Ring-opening reaction of tetrahydrofuran on the penta(organo)[60]fullerenes: synthesis of hydroxybutyl, methacrylate, and norbornene derivatives

Article abstract of DOI:10.1016/j.tetlet.2009.02.155

Ring-opening reaction of tetrahydrofuran takes place on penta(methyl)- and penta(n-butylphenyl)[60]fullerenes in the presence of chlorotrimethylsilane giving penta(organo)fullerene hydroxybutyl derivatives, C₆₀R₅(C₄H₈

Full text of DOI:10.1016/j.tetlet.2009.02.155

Tetrahedron Letters 50 (2009) 3411–3413
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Ring-opening reaction of tetrahydrofuran on the penta(organo)[60]fullerenes:
synthesis of hydroxybutyl, methacrylate, and norbornene derivatives
b
b
a,b,
Yutaka Matsuo a, , Akihiko Iwashita , Hiromi Oyama , Eiichi Nakamura
*
*
a Nakamura Functional Carbon Cluster Project, ERATO, Japan Science and Technology Agency, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
b Department of Chemistry, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Ring-opening reaction of tetrahydrofuran takes place on penta(methyl)- and penta(n-butylphenyl)[60]ful-
lerenes in the presence of chlorotrimethylsilane giving penta(organo)fullerene hydroxybutyl derivatives,
C60R5(C4H8OH) (R = Me, nBuC6H4). The hydroxyl groups were further transformed into methacrylate and
norbornylcarbonyloxy groups via esterification with the corresponding acid chlorides. The methacrylate
derivative, penta(methyl)[60]fullerenylbutyl methacrylates was crystallographically characterized.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 22 January 2009
Revised 16 February 2009
Accepted 19 February 2009
Available online 25 February 2009
Functionalized fullerene derivatives have found many promis-
ing applications in the areas of materials science and nanotechnol-
ogy because of their unique electrochemical and photophysical
properties.1 A wide variety of reactions have been utilized for func-
tionalization of fullerenes—cycloaddditions,2 nucleophilic addi-
tions,3 electrophilic substitution,4 radical reactions,5 and others.6
Diversification of these reactions enhances accessibility to func-
tionalized fullerenes. For instance, we have previously reported
organozinc-mediated addition of tetrahydrofuran (THF) to C60 giv-
ing tetrahydrofuranyl fullerene derivatives.7 We report herein that
an electrophilic ring-opening reaction of THF can selectively pro-
ceed with penta(organo)[60]fullerenes in the presence of Me3SiCl
to afford hydroxybutyl derivatives, C60R5(C4H8OH) (1a: R = Me;
1b: R = nBuC6H4). The alcohol products can be further elaborated
into a variety of new fullerene-containing methacrylate and nor-
bornene derivatives through esterification of the hydroxyl
moieties.
The hydroxybutyl derivatives 1a,b were obtained in excellent
yield, starting from C60 in a one-pot reaction (Scheme 1). Treat-
ment of C60 with 12 Àequiv of a methylcopper reagent afforded an
intermediate C60Me5 (2a), to which was added in situ 5 equiv of
Me3SiCl to generate a ring-opening product C60Me5(C4H8OSiMe3)
(3a), followed by acid treatment to obtain 1a in 91% isolated over-
all yield.8,9 When an n-butylphenylcopper reagent was employed
in this reaction, the product 1b was obtained in similar yield
(92%) even via a bulky intermediate (2b). These reactions can be
carried out with ease. Purification of the products is also easily per-
formed with normal silica gel column chromatography, because
the products have polar hydroxyl groups. The compounds 1a,b
are very stable and can be stored in air, while compounds 3a,b
gradually decomposed to 1 in air.
Optimization of the reaction conditions revealed that the use of
5 equiv of Me3SiCl was the most effective and convenient. We opti-
mized the conditions for the synthesis of 1b. The use of 1, 3, 5, and
10 equiv of Me3SiCl resulted in 65%, 77%, 92%, and 92% yield,
respectively. Me3SiBr (5 equiv) and Me3SiI (5 equiv) were investi-
gated in this reaction, and gave the product in 72% and 57% yield,
respectively. Note that trimethylsilyl bromide and iodide them-
selves can open the cyclic ethers to give, for example,
Br(CH2)4OSiMe3.10 We think that these alkyl halides are less reac-
tive than plausible active species, oxonium cations (see below).
