Cobalt-catalyzed hydroalkylation of [60]fullerene with active alkyl bromides: Selective synthesis of monoalkylated fullerenes

Article abstract of DOI:10.1021/ja204982w

The Co-catalyzed hydroalkylation of C₆₀ with reactive alkyl bromides 1 (RBr) in the presence of Mn reductant and H₂O at ambient temperature gave the monoalkylated C₆₀ (2) in good to high yields. The use of CoLn/Mn/H_2<

Full text of DOI:10.1021/ja204982w

ARTICLE
pubs.acs.org/JACS
Cobalt-Catalyzed Hydroalkylation of [60]Fullerene with Active Alkyl
Bromides: Selective Synthesis of Monoalkylated Fullerenes
Shirong Lu,†,§ Tienan Jin,*,‡ Ming Bao,§ and Yoshinori Yamamoto*,‡
†Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
‡WPI-Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
§State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
S Supporting Information
b
ABSTRACT: The Co-catalyzed hydroalkylation of C60 with
reactive alkyl bromides 1 (RBr) in the presence of Mn reductant
and H2O at ambient temperature gave the monoalkylated C60
(2) in good to high yields. The use of CoLn/Mn/H2O under Ar
atmosphere is crucial for the success of the present transforma-
tion. The reaction most probably proceeds through the Co(0 or I)
complex-promoted generation of a radical (R•) followed by
addition to C60. This hydroalkylation method was applied to
the synthesis of zinc porphyrin attached C60 (2l), dendrimer
attached C60 (2m), and fullerene dimer (2n), which were not easily available through the previously known methods.
’ INTRODUCTION
materials, although an efficient synthetic method of porphyrin-
or dendrimer-bound monoadducts of C60 derivatives and mono-
substituted fullerene dimers has never been reported.1d,g,6ꢀ8
Chemical functionalization of fullerenes provides a variety of
potentially useful molecular materials for biological and electro-
nic devices.1 Numerous efforts for chemical modification of
fullerenes have been made during the last few decades, involving
various cycloadditions,1 addition of free radicals,2,3 and multi-
addition of organocoppers.1f The nuclophilic addition of orga-
nolithiums or Grignard reagents is one of the classical methods
for monofunctionalization of fullerene,4 but this method is
accompanied by the following drawbacks: low chemical yields,
low selectivity of monoalkylation, high loading of organometallic
reagents, and low compatibility with a wide range of functional
groups. Transition-metal-catalyzed functionalization of fullerenes5
has been proved to be a useful method to overcome those
disadvantages; for example, Itami and co-workers reported that
Rh or Pd catalyst can promote the selective monoarylation of
fullerene efficiently by using organoboron compounds.5h,i The
addition of nucleophiles through radical intermediates proceeds
rapidly, but it is difficult to control its selectivity and reactivity;
often polysubstituted fullerenes are obtained.2 It occurred to us
that the combination between a transition-metal-catalyzed
method and radical chemistry may lead to an efficient alkylation
procedure for fullerene.5e,o Herein, we report a novel cobalt-
catalyzed highly selective hydroalkylation of C60 with active alkyl
bromides 1 that affords the monoalkyl-functionalized fullerenes
2 in good to high yields under mild reaction conditions (eq 1).
Moreover, we have successfully applied this method to the
synthesis of monosubstituted fullerenes bearing Zn-porphyrin,
G3-dendrimer, and fullerene dimer in good yields. Porphyrin- or
dendrimer-bound fullerenes and fullerene dimer, which were
previously prepared through the cycloaddition reactions, have been
already proved to be promising materials for the optoelectronic
The combination of transition-metal catalysis and free radical
reaction has emerged as a novel strategy for new efficient
synthetic methodologies.9,10 Recently, Oshima and co-workers
developed an efficient cobalt-catalyzed radical transformation of
alkenes with alkyl halides in the presence of Grignard reagents.10aꢀe
However, this methodology was not applicable for the funtiona-
lization of C60 because of the drawback of Grignard reagents
toward the alkylation of C60, as mentioned above.4 We envi-
sioned that, due to its facile radical accepting characteristics, the
selective monofunctionalization of C60 would become feasible by
the proper choice of transition-metal catalysts, alkyl halides, and
additives.
’ RESULTS AND DISCUSSION
Screening of the Reaction Conditions. Screening of various
transition-metal catalysts (10 mol %) and additives (3 equiv) in
wet 1,2-dichlorobenzene (ODCB) at room temperature for 50 h
under Ar atmosphere (Table 1) was carried out using C60 and
benzyl bromide (1a, 3 equiv). The reaction did not proceed
Received: May 30, 2011
Published: July 11, 2011
r
2011 American Chemical Society
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ARTICLE
Table 1. Optimization of the Reaction Conditionsa
reduction potentials; the reduction potentials (E0/V, Mx+ + xe h
M0)13 of Mn (ꢀ1.185), Zn (ꢀ0.7618), and Fe (ꢀ0.447) have
abilities enough to reduce Co2+ to Co0 or I (ꢀ0.28), while Cu
(0.521) additive cannot reduce Co2+. These results indicate that
the present catalytic hydroalkylation proceeds via a mechanism
involving Co(0 or I).
