Evolution of late transition-metal-catalyzed intermolecular reductive coupling reaction of [60]fullerene and N-sulfonylaldimines: Competing formation of hydrobenzylated [60]fullerenes and 1,2-dihydrofullerene

Article abstract of DOI:10.1002/ejoc.201200055

A system based on late transition-metal halides, phosphanes, water, and reducing agents in 1,2-dichlorobenzene can efficiently catalyze the intermolecular reductive coupling of [60]fullerene with N-sulfonylaldimines to afford novel 1,2-hydrobenzylated [60]fullerene derivatives. We found that both group VII B metals (cobalt, rhodium, iridium) and group VIII B metals (nickel, palladium, platinum) perform this coupling reaction. A control experiment in the absence of aldimines produced C₆₀H₂, which showed that the reaction might proceed via a [60]fullerene metal complex [M(η²-C₆₀)(ligand)]. An isotope labeling experiment with D₂O as deuterium source resulted in deuterioaryzilation with deuterium bonded to the sp³-carbon of C₆₀, providing evidence of a five-membered azametallacycle intermediate. Evaluation of the scope of reductive coupling reaction with versatile aldimines gave access to the hydroaryzilation products. All the reductive coupling products were completely characterized by IR and NMR spectroscopy and ESI mass spectrometry. A possible reaction mechanism based on these results is proposed. This discovery of the formation of reductive coupling compounds and metal-catalyzed formation of C₆₀H₂ are both new to metal catalysis and fullerene chemistry. A system based on late transition-metal halides, phosphanes, water, and reducing agents in o-DCB can efficiently catalyze intermolecular reductive coupling between [60]fullerene and N-sulfonylaldimines to afford new 1,2-hydrobenzylated [60]fullerene derivatives. The reaction yields are moderate, due to the formation of C₆₀H₂ as a byproduct. A possible reaction mechanism is proposed. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Full text of DOI:10.1002/ejoc.201200055

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FULL PAPER
DOI: 10.1002/ejoc.201200055
Evolution of Late Transition-Metal-Catalyzed Intermolecular Reductive
Coupling Reaction of [60]Fullerene and N-Sulfonylaldimines: Competing
Formation of Hydrobenzylated [60]Fullerenes and 1,2-Dihydrofullerene
Venkatachalam Rajeshkumar[a] and Shih-Ching Chuang*[a]
Keywords: Fullerenes / Transition metals / C–C coupling / Reductive coupling
A system based on late transition-metal halides, phosphanes,
water, and reducing agents in 1,2-dichlorobenzene can ef-
ficiently catalyze the intermolecular reductive coupling of
[60]fullerene with N-sulfonylaldimines to afford novel 1,2-
hydrobenzylated [60]fullerene derivatives. We found that
both group VIIB metals (cobalt, rhodium, iridium) and
group VIIIB metals (nickel, palladium, platinum) perform
this coupling reaction. A control experiment in the absence
of aldimines produced C60H2, which showed that the reac-
tion might proceed via a [60]fullerene metal complex [M(η2-
deuterium source resulted in deuterioaryzilation with deute-
rium bonded to the sp3-carbon of C60, providing evidence of
a five-membered azametallacycle intermediate. Evaluation
of the scope of reductive coupling reaction with versatile ald-
imines gave access to the hydroaryzilation products. All the
reductive coupling products were completely characterized
by IR and NMR spectroscopy and ESI mass spectrometry. A
possible reaction mechanism based on these results is pro-
posed. This discovery of the formation of reductive coupling
compounds and metal-catalyzed formation of C60H2 are both
new to metal catalysis and fullerene chemistry.
C60)(ligand)]. An isotope labeling experiment with D2O as
ric amounts of nickel complexes;[5] this study is to date the
only example of [60]fullerene functionalization mediated by
nickel complexes. More recently, Jin and Yamamoto et al.
established that cobalt catalysts, with Mn as a reductant
and H2O as a proton source, can efficiently provide
monohydroalkylated fullerenes from C60 and alkyl brom-
ides at ambient temperature through a radical mecha-
nism.[3l]
On the other hand, transition-metal-catalyzed reductive
couplings of two organic π-frameworks, such as alkyne/alk-
ene,[6] alkyne/carbonyl,[7] alkyne/imine,[8] or alkene/imine[9]
coupling reactions, constitute a convenient method for the
construction of C–C bonds in organic synthesis. Of these
reactions, reductive couplings of an alkyne with an aldehyde
or imine in particular afforded access to synthetically im-
portant allylic alcohols and allylic amines, respectively. To
the best of our knowledge, reductive coupling of two π-
components usually gives products in low yields when C60
Introduction
Functionalized fullerenes[1] have attracted great attention
because of their potential applications in the fields of bio-
logical and material sciences.[2] In this context, a number of
chemical reactions have been extensively developed, and
some of the [60]fullerene derivatives have shown consider-
able potential for applications in organic photovol-
taics.[2g–2p] Although a large variety of chemical reactions
have been discovered to derivatize fullerenes, transition-
metal-catalyzed reactions of fullerenes are comparatively
less developed. The relatively unexplored nature of metal-
mediated reactions with fullerenes might be the conse-
quence of the ease of formation of insoluble complexes,
low-yields of products, and difficulties in characterization.
Previous studies have recognized that some transition met-
als, such as palladium,[3a–3e] rhodium,[3f–3j] cobalt,[3k–3m]
manganese,[3n–3q] iron,[3r,3s] and copper,[3t–3v] can mediate
functionalization of the fullerene sphere. In this context, we
have recently also reported annulations of benzamides with
[60]fullerene through palladium(II)-catalyzed C–H bond ac-
tivation[4] to afford fullero-isoquinolinones. In 1998, Cheng
et al. first reported a nickel-catalyzed [2+2+2] cycloaddition
between C60 and a tethered diyne mediated by stoichiomet-
is used as a coupling partner, such as in the case of the
[1n]
synthesis of C120
.
On the other hand, metal-catalyzed
coupling has not been applied successfully in fullerene
chemistry. Such coupling with fullerenes might be ham-
pered by the highly reversible coordination processes of full-
erenes with transition metals.
Our continuing efforts in exploring the chemistry of
metal-catalyzed reactions of [60]fullerene promoted us to
investigate direct reductive coupling reactions between
[60]fullerene and imines for potential applications. Here we
disclose new late transition-metal-catalyzed coupling reac-
tions between [60]fullerene and N-sulfonylaldimines with
[a] Department of Applied Chemistry, National Chiao Tung
University,
Hsinchu, Taiwan 30010, R.O.C.
Fax: +886-35723764
E-mail: jscchuang@faculty.nctu.edu.tw
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200055.
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V. Rajeshkumar, S.-C. Chuang
FULL PAPER
water as proton source, to afford hydrobenzylated [60]fuller- (20 mol-%), containing a bidentate ligand, Zn as reducing
ene derivatives incorporating sulfonyl-protected amino agent, and water as proton source in anhydrous o-dichloro-
groups (Scheme 1). These reductive coupling reactions offer benzene (o-DCB, 6 mL) under N2 in a sealed tube at 120 °C
a previously inaccessible methodology that opens up a new for 24 h. We found (Entry 1, Table 1) that reductive cou-
route to a new class of fullerene derivatives, as well as a pling product 2a was isolated in a low yield (9%), together
metal-catalyzed method for the formation of C60H2.
with C60H2 (6%). The initial results encouraged us to focus
on developing efficient conditions for this reaction by sur-
veying different nickel complexes. Fortuitously, when we
changed the catalyst to NiBr2 with PPh3 as a ligand, we
obtained 2a in an improved yield (16%) together with
C60H2 in 30% yield (Table 1, Entry 2). In view of the above
results, we switched to a reaction with another prepared
nickel complex, NiCl2(PPh3)2; as expected, the reductive
coupling product 2a was obtained in a slightly higher yield
of 19% (22% based on converted C60, Entry 3). We then
examined other nickel complexes such as NiBr2(PPh3)2 or
NiBr2[P(p-tolyl)3]2 for this coupling reaction. Surprisingly,
when the reactions were performed with these complexes
under the standard conditions described above, the cou-
pling product 2a was isolated in slightly better yields [22
and 21%, respectively (29% and 27% based on converted
C60), Entries 4–5]. Under the standard conditions, we found
that NiBr2(phen) (phen = 1,10-phenanthroline) also pro-
moted this coupling reaction, to afford 2a in 13% yield to-
gether with a 26% yield of C60H2 (Entry 6). However, we
Scheme 1. Reductive coupling of [60]fullerene and N-sulfonyl ald-
imines.
