C59N+: A key intermediate in azaheterofullerene chemistry

Article abstract of DOI:10.1016/S0040-4020(01)00235-6

The thermal treatment of the azaheterofullerene dimer (C₅₉N)₂ in the presence of oxygen and a nucleophilic trapping reagent leads to the facile and selective formation of a variety of monomeric adducts C₅₉NR involving elec

Full text of DOI:10.1016/S0040-4020(01)00235-6

TETRAHEDRON
Pergamon
Tetrahedron 57 "2001) 3697±3708
C59N1: A key intermediate in azaheterofullerene chemistry
Frank Hauke and Andreas Hirschp
È
Institut fur Organische Chemie, Henkestrasse 42, D-91054 Erlangen, Germany
Received 4 October 2000; accepted 12 December 2000
AbstractÐThe thermal treatment ofthe azaheterofullerene dimer "C 59N)2 in the presence ofoxygen and a nucleophilic trapping reagent
leads to the facile and selective formation of a variety of monomeric adducts C59NR involving electronic rich aromatics, carbonyl
compounds, alcohols and ole®ns as terminating addend. These investigations within the ®eld ofsynthetic heteroufllerene chemistry
imply the presence ofC 59N1 as an important key intermediate. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
C59N derivatives. For instance, C59NH "3), where one
C59N moiety is substituted with an H-atom, was obtained
by the thermal treatment of 1 in 1,2-dichlorobenzene
In 1995, the preparative chemistry ofheteroufllerenes
began with the ®rst synthesis and isolation ofthe
nitrogen heterofullerene dimer "C59N)2 "1), elaborated inde-
pendently by Wudl et al. and our group using two different
strategies starting with parent C60.1,2 The availability of
"C59N)2 "1) in bulk quantities allowed further chemical
transformations and the detailed investigation of physical
properties.
n
"ODCB) in the presence of Bu3SnH.5 Other monomeric
derivatives like 4 are also available by radical reactions of
2.4 We recently elaborated another reaction sequence to
obtain monomeric C59N systems. Treatment of 1 with
electron-rich aromatics, e.g. veratrole, in the presence of
air and excess p-TsOH at 1508C causes the formation of
arylated aza[60]fullerene derivatives like 5.6 In this reac-
tion, the intermediate formation of C59N1 "6), which is
isoelectronic to C60, seems likely. C59N1 is presumed to
be formed via thermal homolysis of the dimer, followed
by oxidation ofthe radical "Scheme 2). Subsequently, the
azafulleronium ion 6 undergoes an electrophilic aromatic
substitution with the electron-rich aromatic compound.
Due to steric restrictions only the formation of para
substitution products "8) can be observed.
The substitution of one carbon atom of the fullerene frame-
work with nitrogen leads to the formation of an open-shell
system. Consequently, the simplest nitrogen heterofullerene
can only be isolated as the dimer 1. In this compound two
C59N moieties are connected by an sp3-carbon adjacent to
the nitrogen atom.3
Ofpreparative interest are monomeric substitution
products where one C59N moiety is replaced by a sub-
stituent. Such monomers containing suitable side chains
can exhibit higher solubilities than the parent dimer 1.
This is favorable for the investigation of subsequent
derivatizations and the design ofmaterials involving hetero-
fullerene building blocks. So far two important routes for
the synthesis ofmonomeric C 59N derivatives have been
developed "Scheme 1).
The oxidation is a critical step, since running the reaction
in an argon atmosphere does not yield arylated products
at all. The role ofthe p-TsOH is not yet clear. We
assume that the redox potential ofC 59N/C59N1 depends
on the pH, since in the absence ofthe acid no reaction
takes place.
In this contribution, we present full experimental details of a
whole series oftrapping experiments with diferent types of
nucleophiles including further extension of reactions with
enolizable carbonyl compounds reported in a preceding
short communication.7 These investigations strongly
corroborate the presence of 6 as key intermediate and
demonstrate the wide scope ofthese reactions with respect
to heterofullerene functionalization. All monomeric C59N
derivatives were isolated and fully characterized by MS,
UV, IR and NMR spectroscopy. Moreover, we demonstrate
that the oxidation of 2 leading to 6 can also be promoted by
other oxidizing agents such as chloranil.
Wudl et al. showed that a homolytic cleavage ofthe inter-
dimer C±C bond, which can be achieved thermally or
photochemically, leads to the monomeric radical C59N
"2).4 This species can either dimerize back to 1 or can be
trapped with suitable radical sources to form monomeric
Keywords: fullerenes; azaheterofullerenes; Mannich reaction; enols.
Corresponding author. Fax: 149-9131-8526864;
e-mail: andreas.hirsch@organik.uni-erlangen.de
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020"01)00235-6

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F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
Scheme 1. Possible reaction pathways of 1 leading to monomeric structures.
Scheme 2. Formation ofarylated heterofullerene derivatives.

