Regioselective synthesis of [60]fullerene η5-indenide R 3C60- and η5-cyclopentadienide R5C60- bearing different R groups

Article abstract of DOI:10.1039/b302468g

Synthesis of a symmetrical [60]fullerene indenide, unsymmetrical indenides R₂R′C₆₀^- (B,C), and unsymmetical cyclopentadienides was studied. It was observed that penta-addition reactions almost always give only the penta-ad

Full text of DOI:10.1039/b302468g

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؊
Regioselective synthesis of [60]fullerene ꢀ5-indenide R3C60 and
؊
ꢀ5-cyclopentadienide R5C60 bearing different R groups
Motoki Toganoh, Kazuhiro Suzuki, Rie Udagawa, Atsushi Hirai,† Masaya Sawamura‡ and
Eiichi Nakamura*
Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
E-mail: nakamura@chem.s.u-tokyo.ac.jp; Fax: ϩ81-3-5800-6889; Tel: ϩ81-3-5800-6889
Received 10th March 2003, Accepted 2nd June 2003
First published as an Advance Article on the web 16th June 2003
Treatment of a 1,7-diorgano[60]fullerene with Grignard reagents or organocopper reagents affords a [60]fullerene
indenide or a [60]fullerene cyclopentadienide regioselectively in good to excellent yields. These reactions gave an
insight into the reaction mechanism of the organocopper penta-addition reaction of [60]fullerene, giving [60]fullerene
cyclopentadienide in quantitative yield.
Ϫ
surfaces.7 Ph5C60 has been dissolved in water to form small-
Introduction
size bilayer vesicles,8 and Ar5C60H bearing long aliphatic side
An organocopper compound prepared from a Grignard
chains on the Ar groups was found to give one-dimensional
reagent and CuBrؒSMe2 adds five times to [60]fullerene to give a
stacks of shuttlecock-shaped molecules.9
fullerene cyclopentadienide R5C60Ϫ, which upon protonation
With such growing interest in the fullerene polyadducts, we
gives the corresponding cyclopentadiene R5C60H in quanti-
felt it necessary to address some important issues; that is, the
synthesis of a symmetrical [60]fullerene indenide (A), unsym-
tative yield without giving any regioisomers (Scheme 1a).1 When
the same reaction conditions were applied to [70]fullerene, a tri-
addition reaction takes place to afford a fullerene indenide
Ϫ
metrical indenides R2RЈC60 (B, C), and unsymmetrical cyclo-
pentadienides such as RxRЈyRЉzC60Ϫ (x ϩ y ϩ z = 5, e.g., D, E,
R3C70Ϫ, which then affords the corresponding indene derivative
F).10 In this article, we describe the synthesis of such com-
R3C70H (Scheme 1b).2 These two reactions are apparently
pounds, and also shed light on the reaction pathway of the
related to each other. The latter reaction stops after the third
organocopper penta-addition reaction to [60]fullerene.
addition reaction, however, since the two sp2 carbon atoms
expected to receive the fourth and the fifth addition are in
a relatively flat “equatorial belt region” and hence resist
rehybridization to sp3 centres. These reactions, taking place in
quantitative yield, are unique among a variety of polyaddition
reactions of fullerenes,3,4 which rarely achieve 100%-yield based
on the fullerene molecule used for the reaction.5 Besides the
remarkable regioselectivity and the high product yield, the
products of those organocopper reactions have been found to
open new areas of research. Thus, Me5C60H was converted to
a hybrid of fullerene and ferrocene Fe(Me5C60)(C5H5)6 and
formed molecular epitaxial films on H–Si(111) and MoS2(0001)
Results and discussion
1
Synthesis of fullerene indenides
One remarkable feature of the penta-addition reactions is that
the reactions almost always give only the penta-addition
product (and the starting material, if any). Only under rare
exceptional conditions was the mono-adduct RC60H detected in
a trace amount, but no other intermediary adducts have been
detected. This observation suggests that, once the first addition
occurs, the subsequent additions take place extremely quickly.
Besides the organic products, R5C60H and R–R (detected as
biphenyl when R is phenyl), metallic copper forms partly as a
black solid and partly as a copper mirror.
Scheme 1 Organocopper reactions of [60]fullerene and [70]fullerene.
These observations, combined with the knowledge on organo-
copper mechanisms,11polyalkylation reactions of fullerene-
s,12,13,14 and the experiments described in this article led us to
consider the reaction pathway shown in Scheme 2. One may
consider that a diorganocuprate R2CuϪ first undergoes addition
to [60]fullerene and subsequent one-electron oxidation of the
† Present address: Department of Chemistry, Hokkaido University,
Sapporo, Hokkaido 060-0810, Japan. E-mail: ahirai@sci.hokudai.
ac.jp; Fax: ϩ81-11-706-4920; Tel: ϩ81-11-706-2716.
‡ Present address: Department of Chemistry, Hokkaido University, Sap-
poro, Hokkaido 060-0810, Japan. E-mail sawamura@sci.hokudai.
ac.jp; Fax: ϩ81-11-706-4924; Tel: ϩ81-11-706-4924.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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the protons attached to the fullerene core, eight distinct doub-
lets due to the methylene groups of the benzyl addends, and a
multiplet in the aromatic region in an integration ratio of 1 : 4 :
15. These NMR data are fully consistent with the assigned
molecular formula of 2a/2b and their molecular symmetry (C1).
The position of the phenyl group and the hydrogen atom
of 2a/2b was deduced from a deprotonation experiment with
t-BuOK (Scheme 3, bottom). Treatment of a solution of the
isomeric mixture of 2a/2b in THF with t-BuOK (1.2 equiv.) at
20 ЊC caused immediate colour change from dark brown to
dark green. The 1H NMR spectrum in THF-d8 showed that the
isomeric mixture converged into a single product Kϩ[(PhCH2)2-
PhC60]Ϫ (3) with C1 symmetry. This result indicates that the
isomerism in 2a/2b arises from the positional isomers of the
hydrogen atom, and therefore that the phenyl group was regio-
selectively installed.18 The reactions of 1 with other phenyl-
metal reagents (PhLi, Ph2Mg) also gave the same product but in
much lower yields.
We found that the di-adduct 1 is more reactive than the par-
ent [60]fullerene toward PhMgBr (Scheme 4), which is consist-
ent with the fact that we never detected the formation of a
di-adduct during the organocopper penta-addition reaction.
Thus, when an equimolar mixture of C60 and 1 was treated with
an excess amount of PhMgBr in a molar ratio of 1 : 1 : 6 at
23 ЊC for 20 min, only 21% of C60 was consumed to give a
mono-adduct PhC60H (17% yield), while 1 was converted to 2 in
73% yield.
