Synthesis of New Donor-Acceptor Norbornadiene Derivatives

Article abstract of DOI:10.1246/cl.2003.754

New donor-acceptor norbornadiene derivatives (NBDs) were synthesized from Diels-Alder reaction of methoxyphenyl-pentamethylcyclopendadiene with acetylene derivatives containing electron-withdrawing groups. These NBD derivatives have absorption in the visi

Full text of DOI:10.1246/cl.2003.754

754
Chemistry Letters Vol.32, No.8 (2003)
Synthesis of New Donor–Acceptor Norbornadiene Derivatives
Takabumi Nagai,ꢀ Ikuko Takahashi, and Tadatomi Nishikuboy
Daikin Environmental Laboratory, Ltd., Miyukigaoka 3, Ibaraki 305-0841
yDepartment ofApplied Chemistry, Faculty ofEngineering, Kanagawa University,
Rokkakubashi, Kanagawa-ku, Yokohama, 221-8686
(Received May 6, 2003; CL-030382)
New donor–acceptor norbornadiene derivatives (NBDs)
were synthesized from Diels–Alder reaction of methoxyphenyl-
pentamethylcyclopendadiene with acetylene derivatives con-
taining electron-withdrawing groups. These NBD derivatives
have absorption in the visible region and photoisomerized to
give thermally stable quadricyclane derivatives (QCs) with fair
durability.
a
b
An
OH
COOH
O
5
6
7
c
CO2Me
CO2Me
d
An
An
8
4a
Photochemical valence isomerization between norborna-
diene (NBD) and quadricyclane (QC) is of interest as a solar en-
ergy conversion and storage system,1 because photo energy can
be stored as strain energy (about 20 kcal/mol) in a QC mole-
cule. Recently, this photochemical reaction has also been inves-
tigated as an optical wave-guide utilizing photo-induced refrac-
tive index changes2a,2b or as a photochromic system potentially
applicable to data storage.3a
e
f
CONH2
CONH2
CN
CN
8
An
An
4b
Scheme 2. Synthesis of NBD derivatives 4. Reagents and conditions: a)
Ref. 5; b) p-CH3OC6H5Li, THF, 0 ꢁC, 1 h; c) d.HCl, room temp, 1 h,
78% from 6; d) dimethyl acetylenedicarboxylate, toluene, reflux, 15 h,
82%; e) acetylene-dicarboxamide, DMF, 120 ꢁC, 15 h; f) SOCl2, DMF,
0 ꢁC, 1 h, 20% from 8.
Taking these unique characteristics of NBD into account,
many NBD derivatives3 and photoresponsive polymers contain-
ing NBD moieties have been synthesized.4 However, the photo-
reactivity and the fatigue resistance of these compounds were
insufficient for practical use as advanced materials. Yoshida et
al. reported that donor–acceptor (D–A) NBDs 1 absorb visible
light efficiently, but thermal stability of the corresponding
QCs was not high enough for practical use.3a To overcome these
drawbacks, Nagai et al. synthesized CF3-substituted D–A NBDs
3, recently (Scheme 1).3b These compounds had large absorp-
tion in the visible region and gave thermally stable QCs. How-
ever, because CF3-substituted NBDs contain fluorine atoms,
these compounds are expensive, and, further, incur problems
in the disposal of waste containing the halogen atom after
use. On the other hand, Yoshida et al. also reported that D–A
NBDs 2, containing methyl groups in the 1,4-positions, gave
thermally stable QCs, but they did not absorb visible light so ef-
ficiently.3a Furthermore we could not synthesize new deriva-
tives of 2 which had longer wavelength absorption than that
of 2, because it was difficult to introduce more electron donative
groups than a phenyl group to the donor site of 2. Therefore, this
time we report the synthesis of new D–A NBDs 4, which have
absorption in the visible region, give thermally stable QCs, and
do not contain a halogen atom.
b, c
a
CO2Me
CO2Me
An
OH
10
An
O
9
11a
CN
CN
b, d
e
CONH2
CONH2
10
An
An
11b
Scheme 3. Synthesis of NBD derivatives 11. Reagents and conditions: a)
p-CH3OC6H5MgBr, THF, room temp, 2 h; b) d.HCl, room temp, 1 h; c)
dimethyl acetylene-dicarboxylate, toluene, reflux, 15 h, 73% from 9; d)
acetylene-dicarboxamide, DMF, 120 ꢁC, 15 h; e) SOCl2, DMF, 0 ꢁC, 1 h,
16% from 9.
