Microwave-assisted synthesis of fulleropyrazolines/fulleroisoxazolines mediated by (diacetoxyiodo)benzene: A rapid and green procedure

Article abstract of DOI:10.1039/c3ra44567d

Microwave as a green, rapid and effective procedure has been applied to the synthesis of fulleropyrazolines/fulleroisoxazolines. The reaction mixtures containing substituted phenylhydrazones/oximes, C₆₀ and PhI(OAc) ₂ allowed to achieve products at room temperature in a good yield and short time without any side product.

Full text of DOI:10.1039/c3ra44567d

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Microwave-assisted synthesis of
fulleropyrazolines/fulleroisoxazolines mediated by
(diacetoxyiodo)benzene: a rapid and green
procedure
Cite this: RSC Adv., 2014, 4, 2954
*
Javad Safaei-Ghomi and Reihaneh Masoomi
Received 21st August 2013
Accepted 21st October 2013
Microwave as a green, rapid and effective procedure has been applied to the synthesis of fulleropyrazolines/
fulleroisoxazolines. The reaction mixtures containing substituted phenylhydrazones/oximes, C60 and
PhI(OAc)2 allowed to achieve products at room temperature in a good yield and short time without any
side product.
DOI: 10.1039/c3ra44567d
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attached to the C60 cage were studied to indicate the same or
better acceptor character than C60. It is different from full-
1. Introduction
Since the discovery of fullerenes1 and isolation in bulk,2 the
research of appropriate procedures for their functionalization
has become one of the main challenges in organic chemistry.3
In particular, the most numerous member of the fullerene
family, C60, has obtained the highest interest as C60-based
molecules exhibit a broad range of interesting features, bio-
logical elds such as anti-HIV activity and ability to inhibit
enzymes, DNA cleavage, neuroprotective, antioxidant, antimi-
crobial activities.4 In addition, fullerene derivatives have wide
applications in biomedicine including radiotracers,5 magnetic
resonance imaging (MRI) contrast agents for metallo-full-
erenols6 and drug delivery system.7 The double bonds between
two hexagons in C60 structure are dienophilic, which enables
the molecule to undergo a variety of cycloaddition reactions
including cycloadditions,8 cyclopropanation,9 addition organo-
metallic reagents,10 and photo-induced electron transfer reac-
tions.11 Among the different types of cycloaddition reactions12
available for the preparation of fullerene derivatives, 1,3-dipolar
cycloadditions demonstrate a powerful tool due to the fact that
C60 behaves as an electron-decient olen. Different types of
fullerene derivatives such as fullerene-fused pentagonal
heterocyclic rings, such as fulleropyrolidines,13 fulleroindo-
lines,14 fullerene fused lactones,15 pyrazolo- and oxazolo-fuller-
enes16 have been reported in the literature. Fullerene-fused
pentagonal heterocyclic rings, such as fulleroisoxazolines or
fulleropyrazolines, which is known to show attractive chemical,
electrochemical, and photophysical properties have been made
through 1,3-dipolar cycloadditions like fulleropyrrolidines. The
electrochemical properties of the fulleroisoxazoline and full-
eropyrazoline compounds in which a heteroatom is directly
eropyrrolidines which usually show a decline in electron affinity
17
with respect to the parent C60
eropyrazolines can be readily synthesized through several
methods such as addition of nitrilimine or nitrile oxide to C60
.
Fulleroisoxazolines or full-
.
For the rst time, the addition reaction of C60 with nitrile oxides
was reported by Meier.18 The most commonly used strategy for
the synthesis of fulleroisoxazolines and fulleropyrazolines
include two steps: rst synthesis of hydroximinoyl halides or
hydrazonoyl halides resulted from reaction of aldoxime or
hydrazone with NCS or NBS, then reacting with C60 in the
presence of organic base.19 Also isoxazoline-fused fullerenes can
also be obtained from the reaction of C60 and nitrile oxide.20
Also synthesis of fulleroisoxazolines through the reaction of C60
with N-silyloxynitrones, formed from nitroalkene and Me3SiCl/
Et3N was reported.21 Recently, one-step synthesis of several
fullerene derivatives was reported at room temperature by
Yang's group.22
In the recent years, the synthetic utility of microwave irra-
diation has appeared as a very efficient and clean alternative to
conventional heating for introducing energy in organic reac-
tions has considerably been increased. Microwave includes an
electric and magnetic eld and thus species electromagnetic
energy which can act as a non-ionising energy. This energy
causes molecular movements of ions and rotation of the
dipoles, but does not affect the molecular structure. Under
microwaves, the energy transfer is produced by dielectric loss
not by conduction or convection.23
This methodology is applied in cycloaddition reactions of
compounds that are sensitive and/or have low reactivity such as
heterocycles, natural products and fullerene derivatives.
