Cycloaddition of diazothioates to [60]fullerene

Article abstract of DOI:10.1016/j.tetlet.2012.04.017

The cycloaddition of diazothioates to fullerene C₆₀ has been investigated under thermal and catalytic conditions. The reaction between C ₆₀ and α-non-substituted diazothioates affords individual pyrazolino[60]fullerenes in contrast t

Full text of DOI:10.1016/j.tetlet.2012.04.017

Tetrahedron Letters 53 (2012) 3123–3125
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Cycloaddition of diazothioates to [60]fullerene
⇑
Airat R. Tuktarov , Artur A. Khuzin, Natal’ya R. Popod’ko, Usein M. Dzhemilev
Institute of Petrochemistry and Catalysis, Russian Academy of Sciences, 141 Prospekt Oktyabrya, Ufa 450075, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
The cycloaddition of diazothioates to fullerene C60 has been investigated under thermal and catalytic con-
Received 31 January 2012
Revised 23 March 2012
Accepted 4 April 2012
Available online 20 April 2012
ditions. The reaction between C60 and
no[60]fullerenes in contrast to 2-substituted diazothioates which give rise to [2+1] cycloadducts,
exclusively.
a-non-substituted diazothioates affords individual pyrazoli-
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Fullerene
Diazo compounds
Cycloaddition
Metal complex catalysis
Pyrazolinofullerenes
Homofullerenes
Methanofullerenes
Fulleropyrrolidines and methanofullerenes are considered to be
very promising classes of functionalized fullerenes, classically ob-
tained by the Prato1 and Bingel-Hirsch2 methods. These com-
pounds serve as the basis for creating high-performance solar
batteries as well as medications to treat human diseases.3–5 In
addition, methods based on cycloaddition of diazo compounds to
carbon clusters for the synthesis of fullerocyclopropanes have
found wide application in synthetic practice.
Possibilities to produce 5,6-open and 6,6-closed [2+1] cycload-
ducts, as well as pyrazolines through thermal reactions of C60 ful-
lerenes with diazo compounds make this method more attractive
synthetically. However, the main disadvantage of this reaction is
its low selectivity.6–8
Metal complex catalysts allow a reaction to proceed selectively
with predominant formation of individual compounds. Thus, palla-
dium- and rhodium-catalyzed reactions of C60 with diazometh-
ane,9,10 diazoalkanes,11–16 diazoacetates,17–20 diazoketones,21–23
and diazopyruvates8 lead to selective formation of the correspond-
ing fullerocyclopropanes as well as homo- or pyrazolinofullerenes
in high yields.
In order to optimize the conditions for the cycloaddition be-
tween diazothioates and C60, we examined the influence of temper-
ature, ratio of initial monomers, and concentration of the three-
component palladium catalyst Pd(acac)2–PPh3–Et3Al, previously
developed for analogous fullerene transformations,10–16,18–21 on
the yield and composition of the cycloadducts in the model reaction
of fullerene C60 with diazothioate 1.
We found that diazothioate 1 reacted readily with C60 (20 °C,
7 h, chlorobenzene)24 giving rise to [60]fullerene-fused pyrazoline
225 in 28% yield (Scheme 1). The yield of the target [3+2] cycload-
duct 2 remained the same at a higher reaction temperature (40 °C),
but in this case, the reaction occurred within 2 h. A longer reaction
time and higher temperature (4 h, 40 °C) led to cycloadduct 2 in
43% yield.
Previously10–16,18–21 we showed that homo- and methanofulle-
renes or pyrazolinofullerenes could be obtained selectively in the
reactions of C60 with diazo compounds while using a Pd-based
three-component catalyst. However, reaction between C60 fuller-
ene and 1 mediated by 20 mol % Pd(acac)2–PPh3–Et3Al (1:2:4 or
1:4:4 ratio) afforded pyrazoline 2, exclusively.
In continuation of our investigations on cycloadditions between
diazo compounds and fullerenes, and also for devising effective
syntheses of functionalized sulfur-containing fullerenes, we have
carried out thermal and catalytic reactions between C60 and diazo-
thioates. Diazo compounds synthesized from glycine, methionine
or alkyl mercaptans were selected as the starting diazothioates.
