Aziridination of C60 with simple amides and catalytic rearrangement of the aziridinofullerenes to azafulleroids

Article abstract of DOI:10.1021/jo8025737

The selective formation of aziridinofullerene and azafulleroid, which are isomers of the fullerene derivatives-introduced N₁ unit, is achieved. The ionic aziridination is a very convenient and risk-free procedure compared with the conventional

Full text of DOI:10.1021/jo8025737

Aziridination of C60 with Simple Amides and Catalytic
Rearrangement of the Aziridinofullerenes to Azafulleroids
Ryoji Tsuruoka, Toshiki Nagamachi, Yuta Murakami, Mitsuo Komatsu, and
Satoshi Minakata*
Department of Applied Chemistry, Graduate School of Engineering, Osaka UniVersity,
Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
minakata@chem.eng.osaka-u.ac.jp
ReceiVed NoVember 20, 2008
The selective formation of aziridinofullerene and azafulleroid, which are isomers of the fullerene
derivatives-introduced N1 unit, is achieved. The ionic aziridination is a very convenient and risk-free
procedure compared with the conventional method with azides as nitrogen sources, and gives
aziridinofullerenes from various readily available amides (carbamates, ureas, carboxamides, and
phosphamides). For example, benzyl carbamate was chlorinated by tert-butyl hypochlorite (tert-BuOCl)
and then reacted with C60 in the presence of base to give N-benzyloxycarbonyl aziridinofullerene
exclusively and without formation of its isomer, an azafulleroid. The reaction enabled the synthesis of
functional fullerene derivatives having a trialkoxysilyl group and an amino acid moiety. Azafulleroids
were obtained through the rearrangement of corresponding aziridinofullerenes by using the combination
of a chloramine catalyst and MS4A. Among other chloramines used, chloramine B (CB) showed superior
ability as a catalyst in the rearrangement. It was found that MS4A functions as a Lewis acid in the
reaction.
SCHEME 1. Partial Illustration of Aziridinofullerene and
Azafulleroid
Introduction
The development of a basic and facile method for the
functionalization of C60 remains an important challenge because
of recent demands for carbon nanomaterials.1,2 Among various
methodologies for the functionalization, aziridination of C60 is
a powerful method for the direct introduction of a heteroatom
to the molecule, leading to closed [6,6]-bridged aziridinof-
ullerenes 1 (Scheme 1). Moreover, isomers of 1 and opened
[5,6]-bridged azafulleroids 2 are key precursors for azafullerene
“C59N” synthesis.3 Azides are commonly used as nitrogen
sources for the synthesis of nitrogen unit-substituted fullerenes.4
Some problems remain, however, namely that control of the
distribution of the two products 1 and 2 is rather difficult, and
that azides require careful handling due to their high reactivity,
explosiveness, and toxicity. Other than azides, examples of
aziridination using nitrene5 or iminoiodane6 as an N1 source
have been developed, but generality of the substituents for
nitrogen remains limited. On the other hand, although photo-
chemical7 and thermal5c,8 conversion between 1 and 2 was
revealed, the studies would not test synthetic generality.
Quite recently, our group reported a new method for the ionic
aziridination of C60 using chloramine-T (CT, 3a) as a readily
(1) (a) Hirsch, A.; Brettreich, M. Fullerenes: Chemistry and Reactions; Wiley-
VCH: Weinheim, Germany, 2005. (b) Kadich, K. M.; Ruoff, R. S., Eds.
Fullerenes: Chemistry, Physics, and Technology; Wiley: New York, 2000. (c)
Martin, N. Chem. Commun. 2006, 2093.
(2) For recent reports, see: (a) Minakata, S.; Tsuruoka, R.; Komatsu, M. J. Am.
Chem. Soc. 2008, 130, 1536. (b) Matsuo, Y.; Kanaizuka, K.; Matsuo, K.; Zhong,
Y.-W.; Nakae, T.; Nakamura, E. J. Am. Chem. Soc. 2008, 130, 5016. (c) Yang,
C.; Kim, J. Y.; Cho, S.; Lee, J. K.; Heeger, A. J.; Wudl, F. J. Am. Chem. Soc.
2008, 130, 6444.
(3) (a) Hummelen, J. C.; Knight, B.; Pavlovich, J.; Gonzalez, R.; Wudl, F.
Science 1995, 269, 1554. (b) Nuber, B.; Hirsch, A. Chem. Commun. 1996, 1421.
10.1021/jo8025737 CCC: $40.75
Published on Web 01/22/2009
2009 American Chemical Society
J. Org. Chem. 2009, 74, 1691–1697 1691

Tsuruoka et al.
SCHEME 2. Aziridination of C60 with Chloramine-T and
Rearrangement of Aziridinofullerene
SCHEME 3. Working Hypothesis of Ionic Aziridination of
C60 with Amides
a Based on converted C60.
SCHEME 4. Aziridination of C60 with Benzyl Carbamate
available N1 source, giving predominantly N-tosylated aziridi-
nofullerene 1a with high selectivity9 (89%), and the unique
rearrangement of 1a to 2a using the combination of a catalytic
amount of chloramine and molecular sieves 4A (MS4A), as well
as a thermal rearrangement (Scheme 2).8 Although the aziridi-
nation is unique and unprecedented, the method essentially
requires the use of chloramine salts, some of which are not
stable. However, to our knowledge, ionic aziridination is not
well established, either for fullerenes or for electron-deficient
olefins.10
a Based on converted C60. b Isolated yield is given in parentheses.
