Superbasic system CsOH/DMSO as a reagent for a fast one-step synthesis of symmetrical dialkyl trithiocarbonates

Article abstract of DOI:10.1080/17415993.2015.1079912

Symmetrical dialkyl trithiocarbonates were readily synthesized in excellent yields by one-step reaction of carbon disulfide and various alkyl halides under mild reaction conditions in the presence of cesium hydroxide as a super basic system. This method provides a synthesis of symmetrical dialkyl trithiocarbonates in short reaction times without the use of highly toxic starting materials.

Full text of DOI:10.1080/17415993.2015.1079912

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Superbasic system CsOH/DMSO as a reagent for
a fast one-step synthesis of symmetrical dialkyl
trithiocarbonates
Ali Yousefi
To cite this article: Ali Yousefi (2015): Superbasic system CsOH/DMSO as a reagent for a fast
one-step synthesis of symmetrical dialkyl trithiocarbonates, Journal of Sulfur Chemistry, DOI:
10.1080/17415993.2015.1079912
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Date: 11 September 2015, At: 13:55

Journal of Sulfur Chemistry, 2015
http://dx.doi.org/10.1080/17415993.2015.1079912
Superbasic system CsOH/DMSO as a reagent for a fast one-step
synthesis of symmetrical dialkyl trithiocarbonates
Ali Yousefi∗
Department of Chemistry, Faculty of Sciences, Shahid Rajaee Teacher Training University,
PO Box 16785-163, Tehran, Iran
(Received 12 April 2015; accepted 2 August 2015)
Symmetrical dialkyl trithiocarbonates were readily synthesized in excellent yields by one-step reaction
of carbon disulfide and various alkyl halides under mild reaction conditions in the presence of
cesium hydroxide as a super basic system. This method provides a synthesis of symmetrical dialkyl
trithiocarbonates in short reaction times without the use of highly toxic starting materials.
S
DMSO
R
R
CS2 + CsOH. H2O
o
S
S
2 RX,
50 C
80-96 %
Keywords: organosulfur; symmetrical dialkyl trithiocarbonates; carbon disulfide; alkyl halides; cesium
hydroxide
1. Introduction
The impact of organosulfur chemistry on modern organic synthesis is indisputable and it
has played an enormous role in biology, medicine and industry.[1] Organic trithiocarbonates
constitute an important class of compounds which have been claimed for various applica-
tions in industry, synthesis and medicine.[2–6] They have been widely used as pesticides in
agriculture,[7,8] lubricating additives,[9,10] in material science,[11–13] in froth flotation[14,15]
for the recovery of minerals from ores, and for their absorption properties of the metals,[16–
19] as intermediates in organic synthesis,[20–22] for protection of the thiol functionality,[23]
−
and in free radical polymerization reactions.[24–26] Additionally, they are used in various C C
bond-forming reactions[27] which necessitates their preparation through convenient and safe
methods.
The synthesis of trithiocarbonates has received considerable attention and several meth-
ods have been developed including reactions of thiols with thiophosgene,[28,29] and
chlorodithioformates,[30] or with carbon disulfide and alkyl halides under basic conditions in
a two-step procedure.[31–36] Another general method involves the dialkylation of the trithio-
carbonate anion with halides using phase-transfer catalysts or at elevated temperature.[37–39]
*Email: nmryousefi@yahoo.com
© 2015 Taylor & Francis

