A practical two-step synthesis of tetraselenafulvalene (TSF)

Article abstract of DOI:10.1055/s-2005-872117

The preparation of tetraselenafulvalene (TSF) from commercially available sodium acetylide in xylene-light mineral oil and selenium powder is described. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2005-872117

2
810
PRACTICAL SYNTHETIC PROCEDURES
A Practical Two-Step Synthesis of Tetraselenafulvalene (TSF)
A
K
P
ractica
l
Two-S
a
tepSynthes
z
is of Tetras
u
e
lenafulvale
o
ne (TSF) Takimiya,* Hyung Joon Jeon, Tetsuo Otsubo
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University,
Higashi-Hiroshima 739-8527, Japan
Fax +81(82)4245494; E-mail: ktakimi@hiroshima-u.ac.jp
PSP
Received 31 May 2005; revised 30 June 2005
No57
Abstract: The preparation of tetraselenafulvalene (TSF) from commercially available sodium acetylide in xylene–light mineral oil and
selenium powder is described.
Keywords, tetraselenafulvalenes, selenium, sodium acetylide, electron donors
Procedure 1
H
H
Se, THF
MeOH
Se
Se
Na
SeNa
1
Procedure 2
Se
Se
Se
Se
Se
Se
TSF
Scheme 1 Synthesis of TSF
Tetraselenafulvalene (TSF) derivatives have been impor- The development of materials chemistry based on TSF-
tant electron donors in the field of organic conductors, type electron donors is, however, so far limited, because
since Engler et al. first synthesized the parent TSF and its the synthesis of TSF and its derivatives usually require
highly conducting charge-transfer complex with tetracy- highly toxic selenium reagents such as carbon diselenide
1
6
anoquinodimethane (TCNQ). Since then, the first organ- (CSe ) and hydrogen selenide (H Se). In order to expand
2
2
ic superconductor was generated from the radical cation TSF-based chemistry, like the well-established TTF-
2
salt of tetramethyltetraselenafulvalene (TMTSF). Fur- based chemistry, it is thus desirable to develop practical
thermore, new superconductors based on heterocycle- synthetic methods for such TSF compounds using readily
7
fused TSF derivatives, such as bis(ethylenedithio)tetrase- available, nontoxic selenium reagents. In this regard,
3
lenafulvalene (BETS), methylenedithio-tetraselenaful- Cava et al. reported an unconventional synthesis of TSF,
4
valene (MDT-TSF), and methylenediseleno-tetra- as shown in Scheme 2, which involves the following two
5
selenafulvalene (MDS-TSF) have been reported one after intriguing reactions: (i) the formation of 2-methylene-1,3-
another.
diselenole (1) by spontaneous decomposition of 1,2,3-se-
lenadiazole (2) prepared from acetaldehyde semicarba-
zone and selenium dioxide and (ii) dimerization of 1 to
S
S
S
S
Se
Se
Se
Se
Se
Se
Se
Se
8
TSF induced by iodine–morpholine. In addition, Cava’s
group reported that various TSF derivatives could be ob-
TMTSF
BETS
9
tained by functionalization of TSF itself. Our group also
demonstrated that some elaborate heterocycle-fused TSF
derivatives including BETS and MDT-TSF could be tai-
Se
Se
Se
Se
S
S
Se
Se
Se
Se
Se
Se
10
lored from TSF. Cava’s approach to TSF is quite prom-
ising in terms of the favorable use of nontoxic selenium
dioxide, but has the disadvantages of low yield in the first
MDT-TSF
MDS-TSF
1
1
reaction (25–30%). It is speculated that in the first reac-
tion, 2 decomposes to ethyneselenol (3), which is in equi-
librium with selenoketene 4, and dimerizes to 1. We
expected that, if the intermediate 3 is readily generated us-
ing a common acetylene reagent, then Cava’s approach to
TSF would become more attractive and useful. In this pa-
Figure 1
SYNTHESIS 2005, No. 16, pp 2810–2813
x
x.
x
x
.
