A general method for the synthesis of alkylenedithio- and bis(alkylenedithio)tetraselenafulvalenes

Article abstract of DOI:10.1021/jo034145a

A general synthetic method toward a series of alkylenedithio-and bis(alkylenedithio)tetraselenafulvalenes, i.e., methylenedithio- (MDT-TSF, 1a), ethylenedithio- (EDT-TSF, 1b), propylenedithio-PDT-TSF, 1c), bis(methylenedithio)- (BMDT-TSF, 2a), bis(ethylenedithio)-(BETS, 2b), and bis(propylenedithio)tetraselenafulvalene (BPDT-TSF, 2c), as superior electron donors for organic conductors has been developed. This method is advantageous to ready access to a series of compounds from common synthetic intermediates, 2-methylthio-3-(2-methoxycarbonylethylthio)tetraselenafulvalene (6) and 2,6(7′)-bis(methylthio)-3,7(6′)-bis(2-methoxycarbonylethylthio) tetraselenafulvalene (7), for the asymmetrical alkylenedithio- and symmetrical bis(alkylenedithio)-TSFs, respectively. These key intermediates are readily prepared by phosphite-promoted coupling reactions of 4-methylthio-5-(2-methoxycarbonylethylthio)-1,3-selenole-2-selone (5) or by a reaction of TSF with LDA and methyl 3-thiocyanatopropionate. The latter method provides not only the successful conversion of TSF to these heterocycle derivatives but also a generally acceptable route to them, since TSF is accessible without the toxic and less easily available CSe₂.

Full text of DOI:10.1021/jo034145a

A Gen er a l Meth od for th e Syn th esis of Alk ylen ed ith io- a n d
Bis(a lk ylen ed ith io)tetr a selen a fu lva len es
Kazuo Takimiya,* Yoshiro Kataoka, Naoto Niihara, Yoshio Aso, and Tetsuo Otsubo*
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University,
Kagamiyama 1-4-1, Higashi-Hiroshima 739-8527, J apan
ktakimi@hiroshima-u.ac.jp
Received February 2, 2003
A general synthetic method toward a series of alkylenedithio- and bis(alkylenedithio)tetraselena-
fulvalenes, i.e., methylenedithio- (MDT-TSF, 1a ), ethylenedithio- (EDT-TSF, 1b), propylenedithio-
(PDT-TSF, 1c), bis(methylenedithio)- (BMDT-TSF, 2a ), bis(ethylenedithio)- (BETS, 2b), and bis-
(propylenedithio)tetraselenafulvalene (BPDT-TSF, 2c), as superior electron donors for organic
conductors has been developed. This method is advantageous to ready access to a series of
compounds from common synthetic intermediates, 2-methylthio-3-(2-methoxycarbonylethylthio)-
tetraselenafulvalene (6) and 2,6(7′)-bis(methylthio)-3,7(6′)-bis(2-methoxycarbonylethylthio)tetra-
selenafulvalene (7), for the asymmetrical alkylenedithio- and symmetrical bis(alkylenedithio)-TSFs,
respectively. These key intermediates are readily prepared by phosphite-promoted coupling reactions
of 4-methylthio-5-(2-methoxycarbonylethylthio)-1,3-selenole-2-selone (5) or by a reaction of TSF
with LDA and methyl 3-thiocyanatopropionate. The latter method provides not only the successful
conversion of TSF to these heterocycle derivatives but also a generally acceptable route to them,
since TSF is accessible without the toxic and less easily available CSe2.
CHART 1
In tr od u ction
Tetraselenafulvalene (TSF) derivatives (Chart 1) have
been regarded as essential components for the develop-
ment of superconducting radical cation salts.1 Histori-
cally, the study of organic superconductors was initiated
with the discovery of the first superconducting salt,
(TMTSF)2PF6 (TMTSF: tetramethyltetraselenafulvalene),
in 1980.2 Afterward, many superconductors developed
were rather based on the sulfur-containing electron donor
bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF). In the
past decade, however, not only a series of superconduc-
tors3 but also various intriguing phenomena arising from
interplay between conducting electrons and localized
* To whom correspondence should be addressed. Tel: +81-824-24-
7734. Fax: +81-824-24-5494.
(1) For comprehensive reviews on organic superconductors, see: (a)
Williams, J . M.; Ferraro, J . R.; Thorn, R. J .; Carlson, K. D.; Geiser,
U.; Wang, H. H.; Kini, A. M.; Whangbo, M.-H. Organic Superconductors
(Including Fullerenes): Synthesis, Structure, Properties, and Theory;
Prentice Hall: Englewood Cliffs, NJ , 1992. (b) Ishiguro, T.; Yamaji,
K.; Saito, G. Organic Superconductors, 2nd ed.; Springer-Verlag:
Berlin, 1998.
spins4 have been discovered in the radical cation salts of
bis(ethylenedithio)tetraselenafulvalene (BETS, 2b), a
TSF analogue of BEDT-TTF. In addition, novel organic
superconductors based on the newly developed methyl-
enedithiotetarselenafulvalene (MDT-TSF, 1a )5 and its
related electron donors6 have renewed interest in electron
donors of the TSF-type.
(2) J e´rome, D.; Mazaud, A.; Ribault, M.; Bechgaard, K. J . Phys. Lett.
(Paris) 1980, 41, L95-L98.
(3) (a) Kobayashi, H.; Udagawa, T.; Tomita, H.; Bun, K.; Naito, T.;
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H.; Naito, T.; Kobayashi, A.; Sakai, F.; Watanabe, T.; Cassoux, P. J .
Am. Chem. Soc. 1996, 118, 368-377. (c) Tanaka, H.; Kobayashi, A.;
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768. (d) Otsuka, T.; Kobayashi, A.; Miyamoto, Y.; Kiuchi, J .; Wada,
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2000, 29, 325-333. (f) Gritsenko, V.; Tanaka, H.; Kobayashi, H.;
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(b) Balicas, L.; Brooks, J . S.; Storr, K.; Uji, S.; Tokumoto, M.; Tanaka,
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10.1021/jo034145a CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/22/2003
J . Org. Chem. 2003, 68, 5217-5224
5217

Takimiya et al.