2
A. Yousefi
However, each of the above methods has at least one of the following drawbacks: long reaction
times, tedious work-up, low yields of product, synthetic inconvenience, employment of highly
toxic chemicals with unpleasant odors, unavailability of starting materials, use of 10- to 19-
fold molar excess of carbon disulfide and bases toward alkyl halides and formation of unwanted
side products such as sulfides. Consequently, developing new and convenient methods for the
synthesis of symmetrical trithiocarbonates under mild reaction conditions is very valuable.
2. Results and discussion
Cesium hydroxide continues to attract much attention from organic chemists due to the versatility
of its use in synthetic chemistry; it is non-toxic and a strong inorganic base (pKb = −1.76) that
has been used as an alternative non-nucleophilic base in several reactions.[40–43] We have now
developed an easy rapid one-step synthesis of symmetrical dialkyl trithiocarbonates directly from
carbon disulfide and alkyl halides using cesium hydroxide monohydrate in dimethyl sulfoxide
(DMSO).
To optimize the reaction with respect to solvent, temperature, time, molar ratios of the com-
ponents and to maintain the blood red base sensitive trithiocarbonate anion (CS23− ), we initially
examined the reaction of benzyl bromide and carbon disulfide as a model reaction, at various
conditions under an aerobic atmosphere (Scheme 1, Table 1). The results show that DMSO is the
best solvent (Entry 11, Table 1) due to its ability to support a super basic medium.[40,44,45]
After optimization, a variety of other alkyl halides were shown to undergo the reaction
smoothly, giving the desired products in high to excellent yields (Scheme 2). The results are sum-
marized in Table 2 and the spectral data for the known dialkyl trithiocarbonates are consistent
with the published data.
When carbon disulfide (1 mmol) was added to the solution of CsOH·H2O (1 mmol) in DMSO
(1 ml), and the mixture was stirred vigorously at 50°C, the colorless
Scheme 1. Trithiocarbonation of benzyl bromide in the presence of cesium hydroxide.
Table 1. Screening of the reaction conditions.a
Entry
Solvent
THF
Condition
Yieldb (%)
1
2
3
4
5
6
7
8
25°C; 24 h
50°C; 24 h
25°C; 24 h
25°C; 24 h
25°C; 24 h
25°C; 24 h
25°C; 24 h
25°C; 48 h
50°C; 24 h
50°C; 24 h
50°C; 30 min
N.R.
51
N.R.
N.R.
42
N.R.
24
13
DMF
1,4-Dioxane
CHCl3
Acetonitrile
EtOAc
DMEc
Neat
H2O
EtOH
DMSO
9
10
11
N.R.
N.R.
96
aReaction conditions: carbon disulfide (1 mmol), benzyl bromide (1 mmol), CsOH.H2O (1 mmol), solvent (1 ml).
bIsolated yields.
c1,2-Dimethoxyethane.

Journal of Sulfur Chemistry
3
Scheme 2. Plausible mechanisms for the preparation of various symmetrical dialkyl trithiocarbonates.
Table 2. Synthesis of symmetrical trithiocarbonates mediated by CsOH.H2O.
Entry
Alkyl halide
PhCH2Br
PhCH2Cl
CH3I
CH3CH2I
CH3(CH2)4CH2Br
CH3(CH2)6CH2I
Time
Product
Yield (%)ab
1
2
3
4
5
6
7
8
30 min
45 min
30 min
30 min
60 min
60 min
30 min
45 min
60 min
60 min
24 h
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
96 [33]
94 [33]
84 [33]
90 [33]
91 [33]
91 [33]
94 [33]
93 [33]
80 [46]
81 [33]
N. R.
=
CH2 CHCH2Br
=
CH2 CHCH2Cl
9
4-BrC6H4CH2Br
PhCH(CH3)Br
PhC(CH3)2Br
BrCH2CH2Br
CH3CH2CH(CH3)Br
(CH3)2CHBr
10
11
12
13
14
15
60 min
90 min
90 min
24 h
90 [47]
82 [33]
90 [33]
N. R.
(CH3)3CBr
aIsolated yields.
bReferences are provided for known compounds.
mixture turned blood red immediately, indicating the formation of trithiocarbonate anion
(CS23− ) [46]; in situ alkylation with alkyl halides for the appropriate times (Table 2) afforded
the corresponding symmetrical trithiocarbonates. With progress of the reaction, the color of the
solution changed from blood red to yellow. The structures of all the products were established
1
from their analytical and spectral (IR, H and 13C NMR) properties. Primary, secondary, ben-
zylic and allylic halides are converted to the corresponding trithiocarbonates as exclusive and
1
virtually pure products according to TLC and H NMR, in high to excellent yields (Table 2).
The procedure worked fine with primary, secondary, benzyl as well as allyl halides. However,
under the same reaction conditions, tertiary halides did not produce the expected trithiocarbon-
ates even after 24 h (Entries 11 and 15, Table 2). Moreover, 1,3-dithiolane-2-thione (3l), cyclic
trithiocarbonate, can also be prepared from 1,2- dibromoethane without formation of any poly-
meric by-product. The results clearly show that CsOH is an efficient reagent in trithiocarbonation
of alkyl halides.
3. Conclusion
In conclusion, cesium hydroxide monohydrate in DMSO has been introduced as a potential cata-
lyst for the one-step synthesis of symmetrical dialkyl trithiocarbonates from various alkyl halides

