Synthesis, characterization, and molecular structure of [6](9,10)anthracenophane and its peri-substituted derivatives: The smallest 9,10-bridged anthracenes

Article abstract of DOI:10.1021/ja961562e

[6](9,10)Anthracenophane (1a) was synthesized by the benzoannelation method starting from dibromo[6]paracyclophane 6 via diepoxyanthracenophanes 3a and 4a. In a similar fashion, peri-substituted derivatives, tetramethyl (1b) and tetraphenyl (1c), were syn

Full text of DOI:10.1021/ja961562e

9488
J. Am. Chem. Soc. 1996, 118, 9488-9497
Synthesis, Characterization, and Molecular Structure of
[6](9,10)Anthracenophane and Its Peri-Substituted Derivatives:
The Smallest 9,10-Bridged Anthracenes
Yoshito Tobe,*,† Shinji Saiki,† Naoto Utsumi,† Takuji Kusumoto,† Hideaki Ishii,‡
Kiyomi Kakiuchi,‡ Kazuya Kobiro,§ and Koichiro Naemura†
Contribution from the Department of Chemistry, Faculty of Engineering Science, Osaka
UniVersity, Toyonaka, Osaka 560, Japan, Department of Applied Fine Chemistry, Faculty of
Engineering, Osaka UniVersity, Suita, Osaka 565, Japan, and Niihama National College of
Technology, Niihama, Ehime 792, Japan
ReceiVed May 9, 1996X
Abstract: [6](9,10)Anthracenophane (1a) was synthesized by the benzoannelation method starting from dibromo-
[6]paracyclophane 6 via diepoxyanthracenophanes 3a and 4a. In a similar fashion, peri-substituted derivatives,
tetramethyl (1b) and tetraphenyl (1c), were synthesized through the corresponding diepoxyanthracenes 3b, 4b, and
3c. Molecular structures of tetramethyldiepoxyanthracenophanes 3b and 5b are discussed with regard to the Mills-
Nixon effect on the basis of their X-ray structure analyses. The parent anthracenophane 1a is extremely air- and
acid-sensitive, so it is characterized spectroscopically as a mixture containing its dihydro derivative 8a. The peri-
substituted derivatives 1b and 1c are more stable than 1a, and are fully characterized by spectroscopic methods and
X-ray crystallographic analyses. X-ray structures reveal that the out-of-plane deformation angles of the bridged
aromatic ring of 1b and 1c are the largest observed in any short-bridged [n]cyclophanes. Semiempirical AM1
calculations indicate that the out-of-plane deformation of the aromatic rings 1b and 1c is more severe than that of
1a due to the steric repulsion between the benzylic methylenes and the peri substituents. That the kinetic stability
observed for 1b and 1c was greater than that of 1a is, therefore, ascribable to the steric protection of the reactive
bridgehead carbons by the peri substituents. Acid-catalyzed rearrangement of 1a-c gave the corresponding
methylenedihydro isomers 2a-c, which represent the first examples of bridged methylenedihydroanthracenes.
Photochemical isomerization of 1b and 1c took place readily, giving the corresponding Dewar anthracenes 11b and
11c. Thermal cycloreversion of 11b and 11c gave the cyclophanes 1b and 1c with Ea values of 22.3 and 25.4
kcal/mol, respectively.
Introduction
nophane and [6]anthracenophane and investigated their struc-
tures and unusual reactivities.5 Recently, the lower homologue
in the naphthalene series, a [5](1,4)naphthalenophane derivative,
was characterized below room temperature by Bickelhaupt.6 It
appears, therefore, that the kinetic stabilities of 1,4-bridged [n]-
naphthaleno- and anthracenophanes are similar to those of the
corresponding [n]paracyclophanes. However, in view of the
enhanced reactivity of the 9,10-positions of the anthracene ring
relative to that of the 1,4-positions, the kinetic stability of 9,10-
bridged [n]anthracenophane must be substantially diminished.
Indeed, the smallest known [8]anthracenophanes, the 2,7-diketo,7
3,6-diketo,8 and 2,7-dithia9 compounds, are sensitive to air
oxidation, although the bridged aromatic ring of these com-
The chemistry of short-bridged [n]cyclophanes has attracted
much interest in recent years because the lower limit of their
existence has been explored successfully and their extraordinary
structures and properties have been unveiled.1 The smallest
isolable representative among the series of [n]paracyclophanes
has been [6]paracyclophane,2 whereas the lower homologues,
[5]- and [4]paracyclophanes, were characterized by spectro-
scopic and chemical methods.3 By contrast, little has been
learned about condensed benzenoid cyclophanes, despite the fact
that the aromatic character of such a system would be more
sensitive to strain imposed by the short bridge.1d,4 We
synthesized the smallest isolable 1,4-bridged [6]naphthale-
(3) For [5]paracyclophane see: (a) Jenneskens, L. W.; de Kanter, F. J.
J.; Kraakman, P. A.; Turkenburg, L. A. M.; Koolhaas, W. E.; de Wolf, W.
H.; Bickelhaupt, F.; Tobe, Y.; Kakiuchi, K.; Odaira, Y. J. Am. Chem. Soc.
1985, 107, 3716. For [4]paracyclophane: (b) Tsuji, T.; Nishida, S. J. Chem.
Soc., Chem. Commun. 1987, 1189; (c) J. Am. Chem. Soc. 1988, 110, 2157.
(d) Kostermans, G. B. M.; Bobeldijk, M.; de Wolf, W. H.; Bickelhaupt, F.
Ibid. 1987, 109, 2471.
(4) Reiss, J. A. In Cyclophanes; Keehn, P. M., Rosenfeld, S. M., Eds.;
Academic Press: New York, 1983; Vol. 2, p 443.
(5) (a) Tobe, Y.; Takahashi, T.; Ishikawa, T.; Yoshimura, M.; Suwa,
M.; Kobiro, K.; Kakiuchi, K.; Gleiter, R. J. Am. Chem. Soc. 1990, 112,
8889. (b) Tobe, Y.; Takahashi, T.; Kobiro, K.; Kakiuchi, K. Ibid. 1991,
113, 5804. (c) Tobe, Y.; Takemura, A.; Jimbo, M.; Takahashi, T.; Kobiro,
K.; Kakiuchi, K. Ibid. 1992, 114, 3479.
† Department of Chemistry, Faculty of Engineering Science, Osaka
University.
‡ Department of Applied Fine Chemistry, Faculty of Engineering, Osaka
University.
§ Niihama National College of Technology.
X Abstract published in AdVance ACS Abstracts, September 15, 1996.
(1) For recent reviews see: (a) Bickelhaupt, F.; de Wolf, W. H. Recl.
TraV. Chim. Pays-Bas 1988, 107, 459. (b) Bickelhaupt, F.; de Wolf, W. H.
In AdVances in Strain in Organic Chemistry; Halton, B., Ed.; JAI Press:
Greenwich, CT, 1993; Vol. 3, p 185. (c) Kane, V. V.; de Wolf, W. H.;
Bickelhaupt, F. Tetrahedron 1994, 50, 4575. (d) Tobe Y. In Topics in
Current Chemistry; Weber, E., Ed.; Springer: Heidelberg, 1994; Vol. 172,
p 1.
(2) (a) Kane V. V.; Wolf, A. D.; Jones, M., Jr. J. Am. Chem. Soc. 1974,
96, 2643. (b) Kammula, S. L.; Iroff, L. D.; Jones, M., Jr.; van Straten, J.
W.; de Wolf, W. H.; Bickelhaupt, F. Ibid. 1977, 99, 5815. (c) Tobe, Y.;
Ueda, K. -I.; Kakiuchi, K.; Odaira, Y.; Kai, Y.; Kasai, N. Tetrahedron 1986,
42, 1851.
(6) van Es, D. S.; de Kanter, F. J. J.; de Wolf, W. H.; Bickelhaupt, F.
Angew. Chem., Int. Ed. Engl. 1995, 34, 2553.
(7) Ohta, M.; Tamura, S.; Okajima, T.; Fukazawa Y. 63rd Annual
Meeting of the Chemical Society of Japan, March 28-31, 1992; Abstract
No. 3B234.
S0002-7863(96)01562-4 CCC: $12.00 © 1996 American Chemical Society

Synthesis of [6](9,10)Anthracenophane
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9489
pounds is only slightly deformed from planarity.9d Moreover,
there exists another threat to the stability of the 9,10-bridged
anthracenes; the isomerization to methylenedihydro (isotoluene)
type tautomers. Rosenfeld observed such isomerization of
dithia[n](9,10)anthracenophanes with n ) 8-12 under basic
conditions,9c and predicted difficulties in synthesizing smaller
[n](9,10)anthracenophanes with n e 7 on the basis of MMX
and AM1 calculations.10 Specifically, the methylenedihydroan-
thracene isomer becomes substantially more favorable in the
thermodynamic sense than the anthracenophane structure as the
bridge becomes smaller than n ) 7. In light of these
considerations, we focused our attention on the [6](9,10)-
anthracenophane system as the next synthetic challenge. We
report here the synthesis and characterization of the smallest
known example of 9,10-bridged anthracene, extremely air- and
acid-sensitive [6](9,10)anthracenophane (1a).11a Moreover, we
describe the syntheses, structure determination, and isomeriza-
tion reactions of its kinetically stabilized derivatives 1b and 1c
bearing methyl or phenyl groups at the four peri positions,
respectively.11b We also report the first isolation of bridged
methylenedihydroanthracenes 2a-c, isotoluene type tautomers
of the respective anthracenophanes 1a-c.