Scheme 2 A likely reaction course of the penta-addition reaction of
[60]fullerene.
organocopper() intermediate by a Cu() salt would give 1,7-
R2C60 and Cu(0). The same sequence of reactions takes place on
this initial product to give the 1,7,11,24-R4C60 product. This
type of product has previously been isolated when R was a
bulky fluorenyl group.15 This tetra-adduct contains a fulvene
part structure and therefore readily accepts the fifth R group.
According to this reaction mechanism, we considered that
addition of an organometallic reagent RЈM to the postulated
intermediate 1,7-R2C60 would afford unsymmetrical fullerene
η5-indenide R2RЈC60 as well as fullerene η5-cyclopentadienide
Ϫ
R2RЈ3C60Ϫ, regioselectively.16
1.1 Reaction of 1,7-(PhCh2)2C60 with PhMgBr. A Grignard
reagent reacts with C60 in a “1,2-addition” across a double
bond.17 Hence we conjectured that the reaction of 1,7-R2C60
with a Grignard reagent will take place only once to give a
fullerene tri-adduct. We have chosen 1,7-(PhCH2)2C60 (1) as a
starting compound for the present studies because it is avail-
able in one step from [60]fullerene and shows reasonably high
solubility in common organic solvents.14
Thus 1 was treated with PhMgBr (3.2 equiv.) in 1,2-dichloro-
benzene at 28 ЊC to give, after hydrolysis with aqueous NH4Cl
and preparative HPLC (high pressure liquid chromatography)
purification, (PhCH2)2PhC60H in 76% yield as a mixture of two
isomers (2a–2b = 62 : 38). They differ from each other only in
the position of the hydrogen atom attached directly to the
fullerene core (Scheme 3). The mass spectrum of the isolated
product indicated that the reaction stopped after the addition
of only one phenyl group [atmospheric pressure chemical ioniz-
ation (APCI), Mϩ = 981]. The 1H NMR of the isomeric mixture
shows a pair of singlets (2a: δ 5.65 ppm, 2b: δ 5.22 ppm) due to
Scheme 4 Comparison of the reactivity between C60 and 1.
1.2 Reaction of 1,7-(PhCh2)2C60 with PhCH2MgCl. When
we treated 1,7-(PhCH2)2C60 (1) with 2.6 equiv of PhCH2MgCl
rather than with PhMgBr, we observed the formation of not
only the expected mono-adduct (PhCH2)3C60H (4, 6% yield) but
also a double addition product (PhCH2)4C60 (5, 6% yield) and a
triple addition product (PhCH2)5C60H (6, 26% yield) as shown
in eqn. (1). Such a mixture invariably formed under a variety of
reaction conditions (reaction temperature, control of ambient
light, concentration, and amount of reagents). Similarly, a mix-
ture of higher adducts [(PhCH2)2R2C60 and (PhCH2)2R3C60H]
formed when MeMgBr and BuMgBr were used (data not
shown).
(1)
Scheme 3 Synthesis and structural determination of 2.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
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Structures of the products were determined by spectroscopic
methods as described for the previous compounds (and in the
Experimental Section). The penta-benzylated compound 6 was
converted to the corresponding C5v symmetric cyclopenta-
dienide Kϩ[(PhCH2)5C60]Ϫ (7) by deprotonation with t-BuOK
in THF-d8 (eqn. (2)). The deprotonation markedly simplified
1
the H NMR spectrum, in which the methylene signal of the
five benzyl addends appears as a singlet (δ 3.40 ppm). The
13C NMR spectrum exhibits only eight signals for the fullerene
carbon atoms (one signal for the cyclopentadienyl carbon
atoms, one signal for the sp3 carbon atoms and six signals
for the other sp2 carbon atoms) and five signals for the five
equivalent benzyl addends.
(2)
Scheme 5 Synthesis and structural determination of a mixture of 9
and 10.
1.3. Addition–elimination synthesis of fullerene indenides.
Owing to the lack of a synthetic route to 1,7-diaryl[60]fuller-
ene,12–14 the above synthetic approaches did not allow us to pre-
pare tri-arylated compounds such as 14. The synthesis of 14
was achieved by a rather intriguing arylation–debenzylation
route. Thus we heated 2 in PhCN at 150 ЊC for 2 d to obtain the
dehydrobenzylation product 1-(PhCH2)-7-PhC60 (8) in 49%
yield (eqn. (3)). The mass (APCI, MϪ = 888), 1H and 13C
NMR spectra (63 signals) are consistent with the assigned C1
structure.19 The thermal degradation reaction is facilitated
by a trace amount of water contained in PhCN, and there is
proton exchange between water and 2. Thus, when (PhCH2)2-
PhC60H (2) was heated in D2O-saturated PhCN at 100 ЊC for
2 h, (PhCH2)2PhC60D (2-d) was obtained in 84% deuterium
incorporation with >95% recovery of the starting material
(H/D mixture).
Scheme 6 Synthesis of the tri-arylated fullerene 14.
synthetic sequence provided the tri-arylated compound for the
first time.
2
Structures and electronic states of metal fullerene ꢀ5-
(3)
indenides
None of the compounds reported in this study afforded single
crystals suitable for X-ray analysis. To obtain information on
the nature of the η5-indenyl metal complex, we optimized the
structure of a Cs symmetric model compound K(H3C60) at the
HF/3-21G(*) level (Fig. 1a).21 The optimized structure shares
some important features with the X-ray structure of Tl(Ar3C70)
(Ar = 4-CF3C6H4).2 Thus, the fully delocalized 10-π indenyl
framework attached to the metal atom is electronically distri-
buted in the whole 58-π electron system as noted by the seven
surrounding C–C bonds of rather long bond lengths (1.47–
1.52 Å),22 and the HOMO surface of K(H3C60) is localized on
the indenyl substructure as shown in Fig. 1b (resembling that of
K(H3C70)).2 Such an effective π-electron delocalization within
the indenyl framework of K(H3C60) is rather surprising in view
of the non-planarity of the bicyclo[4.3.0] ring.23
The synthesis of 8 can be achieved in a single pot from 1.
Thus, 1 in 1,2-dichlorobenzene was treated first with PhMgBr
and the mixture was quenched with aq. HCl. The crude product
obtained by removal of the solvent was heated in PhCN to
obtain 8 in 44% yield after HPLC purification (cf. 37% yield by
the multi-pot synthesis).
Next, we examined the reaction of 8 with PhMgBr to obtain
(PhCH2)Ph2C60H (9/10) in 65% yield as a mixture of three iso-
mers; namely, one C1 symmetric compound (9) and two C1
symmetric compounds (10a/10b) which differ only in the pos-
ition of the hydrogen atom. The isomeric ratio was determined
by deprotonation experiments, in which the 9/10 mixture con-
verged into a mixture of two compounds, a Cs symmetric com-
pound 11 and a C1 symmetric compound 12 (Scheme 5, also see
Experimental Section).
