An Efficient and Straightforward Access to Symmetrical Dialkyl Trithiocarbonates Using a Basic Task-Specific Ionic Liquid and Carbon Disulfide

Article abstract of DOI:10.1080/10426507.2014.887078

We report an efficient one-pot route for the synthesis of symmetrical dialkyl trithiocarbonates from alkyl halides using carbon disulfide and a basic ionic liquid 1,1′-bis-methyl-3, 3-methylene-bisimidazolium dihydroxide as a reagent and phase-transfer catalyst.

Full text of DOI:10.1080/10426507.2014.887078

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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An Efficient and Straightforward Access
to Symmetrical Dialkyl Trithiocarbonates
Using a Basic Task-Specific Ionic Liquid
and Carbon Disulfide
Soheil Sayyahia, Saeid Moonesib & Mehdi Fallah-Mehrjardic
a Department of Chemistry, Mahshahr Branch, Islamic Azad
University, Mahshahr, Iran
b Department of Chemistry, Omidieh Branch, Islamic Azad University,
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Omidieh, Iran
c Department of Marine Chemistry, Khoramshahr University of Marine
Science and Technology, Khoramshahr, Iran
Accepted author version posted online: 30 Apr 2014.Published
online: 21 Oct 2014.
To cite this article: Soheil Sayyahi, Saeid Moonesi & Mehdi Fallah-Mehrjardi (2014) An Efficient
and Straightforward Access to Symmetrical Dialkyl Trithiocarbonates Using a Basic Task-Specific
Ionic Liquid and Carbon Disulfide, Phosphorus, Sulfur, and Silicon and the Related Elements, 189:11,
1718-1722, DOI: 10.1080/10426507.2014.887078
To link to this article: http://dx.doi.org/10.1080/10426507.2014.887078
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Phosphorus, Sulfur, and Silicon, 189:1718–1722, 2014
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2014.887078
AN EFFICIENT AND STRAIGHTFORWARD ACCESS
TO SYMMETRICAL DIALKYL TRITHIOCARBONATES
USING A BASIC TASK-SPECIFIC IONIC LIQUID
AND CARBON DISULFIDE
Soheil Sayyahi,1 Saeid Moonesi,2 and Mehdi Fallah-Mehrjardi3
1Department of Chemistry, Mahshahr Branch, Islamic Azad University, Mahshahr,
Iran
2Department of Chemistry, Omidieh Branch, Islamic Azad University, Omidieh,
Iran
3Department of Marine Chemistry, Khoramshahr University of Marine Science and
Technology, Khoramshahr, Iran
GRAPHICAL ABSTRACT
Abstract We report an efficient one-pot route for the synthesis of symmetrical dialkyl trithio-
carbonates from alkyl halides using carbon disulfide and a basic ionic liquid 1,1ꢁ-bis-methyl-3,
3-methylene-bisimidazolium dihydroxide as a reagent and phase-transfer catalyst.
Keywords Trithiocarbonate; basic ionic liquid; alkyl halides; carbon disulfide
INTRODUCTION
Since the introduction of the term “task-specific ionic liquids” (TSILs) by Professor
J. H. Davis to describe a functionalized ionic liquid, this has been an area of rapid interest in
the chemical literature.1–3 Different TSILs are synthesized with a particular application in
mind and employed as a catalyst, reagent, and/or solvent in organic reactions.4,5 Among the
three main classes of TSILs, acidic, neutral, and basic, much less attention has been paid
to the basic ionic liquids in organic chemistry. Otherwise, it has been noted that replacing
traditional bases (NaOH, KOH, NaHCO3) with basic ionic liquids has advantages such as
stability in water and air, easy separation, and high catalytic efficiency.6 They are flexible,
nonvolatile, noncorrosive, and immiscible with many organic solvents.7
Received 21 October 2013; accepted 21 January 2014.
Address correspondence to Soheil Sayyahi, Department of Chemistry, Mahshahr Branch, Islamic Azad
University, Mahshahr, Iran. E-mail: sayyahi.soheil@gmail.com
1718

