Effective synthesis of 1,3-diselenole-2-selone-4,5-diselenolate (dsis) and its utilization for the synthesis of selenocycle-fused tetraselenafulvalene (TSF) derivatives

Article abstract of DOI:10.1055/s-2001-16755

A facile and effective synthetic procedure for 1,3-diselenole-2-selone-4,5-diselenolate (dsis, 2) has been established. The utilization of 2 for the synthesis of selenocycle-fused tetraselenafulvalene derivatives is also reported.

Full text of DOI:10.1055/s-2001-16755

1614
PAPER
Effective Synthesis of 1,3-Diselenole-2-selone-4,5-diselenolate (dsis) and its
Utilization for the Synthesis of Selenocycle-fused Tetraselenafulvalene (TSF)
Derivatives
S
ynthesis of Selenocyc
i
le-fuse
e
d Tetraselenafulv
K
alene
(
TSF
)
Deriv
o
atives dani,a Kazuo Takimiya,*a Yoshio Aso,a Tetsuo Otsubo,*a Takashi Nakayashiki,b Yoji Misakib
a
Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
Fax +81(824)227191; E-mail: ktakimi@hiroshima-u.ac.jp
b
Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
Received 16 April 2001; revised 4 June 2001
chemical reduction of carbon diselenide (CSe2),3 and later
on, by chemical reduction of CSe2 with an alkaline metal.4
These syntheses are analogous to that of 1 which is usual-
ly isolated as the complex of Zn(dmit)2 type.5 In contrast
to Zn(dmit)2, which is now easily synthesized on a large
scale of 90 g by chemical reduction of cheap CS2 with so-
dium metal,6 the analogous synthesis of Zn(dsis)2 is less
effective with a reported yield of 15%.4 In addition, the
formation of one mole of 2 requires four moles of CSe2,
and is accompanied with an equimolar amount of by-
product CSe32– (3), which makes purification of 2 difficult
(Scheme 1).
Abstract: A facile and effective synthetic procedure for 1,3-disele-
nole-2-selone-4,5-diselenolate (dsis, 2) has been established. The
utilization of 2 for the synthesis of selenocycle-fused tetraselenaful-
valene derivatives is also reported.
Key words: lithiation, diselenolate ligands, protecting groups,
ring-closure reaction, selenium-containing heterocycles
In the field of organic conductors, 1,3-dithiole-2-thione-
4,5-dithiolate (dmit, 1) is a very important compound both
as a key intermediate for the synthesis of thio-substituted
tetrathiafulvalene (TTF)-type electron donors and as a
ligand for metal complexes of M(dmit)2 type.1 Indeed, a
great number of organic conductors and superconductors
have been produced from the TTF-type donors and the
M(dmit)2 metal complexes.2 In such organic conductors
and superconductors, intermolecular interactions through
sulfur atoms play an important role in the electrical con-
duction in the solid state. Because the more spatially ex-
tended p- and d-orbitals of the selenium atom, compared
to those of sulfur atom, lead to more effective intermolec-
ular interactions, the selenium counterpart of 1, 1,3-dise-
lenole-2-selone-4,5-diselenolate (2, dsis), is very
interesting.
-Se
-Se
Se
Se
-Se Se
-Se Se
Se
CSe2
2 e-
2 CSe2
Se
Se
Se
Se
Se
2 e-
Se
2
CSe2
+
Se-
Se-
Se
3
Although the formation of 2 was first reported in 1976, its
chemistry has only been sporadically described in the lit-
erature. In the early papers, 2 was synthesized by electro-
Scheme 1 Suggested reaction path for 2 via reduction of CSe2
During the course of our synthetic study on selenium con-
taining electron donors, we have established a facile and
practical synthetic procedure for Zn(dsis)2. In this paper
we would like to describe the synthetic detail of Zn(dsis)2
and its utilization as a key intermediate for the synthesis
of selenocycle-fused tetraselenafulvalene (TSF) type
electron donors through deprotection/realkylation se-
quence of protected TSF selenolate intermediates.
S-
S
S
S
S
S
S
S
S
S
S
S
S
S
M
S-
1 dmit
M(dmit)2
Se-
Se-
Se
Se
Our synthetic procedure for dsis 2 consists of lithiation of
1,3-diselenole-2-selone (4), readily available on a multi-
gram scale,7 followed by introduction of selenium atoms.
