Unsaturated strained cyclophanes based on dibenz[a,j]anthracene by an intramolecular McMurry olefination

Article abstract of DOI:10.1021/ol801163v

(Chemical Equation Presented) A new type of rigid conjugated unsaturated strained cyclophane derivative containing dibenz[a,j]anthracene units was facilely synthesized through an intramolecular McMurry reaction without intermolecular dimerization products

Full text of DOI:10.1021/ol801163v

ORGANIC
LETTERS
2008
Vol. 10, No. 14
3113-3116
Unsaturated Strained Cyclophanes
Based on Dibenz[a,j]anthracene by an
Intramolecular McMurry Olefination
Hai-Bo Chen, Jie Yin, Yi Wang, and Jian Pei*
The Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry
of Education, College of Chemistry and Molecular Engineering, Peking UniVersity,
Beijing 100871, China
jianpei@pku.edu.cn.
Received May 21, 2008
ABSTRACT
A new type of rigid conjugated unsaturated strained cyclophane derivative containing dibenz[a,j]anthracene units was facilely synthesized
through an intramolecular McMurry reaction without intermolecular dimerization products in good yields. The photophysical properties of
these cyclophane derivatives in dilute solution were investigated, and molecular modeling was employed to study their electronic properties.
Cyclophanes and assorted cyclic compounds with novel
shapes and molecular geometries have attracted considerable
attention due to their interesting properties and potential
applications in host-guest systems, molecular recognition,
information storage, bioscience, and nano devices.1 Never-
theless, despite the abundance of molecular designs, the
efficient synthesis of conjugated unsaturated strained cyclo-
phanes,2 whose preparation usually suffered from multiple
synthetic steps and overall low yields, is still of great
challenge.1e,3 Therefore, the design and synthesis of new
cyclophanes and assorted cage compounds with novel shapes
and supramolecular geometries continue to be topics of
current interest. The investigation of the chemical and
physical properties of new cyclophanes with novel skeletons
also gives insight into the relationship between the rigid
structure of cyclophanes and their properties as well as their
applications.
The McMurry reaction, an effective way to form a CdC
bond under moderate conditions, has been employed to form
strained unsaturated conjugated cyclophanes in a few cases.4
In this contribution, we report on the design, synthesis, and
characterization of a new family of unsaturated conjugated
shape-persistent cyclophane derivatives based on a diben-
z[a,j]anthracene unit through the McMurry reaction. The
McMurry reaction, in our case, leads to the reductive
coupling of two carbonyl groups to form intramolecular
cyclization products without intermolecular dimerization to
macrocycles. Our results show that at suitable distances
strained double bonds can be formed effectively using the
classic McMurry coupling reaction, providing a new strategy
in the construction of conjugated unsaturated strained cy-
clophanes. These conjugated cyclophanes possess strained
conformation owing to the unsaturated linkage as well as
the rigid dibenz[a,j]anthracene unit, which shows strong blue
emission in dilute solution. These new members of the
10.1021/ol801163v CCC: $40.75
Published on Web 06/24/2008
2008 American Chemical Society

