenanthrene rings in exo,exo-
1b, connected by the two cyclobutane rings on the one side

1010 J. Am. Chem. Soc., Vol. 118, No. 5, 1996
Nakamura et al.
Table 2. Position of 0-0 Transition in S1 r S0 and S2 r S0
Absorption Bands and Peak Position of S4 r S0 Band in 1b, 5b,
and Phenanthrenea
S1(1Lb) r S0(1A) S2(1La) r S0(1A) S4(1Ba) r S0(1A)
0-0 transition, nm 0-0 transition, nm band peak, nm
(ꢀ, 104 M-1 cm-1
)
(ꢀ, 104 M-1 cm-1
)
1b
5b
355
351
346
307 (1.4)
298 (1.5)
292 (1.4)
249 (10.0)
248 (7.0)
251 (6.4)
phenanthrene
1
a The Bb band due to the S3 r S0 transition was probably masked
1
by the strong absorption of the Ba band. For details, see text.
their position, absorbance, and shape with those for phenan-
threne. The 0-0 transitions of the S1 r S0 and S2 r S0 bands
in 1b and 5b are summarized in Table 2. These bands are
apparently red-shifted and broadened relative to those inphenan-
threne. The strong bands around 250 nm in 1b and 5b are
probably due to the S4(1Ba) r S0(1A) transition, as in phenan-
threne. The peak positions of the bands are almost unchanged
(Table 2), though the shape appears to depend on the compounds
to some extent. The band shape in 1b is similar to that in
phenanthrene, while that in 5b is relatively broad with a shoulder
on the lower wavenumber side. Such difference in the band
shape may be correlated with the relative position and/or
intensity between the S3 r S0 and S4 r S0 bands. Thus, it is
possible that the broadening and shoulder in 5b suggest the
larger contribution of the S3 r S0 band than that in cases of
both 1b and phenanthrene, although the details are unknown at
present. The red shift and broadening of the S1 r S0 and S2
r S0 bands in 1b and 5b are considered to be brought about
not only by the presence of the substituent groups at the C3
and C6 positions but also by the intramolecular electronic
interaction between the two phenanthrene rings. The red shift
in 1b is more remarkable than in 5b, obviously indicating the
greater intramolecular interaction in 1b than in 5b, since
the overlap between the two phenanthrene rings of 1b in a syn
conformation is considered to be larger than that of 5b in an
anti conformation, though much smaller compared to that of
1a.
The absorption spectrum of 1a exhibited considerable broad-
ening. The S1 r S0 band could be hardly appreciated due to
its weakness. The S2 r S0 band is further red-shifted relative
to those in 1b and 5b; the 0-0 transition seems to be located
at 320 nm, though the unambiguous assignment is difficult. Such
broadening and the red shift are apparently ascribable to the
much greater intramolecular transannular interaction between
the two phenanthrene rings tightly held in parallel, in contrast
to those of 1b.
Thus, the difference in the structures among 1a,b, and 5b
was clearly reflected by their absorption spectra. It is surprising
that the spectrum of 1b is similar to that of 5b in an anti
conformation rather than that of 1a in a syn conformation. In
the arrangement of 1b in Figure 1b, the two phenanthrene rings
in a tilted form are not able to interact with each other
sufficiently.
Figure 3. Fluorescence spectra of (a) exo,exo-1a, (b) exo,exo-1b, (c)
5b, and (d) phenanthrene upon 250-nm excitation in cyclohexane at
room temperature.