Thus, to a THF solution of 4 was added freshly prepared
LDA solution at –78 °C, and then selenium powder was
added to the resulting solution. After usual work up with
tetrabutylammonium bromide and zinc chloride, 2 was
isolated as Zn(dsis)2 (n-Bu4N)2 (5) in 82% isolated yield
Se
2 dsis
Figure 1
Synthesis 2001, No. 11, 28 08 2001. Article Identifier:
1437-210X,E;2001,0,11,1614,1618,ftx,en;F03201ss.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

PAPER
Synthesis of Selenocycle-fused Tetraselenafulvalene (TSF) Derivatives
1615
TMS
H
Se-
Se
Se
Se
2
Se
Se
Se
i
iii
Se
Se
Se
Se
ii
Se
Se
Zn
Se
Se (n-Bu4N)2
Se
Se-
ref. 7
Se
82%
4
5
Se
CO2Me
CO2Me
MeO2C
MeO2C
Se
Se
Se
CO2Me
CO2Me
Se
Se
Se
Se
Se
iv
82%
v
Se
74%
Se
Se
Se
6
7
vi
48%
Se
Se
CO2Me
CO2Me
Se
Se
Se
Se
8
Scheme 2 Reagents and conditions: i) n-BuLi, Se, CSe2; ii) LDA, Se; iii) n-Bu4NBr, ZnCl2; iv) Br(CH2)2CO2Me; v) P(OMe)3; vi) P(OMe)3, 4
(Scheme 2). This method is more advantageous than the Selone 6 is also amenable to a cross-coupling reaction;
previous synthesis of 2 based on the reduction of CSe2 in when 6 was reacted with three-fold excess of 4, the corre-
terms of isolated yield and reproducibility even on a rela- sponding unsymmetrical TSF (8) was obtained in 48%
tively large scale (7–8 g of 5 can be synthesized in one isolated yield based on 6 (Scheme 2).
batch). An additional advantage is that, in contrast to the
use of four equivalents of CSe2 for the previous methods,
only one equivalent CSe2 is required here since the start-
ing material 4 is prepared in a quantitative yield from
These TSF derivatives with (2-methoxycarbonyl)ethylse-
leno groups (7 and 8) were then utilized for the synthesis
of selenocycle-fused TSF derivatives. Treatment of 7 or 8
with caesium hydroxide monohydrate in DMF8 generated
equimolar reaction of both selenium powder and CSe2 to
reactive TSF selenolate intermediates in situ, which were
readily alkylated with diiodomethane or 1,2-dibromoet-
lithium trimethylsilylacetylide.7
Alkylation of the zincate (5) with methyl 3-bromopropi- hane to give selenocycle-fused TSF derivatives (9–12) in
onate gave selone 6 (82% yield), which was then good yields (Scheme 3). Thus, 7 and 8 can be regarded as
effectively converted into the symmetrical TSF deriva- excellent synthons of the corresponding TSF bis- or tetra-
tive, 2,3,6,7-tetrakis[(2-methoxycarbonyl)ethylseleno]- selenolate, similarly to the protected TTF thiolates such as
TSF (7) in 74% yield (Scheme 2). Compound 7 is a stable tetrakis[(2-cyanoethyl)thio]-TTF.8
crystalline solid and was fully characterized not only by
spectroscopic analyses but also by X-ray crystallographic
analysis.
As shown in Figure 2, the central C6Se8 moiety of 7 is es- TSF derivatives,9 the present reaction protocol provides a
sentially planar, and the alkyl substituents stand perpen- practical synthetic method for such less accessible hetero-
dicular to the central C6Se8 plane. Owing to thermal cycle-fused TSF-type electron donors.
Since the direct phosphite-mediated coupling of 1,3-dise-
lenole-2-selones having a heterocyclic ring such as 13 and
14 does not proceed smoothly to give the corresponding
motion, the ellipsoids of the alkyl moieties are relatively
larger than those of the core.
In summary, we have established a practical and reliable
synthetic method of Zn(dsis)2 (n-Bu4N)2 (5), and also de-
Figure 2 Molecular structure of 7 (stereo view)
Synthesis 2001, No. 11, 1614–1618 ISSN 0039-7881 © Thieme Stuttgart · New York