Examples of this technology in organic synthesis are
numerous.24 Furthermore, the related literatures on microwave-
assisted synthesized fullerene derivatives have been reported.
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan,
51167, I. R. Iran. E-mail: safaei@kashanu.ac.ir; Fax: +98 361 5552935
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In 1999 Cruz et al., synthesized the 3-(N-phenylpyrazol-4-yl) microwave irradiation (10 min). The same reactions under
isoxazolo[60]fullerene dyad through a microwave induced 1,3- thermal conditions produced the same or lower yields
dipolar cycloaddition between the pyrazole nitrile oxide and because of producing by product comparing to room
25
C60
.
Also microwave-assisted 1,3-dipolar cycloadditions temperature.
According to Table 1, the results demonstrated that method
between C60 and azomethine ylides generated from decarbox-
ylation of imminium ions derived from the condensation of B (microwave irradiation) is excellent in both yields and espe-
glycine with benzaldehydes, was reported.26 Oviedo showed the cially in the reaction times better than method A (conventional
synthesis of [60]fullerene-donor dyads by 1,3-dipolar cycload- conditions). Under microwave irradiation, the high yields
ditions of azomethineylides.27 The same authors reported transformations were carried out without any signicant
microwave-assisted synthesis of [60]fullerene adducts from amounts of undesirable side product.
nitrile imines, generated in situ from the corresponding
Under conventional heating conditions, the reactions
hydrazones and NBS in the presence of Et3N, and C60
.
28 Also the usually need long reaction times, high temperatures and
isoindazolylpyrazolino[60]fullerene dyads were isolated from resulting in partial or total decomposition of sensitive
1,3-dipolar cycloadditions between isoindazolyl nitrile imines, compounds. These problems have been properly overcome by
generated in situ from the related isoindazolehydrazones and the use of microwave irradiation. The short reaction time
C60 under microwave irradiation.29
associated with microwave activation avoids decomposition of
In this contribution we report the efficient microwave- reagents and products, and prevents polymerization of the
assisted synthesis of fulleropyrazolines/fulleroisoxazolines diene or dienophile. Some heterocyclic compounds such as
throughout 1,3-dipolar cycloaddition mediated by (diacetox- pyrazoles and oxazoles systems that are very reluctant to
yiodo)benzene for the rst time.
participate in cycloaddition reactions can be induced to react
under microwave irradiation conditions. The application of this
method to the chemistry of [60]fullerene has permitted deriva-
tization of this system while avoiding the problems of poly-
cycloaddition and cycloreversion.32
2. Results and discussion
2.1. Synthesis
It was found that the process was an easy, mild and appro-
priate method for constructing pyrazoline/oxazoline cycle on
fullerene through 1,3-dipolar reaction and greatly accelerated
under microwave irradiation as compared to conventional
conditions. In all cases, the experimental results showed that
the reaction times are very short and the yields of the products
are higher under microwave conditions.
Mechanistically, at rst the generation of nitrilimine/
nitriloxide dipole is due to contacting phenylhydrazone/
oxime and (diacetoxyiodo)benzene. Then 1,3-dipolar cyclo-
addition reaction occurred by these dipoles with fullerene
(Scheme 3).
(Diacetoxyiodo)benzene was prepared from benzene, AcOH, I2
in the presence of K2S2O8 as an oxidant.30 Compounds (1a–e)
and (3a–d) were synthesised in good yields according to the
literature methods (Scheme 1).31
In this research, microwave irradiation is discussed as a
green and complementary technique to promote 1,3-dipolar
cycloaddition reactions. Cycloaddition reactions of C60 with
substituted phenylhydrazones/oximes in the presence of
PhI(OAc)2 under conventional (25 ꢀC/60 ꢀC) and microwave
conditions occurred to prepare the corresponding full-
eropyrazolines/fulleroisoxazolines in two steps as described in
Scheme 2.
