C602- chemistry: C60 adducts bearing two ester, carbonyl, or alcohol groups

Article abstract of DOI:10.1021/ol034545k

(Matrix presented) Reactions of activated halo compounds XCH₂-A (X = Br, I; A = ester, ketone) with C₆₀^2- anion give rise to C₆₀(CH₂-A)₂ adducts (major products) along with unexpected metha

Full text of DOI:10.1021/ol034545k

ORGANIC
LETTERS
2-
2003
Vol. 5, No. 13
2239-2242
C60 Chemistry: C60 Adducts Bearing
Two Ester, Carbonyl, or Alcohol Groups
Emmanuel Allard,* Jacques Delaunay, and Jack Cousseau*
Laboratoire d’Inge´nierie Mole´culaire et Mate´riaux organiques, UMR CNRS 6501,
UniVersite´ d’Angers, 2 Bd LaVoisier, F-49045 Angers Cedex 01, France
jack.cousseau@uniV-angers.fr
Received March 28, 2003
ABSTRACT
2-
Reactions of activated halo compounds XCH -A (X ) Br, I; A ) ester, ketone) with C60 anion give rise to C60(CH -A)2 adducts (major
2
2
products) along with unexpected methanofullerenes C60>CH-A and monosubstituted dihydrofullerenes C60(H)(CH -A) (minor products).
2
Methanofullerenes are shown to come from side reactions with X CH-A traces.
2
Due to their outstanding physical and chemical properties,
C60 fullerene derivatives have proven to be attractive
compounds in various fields such as photovolta¨ıcs,1 nonlinear
optics,2 artificial photosynthesis,3 organic materials,4 and
biology and medicine.5 Thus, a large development of the
covalent functionalization of C60 was observed in recent
years. The chemical reactivity of C60 is typical of an electron-
deficient olefin,6 and most organo-derivatives of C60 are
obtained through two main methods: [4 + 2] Diels Alder7
and [3 + 2]8 cycloaddition methodology and nucleophilic
additions as exemplified by the Bingel cyclopropanation
reaction.9
Alternatively, the functionalization of the C sphere can
also be achieved by the reaction of C60 anion with
2-
electrophilic reagents. Recently, we have shown that this
anion can be easily and selectively obtained via a chemical
reduction of C60 using an excess of sodium methanethiolate
in acetonitrile.10 Then, after addition of monoiodoalkane R-I
(R ) Me, Et, n-Bu) or diiodoalkane I-(CH2)n-I (n ) 3, 4)
into this medium, we obtain the corresponding adducts C60R2
or fused cycloadducts C60(CH2)n in good yields. The forma-
tion of 1,2- and 1,4-dialkyl adducts C60R2 is highly regio-
selective, the relative molar ratio 1,2/1,4 being ca. 9/1 when
R ) Me and ca. 1/9 with other alkyl groups. We have also
extended our process to reactions with halo-derivatives
bearing a second functional group (halo, ester, ketone).11
These reactions give rise to new organo C60 derivatives such
as the fused cyclopentanone C60(CH2)2CO, which can be used
(1) (a) Sariciftci, N. S.; Smilowitz, L.; Heeger, A. J.; Wudl, F. Science
1992, 258, 1474-1476. (b) Yu, G.; Gao, Y.; Hummelen, J. C.; Wudl, F.;
Heeger, A. J. Science 1995, 270, 1789-1791.
(2) (a) Tutt, L. W.; Kost, A. Nature 1992, 356, 225. (b) Sun, Y.-P.; Riggs,
J. E. Int. ReV. Phys. Chem. 1999, 18, 43-90.
(3) (a) Imahori, H.; Sakata, Y. AdV. Mater. 1997, 9, 537-546. (b) Gust,
D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res. 2001, 34, 40-48.
(4) (a) Prato, M. Top. Curr. Chem. 1999, 199, 173-187. (b) Wudl, F. J.
