Regioselective intramolecular pauson-khand reactions of C60: An electrochemical study and theoretical underpinning

Article abstract of DOI:10.1002/chem.200401200

Suitably functionalized fulleropyrrolidines endowed with one or two propargyl groups at the C-2 position of the pyrrolidine ring (1,6-enynes) react efficiently and regioselectively with [Co₂(CO)₈] to afford the respective Pauson-Khan

Full text of DOI:10.1002/chem.200401200

Regioselective Intramolecular Pauson–Khand Reactions of C60:
An Electrochemical Study and Theoretical Underpinning
Nazario Martꢀn,*[a] Margarita Altable,[a] Salvatore Filippone,[a]
ꢁngel Martꢀn-Domenech,[a] Albert Poater,[b] and Miquel Solꢂ[b]
Dedicated to Professor Josꢀ Elguero on the occasion of his 70th birthday
Abstract: Suitably functionalized fullero-
pyrrolidines endowed with one or two
propargyl groups at the C-2 position of
the pyrrolidine ring (1,6-enynes) react
efficiently and regioselectively with
[Co2(CO)8] to afford the respective
Pauson–Khand products with an unpre-
cedented three (5a–d, 7, and 24) or
five (25) pentagonal rings, respectively,
fused onto the fullerene sphere. Fullero-
pyrrolidines with 1,7-, 1,9-, 1,10-, or
1,11-enyne moieties do not undergo
the PK reaction and, instead, the inter-
mediate dicobalt complexes formed
with the alkynyl group are isolated in
quantitative yields. These differences in
reactivity have been studied by DFT
calculations with a generalized gradient
approximation (GGA) functional and
several important energy and structural
differences were found for the inter-
mediates formed by the interaction be-
tween the coordinatively unsaturated
Co atom and the p system of C60 in
1,6- and 1,7-enynes. The different
lengths of the alkyne chains are re-
sponsible for the observed reactivities.
Cyclic voltammetry reveals that the
presence of the cyclopentenoneꢀs car-
bonyl group connected directly to the
C60 core results in PK compounds with
remarkable electron-accepting ability.
Keywords: cyclic voltammetry
cycloaddition · density functional
calculations fullerenes
Pauson–Khand reaction
·
·
·
Introduction
The [2+2+1] cycloaddition of alkyne, alkene, and carbon
monoxide mediated or catalyzed by a transition metal, also
known as the Pauson–Khand (PK) reaction, has been widely
used in organic synthesis for the construction of biologically
active five-membered carbocycles in a convergent approach
(Scheme 1).[1] In contrast, the use of this successful reaction
has almost been neglected in materials science despite the
potential for the construction of complex modified mole-
cules that exhibit nonconventional properties. With this in
Scheme 1. General scheme for the Pauson–Khand reaction.
mind, we recently reported in a preliminary communication
the first example of a highly efficient and regioselective in-
tramolecular PK reaction in which fullerene C60 was used as
the alkene component in the [2+2+1] cycloaddition reac-
tion.[2]
Fullerenes are a class of molecule made up of carbon
atoms with an unusual hybridization (sp2,3)[3] that exhibit a
chemical reactivity similar to that of electron-deficient ole-
fins.[4] Although electron-poor alkenes are not suitable sub-
strates for PK reactions as a result of their low reactivity
and the competing elimination reaction that can take place
to afford 1,3-dienes, a wide variety of inter- and intramolec-
ular PK reactions involving alkenes with electron-withdraw-
ing substituents have been reported in recent years.[5] There-
fore, fullerenes have emerged as suitable new substrates for
the PK reaction provided that they have a spherical surface
with multiple reactive double bonds and, in addition, the
competing b-hydride elimination reaction has been over-
[a] Prof. Dr. N. Martꢁn, M. Altable, Dr. S. Filippone,
Dr. ꢂ. Martꢁn-Domenech
Departamento de Quꢁmica Orgꢃnica
Facultad de Ciencias Quꢁmicas, Universidad Complutense
28040-Madrid (Spain)
Fax : (+34)91-3944103
E-mail: nazmar@quim.ucm.es
[b] A. Poater, Prof. Dr. M. Solꢄ
Institut de Quꢁmica Computacional and Departamento de Quꢁmica
Universitat de Girona, 17071-Girona, Catalonia (Spain)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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DOI: 10.1002/chem.200401200
Chem. Eur. J. 2005, 11, 2716 – 2729

FULL PAPER
come due to the absence of hydrogen atoms in their struc-
ture.
Results and Discussion
To carry out a systematic study of the PK reaction of the
fullerene sphere we have synthesized a wide variety of novel
suitably functionalized fulleropyrrolidines bearing one or
two alkyne units on the pyrrolidine ring. Thus, suitably de-
signed 1,6- and 1,7-enynes, as well as other enynes with a
larger separation between the alkene and the alkyne groups,
with one fullerene double bond as the alkene component,
have been prepared (see Scheme 2, Scheme 3, and
Scheme 4). Further, [2+2+1] cobalt-mediated carbonylative
cycloaddition of the starting enynes should afford new full-
erene cis-1 bisadducts endowed with unprecedented fused
cyclopentenone structures. An electrochemical study of the
novel modified fullerenes has been carried out by cyclic and
square-wave voltammetry at room temperature in order to
determine the redox behavior of the starting fulleropyrroli-
dines and the respective cis-1 bisadducts obtained in the PK
reaction. Finally, to gain a better understanding of the effect
of the curved fullerene surface as well as the length of the
chain connecting the alkene and the alkyne functional
groups on the PK reaction, theoretical calculations have
been carried out on 1,6- and 1,7-enynes by using density
functional theory (DFT) with a generalized gradient approx-
imation (GGA) functional (see the Computational Details
section).
Synthesis: The Pauson–Khand reaction has a broad scope; it
has proved successful with many functional groups (ethers,
alcohols, tertiary amines, acetals, esters, amides, and hetero-
cycles) as well as with different promoters, metal catalysts,
and experimental conditions.[1] An important disadvantage
of the PK reaction is, however, that the intermolecular pro-
cess is generally limited to strained olefins. Fullerenes are
known to have a strained spherical geometry and, therefore,
they appear to be suitable candidates for the PK reaction.
However, all attempts to carry out the intermolecular PK
reaction with C60, alkynes, and [Co2(CO)8] were unsuccess-
ful. Intramolecular PK reactions of fullerenes require the
design of new fullerene derivatives suitably functionalized
with an alkyne group. With this in mind, fulleropyrrolidines
endowed with an alkyne group at the C-2 position of the
pyrrolidine ring fulfil the requirements of appropriate geom-
etry and variable length between the fullerene double bond
and the alkyne.
Most of the intramolecular PK reactions reported have
been carried out with systems derived from hept-1-en-6-ynes
or propargyl allyl ethers or amines which afford cyclopent-
enones fused to a carbo- or heterocyclic pentagonal ring.
Enynes connected through aromatic rings have also been
successfully used in the PK reaction which has allowed the
synthesis of medium-sized rings (six- to eight-membered
rings).[6]
To carry out a thorough study of the scope of the PK re-
action using C60 as the alkene moiety, we synthesized a wide
variety of suitably functionalized fulleropyrrolidines. Since
hept-1-en-6-ynes are the most widely used substrates in the
PK reaction, we first prepared fulleropyrrolidine 2 which
contains the required 1,6-enyne moiety. Compound 2 was
synthesized by 1,3-cycloaddition of the azomethyne ylide
generated in situ from dl-propargylglycine (1) and formal-
dehyde to C60 in refluxing o-dichlorobenzene (o-DCB) fol-
lowing Pratoꢀs procedure (Scheme 2).[7]
Abstract in Spanish: Fulleropirrolidinas adecuadamente fun-
cionalizadas con uno o dos grupos propargilo en el C-2 del
anillo de pirrolidina (1,6-eninos), reaccionan con [Co2(CO)8]
proporcionando de manera regioselectiva y con altos rendi-
mientos los correspondientes productos Pauson-Khand (PK).
Estos compuestos presentan una estructura sin precedentes
con tres (5a–d, 7, 24) o cinco (25) anillos pentagonales fu-
sionados sobre la esfera del C60. Las fulleropirrolidinas que
contienen los grupos 1,7-, 1,9-, 1,10- o 1,11-enino no reaccio-
nan en las condiciones de PK, aislꢁndose fflnicamente los
complejos de cobalto intermedios con rendimientos cuantita-
tivos.Esta diferente reactividad ha sido estudiada mediante
cꢁlculos teóricos realizados a nivel DFT, utilizando el funcio-
nal de la aproximación del gradiente generalizado (GGA).
Dichos cꢁlculos muestran importantes diferencias energꢀticas
y estructurales entre los intermedios formados por el cobalto
coordinativamente insaturado y el sistema p del C60 en los
1,6- y 1,7-eninos. La diferente longitud de la cadena hidrocar-
bonada que soporta el grupo alquino, es la responsable de la
reactividad observada. El estudio de los productos de PK
mediante voltamperometría cíclica (CV) muestra que la pre-
sencia del grupo CO del anillo de ciclopentenona unido di-
rectamente al C60 es responsable de la notable capacidad
aceptora de estos nuevos compuestos.
Fulleropyrrolidine 2 is suitably functionalized to undergo
the PK reaction provided that it contains the required 1,6-
enyne moiety. However, its reaction with [Co2(CO)8] in tolu-
ene at 608C (or in the presence of molecular sieves) did not
afford the PK product owing to the ability of the lone-pair
of the pyrrolidineꢀs nitrogen atom to coordinate to the
cobalt complex. Note that although secondary amines are
not compatible with the PK reaction, fulleropyrrolidines are
known to exhibit remarkably low basicity and nucleophili-
city owing to the through-space interactions of the nitro-
genꢀs lone-pair and the fullerene p system. This results in a
basicity six orders of magnitude lower than that of pyrroli-
dine.[8] Therefore, we acylated fulleropyrrolidine 2 to pre-
vent the negative effect of the nitrogenꢀs lone-pair as well as
to increase the solubility of the resulting compound for use
in further chemical transformations. Thus, the reaction of 2
with different acyl chlorides afforded soluble N-acylfullero-
pyrrolidines (3a–d) in excellent yields (90–95%). In contrast
1
to fulleropyrrolidine 2, whose H NMR spectrum revealed a
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N. Martꢁn et al.
The PK products 5a–d were
unambiguously confirmed as
the cis-1 biscycloadducts with
an unprecedented structure that
contains three pentagonal rings
fused onto the fullerene sur-
face. The structures of the
novel compounds were estab-
lished by spectroscopy (UV/Vis,
FTIR, 1H, and 13C NMR, and
MS); the proton of the enone
1
moiety at d~6.8 ppm in the H
NMR spectra was used as a di-
agnostic signal. The structures
of 5a–d were further confirmed
by HMQC and HMBC experi-
ments, comparison with UV/Vis
spectra,[12] and by high-resolu-
tion MS (see the Experimental
Section). Since the PK com-
pounds exhibit C1 symmetry,
they were obtained as race-
mates.
The reaction of fulleropyrro-
lidine
2 with allyl bromide
under basic conditions led to
compound 6 which is endowed
with
a highly reactive allyl
group able to compete with the
fullerene double bond in the
PK reaction. Further reaction
of 6 with [Co2(CO)8] under the
same experimental conditions
Scheme 2.
(molecular
sieves,
toluene,
608C) afforded the PK product
7 (41% yield), together with
compound 8 (41%), which results from the PK reaction of
the allyl moiety. Compounds 7 and 8 are formed in the same
well-resolved set of signals, the 1H NMR spectra of com-
pounds 3a–d showed unresolved broad signals at room tem-
ꢀ
perature due to the rotational barrier of the N CO bond.
This dynamic behavior has been found in related systems[8]
and, recently, it has been observed that the presence of the
fullerene fragment close to the amideꢀs nitrogen atom accel-
erates the rotation of the amide by a factor of 103 at room
temperature owing to the strong electron-withdrawing effect
ꢀ
of the C60 unit, thus lowering the N CO rotational barrier
(DH° CO =16.0ꢁ0.1 kcalmolꢀ1).[9] Figure 1 shows the varia-
ꢀ
N
1
ble-temperature high-resolution (500 MHz) H NMR spec-
trum of compound 3a. The signals were well resolved at
333 K; coalescence occurred at 295.12 K and therefore the
energy barrier was DH° CO =14.2ꢁ0.1 kcalmolꢀ1.
ꢀ
N
N-Acylfulleropyrrolidines (3a–d) were treated with stoi-
chiometric amounts of [Co2(CO)8] in toluene at 608C in the
presence of previously activated molecular sieves (4 ꢆ)[10] to
afford the respective PK products 5a–d in almost quantita-
tive yields (see the Experimental Section). Intermediate di-
cobalt carbonyl complexes (4a–d) can be isolated by carry-
ing out the reaction at room temperature.[11]
Figure 1. 1H NMR spectra (500 MHz, CDCl3/CS2) of compound 3a re-
corded at different temperatures: a) 333 K, b) 313 K, c) 303 K, d)
295.12 K.
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Regioselective Intramolecular Pauson–Khand Reactions of C60
FULL PAPER
yields, thus showing that fullerene double bonds are as reac-
tive as those of the allyl moiety in the versatile PK reaction.
