Anodic activation of hydrogen sulfide in reaction with cyclopentane

Full text of DOI:10.1134/S1070363215040416

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 4, pp. 998–1000. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © N.T. Berberova, E.V. Shinkar’, I.V. Smolyaninov, V.F. Abdulaeva, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85,
No. 4, pp. 697–699.
LETTERS
TO THE EDITOR
Anodic Activation of Hydrogen Sulfide
in Reaction with Cyclopentane
N. T. Berberova, E. V. Shinkar’, I. V. Smolyaninov, and V. F. Abdulaeva
Astrakhan State Technical University, ul. Tatishcheva 16, Astrakhan, 414025 Russia
e-mail: berberova@astu.org
Received November 20, 2014
Keywords: hydrogen sulfide, cyclopentane, electrosynthesis, organosulfur compounds
DOI: 10.1134/S1070363215040416
Cyclic thiols are widely used in the synthesis of
non-steroidal anti-inflammatory drugs, immunomodu-
lators, antiseptics, soporific, hypoglycemic, and
antitumor drugs [1–3]. As a rule, cycloalkanethiols are
prepared from cycloalkenes, alcohols, ketones,
halogen-substituted cycloalkanes; as a thiolating agent,
sulfur, hydrogen sulfide, carbonyl sulfide, or carbon
disulfide are applied with the use of photolysis,
thermolysis or catalysts [4]. To date, there are no
examples of direct methods of thiolation of cyclo-
alkanes with hydrogen sulfide at room temperature.
when performing electrosynthesis of organic sulfur
compounds we have successfully used combined redox
systems consisting of anode and chemical activator
[9–11].
In continuation of these studies, in the present work
we have performed the thiolation of cyclopentane,
which belongs to fairly inert hydrocarbons, with
hydrogen sulfide under the conditions of anodic
initiation. As a solvent for electrosynthesis of sulfur-
containing derivatives of cyclopentane, dichloro-
methane was chosen because of poor solubility of the
substrate in acetonitrile. The reaction of cyclopentane
Earlier we have shown that electrochemical
activation of hydrogen sulfide on the anode in the
presence of organic compounds (benzene, toluene,
hexene-1, hexyne-1, furan, thiophene) results in the
formation of the products of thiolation of the
substrates, as well as the corresponding sulfides and
disulfides [5-8]. In order to reduce the energy losses
with H S (molar ratio 1 : 5) was performed via
2
microelectrolysis at the reagent oxidation potential
during 90 min in anaerobic conditions.
Electrochemical analysis of the products of the
reaction by the method of cyclic voltammetry showed
the formation of dicyclopentyl disulfide, cyclopentane-
Scheme 1.
HS
−
e
H2S
HS
H+
H2S
SH
Epa 1.72 V
S
S S
−
e
Epa 1.54 V
H+
SH
S
S
Epa 1.88 V
9
98