In most cases, under microwave irradiation spectacular
accelerations and great improvements in yields and reaction
conditions are observed.
Under microwave irradiation, nitrilimine/nitriloxide dipoles
as very reactive chemical species are produced very fast, thus
facilitating 1,3-dipolar cycloaddition that is a critical step in this
type of cycloaddition reactions.
All known products were conrmed by comparison of their
spectral data with those reported in the literature. The identi-
cation of new compounds 2d–e was conrmed by their MS, 1H
NMR, 13C NMR, FT-IR and CHN analyses. Consider 2e (Table 1,
entry 5) as an example. In the IR spectra, the stretching
frequency of aromatic C]C is produced in the area between m
To our satisfaction, when a mixture of C60 (36.0 mg), benz-
aldehyde phenylhydrazone 1a (1 equiv.) and PhI(OAc)2 (1 equiv.)
was stirred in 20 mL toluene for 60 min at room temperature
(Table 1, entry 1), the desired fulleropyrazoline 2a was obtained.
In order to extend the utility of this reaction, we carried out the
reaction using different types of phenylhydrazone/oxime under
the same conditions. Finally, for the examination of inuence of
green approach in this reaction, it was investigated using
microwave procedure (200 W).
ꢀ
Then we carried out all syntheses at 60 C. For example,
for the synthesis of 2a, when a mixture of reaction was
heated, the related fulleropyrazoline was obtained aer
25 minutes comparing to room temperature (60 min) and
Scheme 1 Synthesis of phenylhydrazone/oxime derivatives.
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Scheme 2 Synthesis of fulleropyrazolines/fulleroisoxazolines under (1) conventional and (2) microwave conditions.
¼ 1490–1600 cmꢁ1. The stretching vibration of C–H in the determined on Electro thermal 9200, and are not corrected. The
aromatic ring was appeared at m ¼ 3050 cmꢁ1. Also the IR spectra were recorded on FT-IR Magna 550 apparatus using
stretching frequency of C]N of pyrazoline ring appears at with KBr plates. 1H NMR and 13C NMR spectra were recorded on
1630 cmꢁ1. In the mass spectrum (EI, 70 eV), the peak at m/z 957 Bruker Avance-400 MHz spectrometers in the presence of tet-
is related to the molecular ion of 2e. In the 1H NMR spectra, an ramethylsilane as internal standard. EIMS (70 eV) was per-
imine proton signal appears around d ¼ 9–10 ppm in phenyl- formed by Finnigan-MAT-8430 mass spectrometer in m/z.
hydrazones while this peak disappears in the fulleropyrazoline Microwave irradiation was carried out using a Litres Solo
spectrum because of connection of phenylhydrazone to C60. The Microwave Oven ME3410W apparatus (200 W). The elemental
signals about d ¼ 6.6–7.6 are assigned by protons of CH–CH of analyses (C, H, N) of the samples were performed using a LECO
aromatic rings in phenylhydrazone while these protons are CHNS 923 analyser.
deshilded in fulleropyrazolines and the related signals appear
in d ¼ 6.8–8.5 (Fig. 1).
3.2. General procedure for synthesis of (diacetoxyiodo)arene
In the 13C NMR spectra, carbon of C]N has a chemical shi
A mixture of benzene, AcOH, C2H4Cl2, concd H2SO4 and I2 was
in d ¼ 88 and 98 ppm is assigned by two carbon-sp3 of pyrazole
heated with stirring to 40 ꢀC for 15 min. Next, K2S2O8 was added
portionwise for 10 min and the stirring was continued for 12–
30 h until TLC analysis indicated completion of the reaction.
Aer the reaction was completed, water was added. Then the
precipitated solid was washed with CH2Cl2 three times and
nally washed with H2O followed by drying (anhydrous
Na2SO4), ltration, and removal of the solvent by evaporation
under reduced pressure. The crude product was puried by
ring on C60 while the signals related to the sp2 carbons of the
C60 skeleton and aromatic rings appear in d ¼ 100–170 ppm
(Fig. 2).
