Ferric chloride-catalyzed reaction of [60]fullerene with tert -butyl N -substituted carbamates: Synthesis of oxazolidino[4,5:1,2][60]fullerenes

Article abstract of DOI:10.1021/jo402354w

The rare oxazolidinofullerenes have been prepared by the ferric chloride-catalyzed reaction of [60]fullerene with various tert-butyl N-substituted carbamates via t-Bu-O bond cleavage and heteroannulation under mild conditions. A possible mechanism for the formation of oxazolidinofullerenes is proposed.

Full text of DOI:10.1021/jo402354w

Article
pubs.acs.org/joc
Ferric Chloride-Catalyzed Reaction of [60]Fullerene with tert-Butyl
N‑Substituted Carbamates: Synthesis of
Oxazolidino[4,5:1,2][60]fullerenes
Xun You† and Guan-Wu Wang*,†,‡
†CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, and Department of
Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
‡State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, People’s Republic of China
S
* Supporting Information
ABSTRACT: The rare oxazolidinofullerenes have been
prepared by the ferric chloride-catalyzed reaction of [60]-
fullerene with various tert-butyl N-substituted carbamates via t-
Bu−O bond cleavage and heteroannulation under mild
conditions. A possible mechanism for the formation of
oxazolidinofullerenes is proposed.
and co-workers described the PCy3-catalyzed ring-expansion
reaction of N-sulfonyl aziridinofullerenes with CO2 affording N-
sulfonyl oxazolidinofullerenes.7c Up to now, the reported
oxazolidinofullerenes all have been generated from the ring-
opening reactions of the preformed aziridinofullerenes. There-
fore, it is still challenging to obtain oxazolidinofullerene
derivatives directly from C60 in a straightforward and efficient
way. Herein, we report an FeCl3-catalyzed reaction of C60 with
tert-butyl N-substituted carbamates to generate oxazolidino-
[4,5:1,2][60]fullerenes with a broad substrate scope.
INTRODUCTION
■
Owing to the potential applications of fullerene derivatives in
materials science, medical chemistry, and nanotechnology,1
considerable effort has been made toward the efficient methods
for their synthesis,2−7 and metal-mediated radical approaches
become increasingly popular.2−6 In addition, iron, as one of the
most important metals in nature, is a cheap, nontoxic, and
effective catalyst for various organic transformations.8 As a
result, a great deal of effort has been put into the iron-mediated
radical reactions of fullerenes.3−6 In 2002, Gan et al. reported
the FeCl3/Fe(NO3)3-catalyzed peroxy radical addition to
fullerenes.4 Later on, Hashiguchi et al. described the
preparation of pentaaryl(chloro)[60]fullerenes by FeCl3-
mediated polyarylation of [60]fullerene (C60).5 Recently, we
have systematically studied the Fe(ClO4)3-promoted reactions
of C60 and realized the synthesis of C60-fused oxazolines,6a
dioxolanes,6b lactones,6c dioxaborolanes,6d and tetrahydrofur-
ans6e from nitriles, aldehydes/ketones, malonate esters,
arylboronic acids, and β-keto esters, respectively. Our group6f
and Hashiguchi et al.6g described the preparation of 1,2-
fullerenols by the reaction of C60 with acyl chlorides or
carboxylic acids in the presence of Fe(ClO4)3 or FeCl3,
respectively. However, most of the reported iron-mediated
reactions required a high temperature or a large amount of iron
reagents.