Scheme 1
When dibromocyclophane 6 was treated with a large excess
of the mixed base NaNH2/NaOtBu14 in the presence of excess
furan at room temperature, three isomers of [4 + 2] cycloadducts
3a, 4a, and 5a were obtained in 17, 10, and 5% yields,
respectively (Scheme 1). Similarly, reaction of 6 in the presence
of 2,5-dimethylfuran afforded the tetramethyl derivatives 3b,
4b, and 5b in 12, 47, and 28% yields, respectively. However,
similar reaction of 6 with 2,5-diphenylfuran did not give the
corresponding [4+2] adducts, presumably because of the low
reactivity of the furan toward cycloaddition with the benzyne
intermediates. The reaction was therefore undertaken in re-
fluxing toluene using KOtBu as the base to yield adducts 3c
and 4c in 9 and 8% yields, respectively. The corresponding
anti,anti adduct 5c was not detected in this case. The stereo-
chemical assignments for the less symmetrical syn,anti isomers
4a-c were readily made on the basis of the NMR spectra. The
structures of syn,syn and anti,anti tetramethyl derivatives 3b
and 5b were unambiguously determined by the X-ray crystal
structure analyses (Figure 1). The structural details are dis-
cussed in the next section. The stereochemistries of the other
Results and Discussion
Syntheses. Because of the expected sensitivity of the central
ring of the small (9,10)anthracenophanes, we thought it would
be difficult to synthesize [6]anthracenophane 1a by introducing
the cyclophane structure of the central ring in the last stage of
the synthesis. We planned instead to start from a molecule
already having the [6]paracyclophane substructure and to
construct thereon the anthracene ring using bis-benzoannela-
tion.12 For the same reason, we also planned to prepare the
tetramethyl and tetraphenyl peri-substituted derivatives 1b and
1c in hope that the substituents would sterically protect the
reactive central ring of the anthracene core. Retrosynthetic
analysis revealed that 8,11-dibromo[6]paracyclophane (6)13
serves as the benzyne source to which 2-fold addition of furan
derivatives gives the diepoxyanthracenophanes 3a-5a and their
peri-substituted derivatives 3b-5b and 3c-5c, from which
reductive deoxygenation furnishes the corresponding anthra-
cenophanes 1a-c without touching the sensitive central ring.
1
products were deduced on the basis of the H NMR chemical
shifts of the bridge methylene protons Hb, Hd, and Hf. In the
case of syn,syn isomers 3a-c, these protons are expected to
suffer from steric compression by the fused oxanorbornadiene
units. Table 1 shows the 1H NMR chemical shifts of the
methylene protons (Ha-Hf) of 3a-c, 4a-c, and 5a,b and their
reference compound 72 measured at -50 °C. At this temper-
ature, the flipping of the methylene bridge is frozen on the NMR
time scale.15 The protons Hf of syn,syn isomers 3a-c are
shifted downfield from that of [6]paracyclophane (7) by more
(8) (a) Helder, R. Ph.D. Thesis, Rijksunversiteit te Groningen, 1974. (b)
Rosenfeld, S. M.; Sanford, E. M. Tetrahedron Lett. 1987, 28, 4775.
(9) (a) Chung, J.; Rosenfeld, S. J. Org. Chem. 1983, 48, 387. (b)
Rosenfeld, S.; Shedlow, A. M.; Kirwin, J. M.; Amaral, C. A. Ibid. 1990,
55, 1356. (c) Rosenfeld, S.; Sheldow, A. Ibid. 1991, 56, 2247. (d) Rosenfeld,
S.; Cheer, C. L. Acta Crystallogr. 1992, C48, 311.
(10) Rosenfeld, S. J. Org. Chem. 1993, 58, 7572.
(11) For preliminary reports of this work see: (a) Tobe, Y.; Ishii, H.;
Saiki, S.; Kakiuchi, K.; Naemura, K. J. Am. Chem. Soc. 1993, 115, 11604.
(b) Tobe, Y.; Utsumi, N.; Saiki, S.; Naemura, K. J. Org. Chem. 1994, 59,
5516.
(12) For bis-annelation of arenes using bis-aryne equivalents see: (a)
Hart, H.; Lai, C.; Nwokogu, G.; Shamouilian, S.; Teuerstein, A.; Zlotogorski,
C. J. Am. Chem. Soc. 1980, 102, 6651. (b) Raymo, F.; Kohnke, F. H.;
Cardullo, F.; Girreser, U.; Stoddart, J. F. Tetrahedron 1992, 48, 6827.
(13) Tobe, Y.; Jimbo, M.; Ishii, H.; Saiki, S.; Kakiuchi, K.; Naemura,
K. Tetrahedron Lett. 1993, 34, 4969.
(14) (a) Bachelet, J. -P.; Caubere, P. J. Org. Chem. 1982, 47, 234. (b)
Bachelet, J. -P.; Caubere, P. Acc. Chem. Res. 1974, 7, 301.
(15) The barriers for the flipping of the methylene bridge of 3a-c, 4a-
c, and 5a,b are listed in Table S17 of the supporting information.

9490 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Tobe et al.
Figure 1. X-ray structures of (a) syn,syn-diepoxy[6](9,10)anthracenophane 3b and (b) anti,anti-diepoxy[6](9,10)anthracenophane 5b.
Table 1. 1H NMR Chemical Shifts of Diepoxyanthracenophanes 3a-5a, 3b-5b, 3c, and 4c, and [6]Paracyclophane (7)a
compd
Ha
Hb
Hc
Hd
He
Hf
3ab
4a
5a
2.94
3.09, 2.76
2.87
2.98
3.09, 2.7
2.83
2.38
2.56, 1.97
2.08
2.62
2.7, 1.9
1.98
1.66
1.62 (2H)
1.43
1.75
1.59 (2H)
1.32
0.87
0.96, 0.31
0.22
0.88
0.90, 0.21
0.15
1.20
1.21, 0.96
0.85
1.35
1.23, 0.90
0.82
-0.01
0.31, -0.67
-0.48
3b
4b
-0.07
0.35, -0.63
-0.49
5bb,c
3cd
4cd
7f
1.73
1.39
1.39
0.77
1.12
0.35
nde
nde
nde
nde
nde
0.35, -0.24
-0.62
2.79
1.97
1.58
0.51
1.06
a Measured in CDCl3 at -50 °C unless otherwise stated. b Measured in CD2Cl2. c Measured at -80 °C. d Measured in toluene-d8. e Not determined
because of ill separation of the signals. f Reference 5a.
Scheme 2
than 0.5 ppm due to steric compression by the oxygen atoms.16
Similarly, Hd protons of 3a and 3b are shifted downfield by
about 0.35 ppm for the same reason. Moreover, the benzylic
protons Hb of 3a and 3b are observed at a lower field than that
of 7 by 0.41 and 0.65 ppm, respectively, because of the steric
compression by the bridgehead hydrogen (for 3a) and the methyl
group (for 3b). By contrast, such apparent shift is not observed
for the methylene protons of anti,anti isomers 5a,b; the chemical
shifts of 5a,b are similar to those of the corresponding protons
of 7. The small (0.2-0.3 ppm) upfield shifts of Hd and He
can be ascribed to the shielding effect16 exerted by the double
bond of the oxanorbornadiene units. Half of the methylene
protons of syn,anti isomers 4a and 4b are shifted downfield,
while the chemical shifts of the other half are similar to those
of anti,anti isomers 5a,b, in accord with the above assignments.
The relative yields of the furan adducts seem to be dependent
on the steric effect of the peri substituents; the more sterically
crowded the substituents are, the more anti isomers are formed.
The reason for the absence of anti,anti isomer 5c is not clear,
however.
cenophane 1b was stable to air but sensitive to acid; even trace
amounts readily induced its isomerization to 2b. For example,
chromatography of the above deoxygenation products on
untreated silica gel or alumina yielded only 2b, and no 1b.
Deoxygenation of 3c as described above afforded tetra-
phenylanthracenophane 1c (yellow-orange solid; mp 310-311
°C) in 58% yield. This anthracenophane is much more stable
in the presence of acid than tetramethyl 1b; treatment of a CDCl3
solution of 1c with a large excess of TFA induced slow
isomerization of 1c to 2c.
After screening several reagents for the reductive deoxygen-
ation using tetramethyl derivatives 3b-5b, we found that low-
valent titanium reagents were most effective. Thus, treatment
of a mixture of 3b-5b with the titanium reagents prepared from
TiCl4, LiAlH4, and triethylamine (TEA) (7:2.5:25)17 furnished
anthracenophane 1b (yellow solid; mp 161-162 °C) in 68%
yield. The use of a large excess of TEA was essential; otherwise
variable amounts of methylenedihydro isomer 2b and the
dihydro derivative 8b were formed (Scheme 2). Anthra-
(16) Jackman, L. M.; Sternhell, S. Applications of Nuclear Magnetic
Resonance Spectroscopy in Organic Chemistry, 2nd ed.; Pergamon Press:
Oxford, 1969.
(17) (a) Xing, Y. D.; Huang, N. Z. J. Org. Chem. 1982, 47, 140. (b)
Wong, H. N. C. Acc. Chem. Res. 1989, 22, 145.