3. Experimental
3.1. Chemicals and apparatus
Crystalline C60 powder used in this work was over 99.90% purity washing with hexane or recrystallized from AcOH.
from TCI (Tokyo Chemical Industry Co.). All solvents and
(Diacetoxyiodo)benzene. White solid; mp ¼ 161–163, yield
chemical reagents were purchased from Aldrich and Fluka and 65%, 1H NMR (400 MHz, DMSO-d6): d (ppm) 1.84 (s, 6H, CH3),
used without further purication. Melting points were 7.2–8.2 (m, 5H, ArH).
Table 1 Synthesis of fulleropyrazoline/fulleroisoxazoline derivatives under conventional and microwave conditions
Method Aa 25 ꢀC/60 ꢀ
C
Method Bb
Recovered
C60 (%)
Recovered
C60 (%)
Entry
Ar in reactant
Product
Time (min)
Yieldc (%)
Time (min)
Yieldc (%)
1a
1b
1c
1d
1e
3a
3b
3c
3d
H
2a22
2b22
2c22
2d
60/25
30/17
45/22
100/30
40/20
90/30
90/35
60/20
90/30
30/28
31/30
25/22
31/27
22/17
36/34
41/35
32/30
34/29
49/48
45/40
46/51
53/49
51/53
41/40
42/45
40/42
45/47
10
5
8
15
10
15
15
10
15
40
43
38
42
39
41
45
41
42
45
39
41
43
45
47
39
42
38
4-NO2
4-OCH3
4-CH3
4-NMe2
4-NO2
4-Cl
2e
4a22
4b22
4c19b
4d22
4-NMe2
4-OCH3
a
Reaction of phenylhydrazone/oxime, C60 and PhI(OAc)2 in toluene under conventional conditions (25 ꢀC/60 ꢀC) and nitrogen atmosphere.
b
Reaction of phenylhydrazone/oxime, C60 and PhI(OAc)2 in toluene under microwave irradiation (200 W). c Isolated yields based on the reacted C60
.
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Scheme 3 Possible mechanism for the formation of fulleropyrazoline/fulleroisoxazoline mediated by PhI(OAc)2.
3.3. General procedure for synthesis of substituted
phenylhydrazone/oxime derivatives
Substituted phenylhydrazones were obtained by mixing equi-
molar quantities of phenylhydrazine and the aldehydes in
ethanol under reux condition. The precipitated hydrazones
were ltered, washed, recrystallized from ethanol. Oxime
derivatives were synthesized from aldehyde and hydroxylamine
hydrochloride in the alkali conditions.
Fig. 2 13C NMR spectrum of 10-phenyl-30-(4-N,N-dimethylamino-
Spectral data for phenylhydrazone/oxime derivatives
Benzaldehyde phenylhydrazone (1a). 1H NMR (400 MHz,
acetone-d6): d (ppm) 6.82 (t, 1H), 7.13 (d, 2H), 7.27 (d, 2H), 7.40–
7.67 (m, 5H), 8.17 (s, 1H). FT-IR (KBr): 3310, 3056, 2916, 1633,
phenyl) pyrazolino-[40,50:1,2][60]fullerene.
4-Nitrobenzaldehyde phenylhydrazone (1b). 1H NMR (400 MHz,
acetone-d6): d (ppm) 6.86 (t, 1H, ArH), 7.22 (d, 2H, ArH), 7.27 (t,
2H, ArH), 7.91 (s, 1H, NH), 7.96 (m, 3H, ArH), 7.46 (m, 1H, ArH),
1594, 1521, 1489, 1258, 1135, 812, 758, 753, 692, 507 cmꢁ1
Cream solid, mp 158 ꢀC.
.
1
Fig. 1 H NMR spectrum of (a): 4-(N,N-dimethylamino)benzaldehyde phenylhydrazone; (b): 10-phenyl-30-(4-N,N-dimethylamino-phenyl)
pyrazolino-[40,50:1,2][60]fullerene.