In the light of these results, we decided to expand the
scope of the PK reaction of the fullerenes to other deriva-
tives with larger enyne moieties. Thus, in addition to the ex-
pected cis-1 biscycloadducts, other regioisomeric bisadducts
may also be formed depending on the length of the chain
connecting the fullerene double bond and the alkyne group.
Thus, we have synthesized novel fulleropyrrolidines (10 and
14) with a 1,7-enyne moiety, which, under PK reaction con-
ditions, should lead to cyclopentenones fused to six-mem-
bered carbocyclic rings. Thus, by following Pratoꢀs proce-
dure[7] we have synthesized fulleropyrrolidines 10a–g from
different 4,5-disubstituted 2-alkynylbenzaldehydes (9a and
9c) by using glycine or sarcosine (N-methylglycine) and C60
(see the Experimental Section). Similarly, fulleropyrroli-
dines 14a–c were synthesized from 4-pentynal (13), which
was generated in situ by oxidation of 4-pentynol (12) with
pyridinium chlorochromate (PCC) (Scheme 3).
Compounds 10a–g and 14a–c were fully characterized by
spectroscopic techniques. Further reaction with [Co2(CO)8]
under the experimental conditions used for the preparation
of 5a–d, 7 and 8 did not afford, in any case, the correspond-
ing PK products. Thus, the reactions carried out with N-sub-
ꢀ
ꢀ
stituted (N CH3, N COPh) pyrrolidines or by activating the
alkynyl group by introducing electron-releasing methoxy
groups onto the benzene ring were futile. Instead, the inter-
mediate dicobalt complexes 11 and 15 were obtained in
almost quantitative yields. Further attempts to synthesize
the PK products from the intermediate complexes by raising
the temperature (RT!608C) either in the presence or ab-
sence of molecular sieves also failed. Note that at tempera-
tures higher than 608C, cobalt atoms were lost to give the
precursor fulleropyrrolidines 10 and 14, together with other
uncharacterized products resulting from extensive decompo-
sition.
Fulleropyrrolidines 18a–c with 1,9-, 1,10-, and 1,11-enyne
moieties, respectively, were prepared in two steps; the rele-
vant propargyloxybenzaldehyde
was prepared from commercial-
ly available o-, m-, and p-hy-
droxybenzaldehyde and prop-
argyl bromide under basic con-
ditions and then treated with
C60 and sarcosine in o-DCB
under standard conditions. At-
tempts to form the PK products
by using the general conditions
described above led only to the
dicobalt complexes 19a–c in
quantitative yield, which be-
haved similarly to the cobalt
complexes 11 and 15 under
thermal treatment (Scheme 3).
All the dicobalt complexes
studied were fully characterized
by spectroscopic techniques. As
a typical signature, three bands
at 2000–2100 cmꢀ1, which corre-
spond to the CO groups of the
cobalt complex, were observed
in the FTIR spectra, as well as
a singlet at around d=6.2 ppm,
which corresponds to the
proton of the carbon atom
linked to the cobalt atoms, in
the 1H NMR spectra of the
complexes.
Note that there are remarka-
ble differences in the reactivi-
ties of the fulleropyrrolidines
endowed with
a
1,6-enyne
moiety, which led to PK prod-
ucts in almost quantitative
yields, and those with longer-
length enynes, which in any
Scheme 3.
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N. Martꢁn et al.
case underwent the [2+2+1] cyclization reaction. In particu-
lar, fulleropyrrolidines 10 and 14 with the 1,7-enyne moiety
seemed to be suitably functionalized to undergo the PK re-
action. Since these experimental findings cannot be rational-
ized in terms of electronic factors, the additional methylene
group in the chain linking the olefin and the alkynyl groups
must introduce important geometrical differences that are
responsible for the observed reactivities.
In the light of the above results and as a result of the high
efficiency of the PK reaction of the 1,6-enynes, we decided
to explore the scope of the PK reaction of fulleropyrroli-
dines endowed with two propargyl groups at the same C-2
position of the pyrrolidine ring. According to the above re-
sults, the PK reaction of the fullerenes seems to be strongly
influenced by their geometry and a twofold cyclization reac-
tion should drastically increase the strain of the resulting
triscycloadduct. Thus, we synthesized fulleropyrrolidine 21
from dipropargyl glycine,[13] formaldehyde, and C60 in reflux-
ing chlorobenzene (Scheme 4).[14] To facilitate the subse-
Intermediate dicobalt complex 23 could be isolated in
95% yield after 2 h reaction at 508C. When 23 was heated
at 608C in toluene for 18 h, the mono-PK compound 24 was
obtained in 30% yield together with the double-PK product
25 in 5% yield. Attempts to obtain compound 25 from 24
under the same PK experimental conditions afforded 25 in
trace amounts (TLC) along with other unidentified decom-
position compounds. The structures of compounds 21–25
were determined by means of a thorough spectroscopic
study (see the Experimental Section). Thus, the 1H NMR
spectrum of fulleropyrrolidine 21 shows the hydrogen atoms
of the alkyne at d=2.28 ppm and of the pyrrolidine rings at
d=5.49 ppm. Compound 22 with a benzoyl moiety exhibited
similar dynamic behavior to that of the related compounds
3a–d due to the presence of the amido group. Intermediate
dicobalt complex 23 shows, in addition to the features found
for the cyclopentenone ring, a proton at d=6.11 ppm corre-
sponding to the CH group linked to the cobalt atoms. The
structures of 24 and 25 were established by using the meth-
ods used to identify the other
PK products (5a–d, 7) and con-
firmed by HMQC and HMBC
experiments. Note that the
highly strained structure of 25,
in which the amido group
should be located on one of the
sides of the pyrrolidine ring,
should be responsible for the C1
symmetry observed in the
NMR spectra.
In the light of the above find-
ings, the Pauson–Khand reac-
tion of C60 emerges as a highly
efficient regioselective proce-
dure to obtain cis-1 biscycload-
ducts 5a–d, 7, and 24 as well as
the rather unusual 1,2,3,4,11,12-
triscycloadduct 25, all of which
are endowed with cyclopente-
none moieties able to undergo
Scheme 4.
further chemical transforma-
tions.
quent PK reaction, the amino pyrrolidine ring was acylated
with benzoyl chloride in refluxing toluene and in the pres-
ence of triethylamine to form compound 22 in 95% yield.
Compound 22 is suitably functionalized with two propargyl
groups able to undergo the PK reaction on treatment with
[Co2(CO)8] in the presence of activated molecular sieves in
toluene at 508C. Interestingly, cis-1 biscycloadduct 24, the
result of only one [2+2+1] cycloaddition reaction, was ob-
tained in 30% yield as the main reaction product.
1,2,3,4,11,12-Triscycloadduct 25 formed from two PK reac-
tions was also obtained, although in a very poor yield (5%),
probably as a result of the high strain of the resulting mole-
cule, an unprecedented structure with five pentagonal rings
fused onto the fullerene surface.[15]
Electrochemistry: The PK products as well as the precursor
fulleropyrrolidines are electroactive molecules that, similarly
to the pristine fullerene C60, should behave as electron-ac-
cepting species. Therefore, we have studied the electrochem-
ical properties of the novel compounds by cyclic voltamme-
try (CV) in o-DCB/MeCN (4:1) as solvent at room tempera-
ture and by using tetrabutylammonium perchlorate as the
supporting electrolyte. The characteristic shapes of the
redox waves and their unequivocal position on the potential
scale virtually fingerprint the individual electrochemical
properties of the different redox systems. For this reason,
CV has been labeled as an electrochemical spectroscopy.[18]
In our case, the saturation of one olefinic double bond in
the suitably functionalized precursor fulleropyrrolidines
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Regioselective Intramolecular Pauson–Khand Reactions of C60
FULL PAPER
should lead, in principle, to different electrochemical behav-
ior to that shown by the related PK products in which two
fullerene double bonds are saturated. This should raise the
LUMO energy level and, therefore, the reduction waves
should be shifted towards more negative potentials, thus
slightly reducing their accepting ability.[19] Therefore, a vol-
tamperometric study of these compounds should allow us to
determine the electronic effect of the substitution pattern
on the electrochemical properties of the compounds ob-
tained and, simultaneously, to use CV as a useful characteri-
zation technique.
The redox potentials of some representative novel com-
pounds are collected in Table 1 together with those of C60 as
a reference. All the systems studied displayed electrochemi-
cally reversible behavior and, therefore, Table 1 gives the
half-wave reduction potential values.
tive to related monocycloadducts,[19,20] in our case the values
observed are a result of the electron-withdrawing effect of
the carbonyl group of the cyclopentenone ring fused to the
fullerene cage. These experimental data are supported by
the BP86 LUMO energy levels calculated for 3 (ꢀ5.795 eV,
R=CH3) and the related PK product 5 (ꢀ5.791 eV, R=
CH3) which have almost identical energy values and similar
shapes (Figure 3). This finding is in full agreement with pre-
vious electrochemical studies carried out on the parent full-
erocyclopentenone which exhibited the same reduction po-
tential as pristine C60 despite the saturation of one of the
double bonds of the fullerene core.[21]
Figure 2 shows that the cyclic voltammograms of biscy-
cloadducts 5a,b have three reversible reduction waves that
correspond to those of the C60 moiety. However, in addition
Table 1. Half-wave reduction potentials [V versus Ag/AgNO3] of com-
pounds 2, 3, 5, 7, 8, 24, 25, and C60.[a]
Compound
E11
E12
E13
E14
= ,red
= ,red
= ,red
= ,red
2
2
2
2
C60
2
ꢀ0.800
ꢀ0.894
ꢀ0.860
ꢀ0.852
ꢀ0.864
ꢀ0.863
ꢀ0.857
ꢀ0.858
ꢀ0.891
ꢀ0.875
ꢀ0.838
ꢀ0.829
ꢀ1.209
ꢀ1.288
ꢀ1.253
ꢀ1.262
ꢀ1.256
ꢀ1.265
ꢀ1.255
ꢀ1.252
ꢀ1.289
ꢀ1.279
ꢀ1.234
ꢀ1.222
ꢀ1.673
ꢀ1.818
ꢀ1.791
ꢀ1.784
ꢀ1.908
ꢀ1.892
ꢀ1.885
ꢀ1.888
ꢀ1.939
ꢀ1.818
ꢀ1.865
ꢀ1.906
ꢀ2.127
ꢀ2.249
3a
3b
5a
5b
5c
5d
7
8
24
25
ꢀ2.205
ꢀ2.215
–
–
–
ꢀ2.232
–
ꢀ2.231
–
–
[a] Working electrode: GCE; reference electrode: Ag/Ag+; counter elec-
trode: Pt; supporting electrolyte: 0.1m Bu4NClO4; scan rate: 100 mVsꢀ1
;
sample concentrations: (0.5–2.0)ꢇ10ꢀ3 m; solvent: o-DCB/MeCN (4:1
v/v).
Figure 2. Cyclic voltammograms of compounds 2, 3a,b, 5a,b, and 25 mea-
All the compounds studied showed three of four reversi-
ble reduction waves that correspond to the reduction steps
of the fullerene moiety (Figure 2). A remarkable negative
shift in the redox potentials relative to the values for pris-
tine C60 was observed in all cases which can be attributed to
the saturation of one (2, 3a, 3b, and 8) or two (5a–d and 7)
fullerene double bonds, which slightly reduces the electron-
accepting ability of the fullerene. Fulleropyrrolidine 2 with a
free secondary amino group showed the highest cathodic
shift relative to C60. Fulleropyrrolidines 3a,b with an acyl
sured in o-DCB/MeCN (4:1) at 100 mVsꢀ1
.
to these waves, another two very weak waves can also be
observed at around 1.50 and 2.00 V. These waves were
better observed in the square-wave voltammograms
(Figure 4) and have been assigned to the reduction of the
ketone and amido groups, respectively, present in the mole-
cules. These assignments were confirmed by CV of the used
solvent mixture (in order to discard the presence of impuri-
ties), as well as by the presence of a weak wave found at
about 1.50 V in the voltammograms of compounds 7 and 8
which only have the cyclopentenone moiety. The amido
group could also be observed as a very weak wave at about
2.00 V in the square-wave voltammograms of the precursor
fulleropyrrolidines (see the Supporting Information).
group linked to the pyrrolidineꢀs nitrogen atom showed a
1=2
red
significant anodic shift in comparison with 2 (DE ~40 mV)
due to the presence of the carbonyl group and the subse-
quent delocalization of the nitrogen atomꢀs lone-pair
(Figure 2 and Table 1).
cis-1 Biscycloadducts 5a–d and 7 resulting from the PK
reaction exhibit half-wave reduction potentials similar to
those observed for their precursor fulleropyrrolidines 3
(Figure 2). Although it is known that the reduction poten-
tials of biscycloadducts have a significant cathodic shift rela-
The above electrochemical data reveal that despite the
saturation of two of the double bonds of the fullerene cage
in biscycloadducts 5a–d and 7, these adducts are remarkable
electron acceptors, like their fulleropyrrolidine precursors,
Chem. Eur. J. 2005, 11, 2716 – 2729
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N. Martꢁn et al.