Reduction of a mixture of 3a and 4a under similar conditions
followed by aqueous workup furnished methylenedihydro
isomer 2a and dihydro derivative 8a in a ratio of 1:2. However,
when the reaction mixture was worked up by being directly

Synthesis of [6](9,10)Anthracenophane
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9491
Table 2. 1H NMR Chemical Shifts of Anthracenophanes 1a-c
and the Corresponding Anthracene Derivatives 10a-c
Table 3. Barriers for the Flipping of the Methylene Bridge of
Anthracenophanes 1a-c and 9
compd Ha Hb Hc
Hd
He
Hf
Hg Hh Hi Hj
peri
∆Gq (298 K)
peri
∆Gq (298 K)
compd substituent (kcal/mol) compd substituent (kcal/mol)
1aa 3.39 2.90 1.43 0.42 0.67 -1.84 7.95 8.05 7.23 7.16
1bb 3.74 2.73 1.47 0.05 0.79 -1.83
1cc 1.68 1.68 0.83 -0.21 0.51 -2.10
7.03 7.03
7.45 7.45
8.51 8.51 7.51 7.51
7.14 7.14
1a
1b
H
Me
13.7a
1c
9
Ph
10.1 (233)b
13.3c
9.5 (217)b
10ad
a Determined by the line-shape analysis. b Determined from the
coalescence temperauture (given in parentheses) and ∆ν values for the
most-shielded protons Hf. c The ∆Gq estimated from the coalescence
temparature (268 K) was 13.4 kcal/mol (ref 5a).
10be
10cf
7.42 7.42
a Measured in toluene-d8 at -50 °C. b Measured in CD2Cl2-CS2 (1:
1) at -110 °C. Methyl protons: δ 2.80 and 2.73 ppm. c Measured in
CD2Cl2-CS2 (1:1) at -110 °C. Phenyl protons: δ 7.70, 7.47, and 7.34
ppm. d Measured in CDCl3 at 30 °C. Methyl protons: δ 3.10 ppm.
e Measured in CDCl3 at 30 °C. Methyl protons: δ 2.93 (6H) and 2.83
Table 4. Absorption Maxima in the UV-vis Spectra of
Anthracenophanes 1a-c and the Corresponding Anthracene
Derivatives 10a-ca
f
(12H) ppm. Measured in C6D6-CD2Cl2 (9:1) at 0 °C. Phenyl protons:
λ
max (nm) (log ꢀ)
compd
δ 7.46, 7.28, and 7.14 ppm. Methyl protons: 1.78 ppm.
1ab,c
1b
435
415
392 (sh)
passed through deactivated alumina in a nitrogen atmosphere,
455 (3.63)
482 (3.71)
398 (3.67)
260 (5.83)
426 (3.58)
453 (3.62)
289 (4.70)
456 (3.67)
377 (3.67)
252 (5.51)
415 (3.52)
427 (3.60)
we obtained a hydrocarbon fraction revealed by the 1H and 13
C
1c
299 (4.44)
358 (3.44)
10ac
341 (3.12)
276 (4.67)
NMR spectra (toluene-d8, -50 °C) to be a 3:2 mixture of 1a
1
and dihydro 8a. In the H NMR spectra, the most-shielded
10bd
10ce
404 (3.60)
291 (4.35)
methylene protons (Hf) appear at δ -1.84; the chemical shift
is similar to that of the corresponding protons of [6](1,4)-
anthracenophane (9; δ -1.81 in CD2Cl2).5a The 13C NMR
a Measured in cyclohexane unless otherwise stated. b Extinction
coefficient was not determined. c Measured in hexane. d References 20
and 21a. e References 20 and 21b.
anthracenes 10a-c. The measurements for 1a-c were under-
taken at low temperature where the flipping of the methylene
bridge is frozen. The assignments for the protons of 1a-c were
done on the basis of 2D NMR spectra. Taking into account
the difference of the solvent,19 the chemical shifts of the aromatic
protons of 1a-c are similar to those of the corresponding model
compounds 10a, 10b,20 and 10c,20 indicating little effect from
strain imposed by the short bridge on the ring current of 1a-c.
Similarly, given the difference of the solvent, the chemical shifts
of the methylene protons of 1a and 1b are quite similar. By
contrast, the methylene protons Ha, Hb, Hc, and Hd of 1c are
remarkably shifted upfield from the corresponding protons of
1a and 1b, owing to the anisotropic shielding effect of the phenyl
groups at the peri positions. The proton Hf of 1b (δ -1.83)
and 1c (δ -2.10), which suffer from the largest shielding effect
of the anthracene ring, appear at the region similar to that of
1a.
The barrier for the flipping of the methylene bridge of 1a-c
is summarized in Table 3. The barrier for 1a (13.7 kcal/mol)
is as large as that of 1,4-bridged anthracene 9 (13.3 kcal/mol),5a
but is considerably larger than those of 1b and 1c. The
flexibility of the methylene bridge might be related to the
distance between the two benzylic positions; the shorter the
distance, the more flexible the bridge must be. Therefore, the
above observations indicate that the out-of-plane deformation
of the bridged aromatic ring of 1b and 1c is larger than that of
parent 1a (i.e., a shorter distance between the benzylic carbons),
despite that 1b and 1c are kinetically more stable than 1a.
Absorption maxima of anthracenophanes 1a-c and their
corresponding reference compounds 10a-c are listed in Table
4. The longest wavelength absorption of 1a exhibits a remark-
able bathochromic shift (0.26 eV) in comparison with that of
10a, indicating a severe out-of-plane deformation of the
anthracene ring of 1a. The bathochromic shifts of the longest
wavelength absorptions of 1b (0.19 eV) and 1c (0.17 eV)
spectrum (-50 °C) exhibited nine signals for 1a (135.6 (s),
133.2 (s), 125.6 (d), 125.0 (d), 124.9 (d), 124.5 (d), 34.2 (t),
33.7 (t), 25.8 (t) ppm)18 along with seven signals for 8a. The
electronic spectrum of the product containing 1a shows absorp-
tion maxima at 435, 415, and 392 (sh) nm in hexane (see also
Table 4) which are characteristic of the anthracene chromophore,
although the absorptions are long-wavelength-shifted and struc-
tureless. Treatment of a mixture of 1a and 8a (3:2) with silica
gel in nitrogen immediately yielded a mixture of 2a and 8a
(1:2). These results strongly indicate that the unstable species
possesses the anthracenophane structure of 1a. We were not
able to purify the parent hydrocarbon 1a because of its extremely
high reactivity. By contrast, it appeared that tetramethyl
derivative 1b is fairly stable and tetraphenyl derivative 1c even
more stable; thus, the steric protection of the reactive central
ring by the peri substituents effectively enhanced the kinetic
stabilities as we expected.
The isomerization products 2a-c represent the first examples
of bridged methylenedihydroanthracenes observed under basic
conditions.9b,c The parent hydrocarbon 2a and the tetramethyl
derivative 2b are not very stable in air. By contrast, tetraphenyl
2c is very stable again due to steric protection of the reactive
bridgehead double bond by the phenyl groups. The vinyl proton
of 2c appears at δ 5.27, which, when compared to the
corresponding proton of 2a, is shifted upfield by 0.46 ppm due
to the shielding effect of one of the phenyl groups at the peri
positions.
(19) It is well known that an aromatic solvent causes an upfield shift by
more than 0.5 ppm relative to chloroform; see p 104 of ref 16.
(20) The reference compounds 10b21a and 10c21b were prepared by the
same bis-benzoannelation method as that used for the syntheses of
anthracenophanes 1b and 1c.
(21) (a) Hart, H.; Nwokogu, G. J. Org. Chem. 1981, 46, 1251. (b)
Dickerman, S. C.; Haase, J. R. J. Am. Chem. Soc. 1967, 89, 5458.
Table 2 lists the 1H NMR chemical shifts of anthracenophanes
1a-c and the corresponding 9,10- and 1,4,5,8,9,10-substituted
(18) The signals for the secondary and tertiary carbons which overlapped
with the solvent peaks were found by the DEPT experiments. One of the
quaternary carbon signals of 1a, however, has not been found yet.

9492 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Tobe et al.
of the reported examples,22,23 while the angles between the
benzeno and etheno bridges (108.9° and 109.5°) are smaller
than those reported. In the case of 5b, by contrast, short
nonbonded contacts are observed between the benzylic hydro-
gens and only one of the methyl hydrogens, because the methyl
groups are directed downward from the base plane of the
benzene ring; the distances H1‚‚‚H20, H2‚‚‚H23, H11‚‚‚H17,
and H12‚‚‚H26 are less than or close to the sum of the van der
Waals radii (2.19-2.55 Å). As a result, the oxanorbornadiene
units of 5b are not deformed from their normal structure (Figure
2). The bond distances for the benzene ring of 3b and 5b are
also shown in Figure 2. The average lengths of the bridged
aromatic bonds (C7-C8, C7-C20, C13-C14, and C14-C15)
of 3b (1.400 Å) and 5b (1.397 Å) are longer than those of the
edge bonds C8-C13 and C15-C20 (3b, 1.388 Å; 5b, 1.381
Å). The observed bond lengths are typical of the [6]paracy-
clophane structures, in which the bridged aromatic bonds are
longer than those of the edge bonds due to an unfavorable
overlap of p orbitals.24 On the other hand, the edge bonds would
grow longer than the bridged bonds if the contribution of the
bond fixation due to the Mills-Nixon effect were important.22,23
It is thus deduced that the deformation of the aromatic bond
lengths is mainly due to the out-of-plane bending, and that the
Mills-Nixon effect is not important in these systems.
Table 5. Deformation Angles Determined by X-ray Crystal
Structure Analyses of Anthracenophanes 1b and 1c and
Diepoxyanthracenophanes 3b and 5b
(A/B)
(B/C)
(deg)d
compd R (deg)a â (deg)b R + â (deg)
(deg)c
1b
1c
3b
5b
24.7
23.0
19.8
20.5
18.5
19.8
20.9
20.4
43.2
42.9
40.7
40.9
9.3
3.1
11.4
1.7
a Average out-of-plane bent angle of the para carbons. b Average
out-of-plane bending angle of the benzylic carbons. c Bending angle
of ring A relative to the base plane of ring B. d Bending angle of ring
C relative to the base plane of ring B.
