Synthesis of [60]fullerene-containing [2]rotaxanes using axle molecules bearing donor moiety

Article abstract of DOI:10.1016/j.tetlet.2010.11.155

[2]Rotaxanes, consisting of a fullerene derivative bearing an electron-donating 1,5-dialkoxynaphthalene moiety and a macrocycle containing electron-deficient naphthalenetetracarboxylic diimide moieties, were first successfully synthesized and characterize

Full text of DOI:10.1016/j.tetlet.2010.11.155

Tetrahedron Letters 52 (2011) 623–625
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis of [60]fullerene-containing [2]rotaxanes using axle molecules
bearing donor moiety
⇑
Yoshinori Kasai, Chika Sakamoto, Naoki Muroya, Shin-ichiro Kato, Yosuke Nakamura
Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
[2]Rotaxanes, consisting of a fullerene derivative bearing an electron-donating 1,5-dialkoxynaphthalene
moiety and a macrocycle containing electron-deficient naphthalenetetracarboxylic diimide moieties,
were first successfully synthesized and characterized.
Received 21 October 2010
Revised 25 November 2010
Accepted 30 November 2010
Available online 4 December 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Rotaxane
Fullerene
Donor–acceptor interaction
Naphthalene diimide
1,5-Dialkoxynaphthalene
Interlocked molecules such as catenanes and rotaxanes have at-
tracted much attention due to their fascinating topological features
and potential application to molecular devices.1 The introduction
of [60]fullerene into these systems promises further enhancement
of the functionality of such molecular assemblies, because of its
[2]rotaxanes 1, while their intramolecular Bingel reactions gave
[2]catenanes 2 with D–A–D–A stacking structure. These results
prompted us to synthesize other fullerene-based [2]rotaxanes.
Thus, reversing the donor and acceptor moieties in 1, we have
examined the synthesis of [2]rotaxanes 3a and 3b, which consist
of a fullerene derivative bearing an electron-donating 1,5-dialk-
oxynaphthalene moiety and a macrocycle including electron-defi-
cient naphthalenetetracarboxylic diimide moieties. In the
synthesis of 3a and 3b, the esterification was employed as the
key reactions, instead of Bingel reaction for 1, in order to suppress
the undesirable side reactions, such as intramolecular reactions
and oligomeric reactions. In 3b, a tris(4-t-butylphenyl)methyl
group was used as one of the stoppers at the two ends of the axle
compound. Herein, we report the synthesis and characterization
of 3a and 3b.
unique electronic properties, especially as
a strong electron
acceptor.2
Recently, we have successfully prepared neutral fullerene-
based [2]rotaxanes 1 and [2]catenanes 2 based on the donor–
acceptor interaction between a fullerene derivative carrying an
electron-deficient aromatic diimide moiety and an electron-
donating dinaphthocrown ether.3 In the presence of 1,5-dinaph-
tho-38-crown-10 ether, the intermolecular Bingel reactions of
[60]fullerene monoadducts bearing a naphthalenetetracarboxylic
diimide moiety with [60]fullerene successfully afforded novel
O
N
O
O
O
O
n
O
O
O
O
O
O
O
O
O
O
O
n
O
O
O
O
O
O
EtO
N
N
O
O
O
O
O
EtO
OEt
O
O
O
n
O
O
O
N
O
O
O
O
O
n
O
O
O
O
O
EtO
O
1
2
⇑
Corresponding author. Tel.: +81 277 30 1310; fax: +81 277 30 1314.
E-mail address: nakamura@chem-bio.gunma-u.ac.jp (Y. Nakamura).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.11.155

