Thermal and microwave assisted reactions of 2,5-disubstituted thienosultines with [60]fullerene: Non-Kekulé biradicals and self-sensitized oxygenation of the cycloadduct

Article abstract of DOI:10.1016/j.tet.2004.09.040

Refluxing an o-dichlorobenzene solution of 2,5-disubstituted thienosultines 10a-f with [60]fullerene for 2-24 h gave both 1:1 and 2:1 cycloadducts in 37-79% isolated yields. The reaction was highly accelerated by microwave irradiation giving comparable yields of cycloadducts. Sultines 10a-f underwent cheletropic extrusion of SO₂ to form the corresponding non-Kekulé biradical intermediates 11a-f, which were subsequently trapped by [60]fullerene to form corresponding cycloadducts. The activation energy barriers (ΔG_c^≠) determined for the boat-to-boat inversion of these 4′,5′,6′,7′-tetrahydrobenzo[c]thieno- [5′,6′:1,2][60]fullerene adducts 12a-f were found to be in the range of 13.5-14.8 kcal/mol. Unexpectedly, one of the monoadduct 12a was found to be labile when kept in air under ambient light. Two new products 15 (a sulfine-enone) and 16 (an endione) were isolated from the decomposed 12a and were found to derive from self-sensitized singlet oxygen reaction on the 2,5-dimethylthieno moiety of 12a.

Full text of DOI:10.1016/j.tet.2004.09.040

Tetrahedron 60 (2004) 10869–10876
Thermal and microwave assisted reactions of 2,5-disubstituted
´
thienosultines with [60]fullerene: non-Kekule biradicals and
self-sensitized oxygenation of the cycloadduct
*
Chih-Chin Chi, I-Feng Pai and Wen-Sheng Chung
Department of Applied Chemistry, National Chiao Tung University, 1001 Ta-Hseuh Rd., Hsinchu 30050, Taiwan, ROC
Received 21 July 2004; revised 13 September 2004; accepted 15 September 2004
Available online 1 October 2004
Abstract—Refluxing an o-dichlorobenzene solution of 2,5-disubstituted thienosultines 10a–f with [60]fullerene for 2–24 h gave both 1:1
and 2:1 cycloadducts in 37–79% isolated yields. The reaction was highly accelerated by microwave irradiation giving comparable yields of
´
cycloadducts. Sultines 10a–f underwent cheletropic extrusion of SO2 to form the corresponding non-Kekule biradical intermediates 11a–f,
which were subsequently trapped by [60]fullerene to form corresponding cycloadducts. The activation energy barriers (DGsc ) determined for
the boat-to-boat inversion of these 40,50,60,70-tetrahydrobenzo[c]thieno-[50,60:1,2][60]fullerene adducts 12a–f were found to be in the range
of 13.5–14.8 kcal/mol. Unexpectedly, one of the monoadduct 12a was found to be labile when kept in air under ambient light. Two new
products 15 (a sulfine-enone) and 16 (an endione) were isolated from the decomposed 12a and were found to derive from self-sensitized
singlet oxygen reaction on the 2,5-dimethylthieno moiety of 12a.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
reasonably low temperatures and yet they are usually stable
indefinitely at room temperature.
Functionalization of [60]fullerene is fascinating and prom-
ising for new ferromagnetic materials and biological
application because of its unique spherical structure,
photochemistry, and radical quenching properties.1 The
Diels–Alder reaction of [60]fullerene with ortho-quinodi-
methanes (o-QDMs)2 has been developed extensively and
represents one of the most powerful methods for synthesiz-
ing a large variety of functionalized fullerenes.1,2 o-QDM is
usually obtained from thermal or photochemical elimination
of a small molecule from various precursors shown in
Scheme 1.2
Despite many reports of using hetero-o-QDM to functiona-
lize [60]fullerene,1,7 relatively little is known about whether
8
the non-Kekule biradicals such as trimethylenemethane
´
(TMM) or tetramethyleneethane (TME) will add to [60]full-
erene efficiently. A pioneering work on the cycloaddition of
TMM with C60 has been reported by Wudl,9a where the TMM
biradical was generated from a 7-alkylidene-2,3-diazabicy-
cloheptene, but the cycloadduct of the TMM-C60 was not
isolated due to its similar polarity with C60.9a Palladium-
mediated addition of TMM to C60 has also been successfully
carried out by Luh.9b Meanwhile, Ohno et al. reported9c the
first success in using TME biradical to functionalize C60,
where 3,4-fused pyrrolo-3-sulfolenes were used as TME
precursors. As our continuous interests in the research of
The diazene 1 can form o-QDM cleanly, but its five-
membered ring heterocyclic analogues are usually unstable
at room temperature.3 Isochromanone 2 will undergo
thermal decarboxylation only under harsh conditions (such
as flash vacuum pyrolysis at 500 8C) unless it is substituted
with electron-donating groups on the aromatic moiety.4
Among the precursors for o-QDM, sulfolene5 3 and sultine6
4 are good choices because they undergo pyrolysis at
´
Keywords: Non-Kekule biradical; TME biradical; Microwave; Cycloaddi-
tion; [60]Fullerene; Singlet oxygen reaction.
* Corresponding author. Tel.: C88 635131517; fax: C88 635723764;
e-mail: wschung@cc.nctu.edu.tw
Scheme 1.