On the other hand, oxazolidino[4,5:1,2][60]fullerenes, as
one of the rare five-membered heterocycle-fused fullerene
derivatives, are difficult to access efficiently by conventional
methods. In 1994, the first synthesis of the nonfunctionalized
and simplest oxazolidinofullerene was achieved by Luh’s group
via the cycloaddition of C60 with N3CO2Et, followed by the
treatment of the obtained N-ethyloxycarbonylaziridinofullerene
with BBr3 at room temperature.7a Coincidently, Taylor’s group
reported the same rearrangement reaction using phenol/
chlorotrimethylsilane instead of BBr3.7b Recently, Minakata
RESULTS AND DISCUSSION
■
A suitable alkyl group is demanded for the alkyl−oxygen bond
cleavage of carbamates, and the tert-butyl group was found to
be superior to the methyl, isopropyl, and benzyl groups.9 Thus,
the reaction of tert-butyl carbamate 1a with C60 was chosen as
the model reaction to optimize conditions (Table 1). When
Fe(ClO4)3 (20 mol %) was chosen as the catalyst and
bis(trifluoroacetoxy)iodobenzene [PhI(O2CCF3)2] as the
oxidant, we could obtain the desired product 2a in 7% yield
at ambient temperature (Table 1, entry 1). Unfortunately,
Fe2(SO4)3 could not promote the reaction with complete
recovery of C60 (Table 1, entry 2). To our satisfaction, the yield
of 2a was sharply improved to 37% when FeCl3 was used as the
catalyst (Table 1, entry 3). However, the usage of FeCl2 led to
only 7% yield of 2a (Table1, entry 4). Surprisingly, only a trace
amount of 2a was generated under the same conditions when
(diacetoxyiodo)benzene [PhI(OAc)2] was used (Table 1, entry
5), indicating that PhI(OAc)2 was much less effective compared
with PhI(O2CCF3)2. Other examined oxidants including
K2S2O8 and p-benzoquinone (BQ) were ineffective for the
formation of 2a (Table 1, entries 6 and 7). It should be noted
Received: October 23, 2013
© XXXX American Chemical Society
A
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Table 1. Optimization of Reaction Conditions for the
Table 2. Results for the Reaction of C60 with tert-Butyl N-
Substituted Carbamates 1a−g Catalyzed by FeCl3
a
Reaction of C60 with tert-Butyl N-Benzylcarbamate 1a
a
Catalyzed by Iron Salt
b
c
entry
catalyst
oxidant
molar ratio
yield of 2a (%)
1
Fe(ClO4)3
Fe2(SO4)3
FeCl3
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(OAc)2
K2S2O8
1:2:0.2:1
1:2:0.2:1
1:2:0.2:1
1:2:0.2:1
1:2:0.2:1
1:2:0.2:1
1:2:0.2:1
1:2:0:1
7 (25)
0
2
3
37 (79)
7 (39)
trace
4
FeCl2
5
FeCl3
6
FeCl3
0
7
FeCl3
BQ
0
8
PhI(O2CCF3)2
4 (33)
trace
9
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
1:2:0.2:0
1:2:0.2:1.5
1:2:0.1:1
1:1:0.2:1
1:1:0.2:1
1:1:0.2:1
1:1:0.2:1
1:1:0.2:1
10
11
12
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
PhI(O2CCF3)2
36 (53)
23 (59)
32 (68)
36 (67)
29 (63)
32 (60)
14 (82)
d
13
d
d
g
,
,
e
f
14
15
16
a
Unless otherwise noted, all reactions were performed in o-
b
dichlorobenzene (ODCB) at 25 °C for 48 h in an open air. Molar
ratio refers to C60/1a/catalyst/oxidant. Yields in parentheses were
based on consumed C60. The reaction was performed at 60 °C. The
reaction time was 36 h. The reaction time was 60 h. The reaction was
carried out under a nitrogen atmosphere.
c
d
e
f
g
that both FeCl3 and PhI(O2CCF3)2 were indispensible for the
present reaction, because a very small amount of the desired
product was obtained in the absence of either FeCl3 or
PhI(O2CCF3)2 (Table 1, entries 8 and 9). Increasing the
amount of PhI(O2CCF3)2 to 1.5 equiv was not beneficial for
the reaction (Table 1, entry 10). A lower yield of 2a was
obtained when the amount of FeCl3 or 1a was reduced (Table
1, entries 11 and 12). Fortunately, a higher temperature (60
°C) further increased the yield from 32% to 36% (Table 1,
entry 3 vs entry 13). Shortening or prolonging the reaction
time led to a lower yield (Table 1, entries 14 and 15).