Other cobalt catalysts having different counteranions and
ligands were also examined. In the presence of Mn additive,
the reaction gave poorer product conversions when CoCl2dppe
catalyst was replaced with CoBr2dppe or CoI2dppe catalyst
(entries 8 and 9). The reaction with other cobalt catalysts having
bidentate ligands, such as CoCl2dppm [dppm = bis(diphenyl-
phosphino)methane] and CoCl2dppf [dppf = bis(diphenyl-
phosphino)ferrocene], were also active, affording 2a in 71%
and 73% yields, respectively (entries 10 and 11). In contrast to
the case for cobalt catalysts bearing bidentate ligands, the cobalt
catalyst having monodentate ligand, such as CoI2(PPh3)2, was
inactive (entry 12).
In addition to cobalt catalysts, we also tested several other
transition metal catalysts, such as Pd, Rh, and Ni with Mn
additive. Pd catalysts having bidentate ligand (dppe) or mono-
dentate ligands (P(OPh)3 and PPh3) were not effective to
produce 2a (entries 13ꢀ15). In sharp contrast, the reaction
proceeded with Rh- and Ni-catalysts bearing phosphine ligands.
For example, RhClPPh3 catalyst gave 29% yield of 2a, while the
phosphine-free [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene)
catalyst was inactive (entries 16 and 17). NiCl2dppf and NiCl2-
(PPh3)2 catalysts showed lower product conversions, producing
2a in 20% and 24% yields, respectively (entries 18 and 19). These
results suggest that the high efficiency of present reaction not
only depends on the transition metal species, but also highly
depends on the attached phosphine ligands.
Overall, the hydroalkylation of C60 with CoCl2dppe catalyst
and Mn additive has been proved to be the most efficient
condition. It should be noted that without H2O the reaction
did not proceed at all. Moreover, in the presence of oxygen, the
reaction results in a very low conversion of C60. Therefore, all of
the handlings were conducted in the glovebox under argon gas.
Co-Catalyzed Synthesis of Various Monoalkylated Full-
erenes. Under optimized conditions, the scope of Co-catalyzed
hydroalkylation of C60 with various active alkyl bromides was
examined (Table 2). All of the reactions were monitored by TLC
and HPLC analysis, and the corresponding products 2 were
isolated by using silica gel column chromatography; it was not
necessary to use HPLC for purification of the products. In each
case, a very small amount of the inseparable multiadducts was
observed as side-products,12 but they were separated by the silica
gel column chromatography. A variety of functional groups, such
as ester, cyano, methoxy, and R-methyl groups on benzyl moiety,
were tolerated, affording the monoalkylated products 2bꢀf in
good yields with excellent monoalkylation-selectivity (entries
1ꢀ5). It should be noted that the products 2bꢀf showed a high
solubility in toluene or o-dichlorobenzene. Moreover, the reac-
tion of C60 with benzyl bromides having an ester (1b and 1c) or a
cyano group (1d) afforded a small amount of the single bonded
fullerene dimers as byproducts (Figure 1).12 Allyl bromide,
cinnamyl bromide, propargyl bromide, and 1-bromo-2-butyne
were also active alkyl sources, producing the corresponding
products 2gꢀj in good to high yields (entries 6ꢀ9). Ethyl
2-bromoacetate 1k showed a lower reactivity, giving 2k in 36%
yield even under longer reaction times (96 h) (entry 10). It
should be noted that although the reaction of C60 with benzyl
additive
yield of
2a (%)b
recovery of
C60 (%)c
entry
catalyst
(3.0 equiv)
1
2
CoCl2dppe
None
none
Mn
Mn
Mn
Fe
0
96
94
88
(8)d
12
25
97
39
24
17
14
85
88
93
84
58
89
68
60
0
3
CoCl2
4
4
CoCl2dppe
CoCl2dppe
CoCl2dppe
CoCl2dppe
CoBr2dppe
CoI2dppe
88 (76)d
5
80e
56
0
6
Zn
7
Cu
8
Mn
Mn
Mn
Mn
Mn
Mn
Mn
Mn
Mn
Mn
Mn
Mn
40
45
71
73
0
9
10
11
12
13
14
15
16
17
18
19
CoCl2dppm
CoCl2dppf
CoI2(PPh3)2
PdCl2dppe
PdCl2[P(OPh)3]2
Pd(PPh3)4
RhCl(PPh3)3
[Rh(COD)Cl]2
NiCl2dppf
0
0
5
29
2
20
24
NiCl2(PPh3)2
a Reaction conditions: A 1,2-dichlorobenzene (ODCB, 4 mL) solution
of catalyst (10 mol %) and additive (3 equiv) under Ar atmosphere was
stirred for 1 h at 25 °C. Next, C60 (21.6 mg), H2O (10 equiv), and benzyl
bromide (3 equiv) were added, and the resulting mixture was stirred for
50 h at 25 °C. b 1H NMR yield determined using 2,4,6-trimethylpyridine
as an internal standard. c HPLC yield determined using C70 as an internal
standard. d Isolated yield. e The reaction time is 5 days.