Results and Discussion
To develop this interesting methodology and to broaden
its scope, we first produced variously substituted N-sulfonyl
aldimines 1a–y by reported procedures[10] and selected
imine 1a (Table 1) as a model substrate for screening of re-
action conditions. We then carried out the reaction between
C60 (36 mg, 0.050 mmol) and aldimine 1a (65 mg,
0.25 mmol) in the presence of nickel complex [Ni(dppe)Br2]
Table 1. Formation of 2a under various conditions.[a]
Entry
Catalysts (20%),
ligand
Reducing
agent
Proton
source
Solvents,
temperature [°C]
Yield of 2a
Yield of 3
Recovered C60
[%][c]
[%][b]
[%][c]
1
NiBr2(dppe)
NiBr2, PPh3
NiCl2(PPh3)2
NiBr2(PPh3)2
NiBr2[P(p-tolyl)3]2
Ni(Phen)Br2
NiBr2(PCy3)2
none
NiBr2(PPh3)2
NiBr2(PPh3)2
NiBr2(PPh3)2
NiBr2(PPh3)2
NiBr2(PPh3)2
NiBr2(PPh3)2
NiBr2(PPh3)2
NiBr2(PPh3)2
none
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
none
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Fe
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (100)
toluene (120)
9 (26) [31]
16 (23) [40]
19 (22) [32]
22 (29) [37]
21 (27) [35]
13 (16) [24]
0
0
6 (17)
30 (42)
27 (30)
17 (22)
17 (22)
26 (33)
0
0
64
29
12
25
24
20
85
92
95
97
50
89
29
29
45
0
2[d]
3
4
5
6
7
8
9
0
0
0
0
10[e]
11
12
13
14[f]
15[g]
16[h]
17[i]
18
19
9 (17) [24]
0
14 (26)
0
24 (33)
32 (45)
0
0
0
0
0
1-Cl-naphthalene (120) trace
CH3COOH o-DCB (120)
13 (18) [34]
0
0
0
none
H2O
H2O
H2O
H2O
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
96
98
81
NiBr2(PPh3)2
NiBr2(PPh3)2
0
Mn
trace
[a] Unless otherwise specified, all reactions were carried out with C60 (0.050 mmol), imine (0.25 mmol), catalyst (0.010 mmol, 20 mol-%),
Zn (0.25 mmol), and H2O (0.10 mmol) in dry o-DCB (6 mL) at 120 °C for 24 h under N2 in a sealed tube. [b] Isolated yields after column
chromatography. Values in parentheses are based on consumed C60. Values in square brackets are based on C60 involved in the catalytic
cycle, excluding that used in forming C60H2. [c] Yields were measured by HPLC analysis. [d] PPh3 (0.5 equiv.). [e] Reaction carried out
without purging with nitrogen gas. [f] Performed with acetic acid (2 equiv.). [g] Carried out with NiBr2(PPh3)2 (1.2 equiv.) and molecular
sieves (4 Å, 100 mg) at 120 °C for 24 h and then addition of excess H2O. [h] Reaction carried out in the absence of C60. [i] Reaction
performed in the absence of imine.
2
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Coupling of [60]Fullerene and N-Sulfonylaldimines
observed that NiBr2(PCy3)2 displayed no catalytic activity
Because the reductive coupling reaction had been suc-
for this reaction, likely due to the greater bulkiness of its cessful with Ni complexes, we further evaluated the per-
ligand (Entry 7). Importantly, the reaction also did not take formances of other transition metals of groups VII B and
place in the absence either of Ni complexes or of zinc (En- VIII B in this coupling reaction. Separate loading of palla-
tries 8–9). It is also noteworthy that the coupling product dium acetate (20 mol-%) with PPh3 as ligand proved totally
2a was not observed without purging of the reaction mix- ineffective for this coupling reaction (Table 2, Entry 1).
ture with nitrogen gas (Entry 10).
However, PdCl2(PPh3)2 yielded the coupling product 2a
Furthermore, we tested this catalytic reaction with dif- (15%, Entry 2). To our surprise, we observed only a limited
ferent solvents, temperatures, and proton sources. We found amount of 2a (5%) when the reaction was performed with
that lowering the reaction temperature diminished the reac- PtCl2(PPh3)2 at 120 °C (Entry 3); formation of stable green-
tion yields (Entry 11) and observed that toluene was ineffec- colored C60 complexes Pt(η2-C60)(PPh3)2 (26%)[15] domi-
tive as a solvent for this coupling reaction; neither 2a nor nated this reaction. We observed no improvements in the
C60H2 was observed (Entry 12). We noted that use of 1- reaction yields on raising the reaction temperature to
chloronaphthalene as solvent brought about a deterioration 150 °C (Entry 4). The group VII B transition metals (Co
in the reaction performance, with only trace amounts of and Ir) also displayed comparable reactivity in this coupling
2a being obtained (Entry 13). The coupling product 2a was reaction. While we performed the reaction with CoI2 and
obtained in 13% yield when acetic acid was employed as (PPh3)2 as a catalyst,[6c] we isolated product 2a in 18% yield
proton source (Entry 14). A control experiment showed (Entry 5), comparable with results achieved with Ni and Pd.
that 2a was not obtained when the reaction was performed The prepared catalyst CoI2(PPh3)2 provided 2a in a low
with a stoichiometric amount of catalyst under anhydrous yield (8%) and produced C60H2 in 55% yield (Entry 6).
conditions in the presence of 4 Å molecular sieves (En- Further, we found that Wilkinson’s catalyst was ineffective
try 15); this confirmed the necessity of the proton source for this reductive coupling and afforded only C60H2 in 35%
at the initial stage. Another control experiment performed yield (Entry 7). Because Wilkinson’s catalyst afforded only
without C60 gave the expected hydrolysis products of the C60H2, we examined the catalytic activity of another form
aldimine (Entry 16). Treatment of C60 with H2O in the pres- of rhodium, RhCl3, in the presence of PPh3 (20 and 40 mol-
ence of zinc gave no products (Entry 17), demonstrating the %) as ligand. We found that its coupling ability was limited;
necessity of nickel catalysts. Other reductants, such as Fe only trace amounts of 2a were observed upon addition of
or Mn, hampered the reaction (Entries 18–19). Overall, the 20 mol-% of ligand (Entry 8). Increasing the molar percent-
overall reaction yields with 2a and C60H2 point to a mono- ages of ligands produced no 2a, but more C60H2 was iso-
functionalized fullerene reaction yield in the 30–60% range. lated (Entry 9). However, use of another chloro-bridged Rh
The isolated yields of 2a based on C60 involved in the cata- catalyst, [Cp*RhCl2]2, afforded coupling product 2a in a
lytic cycle, excluding that used in forming C60H2, are mostly 13% yield (Entry 10). It was interesting to find that the
in the 30–40% range.
analogous iridium complex [Cp*IrCl2]2 showed comparable
Table 2. Evaluation of catalytic activities of other group VII and VIII B metals in the formation of 2a.[a]
Entry
Catalyst (20%),
ligand
Reducing
agent
Proton
source
Solvent
(temperature) [°C]
Yield of 2a
Yield of 3
Recovered C60
[%][c]
[%][b]
[%][c]
1[e]
2
3
Pd(OAc)2, PPh3
PdCl2(PPh3)2
PtCl2(PPh3)2
PtCl2(PPh3)2
CoI2, PPh3
none
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
Zn
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (150)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
o-DCB (120)
0
0
99
15 (17) [24]
5 (26)
0
18 (24) [44]
8 (9) [22]
0
5 (40)
0
13 (14) [21]
17
0
27 (30)
0
0
34 (45)
55 (60)
35 (64)
0
45 (74)
32 (33)
35
11
74 (2)[d]
4
27 (11)[d]
5[e]
6
25
9
46
87
40
5
CoI2(PPh3)2
7
8
9
10
11
12[e]
RhCl(PPh3)3
RhCl3, PPh3 (1:1)
RhCl3, PPh3 (1:2)
[Cp*RhCl2]2
[Cp*IrCl2]2
0
76
IrCl3, PPh3
17 (69)
[a] Unless otherwise specified, all reactions were carried out with C60 (0.050 mmol), imine (0.25 mmol), catalyst (0.010 mmol, 20 mol-%),
Zn (0.25 mmol), and H2O (0.10 mmol) in dry o-DCB (6 mL) at 120 °C for 24 h under N2 in a sealed tube. [b] Isolated yields after column
chromatography. Values in parentheses are based on consumed C60. Values in square brackets are based on C60 involved in the catalytic
cycle, excluding that used in forming C60H2. [c] Yields were determined by HPLC analysis. [d] Values in parentheses are yields of Pt(η2-
C60)(PPh3)2. [e] PPh3 (0.5 equiv.).