F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
3699
Scheme 3. Synthesis of p-methoxy-ethoxy-ethoxy-ethoxy-hydroazafullerene 9.
2. Results and discussion
After 15 min, the conversion was completed. The isolation
ofthe products was achieved by ¯ash chromatography on
silica gel using toluene as a mobile phase. Thereby 10 and
11 eluted as the least polar olive-green colored fractions. For
the reaction of"C 59N)2 with enolizable compounds we
suggested the same mechanism "Scheme 5) as for the forma-
2.1. Synthesis of a well soluble C59N derivative
The ®rst monomeric C59N derivatives we prepared did not
exhibit solubilities that were much higher than that of 1.
They hardly dissolve in most organic solvents. As a conse-
quence, NMR-spectroscopic characterization and further
chemical transformation of these compounds turned out to
be dif®cult. This problem can be avoided by choosing a
suitable side chain, for example as substituent of an
aromatic trapping reagent. An aromatic system with a
triethylenglycol substituent turned out to be a proper choice.
The reaction of"C 59N)2 with methoxy-ethoxy-ethoxy-
ethoxy-benzene and p-TsOH in the presence ofair at
1508C leads to the formation of p-methoxy-ethoxy-
7
tion ofarylated monoazaheterofullerene derivatives.
In the presence of p-TsOH the ketones and aldehydes are in
equilibrium with their enol forms. The intermediate cation
C59N1 "6), formed by oxidation of the C59N radical "2), is
able to attack the enol form of the ketone/aldehyde and after
deprotonation the a-azafullerenated ketone/aldehyde "13) is
formed.
Acetophenone, a compound which offers an aromatic as
well as an enolic moiety clearly shows preferred attack at
the a-CH3 position. This result is not surprising, since aceto-
phenone is certainly not an electron rich aromatic system.
This behavior can indeed be taken as another prooffor our
proposed reaction mechanism, i.e. the azafulleronium cation
6 being the reaction intermediate.
ethoxy-ethoxy-hydroazafullerene
9
in 82% yield
"Scheme 3). The product fraction "Rfˆ0.46, silica gel,
toluene/ethyl acetate 7:3) was isolated by ¯ash chromato-
graphy on silica gel as olive-green colored band using
toluene as eluent.
As mentioned above, the only reaction product is the para
isomer. Compound 9 shows excellent solubility in organic
solvents like toluene, dichloromethane, ODCB or carbon
disul®de "more than 25 mg/ml) and therefore represents a
suitable educt for further transformations of the C59N
system.
Treatment of 1 with aldehydes like propanal under the same
experimental conditions also leads to the formation of the
corresponding mannich bases like 14 "Scheme 6). Next to
1-azafullerenylpropanal "14) the aldol condensation product
15 was formed. The yield of 15 increases with longer
reaction times at the expense of 14. Consequently, the
aldol condensation step takes place after compound 14 has
been formed "Scheme 7). NOE NMR spectra showed that
the isolated product 15 contains a double bond with the
E-con®guration exclusively.
2.2. Mannich functionalization of C59N7
Mannich bases 10 and 11 were obtained in almost quanti-
tative yield by the treatment of"C 59N)2 in ODCB with
20 equiv. ofacetone or acetophenone and 40 equiv. of
p-TsOH at 1508C in a constant stream ofair "Scheme 4).
All C59N derivatives described above, which were obtained
by the reaction of"C 59N)2 with aldehydes or ketones, show
Scheme 4. Reaction of 1 with ketones; formation of a-azafullerenated ketones.

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F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
Scheme 5. Reaction mechanism of 1 with enolizable compounds.
Scheme 6. Formation ofchiral 2-azafullerenylpropanal 14.
Scheme 7. Aldol condensation step leading to 15.
comparatively high solubility in organic solvents and form
olive green colored solutions.
ole®nic proton at dˆ6.2 ppm. Consequently, acetylacetone
reacts with 1 leading to 16, bearing the C59N moiety at a
terminal carbon atom "Scheme 8).7
2.3. Reaction with 1,3-dicarbonyl compounds
In principle, two reasons for the formation of the observed
product 16 can be considered. First, sterical restrictions
leading to a preferred attack of 6 to a terminal carbon
atom ofacetylacetone and second, the product ofrmation
could be controlled by thermodynamic stabilities of
products and intermediates due to electronic factors. In
order to achieve further insight into this question, we used
heptane-3,5-dione, which is sterically more hindered at the
Using acetylacetone as 1,3-dicarbonyl compound under
reaction conditions described above leads to an unexpected
product. Electrophilic attack of 6 at the central C-atom of
acetylacetone containing the most acidic protons would lead
to a symmetrical addition product. The H NMR spectrum
ofthe reaction product, however, is consistent with forma-
tion of 16, since it shows, for example, the resonance of an
1

F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
3701
Scheme 8. Reaction with acetylacetone leading to 16.
Scheme 9. Central versus terminal attack of 6 to a 1,3-dicarbonyl compound.
terminal carbon atom. We obtained a reaction mixture of
three products, probably containing a bisadduct and two
isomeric monoadducts. All three products show signals for
central and the terminal attack of 6 to 1,3-dicarbonyl
compounds are depicted.
1
ole®nic protons at about dˆ6.2 in the H NMR spectra,
Attack of 6 to C3 ofacetylacetone leads to cation 17, which
is stabilized by an O-p-donor. For an attack at C1 one has to
assume a tautomeric equilibrium ofacetylacetone leading to
an enolized C1 carbon atom. The attack at this C-atom
leads to the intermediate 18, which is a bis-donor substituted
indicating that in all three cases C59N1 attacks the terminal
carbon atom instead ofthe central one. Consequently, we
7
assume that electronic factors are responsible for the forma-
tion ofthe observed C 59N derivatives. In Scheme 9 the
Scheme 10. Products formed by the reaction of diethylmalonate with 1.

