DMAP-catalyzed [3 + 2] and [4 + 2] cycloaddition reactions between [60]fullerene and unmodified Morita-Baylis-Hillman adducts in the presence of Ac2O

Article abstract of DOI:10.1021/jo3025797

One-step DMAP-catalyzed [3 + 2] and [4 + 2] cycloaddition reactions between C₆₀ and unmodified Morita-Baylis-Hillman adducts in the presence of Ac₂O have been developed for the easy preparation of cyclopentene- and cyclohexene-fused

Full text of DOI:10.1021/jo3025797

Article
pubs.acs.org/joc
DMAP-Catalyzed [3 + 2] and [4 + 2] Cycloaddition Reactions between
[60]Fullerene and Unmodified Morita−Baylis−Hillman Adducts in the
Presence of Ac2O
Hai-Tao Yang,* Wen-Long Ren, Chun-Bao Miao, Chun-Ping Dong, Yang Yang, Hai-Tao Xi, Qi Meng,
Yan Jiang, and Xiao-Qiang Sun*
School of Petrochemical Engineering, Changzhou University, Changzhou 213164, People’s Republic of China
S
* Supporting Information
ABSTRACT: One-step DMAP-catalyzed [3 + 2] and [4 + 2]
cycloaddition reactions between C60 and unmodified Morita−
Baylis−Hillman adducts in the presence of Ac2O have been
developed for the easy preparation of cyclopentene- and
cyclohexene-fused [60]fullerene derivatives. When the MBH
adducts bear an alkyl group, two different reaction pathways
could be controlled selectively depending on the conditions.
NN12 double bonds. The Lu, Barbas, Liu, and Shi groups have
INTRODUCTION
■
successfully applied this strategy to synthesize enantiopure
The functionalization of [60]fullerene with various organic
spirocyclopenteneoxindole derivatives or functionalized bicyclic
functional groups is an important subject in fullerene chemistry
imides13 and the Tang group has investigated the intramolecular
for further material and medicinal applications. A remarkable
[3 + 2] reaction.14 To the best of our knowledge, the hydroxyl
array of their chemical reactions has been explored over the last
group on MBH adducts must be transformed to OAc, OBoc, or X
two decades.1 Among which, 1,3-dipolar cycloaddition is one of
(X = Cl, Br) and a phosphine must be used as the catalyst in this
the most used methodology to construct five-membered ring-
strategy and this kind of annulation has not been applied to the
fused [60]fullerene derivatives containing one or two heter-
functionalization of C60 yet. In the context of our general interest
oatoms. Only a limited number of methods for the preparation of
in fullerene chemistry,15 herein, we reported the DMAP-
[60]fullerene fused cyclopentane and cyclopentene derivatives
catalyzed [3 + 2] and [4 + 2] cyclization reactions between
have been reported up to now, such as the [3 + 2] reaction of
[60]fullerene and unmodified MBH adducts in the presence of
cyclopropanone or cyclopropenone ketal with C60,2 reaction of
Ac2O to afford cyclopentene- and cyclohexene-fused [60]-
C60 anion with 1,3-dihalogenated compounds or cyano-
fullerene derivatives, respectively.
substituted alkenes,3 cycloaddition reaction of C60 with different
zwitterionic species derived from dimethyl acetylenedicarbox-
ylate,4 phosphine-catalyzed cycloaddition of C60 with 2,3-
dienoates or electron-deficient alkynes,5 and photoreaction of
C60 with alkene linked with a cyclopropyl moiety through a
biradical intermediate.6 Thermal reactions of [60]fullerene with
tertiary amines and aldehydes to give cyclopentafullerene
derivatives were reported by the Wang group.7a Recently, they
also reported the synthesis of C60-Indane derivatives through the
addition of AlCl3 to the Mn (III)-mediated reaction of C60 with
α-aryl active methelene compounds or mesitylenesulfonic acid
mediated rearrangement of C60-fused tetrahydroisoquinoli-
nes.7b,c
■
RESULTS AND DISCUSSION
We initiated our studies by evaluating the reaction of C60 (36.0
mg, 0.05 mmol) with ethyl 2-(acetoxy(phenyl)methyl)acrylate
1a (2 equiv) using 20 mol % PPh3 as the catalyst in toluene at 120
°C (Scheme 1). To our delight, the desired [3 + 2] cycloaddition
product 2a was obtained as the single product in 29% yield after
Scheme 1. Phosphine-Catalyzed [3 + 2] Annulations of C60
with Acetyl-Modified MBH Adduct 1
The Morita−Baylis−Hillman (MBH) reaction is one of the
most atom-economic reactions for the construction of densely
functionalized products, which are useful intermediates in
organic synthesis as C3 synthons.8 In the past few years, Lu
and co-workers pioneered the use of the modified MBH adducts
(-X, -OAc, -OBoc) in [3 + 2] cyclizations and various
cycloadditions.9 Afterward, this new kind of [3 + 2] annulation
reaction was investigated on different CC,10 CN,11 and
Received: December 4, 2012
Published: January 4, 2013
© 2013 American Chemical Society
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a
Table 1. Screening of the One-Step Reaction Conditions
b
entry
C60/4a/Ac2O/base/PPh3
base
T (°C)
time (h)
yield (%)
1
2
1:5:5:5:1
1:5:5:5:1
1:5:5:5:0
1:5:5:5:0
1:5:5:5:0
1:5:5:5:0
1:5:5:5:0
1:5:5:5:0
1:3:3:3:0
1:2:2:2:0
1:1:1:1:0
DMAP
DMAP
DMAP
K2CO3
Et3N
80
120
120
120
120
120
120
120
120
120
120
24
1.5
2
39 (82)
37 (80)
36 (86)
0
3
4
10
10
10
10
10
4
5
0
6
N-methyl imidazole
pyridine
trace
7
trace
8
DBU
0
9
DMAP
36 (83)
30 (89)
19 (90)
10
11
DMAP
6
DMAP
10
a
To a mixture of C60 (36 mg, 0.05 mmol), 4a, base, and PPh3 in 16 mL of dry toluene was added Ac2O. The mixture was then stirred at the indicated
b
temperature in a preheated oil bath. Isolated yield. Values in parentheses were based on consumed C60.
a,b
24 h. As commonly proposed in the literature, an allylic P-ylide
formed through attacking of phosphine on the β-C of 1a. We
conjectured that, if ethyl 2-(acetoxymethyl)-3-phenylacrylate 1b
was used as the substrate, the isomer 3 would be generated.