without Co catalyst or Mn reductant (entries 1 and 2). Combi-
nation of a phosphine-free CoCl2 catalyst with Mn additive gave
a low conversion, producing 2a in a very low yield (entry 3). To
our delight, CoCl2dppe catalyst [dppe = bis(diphenylphos-
phino)ethane] combined with Mn additive11 showed a high
reactivity, affording 2a in 76% isolated yield (entry 4). HPLC
analysis and 1H and 13C NMR spectra showed a high selectivity
for the monoaddition product 2a. As byproduct, a very small
amount of the inseparable multiadducts was produced together
with recovered C60 (8%) (see the Supporting Information).12
The high selectivity of the monoadduct should be attributed to
the mild reaction conditions. The metal additives other than Mn
were also tested. Fe additive gave an appreciable conversion,
although a prolonged reaction time (5 days) was needed (entry 5).
It should be noticed that under additional prolonged reaction
times (5 days plus 1 day), the reaction with Fe additive did not
increase the amount of multiadducts, although with Mn additive
the amount of multiadducts was slightly increased under a
prolonged reaction time (50 h plus 24 h) and the yield of 2a
was decreased. Zn powder was also active, although the yield was
lower than that of Mn and Fe, while copper additive was
completely inactive (entries 6 and 7). The diverse activity of
metal additives may be due to the difference of their standard
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Table 2. Co-Catalyzed Hydroalkylation of C60 with Various Active Alkyl Bromidesa
entry
RꢀBr
1
amount of 1 (equiv)
time (h)
2
yield of 2 (%)b
recovery of C60 (%)b
1
2
3-CO2MeꢀC6H4CH2Br
4-CO2MeꢀC6H4CH2Br
2-NCꢀC6H4CH2Br
4-MeOꢀC6H4CH2Br
C6H5CH(Me)Br
1b
1c
1d
1e
1f
1.5
1.5
1.5
2.0
3.0
4.0
1.5
3.0
3.0
3.0
48
48
40
48
50
86
34
86
60
96
2b
2c
2d
2e
2f
58
66
51
66
48
74
78
75
42
36
30
15
39
21
24
15
13
12
41
38
3
4
5
6
CH2dCHCH2Br
1g
1h
1i
2g
2h
2i
7
(E)-C6H5CHdCHCH2Br
CHtCCH2Br
8
9
MeCtCCH2Br
1j
2j
10
EtO2CCH2Br
1k
2k
a Reaction conditions: A 1,2-dichlorobenzene (ODCB, 4 mL) solution of CoCl2dppe (10 mol %) and Mn (3 equiv) under Ar atmosphere was stirred for
1 h at 25 °C. Next, C60 (21.6 mg), H2O (10 equiv), and RBr (1.5ꢀ4.0 equiv) were added, and the resulting mixture was stirred for 34ꢀ96 h at 25 °C.
b Isolated yields.
the single bonded fullerene dimers produced in the reactions of
C60 with 2l, 2m, and 2n were unable to identify.
Figure 1. Two isomers of single bonded fullerene dimer 3b.
bromides having an electron-withdrawing substituent on ben-
zene ring, such as 1b, 1c, and 1d, produced a small amount of the
single bonded fullerene dimers 3 in ∼3% yields (for the
representative structure 3b, see Figure 1), the corresponding
dimers were unable to identify in the other cases due to their
extremely small amounts. In contrast to these active alkyl
bromides, inactive alkyl bromides, such as butyl bromide or
bromomethylcyclopropane, did not undergo the present cataly-
tic hydroalkylation at elevated temperatures.