SCHEME 5. Chlorination of Benzyl Carbamate
From this point of view, a new practical and highly selective
aziridination of C60 with alternative nitrogen sources instead of
azides and generally applicable isomerization of an aziridinof-
ullerene to an azafulleroid are desired. Here we report a new
type of selective aziridination of C60 with a variety of simple
amides, many of which are either commercially available or
readily prepared from either corresponding acids,11 alcohols,12
or amines.13 Moreover, catalytic rearrangement of the resulting
aziridinofullerenes to azafulleroids with use of a chloramine salt
and an MS4A system was investigated.
a
1
Yields determined by H NMR.
a new methodology for the generation of chloramine anions
from readily accessible amides would directly lead to a general
synthesis of a variety of aziridinofullerenes. As mentioned in
the Introduction, most chloramine salts, even those with an
electron-withdrawing group, cannot be isolated due to their
unstable nature. To expand the generality of the aziridination
of C60, a facile method for the chlorination of amides and their
deprotonation in situ should be explored (Scheme 3). As an
initial experiment for the new aziridination of C60, tert-butyl
hypochlorite (t-BuOCl) was employed in the chlorination of
benzyl carbamate (4b).14 The reaction was carried out in MeOH
and the solvent was exchanged with toluene followed by
addition of C60 and DBU, affording N-benzyloxycarbonyl
aziridinofullerene in moderate selectivity (60%), as shown in
Scheme 4.
Results and Discussion
Preliminary Results of Aziridination of C60 with Benzyl
Carbamate. Provided the ionic reaction path proposed in our
previous aziridination with CT is suitable, the development of
(4) (a) Prato, M.; Li, Q. C.; Wudl, F.; Luccini, V. J. Am. Chem. Soc. 1993,
115, 1148. (b) Ishida, T.; Tanaka, K.; Nogami, T. Chem. Lett. 1994, 561. (c)
Banks, M. R.; Cadogan, J. I. G.; Gosney, I.; Hodgson, P. K. G.; Langridge-
Smith, P. R. R.; Rankin, D. W. H. J. Chem. Soc., Chem. Commun. 1994, 1365.
(d) Yan, M.; Cai, S. X.; Keana, J. F. W. J. Org. Chem. 1994, 59, 5951. (e)
Banks, M. R.; Cadogan, J. I. G.; Gosney, I.; Hodgson, P. K. G.; Langridge-
Smitha, P. R. R.; Millar, J. R. A.; Parkinson, J. A.; Rankin, D. W. H.; Taylor,
A. T. J. Chem. Soc., Chem. Commun. 1995, 887. (f) Averdung, J.; Mattay, J.;
Jacobi, D.; Abraham, W. Tetrahedron 1995, 51, 2543. (g) Schick, G.; Gro¨sser,
T.; Hirsch, A. J. Chem. Soc., Chem. Commun. 1995, 2289. (h) Smith, A. B., III;
Tokuyama, H. Tetrahedron 1996, 52, 5257. (i) Bellavia-Lund, C.; Wudl, F. J. Am.
Chem. Soc. 1997, 119, 943. (j) Ulmer, L.; Mattay, J. Eur. J. Org. Chem. 2003,
2933.
(5) (a) Kuwashima, S.; Kubota, M.; Kushida, K.; Ishida, T.; Ohashi, M.;
Nogami, T. Tetrahedron Lett. 1994, 35, 4371. (b) Banks, M. R.; Cadogan, J. I. G.;
Gosney, I.; Hodgson, P. K. G.; Langridge-Smith, P. R. R.; Millar, J. R. A.;
Taylor, A. T. Tetrahedron Lett. 1994, 35, 9067. (c) Nakahodo, T.; Okada, M.;
Moria, H.; Yoshimura, T.; Ishitsuka, M. O.; Tsuchiya, T.; Maeda, Y.; Fujihara,
H.; Akasaka, T.; Gao, X.; Nagase, S. Angew. Chem., Int. Ed. 2008, 47, 1298.
(6) Zhang, X.; Gan, L.; Huang, S.; Shi, Y. J. Org. Chem. 2004, 69, 5800.
(7) (a) Averdung, J.; Mattay, J. Tetrahedron 1996, 52, 5407. (b) Ouchi, A.;
Hatsuda, R.; Awen, B. Z. S.; Sakuragi, M.; Ogura, R.; Ishii, T.; Araki, Y.; Ito,
O. J. Am. Chem. Soc. 2002, 124, 13364.
Optimization of the Conditions of Aziridination of C60
with Benzylcarbamate. Although the desired aziridinofullerene
was obtained with this method, the efficiency was unsatisfactory.
To first learn the details of the process, the chlorination of
carbamate was investigated. The chlorination of benzyl car-
1
bamate was monitored by using H NMR. Chlorination of the
carbamate with an equimolar amount of t-BuOCl in d3-
acetonitrile gave only the dichlorinated product. In contrast,
monochlorinated carbamate was predominantly produced by
using d4-methanol (Scheme 5).
The reaction of the resulting monochlorinated carbamate with
C60 should be carried out in toluene because the solvent is
suitable for the modification of C60 and is available for organic
reaction. As with our previous report of the aziridination of C60
with CT8 in which the sodium ion of CT was exchanged with
the ammonium ion prior to use, the N-chlorinated nitrogen anion
generated from the resulting carbamate obtained by chlorination
(8) Minakata, S.; Tsuruoka, R.; Nagamachi, T.; Komatsu, M. Chem. Commun.
2008, 323.
(9) Selectivity/100 ) (isolated yield of product)/(conversion of C60).
(10) Shen, Y.-M.; Zhao, M.-X.; Xu, J.; Yian, Y. Angew. Chem., Int. Ed.
2006, 45, 8005, and references cited therein. .
(11) For example, see: Khalafi-Nezhad, A.; Parhami, A.; Rad, M. N. S.; Zarea,
A. Tetrahedron Lett. 2005, 46, 6879.
(12) For example, see: Gorodetskii, L. S.; Volzhina, O. N.; Kuznetsova, I. A.;
Alekseeva, E. N. Pharm. Chem. J. 1982, 16, 474.
(13) For example, see:(a) Weisel, C. A.; Mosher, H. S.; Whitmore, F. C.
