Iptycene quinones: Synthesis and structure

Article abstract of DOI:10.1021/jo0483015

(Chemical Equation Presented) A practical and efficient method to synthesize iptycene quinones has been developed. As a result, a series of pentiptycene quinones 8-16 were conveniently synthesized by one-pot reaction of triptycene quinone 4 or 5 with anthracene 1 or its derivatives 2-3 in refluxing acetic acid in the presence of p-chloranil, followed by CAN oxidative demethylation. Similarly, a series of heptiptycene quinones 17-23 with U-shaped cavities were achieved with pentiptycene quinone 10 and triptycene diquinone 6 as precursors. Non-iptycene triquinones 24 with one tweezer-shaped cavity and 25 with two U-shaped cavities were synthesized by one-pot reactions of anthracene with pentiptycene triquinones 16a and 16b, respectively. Non-iptycene triquinone 26 with a dendritic structure was conveniently obtained by the reaction of anthracene with either pentiptycene diquinone 12 or triptycene triquinone 7. The structures of regioisomers 16a and 16b were determined by the single-crystal structure analysis of 16b. The structures of other regioisomers, including heptiptycene tetraquinones 19a/19b/19c and heptiptycene triquinones 23a/23b, were identified by comparative reactions.

Full text of DOI:10.1021/jo0483015

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Iptycene Quinones: Synthesis and Structure
Xiao-Zhang Zhu†,‡ and Chuan-Feng Chen*,†
Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080,
China, and Graduate School, Chinese Academy of Sciences, Beijing 100080, China
cchen@iccas.ac.cn
Received September 23, 2004
A practical and efficient method to synthesize iptycene quinones has been developed. As a result,
a series of pentiptycene quinones 8-16 were conveniently synthesized by one-pot reaction of
triptycene quinone 4 or 5 with anthracene 1 or its derivatives 2-3 in refluxing acetic acid in the
presence of p-chloranil, followed by CAN oxidative demethylation. Similarly, a series of heptiptycene
quinones 17-23 with U-shaped cavities were achieved with pentiptycene quinone 10 and triptycene
diquinone 6 as precursors. Non-iptycene triquinones 24 with one tweezer-shaped cavity and 25
with two U-shaped cavities were synthesized by one-pot reactions of anthracene with pentiptycene
triquinones 16a and 16b, respectively. Non-iptycene triquinone 26 with a dendritic structure was
conveniently obtained by the reaction of anthracene with either pentiptycene diquinone 12 or
triptycene triquinone 7. The structures of regioisomers 16a and 16b were determined by the single-
crystal structure analysis of 16b. The structures of other regioisomers, including heptiptycene
tetraquinones 19a/19b/19c and heptiptycene triquinones 23a/23b, were identified by comparative
reactions.
Introduction
ties, (3) readily derivative ability, and (4) potential
applications in material4 and supramolecular chemistry.5
Moreover, triptycene quinones exhibit interesting in-
tramolecular charge-transfer characteristics.6 Their de-
rivatives have also found applications as acceptors, with
Triptycene quinones1 form an interesting class of
compounds for their (1) rigid 3D structure of triptycene,
(2) unique electrochemical2 and photochemical3 proper-
† Center for Molecular Science.
(4) (a) Norvez, S.; Simon, J. J. Chem. Soc., Chem. Commun. 1990,
1398-1399. (b) Norvez, S. J. Org. Chem. 1993, 58, 2414-2418. (c)
Long, T. M.; Swager, T. M. J. Am. Chem. Soc. 2003, 125, 14113-14119.
(5) (a) Masao, H.; Hideki, T.; Kimiaki, Y. Tetrahedron Lett. 1999,
40, 6037-6040. (b) Yang, J. S.; Liu, C. P.; Lee, G. H. Tetrahedron Lett.
2000, 41, 7911-7915. (c) Masao, H.; Kimiaki, Y.; Jun, Y. Tetrahedron
2001, 57, 10253-10258. (d) Yang, J. S.; Liu, C. P.; Lin, B. C.; Tu, C.
W.; Lee, G. H. J. Org. Chem. 2002, 67, 7343-7354.
(6) (a) Ichiro, M. Pure Appl. Chem. 1983, 55, 323-330. (b) Kimiaki,
Y.; Kazuhiro, N.; Ichiro, M.; Satoshi, I. J. Chem. Soc., Chem. Commun.