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catalytic activity (Entry 11) whereas IrCl3 with PPh3 as li- low yields were observed in the reactions of imines such
gand was ineffective (Entry 12) in this reductive coupling as 1k and 1l featuring the dimethylamino or the electron-
reaction. After a series of screenings of the reaction condi- withdrawing cyano group (5% and 8% respectively, En-
tions and metal complexes, we decided to choose the opti- tries 11 and 12). This lower reactivity is probably attribut-
mal conditions given in Entry 4 in Table 1 for further explo- able to coordination of nitrogen to the nickel complexes,
ration of the scope of this reductive coupling reaction on reducing the catalytic activity. Under similar reaction con-
the basis of catalyst efficiency and direct availability.
ditions, imines derived from naphthaldehydes such as 1m–
With the optimized reaction conditions to hand, the q underwent the reductive coupling reaction effectively, pro-
scope and reactivity of different N-sulfonylaldimine deriva- viding their corresponding products 2m–q in moderate
tives was investigated. The reactions of aldimines 1a, 1b, yields (10–22%; Entries 13–17). It is worth mentioning that
and 1c with [60]fullerene proceeded smoothly to give 2a–c these naphthalene derivatives had excellent solubilities in
in moderate yields [22, 27, and 21% (29, 47, and 30% based common organic solvents such as chloroform, toluene, o-
on converted C60), respectively] under the selected condi- dichlorobenzene, and carbon disulfide. Interestingly, the
tions (Table 3, Entries 1–3). We observed that aldimines 1d– heteroarylaldimines 1r–u also exhibited good reactivity
h showed lower reactivities in this coupling reaction [11– towards this coupling under the standard conditions, af-
16% (12–29% based on converted C60), Entries 4–8]. Under fording reductive coupling products 2r–u in 21, 27, 21, and
the optimal reaction condition, aldimines 1i and 1j, with 28% isolated yields (42, 35, 27, and 41% based on con-
the electron-donating tert-butyl group on the phenyl ring, verted C60), respectively (Entries 18–21). The reductive cou-
provided their corresponding coupling products 2i and 2j pling was limited only to substrates of aryl N-sulfonylald-
in 21 and 22% isolated yields (Entries 9 and 10). Extremely imines. We observed that aliphatic imine 1v did not provide
Table 3. Nickel-catalyzed reductive coupling of [60]fullerene with a variety of N-sulfonylaldimines and N-alkyl or -aryl imines.[a]
[a] Unless otherwise specified, all reactions were carried out with C60 (0.050 mmol), an aldimine (0.25 mmol), NiBr2(PPh)2 (0.010 mmol,
20 mol-%), Zn (0.25 mmol, 5 equiv.), and H2O (0.10 mmol) in anhydrous o-DCB (6 mL) at 120 °C under N2 over 24 h. [b] Isolated yields
after column chromatography. Values in parentheses are based on converted C60. Values in square brackets are based on C60 involved in
the catalytic cycle, excluding that used in formation of C60H2. [c] Yields were measured by HPLC analysis. [d] Reactions were performed
with H2O (0.20 mmol) for 48 h. [e] Reaction was performed at room temp.
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Coupling of [60]Fullerene and N-Sulfonylaldimines
the corresponding coupling product, but that C60H2 was
Meier et al. observed that treatment of C60 with zinc (ex-
produced, probably due to the instability[11] of imine 1v cess) at room temperature followed by quenching with
(Entry 22). Neither N-alkyl aldimines 1w and 1x, nor N- water produced C60H2 in 50% yield.[13f] Under our stan-
aryl aldimine 1y gave their corresponding products (En- dard reaction conditions, however, we did not observe the
tries 23–25); with these substrates only C60H2 was observed. formation of C60H2 in the absence of a nickel catalyst, due
This suggested that the interaction of oxygen from the sulf- to the limited amount of zinc (5 equiv.) in the system. Re-
onyl group (–SO2–) with the nickel center in the intermedi- placement of H2O by D2O (4 μL, 0.20 mmol) in the reac-
ate might be essential for the formation of these reductive tion between aldimine 1i and C60 resulted in incorporation
coupling products 2a–u, which is consistent with Ogoshi’s of deuterium at the sp3-carbon of C60 to afford [D]-2i in
observations.[15] In short, the observed reductive coupling 19% isolated yield (Scheme 2), thereby providing solid sup-
is highly chemoselective for aryl N-sulfonylaldimine sub- port for our proposed mechanism. However, we did not ob-
strates, providing coupling products in 0–28% yields (0– serve a deuterated amine group because of deuterium/hy-
47% based on converted C60) and C60H2 in 0–58% (0–73% drogen exchange[14] during column chromatography (Fig-
based on converted C60) yields. The yields based on C60 ure 1; see the Supporting Information for detailed isotope
involved in the catalytic cycle, excluding that used in form- exchange experiments).
ing C60H2, are mostly in the 30 to 50% range but can be
up to 62% (Entry 2). The developed methodology should
be useful for functionalization of fullerenes in one-pot ca-
talysis as long as starting materials equipped with aryl aldi-
mine functionalities are available.
To investigate the mechanistic pathway of the reaction
further, controlled experiments were conducted. We heated
a solution of C60 (36 mg, 0.05 mmol) with NiBr2(PPh3)2
(7.3 mg, 0.010 mmol, 20 mol-%), Zn (16 mg, 0.25 mmol),
and H2O (9 μL, 0.50 mmol) in anhydrous o-DCB (6 mL)
under nitrogen for 24 h at 120 °C in a sealed tube. HPLC
[13]
analysis[12] showed a peak corresponding to C60H2
at a
retention time (Rt) of 7.7 min (Buckyprep column, flow
rate: 1 mLmin–1) in 48% yield.
Scheme 2. Evidence for the proposed mechanism.
Figure 1. Deuterium/hydrogen exchange in 2a.
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1
A plausible mechanism for the formation of 2a–u based 1] base peaks. The H NMR spectrum of 2a displayed a
on the controlled experiments is proposed (Scheme 3). The singlet at δ = 7.02 ppm for the proton bonded to the fuller-
reaction could be initiated by the reduction of NiII to Ni0 ene sp3 carbon. The protons on the benzylic carbon and
by zinc, followed by coordination to a [6,6]-ring junction nitrogen atoms in 2a are coupled to each other with a cou-
of C60 to generate the intermediate nickel complex Ni(η2- pling constant of 11.0 Hz and these observations are consis-
C60)(PPh3)2 (Ia). The proposed intermediate complex is tent with known results.[18] In the 13C NMR spectra of 2a,
equivalent to those described by Fagan and Balch et al., excluding addend carbons, there were at least 46 peaks ob-
who reported that C60 binds to transition metals, such as served in the 133–155 ppm range for the 58 sp2-carbons of
Ni, Pd, Pt, Ir, and Rh complexes, in an η2-fashion and the C60 skeleton and two peaks at δ = 59.09 and 70.30 ppm
forms η2-C60 metal complexes.[15] We find that complex- for the two sp3-carbons of the C60. The numbers of sp2-
ation of Ia with aldimine 1a competes with hydrolysis of Ia. carbon atoms in the 13C NMR spectra of 2a–u revealed that
If the complex Ia exists long enough without hydrolysis by these structures lack any planes of symmetry.
H2O, displacement of a PPh3 by an aldimine 1a and se-
Figure 2 displays a 2D-HMBC spectrum of compound
quential oxidative cyclization through Ib could form the 2a. We carried out structural elucidation on the basis of
five-membered-ring azanickelacycle intermediate Ic. Evi- one-bond (2D-HMQC) and two- or three-bond (2D-
dence for the formation of five-membered azanickelacycles HMBC) correlation spectra.[19] The signals of carbon atoms
from imines and alkynes was recently provided by Ogoshi C2 and C4 are easily predicted by one-bond correlation
et al.[16] Similarly, five-membered nickelacycles containing (HMQC). HMBC data show that the sp3-carbon C3 in the
nitrogen or oxygen have been observed or proposed as in- fullerene skeleton correlates with the protons on C2 and C4
termediates in small molecules.[9,16,17] From the isolated through two-bond coupling. The carbon C2 correlates with
yields of 2 and C60H2 (3) in Table 3, we conclude that hy- the proton on C4, which is three bonds away (Figure 2).
drolysis is highly dependent on the coordination capabilities Lastly, the UV/Vis spectra each displayed a characteristic
of aldimine substrates 1. The hydrolysis rate of Ia can be as peak at 429 nm, which corresponds to the electronic ab-
fast as nearly twelve times that of complexation rate of Ia sorption for the 1,2 adduct of C60.
with 1, as shown for the 4-(dimethylamino)phenyl 4-chloro-
phenyl aldimine 1k (Entry 11) and as slow as one-fifth,
Conclusions
exemplified by the 2-methoxynaphthyl phenyl aldimine 1q
(Entry 17). Finally, intermediate Ic could then undergo hy-
drolysis to give derivative 2a and NiII species. Again NiII
could be reduced by zinc, regenerating Ni0 for the next cy-
cle.