J. Am. Chem. Soc. 1945, 67, 1055. (b) Durant, G. J. Chem. Ind. 1965, 32, 1428.
(c) Mosvhel, R. C.; Hudgins, W. R.; Dipple, A. J. Org. Chem. 1986, 51, 4180.
(14) (a) Herranz, E.; Sharpless, K. B. J. Org. Chem. 1980, 45, 2710. (b)
Angert, G.; Li, H. H.; Sharpless, K. B. Angew. Chem., Int. Ed. Engl. 1996, 35,
2813.
1692 J. Org. Chem. Vol. 74, No. 4, 2009

Aziridination of C60 with Simple Amides
TABLE 1. Aziridination of C60 with N-Chlorobenzyl Carbamate
TABLE 2. Aziridination of C60 with Various Amides
entry (%)a b
,
entry
carbamate (equiv)
base
time (min)
1
2
3
4
5
6
7
8
9
1
1
1
1
1
2
1
1.5
2
NaH
300
300
300
300
300
300
30
NRc
NR
85 (15)
NR
50 (10)
25 (12)
60 (9)
80 (12)
53 (10)
tBuONa
tBuONad
nPr3N
DBU
DBU
DBU
DBU
DBU
30
30
a Based on converted C60. b The numbers in parentheses are isolated
yields. c NR: no reaction. d Triethylbenzylammonium chloride was used
as the phase-transfer catalyst.
should be dissolved in toluene. In fact, while the reaction did
not proceed with only NaH or t-BuONa because of their
insolubility, the desired product was obtained by using a
combination of t-BuONa and an equimolar amount of trieth-
ylbenzylammonium chloride (Table 1, entrys 1-3). To facilitate
the manipulation, organic bases were investigated. Although
tripropylamine was ineffective for the aziridination (entry 4),
DBU, which would be a sufficient strong organic base for
abstraction of the hydrogen on the chloroamide, was found to
be a good base for the reaction (entry 5). The use of 2 equiv of
the carbamate decreased the selectivity (entry 6). A decrease
of the reaction time improved the selectivity due to a reduction
of the multiaddition of the amide. Consequently, when 1.5
equiv of carbamate was employed, the desired aziridinofullerene
was obtained in high selectivity (80%), which compares to the
results of entry 3. The structure of the resulting aziridinofullerene
was easily identified by using 1H and 13C NMR techniques and
FAB-MS. In the study of 13C NMR in CDCl3, 15 signals within
the range of δ 135-150 ppm, derived from the C2V symmetry
of the [6,6]-closed adduct,15 were observed. We were able to
assign signals at δ 80.60 and 156.30 ppm to the sp3 carbon of
the aziridine ring and to the carbonyl carbon of the Cbz group,
respectively. This evidence indicates a closed structure of the
C60 sphere.
a Based on converted C60. b The numbers in parenthesss are isolated
yields.
SCHEME 6. Preparation of N-H Aziridinofullerene
Aziridination of C60 with Various Simple Amides. A variety
of simple amides were applied to the aziridination of C60.
Carbamates having a tert-butoxycarbonyl (Boc, 4c) group and
having either long-liner or branched-alkyl chains (4d and 4e,
respectively) gave the corresponding aziridinofullerenes (Table 2,
entries 1-3). Ureas were also applicable to the reaction, affording
the desired products in good yields (entries 4 and 5), and
representing the first example for synthesis of aziridinofullerenes
having urea moieties. Although the yields should be left for
improvement, the aziridinofullerenes derived from benzamide and
picolinamide (1h and 1i) were yielded in good selectivity (entries
6 and 7). When phosphamides were subjected to the reaction,
phosphoryl-substituted aziridinofullerene was furnished (entries 8
and 9). The bulkiness of the diphenylphosphoryl (Dpp) group of
1k would prevent further addition of the amide and the corre-
sponding aziridinofullerene was produced with high efficiency. In
addition, this aziridinofullerene 1k was easily converted to N-H
aziridinofullerene as shown in Scheme 6 (33% from C60 vs 21%
by the previous route16).
Functionalization of C60 by the Aziridination. Recently,
to leverage the unique properties of C60, fullerene derivatives
having functional groups, for example, either a trialkoxysilyl
group17 or an amino acid moiety,18,19 have been given a great
deal of attention in the fields of nanotechnology and biochem-
(16) The Boc group of aziridinofullerene 1c can be easily detached and
substituted, see: (a) Averdung, J.; Luftmann, H.; Mattay, J.; Claus, K.-U.;
Abraham, W. Tetrahedron Lett. 1995, 36, 2957. (b) Averdung, J.; Wolff, C.;
Mattay, J. Tetrahedron Lett. 1996, 37, 4683.
(17) (a) Kraus, A.; Schneider, M.; Gugel, A.; Mullen, K. J. Mater. Chem.
1997, 7, 763. (b) Kordatos, K.; Da, R. T.; Bosi, S.; Pantarotto, D.; Georgakilas,
V.; Spalluto, G.; Prato, M. J. Org. Chem. 2001, 66, 4915. (c) Gasparrini, F.;
Misiti, D.; Della, N. F.; Maggini, M.; Scorrano, G.; Villani, C. Tetrahedron
2001, 57, 6997. (d) Bochio, M.; Carraro, M.; Scoorano, G.; Bango, A. AdV.
Synth. Catal. 2004, 346, 648. (e) Cho, Y.-J.; Ahn, T. K.; Song, H.; Kim, K. S.;
Lee, C. Y.; Seo, W. S.; Lee, K.; Kim, S. K.; Kim, D.; Park, J. T. J. Am. Chem.
Soc. 2005, 127, 2380. (f) Bianco, A.; Maggini, M.; Nogarole, M.; Scorrano, G.
Eur. J. Org. Chem. 2006, 2934. (g) Whitnall, W.; Cademartiri, L.; Ozin, G. A.