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.09.040

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C.-C. Chi et al. / Tetrahedron 60 (2004) 10869–10876
heteroaromatic-fused sultines 5 and their use in the
generation of TME biradicals10a,e or hetero-o-QDMs,10b–d
we report here the reaction of C60 with 2,5-disubstituted-
thienosultines 10a–f and an interesting self-sensitized singlet
oxygen reaction of one of the fullerene adducts.
Table 1). When solutions of sultines 10a–f with C60 were
irradiated with microwave (900 W) under 180 8C for only
4 min, comparable yields of cycloadducts were obtained in
all cases except 10b; where sultine 10b was almost
completely converted to sulfolene instead of reacting with
the C60, therefore, only trace of adduct 12b was observed.
The isolated yields for these cycloadducts 12 and 13 were in
the range of 37–79% (58–96% based on consumed C60,
Table 1). It is remarkable that microwave assisted synthesis
dramatically shortened the reaction time needed compared
to those by conventional heating.13d Furthermore, the ratio
of monoadduct 12 vs. bisadduct 13 also increased from
2–3:1 to 3.5–6:1 when microwave was applied.
2. Results and discussion
All fullerene adducts were separated by column chroma-
tography on silica gel using cyclohexane/toluene as eluents.
The low product yield for sultine 10b was mainly due to its
poor reactivity because there was no solubility problem. The
bisadducts 13a–f are mixtures of regioisomers and are
usually difficult to be separated; therefore, their character-
izations were only done by FAB-MS and 1H NMR
spectroscopy. The UV–vis spectra of compounds 12a–f
revealed a typical weak absorption band around 435 nm,
which is characteristic of a dihydrofullerene structure for
monoadduct.1 Further support of the monoadducts 12a–f
came from FAB-MS by detecting their molecular ion peaks
(MCHC) at following m/z ratios: 859 for 12a, 899 for 12b,
921 for 12c, 983 for 12d, 921 for 12e, and 1047 for 12f.
The syntheses of heterocyclic sultines 10a–d through the
reaction of corresponding bis(chloromethyl)thiophenes with
Rongalite (sodium formaldehyde sulfoxylate) have been
reported elsewhere.10a,e Sultines 10e and 10f were syn-
thesized from 8 and 9 by a similar method, where the
dialkylthio 8 and diarylthio 9 were obtained from lithium
exchange of 2,5-dibromothiophene,11 followed by thiola-
tion, and then chloromethylation3a,12 (Scheme 2). When
refluxed in o-dichlorobenzene (ODCB) with C60 as a
limiting reagent for different duration (2 h for 10a,c–f and
24 h for 10b), sultines 10a–f underwent extrusion of SO2,
´
and the resulting non-Kekule biradicals 11a–f were
intercepted as a mixture of 1:1 cycloadducts 12a–f and
2:1 bisadducts 13a–f in ca. 2–3:1 ratio (Scheme 3 and
1H NMR spectra for 12a showed that the methylene protons
bridging C60 and thiophene displayed a singlet (d 4.43) at
25 8C and the singlet became a well-resolved AB quartet
below 5 8C. Variable-temperature NMR experiments
revealed that these cycloadducts were in their boat forms
and the boat-to-boat inversion rates can be determined. The
coalescence temperature Tc of the two methylene doublets
and their coupling constants were used to determine the
activation energy barriers DGsc .10c,13,14 For 12a, the two
doublets coalesced to a broadened singlet at 291 K (Tc) and
an activation energy, DGsc , of 14.0G0.2 kcal/mol was
calculated (Fig. 1a). Although different Tc values are
expected for the two diastereotopic methylenes of 12c due
to molecular asymmetry, they happen to have same Tc
values (290 K) and therefore have same activation energy
barriers DGsc (Fig. 1b). Furthermore, despite the large
variation in 2,5-disubstituents of 12a–f (such as dimethyl,
dichloro, diphenyl, bis(methylthio), and bis(phenylthio)
groups), their DGsc are all within 13.5–14.8 kcal/mol
Scheme 2. Reagents and conditions: (a) 2.1 equiv nBuLi, THF, K78 8C,
30 min; 2.1 equiv RSSR, K78 8C, 1 h; (b) 37% HCHO, conc. HCl, rt, 8 h
(for 8); (c) ClCH2OCH3, ZnCl2, CHCl3, rt, 3 h (for 9); (d) Rongalite,
TBAB, DMF, rt, 10–24 h.
Scheme 3.

C.-C. Chi et al. / Tetrahedron 60 (2004) 10869–10876
10871
Table 1. Results of the cycloaddition reactions of sultines 10a–f with C60 under microwave irradiation or conventional heating
Sultine
Microwavea, yield (%)
Monoadduct 12
47 (64)c
Conventional heatingb, yield (%)
Time (min)
Bisadduct 13
Time (h)
Monoadduct 12
Bisadduct 13
10a
10b
10c
10d
10e
10f
4
4
4
4
4
4
11 (15)c
2
24
2
2
2
38 (73)c
28 (44)c
47 (62)c
52 (65)c
52 (62)c
51 (63)c
12 (23)c
9 (14)c
d
d
—
—
39 (64)c
53 (81)c
41 (52)c
51 (76)c
16 (20)c
20 (25)c
27 (32)c
27 (33)c
e
—
9 (14)c
10 (13)c
15 (22)c
2
a Power 900 W, ODCB, 180 8C.
b ODCB, reflux.
c Based on consumed C60
.
d Sultine 10b was completely converted to sulfolene without reacting with C60
.
e Trace.