Through another dehydrobenzylation–carbometalation
cycle, a symmetric tri-adduct Ph3C60H (14) was synthesized
(Scheme 6). Thus, when the mixture of 9 and 10 was heated in
PhCN, 1,7-Ph2C60 (13) was obtained in 26% yield (54% yield
based on the isomer content; 9 remained unchanged). The mass
analysis gave the correct molecular weight (APCI, MϪ = 874)
and the 1H NMR spectrum is identical with the authentic one.20
The reaction of 13 with PhMgBr proceeded smoothly to obtain
14 in 27% yield as a single isomer. While it is low-yielding, this
3
Synthesis of unsymmetrical fullerene cyclopentadienide
The stage is now set to describe the synthesis of unsymmetrical
fullerene cyclopentadienides. Starting with 1,7-(PhCH2)2C60 (1),
we first synthesized (PhCH2)2Ph3C60H (15). The reaction of 1
(1,2-dichlorobenzene–THF, 25 ЊC, 1.5 h) with 15 equiv. of an
organocopper reagent prepared from PhMgBr and CuBrؒSMe2
gave, after quenching with aqueous NH4Cl, 15a–c in quanti-
tative yield (86% yield after HPLC purification; Scheme 7).
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
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polyadducts (Scheme 8a).4,24 The carbometallation reaction
would compete with the oxidation reaction, which may account
for the difficulty in controlling the reaction with PhCH2MgCl.
Exclusive formation of the mono-addition product 2 in the
reaction of 1 with PhMgBr can be attributed to the straight-
forward anionic mono-addition, as it is more difficult to oxidize
a phenyl anion to a phenyl radical than to oxidize a benzyl
anion to a benzyl radical (Scheme 8b).
Fig. 1 Calculated molecular structure and the HOMO of K(H3C60) at
the HF/3-21G(*) level. (a) The structure of the indenyl moiety. C–C
bond lengths (Å) are shown next to the respective bonds. K–C bond
lengths (Å): K–C(1), 3.08; K–C(2), 2.98; K–C(3), 2.93. (b) HOMO
surface. Total energy = Ϫ2857.00417344 hartree.
Scheme 8 Possible pathways of reaction of (PhCH2)2C60 (1) with
phenyl and benzyl Grignard reagents. Experimentally observed
products are underlined. (a) Benzyl Grignard reagent. (b) Phenyl
Grignard reagent.
Taking the above considerations into account, we can draw
the overall stoichiometry of the penta-addition of an organo-
copper reagent to [60]fullerene as the one shown in Scheme 9a,
and a stepwise sequential addition–oxidation mechanism of
the penta-addition reaction as in Scheme 9b. All compounds
in the boxes have been isolated and independently subjected to
the reaction conditions,15 which gave support to the feasibility
of this pathway. Note that oxidation of [60]fullerene radical
Scheme 7 Synthesis and deprotonation of (PhCH2)2Ph3C60H (15).
anion by a Cu() salt is highly exothermic (Ϫ21.0 kcal molϪ1
,
Treatment of 15 in THF with t-BuOK (1.2 equiv.) at 20 ЊC gave
a single cyclopentadienide Kϩ[(PhCH2)2Ph3C60]Ϫ (16) of Cs
symmetry. Similarly, (PhCH2)Ph4C60H (17) was synthesized
from 1-(PhCH2)-7-PhC60 (8) in 79% yield (eqn. (4)).
calculated from their redox potential, Scheme 9c),25 indicating
that the Cu() salt can receive an electron from the anionic
Ϫ
intermediates such as (PhCH2)2PhC60
.
In conclusion we developed the stepwise methods for the
regioselective synthesis of unsymmetrical fullerene indenides
and cyclopentadienides. The studies on the stepwise synthesis
(4)
4
Mechanism of polyaddition to [60]fullerene
Several lines of new mechanistic information surfaced during
the present synthetic studies: first, the di-adduct is more
reactive than the parent [60]fullerene and must lie along the
pathway to the penta-adduct as an important intermediate.
Second, the formation of this di-adduct is probably the slowest
step in the organocopper penta-addition reaction, since we did
not see any side products other than the mono-adduct under
all reaction conditions ever examined. Third, an aliphatic
Grignard reagent (e.g. PhCH2MgCl) reacts with 1,7-R2C60 to
produce a mixture of multiadducts. It is most likely that
the Grignard reagent is oxidized by a fullerene compound to
afford an organo radical species which produces a mixture of
Scheme 9 Cu()-mediated penta-addition reaction of a Grignard
reagent to C60. (a) Overall stoichiometry. (b) Stepwise addition–
oxidation route. (c) Oxidation of fullerene radical anion by a Cu() salt.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
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also gave valuable information about the mechanism of the
organocopper penta-addition reaction. The synthetic protocols
presented here will allow us to obtain a wide variety of fuller-
ene ligands, which would play useful roles in organometallic
chemistry, catalysis and nano-sciences.
changed immediately from colorless to red. After stirring for
30 min at this temperature, the resulting red solution was
transferred to the purple suspension of C60 in benzonitrile via a
cannula over 30 min and stirred for a further 30 min, giving
a dark solution. To this solution was added benzyl bromide
(16.6 ml, 139 mmol, 100 equiv.) and the solution was stirred
further for 16 h at 26 ЊC. Then the reaction mixture was treated
with 5 ml of aq. HCl (ca. 1 M), dried over anhydrous MgSO4
and filtered through a pad of silica gel (eluted with toluene).
The filtrate was concentrated under reduced pressure and the
residue was subjected to preparative HPLC purification. The
fractions containing 1 were concentrated to a small volume
under reduced pressure and precipitated with methanol. The
precipitates were washed thoroughly with methanol and dried
under reduced pressure to give 1 in 65% yield (819 mg, 0.907
mmol) as a brown solid.
Experimental
General
All reactions were carried out in an oven-dried reaction vessel
under argon or nitrogen and were analyzed by HPLC (column:
Buckyprep, 4.6 × 250 mm, Nacalai tesque; flow rate: 1.0 ml
minϪ1; eluent: toluene–2-propanol = 7 : 3; detector: SPD-
M10Avp, Shimadzu). Common organic solvents as well as
aqueous solutions used for work up procedure were deoxygen-
ated by freeze–thaw cycles (over 3 times), by bubbling nitrogen
(over 30 min) or by pumping at 0 ЊC (over 30 min). All 1H NMR
spectra were taken at 400 MHz (JEOL EX-400), and 13C NMR
spectra at 100 MHz. Spectra are reported in part per million
from internal tetramethylsilane or the residual protons of
Synthesis of a mixture of 6,18-dibenzyl-9-phenyl-1,6,9,18-
tetrahydro(C60-Ih)[5,6]fullerene (2a) and 6,9-dibenzyl-18-phenyl-
1,6,9,18-tetrahydro(C60-Ih)[5,6]fullerene (2b). ((PhCH2)2PhC60H
(2)). A brown solution of 1 (1.01 g, 1.12 mmol, 1.0 equiv.)
in 300 ml of 1,2-Cl2C6H4 was degassed under reduced pres-
sure over 30 min. To this solution was added PhMgBr in THF
(0.93 M, 3.87 ml, 3.60 mmol, 3.2 equiv) at 28 ЊC. The mixture
was stirred for 4 h at this temperature. The colour of the
solution gradually changed from brown to dark green. HPLC
analysis indicated full consumption of the starting material
after 4 h. The major peak appeared in an 84% area ratio and the
rest 16% was composed of many tiny peaks. After quenching
with 1.0 ml of a degassed saturated NH4Cl aqueous solution,
the mixture was filtered through a pad of silica gel (eluted with
toluene) and concentrated to dryness under reduced pressure.