J. Am. Chem. Soc. 2007, 129, 15644.
(15) The method for identification of aziridinofullerene and azafulleroid with
13C NMR was well established by the literature cited in ref 4.
J. Org. Chem. Vol. 74, No. 4, 2009 1693

Tsuruoka et al.
SCHEME 7. Synthesis of Functionalized Aziridinofullerene
a Based on converted C60. b The numbers in parentheses are isolated yields. c 4m/C60 ) 1.5. d 4m/DBU ) 1.5.
SCHEME 8. Considered Pathways for the Aziridination
istry. The aziridination discovered here would be a powerful
tool for the synthesis of these functional materials. Aziridinof-
ullerenes possessing either a triethoxysilyl group or a proline
moiety were easily synthesized from simple substrates via two
steps (Scheme 7). Carbamate bearing a triethoxysilyl group (4l)
was prepared by the hydrosilylation of allyl carbamate, and the
carbamate obtained was chlorinated with t-BuOCl, followed by
a reaction with C60 to produce the desired aziridinofullerene
with a triethoxy functional group. In the same way, an optically
active unit could be introduced to C60 by reaction with a
N-carbamoyl proline ester (4m) prepared from a proline ester
and potassium cyanate.
Consideration of the Reaction Pathway of Aziridi-
nation. For the present aziridination of C60, there are two
dominant pathways: ionic addition-cyclization, as in the case
of CT, and the addition of nitrene generated by R-elimination
of the haloamide (Scheme 8). To confirm the pathway, the
following reactions were examined. Since it is known that
nitrene had reacted with ꢀ-methylstyrene to afford an aziridine
derivative,20 if an active species in the reaction is nitrene, the
corresponding aziridine should be produced when using styrene.
However, when the styrene was treated with N-chloroamide in
the presence of DBU, the aziridination did not proceed.
Moreover, O2 is a well-known radical scavenger such as triplet
nitrene, but O2 bubbling did not affect the reaction efficiency
compared with the results shown in Table 1 (entry 7). These
results indicate that the active species of this reaction was not
nitrene, but was instead anionic nitrogen generated by the
deprotonation of chloroamide. Therefore, the addition-cyclization
pathway was strongly suggested for the aziridination of C60. In
addition, the completely selective formation of aziridinofullerene
(no azafulleroid)21 corroborates this proposed pathway.
The Catalytic Rearrangement of Aziridinofullerenes to
Azafulleroids. We have already revealed that N-tosylated
aziridinofullerene (1a) was catalytically rearranged to a corre-
sponding azafulleroid (2a) by using a chloramine salt and
MS4A.8 However, the role of the chloramine catalyst and MS4A
is yet to be clarified and the substrate was limited to 1a. Since
a wide range of aziridinofullerenes have been synthesized by
using our original procedure, the catalytic rearrangement of
aziridinofullerenes to azafulleroids was examined.
(18) For recent reports, see: (a) Watanabe, L. A.; Bhuiyan, M. P. I.; Jose,
B.; Kato, T.; Nishino, N. Tetrahedron Lett. 2004, 45, 7137. (b) Enes, R. F.;
Tome, A. C.; Cavaleiro, J. A. S. Tetrahedron 2005, 61, 1423. (c) Rouse, J. G.;
Yang, J.; Ryman-Rasmussen, J. P.; Barron, A. R.; Monteiro-Riviere, N. A. Nano.
Lett. 2007, 7, 155. (d) Yang, J.; Wang, K.; Driver, J.; Yang, J.; Barron, A. R.
Org. Biomol. Chem. 2007, 5, 260.
First, to tune the catalytic activity of chloramine salt, several
chloramines were employed in the rearrangement of aziridi-
(19) For reviews, see: (a) Vol’pin, M. E.; Parnes, Z. N.; Romanova, V. S.
Russ. Chem. Bull. 1998, 47, 1021. (b) Burley, G. A.; Keller, P. A.; Pyne, S. G.
Fullerene Sci. Technol. 1999, 7, 973. (c) Bianco, A.; Da, R. T.; Prato, M.;
Toniolo, C. J. Pet. Sci. 2001, 7, 208.
(20) Minakata, S.; Kano, D.; Fukuoka, R.; Oderaotoshi, Y.; Komatsu, M.
Heterocycles 2003, 60, 289.
(21) It is known that aziridinofullerenes as well as azafulleroids were produced
by the reaction of C60 with a nitrene species. For example, see ref 4j.
1694 J. Org. Chem. Vol. 74, No. 4, 2009

Aziridination of C60 with Simple Amides
TABLE 3. Optimization of a Chloramine Catalyst for the
Rearrangement
TABLE 5. Rearrangement of Aziridinofullerenes to Azafulleroids
a
Determined by H NMR. b Isolated yield. c cat: 10 mol%.
1
the surface (MS3A: K+; MS4A: Na+; MS5A: Ca2+).22 Although
both the basic and neutral aluminum oxides were ineffective in
the rearrangement, the addition of basic alumina gave the
azafulleroid with a relatively better yield than that of the neutral
alumina (entries 4 and 5). From observation of the X-ray
fluorescence, basic alumina contained more than 3-fold the
amount of sodium (0.17 wt %), compared with neutral alumina
(<0.05 wt %), but any other compositional differences between
them were not identified. These results suggest that the surface
cation, especially Na+, might participate in the generation of
azafulleroid.
On the basis of the present study results, various aziridinof-
ullerenes were applied to rearrangement under optimized
conditions. Fortunately, the reaction shows a generality of
substituents on the nitrogen of aziridinofullerene. For example,
azafulleroid having a Cbz group (2b) was afforded in 47% yield
(Table 5, entry 2). Although the yield was insufficient, the
rearrangement was also applicable to aziridinofullerenes 1j to
give the corresponding azafulleroids (entry 3). Aziridinofullerene
1n was also efficiently isomerized to 2n even though 10 mol
% of 3b was used (entry 4).