The reaction was also performed with the use of a readily avail-
able protio compound C60Me5H (4) (Scheme 2). The ring-opening
product 3a was obtained in 88% yield by deprotonation of the
hydrogen atom of 4 with KH in THF, followed by addition of Me3-
SiCl in similar conditions. On this route, the use of KOtBu, instead of
KH, did not result in any product. This is because of t-butanol gen-
erated in this reaction. The t-butanol deactivates cationic species
such as Me3Si+ (see below),11 which is absolutely essential for this
ring-opening reaction of THF.
The mechanistic aspect of this reaction is discussed with forma-
tion of an oxonium compound and a following ring-opening reac-
tion (Scheme 3).12 A transmetalation reaction of the penta-addition
product anion 2 with Me3SiCl generates a Me3Si+ cation formally,11
which immediately forms the oxonium cation of THF. This oxo-
nium species undergoes an electrophilic13 ring-opening reaction
with the cyclopentadienyl anion of 2 to generate the siloxybutyl
product 3. The present reaction course is quite different from those
shown in the syntheses of CpSiMe3 and Cp*SiMe3 (Cp = C5H5;
Cp* = C5Me5).14 NaCp and KCp* react with Me3SiCl in THF to give
the silanes CpSiMe3 and Cp*SiMe3 simply via transmetalation reac-
tions. The cyclopentadienyl part of the penta(organo)[60]fullerene
is located on the concave cavity, which prevents formation of the
* Corresponding authors. Tel.: +81 3 5841 4356; fax: +81 5800 6889 (Y.M.).
E-mail addresses: matsuo@chem.s.u-tokyo.ac.jp (Y. Matsuo), nakamura@chem.
s.u-tokyo.ac.jp (E. Nakamura).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.02.155

3412
Y. Matsuo et al. / Tetrahedron Letters 50 (2009) 3411–3413
OH
OSiMe3
+
CuLn
R
R
R
R
R
R
RMgBr (12 eq)
CuBr·SMe2 (12 eq)
R
–
R
R
R
R
R
Me3SiCl (5 eq)
Cl
R
R
R
aq. HCl
rt, 1 h
C60
Cl
O
(1/1)
O
Cl
Cl
rt, 1 h
R = Me, C6H4-nBu
50 °C, 12 h
1a: 91% (R = Me)
2
3
1b: 92% (R = C6H4-nBu)
Scheme 1. One-pot synthesis of the hydroxybutyl-penta(organo)[60]fullerenes from C60
.
OSiMe3
+
K(thf)n
Me
O
R
H
O
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
–
Me Me3SiCl
(5 eq)
KH
(1.2 eq)
Me
Me
Me
R
O
THF
rt, 30 min
THF
R
R
OH
50 °C, 16 h
R
Cl
(5 eq)
4
3a: 88%
5a: 72% (R = Me)
NEt3 (10 eq)
CH2Cl2
0 °C to rt
20 h
R
R
5b: 71% (R = C6H4-nBu)
R
R
Scheme 2. Synthesis of the ring-opening product from C60Me5H.
R
O
O
O
OSiMe3
R
+
O
Cl
R = Me, C6H4-nBu
(5 eq)
+
SiMe3
CuLn
1
R
R
R
R
NEt3 (10 eq)
CH2Cl2
0 °C to rt
24 h
R
R
R
R
R
–
R
R
R
–
R
R
R
R
R
R
R
ring-opening
Me3SiCl
6: 46% (R = C6H4-nBu)
O
– CuCl
3
2
Scheme 4. Synthesis of methacrylate and norbornene derivatives.
Scheme 3. A proposed reaction mechanism for the ring-opening reaction.
À
C60–Si bond. This effect probably gives the tendency to form C60R5
and Me3Si+.