Nevertheless, the same product 2a was isolated in 27% yield after
24 h under the similar conditions. The compound 3, as the
isomer of 2a, was assumed to be more stable than 2a for the
existence of a conjugation effect between the phenyl group and
double bonds. However, under different conditions, such as
DBU, NaH, t-BuOK, MsOH, Et3N/Pd(OAc)2, or Et3N/
Pd(PPh3)4, 2a could not be converted to 3 either at room
temperature or at 120 °C. We think that the big steric hindrance
between the phenyl group and the fullerene skeleton increases
the instablility of 3.
Table 2. Substrate Scope for the [3 + 2] Annulations
In an attempt to make this approach more efficient, a one-step
[3 + 2] cycloaddition directly from unmodified MBH adduct 4a
and C60 was tried. Ac2O and a base were used as additive reagents
to generate 1a in situ. The influence of base, molar ratio of
reagents, and temperature on the reaction was investigated in
detail (Table 1).
Under the molar ratio of C60/4a/Ac2O/DMAP/PPh3 as
1:5:5:5:1, 2a was obtained as expected in 39% yield after stirring
at 80 °C for 24 h (Table 1, entry 1). When the reaction
temperature was increased to 120 °C, a similar yield was obtained
in a shorter reaction time (1.5 h) (Table 1, entry 2). Moreover, to
our surprise, in the absence of PPh3, 2a also could be formed in
36% yield (Table 1, entry 3). It was the first example that the
amine, but not the phosphine, catalyzed this kind of
intermolecular [3 + 2] reaction. The examination of different
bases, such as K2CO3, Et3N, N-methyl imidazole, pyridine, and
DBU, revealed that only DMAP was the effective base in the
absence of phosphine (Table 1, entries 4−8), and DBU gave an
unidentified precipitate with the full conversion of C60. Reducing
the employed amount of 4a, Ac2O, and DMAP to 3 equiv also
gave 2a in 36% yield in a slightly longer time (Table 1, entry 9).
Further reducing the amount of starting materials led to a longer
reaction time and a lower yield of 2a (Table 1, entries 10 and 11).
Eventually, the molar ratio of C60/4a/Ac2O/DMAP as 1:3:3:3
and the reaction temperature as 120 °C were selected as the
optimal conditions for the [3 + 2] cycloaddition reaction.
To determine the generality of this methodology, a variety of
MBH adducts 4, derived from aromatic aldehydes, were used to
a
All the reactions were performed with 0.05 mmol of C60 in the molar
ratio of C60/4/Ac2O/DMAP = 1:3:3:3 in 16 mL of dry toluene at 120
°C for 3−10 h. Isolated yield. Values in parentheses were based on
consumed C60.
b
react with C60 (Table 2). All of the reactions were completed in
3−10 h with a moderate to good yield of 2. The electronic
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properties of the substituent on the aromatic ring had little or no
influence on the reactions. A substrate with a heteroaromatic
group also reacted, affording the corresponding derivative 2d
with 31% yield (Table 2, entry 4). All in all, different functional
groups such as ester, nitrile, and ketone, could be introduced to
the fullerene skeleton using this method.
Under the DMAP-catalyzed [3 + 2] reaction conditions,
isomerization of the acetyl-modified MBH product 1a into 1b
was observed. When 1a was treated with 1 equiv of DMAP and 1
equiv of HOAc in toluene at 120 °C for 10 h, the ratio of 1a/1b
changed from 100/0 to 6.5/93.5, as determined by the 1H NMR
analysis (Scheme 2). To determine which one is the active
product 6a was isolated as the single product (Table 3, entry 1).
Recently, there was a report on the amine-catalyzed [4 + 2]
annulation of MBH allylic acetates with electron-deficient
alkenes.16 Presumably, the high reaction temperature was
beneficial to the elimination of HOAc and generation of the
diene intermediate. Reducing the temperature to rt resulted in
nearly no reaction (Table 3, entry 2). Various conditions were
tried to get the [3 + 2] product 7a. With an additive of 0.1 equiv
of PPh3, no 7a was observed yet (Table 3, entry 3). We wanted to
reduce the reaction temperature and used more active n-Bu3P
instead of PPh3. When 0.1 equiv of n-Bu3P was used, the reaction
proceeded slowly and only a trace of 6a was observed on TLC
analysis after 14 h (Table 3, entry 4). When the amount of n-Bu3P
was increased to 0.5 equiv, the desired [3 + 2] product 7a was
obtained in 10% yield accompanying with 6% of [4 + 2] product
6a (Table 3, entry 5). A further increase in the amount of n-Bu3P
to 1 equiv resulted in the improvement on the selectivity of the [3
+ 2] product 7a in 24% yield accompanying with 6% of [4 + 2]
product 6a (Table 3, entry 6). A trend toward an increased ratio
of 7a/6a as the increased amount of n-Bu3P was observed. When
Na2CO3 was used as the base, higher selectivity and yield of 7a
could be obtained (Table 3, entry 7). When 5b−5d was
employed in the reaction, the [3 + 2] products 7b−7d and [4 +
2] products 6b−6d also could be selectively formed under
Na2CO3/n-Bu3P and DMAP conditions, respectively (Scheme
3).
Scheme 2. Active Species in the DMAP-Catalyzed [3 + 2]
Reaction
Scheme 3. [3 + 2] and [4 + 2] Cycloaddition between C60 and
Unmodified MBH Adducts Bearing an Alkyl Group
species, C60 was reacted with 3 equiv of 1a and 3 equiv of 1b,
respectively, in the presence of 3 equiv of DMAP and 3 equiv of
HOAc (the in situ generated 1a in a one-step reaction from
unmodified MBH prouduct, Ac2O, and DMAP would produce
the same amount of HOAc). 1a gave the desired product 2a in
33% yield after 3 h. However, 1b only gave a trace of 2a after 24 h.
When a catalytic amount of Ph3P was added to the mixture and it
was stirred for another 2 h, the reaction worked again. This
proved that phosphine was more active than DMAP in this kind
of [3 + 2] reaction and 1a is the actual active species in the
absence of phosphine.