Moreover, an inert atmosphere was unfavorable to achieve a
higher yield (Table 1, entry 16). Thus, a molar ratio of 1:1:0.2:1
for the reagents of C60, 1a, FeCl3, and PhI(O2CCF3)2 and
reaction temperature at 60 °C were chosen as the optimized
reaction conditions (Table 1, entry 13).
a
With the optimized conditions in hand, we started to
investigate the scope of the reaction (Table 2). Both tert-butyl
N-alkylcarbamates and tert-butyl N-arylcarbamates were well
compatible with this reaction (Table 2, entries 1−7). The
treatment of N-alkylcarbamates 1b and 1c under our optimized
reaction conditions afforded the corresponding products 2b
and 2c in 37% and 35% yields, respectively (Table 2, entries 2
and 3). Next, tert-butyl N-branched alkylcarbamate 1d also
produced 2d under the standard conditions successfully.
Nevertheless, a lower temperature (40 °C) and an increased
amount of the substrate were beneficial in avoiding the
formation of byproducts and affording 2d in a higher yield
(Table 2, entry 4). Meanwhile, substrate 1e with an OCH3
group connected directly to the nitrogen atom also led to the
Unless otherwise noted, all reactions were performed with C60 (0.05
mmol), 1 (0.05 mmol), FeCl3 (20 mol %), and PhI(O2CCF3)2 (0.05
b
mmol) in ODCB at 60 °C for 48 h in an open air. Yields in
c
parentheses were based on consumed C60. Two equivalents of the
d
e
substrate were used. The reaction was performed at 40 °C. The
f
reaction was performed at 25 °C. One equivalent of FeCl3 was used.
desired product 2e in 26% yield at room temperature (Table 2,
entry 5). It was found that raising the temperature from 25 to
60 °C was fruitless to get a higher yield. The substrate
possessing an active functional group such as carboxylic ester
(1f) successfully furnished the desired oxazolidinofullerene 2f
in 27% yield (Table 2, entry 6). In addition, an increasing
amount of both FeCl3 and the substrate was beneficial for tert-
B
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Article
butyl N-arylcarbamate 1g to participate in this reaction (Table
2, entry 7). Performing the reaction at a higher temperature (60
°C) or a longer reaction time could not further improve the
yield of 2g. Compared with 1a−f, 1g displayed an obvious
lower reactivity, probably due to the delocalization of the in situ
formed radical to the phenyl group, thus retarding the
subsequent radical addition to C60 (vide infra).
to provide oxazolidinofullerene 2 with the loss of an Fe(II)
species.3,6a,b,d The FeCl3 can be regenerated by the oxidation of
the Fe(II) species with PhI(O2CCF3)2. Alternatively, the
fullerenyl radical 4 may give 2 directly with the elimination
of tert-butyl radical (path B). This process can be corroborated
by the formation of 2a in the absence of FeCl3, albeit in only
4% yield (Table 1, entry 8). However, when a catalytic amount
of FeCl3 was added, the yield of 2a was dramatically increased
to 37% (Table 1, entry 3 vs 8), indicating that FeCl3 plays a
crucial role in this transformation. We suspect that the
coordination of FeCl3 with the carbonyl group in the
intermediate 5 may facilitate the O−tBu bond cleavage. Thus,
in the combination system of FeCl3 and PhI(O2CCF3)2,
oxazolidinofullerene 2 should be formed predominantly via
path A, while path B contributes much less for the product
formation. It should be noted that the pathway via the
oxidation of the fullerenyl radical 4 to the corresponding
fullerenyl cation5 followed by cyclization to afford product 2
cannot be excluded.
