A facile syntheis of asymmetrical 2,3-dicyano-substituted tetrathiafulvalene derivatives

Article abstract of DOI:10.3987/COM-04-10268

The cross-coupling reactions of 4,5-dicyano-l,3-dithiol-2-one (3) and 4,5-bis(alkylthio)- and 4,5-bis(methoxycarbonyl)-1,3-dithiole-2-thiones (4a-e) gave asymmetrical 2,3-dicyanotetrathiafulvalenes (5a-e) having electron-donating or electron-withdrawing s

Full text of DOI:10.3987/COM-04-10268

HETEROCYCLES, Vol. 65, No. 1, 2005
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HETEROCYCLES, Vol. 65, No. 1, 2005, pp. 187 - 193
Received, 27th October, 2004, Accepted, 26th November, 2004, Published online, 26th November, 2004
A FACILE SYNTHEIS OF ASYMMETRICAL 2,3-DICYANO-
SUBSTITUTED TETRATHIAFULVALENE DERIVATIVES
Tie Chen,a Chunlan Wang,a Zhiqi Cong,a Bingzhu Yin,a,*
and Kimiaki Imafukub,*
a Department of Chemistry, School of Science and Technology,
Yanbian University, Yanji, Jilin 133002, China
b Department of Chemistry, Faculty of Science, Kumamoto University,
Kurokami, Kumamoto 860-8555, Japan
Abstract – The cross-coupling reactions of 4,5-dicyano-1,3-dithiol-2-one (3) and
4,5-bis(alkylthio)- and 4,5-bis(methoxycarbonyl)-1,3-dithiole-2-thiones (4a-e)
gave asymmetrical 2,3-dicyanotetrathiafulvalenes (5a-e) having electron-donating
or electron-withdrawing substituents at the 6,7-positions under high dilution
condition.
A pyrrole-fused tetrathiafulvalene (5f) was also obtained.
Their
electrochemical behaviors were measured by means of cyclic voltammetry.
INTRODUCTION
Since the discovery of the first metallic charge-transfer tetrathiafulvalene (TTF) complex with tetracyano-
p-benzoquinone,1 the chemistry of tetrathiafulvalene and its derivatives has been intensively studied on
account of their unique π-electron donating properties.
The developments in synthesis and utility of
TTF derivatives in the field of supramolecular chemistry have led to new elaborate TTF systems.2-4
A
variety of electron-donating or electron-withdrawing substituents has been extensively introduce into the
TTF skeleton. Of them, symmetrically and asymmetrically cyano-substituted tetrathiafulvalenes5 (1a-c)
have been synthesized as compounds bearing strong electron-withdrawing substituents.
cyanotetrathiafulvalene (1a) was used as a building block for the synthesis of new TTF derivatives with
potentially interesting solid-state structures.5
These compounds (1a-c) were obtained by the
Then, 4-
introduction of the cyano substituents into the TTF itself by using p-toluenesulfonyl cyanide.
The
o
reactions were carried out under a very rigorous condition, namely, at –78 C in the presence of lithium
diisopropylamide (LDA).
In addition, there is no systematic report on the synthesis of 2,3-dicyano-

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HETEROCYCLES, Vol. 65, No. 1, 2005
tetrathiafulvalene derivatives.
In the present communication, we report the synthesis of these 2,3-
dicyano-substituted TTF derivatives under the high dilution condition.
also described on the basis of cyclic voltammetry measurements.
Their oxidation potentials are
R1
R2
R3
R4
S
S
S
S
1a-c
R1 = CN, R2 = R3 = R4 = H
R1 = R2 = CN, R3 = R4 = H
R1 = R2 = R3 = R4 = CN
1a
1b
1c
Figure 1
RESULTS AND DISCUSSION
Preparation of 4,5-Dicyano-1,3-dithiol-2-one (3)
Previously, it was reported that 4,5-dicyano-1,3-dithiol-2-one (3) was prepared by passing phosgene into
the solution of disodium dimercaptomaleonitrile (2).6
In the present work, we obtained 4,5-dicyano-
1,3-dithiol-2-one (3) by using solid phosgene, bis(trichloromethyl) carbonate, instead of gaseous phosgene.
A mixture of disodium dimercaptomaleonitrile (2) and a third equivalent of bis(trichloromethyl) carbonate
o
in benzene was stirred for 15 min at 0 C and for additional 1 h at room temperature to give 4,5-dicyano-
1,3-dithiol-2-one (3) in 50% yield. On the other hand, 4,5-bis(alkylthio)-1,3-dithole-2-thiones (4a-d)
were prepared according to the literature.7
Compound (4c) was newly obtained in the present work.
9
Bis(methoxycarbonyl)-substituted and pyrrole-fused 1,3-dithiole-2-thiones (4e8,f ) were previously
reported.
2 CS2
2 NaCN
+
(CH3)2CO-H2O
reflux
NC
NC
NC
NC
SNa
S
S
C6H6
(Cl3CO)2C=O
+
O
rt, 1 h
SNa
2
3
Scheme 1