1982, 396-397. (c) Hiizu, I.; Katsumi, M. J. Chem. Soc., Chem.
Commun. 1978, 720-721. (d) Nobuya, K. Bull. Chem. Soc. Jpn. 1989,
62, 800-807.
‡ Graduate School.
(1) (a) Bartlett, P. D.; Ryan, M. J.; Cohen, S. G. J. Am. Chem. Soc.
1942, 64, 2649-2653. (b) Iwamura, H.; Makino, K. J. J. Chem. Soc.,
Chem. Commun. 1978, 720-721. (c) Russel, G. A.; Suleman, N. K.;
Iwamura, H.; Webster, O. W. J. Am. Chem. Soc. 1981, 103, 1560-
1561.
(2) Yamamura, K.; Miyake, H.; Himeno, S.; Inagaki, S.; Nakasuji,
K.; Murata, I. Chem. Lett. 1988, 1819-1822.
(3) (a) Tai, Y. F.; Janet, N.; Gamlin, G. O.; Scheffer, J. R.; Trotter,
J.; Young, D. T. Tetrahedron Lett. 1995, 36, 2025-2028. (b) Borecka,
B.; Gamlin, J. N.; Gudmundsdottir, A. D.; Olovsson, G.; Scheffer, J.
R.; Trotter, J. Tetrahedron Lett. 1996, 37, 2121-2124.
10.1021/jo0483015 CCC: $30.25 © 2005 American Chemical Society
Published on Web 12/24/2004
J. Org. Chem. 2005, 70, 917-924
917

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Zhu and Chen
Senge and Kurreck7b reported a one-step synthesis of
triptycene quinones by the reaction of anthracene and
excess quinones in acetic acid. Although some simple
pentiptycene quinones and their derivatives are known,13
there is not a practical and efficient method for the
synthesis of iptycene quinones until now. To a great
extent, it restricts the development of iptycene quinone
chemistry.
SCHEME 1
To develop novel receptors14 based on iptycene quino-
nes and their derivatives, iptycene quinones with unique
molecular cavities are required. Initially, we followed the
synthetic strategy of Senge and Kurreck to synthesize
iptycene quinones but found that it had some problems.
First, it consumed excess quinones so that it would be
impractical when the quinones were not easily obtained.
Second, complex results would be obtained if the excess
iptycene multiquinones were used. Moreover, the oxida-
tive capacity of the iptycene quinone is usually weaker
than that of the simple quinone, which has a direct effect
on the reactive result (low yield or only semiquinone
product obtained). Considering that excess quinones only
act as oxidants, we anticipated that p-chloranil, a com-
mercially available stronger oxidant, could be utilized
instead of the excess quinones in the one-pot method to
synthesize iptycene quinones. In this paper, we report a
practical and efficient method for the synthesis of ip-
tycene quinones, including a series of pentiptycene
quinones, heptiptycene quinones, and non-iptycene quino-
nes. Moreover, the structures of regioisomers were
determined by X-ray single-crystal structure analysis and
comparative reactions.
porphyrin and tetrathiafulvalene serving as donors, for
the synthesis of electron-transfer model compounds to
mimic the primary steps in photosynthesis7 and molec-
ular rectifiers.8 Recently, there is increasing attention in
the chemical and biological activities of triptycene quino-
nes.9 In particular, a number of triptycene quinones and
their derivatives were found to show potent anticancer
and antimalarial activities.9a,10
Iptycenes11 are extended triptycenes. They have at-
tracted considerable interest not only from their synthetic
challenge but also for their attractive rigid frameworks,
unique intramolecular cavities, and exceptional thermal
stability. Iptycene quinones9c,12 refer to derivatives of
iptycene bearing at least one triptycene quinone unit.
Pentiptycene monoquinones are a class of the most
simple iptycene quinones. Their derivatives were found
to be promising reagents for the preparation of fluores-
cent porous polymeric sensors for TNT,13a fluorescent
chemosensors for Cu2+ 13b
materials with monolayer
,
assembly structures,13c electron-donor porphyrin quinone
diads and triads,7b,c and building blocks for the construc-
tion of novel chain and channel networks.13d Compared
with triptycene quinones and iptycenes, still less is
known about iptycene quinones, especially complicated
ones.
