Synthesis of [60]fullerene-fused tetrahydronaphthalene and indane derivatives via a pathway switched by aluminum chloride

Article abstract of DOI:10.1021/ol202645z

The addition of aluminum chloride to the manganese acetate-mediated radical reaction of [60]fullerene with 2-arylmalonates, 2-benzylmalonates, and 2-arylcyanoacetates can switch the reaction pathway and affords a variety of structurally novel and scarce [

Full text of DOI:10.1021/ol202645z

ORGANIC
LETTERS
2
011
Vol. 13, No. 22
130–6133
Synthesis of [60]Fullerene-Fused
Tetrahydronaphthalene and
6
Indane Derivatives via a Pathway
Switched by Aluminum Chloride
†
Tong-Xin Liu, Fa-Bao Li, and Guan-Wu Wang*
†
,†,‡
Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of
Soft Matter Chemistry, and Department of Chemistry, University of Science and
Technology of China, Hefei, Anhui 230026, P. R. China, and State Key Laboratory of
Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, P. R. China
gwang@ustc.edu.cn
Received September 30, 2011
ABSTRACT
The addition of aluminum chloride to the manganese acetate-mediated radical reaction of [60]fullerene with 2-arylmalonates, 2-benzylmalonates,
and 2-arylcyanoacetates can switch the reaction pathway and affords a variety of structurally novel and scarce [60]fullerene-fused
tetrahydronaphthalene and indane derivatives. These products are formed probably through radical addition, followed by FriedelÀCrafts-type
annulation.
3
,4
4c
salts such as Mn(OAc) , Cu(OAc)2, Pb(OAc)4, and
4h
Due to immense potential applications of fullerenes in
1
medicinal chemistry, materials, and nanotechnology, a
3
5
Fe(ClO ) . Among them the Mn(OAc) -mediated reac-
4
3
3
number of chemical reactions to functionalize fullerenes
have been developed, and numerous fullerene products
with widely structural diversities have been prepared over
tion of C60 with substituted malonate esters in refluxing
chlorobenzene or toluene generated 1,4-adducts and 1,16-
4
a,b,5c
adducts of C .
We also revealed that replacing
Mn(OAc) with Fe(ClO ) altered the pathway for the
6
0
2
the past 20 years. Radical reactions are important tools in
organic synthetic chemistry. We have recently investigated
radical reactions of [60]fullerene (C ) mediated by metal
3
4 3
reaction of C60 with substituted malonate esters including
diethyl 2-benzylmalonate and diethyl 2-phenylmalonate
6
0
(
3) For a review, see: Wang, G.-W.; Li, F.-B. J. Nanosci. Nanotech-
†
‡
University of Science and Technology of China.
Lanzhou University.
nol. 2007, 7, 1162.
(4) (a) Zhang, T.-H.; Lu, P.; Wang, F.; Wang, G.-W. Org. Biomol.
Chem. 2003, 1, 4403. (b) Wang, G.-W.; Zhang, T.-H.; Cheng, X.; Wang,
F. Org. Biomol. Chem. 2004, 2, 1160. (c) Wang, G.-W.; Li, F.-B. Org.
Biomol. Chem. 2005, 3, 794. (d) Chen, Z.-X.; Wang, G.-W. J. Org. Chem.
2005, 70, 2380. (e) Cheng, X.; Wang, G.-W.; Murata, Y.; Komatsu, K.
Chin. Chem. Lett. 2005, 16, 1327. (f) Wang, G.-W.; Li, F.-B.; Zhang,
T.-H. Org. Lett. 2006, 8, 1355. (g) Wang, G.-W.; Yang, H.-T.; Miao,
C.-B.; Xu, Y.; Liu, F. Org. Biomol. Chem. 2006, 4, 2595. (h) Li, F.-B.;
Liu, T.-X.; Huang, Y.-S.; Wang, G.-W. J. Org. Chem. 2009, 74, 7743.
(i) Li, F.-B.; Zhu, S.-E.; Wang, G.-W. Chin. Sci. Bull. 2010, 55, 2909.
(j) Wang, G.-W.; Wang, C.-Z.; Zhu, S.-E.; Murata, Y. Chem. Commun.