HETEROCYCLES, Vol. 65, No. 1, 2005
189
Synthesis of Tetrathiafulvalenes (5a-f)
In general, TTF derivatives have been prepared by the self-coupling or cross-coupling reactions of
appropriate 1,3-dithiole-2-thione or 1,3-dithiol-2-one in the presence of trialkyl phosphite. However,
this method could not be directly applied to the synthesis of asymmetrical tetrathiafulvalenes which have
two cyano groups in a 1,3-dithiole ring and other two substituents in another ring. After trying a variety
of reactions, we developed a cross-coupling reaction under high dilution condition.
The reactions of
4,5-dicyano-1,3-dithiol-2-one (3) (0.5 mmol) with compounds (4a-f) (0.5 mmol) were carried out in the
presence of triethyl phosphite (4 mL) in 110 mL of toluene (310 mL for 5f) at refluxing temperature and
resulted in 2,3-dicyano-6,7-bis(alkylthio)tetrathiafulvalenes (5a-d) and 6,7-bis(methoxycarbonyl)-
substituted tetrathiafulvalene (5e) in 10-47% yields.
fulvalene (5f) was obtained in 21% yield.
In a similar manner, a pyrrole-fused tetrathia-
R
R
NC
NC
NC
NC
R
R
S
S
S
S
S
S
S
S
P(OC2H5)3
+
O
S
PhCH3
120 oC
4a-e
5a-e
3
4a
5a
5b
5c
5d
5e
R = SCH3
R = SCH3
4b
4c
4d
4e
R = SCH2CH3
R = SCH2CH3
R = SCH2CH2CH2CH3
R = SCH2CH2S
R = SCH2CH2CH2CH3
R = SCH2CH2S
R = COOCH3
R = COOCH3
NC
NC
NC
NC
S
S
S
S
S
S
S
P(OC2H5)3
+
N Ts
S
O
N Ts
S
PhCH3
120 oC
4f
5f
3
Scheme 2
Electrochemical Behavior of Compounds (5a-f)
It is well-known that TTF is a stable and reversible two-electron donor.
radical and dication occur sequentially and at relatively low potentials, E1/21 = 0.34 V and E1/22 = 0.73 V vs
Ag/AgCl in acetonitrile.9
The oxidation potentials of 2,3-dicyano-6,7-bis(alkylthio)tetrathiafulvalenes
(5a-d) and related compounds (5e,f) were obtained in dichloromethane-acetonitrile (1:1) by cyclic
Thus, oxidations to the cation
voltammetry and are summarized in Table 1.
Compounds (5a-d) contain electron-withdrawing cyano
groups and electron-donating alkylthio groups.
Their oxidation potentials were observed between the
1
2
values for tetracyanothiafulvalene (E1/2 = + 1.12 V and E1/2 = + 1.22 V)10 and that for tetrakis-
1
(methylthio)tetrathiafulvalene (E1/2 = + 0.51 V).11
The oxidation potentials of 2,3-dicyano-6,7-

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HETEROCYCLES, Vol. 65, No. 1, 2005
bis(methoxycarbonyl)teterathiafulvalene (5e) resulted in the highest values.
additional electron-withdrawing methoxycarbonyl substituents. Compound (5f) also exhibited higher
oxidation potentials. In this compound, the annelation of a pyrrole unit to the TTF framework might
decrease the electron-donating ability, besides the electron-withdrawing effect of the tosyl group.
This is caused by the
Table 1
Oxidation Potentials E1/2 for Tetrathiafulvalenes (5a-f)a
Compound
E1/21 (V)
E1/22 (V)
ΔEp(V)
5a
5b
5c
5db
5e
5f
1.01
1.02
1.02
1.01
1.20
1.15
1.26
1.29
1.28
1.32
1.44
1.40
0.25
0.27
0.26
0.31
0.24
0.25
a
c = 10-3 M; 0.1 M Bu4NPF6; scan rate 100 mv/s.
b
5d did not completely dissolve under the same condition.
CONCLUSION
A series of asymmetrical 2,3-dicyanotetrathiafulvalene derivatives (5a-f) was synthesized under the high
1
dilution condition. Their oxidation potentials were found to be E1/2 = 1.01-1.20 V and E1/22 = 1.26-1.44
V by means of cyclic voltammetry measurements.
EXPERIMENTAL
The melting points were determined by a Buchi apparatus and are uncorrected. The IR spectra were
1
13
taken on a Varian FT-IR 1730 spectrophotometer.
Bruker AV-300 spectrometer. The MS spectral data were obtained by a Hewlett Pachard 1100-
HPLC/MSD instrument. The cyclic voltammetry were carried out on a Potentiostat/Galvanostat 273A
instrument employing 0.1 M BuN4PF6 as supporting electrode in dichloromethane-acetonitrile (1:1) with a
The H and C NMR spectra were recorded on a