The residue was subjected to HPLC purification. Fractions
containing 2 were collected and concentrated to a small volume
under reduced pressure. Addition of methanol caused precipit-
ation of the product. The precipitates were collected by fil-
tration, washed with methanol and dried under reduced pres-
sure to give 840 mg (76%) of 2 as a brown solid. The ratio of
1
the deuterated solvent for the H NMR spectra, and from the
deuterated solvent for the 13C NMR spectra. IR spectra were
recorded on Applied. Systems. Inc., REACT IR 1000 as
powders on a diamond probe; absorptions are reported in cmϪ1
.
Mass spectra were measured with Shimadzu LCMS-QP8000
(APCI mode) equipped with Buckyprep column or JEOL JMS
SX102 (FAB mode). Preparative HPLC was performed on a
Buckyprep column (20 × 250 mm) using toluene–2-propanol =
7 : 3 as eluent (flow rate 12 to 20 ml minϪ1, detected at 350 nm
with an UV spectrophotometric detector, Shimadzu SPD-6A).
Recycle preparative gel permeation chromatography (GPC) was
performed on a Japan Analytical Industry LC-908 machine
equipped with JAIGEL 1H/2H column and an RI detector
RI-5HC (CHCl3 as eluent, flow rate: 3.5 ml minϪ1).
Solvents and materials
All commercially available reagents were distilled or recrystal-
lized before use unless otherwise noted. THF was purchased
from KANTO KAGAKU and stored over molecular sieves 4 Å
under nitrogen. 1,2-Cl2C6H4 was distilled under reduced pres-
sure from CaH2 and dried over molecular sieves 4 Å. PhCN was
distilled under reduced pressure from P2O5 and dried over
molecular sieves 4 Å. The water content of the solvent was
determined with a Karl-Fisher Moisture Titrator (MK-210,
Kyoto Electronics Company) to be less than 30 ppm. CuBrؒ
SMe2 was freshly prepared from CuBr and precipitated twice
from Me2S–pentane. A solution of t-BuOK in THF (1 M)
was purchased from Sigma Aldrich Japan K. K. and used as
received.
1
2a–2b is determined by H NMR analysis to be 62 : 38, which
was estimated from an integrated area ratio of signals for
the protons attached to the fullerene cage (5.22 ppm for 2b and
5.65 ppm for 2a). Analytically pure material was obtained by
GPC purification.
IR (powder) 3025 (w), 2912 (w), 1602 (w), 1493 (m), 1453 (w),
1030 (w), 739 (m), 729 (w), 697 (s); 1H NMR (CDCl3, 400 MHz)
δ 3.20 (d, J = 13.2 Hz, 1H, PhCHH, 2b), 3.28 (d, J = 13.2 Hz,
1H, PhCHH, 2b), 3.29 (d, J = 13.2 Hz, 1H, PhCHH, 2a), 3.32
(d, J = 13.2 Hz, 1H, PhCHH, 2a), 3.48 (d, J = 13.2 Hz, 1H,
PhCHH, 2a), 3.69 (d, J = 13.2 Hz, 1H, PhCHH, 2b), 3.77 (d,
J = 13.2 Hz, 1H, PhCHH, 2b), 3.85 (d, J = 13.2 Hz, 1H,
PhCHH, 2a), 5.22 (s, 1H, C60H, 2b), 5.65 (s, 1H, C60H, 2a),
7.13–7.64 (m, 13H ϩ 13H, Ph, 2a ϩ 2b), 8.04–8.08 (m, 2H, Ph,
2a), 8.11–8.14 (m, 2H, Ph, 2b); APCI-MS m/z 981 (Mϩ); Anal.
Calcd for C80H20, C 97.95; H, 2.05. Found: C 97.66; H, 2.34%.
Structural determination
The compounds that differ only about the position of the
hydrogen atom were identified on the assumption that the
signal for the hydrogen atom directly attached to the fullerene
sphere is highly affected by the addend on the neighboring sp3
carbon atom; the hydrogen with an aryl (e.g. phenyl) addend on
the neighboring sp3 carbon shows lower field shift than that
with an alkyl (e.g. benzyl) addend. All NMR data are so far
consistent with this assumption. In addition, molecular sym-
metry sometime helps identification of the compounds.
Preparation of potassium 6,9-dibenzyl-12-phenyl-9,12-di-
hydro(C60-Ih)[5,6]fullerene-1(6H)-ide (K[(PhCH2)2PhC60] (3)). A
solution of t-BuOK in THF (1.0 M, 7.0 µl, 7.0 µmol) was added
to a solution of 3 (5.2 mg, 5.3 µmol) in 0.55 ml of degassed
THF-d8 under an argon atmosphere in an NMR tube. The col-
our of the solution changed immediately from dark brown to
dark green, indicating the formation of indenyl anion. Then the
NMR tube was sealed and used in NMR analysis. Since the
fullerene indenide 2 slowly decomposed at ambient temper-
ature, 13C NMR measurement has so far not been achieved. 1H
NMR (THF-d8, 400 MHz) δ 3.73 (d, J = 12.6 Hz, 1H,
PhCHH ), 4.10 (d, J = 12.6 Hz, 1H, PhCHH ), 7.05–7.32 (m,
7H, Ph), 7.41–7.50 (m, 4H, Ph), 7.52–7.56 (m, 2H, Ph), 8.29–
8.34 (m, 2H, Ph). Signals for two methylene protons overlapped
with those of THF.
Preparation of 1,7-dibenzyl-1,7-dihydro(C60-Ih)[5,6]fullerene.