Table 3. Peak Position of Fluorescence Spectra of 1b, 5b, and
Phenanthrene
peak position, nm
1b
5b
357,
352,
347,
377,
371,
365,
396,
390,
384,
∼420sa
414
phenanthrene
357,
375,
∼405sa
a The suffix “s” denotes a shoulder.
in Table 3, and some peaks observed in phenanthrene are too
much weakened to be recognized. The relative intensity of the
0-0 transition in 1b and 5b is increased compared to that in
phenanthrene. These features in 1b and 5b indicate the presence
of the intramolecular interaction between the two aromatic nuclei
in the excited state, though it is not strong enough to lead to
the formation of the excimer, as in the case of the 9-(hydroxy-
methyl)phenanthrene sandwich pair.12 The failure to form
excimers is obvious from the quite small Stokes shifts (∼100
cm-1) in 1b and 5b, which are comparable to that in phenan-
threne, as can be seen from a comparison between Tables 2
and 3. Therefore, the fluorescence of 1b and 5b is interpreted
in terms of that from the locally excited singlet state having a
weak intramolecular interaction. The spectrum of 1b shows a
larger red shift and broadening compared with the case of 5b,
probably resulting from the larger interaction than that in 5b,
in agreement with the results of the absorption spectra.
On the other hand, 1a exhibited an entirely different
fluorescence spectrum, as shown in Figure 3a. It is a broad
and structureless emission with a peak at 410 nm, much red-
shifted in comparison with that of 1b and phenanthrene; the
red shifts are ca. 3600 and 4400 cm-1 relative to the emissions
of 1b and phenanthrene, respectively. These shifts are appar-
ently larger than those in the absorption spectrum of 1a versus
1b and phenanthrene. In the S1 state of 1a, much larger
intramolecular interaction between the two phenanthrene rings
is established than in the ground state. In other words, the
structure in the S1 state of 1a is different from that in the ground
state; the two aromatic moieties get close to each other in the
excited state. Therefore, it is reasonable to assign the fluores-
cence observed for 1a to the intramolecular excimer (1EX*)
emission. Excimer fluorescences are usually observed with a
red shift of 5000-6000 cm-1 relative to the corresponding
Fluorescence Spectra. The fluorescence spectra of 1a,b and
5b were measured in cyclohexane at room temperature. The
spectra were almost independent of the excitation wavelength.
The isomers derived from the direction of their cyclobutane rings
in 1a,b exhibited the same spectra in each case. Figure 3 a-d
illustrates the fluorescence spectra of exo,exo-1a,b, 5b, and
phenanthrene upon 250-nm excitation as representatives.
The fluorescence spectra of 1b and 5b exhibit sharp vibra-
tional structures, corresponding to the mirror image of the S1
r S0 absorption band, as in the case of phenanthrene. In both
1b and 5b, however, all of the peaks are slightly broadened
and red-shifted relative to those in phenanthrene, as summarized

Synthesis of syn-[2.2]Phenanthrenophanes
J. Am. Chem. Soc., Vol. 118, No. 5, 1996 1011
monomer fluorescences.24 The observed red shift in 1a iss-
lightly smaller, probably because the two aromatic moieties
cannot approach to the most stable conformation in the S1 state,
due to its relatively rigid structure. The fluorescence spectrum
of 1a is similar to the delayed excimer fluorescence of
phenanthrene at low temperatures reported by Azumi et al.,11
though the peak is shifted to shorter wavelengths (for phenan-
threne, 430 nm). It is also similar to the excimer fluorescence
of [2.2](2,7)phenanthrenophanes at 4.2 K by Staab et al.,
including the position of the maximum.15 To the best of our
knowledge, the excimer fluorescence so far observed for
phenanthrene derivatives at room temperature contains vibra-
tional structures suggesting monomer-like components. The
emission spectrum of 1a is the first observation of the excimer
fluorescence almost free from the monomer-like fluorescence
for phenanthrene derivatives at room temperature. This easy
detection of the excimer fluorescence in 1a is apparently derived
from the conformation of the two phenanthrene rings which
are kept tightly in parallel by the two cyclobutane rings.
The fluorescence excitation spectra of 1a,b and 5b, monitored
at the maximum of each fluorescence spectrum, were in good
agreement with the corresponding absorption spectra. It is
concluded that the observed fluorescence undoubtedly results
from the lowest excited singlet state of each compound.