In conclusion, we have for the first time successfully dem-
onstrated a late transition-metal-catalyzed [60]fullerene/ald-
imine reductive coupling reaction leading to the synthesis
of 1,2-hydrobenzylated [60]fullerene derivatives. In ad-
dition, our control experiments implied that the reaction
proceeds through a competing [60]fullerene-nickel complex
intermediate, as evidenced by the formation of C60H2.
Furthermore, an isotope-labeling experiment in the pres-
ence of D2O afforded the fullerene derivative incorporating
deuterium on the sp3-carbon, which provides support for
intermediacy of the five-membered azanickelacycle. The de-
veloped π–π reductive coupling involving fullerene and
aided by metal catalysis should complement another meth-
odology based on [2+2] cycloadditions;[20] these discoveries
of the reductive formation of coupling compounds and
metal-catalyzed routes to C60H2 are both new to fullerene
chemistry. Further applications of these reductive coupling
products in materials sciences are under investigation in our
laboratory.
Experimental Section
Typical Procedure for Synthesis of Reductive Coupling Products 2a–
u: Dry o-dichlorobenzene (6 mL) and a stirrer bar were placed in
a flame-dried thick-walled high-pressure glass tube containing C60
Scheme 3. Plausible reaction pathway.
We characterized all these reductive coupling products
2a–u by IR and 1H and 13C NMR spectroscopy and by
electron-spray time-of-flight (ESI-TOF) mass spectrometry
(see the Supporting Information). In their IR spectra, S=O
stretching bands appeared at 1162 and 1331 cm–1. The ESI-
(36 mg, 0.050 mmol), an imine
1 (0.25 mmol), NiBr2(PPh3)2
(7.3 mg, 0.010 mmol), Zn (16 mg, 0.25 mmol), and H2O (1.8–
3.6 μL, 2–4 equiv.). The tube was then purged with nitrogen, sealed
quickly with a screw-type cap under a stream of nitrogen, and
placed in an oil bath at 120 °C. After having been stirred for 24 h,
TOF mass spectra of 2a–u gave all corresponding m/z [M – the reaction mixture was allowed to cool to room temperature and
6
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Coupling of [60]Fullerene and N-Sulfonylaldimines
Figure 2. 2D-HMBC spectrum of compound 2a.
then subjected to flash column chromatography with toluene as
eluent to recover unreacted C60 and C60H2. Continued elution with
toluene then gave the reductive coupling product 2. Spectral data
for compounds 2a–u follow.
6.91 (d, J = 8.1 Hz, 2 H, CH), 6.96 (s, 1 H, C60-H), 7.11 (d, J =
8.0 Hz, 2 H, CH), 7.32 (d, J = 11.1 Hz, 1 H, NH), 7.64 (d, J =
8.2 Hz, 2 H, CH) ppm. 13C NMR [150.7 MHz, CS2/C6D12, with
Cr(acac)3 as relaxation reagent]: δ = 22.8 (CH3), 23.0 (CH3), 60.4
(sp3-C–H in C60), 70.2 (CHNH), 71.9 (other sp3 carbon in C60),
128.9, 130.1, 130.6, 134.4, 137.1, 137.5, 137.7, 138.6, 138.9, 139.2,
140.1, 140.4, 141.7, 142.6, 142.61, 142.63, 142.7, 143.0, 143.02,
143.17, 143.2, 143.36, 143.4, 143.6, 143.61, 143.7, 143.77, 143.8,
143.9, 144.0, 144.2, 144.4, 145.5, 146.0, 146.4, 146.48, 146.49,
146.5, 146.6, 146.7, 146.71, 146.9, 147.3, 147.4, 147.42, 147.5,
147.7, 148.1, 148.2, 148.3, 148.6, 151.0, 153.0, 155.2, 155.5 ppm.
Compound 2a: Yield 0.0106 g. Rf = 0.39 (toluene). 1H NMR
(300 MHz, CS2/CDCl3 1:2): δ = 2.30 (s, 3 H, CH3), 6.12 (d, J =
11.0 Hz, 1 H, CHNH), 6.87 (d, J = 11.0 Hz, 1 H, NH), 7.02 (s, 1
H, C60-H), 7.05 (s, 2 H, CH), 7.12 (t, J = 2.7 Hz, 3 H, CH), 7.33
(dd, J = 3.5, 6.6 Hz, 2 H, CH), 7.73 (d, J = 8.2 Hz, 2 H, CH) ppm.
13C NMR (150 MHz, CS2/CDCl3 1:2): δ = 21.4 (CH3), 59.1 (sp3-
C–H in C60), 69.0 (CHNH), 70.3 (other sp3 carbon in C60), 127.3,
128.0, 128.02, 128.7, 129.3, 135.7, 135.8, 135.9, 136.4, 136.8, 137.8,
138.7, 139.0, 140.3, 140.4, 141.2, 141.23, 141.3, 141.65, 141.7,
141.8, 141.82, 142.0, 142.04, 142.2, 142.24, 142.39, 142.4, 142.5,
142.54, 142.9, 143.0, 143.2, 146.0, 146.03, 146.08, 146.1, 146.2,
146.3, 146.4, 146.5, 146.7, 146.8, 147.0, 147.1, 147.3, 149.3, 151.3,
FT-IR (KBr): ν = 526, 567, 665, 754, 810, 1161, 1328, 1429, 2854,
˜
2921, 3025, 3259 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C75H16NO2S [M – H]– 994.0901; found 994.0956.
Compound 2d: Yield 0.006 g. Rf = 0.43 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 2.13 (s, 3 H, CH3), 5.92 (d, J = 10.9 Hz,
1 H, CHNH), 6.79 (d, J = 8.0 Hz, 2 H, CH), 6.95 (s, 1 H, C60-H),
7.08–7.24 (m, 6 H, CH, NH), 7.76 (d, J = 7.7 Hz, 2 H, CH) ppm.
13C NMR (150 MHz, CS2/C6D12): δ = 23.0 (CH3), 60.6 (sp3-C–H
in C60), 70.4 (CHNH), 72.0 (other sp3 carbon in C60), 129.0, 130.2,
130.4, 133.6, 134.5, 137.3, 137.6, 137.9, 139.2, 139.4, 140.3, 140.6,
141.6, 141.85, 141.9, 142.8, 143.2, 143.4, 143.6, 143.7, 143.8, 143.9,
144.1, 144.5, 144.6, 145.7, 146.2, 146.67, 146.7, 146.9, 147.1, 147.5,
147.6, 147.7, 147.9, 148.3, 148.4, 148.5, 148.7, 151.1, 153.1, 155.3,
153.6, 154.0 ppm. FT-IR (KBr): ν = 526, 551, 700, 809, 1056, 1087,
˜
1162, 1330, 1428, 2921, 3255 cm–1. HRMS (ESI-TOF, negative):
m/z calcd. for C74H14NO2S [M – H]– 980.0745; found 980.0769.
Compound 2b: Yield 0.0128 g. Rf = 0.41 (toluene). 1H NMR
(300 MHz, CS2/CDCl3 1:2): δ = 5.97 (d, J = 10.8 Hz, 1 H, CHNH),
6.98 (s, 1 H, C60-H), 7.00 (d, J = 3.3 Hz, 3 H, CH), 7.12–7.25 (m,
6 H, CH, NH), 7.77 (d, J = 7.4 Hz, 2 H, CH) ppm. 13C NMR
(150 MHz, CS2/C6D12): δ = 60.6 (sp3-C–H in C60), 70.6 (CHNH),
71.9 (other sp3 carbon in C60), 129.0, 129.7, 130.2, 133.8, 137.2,
137.6, 137.9, 139.5, 140.3, 141.4, 141.9, 142.8, 143.2, 143.4, 143.6,
143.7, 143.8, 143.9, 144.1, 144.5, 145.7, 146.2, 146.7, 146.9, 147.1,
147.6, 147.7, 147.9, 148.1, 148.3, 148.4, 148.5, 148.7, 148.8, 150.8,
155.6 ppm. FT-IR (KBr): ν = 525, 545, 606, 684, 723, 748, 763,
˜
876, 901, 960, 1092, 1166, 1325, 1431, 1511, 2359 cm–1. HRMS
(ESI-TOF, negative): m/z calcd. for C74H14NO2S [M – H]–
980.0745; found 980.0789.
