MEM
MEM
N
N
1. n-butylamine
2. ODCB–anisol (5:3)
TsOH, air, reflux
10%
OCH3
N
5
ODCB–anisol (5:3)
TsOH, air, reflux
N
2
O
O
38%
MEM
6
Scheme 2
deactivated aromatics, which allows use of ODCB as solvent. In
the absence of an acid or oxygen these derivatizations do not
take place. The arylation with N,N-dimethylaniline failed. This
is presumably due to the protonation of the Me2N group causing
deactivation towards electrophilic substitution.
Notes and References
* E-mail: hirsch@organik.uni-erlangen.de
† Selected spectroscopic data of the newly synthesised compounds 2–4. 2:
FTIR: n(KBr)/cm21 2995, 2945, 2924, 2900, 2828, 1507, 1421, 1250, 1175,
1032, 966, 899, 840, 822, 718, 638, 587, 555, 523 and 482; UV–VIS
lmax(cyclohexane)/nm 257, 323, 444, 591, 723 and 789; dH(400 MHz, CS2–
20% CDCl3) 8.72 (ddd, JAB 9.02, JABA 3.10, JAAA 2.75, 1 H), 7.35 (ddd, JAB
9.02, JABA 3.10, JAAA 2.75, 1 H) and 4.03 (s, 3 H); dC(100.5 MHz, CS2–20%
CDCl3) 160.36 (C–OMe, 1C), 154.10 (2C), 148.61 (2C), 147.58 (1C),
147.44 (2C), 147.38 (2C), 147.06 (2C), 146.91 (2C), 146.41 (2C), 146.19
(2C), 146.02 (2C), 145.66 (2C), 145.63 (1C), 145.46 (2C), 144.83 (4C),
144.37 (2C), 144.11 (2C), 143.79 (2C), 142.93 (2C), 142.55 (2C), 141.89
(2C), 141.60 (2C), 141.34 (2C), 141.24 (2C), 140.80 (2C), 140.68 (2C),
139.60 (2C), 137.31 (2C), 132.94 [C-(CH)2COMe, 1C], 132.72 (2C),
128.47 (C–CHCOMe, 2C), 123.89 (2C), 115.01 (C–COMe, 2C), 82.33 (1C)
and 54.93 (Me); MALDI-MS m/z 828 (M+), 814 (M+ 2 Me) and 722
(C59N+). 3: FTIR: n(KBr)/cm21 2919, 2845, 1736, 1629, 1509, 1422, 1374,
1344, 1316, 1262, 1236, 1186, 1095, 1020, 968, 901, 844, 803, 774, 719,
707, 679, 554, 525, 495, 483, 438, 428 and 409; UV–VIS lmax(cyclohex-
ane)/nm 263, 323, 440, 588, 722 and 790; dH(400 MHz, CS2–20% CDCl3)
8.70 (ddd, not completely resolved, JAB 7.77, 1 H), 7.67 (ddd, not
completely resolved, JAB 7.77, 1 H) and 2.66 (s, 3 H); dC(100.5 MHz, CS2–
20% CDCl3) 154.19 (2C), 148.69 (2C), 147.59 (1C), 147.42 (2C), 147.39
(2C), 147.08 (2C), 147.01 (2C), 146.41 (2C), 146.21 (2C), 146.03 (2C),
145.67 (2C), 145.65 (1C), 145.46 (2C), 144.84 (4C), 144.39 (2C), 144.11
(2C), 143.80 (2C), 142.95 (2C), 142.56 (2C), 141.90 (2C), 141.62 (2C),
141.34 (2C), 141.25 (2C), 140.80 (2C), 140.69 (2C), 139.61 (2C), 139.22
(q, 1C), 138.02 (q, 1C), 137.34 (2C), 132.75 (2C), 130.42 (C–CMe, 2C),
127.07 (C–CHCMe, 2C), 123.94 (2C), 82.60 (1C) and 21.48 (Me); MALDI-
MS m/z 813 (M+) and 722 (C59N+). 4: FTIR: n(KBr)/cm21 2962, 2923,
2854, 1635, 1508, 1420, 1375, 1318, 1261, 1092, 1028, 800, 747, 722, 524
and 472; UV–VIS lmax(cyclohexane)/nm 256, 320, 436, 580, 711 and 793;
dH(400 MHz, CS2–20% CDCl3) several multiplets between d 7.0 and 10.5;
dC(100.5 MHz, CS2–20% CDCl3) 154.23, 148.34, 147.66, 147.53, 147.41,
147.27, 147.15, 146.73, 146.48, 146.38, 146.27, 146.24, 146.14, 145.74,
145.54, 144.96, 144.43, 144.34, 144.22, 143.79, 143.07, 142.81, 142.08,
141.86, 141.32, 140.96, 140.80, 139.80, 137.39, 137.38, 136.99, 133.34,
133.00, 129.20, 128.76, 128.05, 127.61, 127.45, 126.97, 126.50, 126.30,
125.75, 125.25, 124.82, 124.02 and 122.82; MALDI-MS m/z 884 (M+) and
722 (C59N+).