Mater. Chem. 2002, 12, 1959-1963.
(5) (a) Jensen, A. W.; Wilson, S. R.; Schuster, D. I. Bioorg. Med. Chem.
1996, 4, 767-779. (b) Da Ros, T.; Prato, M. Chem. Commun. 1999, 663-
669.
(8) (a) Maggini, M.; Scorrano, G.; Prato, M. J. Am. Chem. Soc. 1993,
115, 9798-9799. (b) Prato, M.; Maggini, M.; Scorrano, G. Synth. Met.
1996, 77, 89-91.
(9) Bingel, C. Chem. Ber. 1993, 126, 1957-1959.
(10) Allard, E.; Rivie`re, L.; Delaunay, J.; Dubois, D.; Cousseau, J.
Tetrahedron Lett. 1999, 40, 7223-7226.
(6) Hirsch, A. The Chemistry of Fullerenes; Thieme: Stuttgart, 1994.
(7) Belik, P.; Gu¨gel, A.; Spickermann, J.; Mu¨llen, K. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 78-80.
(11) Allard, E.; Delaunay, J.; Cheng, F.; Cousseau, J.; Ordu´na, J.; Gar´ın,
J. Org. Lett. 2001, 3, 3503-3506.
10.1021/ol034545k CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/23/2003

as a starting building block in the synthesis of new donor-
acceptor covalent assemblies.
1H NMR spectra, using the signals issued from the CH2
groups bonded to the C60 core. In the 1,4-adduct 3b, these
two hydrogens are diastereotopic, thus providing an AB
system, while a singlet is characteristic of both CH2 groups
in the 1,2-adduct 3a. Compound 3b has already been isolated
and characterized by Komatsu et al. as a very minor product
(ca. 1.8% yield) from a reaction involving C60, Zn, and
BrCH2CO2Et.13
We now wish to report on the results of the reactions
2-
between C60 anion and 2-haloacetates XCH2-CO2Et 1
(X ) Br) and 2 (X ) I), R-bromoacetophenone C6H5-CO-
CH2Br 6, and the benzyl derivative p-BrCH2-C6H4-CH2OH
13. All the reactions were carried out in a glovebox.12
Reactions of ethyl bromoacetate BrCH2CO2Et 1 or iodo-
2-
acetate ICH2CO2Et 2 with C60 have given rise to results
Similar results have been observed from reaction between
2-
that are slightly different from those observed from previous
reactions of simple haloalkanes (Table 1, Scheme 1). As
C60 and R-bromoacetophenone 6, with the following
compounds being isolated: the 1,4-adduct C60(CH2COPh)2
7 (ca. 25% yield) and a mixture of methanofullerene
C60>CH-COPh 8 (ca. 5% yield) and monosubstituted
dihydrofullerene C60H(CH2COPh) 9 (ca. 10% yield). No 1,2-
adduct could be detected (Scheme 2).
Table 1. Relative Formation Yields (%) of Compounds 3a, 3b,
4, and 5 Starting from Esters 1 and 2
starting ester
3a
3b
4
5
1 (X ) Br)
2 (X ) I)
1-2
1
10
16
2
4
1-2
traces
Scheme 2
might be expected, the corresponding adducts C60(CH2CO2Et)2
have been obtained as a mixture of 1,2- and 1,4-regioisomers,
respectively 3a and 3b, the latter still being the major
product; however, other minor products, methanofullerene
C60>CH-CO2Et 4 and monosubstituted 1,2-dihydrofullerene
C60(H)(CH2CO2Et) 5, were also formed along with undefined
polyadducts.