1616
M. Kodani et al.
PAPER
ry at the Department of Applied Chemistry, Faculty of Engineering,
Hiroshima University. Cyclic voltammetry (CV) was carried out on
a Hokuto Denko HA-301 potentiostat equipped with a Hokuto Den-
ko HB-104 function generator using benzonitrile as solvent, and
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. The midpoint of a reversible redox wave
was determined as a half-wave oxidation potential (E1/2). 1,3-Dise-
lenole-2-selone (4) was synthesized according to the reported pro-
cedures.7
-Se
-Se
Se-
Se-
Se
Se
Se
Se
i
7
Se
Se
Se
Se
Se
Se
ii
(CH2)n
(CH2)n
Se
Se
n = 1 (94%)
n = 2 (93%)
9
10
Tetrabutylammonium 4,5-Bis(2-selenoxo-1,3-diselenole-4,5-
diselenolate)zincate (5)
To a solution of 1,3-diselenole-2-selone (4, 3.3 g, 12 mmol) in an-
hyd THF (90 mL) was slowly added a freshly prepared solution of
lithium diisopropylamide in THF–hexane (43 mL, 0.55 M, 24
mmol) at –90 °C, and the resulting solution was stirred for 1 h at the
same temperature. Selenium powder (1.9 g, 24 mmol) was added in
one portion to the solution, and the mixture was allowed to warm to
approx. –30 °C over 1.5 h, and kept at the same temperature for 1 h.
At this stage, the mixture turned deep blue. Then a solution of tet-
rabutylammonium bromide (3.87 g, 12 mmol) in anhyd MeOH (15
mL) and anhyd ZnCl2 (90%, 0.91 g, 6.0 mmol) in anhyd MeOH (15
mL) were successively added, and the mixture was stirred for 1 h at
r.t. The solvent was evaporated in vacuo below 40 °C, and the re-
sulting residue was carefully washed with H2O and MeOH to give
a crude solid of 5, which was then dissolved in acetone (200 mL),
and the insoluble solid was filtered off. The filtrate was concentrat-
ed to give practically pure 5 as reddish purple microcrystals (6.97 g,
82%). An analytically pure sample was obtained by recrystalliza-
tion from acetone–MeOH (1:10, v/v); mp 172–173 °C.
Se-
Se
Se
Se
i
8
Se-
Se
Se
Se
Se
Se
Se
ii
(CH2)n
Se
n = 1 (90%)
n = 2 (64%)
11
12
Scheme 3 Reagents and conditions: i) CsOH H2O; ii) CH2I2 or
Br(CH2)2Br
Se
Se
Se
13
Se
Se
Se
Se
IR (KBr): = 891 (C=Se) cm–1.
Se
Se
Anal. Calcd for C38H72N2Se10Zn (1412.0): C, 32.32; H, 5.14; N,
1.98. Found: C, 32.07; H, 5.16; N, 1.86.
Se
14
4,5-Bis[(2-methoxycarbonyl)ethylseleno]-1,3-diselenole-2-
selone (6)
Figure 3
A mixture of zincate 5 (1.0 g, 0.71 mmol) and methyl 3-bromopro-
pionate (0.39 mL, 3.6 mmol) in MeCN (10 mL) was refluxed for 1
h. The solvent was evaporated, and the residual solid was extracted
with CH2Cl2 (3 100 mL), which was then washed with H2O (3
100 mL) and sat. NaCl (3 100 mL), dried (MgSO4), and concen-
trated. The crude product was purified with column chromatogra-
phy on silica gel (CH2Cl2) (Rf = 0.3) to give pure 6 as red oil (0.71
g, 82%), which solidified in a freezer at –20 °C.
veloped its utilization as a versatile synthetic intermediate
for selenocycle-fused TSF type electron donors. We
strongly hope that this method and thereby synthesized
new TSF derivatives (9–11) would contribute to the de-
velopment of superior organic conductors.
IR (neat): = 1732 (C=O), 1163 (C-O), 903 (C=Se) cm–1.
1H NMR (400 MHz, CDCl3): = 2.87 (t, 4 H, J = 7.1 Hz), 3.16 (t,
4 H, J = 7.1 Hz), 3.73 (s, 6 H).
13C NMR (100 MHz, CDCl3): = 25.55, 35.00, 52.04, 135.91,
171.81, 211.42.
MS (EI): m/z = 610 (M+) with an isotopic pattern containing five Se
atoms.
All chemicals and solvents were of reagent grade unless otherwise
indicated. All reactions were carried out under a N2 atm. THF was
purified by distillation from sodium benzophenone ketyl under N2
prior to use. MeOH was distilled from Mg under a N2 atm. Toluene
was dried over CaH2 and distilled under a N2 atm. Dry DMF (H2O
< 50 ppm) was purchased from Nacalai tesque and used without pu-
rification. Column chromatography was carried out with silica gel
(Daisogel IR-60, 63–210 m). Mps are uncorrected. IR spectra were
Anal. Calcd for C11H14O4Se5 (609.7): C, 21.84; H, 2.33. Found: C,
21.87; H, 2.34.
