Ferric perchlorate-mediated one-step reaction of [60]fullerene with primary amides for the synthesis of fullerooxazoles

Article abstract of DOI:10.1039/c5nj02503f

The facile one-step reaction of [60]fullerene with primary amides promoted by cheap and easily available ferric perchlorate afforded a series of interesting fullerooxazole derivatives. The reaction was tolerant of a large variety of primary amides containing aryl, alkyl, and cinnamyl groups. A possible reaction mechanism for product formation was proposed.

Full text of DOI:10.1039/c5nj02503f

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Ferric perchlorate-mediated one-step reaction of [60]fullerenDeOI:w10i.1t0h39/C5NJ02503F
primary amides for the synthesis of fullerooxazoles†
Xiao-Feng Zhang, Fa-Bao Li,* Ji-Long Shi, Jun Wu and Li Liu*
Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of
Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules,
and School of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R.
China. E-mail: lfb0615@hubu.edu.cn and liulihubei@hubu.edu.cn
† Electronic supplementary information (ESI) available: NMR spectra of products 2a-o as well as
UV-vis spectra of 2g, 2h, and 2o. See DOI: XXXX
The facile one-step reaction of [60]fullerene with primary amides promoted by cheap
and easily available ferric perchlorate afforded a series of interesting fullerooxazole
derivatives. The reaction was tolerant of a large variety of primary amides containing
aryl, alkyl, and cinnamyl groups. A possible reaction mechanism for the product
formation was proposed.
Introduction
Over the past two decades, chemical modification of fullerenes to produce various
fullerene derivatives with different structural motifs have attracted extensive attention
in chemical community because functionalized fullerenes have exhibited remarkable
potential in areas such as biological and medicinal chemistry, materials, and
nanotechnology.1 Accordingly, the development of functionalization methods for
fullerenes is of great significance. Generally speaking, the majority of chemical
1

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modification of fullerenes includes cycloadditions, nucleophilic additions,DOrIa: d10i.c10a3l9/C5NJ02503F
additions, etc.1,2 Radical additions are one of the first investigated reaction types of
fullerenes and continue to be of interest and important methodologies to functionalize
fullerenes.3 Nevertheless, the radical additions of parent fullerenes induced by
traditional peroxide or light tend to result in the generation of multi-addition fullerene
products, which would be extremely difficult to separate and characterize. In efforts to
avoid the formation of multi-addition products, various types of transition metal
salts3,4 such as Mn(OAc)3,5 Fe(ClO4)3,6 FeCl3,7 TBADT[(n–Bu4N)4W10O32],8
12
Cu(OAc)2,5d,9 Pb(OAc)4,5g,10 CoCl2dppe,11 and Ag2CO3 were employed as new
promoters of fullerene radical reactions. The radical reactions of fullerenes promoted
by transition metal salts were found to proceed well under mild conditions and could
generate a large number of novel mono-addition fullerene adducts that are relatively
easy to isolate and purify. For example, a large variety of rare fullerene derivatives
including oxazolines, 1,3-dioxolanes, disubstituted C60-fused lactones, boronic esters,
1,2-fullerenols,
hemiketals,
oxazolidinofullerenes/thiazolidinofullerenes,
and
dioxanes/dioxepanes could be successfully obtained through the Fe(ClO4)3-mediated
radical reaction of C60 with nitriles,6a aldehydes/ketones,6b malonate esters,6c
arylboronic acids,6d acid chlorides,6e β-keto esters,6f isocyanates/isothiocyanates,6g and
diols,6h respectively. Therefore, the further exploration and development of novel
radical reactions of fullerenes promoted by transition metal salts is still demanded.
Fullerooxazoles are a class of oxazoline-containing fullerene derivatives, which
may have promising applications in life science because a great number of
2

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oxazoline-containing natural products and biologically active compounds areDpOIr:e10s.e10n3t9/C5NJ02503F
in marine organisms.13 On the other hand, fullerooxazoles may have great benefits for
the preparation of a large variety of organic photovoltaic devices because the presence
of two electronegative atoms directly connected to the C60 skeleton enables
fullerooxazoles to have better electron acceptor character than C60.7c Initially,
fullerooxazoles were prepared via either thermal reactions14a,b of C60 with
azidoformates and hydroxamic acid derivatives or photochemical reactions14c of C60
with arylazides, followed by rearrangement of the formed fulleroaziridines to
fullerooxazoles. However, these methods undergo a two-step process and require the
use of highly toxic and explosive azides. Gao15a and Wang6a subsequently developed
a straightforward approach to the preparation of fullerooxazoles via cycloadditions of
C60 with nitriles under electrochemical or Fe(ClO4)3-mediated conditions.