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F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
Scheme 11. Formation of4-azafullerenyl-crotonaldehyde 22.
allyl-cation. Semiempirical calculations "PC Spartan Pro,8
PM3) show that this cation is 14 kcal/mol more stable than
cation 17. Therefore, the attack of C59N1 "6) at one ofthe
two possible positions in acetylacetone should be thermo-
dynamically controlled, leading to the observed product 16.
Differentiation between the13C NMR signals ofthe methine
group "dˆ61.81) and the methylene group "dˆ62.31) was
achieved by DEPT NMR spectroscopy. The second product
is ethyl "2-azafullerenyl)acetate "21) "Rfˆ0.5), formed by
decarboxylation ofcompound 20 after partial saponi®cation
under the acidic conditions. In the 1H NMR spectrum of 21
the signals of2 equiv. methylene protons appear at dˆ4.7.
Both compounds are accessible in high purity. Compound
20 is slightly more soluble in organic solvents like ODCB
or toluene than 21. With longer reaction times the yield of
21 increases at the expense of 20, indicating that the
decarboxylation step takes place after the malonate addition
to the heterofullerene. A reaction using ethyl acetate as
educt does not yield any product at all. These experiments
clearly demonstrate, that the stability ofreaction inter-
mediates caused by a conjugated p-electron system and
not sterical effects determine the regioselectivity of the
addition reactions with acetylacetone.
To show that sterical hindrance ofthe central methylene
group is not too high, we used diethyl malonate as educt
for the reaction. The treatment of 1 with 15 equiv. diethyl
malonate in ODCB in the presence of30 equiv. p-TsOH and
air leads to the formation of two products, which can be
isolated by ¯ash chromatography on silica gel using toluene
as eluent "Scheme 10).
The ®rst fraction "Rfˆ0.7) is compound 20. Here, a substi-
tution ofone ofthe two methylene protons ofdiethyl
malonate by 6 takes place. The resonance ofthe remaining
proton in the 1H NMR spectrum appears at dˆ5.6.
Scheme 12. g versus a addition of 6 to crotonaldehyde.

F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
3703
Scheme 13. Reaction of 1 with mesityl oxide.
2.4. a,b-Unsaturated carbonyl compounds
tion to 25 has to be assumed. As shown with semiempirical
calculations "PC Spartan Pro,8 PM3), the allyl cation 26 is
by about 20 kcal/mol more stable than 23. Consequently, a
thermodynamically controlled vinylogous attack, leading to
the more stable intermediate 26, is more favorable than an
attack at the a-position. An attack to the a-carbon atom is
unlikely due to its acceptor character.
Treatment of 1 with 20 equiv. crotonaldehyde under the
same reaction conditions as described above leads to the
exclusive formation of compound 22 "Rfˆ0.6) "Scheme 11).
1
The H NMR spectrum of 22 shows the signal ofthe alde-
hyde proton at dˆ9.92 appearing as doublet, two different
signals for the ole®nic protons "dˆ8.07, 6.91) and a doublet
for the 2 equiv. protons of the methylene group "dˆ4.79).
The E con®guration ofthe C±C double bond was deter-
mined by NOE NMR spectroscopy. The 13C signals ofthe
two ole®nic carbon atoms "dˆ147.26, 138.09) were identi-
®ed by DEPT NMR spectroscopy. Hence, the reaction of
crotonaldehyde with 1 can be described as a vinylogous
substitution ofa g-proton by C59N1 "6). The preferred addi-
tion to the g instead ofthe a position can also be explained
with the thermodynamic stabilities ofthe intermediates 23
and 26 "Scheme 12).
Since 1 reacts with normal ketones at the a-position leading
to a-azafullerenated ketones and with a,b-unsaturated car-
bonyl compounds to g-substituted products, the question
arises, which position is more reactive. To ®nd out we
used mesityl oxide as test compound, since it contains two
methyl groups in the vinylogous position and one methyl
group in a-position to the carbonyl function. Treatment of 1
with mesityl oxide leads to the formation of three different
products "Scheme 13), which can be monitored by TLC
"silica gel, toluene/ethyl acetate 9:1). The products were
isolated by ¯ash chromatography using toluene as eluent.
The elution sequence is: 27 "Rfˆ0.93), 28 "Rfˆ0.85) and 29
1
An attack ofC 59N1 "6) at the a-carbon atom ofthe non
enolized crotonaldehyde leads to the formation of the inter-
mediate cation 23. This system is stabilized only by an 1I-
effect of the methyl group. After deprotonation compound
24 would be formed. When the attack of 6 takes place at the
g-position ofcrotonaldehyde, a donor stabilized allyl cation
26 is generated. For this process an acid catalyzed enoliza-
"Rfˆ0.60) as the most polar fraction. The H NMR spectra
ofall three compounds look very similar, showing three
signals at about dˆ4.6, 2.9 and 2.3, belonging to one
methylene and two methyl groups. The structure assignment
of 27±29 was carried out by NOE and DEPT spectroscopy.
The yield ratio ofcompounds 27±29 is about 1:1:1, showing
Scheme 14. Isomeric C59N-cyclooctene adducts.