The emission spectra were also measured at 77 K in MP
(methylcyclohexane:isopentane ) 3:1 (v/v)). The obtained
spectra were almost the same as those at room temperature,
though the vibrational structures in 1b and 5b became slightly
sharper at 77 K. No excimer fluorescence was observed for
1b at all because this molecule is conformationally hardly
changeable to form a suitable excimer structure due to its
rigidity.
only parallel forms but also tilted forms and antiparallel forms.8d
The excimer formation of phenanthrenes may be influenced by
the arrangement much more sensitively.
Experimental Section
General Procedure. NMR spectra were recorded on a JEOL Alpha-
500 FT NMR spectrometer. Mass spectra were measured on a JEOL
JMS-DX302 mass spectrometer. HPLC analysis was performed with
a Shimadzu LC-6A pump, an LC-6A UV detector, and an RC4A data
processor. Gel permeation chromatography was performed on a Japan
Analytical Industry LC-08 system. Melting points are uncorrected.
Absorption spectra were recorded on a JASCO Ubest-50 spectropho-
tometer. Fluorescence spectra and fluorescence excitation spectra were
measured on a Hitachi-4010 spectrofluorimeter. These spectra were
obtained in cyclohexane (spectroscopic grade) with a quartz cell of
10-mm optical path. The sample concentration is in the range 10-5
-10-4 M.
1,6-Dibromophenanthrene (4a). The mixture of trans-2,4′-dibro-
mostilbene (3a) (3.0 g, 8.9 mmol) and iodine (56.3 mg, 0.44 mmol)
was dissolved in benzene (450 mL) in a Pyrex flask and then irradiated
by a 400-W high-pressure mercury lamp while being monitored by
TLC (SiO2, hexane). Irradiation was continued until the disappearance
of the reactant olefin (after about 20 h). The reaction mixture was
evaporated and purified by column chromatography (SiO2, hexane-
benzene) to afford 4a as a colorless solid (2.4 g, 79.7%): mp 158-
159 °C; 1H NMR (CDCl3, 500 MHz) δ 8.81 (1H, s, C5-H), 8.59 (1H,
d, J ) 8.5, C4-H), 8.23 (1H, d, J ) 9.2, C8-H), 7.92 (1H, d, J ) 7.6,
C2-H), 7.80 (1H, d, J ) 8.9, C10-H), 7.80 (1H, d, J ) 8.9, C9-H),
7.73 (1H, d, J ) 9.2, C7-H), 7.52 (1H, dd, J ) 7.6 and 8.5, C3-H).
Anal. Calcd for C14H8Br2: C, 50.04; H, 2.40. Found: C, 50.05; H,
2.62.
3,6-Dibromophenanthrene (4b). 3,6-Dibromophenanthrene (4b)
was synthesized in a way similar to that in the literature18 (yield
77.2%): mp 187-188 °C (lit.18 194 °C); 1H NMR (CDCl3, 500 MHz)
δ 8.70 (2H, s, C4- and C5-H), 7.75 (2H, d, J ) 8.6, C1- and C8-H),
7.70 (2H, d, J ) 8.6, C2- and C7-H), 7.69 (2H, s, C9- and C10-H).
1,6-Divinylphenanthrene (2a).16a,b To a solution of 1,6-dibro-
mophenanthrene (4a) (3.0 g, 9.0 mmol) in toluene (357 mL) were added
tri-n-butylvinylstannane (11.4 g, 35.7 mmol), prepared from vinyl-
magnesium bromide and tri-n-butyltin chloride, tetrakis(triphenylphos-
phine)palladium(0) (443.3 mg, 0.36 mmol), and a few crystals of 4-tert-
butylcatechol as a polymerization inhibitor. The resulting suspension
was heated to reflux for 4 h, cooled to room temperature, filtrated,
concentrated, and then diluted with ether. The ether solution was treated
with 20% aqueous potassium fluoride solution (70 mL) and stirred
vigorously for 30 min. The ether phase was decanted from the aqueous
phase containing the solid of tin fluoride polymer and evaporated. The
residue was purified by column chromatography (SiO2, hexane-
benzene) to afford 2a as a colorless solid (1.81 g, 87.6%): mp 79-80
The fluorescence spectra of 1a,b were considerably different
from each other. Although this difference was more remarkable
than that in the absorption spectra, the whole tendency for 1a,b,
and 5b resembled that in the absorption spectra; the deviation
of their absorption and fluorescence spectra from those of
phenanthrene becomes larger in the order 5b < 1b , 1a,
reflecting the magnitude of the intramolecular electronic interac-
tion.