Nevertheless, the two methods require a large amount of nitriles (100 equiv. or
solvent amounts), and the electrochemical method is only limited to benzonitrile,
which dramatically decreases its practicability. Recently, fullerooxazoles were also
synthesized via different reactions of C60 promoted by t-BuOI,15b PhI(OAc)2/I2,15c
CuI/Phen,15d and FeCl2,15e respectively. However, these methods require expensive
and unaccessible reagents as promoters, ligands or reactants. For example, the
reaction promoted by FeCl2 requires the unavailable N-substituted amides as reaction
substrates,15e and the PhI(OAc)2/I2-mediated synthesis must be manipulated under
photo-irradiation conditions.15c Hence, it is still demanding to develop new protocol to
obtain fullerooxazoles in a more practical and convenient way with a broad substrate
3

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scope. In continuation of our interest in fullerene chemistry,6g,h,16 herein we describe a
one-step reaction of C60 with primary amides promoted by cheap and easily available
Fe(ClO4)3 to afford a variety of interesting fullerooxazoles with a high tolerance of
functional groups (Scheme 1).
DOI: 10.1039/C5NJ02503F
Fe(ClO4)3
O
N
O
R
NH2
R
R = aryl, alkyl, and cinnamyl
Scheme 1 Fe(ClO4)3-mediated reaction of C60 with primary amides affording
fullerooxazoles.
Results and discussion
Initially, we investigated the reaction of C60 with benzoyl isothiocyanate in the
presence of Fe(ClO4)3 by the direct dissolution method, that is, Fe(ClO4)3 was first
dissolved in benzoyl isothiocyanate, and then the o-dichlorobenzene (ODCB) solution
of C60 was added. We found that fullerooxazole 2a was unexpectedly obtained as the
o
major product in 17% isolated yield at 100 C for 14 h (Scheme 2). We conjectured
that the formation of fullerooxazole 2a might proceed via the Fe(ClO4)3-mediated
reaction of C60 with benzamide 1a generated in situ by the addition of H2O in our
system to benzoyl isothiocyanate accompanied with the elimination of CO2 and H2S.17
Controlled experiments indicated that the reaction of C60 with benzamide 1a
o
promoted by Fe(ClO4)3 at 100 C for 13 h produced the desired fullerooxazole 2a in
19% yield as a major product (Scheme 2). It should be noted that the easy generation
of benzamide 1a from benzoyl isothiocyanate was attributed to the high reactivity of
benzoyl isothiocyanate due to the existence of the strong electron-withdrawing
4

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DOI: 10.1039/C5NJ02503F
carbonyl group in its molecular structure.
O
N
O
Fe(ClO4)3
N
C
S
ODCB,100 oC,N2
14 h, 17%
2a
13 h, 19%
O
Fe(ClO4)3
NH2
ODCB,100 oC,N2
1a
Scheme 2 Fe(ClO4)3-mediated reaction of C60 with benzoyl isothiocyanate and
benzamide 1a affording fullerooxazole 2a.
These experimental results shown in Scheme 2 provided a good idea for us to
realize the efficient synthesis of fullerooxazoles via a simple one-step reaction
promoted by Fe(ClO4)3. Although benzoyl isothiocyanate and benzamide 1a can be
employed to synthesize fullerooxazole 2a, benzoyl isothiocyanate as starting materials
is relatively expensive and more difficult to attain than the corresponding benzamide.
Therefore, amides were selected as the reaction substrates to extend the synthesis of
fullerooxazoles.
At the onset, the reaction of C60 with benzamide (1a) in the presence of Fe(ClO4)3
was chosen to screen the reaction conditions. In our previous study, we have found
that the reactions of C60 promoted by metal oxidants such as Mn(OAc)35d under air
conditions could result in the generation of C60O. To avoid the formation of C60O,
herein we have manipulated the Fe(ClO4)3-mediated reaction of C60 with amides
under nitrogen atmosphere. As can be seen from Table 1, the reaction of C60,
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Fe(ClO4)3, and 1a in a molar ratio of 1:1:5 gave fullerooxazole 2a in 29% DiOsoI: l1a0.t1e0d39/C5NJ02503F
o
yield at 150 C for 1 h (entry 1, Table 1). Increasing the reaction temperature to 170
oC did not improve the yield of product 2a (entry 2, Table 1). Decreasing the reaction
o
o
temperature to 130 C or 100 C obviously reduced the isolated yield of product 2a
(entries 3 and 4, Table 1). The variation of the amount of benzamide (from 3 to 8
equiv.) and Fe(ClO4)3 (from 1 to 2 equiv.) had also no benefit to the isolated yield of
product 2a (entries 5-8, Table 1). Thus, the reagent molar ratio of C60/Fe(ClO4)3/1a as
1:1:5, the reaction temperature as 150 oC together with the protection of nitrogen were
chosen as the optimized reaction conditions. In addition, other metal oxidants such as
FeCl3, FeCl3·6H2O, CuCl2, CuCl2·2H2O, Cu(OAc)2·H2O, Mn(OAc)3·2H2O, and
Mg(ClO4)2 were also examined under the optimized conditions (entries 9-15, Table 1).
