Design and efficient synthesis of fullerene bismalonates as building blocks for metal organic frameworks and organic nanostructures

Article abstract of DOI:10.1055/s-2008-1077880

The preparation of bismalonate fullerene derivatives bearing useful sticky sides for the generation of nanostructures has been investigated. In this context, pyridine and cyano heading groups on fullerenes have been designed and synthesized in a straightforward manner and in good yields. Thieme Stuttgart.

Full text of DOI:10.1055/s-2008-1077880

1706
LETTER
Design and Efficient Synthesis of Fullerene Bismalonates as Building Blocks
for Metal Organic Frameworks and Organic Nanostructures
Synthesis of
F
h
ullerene
B
ism
i
alona
l
tes ippe Pierrat, Céline Réthoré, Thierry Muller,* Stefan Bräse*
Institut für Organische Chemie, Universität Karlsruhe (TH), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany
Fax +49(721)6088581; E-mail: braese@ioc.uka.de
Received 2 April 2008
N
Abstract: The preparation of bismalonate fullerene derivatives
O
O
bearing useful sticky sides for the generation of nanostructures has
been investigated. In this context, pyridine and cyano heading
groups on fullerenes have been designed and synthesized in a
straightforward manner and in good yields.
O
O
O
O
Key words: fullerenes, malonate esters, Bingel reaction, molecular
recognition, metal organic frameworks
N
1
Figure 1 Bispyridine fullerene monoadduct 1
The regio- and diastereocontrol of the bifunctionalization
of [60]fullerene (C60) have attracted considerable atten-
tion because the bisadducts of C60 have found widespread
applications in the construction of advanced supramolec-
ular materials.1 The ultimate success in this research area
critically depends on the ability to synthesize chiral po-
rous solids with predictable porous topological architec-
tures. Although as far as we know, only few fullerene-
based nanostructures have been described,2 none were de-
veloped with regard to self-assembling processes up to
date, neither for molecular tectonics nor for metal organic
frameworks.
velopment of incremental changes in the structure of our
C60-based ligands. Thus, we have undertaken a systematic
study towards the design of construction units such as
fullerene derivatives bearing pyridine and benzonitrile
species as head groups. The coordination of such bridging
ligands with diverse metal nodes leads to a wide range of
porous coordination networks with some of them showing
really promising storage and catalytic properties.4
Concerning the sticky sides, it is worth noting that in order
to increase their coordination ability, a junction with a do-
nor linker with respect to the nitrile and pyridine unit is
ensured. This should indeed significantly increase the
electronic density on both coordination sites through elec-
tronic delocalization. Dealing with the fullerene-connect-
ing fragment, this spacer may confer many interesting
properties to the nanostructures such as flexible pore size
and electronic, photonic, and nonlinear optical applica-
tions.
In this context, and as a part of a research project dealing
with the design and synthesis of nanostructures based on
different organic core structures, we have been drawn to
investigate the functionalization of C60 in order to build
around its soccer-ball-shaped structure different sticky
sides suitable to generate well-organized networks by re-
versible but strong interactions with metal species.
Fullerenes are particularly interesting building blocks in
this context because of their unique three-dimensional
structure. The possibility to install functional groups on
different positions of the fullerene framework allows in-
deed the design of building blocks with diverse function-
alities and geometries.
In the present contribution, we expand on this idea and re-
port firstly on the synthesis of tecton 1 bearing two pyri-
dine sticky sides (Figure 1).
The general synthetic strategy towards the preparation of
this material is based on the construction of the malonate
monoethyleneglycol ester terminated with two pyridine
units which was further coupled to a C60 fullerene, follow-
ing the Bingel methodology.5 The synthetic route for the
preparation of compound 1 is outlined in Scheme 1. DCC-
mediated coupling of 2-(pyridin-3-yloxy)ethanol with
malonic acid at room temperature in MeCN produced the
malonate 2 in 85% yield.6 Then, treatment of the bis-
malonate thus obtained with C60, CBr4, and 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU) in toluene at room
temperature afforded the desired cyclization product 1 in
26% yield.