2011, 47, 6111. (k) Wang, G.-W.; Wang, C.-Z.; Zou, J.-P. J. Org. Chem.
2011, 76, 6088.
(
1) (a) Prato, M. Top. Curr. Chem. 1999, 199, 173. (b) Nakamura, E.;
Isobe, H. Acc. Chem. Res. 2003, 36, 807.
2) For selected reviews, see: (a) Hirsch, A. Synthesis 1995, 895.
b) Thilgen, C.; Diederich, F. Chem. Rev. 2006, 106, 5049. For some
(
(
ꢀ
´
n-Domenech, A;
recent papers, see:(c) Filippone, S; Maroto, E. E.; Martı
Suarez, M.; Martın, N. Nat. Chem. 2009, 1, 578. (d) Tzirakis, M. D.;
Orfanopoulos, M. Angew. Chem., Int. Ed. 2010, 49, 5891. (e) Zhang, Q.;
Pankewitz, T.; Liu, S.; Klopper, W.; Gan, L. Angew. Chem., Int. Ed.
010, 49, 9935. (f) Wang, G.-W.; Liu, T.-X.; Jiao, M.; Wang, N.; Zhu,
S.-E; Chen, C.; Yang, S.; Bowles, F. L.; Beavers, C. M.; Olmstead, M. M.;
Mercado, B. Q.; Balch, A. L. Angew. Chem., Int. Ed. 2011, 50, 4658.
g) Halim, M.; Kennedy, R. D.; Suzuki, M.; Khan, S. I.; Diaconescu,
´
2
(
P. L.; Rubin, Y. J. Am. Chem. Soc. 2011, 133, 6841. (h) Zhang, Y.;
Matsuo, Y.; Li, C.-Z.; Tanaka, H.; Nakamura, E.J. Am. Chem. Soc. 2011,
(5) (a) Li, F.-B.; Liu, T.-X.; Wang, G.-W. J. Org. Chem. 2008, 73,
6417. (b) Li, F.-B.; Liu, T.-X.; You, X.; Wang, G.-W. Org. Lett. 2010, 12,
3258. (c) Li, F.-B.; You, X.; Wang, G.-W. Org. Lett. 2010, 12, 4896.
133, 8086. (i) Kurotobi, K.; Murata, Y. Science 2011, 333, 613.
1
0.1021/ol202645z r 2011 American Chemical Society
Published on Web 10/27/2011

5
and afforded disubstituted C -fused lactones. Herein,
c
6
0
we disclose that another type of products, i.e., C -fused
6
0
Table 1. Optimization of Reaction Conditions for the Mn-
OAc) -Mediated Reaction of C60 with 1a
tetrahydronaphthalene and indane derivatives, can be
obtained from the reaction of C60 with malonates and
cyanoacetates substituted with an aryl or a benzyl group
mediated by Mn(OAc) in combination with AlCl , via a
(
3
3
3
radical addition and aryl annulation sequence.
At the onset, the reaction of C with diethyl 2-benzylma-
60
lonate (1a) was performed in the presence of only Mn(OAc)3
in a molar ratio of 1:5:2 in o-dichlorobenzene (ODCB) and
under an argon atmosphere (Scheme 1). Disubstituted C -
molar
reaction
reaction Yield of
60
a
b
c
entry
ratio
oxidant
temp (°C)
time (h)
4a (%)
fused-lactone 2a and benzyl-substituted unsymmetrical 1,4-
adduct 3a could be isolated as major products albeit in low
yields, along with other unidentified minor byproducts. The
product distribution of 2a and 3a was highly dependent on
the reaction temperature. 1,4-Adduct 3a was the dominant
product when the reaction was conducted at 120 °C, whereas
the major product was lactone 2a at 140 °C. In comparison
with the Mn(OAc) -mediated reaction of C with diethyl
1
2
3
4
5
6
7
8
9
1:5:2:15
1:5:2:15
1:5:2:15
1:5:2:15
1:5:2:15
1:5:2:15
1:5:2:15
1:5:2:15
1:5:1:15
1:5:3:15
À
120
130
140
130
130
130
130
130
130
130
3
3
3
3
3
3
2
4
3
3
11 (42)
15 (48)
12 (60)
19 (90)
24 (65)
28 (85)
27 (68)
24 (60)
13 (68)
À
À
d
Cu(OAc)
2
d
Oxone
d
2 2 8
K S O
d
2 2 8
K S O
d
d
d
3
60
K S O
2
2
2
2
2
2
8
8
8
2-methylmalonate, the reaction with 1a gave an unsymme-
trical 1,4-adduct 3a instead of symmetrical 1,4- and/or 1,16-
K
K
S
S
O
O
e
10
30 (75)
adducts with a formula of C (CCH Ph(CO Et) ) besides a
2
a
b
60
2
2 2
Molar ratio refers to C60/1a/Mn(OAc)
3
2H
2
O/AlCl
3
.