HETEROCYCLES, Vol. 65, No. 1, 2005
191
sweep rate of 100 mv/s.
respectively, and the reference electrode was Ag/AgCl.
used without further purification. All solvents were purified and dried by standard methods, unless
otherwise stated. Silica gel (100-200 mesh) was purchased from Qing Dao Hai Yang Chemical Factory.
Counter and working electrodes were made of platinum and platinum-carbon,
All reagents were obtained from ACROS and
All the reactions were carried out under dry argon atmosphere.
was prepared according to the literature.6
Disodium dimercaptomaleonitrile (2)
4,5-Dicyano-1,3-dithiol-2-one (3).
A solution of bis(trichloromethyl) carbonate (3.75 g, 0.013 mol) in
benzene (35 mL) was added to a suspension of disodium dimercaptomaleonitrile (2) (7.05 g, 0.04 mol) in
benzene (70 mL) in a period of 15 min under ice cooling. The mixture was stirred for 1 h at rt, filtered,
and evaporated.
The crude product was purified by chromatography on a silica gel column with
The second fraction was collected and recrystallized
petroleum ether-ethyl acetate (10:1) as eluent.
from carbon tetrachloride to give 4,5-dicyano-1,3-dithiol-2-one (3) as colorless needles, yield: 1.57 g
(50%), mp 121-123 oC (lit.,12 123-124 oC).
4,5-Bis(butylthio)-1,3-dithiole-2-thione (4c).
1,3-dithiole-4,5-dithiolato)zincate (2.17 g, 3.0 mmol) in acetonitrile (60 mL) was added 1-bromobutane
(2.48 g, 18 mmol). The solution was refluxed for 6 h. The evaporation residue was chromatographed
To a solution of bis(tetraethylammonium) bis(2-thioxo-
on a silica gel column with petroleum ether-dichloromethane (1:1) to give 4c as a orange yellow oil;
yield 1.69 g (91%), 1H NMR (CDCl3): δ 0.96 (6H, t, J = 7.5 Hz, CH3 x 2), 1.50 (4H, m, CH2CH3 x 2),
1.66 (4H, m, SCH2CH2 x 2), 2.89 (4H, t, J = 7.5 Hz, SCH2 x 2); MS (APCI): m/z 311 ([M+1]+). Anal.
Calcd for C11H18S5: C, 42.54; H, 5.84. Found: C, 42.89; H, 5.65.
2,3-Dicyano-6,7-bis(alkylylthio)tetrathiafulvalenes (5a-e). General Procedure:
A solution of 4,5-
dicyano-1,3-dithiol-2-one (3) (84 mg, 0.50 mmol) and 4,5-bis(alkylthio)-1,3-dithiole-2-thione (4a-d) (0.5
mmol) in toluene (10 mL) was added dropwise to a solution of triethyl phosphite (4 mL, 23 mmol) in
toluene (100 mL) under argon atmosphere.
color of the solution changed to dark purple after 10-15 min.
4-5 h and then allowed to cool to rt. The toluene was removed in vacuo. After adding methanol (40
mL), a purple precipitate was collected, washed with methanol, and dried in vacuo. The product was
When the solution was heated at refluxing temperature, a
The mixture was stirred for an additional
chromatographed on a silica gel column with petroleum ether-dichloromethane (3:1) as eluent to give 2,3-
dicyano-6,7-bis(alkylthio)tetrathiafulvalenes (5a-e).
2,3-Dicyano-6,7-bis(methylthio)tetrathiafulvalene (5a).
This compound was obtained from the
reaction with 4,5-bis(methylthio)-1,3-dithiole-2-thione (4a)13 under heating for 5.5 h as purple flakes
o
(from hexane-benzene); yield 17 mg (10%), mp 164-165 C; IR (KBr): ν 2360 (CN); 1H NMR
(CDCl3): δ 2.46 (6H, s, CH3 x 2); 13C NMR (CDCl3): δ 20.72, 100.90, 109.03, 118.71, 123.39, 127.99;