H
O
N
40 °C, 4 h
N
S
+
N2
S
C5H11 chlorobenzene
1
C5H11
O
2 (~43%)
⇑
Corresponding author. Tel./fax: +7 347 2842750.
E-mail addresses: tuktarovar@gmail.com, airat_1@mail.ru (A.R. Tuktarov).
Scheme 1. Thermal [2+3] cycloaddition of diazothioate 1 to [60]fullerene.
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.04.017

3124
A. R. Tuktarov et al. / Tetrahedron Letters 53 (2012) 3123–3125
S
Me
Cycloadduct 2 was isolated by semi-preparative HPLC and iden-
tified by means of MALDI TOF (negative ion reflector mode) using
elemental sulfur as the matrix. The mass spectrum of 2 contained
an intense molecular ion peak [M]ꢀ at m/z 892.080 (calcd 892.067),
which corresponds to that expected for the proposed structure.
The one- (1H, 13C) and two-dimensional (COSY, HSQC, HMBC)
NMR experiments also confirmed the presence of the pyrazoline
ring conjugated to the carbonyl group in compound 2. In the 13C
NMR spectrum of 2, we observed signals assigned to the amyl moi-
ety (dC 14.41, 22.81, 28.89, 29.74, 31.57) and the fullerene skeleton
(27 signals in the region between dC 140 and 148).
N2
+
S
Am
O
4
O
Me
S
S
Me
O
Am
S
S
Am
40 °C, 1 h
chlorobenzene
+
(48%)
The pyrazoline ring was manifested by three signals. Two (dC
88.69 and 98.30) were associated with the sp3 hybridized fullerene
carbons, and the third signal at dC 139.68 belonged to the carbon
atom which forms the C@N bond in the five-membered heterocy-
cle. In turn, the resonance signal at dC 183.80 was assigned to the
carbonyl group, thus providing evidence for the carbothioyl
moiety.
5
6
toluene
(100%)
80 °C, 4 h
S
Me
O
S
Am
A low field proton signal at dH (NH) 8.09 in the 1H NMR spec-
trum helped to characterize unambiguously the structure of com-
pound 2.
40 °C, 1 h
Pd(acac)2-PPh3-Et3Al
(1:2:4)
(54%)
It should be noted that such a stabilization effect due to the pyr-
azoline ring was observed previously,20,26 however, stable pyrazo-
lino[60]fullerenes have only been obtained via the reaction of C60
with diazoacetates.
7
Scheme 3. Thermal and catalytic cycloaddition of diazothioate 4 to [60]fullerene.
Upon refluxing in 1,2-dichlorobenzene in accord with the previ-
ously described methodology,9 pyrazolino[60]fullerene
2
was
The above reaction under catalytic conditions (40 °C, 1 h,
20 mol % Pd(acac)2–2PPh3–4Et3Al) afforded exclusively methano-
fullerene 7 in 54% yield. Stereoisomers 5 and 6 were identified
by analysis of the 13C and 1H signals belonging to the carbonyl
quantitatively converted into methanofullerene 3 (Scheme 2).27
According to MALDI TOF mass spectrometry with matrix S8-as-
sisted laser desorption of ions, compound 3 was characterized by
the intense molecular ion peak [M]+ at m/z 864.079 (calcd
864.061 for C67H12OS).
group and a-methylene groups at the bridging carbon atom.
Thus, shielding of the carbonyl carbon (dC 190.02) in the minor
isomer 5 relative to the major isomer 6 (dC 194.87) indicated the
location of this group above the plane of the fullerene six-mem-
bered ring in compound 5.28 Together with the carbonyl group,
The 1H and 13C NMR spectra of cycloadduct 3 contained signals
characteristic of the fullerene skeleton (dC 140ꢀ148) and the thi-
opentyl moiety being bound to the fullerene molecule via the car-
bonyl group (dC 188.98). The latter, in turn, is associated with the
cyclopropane fragment through the methine carbon (dC 46.36).
At the same time, signals attributable to the sp3-hybridized car-
bons of the fullerene skeleton at dC 71.98 and the methine proton
(dH 5.01) which correlated (HMBC) to the trans-arranged carbon
atoms of the C60 fullerene (dC 147.87), clearly indicated the forma-
tion of methanofullerene 3 with a cyclopropane fragment.