CH3) and the PK-unreactive species 14b (Scheme 3). From
a thermodynamic viewpoint, the reaction 3e+CO!5e and
the equivalent PK reaction for 14b are exothermic by 73.9
and 64.0 kcalmolꢀ1, respectively. Apparently, the final prod-
uct formed from 14b is more strained than 5e as indicated
ꢀ
by the fact that the fullerene C C bond length of the cen-
trally formed ring is 1.643 ꢆ in the final product formed
from 14b compared with 1.618 ꢆ in 5e. However, although
the thermodynamics of the PK reaction is about
10 kcalmolꢀ1 more favorable starting from 3e than from
14b, the reason for the lack of reactivity in 14b should not
be ascribed to the thermodynamics of the process and must
have a kinetic basis.
Figure 3. Three-dimensional representation of the LUMO of a) reactant
3 and b) product 5 with R=CH3 computed at the BP86 level. Isosurface
values are ꢀ0.05 and 0.05 a.u.
Previous theoretical studies[22,23] have shown that the most
probable rate-determining step in PK reactions is the loss of
CO from intermediate dicobalt carbonyl complexes such as
complex 4. This finding is supported by the fact that these
are the only intermediates that can be experimentally ob-
served. For this reason we have analyzed the energies and
the molecular structures of species 4e and 15b obtained
from the reaction of 3e and 14b with [Co2(CO)8] and the
complexes formed when these intermediates lose a CO
ligand, hereafter labeled complexes 4eꢀCO and 15bꢀCO,
in which the coordinatively unsaturated Co atom interacts
with the p system of the fullerene. Unfortunately, the sizes
of these systems prevented the calculation of the full energy
profile.
Figure 5a and 5b show the geometries of complexes 4e
and 15b, respectively. The differences between the two spe-
cies are not significant. The shortest distance between a Co
atom and the C=C bond on the fullerene to be attacked is
about 4.5–5 ꢆ. The lengths of the C=C double bonds being
attacked are almost the same as those of 3e and 14b (1.390
and 1.386 ꢆ, respectively, by calculation at the BP86 level of
theory). The molecular structures of complexes 4eꢀCO and
15bꢀCO depicted in Figures 6a and 6b, respectively, are
more informative; a clear difference is observed. The distan-
ces between the coordinatively unsaturated Co atoms and
the C=C bond being attacked are 2.131 and 2.108 ꢆ for
complex 4eꢀCO, about 0.1–0.2 ꢆ shorter than those found
for complex 15bꢀCO. This is likely to be due to the fact
that the donation and back-donation interactions between
the coordinatively unsaturated Co atoms and the p system
of the fullerene are stronger in complex 4eꢀCO than in
15bꢀCO. The stronger p interaction in 4eꢀCO is also re-
flected by the length of the C=C double bond attacked,
which increases by 0.064 ꢆ in the conversion of 4e into
4eꢀCO and by no more than 0.050 ꢆ in the conversion of
15b into 15bꢀCO. Therefore the C=C double bond that in-
teracts with the Co atom is sufficiently well activated in 4e
to continue the PK process. Thus, the differences observed
in the two complexes can be attributed to the different
lengths of the organic chain containing the alkyne and
alkene functional groups. The alkynyl chain in 4eꢀCO is of
an appropriate length to favor the metal–p interaction.
Interestingly, this has a relevant effect on the thermody-
namics of the formation of 4eꢀCO and 15bꢀCO by loss of
Figure 4. Square-wave voltammograms of compounds C60, 2, 3b, and 5b
measured in o-DCB/MeCN (4:1).
as a result of the fused cyclopentenone ring and the elec-
tron-withdrawing effect of the carbonyl group directly
linked to the C60 sphere.
The half-wave reduction potentials of PK products 24 and
25 are also given in Table 1. The first reduction potential of
24 is quite similar to those observed for related PK products.
However, compound 25 with two cyclopentenone rings had
the strongest electron-accepting ability of the PK products,
slightly more negative than pristine C60, owing to the elec-
tron-withdrawing effect of the two carbonyl groups directly
attached to the C60 cage. Note that the cyclic voltammogram
of 25 clearly shows the presence of reduction waves arising
from the carbonyl and amido groups (Figure 2).
Theoretical calculations: Calculations at the BP86 level (see
the Computational Details section) were performed on the
PK-reactive complex 3e (complex 3 in Scheme 2 with R=
2722
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Chem. Eur. J. 2005, 11, 2716 – 2729

Regioselective Intramolecular Pauson–Khand Reactions of C60
FULL PAPER
ces in the strength of the inter-
actions between the coordina-
tively unsaturated Co atom and
the p system of the fullerene in
the 4eꢀCO and 15bꢀCO spe-
cies explain the different reac-
tivities of complexes 3e and
14b.
Conclusions
In summary, we have synthe-
sized a wide variety of novel
fulleropyrrolidines
endowed
with one or two propargyl
groups which efficiently and re-
gioselectively undergo the PK
reaction with [Co2(CO)8] to
afford the unprecedented cis-1
Figure 5. BP86-optimized geometry of complexes a) 4e and b) 15b with the most relevant distances given in
ꢆ.
biscycloadduct
and
1,2,3,4,11,12-triscycloadduct
fullerene structures with three
(5a–d, 7, and 24) or five (25)
pentagonal rings, respectively,
fused onto the fullerene sur-
face. Cyclic voltammetry re-
veals that the novel biscycload-
ducts that result from the PK
reaction have the same elec-
tron-accepting ability as the
precursor
fulleropyrrolidines
owing to the electron-withdraw-
ing effect of the carbonyl group
of the cyclopentenone moiety
directly linked to the fullerene
sphere. Remarkably, triscy-
cloadduct 25 with two cyclopen-
tenone rings has a better elec-
tron-accepting ability with
a
first reduction potential value
close to that of pristine C60.
In an attempt to expand the
scope of the PK reaction to
other fullerene derivatives,
Figure 6. BP86-optimized geometry of complexes a) 4eꢀCO and b) 15bꢀCO with the most relevant distances
given in ꢆ.
a CO molecule from 4e and 15b. While the loss of CO from
15b (15b!15bꢀCO+CO) requires 25.3 kcalmolꢀ1, the
same process starting from 4e involves only 15.2 kcalmolꢀ1.
Although the transition states of these processes have not
been identified owing to high computational costs, it is clear
that the loss of CO from 15b needs more than 25.3 kcal-
molꢀ1 and for this reason 15b does not react further when
the temperature is less than 608C. As explained before, an
increase in the reaction temperature leads to the decomposi-
tion of 15b and so the reaction does not take place at
higher temperatures. On the other hand, the loss of CO
from 4e is much more facile. In general terms, the differen-
novel fulleropyrrolidines endowed with 1,7- to 1,11-enynes
were synthesized. However, no PK products were obtained
and, instead, the intermediate dicobalt complexes were iso-
lated in almost quantitative yields. The remarkably different
reactivities exhibited by the fulleropyrrolidines endowed
with the 1,6-enyne moiety and those with the 1,7-enyne frag-
ment have been rationalized by means of DFT theoretical
calculations. The energies and the molecular structures of
the intermediates formed through the interaction between
the coordinatively unsaturated Co atom and the p system of
the fullerene (4eꢀCO versus 15bꢀCO) reveal important
differences between the two systems and clearly confirm
Chem. Eur. J. 2005, 11, 2716 – 2729
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N. Martꢁn et al.
145.97, 146.0, 146.4, 146.5, 146.54, 146.57, 146.6, 146.7, 146.71, 146.76,
146.8, 146.9, 147.1, 147.53, 147.54, 147.56, 147.6, 151.9, 154.0, 154.5,
156.0 ppm; FTIR (KBr): n˜ =1508, 1461, 1425, 526 cmꢀ1; MS (ESI): m/z:
802.1 [M+H]+.
Compound 10e: Yield 35% (65%). 1H NMR (CDCl3/CS2, 298 K,
300 MHz): d=0.28 (s, 9H; (CH3)3Si), 4.94 (d, J=10.3 Hz, 1H; CH2N),
that the interaction in the 1,6-enyne (4eꢀCO) is stronger as
a consequence of the different length of the organic chain
linking the alkyne and alkene functional groups.
These results show that the highly versatile PK reaction
can be applied to the spherical molecular surfaces of C60
and other fullerenes, and that CO loss in longer 1,7-enynes
may be facilitated by photoirradiation. These possibilities
are currently being explored as is the chemical modification
of the reactive cyclopentenone ring formed in the PK reac-
tions of these systems.
ꢀ
5.15 (d, J=10.3, 1H; CH2N), 6.43 ( s, 1H; CHN), 7.28–7.33 (m, 1H; H
ꢀ
ꢀ
Ar), 7.42–7.47 (m, 1H; H Ar), 7.51–7.54 (m, 1H; H Ar), 8.03–8.06 ppm
(m, 1H; H Ar); 13C NMR (CDCl3/CS2, 298 K, 75 MHz): d=0.57, 61.9,
ꢀ
73.0, 74.6, 76.5, 101.4, 104.2, 123.7, 128.5, 128.9, 129.5, 134.0, 135.4, 136.4,
136.7, 137.1, 139.6, 140.1, 140.3, 140.6, 142.1, 142.2, 142.3, 142.4, 142.5,
142.6, 142.64, 142.7, 142.8, 142.9, 143.0, 143.1, 143.4, 143.5, 144.7, 144.8,
144.9, 145.5, 145.65, 145.67, 145.7, 145.75, 145.8, 145.9, 146.1, 146.37,
146.39, 146.4, 146.5, 146.6, 146.66, 146.7, 146.9, 147.3, 147.5, 147.6, 153.1,
154.0, 154.9, 156.5 ppm; FTIR (KBr): n˜ =2850, 2343, 526 cmꢀ1; MS (ESI):
m/z: 936 [M+H]+.
Experimental Section
Compound 14a: Yield 25% (60%). 1H NMR (CDCl3/CS2, 298 K,
200 MHz): d=2.12 (t, J=2.4 Hz, 1H; CH), 2.80–2.96 (m, 4H; 2CH2),
4.76 (d, J=11.9 Hz, 1H; CH2N), 4.87 (dd, J=1.2, 2.7 Hz, 1H; CHN),
4.99 ppm (d, J=11.9 Hz, 1H; CH2N); 13C NMR (CDCl3/CS2, 50 MHz):
d=17.5, 32.4, 62.4, 69.8, 72.9, 74.9, 83.1, 135.3, 135.5, 135.6, 136.5, 139.7,
140.0, 141.1, 141.58, 141.6, 141.7, 141.8, 141.9, 141.98, 142.1, 142.3, 142.4,
142.43, 142.48, 142.5, 142.8, 143.0, 144.1, 144.2, 144.3, 144.9, 144.99, 145.0,
145.08, 145.1, 145.13, 145.18, 145.2, 145.21, 145.4, 145.43, 145.7, 145.75,
145.8, 145.83, 145.9, 145.94, 145.98, 146.0, 146.1, 146.8, 151.9, 153.5, 154.0,
155.2 ppm; FTIR (KBr): n˜ =526.5, 632.6, 1423 cmꢀ1; MS (ESI): m/z:
815.9 [M+H]+.
Computational details: The calculations were carried out by using the
2002.03 release of the Amsterdam density functional (ADF)[24] package
developed by Baerends and co-workers.[25,26] The numerical integration
scheme of te Velde and Baerends was employed.[27] Both geometry opti-
mizations and energy evaluations of the neutral closed-shell singlet
ground-state structures were performed by using a generalized gradient
approximation (GGA) which includes Beckeꢀs GGA exchange correc-
tion[28] and Perdewꢀs GGA correlation correction,[29] the so-called BP86
functional. For geometry optimizations we used an uncontracted double-&
basis set augmented by an extra polarization function to describe the 3s,
3p, 3d, and 4s orbitals of cobalt, while for the carbon (2s, 2p), nitrogen
(2s, 2p), oxygen (2s, 2p), and hydrogen (1s) atoms, double-& basis sets
were employed.[30,31] Electrons in lower orbital shells were treated within
the frozen core approximation.[25] A set of auxiliary s, p, d, f, and g func-
tions, centered in all nuclei, was introduced in order to fit the molecular
density and Coulomb potential accurately in each SCF cycle.[32]
General procedure for the synthesis of N-acylfulleropyrrolidines 3a–d,
10 f, and 14c: NEt3 (0.30 mmol) was added to a solution of fulleropyrroli-
dines 2, 10e or 14a (0.15 mmol) in toluene (50 mL). After 5 minutes, the
corresponding acyl chloride (0.30 mmol) was added and the mixture stir-
red at room temperature for 1 h (for compound 14c heating was necessa-
ry). When the reaction was complete, the solvent was removed in vacuo.
The crude product was purified by flash chromatography over neutral
alumina (eluent: toluene/ethyl acetate 4:1) to afford the final product
(90–95% yield).
General: All reactions were carried out in dry, freshly distilled solvent
under anhydrous conditions: toluene and Et2O were distilled from
sodium benzophenone and o-dichlorobenzene (o-DCB) was used without
further purification. All reagents purchased were of the highest commer-
cial quality available and used without further purification.
Compound 3a: Yield 95%. 1H NMR (CDCl3, 333 K, 500 MHz): d=2.32
(t, J=2.6 Hz, 1H; CH), 3.58 (dd, J=6.4, 2.6 Hz, 2H; CH2), 5.54 (d, J=
12 Hz, 1H; CH2N), 5.71 (d, J=12 Hz, 1H; CH2N), 6.41 (brt, 1H; CHN),
NMR spectra were recorded with Bruker AC-200, Bruker Avance DPX-
300, and Bruker Avance AV-500 spectrometers. Chemical shifts are re-
ported in ppm downfield from tetramethylsilane (TMS). FTIR spectra
were recorded as KBr pellets with a Nicolet-Magna-IR 5550 spectrome-
ter. Electrospray ionization (ESI) mass spectra were recorded with a
HP1100MSD spectrometer.