Molecular structures of 1b and 1c, determined by X-ray
crystallographic analyses, are shown in Figures 3 and 4,
respectively. The lengths of the bridged aromatic bonds (C7-
C8, C7-C20, C13-C14, and C14-C15; average distances: 1b,
1.422 Å; 1c, 1.418 Å) are longer than those of anthracene itself25
because of the poor overlap of the p orbitals due in turn to the
short bridge. However, the other bond distances are similar to
those of anthracene, indicating little perturbation of the electronic
structure of the condensed aromatic ring by the hexamethylene
bridge. Table 5 lists the deformation angles of the bridged
aromatic ring of 1b and 1c. The internal torsion angles of the
central rings of 1b are -25.8°, -3.8°, -30.6°, 27.8°, 1.8°, and
28.6°, and those for 1c are -25.9°, -1.0°, -26.8°, 26.0°, 0.7°,
and 26.8°. The out-of-plane deformation angles (R and â) of
1b and 1c are similar, when the experimental error is taken into
account; the sum of the deformation angles (R + â) of 1b (43.2°)
and 1c (42.9°) represents the largest deformation angle observed
in any small-bridged [n]cyclophane.1d Just as in the anti,anti
isomer of diepoxyanthracenophane 3b, there are short non-
bonded contacts between the benzylic hydrogens and one of
the hydrogens of the methyl groups of tetramethylanthra-
cenophane 1b; the distances H1‚‚‚H7, H2‚‚‚H23, H11‚‚‚H17,
and H12‚‚‚H26 are less than or close to the sum of the van der
Waals radii (2.19-2.44 Å). Likewise, short nonbonded dis-
tances are observed in 1c between the benzylic hydrogens and
the phenyl carbons (H1‚‚‚C27 ) 2.48 Å, H2‚‚‚C33 ) 2.48 Å,
H11‚‚‚C21 ) 2.37 Å, and H12‚‚‚C39 ) 2.46 Å). The aromatic
rings A and C are slightly deformed from planarity (deviations
from the respective mean planes are 0.012 and 0.009 Å for 1b
and 0.024 and 0.023 Å for 1c) to reduce the nonbonded
repulsion. In tetraphenyl derivative 1c, the twist angles between
ring A and the peri-attached phenyl rings D and E are 47.7°
and 55.3°, respectively, and those between ring C and rings F
and G are 62.9° and 45.7°, respectively. A notable difference
Figure 2. Representative dihedral angles (deg) and bond lengths (Å)
of the aromatic ring of (a) syn,syn-diepoxy[6](9,10)anthracenophane
3b and (b) anti,anti-diepoxy[6](9,10)anthracenophane 5b.
relative to the corresponding reference compounds 10b and 10c
are smaller than that of 1a. This is ascribed to the distortion
already present in the reference compounds 10b and 10c due
to the peri interaction between the substituents.
Molecular Structures. X-ray crystallographic structure
analyses of tetramethyldiepoxyanthracenophanes 3b and 5b
(Figure 1) were undertaken not only to determine their stere-
ochemistry, but also to observe the effects of the fusion of the
strained oxanorbornadiene units on the structure of the [6]-
paracyclophane core.22 Out-of-plane deformation angles of the
benzene ring (R and â) are listed in Table 5. The deformation
angles of 3b and 5b are nearly 20°, which are within the range
of those observed for the other [6]paracyclophane derivatives.1d
There are many short nonbonded contacts between the bridge
methylene and the oxanorbornadiene units, both in 3b and 5b,
and particularly between the benzyl methylene and methyl
groups. Thus, in 3b, the following are less than or close to the
sum of van der Waals radii (2.26-2.48 Å): H1‚‚‚H20, H1‚‚‚
H21, H2‚‚‚H23, H2‚‚‚H24, H11‚‚‚H17, H11‚‚‚H18, H12‚‚‚H26,
and H12‚‚‚H27. Since the methyl groups of 3b are inclined
upward from the base plane of the benzene ring (C8-C13-
C15-C20), each benzylic hydrogen is affixed by the two methyl
hydrogens. As a result of the nonbonded repulsion, the
oxanorbornadiene units are considerably deformed, as shown
in Figure 2. The dihedral angles between the oxygen bridge
and the benzeno bridge (124.6° and 124.2°) are larger than those
(23) (a) Hart, H.; Raju, N.; Meador, M. A.; Ward, D. L. J. Org. Chem.
1983, 48, 4357. (b) Kohnke, F. H.; Stoddart, J. F.; Slawin, A. M. Z.;
Williams, D. J. Acta Crystallogr. 1988, C44, 738. (c) Ibid. 1988, C44, 742.
(24) (a) Lee, T. J.; Rice, J. E.; Allen, W. D.; Remington, R. B.; Schaefer,
H. F., III. Chem. Phys. 1988, 123, 1. (b) Gready, J. E.; Hambley, T. W.;
Kakiuchi, K.; Kobiro, K.; Sternhell, S.; Tansey, C. W.; Tobe, Y. J. Am.
Chem. Soc. 1990, 112, 7357. (c) Tobe, Y.; Sorori, T.; Kobiro, K.; Kakiuchi,
K.; Odaira, Y. J. Phys. Org. Chem. 1996, 9, 1.
(22) For the effect of the fusion of oxanorbornadiene units on the structure
of a benzene ring with regard to the Mills-Nixon effects see: Cardullo,
F.; Giuffrida, D.; Kohnke, F. H.; Raymo, F. M.; Stoddart, J. F.; Williams,
D. J. Angew. Chem., Int. Ed. Engl. 1996, 35, 339.
(25) Mason, R. Acta Crystallogr. 1964, 17, 547.

Synthesis of [6](9,10)Anthracenophane
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9493
Figure 3. (a) Top view and (b) side view of the X-ray structure of tetramethyl[6](9,10)anthracenophane 1b.
Figure 4. (a) Top view and (b) side view of the X-ray structure of tetraphenyl[6](9,10)anthracenophane 1c.
Table 6. AM1-Calculated Geometries of Anthracenophanes 1a-c
between the structures of the anthracene rings of 1b and 1c is
the set of dihedral angles between the base plane of the bridged
ring B (C8-C13-C15-C20) and the mean planes of rings A
and C. That is, the tilt angles of rings A and C with respect to
the base plane of ring B of 1b are 9.3° and 11.4°, respectively,
while those of 1c are 3.1° and 1.7°; the bending of the
anthracene ring of 1b along its long axis is substantially larger
than that of 1c.
Since the parent hydrocarbon 1a is too unstable for X-ray
structure determination, we carried out AM1 calculations26 for
1a-c to evaluate the effect of the peri substituents on the
geometries and energies of these anthracenophanes. The
calculated out-of-plane bending angles (R and â) and heats of
formation of 1a-c and 1,4-bridged anthracene 9 are listed in
Table 6. The calculated deformation angles (R and â) for 1b
and 1c are qualitatively in good agreement with the observed
values, though this semiempirical method tends to overestimate
the angle R. While the angles R and â of 1a are similar to
and 9 and Heats of Formation of 1a-c, 9, and Their
Methylenedihydro Isomers 2a-c
compd
R (deg)a
â (deg)b
R + â (deg)
∆Hf° (kcal/mol)
1a
1b
1c
9
2a
2b
2c
25.6
28.8
27.9
25.4
16.1
14.8
15.0
16.0
41.7
43.6
42.9
41.4
68.4
50.0
187.9
66.0
49.4
24.2
164.0
a Average out-of-plane flip angle of the para carbons. b Average out-
of-plane bending angle of the benzyl carbons.
those of 1,4-bridged anthracenophane 9, the calculated as well
as observed values for 1b and 1c are considerably larger than
those for 1a and 9, indicating that the greater deformation in
1b and 1c is due to the additional steric interaction between
the benzylic methylene of the bridge and the peri substituents.
Similarly, the thermodynamic stability of 1a-c, estimated from
comparison of their calculated heats of formation with those of
their corresponding methylenedihydro isomers 2a-c, reveals
(26) Dewar, M. J. S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J. J. P. J.
Am. Chem. Soc. 1985, 107, 3902.

9494 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Tobe et al.
that 1b and 1c are less stable than 1a, as will be described. On
the other hand, in spite of the greater deformations of the
aromatic ring due to the peri interactions, the observed kinetic
stabilities of 1b and 1c are remarkably larger than that of the
parent 1a. The side views of the molecular structures of 1b
and 1c (Figures 3b and 4b) clearly show how the substituents
attached to the peri positions protect the reactive bridgehead
carbons (C7 and C14) from attack of electrophilic reagents,
particularly in the case of 1c.
THF-d8 solvent resulted in the quantitative formation of the
Dewar isomer 11b. Similarly, irradiation (λ > 360 nm) of a
benzene solution of 1c gave the Dewar isomer 11c (quantitative
by NMR). The structures of 11b and 11c were readily assigned
on the basis of the NMR spectra, in particular by the presence
of the signals due to the quaternary carbon in the 13C NMR
spectra (δ 66.2 for 11b and δ 67.8 for 11c).
Thermal cycloreversion of 11b and 11c took place quanti-
tatively to afford the corresponding anthracenophanes 1b and
1c. The rates of cycloreversion 11b (in cyclohexane) and 11c
(in toluene) were measured to give the following activation
parameters: 11b, ∆Hq ) 21.7 kcal/mol, ∆Sq ) -1.5 cal/(deg
mol), Ea ) 22.3 kcal/mol; 11c, ∆Hq ) 24.9 kcal/mol, ∆Sq )
3.4 cal/(deg mol), Ea ) 25.4 kcal/mol. Whereas the activation
enthalpies for the cycloreversion of 11b and 11c are within the
range of those reported for the Dewar 9,10-anthracenes,31 the
value for the reaction of 11c is larger than that of 11b. This
might be because a larger geometrical change is required for
the isomerization of 11c compared for that of 11b.