of methoxyphenylpentamethylcyclopentadiene derivative
8
with acetylene derivatives containing electron-withdrawing
groups as shown in Scheme 2. Cyclopentadiene 8 was synthe-
sized from the addition of an aryl lithium reagent to cyclopen-
tenone 6 obtained from trans-dimethylacrylic acid 5,5 followed
by dehydration catalyzed by p-toluene sulphonic acid. We also
synthesized NBDs 11 and 14 as shown in Schemes 3 and 4. Cy-
clopentenones 96 and 127 were synthesized according to the lit-
erature. Structures of the new compounds were confirmed by
MS, IR, and NMR spectra.
The data of the absorption spectra of NBDs are shown in
Table 1. These NBDs had absorption in the visible region.
The absorption maxima of 4b was 380 nm and the absorption
edge reached 500 nm.
These NBDs 4 were synthesized from Diels–Alder reaction
An
An
CF3
CF3
X
Ph
Ph
X
An
An
X
An
X
X
X
1
2
3
4
An=p-CH3OC6H5; Ph=C6H5
a: X=COOCH3; b: CN
Next, we examined the thermal stability of QCs at room
Scheme 1.
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.8 (2003)
755
Table 2. The Capacity of Heat Storage of NBDs
Capacity of Heat Storage of NBDsa
CO2Me
CO2Me
a, b
c
No. of NBDs
kJ/mol
80b
64
J/g
171b
167
201
An
O
3b
4a
4b
An
12
13
14
64
aMeasured by DSC. bRef. 3b.
Scheme 4. Synthesis of NBD derivatives 14. Reagents and conditions: a)
p-CH3OC6H5MgBr, THF, room temp, 2 h; b) d.HCl, room temp, 1 h, 67%
from 12; c) dimethyl acetylenedicarboxylate, toluene, 80 ꢁC, 1 h, 100%.
temperature (20 ꢁC) in a PMMA solid film. These QCs samples
were prepared from photoisomerization of the corresponding
NBDs contained in PMMA solid film by irradiation with a xe-
non lamp. As shown in Table 1, it was found that 4b not only
had longer wavelength of absorption maxima and absorption
edge but also produced far more stable QCs than 1a, 2b, 11a,
and 11b. It seems that QCs obtained from NBDs which have
methyl groups in the C-1 and C-4 positions are more stable than
QCs obtained from NBDs which have H in the C-1 and C-4 po-
sitions, although NBDs which have H in the C-1 and C-4 posi-
tions have longer wavelength of absorption maxima and absorp-
tion edge than NBDs which have methyl groups in the C-1 and
C-4 positions.
The stored thermal energy in the QCs obtained from 4a and
4b was measured on DSC. As shown in Table 2, the irradiated
4a and 4b released 64 kJ/mol of thermal energy, respectively.8
These compounds have a smaller capacity of heat storage per
molecule than that reported (80–90 kJ/mol) for other QCs.3b,9
However, 4b has a larger capacity of heat storage per weight
than 3, since the molecular weight of 4 is lower than that of
3. It seems that the stored thermal energy in the QCs which have
substituents in the C-1 and C-4 positions is lower than that of
QCs which have H in the C-1 and C-4 positions, since the strain
contained in the QC framework is partly released by introduc-
tion of substituents into the C-1 and C-4 positions of the QC
molecule. Therefore, QCs which have methyl groups in the
C-1 and C-4 positions are more stable than QCs with H in the
C-1 and C-4 positions.
We also examined the ability of the NBDs to turn over the
cycles of photoisomerization (NBDs!QCs) and thermal rever-
sion (QCs!NBDs).3 As shown in Figure 1, 3 showed better du-
rability than 4. While 4a and 4b having methyl groups in the C-
7 positions showed fair durability, 14 having H in the C-7 posi-
tion showed very low durability. The reason why the substituent
in the C-7 position affects the durability is not clear. More work
on examination of the relationship between the structure and du-
rability of NBDs is necessary. Furthermore, it is apparent that
2,6-di-tert-butylphenol,11 a radical scavenger, improves the du-
Figure 1. Durability of NBD derivatives: (X) 3; (l) 4a; (s) 4b; (n) 4a
added 0.5 wt% of 2,6-di-tert-butylphenol; (u) 14.12
rability of NBDs, since the radical scavenger suppresses the for-
mation of byproducts caused by the polymerization of the
NBDs and QCs.