Co-Catalyzed Synthesis of Zn-Porphrin- and Dendrimer-
Bound Hydrofullerenes, and Fullerene Dimer. The present
cobalt catalysis was successfully applied to the construction of
fullerene-bound macromolecules, which may be useful for versa-
tile electronic materials.1d,6,7 For example, under the standard
conditions, C60 reacted with benzyl bromide derivative 1l having
a zinc porphyrin (ZnP) moiety at para-position, affording the
ZnP-C60 product 2l in 30% yield, while in the presence of Fe
additive instead of Mn it gave 2l in 40% yield (eq 2).1d,10
Similarly, the reaction of C60 with single benzylic bromide group
at the focal point of the third-generation dendrimer [G-3]-Br 1m
gave the fullerene-bound dendrimer 2m in 48% yield (eq 3).1d,11
This dendritic macromolecule dramatically improved the solu-
bility of fullerene in various organic solvents. This method also
provides an interesting opportunity for synthesis of the poten-
tially useful fullerene dimer containing two fullerene units
bridged through electroactive spacer.5h,8 The reaction of 1,5-
bis(bromomethyl)-1,4-bis(30,70-dimethyloctyloxy)benzene 1n
and 2 mol equiv of C60 under standard reaction conditions
produced fullerene dimer 2n in 39% yield, which showed a good
solubility in toluene and ODCB (eq 4).5h,12 It was also noted that
Reaction Mechanism. A plausible mechanism for the present
transformation is shown in Scheme 1. Initially, the Co(II)
complex is reduced to the electron-rich Co(0) species by Mn
reductant.11 A single electron transfer from the Co(0) complex
to benzyl bromide 1a generates benzyl radical A along with Co(I)
complex B. Addition of the radical A to C60 forms the delocalized
fullerenyl-radical intermediate C. Intermediate C would be
trapped by the Co(I) complex B to afford the delocalized
fullerenylꢀcobalt(II) complex D. Protonolysis of intermediate
D produces the corresponding product 2a along with the Co(0)
catalyst upon treatment with Mn reductant. Of course, the
reduction of the Co(II) to Co(I) may occur at the beginning,
instead of the reduction to Co(0), and the catalytic cycle may
proceed through Co(I) species.
Several experimental observations support the proposed me-
chanism. When C60 was treated with 1a under standard condi-
tions by using n-Bu3SnH, instead of H2O, 2a was obtained in
good yield.4b Furthermore, as mentioned in Table 2 (entry 1),
the reaction of C60 with 1b gave the single bonded fullerene
dimer RC60ꢀC60R 3b as a side-product in 3% yield (Figure 1).
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ARTICLE
Scheme 1. Proposed Reaction Mechanism
before its reaction with the MLn(n + 1)X species, which may lead
to the formation of the oxidative addition complex RꢀMLn(n + 2)X.
The diverse reactivity of the transition metals suggests that the
combination of different metals and ligands highly affects the
reactivity of LnM(n + 1)X.9 It is also known that a certain
transition-metal catalyst undergoes facile formation of a transi-
tion-metalꢀC60 complex.16,17 It has been reported that Pd
complexes having phosphine ligands react readily with C60 under
ambient temperature, forming LnPdꢀC60 complexes in high
yields.15 Indeed, in the reaction with Pd(PPh3)4 catalyst (Table 1,
entry 15), a very small amount of the corresponding Pd-
(PPh3)2ꢀC60 complex was detected, which was confirmed by
HPLC analysis and 1H NMR spectra as compared to an authentic
sample prepared from the reported method.16d Ni, Rh, and Co
complexes have also been reported to react with C60, although
the use of a higher reaction temperature or special ligands was
needed.17
An alternative reaction pathway, such as the initial generation
of C60 radical anion through the reduction of C60 with metal
reductant followed by reaction with benzyl bromide,3a is unlikely
because the reaction of C60 and H2O in the absence of alkyl
bromides under otherwise the standard conditions gave a trace
amount of dihydrofullerene (C60H2) as shown in eq 7. This
result is completely different from the reported zinc-mediated
monoalkylation of C60, in which Meier and co-workers reported
that the reaction of C60 with H2O in the presence of excess
amounts of zinc dust gave C60H2 in 50% yield.3a
1H NMR spectra showed that this dimer consists of a 1:1 mixture
of two isomers.12 Many experimental and theoretical studies on
those dimers demonstrated that they are generally formed by
coupling of RC60• radicals.14 These observations suggest that the
present reaction must proceed through the formation of the
fullerenyl radical intermediate C. Formation of a very small
amount of dimer also indicates the conversion of fullerenyl-
radical C to fullerenylꢀcobalt(II or III) complex D is a rapid step.
Moreover, the reaction of C60 and 1b in the presence of D2O
instead of H2O under otherwise the standard conditions gave the
corresponding product 2b0 in 46% yield with 94% deuterium
incorporation, implying that a proton in product 2a was derived
from the added water (eq 6). A similar reaction was conducted
with a 1:1 mixture of H2O and D2O, yielding the protonated and
deuterated products 2b and 2b0 in a 54:46 ratio (eq 5). The yield
difference between H2O and D2O is due to the isotope effect of
OꢀD and OꢀH bond,15 which reflects the hydrolysis step of the
intermediate D.
