Synthesis of potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate

Article abstract of DOI:10.3390/50801014

A method of synthesizing bioactive potassium (1,1-dioxothiolan-3-yl) dithiocarbamate in high yield and purity is reported.

Full text of DOI:10.3390/50801014

Molecules 2000, 5, 1014-1017
molecules
ISSN 1420-3049
© 2000 by MDPI
http://www.mdpi.org
Synthesis of Potassium (1,1-Dioxothiolan-3-yl)-dithiocarbamate
A.N. Vasiliev1* and A.D. Polackov2
1National Technological University, CITeQ, C.C.17, Cordoba 5016, Argentina
Tel.: 54-351-469-0585, Fax: 54-351-469-0585, E-mail: a.vasiliev@usa.net
2Institute of Bioorganic Chemistry & Petrochemistry, P.O.Box 305, Kiev 252034, Ukraine
Tel.: 380-44-261-4324
Received:7March 2000;revisedform10 August 2000 / Accepted:11August 2000 / Published: 15 August 2000
Abstract: A method of synthesizing bioactive potassium (1,1-dioxothiolan-3-yl) dithio-
carbamate in high yield and purity is reported.
Keywords: dithiocarbamate, pesticide, catalysis.
Introduction
Metal salts of heterocyclic dithiocarbamates (DTC) are of potential interest in applications such as
pesticides and antioxidants. In particular, potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate is an effec-
tive fungicide with selective action [1, 2]. The synthesis of this compound is difficult because of solvent
effects and low solubility of some reagents in the appropriate solvents. As it was earlier supposed by
Castro [3], the reaction between amines and carbon disulfide involves catalysis by strong base. Some
preliminary investigations were devoted to investigation of mechanism of the reaction and effect of sol-
vent [4, 5]. This paper presents a part of our work on synthesis optimization of this salt.
Results and Discussion
The main synthetic route to dithiocarbamates is based on the interaction between the corresponding
amine and CS in the presence of strong base (Scheme 1). In our work we used 3-aminothiolane as
2
starting material.
S
S -
NH2
NH
-
+ C H O
2 2 5
+
C S
- C
H O H
5
2
S O2
S O2
Scheme 1.

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Molecules 2000, 5
It was found that this method has some limitations. As it was shown earlier in our studies of the sol-
vent effect, upon decreasing of the protoning ability of the solvent, the rate of dithiocarbamate forma-
tion increases [6]. In aprotic systems, the rate of the process increases with the increase of the dielectric
permitivity of the solvent. However, the solubility of KOH in aprotic solvents is very low. Some of the
solvents also possess low stability in alkaline media. Additionally, destruction of C H SO NH and its
4 7
2
2
transformation into the corresponding isocyanate can take place. So, the problem of solvent selection is
critical in the synthesis. Use of water-dioxane mixture did not provide satisfactory yields and purity of
the product. Better results were obtained by carrying out the reaction in ethanol or its mixture with
DMF.
For optimization of the synthesis we studied the reaction mechanism. This investigation was con-
cerned with the clarification of the claimed role of base catalysis in the process of amine addition to CS
2
in ethanol media [3]. As it was supposed, the following reactions are possible in this process:
CS + RNH ↔ RNHCS H
(1)
(2)
(3)
(4)
(5)
(6)
2
2
2
-
+
RNHCS H + RNH ↔ RNHCS + RNH
2
2
2
3
CS + RNH + C H O- ↔ RNHCS + C H OH
-
2
2
2 5 2 5
2
RNHCS H + C H O- → RNHCS + C H OH
-
2
2 5 2 5
2
RNH + C H O- → RNH + C H OH
+
3
2 5 2 5
2
CS + C H O- → C H O CS
-
2
2 5 2 5
2
In our studies [7] both highly reactive methylamine and 1,1-dioxothiolan-3-yl-amine with lower
amino group reactivity were used as model amines and benzylamine and piperidine were considered as
reference materials. For all tested amines, the yield of dithiocarbamates corresponded to twice the
amount of consumed amines in the absence of free ethylate ions. This is possible only if the reaction
proceeds by routes (1) and (2) while route (3) does not take place. The kinetic data obtained [4,5] show
that the effect of C H O- ion concentration on the total rate of dithiocarbamate accumulation is far
2 5
smaller than expected if base catalysis (3) is the sole pathway. For 1,1-dioxothiolan-3-yl-amine as well
as benzylamine the mentioned effect has near-zero value, while for piperidine the reaction rate increases
3-5 times when the concentration of C H O- increases by a factor of 108 (addition of potassium ethy-
2 5
late). This fact provides us with evidence that the direct base catalyzed reaction makes no essential
contribution to dithiocarbamate formation rate, even in the initial phase of the process, and unambigu-
ously confirms the kinetic insignificance of this mechanism at quasi-equilibrium.
Selectivity of the reaction is determined by competition of routes (1) and (6) that requires an excess
of amine to ethylate. For suppression of the reaction (2) an excess of CS is necessary. So, at the time
2
of synthesis the reagents concentrations should satisfy the condition: [CS ] >> [RNH ] >> [C H O-].
2
2
2 5
Considering this condition, an original method of potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate
synthesis was developed. In accordance with this method, solutions of 3-amino-thiolane and KOH are
simultaneously added to solution of CS in ethanol. Final product precipitates as white crystals.
2
Conclusions
An effective method of preparing potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate was developed
and optimized. The investigation showed that in this reaction catalysis by ethylate ion claimed by Castro
does not take place.