Reactions. Parent hydrocarbon 1a is highly sensitive to air;
exposure of a solution of 1a immediately yielded an unchar-
acterized polymeric material. By contrast, the peri-substituted
derivatives 1b and 1c are stable in the presence of air. Acid-
catalyzed isomerization of 1a was affected by silica gel to give
the isotoluene type isomer 2a. Tetramethyl 1b is also sensitive
to acid; isomerization to 2b took place upon treatment with
untreated silica gel or a catalytic amount of TFA. On the other
hand, tetraphenyl 1c is much more stable with acid; isomer-
ization to 2c took place slowly in the presence of excess TFA.
The increasing kinetic stability in the sequence of 1a < 1b <
1c is ascribed to the steric protection of the reactive bridgehead
carbons (C7 and C14) by the peri substituents. It has been
documented that isomerization of highly peri-substituted 9,10-
dimethylanthracene derivatives readily took place to give the
corresponding methylenedihydroanthracenes.21,27 The reaction,
which is inherently endothermic for 9-methylanthracene itself,28
is driven by release of nonbonded interactions between the peri
substituents at the expense of aromatic stabilization. Table 6
lists the AM1-calculated heats of formation of 2a-c and the
energies relative to the corresponding anthracenophanes 1a-c.
As shown in Table 6, isomerization of 1a to 2a is highly
exothermic by 19 kcal/mol. Moreover, isomerization of 1b and
1c to the corresponding isomers 2b and 2c is energetically more
faVorable, despite 1b and 1c being less reactive experimentally
than 1a toward isomerization.
Conclusion
The smallest 9,10-bridged anthracenophanes 1a-c were
synthesized. Although the parent hydrocarbon 1a was too
unstable for isolation, its peri-substituted derivatives 1b and 1c
were fully characterized. X-ray crystallographic structure
analyses of 1b and 1c reveal that the out-of-plane deformation
angles of the bridged aromatic ring are the largest observed in
any small-bridged [n]cyclophanes. Conformational behavior,
semiempirical AM1 calculations, and X-ray analyses indicate
that 1b and 1c are more strained than 1a due to the steric
interaction between the benzylic methylenes and the peri
substituents. On the other hand, the peri-substituted derivatives
1b and 1c are kinetically more stable than the parent 1a, due to
the steric protection of the reactive bridgehead carbons of the
central ring. As a result of the severe deformation of the
aromatic ring, the anthracenophanes 1a-c undergo unusual
reactions, such as acid-catalyzed rearrangement to the corre-
sponding methylenedihydro isomers 2a-c, which represent the
first examples of bridged methylenedihydroanthracenes, and
thermally reversible photochemical isomerization to the corre-
sponding Dewar anthracenes 11b and 11c.
It has been well documented that [6]paracyclophane (7) and
its derivatives undergo photochemical valence isomerization to
their corresponding Dewar isomers.1d,29 Cycloreversion of the
Dewar isomers to the cyclophanes takes place both thermally
and photochemically. It is equally well known that sterically
crowded anthracene derivatives undergo thermally reversible
photochemical isomerization to give Dewar 9,10-anthracenes.27a,30
It may well be anticipated, therefore, that 9,10-bridged anthra-
cenophanes 1b and 1c would undergo photochemical isomer-
ization to the corresponding Dewar anthracenes 11b and 11c.
Experimental Section
Analytical HPLC was carried out with a Shimadzu LC-10AS
chromatograph equipped with a Inertsil ODS column, and preparative
HPLC separation was performed with a JAI LC-908 chromatograph
equipped with JAIGEL 1H and 2H. NMR, IR, UV-vis, and mass
spectra were taken with JEOL JNM-MH-270, Hitachi 260-10, Hitachi
220A, and JEOL JMS-DX-303-HF spectrometers, respectively. X-ray
diffraction data were collected on a Rigaku AFC-7R diffractometer
with Mo KR radiation.
Diepoxy[6](9,10)anthracenophanes 3a, 4a, and 5a. To a suspen-
sion of 1.68 g (43.1 mmol) of sodium amide in 5.0 mL of THF was
added dropwise 1.02 g (13.8 mmol) of tert-butyl alcohol under a
nitrogen atmosphere, and the mixture was heated at 40 °C for 2 h. The
mixture was cooled in an ice bath, and a solution of dibromocyclophane
613 (305 mg, 0.954 mmol) in 6.7 mL (95 mmol) of furan was added
dropwise. The mixture was allowed to warm to room temperature and
stirred for 15 h before it was poured into ice-water. The mixture was
Indeed, irradiation of a solution of 1b in a mixed benzene-d6/
(27) (a) Hart, H.; Ruge, R. Tetrahedron Lett. 1977, 3143. (b) Bowden,
B. F.; Cameron, D. W. J. Chem. Soc., Chem. Commun. 1977, 78.
(28) Bartmas, J. E.; Griffith, S. S. J. Am. Chem. Soc. 1990, 112, 2931.
(29) For more recent reports on the valence isomerization of [6]-
paracyclophanes see: (a) Miki, S.; Shimizu, R.; Nakatsuji, H. Tetrahedron
Lett. 1992, 33, 953. (b) Gleiter R.; Treptow, B. J. Org. Chem. 1993, 58,
7740. (c) Frank, I.; Grimme, S.; Peyerimhoff, S. D. J. Am. Chem. Soc.
1994, 116, 5949. (d) Dreeskamp, H.; Sarge, S. M.; Tochtermann, W.
Tetrahedron Lett. 1995, 51, 3137.
(30) (a) Gu¨sten H.; Mintas, M.; Klasinc, L. J. Am. Chem. Soc. 1980,
102, 7936. (b) Dreeskamp, H.; Jahn, B.; Pabst, J. Z. Naturforsch. 1981,
36a, 665. (c) Jahn, B.; Dreeskamp, H. Ber. Bunsen-Ges. Phys. Chem. 1984,
88, 42. (d) Kraljic, I.; Mintas, M.; Klasinc, L.; Ranogajec, F.; Gu¨sten, H.
NouV. J. Chim. 1983, 7, 239. (e) Meador, M. A.; Hart, H. J. Org. Chem.
1989, 54, 2336. For a review see: (f) Becker, H.-D. Chem. ReV. 1993, 93,
145.
(31) (a) Pritschins, W.; Grimme, W. Tetrahedron Lett. 1979, 4545. (b)
Ibid. 1982, 23, 1151.

Synthesis of [6](9,10)Anthracenophane
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9495
extracted with ether-dichloromethane (2:1). The extract was washed
with 10% HCl, dried (MgSO4), and evaporated. The products were
separated by flash chromatography on silica gel to afford 63 mg (22%)
of 3a, 68 mg (24%) of 4a, and 10 mg (3.6%) of 5a, which were
recrystallized from hexane-ether.
2H), -0.6 to -0.4 (m, 2H); 13C NMR (CDCl3, -40 °C) δ 154.8 (br
s), 150.7 (br s), 145.8 (br d), 144.3 (br d), 132.0 (s), 89.3 (br s), 88.9
(br s), 32.4 (t), 30.6 (t), 23.0 (t), 18.1 (br q), 17.6 (br q); IR (KBr)
1375, 1295, 1150, 1130, 1110, 870, 860, 750 cm-1; UV λmax (CHCl3)
327 (log ꢀ 2.46), 257 (4.30) nm; MS m/z (relative intensity) 348 (M+,
100). Anal. Calcd for C24H28O2: C, 82.71; H, 8.09. Found: C, 82.54;
H, 8.19.
Tetraphenyldiepoxy[6](9,10)anthracenophanes 3c and 4c. To a
suspension of 1.56 g (16.8 mmol) of potassium tert-butoxide in 4.0
mL of toluene was added a solution of 1.95 g (8.88 mmol) of 2,5-
diphenylfuran32 in 14 mL of toluene followed by 533 mg (1.68 mmol)
of dibromocyclophane 6 in 6 mL of the same solvent. The mixture
was heated at 120 °C for 3 days. The mixture was worked up as
described above except that most of excess diphenylfuran was removed
by sublimation prior to chromatography on silica gel. Final purification
of the products was done by preparative HPLC to afford 89 mg (9%)
of 3c and 75 mg (8%) of 4c, which were recrystallized from hexane-
ether.
syn,syn-3c: white solid; mp 261-262 °C; 1H NMR (toluene-d8, -50
°C) δ 8.06 (m, 4H), 7.46 (m, 4H), 6.0-7.2 (m, 16H), 1.73 (dd, J )
12.7, 5.5 Hz, 2H), 1.39 (m, 4H), 1.12 (m, 2H), 0.77 (m, 2H), 0.35 (m,
2H); 13C NMR (toluene-d8, 90 °C) δ 154.7 (br s, hardly discernible at
this temperature but splits into two peaks at 157.1 and 152.3 ppm at
-50 °C), 148.7 (d), 139.0 (s), 131.6 (s), 128.6 (d), 127.9 (d), 126.6
(d), 95.0 (s), 35.6 (t), 28.6 (t), 27.1 (t); IR (KBr) 1305, 1010, 900, 740,
700 cm-1; UV λmax (CHCl3) 333 (log ꢀ 2.75), 264 (4.36) nm; FAB MS
m/z (relative intensity) 597 (M+ + 1, 100); HRMS calcd for C44H36O2
596.2715, found 596.2735.