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F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
Scheme 15. Formation ofmethoxy-ethoxy-ethoxy-ethoxy-hydroazafulleren 30.
As a further nucleophilic trapping reagent for C59N1 "6)
alcohols were chosen. In order to achieve products with
suf®cient solubility, we used triethylenglycol monomethyl-
ether as an example. In a smooth reaction the corresponding
C59N-alcohol adduct 30 was obtained and isolated by ¯ash
chromatography "Rfˆ0.3) in high purity "Scheme 15).
All monoazafullerene adducts described so far contained a
carbon substituent at the sp3-C-atom, which is adjacent to
the nitrogen atom. The corresponding sp3-C-atom in
compound 30 is attached to an O-atom, forming an N,O-
acetale. A similar compound 31 was observed as a by-
product during the synthesis of 1 elaborated by our group
"Fig. 1).9
Figure 1.
that the reactivity ofan a-position is approximately the
same as that ofa vinylogous position.
2.5. Other nucleophiles
The physical properties ofthis type ofadduct are diferent
from other monoazaheterofullerene derivatives mentioned
above. In toluene, 30 forms a red-green solution in contrast
In addition to reactions with carbonyl compounds we also
tested whether the intermediate 6 can also be trapped with
other nucleophiles. First we used cyclooctene. Treatment of
1 with this ole®n under nearly the same conditions as
described before leads to a compound mixture in high
yield, containing at least three products as detected by
HPLC "Cosmosil Buckyprep, toluene as eluent). The reac-
tion is very fast and all compounds elute together as the least
polar fraction on silica gel using toluene as eluent. It was not
possible to obtain any compound in a pure form, not even by
HPLC separation using a Cosmosil Buckyprep column. The
EI-MS spectrum ofthe product mixture only shows a peak
at m/z 861, corresponding to the M1 peak ofa cyclooctene-
C59N adduct, together with a strong fragmentation peak at
to the olive-green solutions ofother C 59N adducts. Due to
3
the attachment ofan O-atom, the signal ofthe sp cage
C-atom ofcompound 30 is shifted about 20 ppm down®eld
in the 13C NMR spectrum as compared to normal azahetero-
fullerene derivatives. The H NMR spectrum shows the
1
expected signals for the polyether side chain. The signals
for the six methylene groups appear in the region at dˆ3.4±
5.0 and the signal for the methyl group appears at dˆ3.36.
Regarding the fact, that the reaction of "C59N)2 "1) with
alcohols leads to the formation of an N,O-acetal, an acidic
cleavage of this acetal forming a cage-opened fullerene
system should be possible. Experiments in this direction
are the subject ofour current research.
1
m/z 722 for C59N1. The H NMR spectrum ofthe mixture
shows signals for three different ole®nic protons at about
dˆ5. We therefore assume that at least three isomers of
C59N-cyclooctene were formed by acid catalyzed double
bond isomerization leading to the isomeric compounds
shown in Scheme 14.
2.6. Other oxidizing reagents
All reactions described so far were carried with molecular
Scheme 16. Reaction of 1 with an allylether leading to 14.

F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
3705
Scheme 17. Reaction of 1 with ehtylacetoacetate leading to 3.
Scheme 18. Oxidation with chloranil leading to 33.
oxygen as oxidizing agent and they required the use of
p-TsOH. The presence ofan acid in the reaction mixture,
however, can be a disadvantage in some cases. For example,
the reaction with the allylpolyether 32 leads to the formation
of2-azaufllerenyl-propanal " 14) instead ofthe expected
adduct "Scheme 16).
p-TsOH. The high reaction temperature is unfavorable for
the quinone system and causes degradation. The search for
alternative oxidizing agents, e.g. ferrocenium hexa¯uoro-
phosphate, is the subject ofour current work.
3. Experimental
The acid effects the cleavage of the polyether, forming an
allylalcohol, which subsequently isomerizes to a propional-
dehyde under acid catalysis. It is unclear, whether this
step takes place at the stage ofan C 59N-ole®n adduct inter-
mediate or prior to the reaction with the heterofullerene.
3.1. General remarks and materials
"C59N)2 was prepared according to literature procedures.1 1
H
and 13C NMR spectra were obtained from JEOL JNM EX
and JEOL JNM GX instruments. Mass spectral data were
obtained on a Varian MAT 311 a mass spectrometer. UV±
VIS spectra were recorded on a Shimadzu UV-3102 spec-
trometer. IR spectra were obtained on a Bruker Vektor 22
instrument. HPLC analyses have been carried out on a
Cosmosil Buckyprep Waters column "250£4.6 mm) using
toluene as eluent.
A similar problem arises when ethyl acetoacetate is used as
a trapping reagent. The only product isolated in this case is
1-azafullerenyl-propan-2-one 3 "Scheme 17).
Here, an acid catalized ester cleavage followed by a decar-
boxylation step takes place. It could not be determined at
which stage this process happens. In addition, other nucleo-
philes like amines can not be used in the presence ofan acid
due to the formation of ammonium ions. Therefore, the
corresponding C59N derivatives are not accessible in this
way.
3.2. General experimental procedure
30 mg "20.83 mmol) "C59N)2 and p-TsOH are dissolved in
100 ml ODCB. The nucleophilic compound is added to this
solution. The reaction mixture is heated to 1508C while
passing a constant stream ofair through the solution until
all ofthe "C 59N)2 has been converted to the corresponding
C59N-adduct. The reaction can be monitored by TLC "silica
gel, toluene/ethyl acetate 9:1). Afterwards the formed
product is isolated by ¯ash chromatography using toluene
as eluent. The product is precipitated from CS2/pentane,
washed three times with pentane and dried in high vacuum.
We therefore tried to generate C59N1 "6) by using other
oxidizing agents. Treatment of"C 59N)2 "1) with anisole in
the presence ofchloranil at 150 8C under an argon
atmosphere leads to the formation of the corresponding
C59N-anisole adduct 33. The same adduct can also be
obtained by using oxygen as oxidizing agent "Scheme 18).6
This demonstrates that chloranil is also able to oxidize the
C59N radical "2) to the cation "6). The yield ofthe adduct
formation, however, is lower than in the case of oxygen and
3.2.1. p-Methoxy-ethoxy-ethoxy-ethoxy-hydroazafulleren
9. 50 equiv. methoxy-ethoxy-ethoxy-ethoxy-benzene,

