[60]Fullerene Adducts with Improved Electron Acceptor Properties

Article abstract of DOI:10.1021/jo0003753

The synthesis of C₆₀-based dyads in which the C₆₀ core is covalently attached to a strong electron acceptor moiety such as quinones, TCNQ or DCNQI derivatives, has been carried out by 1,3-dipolar cycloaddition of "in situ" generated azomethyne ylides or nitrile oxides to C₆₀. As expected, the obtained pyrrolidino[3′,4′:1,2][60]fullerenes exhibit reduction potentials of the C₆₀ framework which are cathodically shifted in comparison with the parent C₆₀. In contrast, isoxazolo[4′,5′:1,2][60]-fullerenes show reduction waves for the fullerene core that are anodically shifted in comparison with the parent C₆₀, which indicates that they are remarkably stronger acceptors than C₆₀.The electron acceptor organic addend also undergoes an anodic shift due to the electronic interaction with the C₆₀ moiety. The molecular geometry of pyrrolidinofullerenes has been calculated at the semiempirical PM3 level and reveals a highly distorted geometry for the acceptor moiety in compound 13, and a most stable conformation in which both dicyanomethylene units are far away from the C₆₀ surface.

Full text of DOI:10.1021/jo0003753

5986
J . Org. Chem. 2000, 65, 5986-5995
[60]F u ller en e Ad d u cts w ith Im p r oved Electr on Accep tor
P r op er ties
Beatriz M. Illescas and Nazario Mart´ın*
Departamento de Quı´mica Orga´nica I, Facultad de Quı´mica, Universidad Complutense,
E-28040 Madrid, Spain
nazmar@eucmax.sim.ucm.es
Received March 15, 2000
The synthesis of C60-based dyads in which the C60 core is covalently attached to a strong electron
acceptor moiety such as quinones, TCNQ or DCNQI derivatives, has been carried out by 1,3-dipolar
cycloaddition of “in situ” generated azomethyne ylides or nitrile oxides to C60. As expected, the
obtained pyrrolidino[3′,4′:1,2][60]fullerenes exhibit reduction potentials of the C60 framework which
are cathodically shifted in comparison with the parent C60. In contrast, isoxazolo[4′,5′:1,2][60]-
fullerenes show reduction waves for the fullerene core that are anodically shifted in comparison
with the parent C60, which indicates that they are remarkably stronger acceptors than C60.The
electron acceptor organic addend also undergoes an anodic shift due to the electronic interaction
with the C60 moiety. The molecular geometry of pyrrolidinofullerenes has been calculated at the
semiempirical PM3 level and reveals a highly distorted geometry for the acceptor moiety in
compound 13, and a most stable conformation in which both dicyanomethylene units are far away
from the C60 surface.
In tr od u ction
atoms as constituents of the fullerene framework (het-
erofullerenes) (8)14 (Chart 1).
[60]Fullerene exhibits a remarkable electron acceptor
character that has been skillfully used for the preparation
of a wide variety of different electroactive systems by the
covalent attachment to electron donor molecules.1 Wudl
et al. proposed that C60 can be chemically modified with
organic groups while retaining its unique electronic
properties.2 However, despite the correctness of this
statement, it is well known that most of the [60]fullerene
derivatives present poorer electron acceptor properties
than the parent C60 as a consequence of the saturation
of a double bond of the C60 framework that raises the
LUMO energy.3 Therefore, the design and synthesis of
new organofullerenes showing better electron acceptor
abilities than the parent C60 are very appealing tasks in
the search of applications to materials science1,4 and
biochemistry.5
Within the past few years, several attempts have been
carried out by different groups directed at the synthesis
of stronger acceptors than the parent C60.1 Basically, the
strategies followed for increasing the electron acceptor
character in fullerene derivatives have been mainly
focused on (i) the presence of electronegative atoms
directly linked to the C60 core (1,6 27), (ii) electron acceptor
groups (3,8 49), (iii) periconjugative effect (5, 6),10-12 (iv)
pyrrolidinium salts (7),13 and (v) the presence of hetero-
On the other hand, only a few examples are known in
which the C60 framework is covalently attached to an
electron acceptor unit.1 In light of a possible electron
transfer from the photoexcited fullerene to the adjacent
strong electron acceptor, we have recently reported dyad
9.15 In this system, formation of the fullerene triplet
excited-state rather than an intramolecular electron-
transfer was observed,16 which can be accounted for by
the inability of C60 to form stable cationic species.17,18
However, modulation of the electronic properties of C60
derivatives showing enhanced acceptor abilities over C60
(8) (a) Keshavarz, K. M.; Knight, B.; Srdanov, G.; Wudl, F. J . Am.
Chem. Soc. 1995, 117, 11371. (b) Keshavarz, K. M.; Knight, B.; Haddon,
R. C.; Wudl, F. Tetrahedron 1996, 52, 5149.
(9) (a) de la Cruz, P.; de la Hoz, A.; Langa, F.; Mart´ın, N.; Pe´rez, M.
C.; Sa´nchez, L. Eur. J . Org. Chem. 1999, 3433, 3. (b) Deviprasad,
Rahman, M. S.; Souza, F. D. Chem. Commun. 1999, 849.
(10) Wudl, F.; Suzuki, T.; Prato, M. Synth. Met. 1993, 59, 297.
(11) Eiermann, M.; Haddon, R. C.; Knight, B.; Li, Q. C.; Maggini,
M.; Mart´ın, N.; Ohno, T.; Prato, M.; Suzuki, T.; Wudl, F. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1591.
(12) Knight, B.; Mart´ın, N.; Ohno, T.; Ort´ı, E.; Rovira, C.; Veciana,
J .; Vidal-Gancedo, J .; Viruela, P.; Viruela, R.; Wudl, F. J . Am. Chem.
Soc. 1997, 119, 9871.
(13) Da Ros, T.; Prato, M.; Carano, M.; Ceroni, P.; Paolucci, F.;
Roffia, S. J . Am. Chem. Soc. 1998, 120, 11645.
(14) Hummelen, J . C.; Knight, B.; Paulovich, J .; Gonza´lez, R.; Wudl,
F. Science 1995, 269, 1554. For recent reviews on heterofullerenes,
see: (a) Hummelen, J . C.; Bellavia-Lund, C.; Wudl, F. Top. Curr. Chem.
1999, 199, 93. (b) Hirsch, A.; Nuber, B. Acc. Chem. Res. 1999, 32, 795.
(15) Illescas, B.; Mart´ın, N.; Pe´rez, I.; Seoane, C. Synth. Met. 1999,
103, 2344.
(1) Mart´ın, N.; Sa´nchez, L.; Illescas, B.; Pe´rez, I. Chem. Rev. 1998,
98, 2527.
(2) Suzuki, T.; Li, Q.; Khemani, K. C.; Wudl, F.; Almarsson, O¨ . J .
Am. Chem. Soc. 1992, 114, 7300.
(3) For a recent review on the electrochemistry of fullerenes, see:
Echegoyen, L.; Echegoyen, L. E. Acc. Chem. Res. 1998, 31, 593.
(4) Prato, M. Top. Curr. Chem. 1999, 199, 173.
