Mendeleev Commun., 2015, 25, 204–206
7
et al.
a–c were synthesized using CBr and DBU according to Hirsch
4
2
2
The FTIR spectra of C monoadducts 7a–c were nearly super
60
imposable with those of compounds 5a–c, but they additionally
5
4
3
–1 23
had a characteristic C monoadduct band at 526 cm . In the
60
UVVIS spectra of compounds 7a–c three intense broad absorp
tion bands at 228, 258 and 326 nm dominated. The characteristic
absorption peak of the benzene ring was at 228 nm and those of
fullerene at 258 and 326 nm.24 In addition, a C monoadduct
2
1
60
25,26
absorption peak was observed at 430 nm.
1
The H NMRspectroscopic characterization of 7a–c at room
temperature was complicated by the presence of hindered rota
tions as a result of the sterically congested environment of hexa
substituted benzene rings and the strong electronwithdrawing
7
.4
7.2
7.0
d/ppm
6.8
6.6
Figure 2 1H NMR spectra (600 MHz, DMSOd ) of compound 8b recorded
at different temperatures: (1) 297.8 K, 16 scans; (2) 318.1 K, 16 scans;
(3) 338.2 K, 16 scans; (4) 358.1 K, 16 scans and (5) 358.1 K, 64 scans.
6
effect of the C unit. The broadening and complexity of the room
60
1
temperature H NMR spectra were caused by a large number of
2
7–30
atropisomers.
Several methods were tried for the benzyl deprotection of
a–c to form target products 8a–c under typical benzyl group
lerene.24 A C monoadduct absorption peak was also observed
at 430 nm.
At room temperature, the H NMR spectra of 8a–c revealed
unresolved broad signals caused by the rotational barrier of the
6
0
2
5,26
7
1
removal catalytic hydrogenation conditions (room temperature,
–
1
2
00 ml min H , atmospheric pressure, Pd/C in THF). However,
2
28
1
debenzylation was not observed by TLC. Thus, the deprotection
conditions were altered: the temperature was raised from 25 to
0°C; the catalyst amount was increased from 10 to 100% Pd/C
of 7a–c (w/w); and the reaction time was increased from 10 to
8 h. Nevertheless, the desired results were not reached. When
N–CO bond. The variabletemperature highresolution H NMR
spectrum of compound 8b is shown in Figure 2. Resonance
signals of catechol protons were resolved at 358.1 K, d: 7.2 (d,
2H, H , J 7.2 Hz), 6.9 (d, 2H, H , J 7.2 Hz) and 6.6 (t, 2H, H ,
4
Ar
Ar
Ar
13
4
J 7.2 Hz). However, the C NMR spectrum (150 MHz, DMSOd ,
6
TFA [10, 50 or 100% TFA/CH2Cl (v/v)] was used to deprotect
the benzyl group, TLC showed that the malonate hydrolysis led
to a complex result, and products 8a–c were still not obtained.
Therefore, another route was selected.
300.3 K, 11216 scans) was difficult to interpret. These results
indicate that the rotation of 6b was more hindered upon addition
to C .
6
0
In conclusion, new C I fullerenebased CAM derivatives
6
0 h
Recently, a new method for the effective cyclopropanation
of C I fullerene through a modified Bingeltype reaction
were synthesized through a modified Bingeltype reaction and
structurally characterized by FTIR, UVVIS, H, C NMR and
mass spectra.
1
13
6
0 h
31
without a basic catalyst was reported. This process provided
an alternative route to methanofullerene using bromomalonates,
which contain unprotected acidic or base labile groups. Thus, we
synthesized 8a–c through the deprotection of 5a–c with the fol
This work was supported by the National Natural Science
Foundation of China (project nos. 21301142 and 51372211),
National Defense Fundamental Research Projects (project no.
A3120133002), Youth Innovation Research Team of Sichuan for
Carbon Nanomaterials (2011JTD0017) and Southwest University
of Science and Technology Researching Project (13zx9107).
†
lowing cyclopropanation (see Scheme 1). The deprotection of
5
a–c using Pd/C as a catalyst led to 6a–c in 99% yields. Target
products 8a–c were obtained by the bromination of 6a–c with
32
NBS in ethyl acetate and subsequent cyclopropanation with C60
using glycine as a catalyst in a mixture of chlorobenzene and
DMSO.
Online Supplementary Materials
The FTIR spectra of C monoadducts 8a–c showed absorp
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2015.05.015.
60
–1
tion bands at 3400, 1731, 1636 and 526 cm , which could be
attributed to the stretching vibrations of N–H, malonate carbonyl,
benzamide carbonyl and characteristic C monoadduct bonds,
6
0
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6
0 h
1
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8
b and (3) malonate 6b in CH Cl .
2 2
–
205 –