1
obtained on a Shimadzu FTIR-8100A spectrometer. H and 13C
NMR spectra were obtained in CDCl3 on a JEOL Lambda 400 spec-
trometer operating at 400 MHz (1H) and 100 MHz (13C) with TMS
as internal reference; are reported in ppm. EI-MS spectra were ob-
tained on a Shimadzu QP-2000 spectrometer using an electron im-
pact ionization procedure (70 eV). FAB-MS spectra were recorded
on a JEOL JMS-SX 102A spectrometer using 3-NBA as matrix.
The molecular ion peaks of the selenium-containing compounds
showed a typical selenium isotopic pattern, and all the selenium-
containing mass peaks are reported for 80Se. Elemental analyses
were performed by Mr. Hideaki Iwatani, Microanalytical Laborato-
2,3,6,7-Tetrakis[(2-methoxycarbonyl)ethylseleno]-
tetraselenafulvalene (7)
A solution of 6 (0.53 g, 0.88 mmol) in anhyd toluene (15 mL) was
refluxed for 1 h. Then trimethyl phosphite (0.6 mL) was added to
the solution, and the resulting mixture was further refluxed for 5 h.
The reaction mixture was concentrated, and the resulting residue
was subjected to column chromatography on silica gel. A fraction
containing 7 was eluted with CH2Cl2–EtOAc (5:1) (Rf = 0.6) and
gave red crystals of pure 7 (0.34 g, 74%) upon concentration. Re-
Synthesis 2001, No. 11, 1614–1618 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Selenocycle-fused Tetraselenafulvalene (TSF) Derivatives
1617
crystallization from CHCl3–hexane (1:1, v/v) gave red needles suit-
able for X-ray analysis; mp 108 °C.
IR (KBr): = 1732 (C=O), 1169 (C-O) cm–1.
1H NMR (400 MHz, CDCl3): = 2.84 (t, 8 H, J = 7.2 Hz), 3.10 (t,
8 H, J = 7.2 Hz), 3.72 (s, 12 H).
13C NMR (100 MHz, CDCl3): = 24.92, 35.09, 51.82, 110.34,
121.51, 172.00.
Bis(ethylenediseleno)tetraselenafulvalene (10)
Compound 10 was synthesized as for 9 using 1,2-dibromoethane
(86 L, 0.91 mmol) in 93% yield. Brown fine needles from carbon
disulfide–hexane (10:1, v/v); mp 250 °C (dec.), [Lit.9 mp 235–240
°C (dec.)]. Since the reported mp was slightly lower than the present
one, a full characterization of 10 including microanalysis was car-
ried out.
IR (KBr): = 2960, 1509, 1410, 1260 cm–1.
1H NMR (400 MHz, CDCl3): = 3.36 (s, 8 H).
MS (FAB): m/z = 1060 (M+) with an isotopic pattern containing 8
Se atoms.
MS (EI): m/z = 768 (M+) with an isotopic pattern containing 8 Se
atoms.
Anal. Calcd for C22H28O8Se8 (1052.1): C, 25.11; H, 2.68. Found: C,
24.92; H, 2.51.
Anal. Calcd for C10H8Se8 (759.9): C, 15.81; H, 1.06. Found: C,
15.65; H, 0.79.
CV (benzonitrile, versus Ag/AgCl): E1/2 = +0.64 V, +0.95 V.
CV (benzonitrile, versus Ag/AgCl): E1/2 = +0.62 V, +0.92 V.
2,3-Bis[(2-methoxycarbonyl)ethylseleno]-tetraselenafulvalene
(8)
Methylenediselenotetraselenafulvalene (11)
A mixture of 6 (2.2 g, 3.7 mmol), 1,3-diselenole-2-selone (4, 3.0 g,
11.0 mmol) in anhyd toluene (75 mL) was refluxed for 1 h. Then tri-
methyl phosphite (5.2 mL) was added, and the resulting mixture
was refluxed for 3 h. The reaction mixture was concentrated in vac-
uo, and the resulting residue containing 8 and two homo-coupling
products was subjected to column chromatography on silica gel.
The first fraction eluted with CH2Cl2 was TSF (Rf = 0.9, 2.14 g,
80% based on 4), and the second red band eluted with CH2Cl2 (Rf =
0.5) gave 8 (1.3 g, 48%) as a red solid upon concentration in vacuo.