Previously,28 we showed that functionalized fullerenes synthe-
sized via catalytic cycloaddition between C60 and diazoacetate, de-
rived from methionine ethyl ester, could be employed as nano
transmission oil additives for heavy equipment.
In continuation of this work to extend the application of fuller-
ene cycloadditions, and in the quest for a new generation of oil
additives, we studied the reaction between C60 and diazothioate 4.
Under optimized conditions (40 °C, 1 h), a stereoisomeric mix-
ture of homofullerenes 5 and 629 (2:3 ratio) were obtained in
48% total yield (Scheme 3). Thermolysis30,31 (80 °C) of the same
mixture in toluene for 4 h gave methanofullerene 7,32 as a result
of isomerization of the 5,6-open fullerene adducts.
the
a-methylene group at the bridging carbon atom also under-
went anisotropic shielding (dC 37.77) in anti-isomer 6 versus the
syn-isomer 5 (dC 39.47). Similar proton shielding was observed in
the case of the
a-methylene group associated with the bridging
carbon (dH 2.71) in the 1H NMR spectra of anti-isomer 6 versus
the syn-isomer 5, where the methylene protons are less shielded
(dH 4.11).
The 13C NMR spectrum of compound 7, obtained from a mixture
of 5 and 6 under both thermal (80 °C, 4 h) and catalytic conditions,
contained 25 resonance signals in the fullerene region between dC
137 and 148, with three of them being twice as intense compared
to the others.
Two resonances at dC 56.03 and 75.97 attributable to the cyclo-
propane moiety indicated the presence of the plane of symmetry in
the fullerocyclopropane molecule 7.
The MALDI TOF mass spectrum of compound 7 exhibited an in-
tense molecular ion peak [M]ꢀ at m/z 938.065 (calcd 938.079)
which provided evidence for formation of the monocycloadduct
with the proposed structure.
Me
S
O
H
O
S
R
S
Me
40 oC, 1 h
H
N2
+
N
S
S
R
180 °C, 5 h
C5H11
Pd(acac)2-PPh3-Et3Al
(1:2:4)
N
S
1,2-dichlorobenzene,
100%
O
8−10
C5H11
O
3
2
8: R = i-Pr (~35%); 9: R = Cy (~52%); 10: R = Bn (~35%)
Scheme 2. Thermal isomerization of pyrazolinofullerene 2 to methanofullerene 3.
Scheme 4. Catalytic cycloaddition of diazothioates to [60]fullerene.

A. R. Tuktarov et al. / Tetrahedron Letters 53 (2012) 3123–3125
3125
color changed from light-yellow to light-brown. To the obtained catalyst,
fullerene C60 (0.0139 mmol) in 1,2-dichlorobenzene (1 mL) was added at
ꢁ20 °C and the solution became deep-green in color. The mixture was heated
to 40 °C, the diazo compound (0.0695 mmol) in 1,2-dichlorobenzene (1 mL)
was added dropwise over 2–3 min, and the mixture was stirred for 1 h at the
respective temperature. The reaction mixture was cooled to ꢁ20 °C, treated
with aqueous HCl. Toluene (7 mL) was added, and the organic layer passed
Similar results were obtained using iso-propyl-, cyclohexyl-,
and benzyl diazothioates (Scheme 4). In all experiments involving
the three-component catalyst Pd(acac)2–2PPh3–4Et3Al, the appro-
priate methanofullerenes 8–1033–35 were formed in moderate
yields.
The structures of cycloadducts 8–10 were established by means
of one- and two-dimensional NMR, IR, and UV spectroscopy as well
as MALDI TOF mass spectrometry.
We are currently, conducting research dealing with the anti-
wear and extreme pressure (EP) properties of transmission oils
containing the above-discussed compounds as effective additives.
In conclusion, we have described the thermal and catalytic
cycloaddition of diazothioates to C60 fullerene. It was established
that the reaction between C60 fullerene and diazothioates led to
the selective formation of methanofullerenes in the presence of a
palladium-based three-component catalyst and afforded a mixture
of stereoisomeric homofullerenes in the absence of catalyst.
through
a column containing a small amount of silica gel. The reaction
products and the starting fullerene C60 were separated by semi-preparative
HPLC, with toluene as the eluent.