Unfortunately, these metal oxidants instead of Fe(ClO4)3 only led to the formation of a
trace amount or no yield of product 2a, and thus Fe(ClO4)3 has been proved to be the
best oxidant.
Table 1 Optimization of reaction conditions for the Fe(ClO4)3-mediated reaction of
C60 with benzamide 1aa
O
additive
N
O
NH2
1a
,
ODCB, N2
2a
Entry
Additive
Molar ratiob Temp. (oC) Time (h) Yield of 2ac
1
2
3
4
5
Fe(ClO4)3·xH2O
Fe(ClO4)3·xH2O
Fe(ClO4)3·xH2O
Fe(ClO4)3·xH2O
Fe(ClO4)3·xH2O
1:1:5
1:1:5
1:1:5
1:1:5
1:1:8
150
170
130
100
150
1
0.5
3
29% (94%)
29% (58%)
22% (88%)
19% (86%)
29% (74%)
5
1.5
6

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DOI: 10.1039/C5NJ02503F
6
7
Fe(ClO4)3·xH2O
Fe(ClO4)3·xH2O
Fe(ClO4)3·xH2O
FeCl3
1:1:3
1:1:2
1:2:5
1:1:5
1:1:5
1:1:5
1:1:5
1:1:5
1:1:5
150
150
150
150
150
150
150
150
150
1
1
19% (86%)
14% (56%)
8
0.5
4
24% (41%)
9
trace
10
11
12
13
14
FeCl3·6H2O
CuCl2
4
0
0
0
0
0
3
CuCl2·2H2O
Cu(OAc)2·H2O
Mn(OAc)3·2H2O
4
3
3
15
Mg(ClO4)2
1:1:5
150
3
0
b
aAll reactions were performed under nitrogen conditions. Molar ratio refers to
C60/additive/1a. c Isolated yield; those in parentheses were based on consumed C60.
To expand the scope of the Fe(ClO4)3-mediated reaction of C60 with primary
amides, the substrates were extended from benzamide (1a) to other representative
amides.
4-methoxybenzamide
(1b),
3,4-dimethoxybenzamide
(1c), 4-methylbenzamide (1d), 2,4-dimethylbenzamide (1e), 4-chlorobenzamide (1f),
2-chlorobenzamide (1g), 2,6-dichlorobenzamide (1h), 4-nitrobenzamide (1i),
3-nitrobenzamide (1j), 1-naphthylamide (1k), 2-furamide (1l), 2-phenylacetamide
(1m), hexanamide (1n), and cinnamamide (1o), were chosen to react with C60 in the
presence of Fe(ClO4)3, and were found to afford the desired fullerooxazoles 2b-o. The
reaction times and yields for the Fe(ClO4)3-mediated reaction of C60 with primary
amides 1a-o under the optimized conditions are summarized in Table 2.
Table 2 Reaction times and yields for the reaction of C60 with primary amides 1a-o in
a
the presence of Fe(ClO4)3
O
Fe(ClO4)3
150 oC, N2
N
O
R
R
NH2
1
2
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DOI: 10.1039/C5NJ02503F
Amide 1
Time (h)
1
Yield of 2b
CONH2
1a
29% (94%)
CH3O
CH3O
CONH2
1b
2
2
23% (92%)
16% (84%)
27% (93%)
25% (89%)
23% (82%)
17% (85%)
CONH2
1c
CH3O
CH3
CH3
CONH2
1d
0.5
1
CONH2
1e
CH3
Cl
CONH2
1f
1
Cl
1
CONH2
1g
Cl
Cl
CONH2
1h
2
1.5
2
18% (82%)
20% (91%)
17% (89%)
NO2
CONH2
1i
NO2
CONH2
1j
CONH2
1.5
16% (84%)
1k
O
CONH2
1l
2
1.5
1
17% (89%)
21% (84%)
19% (76%)
CH2CONH2
1m
CONH2
1n
O
1.5
10% (83%)
NH2
1o
a
All reactions were performed at 150 oC under
nitrogen
atmosphere,
molar
ratio
of
C60/Fe(ClO4)3·xH2O/1 = 1:1:5. b Isolated yield; those
in parentheses were based on consumed C60.