ACCESS TO SYMMETRICAL DIALKYL
1719
Trithiocarbonates are an important class of organic compounds that have found a
wide range of application in industrial and medical chemistry. They have been employed as
key precursors, intermediates, or a protection for thiol functionality in organic synthesis.8–14
From several routes for the synthesis of trithiocarbonates, the dialkylation of in situ
generated trithiocarbonate anion (CS32−) with alkyl halide is most convenient.15,16 The
reaction is carried out in the presence of carbon disulfide and under basic conditions, such
as amberlyst A-26 (OH−),17 Cs2CO3/polar aprotic solvents,18 KF/Al2O3,16 nBu4NOH (20%
in H2O),19 basic Al2O3,20 K3PO4,21 KOH/TBAB/Al2O3.22 Also, a phase-transfer catalyst
has often been used to increase the yield and the reaction rate.23
In the present study, we have discovered that a task-specific dicationic ionic liquid
(TSDIL) 1,1ꢁ-bis-methyl-3, 3-methylenebisimidazolium dihydroxide (2) can act as a basic
reagent and PTC and efficiently promotes the synthesis of trithiocarbonates from alkyl
halides.
Dicationic imidazolium-based ionic liquids have been shown to possess superior
physical properties in terms of thermal stability and volatility compared to traditional ionic
liquids. They are able to dissolve all manner of polar and nonpolar molecules, including
some proteins, peptides, polymers, and simple organic molecules.24
RESULTS AND DISCUSSION
The ionic liquid was readily prepared by treatment of 1,1ꢁ-bis-methyl-3, 3-methyle-
nebisimidazolium dichloride (1)25,26 with KOH in dry dichloromethane for 12 h at room
1
temperature (Scheme 1). The IR and H NMR spectra of 2 exhibited the characteristic
absorption at 3444 cm−1 and resonance at δ = 4.71 ppm corresponding to the hydroxide
functionality.
Scheme 1 Preparation of 1,1ꢁ-bis-methyl-3, 3-methylenebisimidazolium dihydroxide.
Then, benzyl chloride was selected as a model alkyl halide to optimize the reaction
condition by screening different amounts of the ionic liquid as catalyst and basic reagent.
The best result was obtained when 2.0 mmol benzyl chloride reacted with a mixture of
1.5 mmol of the TSDIL in 3 mL CS2 at 50◦C under reflux conditions (Table 1). It was
Table 1 Trithiocarbonation of benzyl chloride: effect of the basic ionic liquid 2a
Conversion
Temperature
Time (min)
Catalyst (mmol)
Entry
N.R
Trace
Completed
Completed
Not completed
50◦C
50◦C
50◦C
50◦C
r.t.
120
120
75
35
120
—
0.25
1.0
1.5
1.5
1
2
3
4
5
aBenzyl chloride (2 mmol), CS2 (3 mL).

1720
S. SAYYAHI ET AL.
Scheme 2 Synthesis of trithiocarbonates using 1,1ꢁ-bis-methyl-3, 3-methylenebisimidazolium dihydroxide.
observed that adding some drops of water increased the reaction rate and conversion to the
desire compounds according to thin layer chromatography analysis. This may be due to the
addition of water causes to the decrease in the viscosity of the ionic liquid, which increases
the solubility of the alkyl halides in CS2.
Under these conditions, different alkyl and benzyl halides afford symmetrical trithio-
carbonates in good to excellent yields (Scheme 2 and Table 2).
Interestingly, the reaction of 1,2-dichloroethane gave 1,3-dithiolane-2-thione as a
cyclic trithiocarbonate without the formation of any polymeric by-product (Entry 13).
Since nucleophilic substitution of trithiocarbonate anion occurs under SN2 conditions,22
a
low yield was obtained in the case of secondary alkyl halide and no product was isolated
for the tertiary halide (Entries 14 and 15).
In all cases, the structure of products was established by comparison of their spec-
troscopic analyses with authentic samples.21,22 The compounds displayed a characteristic
FTIR vibration bands of C S at approximately 1050 to 1070 cm−1. Also, the 13C NMR
resonances at 222 to 227 ppm can be attributed to carbon of CS3 group.
Table 2 Conversion of various alkyl halides into corresponding trithiocarbonates
Entry
Alkyl halide
Time (min)
Yield (%)a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
C6H5CH2Cl
C6H5CH2Br
35
30
60
40
75
45
25
60
20
90
45
40
60
90
120
9216,22
9016,22
9022
C6H5CH2CH2Br
4-BrC6H4CH2Cl
2,4-Cl2C6H3CH2Cl
2-FC6H4CH2Cl
2-ClC6H4CH2Cl
C10H7CH2Cl
9122
9222
9022
9122
8722
CH3I
n-BuCl
6416
7517
CH2 = CHCH2Cl
CH2 = CHCH2Br
ClCH2CH2Cl
(C6H5)2CHBr
C6H5C(CH3)2Br
7717,21
8217,21
6016
5522
—
aYields refer to isolated products.