In conclusion, our result suggests the usefulness of NBDs 4
that do not contain halogen. Namely, NBDs 4 have absorption
in the visible region, to produce thermally stable QCs with fair
durability.
We would like to thank Professor Sadao Miki of Kyoto In-
stitute of Technology for helpful discussions.
References and Notes
R. R. Hautala, R. B. King, and C. Kutal, ‘‘Solar Energy,’’ Hamana, Clifton, NJ
(1979), p 333.
1
2
a) S. Morino, T. Watanabe, Y. Magaya, and K. Horie, J. Photopolym. Sci.
Technol., 7, 121 (1994). b) Y. Kato, H. Muta, S. Takahashi, K. Horie, and
T. Nagai, Polym. J., 33, 868 (2001), and references cited therein.
a) S. Miki, Y. Asako, and Z. Yoshida, Chem. Lett., 1987, 195. b) T. Nagai, K.
Fujii, I. Takahashi, and M. Shimada, Bull. Chem. Soc. Jpn., 74, 1673 (2001),
and references cited therein.
3
4
5
6
T. Nagai, M. Shimada, Y. Ono, and T. Nishikubo, Macromolecules, 36, 1786
(2003), and references cited therein.
C. Morel-Fourrier, J.-P. Dulcere, and M. Santelli, J. Am. Chem. Soc., 113, 8062
(1991).
a) D. D. Faulk and A. Fry, J. Org. Chem., 35, 364 (1970). b) J. Mathew, J. Org.
Chem., 56, 713 (1991).
7
8
G. Gowda and T. B. H. McMurry, J. Chem. Soc., Perkin Trans. 1, 1979, 274.
a) A. Ikeda, A. Kameyama, T. Nishikubo, and T. Nagai, Macromolecules, 34,
1786 (2001). b) Y. Konno, A. Kameyama, T. Nishikubo, and T. Nagai, J. Pol-
ym. Sci., Part A: Polym. Chem., 39, 2683 (2001).
Table 1. Absorption spectra of NBDs and thermal stability of QCs
Absorption spectra of NBDsb
T1=2 of QCs
(at 20 ꢁC)
6.5 h
11 min
10 hd,e
stable
No. of NBDs
9
A. Tsubata, T. Uchiyama, A. Kameyama, and T. Nishikubo, Macromolecules,
30, 5649 (1997), and references cited therein.
ꢀ
max/nm
355
ꢀ
AE/nmc
480
1aa
1ba
2bd
4a
10 Preparation of PMMA solid film: A solution of NBDs (10 mg) and PMMA
(250 mg) in chloroform (2 mL) was cast on a quartz plate. Then, the quartz
plate-cast film was dried in vacuo at 80 ꢁC for 15 h. Examination of the dura-
bility: The experiment was performed under argon atmosphere. Initially, the
polymer film was irradiated by a 500-W xenon lamp (Ushio Electric Co.,
UI-502Q) until the disappearance of the absorbance of the absorption maxima.
Then, the film containing the corresponding QC moieties was heated on a hot
plate until the reversion of the absorbance of the NBD moieties (4 or 14: irra-
diated for 10 min, then heated at 120 ꢁC for 30 min; 3: irradiated for 10 min,
then heated at 130 ꢁC for 40 min.).
395
550
350d
313
454d
414
4b
380
329
378
317
500
460
490
430
170 h
21.8 h
16 min
stable
11a
11b
14
a1a and 1b were synthesized according to Ref. 3a. b1 Â
11 H. Taoda, K. Hayakawa, and K. Kawase, J. Chem. Eng. Jpn., 20, 335 (1987).
12 A0 and An are the differences in the absorbance values between NBDs and
QCs at ꢀmax of the NBDs on the 1st and nth cycles of reactions, respectively.
c
e
10À4 mol dmÀ3 solution in acetonitrile. " ¼ 10. dRef. 3a. T1=2 at
45 ꢁC.
Published on the web (Advance View) July 21, 2003; DOI 10.1246/cl.2003.754