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As can be seen from Table 2, aromatic amides bearing electron-withdrawing groups
or electron-donating groups (1a-l), aliphatic amides (1m and 1n), and cinnamamide
(1o) could be successfully employed to prepare fullerooxazoles. Aromatic amides
(1a-l) and aliphatic amides (1m and 1n) usually gave fullerooxazoles 2a-n in
moderate to good yields (16-29% isolated yields), comparable to the previously
reported data for most monoadducts. As for cinnamamide (1o), only 10% yield of
fullerooxazole 2o was produced probably due to the lower reactivity of 1o owing to
the existence of an additional conjugate double bond in its molecular structure.
Additionally, functional groups such as Cl and NO2 could be tolerated under our
reaction conditions and could be further transformed to other moieties.
Products 2a-f and 2i-n are known compounds, and their identities were confirmed
by comparison of their spectral data with those reported in the literature.6a,14c,15a-e
New compounds 2g, 2h, and 2o were unambiguously characterized by their HR MS,
1H NMR, 13C NMR, FT-IR, and UV-vis spectra. All of high-resolution mass spectra of
1
these fullerooxazole products gave the correct [M+H]+ peaks. Their H NMR spectra
displayed the expected chemical shifts as well as the splitting patterns for all protons.
In their 13C NMR spectra, the typical peak for the C=N carbon appeared at
163.60-164.57 ppm, and no more than 30 peaks in the range of 135-148 ppm for the
58 sp2-carbons of the C60 moiety together with two peaks at 96.17-96.42 ppm and
91.08-91.43 ppm for the two sp3-carbons of the C60 moiety were observed, consistent
with the Cs symmetry of their molecular structures. In their IR spectra, the absorption
at 1638-1672 cm-1 also demonstrated the presence of the C=N moiety. Their UV-vis
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spectra exhibited a diagnostic absorption at 415-416 nm for the 1,2-adduct of C60.
On the basis of the previously suggested mechanisms for the reactions of C60 with
nitriles,6a aldehydes/ketones,6b malonate esters,6c arylboronic acids,6d acid chlorides,6e
β-keto esters,6f isocyanates/isothiocyanates,6g and diols6h in the presence of Fe(ClO4)3.
We propose a possible formation mechanism for fullerooxazoles 2 from the reaction
of C60 with primary amides 1 promoted by Fe(ClO4)3 (Scheme 3). A chosen amide
reacts with Fe(ClO4)3 to generate Fe(III)-complex 3 accompanied with the elimination
of HClO4. Homolytical addition of 3 to C60 produces fullerenyl radical 4 with an
elimination of Fe(ClO4)2, followed by coordination with another molecule of
Fe(ClO4)3 to give Fe(III)-complex 5, in which the radical can either attack the oxygen
atom of the carbonyl group with the loss of a Fe(II) species to afford fullerooxazoles 2
(path a) or attack the nitrogen atom to form N-acyl aziridinofullerene 6 (path b),
followed by rearrangement to give fullerooxazoles 2. It should be noted that the
rearrangement of N-acyl aziridinofullerenes under high temperature conditions (about
o
150 C) to produce fullerooxazoles has been experimentally confirmed by different
groups in previous literature,14a-c and thus the reaction pathway (path b) for the
formation of fullerooxazoles is also reasonable although the crucial aziridinofullerene
intermediate 6 could not be isolated even by decreasing the reaction temperature and
shortening the reaction time.
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DOI: 10.1039/C5NJ02503F
H
O
O
N
R
Fe(ClO4)3
HClO4
C60
R
NHFe(III)
Fe(III)
R
NH2
Fe(ClO4)2
O
3
1
4
2
Fe(ClO4)3
HClO4
N
R
Fe(ClO4)2
N
O
R
path a
attack at "O"
O
5
rearrangement
Fe(III)
Fe(ClO4)3
HClO4
O
N
R
Fe(ClO4)2
N
path b
attack at "N"
O
R
6
5
Scheme 3 Proposed reaction mechanism for the formation of fullerooxazoles 2.
Conclusion
In summary, the simple one-step synthesis of fullerooxazoles has been readily
achieved via the reaction of C60 with primary amides promoted by Fe(ClO4)3. The
current approach to the preparation of fullerooxazoles from cheap and easily
accessible Fe(ClO4)3 and primary amides is obviously more straightforward and
practical than the previous protocols.6a,14,15 A plausible reaction mechanism for the
formation of fullerooxazoles is also suggested.