(5) Da Ros, T.; Prato, M. Chem. Commun. 1999, 663.
(6) Creegan, K. M.; Robbins, J . L.; Robbins, W. K.; Millar, J . M.;
Sherwood, R. D.; Tindall, P. J .; Cox, D. M.; Smith, A. B., III; McCauley,
J . P., J r.; J ones, D. R.; Gallager, R. T. J . Am. Chem. Soc. 1992, 114,
1103.
(16) Mart´ın, N.; Sa´nchez, L.; Illescas, B.; Gonza´lez, S.; Herranz, M.
A.; Guldi, D. M. Carbon, in press.
(17) Nonell, S.; Arbogast, J . W.; Foote, C. S. J . Phys. Chem. 1992,
96, 4169.
(18) The salt [C60
+
]
•[CB11H6Cl6]- has been prepared in the solid
state using a new brominated N-phenylcarbazole cation reagent as the
oxidant. Bolskar, R. D.; Fackler, N. L. P.; Mathur, R. S.; Reed, Ch. A.
193rd Meeting of the Electrochemical Society, San Diego, May 3-8,
1998. Reed, Ch. A.; Kim, K.-Ch; Bolskar, R. D.; Mueller, L. J . Science
2000, 289, 101.
(7) Guldi, D. M.; Gonza´lez, S.; Mart´ın, N.; Anto´n, A.; Gar´ın, J .;
Orduna, J . J . Org. Chem. 2000, 65, 1979, and references therein.
10.1021/jo0003753 CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/24/2000

[60]Fullerene Adducts
J . Org. Chem., Vol. 65, No. 19, 2000 5987
Ch a r t 1. Selected Exa m p les of Mod ified F u ller en es Exh ibitin g High er Electr on Affin ity Th a n th e P a r en t
C60
is still a demanding goal in fullerene chemistry with
potential applications in charge-transfer and light-
induced electron-transfer processes.
fullerenes23 have been reported during the past few years,
the enhanced electron accepting properties, related to the
parent C60, have only recently been reported.24
The target pyrrolidino[3′,4′:1,2][60]fullerenes (12, 13)
were synthesized from the recently reported 2-formyl-
9,10-anthraquinone (10).25 Thus, reaction of sarcosine (N-
methylglycine) and aldehyde 10 in the presence of C60
affords cycloadduct 12 resulting from the addition of the
“in situ” generated azomethine ylide to C60 by following
Prato’s procedure.26 Further reaction of 12 with Lehnert’s
reagent (malononitrile, titanium tetrachloride, pyridine)27
leads to 11,11,12,12-tetracyanoanthraquinodimethane
(TCAQ) derivative 13 in moderate yield.21 Alternatively,
fulleropyrrolidine 13 was also obtained from commer-
cially available 2-hydroxymethylanthraquinone by reac-
tion with Lehnert’s reagent, oxidation, and further
reaction of 11 with C60 and sarcosine (11: C60/sarcosine
1:1:5) affording compound 13 in 20% yield (40% based
on recovered C60). This procedure seemed to be more
appropriate than the former one from 12, which requires
a much longer reaction time (13 days) as well as a much
larger stoichiometric ratio of reactants (12/CH2(CN)2/
TiCl4/pyr 1:95:95:190) (Scheme 1).
In this work we present the synthesis of pyrrolidino-
[3′,4′:1,2][60]fullerenes (12-15, 22, 25) and isoxazolo-
[4′,5′:1,2][60]fullerenes (17, 19, 33) endowed with strong
electron acceptor moieties. We have investigated, by
cyclic voltammetry measurements, the influence of the
organic addends as well as the nature of the heterocycle
fused to the C60 unit on the electron acceptor properties.
In addition, theoretical calculations at the semiempirical
PM3 level have been used to predict the molecular
geometry in pyrrolidino[3′,4′:1,2][60]fullerenes.
Resu lts a n d Discu ssion
Syn th esis. A wide variety of modified fullerenes have
been prepared by cycloaddition reactions to [60]fullerene.
Among them, Diels-Alder19 and 1,3-dipolar20 cycloaddi-
tions have played a very important role.
In a previous communication we reported the facile
formation of pyrrolidino[3′,4′:1,2][60]fullerenes endowed
with strong electron acceptors derived from the well-
known tetracyano-p-quinodimethane (TCNQ) and dicy-
ano-p-quinonediimine (DCNQI).21 We describe herein the
preparation of isoxazolino[4′,5′:1,2][60]fullerenes bearing
strong electron acceptor organic addends. Although a
number of papers dealing with the synthesis22 and
further chemical transformations of isoxazolo[4′5′:1,2][60]-
9,10-Dicyanoanthraquinonediimine (DCAQI) 14 was
prepared from compound 12 in low yield (4%) by reaction
with bis(trimethylsilyl)carbodiimide (BTC) in the pres-
(23) (a) Meier, M. S.; Poplawska, M. Tetrahedron 1996, 52, 5043.
(b) Irngartinger, H.; Weber, A. Tetrahedron Lett. 1997, 38, 2075. (c)
Da Ros, T.; Prato, M.; Novello, F.; Maggini, M.; de Amici, M.; de
Micheli, C. Chem. Commun. 1997, 59.
(19) For a very recent review, see: Segura, J . L.; Mart´ın, N. Chem.
Rev. 1999, 99, 3199.
(20) For a recent review on fulleropyrrolidines, see: Prato, M.;
Maggini, M. Acc. Chem. Res. 1998, 31, 519.
(21) Illescas, B.; Mart´ın, N.; Seoane, C. Tetrahedron Lett. 1997, 38,
2015.
(22) (a) Ohno, M.; Yashiro, A.; Eguchi, S. Synlett 1996, 815. (b)
Irngartinger, H.; Weber, A. Tetrahedron Lett. 1996, 37, 4137. (c)
Irngartinger, H.; Weber, A.; Escher, T. Liebigs Ann. 1996, 1845.
(24) (a) de la Cruz, P.; Espildora, E.; Garc´ıa, J . J .; de la Hoz, A.;
Langa, F.; Mart´ın, N.; Sa´nchez, L. Tetrahedron Lett. 1999, 40, 4889.
(b) Irngartinger, H.; Escher, T. Tetrahedron 1999, 55, 10753.
(25) Mart´ın, N.; Pe´rez, I.; Sa´nchez, L.; Seoane, C. J . Org. Chem.
1997, 62, 5690.
(26) Maggini, M.; Scorrano, G.; Prato, M. J . Am. Chem. Soc. 1993,
115, 9798.
(27) (a) Lehnert, W. Tetrahedron Lett. 1970, 4723. (b) Lehnert, W.
Synthesis 1974, 667.

5988 J . Org. Chem., Vol. 65, No. 19, 2000
Illescas and Mart´ın
Sch em e 1
ence of titanium tetrachloride according to Hu¨nig’s
procedure.28 Monocondensated compound 15 was also
obtained together with 14 in 5% yield as a mixture of
Compound 25 bearing a naphthoquinone moiety was
prepared in two steps from 2331 which in turn was
prepared in three steps from commercially available
p-benzoquinone. Further oxidation of 23 with PCC leads
to 6-formyl-1,4-naphthoquinone in quantitative yield,
which reacts with sarcosine and C60 to form novel
cycloadduct 25 in 22% yield (42% based on consumed C60).