7.57–7.56 (m, 3H; Ar H), 7.91–7.89 ppm (m, 2H; Ar H); 13C NMR
(CDCl3, 298 K, 75 MHz): d=29.9, 65.4, 70.6, 73.5, 80.2, 125.3, 128.2,
128.3, 128.8, 129.0, 130.9, 135.3, 136.9, 138.1, 139.9, 140.3, 140.33, 141.7,
141.8, 141.9, 142.1, 142.12, 142.17, 142.2, 142.3, 142.4, 142.7, 142.77, 142.8,
143.1, 143.2, 144.4, 144.44, 144.5, 144.6, 144.65, 145.3, 145.4, 145.44, 145.5,
145.6, 145.68, 145.7, 145.76, 146.1, 146.2, 146.38, 146.39, 146.4, 147.4,
147.42, 150.1, 152.4, 154.2, 154.7, 170.1 ppm; FTIR (KBr): n˜ =1641, 1400,
526 cmꢀ1; MS (ESI): m/z: 906 [M+H]+.
ꢀ
ꢀ
Cyclic voltammograms were recorded with a potentiostat/galvanostat
AUTOLAB with PGSTAT30 equipped with GPES software for Windows
version 4.8 in a conventional three-compartment cell by using a GCE
(glassy carbon electrode) as the working electrode, Ag/AgNO3 as the ref-
erence electrode, Bu4NClO4 as the supporting electrolyte, o-dichloroben-
Compound 3b: Yield 95%. 1H NMR (CDCl3, 298 K, 500 MHz, mixture
of rotamers, 1:1): d=2.44, 2.25 (brs, brs, 1H), 3.54, 3.37 (brm, brm, 2H),
4.17, 3.93 (brs, brm, 1H), 4.43, 4.21 (d, d, J=14.6 Hz, 1H), 5.49 (brs,
2H), 6.27, 4.93 (d, d, J=12.4 Hz, 1H), 6.39, 5.98 ppm (brt, brm, 1H); 13C
NMR (CDCl3, 298 K, 125 MHz, mixture of rotamers, 1:1): d=25.7, 29.7,
42.4, 42.8, 58.3, 64.4, 66.4, 69.5, 70.3, 72.6, 73.0, 73.7, 74.2, 96.1, 127.5,
127.7, 129.1, 134.9, 135.1, 139.8, 140.2, 141.7, 141.8, 142.0, 142.1, 142.2,
142.7, 143.0, 143.1, 144.4, 144.5, 144.6, 145.2, 145.3, 145.37, 145.4, 145.6,
145.66, 146.0, 146.1, 146.2, 146.3, 146.36, 147.4, 149.5, 169.6, 170.2 ppm;
FTIR (KBr): n˜ =1641, 1400, 526 cmꢀ1; MS (ESI): m/z: 920 [M+H]+.
zene/acetonitrile as the solvent (4:1 v/v), and a scan rate of 100 mVsꢀ1
.
General procedure for the synthesis of fulleropyrrolidines 2, 10e, and
14a: The corresponding aldehyde (0.694 mmol) and dl-propargylglycine
(0.694 mmol for compound 2) or glycine (0.694 mmol for compounds 10e
and 14a) were added to a solution of C60 (250 mg, 0.347 mmol) in o-DCB
(80 mL). The mixture was refluxed for 24 h and after cooling it was con-
centrated under reduce pressure. Flash chromatography over silica gel
eluting initially with CS2 (for the separation of C60) and then with CS2/tol-
uene gave the final product in 25–35% yield (56–65% based on con-
sumed C60).
Compound 2: Yield 25% (56%). 1H NMR (CDCl3/CS2, 298 K,
500 MHz): d=2.22 (t, J=2.7 Hz, 1H; CH), 3.24 (ddd, J=16.7, 4.8,
2.7 Hz, 1H; CH2), 3.49 (ddd, J=16.7, 7.8, 2.7 Hz, 1H; CH2), 4.77 (d, J=
11.3 Hz, 1H; CH2N), 4.87 (dd, J=7.8, 4.8 Hz, 1H; CHN), 4.99 ppm (d,
J=11.3 Hz, 1H; CH2N); 13C NMR (CDCl3/CS2, 298 K, 75 MHz): d=
30.58, 62.6, 72.0, 72.7, 75.1, 77.0, 81.4, 136.11, 136.16, 136.4, 137.7, 140.4,
140.5, 140.7, 140.8, 142.2, 142.3, 142.4, 142.5, 142.53, 142.64, 142.67, 142.7,
142.9, 143.0, 143.14, 143.15, 143.2, 143.5, 143.7, 143.79, 144.8, 144.9, 145.1,
145.66, 145.69, 145.7, 145.72, 145.78, 145.8, 145.82, 145.86, 145.9, 145.96,
Compound 3c: Yield 90%. 1H NMR (CDCl3, 323 K, 500 MHz): d=2.34
(t, J=2.5 Hz, 1H; CH=C), 3.67–3.35 (brm, 2H; CH2), 5.46 (brm, 1H),
6.05 (brm, 1H), 6.34 (brm, 1H), 7.32 (d, J=15.4 Hz, 1H; CH=CH),
ꢀ
ꢀ
7.48–7.42 (m, 3H; Ar H), 7.72–7.69 (m, 2H; Ar H), 8.04 ppm (d, J=
15.4 Hz, 1H; CH=CH); 13C NMR (CDCl3, 298 K, 50 MHz): d=29.9,
65.8, 69.7, 73.6, 77.2, 80.1, 117.1, 128.1, 128.9, 130.1, 134.9, 139.7, 140.1,
140.2, 141.6, 141.7, 141.97, 142.0, 142.02, 142.03, 142.05, 142.1, 142.14,
142.3, 142.6, 142.7, 143.0, 143.1, 144.2, 144.3, 144.4, 144.5, 144.6, 145.2,
145.25, 145.3, 145.35, 145.4, 145.5, 145.6, 146.0, 146.08, 146.1, 146.2,
146.27, 146.3, 147.2, 147.3, 149.8, 152.5, 154.2, 165.0 ppm; FTIR (KBr):
n˜ =1652, 1400, 526 cmꢀ1; MS (ESI): m/z: 932 [M+H]+.
2724
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Chem. Eur. J. 2005, 11, 2716 – 2729

Regioselective Intramolecular Pauson–Khand Reactions of C60
FULL PAPER
Compound 3d: Yield 95%. 1H NMR (CDCl3, 298 K, 500 MHz, mixture
or rotamers): d=2.79 (m, 1H), 2.95 (m, 1H), 3.42, 3.35 (brd, brd, 1H),
3.89, 3.61 (m, brm, 1H), 5.69, 5.49 (d, d, J=11.5 Hz, 1H), 6.19, 4.96 (d,
d, J=12.6 Hz, 1H), 6.37, 5.94 ppm (brt, brm, 1H); 13C NMR (CDCl3,
298 K, 125 MHz, mixture of rotamers): d=14.0, 22.6, 29.6, 31.6, 66.4,
70.3, 72.5, 72.7, 72.9, 73.1, 73.5, 74.4, 96.1, 139.8, 140.3, 141.7, 141.9, 142.1,
142.7, 142.77, 143.1, 143.2, 144.4, 144.48, 144.5, 144.57, 144.6, 144.7,
144.73, 145.3, 145.37, 145.4, 145.44, 145.5, 144.53, 145.6, 145.66, 145.7,
146.1, 146.2, 146.3, 146.35, 146.4, 146.45, 146.6, 147.39, 147.4, 147.44,
149.5, 150.3, 152.3, 164.2 ppm; FTIR (KBr): n˜ =1655, 1410, 526 cmꢀ1; MS
(ESI): m/z: 900 [M+H]+.
9.5 Hz, 1H; CH2N), 5.01 (d, J=9.5 Hz, 1H; CH2N), 5.37 (s, 1H; CHN),
ꢀ
ꢀ
7.23–7.31 (m, 1H; Ar H), 7.42–7.54 (m, 2H; Ar H), 8.09 ppm (m, 1H;
ꢀ
Ar H); 13C NMR (CDCl3/CS2, 298 K, 50 MHz): d=0.05, 39.8, 69.2, 69.7,
79.6, 100.8, 103.4, 124.0, 127.8, 129.0, 120.3, 132.3, 133.1, 134.8, 135.7,
136.5, 139.4, 139.7, 140.06, 140.1, 141.6, 141.63, 141.64, 141.87, 141.9,
142.0, 142.06, 142.07, 142.12, 142.15, 142.2, 142.4, 142.45, 142.5, 142.9,
143.0, 144.2, 144.4, 144.49, 144.5, 145.0, 145.1, 145.13, 145.16, 145.2, 145.3,
145.35, 145.4, 145.5, 145.6, 145.8, 145.85, 145.9, 145.97, 146.0, 146.1,
146.15, 146.2, 146.4, 146.8, 147.2, 153.3, 153.7, 154.5, 156.3 ppm; FTIR
(KBr): n˜ =526, 760, 842, 866, 1230, 1247, 1463, 1506 cmꢀ1; MS (ESI): m/z:
950.3 [M+H]+.
1
Compound 10 f: Yield 90%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
Compound 10c: Yield 43% (55%). 1H NMR (CDCl3/CS2, 298 K,
300 MHz): d=0.25 (s, 9H; (CH3)3Si), 2.80 (s, 3H; CH3), 3.88 (s, 3H;
OCH3), 3.96 (s, 3H; OCH3), 4.33 (d, J=9.5 Hz, 1H; CH2N), 4.99 (d, J=
0.03 (s, 9H; (CH3)3Si), 5.83 (d, J=12.7 Hz, 1H; CH2N), 6.36 (brd, 1H;
ꢀ
ꢀ
CH2N), 7.32–7.37 (m, 1H; H Ar), 7.45–7.54 (m, 5H; H Ar), 7.60 (s, 1H;
CHN), 7.62–7.68 (m, 2H; H Ar), 8.12–8.14 ppm (m, 1H; H Ar); 13C
NMR (CDCl3/CS2, 298 K, 75 MHz): d=ꢀ0.2, 62.0, 66.3, 69.5, 71.5, 76.4,
101.8, 103.7, 123.4, 125.5, 127.9, 128.6, 129.2, 130.3, 131.0, 133.8, 134.9,
135.4, 136.0, 136.4, 136.6, 139.64, 139.7, 140.5, 140.8, 142.05, 142.06, 142.1,
142.3, 142.4, 142.44, 142.46, 142.5, 142.7, 143.0, 143.07, 143.1, 143.13,
143.45, 144.7, 144.8, 144.9, 145.0, 145.5, 145.6, 145.7, 145.75, 145.8, 145.9,
146.0, 146.06, 146.2, 146.4, 146.5, 146.6, 146.66, 146.7, 146.76, 146.8,
146.82, 146.84, 147.7, 147.9, 151.9, 154.0, 154.7, 155.8, 171.7 ppm; FTIR
9.5 Hz, 1H; CH2N), 5.63 (s, 1H; CHN), 6.99 (s, 1H; Ar H), 7.60 ppm (s,
ꢀ
ꢀ
ꢀ
1H; Ar H); 13C NMR (CDCl3/CS2, 298 K, 75 MHz): d=0.5, 40.5, 56.3,
ꢀ
56.7, 69.7, 70.2, 80.1, 99.5, 103.9, 112.0, 113.1, 116.6, 125.7, 128.6, 132.7,
133.0, 135.3, 136.3, 136.6, 136.8, 140.1, 140.3, 140.5, 140.6, 142.0, 142.1,
142.13, 142.2, 142.4, 142.5, 142.53, 142.55, 142.6, 142.66, 142.7, 143.0,
143.1, 143.4, 143.5, 144.8, 144.9, 145.0, 145.05, 145.5, 145.6, 145.7, 145.72,
145.8, 145.9, 145.96, 146.1, 146.4, 146.5, 146.51, 146.6, 146.7, 146.9, 147.4,
147.7, 147.72, 148.6, 150.5, 154.3, 155.1, 156.8 ppm; FTIR (KBr): n˜ =526,
840, 1247, 1267, 1460, 1508 cmꢀ1; MS (ESI): m/z: 1009.9 [M+1]+.
(KBr): n˜ =526, 840, 866, 1388, 1654 cmꢀ1
; MS (ESI): m/z: 1063.0
[M+Na]+, 1077.9 [M+K]+.
Compound 14b: Yield 33% (56%). 1H NMR (CDCl3/CS2, 298 K,
200 MHz): d=2.05 (t, J=2.4 Hz, 1H; CH), 2.64–2.82 (m, 4H; 2CH2),
3.44 (s, 3H; CH3), 4.14 (brt, J=4.8 Hz, 1H; CHN), 4.24 (d, J=9.8 Hz,
1H; CH2N), 4.83 ppm (d, J=9.8 Hz, 1H; CH2N); 13C NMR (CDCl3/CS2,
298 K, 50 MHz): d=16.5, 29.9, 39.7, 69.7, 69.8, 70.0, 70.9, 75.7, 83.4,
135.3, 135.7, 136.0, 136.1, 137.1, 139.6, 139.8, 140.0, 140.05, 140.1, 141.6,
141.7, 141.8, 141.9, 141.96, 141.99, 142.0, 142.45, 142.47, 142.5, 142.51,
142.8, 142.9, 143.0, 144.1, 144.2, 144.3, 144.5, 145.0, 145.03, 145.09, 145.1,
145.2, 145.23, 145.26, 145.3, 145.5, 145.7, 145.8, 145.86, 145.9, 145.96,
145.99, 146.0, 146.06, 146.1, 146.14, 146.9, 147.0, 152.5, 153.8, 154.1, 154.5,
156.0 ppm; FTIR (KBr): n˜ =526.5, 1508.2, 2360 cmꢀ1; MS (ESI): m/z:
830.0 [M+1]+.
