Synthesis of some 2-ylidene-1,3-dithiolanes

Article abstract of DOI:10.1134/S1070428017010304

Convenient procedures have been developed for the synthesis of 2-(1,3-dithiolan-2-ylidene)- malononitriles and 2-cyano-2-(1,3-dithiolan-2-ylidene)acetamides from disodium alk-1-ene-1,1-dithiolates and 1,2-dichloroalkanes, as well as from malononitrile or cyanoacetamide in a one-pot mode.

Full text of DOI:10.1134/S1070428017010304

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2017, Vol. 53, No. 1, pp. 147–149. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © K.V. Lipin, O.V. Ershov, M.Yu. Belikov, S.V. Fedoseev, 2017, published in Zhurnal Organicheskoi Khimii, 2017, Vol. 53, No. 1,
pp. 148–150.
SHORT
COMMUNICATIONS
Synthesis of Some 2-Ylidene-1,3-dithiolanes
K. V. Lipin,* O. V. Ershov, M. Yu. Belikov, and S. V. Fedoseev
I.N. Ul’yanov Chuvash State University, Moskovskii pr. 15, Cheboksary, 428015 Russia
*e-mail: lipinkost@mail.ru
Received July 29, 2016
Abstract—Convenient procedures have been developed for the synthesis of 2-(1,3-dithiolan-2-ylidene)-
malononitriles and 2-cyano-2-(1,3-dithiolan-2-ylidene)acetamides from disodium alk-1-ene-1,1-dithiolates and
1,2-dichloroalkanes, as well as from malononitrile or cyanoacetamide in a one-pot mode.
DOI: 10.1134/S1070428017010304
Five-membered 1,3-dithia heterocycles often con-
stitute structural fragments of compounds possessing
important electronic and optical properties. For ex-
ample, coordination compounds derived from 4,5-di-
sulfanyl-1,3-dithiole-2-tione are used for the synthesis
of charge-transfer complexes [1–3]. Compounds con-
taining a 2-ylidene-1,3-dithiole fragment absorb in the
near UV region and narrow ranges of the visible region
[4] and are light-resistant and stable. Such compounds
have already been used to create materials for optical
data storage [5] and UV-protective coatings [6, 7].
The IR spectra of 2a–2d contained strong absorp-
tion bands in the region 2192–2208 cm–1 due to
stretching vibrations of the conjugated cyano groups
and strong bands at 1457–1461 cm–1 due to C=C
stretching vibrations. Compounds 2c and 2d also
showed in the IR spectra absorption bands typical of
1
amide group. In the H NMR spectra of 2a–2d we
observed signals at δ 1.42–4.67 ppm from protons in
the alkyl substituent and amide proton signals at
δ 7.20–7.50 ppm (2c, 2d). The 13C NMR spectra of
2a–2d were consistent with the given structures. The
intensity of the molecular ion peaks in the mass spectra
of 2a–2d ranged from 10 to 30%.
1,3-Dithia heterocycles containing an electron-
withdrawing substituent in the 2-position exhibit most
valuable electronic and optical properties [1–3].
Development of methods for the synthesis of such
compounds is a topical problem of modern organic
chemistry. It is convenient to obtain compounds with
a 2-ylidene-1,3-dithiolane fragment from 2,2-disubsti-
tuted disodium ethene-1,1-dithiolates [8–10].
We propose several versions of the synthesis of 2a–
2d with the use of different solvents and temperature
conditions: (a) the initial reactants were dissolved in
DMSO, and the mixture was refluxed for 0.5–1 h;
(b) the initial reactants were dissolved in DMF, and the
mixture was stirred for 1–2 h at room temperature;
these solvents were selected because of poor solubility
of initial dithiolates 1a and 1b and dichloroalkanes.
We have developed a new procedure for the syn-
thesis of some 2-ylidene-1,3-dithiolanes by reaction of
2,2-disubstituted disodium alk-1-ene-1,1-dithiolates 1a
and 1b with 1,2-dichloroalkanes. The yields of 2a–2d
were 80–94% (Scheme 1), and their structure was
confirmed by IR, 1H and 13C NMR and mass spectra.
According to the original procedure [11], disodium
2,2-dicyanoethene-1,1-dithiolate (1a) was prepared by
reaction of malononitrile with carbon disulfide in the
presence of sodium ethoxide. We have found that there
is no need of isolating compound 1a and that the cor-
responding dichloroalkane can be added directly to the
reaction mixture (method c; Scheme 2). The procedure
for cyanoacetamide is the same. In this way, com-
pounds 2a–2d can be synthesized in a shorter time, and
the preparative value of the proposed procedure is
higher due to the use of more accessible reagents.
Scheme 1.
CN
R
CN
X
S
R
NaS
+
Cl
X
Cl
S
SNa
1a, 1b
2a–2d
2, X = CN, R = H (a), Me (b); X = CONH2, R = H (c), Me (d).
147