ACCESS TO SYMMETRICAL DIALKYL
1721
Table 3 Comparison of the efficiency of 1,1ꢁ-bis-methyl-3, 3-methylenebisimidazolium dihydroxide with other
reported catalysts in the synthesis of dibenzyl trithiocarbonate
Entry
Substrate, catalyst, condition
Time (min)
Yield (%)
1
2
3
4
5
6
BnCl, basic Al2O3/CS2, reflux20
BnBr, K3PO4/CS2, DMF21
BnCl, TBAH/CS2, 50◦C19
BnBr, A-26 (OH−)/CS2, reflux16
BnCl, basic IL/CS2, 50◦Ca
BnBr, basic IL/CS2, 50◦Ca
240
600
240
90
35
30
85
92
92
96
92
90
aThis work
The superiority of using 1,1ꢁ-bis-methyl-3, 3-methylenebisimidazolium dihydroxide
as reagent and catalyst for the synthesis of a target product (dibenzyl trithiocarbonate) is
shown by comparing with those of the previously reported methods (Table 3).
CONCLUSION
We have introduced a novel TSDIL (1,1ꢁ-bis-methyl-3, 3-methylenebisimidazolium
dihydroxide) as a highly efficient basic reagent as well as a phase-transfer catalyst for
the straightforward access to symmetrical dialkyl trithiocarbonates form alkyl halides. The
reaction is simple, rapid and gives high product yields.
EXPERIMENTAL
All compounds were purchased from the supplier and used as received without further
purification. Progress of the reaction was monitored by TLC on Merck DC-Alufolien plates
precoated with silica gel F254. Nuclear magnetic resonance spectra were recorded in CDCl3
on a Bruker Avance DPX 400 MHz instrument spectrometer using TMS as internal standard.
IR spectra were recorded on a Perkin-Elmer RX1 FTIR spectrometer.
General Procedure
A round-bottomed flask (25 mL) was charged with 1,1ꢁ-bis-methyl-3, 3-methyle-
nebisimidazolium dihydroxide (0.318 g, 1.5 mmol) in carbon disulfide (3 mL) and the
mixture was stirred vigorously for 15 min. To increase the solubility, 10 drops of water
were used. Then, alkyl halide (2 mmol) was added and the suspension was stirred under
reflux conditions (50◦C) for the time as shown in Table 1. TLC analysis [n-hexane/ethyl
acetate (10:1)] indicated the completion of the reaction. Next, the remaining CS2 was
evaporated, product was extracted with EtOAc (15 mL), and the organic phase was washed
with water (3 × 5 mL), dried over Na2SO4 and then concentrated under reduced pressure
to give the desired trithiocarbonate.
FUNDING
The financial support of this work by the Mahshahr Branch, Islamic Azad University,
Iran is greatly appreciated. Also, the author, S. Moonesi, acknowledges the funding support

1722
S. SAYYAHI ET AL.
received for part of this project from the Omidieh Branch Research Council, Islamic Azad
University, Iran.
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