The stability and further functionalization of the obtained
oxazolinofullerenes were also examined using 2a as a
representative compound. Preliminary results showed that 2a
was very stable under strong acidic and high temperature
conditions such as TsOH, TfOH, MeSO3H, or BF3·Et2O at up
to 150 °C. It seems that 2a was relatively unstable under strong
alkaline conditions. When treated with EtONa/EtOH (20
equiv) in chlorobenzene at 120 °C for 12 h, 2a was converted
mostly to C60. Interestingly, we found that the electrochemi-
cally generated dianionic 2a could subsequently undergo the
cleavage of both the C60−O and C60−N bonds to produce C60
in the presence of TFA. Therefore, the oxazoline heterocycle
might be used as a removable template for fullerene
functionalization.14
Products 2a−g were fully characterized by HRMS, 1H NMR,
1
13C NMR, IR, and UV−vis spectra. Their H NMR spectra
displayed the expected chemical shifts as well as the splitting
patterns for all protons. The 13C NMR spectra of 2a−g
exhibited no more than 30 peaks in the range of 135−148 ppm
for the sp2-carbons of the fullerene cage and two peaks at 75−
79 ppm and 90−93 ppm for the two sp3-carbons of the
fullerene skeleton, consistent with the Cs symmetry of their
molecular structures. The chemical shifts at 75−79 ppm and
90−93 ppm for the two sp3-carbons of the fullerene skeleton
are close to the reported data of other fullerene derivatives with
a nitrogen atom and an oxygen atom attached to the fullerene
skeleton.6,7b,c The chemical shifts for the carbonyl group of the
oxazolidone moiety appeared at 150−155 ppm. In their IR
spectra, the strong absorption at 1762−1790 cm−1 also
demonstrated the presence of the carbonyl moiety. Their
UV−vis spectra exhibited an absorption at 416−418 nm, which
is the characteristic absorption for 1,2-adducts of C60, in which
a heteroatom is directly attached to the fullerene cage.6
In order to shed more light on the reaction mechanism, a
free radical scavenger, that is, 2,2,6,6-tetramethylpiperidinooxyl
(TEMPO), was added to the reaction mixture, and no desired
2a for the reaction of 1a with C60 could be obtained. This result
indicates that the reaction likely proceeds through a radical
process.
Based on the above results and previous literature on iron-
mediated radical reactions, a plausible mechanism for the
formation of oxazolidinofullerenes 2a−g is proposed and
depicted in Scheme 1. First, the oxidation of substrate 1 by
CONCLUSION
■
We have successfully developed a unique and efficient FeCl3-
catalyzed reaction of C60 with tert-butyl N-substituted
carbamates, affording the rare oxazolidinofullerenes directly.
This transformation proceeds smoothly under mild conditions
and exhibits good tolerance to various aliphatic and aromatic
carbamates.
Scheme 1. Possible Mechanism for the Formation of 2
EXPERIMENTAL SECTION
■
1
General Methods. H NMR spectra were referenced to TMS at
0.00 ppm, while 13C NMR spectra were referenced to residual CHCl3
at 77.16 ppm or DMSO at 39.52 ppm. High-resolution mass spectra
(HRMS) were obtained by MALDI-TOF in positive mode using sulfur
as the matrix.
General Procedure for the Synthesis of 2a−g from the
FeCl3-Catalyzed Reaction of C60 with 1a−g. A mixture of C60
(36.0 mg, 0.05 mmol), tert-butyl N-benzylcarbamate 1 (0.05 mmol, 1
equiv (0.10 mmol, 2 equiv for 1d and 1g)), FeCl3 (1.6 mg, 0.01 mmol,
0.2 equiv (8.1 mg, 0.05 mmol, 1 equiv for 1g)), and PhI(O2CCF3)2
(21.5 mg, 0.05 mmol, 1 equiv) was dissolved in ODCB (6 mL). Then
the solution was vigorously stirred at the preset temperature (25−60
°C) for 48 h. The resulting solution was directly separated on a silica
gel column with CS2/CH2Cl2 as the eluent; the desired product 2 was
obtained along with recovered C60.
3-Benzyloxazolidino[4,5:1,2][60]fullerene, 2a. By following the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1a
(10.6 mg, 0.05 mmol), FeCl3 (1.7 mg, 0.01 mmol), and PhI-
(O2CCF3)2 (21.5 mg, 0.05 mmol) at 60 °C afforded 2a (15.6 mg,
36%) and recovered C60 (16.5 mg, 46%): amorphous brown solid; 1H
NMR (400 MHz, CS2/CDCl3) δ 7.58−7.52 (m, 2H), 7.29 (tt, J = 7.2,
1.6 Hz, 2H), 7.23 (tt, J = 7.4, 1.4 Hz, 1H), 5.33 (s, 2H); 13C NMR
FeCl3 or PhI(O2CCF3)2 generates the amidyl radical 3,10 which
attacks C60 to afford the fullerenyl radical 4.11 Coordination of
4 with another FeCl3 furnishes the complex 5, which
6b
undergoes an O−tBu bond cleavage to give the Fe(III)
complex 6 (path A). A similar copper-promoted scissure of
the O−tBu bond has been reported.12 It seems that the electro-
deficient nature of the neighboring moiety is important for the
success of the O−tBu bond cleavage.12,13 The attachment of the
electron-deficient fullerene skeleton to the nitrogen atom may
also help the O−tBu bond cleavage in the intermediate 5.