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HETEROCYCLES, Vol. 65, No. 1, 2005
MS (APCI): m/z 347 ([M+1]+).
Anal. Calcd for C10H6N2S6: C, 34.66; H, 1.75; N, 8.08. Found: C,
34.48; H, 1.71; N, 7.83.
2,3-Dicyano-6,7-bis(ethylthio)tetrathiafulvalene (5b). This compound was obtained from the reaction
with 4,5-bis(ethylthio)-1,3-dithiole-2-thione (4b)7 under heating for 3.5 h as purple plates (from hexane);
yield 41 mg (22%), mp 150-152 oC; IR (KBr): ν 2360 (CN); 1H NMR (CDCl3): δ 1.34 (6H, t, J = 7.4
Hz, CH3 x 2), 2.88 (4H, q, J = 7.4 Hz, CH2 x 2); 13C NMR (CDCl3): δ 15.00, 30.81, 109.05, 118.77,
123.26, 128.30; MS (APCI): m/z 375 ([M+1]+).
Anal. Calcd for C12H10N2S6: C, 38.47; H, 2.69; N,
7.48. Found: C, 38.35; H, 2.84; N, 7.43.
2,3-Dicyano-6,7-bis(butylthio)tetrathiafulvalene (5c). This compound was obtained from the reaction
with 4,5-bis(butylthio)-1,3-dithiole-2-thione (4c) under heating for 4 h as purple flakes (from hexane);
yield 87 mg (36%), mp 105-107 oC; IR (KBr): ν 2360 (CN); 1H NMR (CDCl3): δ 0.95 (6H, t, J = 7.3
Hz, CH3 x 2), 1.37-1.60 (4H, m, CH2CH3 x 2), 1.60-1.74 (4H, m, SCH2CH2 x 2), 2.85 (4H, t, J = 7.2 Hz,
SCH2 x 2);
13C NMR (CDCl3): δ 13.54, 21.59, 31.71, 36.30, 100.01, 109.07, 118.76, 123.26, 128.26;
MS (APCI): m/z 431 ([M+1]+).
Anal. Calcd for C16H18N2S6: C, 44.62; H, 4.21; N, 6.50. Found: C,
44.46; H, 3.88; N, 6.30.
2,3-Dicyano-6,7-(ethylenedithio)tetrathiafulvalene (5d).14 This compound was obtained from the
reaction with 4,5-bis(ethylenedithio)-1,3-dithiole-2-thione (4d)7 under heating for 10 h. Methanol (40
mL) was added to the reaction mixture to precipitate purple solid, which was collected and washed with
o
methanol to give 5d as purple crystals (from chlorobenzene); yield 81 mg (47%), mp 236-238 C;
MS (APCI): m/z 345 ([M+1]+).
2,3-Dicyano-6,7-bis(methoxycarbonyl)tetrathiafulvalene (5e).
This compound was obtained from
the reaction with 4,5-bis(methoxycarbonyl)-1,3-dithiole-2-thione (4e)8 under heating for 6.5 h and the
chromatography was performed using petroleum ether-dichloromethane (2:1) as eluent to give as brown
o
needles (from hexane); yield 39 mg (21%), mp 193-194 C; IR (KBr): ν 2340 (CN); 1H NMR
(CDCl3): δ 3.87 (6H, s, CH3 x 2); 13C NMR (CDCl3): δ 53.75, 102.39, 108.79, 118.68, 131.72, 159.04;
MS (APCI): m/z 371 ([M+1]+).
Anal. Calcd for C12H6N2O4S4: C, 38.91; H, 1.63; N, 7.56. Found: C,
38.66; H, 1.54; N, 7.69.
N-Tosyl-2-[4,5-dicyano-1,3-dithiole-2-ylidene]-(1,3)-dithiolo[4,5-c]pyrrole (5f).
tosyl-(1,3)-dithiolo[4,5-c]pyrrole-2-thione (4f)9 (163 mg, 0.5 mmol) was carried out in the thrice amounts
of toluene (300 mL) under heating for 5 h. The product was chromatographed on a silica gel column
The reaction of N-
with petroleum ether-dichloromethane (2:1) as eluent to give 5f as brown microcrystals (from hexane-
o
toluene); yield 55 mg (25%), mp 270 C (decomp); IR (KBr): ν 2360 (CN); 1H NMR (CDCl3):

HETEROCYCLES, Vol. 65, No. 1, 2005
193
δ 2.45 (3H, s, 4’-CH3), 6.59 (2H, s, =CH x 2), 7.34 (2H, d, J = 8.3 Hz, 3’-,5’-H), 7.78 (2H, d, J = 8.3 Hz,
2’-,6’-H); 13C NMR (CDCl3): δ 21.69, 108.89, 111.80, 125.10, 127.09, 130.27, 135.07, 145.86; MS
(APCI): m/z 448 ([M+1]+). Anal. Calcd for C17H9N3O2S5: C, 45.62; H, 2.03; N, 9.39. Found: C, 45.77;
H, 2.11; N, 9.69.
ACKNOWLEDGMENT
We are grateful to the National Science Foundation of China for the financial support (No. 20462001).
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