152.9, 155.2, 155.6 ppm. FT-IR (KBr): ν = 526, 544, 576, 687, 725,
˜
Compound 2e: Yield 0.008 g. Rf = 0.54 (toluene). 1H NMR
(300 MHz, CDCl3): δ = 2.29 (s, 3 H, CH3), 6.16 (d, J = 11.0 Hz, 1
H, CHNH), 6.60 (d, J = 10.7 Hz, 1 H, NH), 6.98 (d, J = 7.9 Hz,
2 H, CH), 7.02 (s, 1 H, C60-H), 7.19–7.25 (m, 4 H, CH), 7.75 (d, J
= 8.5 Hz, 2 H, CH) ppm. 13C NMR (150 MHz, CDCl3): δ = 21.0
749, 875, 903, 960, 1046, 1089, 1166, 1325, 1459, 1510 cm–1. HRMS
(ESI-TOF, negative): m/z calcd. for C73H12NO2S [M – H]–
966.0588; found 966.0625.
Compound 2c: Yield 0.0104 g. Rf = 0.43 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 2.15 (s, 3 H, CH3), 2.20 (s, 3 H, CH3), (CH3), 59.2 (sp3-C–H in C60), 69.0 (CHNH), 70.2 (other sp3 carbon
5.88 (d, J = 11 Hz, 1 H, CHNH), 6.80 (d, J = 7.7 Hz, 2 H, CH),
in C60), 128.66, 128.7, 128.9, 129.0, 132.3, 135.7, 135.8, 136.6,
Eur. J. Org. Chem. 0000, 0–0
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V. Rajeshkumar, S.-C. Chuang
137.7, 138.2, 138.5, 138.9, 139.17, 139.2, 140.4, 140.5, 141.25, CH3), 5.87 (d, J = 11.1 Hz, 1 H, CHNH), 6.86 (d, J = 8.0 Hz, 2
FULL PAPER
141.3, 141.4, 141.7, 141.8, 141.85, 141.9, 142.1, 142.2, 142.3, 142.5,
142.6, 143.05, 143.1, 144.16, 144.2, 144.69, 144.7, 145.2, 145.3,
H, CH), 6.95 (s, 1 H, C60-H), 6.98 (d, J = 8.4 Hz, 2 H, CH), 7.12
(d, J = 8.4 Hz, 2 H, CH), 7.26 (d, J = 11.1 Hz, 1 H, NH), 7.59 (d,
145.35, 145.4, 145.45, 145.5, 145.59, 145.6, 145.7, 146.09, 146.1, J = 8.2 Hz, 2 H, CH) ppm. 13C NMR [150.7 MHz, CS2/C6D12,
146.19, 146.2, 146.29, 146.3, 146.45, 146.5, 146.66, 146.7, 146.9, with Cr(acac)3 as relaxation reagent]: δ = 21.3 (CH3), 31.0
147.1, 147.3, 147.5, 149.3, 151.1, 153.5, 153.9 ppm. FT-IR (KBr):
[C(CH3)3], 34.1 [C(CH3)3], 59.1 (sp3-C–H in C60), 68.7 (CHNH),
70.2 (other sp3 carbon in C60), 124.8, 127.3, 128.3, 129.0, 132.7,
135.6, 135.9, 136.4, 136.7, 137.6, 138.7, 139.0, 140.2, 140.23, 141.1,
141.2, 141.55, 141.6, 141.7, 141.72, 141.9, 141.94, 142.1, 142.14,
142.3, 142.4, 142.43, 142.7, 142.8, 142.9, 144.0, 144.5, 144.53,
145.0, 145.1, 145.2, 145.24, 145.3, 145.4, 145.5, 145.9, 145.92,
145.98, 146.0, 146.1, 146.2, 146.3, 146.6, 146.63, 146.8, 146.9,
147.2, 147.22, 149.6, 150.8, 151.3, 153.6, 153.9 ppm. FT-IR (KBr):
ν = 526, 627, 754, 1035, 1057, 1087, 1163, 1339, 1509, 2851, 2920,
˜
2955, 3257 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C74H13ClNO2S [M – H]– 1014.0355; found 1014.0388.
Compound 2f: Yield 0.0061 g. Rf = 0.24 (toluene). 1H NMR
(300 MHz, CS2/CDCl3 1:2): δ = 2.34 (s, 3 H, CH3), 3.73 (s, 3 H,
OCH3), 6.13 (d, J = 10.7 Hz, 1 H, CHNH), 6.56 (d, J = 10.7 Hz,
1 H, NH), 6.67 (d, J = 8.2 Hz, 2 H, CH), 7.02 (s, 1 H, C60-H), 7.10
(d, J = 8.0 Hz, 2 H, CH), 7.27 (d, J = 6.7 Hz, 2 H, CH), 7.74 (d,
J = 7.6 Hz, 2 H, CH) ppm. 13C NMR [150.7 MHz, CS2/CDCl3 1:2,
with Cr(acac)3 as relaxation reagent]: δ = 21.4 (CH3), 55.1 (OCH3),
59.1 (sp3-C–H in C60), 68.5 (CHNH), 70.6 (other sp3 carbon in
C60), 133.5, 127.3, 127.9, 129.3, 129.8, 135.7, 135.9, 136.5, 136.8,
137.7, 138.8, 139.1, 140.3, 140.4, 141.2, 141.28, 141.3, 141.67,
141.7, 141.8, 141.84, 142.1, 142.2, 142.3, 142.4, 142.5, 142.6, 143.0,
143.02, 143.3, 144.1, 144.14, 144.6, 144.7, 145.2, 145.22, 145.24,
145.3, 145.4, 145.41, 145.5, 145.58, 145.6, 146.01, 146.1, 146.12,
146.14, 146.2, 146.24, 146.4, 146.42, 146.7, 146.72, 146.9, 147.0,
147.2, 147.4, 149.6, 151.4, 153.7, 154.0, 159.2 ppm. FT-IR (KBr):
ν = 525, 574, 664, 729, 903 1161, 1323, 1650, 2960, 3254 cm–1.
˜
HRMS (ESI-TOF, negative): m/z calcd. for C78H22NO2S [M – H]–
1036.1371; found 1036.1422.
Compound 2j: Yield 0.0111 g. Rf = 0.5 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 1.12 [s, 9 H, C(CH3)3], 5.91 (d, J =
11.0 Hz, 1 H, CHNH), 6.96–7.00 (m, 3 H, CH), 7.06–7.17 (m, 5
H, CH), 7.24 (d, J = 11.1 Hz, 1 H, NH), 7.71–7.74 (m, 2 H,
CH) ppm. 13C NMR (150 MHz, CS2/C6D12): δ = 32.5 [C(CH3)3],
35.3 [C(CH3)3], 60.6 (sp3-C–H in C60), 70.3 (CHNH), 71.7 (other
sp3 carbon in C60), 126.4, 128.8, 129.9, 133.3, 134.1, 137.1, 137.4,
137.8, 139.2, 140.2, 140.5, 141.3, 141.6, 141.7, 142.6, 142.64,
142.96, 143.0, 143.1, 143.4, 143.5, 143.6, 143.7, 143.8, 144.26,
144.3, 145.5, 145.9, 146.5, 146.6, 146.65, 146.7, 146.9, 147.3,
147.33, 147.4, 147.5, 147.7, 148.1, 148.2, 148.3, 148.6, 151.0, 151.8,
ν = 526, 545, 671, 810, 1036, 1161, 1243, 1328, 1516, 2921,
˜
3240 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C75H16NO3S [M – H]– 1010.0850; found 1010.0900.