Even if for about two decades, the preparation of metal or-
ganic frameworks has been attracting constant attention
and many examples have been reported with highly inter-
esting properties,3 the fine understanding, both in terms of
connectivity and topology, of the subtle factors governing
the formation of these structures remains a challenge. This
is the reason why, in order to prepare such structures bear-
ing fullerene derivatives and taking into account all the
different contributions in this domain, we opted for the de-
SYNLETT 2008, No. 11, pp 1706–1710
1
1
.0
6
.2
0
0
8
We next investigated the behavior of ligand 1 in coordina-
tion processes with copper ions. To the best of our knowl-
Advanced online publication: 11.06.2008
DOI: 10.1055/s-2008-1077880; Art ID: G11808ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Fullerene Bismalonates
1707
O
N
N
N
DCC
O
O
+
O
O
O
HO
O
MeCN, r.t., 2 h
HO
OH
O
85%
O
2
2
CBr4, DBU
toluene, r.t., 18 h
26%
Scheme 1 Preparation pathway to compound 1
NC
O
O
N
O
O
O
O
O
O
O
O
O
O
O
O
O
O
N
CN
10
6
Figure 2 Bispyridine and benzonitrile C60 bisadducts 6 and 10
O
edge, only few examples of metal complexes with
functionalized C60 ligands bearing either pyridine or por-
phyrin units as ligands have yet been reported.7 In this
context, ligand 1 should exhibit interesting coordination
properties.
O
O
N
N
Cl
CuCl2·2H2O
in MeCN
1
O
O
Cu
Cl
CH2Cl2, r.t.
We thus explored its coordination properties in the pres-
ence of CuCl2. As expected, a very fast reaction occurred
because the endo complex 3 formed quantitatively within
few minutes (Scheme 2). The structure of 3 was con-
firmed by FAB spectroscopy showing clearly M+, [M+ +
MeCN], [M+ – Cl] and [M+ – 2 × Cl], and by elemental
analysis.8 Unfortunately, other characterization data
(NMR) were inaccessible due to insolubility of the brown
solid formed. It has been recently shown that the solubility
of such complex species can be significantly increased us-
ing six-fold functionalized fullerene derivatives.9 In the
near future, we will explore this possibility in order to
completely characterize the complexes formed during
these processes.
99%
O
3
Scheme 2 Formation of complex 3 in the presence of CuCl2
bifunctionalized C60 regio- and stereoselectively.10 Since
the first report of this elegant approach, several motifs
have been utilized as core part of the tether, of which the
length and shape are known to directly affect the addition
pattern. The fullerene derivatives described in this paper
were prepared taking advantage of a versatile regioselec-
tive reaction developed by Diederich et al. which led to
C60 bisadducts in a macrocyclization reaction at the C60
sphere with bismalonates in a double Bingel cyclopropa-
nation.11
In order to avoid the previously described formation of
endo complexes during metal–ligand recognition, we
were drawn to investigate the design of other functional-
ized fullerene cores bearing pyridine sticky sides. In this
context, the tether-directed remote functionalization of
C60 proved to be a versatile and reliable strategy to prepare
Hence, we prepared tectons 6 and 10 bearing either py-
ridines or benzonitriles as sticky sides (Figure 2).12
The cyclic fullerene bisadduct 6 (Figure 2) bearing two
pyridine head groups was obtained in three steps from
Synlett 2008, No. 11, 1706–1710 © Thieme Stuttgart · New York

1708
P. Pierrat et al.
LETTER
4-pyridylmethanol and 1,3-benzenedimethanol. Reaction
of 4-pyridylmethanol with 2,2-dimethyl-1,3-dioxane-4,6-
dione (Meldrum’s acid) was previously reported with
only 26% yield.9 We improved the synthesis of monoester
4 by performing the reaction in refluxing toluene afford-
ing the title compound in 70% yield (Scheme 3). The bis-
malonate 5 was prepared in 95% yield by reaction of 4
with 1,3-benzenedimethanol in the presence of DCC and
4-dimethylaminopyridine (DMAP) in DMF. Treatment of
the bismalonate 5 with C60, I2, and DBU in a mixture of
toluene and acetonitrile at room temperature for 12 hours
afforded the desired cyclization product 6 in 33% yield.