Consideration of the Reaction Pathway for Rear-
rangement. We had already proposed a pathway for rearrange-
ment that deserves consideration.8 As shown in Scheme 9, the
reaction proceeds by the initial attack of chloramine salt,
followed by elimination of the catalyst along with the trans-
formation of the cage of C60. While the function of MS4A was
not clarified at the time, the role of MS4A was newly
investigated. In the absence of MS4A the reaction of aziridi-
nofullerene 1a with a catalytic amount of 3b gave a complex
mixture of poly adducts bearing heterosubstituents in ca. 10%
yield. This result indicates that MS4A would assist the elimina-
tion of the catalyst. From the results of the optimization of
additives (Table 4), the following points were considered.
Because the pore size of all molecular sieves (3-5 nm) used in
this examination was sufficiently less than the diameter of C60
(ca. 10 nm), it is quite unlikely that the pore contributed to the
formation of azafulleroids. Therefore, we focused on the surface
a
1
Determined by H NMR.
TABLE 4. Optimization of Additives
entry
additive
yield (%)a recovery of 1f (%)
1
2
3
4
5
MS4A
MS3A
MS5A
77
0
23
91
84
74
74
0
8
2
aluminum oxide 90 active basic
aluminum oxide 90 active neutral
a
1
Determined by H NMR.
nofullerene 1f as a model substrate. Chloramine having a
benzenesulfonyl group, chloramine-B (CB), 3b, which is one
of the commercially available chloramines, was effective in
rearrangement to give the corresponding azafulleroid 2f in good
yield (Table 3, entry 1). More than 29 signals within the range
of δ 130-150 ppm were observed in the 13C NMR spectra of
2f, indicating that the product had Cs symmetry.15 It was possible
to assign the signals at δ 162.68 ppm to the carbonyl carbon of
urea, and the signal of the sp3 carbon of aziridinofullerene 1f
disappeared. Thus, the structure of the product was determined
to be [5,6]-open azafulleroid. Although the yield of the reaction
with 3a as a catalyst was lower than that of CB, CT could also
catalyze the reaction (entry 2). Chloramines having an electron-
withdrawing group were ineffective for the rearrangement, and
most of the starting 1f was recovered (entries 3-5).
Since an additive plays an important role in the rearrange-
ment, some inorganic porous materials were evaluated in the
reaction. MS3A and MS5A did not function as an additive for
the rearrangement (Table 4, entries 2 and 3), although they have
an elemental composition that is similar to that of MS4A with
the exception of the pore size, owing to the cation species on
(22) See the Supporting Information.
J. Org. Chem. Vol. 74, No. 4, 2009 1695

Tsuruoka et al.
SCHEME 9. Considered Pathways for the Rearrangement
SCHEME 10. Nucleophilic Addition of Toluene Promoted
by Lewis Acid
dissolved in toluene (5 mL), followed by addition of the solution
to a toluene solution (50 mL) of C60 (72 mg, 0.1 mmol). DBU
(13.8 mg, 0.1 mmol) was then added to the solution and the mixture
was stirred at room temperature for the indicated times. The solu-
tion was passed through a short column of silica gel (3 g) and the
solvent was evaporated under reduced pressure. The residue was
purified by column chromatography on silica gel.
1,2-N-(Benzyloxycarbonyl)aziridino[60]fullerene (1b). Black
crystalline solid. FT-IR (KBr) 3429, 2924, 2852, 1743, 1225, 1186,
527 cm-1. 1H NMR (270 MHz, CDCl3) δ 5.53 (s, 2H), 7.39-7.43
(m, 3H), 7.52-7.55 (m, 2H). 13C NMR (68 MHz, CDCl3) δ 70.0,
80.6, 128.6, 128.9, 134.8, 140.0, 141.0, 142.06, 142.10, 142.7,
143.0, 143.1, 143.4, 143.6, 143.8, 144.35, 144.43, 144.8, 145.0,
145.1, 156.3. UV-vis (CH2Cl2) λmax 421, 410, 323, 255, 227 nm.
FAB-MS 869 ([M]+). HR-MS calcd for (C68H7NO2) 869.0476,
found 869.0579. Rf 0.50 (TLC, SiO2, hexane:toluene ) 1:1).
1,2-N-(tert-Butyloxycarbonyl)aziridino[60]fullerene (1c). Black
crystalline solid. FT-IR (KBr) 3440, 1739, 1254, 1147, 1095, 806,
cation of MS4A as described above, namely, that the cation
might function as a weak Lewis acid to promote the elimination
of the chloramine catalyst. To confirm the prediction, aziridi-
nofullerene 1a was treated with a typical Lewis acid: boron
trifluoride etherate. As a result, the quantitative addition of the
solvent (toluene) occurred smoothly even in the absence of a
chloramine salt (Scheme 10). This phenomenon is similar to
the case of fullerene epoxide,23 as reported by Tajima et al.,
and the result supported our hypothesis in that MS4A promotes
the elimination of chloramine as a very weak acid. In contrast
to the strong acidity of BF3 ·Et2O, which led to the complete
elimination of the nitrogen unit, the weaker acidity of MS4A
successfully enabled rearrangement to take place.
1
524 cm-1. H NMR (270 MHz, CDCl3) δ 1.70 (s, 9H). 13C NMR
(150 MHz, CDCl3:CS2 ) 2:1) δ 28.2, 81.3, 84.7, 139.9, 141.1,
142.2, 142.3, 142.8, 143.15, 143.16, 143.8, 144.0, 144.1, 144.5,
144.6, 144.78, 144.81, 145.1, 145.2, 154.8. UV-vis (CH2Cl2) λmax
422, 410, 325, 256, 229 nm. FAB-MS m/z 835 ([M]+). HR-MS
calcd for (C65H9NO2) 835.0668, found 835.0633. Rf 0.62 (TLC,
SiO2, hexane:toluene ) 1:1).