(Table 2 and Figs. S1–S4). Compared to other 4,7-
dihydrobenzo[d]thiophene-[5,6-f]-fullerene adducts such
as 14a and 14b,13b these 4,7-dihydrobenzo[c]thiophene-
[5,6-e]-fullerene adducts 12a–f have larger DGsc by
2.8 kcal/mol on average.
above Tc), where rapid ring inversion is expected and the
symmetry of the molecule is simplified from Cs to C2v,
therefore, an overall of 21 peaks are expected. The 13C
NMR spectrum for 12a showed the characteristic quaternary
sp3-carbon atoms of the 6,6-ring junction on the C60 cage at
d 66.9, the a-methyls of thiophene at d 13.3, and the
methylene bridges between thiophene and C60 at d 41.4.
There are 17 other peaks of quaternary sp2 carbons between
134 and 158 ppm for compound 12a. All spectroscopic
features of 12a–f are consistent with the monoadducts of
thienobiradicals 11a–f that add to C60 on its 6,6-ring
junction. Complete spectroscopic data of 12a–f are
summarized in Section 3.
The activation energy barriers of compounds 12a–f are
close to those of pyrazines10c and other carbocyclic fused
[60]fullerenes.14 Factors that may affect the activation
energy barriers are dependent on the nature of the
heterocyclic systems, such as bond lengths and angles,7k,13b
tortional and angular constraints,13b electronic and steric
effects.10c Bond order may have played an important role
here on the magnitude of DGsc , because 12a–f which
contain two exocyclic double bonds in the bridged
cyclohexene ring have larger values in DGsc , whereas
compounds 14a,b with an endo double bond character in the
cyclohexene rings have smaller ones.7f,13b,c This obser-
vation is consistent with that reported by Illescas et al.7f
where a correlation was found between the activation
energies DGsc and the bond lengths of the cyclohexene
double bond across the fullerene junction; that is, as the
bond length increases the barrier also increases.
Research on the oxygenation15–19 of fullerene derivatives
has attracted considerable attention because it provides an
excellent method for ring-opening of the fullerene cage.1,19
Many oxidizing reagents, such as ozone,15 iodosobenzene,16
and m-CPBA,18 have been employed to prepare fullerene
oxides. Above all, photo-induced ring opening of [60]full-
erene cage by reaction with singlet oxygen (1O2) seems to
have drawn the most attention.19 We were surprised to find
that, short exposure of a non-degassed solution of 12a in
CS2 to ambient light led to its quick decomposition, where
two new products 15 and 16 (in about 1:2 ratio) could be
isolated from this solution in 50–73% yields. Compound
The 13C NMR spectrum of 12a showed only 20 peaks (with
two peaks superimposed) when measured at 70 8C (well
Figure 1. Various temperature 1H NMR spectra (600 MHz, CDCl3/CS2Z1:2) of cycloadducts: (a) 12a, for which Tc is 291 K; and (b) 12c, for which both the
two Tc values are 290 K.

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C.-C. Chi et al. / Tetrahedron 60 (2004) 10869–10876
Table 2. Activation free energies (DGsc ) of [60]fullerene adducts 12a–f from dynamic 1H NMRa studies
Thienoadduct (substituents)
Tc (K)
Dn (Hz)b
JAB (Hz)b
DGsc (kcal/mol)
Reference
12ac (2,5-Dimethyl)
12bd (2,5-Dichloro)
291
286
290
290
304
298
298
53.8
95.6
48.7
42.6
59.1
120.9
152.3
14.0
14.1
14.1
14.0
14.1
14.5
14.4
14.0G0.2
13.5G0.2
14.2G0.2
14.2G0.2
14.8G0.2
14.6G0.2
14.0G0.2
This work
This work
This work
This work
This work
This work
This work
12cc (2-Methyl-5-phenyl)
12dc (2,5-Diphenyl)
12ec (2,5-Bis(methlthio))
12fc (2,5-Bis(phenylthio))
245
26.2
14.7
12.0G0.2
13b
14a
241
223
14.8
51.0
13.9
15.4
11.9G0.2
10.7G0.2
13b
13b
14b
231
86.7
15.4
11.0G0.2
13b
a Various temperature measurements were taken in a 600 MHz NMR (12e in a 500 MHz NMR). The activation free energies were obtained using equation:
kcZ2.22 (Dn2ABC6JA2 B 1/2, DGsc Z4.58 Tc (10.32Clog (Tc/kc))!10K3 kcal/mol.
)
b Data are reported at the highest temperature that affords well-separated quartet: K10 8C for 12a, K15 8C for 12b, 7 8C for 12c, 20 8C for 12d, K5 8C for 12e,
and 0 8C for 12f.
c In CDCl3/CS2Z1:2.
d In d4-ortho-dichlorobenzene.
12a was found to be stable if either oxygen or light was kept
from the system.
several months in air with ambient light. There are two
possibilities from the experimental results: (a) singlet
oxygen was not formed in the solution of 12b–f; therefore,
they are stable in air and ambient light, or (b) singlet oxygen
did form, however, the other cycloadducts 12b–f, with
different 2.5-substituents, simply did not react with it. We
thus carried out two series of experiments to clarify possible
reasons for the big differences in singlet oxygen reactivity
towards 12a and 12b–f. In the first series of experiments, we
found that adding 2,5-dimethylthiophene to the solution of
other fullerene derivatives (e.g., 12d) did result in the
photoinduced oxygenation of 2,5-dimethylthiophene (entry
The new product 15 shows a molecular ion peak (MCHC)
at m/zZ891, which is 32 units more than the cycloadduct
12a. Furthermore, FT-IR spectrum of 15 shows medium
signals at 1700 and 1529 cmK1. Compound 16 shows strong
vibrations at 1685, 1636 and 1617 cmK1 (Fig. S5, Support-
ing Information), but its molecular ion peak is the same with
12a (m/zZ859). The 13C NMR of compound 15 shows the
characteristic absorption of two carbonyl carbons at 197.7
(C]O) and 193.0 ppm (C]S/O) as well as two
quaternary carbons of C60 moiety at 65.8 and 65.5 ppm.