Experimental
Materials and instruments
All reagents and solvents were used directly as obtained commercially unless
otherwise noted. All of primary amides besides benzamide were synthesized by the
reaction of aldehydes with hydroxylamine hydrochloride in the presence of Na2CO3
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DOI: 10.1039/C5NJ02503F
and catalytic quantities of CuBr2. All of fullerene products were purified by flash
chromatography over silica gel (200–300 mesh). The UV-vis spectra were measured
in CHCl3 using a Shimadzu UV-2401 spectrometer. IR spectra were taken on a
SPECTRUM ONE NTS spectrometer with KBr pellets. 1H NMR (400 MHz) and 13C
NMR (100 MHz) spectra were recorded on a WIPM 400 spectrometer. Chemical
1
shifts in H NMR spectra were referenced to tetramethylsilane (TMS) at 0.00 ppm,
13
and chemical shifts in C NMR spectra were referenced to residual CHCl3 at 77.16
ppm or DMSO at 39.52 ppm. High-resolution mass spectrometry (HRMS) was
performed by MALDI-TOF in positive-ion mode with 4-hydroxy-α-cyanocinnamic
acid as the matrix.
General procedure for the Fe(ClO4)3-mediated reaction of C60 with primary
amides 1a–o
To a 50-mL three-neck flask equipped with a reflux condenser, nitrogen inlet and
outlet, and a magnetic stirrer was charged with C60 (36.0 mg, 0.05 mmol),
Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol), and primary amide 1a (1b-o, 0.25 mmol).
After they were completely dissolved in ODCB (6 mL) by sonication, the resulting
o
solution was heated with stirring in an oil bath preset at 150 C under nitrogen
atmosphere. The reaction was carefully monitored by thin-layer chromatography
(TLC) and stopped at the designated time. The reaction mixture was filtered through a
silica gel plug in order to remove any insoluble material. After the solvent was
evaporated in vacuo, the residue was separated on a silica gel column with carbon
disulfide/toluene as the eluent to afford first unreacted C60 and then fullerooxazole 2a
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(2b-o) as an amorphous black solid.
2-Phenyl-oxazolo[4,5:1,2][60]fullerene (2a). According to the general procedure,
the reaction of C60 (36.0 mg, 0.05 mmol) with 1a (30.0 mg, 0.25 mmol) and
Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1 h afforded first unreacted C60 (24.9 mg,
69%) and then 2a6a,14c,15a-e (12.2 mg, 29%) as an amorphous black solid. MP > 300 oC;
1H NMR (400 MHz, CS2/DMSO-d6) δ 8.39 (d, J = 7.0 Hz, 2H), 7.67 (t, J = 7.3 Hz,
13
1H), 7.61 (t, J = 7.3 Hz, 2H); C NMR (100 MHz, CS2/DMSO-d6 with Cr(acac)3 as
relaxation reagent) (all 2C unless indicated) δ 164.05 (1C, C=N), 147.12 (1C), 147.06,
146.71 (1C), 145.32 (4C), 145.18, 145.03, 144.97, 144.69, 144.55, 144.41, 144.16,
144.05, 143.79, 143.53, 143.22, 142.61, 141.75, 141.72, 141.64, 141.32 (4C), 141.23,
141.09, 140.95 (4C), 139.39, 138.58, 136.79, 135.10, 131.66 (1C, aryl C), 128.33
(aryl C), 127.98 (aryl C), 125.92 (1C, aryl C), 96.26 (1C, sp3-C of C60), 91.25 (1C,
sp3-C of C60); FT-IR ν/cm-1 (KBr) 1641, 1578, 1492, 1448, 1430, 1325, 1235, 1179,
1141, 1090, 1068, 983, 932, 841, 773, 690, 576, 562, 525.
2-(4-Methoxyphenyl)-oxazolo[4,5:1,2][60]fullerene (2b). According to the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1b (38.0 mg, 0.25
mmol) and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 2 h afforded first unreacted C60
(27.1 mg, 75%) and then 2b6a,14c,15b-d (9.9 mg, 23%) as an amorphous black solid.
MP > 300 oC; 1H NMR (400 MHz, CS2/CDCl3) δ 8.37 (d, J = 7.5 Hz, 2H), 7.10 (d, J
= 7.5 Hz, 2H), 3.96 (s, 3H).