The hydroxyl functionality in fullerene derivatives is of impor-
tance for building fullerene-based photoelectrochemically and bio-
logically active materials.15 Here we demonstrated the syntheses
of methacrylate and norbornene derivatives via esterification reac-
tions with acid chlorides (Scheme 4). Compounds 1a,b were trea-
ted with methacryloyl chloride in the presence of excess
triethylamine in dichloromethane to produce penta(org-
ano)[60]fullerenylbutyl methacrylates 5a,b in 71–72% yield.16
A
similar reaction with norbornylcarbonyl chloride yielded a nor-
bornene derivative 6. These products 5 and 6 are stable in air,
and can be purified by silica gel column chromatography. The
structure of the methacrylate derivative 5a was unambiguously
determined by single-crystal X-ray analysis (Fig. 1).17 Dark red sin-
gle crystals containing a 1:1 mixture of 5a and dichloromethane
were obtained by slow diffusion of ethanol into a dichloromethane
solution of 5a. A crystal packing view (Fig. 2) shows a honeycomb-
like porous structure, where solvent molecules and part of the
methacrylate moiety are located in the hollows. Polymerization18
of the methacrylate/norbornene parts would be not only interest-
ing but also challenging, because the fullerene part is known to
deactivate radical and anionic initiators by radical quenching and
the electrophilic properties of fullerenes.
Figure 1. Crystal structure of the fullerene-containing methacrylate 5. (a) An
ORTEP diagram with 30% probability level ellipsoids. (b) Side view of a CPK model.
(c) Top view of a CPK model.
ene skeleton. Both pentamethyl and pentaaryl substrates were em-
ployed in this reaction to obtain hydroxybutyl derivatives. The
usefulness of the alcohol functionalities and the respectable total
In summary, we have found an efficient and selective ring-
opening reaction of THF attaching to the penta(organo)[60]fuller-

Y. Matsuo et al. / Tetrahedron Letters 50 (2009) 3411–3413
3413
stirring for 12 h at 50 °C, aqueous hydrochloric acid (1 mL, 1 M) was added to
the reaction mixture, and then it was stirred for 1 h at room temperature. The
solution was passed through a pad of silica gel and evaporated to give a crude
product. Purification was performed with silica gel chromatography using
toluene/hexane (4/1) as eluent to obtain 1b (1.84 g, 92%). 1H NMR (500 MHz,
CDCl3): d 7.66 (d, 4H), 7.55 (d, 4H), 7.24 (t, 2H), 7.10–7.08 (m, 8H), 6.93 (d, 2H),
3.23 (t, 2H), 2.68–2.60 (m, 8H), 2.50 (t, 2H), 1.65–1.57 (m, 8H), 1.51–1.47 (m,
4H), 1.40–1.33 (m, 8H), 1.30–1.26 (m, 4H), 1.02 (t, 2H), 0.98–0.92 (m, 12H),
0.87 (t, 3H). 13C NMR (125 MHz, CDCl3): d 156.99, 156.62, 153.58, 151.55,
148.71, 148.60, 148.45, 148.39, 148.18, 148.10, 147.95, 147.75, 147.69, 147.29,
147.22, 147.00, 145.52, 145.44, 144.78, 144.33, 144.29, 144.24, 144.13, 144.04,
143.98, 143.93, 143.68, 142.56, 142.37, 142.25, 141.52, 140.18, 137.82, 136.29,
130.59, 128.72, 128.69, 128.49, 127.99, 127.80, 65.27, 63.09, 62.82, 60.97,
58.33, 40.48, 35.32, 35.17, 35.04, 33.60, 33.42, 33.28, 32.21, 22.34, 22.26, 22.12,
21.65, 14.00, 13.97, 13.90. Anal. Calcd for C114H74O: C, 93.79: H, 5.11. Found: C,
93.69: H, 5.14.
9. See also, Ref. 3c.
10. (a) Krüerke, U. Chem. Ber. 1962, 95, 174–182; (b) Ohshita, J.; Iwata, A.; Kanetani,
F.; Kunai, A. J. Org. Chem. 1999, 64, 8024–8026.
Figure 2. Crystal packing view from C-axis. Oxygen and chlorine atoms are colored
red and green, respectively.
11. Lickiss, P. D. Silicenium ions–experimental aspects. In The Chemistry of Organic
Silicon Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley & Sons: Chichester,
1998. Chapter 11.
yield from C60 are significant for further synthetic elaboration. Ful-
lerene derivatives bearing polymerizing units are potentially un-
ique monomers in materials science.