1
constitutional isomers according to the H NMR data.21
We have also carried out the synthesis of fulleropyr-
rolidines endowed with other stronger electron-acceptor
quinones such as 1,4-benzo and 1,4-naphthoquinones (22,
25). By following the azomethine ylides approach, we
prepared,29 simultaneously with Iyoda et al.,30 pyrroli-
dino[3′,4′:1,2][60]fullerene derivative 22 bearing a p-
benzoquinone addend. The synthetic procedure is de-
picted in Scheme 2.
1
Compounds 22 and 25 show in the H NMR spectra
typical signals for the pyrrolidine ring as two doublets
at δ 4.34 (J ) 9.3 Hz) and 4.96 (J ) 9.3 Hz), and a singlet
at δ 5.32 for 22 and two doublets at δ 4.37 (J ) 9.6 Hz)
and 5.06 (J ) 9.6 Hz) and a singlet at δ 5.13 for 25. The
13C NMR spectrum of 25 reveals the presence of 59
signals which indicates a lack of symmetry in the
molecule.
(28) Aumu¨ller, A.; Hu¨nig, S. Angew. Chem., Int. Ed. Engl. 1984,
23, 47.
(29) Illescas, B.; Mart´ın, N.; Sa´nchez, L.; Pe´rez, I.; Herranz, M. A.;
Gonza´lez, S.; Ort´ı, E.; Viruela, P. M.; Viruela, R. In Recent Advances
in the Chemistry and Physics of Fullerene and Related Materials;
Kadish, K. M., Ruoff, R. S., Eds.; The Electrochemical Society: NJ ,
1998; Vol. 6, p 1127.
Novel isoxazolo[4′,5′:1,2][60]fullerenes (17, 19) have
been prepared by 1,3-dipolar cycloaddition of the in situ
(30) Iyoda, M.; Sultana, F.; Kato, A.; Yoshida, M.; Kuwatani, Y.;
Komatsu, M.; Nagase, S. Chem. Lett 1997, 63.
(31) Antonini, I.; Lin, T.-S.; Cosby, L. A.; Dai, Y.-R.; Sartorelli, A.
C. J . Med. Chem. 1982, 25, 730.

[60]Fullerene Adducts
J . Org. Chem., Vol. 65, No. 19, 2000 5989
Sch em e 2
Sch em e 3
generated nitrile oxides to C60. Thus, the precursor
oximes 16 and 18 were obtained from the respective
aldehydes 10 and 11 by reaction with hydroxilamine
hydrochloride. Further chlorination of 16 and 18 with
N-chlorosuccinimide (NCS) and subsequent dehydrochlo-
rination of the formed hydroximoyl chlorides yield the
respective nitrile oxides which undergo a [3+2] cycload-
dition reaction with C60 to afford compounds 17 and 19
in 19% and 16% yield, respectively. It is worth mention-
ing that compound 19 was obtained together with the
compounds resulting from the partial and total hydrolysis
of the dicyanomethylene groups. Thus, in addition to 19,
compound 17 was obtained from the reaction mixture in
11% yield as well as the monocondensated compounds
(20) resulting from the hydrolysis of only one dicyano-
methylene group, which was obtained as a mixture of
constitutional isomers in a very low yield (4%).
reveal a Cs symmetry which confirms a [6,6] ring junction
of the organic addend to the C60 core (see Experimental
Section).
In addition to isoxazolofullerenes (17, 19), we have also
carried out the synthesis of the novel 3′[2(p-benzo-
quinonyl)]isoxazolo[4′,5′:1,2][60]fullerene (33) which re-
quires a multistep synthetic procedure (Scheme 3). A first
approach was followed from 2,5-dimethoxybenzaldehyde
(26) by transformation into the respective oxime (27)
which reacted with NCS and C60 in the presence of
pyridine and triethylamine to afford 3′[2(1,4-dimethoxy-
phenyl)]isoxazolo[4′,5′:1,2][60]fullerene (28) in 32% yield.
Further reaction of 28 with boron tribromide in chloro-
form should yield the expected hydroquinone derivative
according to previously related examples.32 However,
reaction of 28 with BBr3 afforded 29 as the only product.
Therefore, we followed an alternative synthetic route by
preparing the formylhydroquinone (30) in the first syn-
thetic step, followed by transformation into the oxime (31)
and subsequent reaction with NCS and C60 leading to
The isoxazolofullerenes prepared (17, 19) were ther-
mally stable brown solids, which is in agreement with
the thermal gravimetric analysis previously reported for
related structures.23a The spectroscopic data are in accord
with the proposed structures. Thus, the 13C NMR spectra
(32) Illescas, B.; Mart´ın, N.; Seoane, C.; Ort´ı, E.; Viruela, P. M.;
Viruela, R.; de la Hoz, A. J . Org. Chem., 1997, 62, 7585.

5990 J . Org. Chem., Vol. 65, No. 19, 2000
Illescas and Mart´ın
32 in low yield (8%) (Scheme 3). Hydroquinone 32 was
further oxidized by reaction with dichlorodicyano-p-
benzoquinone (DDQ) to afford 33 in good yield (88%).
All of the organofullerenes synthesized showed the
presence of a weak absorption band at around 426 nm
in the UV-vis spectra which is a typical feature of most
1,2-dihydrofullerenes.
Electr och em istr y. The compounds reported in this
work are composed of two electroactive moieties (C60 and
quinones, TCNQ or DCNQI derivatives). Therefore, we
have studied their electrochemical properties by cyclic
voltammetric (CV) measurements in solution at room
temperature, using tetrabutylammonium perchlorate as
supporting electrolyte and a glassy carbon as reference
electrode (see Experimental Section).
(DFT) calculations that in Diels-Alder cycloadducts the
LUMO of the p-benzoquinone ring lies slightly below, in
energy, than the LUMO of the C60 unit,32 thus confirming
the CV findings (Table 1).
Compounds bearing the TCAQ fragment show the
presence of only one reduction wave involving two
electrons for the organic addend moiety.34 This behavior
is in agreement with that expected for other tetracyano-
p-quinodemethane (TCNQ) derivatives,35 and it has been
previously rationalized by using theoretical calculations
at semiempirical and ab initio levels.36 In contrast,
organofullerene bearing the DCNQI fragment (14) ex-
hibits two reduction potentials for the organic addend,
similarly to the above quinones. The strong electron
acceptor character of the cyanoimino moieties, similar to
the dicyanomethylene group, is responsible for the po-
tential values found for this compound.21,35
The CV data of the prepared compounds are collected
in Table 1 along with C60 and p-benzoquinone, 6-meth-
ylnaphthoquinone, and TCAQ for comparison purposes.
Both the C60 cage and the organic addend in these
systems are expected to behave as excellent electron
acceptors in which, depending upon the nature of the
organic addend, it is possible to address the attachment
of the first electron in the reduction process either to the
C60 cage or to the organic addend.