2-(3,4-Dimethoxyphenyl)-oxazolo[4,5:1,2][60]fullerene (2c). According to the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1c (45.0 mg, 0.25
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mmol) and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 2 h afforded first unreaDcOteI:d10C.106309/C5NJ02503F
(29.1 mg, 81%) and then 2c6a (7.0 mg, 16%) as an amorphous black solid. MP > 300
oC; 1H NMR (400 MHz, CS2/CDCl3) δ 8.04 (d, J = 8.4 Hz, 1H), 7.95 (s, 1H), 7.06 (d,
J = 8.4 Hz, 1H), 4.06 (s, 3H), 4.02 (s, 3H).
2-(4-Methylphenyl)-oxazolo[4,5:1,2][60]fullerene (2d). According to the general
procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1d (34.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 0.5 h afforded first unreacted C60 (25.4
o
mg, 71%) and then 2d6a (11.4 mg, 27%) as an amorphous black solid: mp > 300 C;
1H NMR (400 MHz, CS2/CDCl3) δ 8.33 (d, J = 7.9 Hz, 2H), 7.42 (d, J = 7.9 Hz, 2H),
2.55 (s, 3H).
2-(2,4-Dimethylphenyl)-oxazolo[4,5:1,2][60]fullerene (2e). According to the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1e (37.0 mg, 0.25
mmol) and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1 h afforded first unreacted C60
(25.9 mg, 72%) and then 2e15c (10.9 mg, 25%) as an amorphous black solid. MP >
300 oC; 1H NMR (400 MHz, CS2/DMSO-d6) δ 8.21 (d, J = 7.4 Hz, 1H), 7.22 (s, 1H),
7.21 (d, J = 7.4 Hz, 1H), 2.94 (s, 3H), 2.47 (s, 3H).
2-(4-Chlorophenyl)-oxazolo[4,5:1,2][60]fullerene (2f). According to the general
procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1f (39.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1 h afforded first unreacted C60 (25.9
mg, 72%) and then 2f15b-d (10.1 mg, 23%) as an amorphous black solid. MP > 300 oC;
1H NMR (400 MHz, CS2/CDCl3) δ 8.39 (d, J = 8.4 Hz, 2H), 7.60 (d, J = 8.4 Hz, 2H).
2-(2-Chlorophenyl)-oxazolo[4,5:1,2][60]fullerene (2g). According to the general
14

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procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1g (39.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1 h afforded first unreacted C60 (28.7
o
mg, 80%) and then 2g (7.3 mg, 17%) as an amorphous black solid. MP > 300 C; 1H
NMR (400 MHz, CS2/CDCl3) δ 8.36 (d, J = 7.6 Hz, 1H), 7.66 (d, J = 7.4 Hz, 1H),
7.51-7.61 (m, 2H); 13C NMR (100 MHz, CS2/CDCl3 with Cr(acac)3 as relaxation
reagent) (all 2C unless indicated) δ 163.60 (1C, C=N ), 147.39 (1C), 146.98 (1C),
146.76, 145.60 (4C), 145.46, 145.29, 145.24, 145.02, 144.84, 144.66, 144.42, 144.32,
144.04, 143.75, 143.45, 142.45, 141.99, 141.95, 141.88, 141.57, 141.47 (4C), 141.32,
141.20, 141.17, 139.63, 138.86, 137.01, 135.49, 133.99 (1C, aryl C), 132.04 (1C, aryl
C), 131.56 (1C, aryl C), 130.68 (1C, aryl C), 126.23 (1C, aryl C), 125.52 (1C, aryl C),
96.42 (1C, sp3-C of C60), 91.43 (1C, sp3-C of C60); FT-IR ν/cm-1 (KBr) 1638, 1591,
1473, 1432, 1326, 1259, 1179, 1141, 1103, 1061, 1041, 981, 951, 931, 776, 763, 728,
562, 526; UV-vis (CHCl3) λmax/nm 257, 317, 415, 686; MALDI-TOF MS m/z calcd
for C67H5ClNO [M+H]+ 874.0060, found 874.0059.
