Synthesis of a series of malonic diester-introduced fullerene derivatives

Article abstract of DOI:10.1080/00397911.2013.804574

A facile preparation method for derivatization of fullerene through the Bingel reaction was introduced. A series of fullerene derivatives, to which malonic diester with different substituents were introduced, were systematically synthesized by Bingel reaction. Malonic diester could be added to fullerene at room temperature in the presence of iodine and 1,8-diazabicyclo[5.4.0]undec-7- ene (DBU), and various substituents such as phenyl, hexyl, thienyl, and pyrenyl were introduced into both sides of the malonic diester. As a result, 17 systematic variations were synthesized. The solubility parameters of the obtained fullerene derivatives calculated by the method reported by Fedors were in the range of 33 to 43 (J cm^-3)^1/2. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]

Full text of DOI:10.1080/00397911.2013.804574

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Synthesis of a Series of Malonic
Diester–Introduced Fullerene Derivatives
Tomohiro Shirosaki a b , Ryota Harisaki c , Maki Horikawa a b , Hideo
Sakurai b c , Shoji Nagaoka a b c & Hirotaka Ihara b c
a Kumamoto Industrial Research Institute , Kumamoto , Japan
b Kumamoto Institute for Photo-electro Organics (PHOENICS) ,
Kumamoto , Japan
c Department of Applied Chemistry and Biochemistry , Kumamoto
University , Kumamoto , Japan
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Accepted author version posted online: 27 Aug 2013.Published
online: 29 Oct 2013.
To cite this article: Tomohiro Shirosaki , Ryota Harisaki , Maki Horikawa , Hideo Sakurai , Shoji
Nagaoka & Hirotaka Ihara (2014) Synthesis of a Series of Malonic Diester–Introduced Fullerene
Derivatives, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 44:2, 275-279, DOI: 10.1080/00397911.2013.804574
To link to this article: http://dx.doi.org/10.1080/00397911.2013.804574
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Synthetic Communications1, 44: 275–279, 2014
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.804574
SYNTHESIS OF A SERIES OF MALONIC
DIESTER–INTRODUCED FULLERENE DERIVATIVES
Tomohiro Shirosaki,1,2 Ryota Harisaki,3 Maki Horikawa,1,2
Hideo Sakurai,2,3 Shoji Nagaoka,1,2,3 and Hirotaka Ihara2,3
1Kumamoto Industrial Research Institute, Kumamoto, Japan
2Kumamoto Institute for Photo-electro Organics (PHOENICS),
Kumamoto, Japan
3Department of Applied Chemistry and Biochemistry, Kumamoto University,
Kumamoto, Japan
GRAPHICAL ABSTRACT
Abstract A facile preparation method for derivatization of fullerene through the Bingel
reaction was introduced. A series of fullerene derivatives, to which malonic diester with differ-
ent substituents were introduced, were systematically synthesized by Bingel reaction. Malonic
diester could be added to fullerene at room temperature in the presence of iodine and
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and various substituents such as phenyl, hexyl,
thienyl, and pyrenyl were introduced into both sides of the malonic diester. As a result, 17
systematic variations were synthesized. The solubility parameters of the obtained fullerene
derivatives calculated by the method reported by Fedors were in the range of 33 to 43
(J cmꢀ3
1/2
)
.
[Supplementary materials are available for this article. Go to the publisher’s online
edition of Synthetic Communications1 for the following free supplemental resource(s):
Full experimental and spectral details.]
Keywords Bingel reaction; fullerene; malonic diester; solubility parameter
Received April 12, 2013.
Address correspondence to Hirotaka Ihara, Department of Applied Chemistry and Biochemistry,
Kumamoto University, 2-39-1, Kurokani, Kumamoto 860-8555, Japan. E-mail: ihara@kumamoto-u.ac.jp
275