25. S-Pentylcarbothioyl-1aH,20H-[1,2]pyrazolino[30,40:1,9](C60-Ih)-[5,6]fullerene (2):
IR: 525, 751, 841, 1023, 1181, 1429, 1456, 1644 cmꢀ1. UV (CHCl3), kmax, nm:
260, 328, 427. 1H NMR (400 MHz, CDCl3): d 0.98 (t, 3H, CH3, J = 6.8 Hz), 1.50 (m,
4H, 2CH2), 1.75 (m, 2H, CH2), 3.11 (t, 2H, CH2, J = 7.2 Hz), 8.09 (s, 1H, NH). 13C
NMR (100 MHz, CDCl3): d 14.41, 22.81, 28.89, 29.74, 31.57, 88.69, 98.30,
139.68, 140.34, 140.38, 141.92, 142.18, 142.25, 142.31, 142.37, 142.69, 142.80,
142.91, 143.08, 143.83, 144.00, 144.08, 144.37, 144.44, 145.22, 145.24, 145.57,
145.69, 145.98, 146.05, 146.25, 146.34, 147.12, 147.48, 147.65, 183.80. MALDI
TOF, m/z 892.080 [M]ꢀ (C67H12N2OS).
26. Wang, G.-W.; Li, Y.-J.; Peng, R.-F.; Liang, Z.-H.; Liu, Y.-C. Tetrahedron 2004, 60,
3921.
27]. 10-(S-Pentylcarbothioyl)-(C60-Ih)[5,6]fullero[20,30:1,9]cyclopropane (3): IR: 527,
577, 722, 748, 1021, 1182, 1431, 1456, 1685 cmꢀ1. UV (CHCl3), kmax, nm: 261,
329, 403, 424. 1H NMR (400 MHz, CDCl3): d 1.04 (t, 3H, CH3, J = 7.2 Hz), 1.40
(m, 4H, 2CH2), 1.83 (m, 2H, CH2), 3.22 (t, 2H, CH2, J = 7.2 Hz), 5.01 (s, 1H, CH).
13C NMR (100 MHz, CDCl3): d 14.59, 22.99, 29.83, 30.58, 31.63, 46.36, 71.98,
136.53, 140.76, 141.03, 141.33, 141.98, 142.18, 142.35, 142.49, 142.87,
143.06, 143.22, 143.44, 143.79, 144.07, 144.51, 144.71, 144.73, 145.12,
145.17, 145.25, 145.27, 145.32, 145.51, 145.63, 146.08, 147.87, 188.98.
MALDI TOF, m/z 864.079 [M]ꢀ (C67H12OS).
Acknowledgment
This work was supported financially by the FTP ‘Scientific and
pedagogical staff of innovative Russian’ (Grant No. P1218 and No.
14.740.11.0014).
28. Tuktarov, A. R.; Akhmetov, A. R.; Kirichenko, G. N.; Glazunova, V. I.; Khalilov, L.
M.; Dzhemilev, U. M. Russ. J. Appl. Chem. 2010, 83, 1238.
References and notes
29. Mixture of stereoisomers 5 and 6: 1H NMR (400 MHz, CDCl3): d 0.96 and 1.38
(both m, 6H, 2CH3), 1.56, 2.2, 2.5–3.2 (all m, 22H, 11CH2), 2.12 and 2.24 (both s,
6H, 2CH3S), 4.11 (m, 2H, CH2). 13C NMR (100 MHz, CDCl3): d 14.43 (2C), 22.82
(2C), 28.49, 29.54, 29.60, 30.79, 31.43, 31.53, 31.98, 32.03, 37.77, 39.47, 49.43
(2C), 133.71, 134.20, 134.61, 138.12, 139.14, 140.38, 141.67, 141.73, 142.13,
142.50, 142.56, 142.98, 143.45, 143.56, 143.74, 143.94, 144.04, 144.73, 144.82,
144.88, 145.16, 145.27, 145.60, 145.64, 146.32, 147.62, 154.04, 190.02, 194.87.
MALDI TOF, m/z 938.065 [M]ꢀ (C70H18OS2).