Compound 2g: Yield 0.006 g. Rf = 0.23 (toluene). 1H NMR
(300 MHz, CDCl3): δ = 3.73 (s, 3 H, OCH3), 6.17 (d, J = 10.8 Hz,
1 H, CHNH), 6.59 (d, J = 11.0 Hz, 1 H, NH), 6.67 (d, J = 8.6 Hz,
2 H, CH), 7.03 (s, 1 H, C60-H), 7.26 (d, J = 8.4 Hz, 2 H, CH), 7.34
(d, J = 8.0 Hz, 2 H, CH), 7.42 (d, J = 7.6 Hz, 1 H, CH), 7.88 (d,
J = 7.5 Hz, 2 H, CH) ppm. 13C NMR (150 MHz, CDCl3): δ =
55.2 (OCH3), 59.2 (sp3-C–H in C60), 68.6 (CHNH), 70.7 (other sp3
carbon in C60), 113.7, 127.4, 128.9, 129.9, 132.7, 135.8, 136.0,
136.6, 136.61, 137.8, 138.9, 139.3, 139.8, 140.4, 140.5, 141.4,
141.42, 141.5, 141.8, 141.83, 142.0, 142.2, 142.3, 142.4, 142.6,
142.68, 142.7, 143.09, 143.1, 143.16, 144.2, 144.3, 144.78, 144.8,
145.3, 145.37, 145.4, 145.49, 145.5, 145.6, 145.7, 145.72, 145.8,
146.16, 146.2, 146.27, 146.3, 146.37, 146.4, 146.5, 146.6, 146.8,
147.0, 147.2, 147.4, 147.5, 149.6, 151.4, 153.8, 154.2, 159.4 ppm.
155.0, 155.4 ppm. FT-IR (KBr): ν = 526, 565, 603, 685, 732, 749,
˜
902, 1165, 1263, 1324, 1429, 1427, 2960, 3263 cm–1. HRMS (ESI-
TOF, negative): m/z calcd. for C77H20NO2S [M – H]– 1022.1214;
found 1022.1257.
Compound 2k: Yield 0.0027 g. Rf = 0.29 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 2.80 [s, 6 H, N(CH3)2], 5.84 (d, J =
11.2 Hz, 1 H, CHNH), 6.26 (d, J = 8.6 Hz, 2 H, CH), 6.91 (s, 1 H,
C60-H), 6.99 (d, J = 8.6 Hz, 2 H, CH), 7.03 (d, J = 8.4 Hz, 2 H,
CH), 7.17 (d, J = 10.6 Hz, 1 H, NH), 7.64 (d, J = 8.6 Hz, 2 H,
CH) ppm. 13C NMR (150 MHz, CS2/C6D12): δ = 41.6 [N(CH3)2],
60.7 (sp3-C–H in C60), 70.5 (CHNH), 72.5 (other sp3 carbon in
C60), 113.1, 124.3, 130.3, 130.5, 131.1, 137.3, 137.6, 137.9, 139.2,
140.1, 140.2, 140.4, 140.8, 141.8, 141.9, 142.8, 142.85, 142.90,
143.2, 143.3, 143.4, 143.6, 143.8, 143.96, 144.0, 144.07, 144.1,
144.14, 144.5, 144.6, 145.7, 146.17, 146.2, 146.7, 146.72, 146.76,
146.78, 146.8, 146.9, 147.0, 147.1, 147.5, 147.57, 147.6, 147.7,
147.8, 147.89, 147.9, 148.3, 148.4, 148.55, 148.6, 148.8, 149.0,
FT-IR (KBr): ν = 525, 544, 605, 686, 749, 875, 1035, 1162, 1250,
˜
1325, 1433, 1451, 1511 cm–1. HRMS (ESI-TOF, negative): m/z
calcd. for C74H14NO3S [M – H]– 996.0694; found 996.0739.
Compound 2h: Yield 0.0058 g. Rf = 0.36 (toluene). 1H NMR
(300 MHz, CDCl3): δ = 3.76 (s, 3 H, OCH3), 6.15 (d, J = 10.9 Hz,
1 H, CHNH), 6.67 (d, J = 10.8 Hz, 1 H, NH), 6.70 (d, J = 8.7 Hz,
2 H, CH), 7.01 (s, 1 H, C60-H), 7.24–7.28 (m, 4 H, CH), 7.77 (d, J
= 8.6 Hz, 2 H, CH) ppm. 13C NMR (150 MHz, CDCl3): δ = 55.4
(OCH3), 59.3 (sp3-C–H in C60), 68.8 (CHNH), 70.5 (other sp3 car-
bon in C60), 113.8, 127.6, 128.8, 129.1, 130.0, 135.8, 135.9, 136.7,
137.8, 138.4, 139.0, 139.3, 139.33, 140.5, 140.6, 141.3, 141.4,
141.47, 141.5, 141.8, 141.9, 141.96, 142.0, 142.2, 142.3, 142.4,
142.6, 142.7, 142.73, 143.16, 143.2, 144.26, 144.3, 144.8, 144.83,
145.3, 145.4, 145.5, 145.52, 145.56, 145.6, 145.68, 145.7, 145.8,
146.2, 146.23, 146.3, 146.32, 146.4, 146.42, 146.55, 146.6, 146.8,
147.0, 147.2, 147.3, 147.6, 149.4, 151.2, 153.6, 154.0, 159.6 ppm.
151.0, 151.5, 153.2, 155.4, 155.6 ppm. FT-IR (KBr): ν = 526, 575,
˜
625, 713, 755, 823, 877, 1028, 1098, 1161, 1339, 2850, 2917, 2956,
3223 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C75H16ClN2O2S [M – H]– 1043.0621; found 1043.0702.
Compound 2l: Yield 0.0041 g. Rf = 0.11 (toluene). 1H NMR
(300 MHz, CDCl3): δ = 6.28 (d, J = 10.7 Hz, 1 H, CHNH), 6.96
(d, J = 10.1 Hz,1 H, NH), 7.02 (s, 1 H, C60-H), 7.37 (d, J = 7.7 Hz,
2 H, CH), 7.44–7.53 (m, 5 H, CH), 7.91 (d, J = 7.4 Hz, 2 H,
CH) ppm. 13C NMR (150 MHz, CDCl3): δ = 59.2 (sp3-C–H in
C60), 68.5 (CHNH), 69.6 (other sp3 carbon in C60), 112.3, 117.9,
127.2, 129.1, 129.4, 131.7, 133.2, 135.5, 135.6, 136.7, 138.1, 139.0,
139.2, 139.4, 140.5, 140.6, 140.9, 141.1, 141.2, 141.4, 141.79, 141.8,
142.1, 142.2, 142.3, 142.6, 142.7, 143.0, 143.1, 143.14, 144.05,
144.1, 144.7, 144.8, 145.28, 145.3, 145.4, 145.5, 145.54, 145.6,
145.8, 145.83, 146.1, 146.2, 146.24, 146.27, 146.3, 146.4, 146.5,
146.6, 146.7, 147.1, 147.5, 147.8, 150.0, 153.0, 153.5 ppm. FT-IR
FT-IR (KBr): ν = 526, 545, 575, 754, 824, 1031, 1088, 1163, 1214,
˜
1253, 1338, 1458, 2853, 2924, 2956 cm–1. HRMS (ESI-TOF, nega-
tive): m/z calcd. for C74H13ClNO3S [M – H]– 1030.0304; found
1030.0314.
(KBr): ν = 526, 560, 603, 687, 753, 1079, 1164, 1214, 1340, 1429,
˜
Compound 2i: Yield 0.011 g. Rf = 0.5 (toluene). 1H NMR 1448, 2921, 3240 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
(300 MHz, CS2/C6D12): δ = 1.13 [s, 9 H, C(CH3)3], 2.15 (s, 3 H,
C74H11N2O2S [M – H]– 991.0541; found 991.0591.
8
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Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20055
/KAP1
Date: 29-05-12 10:38:23
Pages: 12
Coupling of [60]Fullerene and N-Sulfonylaldimines
Compound 2m: Yield 0.0053 g. Rf = 0.45 (toluene). 1H NMR 124.1, 125.4, 128.1, 129.0, 129.7, 129.8, 130.3, 132.1, 133.8, 137.7,
(300 MHz, CS2/C6D12): δ = 1.92 (s, 3 H, CH3), 6.47 (d, J = 8.1 Hz,
2 H, CH), 6.84 (d, J = 11.4 Hz, 1 H, CHNH), 7.17 (t, J = 8.9 Hz,
137.9, 138.4, 139.9, 140.3, 141.7, 142.4, 142.5, 143.0, 143.1, 143.14,
143.2, 143.3, 143.5, 143.54, 143.6, 143.8, 143.84, 143.9, 144.3,
2 H, CH), 7.30 (t, J = 7.4 Hz, 1 H, CH), 7.43–7.63 (m. 7 H, CH, 144.5, 145.3, 145.6, 145.9, 145.94, 146.1, 146.45, 146.5, 146.54,
NH ), 8.35 (d, J = 8.6 Hz, 1 H, CH) ppm. 13C NMR [150.7 MHz, 146.7, 146.8, 147.0, 147.2, 147.22, 147.3, 147.5, 147.7, 148.1, 148.2,
CS2/C6D12, with Cr(acac)3 as relaxation reagent]: δ = 22.7 (CH3), 148.3, 148.5, 148.6, 153.0, 154.5, 156.0, 156.03, 156.1 ppm. FT-IR
61.1 (sp3-C–H in C60), 64.0 (CHNH), 71.8 (other sp3 carbon in
C60), 124.2, 126.3, 127.2, 128.1, 128.3, 128.6, 129.9, 130.0, 130.1,
132.7, 133.8, 134.5, 137.1, 137.6, 137.7, 139.4, 139.9, 140.5, 141.7,
142.4, 142.5, 142.53, 142.6, 143.0, 143.1, 143.4, 143.45, 143.5,
143.6, 143.64, 143.68, 143.7, 143.86, 143.9, 144.2, 144.3, 145.4,
145.5, 146.0, 146.39, 146.4, 146.5, 146.6, 146.63, 146.8, 146.9,
147.0, 147.3, 147.4, 147.55, 147.6, 147.7, 148.1, 148.14, 148.3,
(KBr): ν = 526, 800, 1019, 1078, 1160, 1246, 1320, 1507, 2850,
˜
2922 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C79H18NO3S [M – H]– 1060.1007; found 1060.1063.