LIPIN et al.
148
Scheme 2.
R
CN
Cl
EtONa
Cl
NaS
+
CN
CS2
2a–2d
X
X
SNa
1
1
Thus, we have developed novel methods of syn-
thesis of 2-ylidene-1,3-dithiolanes, including a one-pot
procedure. Dithiolanes 2b and 2d were not described
previously, and the procedures for the synthesis of 2a
and 2c were considerably improved as compared to
known methods [8–10].
1457 (C=C). H NMR spectrum (DMSO-d6), δ, ppm:
3.28 s (2H, CH2), 3.95 s (2H, CH2). 13C NMR spec-
trum (DMSO-d6), δC, ppm: 41.62 (2C, CH2), 64.82
[C(CN)2], 113.56 (CN), 191.70 (SCS). Mass spectrum:
m/z 168 (Irel, 30%) [M]+. Found, %: C 42.93; H 2.37;
N 16.60. C6H4N2S2. Calculated, %: C 42.83; H 2.40;
N 16.65. M 168.23.
2-(1,3-Dithiolan-2-ylidene)malononitrile (2a).
a. Disodium 2,2-dicyanoethene-1,1-dithiolate (1a) tri-
hydrate, 0.24 g (or 1 mmol of anhydrous 1a), was
dissolved in 5 mL of dimethyl sulfoxide, 0.5 g
(5 mmol) of 1,2-dichloroethane was added to the solu-
tion, and the mixture was refluxed for 1 h. When the
reaction was complete (TLC), the mixture was cooled
and diluted with 4–5 volumes of water, and the precip-
itate was filtered off, washed with water, and recrystal-
lized from propan-2-ol.
Compounds 2b–2d were synthesized in a similar
way.
2-(4-Methyl-1,3-dithiolan-2-ylidene)malononi-
trile (2b). Yield 0.18 g (86%, a), 0.20 g (94%, b),
0.31 g (75%, c), mp 95–96°C. IR spectrum, ν, cm–1:
1
2208 (C≡N), 1460 (C=C). H NMR spectrum
(DMSO-d6), δ, ppm: 1.50 d (3H, CH3, J = 6.7 Hz),
3.76–3.82 d.d (1H, CH2, J = 12.1, 5.6 Hz), 4.07 d.d
(1H, CH2, J = 12.1, 5.2 Hz), 4.59–4.67 m (1H, CH).
13C NMR spectrum (DMSO-d6), δC, ppm: 18.59 (CH3),
47.52 (CH2), 53.73 (CH), 64.72 [C(CN)2], 113.46
(CN), 190.56 (SCS). Mass spectrum: m/z 182
(Irel 20%) [M]+. Found, %: C 46.15; H 3.34; N 15.32.
C7H6N2S2. Calculated, %: C 46.13; H 3.32; N 15.37.
M 182.26.
b. Disodium 2,2-dicyanoethene-1,1-dithiolate (1a)
trihydrate, 0.24 g (or 1 mmol of anhydrous 1a), was
dissolved in 2 mL of dimethylformamide, 0.5 g
(5 mmol) of 1,2-dichloroethane was added to the
solution, and the mixture was stirred for 2 h at room
temperature. When the reaction was complete, the
mixture was cooled and diluted with 4–5 volumes of
water, and the precipitate was filtered off, washed with
water, and recrystallized from propan-2-ol.
2-Cyano-2-(1,3-dithiolan-2-ylidene)acetamide
(2c). Yield 0.14 g (80%, a), 0.15 g (86%, b), 0.26 g
(62%, c); mp 199–200°C; published data [8]: mp 202–
203°C. IR spectrum, ν, cm–1: 3435 (NH2), 2192
c. A solution of 0.15 g (2 mmol) of malononitrile in
1 mL of ethanol was added to a solution of sodium
ethoxide prepared from 0.05 g (2 mmol) of sodium and
1 mL of ethanol. Carbon disulfide, 0.15 mL (2 mmol),
was added to the resulting mixture, and an additional
portion of sodium ethoxide prepared from 0.05 g
(2 mmol) of sodium and 1 mL of ethanol was then
added. The precipitate was dissolved in 4 mL of di-
methylformamide, 1 g (10 mmol) of 1,2-dichloro-
ethane was added, and the mixture was stirred for 1 h
(TLC) and diluted with 4–5 volumes of water. The
precipitate was filtered off, washed with water, and
recrystallized from propan-2-ol.
1
(C≡N), 1656 (C=O), 1458 (C=C). H NMR spectrum
(DMSO-d6), δ, ppm: 3.53–3.62 m (4H, CH2), 7.25–
7.45 br.s (2H, CONH2). Mass spectrum: m/z 186
(Irel 11%) [M]+. Found, %: C 38.73; H 3.23; N 15.02.
C6H6N2OS2. Calculated, %: C 38.69; H 3.25; N 15.04.
M 186.25.
2-Cyano-2-(4-methyl-1,3-dithiolan-2-ylidene)-
acetamide (2d). Yield 0.17 g (85%, a), 0.18 g (91%,
b), 0.29 g (65%, c); mp 119–120°C. IR spectrum, ν,
cm–1: 3409 (NH2), 2200 (C≡N), 1636 (C=O), 1461
(C=C). 1H NMR spectrum (DMSO-d6), δ, ppm: 1.42 d
(3H, CH3, J = 6.7 Hz), 3.36–3.40 d.d (1H, CH2, J =
12.0, 4.0 Hz), 3.63–3.67 d.d (1H, CH2, J = 12.0,
5.2 Hz), 4.22–4.28 m (1H, CH), 7.28 s and 7.39 s
(1H each, CONH2). 13C NMR spectrum (DMSO-d6),
δC, ppm: 18.72 (CH3), 46.30 (CH2), 47.91 (CH), 89.40
Yield1 0.14 g (82%, a), 0.15 g (89%, b), 0.25 g
(66%, c); mp 199–200°C; published data: mp 199–200
[8], 203–204°C [9]. IR spectrum, ν, cm–1: 2208 (C≡N),
1
Hereinafter, the yields were calculated on the initial anhydrous
dithiolate 1 (a, b) or malononitrile (cyanoacetamide) (c).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 53 No. 1 2017

SYNTHESIS OF SOME 2-YLIDENE-1,3-DITHIOLANES
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149
[C(CN)2], 117.00 (CN), 163.14 (CONH2), 179.82
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%: C 41.98; H 4.03; N 13.99. M 200.27.
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