The [3 + 2] cycloaddition reaction tolerated different aromatic
moieties in the MBH adducts 4 (R = Ar). When the MBH adduct
5a bearing an alkyl group was employed in the reaction, no [3 +
2] product 7a was observed. Instead, the [4 + 2] cycloaddition
a
Table 3. Reaction between C60 and 5a Bearing an Alkyl Group in the Presence of Ac2O and DMAP
b
b
entry
conditions
DMAP, 120 °C, 3 h
6a (%)
7a (%)
1
2
3
4
5
6
7
8
35 (87)
trace
0
0
0
0
DMAP, rt, 14 h
DMAP, PPh3 (0.1 equiv), 120 °C, 3 h
DMAP, n-Bu3P (0.1 equiv), rt, 14 h
DMAP, n-Bu3P (0.5 equiv), rt, 14 h
DMAP, n-Bu3P (1 equiv), rt, 9 h
Na2CO3, n-Bu3P (1 equiv), rt, 9 h
Na2CO3, PPh3 (0.1 equiv), 120 °C, 9 h
34 (90)
trace
6 (33)
6 (17)
5 (10)
trace
10 (55)
24 (68)
36 (72)
6 (92)
a
All the reactions were performed with 0.05 mmol of C60 in the molar ratio of C60/5/Ac2O/base = 1:3:3:3 and the indicated amount of phosphine in
b
16 mL of dry toluene. Isolated yield. Values in parentheses were based on consumed C60.
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It was clear that DMAP could catalyze both [3 + 2] and [4 + 2]
reactions and phosphine is beneficial to the [3 + 2] reaction. With
the MBH adducts derived from aliphatic aldehyde with an α-H,
the [4 + 2] reaction proceeded much faster than the [3 + 2]
reaction under DMAP conditions. To establish whether the
phosophine could also catalyze the [4 + 2] reaction, the acetyl-
modified BH adduct 8 was prepared and treated with PPh3 and n-
Bu3P, respectively (Scheme 4). When PPh3 was selected as the
Scheme 4. Reaction of C60 with Acetyl-Modified MBH Adduct
8
Figure 1. Difference between 6 and 7 in their 1H NMR spectra.
spectrum of 6b, the two CH2 groups showed a singlet at 4.36
ppm and a doublet at 4.19 ppm, respectively. However, no CH2
group existed in the structure of 7b. The methyl group showed a
doublet at 2.07 ppm, and the methine group showed a qd peak at
5.02 ppm. Furthermore, there were about 30 peaks for the
fullerene skeleton in 6b due to the Cs symmetry. The molecular
structure of 7b had no symmetry and showed about 60 peaks for
the fullerene skeleton.
A plausible mechanism is proposed in Scheme 5. The acetyl-
modified MBH product is generated in situ from the MBH
product, Ac2O, and base. When R is an aromatic group, a
pyridinium salt 9 is formed through an SN process under DMAP
conditions. N-ylide intermediate 10 or the isomer 11 could be,
respectively, formed through SN reaction or deprotonation in the
presence of AcO−. 10 serves as a surrogate of the 1,3-dipole to
undergo a [3 + 2] cycloaddition with C60 to generate 2. 11 is
difficult to regenerate 9 under the action of DMAP. However, in
the presence of phosphine, it can generate the P-ylide, which
reacts with C60 to generate 2. When R is an aliphatic group,
pyridinium salt 14 and phosphonium salt 16 were generated,
respectively, under DMAP or n-Bu3P/Na2CO3 conditions. A
competing deprotonation of the γ-H and then elimination of
DMAP from 14 provide the highly reactive 1,3-diene
intermediate 15, and subsequent Diels−Alder reaction with
catalyst, the [3 + 2] product 7a was isolated as the main product
under thermal conditions (7a/6a = 7:1). However, no reaction
occurred at room temperature. When n-Bu3P was used, an
interesting phenomenon was observed. At 120 °C, the [4 + 2]
reaction was predominant using a catalytic amount of n-Bu3P.
When the temperature was increased to rt, a trend of an increased
ratio of 7a/6a from 19/21 to 38/6 was observed as the amount of
n-Bu3P was increased from 0.1 to 1 equiv. It revealed that the
phosphine catalyzed not only the [3 + 2] reaction but also the [4
+ 2] reaction because it also could act as an organic base like
DMAP. We think that the basicity of n-Bu3P was higher than that
of PPh3, which thus gave more [4 + 2] product when the same
amount of phosphine was used. The origin of the trend of
increased ratio of 7a/6a as the amount of n-Bu3P was increased is
not clear now.
The structures of C60-fused cyclopentene and cyclohexene
derivatives 2a−2h, 7a−7d, 6a, and 6d were fully established by
their HRMS, 1H NMR, 13C NMR, FT-IR, and UV−vis spectral
data.17 Taking 2a as an example, the MALDI-FTMS spectra of 2a
displayed the [M+] peak at 908.0816. The 1H NMR spectrum of
2a showed two doublets at 8.08 and 6.21 ppm with a coupling
constant of 1.8 Hz for the vinyl and methine hydrogen, two dq
peaks at 4.29 and 4.36 ppm and a triplet at 1.28 ppm for the ethyl
proton. It should be noted that all phenyl protons are
magnetically inequivalent, probably due to the restricted rotation
of the phenyl ring.3b In the case of compound 2e, this
phenomenon was not observed due to the long distance between
the phenyl ring and the C60 skeleton. In the 13C NMR spectra of
2a, there are 59 partially overlapped peaks in the region of 127−
157 ppm for all the sp2 carbons, one peak at 164.2 ppm for the
carbonyl group, two peaks at 14.29 and 61.34 ppm for the ethyl
group, one peak at 63.35 ppm for the methine carbon, and two
peaks at 74.86 and 77.26 ppm for the two sp3 carbons of the C60,
consistent with the cyclopentene structure. The UV−vis
spectrum of 2a exhibited a characteristic absorption for the
1,2-adducts of C60 at 431 nm.
C
60 affords the [4 + 2] products 6. As for the phosphonium salt
16, two competing reactions exist depending on the reaction
temperature. At room temperature, a P-ylide 17 is preferentially
formed through an SN-deprotonation process, which undergoes a
[3 + 2] reaction with C60 to give the product 7. More 1,3-diene
intermediate 15 yields along with the increase of temperature,
which leads to the generation of competing product 6.