12. Hrkach, J. S.; Matyjaszewski, K. Macromolecules 1990, 23, 4042–4046.
13. Hamasaki, R.; Matsuo, Y.; Nakamura, E. Chem. Lett. 2004, 33, 328–329.
14. (a) Jutzi, P.; Saleske, H.; Bühl, D.; Grohe, H. J. Organomet. Chem. 1983, 252, 29–
36; (b) Yamamoto, H.; Yasuda, H.; Tatsumi, K.; Lee, K.; Nakamura, A.; Chen, J.;
Kai, Y.; Kasai, N. Organometallics 1989, 8, 105–119; (c) Herrmann, W. A.; Zybill,
C. Commonly Used Starting Materials. In Synthetic Methods of Organometallic
and Inorganic Chemistry; Herrmann, W. A., Salzer, A., Eds.; Georg Thieme:
Stuttgart, 1996; Vol. 1, p 96.
Acknowledgments
This work was partially supported by KAKENHI (#18105004)
and the Global COE Program for Chemistry Innovation of the MEXT,
Japan.
15. (a) An, Y. Z.; Anderson, J. L.; Rubin, Y. J. Org. Chem. 1993, 58, 4799–4801; (b)
Chopin, A. C.; Delaunay, J.; Cousseau, J. Tetrahedron Lett. 2005, 46, 373–376.
16. Synthesis of 5b: To
a solution of 1b (1 g, 0.685 mmol) and triethylamine
(0.954 mL, 6.85 mmol) in dichloromethane (60 mL) was added methacryloyl
chloride (0.277 mL, 3.43 mmol) at 0 °C. After stirring for 2 h at room
temperature, aqueous sodium hydrogen carbonate (10 mL) was added to the
reaction mixture to quench reactive reagents. The organic phase was extracted
and dried over magnesium sulfate. The solution was passed through a pad of
silica gel and evaporated to give a crude product. Purification was performed
with silica gel chromatography by means of toluene/hexane (1/1) as eluent to
obtain 5b (0.75 g, 72%). 1H NMR (500 MHz, CDCl3): d 7.61 (d, J = 8.0 Hz, 4H),
7.50 (d, J = 8.0 Hz, 4H), 7.21 (d, J = 8.6 Hz, 2H), 7.03–7.01 (m, 8H), 6.88 (d,
J = 8.6 Hz, 2H), 5.96 (s, 1H), 5.49 (s, 1H), 3.69 (t, J = 7.7 Hz, 2H), 2.60–2.53 (m,
8H), 2.43 (t, J = 7.8 Hz, 2H), 1.87 (s, 3H), 1.59–1.45 (m, 12H), 1.41–1.21 (m,
12H), 1.03–1.00 (t, J = 7.5, 2H), 0.91–0.84 (m, 12H), 0.80 (t, J = 7.2 Hz, 3H). 13C
NMR (125 MHz, CDCl3): d 167.16, 157.00, 156.77, 153.62, 151.59, 148.80,
148.69, 148.54, 148.47, 148.26, 148.18, 148.05, 147.85, 147.81, 147.37, 147.30,
147.08, 145.59, 145.47, 144.82, 144.39, 144.33, 144.29, 144.15, 144.07, 144.01,
143.98, 142.60, 142.44, 142.32, 141.63, 140.18, 137.80, 136.38, 136.34, 130.62,
128.78, 128.65, 128.54, 127.90, 127.86, 125.31, 65.21, 64.81, 63.13, 60.99,
58.36, 50.90, 40.75, 35.20, 35.18, 35.04, 33.57, 33.42, 33.28, 28.46, 22.36, 22.30,
22.28, 22.15, 18.40, 13.97, 13.94, 13.89. Anal. Calcd for C118H79O2: C, 92.70: H,
5.21. Found: C, 92.67: H, 5.28.
References and notes
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(3.43 g, 16.7 mmol) and n-butylphenyl magnesium bromide (17.2 mL, 0.98 M,
16.7 mmol) in THF (25 mL) was added a 1,2-dichlorobenzene (45 mL) solution
of C60 (1 g, 1.39 mmol) at room temperature. The reaction mixture was stirred
for 1 h at room temperature to complete the penta-addition reaction. Then,
chlorotrimethylsilane (1.76 mL, 13.9 mmol) was added to the mixture. After
17. Crystallographic data for 5b have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no. CCDC-
716910. Copies of the data can be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44-(0)1223-336033 or e-
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