SCHEME 1
From the viewpoint of synthetic chemistry, on the other
hand, the synthesis of TSF donors has not been well
explored, although a few important methods, for example,
a titanocene-involving one for the synthesis of BETS
(2b),7 bis(propylenedithio)tetraselenafulvalene (BPDT-
TSF, 2c),8 and their asymmetrical derivatives,9 are
known. We have thus recognized the importance of
developing a versatile synthetic method for preparing
TSF derivatives, especially the heterocycle-fused TSFs,
and have recently established several reactions suitable
for the synthesis of such TSFs. Among them, two
breakthrough reactions consist of a one-pot synthesis of
1,3-selenole-2-selones10 and an outer heterocycle forma-
tion via an intramolecular trans-alkylation reaction of a
TSF core.11 A combination of these has opened the way
to various heterocycle-fused TSFs; for example, starting
from tetrahydropyranyl-protected hydroxyalkyl-12 or 2-
hydroxyethylthioacetylenes,13 bis(alkylenechalcogeno)-
and bis(ethylenedichalcogeno)-TSFs are effectively syn-
thesized, respectively (Scheme 1). The merit of this
synthesis is that one can obtain various TSF derivatives
possessing the same framework but different chalcogen
atoms from the same starting acetylene derivative by
choosing the chalcogen reagents in the synthetic se-
quence.14
On the other hand, a drawback of this method is that
the size and type of the outer heterocycles attached to
the TSF core are exclusively determined by the substitu-
ent of the starting acetylene compound, i.e., the R groups
in Scheme 1. This means that the method is not neces-
sarily suitable for the synthesis of alkylenedithio- and
bis(alkylenedithio)-TSFs with other outer ring sizes.
To solve this problem, we have introduced a deprotec-
tion/realkylation procedure on the protected TSF thio-
lates15 into the synthetic route described above and found
that it provides easy access to a series of alkylenedithio-
(1) and bis(alkylenedithio)-TSFs (2).16 In this paper, a
synthetic method toward these TSF derivatives consist-
ing of the one-pot synthesis of 1,3-selenole-2-selones,
deprotection/realkylation of the protected TSF thiolates,
and intramolecular trans-alkylation reaction forming the
alkylenedithio moiety are described. In addition, an
alternative synthetic route to these TSFs from the parent
TSF is also mentioned in a carbon diselenide (CSe2)-free
synthesis.
(5) (a) Takimiya, K.; Kataoka, Y.; Aso, Y.; Otsubo, T.; Fukuoka, H.;
Yamanaka, S. Angew. Chem., Int. Ed. 2001, 40, 1122-1125. (b)
Kawamoto, T.; Mori, T.; Takimiya, K.; Kataoka, Y.; Aso, Y.; Otsubo,
T. Phys. Rev. B 2002, 65, 140508(R). (c) Kawamoto, T.; Mori, T.;
Terakura, C.; Terashima, T.; Uji, S.; Takimiya, K.; Aso, Y.; Otsubo, T.
Phys. Rev. B 2003, 67, 020508(R). (d) Takimiya, K.; Kataoka, Y.;
Kodani, M.; Aso, Y.; Otsubo, T. Synth. Met. 2003, 133-134, 185-187.
(6) (a) Kodani, M.; Takamori, A.; Takimiya, K.; Aso, Y.; Otsubo, T.
J . Solid State Chem. 2002, 168 582-589. (b) Takimiya, K.; Takamori,
A.; Aso, Y.; Otsubo, T.; Kawamoto, T.; Mori, T. Chem. Mater. 2003,
15, 1225-1227.
(7) (a) Kato, R.; Kobayashi, H.; Kobayashi, A. Synth. Met. 1991, 42,
2093-2096. (b) Courcet, T.; Malfant, I.; Pokhodnia, K.; Cassoux, P. N.
J . Chem. 1998, 5, 585-589.
(8) (a) Kato, R.; Aonuma, S.; Okano, Y.; Sawa, H.; Kobayashi, A.;
Kobayashi, H. Synth. Met. 1993, 55-57, 2084-2089.
Resu lts a n d Discu ssion s
Syn t h esis of Alk ylen ed it h io-TSF s (1a -c). The
synthesis of asymmetrical alkylenedithio-TSF is outlined
in Scheme 2. In the preliminary report on the synthesis
of MDT-TSF (1a ),5a methylthioacetylene (3) was used as
a starting material, but the preparation and purification
of 3 were not very easy owing to its low boiling point (70
(9) (a) Kobayashi, A.; Kato, R.; Naito, T.; Kobayashi, H. Synth. Met.
1993, 55-57, 2078-2083. (b) Kato, R.; Aonuma, S.; Okano, Y.; Sawa,
H.; Tamura, M.; Kinoshita, M.; Oshima, K.; Kobayashi, A.; Bun, K.;
Kobayashi, H. Synth. Met. 1993, 61, 199-1162. (c) Okano, Y.; Sawa,
H.; Aonuma, S.; Kato, R. Synth. Met. 1995, 70, 1161-1162. (d) Naito,
T.; Kobayashi, H.; Kobayashi, A.; Underhill, A. E. Chem. Commun.
1996, 521-522. (e) Naito, T.; Kobayashi, H.; Kobayashi, A. Bull. Chem.
Soc. J pn. 1997, 70, 107-114. (f) Imakubo, T.; Sawa, H.; Kato, R. Synth.
Met. 1997, 86, 1883-1884. (g) Ojima, E.; Fujiwara, F.; Kobayashi, H.
Adv. Mater. 1999, 11, 459-462. (h) Sato, A.; Ojima, E.; Kobayashi,
H.; Kobayashi, A. J . Mater. Chem. 1999, 9, 2365-2371. (i) Sakurai,
N.; Mori, H.; Tanaka, S.; Moriyama, H. Chem. Lett. 1999, 1191-1192.
(j) Imakubo, T.; Tajima, N.; Tamura, M.; Kato, R.; Nishio, Y.; Kajita,
K. J . Mater. Chem. 2002, 12, 159-161.
(13) Takimiya, K.; J igami, T.; Kawashima, M.; Kodani, M. T.; Aso,
Y.; Otsubo, T. J . Org. Chem. 2002, 67, 4218-4227.
(14) Kodani, M.; Murakami, S.; Takimiya, K.; Aso, Y.; Otsubo, T.
Heterocycles 2001, 54, 225-234.
(15) (a) Svenstrup, N.; Rasmussen, K. M.; Hansen, T. K.; Becher,
J . Synthesis 1994, 809-812. (b) Simonsen, K. B.; Svenstrup, N.; Lau,
J .; Simonsen, O.; Mørk, P.; Kristensen, G. J .; Becher, J . Synthesis 1996,
407-418. (c) Becher, J .; Lau, J .; Leriche, P.; Mørk, P.; Svenstrup, N.
J . Chem. Soc., Chem. Commun. 1994, 2715-2716. (d) Takimiya, K.;
Oharuda, A.; Morikami, A.; Aso, Y.; Otsubo, T. Eur. J . Org. Chem.
2000, 3013-3019. (e) Kodani, M.; Takimiya, K.; Aso, Y.; Otsubo, T.;
Nakayashiki, T.; Misaki, Y. Synthesis 2001, 1614-1618.