CONCLUSION
■
In conclusion, one-step DMAP-catalyzed [3 + 2] and [4 + 2]
cycloaddition reactions of C60 with unmodified MBH products in
the presence of Ac2O were realized and led to the easy
preparation of cyclopentene- and cyclohexene-fused [60]-
fullerene derivatives, respectively. The MBH adducts bearing
aromatic groups only undertake the [3 + 2] process. It was the
first example that DMAP catalyzed this kind of [3 + 2] reaction
through the N-ylide, but not the P-ylide. The MBH adducts
bearing alkyl groups could give the [3 + 2] and [4 + 2] products
selectively depending on the reaction conditions. Moreover, the
The structures of 6 and 7 could be easily discriminated
through their 1H NMR spectra (Figure 1). For the example of 6a
versus 7a, the Ha and Hb in 6a directly attached with the fullerene
had a noticeable downfield shift and the splitting pattern was
1
different from that of the CH2 group in 7a. In the H NMR
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Scheme 5. Plausible Mechanism
2a: Brown solid, 16.5 mg, 36%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3) δ 8.08 (d, J = 1.8 Hz, 1H), 7.76 (br, 1H), 7.64 (br, 1H), 7.49 (br,
1H), 7.39 (br, 1H), 7.31 (t, J = 7.4 Hz, 1H), 6.21 (d, J = 1.8 Hz, 1H), 4.36
(dq, J = 10.8, 7.2 Hz, 1H), 4.29 (dq, J = 10.8, 7.2 Hz, 1H), 1.28 (t, J = 7.1
Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 164.22 (CO), 156.63,
154.14, 151.32, 151.14, 147.67, 147.56, 146.61, 146.53, 146.34 (2C),
146.27 (2C), 146.24, 146.21, 146.12, 145.99, 145.95, 145.88, 145.82,
145.74, 145.68, 145.65, 145.61, 145.53, 145.32 (2C), 145.22, 145.19,
144.83 (2C), 144.67, 144.65, 144.60, 144.43, 143.32, 143.29, 142.89,
142.83, 142.76, 142.74, 142.62, 142.41 (2C), 142.36, 142.28, 142.18,
142.17, 142.00, 141.99, 141.97, 141.93, 141.83, 141.25, 140.74, 140.53,
140.31, 139.56, 139.11, 137.02, 136.33, 135.72, 134.37, 129.20 (br, 2C,
aryl C), 127.96 (2C, aryl C), 77.26 (sp3-C of C60), 74.86 (sp3-C of C60),
63.35, 61.34, 14.29; UV−vis (CHCl3) λmax/nm 257, 310, 431; FT-IR
(KBr) ν/cm−1 2920, 2850, 1717, 1645, 1259, 1095, 1020, 802, 752, 698,
526; HRMS (MALDI-FTMS) m/z [M+] Calcd for C72H12O2,
908.0837; found, 908.0816.
difference between PPh3 and n-Bu3P on the [3 + 2] reaction was
also investigated. A possible reaction mechanism was proposed
to explain the formation of C60-fused cyclopentene/cyclohexene
derivatives.
EXPERIMENTAL SECTION
■
Preparation of 1a and 1b. To a mixture of 4a (228 mg, 1.1 mmol)
and pyridine (119 mg, 1.5 mmol) in 8 mL of dry dichloromethane was
added dropwise a solution of acetyl chloride (117 mg, 1.5 mmol) in 5
mL of dichloromethane at 0 °C. The temperature was kept for 5−10
min, and then warmed to room temperature, and the mixture continued
to stir for 4−5 h. After completion of the reaction, detected by TLC, 20
mL of water was added to the mixture and then extracted with
dichloromethane. The organic phase was dried over anhydrous Na2SO4.
Evaporation of the solvent, followed by column chromatography on
silica gel using petroleum ether/EtOAc (10:1) as the eluent, gave the
corresponding product 1a (219 mg, 80%) as a colorless oil. 1a:18 1H
NMR (300 MHz, CDCl3) δ 7.30−7.40 (m, 5H), 6.68 (s, 1H), 6.40 (t, J =
0.9 Hz, 1H), 5.84 (dd, J = 1.3, 1.0 Hz, 1H), 4.17 (dq, J = 10.8, 7.2 Hz,
1H), 4.13 (dq, J = 10.8, 7.2 Hz, 1H), 2.11 (s, 3H), 1.22 (t, J = 7.2 Hz,
3H).
2b: Brown solid, 13.9 mg, 29%, mp > 300 °C. 1H NMR (500 MHz,
CS2-CDCl3) δ 8.32 (br, 1H), 8.22 (br, 1H), 8.11 (s, 1H), 7.91 (br, 1H),
7.79 (br, 1H), 6.26 (d, J = 1.5 Hz, 1H), 4.24−4.36 (m, 2H), 1.31 (t, J =
7.1 Hz, 3H); 13C NMR (125 MHz, CS2-CDCl3) δ 162.93 (CO),
155.47, 152.43, 150.29, 150.12, 148.10, 147.48, 147.40, 147.34, 146.41,
146.37, 146.19 (2C), 146.14, 146.11, 146.09, 146.05, 145.80 (2C),
145.59 (4C), 145.51, 145.44 (2C), 145.43, 145.38, 145.27, 145.19,
144.95, 144.43, 144.37 (3C), 144.22, 143.19, 143.16, 142.72, 142.71,
142.67, 142.61, 142.29, 142.14, 142.13, 142.08, 141.99, 141.96, 141.81
(2C), 141.75, 141.69, 141.67, 140.68, 140.56, 140.22, 139.60, 137.89,
136.43, 135.97, 135.70, 134.30, 128.36 (br, 2C), 124.18 (br, 2C), 77.06
(sp3-C of C60), 76.91 (sp3-C of C60), 62.79, 61.38, 14.34; UV−vis
(CHCl3) λmax/nm 257, 309.5, 430.5; FT-IR (KBr) ν/cm−1 2920, 2850,
1714, 1652, 1514, 1342, 1263, 1226, 1096, 1022, 843, 702, 526; HRMS
(MALDI-FTMS) m/z [M+] Calcd for C72H11NO4, 953.0688; found,
953.0669.
To a 25 mL one-neck flask was added 4a (103 mg, 0.5 mmol),
followed by 5 mL of dry toluene, then DMAP (92 mg, 0.75 mmol) and
Ac2O (77 mg, 0.75 mmol). The mixture was stirred at 80 °C for 24 h.
After the same workup process as the preparation of 1a and column
chromatographic purification, pure 1b (97 mg, 78%) was obtained as a
colorless oil. 1b:19 1H NMR (300 MHz, CDCl3) δ 7.98 (s, 1H), 7.35−
7.45 (m, 5H), 4.96 (s, 2H), 4.31 (q, J = 7.2 Hz, 2H), 2.11 (s, 3H), 1.35 (t,
J = 7.2 Hz, 3H).