Conclusion
We have succeeded in the selective synthesis of syn-[2.2]-
phenanthrenophanes (1a,b) for the first time by means of
intermolecular [2 + 2] photocycloaddition of the corresponding
divinylphenanthrenes. Although both 1a and 1b are apparently
in a syn conformation, the arrangements of the two phenanthrene
rings were found to be quite different from each other. This
structural difference had a significant effect on their electronic
properties in the ground state as well as the excited state, as
revealed by the absorption and fluorescence spectra. Especially,
the fluorescence spectra are entirely different from each other:
the intramolecular excimer fluorescence was observed for 1a
in a parallel form, whereas the fluorescence from the locally
excited state for 1b was in a tilted form. The former is the
first observation of excimer fluorescence almost free from the
monomer-like components of phenanthrene derivatives at room
temperature. It is enabled by the presence of the two cyclobu-
tane rings; they keep the two phenanthrene rings rigidly in a
parallel conformation favorable for the excimer formation and
prevent the dissociation which would be extremely rapid without
such bridging units. The fact that no excimer fluorescence is
detected for 1b is in contrast to the case of the naphthale-
nophanes, in which the excimer fluorescence is detected for not
1
°C; H NMR (CDCl3, 500 MHz) δ 8.68 (1H, d, J ) 8.3, C4-H), 8.63
(1H, s, C5-H), 8.03 (1H, d, J ) 9.2, C8-H), 7.85 (1H, d, J ) 8.2,
C10-H), 7.74 (1H, d, J ) 8.2, C9-H), 7.73 (1H, d, J ) 7.3, C2-H),
7.75 (1H, d, J ) 9.2, C7-H), 7.63 (1H, dd, J ) 8.3 and 7.3, C3-H),
7.54 (1H, dd, J ) 17.4 and 11.0, C1-CH)CH2), 7.00 (1H, dd, J )
17.4 and 11.0, C6-CHdCH2), 5.96 (1H, d, J ) 17.4, C6-CHdCH2
(trans)), 5.81 (1H, dd, J ) 17.4 and 1.5, C1-CHdCH2 (trans)), 5.52
(1H, dd, J ) 11.0 and 1.5, C1-CHdCH2 (cis)), 5.39 (1H, d, J ) 11.0,
C6-CHdCH2 (cis)); LRMS m/z (relative intensity) 230 (100, M+), 202
(35). Anal. Calcd for C18H14: C, 93.87; H, 6.13. Found: C, 93.66;
H, 6.19.
3,6-Divinylphenanthrene (2b). 3,6-Divinylphenanthrene (2b) was
1
synthesized in the same way as 2a (yield 93.8%): mp 69-70 °C; H
NMR (CDCl3, 500 MHz) δ 8.60 (2H, s, C4- and C5-H), 7.82 (2H, d,
J ) 8.3, C1- and C8-H), 7.73 (2H, d, J ) 8.3, C2- and C7-H), 7.67
(2H, s, C9- and C10-H), 7.00 (2H, dd, J ) 17.2 and 11.0, Ar-CHdCH2),
5.95 (2H, d, J ) 17.2, Ar-CHdCH2 (trans)), 5.39 (2H, d, J ) 11.0,
Ar-CHdCH2 (cis)); LRMS m/z (relative intensity) 230 (100, M+), 202
(20). Anal. Calcd for C18H14: C, 93.87; H, 6.13. Found: C, 93.78;
H, 6.12.