ANODIC ACTIVATION OF HYDROGEN SULFIDE
999
thiol, and dicyclopentyl sulfide. The formation of
cyclopentanethiol during the electrolysis was in-
dependently proved by gas chromatography. The total
current yield of organosulfur compounds increases
from 15.7 to 49.2% when the time of the reaction
increases from 30 to 90 min. A similar dependence is
observed for the conversion of the substrate into
cyclopentanethiol: 30 min, 12.9%; 60 min, 21.2%; and
vibrations of the following bonds are observed: S–S
–
1
–1
–1
(507 cm ), C–S (690 cm ), and S=O (1021 cm ). In
the mass spectrum, the peaks of molecular ions of
dicyclopentyl sulfoxide (m/z = 186.22), dicyclopentyl
disulfide (m/z = 202.00) and 1,3-dicyclopentyltri-
sulfane (m/z = 234.01) are observed.
Therefore, a new electrochemical method for pre-
paration of organosulfur compounds from cyclo-
pentane and hydrogen sulfide by means of anodic
activation of the reagent is developed. The elaborated
method is an alternative to the known reactions of
nucleophilic substitution with participation of halo-
genated derivatives of hydrocarbons and allows
controlling the composition and the yield of the target
products.
9
0 min, 34.8%. The reaction of cyclopentane with
hydrogen sulfide under anodic activation of the reagent
can be represented by a series of consecutive-parallel
reactions described by Scheme 1.
Taking into account that radical-cation of hydrogen
sulfide is unstable and decomposes to proton and thiyl
radical, the thiolation of cyclopentane occurs
predominantly by the radical substitution mechanism.
Cyclopentanethiol formed during the electrosynthesis
may undergo single electron oxidation under the
conditions of the experiment leading to the formation
of cyclopentanethiyl radical. Its transformations into
the sulfide occurs with a higher rate than into the
disulfide. As a by-product, active sulfur is adsorbed on
the surface of the platinum anode, favoring fast
accumulation of the sulfide and 1,3-dicyclopentyl-
trisulfane (2.02 V) [12]. The obtained results are in
agreement with those reported in [13], where it has
been shown that theunctionalization of cycloalkanes
with molecular sulfur in superacidic medium also
gives rise to the the formation of sulfides in high yields
Electrochemical analysis was performed by the
method of cyclic voltammetry in three-electrode cell
under an argon atmosphere using potentiostat IPC-Pro.
The working electrode was a stationary platinum
electrode of 2 mm diameter, the auxiliary electrode
2
was a platinum plate (S = 60 mm ), the reference
electrode (Ag/AgCl/KCl) was with a water-proof
–1
diaphragm. The potential sweep rate was 0.2 V s .
The background electrolyte, 0.1М Bu NClO (+99%,
4
4
electrochemical grade) was dried in a vacuum for 48 h
at 50ºС. Methylene chloride (chemically pure) was
purified by the known procedure [15]. The concentra-
tion of cyclopentanethiol was 5 mmol/L. Micro-
electrolysis of the mixture (H S + cyclopentane) was
2
(
up to 90%).
carried out at the hydrogen sulfide oxidation potential
2
When performing the reaction of cyclopentane with
(1.8 V) using platinum electrodes (S = 60 mm ) during
hydrogen sulfide in aerobic conditions and increasing
the time of electrolysis (4 h) and the surface of the
electrode (5-fold), the composition of the products was
substantially different due to the deep oxidation of the
formed organosulfur compounds. Under these
conditions, disulfide and sulfoxide are formed as final
products (1.96 V):
1.5 h in anaerobic conditions (argon). Molar ratio
cyclopentane : hydrogen sulfide was 1 : 5.
Preparative electrolysis was carried out in a
diaphragm-free three-electrode electrochemical cell
2
using platinum electrodes (S = 300 mm ) for 4 h in
aerobic conditions. Molar ratio substrate : reagent was
1
: 5. The products after preparative electrolysis were
isolated in the following way: the reaction mixture was
degassed with argon for 2 h; the background
electrolyte was precipitated with hexane, which also
acted as an extractant of organosulfur compounds; to
increase the degree of extraction of the reaction
products, three-step extraction with hexane was
performed, the extract was concentrated in a vacuum,
the content of organosulfur compounds was monitored
on a X-ray fluorescent analyzer АSE-1.
−
2e
S
S
O
The mass ratio (С H S) : (С H ) SO was 1 : 1.5.
5
11
2
5
11 2
The results of the experiment correlate with the
available data on the electrochemical transformations
of thiols and disulfides [14]. The composition of the
products of the reaction was proved by the methods of
IR spectroscopy and high-resolution mass spectro-
metry. In the IR spectrum, the bands of stretching
For identification of the obtained organosulfur
compounds the methods of IR spectroscopy, high-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 4 2015

1
000
BERBEROVA et al.
resolution mass spectrometry, gas chromatography,
electrochemistry, and X-ray fluorescent analysis were
employed. IR spectra were taken on an IR Fourier
spectrometer FSM-1201 in KBr. High-resolution mass
spectra were registered on a Bruker Maxis instrument
Bioorg. Med. Chem. Lett., 2006, vol. 16, p. 202. DOI:
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Pharmazie, 1997, vol. 52, p. 558
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. Metwally, M.A. and Abdel-Wahab, B.F., Org. Commun.,
009, nos. 2–4, p. 84.
2
(
electrospray ionization, solution in СН СN,
3
. Letichevskaya, N.N., Shinkar, E.V., Berberova, N.T.,
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calibration using HCO Na/HCO H). Chromatographic
2
2
analysis of the product mixture was performed on a
gas chromatograph Kristallux-4000М (Meta-Chrom
Ltd.) in isothermal regime, carrier gas helium, capillary
column Agilent (100 m × 0.25 mm), column tempera-
ture 80°С, flame ionization detector, temperature of
detector 250°С, stationary phase HP-1. Commercial
cyclopentane (95%, Alfa Aesar), cyclopentanethiol
6
7
. Berberova, N.T. and Shinkar’, E.V., Russ. Chem. Bull.,
2
000, vol. 49, p. 1178. DOI: 10.1007/BF02495758.
. Girenko, Е.Е., Shinkar’, E.V., Pashchenko, K.P.,
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Khim. Khim. Tekhnol., 2004, vol. 47, no. 8, p. 10.
. Shinkar’, E.V., Khokhlov, V.A., Berberova, N.T.,
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Komplekse, 2008, no. 5, p. 83.
8
(
97%, Aldrich), hexane (95%, Alfa Aesar) were used
without additional purification. Hydrogen sulfide was
obtained as described earlier [6].
9
. Okhlobystin, A.O., Okhlobystina, A.V., Shinkar’, E.V.,
Berberova, N.T., and Eremenko, I.L., Dokl. Chem.,
ACKNOWLEDGMENTS
2
010, vol. 435, no. 1, p. 302. DOI: 10.1134/
S001250081011008X.
This work was supported by the Russian Scientific
Foundation (grant no. 14-03-00967).
10. Shinkar’, E.V., Okhlobystina, A.V., Koldaeva, Yu.Yu.,
Vasil’eva, E.A., Petrova, N.V., Smolyaninov, I.V., and
Berberova, N.T., Zashchita Okruzhayushchei Sredy v
Neftegazovom Komplekse, 2011, no. 10, p. 67.
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