All of the pyrrolidino[3′4′:1,2][60]fullerenes (12, 13, 14,
22, 25) and the isoxazolo[4′,5′:1,2][60]fullerenes (17, 19,
33) show three or four quasireversible reduction waves
for the fullerene moiety, similarly to that found for the
parent C60. In addition, another quasireversible reduction
wave(s) is observed corresponding to the reduction of the
electroactive organic addend. Interestingly, a remarkable
difference is found between the reduction potentials
corresponding to the fullerene moiety in pyrrolidino-
fullerenes and isoxazolofullerenes. Thus, pyrrolidino-
fullerenes show reduction waves shifted to more negative
potentials than the parent C60 due to the saturation of a
double bond in the C60 cage which raises the LUMO
energy.33 This cathodic shift is the standard behavior
found in most of 1,2-dihydrofullerenes.3 In contrast,
isoxazolofullerenes exhibit reduction potentials which are
anodically shifted (70-110 mV) in comparison with the
parent C60, which indicates that they are stronger
electron acceptors than C60. This finding can be accounted
for by the presence of the oxygen atom directly linked to
the C60 cage as well as by the electronic effect of the
electron accepting organic addend covalently attached to
the isoxazole ring.
The organic addends present in the studied organo-
fullerenes show the presence of two quasireversible
reduction waves for the quinone moiety, which appear
remarkably shifted to more positive values than the
respective unsubstituted quinones (Table 1). The ob-
served shifts are stronger in the isoxazolofullerenes,
which confirms the higher electron affinity of these
systems related to the analogous pyrrolidinofullerenes.
As shown in Table 1, substitution on the p-benzo-
quinone ring has a striking influence on the redox
behavior. The presence of one (25) or two (12, 17) benzene
rings fused to the p-benzoquinone moiety cathodically
shifts the first reduction potential of the organic addend
and, in a lesser extent, of the C60 core. It is worth
mentioning that the first reduction wave of the naph-
thoquinone moiety in 25 appears together with the first
reduction wave on the C60 core giving rise to a broad
reduction wave involving two electrons.
Th eor etica l Ca lcu la tion s. The molecular geometries
or pyrrolidinofullerenes 25 and 13 were determined by
theoretical calculations at the semiempirical PM3 level.37
Depending upon the orientation of the oxygen atoms, two
rotational isomers are possible for 25 (Figure 1). A
difference of only 0.7 kcal/mol was found between them,
which suggests that both isomers are present in solution,
thus supporting the broad signals found for the aromatic
1
protons in the H NMR spectrum at room temperature.
These signals are well defined when the 1H NMR
spectrum was recorded at 60 °C, which indicates the
presence of an equilibrium between both isomers that is
accelerated at high temperature.
The bond length predicted between C1 and C2 (1.588
Å) is similar to that found by X-ray analysis for other
pentagonal fused rings to C60 such as triazolino[4′,5′:1,2]-
[60]fullerenes (1.574 Å)38 and isoxazolo[4′,5′:1,2][60]-
fullerenes (1.576 Å),22c being shorter than that found for
methanofullerenes,39 benzocyclobutene structures (1.645
Å),40 or Diels-Alder cycloadducts (1.62 Å).41
Organofullerene 13 presents a geometry in which the
TCAQ fragment is severely distorted from planarity due
to the strong steric interactions between the cyano groups
and the CH units in adjacent peri positions. To avoid
(34) The single-wave reduction involving two electrons for the parent
TCAQ has been previously confirmed by coulometric analysis. See:
Kini, A. M.; Cowan, D. O.; Gerson, F.; Mo¨ckel, R. J . Am. Chem. Soc.
1985, 107, 556.
(35) (a) Mart´ın, N.; Behnish, R.; Hanack, M. J . Org. Chem. 1989,
54, 2563. (b) For a recent review on TCNQ and DCNQI derivatives,
see: Mart´ın, N.; Segura, J . L.; Seoane, C. J . Mater. Chem. 1997, 7,
1661.
(36) (a) Viruela, R.; Viruela, P. M.; Ort´ı, E.; Mart´ın, N. Synth. Met.
1995, 70, 1031. (b) Ort´ı, E.; Viruela, R.; Viruela, P. M. J . Mater. Chem.
1995, 5, 1697.
(37) Stewart, J . J . P. J . Comput. Chem. 1989, 10, 209; 1989, 10,
221. The calculations were carried out using the Hyperchem 5.1
program.
(38) Nuber, B.; Hampel, F.; Hirsch, A. Chem. Commun. 1996,
1799.
(39) Djojo, F.; Herzog, A.; Lamparth, I.; Hampel, F.; Hirsch, A. Chem.
Eur. J . 1996, 2, 1537 and references therein.
(40) Ishida, T.; Shinozuka, K.; Nogami, T.; Sasaki, S.; Iyoda, M.
Chem. Lett. 1995, 317.
The first reduction potential of the p-benzoquinone
moiety appears very close to that of the C60 unit. We have
previously reported by using density functional theory
(33) Suzuki, T.; Maruyama, Y.; Akasaka, T.; Ando, W.; Kobayashi,
K.; Nagase, S. J . Am. Chem. Soc. 1994, 116, 1359.
(41) Khan, S. I.; Oliver, A. M.; Paddon-Row, M. N.; Rubin, Y. J . Am.
Chem. Soc. 1993, 115, 4919.

[60]Fullerene Adducts
J . Org. Chem., Vol. 65, No. 19, 2000 5991
Ta ble 1. Red ox P oten tia ls of Novel Or ga n ofu ller en esa
V vs SCE; GCE as working electrode; 0.1 mmol/dm3 NBu4+ClO4-; Toluene/MeCN (5:1); 200 mV/s. *Halfwave potential.
a
these interactions the TCNQ central ring and the dicya-
nomethylene units are folded in opposite directions. The
TCAQ moiety therefore adopts a butterfly-type structure,
similar to that observed for the parent TCAQ from X-ray
data,42 and theoretical calculations,43 in which the lateral
aromatic rings preserve their planarity, with the central
ring in a boat conformation.
The presence of the fulleropyrrolidine fragment co-
valently attached to the TCAQ moiety gives rise to two
possible isomers depending upon the orientation of the
(42) Schubert, U.; Hu¨nig, S.; Aumu¨ller, A. Liebigs Ann. Chem. 1985,
1216.
(43) Ort´ı, E.; Viruela, R.; Viruela, P. M. J . Phys. Chem. 1996, 15,
6138.

5992 J . Org. Chem., Vol. 65, No. 19, 2000
Illescas and Mart´ın
moiety. In addition, the striking electron acceptor be-
havior of the organic substituents makes these systems
truly electron sponges that are able to accept up to eight
electrons in solution.
This remarkable electron acceptor character of the
systems now reported is of interest for further applica-
tions in the preparation of optoelectronic devices. Work
is in progress directed to the preparation of blends with
conjugated semiconducting polymers in the search of
photovoltaic applications.