The formation of methanofullerenes 4 and 8 appeared to
be surprising, since such compounds are essentially reported
to be obtained via the Bingel reaction. However, a careful
analysis (GC-MS and 1H NMR) of the commercially
available ester BrCH2CO2Et 1 revealed the presence of a
very small amount of Br2CHCO2Et. Due to the large excess
of ester 1 used in our process, methanofullerene 4 is likely
to be formed from reaction of Br2CHCO2Et with C602-. A
similar reaction issued from various gemdihalo compounds
has been described by Echegoyen et al.,14 and we have
effectively observed in a control experiment that reaction of
pure Br2CHCO2Et with C602- leads to compound 4 (Scheme
3). A similar explanation could hold for the formation of
methanofullerenes from ester 2 and ketone 6.
Scheme 1
Scheme 3
The two regioisomers 3a and 3b are easily separated by
column chromatography, such a separation being pre-
viously impossible in the case of dialkylated derivatives
C60R2.10,11 They have been unambiguously identified from
(12) General Experimental Conditions. In a glovebox, an excess (10
equiv) of sodium methanethiolate was added to a carefully deoxygenated
suspension of C60 (150 mg, 0.21 mmol) in dry acetonitrile (100 mL). The
mixture was stirred at room temperature for 24 h. A deep red color
developed progressively in the medium due to the formation of C602- anion,
which was usually achieved in 24 h. The reaction mixture was filtered off
to eliminate unreacted C60 and excess sodium methanethiolate. Then, an
excess (ca. 20 equiv) of halogenated derivative, either neat liquid or
dissolved in dry acetonitrile when solid, was added to the resultant solution,
which was stirred at room temperature overnight. After reaction, the obtained
solid products were filtered off, washed with acetonitrile, isolated through
column chromatography, and identified from MS and NMR analyses.
The formation of dihydrofullerene 5 and 9 seems to be
more difficult to explain. If we consider the mechanism
proposed by Kadish et al.,15 [C60(CH2A)]- (A ) CO2Et,
(13) Wang, G.-W.; Murata, Y.; Komatsu, K.; Wan, T. S. M. Chem.
Commun. 1996, 2059-2060.
(14) Boulas, P.; Zuo, Y.; Echegoyen, L. Chem. Commun. 1996, 1547-
1548.
2240
Org. Lett., Vol. 5, No. 13, 2003

COPh) anion is formed in the first step. This ion could then
lead to dihydrofullerenes 5-9 if a strong acid is added to
the reaction medium as we have recently shown.16 But, of
course, such an acid cannot be available in this medium,
and dihydrofullerenes thus cannot be formed.
Scheme 5a
Another possibility might be considered if C60H- anion
is first formed; in this case, a further reaction with XCH2A
(X ) Br, I) should provide dihydrofullerenes. However, this
ion is unlikely to come from an acid-base reaction between
C602- and XCH2A since the basic character of C602- has been
estimated to be weaker than that of benzoate anion.17 We
put forward a new hypothesis. In the first stage the single-
a Conditions: (i) excess DIBAL-H (20 equiv), toluene, 2 h, -80
°C, then acidic (aqueous 1 M HCl/MeOH) hydrolysis.
2-
electron transfer between C60 and BrCH2A could occur
according two competitive pathways (Scheme 4), a major
leads to the corresponding 1,4-adduct C60(p-CH2-C6H4-
CH2OH)2 12 (ca. 15% yield) (Scheme 6).
Scheme 4
Scheme 6
•
-• 14
one leading as expected to CH2A and C60
, and a minor
one leading to H• and C60-• due to the strong polarity of the
C-H bonds in XCH2A (stronger than that in simple
haloalkanes R-CH2X for instance).18 Then, of course, the
overall process will continue through coupling of the radical
moieties, followed by the reaction with a second molecule
of XCH2A (Scheme 4).
In conclusion, new functional organo derivatives of C60
were synthesized and characterized.19 C602- anion chemistry
is thus emphasized, since the obtained compounds appear
(19) Selected Spectroscopic Data. Compound 3a: 1H NMR (500 MHz,
CDCl3) δ 4.68 (s, 4H), 4.47 (q, 4H, J ) 7.1 Hz), 1.45 (t, 6H, J ) 7.1 Hz);
13C NMR (125.75 MHz, CDCl3) δ 172.3, 156.2, 147.9, 146.6, 146.3, 146.0,
145.5, 145.4, 144.8, 143.3, 142.6, 142.2, 141.8, 141.4, 139.8, 136.2, 62.7,
61.8, 46.2, 14.3; ES-MS calcd for C68H14O4 894.089, found M-• 894.086.