276
T. SHIROSAKI ET AL.
INTRODUCTION
Fullerene has attracted much attention in various fields such as electronic
engineering and bioengineering because of its unique chemical and physical proper-
ties.[1–3] However, because its solubility or dispersibility in water and organic
solvents and compatibility between fullerene and other materials are poor, the use
of fullerene is limited. Therefore, the derivatization of fullerene is important to
improve its solubility, dispersibility, and compatibility. [6.6]-Phenyl-C61-butyric acid
methyl ester (PCBM)[4,5] and bis(dimetylphenylsililmethyl)[60]fullerene (SIMEF)[6]
for acceptor materials for organic photovoltaics, tetra(piperazino)[60]fullerene epox-
ide (TPFE) for gene delivery,[7] (1,2-methanofullerene C60)-61-carboxylic acid,[8] and
polyhydroxylated fullerene[9] for antioxidants are well known as fullerene deriva-
tives. Although a large variety of fullerene derivatives has been synthesized for each
purpose, there were few studies concerning systematic synthesis of a series of fuller-
ene derivatives. For optimal use of fullerene, the control of compatibility between
fullerene derivatives and other materials is important.
Recently, solubility parameters were used to make a prediction of the mixed state
of fullerene derivatives and conjugated polymers. The solubility parameters are the
square root of the cohesion energy density. The compatibility of fullerene derivatives
and conjugated polymers is assumed to be high if solubility parameters of fullerene
derivatives and conjugated polymers are close.[10–13] The solubility parameter of full-
erene [54 (J cm
than those of the polymer materials [20–30 (J cm
)
ꢀ3 1=2] calculated by the method reported by Fedros[14] is much greater
ꢀ3 1=2] used for mixing with fullerene.
)
In this study, we introduce a facile preparation method for derivatization of
fullerene through the Bingel reaction,[15–18] and 17 systematic variations [solubility
parameter: 33–43 (J cm )
ꢀ3 1=2] were synthesized.
RESULTS AND DISCUSSION
All the fullerene derivatives were synthesized in the same synthetic route as
shown in Scheme 1. A typical reaction procedure is as follows: (1) The esterification
Scheme 1. Synthesis of malonic diester–introduced fullerene derivatives.

MALONIC DIESTER–INTRODUCED FULLERENE DERIVATIVES
277
of 3-(benzyloxy)-3-oxopropanoic acid was carried out by reacting 3-(benzyloxy)-
3-oxopropanoic acid with corresponding diol compound, using N,N0-
diisopropylcarbodiimide as condensation agent and 4-dimethylaminopyridine as
catalyst. (2) The esterification of obtained malonic diesters (benzyl 2-hydroxyethyl
malonate) was carried out by reacting the malonic diesters [2-(benzoyloxy)ethyl
malonate] with corresponding carboxylic acid chlorides, using triethylamine as base.
(3) Malonate diester–introduced fullerene derivatives were synthesized by the Bingel
reaction, by treatment of [60]fullerene with malonate diester in the presence of iodine
and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at room temperature. The fullerene
derivatives were obtained in yields from 20 to 53%.
The solubility parameters of the obtained fullerene derivatives were calculated
by the following formula reported by Fedors:[14]
1=2
d ¼ ðDE=VÞ
where DE is total of the additive atomic and group contribution for energy of vapor-
ization and V is molar volume. DE and V were calculated using the method and the
values reported in the literature.[14] The structures, yield, and solubility parameters of
obtained fullerene derivatives are summarized in Table 1. The solubility parameters
of obtained fullerene derivatives were in the range of 33.5 to 43 (J cm
are values between the value of fullerene [54.3 (J cm
ꢀ3 1=2] and conjugated
polymers that are generally used for organic photovoltaics (for example, poly(3-
hexylthiopehe): 22.7 (J cmꢀ3 1=2 poly[2-methoxy-5-(30,70-dimethyl-octyloxy)-1,
4-phenylenevinylene]: 19.6 [J cm
ꢀ3 1=2]. Thus, those fullerene derivatives are con-
)
ꢀ3 1=2. These
)
)
,
)
sidered to be useful for the optimization of the bulk heterojunction photoactive
layer of organic photovoltaics.
Table 1. Synthesized malonic diester–introduced fullerene derivatives
Product
X
Y
Z
Yield (%)
da ((J cmꢀ3 1=2
) )
1
2
Phenyl
(CH2)2O
(CH2)5O
Phenyl
Phenyl
Phenyl
Phenyl
Phenyl
Hexyl
53
34
27
21
43
36
39
45
38
49
30
34
33
36
36
30
29
38.5
36.4
34.7
34.2
37.0
36.0
34.4
35.0
39.2
37.6
33.5
33.8
38.4
38.0
38.7
38.9
43.0
3
(CH2)8O
(CH2)10O
4
5
(CH2CH2O)2
(CH2)2O
(CH2)5O
6
7
Hexyl
Hexyl
8
(CH2CH2O)2
(CH2)2O
9
Thienyl
Thienyl
Pyrenyl
Pyrenyl
Ethyl
10
11
12
13
14
15
16
17
(CH2CH2O)2
(CH2)5O
Methyl
(CH2CH2O)2
(CH2CH2O)2
(CH2CH2O)2
(CH2CH2O)2
(CH2CH2O)2
(CH2CH2O)2
Phenyl
Thienyl
Vinyl
Hydroxyl
aThe solubility parameters.