(1,7-(PhCH2)2C60 (1)). Both a solution of trimethylhydro-
quinone (1.14 g, 7.49 mmol, 5.4 equiv.) in 1300 ml of benzo-
nitrile and a suspension of C60 (1.00 g, 1.39 mmol, 1.0 equiv.)
in 700 ml of benzonitrile were degassed under reduced pres-
sure over 30 min. Tetrabutylammonium hydroxide (1 M in
methanol, 15.3 ml, 11.0 equiv.) was added to a solution of
trimethylhydroquinone at 26 ЊC. The color of the solution
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
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Synthesis of 6,9,18-tribenzyl-1,6,9,18-tetrahydro(C60-Ih)[5,6]-
fullerene (4), 1,7,11,24-tetrabenzyl-1,7,11,24-tetrahydro(C60-Ih)-
[5,6]fullerene (5), and 6,9,12,15,18-pentabenzyl-1,6,9,12,15,18-
hexahydro(C60-Ih)[5,6]fullerene (6) ((PhCH2)3C60H (4), (Ph-
CH2)4C60 (5), and (PhCH2)5C60H (6)). PhCH2MgCl (0.98 M in
Et2O, 0.020 ml, 0.022 µmol) was added to a degassed solution
of 1 (30.6 mg, 0.0339 µmol) in 25 ml of 1,2-dichlorobenzene in
four portions at 5 min intervals at ambient temperature. After
stirring for 1.5 h, the reaction mixture was quenched with 0.5 ml
of sat. aq. NH4Cl and dried over anhydrous Na2SO4. The
supernatant was passed through a pad of silica gel (eluted with
toluene) and concentrated to dryness under reduced pressure.
The residue was purified by GPC to give 4 (2.1 mg, 6.2%), 5
(2.6 mg, 6.1%), and 6 (10.3 mg, 26%). Structural assignments of
4, 5 and 6 came from the mass and the 1H NMR data. The mass
spectra are fully consisted with assigned structures (see below).
reduced pressure to give 8 as a brown solid (91.0 mg, 49%
yield).
IR (powder) 3058 (w), 3026 (w), 1493 (m), 1430 (m), 1188
(m), 1081 (m), 1031 (m), 731 (s), 694 (s); 1H NMR (CDCl3, 400
MHz) δ 4.18 (d, J = 13.2 Hz, 1H), 4.30 (d, J = 13.2 Hz, 1H),
7.23–7.28 (m, 1H), 7.31–7.36 (m, 2H), 7.48–7.53 (m, 2H), 7.54–
7.59 (m, 1H), 7.66–7.72 (m, 2H), 8.34–8.38 (m, 2H); 13C NMR
(CS2, 100 MHz) δ 48.20, 59.95, 61.33, 126.77 (2C), 127.11,
127.97, 128.01 (2C), 129.39 (2C), 130.21 (2C), 134.91, 136.70,
138.30, 138.32, 138.67, 140.55, 140.58, 141.59, 141.61, 141.84,
142.05, 142.09, 142.17, 142.30 (1C ϩ 1C), 142.60, 142.74,
142.77 (1C ϩ 1C), 142.79 (1C ϩ 1C), 143.34, 143.38, 143.56,
143.58 (1C ϩ 1C), 143.68, 143.77, 143.84, 143.94 (1C ϩ 1C),
143.95, 144.00, 144.01, 144.13, 144.33, 144.44, 144.46, 144.52,
144.69 (1C ϩ 1C), 145.11, 145.16, 145.86, 146.30, 146.46,
146.49, 146.52, 146.57, 146.65, 146.78, 147.02, 148.15, 148.19,
148.21, 148.23, 150.41, 150.92, 155.64, 156.83; APCI-MS m/z
888 (MϪ).
1
The H NMR spectrum (CDCl3–CS2 = 1 : 1) of 4 shows a
singlet assignable to the proton directly attached to the C60
cage at δ 4.35 ppm, six distinct doublets assigned to the three
methylene groups of the benzyl addends at δ 3.00, 3.17,
3.19, 3.26, 3.38, 3.48 ppm and a multiplet in the aromatic region
Synthesis of a mixture of 6-benzyl-9,18-diphenyl-1,6,9,18-
tetrahydro(C60-Ih)[5,6]fullerene (9), 18-benzyl-6,9-diphenyl-1,6,9,
18-tetrahydro(C60-Ih)[5,6]fullerene (10a) and 9-benzyl-6,18-di-
phenyl-1,6,9,18-tetrahydro(C60-Ih)[5,6]fullerene (10b) ((PhCH2)-
Ph2C60H (9/10)). These compounds were synthesized in the
same manner as 2. Starting from 49.7 mg of 8 (55.9 µmol),
35.0 mg of a mixture of 9 and 10a/b was obtained as a brown
solid (36.2 µmol, 65% yield); namely, one C1 symmetric com-
pound (9) and two C1 symmetric compounds (10a/10b) which
differ only in the position of the hydrogen atom. An isomeric
ratio was determined by the deprotonation experiment (vide
infra). Treatment of a mixture of (PhCH2)Ph2C60H (9/10) with
a THF solution of t-BuOK gave K[C60(PhCH2)Ph2] as a mix-
ture of a Cs symmetric compound 11 and a C1 symmetric com-
pound 12. In the 1H NMR spectrum, three singlet signals
(δ 5.78, 5.94, 5.99 ppm) assignable to the hydrogen atoms
directly attached to the C60 cage disappeared and signal pattern
became simple. Three doublet peaks were observed at δ 8.06,
8.29, 8.46 ppm in an integrated ratio of 24 : 52 : 24, which were
assigned to protons ortho to phenyl groups (not the benzyl
groups). From the integration ratio of these three peaks, the
ratio of 11 : 12 was determined to be 52 : 48. Subsequently, the
ratio of 9 : 10a : 10b was determined to be 52 : 15 : 33 from peak
intensities for the three singlet peaks assigned to the hydrogen
atoms attached to the fullerene cage in the 1H NMR spectrum
of (PhCH2)Ph2C60H (9/10).
1
in an integration ratio of 1 : 6 : 15. The H NMR spectra
(CDCl3–CS2 = 1 : 1) of 5 and 6 indicate that these com-
pounds are Cs symmetric. In the 1H NMR spectrum of 5, four
doublets due to the two methylene groups of the benzyl
addends appears at δ 2.89, 2.98, 3.23, 3.32 ppm. The spectrum
of 6 shows a singlet assignable to the proton attached to the C60
cage at δ 4.35 ppm, a singlet due to the methylene group of the
benzyl addend at δ 2.39 ppm, four doublets due to the remain-
ing four benzyl addends at δ 2.66, 2.71, 2.75, 2.94 ppm, and a
multiplet in the aromatic region with an integration ratio of
1 : 2 : 8 : 25.