Finally, the complex 6 undergoes an intramolecular cyclization
C
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The Journal of Organic Chemistry
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(100 MHz, CS2/CDCl3 with Cr(acac)3 as relaxation reagent, all 2C
unless indicated) δ 154.88 (1C), 147.95 (1C), 147.75 (1C), 146.12,
146.11, 146.06, 145.89, 145.86, 145.81, 144.84, 144.82, 144.79, 144.56,
144.24, 144.20, 144.15, 144.01, 143.72, 142.46, 142.41, 142.39, 141.98,
141.94, 141.73, 141.55, 141.45, 141.03, 139.62, 139.06, 137.00, 136.61,
135.84 (1C), 128.50, 128.40, 127.97 (1C), 92.39 (1C), 77.77 (1C),
47.86 (1C); FT-IR ν/cm−1 (KBr) 2920, 2848, 1767, 1429, 1385, 1182,
1152, 1084, 1012, 978, 741, 702, 526; UV−vis (CHCl3) λmax/nm (log
ε) 256 (5.09), 319 (4.82), 416 (3.68); MALDI-TOF m/z calcd for
C68H7NO2 [M+] 869.0471, found 869.0443.
90.90 (1C), 75.34 (1C), 64.66 (1C); FT-IR ν/cm−1 (KBr) 2923, 2849,
1790, 1505, 1431, 1263, 1143, 1110, 999, 947, 866, 797, 730, 526;
UV−vis (CHCl3) λmax/nm (log ε) 258 (5.13), 317 (4.82), 418 (3.66);
MALDI-TOF m/z calcd for C62H3NO3 [M+] 809.0107, found
809.0110.
3-(Ethoxylcarbonylmethyl)oxazolidino[4,5:1,2][60]fullerene, 2f.
By following the general procedure, the reaction of C60 (35.9 mg,
0.05 mmol) with 1f (10.4 mg, 0.05 mmol), FeCl3 (1.6 mg, 0.01
mmol), and PhI(O2CCF3)2 (21.7 mg, 0.05 mmol) at 60 °C afforded 2f
(11.9 mg, 27%) and recovered C60 (17.7 mg, 49%): amorphous brown
1
3-Methyloxazolidino[4,5:1,2][60]fullerene, 2b. By following the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1b
(6.8 mg, 0.05 mmol), FeCl3 (1.6 mg, 0.01 mmol), and PhI(O2CCF3)2
(21.3 mg, 0.05 mmol) at 60 °C afforded 2b (14.7 mg, 37%) and
solid; H NMR (400 MHz, CS2/CDCl3) δ 4.78 (s, 2H), 4.27 (q, J =
7.0 Hz, 2H), 1.31 (t, J = 7.0 Hz, 3H); 13C NMR (100 MHz, CS2/
DMSO-d6 with Cr(acac)3 as relaxation reagent, all 2C unless
indicated) δ 166.00 (1C), 152.95 (1C), 147.18 (1C), 146.95 (1C),
145.31 (4C), 145.24, 145.09, 145.05, 145.01, 144.10, 143.99, 143.93,
143.66, 143.48, 143.31, 143.25, 143.07, 142.77, 141.61 (4C), 141.53,
141.18, 141.02, 140.86, 140.83, 140.68, 140.30, 138.68, 138.57, 136.43,
136.38, 91.61 (1C), 76.55 (1C), 60.66 (1C), 43.53 (1C), 13.43 (1C);
FT-IR ν/cm−1 (KBr) 2961, 2921, 2852, 1773, 1747, 1414, 1378, 1303,
1
recovered C60 (17.3 mg, 48%): amorphous brown solid; H NMR
(400 MHz, CS2/CDCl3) δ 3.74 (s, 3H); 13C NMR (100 MHz, CS2/
DMSO-d6 with Cr(acac)3 as relaxation reagent, all 2C unless
indicated) δ 152.22 (1C), 147.07 (1C), 146.85 (1C), 145.20 (6C),
145.11, 144.98, 144.96, 143.96, 143.93, 143.90 (4C), 143.41, 143.33,
143.14 (4C), 143.03, 141.55, 141.52, 141.48, 141.09, 140.97, 140.79,
140.76, 140.62, 140.27, 138.67, 138.56, 136.48, 136.11, 90.69 (1C),
77.18 (1C), 28.82 (1C); FT-IR ν/cm−1 (KBr) 2918, 2850, 1767, 1421,
1372, 1266, 1180, 1146, 1033, 1010, 949, 872, 745, 526; UV−vis
(CHCl3) λmax/nm (log ε) 254 (5.01), 317 (4.70), 417 (3.55); MALDI-
TOF m/z calcd for C62H3NO2 [M+] 793.0158, found 793.0160.