1. Prato, M.; Maggini, M.; Giacometti, C.; Scorrano, G.; Sandona, G.; Farnia, G.
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5. Cataldo, F.; DaRos, T. Medicinal Chemistry and Pharmacological Potential of
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32. 10-[200-(Methylthio)ethyl]-10-[S-pentylcarbothioyl]-(C60-Ih)[5,6]fullero[20,30:1,9]
cyclopropane (7). IR: 526, 562, 740, 1180, 1428, 1455, 1658 cmꢀ1. UV (CHCl3),
kmax
J = 6.8 Hz), 1.40–1.55 (m, 4H, 2CH2), 1.81 (m, 2H, CH2), 2.30 (s, 3H, CH3), 3.12 (t,
2H, CH2, J = 7.2 Hz), 3.23 (t, 2H, CH2, J = 7.2 Hz), 3.25 (t, 2H, CH2, J = 7.2 Hz). 13
, d 1.01 (t, 3H, CH3,
nm: 259, 328, 426. 1H NMR (400 MHz, CDCl3):
8. Roberti, M.; Natalini, B.; Andrisano, V.; Seraglia, R.; Gioiello, A.; Pellicciari, R.
Tetrahedron 2010, 66, 7329.
C
9. Smith, A. B., III; Strongin, R. M.; Brard, L.; Furst, G. T.; Romanov, W. J.; Owens, K.
G.; Goldschmidt, R. J.; King, R. C. J. Am. Chem. Soc. 1995, 117, 5492.
10. Tuktarov, A. R.; Korolev, V. V.; Khalilov, L. M.; Ibragimov, A. G.; Dzhemilev, U.
M. Russ. J. Org. Chem. 2009, 45, 1594.
11. Tuktarov, A. R.; Korolev, V. V.; Tulyabaev, A. R.; Yanybin, V. M.; Khalilov, L. M.;
Dzhemilev, U. M. Russ. Chem. Bull. 2010, 59, 977.
12. Tuktarov, A. R.; Korolev, V. V.; Sabirov, D. Sh.; Dzhemilev, U. M. Russ. J. Org.
Chem. 2011, 47, 41.
13. Dzhemilev, U. M.; Tuktarov, A. R.; Korolev, V. V.; Khalilov, L. M. Petrol. Chem.
2011, 51, 123.
NMR (100 MHz, CDCl3): d 14.32, 16.39, 22.64, 29.50, 30.41, 30.89, 31.29, 31.56,
56.03, 75.97, 137.60, 138.08, 140.97, 141.24, 142.10, 142.14, 142.19, 142.28,
142.93, 143.03, 143.13, 143.25, 143.72, 143.94, 144.37, 144.71, 144.88, 145.14,
145.24, 145.26, 145.29, 145.31, 145.60, 145.62, 147.51, 192.60. MALDI TOF, m/z
938.065 [M]ꢀ (C70H18OS2).
33. 10-[200-(Methylthio)ethyl]-10-[S-iso-propylcarbothioyl]-(C60-Ih)[5,6]fullero[20,30:
1,9]cyclopropane (8): IR: 526, 1022, 1186, 1428, 1461, 1632 cmꢀ1. UV (CHCl3),
kmax, nm: 259, 327, 423. 1H NMR (400 MHz, CDCl3): d 1.58 (d, 6H, 2CH3,
J = 7.2 Hz), 2.30 (s, 3H, CH3), 3.11 (t, 2H, CH2, J = 7.2 Hz), 3.23 (t, 2H, CH2,
J = 7.2 Hz), 3.98 (m, 1H, CH). 13C NMR (100 MHz, CDCl3): d 16.56, 23.17, 30.94,
31.72, 36.71, 56.12, 76.01, 137.59, 138.06, 140.98, 141.27, 142.11, 142.16,
142.22, 142.31, 142.94, 143.05, 143.15, 143.27, 143.73, 143.96, 144.38, 144.72,
144.89, 145.16, 145.24, 145.26, 145.30, 145.32, 145.61, 145.65, 147.61, 192.02.
MALDI TOF, m/z 910.023 [M]ꢀ (C68H14OS2).
14. Tuktarov, A. R.; Korolev, V. V.; Tulyabaev, A. R.; Popod’ko, N. R.; Khalilov, L. M.;
Dzhemilev, U. M. Tetrahedron Lett. 2011, 52, 834.