4
A. Yousefi
and carbon disulfide. The specific advantages of this methodology include: mild reaction condi-
tions, simple reaction work-up, short reaction times and high to excellent yield of the products
without using large excess amount of toxic carbon disulfide.
4. Experimental
4.1. Chemicals
All chemicals were purchased from Merck. All products were identified by comparison of their
spectral and physical data with those of the known samples.
4.2. Apparatus
1
IR spectra were obtained using an ABB FTLA 2000 instrument. H NMR (400 MHz) and
13C NMR (100 MHz) spectra were recorded on a Bruker DRX-400 Advance instrument with
CDCl3 as the solution and the chemical shifts are determined by reference to residual CHCl3 in
CDCl3. All compounds were characterized by comparing their physical data with those in the
literature.
4.2.1. General procedure
Typical procedure for preparation of dibenzyltrithiocarbonate (3a): To the solution of
CsOH.H2O (167 mg, 1.0 mmol) and carbon disulfide (76 mg, 1.0 mmol) in DMSO(1 ml), alkyl
halide (171 mg, 1.0 mmol) was added and the reaction mixture was stirred at that tempera-
ture until the reaction was completed (monitored by TLC). On completion of the reaction,
the mixture was filtered and evaporated, EtOAc (25 ml) was added and washed with water
(2 × 15 ml) and dried over anhydrous MgSO4. The solution was concentrated to give the crude
product, which was purified by preparative TLC (silica gel, eluent, n-hexane) to afford the pure
dibenzyltrithiocarbonate (3a, 139 mg, 96%) as a light yellow oil.
4.2.1.1. Dibenzyl carbonotrithioate (3a, 3b) IR (neat)/υ(cm−1): 1062 (C S), 1494, 1602;
=
1H NMR (CDCl3)/δ ppm: 4.67 (s, 4H), 7.28–7.40 (m, 10H); 13C NMR (CDCl3)/δ ppm: 41.59,
127.86, 128.77, 129.34, 134.96, 222.80.
1
4.2.1.2. Di-n-hexyl carbonotrithioate (3e) Yellow oil; IR (neat)/υ(cm−1): 1052 (C S); H
=
NMR (CDCl3)/δ ppm: 0.92 (t, 6H, J = 6.8 Hz), 1.27–1.35 (m, 8H), 1.40–1.45 (m, 4H), 1.72
(quin, 4H, J = 7.6 Hz), 3.39 (t, 4H, J = 7.6 Hz); 13C NMR (CDCl3)/δ ppm: 14.04, 22.53, 28.02,
28.64, 31.33, 36.88, 224.78.
4.2.1.3. Diallyl carbonotrithioate (3g, 3h) Light yellow oil; IR (neat)/υ(cm−1): 1062 (C S),
=
1638; 1H NMR (CDCl3)/δ ppm: 4.07 (d, 4H, J = 6.8 Hz), 5.23 (d, 2H, J = 10.0 Hz), 5.36 (d, 2H,
J =17.0, 1.3 Hz), 5.85–5.95 (m, 2H); 13C NMR (CDCl3)/δ ppm: 39.72, 119.72, 130.97, 222.48.
4.2.1.4. Bis(1-phenylethyl) carbonotrithioate (3j) Yellow oil; IR (neat)/υ(cm−1): 1067
1
=
(C S), 1449, 1493, 1596; H NMR (CDCl3)/δ ppm: 1.82 (d, 6H, J = 7.6 Hz), 5.39 (q, 2H,
J = 7.6 Hz), 7.35–7.41 (m, 10H); 13C NMR (CDCl3)/δ ppm: 21.41, 50.10, 127.77, 128.44,
128.71, 141.13, 221.44.

Journal of Sulfur Chemistry
5
1
4.2.1.5. 1, 3-Dithiolane-2-thione (3l) Yellow oil; IR (neat)/υ(cm−1): 1072 (C S); H NMR
=
(CDCl3)/δ ppm: 3.99 (s, 4H); 13C NMR (CDCl3)/δ ppm: 43.86, 228.68.
4.2.1.6. Di-sec-butyl carbonotrithioate (3m) Light yellow oil; IR (neat)/υ(cm−1): 1078
1
=
(C S); H NMR (CDCl3)/δ ppm: 1.03 (t, 6H, J = 7.4 Hz), 1.41 (d, 6H, J = 6.8 Hz), 1.66–1.83
(m, 4H), 4.136 (sext, 2H, J = 6.8 Hz); 13C NMR (CDCl3)/δ ppm: 11.46, 19.61, 28.81, 47.98,
224.03.
4.2.1.7. Diisopropyl carbonotrithioate (3n) Light yellow oil; IR (neat)/υ(cm−1): 1042
1
(C S); H NMR (CDCl3)/δ ppm: 1.42 (d, 12H, J = 7.2 Hz), 4.22 (sept, 2H, J = 7.2 Hz); 13C
=
NMR (CDCl3)/δ ppm: 22.07, 41.63, 223.48.
Acknowledgements
The author is also thankful to Professor Barahman Movassagh for helpful guidance.
Disclosure statement
No potential conflict of interest was reported by the author.
Funding
The virtual support of this study by Shahid Rajaee Teacher training University is acknowledged.
Supplemental data
Supplemental data for this article can be accessed at doi:10.1080/17415993.2015.1079912 description of location.
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