3-Butyloxazolidino[4,5:1,2][60]fullerene, 2c. By following the
general procedure, the reaction of C60 (35.9 mg, 0.05 mmol) with
1c (8.7 mg, 0.05 mmol), FeCl3 (1.7 mg, 0.01 mmol), and
PhI(O2CCF3)2 (21.7 mg, 0.05 mmol) at 60 °C afforded 2c (14.8
mg, 35%) and recovered C60 (18.8 mg, 52%): amorphous brown solid;
1H NMR (400 MHz, CS2/CDCl3) δ 4.13 (t, J = 7.6 Hz, 2H), 2.11−
2.03 (m, 2H), 1.59 (sextet, J = 7.4 Hz, 2H), 1.04 (t, J = 7.2 Hz, 3H);
13C NMR (100 MHz, CS2/DMSO-d6 with Cr(acac)3 as relaxation
reagent, all 2C unless indicated) δ 152.85 (1C), 147.24 (1C), 147.05
(1C), 145.37 (6C), 145.17, 145.16 (4C), 144.21, 144.20, 144.10,
144.06, 144.01, 143.60, 143.47, 143.34, 143.06, 141.74, 141.73, 141.70,
144.29, 141.19, 141.02, 140.99, 140.82, 140.43, 138.88, 138.70, 136.27,
136.22, 91.21 (1C), 77.09 (1C), 43.11 (1C), 30.77 (1C), 19.76 (1C),
13.28 (1C); FT-IR ν/cm−1 (KBr) 2952, 2923, 2861, 1767, 1435, 1386,
1259, 1189, 1088, 1058, 1015, 801, 742, 526; UV−vis (CHCl3) λmax
/
nm (log ε) 254 (5.08), 317 (4.79), 416 (3.62); MALDI-TOF m/z
calcd for C65H7NO4 [M+] 865.0370, found 865.0379.
3-(p-Tolyl)oxazolidino[4,5:1,2][60]fullerene, 2g. By following the
general procedure, the reaction of C60 (36.3 mg, 0.05 mmol) with 1g
(20.6 mg, 0.10 mmol), FeCl3 (8.3 mg, 0.05 mmol), and PhI-
(O2CCF3)2 (21.8 mg, 0.05 mmol) at 25 °C afforded 2g (7.0 mg, 16%)
and recovered C60 (29.0 mg, 80%): amorphous brown solid; 1H NMR
(400 MHz, CS2/CDCl3) δ 7.70 (d, J = 8.2 Hz, 2H), 7.37 (d, J = 8.2
Hz, 2H), 2.42 (s, 3H); 13C NMR (100 MHz, CS2/DMSO-d6 with
Cr(acac)3 as relaxation reagent, all 2C unless indicated) δ 152.25 (1C),
147.32 (1C), 147.10 (1C), 145.47 (4C), 145.42, 145.21 (4C), 145.18,
144.30, 144.18, 144.14, 144.10, 143.99, 143.62 (4C), 143.49, 143.42,
141.79, 141.72 (4C), 141.36, 141.26, 141.02, 141.00, 140.79, 140.52,
138.90, 138.58, 138.13 (1C), 136.59, 136.20, 131.94 (1C), 129.37,
128.83, 91.38 (1C), 78.81 (1C), 20.63 (1C); FT-IR ν/cm−1 (KBr)
2946, 2857, 1772, 1510, 1431, 1363, 1232, 1179, 1154, 1087, 1013,
954, 864, 792, 740, 595, 525; UV−vis (CHCl3) λmax/nm (log ε) 257
(5.04), 318 (4.74), 417 (3.57); MALDI-TOF m/z calcd for C68H7NO2
[M+] 869.0471, found 869.0468.