’ CONCLUSION
We have found a new and efficient Co-catalyzed selective
monoalkylation of C60 with active alkyl bromides. A wide range
of functional groups are tolerated in the present catalytic hydro-
alkylation. In contrast to the classical organometallic addition
methods, the present catalytic reaction is carried out under very
mild reaction conditions with remarkably higher yields. Mono-
substituted zincporphyrinꢀfullerene, fullerene-bound dendri-
mer, and fullerene dimer have thus been synthesized in good
yields for the first time, which are otherwise difficult to obtain.
The present hydroalkylation of C60 seems to proceed through a
Co-catalyzed generation of an active alkyl radical followed by
addition to C60. Cobalt catalyst combined with Mn reductant in
the presence of H2O under argon is crucial for the efficient and
selective formation of the fullerene monoadducts. Investigation
on further catalytic functionalization of fullerenes and application
to materials science are in progress.
’ EXPERIMENTAL PROCEDURES
Materials. Anhydrous 1,2-dichlorobenzene (Aldrich), toluene, car-
bon disulfide, hexane, (WAKO), transition metal catalysts, reductants
(Aldrich), n-Bu3SnH (Aldrich), and alkyl bromides (1) (Aldrich) were
purchased and used as received. CoX2(ligand)18 and zinc porphyrin
(ZnP) benzyl bromide 1l19 were prepared following the reported
A reason for the yield difference of 2a depending on transition
metals (Co, Pd, Ni, and Rh: Table 1, entries 4, 13ꢀ15, 16, and
18,19) is perhaps due to the reactivity difference of the LnM-
(n + 1)X (Ln = ligand; X = halogen) complex, which is similar to
the intermediate B in Scheme 1, toward R• (eq 6). To obtain a
high product yield, the alkyl radical (R•) must react with C60
1
literature. The structures of products were determined by using H
NMR, 13C NMR, HMRS, and by comparison of representative products
2a,3a,19 2f,3d 2g,3a,5j,20 2i,21 and 2k3a with reported literature.
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Representative Procedures of Co-Catalyzed Hydroalkyla-
tion of C60 and Benzyl Bromide. A suspension of CoCl2dppe
(1.6 mg, 0.003 mmol) and Mn (5 mg, 0.09 mmol) in 1,2-dichloroben-
zene (ODCB, 4 mL) was stirred for 1 h under Ar atmosphere at 25 °C.
To the suspension were added C60 (21.6 mg, 0.03 mmol), benzyl
bromide (11 μL, 0.09 mmol), and H2O (5.4 μL, 0.3 mmol) subsequently
in a glovebox. The reaction mixture was stirred at 25 °C for 50 h and
monitoredbyTLCandHPLCanalysis(elutionwithtolueneat0.6mL/min
flow rate, detection at 320 nm, 4 °C). The mixture was filtered through a
short florisil pad using 1,2-dichlorobenzene as an eluent. After concen-
tration, the residue was purified with silica gel chromatography (toluene/
hexane = 1/4) to afford 2a in 76% yield (18.5 mg).
Methyl 3-[([60]Fulleren-1(2H)-yl)methyl]benzoate (2b).
Dark brown solid; soluble solvents: CHCl3, toluene, ODCB; 1H
NMR (500 MHz) δ 3.99 (3H, s), 4.81 (2H, s), 6.61 (1H, s), 7.62
(1H, t, J = 8.0 Hz), 8.02 (1H, d, J = 8.0 Hz), 8.13 (1H, d, J = 8.0 Hz), 8.52
(1H, s); 13C NMR (125 MHz) δ 52.35, 52.65, 59.12, 65.64, 128.84,
129.05, 130.62, 132.44, 135.85, 136.18, 136.27, 136.33, 139.97, 140.23,
141.61, 141.68, 141.90, 141.99, 142.08, 142.23, 142.58, 142.61, 143.25,
144.57, 144.76, 145.43, 145.46, 145.56, 145.82, 146.18, 146.23, 146.29,
146.44, 146.46, 146.93, 147.37, 147.54, 153.64, 154.83, 166.98; UVꢀvis
λmax/nm (CHCl3) 256, 307, 327, 433; HRMS (ESI, positive) calcd for
C69H10O2Na [M + Na]+, 893.0573; found, 893.0567.
Methyl 3-[([60]Fulleren-1(2D)-yl)methyl]benzoate (2b0).