Oil bath
3
c
similar C -fused lactone 2a. Reaction of 1a with Mn(OAc)
3
temperature. Isolated yield; that in parentheses was based on consumed
d e
C . 2 equiv of oxidant were employed. Recovered C60 was impure.
60
60
gave a CCH Ph(CO Et) radical, and subsequent addition
2
3
2
2
to C60 afforded a C (CCH Ph(CO Et) ) radical. Follow-
2
3
60
2
2
ing similar sequential processes as promoted by Fe(ClO )
4
3
5
c
provided lactone 2a. Coupling of the C (CCH Ph-
2
product yield and selectivity, and even to obtain a new
product by changing the reaction pathway. Olah and co-
workers described the formation of multihydroarylated
3
60
(CO Et) ) radical with the CH Ph radical generated in situ
2 2 2
from the CCH Ph(CO Et) species would give benzyl-
substituted unsymmetrical 1,4-adduct 3a.
3
3
2
2
2
fullerenes by the AlCl -mediated FriedelÀCrafts-type
3
6
a,b
reaction of C with benzene or toluene.
6
Later
0
Nakamura, Kokubo, and their co-workers systematically
investigated the FriedelÀCrafts-type reaction that selec-
tively produced a series of mono-, di-, and trihydroaryla-
3
Scheme 1. Mn(OAc) -Mediated Reaction of C60 with 1a Af-
fording C60-Fused Lactone 2a and 1,4-Adduct 3a
6
cÀe
tion of [60]fullerene.
AlCl -catalyzed acetylation of monohydroarylated [60]-
Kokubo’s group also reported the
3
6
e
fullerenes withacetyl chloride. Recently we disclosed that
the reaction of a C -fused 1,3-dioxolane with chloroben-
zene and 1,2-dichlorobenzene in the presence of AlCl
6
0
3
5
b
afforded the rare arylated 1,4-fullerenols. Intriguingly,
we discovered that the addition of AlCl (15 equiv) to the
3
Mn(OAc) -promoted reaction of C with diethyl 2-ben-
3
60
zylmalonate switched the reaction pathway and afforded
the aryl-annulated product 4a.
We found that AlCl played a crucial role on the
3
selectivity and product yield. For example, if 5 equiv of
AlCl were employed lactone 2a was also formed besides
3
4a. To achieve the selective formation of 4a, 15 equiv of
AlCl were necessary. Product 4a was obtained in 11%
3
yield when the reaction of C60 with 1a and Mn(OAc) in a
3
The poor results shown in Scheme 1 prompted us to
search for better conditions in order to improve the
molar ratio of 1:5:2 was allowed to proceed in an oil bath
preset at 120 °C for 3 h (Table1, entry 1). The presence or
absence of an inert atmosphere had a negligible effect on
the product yield. Consequently, the reaction was then
performed in open air. The yield was improved to 15% at
(
6) (a) Olah, G. A.; Bucsi, I.; Lambert, C.; Aniszfeld, R.; Trivedi,
N. J.; Sensharma, D. K.; Prakash, G. K. S. J. Am. Chem. Soc. 1991, 113,
387. (b) Olah, G. A.; Bucsi, I.; Ha, D. S.; Aniszfeld, R.; Lee, C. S.;
9
130 °C under otherwise the same conditions (Table1, entry 2).
Prakash, G. K. S. Fullerene Sci. Technol. 1997, 5, 389. (c) Iwashita, A.;
Matsuo, Y.; Nakamura, E. Angew. Chem., Int. Ed. 2007, 46, 3513.
However, the yield dropped to 12% if the reaction tem-
perature was further increased to 140 °C (Table1, entry 3 vs 2).