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7.56 (m, 2H, ArH), 7.71 (m, 5H, ArH), 8.14 (m, 1H, ArH), 8.26 (s,
1H, CH), 8.23 (d, 2H, ArH). FT-IR (KBr): 3298, 3050, 2900, 1596,
Representative spectral data for different cycloadducts
reported in Table 1
1539, 1493, 1325, 848, 750, 691 cmꢁ1. Red solid, mp 159 C.
ꢀ
10-Phenyl-30-phenyl pyrazolino-[40,50:1,2][60]fullerene (2a, Table
1, entry 1). Brown solid; 1H NMR (400 MHz, CDCl3–CS2): d (ppm)
7.30 (d, 1H, ArH), 7.34 (d, 1H, ArH), 7.53 (m, 3H, ArH), 7.69 (m,
3H, ArH), 8.02 (d, 1H, ArH), 8.26 (d, 1H, ArH). FT-IR (KBr): 3005,
4-Methoxybenzaldehyde phenylhydrazone (1c). 1H NMR
(400 MHz, acetone-d6): d (ppm) 3.82 (s, 3H, CH3), 6.75 (t, 1H,
ArH), 6.95 (d, 2H, ArH), 7.12 (d, 2H, ArH), 7.20 (t, 2H, ArH), 7.62
(d, 2H, ArH), 7.83 (s, 1H, CH), 9.27 (s, 1H, NH). FT-IR (KBr):
2924, 1726, 1633, 1457, 1262, 1098, 802, 730, 524, 464 cmꢁ1 13C
;
3313, 3024, 2951, 1597, 1501, 1245, 1128, 823, 748, 693 cmꢁ1
Yellowish solid, mp 121 C.
.
NMR (100 MHz, CDCl3–CS2): d (ppm) 82, 92, 124.2, 125.5, 129.3,
129.4, 129.7, 129.8, 131.09, 132.9, 136.7, 136.8, 140.1, 140.7,
142.3, 142.6, 142.7, 142.8, 142.90, 143.2, 143.3, 144.6, 144.5,
144.7, 145.1, 145.3, 145.6, 145.8, 146.2, 146.3, 146.4, 146.5,
146.6, 146.8, 146.9, 147.61, 148.01.
ꢀ
4-Methylbenzaldehyde phenylhydrazone (1d). 1H NMR
(400 MHz, acetone-d6): d (ppm) 2.33 (s, 3H, CH3), 6.77 (t, 1H,
ArH), 7.13 (d, 2H, ArH), 7.20 (d, 2H, ArH), 7.22 (t, 2H, ArH), 7.56
(d, 2H, ArH), 7.84 (s, 1H, CH), 9.38 (s, 1H, NH). FT-IR (KBr):
10-Phenyl-30-(4-nitrophenyl) pyrazolino-[40,50:1,2][60]fullerene
3308, 3024, 2918, 1596, 1503, 1256, 1131, 816, 748, 692 cmꢁ1
.
1
(2b, Table 1, entry 2). Brown solid; H NMR (400 MHz, CDCl3–
ꢀ
Light yellow solid, mp 115 C.
CS2): d (ppm) 7.19 (d, 1H, ArH), 7.37 (d, 2H, ArH), 7.53 (t, 2H,
ArH), 7.97 (d, 2H, ArH), 8.67 (d, 2H, ArH); 13C NMR (100 MHz,
CDCl3–CS2): d (ppm) 89, 97, 109, 114, 117, 120, 122 (2C), 124
(2C), 126 (2C), 128 (2C), 129 (2C), 131, 138, 140 (2C), 142 (2C),
143 (2C), 146, 147 (2C), 148.5, 149, 150, 152, 154 (2C), 156, 161
(2C), 162, 165 (2C), 168. FT-IR (KBr): 3001, 2920, 1731, 1595,
1
4-(N,N-Dimethylamino)benzaldehyde phenylhydrazone (1e). H
NMR (400 MHz, acetone-d6): d (ppm) 6.72 (t, 1H, ArH), 6.75 (d,
2H, ArH), 7.11 (d, 2H, ArH), 7.19 (t, 2H, ArH), 7.52 (d, 2H, ArH),
7.77 (s, 1H, CH), 9.10 (s, 1H, NH). FT-IR (KBr): 3312, 3030, 2890,
1599, 1509, 1259, 1129, 811, 748, 692 cmꢁ1. Yellow solid,
mp 149 ꢀC.