UV-vis (hexane), λmax [nm] 431, 307-308, 254, 214. Compound 4: 1H
NMR (500 MHz, CS2/C6D6) δ 4.57 (s, 1H), 4.35 (q, 2H, J ) 7.1 Hz), 1.40
(t, 3H, J ) 7.1 Hz); 13C NMR (125.75 MHz, CS2/C6D6) δ 164.8, 148.5,
145.9, 145.7, 145.4, 145.4, 145.3, 145.3, 145.0, 144.9, 144.9, 144.8, 144.6,
144.2, 143.9, 143.6, 143.3, 143.3, 143.2, 143.0, 142.7, 142.5, 142.3, 142.2,
141.4, 141.2, 141.0, 136.6, 71.0, 62.3, 39.6, 15.0; MALDI-TOF MS calcd
for C64H6O2 806.0, found M+• 806.0; UV-vis (hexane), λmax [nm] 425,
256, 214. Compound 7: 1H NMR (500 MHz, CS2/CDCl3) δ 8.19 (d, 4H),
7.65 (t, 2H), 7.53 (t, 4H), 4.75 (d, 2H, J ) 15.8 Hz), 4.72 (d, 2H, J ) 15.8
Hz); 13C NMR (125.75 MHz, CS2/CDCl3) δ 194.9, 155.9, 150.9, 148.3,
147.8, 146.9, 146.7, 146.7, 146.6, 145.2, 145.2, 144.9, 144.9, 144.5, 144.4,
144.2, 144.0, 144.0, 143.7, 143.6, 143.4, 142.9, 142.9, 142.8, 142.4, 142.0,
141.8, 141.6, 140.5, 138.6, 138.5, 136.6, 133.2, 128.6, 128.4, 55.1, 49.3;
MALDI-TOF MS calcd for C76H14O2 958.1, found M-• 958.1; UV-vis
(o-dichlorobenzene) λmax [ nm] 443 (broad). Compound 8: 1H NMR (500
MHz, CS2/CDCl3) δ 8.44 (dd, 2H, J ) 7.2 Hz, J′ ) 1.5 Hz), 7.76-7.73
(m, 1H), 7.70-7.65 (m, 2H), 5.61 (s, 1H); MALDI-TOF MS calcd for
C68H6O 838.0, found M-• 838.0. Compound 9: 1H NMR (500 MHz, CS2/
CDCl3) δ 8.36 (dd, 2H, J ) 7.2 Hz, J′ ) 1.5 Hz), 7.76-7.73 (m, 1H),
7.70-7.65 (m, 2H), 6.72 (s, 1H), 5.20 (s, 2H); MALDI-TOF MS calcd for
C68H8O 840.0, found M-• 840.0. Compound 10: 1H NMR (500 MHz,
CS2/C6D6) δ 10.27 (t, 2H, J ) 1.8 Hz), 3.98 (dt, 2H, J ) 1.8 Hz, J′ ) 16
Hz), 3.93 (dt, 2H, J ) 1.8 Hz, J′ ) 16 Hz); 13C NMR (125.75 MHz, CS2/
C6D6) δ 195.8, 155.4, 150.4, 148.9, 148.2, 147.6, 147.2, 146.9, 145.8, 145.6,
145.0, 145.0, 144.8, 144.6, 144.6, 144.5, 144.4, 144.2, 143.8, 143.6, 143.4,
142.9, 142.5, 142.3, 139.1, 138.9, 54.3, 54.0; ES-MS calcd for C64H6O2
806.037, found M-• 806.036. UV-vis (o-dichlorobenzene), λmax [ nm] 442
(broad). Compound 12: 1H NMR (500 MHz, CS2/acetone-d6), δ 7.56 (d,
4H, J ) 7.9 Hz), 7.43 (d, 4H, J ) 7.9 Hz), 4.61 (d, 4H, J ) 5.6 hz), 3.92
(m, 4H, J ) 13.7 Hz), 3.90 (t, 2H, J ) 5.6 Hz); 13C NMR (125.75 MHz,
CS2/C6D6) δ 158.7, 152.6, 149.4, 149.2, 147.8, 147.8, 147.6, 147.5, 146.9,
146.1, 145.7, 145.5, 145.5, 145.4, 145.0, 144.9, 144.9, 144.7, 144.5, 144.4,
143.8, 143.7, 143.6, 143.3, 143.2, 143.1, 142.7, 142.6, 142.4, 141.1, 139.5,
138.6, 135.1, 131.5, 127.2, 64.4, 61.4, 48.9; MALDI-TOF MS calcd for
C76H18O2 962.0, found M-• 962.0; UV-vis (dichloromethane), λmax [nm]