cyclophane family may have potential applications in
theoretical chemistry, guest-host systems, and optoelec-
tronics.
Scheme 1 illustrates the synthetic approaches to the
cyclophane 7a. The alkylation of the commercially available
material, 3,4-dihydroxy-benzaldehyde, followed by the
2,4-diiodobenzene with catalyst Pd(PPh3)2Cl2 followed by a
Suzuki coupling reaction with phenylboronic acid gave
compound 4 in 84% yield. Dibenz[a,j]anthracene iodide 5
was prepared in almost quantitative yield following the
classical procedure via ICl induced intramolecular cyclization
of 4.5 Dicarbonyl 6a was synthesized through another Suzuki
coupling reaction between dibenz[a,j]anthracene iodide 5
and 4-formylphenylboronic acid in 88% yield. Finally, the
McMurry reaction was employed for the coupling of
aldehyde groups of 6a. It is quite worth noting that the
intramolecular coupling product 7a was observed without
any intermolecular dimerization side product. This result
was in sharp contrast to our recently reported results on
the synthesis of another type of macromolecule, indicating
the importance of distances between the reacting groups
in the McMurry reaction.6
Scheme 1. Synthesis of Cyclophane 7a
The intramolecular coupling was unambiguously con-
1
1
firmed by H NMR spectra and MALDI-TOF MS. The H
NMR spectra in CDCl3 showed the evident change of the
proton signal from molecule 6a to cyclophane 7a, as was
shown in Figure 1. After the Suzuki reaction, the signal
assigned to Hb in 5 at a chemical shift of 9.85 ppm (see the
Supporting Information) shifted to δ 7.25 ppm in compound
6a. Such a shift resulted from the shielding effect from the
benzene rings connected to the dibenz[a,j]anthracene unit.
This signal further shifted upfield at an unusual chemical
shift δ of 5.91 ppm after the intramolecular McMurry
olefination, which was due to the additional shielding effect
(1) (a) Mason, P. E.; Bryant, W. S.; Gibson, H. W. Macromolecules
1999, 32, 1559–1569. (b) Brown, C. L.; Jonas, U.; Preece, J. A.; Ringsdorf,
H.; Seitz, M.; Stoddart, J. F. Langmuir 2000, 16, 1924–1930. (c) Dvornikovs,
V.; House, B. E.; Kaetzel, M.; Dedman, J. R.; Smithrud, D. B. J. Am. Chem.
Soc. 2003, 125, 8290–8301. (d) Wang, W.; Xu, J.; Lai, Y. H. Org. Lett.
2003, 5, 2765–2768. (e) Jeppesen, J. O.; Nielsen, M. B.; Becher, J. Chem.
ReV. 2004, 104, 5115–5131. (f) Camacho, D. H.; Salo, E. V.; Guan, Z.
Org. Lett. 2004, 6, 865–868. (g) Katz, E.; Lioubashevsky, O.; Willner, I.
J. Am. Chem. Soc. 2004, 126, 15520–15532. (h) Ariga, K.; Nakanishi, T.;
Terasaka, Y.; Tsuji, H.; Sakai, D.; Kikuchi, J. Langmuir 2005, 21, 976–
981. (i) Das, B.; Abe, S. J. Phys. Chem. B 2006, 110, 23806–23811. (j)
Bogdan, N.; Grosu, I.; Benoˆıt, G.; Toupet, L.; Ramondenc, Y.; Condamine,
E.; Dumitrescu, I. S.; Ple´, G. Org. Lett. 2006, 8, 2619–2622. (k) Cooke,
G.; Woisel, P.; Bria, M.; Delattre, F.; Garety, J. F.; Hewage, S. G.; Rabani,
G.; Rosair, G. M. Org. Lett. 2006, 8, 1423–1426. (l) Tanaka, K.; Hori, T.;
Osaka, T.; Noguchi, K.; Hirano, M. Org. Lett. 2007, 9, 4881–4884. (m)
Aprahamian, I.; Dichtel, W. R.; Ikeda, T.; Heath, J. R.; Stoddart, J. F. Org.
Lett. 2007, 9, 1287–1290. (n) Bunker, B. C.; Huber, D. L.; Kushmerick,
J. G.; Dunbar, T.; Kelly, M.; Matzke, C.; Cao, J.; Jeppesen, J. O.; Perkins,
J.; Flood, A. H.; Stoddart, J. F. Langmuir 2007, 23, 31–34. (o) Rulkens,
R.; Gates, D. P.; Balaishis, D.; Pudelski, J. K.; McIntosh, D. F.; Lough,
A. J.; Manners, I. J. Am. Chem. Soc. 1997, 119, 10976–10986.
(2) (a) Rubin, Y.; Parker, T. C.; Khan, S. I.; Holliman, C. L.; McElvany,
S. W. J. Am. Chem. Soc. 1996, 118, 5308–5309. (b) Nitschke, J.; Tilley,
T. D. J. Org. Chem. 1998, 63, 3673–3676. (c) Fox, J. M.; Lin, D. J. Org.
Chem. 1998, 63, 2031–2038. (d) Hinrichs, H.; Fischer, A. K.; Jones, P. G.;
Hopf, H.; Haley, M. M. Org. Lett. 2000, 2, 969–972. (e) Iyoda, M.; Kondo,
T.; Nakao, K.; Hara, K.; Kuwatani, Y.; Yoshida, M.; Matsuyama, H. Org.
Lett. 2000, 2, 2081–2083. (f) Nitschke, J. R.; Zu1rcher, S.; Tilley, T. D.
J. Am. Chem. Soc. 2000, 122, 10345–10352. (g) Sun, S. S.; Anspach, J. A.;
Lees, A. J.; Zavalij, P. Y. Organometallics 2002, 21, 685–693. (h) Collins,
S. K.; Yap, G. P. A.; Fallis, A. G. Org. Lett. 2002, 4, 11–14. (i) Lin, C. H.;
Tour, J. J. Org. Chem. 2002, 67, 7761–7768. (j) Wang, W.; Xu, J.; Lai,
Y. H. Org. Lett. 2003, 5, 2765–2768. (k) Baxter, P. N. W. J. Org. Chem.
2004, 69, 1813–1821. (l) Odermatt, S.; Alonso-Go´mez, J. L.; Seiler, P.;
Cid, M. M.; Diederich, F. Angew. Chem. 2005, 117, 5203–5207. (m)
Morisaki, Y.; Chujo, Y. Angew. Chem., Int. Ed. 2006, 45, 6430–6437.
(3) (a) Sasaki, S.; Mizuno, M.; Naemura, K.; Tobe, Y. J. Org. Chem.
2000, 65, 275–283. (b) Baxter, P. N. W. J. Org. Chem. 2004, 69, 1813–
1821. (c) Clay, M. D.; Fallis, A. G. Angew. Chem. 2005, 117, 4107–4110.
(d) Tseng, J. C.; Huang, S. L.; Lin, C. L.; Lin, H. C.; Jin, B. Y.; Chen,
C. Y.; Yu, J. K.; Chou, P. T.; Luh, T. Y. Org. Lett. 2003, 5, 4381–4384.
Corey-Fuchs reaction afforded alkyne 3 in 91% yield. A
Sonogashira coupling reaction between 3 and 1,5-dibromo-
3114
Org. Lett., Vol. 10, No. 14, 2008