1519, 1456, 1336, 1259, 850, 752, 692, 527 cmꢁ1
.
4-Nitro benzaldehyde oxime (3a). 1H NMR (400 MHz, acetone-
d6): d (ppm) 7.89 (d, 2H, ArH), 8.26 (d, 2H, ArH), 8.30 (s, 1H, CH),
8.79 (s, 1H, OH). FT-IR (KBr): 3306, 1603, 1536, 1347, 1214, 1107,
969, 847, 748, 686 cmꢁ1. Cream solid, mp 132 ꢀC.
10-Phenyl-30-(4-methoxyphenyl) pyrazolino-[40,50:1,2][60] fullerene
(2c, Table 1, entry 3). Brown solid; 1H NMR (400 MHz, CDCl3–CS2):
d (ppm) 3.88 (s, 3H, OCH3), 7.05 (d, 2H, ArH), 7.25 (t, 1H, ArH),
7.48 (t, 2H, ArH), 7.96 (d, 2H, ArH), 8.24 (d, 2H, ArH); 13C NMR
(100 MHz, CDCl3–CS2): d (ppm) 55, 96, 99, 100, 104, 105, 107, 108,
109.5, 110, 112, 114 (2C), 115, 123 (2C), 124, 125, 126, 127.5, 128,
129 (2C), 130 (2C), 132, 133, 135, 136, 140, 141, 142, 143, 144, 145
(2C), 146, 159, 160, 161, 163, 165. FT-IR (KBr): 3000, 2980, 1650,
4-Chloro benzaldehyde oxime (3b). 1H NMR (400 MHz,
acetone-d6): d (ppm) 7.43 (d, 2H, ArH), 7.65 (d, 2H, ArH), 8.12 (s,
1H, CH), 10.45 (s, 1H, OH). FT-IR (KBr): 3299, 3996, 1594, 1398,
1594, 1492, 1313, 1212, 1087, 969, 873, 824, 691, 505 cmꢁ1
.
1603, 1497, 1332, 1251, 820, 752, 692, 526 cmꢁ1
.
White solid, mp ¼ 110 ꢀC.
4-(N,N-Dimethylamino)benzaldehyde oxime (3c). 1H NMR
(400 MHz, acetone-d6): d (ppm) 2.97 (s, 6H, CH3), 7.72 (d, 2H,
ArH), 7.44 (d, 2H, ArH), 7.99 (s, 1H, CH), 9.74 (s, 1H, OH). FT-IR
(KBr): 3239, 2911, 2803, 1605, 1524, 1359, 1303, 1224, 1176, 954,
865, 811, 730, 569 cmꢁ1. White solid, mp 185 ꢀC.
10-Phenyl-30-(4-methylphenyl) pyrazolino [40,50:1,2][60] fullerene
1
(2d, Table 1, entry 4). Brown solid; H NMR (400 MHz, CDCl3–
CS2): d (ppm) 1.11 (s, 3H, CH3), 7.18 (d, 1H, ArH), 7.26 (d, 1H,
ArH), 7.21 (t, 1H, ArH), 7.33 (m, 3H, ArH), 7.46 (t, 2H, ArH), 7.95
(d, 1H, ArH), 8.16 (d, 1H, ArH); 13C NMR (100 MHz, CDCl3–CS2):
d (ppm) 29, 86, 90, 104, 110, 111, 114, 115 (2C), 116, 117, 118,
120, 124 (2C), 125, 128 (2C), 129 (2C), 131, 132 (2C), 134, 135,
137 (2C), 138, 139, 140 (2C), 142, 143, 147 (2C), 150, 154 (2C),
165, 166, 179 (2C). FT-IR (KBr): 3000, 2917, 1636, 1455, 1367,
1256, 801, 751, 573, 525 cmꢁ1. MS (EI, 70 eV): m/z (%) ¼ 928 (M+,
2), 207 (71), 130 (37), 129 (52), 191 (49), 117 (34), 105 (75), 91
(100), 77 (69), 57 (69); anal. calcd for C74H9N2: C, 95.69; H, 1.30;
N, 3.02%. Found: C, 95.47; H, 1.25; N, 3.19%.