Dark brown solid; soluble solvents: CHCl3, toluene, ODCB; 1H
NMR (400 MHz, CDCl3/CS2 = 1/4) δ 3.96 (3H, s), 4.82 (2H, s),
7.60 (1H, t, J = 7.6 Hz), 8.00 (1H, d, J = 7.6 Hz), 8.12 (1H, d, J = 7.6 Hz),
8.48 (1H, s); 13C NMR (100 MHz, CDCl3/CS2 = 1/4) δ 51.72, 52.41,
58.47 (CꢀD, t, J = 21.5 Hz), 65.11, 128.42, 128.72, 130.33, 132.02,
135.18, 135.76, 135.78, 135.90, 139.61, 139.84, 141.18, 141.24, 141.43,
141.63, 141.72, 142.15, 142.80, 144.10, 144.28, 144.95, 144.97, 145.06,
145.14, 145.31, 145.63, 145.75, 145.81, 145.96, 145.99, 146.46, 146.86,
147.02, 152.94, 153.01, 154.13, 165.55; UVꢀvis λmax/nm (CHCl3) 255,
307, 326, 433; HRMS (ESI, positive) calcd for C69H9DO2Na [M +
Na]+, 894.0636; found, 894.0633.
Methyl 4-[([60]Fulleren-1(2H)-yl)methyl)benzoate (2c). Dark
brown solid; soluble solvents: CHCl3, toluene, ODCB; 1H NMR
(400 MHz, CDCl3/CS2 = 1/4) 3.94 (3H, s), 4.85 (2H, s), 6.61 (1H, s),
7.87 (2H, d, J = 8.4 Hz), 8.16 (2H, d, J = 8.4 Hz); 13C NMR (100 MHz,
CDCl3/CS2 = 1/4) 51.62, 52.85, 59.09, 65.18, 129.40, 129.68, 131.00,
135.72, 135.86, 139.58, 139.91,140.41, 141.20, 141.30, 141.44, 141.58,
141.66, 141.76,142.20, 142.21, 142.86, 144.13, 144.31, 144.98, 145.02,
145.08, 145.17, 145.33, 145.65, 145.79, 145.86, 146.01, 146.03, 146.40,
146.90, 147.06, 152.94, 154.03, 165.47; UVꢀvis λmax/nm (CHCl3) 256,
308, 326, 433; HRMS (ESI, negative) calcd for C69H9O2 [M ꢀ H]ꢀ,
869.0608; found, 869.0610.
141.84, 141.90, 142.07, 142.42, 143.09, 144.44, 144.57, 145.24, 145.29,
145.33, 145.65, 146.03, 146.10, 146.23, 146.25, 146.27, 146.83, 147.16,
147.30, 153.75, 155.30, 159.00; UVꢀvis λmax/nm (CHCl3) 256, 308,
326, 433; HRMS (ESI, positive) calcd for C68H10ONa [M + Na]+,
865.0624; found, 865.0621.
2-((E)-Cinnamyl)-1,2-dihydro[60]fullerene (2h). Dark brown
solid; soluble solvents: CHCl3, toluene, ODCB; 1H NMR (500 MHz,
CDCl3/CS2 = 1/4) δ 4.35 (2H, d, J = 7.0 Hz), 6.61 (1H, s), 7.18ꢀ7.35
(3H, m), 7.44 (2H, t, J = 7.5 Hz), 7.64 (2H, d, J = 7.5 Hz); 13C NMR
(125 MHz, CDCl3/CS2 = 1/4) δ 50.31, 58.68, 64.71, 124.37, 126.66,
127.98, 128.72, 136.00, 136.21, 136.57, 136.74, 140.13, 140.21, 141.54,
141.56, 141.86, 141.94, 142.16, 142.46, 143.15, 144.47, 144.61, 145.28,
145.30, 145.33, 145.44, 145.70, 146.06, 146.08, 146.13, 146.30, 147.19,
147.34, 153.68, 155.31; UVꢀvis λmax/nm (CHCl3) 257, 326, 433;
HRMS (ESI, negative) calcd for C69H10ꢀH [M ꢀ H]ꢀ, 837.0710;
found, 837.0712.
2-(But-2-ynyl)-1,2-dihydro[60]fullerene (2j). Dark brown
1
solid; soluble solvents: toluene, ODCB, low in CHCl3; H NMR
(500 MHz, CDCl3/CS2 = 1/4) δ 2.16 (3H, t, J = 2.5 Hz), 4.27 (2H,
q, J = 2.5 Hz), 6.70 (1H, S); 13C NMR (125 MHz, CDCl3/CS2 = 1/4) δ
3.96, 37.42, 59.24, 63.92, 74.89, 81.29, 140.02, 140.06, 141.48, 141.60,
141.81, 141.86, 142.18, 142.37, 142.39, 142.87, 143.02, 144.38, 144.52,
145.15, 145.22, 145.25, 145.42, 145.58, 145.88, 145.97, 146.02, 146.21,
146.78, 147.08, 147.26, 153.54, 154.35; UVꢀvis λmax/nm (CHCl3) 256,
326, 433; HRMS (ESI, negative) calcd for C64H6ꢀH [M ꢀ H]ꢀ,
773.0397; found, 773.0395.