Results and Discussion
Pentiptycene Quinones. Triptycene monoquinones
4
1a and 51b were prepared by the reactions of anthracene
1 and 1,4-dimethoxyanthracene 2 with excess p-benzo-
quinone in a one-pot approach, respectively. Bisquinone
61b was obtained by the oxidation of 5 with cerium (IV)
ammonium nitrate (CAN).15 Triptycene triquinone 71c
was synthesized by the reaction of 1,4,5,8-tetramethoxy-
anthracene 3 with excess p-benzoquinone in refluxing
acetic acid, followed by demethylation with hydriodic acid
and then oxidized by sodium bichromate in acetic acid.
Typically, triptycene quinones are synthesized by the
multistep method1 as shown in Scheme 1. Recently,
(7) (a) Wasielewski, M.; Niemczyk, M. P.; Johson, S. G.; Svec, W.
A.; Minsek, D. W. Tetrahedron 1989, 45, 4785-4806. (b) Wiehe, A.;
Senge, M. O.; Kurreck, H. Liebigs Ann. Recl. 1997, 1951-1963. (c)
Wiehe, A.; Senge, M. O.; Scha¨fer, A.; Speck, M.; Tannert, S.; Kurreck,
H.; Ro¨der, B. Tetrahedron 2001, 57, 10089-10110. (d) Springer, J.;
Kodis, G.; Garza, L.; Moore, A. L.; Moore, T. A.; Gust, D. J. Phys. Chem.
A 2003, 107, 3567-3575.
(8) Scheib, S.; Cava, M. P.; Baldwin, J. W.; Metzger, R. M. J. Org.
Chem. 1998, 63, 1198-1204.
(9) (a) Hua, D. H.; Tamura, M.; Huang, X.; Stephany, H. A.; Helfrich,
B. A.; Perchellet, E. M.; Sperfslage, B. J.; Perchellet, J.-P.; Jiang, S.;
Kyle, D. E.; Chiang, P. K. J. Org. Chem. 2002, 67, 2907-2912. (b)
Spyroudis, S.; Xanthopoulou, N. J. Org. Chem. 2002, 67, 4612-4614.
(c) Spyroudis, S.; Xanthopoulou, N. Tetrahedron Lett. 2003, 44, 3767-
3770.
(10) Perchellet, E. M.; Magill, M. J.; Huang, X.; Brantis, C. E.; Hua,
D. H.; Perchellet, J. P., Anti-Cancer Drugs 1999, 10, 749-766.
(11) (a) Hart, H.; Shamouilian, S.; Takehira, Y. J. Org. Chem. 1981,
46, 4427-4432. (b) Hart, H.; Bashir-Hashemi, A.; Luo, J.; Meador, M.
A. Tetrahedron 1986, 42, 1641-1654. (c) Hart, H. Pure Appl. Chem.
1993, 65, 27-34.
(12) (a) Williams, V. E.; Swager, T. M. Macromolecules 2000, 33,
4069-4073. (b) Lipczynska-Kochany, E.; Iwamura, H. Chem. Lett.
1982, 1075-1078.
(14) (a) Kla¨rner, F. G.; Benkhoff, J.; Boese, R.; Burkert, U.; Kamieth,
M.; Naatz, U. Angew. Chem. Int. Ed. Engl. 1996, 35, 1130-1133. (b)
Klarner, F. G.; Burkert, U.; Kamieth, M.; Boese, R.; Benet-Buchholz,
J. Chem.sEur. J. 1999, 5, 1700-1707. (c) Harmata, M.; Barnes, C.
L.; Karra, S. R.; Elahmad, S. J. Am. Chem. Soc. 1994, 116, 8392-
8393.
(13) (a) Yang, J. S.; Swager, T. M. J. Am. Chem. Soc. 1998, 120,
11864-11873. (b) Yang, J. S.; Lin, C. S.; Hwang, C. Y. Org. Lett. 2001,
3, 889-892. (c) Yang, J. S.; Lee, C. C.; Yau, S. L.; Chang, C. C.; Lee,
C. C.; Leu, J. M. J. Org. Chem. 2000, 65, 871-877. (d) Yang, J. S.;
Liu, C. P.; Lee, G. H. Tetrahedron Lett. 2000, 41, 7911-7915.
(15) Jacob, P., III; Callery, P. S.; Shulgin, A. T.; Castagoli, N. Jr. J.