1
syn,syn-3a: white solid; mp 203-205 °C; H NMR (CD2Cl2, -50
°C) δ 7.06 (dd, J ) 5.5, 1.5 Hz, 2H), 7.05 (dd, J ) 5.4, 1.8 Hz, 2H),
5.72 (s, 2H), 5.67 (s, 2H), 2.94 (dd, J ) 13.2, 4.8 Hz, 2H), 2.38 (ddd,
J ) 12.7, 12.7, 5.6 Hz, 2H), 1.6-1.7 (m, 2H), 1.1-1.3 (m, 2H), 0.87
(tt, J ) 13.0, 6.0 Hz, 2H), -0.1 to +0.1 (m, 2H); 13C NMR (CDCl3,
-40 °C) δ 154.0 (s), 149.8 (s), 143.8 (d), 143.6 (d), 132.0 (s), 81.4
(d), 81.2 (d), 33.2 (t), 31.3 (t), 25.0 (t); IR (KBr) 1290, 1030, 1010,
870, 850, 760, 745 cm-1; UV λmax (CHCl3) 250 (log ꢀ 4.36) nm; MS
m/z (relative intensity) 292 (M+, 100). Anal. Calcd for C20H20O2: C,
82.15; H, 6.89. Found: C, 82.15; H, 7.05.
1
syn,anti-4a: white solid; mp 195 °C dec; H NMR (CDCl3, -50
°C) δ 7.18 (dd, J ) 5.4, 1.9 Hz, 1H), 7.14 (d, J ) 1.2 Hz, 2H), 7.04
(dd, J ) 5.2, 1.7 Hz, 1H), 5.85 (s, 2H), 5.80 (s, 1H), 5.69 (s, 1H), 3.09
(dd, J ) 12.9, 5.0 Hz, 1H), 2.76 (br d, J ) 8.2 Hz, 1H), 2.5-2.7 (m,
1H), 1.97 (ddd, J ) 12.9, 12.4, 4.9 Hz, 1H), 1.5-1.7 (m, 2H), 1.1-
1.3 (m, 1H), 0.9-1.1 (m, 2H), 0.2-0.4 (m, 2H), -0.8 to -0.6 (m, 1H);
13C NMR (CDCl3, -40 °C) δ 152.9 (s), 151.4 (s), 149.1 (s), 146.3 (s),
143.6 (d), 143.5 (d), 142.1 (d), 140.2 (d), 132.8 (s), 132.3 (s), 81.5 (d),
81.3 (d), 81.2 (d), 81.1 (d), 32.8 (t), 32.7 (s), 31.7 (s), 31.1 (t), 25.0 (t),
22.4 (t); IR (KBr) 1280, 1030, 1000, 860, 740 cm-1; UV λmax (CHCl3)
323 (log ꢀ 2.63), 252 (4.33) nm; MS m/z (relative intensity) 292 (M+,
100); HRMS calcd for C20H20O2 292.1463, found 292.1449.
1
anti,anti-5a: white solid; mp 192-194 °C dec; H NMR (CDCl3,
syn,anti-4c: white solid; mp 218-220 °C; 1H NMR (toluene-d8, 90
°C) δ 7.7-7.8 (m, 8H), 6.9-7.3 (m, 16H), 1.82 (m, 4H), 0.95 (m,
2H), 0.80 (m, 4H), 0.50 (m, 2H); 13C NMR (toluene-d8, 90 °C) δ 156.0
(br s, hardly discernible at this temperature but splits into two peaks at
157.1 and 153.6 ppm at -50 °C), 154.2 (br s, hardly discernible at
this temperature but splits into two peaks at 156.2 and 151.3 ppm at
-50 °C), 148.8 (d), 144.6 (d), 138.9 (s), 138.2 (s), 133.7 (s), 129.2
(d), 128.9 (d), 128.7 (d), 128.6 (d), 127.9 (d), 126.5 (d), 95.6 (s), 95.0
(s), 34.2 (t), 30.2 (t), 25.6 (t); IR (KBr) 1020, 1010, 970, 740, 695
cm-1; UV λmax (CHCl3) 265 (log ꢀ 4.27) nm; FAB MS m/z (relative
intensity) 597 (M+ + 1, 100); HRMS calcd for C44H37O2 597.2794,
found 597.2753.
-50 °C) δ 7.17 (d, J ) 5.2 Hz, 2H), 7.03 (d, J ) 4.5 Hz, 2H), 5.90 (s,
2H), 5.72 (s, 2H), 2.87 (dd, J ) 12.9, 5.7 Hz, 2H), 2.08 (ddd, J )
12.5, 12.5, 5.7 Hz, 2H), 1.4-1.45 (m, 2H), 0.75-0.95 (m, 2H), 0.15-
0.3 (m, 2H), -0.5 to -0.4 (m, 2H); 13C NMR (CDCl3, -40 °C) δ
150.2 (s), 145.5 (s), 142.0 (d), 139.9 (d), 133.1 (s), 81.6 (d), 81.3 (d),
32.1 (t), 31.9 (t), 22.5 (t); IR (KBr) 1270, 1020, 870, 850, 740 cm-1
;
UV λmax (CHCl3) 321 (log ꢀ 2.69), 252 (4.34) nm; MS m/z (relative
intensity) 292 (M+, 100); HRMS calcd for C20H20O2 292.1463, found
292.1448.
Tetramethyldiepoxy[6](9,10)anthracenophanes 3b, 4b, and 5b.
The reaction of dibromocyclophane 6 (155 mg, 0.487 mmol) and 3.4
mL (32 mmol) of 2,5-dimethylfuran was carried out as described above
using 569 mg (14.6 mmol) of sodium amide and 360 mg (4.87 mmol)
of tert-butyl alcohol in 3.1 mL of THF. The products were separated
by flash chromatography on silica gel to afford 21 mg (12%) of 3b, 80
mg (47%) of 4b, and 48 mg (28%) of 5b, which were recrystallized
from hexane-ether.
Reductive Deoxygenation of Diepoxyanthracenophanes 3a and
4a. All the operations were undertaken under a nitrogen atmosphere.
TiCl4 (740 mg, 3.90 mmol) was added to 5.0 mL of THF cooled in an
ice bath followed by addition of 58 mg (1.51 mmol) of LiAlH4 in two
portions. To the resulting black suspension was added dropwise 1.52
g (15.1 mmol) of triethylamine (TEA), and the mixture was heated at
65 °C for 20 min. After the mixture was allowed to cool to room
temperature, a solution of 100 mg (0.342 mmol) of a mixture of 3a
and 4a in 2.6 mL of THF was added dropwise. After 2 h, the mixture
was filtered through a column of alumina (activity III) under nitrogen
using deaerated ether as an eluent. Removal of the solvent under
nitrogen gave a yellow solid, which was chromatographed again on
alumina (activity V) with deaerated hexane as an eluent to furnish 27
mg (31%) of a yellow solid containing anthracenophane 1a and the
1
syn,syn-3b: white solid; mp 195 °C dec; H NMR (CDCl3, -50
°C) δ 6.84 (d, J ) 5.4 Hz, 2H), 6.81 (d, J ) 5.4 Hz, 2H), 2.98 (dd, J
) 13.5, 5.6 Hz, 2H), 2.62 (ddd, J ) 12.8, 12.8, 5.3 Hz, 2H), 2.02 (s,
6H), 1.93 (s, 6H), 1.6-1.9 (m, 2H), 1.3-1.5 (m, 2H), 0.8-1.0 (m,
2H), -0.2-0.0 (m, 2H); 13C NMR (CDCl3, -40 °C) δ 155.0 (s), 150.6
(s), 149.3 (d), 148.3 (d), 129.5 (s), 90.8 (s), 90.0 (s), 34.8 (t), 28.9 (t),
26.2 (t), 18.8 (q), 17.4 (q); IR (KBr) 1375, 1300, 1240, 1155, 1110,
890, 860, 820, 800, 750, 730 cm-1; UV λmax (CHCl3) 338 (log ꢀ 2.57),
258 (4.34) nm; MS m/z (relative intensity) 348 (M+, 100). Anal. Calcd
for C24H28O2: C, 82.71; H, 8.09. Found: C, 82.46; H, 8.12.
1
dihydro derivative 8a in a ratio of 3:2 (by H NMR in toluene-d8).
1
syn,anti-4b: white solid; mp 186-188 °C; H NMR (CDCl3, -50
Irrespective of the reaction conditions, extractive workup resulted in
the formation of only 8a and 2a due to rapid decomposition of 1a in
air. Further separation of 8a and 2a was done by preparative HPLC.
While 8a was recrystallized from hexane, attempts to recrystallize
bridgehead olefin 2a failed due to rapid oxidation to the corresponding
epoxide.
°C) δ 6.88 (d, J ) 5.2 Hz, 1H), 6.84 (d, J ) 5.7 Hz, 1H), 6.81 (d, J
) 5.4 Hz, 1H), 6.77 (d, J ) 5.0 Hz, 1H), 3.09 (br dd, 1H), 2.6-2.8
(m, 2H), 2.03 (s, 3H), 1.93 (s, overlapping with a multiplet, 7H), 1.81
(s, 3H), 1.5-1.7 (m, 2H), 1.1-1.3 (m, 1H), 0.8-1.0 (m, 2H), 0.3-0.4
(m, 1H), 0.1-0.3 (m, 1H), -0.7 to -0.5 (m, 1H); 13C NMR (CDCl3,
-40 °C) δ 155.9 (s), 154.2 (s), 151.2 (s), 150.2 (s), 149.2 (d), 148.4
(d), 146.0 (d), 144.5 (d), 131.5 (s), 130.4 (s), 91.0 (s), 89.7 (s), 89.4
(s), 88.8 (s), 34.5 (t), 32.7 (t), 31.2 (t), 28.1 (t), 25.5 (t), 23.5 (t), 18.6
(q), 18.0 (q), 17.6 (q), 17.0 (q); IR (KBr) 1380, 1300, 1150, 1130,
1120, 860, 750 cm-1; UV λmax (CHCl3) 331 (log ꢀ 2.45), 259 (4.33)
nm; MS m/z (relative intensity) 348 (M+, 100). Anal. Calcd for
C24H28O2: C, 82.71; H, 8.09. Found: C, 82.70; H, 8.20.