1
Compound 14c: Yield 90%. H NMR (CDCl3/CS2, 298 K, 500 MHz): d=
2.07 (s, 1H; CH), 2.76–2.83 (m, 3H; CH2), 2.93–3.06 (m, 1H; CH2), 5.31
(d, J=11.8 Hz, 1H; CH2N), 5.64 (brs, 1H; CH2N), 6,46 (brs, 1H; CHN),
7.52–7.56 (m, 3H; H Ar), 7.82–7.86 ppm (m, 2H; H Ar); 13C NMR
(CDCl3/CS2, 298 K, 125 MHz): d=17.2, 35.0, 58.7, 66.2, 70.3, 71.5, 74.6,
83.7, 128.7, 129.3, 131.3, 135.3, 135.5, 135.8, 137.2, 137.7, 140.5, 140.6,
140.7, 140.8, 142.1, 142.12, 142.4, 142.47, 142.5, 142.57, 142.6, 142.64,
142.7, 142.8, 142.9, 143.1, 143.16, 143.19, 143.2, 143.6, 143.7, 144.7, 144.8,
144.9, 145.0, 145.1, 145.3, 145.7, 145.8, 145.82, 145.85, 145.9, 146.0, 146.02,
146.1, 146.2, 146.4, 146.6, 146.7, 146.8, 147.8, 151.2, 152.8, 154.4, 155.3,
170.7 ppm; FTIR (KBr): n˜ =526.5, 1637 cmꢀ1; MS (ESI): m/z: 919.8
[M+1].
ꢀ
ꢀ
Compound 18a: Yield 55% (70%). 1H NMR (CDCl3/CS2, 298 K,
200 MHz): d=2.42 (t, J=2.38 Hz, 1H; CH), 2.86 (s, 3H; CH3N), 4.34 (d,
J=9.33 Hz, 1H; CH2N), 4.58 (AB syst., 2H; CH2O), 4.99 (d, J=9.33 Hz,
Synthesis of N-allylfulleropyrrolidine 6: NaH (0.625 mmol) was added to
solution of fulleropyrrolidine 2 (100 mg; 0.125 mmol) in o-DCB
a
ꢀ
(40 mL). After 5 min allyl bromide was added (0.375 mmol). The solution
was stirred for 18 h at 608C. The reaction was quenched with water
(20 mL). The organic layer was dried (MgSO4) and, after solvent remov-
al, the crude product was purified by flash chromatography over silica gel
(eluent: toluene/CS2 8:2) to give pure 6 in 55% yield. 1H NMR (CDCl3/
CS2, 298 K, 200 MHz): d=2.19 (t, J=2.7 Hz, 1H; CH), 3.24 (ddd, J=
17.3, 6.1, 2.7 Hz, 1H; CH2), 3.51 (ddd, J=17.3, 5.3, 2.7 Hz, 1H; CH2),
1H; CH2N), 5.61 (s, 1H; CHN), 6.87–7.33 (m, 3H; Ar H), 8.04 ppm (m,
1H; Ar H); 13C NMR (CDCl3/CS2, 298 K, 50 MHz): d=40.1, 56.1, 69.2,
ꢀ
69.7, 75.3, 75.6, 76.3, 78.1, 112.2, 122.2, 125.3, 128.2, 129.1, 130.1, 134.8,
136.1, 136.6, 139.5, 139.6, 140.1, 140.2, 141.5, 141.7, 141.8, 142.0, 142.1,
142.21, 142.26, 142.3, 142.35, 142.57, 142.58, 142.65, 142.68, 143.0, 143.07,
144.3, 144.4, 144.6, 145.1, 145.24, 145.27, 145.32, 145.35, 145.4, 145.6,
145.7, 145.95, 145.97, 146.0, 146.13, 146.17, 146.21, 146.26, 146.27, 146.6,
146.7, 147.2, 147.3, 156.3 ppm.
Compound 18b: Yield 50% (65%). 1H NMR (CDCl3/CS2, 298 K,
200 MHz): d=2.38 (t, J=2.3 Hz, 1H; CH), 2.78 (s, 3H; CH3N), 4.22 (d,
J=9.3 Hz, 1H; CH2N), 4.64 (d, J=2.3 Hz, 2H; CH2O), 4.86 (s, 1H;
ꢀ
ꢀ
3.56 (brdd, 1H; N CH2 C=), 4.14 (d, J=9.7 Hz, 1H; CH2N), 4.30 (brt,
ꢀ
ꢀ
1H; CHN), 4.36 (ddt, J=13.7, 5.1, 1.6 Hz, 1H; N CH2 C=), 4.86 (d, J=
9.7 Hz, 1H; CH2N), 5.43 (brd, 1H; C=CH2), 5.59 (ddd, J=17.09, 2.9,
1.6 Hz, 1H; CH=CH2), 6.35 ppm (m, 1H; CH=CH2); 13C NMR (CDCl3/
CS2, 298 K, 50 MHz): d=29.9, 66.5, 69.1, 72.6, 73.5, 75.0, 81.7, 118.8,
135.5, 135.6, 135.9, 136.2, 137.2, 137.7, 139.6, 140.1, 140.2, 140.9, 141.6,
141.8, 141.9, 142.07, 142.1, 142.5, 142.57, 142.6, 142.9, 143.9, 144.0, 144.3,
144.33, 144.5, 144.7, 145.1, 145.28, 145.2, 145.3, 145.4, 145.46, 145.5, 145.6,
145.8, 145.88, 145.9, 145.96, 146.0, 146.06, 146.1, 146.16, 146.2, 146.26,
146.3, 146.5, 146.9, 147.1, 147.2, 151.7, 153.8, 154.1, 155.9 ppm; FTIR
ꢀ
CHN), 4.92 (d, J=9.3 Hz, 1H; CH2N), 6.82–6.88 (m, 1H; Ar H), 7.20–
7.36 ppm (m, 3H; Ar H); 13C NMR (CDCl3/CS2, 298 K, 50 MHz): d=
ꢀ
40.1, 55.8, 69.0, 70.1, 75.7, 76.6, 78.8, 83.4, 115.5, 122.1, 125.0, 128.2, 128.6,
129.8, 135.0, 135.9, 136.6, 138.6, 139.6, 140.0, 141.6, 141.7, 141.8, 142.10,
142.11, 142.16, 142.3, 142.6, 143.7, 144.43, 144.69, 145.0, 145.2, 145.3,
145.4, 145.56, 145.59, 145.65, 146.0, 146.1, 146.2, 146.3, 146.4, 146.45,
146.6, 146.9, 147.3, 147.4, 147.63, 147.65, 147.7, 147.75, 147.8, 147.9, 148.1,
148.15, 153.3 ppm.
(KBr): n˜ =1558, 1508, 1458, 1419, 526 cmꢀ1
[M+H]+.
; MS (ESI): m/z: 842.3
Compound 18c: Yield 55% (70%). 1H NMR (CDCl3/CS2, 298 K,
200 MHz): d=2.49 (t, J=2.3 Hz, 1H; CH), 2.79 (s, 3H; CH3N), 4.25 (d,
J=9.2 Hz, 1H; CH2N), 4.67 (d, J=2.3 Hz, 2H; CH2O), 4.89 (s, 1H;
General procedure for the synthesis of N-methylfulleropyrrolidines 10a,
10c, 14b and 18a–c: mixture of the corresponding aldehyde
A
(0.694 mmol), C60 (250 mg, 0.347 mmol), and sarcosine (0.694 mmol) in o-
DCB (80 mL) was refluxed for 24 h. After cooling to room temperature,
the solvent was removed in vacuo and the crude product was purified by
flash chromatography over silica gel initially with CS2 as eluent (to sepa-
rate the unreacted fullerene) and then with toluene/CS2 (4:1) [for com-
pound 10a cyclohexane/CH2Cl2 (4:1) was used] to yield the correspond-
ing products.
ꢀ
CHN), 4.97 (d, J=9.2 Hz, 1H; CH2N), 7.00 (d, J=8.4 Hz, 2H; Ar H),
7.71 ppm (brs, 2H; Ar H); 13C NMR (CDCl3/CS2, 298 K, 50 MHz): d=
ꢀ
40.5, 56.3, 69.2, 70.1, 76.1, 79.0, 83.5, 115.5, 125.8, 127.8, 129.7, 136.2,
136.7, 137.0, 142.0, 142.1, 142.3, 142.4, 142.5, 142.52, 142.55, 142.58, 142.6,
142.7, 142.74, 143.0, 143.01, 143.04, 143.1, 143.4, 143.6, 144.8, 145.1, 145.2,
145.6, 145.7, 145.74, 145.8, 145.87, 145.9, 145.99, 146.0, 146.1, 146.2, 146.4,
146.42, 146.5, 146.62, 146.66, 146.7, 146.78, 146.8, 146.9, 147.1, 147.7,
157.8 ppm.
Compound 10a: Yield 24% (35%). 1H NMR (CDCl3/CS2, 298 K,
200 MHz): d=0.25 (2, 9H; (CH3)3Si), 2.81 (s, 3H; CH3), 4.35 (d, J=
Chem. Eur. J. 2005, 11, 2716 – 2729
www.chemeurj.org
ꢅ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2725

N. Martꢁn et al.
1
Synthesis of fulleropyrrolidines 10b, 10d, and 10 g: Anhydrous nBu4NF
(0.099 mmol) dissolved in dry CH2Cl2 (10 mL) was added to a solution of
fulleropyrrolidines 10a, 10c, or 10 f (0.099 mmol) in dry CH2Cl2 under
argon at 08C. After 10 minutes, the reaction mixture was allowed to
warm to room temperature and stirred for 2 h. The solution was washed
with water. The organic layer was dried (MgSO4) and the solvent was re-
moved in vacuo. The crude reaction was purified by flash chromatogra-
phy over silica gel with toluene/ethyl acetate (9:1) as eluent for com-
pounds 10d and 10 g and cyclohexane/CH2Cl2 (9:1) as eluent for com-
pound 10b (85–95% yield).
Compound 15b: Yield 90%. H NMR (CDCl3/CS2, 298 K, 500 MHz): d=
2.76–2.84 (m, 2H; CH2), 3.00 (s, 3H CH3), 3.39–3.63 (m, 2H CH2), 4.05
(brt, 1H; CHN), 4.19 (d, J=9.5 Hz, 1H; CH2N), 4.86 (d, J=9.5 Hz, 1H;
CH2N), 6.06 ppm (s, 1H; CH); 13C NMR (CDCl3/CS2, 298 K, 125 MHz):
d=30.4, 33.3, 40.4, 70.3, 70.8, 73.7, 76.3, 97.0, 125.3, 134.9, 135.9, 136.4,
136.7, 137.6, 137.7, 138.5, 140.3, 140.4, 140.7, 140.8, 141.1, 142.2, 142.3,
142.4, 142.6, 142.62, 142.64, 142.9, 143.1, 143.2, 143.3, 143.5, 143.7, 144.2,
144.8, 144.9, 145.0, 145.2, 145.7, 145.74, 145.8, 145.87, 145.9, 145.93, 146.0,
146.2, 146.3, 146.4, 146.5, 146.54, 146.6, 146.63, 146.66, 146.7, 146.75,
146.8, 147.7, 147.72, 153.1, 154.4, 154.7, 156.5, 200.1, 200.2 ppm; FTIR
(KBr): n˜ =526.5, 2013.5, 2046.3, 2090.7 cmꢀ1; MS (ESI): m/z: 1114.4
[M+1]+.
1
Compound 10b: Yield 85%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
2.81 (s, 3H; CH3), 3.32 (s, 1H; CH), 4.37 (d, J=9.4 Hz, 1H; CH2N), 5.00
1
ꢀ
(d, J=9.4 Hz, 1H; CH2N), 5.73 (s, 1H; CHN), 7.26–7.33 (m, 1H; Ar H),
Compound 19a: Yield 90%. H NMR (CDCl3/CS2, 298 K, 500 MHz): d=
7.47–7.57 (m, 2H; Ar H), 8.11–8.13 ppm (m, 1H; Ar H); 13C NMR
(CDCl3/CS2, 298 K, 75 MHz): d=40.3, 66.4, 69.6, 70.0, 75.9, 79.9, 84.2,
123.5, 128.5, 129.9, 130.0, 133.9, 135.3, 136.5, 140.0, 140.2, 140.6, 142.2,
142.36, 142.38, 142.4, 142.6, 143.0, 143.1, 143.5, 143.52, 144.8, 144.9, 145.0,
145.6, 145.7, 145.8, 145.9, 146.15, 146.17, 146.4, 146.5, 146.67, 146.7, 146.9,
147.7 ppm; FTIR (KBr): n˜ =526, 759, 1508 cmꢀ1; MS (ESI): m/z: 878.1
[M+1]+.