Intermolecular [2 + 2] Photocycloaddition toward 1,2-Ethano-
syn-[2.2](1,6)phenanthrenophane (1a). 1,6-Divinylphenanthrene 2a
(1.0 g, 4.3 mmol) dissolved in dry benzene (40 mL) was placed in a
(24) Klo¨pffer, W. Organic Molecular Photophysics; Birks, J. B., Ed.;
John Wiley and Sons: New York, 1973; Vol. 1, p 357.

1012 J. Am. Chem. Soc., Vol. 118, No. 5, 1996
Nakamura et al.
Pyrex flask equipped with a magnetic stirrer, reflux condenser, and
nitrogen inlet. It was irradiated with a 400-W high-pressure mercury
lamp under a nitrogen atmosphere while being monitored by TLC (SiO2,
hexane/benzene ) 7/3). When polymerization predominated over the
formation of the desired cyclophanes after about 5 h, irradiation was
ceased. The reaction mixture was evaporated and then purified by
column chromatography (SiO2, hexane-benzene) to afford the mixture
of exo,exo- and exo,endo-1a as a colorless solid (total: 0.33 g, 33%).
Both isomers were separated by the reversed-phase HPLC (ODS
column, methanol).
ammonia was allowed to evaporate slowly in a hood. The residue was
extracted with benzene (20 mL). The benzene extract was washed with
water (20 mL × 3) and dried over anhydrous MgSO4. After filtration
and evaporation, the residue was purified by column chromatography
(SiO2, benzene-hexane) to give the Birch reduction product (ca. 250
mg).
In a 50-mL flask equipped with a magnetic stirrer, reflux condenser,
and nitrogen inlet were placed the Birch reduction product prepared
above and DDQ (980 mg, 5.4 mmol), which were dissolved in decalin
(15 mL) under a nitrogen atmosphere. The reaction mixture was heated
with stirring at 180 °C for 1 h. After the decalin was removed, the
desired product 5b was isolated by column chromatography (SiO2,
hexane-benzene) as a colorless solid (110 mg, 36.3%): mp 228-229
1
exo,exo-1a: mp > 250 °C; H NMR (CDCl3, 500 MHz) δ 7.72
(2H, dd, J ) 4.9 and 4.6, C3-H), 7.44 (2H, d, J ) 9.0, C10-H), 7.30
(2H, s, C5-H), 7.12 (2H, d, J ) 8.3, C8-H), 7.07 (2H, d, J ) 4.9,
C2-H), 7.07 (2H, d, J ) 4.6, C4-H), 7.00 (2H, d, J ) 9.0, C9-H), 6.95
(2H, d, J ) 8.3, C7-H), 5.1 (2H, m, C1-methine), 4.4 (2H, m, C6-
methine), 2.9 (8H, m, methylene); 13C NMR (CDCl3, 125 MHz) δ
137.95, 137.24, 130.25, 129.85, 129.75, 129.28, 126.94, 126.35, 125.08,
125.04, 124.76, 124.52, 121.19, 119.93, 47.20, 42.20, 22.27, 21.37;
LRMS m/z (relative intensity) 460 (1.3, M+), 230 (100); HRMS m/z
460.2178, calcd for C36H28 460.2192.
1
°C; H NMR (CDCl3, 500 MHz) δ 8.52 (4H, s, C4- and C5-H), 7.76
(4H, d, J ) 8.3 Hz, C1- and C8-H), 7.60 (4H, s, C9- and C10-H), 7.41
(4H, d, J ) 8.3 Hz, C2- and C7-H), 3.00 (8H, m, ArCH2CH2-), 1.92
(8H, m, Ar-CH2-CH2-); 13C NMR (CDCl3, 125 MHz) δ 140.40, 130.38,
129.95, 128.57, 127.45, 125.82, 121.39, 35.81, 29.35; LRMS m/z
(relative intensity) 464 (100, M+), 245 (6), 231 (21), 219 (12), 218
(15), 217 (22), 205 (21), 191 (25); HRMS m/z 464.2504, calcd for
C36H32 464.2499.