1
1a: H NMR (toluene-d8, -50 °C) δ 8.03-8.06 (m, 2H), 7.93-
7.97 (m, 2H), 7.22-7.25 (m, 2H), 7.15-7.17 (m, 2H), 3.39 (dd, J )
12.5, 5.6 Hz, 2H), 2.90 (ddd, J ) 18.1, 6.0, 6.0 Hz, 2H), 1.4-1.5 (m,
2H), 0.56-0.76 (m, 2H), 0.35-0.48 (m, 2H), -1.86 to -1.77 (m, 2H);
13C NMR (toluene-d8, -50°C) δ 135.6 (s), 133.2 (s), 125.6 (d), 125.0
(d), 124.9 (d), 124.5 (d), 34.2 (t), 33.7 (t), 25.8 (t); UV-vis λmax
(hexane) 435, 415 nm.
anti,anti-5b: white solid; mp 180-182 °C; 1H NMR (CD2Cl2, -80
°C) δ 6.86 (d, J ) 5.5 Hz, 2H), 6.76 (d, J ) 5.5 Hz, 2H), 2.83 (dd, J
) 12.8, 4.7 Hz, 2H), 1.98 (ddd, J ) 12.6, 12.6, 4.9 Hz, 2H), 1.84 (s,
6H), 1.71 (s, 6H), 1.2-1.4 (m, 2H), 0.7-0.9 (m, 2H), 0.0-0.2 (m,
1
8a: white solid; mp 128-129 °C; H NMR (CDCl3, 30 °C) δ 7.25
(d, J ) 9.2 Hz, 1H), 7.21 (d, J )9.2 Hz, 1H), 4.42 (dd, J ) 4.4, 4.2
(32) Nowlin, G. J. Am. Chem. Soc. 1950, 72, 5754.

9496 J. Am. Chem. Soc., Vol. 118, No. 40, 1996
Tobe et al.
1
Hz, 2H), 2.22 (ddd, J ) 6.2, 5.0, 5.0 Hz, 4H), 1.1-1.2 (m, 4H), 0.8-
0.9 (m, 4H); 13C NMR (CDCl3, 30 °C) δ 139.4 (s), 128.1 (d), 126.1
(d), 42.5 (d), 37.9 (t), 25.7 (t), 20.3 (t); IR (KBr) 770, 700 cm-1; MS
m/z (relative intensity) 262 (M+, 100); HRMS calcd for C20H22
262.1721, found 262.1707.
m, 2H); H NMR (CD2Cl2, 30 °C) δ 7.70 (dt, J ) 6.9, 1.5 Hz, 8H),
7.47 (dt, J ) 1.2, 6.9 Hz, 8H), 7.45 (s, 4H), 7.34 (tt, J ) 7.1, 1.2 Hz,
4H), 1.89 (t, J ) 6.1 Hz, 4H), 0.45 (br m, 4H), -0.61 (br m, 4H); 13
C
NMR (CD2Cl2, 30 °C) δ 145.2 (s), 140.6 (s), 139.7 (s), 138.6 (s), 129.1
(d), 128.9 (d), 128.8 (d), 127.1 (d), 40.4 (t), 34.4 (t), 26.6 (t); IR (KBr)
1080, 855, 850, 760, 705, 695 cm-1; UV-vis λmax (cyclohexane) 482
(log ꢀ 3.71), 456 (3.67), 299 (4.44), 248 (4.20) nm; FAB MS m/z
(relative intensity) 565 (M+ + 1, 100); HRMS calcd for C44H36
564.2817, found 564.2807.
2a: white solid; this compound did not show a sharp melting point
1
probably due to partial oxidation during the measurement; H NMR
(CDCl3, 30 °C) δ 7.17-7.48 (m, 8H), 5.73 (dd, J ) 11.6, 5.2 Hz, 1H),
4.06 (t, J ) 11.6, 5.2 Hz, 1H), 2.79 (ddd, J ) 24.5, 12.1, 4.0 Hz, 1H),
1.9-2.2 (m, 3H), 1.5-1.6 (m, 2H), 0.9-1.4 (m, 3H), 0.3-0.4 (m, 1H);
13C NMR (CDCl3, 30 °C) δ 143.9 (s), 142.5 (s), 141.2 (s), 138.9 (s),
138.7 (s), 132.9 (d), 127.0 (d), 126.74 (d), 126.67 (d), 126.62 (d), 126.54
(d), 126.0 (d), 125.6 (d), 122.4 (d), 47.4 (d), 40.8 (t), 30.2 (t), 29.3 (t),
26.5 (t), 26.4 (t); IR (KBr) 890, 770, 760, 750, 720 cm-1; MS m/z
(relative intensity) 260 (M+, 100); HRMS calcd for C20H20 260.1565,
found 260.1564.
Acid-Catalyzed Isomerization of Anthracenophanes 1a-c. To
a solution of a mixture of 1a, 8a, and 2a (approximately 1:0.7:1.4) in
benzene-d6/acetone-d6 mixture (1:4) was added one drop of trifluoro-
acetic acid via a syringe. The yellow color of the solution disappeared
1
immediately, and white insoluble material appeared. The H NMR
spectrum of the solution indicated the disappearance of the peaks due
to 1a while the peaks of 8a and 2a remained unchanged, indicating
that 1a had polymerized. Alternatively, a solution of a mixture of 1a
and 8a (3:2) in toluene-d8 was added under nitrogen to a degassed slurry
of silica gel in hexane. After the yellow color disappeared, the mixture
Reductive Deoxygenation of Tetramethyldiepoxyanthracenophanes
3b-5b. Reduction of 71 mg (0.20 mmol) of a mixture of 3b-5b with
the reducing agent prepared from 552 mg (2.9 mmol) of TiCl4, 43 mg
(1.1 mmol) of LiAlH4, and 1.13 g (11.2 mmol) of TEA in 6 mL of
THF was carried out at room temperature as described above for 18 h.
The reaction was quenched by dropwise addition of the mixture to a
solution of 20% potassium carbonate (40 mL) solution under nitrogen.
Reverse addition of the carbonate solution to the reaction mixture
resulted in the formation of the isomerization product 2b. The mixture
was extracted with ether, and the extract was washed with saturated
sodium chloride solution and dried over MgSO4. After removal of the
solvent, the residue was chromatographed on alumina (activity III) to
afford 44 mg (68%) of tetramethylanthracenophane 1b as a yellow solid.
Reduction of 117 mg (0.336 mmol) of a mixture of 3b-5b with 912
mg (4.81 mmol) of TiCl4, 70 mg (1.9 mmol) of LiAlH4, and 75 mg
(0.74 mmol) of TEA in 10 mL of THF gave 46 mg of a mixture of 1b,
dihydro derivative 8b, and 2b in a ratio of 11:2:1 (by 1H NMR), which
were separated by preparative HPLC.
1
was filtered and the solvent was evaporated. The H NMR spectrum
of the residue exhibited peaks due to 8a and 2a in a ratio of 2:1. This
indicates that about 30% of 1a had isomerized to 2a by treatment with
silica gel, while the remainder had presumably polymerized during these
operations.
To a solution of 1b in CDCl3 was added one drop of TFA via a
microsyringe. The yellow color disappeared immediately. 1H NMR
spectra of the solution indicated the formation of the isomer 2b as a
sole product.
To a solution of 35 mg (0.044 mmol) of 1c in 1.5 mL of chloroform
was added 60 µL (0.78 mmol) of TFA, and the solution was stirred at
room temperature for 47 h. The solution was diluted with ether and
washed with aqueous NaHCO3. After removal of the solvent, the
residue was chromatographed on silica gel to give 25 mg (71%) of the
isomer 2c as a yellow solid which was recrystallized from hexane-
ether: mp 224-225 °C; 1H NMR (CDCl3, 30 °C) δ 7.1-7.5 (m, 24H),
5.27 (dd, J ) 6.9, 4.9 Hz, 1H), 4.61 (t, J ) 4.5 Hz, 1H), 1.7-1.9
(m,1H), 1.1-1.4 (m, 7H), 0.7-0.9 (m, 1H), 0.2-0.3 (m, 1H); 13C NMR
(CDCl3, 30 °C) δ 142.0 (s), 141.7 (s), 141.5 (s), 141.1 (s), 141.0 (s),
140.2 (br s), 139.7 (s), 138.7 (s), 138.1 (br s), 137.9 (br d), 137.7 (br
s), 137.4 (s), 135.1 (s), 130.2 (d), 129.6 (d), 129.2 (d), 129.1 (d), 129.0
(d), 128.5 (d), 127.91 (d), 129.87 (d), 127.51 (d), 127.48 (d), 127.2
(d), 126.73 (d), 127.70 (d), 126.6 (d), 126.3 (d), 39.7 (d), 36.6 (br t),
30.7 (t), 28.9 (br t), 27.2 (t), 26.7 (t); IR (KBr) 755, 695 cm-1; MS m/z
(relative intensity) 564 (M+, 13), 69 (100); HRMS calcd for C44H36
564.2817, found 564.2849.