2-(4-(ZnP)-benzyl)-1,2-dihydro[60]fullerene (2l). Dark pur-
ple red solid; soluble solvents: ODCB, low in CHCl3 and toluene; 1H
NMR (500 MHz, CDCl3/CS2 = 1/4) δ 5.06 (2H, s), 6.80 (1H, s)
7.71ꢀ7.76 (9H, m), 8.16ꢀ8.18 (8H, m), 8.35 (2H, d, J = 8.5 Hz),
8.87ꢀ8.90 (8H, m); 13C NMR (125 MHz, CDCl3/CS2 = 1/4) δ 53.06,
59.18, 65.85, 120.94,126.37, 127.24, 129.38, 131.60, 131.92, 131.99,
134.21, 134.45, 135.83, 136.02, 139.68, 139.97, 141.35, 141.38, 141.65,
141.74, 141.92, 142.30, 142.41, 142.77, 142.92, 144.30, 144.40, 145.10,
145.17, 145.30, 145.46, 145.90, 145.96, 146.05, 146.12, 146.59, 149.72,
149.89, 149.97, 153.42, 154.80; UVꢀvis λmax/nm (CHCl3) 291, 299,
425, 550; HRMS (ESI, positive) calcd for C105H30N4ZnNa [M + Na]+,
1433.1654; found, 1433.1650.
2-(3,5-Bis(3,5-bis(3,5-dimethoxybenzyloxy)benzyloxy)-
benzyl)-1,2-dihydro[60]fullerene (2m). Dark brown solid; solu-
ble solvents: THF, CHCl3, toluene, ODCB; 1H NMR (500 MHz,
CDCl3/CS2 = 1/4) δ 3.77 (24H, s), 4.62 (2H, s), 4.92 (8H, s), 5.10 (4H,
s), 6.39 (4H, t, J = 2.5 Hz), 6.51ꢀ6.54 (11H, m), 6.70 (4H, d, J = 2.5 Hz),
6.72 (1H, t, J = 2.5 Hz), 7.01 (2H, d, J = 2.5 Hz); 13C NMR (125 MHz,
CDCl3/CS2 = 1/4) δ 53.04, 55.36, 58.69, 65.63, 70.01, 70.07, 100.01,
101.60, 101.89, 105.23, 105.36, 106.08, 110.69, 135.84, 136.21, 138.11,
139.00, 139.48, 139.85, 140.06, 141.52, 141.58, 141.79, 141.95, 142.01,
142.19, 142.49, 142.53, 143.09, 144.48, 144.65, 145.29, 145.35, 145.38,
145.80, 146.17, 146.22, 146.31, 146.38, 147.03, 147.30, 147.47, 153.90,
155.40, 159.90, 160.16, 160.96; UVꢀvis λmax/nm (CHCl3) 256, 308,
326, 434; HRMS (ESI, positive) calcd for C117H60O14Na [M + Na]+,
1711.3875; found, 1711.3868.
2-[([60]Fulleren-1(2H)-yl)methyl]benzonirile (2d). Dark
brown solid; soluble solvents: toluene, ODCB, low in CHCl3; 1H
NMR (500 MHz, CDCl3/CS2 = 1/4) δ 5.05 (2H, s), 6.65 (1H, s),
7.54 (1H, t, J = 7.5 Hz), 7.72 (1H, t, J = 7.5 Hz), 7.82 (1H, d, J = 7.5 Hz),
7.94 (1H, d, J = 7.5 Hz); 13C NMR (125 MHz, CDCl3/CS2 = 1/4) δ
50.56, 59.77, 65.21, 115.06, 117.53, 128.00, 132.12, 132.20, 132.95,
136.01, 136.17, 139.29, 139.46, 140.08, 141.28, 141.46, 141.68, 141.83,
141.86, 142.29, 142.35, 142.96, 144.19, 144.46, 145.09, 145.15, 145.23,
145.34, 145.48, 145.72, 145.91, 145.97, 146.15, 146.47, 147.01, 147.21,
152.78, 153.08; UVꢀvis λmax/nm (CHCl3) 255, 309, 325, 432; HRMS
(ESI, positive) calcd for C68H7NNa [M + Na]+, 860.0471; found,
860.0469.