Preparation of 8. An acetyl chloride (188 mg, 2.4 mmol) solution in
5 mL of dichloromethane was added dropwise to a mixture of 5a (344
mg, 2 mmol) and pyridine (206 mg, 2.6 mmol) in 8 mL of dry
dichloromethane at 0 °C. The temperature was kept for 5−10 min, and
then the mixture was warmed to room temperature and continued to stir
overnight. After the same workup process as the preparation of 1a and
column chromatographic purification, the product 8 (312 mg, 73%) was
obtained as a colorless oil. 8:20 1H NMR (300 MHz, CDCl3) δ 6.28 (s,
1H), 5.75 (t, J = 1.0 Hz, 1H), 5.64 (dd, J = 7.8, 4.6 Hz, 1H), 4.26 (dq, J =
10.8, 7.1 Hz, 1H), 4.21 (dq, J = 10.8, 7.1 Hz, 1H), 2.08 (s, 3H), 1.58−
1.80 (m, 2H), 1.26−1.46 (m, 2H), 1.31 (t, J = 7.1 Hz, 3H), 1.22 (t, J = 7.3
Hz, 3H).
General Procedure for the DMAP-Catalyzed [3 + 2] Reaction
between C60 and MBH Adducts (4a−4h) in the Presence of
Ac2O. To a 25 mL one-neck flask was sequentially added C60 (36.0 mg,
0.05 mmol), DMAP (18.3 mg, 0.15 mmol), BH adducts 4a−4h (0.15
mmol), and 16 mL of dry toluene. After ultrasonic dissolving, Ac2O
(15.3 mg, 0.15 mmol) was added and the mixture was stirred at 120 °C
for 3−10 h. The solvent was evaporated in vacuo, and the residue was
purified on a silica gel column using CS2 as the eluent to give unreacted
C60. Subsequent elution with CS2/toluene in the appropriate ratio
afforded the [3 + 2] products 2a−2h.
2c: Brown solid, 15.5 mg, 33%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3−CS2) δ 7.99 (s, 1H), 7.15−7.04 (m, 2H), 6.88−6.75 (m, 1H),
6.10−5.94 (m, 3H), 3.88 (s, 3H); 13C NMR (125 MHz, CS2-CDCl3) δ
163.91 (CO), 156.24, 153.72, 150.95, 150.70, 147.41, 147.32, 147.21,
146.38, 146.32, 146.10 (2C), 146.04 (2C), 146.02, 145.99, 145.79,
145.66, 145.64, 145.58, 145.54, 145.51, 145.43, 145.37, 145.28, 145.14,
145.09, 145.06 144.88, 144.51, 144.41, 144.36, 144.19, 143.12, 143.08,
142.70, 142.62, 142.57, 142.53, 142.44, 142.21, 142.18, 142.15, 142.06,
141.95, 141.93, 141.84, 141.79, 141.76 (2C), 141.61, 140.34, 140.16,
139.48, 138.58, 136.84, 136.04, 135.54, 134.71 (br), 134.05, 123.71 (br),
120.74 (br), 108.52 (br), 107.41 (br), 101.24, 76.78 (sp3-C of C60),
74.62 (sp3-C of C60), 62.85, 52.01; UV−vis (CHCl3) λmax/nm 257, 309,
430.5; FT-IR (KBr) ν/cm−1 2943, 2893, 1725, 1644, 1512, 1502, 1482,
1431, 1337, 1247, 1227, 1131, 1095, 1034, 928, 526; HRMS (MALDI-
FTMS) m/z [M+] Calcd for C72H10O4, 938.0597; found, 938.0586.
2d: Brown solid, 13.9 mg, 31%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3-CS2) δ 7.97 (d, J = 2.0 Hz, 1H), 7.41 (d, J = 1.2 Hz, 1H), 6.51 (d,
J = 3.2 Hz, 1H), 6.36 (dd, J = 3.2, 1.9 Hz, 1H), 6.21 (d, J = 1.9 Hz, 1H),
4.38 (dq, J = 10.7, 7.1 Hz, 1H), 4.32 (dq, J = 10.7, 7.1 Hz, 1H), 1.37 (t, J =
1167
dx.doi.org/10.1021/jo3025797 | J. Org. Chem. 2013, 78, 1163−1170

The Journal of Organic Chemistry
Article
7.1 Hz, 3H); 13C NMR (125 MHz, CDCl3-CS2) δ 163.11 (CO),
155.50, 153.24, 152.80, 150.80, 150.58, 147.39, 147.28, 146.33, 146.29,
146.13, 146.07, 146.05, 146.03, 145.99, 145.97 (2C), 145.72, 145.66,
145.61, 145.59, 145.49 (2C), 145.39, 145.33, 145.23 (2C), 145.12,
145.07 (2C), 144.85 (2C), 144.52, 144.37, 144.33, 144.19, 143.06,
143.03, 142.69, 142.57, 142.55, 142.52, 142.41 (2C), 142.29, 142.20
(2C), 142.15, 142.04, 141.94, 141.90, 141.78 (2C), 141.76, 141.75,
141.55, 140.56, 140.31, 140.04, 139.34, 136.93, 136.27, 135.95, 135.52,
134.32, 110.94, 108.74, 76.61 (sp3-C of C60), 73.93 (sp3-C of C60),
61.12, 56.55, 14.42; UV−vis (CHCl3) λmax/nm 256.5, 310, 431; FT-IR
(KBr) ν/cm−1 2920, 2850, 1716, 1645, 1368, 1255, 1226, 1095, 1073,
1010, 738, 526; HRMS (MALDI-FTMS) m/z [M+] Calcd for
C70H10O3, 898.0630; found, 898.0647.
140.16, 139.40, 136.90, 136.14, 135.44, 134.00, 129.13 (br, 2C), 127.82
(2C), 74.33 (sp3-C of C60), 63.16, 27.96; UV−vis (CHCl3) λmax/nm
257, 310, 431; FT-IR (KBr) ν/cm−1 2919, 2850, 1679, 1622, 1423, 1359,
1261, 1221, 1093, 1021, 799, 702, 526; HRMS (MALDI-FTMS) m/z
[M+] Calcd for C71H10O, 878.0732; found, 878.0719.
General Procedure for [4 + 2] Reaction between C60 and MBH
Adducts (5a−5d) in the Presence of Ac2O and DMAP. To a 25 mL
one-neck flask was sequentially added C60 (36.0 mg, 0.05 mmol),
DMAP (18.3 mg, 0.15 mmol), MBH adducts 5a−5d (0.15 mmol), and
16 mL of dry toluene. After ultrasonic dissolving, Ac2O (15.3 mg, 0.15
mmol) was added and the mixture was stirred at 120 °C for 2−5 h. The
solvent was evaporated in vacuo, and the residue was purified on a silica
gel column using CS2 as the eluent to give unreacted C60. Subsequent
elution with CS2/toluene in the appropriate ratio afforded the [4 + 2]
products 6a−6d.
