Chemistry Reference
In-Depth Information
OSiEt
3
OSiEt
3
OHC
CHO
O
O
R
1
R
2
64
: R
1
=
65
: R
1
=
66
: R
2
=
67
: R
2
=
SiMe
2
SiMe
2
(CH
2
)
2
SiMe
2
SiMe
2
SiMe
2
(CH
2
)
2
SiMe
2
O
OH
O
O
OH
O
O
O
N
B
HN
R
1
Ts
Ar
R
2
Ar = 3,5-(CF
3
)
2
C
6
H
3
n
68
69
13.2.1.6. Oxidative-Coupling Polymerization
13.2.1.6.1. 2,3 - Dihydroxynaphthalenes
The asymmetric oxidative - coupling polymer-
ization (AOCP) of 2,3-dihydroxynaphthalenes has been developed. The reaction of
70
in the presence of CuCl/(
R
) - bisoxazoline (
71
) under O
2
atmosphere followed by acetyla-
tion produced optically active poly(2,3 - acetoxy - 1,4 - naphthalene) (
72
) although the
enantioselectivity was estimated to be low (
ca.
40% ee) from the model reaction [113].
Later on, oxovanadium(IV) catalysts were found to be more effective for AOCP of
70
[114,115]. For instance, the polymerization of
70
using VOSO
4
/(
R
) -
71
[114] or
VO(stearate)
2
/disodium D - ( − ) - tartarate [115] as catalysts under O
2
atmosphere and the
subsequent acetylation of hydroxy groups gave polymers
72
with optical rotations of
[α ]
405
+147° and +223°, respectively. The enantiomeric excess was estimated to be over
80% ee. The cobalt(II)-salen complex (
9
) was also reported to promote the AOCP
effi ciently [116]. The AOCP of tetrahydroxybinaphthalene or hexahydroxyternaphtha-
lene derivatives were accomplished by using CuCl/TMEDA, CuCl/(+)PMP, or CuCl/
71
under O
2
atmosphere or by using CuCl
2
/( − ) -
Sp
as a stoichiometric oxidant [117-119].
AcO
OAc
HO
OH
O
O
N
N
Ph
Ph
n
70
71
72
13.2.1.6.2. 2,2
- Binaphthyls
A variety of optically active polybinaphthyls have been
synthesized by AOCP of 2,2
′
- binaphthyl derivatives. The AOCP of unsymmetrical
binaphthyls such as methyl and benzyl 6,6
′
- binaphthyl - 7 - carboxylate (
73
)
produces polybinaphthyls (
76
) having three different types of 1,1
′
- dihydroxy - 2,2
′
- bi - 2 - naphthol units,
X
,
Y
, and
Z
. Highly cross-coupling selective polymerization of
73a
and
73b
was achieved
by means of CuCl/
7a
catalyst to afford a polymer with the selectivity of
Y
= 96% and
99%, respectively [120,121]. The catalytic system of CuCl/
7a
also showed remarkable
activity for cross - coupling - selective, asymmetric oxidative - coupling copolymerization
of two different binaphthyls,
74
and
75
, to give an alternating-type copolymer with
′