2
0
0
5
Advanced online publication: 04.08.2005
DOI: 10.1055/s-2005-872117; Art ID: F10005SS
Georg Thieme Verlag Stuttgart · New York
©

PRACTICAL SYNTHETIC PROCEDURES
A Practical Two-Step Synthesis of Tetraselenafulvalene
2811
per, we report a one-pot synthesis of 1 from commercial amount of water to the reaction mixture did not take place.
sodium acetylide and elemental selenium. In combination Instead, extraction with pentane turned out to be satisfac-
with Cava’s conversion procedure of 1 to TSF it has tory (69% yield) for the isolation of 1. Treatment of 1 with
turned out that this procedure provides a practical two- an iodine–morpholine mixture in DMF gave TSF in al-
step, gram-scale synthesis of TSF.
most the same yield (25–37%) as the literature.8
We also examined the synthesis of TSF without isolation
of 1. Reaction of sodium acetylide in xylene–light mineral
oil with selenium powder in THF, followed by the addi-
tion of methanol gave a solution of 1 in xylene–light min-
eral oil after the same workup as above. This solution
without further purification was successfully utilized to
synthesize TSF and the yield of TSF, based on the amount
of selenium powder used in the first step, is basically the
same as above. By both reactions, more than 2 g of TSF
was routinely obtained from sodium acetylide in xylene–
light mineral oil (32 mL, ca. 0.1 mol) and selenium pow-
der (7.6 g).
NHCONH2
H
H
H
N
SeO2
Se
N
N
·
H3C
H
Se
SeH
2
3
4
Se
I2, morpholine
Se
Se
Se
Se
Se
TSF
1
Scheme 2 Cava’s method for the synthesis of TSF.
Sodium acetylide is a commercial reagent available as
slurry in xylene–light mineral oil. As a result of the chem-
ical instability of 2-methylene-1,3-diselenole (1) we
As reported in the proceeding papers, alkylenedithio-,
bis(alkylenedithio)-, and alkylenediseleno-TSFs via the
8
10
10
protected TSF-dithiolate (5), -tetrathiolate (6), and
were afraid that the existence of these stabilizing solvents
with high boiling points would make purification of 1 dif-
ficult. Thus, the solvents were first removed from solid
sodium acetylide by repeated centrifugation/washing (an-
hydrous hexane) cycles, and the resulting solvent-free so-
dium acetylide was utilized in the reaction with selenium
powder in THF. This reaction proceeded smoothly, as was
observed by the gradual consumption of selenium pow-
der, in situ, producing ethyneselenate anion, which was
then protonated by the addition of methanol and dimer-
ized into 1. In Cava’s method, compound 1 was isolated
by precipitation from DMF–water. In the present case,
however, precipitation of 1 by the addition of even a large
5
-
diselenolate (7) were synthesized from TSF. In a similar
manner, protected TSF tetraselenolate 8 was prepared as
shown in Scheme 3. With these intermediates in hand,
various kinds of heterocycle-fused TSF derivatives are
easily obtained via the deprotection/realkylation proto-
12
col.
In conclusion, we have established a convenient and prac-
tical synthesis of TSF from commercially available sodi-
um acetylide. The present procedure has the advantage of
using cheap, non-toxic selenium powder as the selenium
source, only two synthetic steps are required, and the
method is suitable for laboratory-scale preparation (>2 g
batch). In combination with their functionalization as pro-
S
S
S
Se
Se
Se
Se
S
S
Se
Se
Se
Se
(
CH2)n
(CH2)n
(CH2)n
S
Ref. 10
2%
60%
SR
Se
Se
Se
RS
RS
SR
SR
Se
Se
Se
Se
8
Se
, R = CH2CH2CO2Me
SR
1
2
) LDA
) RSCN
5
6
, R = CH2CH2CO2Me
Se
Se
Se
Se
TSF
1
2
) LDA
) RSeCN
SeR
SeR
Ref. 5
RSe
RSe
SeR
SeR
Se
Se
Se
Se
Se
Se
Se
Se
73%
74%
7, R = CH2CH2CO2Me
8, R = CH2CH2CO2Me
Se
CH2)n
Se
Se
Se
Se
Se
Se
Se
Se
Se
Se
Se
Se
Se
(
(CH2)n
(
CH2)n
Scheme 3 Synthesis of hetecocycle-fused TSFs from TSF.5,10
Synthesis 2005, No. 16, 2810–2813 © Thieme Stuttgart · New York