Recrystallization from CHCl3–hexane (1:1, v/v) gave analytically
pure 8 as orange needles; mp 78 °C. From the third fraction (Rf =
0.1, CH2Cl2), 7 (0.69 g, 36% based on 6) was obtained.
To a degassed dry DMF solution (23 mL) of 8 (0.8 g, 1.1 mmol) was
added CsOH H2O (0.41 g, 2.42 mmol) in MeOH (23 mL) over 5
min with stirring at r.t. After stirring further for 1 h, diiodomethane
(89 L, 1.1 mmol) in DMF (23 mL) was slowly added, and the mix-
ture was stirred for an additional hour. To the mixture was added
H2O (100 mL), and the resulting brown precipitate was collected by
filtration, washed with H2O, and dried. The crude solid was then
dissolved in carbon disulfide (200 mL), and the solution was
washed with H2O (3 100 mL) and sat. NaCl (100 mL), dried
(MgSO4), and concentrated. Column chromatography of the residue
on silica gel (carbon disulfide) gave 11 (Rf = 0.6, 0.47 g, 90%) as
red crystals. An analytical sample was obtained by recrystallization
from chlorobenzene as red plates; mp 192–194 °C (dec.).
IR (KBr): = 1732 (C=O), 1182 (C-O) cm–1.
1H NMR (400 MHz, CDCl3): = 2.84 (t, 4 H, J = 7.2 Hz), 3.10 (t,
4 H, J = 7.2 Hz), 3.71 (s, 6 H), 7.25 (s, 2 H).
13C NMR (100 MHz, CDCl3): = 24.90, 35.16, 51.87, 106.92,
110.58, 121.68, 122.67, 172.10.
MS (EI): m/z = 728 (M+) with an isotopic pattern containing 6 Se
atoms.
IR (KBr): = 3030, 2990, 1541, 718, 634, 625 cm–1.
1H NMR (400 MHz, CDCl3): = 4.84 (s, 2 H), 7.18 (s, 2 H).
MS (EI): m/z = 568 (M+) with an isotopic pattern containing 6 Se
atoms.
Anal. Calcd for C7H4Se6 (561.9): C, 14.96; H, 0.72. Found: C,
14.90; H, 0.71.
Anal. Calcd for C14H16O4Se6 (722.0): C, 23.29; H, 2.23. Found: C,
23.31; H, 2.23.
CV (benzonitrile, versus Ag/AgCl): E1/2 = +0.51 V, +0.81 V.
CV (benzonitrile, versus Ag/AgCl): E1/2 = +0.56 V, +0.90 V.
Ethylenediselenotetraselenafulvalene (12)
Compound 12 was synthesized as for 11 using 1,2-dibromoethane
(190 L, 2.19 mmol) in 64% yield. Red needles from carbon disul-
fide–hexane (1:1, v/v); mp 182–184 °C (dec.).
IR (KBr): = 3030, 3010, 2970, 1540, 1510, 1260, 712, 630 cm–1.
1H NMR (400 MHz, CDCl3): = 3.36 (s, 4 H), 7.19 (s, 2 H).
Deprotection, Realkylation of 7 and 8
Bis(methylenediseleno)tetraselenafulvalene (9)
To a degassed dry DMF solution (15 mL) of 7 (0.24 g, 0.23 mmol)
was added CsOH H2O (0.17 g, 1.0 mmol) in MeOH (15 mL) over
10 min with stirring at r.t. After stirring further for 1 h, di-
iodomethane (37 L, 0.46 mmol) in anhyd DMF (10 mL) was slow-
ly added, and the mixture was stirred for an additional 20 h. To the
mixture was added H2O (50 mL), and the resulting brown precipi-
tate was collected by filtration, washed with H2O, and dried. The
solid was then washed successively with hexane and acetone until
the washings became clear. Recrystallization from carbon disul-
fide–hexane (10:1, v/v) gave brown fine needles of 9 (26 mg, 94%);
mp 240 °C (dec.).
MS (EI): m/z = 582 (M+) with an isotopic pattern containing 6 Se
atoms.
Anal. Calcd for C8H6Se6 (575.9): C, 16.69; H, 1.05. Found: C,
16.66; H, 1.20.
CV (benzonitrile, versus Ag/AgCl): E1/2 = +0.55 V, +0.88 V.
Crystallographic Structure Analysis of 7
IR (KBr): = 2980, 1510 cm–1.