An oxidant was then added to examine if it had a beneficial
(d) Tochika, S.; Kato, M.; Kuang, C.; Kokubo, K.; Oshima, T. Abstracts of
the 31st Fullerene-Nanotubes General Symposium 2006, 62. (e) Kokubo, K.;
Tochika, S.; Kato, M.; Sol, Y.; Oshima, T. Org. Lett. 2008, 10, 3335.
Org. Lett., Vol. 13, No. 22, 2011
6131

AlCl . Therefore, AlCl was essential for the selective for-
3
3
mation of 2a. Acetonitrile was added as the cosolvent to
increase the solubility of the employed inorganic oxidant,
and it gave better results than THF, DMF, DMSO, and
CH CH OH. Therefore, the molar ratio of 1:5:2:2:15 for the
Table 2. Reaction Conditions and Yields for the Reaction of C60
with 2-Benzylmalonates/2-Arylmalonate/2-Arylcyanoacetates
in the Presence of Mn(OAc) and AlCl
3 3
a
3
2
reagents C , 1a, Mn(OAc) 2H O, K S O , and AlCl and
8
6
0
3
3
2
2 2
3
the reaction temperature of 130 °C in ODCB/CH CN were
3
chosen as the optimized reaction conditions.
With the optimized conditions in hand, the scope of the
present Mn(OAc) /AlCl -mediated reaction was extended
3
3
to other 2-benzylmalonates (1bÀ1d), 2-arylmalonates (1e),
and 2-arylcyanoacetates (1f and 1g). The reaction condi-
tions and yields are summarized in Table 2. The Mn(OAc)3/
AlCl -mediated reaction of C with 2-benzylmalonates
3
60
(
position of the phenyl ring could successfully produce C -
1bÀd) bearing a substituent at the para, meta, or ortho
6
0
fused tetrahydronaphthalenes 4bÀd in synthetically accep-
tableyields(Table2, entries1À3). When2-arylmalonate1e
and 2-arylcyanoacetates (1f and 1g) were used to replace
2
-benzylmalonates, C -fused indanes 4eÀg were obtained.
60
Compared with 1aÀd, 1eÀg displayed a lower reactivity
and required a higher temperature (140 °C) and longer
reaction time (4 h), yet generally gave lower yields prob-
ably because the in situ formed radical was delocalized to
the phenyl ring and, thus, retarded the radical addition to
C . The isolatedyields of 4aÀg wererelatively lowbecause
6
0
we stopped the reactions at an early stage to avoid the
formation of bisadducts and byproducts. In this way, we
could recover more C and achieve higher yields based on
6
0
consumed C .
6
0
Lactone 2a is a known product, and its identity was
confirmed by comparison of its spectral data with the
5
reported ones. The structures of 1,4-adduct 3a, C -fused
c
6
0
tetrahydronaphthalenes 4aÀd, and C -fused indanes
6
0
1
4
eÀg were fully established by their HRMS, H NMR,
13
C NMR, FT-IR, and UVÀvis spectra. All products exhib-
ited correct molecular weights in their high-resolution
mass spectra and the expected chemical shifts as well as
a
Unless otherwise indicated, all reactions were performed with a
2H O/K /AlCl = 1:5:2:2:15.
Oil bath temperature. Isolated yield; that in parentheses was based
1
the splitting patterns for all protons in their H NMR
molar ratio of C60/1/Mn(OAc)
3
2
2
S
2
O
8
3
3
13
spectra. The C NMR spectrum of 3a displayed 51 peaks
b
c
d
on consumed C60. The reaction was carried out in the absence of
with 6 overlapping ones in the 136À157 ppm range for the
acetonitrile.
2
8 sp -carbons of the C moiety, two peaks for the two
5
sp -carbons of the C skeleton at about 60 and 62 ppm,
6
0
3
6
0
effect on the product yield at the reaction temperature of
30 °C. Both Cu(OAc) and Oxone increased the yield to
and the signals for the CH Ph and C(CH Ph)(CO Et)
2 2 2 2
1
groups, fully consistent with its molecular structure with
C symmetry. The UVÀvis spectrum of 3a showed a broad
2
1
our delight, K S O could further enhance the yield to
9% and 24%, respectively (Table1, entries 4 and 5). To
1
peak at 445 nm, which is a characteristic absorption band
2
2
8
4
for a 1,4-adduct of C . There were at least 38 lines
2
8% (85% based on consumed C ) (Table1, entry 6).