1
2e: Brown solid, 8.8 mg, 19%, mp > 300 °C. H NMR (500 MHz,
CS2-CDCl3) δ 7.90 (d, J = 1.7 Hz, 1H), 7.41 (d, J = 7.3 Hz, 2H), 7.30 (t, J
= 7.4 Hz, 2H), 7.22 (t, J = 7.3 Hz, 1H), 6.90 (d, J = 15.5 Hz, 1H), 6.74
(dd, J = 15.5, 9.8 Hz, 1H), 5.68 (dd, J = 9.7, 1.7 Hz, 1H), 4.44 (dq, J =
10.8, 7.2 Hz, 1H), 4.38 (dq, J = 10.8, 7.2 Hz, 1H), 1.43 (t, J = 7.2 Hz,
3H); 13C NMR (125 MHz, CS2-CDCl3) δ 163.83 (CO), 156.12,
153.20, 151.05, 150.81, 147.50, 147.41, 146.43, 146.40, 146.29, 146.22
(2C), 146.19, 146.16, 146.13, 146.10, 145.90, 145.86, 145.81, 145.75,
145.61 (2C), 145.50 (2C), 145.41, 145.34, 145.25, 145.22 (2C), 144.61,
144.54, 144.41, 144.30, 143.88 (3C), 143.24, 143.17, 142.75 (2C),
142.69, 142.62, 142.44, 142.32, 142.30, 142.27, 142.13, 142.11, 142.07
(2C), 141.94 (2C), 141.78, 141.73, 140.60, 140.49, 140.22, 139.93,
138.83, 136.67, 136.65, 136.11, 135.60, 134.25, 134.18, 129.25, 128.68
(2C), 128.02, 126.84 (2C), 76.98 (sp3-C of C60), 73.86 (sp3-C of C60),
61.24, 60.86, 14.51; UV−vis (CHCl3) λmax/nm 257.5, 310, 431; FT-IR
(KBr) ν/cm−1 2922, 2850, 1717, 1642, 1258, 1244, 1225, 1093, 959,
902, 745, 729, 690, 526; HRMS (MALDI-FTMS) m/z [M+] Calcd for
C74H14O2, 934.0994; found, 934.1005.
6a: Brown solid, 15.3 mg, 35%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3-CS2) δ 7.81 (br, 1H), 4.65 (d, J = 14.2 Hz, 1H), 4.33−4.43 (m,
2H), 4.12 (d, J = 13.9 Hz, 1H), 3.85 (d, J = 11.5 Hz, 1H), 2.81−2.89 (m,
1H), 2.26−2.29 (m, 1H), 1.46 (t, J = 7.3 Hz, 3H), 1.44 (t, J = 7.1 Hz,
3H); 13C NMR (125 MHz, CDCl3-CS2) δ 164.67 (CO), 157.09,
156.91, 153.88, 147.69, 147.56, 146.86, 146.62 (2C), 146.52 (2C),
146.40, 146.26 (3C), 146.23, 145.87, 145.84, 145.79 (2C), 145.59,
145.56, 145.49, 145.45 (4C), 145.40, 145.37, 145.23, 144.80, 144.75,
144.61 (2C), 143.14 (2C), 142.73, 142.71, 142.67 (2C), 142.24 (3C),
142.16, 142.15, 142.11, 142.10, 141.92, 141.79, 141.66, 141.49, 141.41,
140.39 (2C), 139.06, 138.94, 136.32, 135.81, 135.74, 135.05, 134.93,
70.06 (sp3-C of C60), 67.49 (sp3-C of C60), 61.18, 49.75, 39.42, 26.09,
14.57, 13.71; UV−vis (CHCl3) λmax/nm 257, 309, 432.5; FT-IR (KBr)
ν/cm−1 2923, 2867, 1702, 1541, 1429, 1371, 1267, 1231, 1206, 1132,
1078, 730, 527; HRMS (MALDI-FTMS) m/z [M+] Calcd for
C69H14O2, 874.0994; found, 874.0962.
2f: Brown solid, 15.1 mg, 35%, mp > 300 °C. 1H NMR (500 MHz,
CS2-CDCl3) δ 7.90 (d, J = 2.1 Hz, 1H), 7.65 (br, 2H), 7.48 (br, 2H),
7.37 (t, J = 7.4 Hz, 1H), 6.07 (d, J = 2.0 Hz, 1H); 13C NMR (125 MHz,
CS2-CDCl3) δ 155.09, 152.03, 149.62, 148.96, 148.93 (2C), 148.87,
147.35, 147.25, 146.34, 146.28, 146.04 (3C), 146.00, 145.98, 145.92,
145.62, 145.53 (2C), 145.46, 145.38, 145.35, 145.31, 145.22 (2C),
145.17, 145.09, 145.06, 145.03, 144.45, 144.32, 144.28, 144.14, 144.10,
143.04, 143.02, 142.63, 142.57, 142.56, 142.51, 142.16, 142.08, 142.06,
141.94, 141.91, 141.84, 141.80,141.72, 141.67, 141.65 (2C), 141.56,
140.54, 140.32, 140.10, 139.44, 137.56, 136.47, 136.21, 135.32, 134.00,
129.44 (2C), 128.82 (2C), 119.22, 114.15, 73.58 (sp3-C of C60), 64.69;
UV−vis (CHCl3) λmax/nm 256, 310.5, 430; FT-IR (KBr) ν/cm−1 2920,
2850, 2223, 1511, 1453, 1428, 901, 883, 729, 705, 526; HRMS (MALDI-
FTMS) m/z [M+] Calcd for C70H7N, 861.0578; found, 861.0590.
2g: Brown solid, 14.9 mg, 33%, mp > 300 °C. 1H NMR (500 MHz,
CS2-CDCl3) δ 7.86 (d, J = 2.2 Hz, 1H), 7.10 (br, 2H), 6.86 (br, 1H),
6.01 (s, 2H), 5.98 (d, J = 1.7 Hz, 1H); 13C NMR (125 MHz, CS2-
CDCl3) δ 155.12, 152.07, 149.71, 148.98, 148.63 (3C), 148.04, 147.38,
147.28, 146.37, 146.31, 146.08, 146.06 (2C), 146.03, 146.01, 145.95,
145.64, 145.55 (2C), 145.46, 145.43, 145.39, 145.34, 145.35, 145.24,
145.20, 145.15, 145.09, 145.07, 144.47, 144.35, 144.33, 144.18, 144.14,
143.08, 143.04, 142.67, 142.59 (2C), 142.54, 142.20, 142.13, 142.09,
141.98, 141.94, 141.85 (2C), 141.77, 141.75, 141.70 (2C), 141.58,
140.56, 140.34, 140.14, 139.57, 136.53, 136.20, 135.39, 133.96, 131.30,
119.46, 114.12, 108.95 (br), 101.48, 76.84 (sp3-C of C60), 73.74 (sp3-C
of C60), 64.54; UV−vis (CHCl3) λmax/nm 256.5, 310.5, 430; FT-IR
(KBr) ν/cm−1 2920, 2851, 2223, 1501, 1482, 1443, 1236, 1099, 1038,
928, 706, 526; HRMS (MALDI-FTMS) m/z [M+] Calcd for
C71H7NO2, 905.0477; found, 905.0471.