(16) The synthesis of MDT-TSF (1a ) in the present work has been
previously reported in ref 5a.
(10) Takimiya, K.; Morikami, A.; Otsubo, T. Synlett, 1997, 319-
321.
(11) J igami, T.; Takimiya, K.; Aso, Y.; Otsubo, T. Chem. Lett. 1997,
1091-1092.
(12) (a) J igami, T.; Takimiya, K.; Otsubo, T.; Aso, Y. J . Org. Chem.
1998, 63, 8865-8872. (b) J igami, T.; Kodani, M.; Murakami, S.;
Takimiya, K.; Aso, Y.; Otsubo, T. J . Mater. Chem. 2001, 11, 1026-
1033.
5218 J . Org. Chem., Vol. 68, No. 13, 2003

Synthesis of Alkylenedithio- and Bis(alkylenedithio)-TSFs
SCHEME 2. Syn th esis of Alk ylen ed ith io-TSF s (1a -c)
CHART 2
°C at 760 Torr) and thermal instability.17 Thus, 1,2-
dichloro-1-methylthioethane (4), which is rather stable
and easily accessible from cheap reagents, was examined
as a synthetic equivalent of 3,18 and it turned out that
the synthesis of 4-methylthio-5-(2-methoxycarbonyl-
ethylthio)-1,3-selenole-2-selone (5) from 4 is very effec-
tive: treatment of 4 with 2 equiv of n-BuLi in situ
generating lithium 2-methylthioacetylide (3′), followed
by subsequent reactions with selenium, methyl 3-
thiocyanatopropionate, and CSe2 gave 5 in 88% isolated
yield.
in refluxing 2-butanone (bp 80 °C) gave 1a in 50% yield.5a
After examinations of several different solvents, it turned
out that the yield of 1a was improved up to 65% in
refluxing 2-pentanone (bp 101 °C).
We have examined the synthesis of EDT-TSF (1b )
under the optimal reaction conditions obtained for 1a .
However, 1b was obtained in only 10% yield together
with byproducts that were not easily characterized.
By contrast, a similar reaction of 8b with sodium iodide
in DMF was very effective. After examinations of re-
action temperature and time, this conversion was op-
timized (DMF, 90 °C, 15 h) to give 1b in 75% isolated
yield.
When an equimolar mixture of 5 and 1,3-diselenole-
2-selone in the presence of trimethyl phosphite was
allowed to react in refluxing benzene, 6 was obtained in
less than 10% yield, and the major products were the
unsubstituted TSF and 2,6(7′)-bis(methylthio)-3,7(6′)-
bis(2-methoxycarbonylethylthio)tetraselenafulvalene (7).
Although use of excess 1,3-diselenole-2-selone (3-5-fold)
increased the yield of 6 (40-60% yield based on 5),5a
a
large amount of TSF was concomitantly produced. Al-
ternatively, slow addition of a mixture of 5 and trimethyl
phophite in benzene to a refluxing benzene solution of
1,3-diselenole-2-selone improved the yield of 6 (typically
40% isolated yield), even though the ratio of the reactants
was 1:1.
Construction of the alkylenedithio moiety was achieved
by a two-step reaction. First, the methyl propionate
protecting group was cleaved by cesium hydroxide, the
resulting TSF thiolate being effectively realkylated with
bromochloroalkane.15 Regardless of the number of meth-
ylene moieties, compounds 8a -c were obtained in mod-
erate to good isolated yields. Then, a ring-closing reaction
promoted by sodium iodide was carried out. As reported
in the previous paper, a reaction of 8a with sodium iodide
The synthesis of PDT-TSF (1c) was rather trouble-
some; application of the reaction conditions optimized for
1a (2-pentanone, reflux, 1.5 h) to 8c did not allow
formation of 1c, and the major product isolated was
2-methylthio-3-iodopropylthio-TSF (9, Chart 2). Although
a reaction in DMF at 90 °C gave 1c in 15% yield,
concomitant byproducts made it difficult to purify 1c by
column chromatography. Thus, a step-by-step conversion
from 8c to 1c was examined. Treatment of 8c with
sodium iodide in refluxing 2-butanone gave 9 quantita-
tively, and then 9 was again treated with sodium iodide
in refluxing DMF for 1.5 h effecting the formation of 1c
in 64% yield (two steps).
In these final ring-closing reactions, the optimum
reaction conditions depend strongly on the substrates,
i.e., the size of the outer alkylenedithio moiety in the
products. Generally, the smaller rings form more easily
in this series, and the formation of the seven-membered
ring in PDT-TSF (1c) requires a two-step reaction under
harsh reaction conditions. These results are explained
(17) (a) Brandsma, L.; Wijers, H. E.; J onker, M. C. Rec. Trav. Chem.
1963, 82, 208-216. (b) Brandsma, L. Preparative Acetylenic Chemistry,
2nd ed.; Elsevier: Amsterdam, 1988; pp 172-173.
(18) Delavareme, S. Y.; Viehe, H. G. Tetrahedron Lett. 1969, 4761-
4764.
J . Org. Chem, Vol. 68, No. 13, 2003 5219

Takimiya et al.
SCHEME 3. Syn th esis of Bis(a lk ylen ed ith io)-TSF s (2a -c)
SCHEME 4. Selective Difu n ction a liza tion of TSF
F IGURE 1. Molecular structure of 11.
TSF with LDA followed by a reaction with appropriate
electrophiles.
by the effects of ring strain and are in accord with the
general tendency of ease of ring formation in other
cyclization reaction.
We first examined the lithiation of TSF with 2 equiv
of LDA followed by a reaction with methyl 3-thiocyanato-
Sym m etr ica l TSF Der iva tives. The synthesis of the
bis(alkylenedithio)-TSFs (2a -c) by the same method is
summarized in Scheme 3. The protected TSF dithiolate
(7) was readily prepared by a phosphite-promoted cou-
pling of 5 in 77% yield as a cis and trans mixture about
the central double bond of the TSF core owing to the two
different substituents on each 1,3-diselenole moiety. The
ensuing conversion to bis(alkylenedithio)-TSFs (2a -c)
via bis(chloroalkyl) intermediates (10a -c) was accom-
plished using the optimized reaction conditions for the
corresponding asymmetrical TSFs. The isolated yields of
10 (77-81%) were almost comparable to those of 8, and
the final ring-closing reactions also proceed smoothly in
around 50% isolated yields.