Compound 16 shows the characteristic absorption of only
one carbonyl carbon at 200.6 ppm and one quaternary
carbon of C60 moiety at 65.3 ppm.
Based on all structural information available for 15 and 16
and literature precedents,19–21 we speculated that singlet
oxygen reaction must have occurred on the thiophene
moiety first and forming an endoperoxide 17. Subsequent
rearrangement of the endoperoxide 17 should lead to two
fullerene products: one, an asymmetrical sulfine-enone 15,
and the other, a symmetrical endione 16 (see Scheme 4).
Similar reactions have been reported in the methylene blue
sensitized singlet oxygen reactions of cyclohexenone-fused
thiophenes20b,c and 2,5-dimethylthiophene.21 All spectro-
scopic data for 15 and 16 are consistent with the proposed
structures.
It should be noted that other thienoadducts, such as 2,5-
dichloro-, diphenyl-, bis(methylthio)-, bis(phenylthio)-, and
2-methyl-5-phenylthienofullerenes 12b–f, are free from the
singlet oxygen induced reaction and can be stored for
Scheme 4.

C.-C. Chi et al. / Tetrahedron 60 (2004) 10869–10876
10873
3 in Table 3 of Supporting Information). The results suggest
that singlet oxygen is formed in all solutions of fullerene
adducts 12a–f and yet it reacts with them in very different
rates.22 In the second series of experiments, we prepared
d-chloroform solutions of various 2,5-disubstituted thio-
phenes (A–F) with C60 (1.5 mol %) as a singlet oxygen
sensitizer and irradiated them simultaneously with tungsten
lamp to make sure that they were exposed to the same
doses of light. The relative reactivity of singlet oxygen
towards these 2,5-disubstituted thiophenes are: 2,5-
dimethylthiophene A (37%), 2,5-bis(methylthio)thiophene
E (26%), 2-methyl-5-phenylthiophene C (!6%) (Table 3,
Supporting Information).21c The rest of the other 2,5-
disubstituted-thiophenes (B, D, and F) did not show any
observable reactivity toward singlet oxygen (namely !1%
conversion) even after 42 h irradiation by tungsten lamp.
(5.00 g, 20.7 mmol) was allowed to react with n-butyl-
lithium (2.5 M in hexane, 43.4 mmol), and then with
diphenyl disulfide (9.48 g, 43.4 mmol). The crude product
was purified by column chromatography (hexane) to give
5.79 g (19.3 mmol, 93%) of 7 as a colorless solid: mp 42–
1
43 8C (hexane); RfZ0.33 (hexane); H NMR (300 MHz,
CDCl3) d 7.30–7.18 (10H, m), 7.16 (2H, s); 13C NMR
(75.4 MHz, CDCl3) d 137.4 (Cq), 136.9 (Cq), 135.5 (CH),
129.1 (CH), 128.1 (CH), 126.7 (CH); MS (EI) m/z 303/302/
301/300 (MC, 3/16/24/100), 299 (MCK1, 23), 190 (78);
HRMS m/z calcd for C16H12S3 300.0103, found 300.0096;
Anal. Calcd for C16H12S3: C, 63.96; H, 4.03. Found: C,
63.73; H, 4.17.
3.1.3. 3,4-Bis(chloromethyl)-2,5-bis(methyl)thiophene
8.12 Concentrate hydrochloric acid (12 M, 20 mL) was
added to the mixture of 6 (2.00 g, 11.3 mmol) and 37%
formaldehyde aqueous solution (1.70 g, 56.7 mmol). The
mixture was stirred at room temperature for 8 h, then poured
into water (30 mL), and extracted with CH2Cl2 (3!20 mL).
The organic layers were combined, washed with water
(2!30 mL), brine, dried over MgSO4, filtered, and
concentrated in vacuum to yield 2.71 g (9.92 mmol, 87%)
of 8 as a pale green solid. Product 8 decomposed after
chromatography on silica gel; therefore, crude product was
used without further purification. Mp 75.5–77 8C (a color-
less solid after recrystallization from hexane). (lit.23
78–78.5 8C); RfZ0.75 (hexane/ethyl acetateZ4:1); 1H
NMR (300 MHz, CDCl3) d 4.77 (4H, s), 2.47 (6H, s); 13C
NMR (75.4 MHz, CDCl3) d 139.2 (Cq), 138.9 (Cq), 37.2
(CH2), 21.7 (CH3); MS (EI) m/z 276/275/274/273 (MC, 7/6/
In summary, we report here the syntheses of a series of
thieno-fused fullerenes which represents one of the rare
examples in the derivatization of [60]fullerene through
9
´
TME non-Kekule biradicals. When ODCB solutions of
sultines 10a–f and C60 were refluxed for 2–24 h or under
microwave irradiation (900 W, !180 8C) for only 4 min,
moderate to good yields (37–79%) of cycloadducts 12a–f
were obtained in all cases except 10b. To our surprise, of the
six thieno-[60]fullerene adducts 12a–f, only 12a was
unstable in the presence of oxygen and ambient light. The
decomposed products from 12a were characterized and
found to derive from singlet oxygen reaction on the 2,5-
dimethylthiophene moiety of 12a. Why some of the
fullerene derivatives attract oxygen on standing, while
others resist oxidation, deserves further photophysical and
theoretical calculation study.