3706
F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
20 equiv. p-TsOH, 4 h, 82% yield, Rf "silica gel, toluene/
ethyl acetate 7:3): 0.46. IR "KBr): n "cm21)ˆ2916, 2866,
1606, 1507, 1421, 1251, 1178, 1108, 578, 523; UV±Vis
"CH2Cl2): lmax "nm)ˆ257, 320, 445, 589, 724; MS "EI):
147.32, 147.13, 146.88, 146.41, 146.28, 145.62, 145.58,
144.90, 144.74, 144.30, 143.76, 142.95, 142.60, 142.29,
141.94, 141.56, 141.28, 140.83, 140.71, 139.51, 137.26,
133.94, 133.74, 123.96, 85.14 "1C; sp3), 56.98 "1C; CH),
10.11 "1C; CH3).
1
m/z 961 "M1), 722 "C59N1); H NMR "400 MHz, CS2±
20% CDCl3): dˆ8.69 "m, 2H), 7.34 "m, 2H), 4.30 "m, 2H;
CH2), 3.94 "m, 2H; CH2), 3.73 "m, 2H; CH2), 3.67 "m, 2H;
CH2), 3.62 "m, 2H; CH2), 3.51 "m, 2H; CH2), 3.35 "s, 3H;
CH3); 13C NMR "100.5 MHz, CS2±20% CDCl3): dˆ159.62
"1C; C-"CH)2-OR), 154.08, 148.60, 147.54, 147.39, 147.36,
147.03, 147.00, 146.73, 146.37, 146.15, 145.99, 145.62,
145.42, 144.80, 144.32, 144.07, 143.76, 142.90, 142.52,
141.86, 141.57, 141.31, 141.20, 140.76, 140.65, 139.57,
137.29, 133.01, 132.69, 128.41 "2C; C-CHCOR), 123.86,
115.62 "2C; C-COR), 82.30 "1C; sp3), 71.85 "1C; CH2),
70.84 "1C; CH2), 70.64 "1C; CH2), 70.48 "1C; CH2),
69.53 "1C; CH2), 67.48 "1C; CH2), 58.49 "1C; CH3).
Compound 15: IR "KBr): n "cm21)ˆ2950, 2921, 1726,
1686, 1508, 1446, 1422, 1317, 1238, 1185, 990, 577, 555,
524; UV±Vis "CH2Cl2): lmax "nm)ˆ257, 320, 445, 589,
724; MS "EI): m/z 819 "M1), 722 "C59N1); 1H NMR
"400 MHz, CS2±20% CDCl3): dˆ9.81 "s, 1H; CHO), 7.68
4
"dq, 1H, Jˆ1.46 Hz, Jˆ10.1 Hz; vCH), 5.00 "dq, 1H,
Jˆ10.1, 6.84 Hz; CH), 2.50 "d, 3H, Jˆ6.84 Hz; CH3),
4
2.40 "d, 3H, Jˆ1.46 Hz; CH3); 13C NMR "100.5 MHz,
CS2±20% CDCl3): dˆ192.52 "1C; CHO), 155.25, 149.77,
147.60, 147.38, 147.28, 147.23, 146.98, 146.72, 146.35,
146.12, 145.67, 144.96, 144.76, 144.21, 143.76, 142.99,
142.77, 142.64, 141.97, 141.60, 141.33, 140.87, 140.80,
139.54, 137.31, 133.78, 130.20, 127.26, 124.01, 85.19
"1C; sp3), 45.59 "1C; CH), 15.43 "1C; CH3), 10.11 "1C;
CH3).
3.2.2. 1-Azafullerenylpropan-2-one 10. 20 equiv. acetone,
40 equiv. p-TsOH, 15 min, 96% yield, Rf "silica gel,
toluene/ethyl acetate 9:1): 1.00. IR "KBr): n "cm21)ˆ
2920, 2850, 1729, 1550, 1422, 1358, 1185, 1166, 578,
524; UV±VIS "CH2Cl2): lmax "nm)ˆ257, 320, 445, 589,
724; MS "EI): m/z 772 "M1), 722 "C59N1); 1H NMR
"400 MHz, CS2±20% CDCl3): dˆ4.91 "s, 2H; CH2), 2.79
"s, 3H; CH3); 13C NMR "100.5 MHz, CS2±20% CDCl3):
dˆ201.80 "1C; CvO), 154.94, 148.31, 147.37, 147.11,
146.90, 146.38, 146.31, 146.02, 145.75, 145.50, 144.90,
144.74, 144.14, 143.79, 142.89, 142.54, 141.88, 141.56,
141.22, 141.01, 140.83, 140.78, 139.43, 137.41, 137.35,
127.26, 124.63, 78.37 "1C; sp3), 53.84 "1C; CH2), 30.90
"1C; CH3).
3.2.5. 1-Azafullerenyl-2,4-pentanedione 16. 15 equiv.
acetylacetone, 20 equiv. p-TsOH, 20 min, 89% yield, Rf
"silica gel, toluene/ethyl acetate 9:1): 0.95. IR "KBr): n
"cm21)ˆ2924, 2853, 1600, 1447, 1421, 1321, 1236, 1194,
577, 542, 523; UV±VIS "CH2Cl2): lmax "nm)ˆ257, 320,
1
445, 589, 724; MS "EI): m/z 821 "M1), 722 "C59N1); H
NMR "400 MHz, CS2±20% CDCl3): dˆ15.76 "s, 1H; O±
H±O), 6.21 "s, 1H; vCH), 4.72 "s, 2H; CH2), 2.27 "s, 3H,