Org. Chem. 1976, 41, 3627-3629.
918 J. Org. Chem., Vol. 70, No. 3, 2005

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Iptycene Quinones: Synthesis and Structure
We first examined the reaction of 1 equiv of triptycene
quinone 4 with anthracene in refluxing acetic acid in the
presence of 1 equiv of p-chloranil and found that the
pentiptycene monoquinone 813a could be directly obtained
in 78% yield. Furthermore, the same reaction conditions
were found to be suitable for the synthesis of other
pentiptycene quinones with open cavities. Consequently,
one-pot reaction of triptycene quinone 4 with 1,4-
dimethoxyanthracene 2 gave dimethoxypentiptycene
quinone 9 in 82% yield. Compound 9 was then demethyl-
ated by CAN oxidation to give pentiptycene diquinone
109c in a nearly quantitative yield. Similarly, the pen-
tiptycene triquinone 12 was conveniently synthesized by
the CAN oxidation of tetramethoxypentiptycene quinone
11, which was obtained in 80% yield by the reaction of 4
with 1,4,5,8-tetramethoxyanthracene 3 in HOAc in the
presence of p-chloranil. The 1H NMR spectrum of 12
showed two singlets for the bridgehead protons (δ 6.55,
5.81), a singlet for the CHdCH protons of the quinoid
ring (δ 6.66), and two 4-proton multiplets for the aryl
protons. Its 13C NMR spectrum showed two signals for
the bridgehead carbons (δ 47.5, 38.7) and one signal for
the carbonyl carbons (δ 180.9), which is consistent with
its structure with D2h symmetry.
two regioisomers 15a and 15b was obtained in 82% of
total yield, which is obviously higher than the result with
excess triptycene quinone as oxidant.9c The isomers 15a
and 15b could hardly be separated by column chroma-
tography; however, we found that their CAN oxidation
products of pentiptycene triquinones 16a and 16b could
be separated by column chromatography in 45% and 28%
yields, respectively. The polarity of 16b is smaller than
that of 16a when a mixture of dichloromethane/petro-
leum ether (3:1 v/v) was used as eluent. The isomers 16a
and 16b showed almost the same 1H NMR spectrum (one
singlet for the bridgehead protons, one singlet for the
CHdCH protons of the quinoid ring, and two 2-proton
multiplets for the aryl protons) and 13C NMR spectrum
(two peaks for the carbonyl carbons, six peaks for the
aromatic carbons, and one peak for the bridgehead
carbons) and could not be distinguished by ordinary
spectroscopic methods. Fortunately, we obtained the
single crystals of the isomer 16b from dichloromethane
and n-hexane. The result of X-ray crystal structure
analysis of 16b showed that the two terminal quinoid
rings are in the trans position (see Supporting Informa-
tion). Interestingly, dichloromethane molecules were
found to be incorporated in the crystal. Moreover, this
combination strength between 16b and dichloromethane
was so strong that dichloromethane could not easily be
removed even if the sample was heated more than one
week under reduced pressure. Similar cases also occurred
in the other iptycene multiquinones, but most of the
precursor methoxy-substituted iptycene quinones did not
show this phenomenon.
The reaction of dimethoxytriptycene quinone 5 with
1,4,5,8-tetramethoxyanthracene 3 in HOAc in the pres-
ence of p-chloranil gave pentiptycene quinone 13 in 63%
yield. Further treatment of 13 with CAN in aqueous
acetonitrile produced pentiptycene tetraquinone 14 in
82% yield. The 1H NMR spectrum of 14 showed two
singlets for the bridgehead protons (δ 6.56, 6.17), three
singlets for the CHdCH protons of the quinoid ring (δ
6.67, 6.65, 6.63), and two 2-proton multiplets for the aryl
protons. In its 13C NMR spectrum, three peaks for the
carbonyl carbons (δ 182.0, 180.8, 176.3) and two peaks
for the bridgehead carbons (δ 42.3, 38.8) were observed.