30/15), 272 (MCK1, 61), 239 (30), 237 (MCKCl, 100),
35
186 (38), 69 (57); HRMS m/z calcd for C8H Cl2S3
271.9324, found 271.9318.
10
3. Experimental
3.1. General
3.1.4.
5,7-Bis(methylthio)-1,4-dihydro-1HK3l4-
thieno[3,4-d][2,3]oxathiin-3-oxide, sultine 10e. A solution
of 8 (2.86 g, 10.5 mmol), Rongalite (3.33 g, 20.9 mmol),
and TBAB (1.71 g, 5.24 mmol) in DMF (50 mL) was stirred
at room temperature for 24 h. The mixture was diluted with
H2O (40 mL) and extracted with CH2Cl2 (3!20 mL). The
organic layer was dried over MgSO4, concentrated, and
purified by column chromatography (6:1 hexane/ethyl
acetate) to give 0.68 g (2.55 mmol, 24%) of 10e, as a
white solid after recrystallization from a solvent of CH2Cl2
and hexane: mp 71–73 8C (CH2Cl2/hexane); RfZ0.45
3.1.1. 2,5-Bis(methylthio)thiophene 6. The preparation of
6 followed a literature11 procedure. To a solution of 2,5-
dibromothiophene (5.00 g, 20.7 mmol) in diethyl ether
(100 mL) at K78 8C was added n-butyllithium (2.5 M in
hexane, 43.4 mmol) via syringe under nitrogen. After the
solution was stirred for 30 min, dimethyl disulfide (4.28 g,
45.5 mmol) in ether (20 mL) was added dropwise with
vigorous stirring. The mixture was stirred at K78 8C for 1 h
and then slowly warmed to room temperature. An ice-cold
saturated ammonium chloride solution (50 mL) was added.
The two layers were separated, and the aqueous layer was
extracted with ether (3!30 mL). The organic layers were
combined, dried over MgSO4, filtered, and concentrated.
The residue was subjected to silica gel chromatography
using hexane as the eluent to yield 2.89 g (16.4 mmol, 79%)
of 6 as a colorless oil: RfZ0.68 (hexane); 1H NMR
(300 MHz, CDCl3) d 6.90 (2H, s), 2.48 (6H, s); 13C NMR
(75.4 MHz, CDCl3) d 139.1 (Cq), 131.0 (CH), 21.9 (CH3);
MS (EI) m/z 178/177/176 (MC, 9/5/95), 161 (MCKCH3,
100), 114 (MCKCH3KSCH3, 42), 69 (42); HRMS m/z
calcd for C6H382S3 175.9789, found 175.9788.
1
(hexane/ethyl acetateZ4:1); H NMR (300 MHz, CDCl3)
d 5.19, 5.10 (2H, ABq, JZ14.7 Hz), 3.91, 3.81 (2H, A0B0q,
JZ15.9 Hz), 2.44 (3H, s), 2.42 (3H, s); 13C NMR
(75.4 MHz, CDCl3) d 137.1 (Cq), 132.8 (Cq), 132.0 (Cq),
126.8 (Cq), 58.8 (CH2), 51.1 (CH2), 21.3 (CH3), 21.3 (CH3);
MS (EI) m/z 268/267/266 (MC, 3/5/13), 265 (MCK1, 22),
202 (MCKSO2, 32), 201 (40), 187 (100); HRMS m/z calcd
for C8H10O2S4 265.9565, found 265.9577; Anal. Calcd for
C8H10O2S4: C, 36.07; H, 3.78. Found: C, 36.42; H, 4.20.
3.1.5. 3,4-Bis(chloromethyl)-2,5-bis(phenylthio)thio-
phene 9 and 5,7-bis(phenylthio)-1,4-dihydro-1H-3l4-
thieno[3,4-d][2,3]oxathiin-3-oxide, sultine 10f. Adapted
from a literature method.4b To a stirred solution of 7 (2.00 g,
6.66 mmol) and zinc chloride (1.4 g, 10 mmol) in dry
chloroform (20 mL) was added dropwise chloromethyl-
methyl ether (1.6 g, 20 mmol) via syringe. The mixture
3.1.2. 2,5-Bis(phenylthio)thiophene 7. Follow the same
procedures as in the preparation of 6. 2,5-Dibromothiophene

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C.-C. Chi et al. / Tetrahedron 60 (2004) 10869–10876
turned dark green upon addition. The reaction mixture was
stirred at room temperature under nitrogen for 3 h, and then
poured into ice–water (20 mL), and CH2Cl2 (40 mL) was
added. After stirring for 10 min, the layers were separated
and the organic layer was washed with water (20 mL) and
dried over MgSO4. The solvent distilled off in vacuum to
yield 2.67 g of crude product as viscous orange oil. Without
purification, the crude product was dissolved in DMF
(50 mL), and added Rongalite (5.16 g, 33.5 mmol) and
TBAB (1.08 g, 3.45 mmol). The reaction mixture was
stirred at room temperature for 10 h. The mixture diluted
with H2O (40 mL) and extracted with CH2Cl2 (3!20 mL).