444 (broad), 327, 270.
Most of these new C60 derivative compounds possess great
synthetic potential due to the presence of ketone and ester
groups. Thus, the diester 3b was easily reduced into the
corresponding dialdehyde 10 (ca. 50% yield) upon reaction
with DIBAL-H in toluene at low temperatures (-80 °C).
This compound was isolated and characterized by NMR and
mass spectrometry analyses. Unfortunately, further reactions
of DIBAL-H, at different temperatures, versus dialdehyde
10 did not allow the isolation of the corresponding diol
C60(CH2CH2OH)2, which could not be obtained from reduc-
tion of diester 3b either.
Nevertheless, to obtain organo derivatives of C60 bearing
2-
two alcohol groups, we studied the reaction between C60
and p-BrCH2-C6H4-CH2OH 11, this alcohol being easily
obtained from reduction of the commercially available methyl
ester p-BrCH2-C6H4-CO2Me. As expected, the reaction
(15) (a) Subramanian, R.; Kadish, K. M.; Vijayashree, M. N.; Gao, X.;
Jones, M. T.; Miller, M. D.; Krause, K. L.; Suenobu, T.; Fukuzumi, S. J.
Phys. Chem. 1996, 100, 16327-16335. (b) Fukuzumi, S.; Suenobu, T.;
Hirasaka, T.; Arakawa, R.; Kadish, K. M. J. Am. Chem. Soc. 1998, 120,
9220-9227.
(16) Allard, E., Cheng, F.; Chopin, S.; Delaunay, J.; Rondeau, D.;
Cousseau, New. J. Chem. 2003, 27, 188-192.
(17) Cliffel, D. E.; Bard, A. J. J. Phys. Chem. 1994, 98, 8140-8143.
(18) This hypothesis may be related to the redox reactions of sodium or
potassium with alcohols, the initial step being considered as a single-electron
transfer from the alkali metal to the hydrogen atom of an OH group. This
reaction appears to be strongly dependent on the polarity of the O-H bond,
since the generation of hydrogen is very easy and even violent from primary
alcohols but very sluggish from tertiary alcohols.
Org. Lett., Vol. 5, No. 13, 2003
2241

to be difficult, if not even impossible, to prepare starting
from C60 itself. In particular, dialdehyde 10 and diol 12 may
constitute promising intermediates in synthesis of new triads,
and this possibility is currently under study.
Supporting Information Available: Experimental pro-
cedure for the preparation of dialdehyde 10 and alcohol 11
and H NMR spectra of compounds 3a, 3b, and 10. This
material is available free of charge via the Internet at
http://pubs.acs.org.
1
Acknowledgment. The CNRS is gratefully acknowledged
for financial support.
OL034545K
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Org. Lett., Vol. 5, No. 13, 2003