CSe2-F r ee Syn th esis of Asym m etr ica l a n d Sym -
m etr ica l TSF s. In the synthesis of alkylenedithio- (1)
and bis(alkylenedithio)-TSFs (2) described above, one of
the key synthetic steps is the preparation of the 1,3-
diselenole-2-selone substructure, the synthesis of which
requires the toxic and not easily available CSe2 as a
crucial reagent. Because this may be regarded as a
disadvantage, we have explored an alternative synthetic
route free from CSe2. One potential approach is to directly
functionalize the parent TSF,19 which is accessible by a
CSe2-free procedure.20 In fact, there have been several
reports on the synthesis of functionalized TSFs such as
tetrakis(methylthio)-, tetrakis(methylseleno)-, tetrakis-
(phenylthio)-, tetrakis(phenylseleno)-, tetrakis(methoxy-
carbonyl)-, and tetrakis(carboxy)-TSFs21 via lithiation of
1
propionate (Scheme 4). H and 13C NMR spectra of the
isolated product were apparently different from those of
the known 2,6(7)-bis(2-methoxycarbonylethylthio)tetra-
selenafulvalene (11′),15d suggesting the selective forma-
tion of 2,3-bis(2-methoxycarbonylethylthio)tetraselena-
fulvalene (11) in this reaction.6a,22 An unambiguous
structural determination was done by an X-ray crystal-
lographic analysis of 11 as shown in Figure 1.
Since 11 is regarded as the synthetic equivalent of the
TSF 2,3-dithiolate dianion (12), a direct precursor for 1,
a one-step ring formation through the deprotection/
realkylation of 11 was attempted as shown in Scheme 5.
Contrary to our expectations, reaction of 12, generated
in situ from 11 with 2 equiv of cesium hydroxide, with
dihaloalkane resulted in a failed reaction: EDT-TSF (1b)
and PDT-TSF (1c) were isolated in low yields, and no
MDT-TSF (1a ) was obtained at all (Scheme 5).23
Instead of the above one-step approach, a stepwise
route via a selective monodeprotection of 11 was exam-
ined: treatment of 11 with 1 equiv of cesium hydroxide
followed by quenching with excess iodomethane gave 6
quantitatively,15a-c which was readily converted to the
alkylendithio-TSFs (1a -c) following the reaction se-
quence depicted in Scheme 2.
Application of the same method to the synthesis of the
bis(alkylenedithio)-TSFs (2) was also carried out: the
protected TSF tetrathiolate 13 obtained in 55% yield from
TSF using excess LDA and methyl 3-thiocyanatopropi-
onate was readily converted into 7 in 75% yield by
treatment with a controlled amount of the base and
excess iodomethane (Scheme 6). Thus, it follows that
(19) A synthetic route to BETS from the parent TSF have been
suggested; Montgomery, L. K.; Burgin, T.; Husting, L.; Tilley, L.;
Huffman, J . C.; Carlson, K. D.; Dudek, J . D.; Yaconi, G. A.; Geiser, U.;
Williams, J . M. Mol. Cryst. Liq. Cryst. 1992, 211, 283-288.
(20) J ackson, Y. A.; White, C. L.; Lakshimikantham, M. V.; Cava,
M. P. Tetrahedron Lett. 1987, 28, 5635-5636.
(22) Takimiya, K.; Kataoka, Y.; Morikami, A.; Aso, Y.; Otsubo, T.
Synth. Met. 2001, 120, 875-876.
(21) (a) Iwasawa, N.; Saito, G.; Imaeda, K.; Mori, T.; Inokuchi, H.
Chem. Lett. 1987, 2399-2402. (b) Rajeswari, A.; J ackson, Y. A.; Cava,
M. P. J . Chem. Soc., Chem. Commun. 1988, 1089-1090. (c) Zambonius,
J . S.; Mayer, C. W. Tetrahedron Lett. 1991, 32, 2741-2742.
(23) Successful outer-ring formation of related compounds via
similar 2-fold deprotection/realkylation protocol has been reported; for
example, Binet L.; Fabre, J . M.; Becher J . Synthesis 1997, 26-28. See
also ref 15a,e.
5220 J . Org. Chem., Vol. 68, No. 13, 2003

Synthesis of Alkylenedithio- and Bis(alkylenedithio)-TSFs
SCHEME 5. Syn th esis of Alk ylen ed ith io-TSF s
(1a -c) fr om 11
lished. This gives a generally acceptable route to alkyl-
enedithio- (1) and bis(alkylenedithio)-TSFs (2), in par-
ticular, MDT-TSF (1a ) that has been so far impossible
to synthesize without CSe2. Thus, we strongly hope that
the present synthetic method will be accepted by many
researchers in this field and contribute to the develop-
ment of novel conducting and superconducting radical
cation salts.
Exp er im en ta l Section
All chemicals and solvents are of reagent grade unless
otherwise indicated. All reactions were carried out under a
nitrogen atmosphere. THF was purified by distillation from
sodium benzophenone ketyl under nitrogen prior to use.
Methanol was distilled from Mg under a nitrogen atmosphere.
Dry DMF was purchased and used without purification.
Carbon diselenide,24 1,2-dichloro-1-methylthioethane,18 methyl
3-thiocyanatopropionate,25 1,3-diselenole-2-selone,10,24b and TSF
(by CSe2-free method)20 were synthesized according to the
literature procedures.
Column chromatography was carried out with silica gel (63-
210 µm). Melting points are uncorrected. 1H NMR and 13C
NMR spectra were recorded at 400 and 100 MHz, respectively,
in deuterated chloroform with TMS as internal reference;
chemical shifts (δ) are given in parts per million and coupling
constants in hertz. MS spectra were obtained using an electron
impact ionization procedure (70 eV). The molecular ion peaks
of the selenium- and/or chlorine-containing compounds showed
a typical isotopic pattern, and all the mass peaks are reported
based on 80Se and 35Cl. Preparative gel permeation chroma-
tography (GPC) was performed on a J apan Analytical Industry
Co., Ltd. LC-908 equipped with a J AI-GEL 1H, 2H column
assembly. Cyclic voltammetry (CV) was carried out in benzo-
nitrile containing tetrabutylammonium hexafluorophosphate
(n-Bu4NPF6; 0.1 M) as supporting electrolyte with a sweep rate
of 100 mV/s. Counter and working electrodes were made of
Pt, and the reference electrode was Ag/AgCl.