1,2-N-(n-Hexadecyloxycarbonyl)aziridino[60]fullerene (1d).
Black solid. FT-IR (KBr) 3427, 2920, 2848, 1745, 1462, 1228,
1
1095, 527 cm-1. H NMR (270 MHz, CDCl3) δ 0.88 (t, J ) 6.6
Conclusions
Hz, 3H), 1.19-1.54 (m, 26H), 1.84 (t, J ) 7.2 Hz, 2H), 4.51 (t, J
) 6.5 Hz, 2H). 13C NMR (68 MHz, CDCl3) δ 14.1, 22.7, 25.8,
28.8, 29.2, 29.3, 29.55, 29.58, 29.7, 31.9, 68.4, 80.7, 139.8, 140.9,
142.0, 142.6, 142.9, 143.0, 143.5, 143.8, 144.27, 144.32, 144.6,
144.7, 144.9, 145.0, 156.2. FAB-MS m/z 1003 ([M]+). UV-vis
(CH2Cl2) λmax 421, 409, 323, 256, 227 nm. HR-MS calcd for
(C77H33NO2) 1003.2511, found 1003.2502. Rf 0.65 (TLC, SiO2,
hexane:toluene ) 1:1).
A variety of simple amides are useful for the efficient ionic
aziridination of C60, and the resulting aziridinofullerenes are
rearranged to azafulleroids by the combination of a chloramine
catalyst and MS4A. Monochloroamides, which are key reagents
for the aziridination of C60, were easily synthesized by t-BuOCl
in methanol. In the present study, treatment of the chlorinated
amides with C60 in the presence of an organic base smoothly
gave the desired aziridinofullerene as a single isomer. The
aziridination pathway is deduced to be addition-cyclization.
The rearrangement of aziridinofullerenes to azafulleroid was
applicable to the broad aziridinofullerenes prepared by using
our original method, and was promoted by a chloramine catalyst
and by MS4A. In the rearrangement, MS4A functions as a weak
Lewis acid for the elimination of the catalyst. Thus far, the
introduction of a N1 unit to C60 by using organic azides has
been the only procedure for the general formation of aziridi-
nofullerenes and/or azafulleroids. This efficient and convenient
method for the introduction of a N1 unit to C60, including the
unique rearrangement, could be included among the general
methods for the synthesis of functionalized C60 derivatives.
1,2-N-(2-Ethylhexyloxycarbonyl)aziridino[60]fullerene (1e).
Black crystalline solid. FT-IR (KBr) 3442, 2921, 1743, 1654, 1403,
1
1226 cm-1. H NMR (270 MHz, CDCl3) δ 0.90 (t, J ) 7.0 Hz,
3H), 0.97 (t, J ) 7.4 Hz, 3H), 1.26-1.55 (m, 8H), 1.77-1.82 (m,
1H), 4.44 (dd, J ) 1.1 Hz, 5.7 Hz, 2H). 13C NMR (68 MHz, CDCl3)
δ 11.1, 14.1, 23.1, 23.9, 28.9, 30.4, 39.1, 70.6, 80.9, 140.1, 141.1,
142.3, 142.8, 143.20, 143.23, 143.80, 143.84, 144.0, 144.5, 144.6,
144.86, 144.90, 145.2, 145.3, 156.6. FAB-MS m/z 891 ([M]+).
UV-vis (CH2Cl2) λmax 325, 256, 227 nm. HR-MS calcd for
(C69H17NO2) 891.1259, found 891.1265. Rf 0.63 (TLC, SiO2,
hexane:toluene ) 1:1).
1,2-N-(N′,N′-Dimetylaminocarbonyl)aziridino[60]fullerene (1f).
Black crystalline solid. FT-IR (KBr) 3436, 2924, 2852, 1691, 1381,
1150, 527 cm-1. 1H NMR (270 MHz, CDCl3) δ 3.27 (s, 3H), 3.67
(s, 3H). 13C NMR (150 MHz, CDCl3:CS2 ) 2:1) δ 37.1, 37.3, 80.8,
140.5, 141.0, 142.2, 142.3, 142.9, 143.09, 143.10, 143.9, 144.1,
144.4, 144.6, 144.89, 144.93, 145.2, 145.3, 156.8. UV-vis (CH2Cl2)
λmax 423, 410, 324, 257, 228 nm. FAB-MS m/z 806 ([M]+). HR-
MS calcd for (C63H6N2O) 806.0480, found 806.0504. Rf 0.20 (TLC,
SiO2, toluene).
Experimental Section
General Procedure for the Synthesis of Aziridinofuller-
enes. A solution of amides (0.15 mmol) and t-BuOCl (16 mg, 0.15
mmol) was stirred in MeOH (1 mL) at room temperature for 2 h.
The solvent was then concentrated under vacuum and the residue
1,2-N-(N′,N′-Didodecylylaminocarbonyl)aziridino[60]fuller-
ene (1g). Black solid. FT-IR (KBr) 3448, 2922, 2850, 1689, 1462,
1
1417, 527 cm-1. H NMR (270 MHz, CDCl3) δ 0.85-0.88 (m,
(23) Tajima, Y.; Hara, T.; Honma, T.; Matsumoto, S.; Takeuchi, K. Org.
Lett. 2006, 8, 3203.
