Russian Journal of General Chemistry, Vol. 74, No. 11, 2004, pp. 1754 1756. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004,
pp. 1884 1886.
Original Russian Text Copyright
2004 by Korchevin, Russavskaya, Yakimova, Deryagina.
New Ways of Synthesis of 1,2-Dithiole-3-thione
N. A. Korchevin, N. V. Russavskaya, G. A. Yakimova, and E. N. Deryagina
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
Received October 9, 2002
Abstract Two new synthetic approaches to 1,2-dithiole-3-thione are proposed. The title compound is
formed by thermolysis of dipropyl polysulfides (n-Pr)2Sx (x = 3 4) and thermal decomposition of polysulfide
dendrimers under reduced pressure. The latter reaction may be recommended for utilization of organochlorine
waste products in the manufacture of epichlorohydrin, which are used for the synthesis of dendrimers.
1,2-Dithiole-3-thiones are used as wear-proof
additives to motor oils and inhibitors of metal cor-
rosion [1]. Some 1,2-dithiole-3-thiones exhibit
pronounced physiological activity [2] and are im-
portant reagents in the synthesis of various organo-
sulfur compounds [2, 3]. Methods for the preparation
of substituted 1,2-dithiole-3-thiones have been de-
veloped most thoroughly [2, 3]. However, this pro-
cedures ensure a poor yield of unsubstituted 1,2-di-
thiole-3-thione (I). It can be obtained in a good yield
(66 78%) via sulfurization of difficultly accessible
malonaldehyde tetramethyl acetal with a mixture of
elemental sulfur and phosphorus pentasulfide in an-
hydrous pyridine at 130 C; the target product is
isolated by column chromatography [4]. More com-
plex procedures for the synthesis of I have also been
reported [4]; however, the yields are generally poor.
The maximal yield of compound I (52%) was reached
in the thermolysis of dipropyl tetrasulfide (n-Pr)2S4
at 350 C. In all cases, the process was accompanied
by evolution of gaseous products, such as hydrogen
sulfide, propylene, and hydrogen. The overall scheme
of thermolysis of dipropyl polysulfides II (a 1:1 mix-
ture of tri- and tetrasulfide) may be represented as
follows:
S
S
(1)
+ C3H6 + H2S + 2H2,
(CH3CH2CH2)2Sx
S
II
I
x = 3, 3.5.
Most probably, compound I is formed from fairly
stable propyltrisulfanyl radicals III which are primary
products of thermal decomposition of polysulfides II.
The formation of radicals III is favored by simulta-
neous formation of thermodynamically stable pro-
pylene. Intramolecular cyclization of III leads to
We now propose two novel synthetic approaches
to 1,2-dithiole-3-thione. The first of these is based on
thermal transformations of dipropyl polysulfides
(n$(240-Pr)2Sx (II, x = 3 4). Polysulfides II are readily obp-seudoaromatic system I, which is also favorable
tained by alkylation with propyl halides of sodium
polysulfides generated by dissolution of sulfur in the
system aqueous hydrazine hydrate alkali [5]. Table 1
contains the results obtained by thermolysis of poly-
sulfides II in the gas phase at 300 400 C. In the
temperature range from 350 to 400 C, the major
thermolysis product is 1,2-dithiole-3-thione (I). The
other products are the corresponding thiol n-PrSH,
sulfide (n-Pr)2S, and disulfide (n-Pr)2S2. As the
temperature rises, the fraction of propanethiol and
dipropyl disulfide decrease, while the yield of di-
propyl sulfide somewhat increases [6]. Considerably
different results were obtained in the thermolysis of
dipropyl and dibutyl polysulfides under analogous
conditions. The major product in the thermolysis of
dibutyl polysuifide was thiophene, and the yield of
5-methyl-1,2-dithiole-3-thione was as low as 6% [6].
from the thermodynamic viewpoint [3].
Table 1. Thermolysis of dipropyl polysulfides (n-Pr)2Sx (II)
Yield, % (based on the
Temperature,
C
initial polysulfide)
x
PrSH
Pr2S
Pr2S2
I
3
3.5
4
4
4
350
350
300
350
400a
11
13
2
3
6
7
15
15
4
29
44
6
52
37
14
8
4
10
a
Further rise in temperature leads to strong tarring.
1070-3632/04/7411-1754 2004 MAIK Nauka/Interperiodica