6b: Brown solid, 16.1 mg, 38%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3-CS2) δ 8.01 (t, J = 5.8 Hz, 1H), 4.40 (q, J = 7.1 Hz, 2H), 4.36 (s,
2H), 4.19 (d, J = 5.8 Hz, 2H), 1.45 (t, J = 7.1 Hz, 3H); 13C NMR (125
MHz, CDCl3-CS2) (all 2C unless indicated) δ 164.72 (1C, CO),
156.40, 156.30, 147.71 (1C), 147.66 (1C), 146.58, 146.53, 146.29,
146.26, 145.81, 145.57 (4C), 145.48 (4C), 145.34, 145.13, 144.76,
144.65, 143.15, 142.65, 142.62, 142.24, 142.20, 142.14, 142.05, 141.70,
141.66, 141.18 (1C), 140.28, 140.18, 136.16 (1C), 135.76, 135.58, 65.66
(1C, sp3-C of C60), 65.13 (1C, sp3-C of C60), 61.20 (1C), 41.21 (1C),
38.89 (1C), 14.56 (1C);
6c: Brown solid, 10.4 mg, 25%, mp > 300 °C. 1H NMR (500 MHz,
CS2-DMSO-d6) δ 7.74 (s, 1H), 4.47 (d, J = 14.3 Hz, 1H), 4.29 (d, J =
14.3 Hz, 1H), 4.03−4.09 (m, 1H), 2.82−2.92 (m, 1H), 2.27−2.38 (m,
1H), 1.52 (t, J = 7.1 Hz, 3H); UV−vis (CHCl3) λmax/nm 256, 310, 431;
FT-IR (KBr) ν/cm−1 2955, 2925, 2869, 2219, 1513, 1454, 1428, 1184,
765, 572, 527; HRMS (MALDI-FTMS) m/z [M+] Calcd for C67H9N,
827.0735; found, 827.0767.
6d: Brown solid, 14.8 mg, 35%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3-CS2) δ 7.69 (s, 1H), 4.78 (d, J = 12.4 Hz, 1H), 3.88−4.00 (m,
2H), 2.85−2.94 (m, 1H), 2.67 (s, 3H), 2.25−2.36 (m, 1H), 1.48 (t, J =
7.1 Hz, 3H); 13C NMR (125 MHz, CDCl3-CS2) δ 194.78 (CO),
157.12, 156.92, 153.78, 147.73, 147.55, 146.80, 146.65, 146.64, 146.52,
146.49, 146.37, 146.29, 146.27 (3C), 145.86, 145.78, 145.67 (2C),
145.60, 145.56, 145.51, 145.46 (3C), 145.43 (2C), 145.39, 145.29,
144.84, 144.80, 144.58, 144.55, 143.49, 143.16, 143.15, 142.74, 142.72,
142.67 (2C), 142.26, 142.22 (2C), 142.17, 142.12, 142.10, 142.06,
141.91, 141.80, 141.70, 141.45, 141.43, 140.46, 140.44, 139.06, 138.95,
136.19, 135.90, 135.32, 134.95, 70.01 (sp3-C of C60), 67.32 (sp3-C of
C60), 49.77, 37.57, 26.10, 24.95, 13.79; UV−vis (CHCl3) λmax/nm 255,
310, 431; FT-IR (KBr) ν/cm−1 2956, 2922, 2851, 1668, 1511, 1427,
1376, 1264, 1182, 1084, 764, 527; HRMS (MALDI-FTMS) m/z [M+]
Calcd for C68H12O, 844.0888; found, 844.0859.
General Procedure for the n-Bu3P-Catalyzed [3 + 2] Reaction
between C60 and MBH Adducts 5a−5d in the Presence of Ac2O
and Na2CO3. To a 25 mL one-neck flask was sequentially added C60
(36.0 mg, 0.05 mmol), Na2CO3 (15.9 mg, 0.15 mmol), BH adducts 5a−
5d (0.15 mmol), and 16 mL of dry toluene. After ultrasonic dissolving,
Ac2O (15.3 mg, 0.15 mmol) and n-Bu3P (10.1 mg, 0.05 mmol) were
added and the mixture was stirred at room temperature for the
2h: Brown solid, 12.7 mg, 29%, mp > 300 °C. 1H NMR (500 MHz,
CS2-CDCl3) δ 7.96 (d, J = 1.7 Hz, 1H), 7.61 (br, 2H), 7.42 (br, 1H),
7.36 (br, 1H), 7.27 (t, J = 7.4 Hz, 1H), 6.20 (d, J = 1.6 Hz, 1H), 2.65 (s,
3H); 13C NMR (125 MHz, CS2-CDCl3) δ 194.12 (CO), 156.26,
153.81, 150.82, 150.71, 147.35, 147.29, 146.41, 146.37, 146.30, 146.07,
146.05, 146.01 (2C), 145.98, 145.96, 145.66, 145.60 (2C), 145.59,
145.53, 145.49 (2C), 145.40, 145.35, 145.26, 145.11, 145.05, 144.98,
144.86, 144.49, 144.40, 144.31, 144.11, 143.70 (2C), 143.10, 143.07,
142.68, 142.59, 142.55, 142.50, 142.43, 142.16 (2C), 142.09, 141.99,
141.90 (2C), 141.74 (2C), 141.73 (2C), 141.60, 140.87, 140.55, 140.33,
1168
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The Journal of Organic Chemistry
Article
designated time. After completion of the reaction, a solution of I2 (32
mg) in methanol (0.5 mL) was added and the mixture was stirred for
another 5 min (Caution! Transform the n-Bu3P to n-Bu3PO; avoid the
further reaction at a higher temperature in the process of removing solvent).
The solvent was then evaporated in vacuo, and the residue was purified
on a silica gel column using CS2 as the eluent to give unreacted C60.
Subsequent elution elution with CS2/toluene in the appropriate ratio
afforded the major or exclusive [3 + 2] products 7a−7d.