4: 1H NMR (CS2–CDCl3 = 1 : 1) δ 3.00 (d, J = 13.2 Hz, 1H),
3.17 (d, J = 13.2 Hz, 1H), 3.19 (d, J = 13.2 Hz, 1H), 3.26 (d,
J = 13.2 Hz, 1H), 3.38 (d, J = 13.2 Hz, 1H), 3.48 (d, J = 13.2 Hz,
1H), 4.35 (s, 1H), 7.25–7.51 (m, 15H); FAB-MS m/z 995
(MHϩ); 5:1H NMR (CS2–CDCl3 = 1 : 1) δ 2.89 (d, J = 13.2 Hz,
2H), 2.98 (d, J = 13.2 Hz, 2H), 3.23 (d, J = 13.2 Hz, 2H), 3.32 (d,
J = 13.2 Hz, 2H), 7.14–7.41 (m, 20H); FAB-MS m/z 1085
(MHϩ); 6: 1H NMR (CS2–CDCl3 = 1 : 1) δ 2.39 (s, 2H), 2.66 (d,
J = 13.2 Hz, 2H), 2.71 (d, J = 13.2 Hz, 2H), 2.75 (d, J = 13.2 Hz,
2H), 2.94 (d, J = 13.2 Hz, 2H), 4.35 (s, 1H), 7.01–7.41 (m, 25H);
FAB-MS m/z 1177 (MHϩ).
Preparation of potassium 6,9,12,15,18-pentabenzyl-9,12,15,
18-tetrahydro(C60-Ih)[5,6]fulleren-1(6H)-ide (K[(PhCH2)5C60]
(7)). A solution of t-BuOK in THF (1.0 M, 10 µl, 10 µmol) was
added to a solution of 6 (4.8 mg, 4.1 µmol) in 1 ml of degassed
THF at ambient temperature and stirred for 3 min at this tem-
perature. The resulting dark green solution was concentrated
under reduced pressure. The residue was rinsed into an NMR
IR (powder) 3059 (w), 3027 (w), 1493 (m), 1446 (m), 1030
1
(m), 911 (m), 736 (s), 693 (s); H NMR (THF-d8, 400 MHz)
δ 3.94–4.14 (m, 2H ϩ 2H ϩ 2H, PhCH2, 9 ϩ 10), 5.78 (s, 1H,
C60H, 10b), 5.94 (s, 1H, C60H, 9), 5.99 (s, 1H, C60H, 10a), 7.07–
7.69 (m, 11H ϩ 11H ϩ 11H, Ph, 9 ϩ 10), 7.82 (d, J = 7.2 Hz,
2H, Ph, 10), 7.98 (d, J = 8.0 Hz, 2H ϩ 2H, Ph, 10), 8.10 (d,
J = 8.0 Hz, 2H, Ph, 9), 8.16 (d, J = 8.0 Hz, 2H, Ph, 9), 8.34 (d,
J = 7.2 Hz, Ph, 2H, 10); 13C NMR (CS2–CDCl3 = 5 : 1, 100
MHz) (9, recovered in the dehydrobenzylation reaction des-
cribed below.) δ 46.44, 59.29, 61.62, 63.58, 126.60 (2C), 126.64
(2C), 127.09, 127.24, 127.62, 128.07 (2C), 129.09 (2C), 129.18
(2C), 130.01 (2C), 132.85, 133.62, 134.61, 135.04, 136.97,
140.39, 140.48, 140.62, 141.38, 141.57, 141.86, 142.27, 142.40,
143.13, 143.37, 143.47, 143.64, 143.66, 144.02, 144.05, 144.13,
144.17, 144.21, 144.25, 144.50, 144.54, 144.59, 144.60, 144.94,
144.96, 145.04, 145.05, 145.27, 145.30, 145.42, 145.45, 145.63,
146.06, 146.09, 146.10, 146.13, 146.22, 146.27, 146.33, 146.35,
146.36, 146.37, 147.01, 147.26, 147.37, 148.33, 148.76 (1C ϩ
1C), 149.04, 149.63, 150.86, 153.47, 153.54, 154.57, 155.36,
159.48; APCI-MS m/z 966 (MϪ).
1
tube with 0.7 ml of THF-d8 to measure the H and 13C NMR
spectra.
1H NMR (400 MHz, THF-d8) δ 3.40 (s, 10H, CH2), 7.04 (t,
J = 7.2 Hz, 5H, p-Ph), 7.23 (t, J = 8.4 Hz, 10H, m-Ph), 7.41 (d,
J = 8.0 Hz, 10H, o-Ph); 13C NMR (100 MHz, THF-d8) δ 26.44
(5C), 31.76 (5C), 126.18 (5C), 128.07 (10C), 131.39 (5C), 131.87
(10C), 141.49 (10C), 142.58 (10C), 146.13 (5C), 146.94 (10C ϩ
5C), 148.70 (5C), 148.89 (10C).
Synthesis of 1-benzyl-7-phenyl-1,7-dihydro(C60-Ih)[5,6]fuller-
ene (1-(PhCH2)-7-PhC60 (8)). A solution of 2 (203 mg, 207
µmol) in PhCN (200 ml) was degassed under reduced pressure
over 30 min and was heated at 150 ЊC for 2 d. HPLC analysis
indicated the full consumption of the starting material after 2 d.
Then the reaction mixture was concentrated to dryness under
reduced pressure and the resulting crude product was purified
by preparative HPLC. The fractions containing 8 were concen-
trated and precipitated with methanol. The precipitates were
collected by filtration, washed with methanol and dried under
Preparation of a mixture of potassium 9-benzyl-6,12-diphenyl-
9,12-dihydro(C60-Ih)[5,6]fullerene-1(6H)-ide (11) and potassium
6-benzyl-9,12-diphenyl-9,12-dihydro(C60-Ih)[5,6]fullerene-1(6H)-
ide (12) (K[(PhCH2)Ph2C60] (11/12)). This was prepared in the
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
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same manner as 3. Since the fullerene indenide 11/12 was slowly
reduced pressure and precipitated by addition of methanol.
The precipitates were collected and washed with methanol
to afford 53.7 mg (86%) of 15 as an orange solid. The 1H
NMR analysis indicated a ratio of 15a : 15b : 15c was 10 : 25 :
65, which was determined from an integrated area ratio
of the signals due to the protons directly attached to the fuller-
ene core. Analytically pure material was obtained by GPC
purification.
decomposed even at ambient temperature, 13C NMR measure-
1
ment was so far unsuccessful. H NMR (THF-d8, 400 MHz)
δ 4.35 (s, 2H, PhCH2, 11 or 12), 6.97–7.45 (m, 11H ϩ 11H, Ph,
11 ϩ 12), 8.06 (d, J = 8.0 Hz, 2H, o-Ph, 12), 8.29 (d, J = 8.0 Hz,
4H, o-Ph, 11), 8.46 (d, J = 8.0 Hz, 2H, o-Ph, 12), Signals due
to the two methylene protons were overlapped with that of
THF.