CH3); 13C NMR "100.5 MHz, CS2±20% CDCl3): dˆ190.46
"1C; CvO), 188.59 "1C; CvO), 154.74, 148.33, 147.65,
147.34, 147.18, 146.92, 146.44, 146.33, 146.08, 145.71,
145.53, 144.95, 144.78, 144.25, 144.16, 143.83, 142.94,
142.61, 141.91, 141.60, 141.27, 141.09, 140.84, 140.76,
139.48, 137.38, 133.87, 124.30, 102.01 "1C, vCH), 79.32
"1C; sp3), 50.84 "1C; CH2), 24.47 "1C; CH3).
3.2.3. 1-Azafullerenyl-2-phenylethan-2-one 11. 20 equiv.
acetophenone, 40 equiv. p-TsOH, 15 min, 92% yield, Rf
"silica gel, toluene/ethyl acetate 9:1): 1.00. IR "KBr): n
"cm21)ˆ2921, 2851, 1692, 1550, 1446, 1422, 1215, 1175,
1092, 577, 524; UV±VIS "CH2Cl2): lmax "nm)ˆ257, 320,
1
445, 589, 724; MS "EI): m/z 841 "M1), 722 "C59N1); H
3.2.6. Diethyl 2-azafullerenylmalonate 20. 15 equiv.
malonic acid, 30 equiv. p-TsOH, 30 min, 49% yield, Rf
"silica gel, toluene/ethyl acetate 9:1): 0.70. IR "KBr): n
"cm21)ˆ2974, 2925, 1735, 1551, 1460, 1424, 1365, 1186,
1093, 1016, 579, 524; UV±Vis "CH2Cl2): lmax "nm)ˆ257,
320, 445, 589, 724; MS "EI): m/z 821 "M1), 722 "C59N1); 1H
NMR "400 MHz, CS2±20% CDCl3): dˆ5.56 "s, 1H; CH),
4.56 "m, 2H; CH2), 1.51 "t, 3H; CH3); 13C NMR
"100.5 MHz, CS2±20% CDCl3): dˆ165.40 "2C; CvO),
155.06, 147.49, 147.28, 147.07, 146.96, 146.73, 146.25,
146.16, 145.93, 145.66, 145.50, 145.44, 144.84, 144.62,
144.06, 143.71, 142.88, 142.57, 141.91, 141.65, 141.19,
140.78, 140.59, 139.04, 137.19, 134.86, 124.72, 79.35
"1C; sp3), 62.31 "1C; CH2), 64.81 "1C; CH).
NMR "400 MHz, CS2±20% CDCl3): dˆ8.40 "m, 2H),
7.74 "m, 1H), 7.70 "m, 2H), 5.45 "s, 2H; CH2); 13C NMR
"100.5 MHz, CS2±20% CDCl3): dˆ193.80 "1C; CvO),
155.02, 148.57, 147.57, 147.36, 147.10, 146.93, 146.87,
146.34, 146.26, 145.97, 145.73, 145.55, 145.44, 144.85,
144.71, 144.09, 143.77, 142.85, 142.54, 141.83, 141.53,
141.18, 141.03, 140.80, 140.75, 139.39, 137.42, 136.58,
134.93 "1C; i-Ar), 133.50 "1C; p-Ar), 128.76 "2C;
Ar), 128.23 "2C; Ar), 124.78, 78.59 "1C; sp3), 49.45 "1C,
CH2).
3.2.4. 2-Azafullerenylpropanal 14 and E-4-azafullerenyl-
2-methylpent-2-enal 15. 45 equiv. propionaldehyde,
90 equiv. p-TsOH, 15 min, HPLC puri®cation, Rf "silica
gel, toluene/ethyl acetate 9:1): 1.00.
3.2.7. Ethyl 42-azafullerenyl)acetate 21. 15 equiv. malonic
acid, 30 equiv. p-TsOH, 30 min, 49% yield, Rf "silica gel,
toluene/ethyl acetate 9:1): 0.50. IR "KBr): n "cm21)ˆ2972,
2951, 2921, 2850, 1737, 1551, 1459, 1439, 1423, 1366,
1343, 1188, 1093, 1022, 579, 556, 525; UV±Vis
"CH2Cl2): lmax "nm)ˆ257, 320, 445, 589, 724; MS "EI):
Compound 14: IR "KBr): n "cm21)ˆ2950, 2921, 1728,
1508, 1446, 1422, 1238, 1185, 990, 577, 555, 524; UV±
Vis "CH2Cl2): lmax "nm)ˆ257, 320, 445, 589, 724; MS
1
"EI): m/z 772 "M1), 722 "C59N1); H NMR "400 MHz,
1
CS2±20% CDCl3): dˆ11.07 "d, 1H, Jˆ1.46 Hz; CHO),
4.63 "dq, 1H, Jˆ1.46, 7.08 Hz; CH), 2.50 "d, 3H,
Jˆ7.08 Hz; CH3); 13C NMR "100.5 MHz, CS2±20%
CDCl3): dˆ198.79 "1C; CHO), 155.19, 149.50, 147.54,
m/z 821 "M1), 722 "C59N1); H NMR "400 MHz, CS2±
20% CDCl3): dˆ4.75 "s, 1H; CH2), 4.55 "q, 2H; CH2),
1.55 "t, 3H; CH3); 13C NMR "100.5 MHz, CS2±20%
CDCl3): dˆ168.29 "1C; CvO), 154.87, 148.04, 147.60,