O
O
O
HO
O
O
O
O
N
HO
N
toluene, reflux, 12 h
4
70%
N
O
OH
O
O
O
We next investigated the preparation of such fullerene de-
rivatives having benzonitrile coordination sites. This
sticky side is indeed well known to strongly coordinate
metal ions such as Ag(I).4 To this end, we used the same
synthetic route as depicted above.
C60, I2, DBU,
OH
6
toluene–MeCN
r.t., 18 h
DCC, DMAP, DMF
0 °C – r.t., 12 h
O
O
33%
95%
O
5
The macrocyclic fullerene bisadduct 10 bearing benzoni-
trile head groups was obtained in four steps (Scheme 4).
Reduction of 4-cyanobenzaldehyde in the presence of a
stoichiometric amount of NaBH4 in ethanol afforded com-
pound 7 in 92% yield. Reaction of 4-(hydroxymethyl)ben-
zonitrile with Meldrum’s acid at 120 °C for four hours
gave the monoester 8 in 98% yield. Bismalonate 9 was
then prepared in 42% yield by reaction of 8 with the 1,3-
benzenedimethanol using DCC and DMAP in CH2Cl2.
Treatment of the bismalonate 9 with C60, I2, and DBU in
toluene at room temperature afforded the desired cycliza-
tion product 10 in 31% yield.
O
N
Scheme 3 Synthetic pathway for the preparation of derivative 6
shape on this substrate in order to avoid the formation of
endo complexes. Nevertheless, by using the synthetic
strategy developed by Diederich et al. and with the help of
modeling studies, the preparation of potential exo ligands
became accessible in a straightforward manner and in
good yields. Work is now in progress with the intention of
examining in detail the ability of such ligands to build
multidimensional metal organic frameworks and to ex-
plore their potential chemical and physical properties.
In conclusion, we have demonstrated through this prelim-
inary work that the formation of nanostructures based on
fullerene core structures requires an important design
study to obtain suitable ligands for metal coordination. In-
deed, the most challenging task is to find the best addition
O
O
O
O
O
HO
H
NaBH4 (1.1 equiv)
EtOH, r.t., 5 h
92%
O
O
HO
O
120 °C, 4 h
98%
CN
CN
CN
7
8
CN
CN
OH
C60, I2, DBU
toluene, r.t., 18 h
OH
O
O
O
O
10
DCC, DMAP, CH2Cl2
0 °C to r.t., 12 h
31%
O
O
O
42%
O
9
Scheme 4 Synthetic pathway for the preparation of derivative 10
Synlett 2008, No. 11, 1706–1710 © Thieme Stuttgart · New York

LETTER
Synthesis of Fullerene Bismalonates
1709
(12) Experimental Procedure for the Preparation of
Acknowledgment
Malonate 2: To a solution of malonic acid (464 mg, 4.4
mmol) and 2-(pyridin-3-yloxy)ethanol (1.21 g, 8.7 mmol) in
anhyd MeCN (16 mL) was added dropwise a solution of
DCC (1.79 g, 8.7 mmol) in anhyd MeCN (16 mL) over 20
min under argon during which time a white precipitate
formed. The reaction mixture was stirred overnight at r.t.
Then, the precipitate was filtered off and washed with
CH2Cl2 (2 × 10 mL). The filtrate was evaporated and dried
in vacuo affording a yellow oil which was purified by
column chromatography on silica gel using CH2Cl2–MeOH
(95:5) as eluent. The expected compound was obtained as a
yellow oil (1.23 g, 82%). IR: 3061, 2969, 2884, 1763, 1670,
1577, 1477, 1457, 1429, 1377, 1272, 1189, 1050 cm–1.
1H NMR (500 MHz, CDCl3): d = 3.50 (s, 2 H), 4.22 (t, J =
4.5 Hz, 4 H), 4.51 (t, J = 4.5 Hz, 4 H), 7.20–7.26 (m, 4 H),
We thank the Alexander von Humboldt foundation (fellowship to
P.P.) and the DFG Center for Functional Nanostructures (CFN) (C5
project) for financial support.