6H), 1.15-1.58 (m, 36H), 1.71 (m, 2H), 2.01 (m, 2H), 3.58 (t, J )
1696 J. Org. Chem. Vol. 74, No. 4, 2009

Aziridination of C60 with Simple Amides
7.3 Hz, 2H), 3.93 (t, J ) 7.6 Hz, 2H). 13C NMR (68 MHz, CDCl3)
δ 14.2, 22.7, 27.0, 27.1, 28.0, 28.5, 29.4, 29.4, 29.4, 29.6, 29.6,
29.7, 31.9, 47.5, 48.3, 80.7, 140.1, 140.7, 141.9, 142.0, 142.6,
142.79, 142.82, 143.6, 143.9, 144.3, 144.4, 144.6, 144.9, 145.0,
156.4. UV-vis (CH2Cl2) λmax 423, 325, 257, 228 nm. FAB-MS
m/z 1114 ([M]+). HR-MS calcd for (C85H50N2O) 1114.3923, found
1114.3904. Rf 0.38 (TLC, SiO2, hexane:toluene ) 1:1).
1,2-N-[{(S)-2-(Methoxycarbonyl)-1-pyrrolidino}carbonyl]-
aziridino[60]fullerene (1m). Black crystalline solid. FT-IR (KBr)
1
3448, 2924, 2852, 1743, 1687, 1388, 1184, 52 cm-17. H NMR
(270 MHz, CDCl3) δ 2.21-2.45 (m, 4H), 3.81 (s, 3H), 4.34-4.38
(m, 2H), 4.76 (dd, J ) 4.2, 8.2, 1H). 13C NMR (68 MHz, CDCl3)
δ 25.1, 29.7, 47.8, 52.5, 56.0, 80.5, 140.36, 140.39, 140.9,
142.05,142.11, 142.2, 142.7, 143.0, 143.7, 144.0 144.07, 144.11,
144.37, 144.43, 144.8, 145.0, 145.1, 155.3, 172.0. UV-vis (CH2Cl2)
λmax 421, 323, 256, 227 nm. FAB-MS m/z 840 ([M]+ + 1). HR-
MS calcd for (C67H5NO2) 839.0371, found 839.0391. Rf 0.20 (TLC,
SiO2, toluene:AcOEt ) 98:2).
1,2-N-Benzoylaziridino[60]fullerene (1h). Black crystalline
solid. FT-IR (KBr) 3436, 2923, 2856, 1699, 1645, 1392, 1259, 1176,
1089, 1033, 806, 700 cm-1 1H NMR (270 MHz, CDCl3) δ
.
7.73-7.63 (m, 3H), 8.55 (d, J ) 4.3 Hz, 2H). 13C NMR (68 MHz,
CDCl3) δ 81.0, 125.2, 128.1, 128.9, 129.1, 129.3, 130.9, 134.1,
140.0, 141.1, 142.0, 142.1, 142.7, 143.1, 143.5, 143.7, 144.0, 144.5,
144.8, 145.1, 145.2, 170.8. UV-vis (CH2Cl2) λmax 421, 410, 323,
257, 229 nm. FAB-MS m/z 840 ([M]+ + 1). HR-MS calcd for
(C67H5NO) 839.0371, found 839.0391. Rf 0.27 (TLC, SiO2, hexane:
toluene ) 1:1).
General Procedure for the Synthesis of Azafulleroids. In the
presence of 400 mg of MS4A, a solution of aziridinofullerenes (0.1
mmol) and ion-exchanged chloramine B8 (11 mg, 0.02 mmol) in
toluene (30 mL) was heated for the indicated times under reflux
and vigorous stirring. The solution was passed through a short
column of silica gel (3 g) and the solvent was then evaporated under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel to give corresponding azafulleroid 2 and C60.
1,6-N-(Benzyloxycarbonyl)aza[60]fulleroid (2b). Black crystal-
line solid. FT-IR (KBr) 3423, 2922, 2852, 1743, 1655, 1390, 1336,
1,2-N-(2-Picolylcarbonyl)aziridino[60]fullerene (1i). Black crys-
talline solid. FT-IR (KBr) 3448, 2924, 2852, 1653, 1637, 1585,
1
1429, 1086, 527 cm-1. H NMR (270 MHz, CDCl3:CS2 ) 2:1) δ
7.16-7.20 (m, 1H), 7.62-7.66 (m, 1H), 7.82-7.88 (m, 1H),
8.53-8.55 (m, 1H). 13C NMR (68 MHz, CDCl3:CS2 ) 2:1) δ 82.6,
115.8, 119.5, 137.7, 140.0, 140.7, 141.89, 141.93, 142.4, 142.5,
142.8, 143.5, 143.8, 144.2, 144.4, 144.5, 144.8, 144.9, 148.4, 157.2.
UV-vis (CH2Cl2) λmax 325, 258, 227 nm. HR-MS calcd for
(C66H4N2O) 840.0324, found 840.0300. Rf 0.40 (TLC, SiO2,
toluene).
1
987, 526 cm-1. H NMR (270 MHz, CDCl3) δ 5.77 (s, 2H), 7.48
(m, 3H), 7.65 (d, 2H). 13C NMR (68 MHz, CDCl3) δ 74.0, 128.0,
128.4, 128.6, 128.8, 134.5, 136.0, 138.1, 139.3, 140.1, 141.5, 141.8,
141.9, 142.1, 142.5, 142.6, 143.1, 143.5, 144.1, 144.4, 144.9, 145.0,
145.3, 145.6, 145.9, 146.1, 146.2, 147.7, 148.1, 148.3, 164.6.
UV-vis (CH2Cl2) λmax 316, 255, 228 nm. FAB-MS m/z 870 ([M]+
+ 1). HR-MS calcd for (C67H7NO2S) 869.0477, found 869.0579.
Rf 0.40 (TLC, SiO2, hexane:toluene ) 1:1).
1,2-N-(Diethoxyphosphino)aziridino[60]fullerene (1j). Black
crystalline solid. FT-IR (KBr) 3450, 2978, 1275, 1051, 1024, 968,
1
527 cm-1. H NMR (270 MHz, CDCl3) δ 1.51 (t, J ) 7.0, 3H),
1,6-N-(N′,N′-Dimetylaminocarbonyl)aza[60]fulleroid (2f).
Black crystalline solid. FT-IR (KBr) 3444, 1654, 1382, 1103, 972,
800 cm-1. 1H NMR (270 MHz, CDCl3:CS2 ) 2:1) δ 3.41 (s, 6H).