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Molecules 2000, 5
Experimental
General
2-Sulfolene (1) and 3-sulfolene (2) were analysed by GLC on a Hewlett Packard 5732A GC
equipped with FID. Analysis conditions: 1,2 m x 3 mm column; mobile phase: 4,3% of Carbowax 1500
on Gat chrome (80/100 mesh); column temperature:130oC; carrier gas, helium (85 mL/min.); internal
standard, sulfolane (3). Rt (min.): 1, 26,5; 2, 10,5; 3, 11,7. The contents of 1 and bis-(1,1-dioxothiolan-
3-yl)amine in the crude product was determined by potentiometric titration using HClO4 in AcOH. The
concentration of potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate (5) was determined by consecutive
1
titration of the product by HCl to neutralize the reaction mixture, followed by iodometric titration. H-
NMR spectra were recorded on a Bruker-200X. instrument. IR spectra were recorded on a Jasco
FT/IR-5300 spectrometer.
3-Aminothiolane
Compound 2 (1 kg), 25% NH4OH (3 L) and CaO (30-50 g) were loaded into a 5L reactor. The
mixture was stirred while the temperature was slowly rised to 80oC and maintained for 8 h. Then the
reaction mixture was cooled, treated with charcoal, filtered and the solvent was evaporated at reduced
pressure. The resulting oily product contained >90% of 3-aminothiolane (4). For purification, the crude
product was taken up in acidic water (pH = 4-5) and the resulting solution was refluxed in the presence
of charcoal, cooled, filtered and the water was then removed under reduced pressure. The resulting
solid 3-aminothiolane hydrochloride salt was washed with acetone, redissolved in water, neutralized
with a solution of Na2CO3 and the resulting emulsion was extracted with CHCl3. The organic phase was
dried over anhydrous Na2SO4 and the solvent was removed. The final product had a purity of almost
100%.
Potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate
To a solution of CS2 (0,692 L) in ethanol (1 L), solutions of KOH (663 g) in 96% ethanol (3 L) and
compound 4 (1,35 kg) in 96% ethanol (2 L) were slowly added while the temperature was kept between
10-15oC. Then the reaction mixture was stirred for 12 h at ambient temperature. The resulting white
precipitate was filtered off, washed with ethanol and dried. The yield of 5 was 91%, m.p. 196-200oC.
1
Spectral data: H-NMR (200.13 MHz, DMSO-d6) δ: 2.35 (m, 2H, 4-CH2), 2.98 (m, 4H, 2,5-CH2),
5.07 (sextet, 1H, 3-CH), 8.36 (d, 1H, NH). IR (KBr) cm-1: 3146, 2970, 1518, 1321, 1302, 1122, 958,
815, 761.
References and Notes
1. Parkhomenko P.I., Vasiliev A.N. SCK - a new low toxic fungicide from the family of dithiocarba-
mates, Abstr. 9th Int. Congress of Pesticide Chemistry, London, 1998, Abstr. 1B-012.
2. Register of pesticides and agrochemicals permitted for use in Ukraine; Univest Marketing: Kiev,
1999; p. 75.
3. Castro, E.; Cortes, K.; Santos, J. Kinetics and mechanism of the reaction of carbon disulfide with

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Molecules 2000, 5
piperidine in ethanol. J. Org. Chem. 1982, 47, 3774-3777.
4. Polackov, A.D.; Vasiliev, A.N. Optimization of the synthesis of potassium (1,1-dioxothiolan-3-yl)
dithiocarbamate. Rus. Journ. Appl. Chem. 1995, 68, 1666-1668.
5. Shkaraputa, L.N. Kononov, A.V.; Polackov, A.D. Preparation of dithiocarbamates. Ukr. Chem. J.
1991, 9, 979-989.
6. Polackov, A.D. Modelling and optimization of potassium (1,1-dioxothiolan-3-yl)-dithiocarbamate
synthesis. Ph.D. Thesis. Institute of Bioorganic Chemistry and Petrochemistry, Kiev, 1992.
7. Polackov, A.D.; Vasiliev, A.N. Investigation of base catalysis in dithiocarbamate formation, Abstr.
35th Congr. IUPAC, Istanbul, 1995, Sec. 1-3, -p. 624.
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