4-Phenyl-2-[(Z)-phenylmethylidene]-1,3-dithiole from elemental sulfur and phenylacetylene [1]

Full text of DOI:10.1023/A:1023093313803

Chemistry of Heterocyclic Compounds, Vol. 39, No. 1, 2003
LETTERS TO THE EDITOR
Z
4-PHENYL-2-[( )-PHENYLMETHYLIDENE]-
1,3-DITHIOLE FROM ELEMENTAL
SULFUR AND PHENYLACETYLENE
N. K. Gusarova, N. A. Chernysheva, B. G. Sukhov, A. V. Afonin, S. V. Fedorov,
G. A. Yakimova, and B. A. Trofimov
Keywords: distyryl sulfide, phenylacetylene, 4-phenyl-2[(Z)-phenylmethylidene]-1,3-dithiole,
elemental sulfur, superbase.
In previous work [1], we briefly reported that heating elemental sulfur and phenylacetylene at 90-97°C
in the KOH–DMSO–SnCl2–H2O system leads to Z,E-distyryl sulfide in 20% yield. No experimental details were
given.
We have now found that phenylacetylene reacts with the S8–KOH–DMSO triad stereoselectively in the
presence of a small amount of water at 49-52°C to give 4-phenyl-2-[(Z)-phenylmethylidene]-1,3-dithiole (1) in
10% yield as well as the Z,Z-distyryl sulfide (2a) in 9% yield and Z,E-distyryl sulfide (2b) in 11% yield. These
yields were not optimized.
Ph
Ph
S8 /DMSO/KOH/(H2O)
S
Ph
+
+
Ph
H
Ph
S
Ph
S
Ph
S
2b
1
2a
The formation of 1,3-dithiole 1 should probably be ascribed to the cyclodimerization of phenylethynyl
sulfide anions generated from elemental sulfur and phenylacetylene in the superbase system.
_
_
_
B
S8
C
C
C
Ph
Ph
CS
C
H
Ph
C
Ph
_
_
Ph
S
S
H2O
Ph
1
_
_
S
S
Ph
__________________________________________________________________________________________
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences,
664033 Irkutsk, Russia; e-mail: gusarova@irioch.irk.ru. Translated from Khimiya Geterotsiklicheskikh
Soedinenii, No. 1, pp. 137-138, January, 2003. Original article submitted December 16, 2002.
128
0009-3122/03/3901-0128$25.00©2003 Plenum Publishing Corporation

A similar scheme was discussed by Mayer et al. [2], who obtained dithiole 1 by a more complicated
method involving a synthesis of the corresponding phenylacetylenide from phenylacetylene and metallic sodium
in dry ether, treatment of phenylacetylenide with elemental sulfur, and passing dry HCl through the suspension
of sodium phenylethynyl sulfide in ether.
The preparative scope and reaction mechanism are under study.
Thus, a new, convenient method has been discovered for obtaining 1,3-dithiole 1 from elemental sulfur
and phenylacetylene in a single step under mild conditions. 1,3-Dithiole 1 is a promising synthetic intermediate
used for the manufacture of semiconductors [3], efficient radioprotectors [4], and active cathode materials for
lithium power sources [5].
Z
A mixture of phenylacetylene (4 g, 40 mmol),
4-Phenyl-2-[( )-phenylmethylidene]-1,3-dithiole (1).
elemental sulfur (1.6 g, 50 mmol), water (1 ml, 50 mmol), and KOH (5.6 g, 100 mmol) in DMSO (40 ml) was
stirred at 49-52°C for 4 h. The reaction mixture was diluted with water (150 ml) and extracted with benzene.
The extract was washed with water and dried over potassium carbonate. Benzene was distilled off in vacuum.
The residue was dissolved in ether. The yellow crystalline precipitate formed was filtered off, washed with
ether, and dried in vacuum to give 0.51 g (10%) of 1,3-dithiole 1; mp 198-200°C (CHCl3). Mass spectrum,
1
m/z (Irel, %): 268 [M]+ (100), 134 [M - PhCH=CS]+ (45), 121 (18), 102 (8), 89 (15), 77 [Ph]+ (4). H NMR
5
spectrum (400 MHz, CDCl3, with HMDS as the internal standard), δ, ppm (J, Hz): 6.44 (1H, d, JHH = 1.2,
5
=CH); 6.59 (1H, d, JHH = 1.2, =CH); 7.10-7.40 (10H, m, Ph). Found, %: C 71.94; H 5.14; S 23.37. C16H12S2.
Calculated, %: C 71.60; H 4.51; S 23.89. The ethereal solution was passed through a layer of alumina and ether
was evaporated. The residue was dried in vacuum to obtain 0.95 g (20%) of a 1:1.1 mixture of 2a and 2b.
1H NMR spectrum (CDCl3, 400 MHz, with HMDS as the internal standard), δ, ppm (J, Hz): for 2a: 6.45 (2H, d,
J = 10.5, =CH); 6.57 (2H, d, J = 10.5, =CH); 7.26-7.53 (10H, m, Ph); for 2b: 6.34 (1H, d, J = 10.8, =CH); 6.51
(1H, d, J = 10.8, =CH); 6.65 (1H, d, J = 15.5, =CH); 6.80 (1H, d, J = 15.5, =CH); 7.26-7.53 (10H, m, Ph).
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