Scheme 3. Synthesis of Cyclophanes 7b-7d
Figure 1.
1H NMR spectra of dicarbonyl compound 6a and
cyclophane 7a in CDCl3 at the aromatic range.
from the CdC double bond. MALDI-TOF MS analysis of
7a (see the Supporting Information) further confirmed the
intramolecular cyclization structure. It is assumed that the
rigid scaffold offers a proper distance between two carbonyl
groups to form the strained double bond in the key step.
With the above results in hand, it is very important to
understand the effect of structural rigidity and hindrance in
this intramolecular cyclization. As shown in Scheme 2, three
Scheme 2. Synthesis of Dicarbonyl Compounds 6b-6d
solutions was ca. 10-6 M. Figure 2 illustrates the absorption
spectra of 7a-7d in solution. The absorption λmax of 7a-7d
peaked at 312 nm, assignable to the dibenz[a,j]anthracene.7
Another absorption peak at 270 nm was observed from 7c
dicarbonyl compounds 6b-d were synthesized through the
similar Suzuki coupling procedures between 5 and various
boronic acids in 74-86% yields. Herein, due to the poor
solubility of 6c and 6d in THF, the McMurry reaction of 6c
and 6d was processed in a mixed solvent of CH2Cl2 and
THF. Cyclophane 7b was obtained in a moderate yield of
53%. With the increase in length of the “arm”, cyclophanes
7c and 7d were prepared in relatively high yields of 67%
and 71%, respectively (as shown in Scheme 3), which might
come from the decrease of the torsion angles in the desired
products. The structures and the purity of all new cyclo-
phanes were confirmed by 1H and 13C NMR spectra,
MALDI-TOF MS, and elemental analysis (see the Supporting
Information). Again, no intermolecular olefination products
were observed.
Figure 2
solutions.
. Normalized absorption spectra of 7a-7d in dilute CH2Cl2
and 7d, which was closed to the absorption band of the 1,4-
diphenylbenzene section.8 Because of the slight increase in
effective conjugation length, the onset of the absorption
spectra of 7c and 7d red-shifted to about 400 nm in
comparison to that of 7a and 7b (about 390 nm).
Molecular modeling was employed to study the electronic
properties of these cyclophanes. We have optimized the
structures of cyclophanes using density functional theory
(DFT) as implemented in Gaussian 039 software with a
6-31G* basis set for carbon and hydrogen atoms. The
features of the highest occupied molecular orbital (HOMO)
and the lowest unoccupied molecular orbitals (LOMO) of
the optimized structures of cyclphanes 7a-7d are shown in
The absorption spectra of 7a-7d in dilute CH2Cl2 solu-
tions were recorded. The concentration of all compounds in
Org. Lett., Vol. 10, No. 14, 2008
3115