1311, 1185, 1146, 1070, 1013, 963, 744, 526; UV−vis (CHCl3) λmax
/
ASSOCIATED CONTENT
nm (log ε) 255 (5.14), 318 (4.83), 417 (3.81); MALDI-TOF m/z
■
calcd for C65H9NO2 [M+] 835.0628, found 835.0623.
S
* Supporting Information
1H NMR, 13C NMR, and UV-vis spectra of products 2a−g.
This material is available free of charge via the Internet at
http://pubs.acs.org.
3-Isopropyloxazolidino[4,5:1,2][60]fullerene, 2d. By following the
general procedure, the reaction of C60 (36.0 mg, 0.05 mmol) with 1d
(15.9 mg, 0.10 mmol), FeCl3 (1.6 mg, 0.01 mmol), and PhI-
(O2CCF3)2 (21.5 mg, 0.05 mmol) at 40 °C afforded 2d (9.8 mg, 24%)
and recovered C60 (21.7 mg, 60%): amorphous brown solid; 1H NMR
(400 MHz, CS2/CDCl3) δ 4.65 (septet, J = 6.8 Hz, 1H), 1.85 (d, J =
6.8 Hz, 6H); 13C NMR (100 MHz, CS2/DMSO-d6 with Cr(acac)3 as
relaxation reagent, all 2C unless indicated) δ 151.43 (1C), 147.18
(1C), 147.01 (1C), 145.36, 145.34, 145.31, 145.15, 145.12 (4C),
144.34, 144.21, 144.04, 144.02, 143.79, 143.61, 143.34, 143.29, 143.16,
141.71 (4C), 141.63, 141.29, 141.14, 140.99, 140.91, 140.75, 140.41,
138.80, 138.64, 136.32, 136.14, 91.12 (1C), 77.33 (1C), 46.83 (1C),
19.36; FT-IR ν/cm−1 (KBr) 2960, 2922, 2853, 1762, 1505, 1455,
1418, 1374, 1316, 1262, 1218, 1095, 1013, 958, 803, 744, 570, 526;
UV−vis (CHCl3) λmax/nm (log ε) 259 (5.18), 318 (4.85), 416 (3.71);
MALDI-TOF m/z calcd for C64H7NO2 [M+] 821.0471, found
821.0443.
AUTHOR INFORMATION
Corresponding Author
*E-mail: gwang@ustc.edu.cn.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful for financial support from the National Natural
Science Foundation of China (Grant 21132007), Specialized
Research Fund for the Doctoral Program of Higher Education
(Grant 20123402130011), and Open Project of State Key
Laboratory Cultivation Base for Nonmetal Composites and
Functional Materials (Grant 11zxfk15).
3-Methoxyloxazolidino[4,5:1,2][60]fullerene, 2e. By following the
general procedure, the reaction of C60 (36.7 mg, 0.05 mmol) with 1e
(7.7 mg, 0.05 mmol), FeCl3 (1.5 mg, 0.01 mmol), and PhI(O2CCF3)2
(22.0 mg, 0.05 mmol) at 25 °C afforded 2e (10.9 mg, 26%) and
1
REFERENCES
recovered C60 (21.2 mg, 58%): amorphous brown solid; H NMR
■
(400 MHz, CS2/CDCl3) δ 4.43 (s, 3H); 13C NMR (100 MHz, CS2/
DMSO-d6 with Cr(acac)3 as relaxation reagent, all 2C unless
indicated) δ 150.52 (1C), 147.15 (1C), 146.84 (1C), 145.31,
145.28, 145.22, 145.11, 145.02 (4C), 143.98, 143.97, 143.89, 143.53,
143.32, 143.26, 143.25, 143.10, 143.01, 141.60, 141.57, 141.53, 141.11,
141.07, 140.91, 140.83, 140.73, 140.16, 138.83, 138.70, 136.49, 135.96,
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