F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
3707
147.32, 147.16, 147.05, 146.84, 146.40, 146.32, 146.05,
145.70, 145.62, 145.52, 144.91, 144.76, 144.20, 144.14,
143.82, 142.92, 142.60, 141.91, 141.60, 141.27, 140.96,
140.84, 140.78, 139.46, 137.38, 134.16, 124.37, 78.35
"1C; sp3), 61.44 "1C; CH2), 46.72"1C; CH3).
Vis "CH2Cl2): lmax "nm)ˆ257, 319, 442, 556, 717; MS
1
"EI): m/z 819 "M1), 722 "C59N1); H NMR "400 MHz,
CS2±20% CDCl3): dˆ6.94 "s, 1H; vCH), 4.59 "s, 2H;
CH2), 2.92 "s, 3H; CH3), 2.35 "s, 3H; CH3); 13C NMR
"100.5 MHz, CS2±20% CDCl3): dˆ196.36 "1C; CvO),
154.67, 149.39, 148.55, 147.69, 147.38, 147.28, 147.19,
146.88, 146.52, 146.39, 146.17, 145.79, 145.71, 145.60,
145.00, 144.84, 144.36, 144.22, 143.85, 142.99, 142.66,
141.97, 141.60, 141.35, 141.15, 140.85, 140.74, 139.61,
137.35, 133.44, 129.86 "1C; vCH), 123.97, 81.51
"1C; sp3), 54.31 "1C; CH2), 31.57 "1C; CH3), 22.59 "1C;
CH3).
3.2.8. 4-Azafullerenylcrotonaldehyde 22. 15 equiv. croton-
aldehyde, 20 equiv. p-TsOH, 30 min, 71% yield, Rf "silica
gel, toluene/ethyl acetate 9:1): 0.60. IR "KBr):
n
"cm21)ˆ2935, 2922, 1691, 1550, 1508, 1423, 1363, 1185,
1175, 1093 1033, 765, 720, 577, 556, 529, 523; UV±Vis
"CH2Cl2): lmax "nm)ˆ257, 321, 441, 554, 591, 719; MS
1
"EI): m/z 791 "M1), 722 "C59N1); H NMR "400 MHz,
CS2±20% CDCl3): dˆ9.92 "d, 1H, Jˆ7.57 Hz; CHO), 8.07
"m, 1H, Jˆ7.57, 15.63 Hz; vCH), 6.91 "m, 1H, Jˆ15.63,
7.57 Hz; vCH), 4.79 "d, 2H, Jˆ7.57 Hz; CH2); 13C NMR
"100.5 MHz, CS2±20% CDCl3): dˆ164.81 "1C; CvO),
154.57, 147.60, 147.27 "1C; vCH), 147.19, 146.72,
146.48, 146.37, 146.13, 145.73, 145.66, 145.59, 144.98,
144.78, 144.38, 144.22, 143.80, 142.99, 142.64, 141.95,
141.55, 141.37, 140.98, 140.93, 140.74, 139.74, 138.09
"1C; vCH), 137.31, 133.60, 123.75, 80.89 "1C; sp3), 46.42
"1C; CH2).
3.2.12. Isomeric C59N-cyclooctene-adducts. 50 equiv.
Cyclooctene, 20 equiv. p-TsOH, 10 min, 91% yield of
isomeric compounds, Rf "silica gel, toluene/ethyl acetate
9:1): 1.00. MS "EI): m/z 831 "M1), 722 "C59N).
3.2.13. Methoxy-ethoxy-ethoxy-ethoxy-hydroazafullerene
30. 50 equiv. triethylenglycol, 20 equiv. p-TsOH, 1 h, 43%
yield, Rf "silica gel, toluene/ethyl acetate 9:1): 0.30. IR
"KBr): n "cm21)ˆ2921, 2865, 1585, 1550, 1439, 1423,
1239, 1196, 1184, 1146, 1096, 1022, 575, 524; UV±VIS
"CH2Cl2): lmax "nm)ˆ260, 324, 436, 687, 762; MS "EI):
1
3.2.9.
1-Azafullerenyl-4-methylpent-3-en-2-one
27.
m/z 885 "M1), 722 "C59N1); H NMR "400 MHz, CS2±
15 equiv. mesityloxide, 20 equiv. p-TsOH, 45 min, 27%
yield, Rf "silica gel, toluene/ethyl acetate 9:1): 0.93. IR
"KBr): n "cm21)ˆ2949, 2922, 2851, 1728, 1690, 1617,
1550, 1423, 1238, 1186, 1117, 1092, 1033, 766, 746, 529,
523; UV±Vis "CH2Cl2): lmax "nm)ˆ256, 322, 443, 589,
727; MS "EI): m/z 819 "M1), 722 "C59N1); 1H NMR
"400 MHz, CS2±20% CDCl3): dˆ6.72 "s, 1H; vCH),
4.87 "s, 2H; CH2), 2.46 "s, 3H; CH3), 2.16 "s, 3H; CH3);
13C NMR "100.5 MHz, CS2±20% CDCl3): dˆ194.07 "1C;
CvO), 158.10, 155.09, 148.93, 147.43, 147.12, 147.08,
147.03, 146.43, 146.32, 146.04, 145.79, 145.51, 144.91,