15. Tuktarov, A. R.; Khuzin, A. A.; Korolev, V. V.; Dzhemilev, U. M. Russ. J. Org. Chem.
2012, 48, 99.
34. 10-[200-(Methylthio)ethyl]-10-[S-cyclohexylcarbothioyl]-(C60-Ih)[5,6]fullero[20,30:
1,9]cyclopropane (9): IR: 525, 578, 735, 1028, 1182, 1428, 1675 cmꢀ1. UV
(CHCl3), kmax, nm: 260, 328, 426. 1H NMR (400 MHz, CDCl3): d 1.43 and 1.73 (m,
2H, CH2), 1.63-1.67 (m, 4H, 2CH2), 1.85 (m, 2H, CH2), 2.15 (m, 2H, CH2), 2.30 (s,
3H, CH3), 3.10 (t, 2H, CH2, J = 6.4 Hz), 3.24 (t, 2H, CH2, J = 6.4 Hz), 3.86 (m, 1H,
CH). 13C NMR (100 MHz, CDCl3): d 16.53, 26.60 (2C), 26.14, 30.92, 31.68, 33.39
(2C), 44.29, 56.19, 76.05, 137.57, 138.06, 140.96, 141.25, 142.11, 142.16,
142.21, 142.30, 142.93, 143.04, 143.14, 143.26, 143.73, 143.95, 144.36, 144.71,
144.89, 145.16, 145.23, 145.25, 145.29, 145.62, 145.66, 147.63, 192.50. MALDI
TOF, m/z 950.029 [M]ꢀ (C71H18OS2).
16. Tuktarov, A. R.; Akhmetov, A. R.; Korolev, V. V.; Khuzin, A. A.; Khasanova, L. L.;
Popod’ko, N. R.; Khalilov, L. M. Arkivoc 2011, viii, 54.
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20. Tuktarov, A. R.; Khuzina, L. L.; Dzhemilev, U. M. Russ. Chem. Bull. 2011, 60, 662.
21. Tuktarov, A. R.; Akhmetov, A. R.; Khalilov, L. M.; Dzhemilev, U. M. Russ. Chem.
Bull. 2010, 59, 611.
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23. Pellicciari, R.; Natalini, B.; Potolokova, T. V.; Marinozzi, M.; Nefedova, M. N.;
Peregudov, A. S.; Sokolov, V. I. Synth. Commun. 2003, 33, 903.
24. Catalytic cycloaddition of diazothioates to [60]fullerene (general procedure):
Pd(acac)2 (0.00278 mmol) in 1,2-dichlorobenzene (0.2 mL) and PPh3
(0.00556 mmol) in 1,2-dichlorobenzene (0.21 mL) were loaded into a glass
reactor. The mixture was cooled to ꢀ5–0 °C. Et3Al (0.01112 mmol) in toluene
(0.1 mL) was added under a dry argon current and on stirring the mixture, the
35. 10-[200-(Methylthio)ethyl]-10-[S-benzylcarbothioyl]-(C60-Ih)[5,6]fullero[20,30:1,9]
cyclopropane (10): IR: 526, 699, 750, 1033, 1186, 1430, 1453, 1678 cmꢀ1. UV
(CHCl3), kmax, nm: 261, 329, 423. 1H NMR (400 MHz, CDCl3): d 2.21 (s, 3H, CH3),
3.02 (t, 2H, CH2, J = 7.2 Hz), 3.18 (t, 2H, CH2, J = 7.2 Hz), 4.45 (s, 2H, CH2), 7.28-
7.40 (m, 5H, 5CH). 13C NMR (100 MHz, CDCl3): d 16.41, 30.83, 31.53, 34.73,
55.71, 75.86, 127.88, 128.88 (2C), 129.17 (2C), 136.87, 137.64, 138.11, 140.98,
141.26, 142.08, 142.12, 142.20, 142.29, 142.94, 143.03, 143.14, 143.18, 143.26,
143.72, 143.95, 144.38, 144.72, 144.85, 144.89, 145.10, 145.24, 145.26, 145.30,
145.52, 145.56, 147.27, 191.95. MALDI TOF, m/z 958.001 [M]ꢀ (C72H14OS2).