Exp er im en ta l Section
Gen er a l Deta ils. Mass spectra were recorded operat-
ing at 30 kV by using a bombardment of Cs+ ions and
2-NPOE or 3-NBA as matrix. Cyclic voltammetry mea-
surements were performed using a glassy carbon elec-
trode as indicator electrode in voltammetric studies (1
× 10-5 M solutions of the compound in toluene/acetoni-
trile 5:1, 0.1 M Bu4NClO4 as the supporting electrolyte,
platinum working as counter electrode, SCE as reference
electrode at 20 °C). All chromatography was performed
using Merck silica gel (70-230 mesh). All reagents were
used as purchased unless otherwise stated. All solvents
were dried according to standard procedures. Calcula-
tions were performed using the semiempirical PM3
method.
F or m yl Der iva tives 11, 24. General Procedure. To a
solution of the corresponding hydroxymethyl derivative
(1 equiv) in methylene dichloride, piridinium chlorochro-
mate (1.5 equiv) was added. After 12 h with stirring, the
solvent was removed under reduced pressure and the
solid residue was purified by column chromatography
over silica gel using hexane/ethyl acetate 3:1 as eluent.
6-F or m yl-1,4-n a p h th oqu in on e (24). 99% yield; mp
153 °C (dec); IR (KBr) ν/cm-1 1700, 1675, 1605, 1315,
1195, 1155, 1055, 845; 1H NMR (300 MHz, Acetone-d6) δ
7.09 (s, 2H), 8.27 (m, 2H), 8.60 (m, 1H), 10.20 (s, 1H);
MS m/z (%) 186 (M+, 100), 157 (44), 129 (23), 103 (46),
75 (93), 63 (12), 51 (40). Anal. Calcd for C11H6O3: C,
70.96; H, 3.23. Found: C, 70.66; H, 3.65.
F igu r e 1. Favored geometries calculated by semiempirical
PM3 method for compounds 25 and 13.
two dicyanomethylene units (up and down). Theoretical
calculations predict that conformation B, with the dicya-
nomethylene unit pointing upward, is 2.1 kcal/mol more
stable than A (Figure 1).
In agreement with the above data, the distance pre-
dicted for the C1-C2 bond (1.584 Å) resulted to be similar
to that found for other organofullerenes endowed with a
fused pentagonal ring.22c,38
Su m m a r y a n d Con clu sion s
2-F o r m y l-9,10-b is (d ic y a n o m e t h y le n e )a n t h r a -
cen e (11). 72% yield; mp 273 °C (dec); IR (KBr) ν/cm-1
2240, 1705, 1565, 1280, 1225, 835, 775, 700; 1H NMR (300
MHz, CDCl3) δ 7.80 (m, 2H), 8.24 (dd, 1H, J ) 8.1 and
1.5 Hz), 8.28 (m, 2H), 8.43 (d, 1H, J ) 8.1 Hz), 8.73 (d,
1H, J ) 1.5 Hz), 10.17 (s, 1H); 13C NMR (75 MHz, CDCl3)
δ 112.6, 127.7, 127.8, 127.9, 128.3, 128.5, 129.7, 130.0,
131.2, 132.3, 132.9, 132.9, 134.7, 138.1, 158.9, 189.1.
Anal. Calcd for C21H10N4O: C, 75.90; H, 2.41; N, 16.87.
Found: C, 75.87; H, 2.47; N, 16.61.
N-Meth yl-2′[6(1,4-n a p h th oqu in on yl)]p yr r olid in o-
[3′,4′:1,2][60]fu ller en e (25). To a solution of C60 (100
mg, 0.14 mmol) in 40 mL of toluene, 6-formyl-1,4-
naphthoquinone 24 (26 mg, 0.14 mmol) and N-methyl-
glycine (62 mg, 0.69 mmol) were added. After refluxing
for 18 h, the solvent was removed under reduced pressure
and the solid residue obtained was purified by column
chromatography over silica gel, using cyclohexane/toluene
to elute the nonreacted C60 and toluene/ethyl acetate to
elute the monoadduct. Further purification was ac-
complished by washing the solid three times with hexane/
methanol. 22% yield (42% based on consumed C60); FTIR
(KBr) ν/cm-1 1667, 1601, 1300, 1044, 842, 526; 1H NMR
(300 MHz, CDCl3, 60 °C) δ 2.84 (s, 3H), 4.36 (d, 1H, J )
9.6 Hz), 5.06 (d, 1H, J ) 9.6 Hz), 5.13 (s, 1H), 6.98 (s,
2H), 8.18 (d, 1H, J ) 8.4 Hz), 8.31 (broad d, 1H), 8.53 (s,
We have described the synthesis of novel organo-
fullerenes in which the C60 core is covalently attached to
strong electron acceptor moieties such as quinones and
TCNQ and DCNQI derivatives. The synthesis has been
carried out by formation of the respective formyl-
substituted electron acceptors and subsequent 1,3-dipolar
cycloaddition of the in situ generated azomethyne ylides
and nitrile oxides, respectively, to C60.
The molecular geometry of compounds 25 and 13 was
calculated from semiempirical PM3 calculations and
reveals the presence of two favorable isomers and a
highly distorted electron acceptor moiety with a butterfly-
type structure for 13, in full agreement with previously
reported data for the parent acceptor molecule by X-ray
diffraction and theoretical calculations.
Pyrrolidino[3′,4′:1,2][60]fullerenes (12, 13, 14, 22, 25)
exhibit reduction potential values for the C60 moiety
which are cathodically shifted related to the parent C60
(40-100 mV). In contrast, isoxazolo[4′,5′:1,2][60]fullerenes
(17, 19, 33) present a remarkable anodic shift in com-
parison with the parent C60 (70-110 mV). These findings
clearly indicate that these systems are stronger electron
acceptors than C60, which has been accounted for by the
electronic effects of both oxygen atom and electron
accepting organic addends covalently linked to the C60

[60]Fullerene Adducts
J . Org. Chem., Vol. 65, No. 19, 2000 5993
1H);13C NMR (75 MHz, CDCl3/CS2) δ 40.10, 68.98, 69.89,
82.69, 82.89, 126.96, 127.32, 131.78, 131.93, 134.24,
134.43, 135.55, 136.05, 136.29, 137.24, 138.12, 139.00,
139.43, 140.05, 140.18, 140.21, 141.54, 141.64, 141.75,
141.82, 141.94, 141.98 (2C), 142.07, 142.11, 142.16 (2C),
142.47, 142.55 (2C), 142.66, 142.97, 143.08, 144.02 (2C),
144.24, 144.35, 144.39, 144.65, 145.13 (2C), 145.22 (2C),
145.31 (2C), 145.42, 145.51, 145.61 (2C), 145.89 (2C),
146.00, 146.07 (2C), 146.17 (2C), 146.24 (2C), 147.23,
147.27, 151.71, 152.36, 153.42, 155.64, 184.46, 184.66;
MS m/z (%) 934 (M+, 26), 720 (C60, 100); UV-vis (CHCl3)
of TiCl4 (0.14 mmol, 0.14 mL of a 1 M solution in CH2-
Cl2) and BTC (1.4 mL, 6.6 mmol) were added after 24
and 48 h. After 5 days, the solvent was removed under
reduced pressure and the brown solid obtained was
chromatographed on a silica gel column, using cyclohex-
ane/chloroform 1:1 as eluent. The monocondensated
product was eluted in first place (15, 6.2 mg) followed by
the dicondensated one (14, 5.6 mg).