References and Notes
(1) (a) Diederich, F.; Thilgen, C. Science 1996, 271, 317.
(b) Cardinali, F.; Nierengarten, J. F. Tetrahedron Lett. 2003,
44, 2673. (c) Khoudy, M. E.; Kang, E. S.; Kay, K. Y.; Choi,
C. S.; Aaraki, Y.; Ito, O. Chem. Eur. J. 2007, 13, 2854.
(d) Brettreich, M.; Burghardt, S.; Bottcher, C.; Bayerl, T.;
Bayerl, S.; Hirsch, A. Angew. Chem. Int. Ed. 2000, 39, 1845.
(2) (a) Nakanishi, T.; Miyashita, N.; Michinobu, T.; Wakayama,
Y.; Tsuruoka, T.; Ariga, K.; Kurth, D. G. J. Am. Chem. Soc.
2006, 128, 6328. (b) Zhou, S. Q.; Burger, C.; Chu, B.;
Sawamura, M.; Nagahama, N.; Toganoh, M.; Hackler, U. E.;
Isobe, H.; Nakamura, E. Science 2001, 291, 1944.
(c) Sawamura, M.; Kawai, K.; Matsuo, Y.; Kanie, K.; Kato,
T.; Nakamura, E. Nature (London) 2002, 419, 702.
(3) (a) Yaghi, O. M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi,
M.; Kim, J. Nature (London) 2003, 423, 705. (b) Rosi, N.
L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M.
CrystEngComm 2002, 4, 401.
8.24 (dd, J = 2.8, 5.0 Hz, 2 H), 8.31 (d, J = 2.8 Hz, 2 H). 13
NMR (125 MHz, CDCl3): d = 166.1, 154.5, 142.7, 137.9,
C
123.9, 121.3, 65.9, 63.5, 41.1. EI–MS: m/z (%) = 346 (52)
[M+], 157 (85), 95 (100).
Experimental Procedure for the Preparation of
Fullerene Derivative 1: To a solution of C60 (500 mg, 690
mmol) in freshly distilled toluene (250 mL) were added CBr4
(347 mg, 1.03 mmol) and malonate 2 (358 mg, 1.03 mmol)
under argon. Then, DBU (3 equiv, 0.31 mL, 2.07 mmol) was
added slowly to the reaction medium which was stirred for
18 h at r.t. The volatiles were removed and the crude residue
was purified by flash column chromatography using CH2Cl2
and then CH2Cl2–MeOH (95:5) as eluent. The expected
compound was recovered as a brown solid (192 mg, 26%).
IR: 3053, 2953, 2872, 2329, 1748, 1575, 1474, 1427, 1186,
1110 cm–1. 1H NMR (500 MHz, CDCl3): d = 4.04 (t, J = 4.5
Hz, 4 H), 4.87 (t, J = 4.5 Hz, 4 H), 7.20–7.26 (m, 4 H), 8.27
(dd, J = 2.5, 4.3 Hz, 2 H), 8.34 (d, J = 2.5 Hz, 2 H). 13C NMR
(125 MHz, CDCl3): d = 163.4, 154.4, 145.3, 145.2, 145.0,
144.9, 144.9, 144.7, 144.6, 144.5, 143.8, 143.0, 143.0,
142.8, 142.2, 141.7, 141.0, 138.9, 137.9, 124.0, 121.1, 71.1,
65.8, 65.1, 51.6. MS (FAB, NBA): m/z = 1067.5 [M+ + H],
1067.7 [M+].