278
T. SHIROSAKI ET AL.
EXPERIMENTAL
All chemical reagents were obtained from commercial suppliers and used
1
without further purification. H and 13C NMR spectra were recorded with a Jeol
JNM-EX400 FT-NMR system using tetramethylsilane (TMS) as an internal
standard in CDCl3. Mass spectra were taken with a Voyager RP and Tektronix
TDS 540D. Elemental analyses were performed on a Elementar Vario Micro cube.
Synthesis
All fullerene derivatives with phenyl group as terminal group X (fullerene
derivatives 1–12) were synthesized in the same procedure. A typical reaction
procedure is shown in the next section. The synthetic procedure of the fullerene
derivatives with methyl group as X (fullerene derivative 13–17) was almost the
same (see Supplementary Material).
Synthesis of Fullerene Derivative 1
Ethylene glycol (43 g, 700 mmol), 4-dimethylaminopyridine (DMAP, 9.6 g,
78 mmol), and N,N0-diisopropylcarbodiimide (8.1 g, 64 mmol) were mixed in tetrahy-
drofuran (40 ml) at 0 ꢁC. 3-(Benzyloxy)-3-oxopropanoic acid (5.7 g, 28 mmol) was
added to the solution from a dropping funnel for 2 h. The mixture was stirred at
room temperature for 24 h. The reaction mixture was washed three times with 1 N
HCl solution (100 ml) and brine (100 ml). The organic layer was dried over Na2SO4.
After evaporation, the residue was purified by column chromatography (silica gel,
hexane = ethyl acetate ¼ 60=40) to produce benzyl 2-hydroxyethyl malonate as
a yellow oil (2.5 g, 10.4 mmol). The structure of the obtained compound was checked
by 1H NMR spectrum (see Supplementary Material). The obtained compound
was used for the next reaction without further purification. The obtained benzyl
2-hydroxyethyl malonate (0.92 g, 4.0 mmol) and triethylamine (1.0 g, 6.1 mmol) were
mixed in dichloromethane (20 ml) at 0 ꢁC. Benzoyl chloride (0.51 g, 3.6 mmol) was
added to the solution from a dropping funnel. The mixture was stirred at 0 ꢁC
for 2 h in the dark. The reaction mixture was washed twice with 1 N HCl solution
(20 ml) and brine (20 ml). The organic layer was dried over Na2SO4. After evapor-
ation, the reaction mixture was purified by column chromatography (silica gel,
hexane=ethyl acetate ¼ 80=20) to produce benzyl 2-(benzoyloxy)ethyl malonate
as a yellow oil (0.61 g, 1.8 mmol). The obtained compound was used for the next
reaction without further purification. The structure of the obtained compound was
1
checked by H NMR spectrum (see Supplementary Material). The obtained benzyl
2-(benzoyloxy) ethyl malonate (0.48 g, 1.4 mmol) and C60 fullerene (1.0 g, 1.4 mmol)
were mixed in toluene (350 ml) at room temperature. 1,8-Diazabicyclo[5. 4. 0]undec-
7-ene (DBU, 0.42 ml, 0.43 g, 2.78 mmol) and I2 (0.35 g, 1.4 mmol) to the solution
were added. The mixture was stirred at room temperature for 24 h. After filtration,
the reaction mixture was washed twice with distilled water (100 ml) and brine
(100 ml). The organic layer was dried over Na2SO4. After evaporation, the reaction
mixture was purified by column chromatography (silica gel, toluene) to produce
1
a dark brown powder 1 (0.78 g, 0.74 mmol, 53%), mp > 300 ꢁC. H NMR (CDCl3,

MALONIC DIESTER–INTRODUCED FULLERENE DERIVATIVES
279
TMS): d (ppm) 4.62–4.64 (t, J ¼ 4.8 Hz, 2H, CH2), 4.77–4.80 (t, J ¼ 4.4 Hz, 2H,
CH2), 5.47 (s, 2H, CH2), 7.36–7.41 (m, 5H, Ar-H), 7.45–7.47 (t, J ¼ 3.4 Hz, 2H,
Ar-H), 7.53–7.56 (dd, 1H, Ar-H), 8.02–8.03 (d, J ¼ 1.7 Hz, 2H, Ar-H). 13C NMR
(100 MHz, in CDCl3): d (ppm) 62.29, 64.78, 69.01, 71.61, 128.50, 128.74, 128.96,
128.99, 129.85, 133.30, 134.56, 139.00, 139.06, 140.94, 141.85, 141.87, 142.20,
142.94, 143.00, 143.82, 143.89, 144.58, 144.69, 144.92, 145.02, 145.08, 145.20,
145.26, 163.38, 166.23. MS (MALDI-TOF=MS) m=z: 1059.9 [M-H]ꢀ. Anal. calcd.
for C79H16O6: C, 89.43; H, 1.52. Found: C, 88.60; H, 1.53.
SUPPORTING INFORMATION
Characterization of all synthesized fullerene derivatives is described in the
Supplementary Material section of this article’s Web page.
ACKNOWLEDGMENTS
This work was supported in part by a Grant-in-Aid for Scientific Research
from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.
The authors are grateful to Mr. Baba for the capable assistance.
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