Novel π-conjugated cyclophanes: Magazine rack molecules

Article abstract of DOI:10.1246/cl.2002.136

Synthesis of cyclophanes having alternating arylene-ethynylene as well as-ethenylene arrays is described. It is disclosed that these compounds are chiral on the basis of X-ray analysis and fluxional in solution on the basis of NMR spectra.

Full text of DOI:10.1246/cl.2002.136

136
Chemistry Letters 2002
Novel ꢀ-Conjugated Cyclophanes: Magazine Rack Molecules
Akihiro Orita, Lasheng Jiang, Madoka Tsuruta, and Junzo Oteraꢀ
Department of Applied Chemistry, Okayama University of Science, Ridai-cho, Okayama 700-0005
(Received October 31, 2001; CL-011086)
Synthesis of cyclophanes having alternating arylene-ethy-
nylene as well as-ethenylene arrays is described. It is disclosed
that these compounds are chiral on the basis of X-ray analysis and
fluxional in solution on the basis of NMR spectra.
The construction of cyclic ꢀ-conjugated array is one of the
challenging topics.1 Above all, topologically interesting ꢀ-
conjugated molecules are attracting considerable attention from
the viewpoint of their structural and electronic properties2 as well
as host/guest interaction.3 Therefore, a variety of ꢀ-conjugated
cyclophanes bearing iterative arylene-ethynylene4 or -etheny-
lene5 moieties have been synthesized so far. As part of our project
to explore ꢀ-conjugated cyclophanes bearing unique structural
features, we have tackled the synthesis of cyclophanes 1 since
these compounds were expected to adopt a magazine rack-like
structure on the basis of molecular modeling.
Figure 1. The ORTEP view of (Z; Z)-1a (thermal ellipsoids
ꢁ
ꢀ
for 50% probability). Selected bond lengths (A) and angles ( ):
C(1)-C(2) 1.212(8), C(17)-C(18) 1.200(8), C(3)-C(8)-C(9)-
C(10) 68.2(8), C(9)-C(10)-C(11)-C(12) 34.0(9), C(15)-C(16)-
C(19)C(20) 23.0.
tion of (E; E) and (Z; E) isomers to (Z; Z) by UV irradiation8 or
thiol/AIBN catalysis9 was not successful, recrystallization from
AcOEt/hexane furnished single crystals of pure (Z; Z) isomer
which were suitable for X-ray analysis (Figure 2).10
The desired compounds 1 were readily synthesized by Wittig
reaction between 2 and 3 (Scheme 1).6
Figure 2. The ORTEP view of (Z; Z)-1b (thermal ellipsoids
ꢁ
ꢀ
for 50% probability). Selected bond lengths (A) and angles ( ):
C(1)-C(2) 1.207(4), C(25)-C(26) 1.199(4), C(3)-C(12)-C(13)-
C(14) 52.4(5), C(13)-C(14)-C(15)-C(16) 34.5(5), C(23)-
C(24)-C(27)-C(28) 41.6. Several hydrogens are omitted for
clarity.
X-ray analyses revealed both cyclophanes 1a and 1b adopt
the magazine rack motif as expected, yet, surprisingly, dihedral
angles of arylenes connected by the ethynylene unit are 23.0 ꢁ and
41.6 ꢁ, respectively, indicating that the structure is distorted from
the symmetrical one. As a consequence, the compounds are chiral
and the (M)- and (P)-isomers are packed alternatively in the
crystal as depicted schematically in Figure 3.
Scheme 1.
With LiOEt (2.1 equiv) in THF, Wittig olefination of 2a, with
dialdehyde 3a (1.1 equiv) proceeded quite smoothly to furnish 1a
in a pure form (68%, Z; Z=E; E ¼ 91=9). Recrystallization from
EtOAc/hexane furnished pure crystals of (Z; Z)-1a, which was
subjected to X-ray analysis (Figure 1).7
Naphthylene analog 1b was obtained similarly in 60% yield
(Z; Z=E; E=Z; E ¼ 43=17=40). Although attempted isomeriza-
On the other hand, NMR spectra of 1a and 1b showed totally
symmetric patterns at rt. Upon lowering the temperature, signals
Copyright Ó 2002 The Chemical Society of Japan