2-(4-Methoxybenzyl)-1,2-dihydro[60]fullerene (2e). Dark
brown solid; soluble solvents: CHCl3, toluene, ODCB; 1H NMR
(500 MHz, CDCl3/CS2 = 1/4) δ 3.88 (3H, s), 4.71 (2H, s), 6.62
(1H, s), 7.04 (1H, d, J = 8.5 Hz), 7.72 (1H, d, J = 8.5 Hz); 13C NMR
(125 MHz, CDCl3/CS2 = 1/4) δ 52.24, 54.96, 58.98, 66.08, 114.03,
127.57, 132.28, 135.90, 136.23, 139.84, 140.05, 141.45, 141.51, 141.79,
(2,5-Bis(2,6-dimethylheptyloxy)-1,4-phenylene)bis(methy-
lene)difullerene (2n). Dark brownish red solid; soluble solvents:
1
CHCl3, toluene, ODCB; H NMR (400 MHz, CDCl3/CS2 = 1/4) δ
0.84 (6H, d, J = 2.8 Hz), 0.85 (6H, d, J = 3.2 Hz), 1.00 (6H, d,
J = 6.8 Hz), 1.14ꢀ1.51 (18H, m), 1.66ꢀ1.70 (2H, m), 1.79ꢀ1.85
(2H, m), 1.92ꢀ1.99 (2H, m), 4.12 (2H, d, J = 6.8 Hz), 4.13 (2H, d, J =
6.8 Hz), 4.80ꢀ4.90 (4H, m), 6.66 (2H, s), 7.37 (2H, s); 13C NMR
(100 MHz, CDCl3/CS2 = 1/4) δ 19.68, 22.71, 22.79, 25.04, 28.14,
30.15. 36.50, 37.58, 39.37, 46.06, 58.89, 65.75, 66.97, 116.73, 124.51,
135.17, 135.25, 135.86, 135.87, 139.37, 139.81, 141.03, 141.20, 141.34,
141.45, 141.56, 141.80, 142.12, 142.83, 144.12, 144.25, 144.90, 144.95,
145.28, 145.70, 145.77, 145.90, 146.53, 146.80, 147.01, 150.75, 153.57,
12846
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Journal of the American Chemical Society
ARTICLE
155.22, 155.30; UVꢀvis λmax/nm (CHCl3) 255, 326, 435; HRMS (ESI,
negative) calcd for C148H49O2 [M ꢀ H]ꢀ, 1857.3732; found, 1857.3733.
Single Bonded Fullerene Dimer (3b). A 1:1 mixture of two
isomers; dark brown solid; soluble solvents: ODCB, low in CHCl3 and
toluene; 1H NMR (500 MHz, CDCl3/CS2 = 1/4) δ 3.87 (6H, s), 4.52
(1H, d, J = 5.5 Hz), 4.55 (1H, d, J = 5.5 Hz), 4.75 (2H, d, J = 13.0 Hz),
7.44 (2H, t, J = 8.0 Hz), 7.78ꢀ7.79 (2H, m), 7.98ꢀ8.00 (2H, m), 8.30
(1H, s), 8.32 (1H, s); 13C NMR (125 MHz, CDCl3/CS2 = 1/4) δ 48.78,
49.08, 51.77, 60.30,128.13, 128.66, 128.68, 130.20, 131.78, 134.88, 135.58,
138.00, 138.96, 139.00, 139.41, 139.44, 140.97, 141.05, 141.89, 141.93,
142.01, 142.16, 142.38, 142.57, 142.59, 142.61, 142.62, 142.65, 142.95,
142.98, 143.01, 143.04, 143.17, 143.19, 143.23, 143.29, 143.35, 143.70,
143.79, 143.86, 144.09, 144.09, 144.10, 144.14, 144.16, 144.21, 144.23,
144.26, 144.30, 144.32, 144.37, 144.39, 144.52, 144.55, 144.58, 144.77,
144.97, 145.08, 145.54, 145.57, 145.58, 145.61, 145.64, 146.59, 146.79,
146.84, 146.86, 146.93, 147.12, 147.22, 147.24, 147.48, 148.30, 148.42,
148.50, 148.52, 148.59, 148.71, 148.73, 148.96, 149.32, 152.54, 152.83,
153.62, 153.79, 156.12, 165.82; UVꢀvis λmax/nm (CHCl3) 257, 331, 445;
HRMS (ESI, positive) calcd for C138H18O4Na [M + Na]+, 1761.1097;
found, 1761.1102.
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’ ASSOCIATED CONTENT
S
Supporting Information. Experimental procedures and
b
characterization data. This material is available free of charge via
the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
tjin@m.tohoku.ac.jp; yoshi@m.tohoku.ac.jp
’ ACKNOWLEDGMENT
We thank the faculty members of the Instrumental Analysis
Center at Tohoku University for the measurement of NMR and
mass spectra. S.L. acknowledges the support of the China
Scholarship Council (CSC).
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