1566
Published on the web November 17, 2012
Nickel-catalyzed Decarbonylative Polymerization of 5-Alkynylphthalimides:
A New Methodology for the Preparation of Polyheterocycles
Makoto Takeuchi,1 Takuya Kurahashi,*1,2 and Seijiro Matsubara*1
1Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510
2JST, ACT-C, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012
(Received August 22, 2012; CL-120875; E-mail: kurahashi.takuya.2c@kyoto-u.ac.jp,
matsubara.seijiro.2e@kyoto-u.ac.jp)
A
nickel-catalyzed decarbonylative cycloaddition was
which was prepared in situ from [Ni(cod)2] (10 mol %) and
PMe3 (20 mol %), in refluxing toluene for 24 h (Scheme 3).
However, this provided polyisoquinolone as a polymer consist-
ing of two different components 9 and 10. The examination of
other reaction conditions such as phosphine ligands, reaction
medium, and temperature did not improve the situation.
developed, in which 5-alkynylphthalimides reacted to afford a
new type of polyisoquinolone. It was demonstrated for the first
time that decarbonylative cycloaddition can be an elementary
process of polycondensation for the preparation of heterocyclic
polymers.
To our delight, we found that the cycloaddition of the
methoxy-substituted phthalimide 11 with 12 in the presence of
the nickel catalyst furnished 13 as the sole product (Scheme 4).
Poly- and oligoheterocycles are important classes of organic
functional materials for such as semiconductors, conductors, and
light-emitting materials.1 In this context, the development of
new methods that would allow for unprecedented types of ³-
conjugated polymers remains an important research topic.2
Recently, we demonstrated the nickel-catalyzed reaction of
6-alkynylisatoic anhydride to afford polyquinolone through
decarboxylative cycloaddition (Scheme 1a).3 Our success in
the synthesis of polyquinolone with iterative cycloadditions
prompted us to investigate a new polymerization reaction, which
would allow us to prepare polyisoquinolone from 5-alkynylph-
thalimides (Scheme 1b).4 Herein, we report our results on
nickel-catalyzed iterative decarbonylative cycloaddition to give
polyisoquinolone, which is a structural isomer of polyquinolone.
Our investigation began with the preparation of the
alkynylphthalimide monomer 1 (Scheme 2). The palladium-
catalyzed Sonogashira reaction of 4-iodoaniline (2) with 1-
decyne (3) provided 4 in 57% yield. The hydrogenation of 4 in
the presence of a platinum oxide catalyst furnished 5, which was
reacted with 5-bromophthalic anhydride (6) to give the
phthalimide 7 in quantitative yield. The coupling reaction of 7
with trimethylsilylacetylene (8) gave the monomer 1. We then
examined the polymerization with the decarbonylative cyclo-
addition of monomer 1 in the presence of a nickel catalyst,
3
H
7
[Pd(PPh3)2Cl2]
CuI, NEt3
7
I
THF, r.t., 12 h
57%
H2N
H2N
4
2
PtO2, H2
MeOH,
r.t., 24 h
83%
O
O
Br
Br
9
+
O
N
9
H2N
toluene
140 °C, 24 h
99%
O
O
6
5
7
H
SiMe3
8
[Pd(PPh3)2Cl2]
CuI, NEt3
DMF, r.t., 12 h
96%
Me3Si
O
N
9
O
1
Scheme 2. Synthesis of 5-alkynylphthalimide.
(a) Previous Report: Iterative Decarboxylative Cycloaddition
R1
O
Me3Si
O
O
[Ni(cod)2] (10 mol %)
PMe3 (20 mol %)
R1
Ni cat.
O
N
9
toluene, refulx, 24 h
– n CO2
N
R2
O
N
R2
O
1
n
polyquinolone
9
O
N
(b) Present Work: Iterative Decarbonylative Cycloaddition
SiMe3
R1
SiMe3
O
O
n
R2
N
O
9
Ni cat.
N
N
R2
– n CO
m
9
O
R1
10
n
polyisoquinolone
Scheme 3. Nickel-catalyzed decarbonylative cycloaddition of
monomer 1 to form polyisoquinolone.
Scheme 1. Synthesis of polyquinolone and polyisoquinolone.
Chem. Lett. 2012, 41, 1566-1568
© 2012 The Chemical Society of Japan
Takeuchi, Makoto