Chemistry Letters 2002
137
F. See, M. Churchill, and J. D. Ferrara, J. Organomet. Chem.,
470, 231 (1994). b) H. A. Staab and F. Graf, Chem. Ber., 103,
1107 (1970).
5
6
a) Y. Kuwatani, T. Yoshida, A. Kusaka, M. Oda, K. Hara, M.
Yoshida, H. Matsuyama, and M. Iyoda, Tetrahedron, 57,
3567 (2001). b) M. Iyoda, Y. Kuwatani, T. Yamauchi, and M.
Oda, J. Chem. Soc., Chem. Commun., 1988, 65.
Preparation of 2 and 3: 2,20-Dibromo-1,10-diphenylacetylene
was prepared from 2-bromobenzyl sulfone and 2-bromobenz-
aldehyde according to our method.13 The treatment of
dibromide with BuLi and DMF in THF afforded dialdehyde
3a in 79% yield. Reduction of 3a with LiAlH4 and the
following chlorination of crude product by NCS/PPh3
provided dichloride in 82% yield. The reaction of dichloride
with PPh3 (4 equiv) gave 2a in 87% yield. Naphthylene
analogue 3b was prepared by conventional methods:
Sonogashira coupling14 of 1-bromo-2-formylnaphthalene
with trimethylsilyl acetylene, deprotection and coupling with
another bromoaldehyde. Dialdehyde 3b was transformed to
2b analogously.
Figure 3. Partial view of (Z; Z)-1a in the crystal.
experienced broadening to some extent although no splitting was
observed even at À80 ꢁC.11 This phenomenon may possibly be
explained interms of the rapid fluxional conformational change in
solution between the enantiomeric species which innately should
give rise to unsymmetrical patterns.12
In summary, we have succeeded in the syntheses of
cyclophanes with a magazine rack motif which is distorted into
chiral conformations in the solid state. In solution, these
molecules are quite fluxional even at low temperature.
1
7
(Z; Z)-1a: H NMR (CDCl3) ꢁ 6.90 (s, 4H), 7.06–7.09 (m,
4H), 7.11–7.15 (m, 8H), 7.21–7.25 (m, 4H); 13CNMR
(CDCl3) ꢁ 92.3, 122.6, 126.7, 127.6, 128.6, 131.2, 131.8,
140.3. The crystal data are as follows; C32H20, FW ¼ 404:51,
Monoclinic, Space Group P21 (#4), a ¼ 8:038(2), b ¼
11:138(5),
c ¼ 24:128(4),
ꢂ ¼ 94:28(2) ꢁ,
Dcalc
¼
¼
ꢀ 3
1:25 g cmÀ3, V ¼ 2154:0(9) A , Z ¼ 4, R ¼ 0:039, Rw
This work was partially supported by a Grant-in-Aid for
Science Research (No. 12750752) from the Ministry of Educa-
tion, Culture, Sports, Science and Technology, Japan.
0:051 for 3931 reflections with I > 3ꢃ(I) and 738 variable
parameters.
8
9
V. Ramamurthy, Y. Butt, C. Yang, P. Yang, and R. S. H. Liu,
J. Org. Chem., 38, 1247 (1973).
M. Schwarz, G. F. Graminski, and R. M. Water, J. Org.
Chem., 51, 260 (1986).
This paper is dedicated to Prof. Teruaki Mukaiyama on the
occasion of his 75th birthday.
10 (Z; Z)-1b: 1H NMR (CD2Cl2) ꢁ 7.12 (t, J ¼ 7:5 Hz, 4H), 7.20
(s, 4H), 7.26 (d, J ¼ 8:5 Hz, 4H), 7.33 (t, J ¼ 7:5 Hz, 4H), 7.61
(d, J ¼ 8:5 Hz, 4H), 7.72 (d, J ¼ 8:5 Hz, 8H); 13CNMR
(CDCl3) ꢁ 96.8, 119.5, 125.8, 125.9, 126.2, 126.5, 127.7,
132.0, 132.3, 133.3, 139.2. The crystal data are as follows;
C48H28, FW ¼ 604:75, Monoclinic, Space Group P21 (#4),
a ¼ 9:417(1), b ¼ 14:999(3), c ¼ 23:142(3), ꢂ ¼ 98:50(1) ꢁ,
References and Notes
1
a) G. J. Palmer, S. R. Parkin, and J. E. Anthony, Angew.
Chem., Int. Ed. Engl., 40, 2509 (2001). b) M. J. Marsella, Z-Q.
Wamg, R. J. Reid, and K. Yoon, Org. Lett., 3, 885 (2001). c)T.
Kawase, N. Ueda, K. Tanaka, Y. Seirai, and M. Oda,
Tetrahedron Lett. 42, 5509 (2001). d) H. N. C. Wong, P. J.
Garratt, and F. Sondheimer, J. Am. Chem. Soc., 96, 5604
(1974). e) M. Chakraborty, C. A. Tessie, and W. J. Young, J.
Org. Chem., 64, 2947 (1999).
ꢀ 3
Dcalc ¼ 1:24 g cmÀ3, V ¼ 3232:9(3) A , Z ¼ 4, R ¼ 0:034,
Rw ¼ 0:033 for 5434 reflections with I > 3ꢃ(I) and 1089
variable parameters.
11 Further decreasing the temperature caused precipitation due
to relatively low solubility of 1b.
2
3
a) S. Kammermeier, P. G. Jones, and R. Herges, Angew.
Chem., Int. Ed. Engl., 36, 2200 (1997). b) R. Saito, G.
Dresselhaus, and M. S. Dresselhaus, ‘‘Physical Properties of
Carbon Nanotubes,’’ Imperial College Press, London (1998).
a) J. Gross, G. Harder, A. Siepen, J. Harren, F. Vogtle, H.
¨
Stephan, K. Gloe, B. Ahlers, K. Cammann, and K. Rissanen,
12 PM3 calculations suggested that the distorted structure is the
most stable conformation of 1a and the interchange barrier
between (P)- and (M)-1a was estimated less than 5 kcal/mol:
MOPAC2000; Fujitsu Ltd.: Tokyo, Japan.
Chem. Eur. J., 2, 1585 (1996). b) C. Muller, J. A. Whiteford,
¨
13 A. Orita, N. Yoshioka, P. Struwe, A. Braier, A. Beckmann,
and J. Otera, Chem. Eur. J., 5, 1355 (1999).
14 K. Sonogashira, Y. Tohda, and N. Hagihara, Tetrahedron
Lett., 1975, 4467.
and P. J. Stang, J. Am. Chem. Soc., 120, 9827 (1998). c) M.
Iyoda, T. Horino, F. Takahashi, M. Hasegawa, M. Yoshida, Y.
Kuwatani, Tetrahedron Lett., 42, 6883 (2001).
4
a) D. Solooki, J. D. Bradshaw, C. A. Tessier, W. J. Youngs, R.