1
The monoadducts 2–4 were characterized by H NMR, 13C
NMR, UV–VIS and FTIR spectroscopy as well as by mass
spectrometry.† The 1H NMR spectrum of 2, for example, shows
the expected ddd-pattern of an AAABBA-spin system for a para-
substituted aromatic ring. The protons of the methoxy group
resonate at d 4.03. The 13C NMR spectrum of 2 (Fig. 1) clearly
proves Cs symmetry showing the 30 expected fullerene
resonances in the sp2 region between d 155 and 123. The five
different C-atoms of the anisyl addend resonate at d 160.36,
132.94, 128.47, 115.01 and 54.93. The peak at d 82.33 is due to
the resonance of the sp3 carbon of the fullerene skeleton, which
is a typical value for a corresponding C atom in RC59N.6 The
UV–VIS spectra of 2–4 displaying the most intensive absorp-
tions† at ca. 260, 320 and 440 nm are basically identical to that
of 1. All three compounds are green in solution. The FTIR
spectra† of 2–4 show the typical characteristics for fullerene
derivatives (monoadducts), especially the absorptions in the
fingerprint region between 480 and 590 cm21 with the strongest
peak at about 523 cm21. MALDI-TOF mass spectrometry
shows the M+ peak of each compound together with a strong
fragmentation peak at m/z 722 for C59N+.
We assume that the mechanism of this reaction is an
electrophilic aromatic substitution (SEAr). The electrophile is
presumably C59N+, which might be formed via thermal
homolysis of 1 and subsequent oxidation with O2. The reaction
times depend on the nature of the aromatic reagent used. For
example, the reaction of 1 with toluene took almost 5 h, whereas
quantitative conversion with anisole was achieved within 2 h,
which is in line with the lower SEAr activity of toluene. The role
of the acid is not clear. It is possible that it is needed to trap the
reduced oxygen species.
It is important to mention that arylated adducts like 2 can also
be obtained starting directly from the precursor molecules 5 and
6, which are usually used for the synthesis of the heterofullerene
dimer 1 (Scheme 2). Although the yields are considerably lower
than those of the corresponding conversions using isolated 1,
one separation step can be avoided. However, the yields can be
increased upon raising the reaction temperature. The direct
treatment of 5 in 1-chloronaphthalene at 220 °C leads to the
formation of 4 in 46% isolated yield.
Investigations on the chemical behaviour as well as on the
electronic and photophysical properties of the stable arylated
heterofullerene derivates like 2–4 are currently underway.
We thank the DFG for financial support.
1 J. C. Hummelen, B. Knight, J. Pavlovich, R. Gonzalez and F. Wudl,
Science, 1995, 269, 1554.
2 B. Nuber and A. Hirsch, Chem. Commun., 1996, 1421.
3 Gruss, K.-P. Dinse, A. Hirsch, B. Nuber and U. Reuther, J. Am. Chem.
Soc., 1997, 19, 8728.
4 M. Keshavarz-K., R. Gonzalez, R. G. Hicks, G. Srdanov, V. I. Srdanov,
T. G. Collins, J. C. Hummelen, C. Bellavia Lund, J. Pavlovich, F. Wudl
and K. Holczer, Nature, 1996, 383, 147.
5 C. Bellavia-Lund, R. Gonzalez, J. C. Hummelen, R. G. Hicks, A. Sastre
and F. Wudl, J. Am. Chem. Soc., 1997, 119, 2946.
6 C. Bellavia-Lund, M. Keshavarz-K., T. Collins and F. Wudl, J. Am.
Chem. Soc., 1997, 119, 8101.
Received in Cambridge UK, 27th October 1997; 7/07704A
406
Chem. Commun., 1998