2-(2,6-Dichlorophenyl)-oxazolo[4,5:1,2][60]fullerene (2h). According to the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1h (48.0 mg, 0.25
mmol) and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 2 h afforded first unreacted C60
(27.9 mg, 78%) and then 2h (8.1 mg, 18%) as an amorphous black solid. MP > 300
oC; 1H NMR (400 MHz, CS2/CDCl3) δ 7.58 (d, J = 8.0 Hz, 2H), 7.52 (t, J = 7.9 Hz,
1H); 13C NMR (100 MHz, CS2/DMSO-d6 with Cr(acac)3 as relaxation reagent) (all 2C
unless indicated) δ 160.64 (1C, C=N ), 147.05 (1C), 146.65 (1C), 146.14, 145.30,
145.26, 145.15, 144.97, 144.91, 144.71, 144.48, 144.37, 144.09, 143.99, 143.69,
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143.41, 143.13, 141.89, 141.67, 141.62, 141.56, 141.24, 141.17, 141.14, D1O4I:110..01003,9/C5NJ02503F
140.87 (4C), 139.35, 138.60, 136.63, 135.15, 134.18 (aryl C), 132.14 (1C, aryl C),
127.61 (aryl C), 126.37 (1C, aryl C), 96.17 (1C, sp3-C of C60), 91.08 (1C, sp3-C of
C60); FT-IR ν/cm-1 (KBr) 1672, 1561, 1431, 1384, 1295, 1275, 1236, 1194, 1128,
1084, 1042, 977, 957, 927, 841, 794, 771, 562, 526; UV-vis (CHCl3) λmax/nm 256,
317, 416, 688; MALDI-TOF MS m/z calcd for C67H4Cl2NO [M+H]+ 907.9670, found
907.9671.
2-(4-Nitrophenyl)-oxazolo[4,5:1,2][60]fullerene (2i). According to the general
procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1i (42.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1.5 h afforded first unreacted C60 (28.1
mg, 78%) and then 2i6a,15b-d (8.9 mg, 20%) as an amorphous black solid. MP > 300 oC;
1H NMR (400 MHz, CS2/CDCl3) δ 8.67 (d, J = 8.8 Hz, 2H), 8.49 (d, J = 8.8 Hz, 2H).
2-(3-Nitrophenyl)-oxazolo[4,5:1,2][60]fullerene (2j). According to the general
procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1j (42.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 2 h afforded first unreacted C60 (29.2
mg, 81%) and then 2j15c (7.4 mg, 17%) as an amorphous black solid. MP > 300 oC; 1H
NMR (400 MHz, CS2/CDCl3) δ 9.28 (s, 1H), 8.81 (d, J = 7.6 Hz, 1H), 8.54 (d, J = 8.2
Hz, 1H), 7.86 (t, J = 7.9 Hz, 1H).
2-(1-Naphthylphenyl)-oxazolo[4,5:1,2][60]fullerene (2k). According to the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1k (43.0 mg, 0.25
mmol) and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1.5 h afforded first unreacted
C60 (29.1 mg, 81%) and then 2k15c (7.1 mg, 16%) as an amorphous black solid. MP >
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o
DOI: 10.1039/C5NJ02503F
300 C; 1H NMR (400 MHz, CS2/CDCl3) δ 9.78 (d, J = 8.6 Hz, 1H), 8.70 (d, J = 7.3
Hz, 1H), 8.14 (d, J = 8.2 Hz, 1H), 7.97 (d, J = 8.4 Hz, 1H), 7.68-7.75 (m, 2H),
7.60-7.64 (m, 1H).
2-(2-Furylphenyl)-oxazolo[4,5:1,2][60]fullerene (2l). According to the general
procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1l (28.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 2 h afforded first unreacted C60 (29.1
mg, 81%) and then 2l15d (7.1 mg, 17%) as an amorphous black solid. MP > 300 oC; 1H
NMR (400 MHz, CS2/CDCl3) δ 7.81 (d, J = 1.8 Hz, 1H), 7.50 (d, J = 3.4 Hz, 1H),
6.75 (dd, J = 3.4, 1.8 Hz, 1H).
2-Benzyl-oxazolo[4,5:1,2][60]fullerene (2m). According to the general procedure,
the reaction of C60 (36.0 mg, 0.05 mmol) with 1m (34.0 mg, 0.25 mmol) and
Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1.5 h afforded first unreacted C60 (27.1 mg,
75%) and then 2m6a,15c,d (8.9 mg, 21%) as an amorphous black solid. MP > 300 oC; 1H
NMR (400 MHz, CS2/CDCl3) δ 7.67 (d, J = 7.8 Hz, 2H), 7.47 (t, J = 7.5 Hz, 2H),
7.38 (t, J = 7.4 Hz, 1H), 5.87 (s, 2H).
2-(n-Pentyl)-oxazolo[4,5:1,2][60]fullerene (2n). According to the general
procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1n (29.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1 h afforded first unreacted C60 (26.9
mg, 75%) and then 2n15c,d (7.8 mg, 19%) as an amorphous black solid. MP > 300 oC;
1H NMR (400 MHz, CS2/CDCl3) δ 2.93 (t, J = 7.6 Hz, 2H), 2.06-2.17 (m, 2H),
1.64-1.72 (m, 2H), 1.51-1.60 (m, 2H), 1.05 (t, J = 7.3 Hz, 3H).