SCHEME 6. Syn th esis of Bis(a lk ylen ed ith io)-TSF s
(2a -c) fr om 13
4-Meth ylth io-5-(2-m eth oxyca r bon yleth ylth io)-1,3-d is-
elen ole-2-selon e (5).26 To a solution of 1,2-dichloro-1-methyl-
thioethene (4, 1.43 g, 10 mmol) in dry THF (40 mL) at -78 °C
was added a hexane solution of n-BuLi (1.56 M, 13.5 mL, 21
mmol), and the resulting solution was stirred and warmed to
-10 °C over a period of 1.5 h. The resulting lithium acetylide
solution was cooled again to -78 °C, and then selenium powder
(790 mg, 10 mmol) was added in one portion. The reaction
mixture was allowed to warm to ice-cooled temperature over
the period of 1.5 h. To the resulting selenolate solution were
subsequently added methyl 3-thiocyanatopropionate (2.1 g, 14
mmol) and carbon diselenide (0.7 mL, 10 mmol) at -100 °C,
and the resulting mixture was kept at -90 °C for 5 min,
whereupon water (50 mL) was added, and the mixture was
allowed to warm to room temperature. The mixture was
poured into diluted HCl aqueous solution (1 M, 200 mL) and
extracted with CH2Cl2 (100 mL × 3), and the extract was
washed with water (100 mL) and then dried over MgSO4.
Evaporation of the solvent gave crude 3 as a red viscous oil,
which was then purified by column chromatography on silica
gel eluted first with dichloromethane-hexane (1:1, v/v) and
then with neat dichloromethane. Concentration of the fraction
obtained from the latter gave a red solid, which was dissolved
in 20 mL of dichloromethane, and the resulting solution was
diluted with methanol (50 mL). The solution was cooled in a
freezer (-20 °C) to give red crystals of 5 (3.68 g). The second
bis(alkylenedithio)-TSFs (2a -c) can also be synthesized
through the functionalization of the parent TSF.
Con clu sion
Combining the one-pot synthesis of 1,3-selenole-2-
selones, the deprotection/realkylation of the protected
TSF thiolates, and the intramolecular trans-alkylation
reaction forming alkylenedithio moiety on a TSF core, a
general and versatile method for the synthesis of alkyl-
enedithio- (1) and bis(alkylenedithio)-TSFs (2) is estab-
lished. The advantage of the present method is that these
TSF derivatives can be obtained from the common
synthetic intermediates 6 and 7 via the same reaction
sequence. These intermediates are conveniently synthe-
sized from 4-methylthio-5-(2-methoxycarbonylethylthio)-
1,3-diselenole-2-selones (5), prepared from readily avail-
able 1,2-dichloro-1-methylthioethane (4). For the synthesis
of the asymmetrical intermediate 6, an effective cross-
coupling reaction was achieved by slow addition of 5 into
a solution of 1,3-diselenole-2-selone. These synthetic
improvements enable us to obtain a practical amount of
the donors for further complexation studies to develop
novel conducting and superconducting radical cation
salts.
(24) (a) Pan, W.-H.; Fackler, J . P., J r. In Inorganic Syntheses;
Fackler, J . P., J r., Ed.; J ohn Wiley & Sons: New York, 1982; Vol. 21,
pp 6-11. (b) Ogura, F.; Takimiya, K. In Organoselenium Chemistry;
A Practical Approach, Back, T. G., Ed.; Oxford University Press: New
York, 1999; pp 258-260.
Furthermore, a CSe2-free synthesis of the key inter-
mediates 6 and 7 from the parent TSF was also estab-
(25) Hiskey, R. G.; Carroll, F. I. J . Am. Chem. Soc. 1961, 83, 4644-
4647.
J . Org. Chem, Vol. 68, No. 13, 2003 5221

Takimiya et al.
crop (0.18 g) was also collected, and the combined yield
amounts to 88%, mp 62-63 °C. The spectroscopic data were
identical with the authentic sample.5a
3021 cm-1 (CH); MS m/z 484 (M+). Anal. Calcd for C8H6S2Se4:
C, 19.93; H, 1.25. Found: C, 19.96; H, 1.30. CV: E1/2 ) +0.58,
+0.90 V.
2-Met h ylt h io-3-(2-m et h oxyca r b on ylet h ylt h io)t et r a -
selen a fu lva len e (6). To a refluxing solution of 1,3-diselenole-
2-selone (2.75 g, 10 mmol) in benzene (80 mL) was added a
mixture of 3 (4.39 g, 10 mmol) and trimethyl phosphate (5 mL)
in benzene (80 mL) over 30 min, and the resulting mixture
was further refluxed for 1 h. After the excess trimethyl
phospite and benzene were evaporated off, the residue consist-
ing of the desired asymmetrical TSF (6) together with TSF
and the symmetrical TSF (7) was subjected to column chro-
matography on silica gel eluted with hexane-dichloromethane
(1:1 v/v); after the first fraction (TSF, Rf ) 0.9, 0.61 g, 31%), 6
was obtained as a red solid (Rf ) 0.5, 2.21 g, 40%), mp 93-94
°C. All the spectroscopic data were identical with those
previously reported.5a The last fraction eluted with neat
dichloromethane contained 7 (Rf ) 0.3 with dichloromethane,
0.87 g, 24%).
Gen er al Syn th etic P r ocedu r e for 2-Meth ylth io-3-ch lor o-
a lk ylth iotetr a selen a fu lva len e (8a -c). To a degassed DMF
solution (20 mL) of 6 (513 mg, 1.08 mmol) was added CsOH‚
H2O (181 mg, 1.08 mmol) in methanol (5 mL) during 5 min
with stirring at room temperature. After the mixture was
stirred for further 0.5 h, excess bromochloroalkane (ca. 1.5 mL)
was added, and the mixture was stirred for 2 h. The reaction
mixture was concentrated in vacuo, and the resulting residue
was dissolved in dichloromethane (80 mL). The solution was
washed with water (100 mL), dried over Na2SO4, and concen-
trated. The resulting crude product was purified by column
chromatography on silica gel eluted with dichloromethane (Rf
) 0.8-0.9).
P r op ylen ed ith iotetr a selen a fu lva len e (P DT-TSF , 1c).
A mixture of 8c (109 mg, 0.2 mmol) and sodium iodide (90
mg, 0.6 mmol) in 2-butanone (15 mL) was refluxed for 20 h.
The reaction mixture was concentrated, and the residue was
treated with dichloromethane (50 mL), which was washed with
water (30 mL) and dried (Na2SO4). Evaporation of the solvent
gave 2-methylthio-3-(3-iodopropylthio)tetraselenafulvalene (9,
125 mg, quant). Crude 9 was directly treated with sodium
iodide (270 mg, 1.8 mmol) in refluxing DMF (15 mL) for 1.5 h.