The organic layer was dried over MgSO4, concentrated, and
purified by column chromatography (10:1 hexane/ethyl
acetate) to give 0.29 g (0.47 mmol, 11% overall yield from 7
in two steps) of 10f.
lmax, nm (log 3) 434 (3.33), 308 (4.47), 256 (4.97); HRMS
(FABC) calcd for C68H10S 858.0504, found 858.0523.
3.1.10. Adduct 13a. A brown solid; RfZ0.45 (cyclo-
hexane); FAB-MS (MNB) m/z 997/998 (MCHC, 5/3),
857/858 (4/3), 721 (100); HRMS (FABC) calcd for
C76H20S2 996.1006, found 996.1751.
3.1.11. 10,30-Dichloro-40,50,60,70-tetrahydrobenzo[c]-
thieno-[50,60:1,2][60]fullerene (12b). A brown solid;
mpO495 8C; RfZ0.75 (cyclohexane); 1H NMR (25 8C,
1
600 MHz, o-C6D4Cl2) d 4.49 (4H, s); H NMR (K15 8C,
600 MHz, o-C6D4Cl2) d 4.54, 4.38 (4H, ABq, JZ14.1 Hz);
13C NMR (70 8C, 150 MHz, o-C6D4Cl2) d 156.5, 148.5,
147.3, 147.1, 146.5, 146.3, 146.2, 145.8, 145.4, 143.8,
143.4, 142.9, 142.4, 141.1, 136.2, 135.8, 122.7, 65.8 (sp3 C
of C60), 40.6 (CH2); FAB-MS (MNB) m/z 899 (MCHC, 3),
898 (MC, 3), 720 (8), 460 (100); UV (CHCl3) lmax, nm
(log 3) 434 (3.57), 310 (4.37), 257 (4.89); HRMS (FABC)
calcd for C66H4Cl2S 897.9712, found 897.9510.
3.1.6. Data of compound 9. a colorless liquid; RfZ0.3
1
(hexane); H NMR (300 MHz, CDCl3) d 7.32–7.20 (10H,
m), 4.85 (4H, s); 13C NMR (75.4 MHz, CDCl3) d 141.5
(Cq), 136.6 (Cq), 135.7 (Cq), 129.3 (CH), 128.9 (CH), 127.3
(CH), 37.1 (CH2); MS (EI) m/z 398/399/400 (MC, 87/76/
13), 396 (MCK1, 100), 348 (37), 231 (51), 216 (69), 215
3.1.12. Adduct 13b. A brown solid; RfZ0.63 (cyclo-
hexane); FAB-MS (MNB) m/z 1074/1076/1077/1078/1079/
1080 (MCHC, 0.7/0.9/0.9/1/1/0.8), 720 (8), 307 (100);
HRMS (FABC) calcd for C72H8Cl4S2 1075.8821, found
1075.8821.
(81), 203 (61), 184 (43), 171 (40), 51 (50), 50 (74), 38 (55);
HRMS m/z calcd for C18H Cl2S3 395.9637, found
35
14
395.9625.
3.1.13. 10-Methyl-30-phenyl-40,50,60,70-tetrahydroben-
zo[c]thieno-[50,60:1,2][60]fullerene (12c). A brown solid;
mpO495 8C; RfZ0.6 (cyclohexane); 1H NMR (25 8C,
600 MHz, 1:2 CDCl3/CS2) d 7.53–7.51 (2H, m), 7.38–
7.36 (2H, m), 7.29–7.26 (1H, m), 4.66 (2H, br s), 4.52 (2H,
br s), 2.67 (3H, s); 1H NMR (K20 8C, 600 MHz, 1:2 CDCl3/
CS2) d 7.53–7.52 (2H, m), 7.40–7.38 (2H, m), 7.31–7.28
(1H, m), 4.72, 4.63 (2H, ABq, JZ14.1 Hz), 4.56, 4.48 (2H,
ABq, JZ14.0 Hz), 2.69 (3H, s); 13C NMR (25 8C,
150 MHz, 1:2 CDCl3/CS2) d156.4 (br), 147.4, 146.2,
146.2, 146.0, 145.6, 145.2, 144.7, 144.5, 142.9, 142.4,
141.9, 141.8, 141.4 (br), 140.0, 134.6, 133.6, 133.1, 132.6,
128.8 (CH), 128.6 (CH), 127.4 (CH), 65.5 (sp3 C of C60),
65.4 (sp3 C of C60), 40.5 (CH2), 34.0 (CH2), 12.8 (CH3);
FAB-MS (MNB) m/z 921 (MCHC, 5), 920 (MC, 5), 720
(100); UV (CHCl3) lmax, nm (log 3) 487 (3.34), 432 (3.64),
257 (5.07); HRMS (FABC) calcd for C73H12S 920.0661,
found 920.0663.