General Procedure for Phosphine-Catalyzed Reaction be-
tween C60 and Acetyl-Modified MBH Adduct 8. To a 25 mL one-
neck flask were sequentially added C60 (36.0 mg, 0.05 mmol), 8 (0.15
mmol), and 16 mL of dry toluene. After ultrasonic dissolving, phosphine
catalyst (PPh3, 0.005 mmol; or n-Bu3P, 0.005−0.05 mmol) was added
and the mixture was stirred at 120 °C or room temperature for the
designated time. The solvent was evaporated in vacuo, and the residue
was purified on a silica gel column using CS2 as the eluent to give
unreacted C60. Subsequent elution with CS2/toluene in the appropriate
ratio afforded the [3 + 2] products 7a and [4 + 2] products 6a. (When n-
Bu3P was used, the same workup process was applied as that of the one-
step reaction mentioned above.)
7a: Brown solid, 15.7 mg, 36%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3-CS2) δ 7.77 (d, J = 1.4 Hz, 1H), 5.02 (d, J = 7.4 Hz, 1H), 4.45−
4.55 (m, 2H), 2.55−2.62 (m, 1H), 2.38−2.45 (m, 1H), 1.94−2.02 (m,
1H), 1.79−1.87 (m, 1H), 1.51 (t, J = 7.1 Hz, 3H), 1.05 (t, J = 7.3 Hz,
3H); 13C NMR (125 MHz, CDCl3-CS2) δ 164.91 (CO), 157.23,
153.20, 151.73, 151.67, 147.66, 147.54, 146.77, 146.59, 146.54, 146.52,
146.35, 146.33, 146.30 (2C), 146.28, 146.25, 146.04, 145.94, 145.87,
145.69, 145.67, 145.63, 145.61 (2C), 145.47, 145.34, 145.30, 145.09,
144.77, 144.66 (2C), 144.52, 143.42, 143.34, 143.03 (2C), 142.97,
142.85 (2C), 142.77, 142.69, 142.49, 142.47, 142.43, 142.31, 142.24,
142.21, 142.11, 142.05, 141.93 (2C), 141.90, 140.69, 140.64, 140.25,
139.44, 136.92, 136.66, 136.03, 134.23, 77.77 (sp3-C of C60), 73.77 (sp3-
C of C60), 61.40, 56.66, 36.79, 21.21, 14.65, 14.57; UV−vis (CHCl3)
λmax/nm 257, 309, 431; FT-IR (KBr) ν/cm−1 2922, 2864, 1714, 1643,
1241, 1224, 1130, 1087, 902, 729, 526; HRMS (MALDI-FTMS) m/z
[M+] Calcd for C69H14O2, 874.0994; found, 874.1005.
ASSOCIATED CONTENT
* Supporting Information
NMR spectra of 1a, 1b, 2a−2h, 6a−6d, 7a−7d, and 8. This
material is available free of charge via the Internet at http://pubs.
acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: yanght898@yahoo.com.cn, chemsxq@yahoo.com.cn.
■
Notes
7b: Brown solid, 16.9 mg, 40%, mp > 300 °C. 1H NMR (500 MHz,
CDCl3-CS2) δ 7.77 (d, J = 1.7 Hz, 1H), 5.02 (qd, J = 7.2, 1.6 Hz, 1H),
4.42−4.52 (m, 2H), 2.07 (d, J = 7.3 Hz, 3H), 1.51 (t, J = 7.2 Hz, 3H); 13C
NMR (125 MHz, CDCl3-CS2) δ 164.11 (CO), 156.63, 153.32,
151.44, 151.24, 147.50, 147.40, 146.43, 146.39, 146.36, 146.31, 146.22,
146.17 (2C), 146.13 (2C), 145.99, 145.88, 145.84, 145.77, 145.57 (2C),
145.51 (2C), 145.41, 145.35, 145.21 (3C), 144.63, 144.54, 144.45,
144.36, 143.28, 143.20, 142.80, 142.75 (4C), 142.69, 142.63, 142.52,
142.30, 142.29 (2C), 142.22, 142.13, 142.08 (2C), 141.99, 141.82,
141.76 (2C), 141.25, 140.59, 140.53, 140.20, 139.82, 136.60, 136.18,
136.04, 134.10, 73.38 (sp3-C of C60), 61.20, 51.95, 21.32, 14.59; UV−vis
(CHCl3) λmax/nm 257, 309, 430.5; FT-IR (KBr) ν/cm−1 2922, 2864,
1714, 1509, 1258, 1241, 1224, 1131, 765, 729, 526; HRMS (MALDI-
FTMS) m/z [M+] Calcd for C67H10O2, 846.0681; found, 846.0699.
7c: Brown solid, 12.4 mg, 30%, mp > 300 °C. 1H NMR (500 MHz,
CS2-DMSO-d6) δ 7.59 (br, 1H), 4.78−4.86 (m, 1H), 2.44−2.56 (m,
1H), 2.33−2.43 (m, 1H), 2.05−2.17 (m, 1H), 1.92−2.02 (m, 1H), 1.15
(t, J = 7.1 Hz, 3H); 13C NMR (125 MHz, CS2-DMSO-d6) δ 154.92,
150.52, 149.58, 149.12, 146.74 (2C), 146.54, 146.40, 145.52, 145.47,
145.45, 145.34, 145.26 (2C), 145.22, 145.20, 145.18, 144.87, 144.80
(2C), 144.78, 144.72, 144.68, 144.55 (2C), 144.53, 144.49, 144.36,
144.26, 143.76, 143.54 (2C), 143.45 (2C), 142.33, 142.26, 142.18,
141.89, 141.85, 141.80, 141.74, 141.43, 141.38, 141.34, 141.20 (2C),
141.15, 141.13, 141.07. 140.97, 140.88, 140.86, 140.82, 139.61 (2C),
139.20, 138.57, 135.43, 135.34, 135.23, 133.25, 120.15, 114.10 (CN),
76.84 (sp3-C of C60), 71.45 (sp3-C of C60), 57.35, 36.94, 20.92, 13.94;
UV−vis (CHCl3) λmax/nm 256, 310, 431; FT-IR (KBr) ν/cm−1 2953,
2921, 2853, 2216, 1511, 1461, 1428, 1183, 1096, 883, 767, 574, 526;
HRMS (MALDI-FTMS) m/z [M+] Calcd for C67H9N, 827.0735;
found, 827.0728.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors are grateful for financial support from the National
Natural Science Foundation of China (Nos. 20902039 and
21202011) and the Priority Academic Program Development of
Jiangsu Higher Education Institutions.
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