13C NMR (150 MHz, CDCl3:CS2 ) 2:1) δ 38.3, 135.7, 138.4, 139.3,
140.2, 141.8, 141.98, 142.03, 142.2, 142.2, 142.56, 142.58, 142.64,
142.7, 144.3, 144.66, 144.70, 145.0, 145.1, 145.4, 145.5, 145.6,
146.00, 146.03, 146.1, 146.3, 146.4, 147.8, 148.2, 150.4, 162.7.
UV-vis (CH2Cl2) λmax 316, 255, 228 nm. FAB-MS m/z 807 ([M]+
+ 1), 720 (C60). HR-MS calcd for (C63H6N2O) 806.0480, found
806.0465. Rf 0.10 (TLC, SiO2, toluene).
4.49 (q, J ) 7.0 Hz, 2H). 13C NMR (68 MHz, CDCl3) δ 16.5,
16.6, 65.0, 65.1, 78.4, 78.8, 140.6, 141.0, 141.8, 141.9, 142.5,
142.86, 142.91, 143.7, 143.8, 144.1, 144.3, 144.8, 144.90, 145.0,
145.1. UV-vis (CH2Cl2) λmax 421, 409, 324, 255, 227 nm. FAB-
MS m/z 872 ([M]+ + 1). HR-MS calcd for (C64H10NO3P) 871.0398,
found 871.0422. Rf 0.40 (TLC, SiO2, toluene:AcOEt ) 10:1).
1,2-N-(Diphenylphosphino)aziridino[60]fullerene (1k). Black
crystalline solid; FT-IR (KBr) 3444, 1635, 1431, 1381, 1223, 1117,
858, 831, 729, 696, 525 cm-1. 1H NMR (270 MHz, CDCl3) δ 7.63
(m, 6H), 8.31 (m, 4H). 13C NMR (150 MHz, CDCl3) δ 79.6, 79.6,
129.3, 129.4, 131.2, 132.1, 132.37, 132.43, 133.1, 133.2, 141.0,
141.6, 142.4, 143.0, 143.33, 143.34, 143.4, 144.2, 144.3, 144.7,
144.8, 145.1, 145.1, 145.4, 145.5, 145.86, 145.89. UV-vis (CH2Cl2)
λmax 423, 410, 325, 256, 228 nm. FAB-MS m/z 936 ([M]+ + 1).
HR-MS calcd for (C72H10NOP) 935.0500, found 935.0490. Rf 0.45
(TLC, SiO2, toluene:AcOEt ) 10:1).
1,6-N-(Diethoxyphosphino)aza[60]fulleroid (2j). Black crystal-
line solid. FT-IR (KBr) 3448, 2923, 2852, 1737, 1720, 1639, 1093,
1
526 cm-1. H NMR (270 MHz, CDCl3) δ 1.48 (t, 3H, J ) 7.0),
1.49 (t, 3H, J ) 7.0 Hz), 4.46 (m, 4H). 13C NMR (68 MHz, CDCl3)
δ 16.5, 16.6, 64.6, 64.7, 134.2, 134.3, 134.4, 136.7, 136.8, 137.6,
137.7, 138.4, 139.1, 139.7, 141.3, 141.9, 142.7, 142.8, 142.9, 143.1,
143.3, 143.4, 143.6, 143.9, 144.06, 144.14, 144.3, 144.4, 144.7,
146.4, 146.5, 147.3. UV-vis (CH2Cl2) λmax 328, 260, 228 nm. FAB-
MS m/z 872 ([M]+ + 1). HR-MS calcd for (C64H10NO3P) 871.0398,
found 871.0414. Rf 0.30 (TLC, SiO2, toluene:AcOEt ) 10:1).
1,2-N-(3-Trimethoxysilylpropyloxycarbonyl)aziridino[60]ful-
lerene (1l′). In the step of the chlorination of amide 4l in MeOH,
ethoxy groups on the silicon atom were exchanged with methoxy
groups. Because of high reactivity of the alkoxysilyl group toward
the surface of silica, isolation of this product by silica gel column
chromatography was very difficult (3% yield). FT-IR (KBr) 3425,
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Scientific Research from the Japan Society for
the Promotion of Science. One of the authors (R.T.) would like
to express his special thanks for The Global COE (center of
excellence) Program “Global Education and Research Center
for Bio-Environmental Chemistry” of Osaka University.
1
3203, 2924, 2854, 1741, 1425, 1230, 1093, 527 cm-1. H NMR
(270 MHz, CDCl3) δ 0.77-0.83 (m, 2H), 1.95-2.01 (m, 2H), 3.59
(s, 9H), 4.49 (t, J ) 6.6, 2H). 13C NMR (68 MHz, CDCl3) δ 5.3,
22.4, 50.6, 70.1, 80.7, 139.9, 140.9, 142.0, 142.6, 142.8, 142.94,
142.96, 143.5, 143.6, 143.8, 144.26, 144.33, 144.60, 144.64, 144.9,
145.0, 156.1. FAB-MS m/z 941 ([M]+). UV-vis (CH2Cl2) λmax 495,
421, 325, 255, 228 nm. HR-MS calcd for (C67H15NO5Si) 941.0719,
found 941.0743. Aziridinofullerene 1l was obtained without
exchanging the alkoxy groups by using EtOH in the step of the
Supporting Information Available: 1H and 13C NMR
spectra for all fullerene derivatives and experimental procedure
for the preparation of new amides and their characterization.
This material is available free of charge via the Internet at
http://pubs.acs.org.
1
chlorination of 4l. H NMR (270 MHz, CDCl3) δ 0.74-0.81 (m,
2H), 1.20-1.56 (m, 9H), 1.92-2.04 (m, 2H), 3.79-3.88 (m, 6H),
4.50 (t, J ) 6.9, 2H).
JO8025737
J. Org. Chem. Vol. 74, No. 4, 2009 1697