The reaction mixture was diluted with water (100 mL) and
extracted with carbon disulfide (20 mL × 3). The extract was
washed with water (50 mL × 3) and dried (Na2SO4), and
evaporation of the solvent gave crude 1c as a red solid. Column
chromatography on silica gel eluted with carbon disulfide gave
a red solid (Rf ) 0.5), which was then further purified by
recrystallization from carbon disulfide-hexane to give 1c (64
1
mg, 66% from 8c) as red needles: mp 197-198.5 °C dec; H
NMR δ 2.37 (m, 2H), 2.69 (m, 4H), 7.20 (s, 2H); IR (KBr) 3080,
3030 cm-1 (CH); MS m/z 498 (M+). Anal. Calcd for C9H6S2Se4:
C, 21.79; H,1.63. Found: C, 21.99; H, 1.63. CV: E1/2 ) +0.57V,
+0.92.
2-Me t h y lt h io -3-(3-io d o p r o p y lt h io )t e t r a s e le n a fu l-
va len e (9): red powder from dichloromethane-hexane (1:1,
1
v/v); mp 60-61.5 °C; H NMR δ 2.12 (quint, J ) 6.8 Hz, 2H),
2.48 (s, 3H), 2.93 (t, J ) 6.8 Hz, 2H), 3.35 (t, J ) 6.8 Hz, 2H),
7.22 (s, 2H); IR (KBr) 2907 cm-1 (C-H); MS m/z 638 (M+).
Anal. Calcd for C10H11S2ISe4: C, 18.82; H, 1.74. Found: C,
18.81; H, 1.72.
2,6(7′)-Bis(m eth ylth io)-3,7(6′)-bis(2-m eth oxyca r bon yl-
eth ylth io)tetr a selen a fu lva len e (7). To a refluxing mixture
of 5 (907 mg, 2.1 mmol) in benzene (30 mL) was added
trimethyl phosphite (1.2 mL), and the mixture was further
refluxed for 2.5 h. After evaporation of the solvent and the
excess trimethyl phospite, the residue was subjected to a
column chromatography on silica gel eluted with dichloro-
methane to give 7 as a red solid. An analytical sample was
obtained by recrystallization from dichloromethane-hexane
(1:2, v/v) as red fine crystals (510 mg, 77%): mp 72-73 °C; 1H
NMR δ 2.47 (s, 6H), 2.705 and 2.708 (t, J ) 7.4 Hz, 4H), 3.07
(t, J ) 7.4 Hz, 4H), 3.71 (s, 6H,); 13C NMR δ 20.6, 32.1, 34.5,
51.9, 107.2, 125.8 and 126.1, 135.7 and 135.9, 171.7; IR (KBr)
1732.3 cm-1 (CdO); MS m/z 724 (M+). Anal. Calcd for
2-Me t h ylt h io-3-ch lor om e t h ylt h iot e t r a se le n a fu lva -
len e (8a ): red plates from dichloromethane-hexane (1:2, v/v);
64% yield; mp 91-92 °C (lit.5a mp 91-92 °C).
2-Me t h ylt h io-3-(2-c h lo r o e t h y lt h io )t e t r a se le n a fu l-
va len e (8b): orange powder from dichloromethane-hexane
(1:2, v/v); 81% yield; mp 82-84 °C; 1H NMR δ 2.48 (s, 3H),
3.12 (t, J ) 7.8 Hz, 2H), 3.69 (t, J ) 7.8 Hz, 2H), 7.24 (s, 2H);
13C NMR δ 20.6, 38.8, 42.5, 101.8, 112.9, 122.5, 122.6, 124.2,
137.3; IR (KBr) 3018, 2910 cm-1 (CH); MS m/z 536 (M+). Anal.
Calcd for C9H9S2ClSe4: C, 20.30; H, 1.70. Found: C, 20.26;
H, 1.69.
2-Me t h y lt h io -3-(3-c h lo r o p r o p y lt h io )t e t r a s e le n a -
fu lva len e (8c): red powder from dichloromethane-hexane
(1:1,v/v); 95% yield; mp 60-61.5 °C; 1H NMR δ 2.10 (quint, J
) 6.6 Hz, 2H), 2.47 (s, 3H), 2.98 (t, J ) 6.6 Hz, 2H), 3.71 (t, J
) 6.6 Hz, 2H), 7.23 (s, 2H); 13C NMR δ 20.6, 31.9, 34.3, 42.9,
102.3, 112.5, 122.5, 122.6, 126.7, 135.3; IR (KBr) 3044, 2914
cm-1 (CH); MS m/z 548 (M+). Anal. Calcd for C10H11S2ClSe4:
C, 21.97; H, 2.03. Found: C, 21.95; H, 1.98.
Meth ylen ed ith iotetr a selen a fu lva len e (MDT-TSF , 1a ).
A mixture of 8a (104 mg, 0.2 mmol) and sodium iodide (180
mg, 1.2 mmol) in 2-pentanone (5 mL) was refluxed for 1.5 h.
The mixture was diluted with water (50 mL), and a resulting
precipitate was collected by filtration. The solid was dissolved
in carbon disulfide (100 mL), and the solution was washed with
water (100 mL × 2), dried over Na2SO4, and then concentrated.
Recrystallization of the resulting solid from carbon disulfide-
hexane (1:1, v/v) gave 1a (61 mg, 65%) as orange plates: mp
152-153 °C (lit.5a mp 152-153 °C); CV E1/2 ) +0.56, +0.83 V.
Eth ylen ed ith iotetr a selen a fu lva len e (EDT-TSF , 1b). A
mixture of 8b (106 mg, 0.2 mmol) and sodium iodide (90 mg,
0.6 mmol) in DMF (2 mL) was stirred at 90 °C for 15 h. The
reaction mixture was concentrated in vacuo, diluted with water
(30 mL), and extracted with carbon disulfide (20 mL × 3). The
extract was washed with water (50 mL) and dried (MgSO4).
Evaporation of the solvent followed by column chromatography
on silica gel eluted with carbon disulfide gave 1b (Rf ) 0.5),
which was purified by recrystallization from carbon disulfide-
hexane to give 1b as red needles (73 mg, 75% yield): mp 203-
204 °C dec; 1H NMR δ 3.30 (s, 4H), 7.25 (s, 2H); IR (KBr) 3075,
C
16H20O4S4Se4: C, 26.67; H 2.80. Found: C, 26.79; H 2.66.
Gen er a l Syn th etic P r oced u r e for 2,6(7′)-Bis(m eth yl-
th io)-3,7(6′)-bis(ch lor oalkylth io)tetr aselen afu lvalen e (10a-
c). To a degassed DMF solution (20 mL) of 7 (966 mg, 1.5
mmol) was added CsOH‚H2O (586 mg, 3.5 mmol) in methanol
(18 mL) during 5 min with stirring at room temperature. After
the mixture was stirred for a further 1 h, excess bromochloro-
alkane (ca. 1.5 mL) was added, and the mixture was stirred
for 2 h. The reaction mixture was concentrated in vacuo, and
the resulting residue was diluted with water (50 mL) and
extracted with dichloromethane (30 mL × 3). The extract was
washed with water (50 mL), dried (MgSO4), and concentrated.