624
Y. Kasai et al. / Tetrahedron Letters 52 (2011) 623–625
O O
O
EtO
O
OH
O
O
3 OH
O
O
O
EtO
O
3 O
O
O
, DCC, DMAP
6a
CHCl3, r.t., 20 h
4a: Y = 40%
O
O
3 OH
O
HO
O
O
3
O
OH
4c: Y = 86%
O
6b
O
3OH
, DCC, DMAP
O
O
3 O
O
O
CHCl3, r.t., 20 h
4b: Y = 56%
O
O
Hd
O
O O
EtO
O
N
O
N
O
O
O
N
O
N
O
OH
O
O
O
(CH2)4
(CH2)4
O
O
O
O
(CH2)4
O
N
O
O
N
O
O
OEt
EtO
O
O 3
O
O
O
He
O 3
Ha
(CH2)4
Hc
He
Hb
, MNBA, DMAP
5a
O
6a
O
N
O
4a
N
CHCl3, -30 or -10 ºC, 30 min
CHCl3, -30 or -10 ºC, 10 h
O
3a
O
O
O O
EtO
O
N
O
N
O
Hd
O
O
N
O
OH
(CH2)4
N
O
(CH2)4
O
O
O
O
O
N
O
O
N
O
(CH2)4
O
O
OEt
O
O
O 3
O
O
O
O
3
He
Ha
(CH2)4
Hc
Hf
, MNBA, DMAP
CHCl3, -30 ºC, 10 h
5a
6a
Hb
4b
O
N
O
N
O
CHCl3, -30 ºC, 30 min
O
3b
Scheme 1. Synthesis of [2]rotaxanes 3a and 3b.
Scheme 1 depicts the overall synthetic route of rotaxanes 3a
broadening and shift were observed for the aromatic proton peaks.
With decreasing temperature, each aromatic peak gradually re-
solved into two peaks due to the complexed and uncomplexed spe-
cies (Supplementary data). These observations undoubtedly
indicate the pseudorotaxane formation between 4c and 5a. Similar
behavior was observed for 4a (or 4b) and 5a. Thus, 5a was em-
ployed as the electron-deficient macrocycle in the synthesis of
rotaxanes.
and 3b, which were synthesized by the reactions of axle mole-
cules 4a and 4b bearing a 1,5-dialkoxynaphthalene moiety with
carboxylic acid 6a4 in the presence of electron-deficient macrocy-
cles 5.
A 1,5-dialkoxynaphthalene derivative 4c5 bearing two tetraeth-
ylene glycol residues was allowed to react with carboxylic acids 6a
and 6b6 in the presence of DCC and DMAP to give 4a and 4b,
respectively.
Prior to the synthesis of [2]rotaxanes 3a and 3b, the pseudoro-
taxane formation between 4c and some electron-deficient macro-
cycles was investigated by 1H NMR spectroscopy in order to find
out the suitable electron-deficient macrocycles. There have been
fewer examples of electron-deficient macrocycles than electron-
rich macrocycles. As electron-deficient macrocycles, 5b, 5c, and
5d in the literature7 were examined, in which two naphthalenetet-
racarboxylic diimide moieties are bridged by oligomethylene or
oligooxyethylene linkages. The 1H NMR spectra of the mixture of
4c and 5b–d at rt showed almost the sum of each component with-
out any broadening or shift for the aromatic proton peaks, suggest-
ing that the pseudorotaxane is hardly formed. Probably, the two
naphthalenetetracarboxylic diimide moieties in 5b–d are too much
separated to accommodate the 1,5-dialkoxynaphthalene moiety of
4c. Thus, 5a with shorter oligomethylene linkages was synthesized,
and the pseudorotaxane formation between 4c and 5a was
examined. In the 1H NMR spectra of 4c and 5a at rt, remarkable
O
O
5a: R = -(CH2)6-
5b: R = -(CH2)8-
5c: R = -(CH2)12
N
O
N
O
R
R
-
O
N
O
O
N
O
5d: R = -(CH2CH2O)3CH2CH2-
In the synthesis of [2]rotaxane 3a, 4a and 5a were first mixed in
CHCl3 at low temperatures (À30 or À10 °C) to form pseudorotax-
ane. After 30 min, carboxylic acid 6a, DMAP, and MNBA (2-
methyl-6-nitrobenzoic anhydride) were added to the mixture,
which was stirred for further 10 h at the same temperature.
[2]Rotaxane 3a was isolated by column chromatography and GPC
in 2–3% yield. The yield was almost independent of the tempera-
ture. The dumbbell-like compound resulting from 4a and 6a was
also obtained, and the unreacted starting materials were
recovered.