N-Meth yl-2′[2(9,10-d icya n im in oa n th r a cen yl)]p yr -
r olid in o[3′,4′:1,2][60]fu ller en e (14). 4% yield; FTIR
1
(KBr) ν/cm-1 2169, 1465, 1334, 1225, 789, 766, 527; H
λ
max/nm 250, 268, 304, 316, 422, 690.
NMR (300 MHz, CDCl3) δ 2.86 (s, 3H), 4.36 (d, 1H, J )
9.6 Hz), 5.07 (d, 1H, J ) 9.6 Hz), 5.17 (s, 1H), 7.53 (dd,
2H, J ) 5.7 y 3.3 Hz), 7.71 (dd, 2H, J ) 5.7 and 3.3 Hz),
7.90 (broad m, 2H), 8.42 (broad m, 1H); MS m/z (%) 1031
(M+, 28), 720 (C60, 100); UV-vis (CHCl3) λmax/nm 258,
298, 358, 430, 698.
N-Meth yl-2′[2(9-cya n im in o-10-oxoa n th r a cen yl)]-
p yr r olid in o[3′,4′:1,2][60]-fu ller en e a n d N-Meth yl-2′-
[2(10-cyan im in o-9-oxoan th r acen yl)]pyr r olidin o-[3′,4′:
1,2][60]fu ller en e (15). 5% yield (isomeric mixture);
FTIR (KBr) ν/cm-1 2162, 1674, 1646, 1558, 1329, 1008,
804, 791, 527; 1H NMR (300 MHz, CDCl3) δ 2.84 (s), 2.87
(s), 4.35 (d), 4.38 (d), 5.05 (d), 5.08 (d), 5.17 (s), 5.18 (s),
7.54 (dd, J ) 6.0 and 3.3 Hz), 7.72 (dd, J ) 6.0 and 3.3
Hz), 7.86 (broad m), 8.43 (broad m); MS m/z (%) 1008
(M++1, 19), 720 (C60, 100); UV-vis (CHCl3) λmax/nm 254,
298, 358, 428, 698.
Syn th esis of Oxim es. General Procedure. To a solu-
tion of the corresponding aldehyde (1 eq) in ethanol at
70 °C, a solution of hydroxylamine hydrochloride in water
(2.5 equiv for 27 and 28 equiv for 31, 16, and 18) was
added. The mixture was kept at 70 °C for a variable
period of time and then diluted with 100 mL of water.
The workup procedure was different in any case.
2,5-Dim eth oxyben za ld eh yd e Oxim e (27). Reaction
time: 2 h. The reaction mixture was extracted three
times with chloroform. The organic extracts were dried
over MgSO4 and evaporated to dryness, giving 27 in a
94% yield; mp 103-104 °C; FTIR (KBr) ν/cm-1 3242,
2908, 1655, 1578, 1504, 1460, 1279, 1234, 1040, 972, 743;
1H NMR (300 MHz, CDCl3) δ 3.80 (s, 3H), 3.83 (s, 3H),
6.86 (d, 1H, J ) 9.2 Hz), 6.93 (dd, 1H, J ) 9.2 and 3.1
Hz), 7.26 (d, 1H, J ) 3.1 Hz), 8.26 (broad s, 1H), 8.48 (s,
1H); 13C NMR (300 MHz, DMSO-d6) δ 55.42, 56.28,
109.74, 113.30, 116.44, 121.61, 143.39, 151.31, 153.16;
MS m/z (%) 181 (M+, 81), 149 (100), 121 (39).
2,5-Dih yd r oxyben za ld eh yd e Oxim e (31). Reaction
time: 1 h 30 min. After extracting the mixture three
times with chloroform, the organic extracts were dried
over MgSO4 and evaporated to dryness, obtaining a solid
residue that was purified by column chromatography over
silica gel using hexane/ethyl acetate as eluent. 76% yield;
mp 129-131 °C; FTIR (KBr) ν/cm-1 3277, 2924, 1638,
1506, 1360, 1283, 1260, 1005, 961, 822, 785, 677; 1H NMR
(300 MHz, CDCl3) δ 6.64 (dd, 1H, J ) 8.8 and 2.9 Hz),
6.69 (d, 1H, J ) 8.8 Hz), 6.88 (d, 1H, J ) 2.9 Hz), 8.22 (s,
1H), 8.93 (s, 1H), 9.38 (s, 1H), 11.24 (s, 1H); 13C NMR
(75 MHz, DMSO-d6) δ 112.9, 116.9, 117.9, 118.6, 147.2,
148.8, 149.9; MS m/z (%) 153 (M+, 100), 135 (77), 107
(37).
N-Meth yl-2′[2(9,10-bis(d icya n om eth ylen e)a n th r a -
cen yl)]pyr r olidin o[3′,4′:1,2]-[60]fu ller en e (13). Method
A. To a solution of N-methyl-2′[2(9,10-anthraquinonyl)]-
pyrrolidino-[3′,4′:1,2][60]fullerene 12 (53 mg, 0.054 mmol)
and malononitrile (9 mg, 0.14 mmol) in 50 mL of dry
methylene dichloride at room temperature and under
argon atmosphere, titanium tetrachloride (0.14 mmol,
0.14 mL of a 1 M solution in CH2Cl2) and dry pyridine
(0.022 mL, 0.27 mmol) were added dropwise with a
syringe. The reaction was monitored by tlc, and new
portions of malononitrile (90 mg, 1.4 mmol), TiCl4 (1.4
mmol, 1.4 mL of a 1 M solution in CH2Cl2), and dry
pyridine (0.22 mL, 2.7 mmol) were added every 24 or 48
h. After 13 days, no evolution is observed (final sto-
ichoimetry relation 12/malononitrile/TiCl4/py 1:95:95:
190). The solvent was removed under reduced pressure,
and the obtained residue was chromatographed over
silica gel using toluene/chloroform as eluent. Further
purification was accomplished by washing the solid three
times with hexane/methanol. 19% yield.
Method B. A solution of 2-formyl-9,10-bis(dicyano-
methylene)anthracene 11 (50 mg, 0.15 mmol), C60 (108
mg, 0.15 mmol), and N-methylglycine (67 mg, 0.76 mmol)
in 70 mL of toluene was refluxed for 24 h. The solid
obtained by evaporation to dryness was purified on a
silica gel column using toluene/chloroform as eluent.