2-(1-Styryl)-oxazolo[4,5:1,2][60]fullerene (2o). According to the general
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procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1o (37.0 mg, 0.25 mmol)
and Fe(ClO4)3·xH2O (23.0 mg, 0.05 mmol) for 1.5 h afforded first unreacted C60 (31.6
o
mg, 88%) and then 2o (4.2 mg, 10%) as an amorphous black solid. MP > 300 C; 1H
NMR (400 MHz, CS2/CDCl3) δ 7.98 (d, J = 16.3 Hz, 1H), 7.68 (d, J = 7.1 Hz, 2H),
7.40-7.48 (m, 3H), 7.13 (d, J = 16.3 Hz, 1H); 13C NMR (100 MHz, CS2/CDCl3 with
Cr(acac)3 as relaxation reagent) (all 2C unless indicated) δ 164.57 (1C, C=N ), 147.50
(1C), 147.26, 147.08 (1C), 145.68, 145.65, 145.54, 145.38, 145.33, 145.06, 144.81,
144.74, 144.51, 144.41, 144.07, 143.86, 143.56, 142.89, 142.34 (1C), 142.08, 142.04,
141.98, 141.64, 141.61, 141.55, 141.40, 141.29, 141.26, 139.73, 138.92, 137.12,
135.52, 134.23 (1C, aryl C), 129.70 (1C, aryl C), 128.53 (aryl C), 127.44 (aryl C),
113.39 (1C), 96.35 (1C, sp3-C of C60), 91.29 (1C, sp3-C of C60); FT-IR ν/cm-1 (KBr)
1648, 1626, 1604, 1495, 1447, 1423, 1313, 1276, 1178, 1137, 1062, 1024, 982, 970,
941, 852, 769, 752, 691, 575, 562, 525; UV-vis (CHCl3) λmax/nm 257, 316, 415, 686;
MALDI-TOF MS m/z calcd for C69H8NO [M+H]+ 866.0606, found 866.0607.
Fe(ClO4)3-mediated reaction of C60 with benzoyl isothiocyanate in scheme 2.
A mixture of benzoyl isothiocyanate (336 uL, 2.5 mmol) and Fe(ClO4)3·xH2O (115.0
mg, 0.25 mmol) was added to a 50-mL three-neck flask equipped with a reflux
condenser, nitrogen inlet and outlet, and a magnetic stirrer. The mixture was heated in
o
an oil bath preset at 100 C for 10 min to allow ferric perchlorate to dissolve in the
liquid isothiocyanate. Then to the flask was added the o-dichlorobenzene (6 mL)
solution of C60 (36.0 mg, 0.05 mmol). The resulting solution was heated with
vigorous stirring in the oil bath at the same temperature for 14 h under nitrogen
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atmosphere. The reaction mixture was passed through a silica gel plug to remove any
insoluble material. After the solvent was evaporated in vacuo, the residue was
separated on a silica gel column with carbon disulfide/toluene as the eluent to afford
unreacted C60 (21.0 mg, 58%) and fullerooxazole 2a6a,14c,15a-e (7.1 mg, 17%) as an
amorphous black solid.
Fe(ClO4)3-mediated reaction of C60 with benzamide 1a in scheme 2.
According to the general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1a
o
(303 mg, 2.5 mmol) and Fe(ClO4)3·xH2O (115.0 mg, 0.25 mmol) at 100 C for 13 h
afforded first unreacted C60 (25.1 mg, 70%) and then fullerooxazole 2a6a,14c,15a-e (7.9
mg, 19%) as an amorphous black solid.
Acknowledgements
The authors are grateful for the financial support from National Natural Science
Foundation of China (Nos. 21102041 and 21071049), Natural Science Foundation of
Hubei Province (Nos. 2014CFB550 and 2013CFA087), Natural Science Fund for
Creative Research Groups of Hubei Province of China (No. 2014CFA015), and
Innovation and Entrepreneurship Training Program for Undergraduates of Hubei
Province (No. 201310512011).
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Graphical content:
Ferric perchlorate-mediated one-step reaction of [60]fullerene with
primary amides for the synthesis of fullerooxazoles
Xiao-Feng Zhang, Fa-Bao Li, Ji-Long Shi, Jun Wu and Li Liu
Reaction of [60]fullerene with amides promoted by cheap and easily available ferric
perchlorate affords a series of interesting fullerooxazole derivatives.
Fe(ClO4)3
O
N
O
R
R
NH2
cheap and easily available reagents
15 examples
R = aryl, alkyl, and cinnamyl