Figure 3. Ethoxy-substituted cyclophanes were employed to
which was in good agreement with the experimental data
above. The slight bend of the C-C single bonds and the
benzene rings between dibenz[a,j]anthracene and CdC
double bonds was observed in the models.
In conclusion, a new class of π-conjugated strained
cyclophanes were prepared through an intramolecular Mc-
Murry reaction. Such a facile synthetic approach is useful
for us to construct novel unsaturated strained cyclophanes
with different conjugation lengths, which are suitable build-
ing blocks for supramolecular assemblies and optoelectronics.
In these molecules, intramolecular coupling reactions oc-
curred in preference to intermolecular dimerization due to
the preferable distance between the two carbonyl groups. The
strained structure of the cyclophanes and the luminescent
dibenz[a,j]anthracene section provides potential applications
such as organic optoelectronics, and the CdC double bond
in the products can be employed for further modifications
for more complex structures in future studies. Also, the
combination of the number and type of unsaturated linkages
in these molecules might create a twisted conformation that
imparts helical chirality.
Acknowledgment. This work was supported by the
National Basic Research Program (No. 2006CB921602) from
the Ministry of Science and Technology and the National
Natural Science Foundation of China (NSFC 20425207,
50473016, and 20521202, and 20604001).
Figure 3. Highest occupied molecular orbitals and lowest unoc-
cupied molecular orbitals of optimized structures of 7a-7d.
Supporting Information Available: Experimental pro-
cedures and 1H and 13C NMR spectra for all new compounds
(PDF, 46 pages). This material is available free of charge
via the Internet at http://pubs.acs.org.
simplify the calculations. The highest occupied molecular
orbitals of cyclophane 7a and 7b are localized on the
dibenz[a,j]anthracene section, and so are the lowest unoc-
cupied molecular orbitals. However, for cyclophane 7c and
7d, the highest occupied molecular orbitals delocalized over
the dibenz[a,j]anthracene and benzene groups connected
through a Suzuki reaction. The extension in the conjugated
system results in a slight red shift in the absorption spectra,
OL801163V
(8) Svetlichnyi, V. A.; Kopylova, T. N.; Mayer, G. V.; Lapin, I. N. Russ.
Phys. J. 2005, 48, 901–906.
(9) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cio-slowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaro-mi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03,
ReVision B.03; Gaussian, Inc.: Wallingford, CT, 2004.
(4) (a) McMurry, J. E.; Fleming, M. P. J. Am. Chem. Soc. 1974, 96,
4708–4709. (b) Lee, E.; Yoon, H. Tetrahedron Lett. 1996, 37, 5929–5930.
(c) Furstner, A.; Thiel, O. R.; Kindlar, N.; Bartkowska, B. J. Org. Chem.
2000, 65, 7990–7995. (d) Mallory, F. B.; Butler, K. E.; Be´rule´, A., Jr.;
Mallory, C. W.; Brondyke, E. J.; Hiremath, R.; Ngo, P.; Carroll, P.
Tetrahedron 2001, 57, 3715–3724. (e) Chung, M.-K.; Qi, G.; Stryker, J. M.
Org. Lett. 2006, 8, 1491–1494.
(5) Yao, T.; Campo, M. A.; Larock, R. C. J. Org. Chem. 2005, 70, 1423–
1437.
(6) Liu, W.-J.; Zhou, Y.; Zhou, Q.-F.; Ma, Y.; Pei, J. Org. Lett. 2008,
10, 2123–2126.
(7) Bayrakceken, F. Spectrochim. Acta, Part A: Mol. Biomol. Spectrosc.
2004, 60, 3033–3036.
3116
Org. Lett., Vol. 10, No. 14, 2008