Further purification was accomplished by washing the
solid three times with hexane/methanol. 20% yield (40%
based on consumed C60); FTIR (KBr) ν/cm-1 2224, 1553,
1463, 1261, 1031, 803, 767, 527; 1H NMR (300 MHz,
CDCl3) δ 2.88 (s, 3H), 4.33 (d, 1H, J ) 9.6 Hz), 5.06 (d,
1H, J ) 9.6 Hz), 5.12 (s, 1H), 7.77 (dd, 2H, J ) 5.7 and
3.3 Hz), 8.29 (m, 4H), 8.78 (broad m, 1H);13C NMR (75
MHz, CDCl3) δ 40.28, 69.17, 70.00, 77.25, 83.27, 112.94,
112.95, 112.98, 113.05, 127.77 (2C), 127.82 (2C), 130.12,
130.14, 132.60 (2C), 132.65 (2C), 133.27, 133.33, 136.07,
136.34, 140.36, 140.42, 141.19, 141.60, 141.65, 141.82,
142.04, 142.14, 142.21, 142.23, 142.27, 142.30, 142.60
(2C), 142.68, 142.70 (2C), 142.82, 143.12, 143.20, 143.43,
144.29, 144.52, 144.57, 145.17 (2C), 145.30, 145.39,
145.45, 145.50, 145.55, 145.63, 145.66, 145.70, 145.97,
146.03 (2C), 146.05, 146.19, 146.22 (2C), 146.24, 146.29,
146.31, 146.34, 146.40, 147.26, 147.37, 147.53, 152.21,
153.45, 155.67, 159.61; MS m/z (%) 1079 (M+, 17), 720
(C60, 100); UV-vis (CHCl3) λmax/nm 258, 286, 314, 430,
698.
Rea ction of N-Meth yl-2′[2(9,10-a n th r a qu in on yl)]-
p yr r olid in o[3′,4′:1,2][60]-fu ller en e (12) w ith BTC. To
a solution of 12 (130 mg, 0.13 mmol) in 50 mL of dry
chloroform under argon atmosphere, titanium tetrachlo-
ride (0.14 mmol, 0.14 mL of a 1 M solution in CH2Cl2)
followed by bis(trimethylsilyl)carbodiimide (BTC) (1.4
mL, 6.6 mmol) were added dropwise with a syringe. The
mixture was refluxed and monitored by tlc. New portions
9,10-An th r a qu in on e-2-ca r ba ld oxim e (16). Reaction
time: 1 h. The product precipitated in the medium and
it was filtrated and washed with ethanol. 97% yield; mp
241-243 °C (dec); FTIR (KBr) ν/cm-1 3381, 1668, 1587,
1340, 1286, 982, 723, 710, 638; 1H NMR (300 MHz,

5994 J . Org. Chem., Vol. 65, No. 19, 2000
Illescas and Mart´ın
DMSO-d6) δ 7.93 (m, 2H), 8.10 (dd, 1H, J ) 8.1 and 1.5
Hz), 8.20 (m, 3H), 8.38 (m, 2H), 11.86 (s, 1H); 13C NMR
(75 MHz, DMSO-d6) δ 124.47, 126.74, 126.77, 127.40,
131.36, 132.91, 132.97, 133.04, 133.39, 134.51, 134.62,
138.75, 147.17, 181.96, 182.21; MS m/z (%) 251 (M+, 61),
233 (100), 205 (86), 177 (74).
8.44 (d, 1H, J ) 8.3 Hz), 8.66 (dd, 1H, J 8.3 and 1.7 Hz),
9.14 (d, 1H, J ) 1.7 Hz); 13C NMR (75 MHz, CDCl3/CS2
1/1) δ 77.21, 98.36, 112.13, 112.36, 112.41, 112.44, 127.02,
127.50, 127.58, 128.00, 129.79, 130.00, 131.02, 131.05,
131.33, 131.75, 132.38, 132.42 (2C), 133.51, 135.34,
136.52, 136.55, 137.35, 140.23, 140.62, 141.66, 141.78,
142.12, 142.32, 142.76, 142.79, 142.86, 143.10, 143.31,
143.87, 144.23, 144.33, 145.01, 145.07, 145.12, 145.16,
145.71, 145.86, 145.89, 146.14, 146.18, 146.30, 147.16,
151.43, 158.27, 158.48; MS m/z (%) 1066 (M++1, 45) 1070
(M++3, 100); UV-vis (CHCl3) λmax/nm 256, 276, 318, 426,
684.
2-F o r m y l-9,10-b is (d ic y a n o m e t h y le n e )a n t h r a -
qu in on e Oxim e (18). Reaction time: 30 min. After
extracting the reaction mixture three times with chloro-
form, the organic extracts were dried over MgSO4 and
evaporated to dryness, giving rise to a solid residue that
was purified by column chromatography over silica gel
using hexane/ethyl acetate 3:1 as eluent. 52% yield; mp
208-210 °C (dec); FTIR (KBr) ν/cm-1 3392, 2923, 2226,
1670, 1587, 1560, 1285, 980, 941, 775, 710, 608; 1H NMR
(300 MHz, DMSO-d6) δ 7.87 (m, 2H), 8.01 (dd, 1H, J )
8.2 and 1.7 Hz), 8.34 (m, 4H), 8.59 (d, 1H, J ) 1.4 Hz),
11.16 (s, 1H); 13C NMR (75 MHz, DMSO-d6) δ 115.10,
115.20, 115.28, 126.20, 129.12, 129.18, 129.68, 131.50,
132.19, 132.25, 132.32, 132.84, 133.72, 133.78, 138.55,
148.36, 161.53, 161.77; MS m/z (%) 347 (M+, 6), 329 (41),
304 (100).
Rea ction of Oxim es w ith C60. General Procedure. To
a solution of N-chlorosuccinimide (NCS, 50 mg, 0.2 mmol)
and dry pyridine (0.1 mL) in 5 mL of dry chloroform, the
corresponding oxime (0.2 mmol) was added in one portion
at 25 °C. The chlorination was usually over in ca. 10 min.
A solution of C60 (180 mg, 0.25 mmol) in 15 mL of ODCB
was added, and the temperature raised to 40-50 °C.
Triethylamine (21 mg, 0.21 mmol) in 3 mL of dry CHCl3
was added dropwise. After a variable period of time at
the same temperature, the solvent was removed under
reduced pressure and the solid residue thus obtained was
purified by column chromatography over silica gel using
a different eluent in any case.
3′[2(9,10-An th r a qu in on yl)]isoxa zolo[4′,5′:1,2][60]-
fu ller en e (17). Reaction time: 16 h. Eluent used in
column chromatography: toluene. 19% yield (90% based
on consumed C60); FTIR (KBr) ν/cm-1 2920, 1673, 1589,
1323, 1278, 1255, 929, 865, 711, 526; 1H NMR (300 MHz,
CDCl3/ CS2 1/1) δ 7.85 (m, 2H), 8.34 (m, 2H), 8.51 (d, 1H,
J ) 8.4 Hz), 8.69 (dd, 1H, J ) 8.4 and 1.8 Hz), 9.23 (d,
1H, J ) 1.8 Hz); 13C NMR (75 MHz, CDCl3/CS2 1/1) δ
77.21, 78.12, 127.09, 127.17, 127.19 (2C), 127.86, 133.13,
133.20, 133.71 (2C), 134.03, 134.06, 134.13, 134.50,
136.51, 137.09, 140.18, 140.31, 141.60, 141.82, 142.07,
142.11, 142.28, 142.68, 142.69, 142.81, 143.67, 143.70,
143.88, 144.20, 144.43, 144.95, 145.08, 145.13, 145.27,
145.61, 145.78, 145.82, 146.09, 146.11, 146.22, 147.08,
147.60, 181.42, 181.51; MS m/z (%) 970 (M++1, 100);
UV-vis (CHCl3) λmax/nm 256, 290, 318, 426, 458, 684.