IR (powder) 3060 (w), 3027 (w), 1600 (w), 1493 (m), 1455 (w),
1077 (w), 1030 (w), 735 (m), 695 (s); 1H NMR (400 MHz,
CDCl3) δ 2.71 (d, J = 13.0 Hz, 1H, PhCHH, 15c), 2.89 (d,
J = 13.2 Hz, 1H, PhCHH, 15b), 2.96 (d, J = 13.0 Hz, 1H,
PhCHH, 15c), 3.10 (d, J = 13.2 Hz, 1H, PhCHH, 15b), 3.23 (d,
J = 13.2 Hz, 2H, PhCHH, 15a), 3.40 (d, J = 13.2 Hz, 1H,
PhCHH, 15c), 3.48 (d, J = 13.2 Hz, 1H ϩ 2H, PhCHH, 15a ϩ
15b), 3.50 (d, J = 13.2 Hz, 1H, PhCHH, 15b), 3.55 (d, J = 13.0
Hz, 1H, PhCHH, 15c), 4.66 (s, 1H, C60H, 15c), 5.14 (s, 1H,
C60H, 15b), 5.24 (s, 1H, C60H, 15a), 7.00–7.68 and 7.83–8.05 (m,
25H ϩ 25H ϩ 25H, Ph, 15a ϩ 15b ϩ 15c); Anal. Calcd for
(PhCH2)2Ph3HC60ؒ(CHCl3)0.9 (C92.9H30.9Cl2.7): C, 89.79; H, 2.78.
Found: C, 90.05; H, 3.08.
Synthesisof1,7-diphenyl-1,7-dihydro(C60-Ih)[5,6]fullerene(1,7-
Ph2C60 (13)). A solution of a mixture of (PhCH2)Ph2C60H (9/10,
13.0 mg, 13.4 µmol) in 13 ml of benzonitrile was degassed
under reduced pressure at ambient temperature over 30 min.
This solution was heated at 150 ЊC for 1.5 d and then concen-
trated under reduced pressure to give a crude product. The
crude product was subjected to preparative HPLC purification.
The fractions containing 13 were concentrated and dried under
reduced pressure to give 13 (3.0 mg, 26% yield) as a dark brown
solid.
IR (powder) 3056 (w), 3029 (w), 1493 (m), 1492 (m), 1446
1
(m), 1432 (m), 1188 (m), 1032 (m), 735 (s), 692 (s); H NMR
(CDCl3, 400 MHz) δ 7.43–7.51 (m, 6H, Ph), 8.06–8.09 (m, 4H,
Ph); APCI-MS m/z 874 (MϪ).
Preparation of potassium 6,9-dibenzyl-12,15,18-triphenyl-
9,12,15,18-tetrahydro(C60-Ih)[5,6]fulleren-1(6H)-ide (K[C60(Ph-
CH2)2Ph3] (16)). This compound was prepared in the same
manner as 3.
Synthesis of 6,9,18-triphenyl-1,6,9,18-tetrahydro(C60-Ih)[5,6]-
fullerene (Ph3C60H (14)). A solution of PhMgBr in THF (1.35
M, 15.0 µl, 20.3 µmol, 3.73 equiv.) was added to a degassed
solution of 13 (4.75 mg, 5.43 µmol) in 1.50 ml of 1,2-
dichlorobenzene at 19 ЊC and the resulting mixture was stirred
for 6 min at this temperature. After quenching with 10 µl of
10% HCl aqueous solution, the crude mixture was filtered
through a pad of silica gel and concentrated under reduced
pressure. The residue was subjected to HPLC purification.
Fractions containing 14 were collected and concentrated to a
small volume. Precipitation by addition of methanol afforded
14 (27%) as a brown solid.
1H NMR (THF-d8, 400 MHz) δ 3.34 (d, 2H, J = 13.1 Hz,
PhCHH ), 3.66 (d, 2H, J = 13.1 Hz, PhCHH ), 6.98 (t,
J = 7.3 Hz, 2H, Ph), 7.03 (deformed d, J = 5.1 Hz, 3H, Ph), 7.11
(t, J = 7.6 Hz, 4H, Ph), 7.17 (t, J = 7.7 Hz, 2H, Ph), 7.28
(deformed t, 8H, Ph), 7.84–7.88 (m, 2H, Ph), 8.25 (deformed d,
J = 7.7 Hz, 4H, Ph); 13C NMR (THF-d8, 100 MHz) δ 50.74
(2C), 60.66 (2C), 62.09 (2C), 62.42, 125.80, 126.14 (2C), 126.16
(2C), 127.84 (2C), 127.96 (2C), 127.98 (4C), 128.27 (4C),
128.99, 129.13 (4C), 129.22 (2C), 129.95 (2C), 131.52 (4C),
140.96 (3C), 142.68 (2C), 142.71 (2C), 142.84 (4C), 142.92 (2C),
146.19 (2C), 146.24, 146.37 (2C), 146.74, 146.87 (2C), 146.88
(2C), 146.89 (2C), 147.09 (4C), 147.19 (2C), 148.82 (2C), 148.83
(2C), 148.98 (2C), 149.02 (2C), 149.25 (2C), 149.29 (2C), 149.59
(2C), 159.26 (2C), 159.61 (2C), 159.75 (2C), 160.29 (2C), 160.31
(2C).
IR (powder) 3058 (w), 3029 (w), 2924 (w), 1492 (m), 1446
(m), 1031 (m), 736 (s), 693 (s); H NMR (CDCl3, 400 MHz)
1
δ 5.69 (s, 1H), 7.34–7.43 (m, 9H), 7.81 (d, J = 7.2 Hz, 2H), 7.96–
7.97 (m, 4H); 13C NMR (CS2–CDCl3 = 1 : 1, 100 MHz) δ 29.90,
62.18, 63.69 (1C ϩ 1C), 127.09 (2C), 127.32 (1C ϩ 1C), 127.35,
127.53 (2C), 127.83 (2C), 128.95 (2C), 129.04 (2C), 129.11 (2C),
133.89, 133.99, 135.47, 136.94, 137.18, 139.85, 140.06, 140.70,
140.76, 141.55, 141.83, 142.12, 142.51, 142.67, 143.63 (1C ϩ
1C), 143.82, 144.00, 144.26, 144.29, 144.35, 144.39, 144.46,
144.71 (1C ϩ 1C), 144.75, 144.78, 144.91, 145.03, 145.16,
145.24, 145.58, 145.59, 145.62, 146.10, 146.12, 146.23, 146.33,
146.35, 146.40, 146.55, 146.64, 146.66, 146.83, 147.26, 147.43,
147.50, 148.53, 149.04 (1C ϩ 1C), 149.33, 149.92, 152.59,
152.85, 152.92, 153.87, 154.52, 155.55, 157.74; APCI-MS m/z
952 (MϪ).
Synthesis of a mixture of 9-benzyl-6,12,15,18-tetraphenyl-
1,6,9,12,15,18-hexahydro(C60-Ih)[5,6]fullerene (17a), 6-benzyl-
9,12,15,18-tetraphenyl-1,6,9,12,15,18-hexahydro(C60-Ih)[5,6]-
fullerene (17b) and 15-benzyl-6,9,12,18-tetraphenyl-1,6,9,12,15,
18-hexahydro(C60-Ih)[5,6]fullerene (17c) ((PhCH2)Ph4C60H
(17)). These compounds were synthesized in the same manner
as 15. Starting from 20.5 mg of 8 (23.1 µmol), 20.5 mg of 17 was
obtained as near 1 : 1 : 1 mixture of three isomers (an orange
solid, 18.2 µmol, 79% yield). The isomeric ratio remains
ambiguous due to the difficulty in distinguishing between 17b
and 17c.