3.1.7. Data of compound 10f. A white solid after
recrystallization from a solvent of CH2Cl2 and hexane; mp
71–72 8C (CH2Cl2/hexane); RfZ0.65 (hexane/ethyl
acetateZ4:1); 1H NMR (300 MHz, CDCl3) d 7.30–7.18
(10H, m), 5.17, 5.10 (2H, ABq, JZ15.0 Hz), 3.87, 3.81 (2H,
A0B0q, JZ16.4 Hz); 13C NMR (75.4 MHz, CDCl3) d 136.0
(Cq), 135.7 (Cq), 135.5 (Cq), 134.2 (Cq), 130.6 (Cq), 129.5
(CH), 129.4 (CH), 128.0 (CH); MS (EI) m/z 390/391 (MC,
2/14), 326 (MCKSO2, 80), 325 (MCK1 KSO2, 100), 216
(38), 215 (41), 184 (67), 77 (40), 51 (71); HRMS m/z for
C18H14O2S4 389.9878, found 389.9885; Anal. Calcd for
C18H14O2S4: C, 55.36; H, 3.61. Found: C, 55.19; H, 3.73.
3.1.8. Cycloaddition reactions of thienosultines 10a–f
with C60. General procedure. A solution of C60 (50 mg,
0.069 mmol) and thienosultine (1.5 equiv. for 10a–f) in
ODCB (20 mL) was refluxed under nitrogen or irradiated
with microwave (900 W, %180 8C). The resulting brown
reaction mixture was evaporated to dryness under reduced
pressure. The residue was subjected to silica gel chroma-
tography with cyclohexane/toluene (4/1) as the eluent. The
reaction conditions and yields after purification are shown in
Table 1.
3.1.14. Adduct 13c. A brown solid; RfZ0.3 (cyclohexane);
FAB-MS (MNB) m/z 1121 (MCHC, 8), 721 (18), 392
(100); HRMS (FABC) calcd for C86H24S2 1120.1321,
found 1120.1461.
3.1.15. 10,30-Diphenyl-40,50,60,70-tetrahydrobenzo[c]
thieno-[50,60:1,2][60]fullerene (12d). A brown solid;
mpO495 8C; RfZ0.54 (cyclohexane); 1H NMR (25 8C,
600 MHz, 1:2 CDCl3/CS2) d 7.59–7.57 (4H, m), 7.42–7.39
(4H, m), 7.33–7.31 (2H, m), 4.76 (2H, br s), 4.69 (2H, br s);
1H NMR (K20 8C, 600 MHz, 1:2 CDCl3/CS2) d 7.59–7.58
(4H, m), 7.44–7.41 (4H, m), 7.34–7.32 (2H, m), 4.79, 4.69
(4H, ABq, JZ14.2 Hz); 13C NMR (K20 8C, 150 MHz, 1:2
CDCl3/CS2) d 156.0, 155.9, 147.1, 145.98, 145.96, 145.8,
145.7, 145.32, 145.27, 145.1, 145.1, 144.95, 144.91, 144.88,
144.4, 144.2 (2C), 142.7, 142.6, 142.1, 142.1, 141.7, 141.6,
141.6, 141.5, 141.3, 141.1, 139.78, 139.76, 137.9, 135.7,
3.1.9. 10,30-Dimethyl-40,50,60,70-tetrahydrobenzo[c]-
thieno-[50,60:1,2][60]fullerene (12a). A brown solid;
mpO495 8C; RfZ0.75 (cyclohexane); 1H NMR (25 8C,
600 MHz, o-C6D4Cl2) d 4.43 (4H, s), 2.56 (6H, s); 1H NMR
(5 8C, 600 MHz, o-C6D4Cl2) d 4.43, 4.38 (4H, ABq, JZ
13.5 Hz), (2H, ABq, JZ13.3 Hz), 2.55 (6H, s); 13C NMR
(70 8C, 150 MHz, o-C6D4Cl2) d 159.9, 148.5, 147.3, 147.0,
146.6, 146.3, 146.2, 146.1, 145.5, 143.9, 143.4, 143.1,
142.9, 142.4, 141.1, 136.4, 135.8, 134.7, 66.9 (sp3 C of C60),
41.4 (CH2), 13.3 (CH3); FAB-MS (MNB) m/z 859 (MCHC,
4), 858 (MC, 4), 721 (90), 461 (100), 460 (95); UV (CHCl3)

C.-C. Chi et al. / Tetrahedron 60 (2004) 10869–10876
10875
134.7, 133.9, 132.9, 128.8 (CH), 128.5 (CH), 127.7 (CH),
65.0 (sp3 C of C60), 40.1 (CH2); FAB-MS (MNB) m/z 984/
983 (MCHC, 2/3), 982 (MC, 3), 721 (24), 461 (67), 392
(100); UV (CHCl3) lmax, nm (log 3) 432 (3.55), 257 (5.10);
HRMS (FABC) calcd for C78H14S 982.0817, found
982.0905.
(cyclohexane: CHCl3Z1:1); FT-IR (KBr, cmK1) 1700
(C]O), 1529 (C]C); 1H NMR (25 8C, 600 MHz,
CDCl3) d 4.56 (2H, br s), 4.45 (2H, br s), 2.71 (3H, s),
2.53 (3H, s); 13C NMR (25 8C, 150 MHz, CDCl3) d 197.7
(C]O), 193.0 (C]S/O), 155.5, 155.4, 147.7 (2C), 146.6
(2C), 146.3 (2C), 145.8, 145.6 (3C), 145.5 (2C), 145.2,
144.7 (2C), 143.2, 142.7, 142.6, 142.3, 142.2, 142.1 (2C),
141.7 (2C), 140.2 (2C), 137.9, 135.8, 135.7, 65.8 (sp3 C of
C60), 65.5 (sp3 C of C60), 49.1 (CH2), 42.6 (CH2), 30.9
(CH3), 30.3 (CH3); FAB-MS (MNB) m/z 891 (MCHC, 2),
890 (MC, 3), 889 (MCK1, 2), 721 (100); HRMS (FABC)
calcd for C68H10O2S 890.0402, found 890.0382.