R ea ct ion of 2-Ca r b a ld oxim e-9,10-b is(d icya n o-
m eth ylen e)a n th r a qu in on e (18) w ith C60. After stir-
ring at 40-50 °C for 22 h, the solid residue was purified
using cyclohexane/toluene 1:1 as eluent, recovering un-
reacted C60, 3′[6(1,4-anthraquinonyl)]isoxazolo[4′,5′:1,2]-
[60]fullerene (17, 11%), 3′[2(9-dicyanomethylene-10-
3′[2(9-Dicyan om eth ylen e-10-oxoan th r acen yl)]isox-
a zolo[4′,5′:1,2][60]fu ller en e a n d 3′[2(10-Dicya n o-
m et h ylen e-9-oxoa n t h r a cen yl)]isoxa zolo[4′,5′:1,2]-
[60]fu ller en e (20). Isomeric mixture; FTIR (KBr) ν/cm-1
2922, 2221, 1732, 1672, 1578, 1455, 1280, 1120, 750, 699,
1
526; H NMR (300 MHz, CDCl3) δ 9.23 (d, J ) 1.7 Hz),
9.20 (d, J ) 1.5 Hz), 8.66 (m), 8.50 (m), 8.34 (m), 7.81
(m); MS m/z (%) 1018 (M++1, 58), 1020 (M++3, 100);
UV-vis (CHCl3) λmax/nm 258, 286, 318, 426, 684.
3′[2(1,4-Ben zoh yd r oqu in on yl)]isoxa zolo[4′,5′:1,2]-
[60]fu ller en e (32). Reaction time: 1 h 30 min. Eluent
used in column chromatography: toluene/ethyl acetate.
8% yield (48% based on consumed C60); FTIR (KBr)
ν/cm-1 3384, 2923, 1703, 1662, 1460, 1203, 1103, 847,
786, 527; 1H NMR (300 MHz, CDCl3) δ 4.80 (broad s, 1H),
6.96 (dd, 1H, J ) 9.2 and 2.9 Hz), 7.16 (d, 1H, J ) 9.2
Hz), 8.10 (d, 1H, J ) 2.9 Hz), 9.81 (s, 1H); MS m/z (%)
872 (M++1, 100); MS m/z (%) 872 (M++1, 100); UV-vis
(CHCl3) λmax/nm 256, 318, 424, 686.
3′[2(1,4-Dim eth oxyp h en yl)]isoxa zolo[4′,5′:1,2][60]-
fu ller en e (28). Reaction time: 2 h. Eluent used in
column chromatography: toluene. 32% yield (71% based
on consumed C60); FTIR (KBr) ν/cm-1 2922, 1628, 1498,
1421, 1268, 1218, 1043, 804, 575, 527; 1H NMR (300
MHz, CDCl3) δ 3.77 (s, 3H), 3.84 (s, 3H), 6.97 (d, 1H, J )
9.0 Hz), 7.04 (dd, 1H, J ) 9.0 and 2.9 Hz), 7.22 (d, 1H, J
) 2.9 Hz); MS m/z (%) 900 (M++1, 100); UV-vis (CHCl3)
λ
max/nm 258, 318, 426, 488, 682.
3′[2(1-Hyd r oxy-4-m eth oxyp h en yl)]isoxa zolo[4′,5′:
1,2][60]fu ller en e (29). To a solution of compound 28 (55
mg, 0.076 mmol) in dry chloroform, BBr3 (0.38 mmol, 0.38
mL of a 1 M solution in CH2Cl2) was added dropwise
under argon at room temperature. After 2 h 30 min with
stirring, the mixture was washed three times with water,
the organic layer was dried over MgSO4, and the solvent
removed under reduced pressure. The solid residue thus
obtained was purified by column chromatography over
silica gel using toluene as eluent obtaining 29 with
quantitative yield; FTIR (KBr) ν/cm-1 3444, 2920, 1489,
1459, 1379, 1285, 1261, 1223, 1097, 1035, 802, 564, 526;
1H NMR (300 MHz, CDCl3) δ 3.61 (s, 3H), 7.04 (dd, 1H,
J ) 9.0 and 2.9 Hz), 7.21 (d, 1H, J ) 9.0 Hz), 8.20 (d,
1H, J ) 2.9 Hz), 9.85 (s, 1H); 13C NMR (75 MHz, CDCl3/
CS2 1/1) δ 55.39, 78.32, 98.45, 102.91, 112.16, 112.33,
113.63, 118.63, 118.67, 118.91, 136.60, 137.29, 139.76,
140.36, 141.45, 141.78, 142.23, 142.27, 142.42, 142.46,
142.86, 142.96, 143.98, 144.33, 144.42, 144.51, 145.09,
145.20, 145.27, 145.52, 145.72, 145.92, 145.96, 146.19,
146.28, 146.40, 147.27, 147.71, 152.21, 152.37, 152.50;
MS m/z (%) 886 (M++1, 100); UV-vis (CHCl3) λmax/nm
254, 282, 320, 426, 458, 678.
oxoanthracenyl)]isoxazolo[4′,5′:1,2][60]fullerene
and
3′[2(10-dicyanomethylene-9-oxoanthracenyl)]isoxazolo-
[4′,5′:1,2][60]fullerene as isomers mixture (20, 4%) and
3′[2(9,10-bis(dicyanomethylene)anthracenyl)]isoxazolo-
[4′,5′:1,2][60]fullerene (19, 16%).
3′[2(9,10-b is(Dicya n om et h ylen e)a n t h r a cen yl)]-
isoxazolo[4′,5′:1,2][60]fu ller en e (19). FTIR (KBr) ν/cm-1
2923, 2226, 1718, 1676, 1559, 1277, 860, 770, 694, 527;
1H NMR (300 MHz, CDCl3) δ 7.79 (m, 2H), 8.29 (m, 2H),
3′[2(1,4-Ben zoq u in on yl)]isoxa zolo[4′,5′:1,2][60]-
fu ller en e (33). A solution of 32 (44 mg, 0.051 mmol) and
DDQ (32 mg, 0.14 mmol) in 50 mL of dry chloroform was

[60]Fullerene Adducts
J . Org. Chem., Vol. 65, No. 19, 2000 5995
stirred at room temperature for 4 h 30 min. The solvent
was removed under reduced pressure, and the solid
residue thus obtained was chromatographed over silica
gel using toluene as eluent. 88% yield; FTIR (KBr) ν/cm-1
Ack n ow led gm en t. We are indebted to DGES of
Spain (Project PB98-0818) for financial support.
Su p p or tin g In for m a tion Ava ila ble: Cyclic voltammo-
grams for compounds 13, 19, and 25. This material is available
free of charge via the Internet at http://pubs.acs.org.
1
2921, 1659, 1384, 1280, 751, 526; H NMR (300 MHz,
CDCl3) δ 6.96 (dd, 1H, J ) 10.3 and 2.6 Hz), 7.02 (d, 1H,
J ) 10.3 Hz), 7.42 (d, 1H, J ) 2.6 Hz); MS m/z (%) 870
(M++1, 100); UV-vis (CHCl3) λmax/nm 256, 318, 424, 684.
J O0003753