ꢀ
ꢀ
2.78 (s, 3H; CH3), 4.25 (d, J=9.03 Hz, 1H; CH2N), 4.96 (d, J=9.03 Hz,
1H; CH2N), 4.97 (d, J=12.9 Hz, 1H; CH2O), 5.33 (d, J=12.9 Hz, 1H;
CH2O), 5.67 (s, 1H; CHN), 6.03 (s, 1H; CH Cobalt), 7.03 (d, J=7.8 Hz,
ꢀ
ꢀ
ꢀ
ꢀ
1H; Ar H), 7.15–7.21 (m, 2H; Ar H), 8.09 ppm (d, J=7.8 Hz, 1H; Ar
H); 13C NMR (CDCl3/CS2, 298 K, 125 MHz): d=40.2, 68.9, 69.8, 70.2,
73.6, 75.2, 77.0, 88.7, 112.1, 122.2, 125.7, 126.2, 128.6, 129.4, 131.0, 135.6,
136.5, 136.7, 137.0, 139.9, 139.94, 140.5, 140.6, 142.0, 142.1, 142.16, 142.2,
142.44, 142.45, 142.52, 142.54, 142.57, 142.6, 142.7, 142.98, 143.0, 143.02,
143.07, 143.4, 143.5, 144.8, 144.86, 145.0, 145.02, 145.5, 145.56, 145.6,
145.7, 145.8, 145.94, 145.98, 146.0, 146.1, 146.3, 146.37, 146.47, 146.5,
146.51, 146.54, 146.6, 146.65, 146.67, 147.12, 146.15, 147.7, 147.73, 154.4,
154.6, 155.4, 157.2, 199.54 ppm.
1
Compound 10d: Yield 92%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
2.79 (s, 3H; CH3), 3.26 (s, 1H; CH), 3.89 (s, 3H; OCH3), 3.96 (s, 3H;
OCH3), 4.36 (d, J=9.4 Hz, 1H; CH2N), 4.98 (d, J=9.4 Hz, 1H; CH2N),
5.64 (s, 1H; CHN), 6.99 (s, 1H; Ar H), 7.69 ppm (s, 1H; Ar H); 13C
NMR (CDCl3/CS2, 298 K, 75 MHz): d=40.3, 56.2, 56.3, 68.9, 76.6, 79.2,
80.0, 82.7, 113.0, 115.4, 115.8, 144.72, 144.78, 144.8, 144.9, 145.0, 145.07,
145.1, 145.15, 145.2, 145.4, 145.5, 145.6, 145.65, 145.68, 145.7, 145.8, 145.9,
146.0, 146.2, 146.4, 146.5, 146.53, 146.6, 146.7, 146.75, 146.8, 147.7, 147.8,
147.9, 151.1 ppm; FTIR (KBr): n˜ =526, 1267, 1458, 1508, 1650 cmꢀ1; MS
(ESI): m/z: 938.1 [M+1]+.
ꢀ
ꢀ
1
Compound 19b: Yield 90%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
2.85 (s, 3H; CH3), 4.28 (d, J=9.3 Hz, 1H; CH2N), 4.93 (s, 1H; CHN),
4.99 (d, J=9.3 Hz, 1H; CH2N), 5.18–5.28 (AB syst., 2H; CH2O), 5.99 (s,
ꢀ
ꢀ
ꢀ
1H; CH Cobalt), 6.89–6.93 (m, 1H; Ar H), 7.33–7.51 ppm (m, 3H; Ar
H); 13C NMR (CDCl3/CS2, 298 K, 75 MHz): d=39.8, 68.1, 68.7, 69.8,
71.9, 76.5, 83.2, 89.0, 114.7, 122.2, 129.6, 135.5, 135.6, 136.3, 136.4, 138.6,
139.3, 139.6, 139.9, 140.0, 141.3, 141.4, 141.61, 141.69, 141.7, 141.83,
141.89, 141.93, 141.95, 142.0, 142.3, 142.4, 142.48, 142.8, 142.9, 144.16,
144.17, 144.41, 144.49, 144.9, 144.99, 145.0, 145.04, 145.08, 145.1, 145.19,
145.2, 145.3, 145.4, 145.5, 145.7, 145.8, 145.88, 145.9, 145.96, 146.0, 146.05,
146.1, 146.18, 146.5, 147.0, 153.0, 153.06, 154.6, 155.8, 157.1, 198.2 ppm.
1
Compound 10g: Yield 95%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
3.15 (br, 1H; CH), 5.89 (d, J=12.6 Hz, 1H; CH2N), 6.13 (br, 1H;
ꢀ
ꢀ
CH2N), 7.34–7.38 (m, 1H; Ar H), 7.50–7.55 (m, 4H; Ar H, CHN), 7.61–
7.70 (m, 4H; Ar H), 8.13–8.15 ppm (m, 1H; H Ar); 13C NMR (CDCl3/
CS2, 298 K, 75 MHz): d=69.0, 75.0, 75.4, 75.9, 82.2, 84.2, 121.9, 125.4,
127.5, 128.1, 128.6, 130.0, 130.7, 133.8, 135.4, 139.18, 139.2, 140.0, 140.2,
140.6, 141.5, 141.6, 141.7, 141.8, 141.9, 141.94, 142.0, 142.03, 142.1, 142.15,
142.2, 142.3, 142.5, 142.6, 142.8, 142.9, 142.95, 143.1, 143.12, 143.3, 143.4,
143.6, 143.7, 143.77, 143.8, 143.9, 144.2, 144.3, 144.4, 144.5, 144.7, 144.9,
145.1, 145.17, 145.2, 145.3, 145.45, 145.5, 145.53, 145.6, 145.9, 146.0,
146.06, 146.1, 146.2, 146.3, 146.32, 146.4, 147.3, 147.35, 151.4, 153.4, 153.9,
155.0, 170.8 ppm; FTIR (KBr): n˜ =526, 1541, 1560, 1654 cmꢀ1; MS (ESI):
m/z: 967.7 [M]+.
ꢀ
ꢀ
1
Compound 19c: Yield 90%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
2.81 (s, 3H; CH3), 4.26 (d, J=9.5 Hz, 1H; CH2N), 4.91 (s, 1H; CHN),
4.99 (d, J=9.5 Hz, 1H; CH2N), 5.22 (s, 2H; CH2O), 5.98 (s, 1H; CH
ꢀ
cobalt), 7.02 (d, J=8.5 Hz, 2H; Ar H), 7.75 ppm (brs, 2H; Ar H); 13C
NMR (CDCl3/CS2, 298 K, 75 MHz): d=40.4, 68.5, 69.3, 70.4, 72.4, 77.7,
83.5, 89.6, 115.3, 130.0, 130.9, 136.22, 136.29, 137.0, 137.3, 140.0, 140.4,
140.61, 140.65, 142.0, 142.1, 142.2, 142.45, 142.48, 142.5, 142.6, 142.7,
143.0, 143.1, 143.4, 143.6, 144.8, 145.0, 145.1, 145.5, 145.6, 145.7, 145.74,
145.82, 145.88, 145.9, 146.0, 146.2, 146.3, 146.5, 146.6, 146.65, 146.7, 146.9,
147.1, 147.7, 153.8, 153.9, 154.4, 156.7, 158.5, 199.6 ppm.
ꢀ
ꢀ
General procedure for the synthesis of metal complexes: The respective
enyne (0.055 mmol) was dissolved in toluene (25 mL) at room tempera-
ture under argon in a flask containing powdered molecular sieves (eight
times the mass of the enyne, oven-dried for 4 h at 1208C in a vacuum).
[Co2(CO)8] (0.055 mmol) was added to this solution and the resulting
mixture was stirred for 30 min until total complexation of the enyne
(TLC). The reaction was then filtered over Celite and purified by flash
chromatography over silica gel using cyclohexane/toluene (1:1) as eluent
(80–90% yield).
General procedure for the PK reaction—the formation of compounds
5a–d, 7, and 8: Powdered 4 ꢆ molecular sieves (7 g per mmol of propar-
gylglycine, oven dried for 4 h at 1208C) were added to a solution of 3a–d
or 6 (0.05 mmol) in dry toluene (45 mL) at room temperature and the
mixture was stirred for 15 min under argon. Then [Co2(CO)8]
(0.05 mmol) was added in one portion and the mixture was stirred at
608C. After 2–3 h, the reaction mixture was filtered through Celite and
the solvent was evaporated under vacuum. Flash chromatography over
neutral silica gel (eluent: CH2Cl2/cyclohexane 1:1) afforded the pure
product (5a–d in 95–98% yield; 7 and 8 in 41% yield).
1
Compound 11a: Yield 80%. H NMR (CDCl3/CS2, 298 K, 300 MHz): d=
0.51 (s, 9H; (CH3)3Si), 2.84 (s, 3H; CH3), 4.55 (d, J=9.3 Hz, 1H; CH2N),
ꢀ
4.93 (d, J=9.3 Hz, 1H; CH2N), 7.34–7.48 (m, 2H; H Ar), 7.65–7.68 (m,
1H; Ar H), 8.27–8.29 ppm (m, 1H; Ar H); 13C NMR (CDCl3/CS2,
298 K, 75 MHz): d=0.0, 36.6, 67.2, 68.1, 73.2, 84.8, 99.2, 123.8, 126.5,
126.7, 126.8, 127.5, 131.2, 132.3, 134.7, 135.9, 136.9, 137.8, 138.6, 138.7,
140.0, 140.1, 140.2, 140.5, 140.6, 140.8, 141.0, 141.1, 141.4, 141.7, 142.7,
142.9, 143.0, 143.2, 143.6, 143.7, 143.8, 143.85, 143.9, 144.2, 144.3, 144.4,
144.5, 144.6, 144.7, 144.75, 144.8, 144.9, 145.1, 145.7, 151.0, 152.3, 152.6,
155.5, 198.2, 198.7 ppm; MS (ESI): m/z: 950 [Mꢀ[Co2(CO)6]].
ꢀ
ꢀ
Compound 5a: Yield 98%. 1H NMR (CDCl3, 298 K, 500 MHz): d=3.76
(dd, J=14.6, 5.6 Hz, 1H; CH2), 4.64 (d, J=14.6 Hz, 1H; CH2), 4.87 (d,
J=11.5 Hz, 1H; CH2N), 5.28 (d, J=11.5 Hz, 1H; CH2N), 5.34 (d, J=
ꢀ
5.6 Hz, 1H; CHN), 6.92 (s, 1H; CH=C), 7.59–7.55 (m, 3H; Ar H), 7.75–
7.74 ppm (m, 2H; Ar H); 13C NMR (CDCl3, 298 K, 125 MHz): d=33.68
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
(CH2), 62.99 (CH2 N), 64.26 (Csp3 C60), 70.10 (Csp3 C60), 72.08 (CH N),
1
ꢀ
ꢀ
ꢀ
73.56 (Csp3 C60), 73.95 (Csp3 C60), 126.05 (C=CH), 127.91 (2C, Ar C),
Compound 11d: Yield 80%. H NMR (CDCl3/CS2, 298 K, 200 MHz): d=
ꢀ
ꢀ
2.64 (s, 3H; CH3), 3.84 (s, 3H; OCH3), 3.88 (s, 3H; OCH3), 4.24 (d, J=
9.3 Hz, 1H; CH2N), 4.92 (d, J=9.3 Hz, 1H; CH2N), 5.51 (s, 1H; CHN),
129.17 (2C, Ar C), 131.65 (Ar C), 135.0, 135.3, 135.6, 135.7, 138.5, 138.7,
140.7, 141.1, 141.6, 141.7, 141.9, 142.4, 142.5, 142.6, 142.8, 143.0, 143.63,
143.65, 143.67, 143.7, 143.76, 143.8, 144.1, 144.3 (2C), 144.33, 144.4, 144.5
(2C), 144.6, 144.7, 144.84, 144.85, 145.03, 145.05, 145.3, 145.4, 145.5,
145.7, 146.0, 146.3, 146.5, 146.6, 146.7, 146.9, 147.4, 147.5, 147.62, 147.63,
ꢀ
ꢀ
6.54 (s, 1H; CH-Cobalt), 7.16 (s, 1H; Ar H), 7.63 ppm (s, 1H; Ar H);
FTIR (KBr): n˜ =526.5, 2017.4, 2048.3, 2086.8 cmꢀ1
; MS (ESI): m/z:
1223.5 [M]+, 1139.7 [Mꢀ3CO], 721.4 [M+1]C60, 285.2 [Mꢀ2Co(CO)3].
2726
ꢅ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 2716 – 2729

Regioselective Intramolecular Pauson–Khand Reactions of C60
FULL PAPER
ꢀ
148.33, 148.34, 148.4, 149.08, 149.09, 149.13, 149.15, 150.6, 173.7 (CO N),
144.16, 144.2, 144.3, 144.4, 144.5, 144.6, 144.7, 144.8, 144.85, 144.9, 145.0,
145.1, 145.3, 145.4, 145.9, 146.2, 146.4, 146.45, 146.6, 146.9, 147.3, 147.9,
148.1, 148.3, 148.34, 148.6, 149.0, 149.1, 149.2, 149.6, 150.3, 152.6, 184.1
184.5 (C=CH), 202.2 ppm (CO); FTIR (KBr): n˜ =1718, 1637, 526 cmꢀ1
;
UV/Vis (CH2Cl2): l (e)=692 (176), 425 (3932), 322 (22810), 252 nm
(76727 dm3 molꢀ1 cmꢀ1); HRMS (MALDI-TOF): calcd. for [C73H11NO2]+:
933.07892; found: 933.07811.
