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Chemistry Letters Vol.36, No.10 (2007)
Dual Polyrotaxane: One-pot Synthesis of Topological Polymer
by Using Metathesis Reaction
Kazuhiro Yamabuki, Yukio Isobe, Kenjiro Onimura, and Tsutomu OishiÃ
Graduate School of Science and Engineering, Yamaguchi University,
2-16-1 Tokiwadai, Ube 755-8611
(Received June 21, 2007; CL-070667; E-mail: oishi@yamaguchi-u.ac.jp)
The topological polyrotaxane was built from an ammonium
of pseudorotaxanes are cross-linked.2a In these methods, because
these components have different reaction groups between a
wheel and an axle, the methods demand a lot of procedures to
synthesize topological polyrotaxanes.
In this paper, we report on the one-pot synthesis of the
topological polyrotaxane consisting of the non-dumbbell-shaped
axle component, which is the ammonium salt 1 bearing one
terminal olefin and one terminal bulky unit, and the modified
dibenzo-24-crown-8 (DB24C8) 2 having one olefin chain as a
wheel by metathesis reaction.
salt as an axle component bearing one olefin and one bulky unit
at the end of chain and the derivative of dibenzo-24-crown-8
(DB24C8) as a wheel component having one terminal olefin.
In this system, two kinds of reactions work at the same time as
a driving force of the polymer construction. One is the inclusion
reaction between the ammonium salt part of axle and the wheel,
another is metathesis reaction between olefins of the axle and
olefins of the wheel.
To understand the basic structure of our aimed polyrotaxane,
we synthesized the model compound, as shown in Scheme 2.
A catalytic amount of the ruthenium complex 43 was added
to a solution of the axle 1 and the wheel 3 in CH2Cl2 at room
temperature. After 24 h, a few drops of ethyl vinyl ether were
put in the solution, and then the solution was stirred at room tem-
perature. The solution was evaporated and the resulting residue
was purified by precipitation into MeOH to afford [3]rotaxane 5
as pale purple solid.
In a manner similar to synthesis of 5, the desirable topolog-
ical polyrotaxane 6 was synthesized by heating the mixture of 1,
2, and 4 in CDCl3 as shown in Scheme 3.4 After 85 h, a few drops
of ethyl vinyl ether were put in the solution, and then the solution
was stirred at room temperature. Then, the solution was evapo-
rated to give the crude product as a viscous liquid. The structure
of the product was analyzed by 1H NMR spectroscopy and GPC
measurement. The 1H NMR profile of the product consisting
of 1 and 2 represented broad signals. In addition, the methylene
protons neighboring the ammonium salt unit displayed the
downfield shift and the spectrum was similar to one of rotaxane
5 consisting of 1 and 3.5 These results present that a topological
polyrotaxane was constructed by the inclusion reaction and
metathesis reaction.
Rotaxane has many possibilities in some fields of electronic
devices, medical materials, etc.1 Moreover, interlocked poly-
mers such as topological polyrotaxanes are capable of exercising
new physical properties, in contrast with low-molecular-weight
rotaxanes and rigid polyrotaxanes.2 In these topological polyro-
taxanes, the wheel-connected compound takes some axles into
the interior cavities as shown in Scheme 1. Therefore, topologi-
cal connections made by wheel components allow included axles
to move freely, unlike the rigid and typical polyrotaxane.
This time, we paid attention to the unique and simple syn-
thetic method of the above topological polyrotaxanes. In synthe-
ses of reported topological polyrotaxanes, the wheel-connected
compound and the dumbbell-shaped axle compound are sepa-
rately synthesized, and then these components are made to react
in the same container to give topological polyrotaxanes, using
the slipping method or the entering method.2b–d The other way
is that wheels in typical polyrotaxanes prepared by capping ends
Typical Polyrotaxane
Dumbbell-shaped Axle
Wheel
Moreover, the GPC measurement clearly revealed that the
Topological Polyrotaxanes
Wheel-connected compound
3
1
4
5
Scheme 1. Illustration of the typical rotaxane and topological
polyrotaxane structures.
Scheme 2. Syntehsis of [3]rotaxane 5 by metathesis reaction.
Copyright Ó 2007 The Chemical Society of Japan