1
exo,endo-1a: mp > 250 °C; H NMR (CDCl3, 500 MHz) δ 7.85
(2H, dd, J ) 6.0 and 3.4, C3-H), 7.67 (2H, s, C5-H), 7.46 (2H, d, J )
9.2, C10-H), 7.10 (2H, d, J ) 6.0, C2-H), 7.10 (2H, d, J ) 3.4, C4-H),
6.99 (2H, d, J ) 8.6, C8-H), 6.99 (2H, d, J ) 9.2, C9-H), 6.52 (2H, d,
J ) 8.6, C7-H), 5.1 (2H, m, C1-methine), 4.4 (2H, m, C6-methine),
2.9 (8H, m, methylene); 13C NMR (CDCl3, 125 MHz) δ 137.74, 137.26,
130.48, 130.21, 129.82, 129.41, 129.16, 126.78, 125.00, 124.75, 124.60,
123.04, 121.22, 119.96, 46.69, 42.56, 22.31, 21.05; LRMS m/z (relative
intensity) 460 (2.5, M+), 230 (100); HRMS m/z 460.2192, calcd for
C36H28 460.2192.
X-ray Crystallographic Analysis.25 A colorless prismatic crystal
with approximate dimensions of 0.20 × 0.20 × 0.15 mm was mounted
on a glass fiber. All measurements were made on a Rigaku AFC7S
diffractometer with graphite monochromated Cu KR radiation. Cell
constants and an orientation matrix for data collection, obtained from
a least-squares refinement using the setting angles of 25 carefully
centered reflections in the range 55.21 < 2θ < 56.94°, corresponded
to a primitive monoclinic cell with dimensions: a ) 10.79(3) Å, b )
8.44(4) Å, c ) 26.01(4) Å, â ) 96.0(2)°, V ) 2357(11) Å3. For Z )
4 and fw ) 460.62, the calculated density is 1.30 g/cm3. The space
group was determined to be P21/n (no. 4). The data were collected at
a temperature of 20 ( 1 °C using the ω-2θ scan technique to a
maximum 2θ value of 120.3°. Omega scans of several intense
reflections, made prior to data collection, had an average width at half-
height of 0.38° with a take-off angle of 6.0°. Scans of (1.73 + 0.30
tan θ)° were made at a speed of 16.0 deg/min (in Ω). The weak
reflections (I < 10.0σ(I)) were rescanned (maximum of three scans),
and the counts were accumulated to ensure good counting statistics.
The ratio of peak counting time to background counting time was 2:1.
The diameter of the incident beam collimator was 1.0 mm, the crystal
to detector distance was 235 mm, and the computer-controlled detector
aperture was set to 9.0 × 13.0 mm (horizontal × vertical). Of the
4001 reflections which were collected, 3774 were unique (Rint ) 0.107).
The intensities of three representative reflections were measured after
every 150 reflections. No decay correction was applied. The linear
absorption coefficient, µ, for Cu KR radiation is 5.5 cm-1. The structure
was solved by the direct method, SAPI91, and expanded using Fourier
techniques. The non-hydrogen atoms were refined anisotropically. The
hydrogen atom coordinates were refined, but their isotropic B’s were
held fixed. The final cycle of full-matrix least-squares refinement was
based on 2616 observed reflections (I > 3.00σ(I)) and 410 variable
parameters and converged (largest parameter was 0.18 times its esd)
with unweighted and weighted agreement factors of R ) 0.072 and Rw
) 0.050. The standard deviation of an observation of unit weight was
6.34.
Intermolecular [2 + 2] Photocycloaddition toward 1,2-Ethano-
syn-[2.2](3,6)phenanthrenophane (1b). 3,6-Divinylphenanthrene 2b
(0.48 g, 2.1 mmol), irradiated in the same way as 2a, afforded the
three-isomer mixture of 1b as a colorless solid (total: 0.22 g, 46%).