Compound 2q: Yield 0.0103 g. Rf = 0.43 (toluene). 1H NMR
(300 MHz, CS2/CDCl3 1:2): δ = 3.70 (s, 3 H, OCH3), 6.83–6.94 (m,
3 H), 7.01–7.06 (m, 2 H), 7.33–7.40 (m, 2 H), 7.60–7.67 (m, 5 H),
7.95 (d, J = 20.0 Hz, 1 H), 8.47 (d, J = 9.18 Hz, 1 H) ppm. 13C
NMR (150 MHz, CS2/CDCl3 1:2): δ = 55.4 (OCH3), 59.7 (sp3-C–
H in C60), 63.4 (CHNH), 70.5 (other sp3 carbon in C60), 112.7,
115.9, 122.6, 124.0, 126.6, 127.8, 128.0, 128.5, 129.0, 131.4, 132.1,
132.5, 135.6, 135.7, 136.4, 136.6, 138.7, 138.9, 139.2, 140.4, 141.1,
141.3, 141.7, 141.8, 142.1, 142.2, 142.4, 142.5, 142.59, 142.6, 143.0,
143.2, 144.0, 144.3, 144.6, 144.8, 145.2, 145.28, 145.3, 145.4, 145.6,
145.9, 146.0, 146.1, 146.3, 146.4, 146.8, 146.96, 147.0, 147.3, 147.4,
148.6, 148.9, 151.0, 152.6, 154.9, 155.7 ppm. FT-IR (KBr): ν = 527,
˜
671, 773, 1088, 1160, 1380, 1429, 1508 cm–1. HRMS (ESI-TOF,
negative): m/z calcd. for C78H16NO2S [M – H]– 1030.0901; found
1030.0955.
Compound 2n: Yield 0.0102 g. Rf = 0.44 (toluene). 1H NMR
(300 MHz, CS2/CDCl3 1:2): δ = 1.92 (s, 3 H, CH3), 6.33 (d, J =
11.0 Hz, 1 H, CHNH), 6.78 (d, J = 8.1 Hz, 2 H, CH), 6.97 (d, J =
11.1 Hz, 1 H, NH), 7.13 (s, 1 H, C60-H), 7.42–7.47 (m, 2 H, CH),
7.55 (d, J = 8.9 Hz, 1 H, CH), 7.64–7.79 (m, 6 H, CH) ppm. 13C
NMR [150.7 MHz, CS2/CDCl3 1:2, with Cr(acac)3 as relaxation
reagent]: δ = 21.0 (CH3), 59.3 (sp3-C–H in C60), 69.4 (CHNH), 70.3
(other sp3 carbon in C60), 125.9, 126.3, 126.4, 127.2, 127.5, 127.9,
128.1, 128.7, 129.1, 132.4, 132.6, 132.9, 135.7, 136.0, 136.4, 136.5,
137.8, 138.8, 139.2, 140.3, 140.4, 141.27, 141.3, 141.67, 141.7,
141.8, 141.83, 142.05, 142.1, 142.2, 142.3, 142.4, 142.5, 142.6,
143.0, 143.02, 143.5, 144.1, 144.6, 144.7, 145.18, 145.2, 145.37,
145.4, 145.43, 145.55, 145.6, 145.7, 146.0, 146.1, 146.12, 146.15,
146.2, 146.36, 146.4, 146.6, 146.7, 146.9, 147.0, 147.2, 147.4, 149.5,
151.6, 153.0, 154.7, 154.75, 154.8 ppm. FT-IR (KBr): ν = 527, 577,
˜
596, 639, 686, 750, 804, 871, 912, 960, 1022, 1082, 1166, 1215, 1249,
1340, 1428, 1460, 1515, 1597 cm–1. HRMS (ESI-TOF, negative):
m/z calcd. for C78H16NO3S [M – H]– 1046.0850; found 1046.0879.
Compound 2r: Yield 0.01 g. Rf = 0.13 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 2.29 (s, 3 H, CH3), 6.0–6.05 (m, 1 H),
6.17 (d, J = 2.7 Hz, 1 H) 6.61 (d, J = 10.8 Hz, 1 H, NH), 6.84 (s,
1 H, C60-H), 7.09 (t, J = 4.5 Hz, 4 H, CH), 7.68 (d, J = 7.8 Hz, 2
H, CH) ppm. 13C NMR [150.7 MHz, CS2/C6D12, with Cr(acac)3
as relaxation reagent]: δ = 23.2 (CH3), 59.6 (sp3-C–H in C60), 63.8
(CHNH), 71.2 (other sp3 carbon in C60), 111.8, 111.9, 128.8, 130.9,
137.2, 137.5, 138.1, 138.8, 139.0, 140.5, 140.7, 141.7, 141.8, 142.7,
142.8, 143.1, 143.3, 143.4, 143.6, 143.7, 143.9, 143.94, 144.0, 144.3,
144.4, 144.41, 145.6, 146.0, 146.1, 146.6, 146.63, 146.67, 146.7,
146.8, 146.9, 146.92, 146.95, 147.0, 147.4, 147.5, 147.6, 147.8,
147.9, 148.2, 148.24, 148.3, 148.4, 148.8, 151.1, 151.7, 152.6, 155.0,
151.2, 153.6, 154.0 ppm. FT-IR (KBr): ν = 526, 566, 672, 784, 808,
˜
900, 1059, 1079, 1161, 1324, 1428, 15132884, 2918, 3053,
3258 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C78H16NO2S [M – H]– 1030.0901; found 1030.0948.
Compound 2o: Yield 0.0097 g. Rf = 0.43 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 6.13 (d, J = 11.2 Hz, 1 H, CHNH),
6.88 (d, J = 2.4 Hz, 3 H, CH), 7.04 (s, 1 H, C60-H), 7.25 (dd, J =
3.2, 6.1 Hz, 2 H), 7.43 (t, J = 1.6 Hz, 2 H), 7.51 (dd, J = 3.4,
5.9 Hz, 2 H), 7.63 (s, 1 H), 7.78–7.81 (m, 3 H) ppm. 13C NMR
[150.7 MHz, CS2/CDCl3, with Cr(acac)3 as relaxation reagent]: δ =
60.6 (sp3-C–H in C60), 70.7 (CHNH), 71.8 (other sp3 carbon in
C60), 127.3, 128.0, 128.2, 128.7, 129.1, 129.4, 129.5, 129.86, 129.9,
133.5, 133.7, 134.0, 134.5, 134.8, 137.2, 137.5, 137.8, 139.3, 140.2,
140.6, 141.3, 141.7, 141.8, 142.7, 142.74, 142.9, 143.1, 143.11,
143.2, 143.23, 143.4, 143.5, 143.6, 143.7, 143.78, 143.8, 143.9,
144.0, 144.3, 144.4, 145.5, 146.0, 146.5, 146.56, 146.6, 146.7,
146.75, 146.8, 146.9, 146.96, 147.0, 147.4, 147.43, 147.47, 147.5,
147.6, 147.7, 147.9, 148.2, 148.24, 148.4, 148.5, 148.7, 150.8, 152.7,
155.1 ppm. FT-IR (KBr): ν = 526, 595, 665, 785, 812, 902, 1085,
˜
1162, 1331, 1422, 1509 cm–1. HRMS (ESI-TOF, negative): m/z
calcd. for C72H12NO3S [M – H]– 970.0537; found 970.0561.