3.1.16. Adduct 13d. A brown solid; RfZ0.2 (cyclohexane);
FAB-MS (MNB) m/z 1246/1245 (MCHC, 4/5), 721 (67),
461 (57), 392 (100); HRMS (FABC) calcd for C96H28S2
1244.1634, found 1244.1669.
3.1.17. 10,30-Bis(methylthio)-40,50,60,70-tetrahydroben-
zo[c]thieno-[50,60:1,2][60]fullerene (12e). A brown solid;
mpO495 8C; RfZ0.45 (cyclohexane); 1H NMR (25 8C,
500 MHz, 1:2 CDCl3/CS2) d 4.62 (4H, br s), 2.46 (6H, s); 1H
NMR (K25 8C, 500 MHz, 1:2 CDCl3/CS2) d 4.74, 4.49
(4H, ABq, JZ14.5 Hz), 2.46 (6H, s); 13C NMR (70 8C,
150 MHz, o-C6D4Cl2) d 157.3, 148.5, 147.3, 147.0, 146.5,
146.2, 146.2, 146.0, 145.5, 143.9, 143.4, 142.9, 142.4,
141.1, 136.2, 135.8, 135.0, 66.5 (sp3 C of C60), 41.8 (CH2),
23.2 (CH3); FAB-MS (MNB) m/z; 923 (MCHC, 3), 614
(32), 462 (100), 444 (26); UV (CHCl3) lmax, nm (log 3) 435
(3.67), 310 (4.80), 256 (5.31); HRMS (FABC) calcd for
C68H10S3 921.9946, found 922.0023.
3.1.23. Data of 16. A brown solid; mpO495 8C; RfZ0.25
(cyclohexane/CHCl3Z2:3); FT-IR (KBr, cmK1) 1685
(C]O); H NMR (25 8C, 600 MHz, CDCl3) d 4.31 (4H,
1
s), 2.63 (6H, s); 13C NMR (25 8C, 150 MHz, CDCl3) d 200.6
(C]O), 155.2, 147.5, 146.6, 146.4, 145.7, 145.7, 145.6,
145.2, 144.9, 144.7, 143.2, 142.7, 142.3, 142.1, 141.7,
140.3, 135.7, 65.3 (sp3 C of C60), 41.7 (CH2), 29.2 (CH3);
FAB-MS (NMB) 859 (MCHC, 2), 858 (MC, 2), 720 (100);
HRMS (FABC) calcd for C68H10O2 858.0681, found
858.0712.
Acknowledgements
3.1.18. Adduct 13e. A brown solid; RfZ0.41 (cyclohexane:
tolueneZ9:1); FAB-MS (MNB) m/z 1124 (MCHC, 3),
1123 (MC, 3) 720 (18), 442 (25), 308 (100); HRMS
(FABC) calcd for C76H20S6 1123.9892, found 1123.9897.
We thank the National Science Council of the Republic of
China for financial support (Grant No. NSC92-2113-M-
009-013). We also thank the National Chiao Tung
University for supporting the Center of Interdisciplinary
Molecular Science.
3.1.19. 10,30-Bis(phenylthio)-40,50,60,70-tetrahydroben-
zo[c]thieno-[50,60:1,2][60]fullerene (12f). A brown solid;
1
mpO 495 8C; RfZ0.35 (cyclohexane); H NMR (40 8C,
600 MHz, 1:2 CDCl3/CS2) d 7.32–7.30 (4H, m), 7.17–7.15
1
(4H, m), 7.10–7.09 (2H, m), 4.66 (4H, br s); H NMR
Supplementary data
(K30 8C, 600 MHz, 1:2 CDCl3/CS2) d 7.28–7.24 (4H, m),
7.19–7.16 (4H, m), 7.11–7.10 (2H, m), 4.78, 4.52 (4H, ABq,
JZ14.4 Hz); 13C NMR (40 8C, 150 MHz, 1:2 CDCl3/CS2) d
156.0, 147.5, 146.3, 146.1, 145.6, 145.4, 145.3, 144.9,
144.5, 144.4, 143.0, 142.4, 141.9, 141.9, 141.4, 140.1,
136.8, 135.2, 131.2, 129.0 (CH), 128.3 (CH), 126.7 (CH),
65.0 (sp3 C of C60), 40.7 (CH2); FAB-MS (MNB) m/z 1047
(MCHC, 5), 1046 (MC, 5), 766 (5), 720 (20), 613 (40), 460
(100); UV (CHCl3) lmax, nm (log 3) 435 (3.67), 310 (4.80),
256 (5.31); HRMS (FABC) calcd for C78H14S3 1046.0259,
found 1046.0404.
1
Various temperature H NMR spectra of compounds 12b,
d–f, 1H NMR spectra of compounds 6, 8, 9, and 10e, 1H and/
or 13C NMR spectra of compounds 12, 13, 15 and 16 and
FTIR spectra of adducts 15 and 16.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tet.2004.09.
040
3.1.20. Adduct 13f. A brown solid; RfZ0.28 (cyclohexane/
tolueneZ9:1); FAB-MS (MNB) m/z 1373 (MCHC, 5),
1372 (MC, 5), 721 (32), 442 (37), 308 (100); HRMS
(FABC) calcd for C96H28S6 1372.0518, found 1372.0522.
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