0
6
60
Prolonging or shortening the reaction time gave inferior
results (Table1, entries 7 and 8). Decreasing the amount of
Mn(OAc) from 2 to 1 equiv significantly reduced the yield
including some overlapped ones in the range of 132À160
2 13
ppm for the 58 sp -carbons of the C cage in the C NMR
6
0
spectra of 4aÀg except for that of 4e, agreeing well with
3
to 13% (Table1, entry 9). Increasing the quantity of Mn-
(
their C molecular symmetry due to the nonplanar geo-
1
OAc) to 3 equiv only afforded a comparable product
3
metry of the annulated six-membered ring of 4aÀd or
nonequivalent ester and cyano substituents of 4f and 4g.
In contrast, 26 peaks with three overlapping and two half-
yield, yet more byproducts were formed and the recovered
C60 was contaminated by impurities (Table1, entry 10).
It should be noted that other Lewis acids such as BF were
2
intensity ones in the 134À154 pm range for the 58 sp -
3
also examined; both selectivity and yield were poorer than
those for AlCl under the same conditions. Product 2a could
carbons of the C skeleton and 2 peaks at ca. 74 and
6
0
3
75 ppm for the two sp -carbons of the C cage were observed
3
60
not be obtained in the presence of K S O without the aid of
2
for 4e, consistent with its C molecular symmetry.
s
2
8
6
132
Org. Lett., Vol. 13, No. 22, 2011

7
fullerenyl radical to the fullerenyl cation, hence altering
the reaction pathway. The plausible reaction mechanism
for the cascade formation of 4aÀg is shown in Scheme 2.
Scheme 2. Proposed Reaction Mechanism for the Formation of
aÀg
4
Radical 5 is formed via the reaction of 1 with Mn(OAc) .
3
Addition of radical 5 to C60 provides fullerenyl radical 6,
which is oxidized by another molecule of Mn(OAc) with
3
the assistance of AlCl togenerate fullerenylcarbocation7.
3
Intramolecular cyclization of carbocation 7 via the FriedelÀ
8
Crafts-type process affords aryl-annulated product 4.
K S O is a stronger oxidant than Mn(OAc) and facil-
2
2
8
3
itates the formation of intermediate 7, thus leading to a
higher product yield.
In summary, we have disclosed that the addition of
AlCl to the Mn(OAc) -mediated reaction of C with
3
3
60
active methylene compounds substituted with an aryl
or a benzyl group can switch the reaction mechanism
and selectively afford aryl-annulated products. The
intriguing formation of C -fused tetrahydronaphtha-
6
0
lene and indane derivatives is believed to proceed via
the Mn(OAc) -mediated radical addition, followed by
3
the FriedelÀCrafts-type annulation with the assistance
The reaction of C60 with 2-benzylmalonate 1a in the
presence of Mn(OAc) gave C -fused-lactone 2a and
unsymmetrical 1,4-adduct 3a. However, the addition of
of AlCl .
3
3
60
Acknowledgment. We are grateful for the financial
support from the National Natural Science Foundation
of China (21132007, 20972145, 91021004) and National
Basic Research Program of China (2011CB921402).
AlCl switched the reaction pathway and afforded aryl-
3
annulatedproduct4a. Theexact role playedbyAlCl isnot
3
clear right now. We suspect that AlCl helps to oxidize the
3
(
oxidation and reduction potentials, see: Hashiguchi, M.; Watanabe,
K.; Matsuo, Y. Org. Biomol. Chem. 2011, 9, 6417.
3
7) It was noted that coordination of C60 to FeCl may change
Supporting Information Available. Experimental pro-
cedures, spectral data, and NMR spectra of products 3a
and 4aÀg. This material is available free of charge via the
Internet at http://pubs.acs.org.
2
(8) A strong electron-withdrawing group such as NO on the phenyl
ring prohibited the cyclization process and instead afforded the corre-
sponding C60-fused lactone, thus supporting the proposed mechanism.
Org. Lett., Vol. 13, No. 22, 2011
6133