The resulting crude product was purified by column chroma-
tography on silica gel eluted with dichloromethane (Rf ) 0.4-
0.5.)
2,6(7′)-Bis(m et h ylt h io)-3,7(6′)-b is(ch lor om et h ylt h io)-
t et r a selen a fu lva len e (10a ). Red plates from dichloro-
methane-hexane (1:1, v/v); 81% yield; mp 91-92 °C; 1H NMR
δ 2.48 (s, 3H), 4.82 (s, 4H); 13C NMR δ 20.9, 50.9, 107.8, 123.4
and 123.8, 137.9 and 138.2; IR (KBr) 3003, 2915 cm-1 (CH);
MS m/z 648 (M+); Anal. Calcd for C10H10S4Cl2Se4: C, 18.62;
H, 1.56. Found: C, 18.47; H 1.48.
2,6(7′)-Bis(m et h ylt h io)-3,7(6′)-b is(2-ch lor oet h ylt h io)-
t et r a selen a fu lva len e (10b ): brown plates from dichloro-
methane-hexane (1:1, v/v); 77% yield; mp 87-89 °C; 1H NMR
δ 2.49 (s, 6H), 3.132, 3.134 (t, J ) 7.7 Hz, 4H), 3.700 and 3.704
(t, J ) 7.7 Hz, 4H); 13C NMR δ 20.7, 38.8 and 38.9, 42.5, 107.4,
5222 J . Org. Chem., Vol. 68, No. 13, 2003

Synthesis of Alkylenedithio- and Bis(alkylenedithio)-TSFs
123.9 and 124.2, 137.1 and 137.3; IR (KBr) 2970, 2886 cm-1
(CH); MS m/z 676 (M+). Anal. Calcd for C12H14S4Cl2Se4: C,
21.41, H 2.10. Found: C, 21.44; H 2.11.
2,6(7′)-Bis(m eth ylth io)-3,7(6′)-bis(3-ch lor op r op ylth io-
tetr a selen a fu lva len e (10c): reddish purple needles from
dichloromethane-hexane (1:1, v/v); 81% yield; mp 68-70 °C;
1H NMR δ 2.09 (m, J ) 6.4, 6.8 Hz, 4H), 2.46 (s, 6H), 2.96 (t,
J ) 6.8 Hz, 4H), 3.687 and 3.689 (t, J ) 6.4 Hz, 4H); 13C NMR
δ 20.8, 32.1, 34.5, 43.0, 107.5, 126.6 and 126.8, 135.2 and 135.3;
IR (KBr) 2921 cm-1 (CH); MS m/z 704 (M+). Anal. Calcd for
(anhydride). The extract was concentrated in vacuo, and the
resulting residue containing crude 11 was subjected to column
chromatography on silica gel. The first fraction eluted with
dichloromethane-hexane (1:1, v/v) contained TSF recovered
(Rf 0.9, trace), and the second red band (Rf ) 0.3) gave 11 (880
mg, 82%) as a red solid upon concentration in vacuo. Recrys-
tallization from dichloromethane-hexane (1:1, v/v) gave ana-
lytically pure and X-ray-quality orange plates of 11: mp 55-
56 °C; 1H NMR δ 2.68 (t, J ) 7.3 Hz, 4H), 3.07 (t, J ) 7.3 Hz,
4H), 3.69 (s, 6H), 7.24 (s, 2H); 13C NMR δ 32.2, 34.4, 51.9,
101.7, 112.5, 122.5, 131.4, 171.5; IR (KBr) 1734 (CdO), 1362,
1055 cm-1 (CO); MS m/z 630 (M+). Anal. Calcd for C14H16O4-
S2Se4: C, 26.76; H, 2.57. Found: C, 26.67; H, 2.47.
C
14H18S4Cl2Se4: C, 23.98; H, 2.59. Found: C, 23.93; H 2.54.
Bis(m et h ylen ed it h io)t et r a selen a fu lva len e (BMDT-
TSF , 2a ). A mixture of 10a (130 mg, 0.2 mmol) and sodium
iodide (540 mg, 3.6 mmol) in 2-pentanone (15 mL) was refluxed
for 1.5 h. The mixture was diluted with water (100 mL), and
a resulting precipitate was collected by filtration. The solid
was dissolved in carbon disulfide (200 mL), and the solution
was washed with water (100 mL × 3), dried (Na2SO4), and
then concentrated. Column chromatography on silica gel eluted
with carbon disulfide gave 2a (Rf ) 0.7), which was then
further purified by recrystallization from chlorobenzene to give
an analytical pure sample as pale orange plates (55 mg,
50%): mp 209-210 °C; 1H NMR δ 4.85 (s, 4H); IR (KBr) 3000,
2909 cm-1 (CH); MS m/z 548 (M+). Anal. Calcd for C8H4S4Se4:
C, 17.66; H, 0.74. Found: C, 17.66; H, 0.80. CV: E1/2 ) +0.63,
0.88 V.
Bis(eth ylen ed ith io)tetr a selen a fu lva len e (BETS, 2b). A
mixture of 10b (134 mg, 0.2 mmol) and sodium iodide (90 mg,
0.6 mmol) in DMF (2 mL) was stirred at 90 °C for 15 h. The
reaction mixture was diluted with water (30 mL), and the
resulting precipitate was collected by filtration and dried. The
precipitate was dissolved in carbon disulfide (200 mL), and
the solution was washed with water (50 mL), dried (MgSO4),
and passed through a short column of silica gel. The resulting
solution was concentrated to ca. 30 mL, precipitating micro-
crystals of 2b, which were collected by filtration, washed with
dichloromethane, and dried. Recrystallization from carbon
disulfide-hexane gave brown fine crystals of 2b (59 mg, 52%
yield): mp 250 °C dec (lit.7 mp 250 °C dec). CV: E1/2 ) +0.69,
0.96 V.
2,3,6,7-Tet r a k is[(2-m et h oxyca r bon yl)et h ylt h io]t et r a -
selen a fu lva len e (13). A similar procedure for 11 was applied
to the synthesis of 13 using 7.0 equiv of LDA. After pretreat-
ment with a short column of silica gel eluted with dichloro-
methane, the crude product was purified by GPC; the first
fraction (VR ) 168 mL) contained the desired product 13 (55%
yield) and the second fraction (VR ) 175 mL) the tris-
substituted one (30% yield). 13: red plates from dichloro-
1
methane-hexane (1:1, v/v); mp 96-97 °C; H NMR δ 2.70 (t,
J ) 7.3 Hz, 8H), 3.10 (t, J ) 7.3 Hz, 8H), 3.69 (s, 12H); 13C
NMR δ 32.3, 34.5, 51.9, 107.0, 131.4, 171.6; IR (KBr) 1732
(CdO), 1363, 1051 cm-1 (CO); MS m/z 866 (M+). Anal. Calcd
for C22H28O8S4Se4: C, 30.56; H, 3.26. Found: C, 30.44; H 3.24.