1
1b: yellow solid from hexane-ether; mp 161-162 °C; H NMR
(CD2Cl2:CS2 ) 1:1, -110 °C) δ 7.03 (br s, 4H), 3.74 (br m, 2H), 2.80
(br s, 6H), 2.73 (br s, 6H), 2.73 (br m, 2H), 1.47 (br m, 2H), 0.79 (br
m, 2H), 0.05 (br m, 2H), -1.83 (br m, 2H); 1H NMR (CD2Cl2, 30 °C)
δ 7.11 (s, 4H), 3.31 (t, J ) 5.9 Hz, 4H), 2.80 (s, 12H), 0.87 (m, 4H),
-0.38 (m, 4H); 13C NMR (THF-d8, 30 °C) δ 139.1 (s), 138.2 (s), 131.0
(s), 127.3 (d), 40.2 (t), 34.8 (t), 27.6 (t), 24.9 (q); IR (KBr) 820 cm-1
;
UV-vis λmax (cyclohexane) 455 (log ꢀ 3.63), 289 (4.70) nm; MS m/z
(relative intensity) 316 (M+, 100); HRMS calcd for C24H28 316.2191,
found 316.2186.
8b: white solid from hexane-ether; mp 154-156 °C; 1H NMR
(CDCl3, 30 °C) δ 6.99 (s, 4H), 4.55 (t, J ) 5.8 Hz, 2H), 2.39 (s, 12H),
2.14 (q, J ) 6.0 Hz, 4H), 1.2-1.3 (br m, 4H), 0.9-1.0 (br m, 4H); 13
C
Photochemical Valence Isomerization of Anthracenophanes 1b
and 1c. A solution of 20 mg of 1b in benzene-d6 and THF-d8 (3:1) in
an NMR tube was irradiated through a Pyrex filter with a 300 W high-
pressure mercury lamp at room temperature until the yellow color
disappeared. NMR measurement indicated the quantitative formation
of the Dewar isomer 11b: 1H NMR (benzene-d6:THF-d8 ) 3:1, 0 °C)
δ 6.78 (s, 4H), 2.48 (t, J ) 6.0 Hz, 4H), 2.19 (s, 12H), 1.61 (br m,
4H), 1.26 (br m, 4H); 13C NMR (benzene-d6:THF-d8 ) 3:1, 0 °C) δ
149.1 (s), 130.0 (s), 128.3 (d), 66.2 (s), 27.4 (t), 26.3 (t), 25.5 (t), 17.0
(q).
NMR (CDCl3, 30 °C) δ 139.1(s), 132.9 (s), 128.2 (d), 38.1 (d), 32.1
(t), 26.6 (t), 22.2 (t), 19.9 (q); IR (KBr) 820, 800 cm-1; MS m/z (relative
intensity) 318 (M+, 58), 234 (100); HRMS calcd for C24H30 318.2347,
found 318.2336.
2b: white solid from hexane-ether; mp 156-157 °C; 1H NMR
(CDCl3, 30 °C) δ 7.03 (d, J ) 7.7 Hz, 1H), 6.95 (s, 1H), 6.93 (d, J )
7.7 Hz 1H), 5.64 (dd, J ) 11.5, 5.1 Hz, 1H), 4.40 (dd, J ) 4.5, 3.7 Hz,
1H) 2.49 (s, 3H), 2.38 (s, 9H), 2.2-2.3 (m, 1H), 2.1-2.2 (m, 2H),
1.9-2.0 (m, 1H), 1.5-1.6 (m, 1H), 1.2-1.4 (m, 3H), 1.0-1.1 (m, 1H),
0.3-0.5 (m, 1H); 13C NMR (CDCl3, 30 °C) δ 143.3 (s), 141.1 (s),
139.4 (s), 137.9 (s), 136.8 (s), 133.6 (d), 132.0 (s), 131.4 (s), 130.5
(s), 129.3 (s), 128.4 (d), 128.3 (d), 127.6 (d), 40.2 (d), 34.0 (t), 31.2
(t), 29.2 (t), 27.5 (t), 27.2 (t), 19.7 (q), 19.2 (q), 19.0 (q), 18.5 (q); IR
(KBr) 810, 800 cm-1; MS m/z (relative intensity) 316 (M+, 45), 234
(100); HRMS calcd for C24H28 316.2191, found 316.2209.
A solution of 40 mg of 1c in 3 mL of benzene was irradiated through
a solution filter of 1,4-diphenyl-1,3-butadiene (0.12 M in THF) with a
300 W high-pressure mercury lamp at room temperature for 3 h. The
white precipitate formed was filtered and washed with a small portion
of hexane to give 20 mg (50%) of the Dewar isomer 11c. Preliminary
experiments by 1H NMR for photoisomerization of 1c as described for
the reaction of 1b indicated quantitative formation 11c: white solid;
1H NMR (CD2Cl2, 0 °C) δ 7.27-7.36 (m, 12H), 7.26 (s, 4H), 7.15 (m,
8H), 2.60 (t, J ) 5.8 Hz, 4H), 1.12 (br m, 4H), 0.99 (br m, 4H); 13C
NMR (CD2Cl2, 0 °C) δ 148.4 (s), 139.2 (s), 137.4 (s), 128.8 (d), 128.5
(d), 128.3 (d), 127.5 (d), 67.8 (s), 28.4 (t), 26.3 (t), 25.3 (t); IR (KBr)
1010, 760, 700 cm-1; UV λmax (CHCl3) 260 (log ꢀ 4.65) nm.
Reductive Deoxygenation of Tetraphenyldiepoxyanthracenophane
3c. Reduction of 141 mg (0.237 mmol) of 3c with 896 mg (6.16 mmol)
of TiCl4, 90.8 mg (2.37 mmol) of LiAlH4, and 4.78 g (4.73 mmol) of
TEA in 8 mL of THF was carried out under reflux for 6 h. The mixture
was worked up as described above to give 78 mg (58%) of tetraphen-
ylanthracenophane 1c, which was recrystallized from hexane-ether.
1
Thermal Cycloreversion of Dewar Anthracenophanes 11b and
11c. A solution of 1b (1.4 × 10-4 M) in cyclohexane was irradiated
in a quartz cell with a high-pressure mercury lamp to give a solution
1c: yellow-orange solid; mp 310-311 °C (sealed tube); H NMR
(CD2Cl2:CS2 ) 1:1, -110 °C) δ 7.2-7.7 (br m, 24H), 1.68 (br m,
4H), 0.83 (br m, 2H), 0.51 (br m, 2H), -0.21 (br m, 2H), -2.10 (br

Synthesis of [6](9,10)Anthracenophane
J. Am. Chem. Soc., Vol. 118, No. 40, 1996 9497
of 11b, which was then placed in a thermocontrolled cell holder. The
progress of the cycloreversion was followed by measuring the appear-
ance of absorption at 455 nm by a spectrometer. For the measurement
of the cycloreversion of 11c, a solution of 11c and 9,10-dibromoan-
thracene (internal standard) in toluene was placed in a thermocontrolled
bath in the dark. Aliquots of the solution were taken and analyzed by
HPLC at λ ) 350 nm. The kinetic results are given in Table S18 of
the supporting information.
X-ray Crystallographic Analyses of Diepoxyanthracenophanes
3b and 5b and Anthracenophanes 1b and 1c. The structures were
solved by direct methods and refined using the program package
TEXSAN.33 Bond distances, bond angles, fractional atomic coordinates,
and anisotropic thermal parameters are given in the supporting
information.
4, dcalcd ) 1.164 g/cm3, R ) 0.064 (Rw ) 0.038), and GOF ) 5.91 for
2611 reflections.
1b: C24H28, MW ) 316.49, monoclinic P21/c, a ) 13.620(4) Å, b
) 9.286(2) Å, c ) 15.645(2) Å, â ) 115.10(1)°, V ) 1792.1(6) Å3, Z
) 4, dcalcd ) 1.173 g/cm3, R ) 0.066 (Rw ) 0.034), and GOF ) 1.64
for 4392 reflections.
1c: C44H36, MW ) 564.77, triclinic P1h, a ) 11.439(2) Å, b )
14.498(2) Å, c ) 9.668(2)Å, R ) 97.37(2)°, â ) 101.40(2)°, γ ) 92.56-
(1)°, V ) 1554.7(5) Å3, Z ) 2, dcalcd ) 1.206 g/cm3, R ) 0.039 (Rw )
0.029), and GOF ) 3.34 for 3150 reflections.
Supporting Information Available: 1H NMR and 13C NMR
data for 1a-c, 2a-c, 3a-c, 4a-c, 5a,b, 8a,b, and 11b,c, data
for the crystallographic structure analyses of 3b, 5b, 1b, and
1c, tables of barriers for flipping of the methylene bridge of
diepoxyanthracenophanes 3a-c, 4a-c, and 5a,b, and the kinetic
data for thermal cycloreversion of Dewar anthracenophanes 11b
and 11c (90 pages). See any current masthead page for ordering
and Internet access instructions.
syn,syn-3b: C24H28O2, MW ) 348.48, monoclinic P21/c, a ) 14.017-
(4) Å, b ) 8.559(2) Å, c ) 17.595(3) Å, â ) 112.59(2)°, V ) 1948.8-
(8) Å3, Z ) 4, dcalcd ) 1.188 g/cm3, R ) 0.074 (Rw ) 0.049), and GOF
) 4.29 for 4768 reflections.
anti,anti-5b: C24H28O2, MW ) 348.48, orthorhombic Pca21, a )
13.045(3) Å, b ) 14.439(3) Å, c ) 10.555(6) Å, V ) 1988(1) Å3, Z )
(33) TEXRAY Structure Analysis Package, Molecular Structure Corp.,
1985.
JA961562E