144.78, 144.14, 143.85, 142.90, 142.59, 141.88, 141.58,
141.20, 141.15, 140.82, 140.78, 139.41, 137.49, 134.31,
124.72, 123.68 "1C; vCH), 78.94 "1C; sp3), 54.58 "1C;
CH2), 27.89 "1C; CH3), 21.15 "1C; CH3).
20% CDCl3): dˆ4.99 "m, 2H; vCH2), 4.23 "m, 2H;
CH2), 3.90 "m, 2H; CH2), 3.76 "m, 2H; CH2), 3.68 "m,
2H; CH2), 3.54 "m, 2H; CH2), 3.36 "s, 3H; CH3); 13C
NMR "100.5 MHz, CS2±20% CDCl3): dˆ153.49, 146.93,
146.87, 146.66, 146.61, 145.67, 145.50, 145.20, 145.11,
145.05, 144.59, 144.40, 144.30, 143.77, 143.55, 142.91,
142.56, 142.41, 141.91, 141.81, 141.18, 141.03, 140.83,
140.63, 139.14, 136.53, 135.17, 124.92, 100.30 "1C; sp3),
71.89 "1C; CH2), 71.02 "1C; CH2), 70.73 "1C; CH2), 70.53
"1C; CH2), 70.25 "1C; CH2), 65.62 "1C; CH2), 58.60 "1C;
CH3).
3.2.14. p-Methoxyphenylhydroazafullerene 33. "C59N)2
"15 mg, 10.41 mmol) is dissolved in 20 ml dry ODCB.
The solution is degassed to remove any traces ofoxygen.
To the argon saturated solution 8 ml anisole and 215 mg
"25 equiv.) chloranil are added. The reaction mixture is
heated to 1508C while passing a constant stream ofargon
through the solution until all ofthe "C 59N)2 has been
converted to the corresponding C59N-anisol adduct. The
reaction can be monitored by HPLC "Cosmosil Buckyprep,
toluene). Afterwards the formed product is isolated by ¯ash
chromatography using toluene as eluent. The product is
precipitated from CS2/pentane, washed three times with
pentane and dried in high vacuum. p-Methoxyphenylhydro-
azafullerene is obtained in 29% yield.
3.2.10. Z-5-Azafullerenyl-4-methylpent-3-en-2-one 28.
15 equiv. mesityloxide, 20 equiv. p-TsOH, 45 min, 22%
yield, Rf "silica gel, toluene/ethyl acetate 9:1): 0.85. IR
"KBr): n "cm21)ˆ2950, 2921, 2851, 1685, 1617, 1559,
1550, 1423, 1239, 1197, 1186, 1176, 1094, 765, 580, 530,
524; UV±Vis "CH2Cl2): lmax "nm)ˆ257, 323, 446, 577,
730; MS "EI): m/z 819 "M1), 722 "C59N1); 1H NMR
"400 MHz, CS2±20% CDCl3): dˆ6.82 "s, 1H; vCH),
5.18 "s, 2H; CH2), 2.78 "s, 3H; CH3), 2.31 "s, 3H; CH3);
13C NMR "100.5 MHz, CS2±20% CDCl3): dˆ196.60 "1C;
CvO), 154.85, 149.88, 149.29, 147.65, 147.39, 147.32,
147.23, 147.07, 146.44, 146.28, 146.08, 145.71, 145.48,
144.91, 144.80, 144.32, 144.12, 143.85, 142.94, 142.55,
141.90, 141.62, 141.24, 140.76, 140.67, 139.39, 137.35,
133.29, 128.87 "1C; vCH), 124.26, 81.40 "1C; sp3), 45.21
"1C, CH2), 31.56 "1C; CH3), 28.33 "1C; CH3).
3.3. Spectral data
See Ref. 2.
3.2.11. E-5-Azafullerenyl-4-methylpent-3-en-2-one 29.
15 equiv. mesityloxide, 20 equiv. p-TsOH, 45 min, 35%
yield, Rf "silica gel, toluene/ethyl acetate 9:1): 0.60. IR
"KBr): n "cm21)ˆ2950, 2921, 2851, 1690, 1617, 1550,
1423, 1239, 1186, 1095, 1027, 963, 765, 530, 524; UV±
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft "DFG) for
®nancial support.

3708
F. Hauke, A. Hirsch / Tetrahedron 57 ,2001) 3697±3708
Â
5. Keshavarz-K, M.; Gonzalez, R.; Hicks, R. G.; Srdanov, G.;
Srdanov, V. I.; Collins, T. G.; Hummelen, J.; Bellavia-Lund,
C.; Pavlovich, J.; Wudl, F.; Holczer, K. Nature 1996, 383, 147±
150.
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