2-Met h ylt h io-3-(2-m et h oxyca r b on ylet h ylt h io)t et r a -
selen a fu lva len e (6) fr om 11. To a degassed dry DMF
solution (15 mL) of 11 (266 mg, 0.42 mmol) was added CsOH‚
H2O (81 mg, 0.42 mmol) in methanol (4 mL) over a period of
10 min with stirring at room temperature. After the mixture
was further stirred for 0.5 h, excess iodomethane (0.2 mL) was
added, and the mixture was stirred for an additional 2 h. The
solvent was evaporated, and the resulting residue was diluted
with water and extracted with dichloromethane (30 mL × 3).
The extract was washed with water (60 mL), dried over MgSO4
(anhydride), and concentrated in vacuo to give crude 6, which
was purified by silica gel column chromatography eluted with
dichloromethane-hexane (1:1, v/v) (Rf ) 0.5). Recrystallization
from dichloromethane-hexane (1:2, v/v) gave 6 (190 mg,
quantitative) as an orange solid, mp 93-94 °C.
Bis(pr opylen ed ith io)tetr a selen a fu lva len e (BP DT-TSF,
2c). A mixture of 10c (140 mg, 0.2 mmol) and sodium iodide
(180 mg, 1.2 mmol) in 2-butanone (15 mL) was refluxed for
18 h. The reaction mixture was concentrated, and the residue
was extracted with dichloromethane (50 mL), washed with
water (50 mL × 2), and dried (Na2SO4). Evaporation of the
solvent gave 2,6(7)-bis(methylthio)-3,7(6)-bis(3-iodopropylthio)-
tetraselenafulvalene (164 mg, 93%). The crude iodide was
allowed to react with sodium iodide (502 mg, 3.34 mmol) in
refluxing DMF (20 mL) for 1.5 h. The reaction mixture was
diluted with water (100 mL) and extracted with carbon
disulfide (30 mL × 3). The extract was washed with water (50
mL × 3) and dried (Na2SO4). Evaporation of the solvent gave
crude 2c as a red solid. Column chromatography on silica gel
eluted with carbon disulfide gave a red solid (Rf ) 0.7), which
was then further purified by recrystallization from carbon
disulfide-hexane to give 2c (68 mg, 61% from 10c) as red
plates: mp 288.5-289.5 °C dec; 1H NMR δ 2.37 (m, 4H), 2.67
(m, 8H); IR (KBr) 2903, 2874 cm-1 (CH); MS m/z 602 (M+).
Anal. Calcd for C12H12S4Se4: C, 24.01; H, 2.01. Found: C,
23.93; H 1.95. CV: E1/2 ) + 0.66, +0.99 V.
2,6(7′)-Bis(m eth ylth io)-3,7(6′)-bis(2-m eth oxyca r bon yl-
eth ylth io)tetr a selen a fu lva len e (7) fr om 13. The synthesis
of 7 from 13 was carried out in a similar manner as for 6 from
11: 74% yield; red fine crystals; mp 72-73 °C.
Cr ysta llogr a p h ic Str u ctu r e An a lysis of 11. X-ray crystal
structure analysis was made on a Rigaku AFC7R four-circle
diffractometer (Mo KR radiation, λ ) 0.710 69 Å, graphite
monochromator, ω scan, 2θmax ) 55.0°). The structure was
solved by direct methods and refined by full-matrix least-
squares on |F|. All the non-hydrogen atoms were refined
anisotropically, and the hydrogen atoms were not included in
the refinement. All calculations were performed using the
crystallographic software package teXsan.27
Crystal data for 11: C14H16O4S2Se4, M ) 628.24, crystal size
0.50 × 0.34 × 0.02 mm, monoclinic, a ) 22.502(4) Å, b )
8.811(1) Å, c ) 10.208(1) Å, â ) 92.73(1)°, V ) 2021.6(5) Å3,
space group P21/c (no. 14), Z ) 4, Dc ) 2.064 g cm-3, F(000) )
1200.00, µ ) 74.82 cm-1, R ) 0.046, Rw ) 0.069, 4644 unique
reflections (Rint ) 0.025), 2725 observed reflections [I > 3.0σ(I)],
218 refined parameters.
2,3-Bis[(2-m e t h oxyca r b on yl)e t h ylt h io]t e t r a se le n a -
fu lva len e (11). To a solution of TSF20 (670 mg, 1.7 mmol) in
dry THF (60 mL) was added slowly a solution of freshly
prepared LDA (3.4 mmol) in THF-hexane (3.4 mL) at -90
°C, and the resulting solution was stirred for 40 min at -78
°C. Methyl thiocyanatopropionate (290 mg, 2.0 mmol) was
added via a syringe to the solution, and the mixture was
allowed to warm to -50 °C over a period of 1 h and finally
quenched by addition of water (60 mL). The mixture was
extracted with dichloromethane (20 mL × 4), and the extract
was washed with water (60 mL) and dried over MgSO4
Ack n ow led gm en t. This work was partially sup-
ported by a Grant-in Aid for Scientific Research (No.
13740399) from the Ministry of Education, Culture,
(26) Carbon diselenide is highly toxic and is especially irritating to
eyes and respiratory system. It is advisable to avoid direct contact with
the skin. Thus, this synthesis must be carried out in an efficient hood
with using disposable vinyl or latex gloves and chemical-resistant
safety goggles.
(27) teXsan: Single-Crystal Structure Analysis Software, Version
1.11, Molecular Structure Corp., Rigaku Corp., 2000.
J . Org. Chem, Vol. 68, No. 13, 2003 5223

Takimiya et al.
Su p p or tin g In for m a tion Ava ila ble: Procedures for the
CSe2-free synthesis of TSF and a CIF file giving full crystal-
lographic data for 11. This material is available free of charge
via the Internet at http://pubs.acs.org.
Sports, Science and Technology of J apan and Industrial
Technology Research Grant Program in ‘01 from New
Energy and Industrial Technology Development Or-
ganization (NEDO) of J apan. We also thank Izumi
Science and Technology Foundation for financial sup-
port.
J O034145A
5224 J . Org. Chem., Vol. 68, No. 13, 2003