From the mixture, only the exo,exo-1b was isolated by the reversed-
phase HPLC (ODS column, methanol). The residual two isomers
(exo,endo- and endo,endo-1b) were separated by gel permeation
chromatography (polystyrene gel column, chloroform).
1
exo,exo-1b: mp > 250 °C; H NMR (CDCl3, 500 MHz) δ 8.61
(4H, s, C4- and C5-H), 7.49 (4H, d, J ) 8.4, C1- and C8-H), 7.28
(4H, d, J ) 8.4, C2- and C7-H), 7.28 (4H, s, C9- and C10-H), 4.59
(4H, m, methine), 2.73 (8H, m, methylene); 13C NMR (CDCl3, 125
MHz) δ 138.81, 129.81, 128.95, 127.97, 125.51, 124.23, 124.00, 45.50,
23.71; LRMS m/z (relative intensity) 460 (1.5, M+), 230 (100); HRMS
m/z 460.2211, calcd for C36H28 460.2192.
1
exo,endo-1b: mp > 250 °C; H NMR (CDCl3, 500 MHz) δ 8.99
(2H, s, C5-H), 8.72 (2H, s, C4-H), 7.50 (2H, d, J ) 8.1, C1-H), 7.38
(2H, d, J ) 8.1, C8-H), 7.31 (2H, d, J ) 8.1, C2-H), 7.27 (2H, s,
C10-H), 7.26 (2H, s, C9-H), 7.03 (2H, d, J ) 8.1, C7-H), 4.65 (2H, m,
exo-methine), 4.43 (2H, m, endo-methine), 2.92 (4H, m, endo-
methylene), 2.74 (4H, m, exo-methylene); 13C NMR (CDCl3, 125 MHz)
δ 139.32, 138.96, 130.11, 129.84, 129.12, 128.13, 128.04, 128.04,
127.70, 125.65, 125.43, 124.26, 124.01, 121.46, 46.71, 45.57, 24.88,
23.81; LRMS m/z (relative intensity) 460 (0.4, M+), 230 (100); HRMS
m/z 460.2210, calcd for C36H28 460.2192.
1
endo,endo-1b: mp > 250 °C; H NMR (CDCl3, 500 MHz) δ 9.11
(4H, s, C4- and C5-H), 7.40 (4H, d, J ) 7.9, C1- and C8-H), 7.28
(4H, s, C9- and C10-H), 7.06 (4H, d, J ) 7.9, C2- and C7-H), 4.46
(4H, m, methine), 2.96 (8H, m, methylene); 13C NMR (CDCl3, 125
MHz) δ 139.42, 130.17, 129.29, 128.06, 127.74, 125.56, 121.33, 46.64,
25.12; LRMS m/z (relative intensity) 460 (0.3, M+), 230 (100); HRMS
m/z 460.2169, calcd for C36H28 460.2192.
Acknowledgment. This work was partly supported by the
Grant-in-Aid for Scientific Research on Priority Areas from the
Ministry of Education, Science, and Culture, Japan (Nos.
05233105 and 06242202).
Supporting Information Available: ORTEP drawing, tables
[4.4](3,6)Phenanthrenophane (5b) (Birch Reduction). A 200-mL
three-necked round-bottomed flask equipped with a magnetic stirrer,
nitrogen inlet, and gas inlet was cooled to ca. -60 °C over a dry ice-
methanol bath. Ammonia gas was introduced into the system. When
liquid ammonia (ca. 65 mL) was condensed, the gas inlet tube was
replaced with a glass stopper. Sodium (ca. 1.3 g) was added carefully
piece by piece into the liquid ammonia, and the mixture was stirred
for 10 min. The three-isomer mixture of phenanthrenophanes 1b (0.30
g, 0.65 mmol) and tert-butyl alcohol (2.6 mL) dissolved in dry THF
(26 mL) were added slowly, and the mixture was stirred for 30 min.
The excess sodium was destroyed by cautious addition of water. The
listing atomic and thermal parameters and bond lengths and
angles for exo,endo-1a, and H NMR spectra of 1a,b, and 5b
1
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