Compound 5b: Yield 95%. 1H NMR (CDCl3, 298 K, 500 MHz): d=3.67
(ddd, J=14.9, 6.3, 1.5 Hz, 1H; CH2), 3.99 (AB syst., 2H; CH2 CO), 4.82
(d, J=14.9 Hz, 1H; CH2), 5.02 (d, J=11.0 Hz, 1H; CH2N), 5.25 (d, J=
6.3 Hz, 1H; CHN), 5.28 (d, J=11.0 Hz, 1H; CH2N), 6.81 (d, J=1.5 Hz,
(C=CH), 202.2 ppm (CO); FTIR (KBr): n˜ =1712, 524 cmꢀ1
; UV/Vis
(CH2Cl2):
l (e)=555 (1113), 424 (3686), 323 (20294), 253 nm
(66769 dm3 molꢀ1 cmꢀ1); HRMS (MALDI-TOF): calcd. for [C69H12NO]+
([M+1]+): 870.09134; found: 870.09094.
ꢀ
Compound 8: Aleatory numbering is used for the spectroscopic assign-
ment of compound 8.
Yield 41%. 1H NMR (CDCl3/CS2, 298 K, 500 MHz): d=2.27 (dd, J=
18.5, 2.5 Hz, 1H; 8-H), 2.47 (brt, 1H; 6-H), 2.78 (dd, J=18.5, 6.6 Hz,
1H; 8-H), 3.25 (brt, 1H; 12-H), 3.47 (m, 1H; 7-H), 3.81 (dd, J=13.0,
3.1 Hz, 1H; 12-H), 3.89 (dd, J=11.5, 3.1 Hz, 1H; 2-H), 4.04 (dd, J=10.5,
6.0 Hz, 1H; 6-H), 4.12 (d, J=9.1 Hz, 1H; 5-H), 4.86 (d, J=9.1 Hz, 1H;
5-H), 6.19 ppm (s, 1H; 10-H); 13C NMR (CDCl3/CS2, 298 K, 125 MHz):
ꢀ
ꢀ
1H; CH=C), 7.37–7.34 (m, 1H; Ar H), 7.47–7.41 ppm (m, 4H; Ar H);
13
ꢀ
C NMR (CDCl3, 298 K, 125 MHz): d=33.8 (CH2), 43.7 (CH2 CO), 60.6
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
(CH2 N), 63.9 (Csp3 C60), 69.8 (Csp3 C60), 73.0 (CH N), 73.7 (Csp3 C60),
ꢀ
ꢀ
ꢀ
74.0 (Csp3 C60), 126.1 (C=CH), 127.5 (Ar C), 128.2, 128.96 (2C, Ar C),
ꢀ
129.0, 129.1 (2C, Ar C), 133.6, 134.9, 135.2, 135.3, 138.5, 138.6, 140.8,
140.9, 141.7, 141.9, 142.4, 142.6, 142.7, 142.8, 143.1, 143.6, 143.61, 143.65,
143.67, 143.7, 143.8, 144.2, 144.25, 144.3, 144.34, 144.5, 144.6, 144.63,
144.7, 144.8, 144.84, 145.0, 145.06, 145.3, 145.4, 145.45, 145.9, 146.1, 146.4,
146.5, 146.7, 146.9, 147.1, 147.44, 147.46, 147.6, 148.3, 148.37, 148.4, 149.1,
ꢀ
d=35.6 (CH2), 39.8 (C-8), 40.9 (C-7), 59.1 (C-6), 67.8 (C-5), 70.3 (Csp3
ꢀ
C60), 74.7 (Csp3 C60), 75.4 (C-2), 128.7, 129.7 (2C), 136.2, 136.6, 136.8,
138.1, 140.4, 140.7, 140.74, 140.8, 142.2, 142.24, 142.4, 142.44, 142.48,
142.5, 142.54, 142.6 (2C), 142.64, 143.1, 143.14, 143.2, 143.22, 143.5, 143.6,
ꢀ
149.14, 149.15, 149.2, 150.5, 172.9 (CO N), 184.2 (C=CH), 201.9 ppm
(CO); FTIR (KBr): n˜ =1718, 1637, 524 cmꢀ1; UV/Vis (CH2Cl2): l (e)=
632 (183), 425 (3553), 323 (20230), 252 nm (66941 dm3 molꢀ1 cmꢀ1); MS
(FAB): m/z: 947 [M]+.
Compound 5c: Yield 95%. 1H NMR (CDCl3, 298 K, 500 MHz): d=3.77
(ddd, J=15.1, 6.5, 1.5 Hz, 1H; CH2), 4.67 (d, J=15.1 Hz, 1H; CH2), 5.20
(d, J=10.9 Hz, 1H; CH2N), 5.42 (d, J=6.5 Hz, 1H; CHN), 5.50 (d, J=
10.9 Hz, 1H; CH2N), 6.87 (d, J=1.5 Hz, 1H; CH=C), 7.02 (d, J=
ꢀ
ꢀ
15.4 Hz, 1H; CH=CH), 7.46–7.44 (m 3H; Ar H), 7.67–7.65 (m, 2H; Ar
H), 7.93 ppm (d, J=15.4 Hz, 1H; CH=CH); 13C NMR (CDCl3, 298 K,
ꢀ
ꢀ
ꢀ
125 MHz): d=34.5 (CH2), 60.8 (CH2 N), 63.8 (Csp3 C60), 69.5 (Csp3 C60),
ꢀ
ꢀ
ꢀ
73.3 (CH N), 74.0 (Csp3 C60), 74.2 (Csp3 C60), 118.3 (CH=CH), 126.3 (C=
CH), 128.3, 129.0, 130.5, 134.5, 134.8, 134.9, 135.4, 138.7, 140.8, 140.9,
141.6, 141.8, 141.9, 142.4, 142.6, 142.7, 142.8, 143.1, 143.6, 143.67, 143.7,
143.9, 144.2, 144.24, 144.3, 144.35, 144.4, 144.5, 144.6, 144.7, 144.8, 144.83,
144.9, 145.0, 145.1, 145.4, 145.45, 145.5, 146.2, 146.3, 146.4, 146.5, 146.6,
146.7, 146.9, 147.3, 147.5, 147.7, 148.37, 148.4, 148.42, 149.1, 149.13, 149.2,
144.8, 144.85, 145.0, 145.2, 145.7, 145.73, 145.8, 145.82 (2C), 145.85, 145.9,
146.0, 146.03, 146.1, 146.14, 146.5 (2C), 146.52, 146.6, 146.61, 146.68,
146.7, 146.75, 146.77, 146.83, 146.86, 147.7, 147.8, 152.2, 153.1, 153.7,
156.0, 179.1 (C=CH), 207.7 ppm (CO); IR (KBr): n˜ =1706, 1624,
526 cmꢀ1; UV/Vis (CH2Cl2): l (e)=696 (1215), 428 (4219), 307 (29631),
252 nm (86782 dm3 molꢀ1 cmꢀ1); HRMS (MALDI-TOF): calcd. for
[C69H12NO]+ ([M+1]+): 870.09134; found: 870.09117.
Synthesis of fulleropyrrolidine 21: Compound 20[13] (2 mmol) and formal-
dehyde (1 mmol) were added to a solution of C60 (720 mg, 1 mmol) in
chlorobenzene (200 mL) under argon. The mixture was refluxed for 1 h
and, after cooling, it was concentrated under reduced pressure. The crude
product was purified by flash chromatography over silica gel eluting ini-
tially with CS2 (to separate C60) and then with toluene to yield the final
product in 30% yield. 1H NMR (CDCl3/CS2, 298 K, 500 MHz): d=2.29
(t, J=2.6 Hz, 2H; CH), 3.64 (dq, J=17.1, 2.6 Hz, 4H; CH2), 4.90 ppm (s,
2H; CH2N); MS (ESI): m/z: 840 [M+1]+.
ꢀ
149.23, 150.7, 168.4 (CO N), 184.4 (C=CH), 202.0 ppm (CO); FTIR
(KBr): n˜ =1716, 1654, 1375, 524 cmꢀ1; UV/Vis (CH2Cl2): l (e)=693
(408),
631
(605),
422
(4066),
323
(
23560),
253 nm
(78290 dm3 molꢀ1 cmꢀ1); MS (FAB): m/z: 960 [M+1]+, 959 [M]+.
1
Compound 5d: Yield 98%. H NMR (CDCl3, 298 K, 500 MHz): d=1.01–
0.97 (m, 3H; CH3), 1.51–1.45 (m, 4H; 2CH2), 1.86–1.81 (m, 2H; CH2),
2.74–2.49 (m, 2H; CH2 CO), 3.68 (ddd, J=14.8, 6.3, 1.5 Hz, 1H; CH2),
4.72 (d, J=14.8 Hz, 1H; CH2), 5.06 (d, J=11.1 Hz, 1H; CH2N), 5.23 (d,
J=6.3 Hz, 1H; CHN), 5.24 (d, J=11.1 Hz, 1H; CH2N), 6.84 ppm (d, J=
1.5 Hz, 1H; CH=C); 13C NMR (CDCl3, 298 K, 125 MHz): d=14.02
(CH3), 22.55 (CH2), 24.51 (CH2), 31.55 (CH2), 34.24 (CH2), 36.34 (CH2
CO), 60.64 (CH2 N), 63.88 (Csp3 C60), 69.71 (Csp3 C60), 72.96 (CH N),
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
73.87 (Csp3 C60), 74.1 (Csp3 C60), 126.1 (C=CH), 134.9, 135.0, 135.3, 138.6,
138.7, 140.8, 141.0, 141.6, 141.8, 141.9, 142.4, 142.6, 142.7, 142.8, 143.1,
143.58, 143.6, 143.65, 143.7, 143.73, 144.0, 144.2, 144.26, 144.3, 144.34,
144.4, 144.5, 144.6, 144.7, 144.8, 144.84, 144.85, 145.0, 145.1, 145.3, 145.5
(2C), 146.1, 146.2, 146.4, 146.5, 146.6, 146.7, 146.9, 147.0, 147.4, 147.5,
Synthesis of N-acylfulleropyrrolidine 22: NEt3 (0.15 mmol) was added to
a
solution of fulleropyrrolidine 21 (840 mg, 0.1 mmol) in toluene
ꢀ
147.7, 148.3, 148.4, 148.5, 149.1, 149.14, 149.17, 149.2, 150.7, 175.4 (CO
(100 mL). After 5 min, benzoyl chloride (0.15 mmol) was added and the
mixture refluxed for 18 h. When the reaction was complete, the solvent
was removed in vacuo. The crude product was purified by flash chroma-
tography over neutral alumina, with toluene as the eluent, to afford the
final product in 95% yield. 1H NMR (CDCl3, 298 K, 500 MHz): d=2.28
(t, J=2.5 Hz, 2H; CH), 4.18 (t, J=2.5 Hz, 4H; CH2), 5.49 (s, 2H;
N), 184.4 (C=CH), 202.0 ppm (CO); FTIR (KBr): n˜ =1718, 1637,
524 cmꢀ1; UV/Vis (CH2Cl2): l (e)=425 (9152), 292 (103491), 259 nm
(164778 dm3 molꢀ1 cmꢀ1); MS (FAB): m/z: 927 [M]+.
Compound 7: Yield 41%. 1H NMR (CDCl3, 298 K, 500 MHz): d=3.29
(brdd, J=13.9, 7.4 Hz, 1H; CH2 CH=), 3.54 (ddd, J=13.9, 4.6, 1.6 Hz,
1H; CH2), 3.72 (d, J=13.9 Hz, 1H; CH2), 3.86 (ddt, J=13.9, 5.0, 1.6 Hz,
ꢀ
CH2N), 7.60 (m, 3H; Ar H), 7.93 ppm (m, 2H; Ar-H); 13C NMR
ꢀ
ꢀ
1H; CH2 CH=), 3.89 (d, J=9.6 Hz, 1H; CH2N), 4.06 (d, J=4.6 Hz, 1H;
CHN), 4.58 (d, J=9.6 Hz, 1H; CH2N), 5.36 (ddd, J=10.0, 2.6, 1.6 Hz,
(CDCl3, 298 K, 125 MHz) d=28.6, 62.4, 68.4, 73.4, 74.5, 79.1, 81.0, 115.5,
127.9, 129.4, 131.2, 136.4, 137.7, 137.8, 139.5, 140.7, 141.8, 142.2, 142.3,
142.5, 142.8, 143.2, 143.6, 144.9, 145.0, 145.6, 145.7, 145.8, 145.9, 146.0,
146.2, 146.5, 146.8, 146.9, 147.2, 147.8, 147.9, 151.7, 154.5, 173.0 ppm;
FTIR (KBr): n˜ =526, 1961, 2119, 2350, 1922 cmꢀ1; MS (ESI): m/z: 944
[M+H]+.