Y. Kasai et al. / Tetrahedron Letters 52 (2011) 623–625
625
Figure 1. 1H NMR spectra (500 MHz) of (a) [2]rotaxane 3a, (b) axle molecule 4a, and (c) macrocycle 5a in CDCl3 at 298 K. d: Residual solvent peak.
[2]Rotaxane 3b bearing a tris(4-t-butylphenyl)methyl stopper
was also prepared in a similar manner at À10 °C. The yield was
comparable to that of 3a.
Acknowledgment
This work was partially supported by a Grant-in-Aid for Scien-
tific Research from the Ministry of Education, Culture, Sports, Sci-
ence and Technology, Japan.
Both 3a and 3b were identified by NMR, UV–vis, and mass
spectroscopies. In their FD mass spectra, the molecular ion peaks
(m/z = 2988 and 2643, respectively) were clearly observed. Their
UV–vis spectra showed a weak, broad band around 700 nm, which
is characteristic of [60]fullerene monoadducts. In the 1H NMR
spectrum of 3a, the intensity of the COOCH2COO methylene pro-
tons (He; d 5.04) is twice of that of Ha, Hb, and Hc protons of the axle
components (Fig. 1). In 3b, two methylene proton peaks (He; d 5.05,
Hf; d 4.64) are observed (Fig. S1). These observations indicate that
the esterification definitely proceeded between 4a (or 4b) and 6a.
No aromatic proton peaks due to pristine 4a and 5a were detected
in 3a. Instead, only one set of remarkably high-field shifted aro-
Supplementary data
Supplementary data (experimental procedures, 1H NMR spec-
tra, mass spectra, and VT 1H NMR spectra) associated with this arti-
cle can be found, in the online version, at doi:10.1016/j.tetlet.
2010.11.155.
References and notes
matic peaks (Ha, Hb, Hc, and Hd) of 4a and 5a were observed (Dd
ꢀ0.3–0.5 ppm). These high-field shifts are comparable to those in
rotaxane 1,3 and ascribed to the shielding effect of the opposite
aromatics, apparently indicating that 5a encircles the 1,5-dialkoxy-
naphthalene moiety of 4a. The composition of 4a and 5a in 3a was
found to be 1:1 based on the integral ratio. Therefore, it was
undoubtedly demonstrated that 3a is a [2]rotaxane composed of
4a, 5a, and 6a. [2]Rotaxane 3b bearing a tris(4-t-butylphenyl)
methyl group showed spectroscopic features similar to those of 3a.
In summary, we have successfully synthesized fullerene-based
[2]rotaxanes 3a and 3b by the reactions of axle molecules 4a
and 4b with carboxylic acid 6a in the presence of macrocycle 5a
by using the donor-acceptor interaction between the electron-
donating 1,5-dialkoxynaphthalene moiety and the electron-
deficient naphthalenetetracarboxylic diimide moieties. These results
show the versatility of the synthetic method. To the best of our
knowledge, rotaxanes 3a and 3b are the first examples of rotaxanes
containing a naphthalenetetracarboxylic diimide-based macrocyle.
The investigation on the electronic, electrochemical, and photo-
physical properties of 3a and 3b is now in progress.
1. (a) Rowan, S. J.; Cantrill, S. J.; Cousins, G. R. L.; Sanders, J. K. M.; Stoddart, J. F.
Angew. Chem., Int. Ed. 2002, 41, 899; (b) Molecular Catenanes, Rotaxanes and
Knots; Sauvage, J.-P., Dietrich-Buchecker, C., Eds.; Wiley-VCH: Weinheim, 1999;
(c) Molecular Devices and Machines: A Journey into the Nano World; Balzani, V.,
Credi, A., Venturi, M., Eds.; Wiley-VCH: Weinheim, 2003.
2. (a) Diederich, F.; Dietrich-Buchecker, C.; Nierengarten, J.-F.; Sauvage, J.-P. J.
Chem. Soc., Chem. Commun. 1995, 781; (b) Ashton, P. R.; Diederich, F.; Gómez-
López, M.; Nierengarten, J.-F.; Preece, J. A.; Raymo, F. M.; Stoddart, J. F. Angew.
Chem., Int. Ed. 1997, 36, 1448; (c) Watanabe, N.; Kihara, N.; Furusho, Y.; Takata,
T.; Araki, Y.; Ito, O. Angew. Chem., Int. Ed. 2003, 42, 681; (d) Mateo-Alonso, A.;
Guldi, D. M.; Paolucci, F.; Prato, M. Angew. Chem., Int. Ed. 2007, 46, 8120.
3. Nakamura, Y.; Minami, S.; Iizuka, K.; Nishimura, J. Angew. Chem., Int. Ed. 2003,
42, 3158.
4. Nierengarten, J.-F.; Herrmann, A.; Tykwinski, R. R.; Ruttimann, M.; Diederich, F.;
Boudon, C.; Gisselbrecht, J.-P.; Gross, M. Helv. Chim. Acta 1997, 80, 293.
5. Ashton, P. R.; Huff, J.; Menzer, S.; Parsons, I. W.; Preece, J. A.; Stoddart, J. F.;
Tolley, M. S.; White, A. J. P.; Williams, D. J. Chem. Eur. J. 1996, 2, 31.
6. Ashton, P. R.; Ballardini, R.; Balzani, V.; Philp, D.; Prodi, L.; Raymo, F. M.;
Reddington, M. V.; Spencer, N.; Stoddart, J. F.; Venturi, M.; Williams, D. J. J. Am.
Chem. Soc. 1996, 118, 4931.
7. (a) Jazwinski, J.; Blacker, A. J.; Lehn, J.-M.; Cesario, M.; Guilhem, J.; Pascard, C.
Tetrahedron Lett. 1987, 28, 6057; (b) Ozser, M. E.; Uzun, D.; Elci, I.; Demuth, M.
Photochem. Photobiol. Sci. 2003, 2, 218; (c) Hansen, J. G.; Feeder, N.; Hamilton, D.
G.; Gunter, M. J.; Becker, J.; Sanders, J. K. M. Org. Lett. 2000, 2, 449.