Experimental Procedure for the Preparation of
Compound 4: A mixture of Meldrum’s acid (1.44 g, 10
mmol) and 4-pyridylmethanol (1.10 g, 10 mmol) in anhyd
toluene (50 mL) was refluxed overnight. After the reaction
mixture was cooled, a white precipitate formed which was
filtered off and washed with toluene (2 × 50 mL) and then
with pentane. The expected compound was obtained as a
white solid (1.38 g, 70%). IR: 3400, 3040, 2991, 2952, 1734,
1617, 1513, 1416, 1337, 1297, 1248, 1215, 1150, 1071, 1036
cm–1. 1H NMR (500 MHz, DMSO-d6): d = 3.54 (s, 2 H), 5.22
(s, 2 H), 7.37 (d, J = 6.0 Hz, 2 H), 8.57 (d, J = 6.0 Hz, 2 H),
12.90 (br s, 1 H). 13C NMR (125 MHz, DMSO-d6): d =
170.6, 168.4, 150.3, 145.6, 122.3, 64.6, 42.1. EI–MS:
m/z (%) = 195 (63) [M+], 109 (100). Anal. Calcd for
C9H9NO4: C, 55.38; H, 4.64; N, 7.17. Found: C, 55.21; H,
4.67; N, 7.12.
(4) (a) Bourlier, J.; Hosseini, M. W.; Planeix, J. M.; Kyritsakas,
N. New J. Chem. 2007, 31, 25. (b) Wu, C. D.; Lin, W.
Dalton Trans. 2006, 4563. (c) Huang, K.; Xu, Z.; Li, Y.;
Zheng, H. Cryst. Growth Des. 2007, 2, 202.
(5) Camps, X.; Hirsch, A. J. Chem. Soc., Perkin Trans. 1 1997,
1595.
(6) Hartnagel, U.; Balbinot, D.; Jux, N.; Hirsch, A. Org. Biomol.
Chem. 2006, 4, 1785.
(7) (a) Tat, F. T.; Zhou, Z.; MacMahon, S.; Song, F.; Rheingold,
A. L.; Echegoyen, L.; Schuster, D. I.; Wilson, S. R. J. Org.
Chem. 2004, 69, 4602. (b) Milanesio, M. E.; Alvarez, M. G.;
Rivarola, V.; Silber, J. J.; Durantini, E. N. Photochem.
Photobiol. 2005, 891. (c) Habicher, T.; Nierengarten, J. F.;
Gramlich, V.; Diederich, F. Angew. Chem. Int. Ed. 1998, 37,
1916.
(8) Experimental Procedure for the Preparation of the
Fullerene Complex 3: To a solution of CuCl2·2H2O (3.1
mg, 18.2 mmol) in MeCN (1 mL) was added a solution of
fullerene derivative 1 (5 mg, 4.7 mmol) in CH2Cl2 (1 mL).
The resulting mixture was shaken leading to the
precipitation of a brown solid which was washed with THF,
MeCN and CH2Cl2 and finally dried in vacuo for 12 h. The
expected compound was obtained as a brownish solid (5.4
mg, 95%). Complex 3 has been characterized by FAB
spectroscopy, IR and elemental analysis. Unfortunately, we
were unable to get single crystals of this complex. IR: 3454,
3071, 2951, 2873, 1751, 1575, 1480, 1434, 1266, 1229, 1111
cm–1. MS (FAB, NBA): m/z = 1238 [M+ + MeCN], 1199
[M+], 1163 [M+ – Cl], 1130 [M+ – 2 × Cl]. Anal. Calcd for
C77H16N2O6CuCl2: C, 77.11; H, 1.34; N, 2.34. Found: C,
76.78; H, 1.48; N, 2.19.
(9) Bourgeois, J. P.; Woods, C. R.; Cardullo, F.; Habicher, T.;
Nierengarten, J. F.; Gehrig, R.; Diederich, F. Helv. Chim.
Acta 2001, 84, 1207.
(10) (a) Thilgen, C.; Sergeyev, S.; Diederich, F. Top. Curr.
Chem. 2004, 248, 1. (b) Diederich, F.; Kessinger, R. Acc.
Chem. Res. 1999, 32, 537.
(11) Felder, D.; Guitierrez, M.; Carcon, M. P.; Eckert, J. F.;
Schall, M. L. C.; Masson, P.; Gallani, J. L.; Heinrich, B.;
Guillon, D.; Nierengarten, J. F. Helv. Chim. Acta 2002, 85,
288.