1H NMR (400 MHz, CDCl3): = 4.86 (s, 4 H).
MS (EI): m/z = 740 (M+) with an isotopic pattern containing 8 Se
atoms.
X-ray crystal structure analysis was made on a Rigaku AFC7R four-
circle diffractometer (MoK radiation, = 0.71069 Å, graphite
monochromator, T = 296 K, -2 scan, 2 max = 55.0°). The structure
was solved with Patterson methods and refined by full-matrix least-
squares on |F|. All calculations were performed using the crystallo-
graphic software package teXsan (Molecular Structure Corpora-
tion, 1985 & 1992).
Anal. Calcd for C8H4Se8 (731.8): C, 13.13; H, 0.55. Found: C,
13.39; H, 0.57.
Crystal data for 7: C20H28O8Se8, Mr = 1052.14, Crystal size 0.50
0.10 0.05 mm, triclinic, a = 8.260(3) Å, b = 19.045(7) Å, c =
5.441(3) Å, = 97.93(4)°, = 104.32(3)°, = 95.33(3)°, V =
814.1(6) Å3, space group P–1 (no. 2), Z = 1, calcd = 2.146 g cm–3,
CV (benzonitrile, versus Ag/AgCl): E1/2 = +0.59 V, +0.84 V.
Synthesis 2001, No. 11, 1614–1618 ISSN 0039-7881 © Thieme Stuttgart · New York

1618
M. Kodani et al.
PAPER
(4) Matsubayashi, G.; Akiba, K.; Tanaka, T. J. Chem. Soc.,
Dalton Trans. 1990, 115.
(5) Steimecke, G.; Sieler, H.-J.; Kirmse, R.; Hoyer, E.
Phosphorus Sulfur 1979, 7, 49.
(6) Wang, C.; Batsanov, A. S.; Bryce, M. R.; Howard, J. A. K.
Synthesis 1998, 1615.
(7) (a) Takimiya, K.; Morikami, A.; Otsubo, T. Synlett 1997,
319. (b) Ogura, F.; Takimiya, K. In Organoselenium
Chemistry, A Practical Approach; Back, T. G., Ed.; Oxford
University Press: New York, 1999, 262–263.
F(000) = 496.00, = 90.19 cm–1, R1 = 0.044, wR2 = 0.033, 4002
measured reflections, 2302 observed reflections [I>3.0 (I)], 193 re-
fined parameters. Crystallographic data (excluding structure fac-
tors) for the structure reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-161839. Copies of the data can be obtained
free of charge on application to The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: Int. code +(1223) 336-033; e-
mail: deposit@chemcrys.cam.ac.uk).
(8) (a) Svenstrup, N.; Rasmussen, K. M.; Hansen, T. K.; Becher,
J. Synthesis 1994, 809. (b) Simonsen, K. B.; Svenstrup, N.;
Lau, J.; Simonsen, O.; Mørk, P.; Kristensen, G. J.; Becher, J.
Synthesis 1996, 407. (c) Essentially there should be no
difference between cyanoethyl- and methoxycarbonylethyl-
groups as a protecting group for thiolate or selenolate.
However, in case of TSF selenolate derivatives,
incorporation of cyanoethyl groups often leads to a serious
decrease of solubility, making the subsequent deprotection/
realkylation protocol difficult. Thus, we prefer the
methoxycarbonylethyl group as a protecting group for the
TSF selenolates.
(9) Bis(ethylenediseleno)TSF (10) was synthesized in a low
yield from 14 via corresponding ketone; (a) Lee, V. Y.;
Engler, E. M.; Schumaker, R. R.; Parkin, S. S. P. J. Chem.
Soc., Chem. Commun. 1983, 235. (b) Lee, V. Y. Synth. Met.
1987, 20, 161.
References and Notes
(1) Svenstrup, N.; Becher, J. Synthesis 1995, 215.
(2) 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:
New Jersey, 1992. (b) Ishiguro, T.; Yamaji, K.; Saito, G.
Organic Superconductors, 2nd ed.; Springer–Verlag: Berlin,
1998.
(3) (a) Engler, E. M.; Green, D. C.; Chambers, J. Q. J. Chem.
Soc., Chem. Commun. 1976, 148. (b) Olk, R.-M.; Dietzsch,
W.; Hoyer, E. Synth. React. Inorg. Met.-Org. Chem. 1984,
14, 915.
Synthesis 2001, No. 11, 1614–1618 ISSN 0039-7881 © Thieme Stuttgart · New York