Synthesis of a mixture of 15,18-dibenzyl-6,9,12-triphenyl-1,6,
9,12,15,18-hexahydro(C60-Ih)[5,6]fullerene (15a), 6,18-dibenzyl-
9,12,15-triphenyl-1,6,9,12,15,18-hexahydro(C60-Ih)[5,6]fullerene
(15b) and 6,9-dibenzyl-12,15,18-triphenyl-1,6,9,12,15,18-hexa-
hydro(C60-Ih)[5,6]fullerene (15c) ((PhCH2)2Ph3C60H (15)). A
solution of PhMgBr in THF (0.89 M, 0.951 ml, 847 µmol,
15 equiv.) was added to a suspension of CuBrؒSMe2 (176 mg,
847 µmol, 15 equiv.) in 5 ml of degassed THF at 23 ЊC.
To this suspension was added a degassed solution of 1
(51.0 mg 56.5 mmol) in 5 ml of 1,2-Cl2C6H4, and the
mixture was stirred for 1.5 h at 23 ЊC. HPLC analysis indi-
cated full consumption of the starting material. The
reaction mixture (brownish-green suspension) was quenched
with 0.2 ml of degassed saturated NH4Cl solution. The
resulting brown suspension was filtered through a pad of
silica gel and concentrated to dryness under reduced pressure.
The residue was subjected to HPLC purification. Fractions
containing 15 were concentrated to a small volume under
IR (powder) 3059 (w), 3028 (w), 1599 (m), 1493 (m), 1447
1
(m), 1077 (w), 1031 (m), 741 (m), 735 (m), 694 (s), 684 (s); H
NMR (THF-d8, 400 MHz) δ 3.63 (d, J = 13.2 Hz, PhCHH, 1H,
17b or 17c), 3.72 (s, PhCH2, 2H, 17a), 3.74, (d, J = 13.4 Hz,
PhCHH, 1H, 17b or 17c), 3.75 (d, J = 13.4 Hz, PhCHH, 1H,
17b or 17c), 3.83 (d, J = 13.2 Hz, PhCHH, 1H, 17b or 17c), 5.05
(s, 1H, 17a), 5.18 (s, 1H, 17b or 17c), 5.27 (s, 1H, 17b or 17c),
6.85–8.05 (m, 25H ϩ 25H ϩ 25H, Ph, 17a ϩ 17b ϩ 17c); APCI-
MS m/z 1120 (MϪ).
Nomenclature
All fullerene compounds in this paper are named on the basis
of the latest IUPAC recommendation.26 Recently numbering
system of the fullerene skeletons has changed into a more sys-
tematic method than the previous one. A comparison between
the new and the old methods is shown below.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
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9 M. Sawamura, K. Kawai, Y. Matsuo, K. Kanie, T. Kato and
E. Nakamura, Nature, 2002, 419, 702.
10 Preliminary communication: M. Sawamura, M. Toganoh,
K. Suzuki, A. Hirai, H. Iikura and E. Nakamura, Org. Lett., 2000,
2, 1919.
11 E. Nakamura and S. Mori, Angew. Chem., Int. Ed., 2000, 39,
3750.
12 (a) H. Nagashima, H. Terasaki, E. Kimura, K. Nakajima and
K. Itoh, J. Org. Chem., 1994, 59, 1246; (b) H. Nagashima,
H. Terasaki, E. Kimura, K. Nakajima and K. Itoh, J. Org. Chem.,
1995, 60, 4996; (c) S. Miki, M. Kitao and K. Fukunishi, Tetrahedron
Lett., 1996, 37, 2049; (d ) Y. Murata, K. Komatsu and T. S. M. Wan,
Tetrahedron Lett., 1996, 37, 7061; (e) G.-W. Wang, Y. Murata,
K. Komatsu and T. S. M. Wan, Chem. Commun., 1996, 2059.
13 (a) C. Caron, R. Subramanian, F. D’Souza, J. Kim, W. Kunter,
M. T. Jones and K. M. Kadish, J. Am. Chem. Soc., 1993, 115, 8505;
(b) T. Kitagawa, T. Tanaka, Y. Tanaka, K. Takeuchi and
K. Komatsu, J. Org. Chem., 1995, 60, 1490; (c) T. Kitazawa,
T. Tanaka, Y. Takata, K. Takeuchi and K. Komatsu, Tetrahedron,
1997, 53, 9965; (d ) E. Allard, L. Riviere, J. Delaunay, D. Dubois and
J. Cousseau, Tetrahedron Lett., 1999, 40, 7223; (e) E. Allard,
J. Delaunay, F. Cheng, J. Cousseau, J. Orduna and J. Garin.,
Org. Lett., 2001, 3, 3503.
14 (a) R. Subramanian, M. Kadish, M. N. Vijayashree, X. Gao, M. T.
Jones, M. D. Miller, K. L. Krause, T. Suenobu and S. Fukuzumi,
J. Phys. Chem., 1996, 100, 16327; (b) S. Fukuzumi, T. Suenobu,
T. Hirasaka, R. Arakawa and K. M. Kadish, J. Am. Chem. Soc.,
1998, 120, 9220; (c) K. M. Kadish, X. Gao, E. V. Caemelbecke,
T. Hirasaka, T. Suenobu and S. Fukuzumi, J. Phys. Chem. A, 1998,
102, 3898.
Acknowledgements
We thank Dr Y. Matsuo for helpful suggestions. This study was
supported by a Grant-in-Aid for Scientific Research (Specially
Promoted Research) and by the 21st Century COE Program for
Frontiers in Fundamental Chemistry from the Ministry of
Education, Culture, Sports, Science and Technology. M. T.
thanks JSPS for a predoctoral fellowship.
References
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16 The mechanism of the formation of the 1,7-R2C60 product as an
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equilibrium constant.
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18 Upon treatment of (PhCH2)2PhC60H (2) with a phenylcopper
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This experiment also supports the structural assignment.
19 cf. 1-(PhCH2)-9-PhC60 has Cs symmetry.
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5 An exception is a photo-driven tetra-amination reaction that takes
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22 The most obvious difference is found in the shorter C(3)–C(4) bond
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23 Note that the indenyl plane of K(H3C70) is rather flat due to the
decreased degree of curvature in the equatorial belt region of C70
cage.
24 Benzyl radical would also add to the anionic species such as
Ϫ
.
(PhCH2)3C60
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O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 6 0 4 – 2 6 1 1
2611