1H; CH=CH2), 5.48 (ddd, J=17.1, 2.6, 1.7 Hz, 1H; CH=CH2), 6.15 (m,
1H; CH=CH2), 6.81 ppm (d, J=1.6 Hz, 1H; CO CH=); 13C NMR
ꢀ
ꢀ
(CDCl3/CS2, 298 K, 125 MHz): d=33.4 (CH2), 55.0 (CH2 CH=), 64.9
(Csp3 C60), 66.5 (CH2 N), 71.1 (Csp3 C60), 73.0 (Csp3 C60), 73.9 (CH N),
77.3 (Csp3 C60), 118.5 (CH=CH2), 125.3, 126.5 (C=CH), 128.2, 129.0,
130.8, 134.2, 134.5, 134.7, 135.5, 136.3, 137.7, 138.2, 138.5, 140.9, 141.7,
141.8, 141.9, 142.3, 142.6, 142.7, 142.8, 143.0, 143.5, 143.6, 143.65, 144.1,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Synthesis of metal complex 23: [Co2(CO)8] (0.3 mmol) was added to a so-
lution of N-acylfulleropyrrolidine 22 (94 mg, 0.1 mmol) in toluene
Chem. Eur. J. 2005, 11, 2716 – 2729
www.chemeurj.org
ꢅ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2727

N. Martꢁn et al.
(100 mL) at room temperature under argon and the resulting mixture
was stirred at 508C for 1 h until total complexation of the enyne (TLC).
The reaction was then purified by flash chromatography over silica gel
using toluene as eluent (95% yield). H NMR (CDCl3, 298 K, 300 MHz):
d=3.58 (d, J=13.5, 1H; CH2), 4.11 (d, J=17.13 Hz, 1H; CH2), 4.57 (d,
c) T. Sugihara, M. Tamaguchi, M. Nishizawa, Chem. Eur. J. 2001, 7,
3315–3318; d) S. E. Gibson, A. Stevenazzi, Angew. Chem. 2003, 115,
1844–1854; Angew. Chem. Int. Ed. 2003, 42, 1800–1810; e) J.
Blanco-Urgoiti, L. AÇorbe, L. Pꢉrez-Serrano, G. Domꢁnguez, J.
Pꢉrez-Castells, Chem. Soc. Rev. 2004, 33, 32–42.
1
J=17.3 Hz, 1H; CH2), 4.97 (d, J=12.5 Hz, 1H; CH2N), 5.27 (d, J=
[2] N. Martꢁn, M. Altable, S. Filippone, A. Martꢁn-Domenech, Chem.
Commun. 2004, 1338–1339.
ꢀ
12.5 Hz, 1H; CH2N), 5.50 (d, J=13.5 Hz, 1H; CH2), 6.11 (s, 1H; CH
cobalt), 6.92 (s, 1H; CH=C), 7.60 ppn (m, 5H; Ar H); 13C NMR
ꢀ
[3] R. C. Haddon, Acc. Chem. Res. 1992, 25, 127–133.
[4] a) A. Hirsch, The Chemistry of Fullerenes, Thieme, New York, 1994;
b) F. Diederich, C. Thilgen, Science 1996, 271, 317–323; c) R.
Taylor, Lecture Notes on Fullerene Chemistry. A Handbook for
Chemists, Imperial College Press, London, 1999; d) Fullerenes and
Related Structures, Topics in Current Chemistry, Vol. 199 (Ed.: A.
Hirsch), Springer, Berlin, 1999, ; e) Fullerenes: From Synthesis to
Optoelectronic Properties (Eds.: D. M. Guldi, N. Martꢁn), Kluwer
Academic Publishers, Dordrecht, 2002.
[5] For a recent review, see: M. R. Rivero, J. Adrio, J. C. Carretero, Eur.
J. Org. Chem. 2002, 2881–2889.
[6] a) L. Pꢉrez-Serrano, J. Blanco-Urgoiti, L. Casarrubios, G. Domin-
guez, J. Pꢉrez-Castells, J. Org. Chem. 2000, 65, 3513–3519; b) C. J.
Lovely, H. Seshadri, B. R. Wayland, A. W. Cordes, Org. Lett. 2001,
3, 2607–2610.
(CDCl3, 298 K, 125 MHz): d=37.0, 42.0, 60.9, 65.1, 69.6, 73.9, 74.2, 75.4,
77.9, 79.8, 87.7, 126.4, 127.2, 129.7, 131.3, 135.3, 136.6, 137.0, 137.9, 138.9,
141.0, 141.3, 142.0, 142.3, 142.4, 142.9, 143.0, 143.1, 143.5, 143.6, 143.7,
143.9, 144.0, 144.1, 144.2, 144.6, 144.7, 144.78, 144.8, 144.9, 145.0, 145.07,
145.1, 145.2, 145.5, 145.9, 146.9, 147.2, 147.3, 147.4, 148.2, 148.3, 148.8,
149.5, 149.6, 150.8, 171.4, 183.9, 199.9, 202.3 ppm; FTIR (KBr): n˜ =1641,
1718, 2017, 2350, 2922 cmꢀ1
.
Synthesis of compounds 24 and 25: A solution of compound 23 (60 mg,
0.047 mmol) in toluene (80 mL) was stirred at 608C for 18 h under argon.
The solvent was evaporated under reduced pressure and the crude prod-
uct was purified by flash chromatography over silica gel eluting with tolu-
ene/ethyl acetate (9:1) to yield compounds 24 (30% yield) and 25 (5%
yield).
Compound 24: 1H NMR (CDCl3, 298 K, 500 MHz): d=2.22 (t, J=
[7] a) M. Prato, M. Maggini, Acc. Chem. Res. 1998, 31, 519–526; b) M.
Maggini, G. Scorrano, M. Prato, J. Am. Chem. Soc. 1993, 115, 9798–
9799; c) N. Tagmatarchis, M. Prato, Synlett 2003, 768–779.
[8] A. Bagno, S. Claeson, M. Maggini, M. L. Martini, M. Prato, G. Scor-
rano, Chem. Eur. J. 2002, 8, 1015–1023.
[9] G. Borsato, F. Della Negra, F. Gasparrini, D. Misiti, V. Lucchini, G.
Possamai, C. Villani, A. Zambon, J. Org. Chem. 2004, 69, 5785–
5788.
[10] a) L. Pꢉrez-Serrano, L. Casarrubios, G. Domꢁnguez, J. Pꢉrez-Cas-
tells, Org. Lett. 1999, 1 1187–1188; b) J. Blanco-Urgoiti, L. Casarru-
bios, G. Domꢁnguez, J. Pꢉrez-Castells, Tetrahedron Lett. 2002, 43,
5763–5765. Note that the PK reaction also proceeds in the absence
of molecular sieves although in a lower yield.
[11] Acetylene-linked di- and tetracobalt carbonyl clusters covalently
linked to C60 have also been reported: S. M. Draper, M. Delamesier,
E. Champeil, B. Twamley, J. J. Byrne, C. J. Long, J. Organomet.
Chem. 1999, 589, 157–167.
[12] a) K. Kordatos, S. Bossi, T. Da Ros, A. Zambon, V. Lucchini, M.
Prato, J. Org. Chem. 2001, 66, 2802–2808; b) Y. Nakamura, N.
Takano, T. Nishimura, E. Yashima, M. Sato, T. Kudo, Org. Lett.
2001, 3, 1193–1196.
[13] a) S. Kotha, E. Brahmachary, Bioorg. Med. Chem. 2002, 10, 2291–
2295; b) S. Kotha, K. Mohanraja, S. Durani, Chem. Commun. 2000,
1909–1910.
[14] The preparation of fulleropyrrolidine 21 is accompanied by the for-
mation of a by-product in very low yield (ꢂ5%) whose structure is
currently under investigation.
[15] AM1 calculations (see ref. [16]) with the AMPAC 6.55 program (see
ref. [17]) have been performed on carbon monoxide and complexes
22, 24, and 25 in which the phenyl group has been substituted by a
methyl group. The results give a reaction enthalpy of ꢀ73.3 and
ꢀ116.2 kcalmolꢀ1 for the reactions 22+CO!24 and 22+2CO!25,
respectively. The difference of 30.4 kcalmolꢀ1 [(ꢀ116.2)ꢀ2ꢇ(ꢀ73.3)]
can be taken as an indication of the excess strain energy in 25 as
compared with 24.
[16] M. J. S. Dewar, E. G. Zoebisch, E. F. Healy, J. J. P. Stewart, J. Am.
Chem. Soc. 1985, 107, 3902–3909.
[17] AMPAC 6.55, 1997, Semichem, 7204 Mullen, Shawnee, KS 66216
(USA).
[18] J. Heinze, Angew. Chem. 1984, 96, 823–840; Angew. Chem. Int. Ed.
Engl. 1984, 23, 831–847.
[19] a) L. Echegoyen, L. E. Echegoyen, Acc. Chem. Res. 1998, 31, 593–
601; b) N. Martꢁn, L. Sꢃnchez, B. Illescas, I. Pꢉrez, Chem. Rev. 1998,
98, 2527–2547.
2.6 Hz, 1H; CH), 3.47 (dd, J=17.3, 2.6 Hz, 1H; CH2), 3.87 (dd, J=14.5,
ꢀ
1.3 Hz, 1H; CH2 C=C), 3.88 (dd, J=17.3, 2.6 Hz, 1H; CH2), 5.14 (d, J=
ꢀ
11.9 Hz, 1H; CH2N), 5.24 (d, J=14.5 Hz, 1H; CH2 C=C), 5.28 (d, J=
ꢀ
11.9 Hz, 1H; CH2N), 6.97 (d, J=1.3 Hz, 1H; CH CO), 7.57–7.67 ppm
(m, 5H; Ar H); 13C NMR (CDCl3, 298 K, 125 MHz): d=24.7 (CH2),
ꢀ
ꢀ
36.7 (CH2 C=C), 62.0 (CH2N), 64.1, 74.1, 74.4, 74.6, 75.0, 78.8, 80.0,
125.7, 127.0, 129.2, 130.9, 134.9, 136.7, 137.1, 137.5, 138.2, 138.4, 140.6,
140.7, 141.5, 141.8, 142.0, 142.4, 142.6, 142.7, 142.75, 143.1, 143.3, 143.4,
143.5, 143.69, 143.7, 143.73, 144.2, 144.3, 144.37, 144.4, 144.5, 144.58,
144.6, 144.8, 144.9, 145.0, 145.1, 145.3, 145.4, 145.5, 146.2, 146.3, 146.4,
146.5, 146.7, 146.8, 146.9, 147.4, 148.0, 148.02, 148.3, 148.35, 148.4, 149.0,
149.1, 150.6, 172.0, 183.8, 202.0 ppm; FTIR (KBr): n˜ =526, 1365, 1647,
1718 cmꢀ1; MS (ESI): m/z: 972 [M+H]; UV/Vis (CH2Cl2): l (e)=551
(693), 429 (3048), 325 (17976), 254 nm (70866 dm3 molꢀ1 cmꢀ1).
Compound 25: 1H NMR (CDCl3, 298 K, 500 MHz): d=3.45 (d, J=
8.5 Hz, 1H; CH2), 3.75 (d, J=8.5 Hz, 1H; CH2), 3.96 (d, J=8.4 Hz, 1H;
CH2), 5.09 (d, J=7.1 Hz, 1H; CH2N), 5.20 (d, J=7.1 Hz, 1H; CH2N),
5.55 (d, J=8.4 Hz, 1H; CH2), 6.92 (s, 1H), 6.98 (s, 1H), 7.53–7.57 ppm
(m, 5H; Ar H); 13C NMR (CDCl3, 298 K, 125 MHz): d=32.4 (CH2),
ꢀ
37.3 (CH2), 47.9 (CH2N), 60.8, 64.4, 73.8, 76.3, 125.6, 126.7, 129.2, 130.7,
134.9, 136.1, 136.6, 137.2, 137.4, 137.7, 137.8, 138.0, 138.4, 138.5, 139.1,
139.5, 139.8, 140.6, 140.9, 141.5, 141.6, 141.9, 141.92, 142.0, 142.5, 142.6,
142.7, 142.8, 143.0, 143.1, 143.2, 143.4, 143.5, 143.6, 143.64, 143.7, 143.71,
143.8, 144.3, 144.36, 144.4, 144.5, 144.56, 144.6, 144.7, 144.8, 145.1, 145.4,
145.5, 146.2, 146.46, 146.5, 146.55, 146.8, 146.9, 147.4, 147.8, 148.0, 148.4,
148.5, 148.6, 149.1, 149.2, 150.5, 171.9, 183.5, 201.9, 105.4 ppm; UV/Vis
(CH2Cl2):
l (e)=428 (2838), 338 (15165), 323 (19017), 256 nm
(93789 dm3 molꢀ1 cmꢀ1); MS (ESI): m/z: 1022 [M+Na]+.
Acknowledgements
Financial support has been provided by the Spanish MCyT (Project No.
BQU2002-00855 and BQU2002-0412-C02-02) and by the DURSI (Pro-
ject No. 2001SGR-00290). M.S. is indebted to the DURSI of the Generali-
tat de Catalunya for financial support through the Distinguished Univer-
sity Research Promotion, 2001. A.P. thanks the Secretarꢁa de Estado de
Educaciꢈn y Universidades of the MECD for a doctoral fellowship. S.F.
thanks CAM for a postdoctoral contract and M.A. thanks the MCyT of
Spain for a doctoral fellowship.
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2728
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Regioselective Intramolecular Pauson–Khand Reactions of C60
FULL PAPER
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Received: November 24, 2004
Published online: February 24, 2005
Chem. Eur. J. 2005, 11, 2716 – 2729
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ꢅ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2729