Chemistry Reference
In-Depth Information
13.2.1.2. Polymerization of Dienes
13.2.1.2.1. 1,3 - Dienes
Polymerization of 1,3 - diene (
10
) yields the polymer (
11
), having
stereogenic carbon centers in the main chain [18]. The enantioselective anionic polym-
erization of 1,3-dienes such as methyl and butyl 2,4-hexadienoates (sorbates), and butyl
styrylacrylates successfully proceeded in the presence of ((+)-2-methylbutyl)lithium or
BuLi/(
)-menthyl ethyl ether [52]. 1,3-Pentadiene also successfully underwent asym-
metric polymerization in the presence of Et
3
Al/titanium
−
) - menthoxide or
(+) - tris(2 - methylbutyl)aluminum/Ti(OBu)
4
catalysts to give optically active polymers
[53]. The extent of chiral induction in the polymerization can be determined by analyses
of chiral diacid compounds (
12
) obtained after ozonolysis of
11
(Scheme 13.3 ).
tetra(
−
R
2
R
2
O
3
CO
2
H
R
2
∗
∗
R
1
R
1
∗
n
HO
2
C
R
1
10
11
12
Scheme 13.3.
The polymerization of monomeric guest components in host components as a mo-
lecular fl ask is called “ inclusion polymerization ” [54,55] . If a host component is optically
active, a monomer molecule is included in chiral environment, thus giving optically
active polymers. A number of chiral solid matrices have been used for asymmetric inclu-
sion polymerization. In 1967, the synthesis of an optically active polymer from
trans
- 1,3 -
pentadiene (
13
) by means of
trans
-
anti
-
trans
-
anti
-
trans
- perhydrotriphenylene (
14
) as a
host container was reported for the fi rst time: The
- ray irradiation of
13
included in
14
gives an optically active, isotactic
trans
- 1,4 - polypentadiene (
15
) (Scheme 13.4 ) [56] .
Deoxycholic acid (
16
) [57,58] and apocholic acid (
17
) [59,60] were also reported to be
effective matrices for asymmetric inclusion polymerization of 1,3-dienes such as
cis
- or
trans
- 1,3 - pentadiene and
cis
- or
trans
- 2 - methyl - 1,3 - pentadiene in a highly stereoselective
manner.
γ
H
O
H
O
C
O
2
H
C
O
2
H
HO
HO
H
H
14
16
17
γ
rays
∗
∗
∗
∗
14
n
13
15
Scheme 13.4.