Compound 2s: Yield 0.0134 g. Rf = 0.35 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 2.26 (s, 3 H, CH3), 6.23 (d, J = 10.7 Hz,
1 H, CHNH), 6.71–6.73 (m, 2 H, CH, NH), 6.84 (s, 1 H, C60-H),
7.02 (t, J = 7.6 Hz, 4 H, CH), 7.66 (d, J = 8.2 Hz, 2 H, CH) ppm.
13C NMR [150.7 MHz, CS2/C6D12, with Cr(acac)3 as relaxation
reagent]: δ = 23.2 (CH3), 60.0 (sp3-C–H in C60), 65.8 (CHNH), 72.1
(other sp3 carbon in C60), 127.3, 128.0, 128.9, 129.6, 130.8, 137.2,
137.4, 138.2, 138.7, 139.3, 140.2, 140.7, 141.2, 141.7, 141.8, 142.56,
142.6, 142.7, 142.8, 143.1, 143.27, 143.3, 143.5, 143.6, 143.64,
143.8, 143.9, 143.94, 144.0, 144.3, 144.31, 144.4, 145.6, 146.0,
146.6, 146.7, 146.9, 147.1, 147.4, 147.42, 147.5, 147.6, 147.8, 148.1,
148.14, 148.4, 148.7, 148.8, 150.9, 152.4, 154.8, 155.2 ppm. FT-IR
155.1, 155.4 ppm. FT-IR (KBr): ν = 527, 602, 727, 749, 896, 1059,
˜
1079, 1163, 1328, 1423, 2850, 2919, 3257 cm–1. HRMS (ESI-TOF,
negative): m/z calcd. for C77H14NO2S [M – H]– 1016.0745; found
1016.0821.
(KBr): ν = 526, 669, 700, 809, 901, 1031, 1159, 1263, 1326, 1420,
˜
1507, 1559 cm–1. HRMS (ESI-TOF, negative): m/z calcd. for
C72H12NO2S2 [M – H]– 986.0309; found 986.0343.
Compound 2p: Yield 0.0117 g. Rf = 0.41 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 1.95 (s, 3 H, CH3), 3.62 (s, 3 H, OCH3), Compound 2t: Yield 0.0101 g. Rf = 0.37 (toluene). 1H NMR
6.44 (d, J = 8.1 Hz, 2 H, CH), 6.73 (d, J = 11.1 Hz, 1 H, CHNH), (300 MHz, CS2/CDCl3 1:2): δ = 6.15 (d, J = 10.8 Hz, 1 H, CHNH),
6.84 (d, J = 9.1 Hz, 1 H, CH), 7.20 (d, J = 7.4 Hz, 1 H, CH), 7.24
(s, 1 H, C60-H), 7.30 (d, J = 8.2 Hz, 2 H, CH), 7.46–7.52 (m, 3 H,
6.48 (d, J = 10.5 Hz, 1 H, NH), 6.84 (dd, J = 3.7, 5.0 Hz, 1 H,
CH), 6.92 (s, 1 H, C60-H), 7.09 (d, J = 3.7 Hz, 1 H, CH), 7.18 (d,
CH), 7.63 (d, J = 10.5 Hz, 1 H, NH), 8.28 (d, J = 9.2 Hz, 1 H, J = 5.1 Hz, 1 H, CH), 7.39 (t, J = 7.2 Hz, 2 H, CH), 7.49 (t, J =
CH) ppm. 13C NMR [150.7 MHz, CS2/C6D12, with Cr(acac)3 as 7.5 Hz, 1 H, CH), 7.89 (d, J = 7.5 Hz, 2 H, CH) ppm. 13C NMR
relaxation reagent]: δ = 22.6 (CH3), 56.5 (OCH3), 61.0 (sp3-C–H in
C60), 64.3 (CHNH), 71.7 (other sp3 carbon in C60), 114.1, 118.2,
[150.7 MHz, CS2/C6D12, with Cr(acac)3 as relaxation reagent]: δ =
60.0 (sp3-C–H in C60), 65.8 (CHNH), 72.0 (other sp3 carbon in
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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Job/Unit: O20055
/KAP1
Date: 29-05-12 10:38:23
Pages: 12
V. Rajeshkumar, S.-C. Chuang
FULL PAPER
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C60), 127.5, 128.1, 128.7, 128.8, 129.7, 130.1, 130.2, 133.7, 133.9,
137.3, 137.4, 138.2, 139.3, 140.2, 140.7, 140.8, 141.4, 141.8, 141.81,
142.1, 142.2, 142.24, 142.6, 142.61, 142.7, 142.9, 143.1, 143.3,
143.32, 143.5, 143.6, 143.7, 143.86, 143.9, 144.0, 144.3, 144.4,
144.7, 145.1, 145.2, 145.6, 146.1, 146.6, 146.63, 146.8, 146.9, 147.1,
147.4, 147.44, 147.5, 147.7, 147.8, 147.9, 148.1, 148.12, 148.2,
148.4, 148.8, 148.9, 149.1, 150.8, 152.4, 154.8, 155.2 ppm. FT-IR
(KBr): ν = 526, 595, 686, 899, 1059, 1163, 1329, 1447, 1513 cm–1.
˜
HRMS (ESI-TOF, negative): m/z calcd. for C71H10NO2S2 [M – H]
–
972.0152; found 972.0190.
Compound 2u: Yield 0.014 g. Rf = 0.39 (toluene). 1H NMR
(300 MHz, CS2/C6D12): δ = 2.23 (s, 1 H, CH3), 6.01 (d, J = 10.8 Hz,
1 H, CHNH), 6.92 (s, 1 H, C60-H), 6.96–7.06 (m, 5 H, CH), 7.47
(d, J = 11.2 Hz, 1 H, NH), 7.69 (d, J = 8.2 Hz, 2 H, CH) ppm.
13C NMR [150.7 MHz, CS2/C6D12, with Cr(acac)3 as relaxation
reagent]: δ = 23.1 (CH3), 60.1 (sp3-C–H in C60), 66.1 (CHNH), 71.7
(other sp3 carbon in C60), 126.3, 127.4, 128.3, 128.4, 128.6, 128.8,
128.9, 137.1, 137.5, 137.8, 138.3, 138.9, 139.2, 140.2, 140.6, 141.7,
145.6, 146.0, 146.4, 146.5, 146.54, 146.6, 146.7, 146.71, 146.8,
146.85, 146.9, 146.93, 147.3, 147.4, 147.5, 147.56, 147.6, 147.7,
147.73, 148.1, 148.13, 148.2, 148.4, 148.5, 148.7, 151.2, 152.9,
[3]
155.1, 155.3 ppm. FT-IR (KBr): ν = 526, 672, 905, 1059, 1079,
˜
1159, 1330, 2850, 2918, 3235 cm–1. HRMS (ESI-TOF, negative):
m/z calcd. for C72H12NO2S2 [M – H]– 986.0309; found 986.0363.
Supporting Information (see footnote on the first page of this arti-
cle): Detailed experimental procedures and full spectroscopic data
1
for all new compounds are given, as well as copies of H and 13C
NMR spectra and HRESI mass spectra.
Acknowledgments
We thank the National Science Council for financial support of this
research (NSC962113-M009-028-MY2 and NSC982119-345M009-
001-MY2). We also thank Mr. R.-L. Cheng for helping to take
some of the spectroscopic data.
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10
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C60H2 and C60. The higher hydrofullerenes are very trace.
Received: January 16, 2012
Published Online: ᭿
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11

Job/Unit: O20055
/KAP1
Date: 29-05-12 10:38:23
Pages: 12
V. Rajeshkumar, S.-C. Chuang
FULL PAPER
Fullerene Functionalization
V. Rajeshkumar, S.-C. Chuang* ...... 1–12
Evolution of Late Transition-Metal-Cata-
lyzed Intermolecular Reductive Coupling
Reaction of [60]Fullerene and N-Sulfonyl-
aldimines: Competing Formation of
Hydrobenzylated [60]Fullerenes and 1,2-
Dihydrofullerene
A system based on late transition-metal
halides, phosphanes, water, and reducing
agents in o-DCB can efficiently catalyze in-
termolecular reductive coupling between
[60]fullerene and N-sulfonylaldimines to
afford new 1,2-hydrobenzylated [60]fuller-
ene derivatives. The reaction yields are
moderate, due to the formation of C60H2
as a byproduct. A possible reaction mech-
anism is proposed.
Keywords: Fullerenes / Transition metals /
C–C coupling / Reductive coupling
12
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