Heptiptycene Quinones. Heptiptycene diquinone 17
with a U-shaped cavity is composed of two equivalent
pentiptycene diquinone 10 units. It was conveniently
synthesized by a one-pot reaction of compound 10 with
anthracene in refluxing acetic acid in the presence of
p-chloranil. Under the same conditions, the reaction of
triptycene diquinones 6 with 2 equiv of anthracenes
produced heptiptycene diquinone 17 along with semi-
quinone 17′ obtained in considerable yield. In this case,
the yield of compound 17 could be improved with the
1
increase of the reaction time. The H NMR spectrum of
17 showed two singlets for the bridgehead protons (δ
6.09, 5.72) and two 10-proton multiplets for the aryl
protons. Its 13C NMR spectrum showed two peaks for the
bridgehead carbons (δ 47.3, 42.2) and one signal at δ
178.9 for the carbonyl carbons. Although there are two
possible isomers, a single adduct of 17′ could be deduced
1
When the reaction of dimethoxytriptycene monoquino-
ne 5 with dimethoxyanthracene 2 took place in refluxing
acetic acid in the presence of p-chloranil, a mixture of
from its H NMR spectrum in which only three singlets
for the bridgehead protons (δ 5.81, 5.78, 4.55) and one
singlet for the CH-CH protons of the semiquinoid ring
J. Org. Chem, Vol. 70, No. 3, 2005 919

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Zhu and Chen
(δ 3.06) besides aromatic proton signals were observed.
The 13C NMR spectrum of 17′ showed one magnetically
unique sp3-hybridized carbon (δ 38.8) of the semiquinoid
ring, three peaks for the bridgehead carbons (δ 51.1, 50.3,
42.3), and two peaks for the carbonyl carbons (δ 193.3,
178.5), which is also consistent with its structure. Fur-
thermore, we found that the chemical shift of its aromatic
proton H2 positioned remarkably upfield (δ 5.48), which
suggested that 17′ is an endo-adduct.
The reaction of pentiptycene quinone 10 with 1,4,5,8-
tetramethoxyanthracene in acetic acid in the presence
of p-chloranil gave the adduct 20 in 93% yield, which was
further oxidized by CAN to yield heptiptycene tetra-
quinone 21 in 35% yield. 21 with U-shaped structure is
composed of a pentiptycene diquinone unit and a pen-
tiptycene tetraquinone unit. Its 1H NMR spectrum
showed three singlets for the bridgehead protons (δ 6.51,
6.11, 5.74) and two singlets for the CHdCH protons of
terminal quinoid rings (δ 6.62, 6.60). Its 13C NMR
spectrum showed four signals for the carbonyl carbons
(180.8, 180.7, 178.6, 176.4) and three signals for the
bridgehead carbons (47.3, 42.3, 38.7) as required.
In the presence of p-chloranil, the reaction of triptycene
diquinone 6 with 2 equiv of 2 in acetic acid gave a mixture
of three adducts 18a, 18b, and 18c, which could not be
separated by the conventional column chromatography
method. However, their CAN oxidative products 19a,
19b, and 19c could be obtained by careful separation with
column chromatography. The structure of heptiptycene
tetraquinone 19a was easily distinguished from the other
two isomers by the NMR spectra. The 1H NMR spectrum
of 19a had three magnetically unique bridgehead protons
(δ 6.04, 6.03, 6.01) and two unique vinyl protons of the
quinoid rings (δ 6.50, 6.46). However, the isomers 19b
and 19c showed very similar 1H NMR and 13C NMR
spectra so that their structures could not be directly
determined. To solve this problem, comparative reactions
were carried out. Thus, by the reaction of 2 equiv of 16a
with 1,4-dimethoxyanthracene 2 in HOAc in the presence
of p-chloranil and then CAN oxidation, two isomers of
heptiptycene tetraquinones 19a and 19c were obtained.
Similarly, the isomers of 19a and 19b were produced
from 16b with 2 (Scheme 2). The structures of the
isomers 19b and 19c could be determined by TLC
analysis compared with those for the products obtained
from the reaction of 6 and 2 shown as above. The polarity
order for the isomers in dichloromethane and petroleum
ether (1:1 v/v) is as follows: 19a < 19b < 19c.
Similarly, the one-pot reaction of pentiptycene quinone
10 with 1,4-dimethoxyanthracene gave a mixture of two
isomers 22a and 22b, which were then demethylated to
the mixture of heptiptycene triquinone 23a and 23b in
80% yield. Similar to the case of 18, 22a and 22b were
hardly separated, but their oxidative products 23a and
23b could be obtained by the column chromatography
1
method. The isomers 23a and 23b showed similar H
SCHEME 2
920 J. Org. Chem., Vol. 70, No. 3, 2005