10-Phenyl-30-(4-N,N-dimethylaminophenyl) pyrazolino-[40,50:1,2]-
[60] fullerene (2e, Table 1, entry 5). Brown solid; 1H NMR
(400 MHz, CDCl3–CS2): d (ppm) 3.05 (s, 6H, NMe2), 6.82 (d, 2H,
ArH), 7.21 (dd, 1H, ArH), 7.46 (t, 2H, ArH), 7.95 (d, 2H, ArH),
8.21 (d, 2H, ArH); 13C NMR (100 MHz, CDCl3–CS2): d (ppm) 40,
58, 82, 91, 101, 104, 106, 108, 109.5, 110.8, 112 (2C), 114, 118,
119, 120, 123 (2C), 124, 129.2 (2C), 129.7 (2C), 130 (2C), 132, 133,
136.3 (2C), 137, 139, 142, 143 (2C), 143.5 (2C), 144, 145, 146.9
(2C), 151, 162, 163, 165, 168. FT-IR (KBr): 3000, 2919, 1603, 1522,
1488, 1431, 1357, 1097, 753, 692, 526 cmꢁ1. MS (EI, 70 eV): m/z
(%) ¼ 957 (M+, 5), 238 (6), 207 (82), 105 (89), 77 (66), 91 (100), 57
(66); anal. calcd for C75H15N3: C, 94.04; H, 1.57; N, 4.39. Found:
C, 94.25; H, 1.46; N, 4.17%.
4-Methoxybenzaldehyde oxime (3d). 1H NMR (400 MHz,
acetone-d6): d (ppm) 3.82 (s, 3H, CH3), 6.94 (d, 2H, ArH), 7.55 (d,
2H, ArH), 8.07 (s, 1H, CH), 10.07 (s, 1H, OH). FT-IR (KBr): 3320,
3006, 2968, 1607, 1512, 1307, 1249, 1169, 1028, 960, 871, 825,
591 cmꢁ1. White solid, mp 45 C.
ꢀ
3.4. General procedure for the synthesis of
fulleropyrazolines/fulleroisoxazolines
Typical stirring method (method A). A mixture of C60
(36.0 mg, 0.05 mmol), hydrazones (1a–e)/oximes (3a–d) (0.05
mmol), and PhI(OAc)2 (0.05 mmol) was dissolved in 20 mL of
toluene and stirred under nitrogen atmosphere at room
temperature and 60 ꢀC for a desired time. The course of the
reaction was monitored by TLC with toluene as an eluent. At
the end of reaction, the solvent was evaporated in vacuo, and the
residue was separated on a silica gel column using toluene to
afford adducts (2a–e)/(4a–d).
Microwave irradiation method (method B). In a similar
process, the mixture was irradiated by microwave irradiation
ꢀ
(200 W) for the desired times at 25 C.
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30-(4-Nitrophenyl) isoxazoline-[40,50:1,2][60] fullerene (4a, Table
RSC Advances
References
1, entry 6). Brown solid; 1H NMR (400 MHz, CDCl3–CS2): d
(ppm); 8.41 (d, 2H, ArH), 8.48 (d, 2H, ArH); 13C NMR (100 MHz,
CDCl3–CS2): d (ppm) 85, 95, 110, 124.2 (2C), 126.0, 128.0, 129.08,
129.7 (2C), 135, 136.7, 138, 139, 140.4, 140.5, 141.8, 142.04,
142.3, 142.5, 142.9 (2C), 143.1 (2C), 143.6, 143.7 (2C), 144, 144.4,
144.6, 145.2, 145.3 (2C), 145.8, 146.0 (2C), 146.1, 146.4, 146.5.
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cmꢁ1
30-(4-N,N-Dimethylaminophenyl)
.
isoxazoline-[40,50:1,2][60]-
1
fullerene (4c, Table 1, entry 8). Brown solid; H NMR (400 MHz,
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(d, 2H, ArH); 13C NMR (100 MHz, CDCl3–CS2): d (ppm) 49, 60,
85, 96, 102, 104, 105.2, 109, 112 (2C), 116 (2C), 130, 137 (2C),
137.2, 139 (2C), 140.5 (2C), 142.6, 142.7 (2C), 143.1 (2C), 144.0
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