Experimental Procedure for the Preparation of
Malonate 5: DCC (1.22 g, 5.9 mmol) dissolved in DMF (2
mL) was added dropwise to an anhyd DMF solution of 4
(1.15 g, 5.9 mmol), 1,3-benzenedimethanol (338 mg, 2.4
mmol) and DMAP (50 mg, 400 mmol) cooled to 0 °C under
an argon atmosphere. The reaction mixture was maintained
at 0 °C for 2 h and then allowed to warm to r.t. overnight.
The crude mixture was filtered and the obtained solid was
washed with CH2Cl2. The filtrate was evaporated and dried
in vacuo affording a yellow oil which was purified by flash
chromatography using EtOAc–MeOH (90:10) as eluent.
The expected compound was obtained as a pale yellow oil
Synlett 2008, No. 11, 1706–1710 © Thieme Stuttgart · New York

1710
P. Pierrat et al.
LETTER
(1.13 g, 95%). IR: 3032, 2951, 1735, 1604, 1563, 1450,
1415, 1381, 1334, 1273, 1147, 1015 cm–1. 1H NMR (500
MHz, CDCl3): d = 3.56 (s, 8 H), 5.20 (s, 8 H), 7.23 (d, J =
6.0 Hz, 4 H), 7.33–7.37 (m, 4 H), 8.58 (d, J = 6.0 Hz, 4 H).
13C NMR (125 MHz, CDCl3): d = 165.9, 165.9, 150.1, 144.1,
135.6, 129.0, 128.4, 128.1, 121.8, 67.0, 65.1, 41.3. EI–MS:
m/z (%) = 492 (25) [M+ + H], 286 (70), 109 (100). Anal.
Calcd for C26H24N2O8: C, 63.41; H, 4.91; N, 5.68. Found: C,
63.48; H, 4.96; N, 5.74.
133.1 (75), 116.1 (100).
Experimental Procedure for the Preparation of
Malonate 9: DCC (605 mg, 2.9 mmol) dissolved in CH2Cl2
(2 mL) was added dropwise to a CH2Cl2 solution of 8 (630
mg, 2.8 mmol), 1,3-benzenedimethanol (187 mg, 1.36
mmol) and DMAP (53 mg, 0.42 mmol) cooled at 0 °C under
an argon atmosphere. The reaction mixture was maintained
at 0 °C for 2 h and then allowed to warm to r.t. overnight.
The solution was filtered and washed with CH2Cl2. The
filtrate was evaporated and dried in vacuo affording a yellow
oil which was purified by flash chromatography using
CH2Cl2–Et2O (97:3) as eluent. The expected compound was
obtained as a pale yellow oil (310 mg, 42%). IR: 3062, 2952,
2229, 1927, 1735, 1612, 1509, 1452, 1378, 1332, 1271, 1015
cm–1. 1H NMR (400 MHz, CDCl3): d = 3.54 (s, 4 H), 5.19 (s,
4 H), 5.24 (s, 4 H), 7.32–7.36 (m, 4 H), 7.43 (d, J = 8.0 Hz,
4 H), 7.63 (d, J = 8.0 Hz, 4 H). 13C NMR (100 MHz, CDCl3):
d = 165.9, 140.4, 135.6, 132.4, 129.0, 128.3, 128.2, 128.0,
118.4, 112.2, 67.0, 65.9, 41.3. EI–MS: m/z (%) = 540.2 (42)
[M+], 203 (100).