2
812
K. Takimiya et al.
PRACTICAL SYNTHETIC PROCEDURES
, 400 MHz): d = 7.22 (s, 4 H).
tected thiolate or selenolate moieties, followed by their 1H NMR (CDCl
deprotection/realkylation chemistry, the present method MS (EI): m/z = 396 (M+, 80Se).
3
paves a practical way to various heterocycle-fused TSF-
Anal. Calcd for C H Se : C, 18.39; H, 1.03. Found: C, 18.39; H,
6
4
4
type donors, including MDT-TSF and MDS-TSF which
can be used to produce superconducting radical cation
salts.
1
.02.
Synthesis of TSF without Isolation of 1
Sodium acetylide (18% wt., slurry in xylene–light mineral oil, 32
mL, ca. 4.8 g, 0.1 mol) was transferred to a 500-mL three-necked
flask and diluted with anhyd THF (100 mL). This sodium acetylide
suspension was used in the reaction with Se powder as mentioned
above, and the reaction work-up was carried out in the same man-
ner. The pentane extract was concentrated to give a dark red solu-
tion of 1, which was treated with an iodine–morpholine mixture
(26.5 g and 27.5 mL, respectively) in DMF (150 mL) in the same
manner as above. Concentration of the CH Cl extract gave a solu-
All chemicals and solvents used were of reagent grade. Sodium
acetylide was purchased from Aldrich. All reactions were carried
out under a nitrogen atmosphere with anhyd solvents. Column chro-
matography was carried out with Daisogel IR-60 (63–210 mm).
Melting points are uncorrected. NMR spectra were obtained in
CDCl with a JEOL Lambda 400 spectrometer operating at 400
3
1
13
MHz for H NMR and 100 MHz for C NMR, with TMS as the in-
ternal reference; chemical shifts (d) are reported in ppm. EI-MS
spectra were obtained on a Shimadzu QP-5050A spectrometer us-
ing an electron impact ionization procedure (70 eV). The molecular
ion peaks of the selenium-containing compounds showed a typical
selenium isotopic pattern, and all the selenium-containing mass
2
2
tion of TSF in xylene–light mineral, which was purified directly by
column chromatography (silica gel, 6 cm × 20 cm; hexane was used
as the first eluent until both the xylene and light mineral were com-
pletely eluted, and then CH Cl –hexane, 1:2).
2
2
8
0
Yield: 2.2–2.4 g (ca. 25%).
peaks are reported for Se.
2
,3,6,7-Tetrakis[(2-methoxycarbonyl)ethylseleno]tetraselena-
2
-Methylene-1,3-diselenole (1); Synthesis of TSF from Sodium
fulvalene (8)
Acetylide
To a solution of TSF (225 mg, 0.57 mmol) in anhyd THF (20 mL)
was added freshly prepared LDA in THF–hexane (1.0 M, 2.4 mL,
2
–
added via syringe to the solution, the mixture was allowed to warm
to –50 °C over a period of 1 h, and finally quenched by the addition
of H O (30 mL). The mixture was extracted with CH Cl (4 × 15
mL), the extract was washed with H O (30 mL), and dried over
MgSO (anhyd). The extract was concentrated in vacuo and the re-
sulting residue was subjected to column chromatography (silica gel;
CH Cl –EtOAc, 6:1). Recrystallization from CHCl –hexane (1:1)
gave fine red needles.