Experimental Procedure for the Preparation of
Fullerene Derivative 6: To a solution of C60 (200 mg, 277
mmol) in freshly distilled toluene (420 mL) and anhyd
MeCN (40 mL) were added I2 (161 mg, 636 mmol) and
bismalonate 5 (136 mg, 228 mmol) under argon. Then, DBU
(6 equiv, 240 mL, 1.63 mmol) was added slowly to the
reaction medium which was then stirred for 18 h at r.t. The
crude reaction mixture was directly purified by flash column
chromatography using first toluene as eluent in order to
remove unreacted C60 and then CH2Cl2–acetone–Et3N
(70:29:1). The expected compound was obtained as a brown
solid (112 mg, 33%). IR: 3030, 2946, 2331, 1750, 1603,
1432, 1414, 1230, 1204 cm–1. 1H NMR (500 MHz, CDCl3):
d = 5.03 (d, J = 13.0 Hz, 2 H), 5.32 (d, J = 13.0 Hz, 2 H), 5.47
(d, J = 13.0 Hz, 2 H), 5.87 (d, J = 13.0 Hz, 2 H), 7.32–7.52
(m, 8 H), 8.65 (d, J = 4.0 Hz, 4 H). 13C NMR (125 MHz,
CDCl3): d = 162.7, 162.4, 150.2, 148.4, 147.6, 146.1, 145.8,
145.7, 145.7, 145.6, 145.5, 145.3, 144.9, 144.7, 144.4,
144.2, 144.1, 143.9, 143.9, 143.6, 143.3, 142.5, 142.3,
141.4, 140.9, 140.1, 136.5, 136.2, 135.8, 134.1, 128.8,
127.0, 124.1, 122.6, 70.4, 67.5, 66.6, 48.7. MS (FAB, NBA):
m/z = 1209 [M+ + H], 1208 [M+].
Experimental Procedure for the Preparation of
Fullerene Derivative 10: To a solution of C60 (150 mg, 207
mmol) in freshly distilled toluene (360 mL) were added I2
(132 mg, 518 mmol) and the bismalonate 9 (123 mg, 228
mmol) under argon. Then, DBU (5 equiv, 160 mL, 1.06
mmol) was added slowly to the reaction medium which was
stirred for 18 h at r.t. Then, the crude reaction mixture was
directly purified by flash column chromatography using first
toluene as eluent in order to remove unreacted C60 and then
CH2Cl2. The expected compound was obtained as a brown
solid (81 mg, 31%). IR: 2953, 2228, 1750, 1611, 1444, 1371,
1282, 1232, 1204, 1102 cm–1. 1H NMR (500 MHz, CDCl3):
d = 5.10 (d, J = 13.0 Hz, 2 H), 5.40 (d, J = 13.0 Hz, 2 H), 5.53
(d, J = 13.0 Hz, 2 H), 5.87 (d, J = 13.0 Hz, 2 H), 7.36 (m, 2
H), 7.46 (d, J = 7.0 Hz, 2 H), 7.57 (d, J = 8.3 Hz, 4 H), 7.72
(d, J = 8.3 Hz, 4 H). 13C NMR (125 MHz, CDCl3): d = 162.7,
162.5, 148.4, 147.6, 147.6, 147.4, 146.2, 145.9, 145.8,
145.7, 145.6, 145.5, 145.4, 145.3, 144.9, 144.8, 144.5,
144.3, 144.2, 144.2, 143.9, 143.7, 143.3, 142.6, 142.3,
141.4, 140.9, 140.1, 139.7, 138.1, 136.5, 136.1, 135.8,
134.1, 132.5, 129.2, 128.9, 127.0, 124.1, 118.3, 112.8, 70.4,
67.6, 48.8. MS (FAB, NBA): m/z = 1256.9 [M+].
Experimental Procedure for the Preparation of
Compound 8: A mixture of Meldrum’s acid (441 mg, 3
mmol) and 4-cyanobenzylalcohol (400 mg, 3 mmol) was
heated at 120 °C for 4 h. Then, the crude mixture was cooled
and dried in vacuo for 12 h. The expected compound was
obtained as a yellow oil (652 mg, 98%). IR: 3220, 3062,
2951, 2230, 1928, 1738, 1612, 1567, 1508, 1414, 1379,
1332, 1230, 1148, 1034, 1018 cm–1. 1H NMR (400 MHz,
CDCl3): d = 3.53 (s, 2 H), 5.27 (s, 2 H), 7.48 (d, J = 8.1 Hz,
2 H), 7.68 (d, J = 8.1 Hz, 2 H), 10.20 (br s, 1 H). 13C NMR
(100 MHz, CDCl3): d = 171.3, 166.0, 140.3, 132.4, 128.4,
118.4, 112.2, 66.2, 40.9. EI–MS: m/z (%) = 219.1 (29) [M+],
Synlett 2008, No. 11, 1706–1710 © Thieme Stuttgart · New York