Yield: 474 mg (78%); mp 107–108 °C (Lit.12b 108 °C); R 0.5
Sodium acetylide (18% wt., slurry in xylene–light mineral oil, 32
mL, ca. 4.8 g, 0.1 mol) was transferred to four test tubes (16.5 mm
diameter × 105 mm length) and centrifuged to precipitate the salt.
The upper solvent layer was removed with a syringe, and the result-
ing solid was shaken with anhyd hexane (6 mL) under a nitrogen at-
mosphere, and then the mixture was once again centrifuged. This
operation was repeated three times, and the resulting xylene–light
mineral oil-free sodium acetylide was suspended in THF (100 mL)
and transferred into a 500 mL three-necked flask via double-ended
transfer needle. To this suspension cooled to –70 °C was added Se
powder (7.6 g, 0.096 mol) in one portion, the resulting mixture was
allowed to warm to 0 °C, and stirred for 1 h at 0 ºC. Then, MeOH
.4 mmol) at –90 °C, and the mixture was stirred for 40 min at
78 °C. Methyl selenocyanatopropionate (480 mg, 2.5 mmol) was
2
2
2
2
4
2
2
3
(
60 mL) was added at –78 °C, the resulting mixture was gradually
f
warmed to 0 °C, and stirred for 2 h at the same temperature. The so-
(CH Cl –EtOAc, 6:1).
2
2
lution was diluted with H O (120 mL), extracted with pentane (4 ×
2
Spectroscopic data were identical to those reported previously.
8
0 mL), the extract was washed with H O (3 × 60 mL), dried over
2
Na SO , and concentrated in vacuo (to avoid decomposition of 1, it
2
4
is advisable that this is carried out below r.t. in the dark) to give 2-
methylene-1,3-dislenole (7.0 g, 69%). The product was used in the
next reaction without further purification.
Acknowledgment
This work was partially supported by a Grant-in-Aid for Scientific
Research on Priority Areas of Molecular Conductors (No.
8
Mp 51–53 °C (Lit. 58–60 °C).
1
5073218) from the Ministry of Education, Science, Sports, and
1
H NMR (CDCl , 400 MHz): d = 6.93 (dd, J = 1.0, 1.5 Hz, 2 H),
Culture, Japan. The authors are grateful to Prof. J. Ohshita, Hiro-
shima university, for helpful discussion.
3
5
.62 (dd, J = 1.0, 1.5 Hz, 2 H).
1
3
C NMR (CDCl , 100 MHz): d = 107.98, 120.29, 132.41.
3
MS (EI): m/z = 212 (M+, 80Se).
References
(
(
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(
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(
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2
Watanabe, T.; Cassoux, P. J. Am. Chem. Soc. 1996, 118,
(
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2
2
3
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2
2
3
2
2
4
(
Column chromatography (silica gel, 6 cm × 20 cm; CH Cl –hexane,
2
2
Wada, N.; Ojima, E.; Fujiwara, H.; Kobayashi, H. Chem.
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1
:2) gave TSF (2.4 g, 37%) as a red solid. This product was practi-
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cally pure sample was obtained by recrystallization from hexane.
Mp 132–133 °C (Lit.1 132.5–133 °C, Lit.8 132–133 °C); R 0.4
f
2
001, 11, 2410. (g) Fujiwara, H.; Fujiwara, E.; Nakazawa,
(
CH Cl –hexane, 1:2).
2 2
Y.; Narymbetov, B. Z.; Kato, K.; Kobayashi, H.; Kobayashi,
Synthesis 2005, No. 16, 2810–2813 © Thieme Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
A Practical Two-Step Synthesis of Tetraselenafulvalene
2813
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(
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(
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Synthesis 2005, No. 16, 2810–2813 © Thieme Stuttgart · New York