Cyclic ammonium salts of dithiocarbamic acid: stable alternative reagents for the synthesis of S-alkyl carbodithioates from organyl thiocyanates in water

Article abstract of DOI:10.1080/17415993.2016.1166225

ABSTRACT: Carbodithioate esters are important functional organosulfur compounds widely used in diverse fields such as pharmaceuticals, agrochemicals and material sciences. Common preparative methods include reaction of alkyl halides, carbon disulfide and bases under both metal-free and metal-catalyzed conditions. However, organyl thiocyanates have not been previously explored, possibly because of their conversion to organyl disulfides under basic conditions. Here, we report an efficient and practical method for the preparation of libraries of carbodithioate esters from organyl thiocyanates by reacting with cyclic amine-based dithiocarbamic acid salts in water. The protocol is found to be applicable in general to various thiocyanates such as benzyl/aroyl methyl/cinnamyl and so on. Other notable features include no by-products such as disulfides, metal- and alkali-free, aqueous conditions, and finally easy and near-quantitative formation of cyclic amine-based dithiocarbamic acid salt as a stable alternative reagent.

Full text of DOI:10.1080/17415993.2016.1166225

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Cyclic ammonium salts of dithiocarbamic acid:
stable alternative reagents for the synthesis of S-
alkyl carbodithioates from organyl thiocyanates in
water
Kinkar Biswas, Sujit Ghosh, Pranab Ghosh & Basudeb Basu
To cite this article: Kinkar Biswas, Sujit Ghosh, Pranab Ghosh & Basudeb Basu (2016): Cyclic
ammonium salts of dithiocarbamic acid: stable alternative reagents for the synthesis of S-
alkyl carbodithioates from organyl thiocyanates in water, Journal of Sulfur Chemistry, DOI:
10.1080/17415993.2016.1166225
To link to this article: http://dx.doi.org/10.1080/17415993.2016.1166225
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Date: 08 May 2016, At: 08:01

JOURNAL OF SULFUR CHEMISTRY, 2016
http://dx.doi.org/10.1080/17415993.2016.1166225
SHORT COMMUNICATION
Cyclic ammonium salts of dithiocarbamic acid: stable
alternative reagents for the synthesis of S-alkyl
carbodithioates from organyl thiocyanates in water
Kinkar Biswas, Sujit Ghosh, Pranab Ghosh and Basudeb Basu
Department of Chemistry, North Bengal University, Darjeeling 734013, India
ABSTRACT
ARTICLE HISTORY
Received 5 January 2016
Accepted 9 March 2016
Carbodithioate esters are important functional organosulfur com-
pounds widely used in diverse fields such as pharmaceuticals, agro-
chemicals and material sciences. Common preparative methods
include reaction of alkyl halides, carbon disulfide and bases under
both metal-free and metal-catalyzed conditions. However, organyl
thiocyanates have not been previously explored, possibly because of
their conversion to organyl disulfides under basic conditions. Here,
we report an efficient and practical method for the preparation of
libraries of carbodithioate esters from organyl thiocyanates by react-
ing with cyclic amine-based dithiocarbamic acid salts in water. The
protocol is found to be applicable in general to various thiocyanates
such as benzyl/aroyl methyl/cinnamyl and so on. Other notable fea-
turesincludenoby-productssuchasdisulfides, metal-andalkali-free,
aqueous conditions, and finally easy and near-quantitative formation
of cyclic amine-based dithiocarbamic acid salt as a stable alternative
reagent.
KEYWORDS
Alkyl thiocyanate; aqueous
medium; carbodithioate
ester; cyclic sec. amine;
dithiocarbamate salt
1. Introduction
S-alkyl carbodithioate esters, also known as dithiocarbamate esters, are functional
organosulfur compounds that were first utilized as fungicides during the Second World
War.[1] These are also largely used as important fungicides of crops, vegetables and
CONTACT Basudeb Basu
basu_nbu@hotmail.com
Department of Chemistry, North Bengal University,
Darjeeling 734013, India
Supplemental data for this article can be accessed here. http://dx.doi.org/10.1080/17415993.2016.1166225
© 2016 Informa UK Limited, trading as Taylor & Francis Group

2
K. BISWAS ET AL.
NH
S
SCH3
O
S
S
CH3
N
H3C
N
S
H
H
Brassinin,
cancer chemopreventive activity
Sulforamate
cancer chemopreventive agent
N
N
S
NC
S
S
N
N
S
NMe2
Cl
RWJ-025856
990207
attenuating effects on tumor
necrosis factor a (TNFa)-induced apoptosis in murine
fibrosarcoma WEHI 164 cells
inhibiting the tumor growth of sarcoma
180 (S180), hepatocyte carcinoma 22 (H22
)
Figure 1. Examples of compounds of potential therapeutic value bearing the S-alkyl carbodithioate
ester function.
plants.[2–4] Many literature reports demonstrate that the S-alkyl carbodithioate esters
and its derivatives exhibit antibacterial,[5–7] anthelmintic,[8] anticandidal activity and
cytotoxicity,[9] antihistaminic,[10] as well as anticancer properties.[8,11–13] They can also
be helpful for the treatment of cardiovascular disorders and inflammatory diseases.[14]
They show in vitro antitumor activity against human myelogenous leukemia K562
cells,[15] and can be used as HIV-I NCp7 inhibitors,[16] or non-vanilloid TRPV1
antagonists.[17] A few structures of S-alkyl carbodithioate esters with potential thera-
peutic value are shown in Figure 1. Further utility of carbodithioate esters as linkers
in solid-phase organic synthesis is also well documented.[18,19] In surface science and
nanomaterial chemistry, carbodithioate esters are widely used as suitable ligands for assem-
bly on metal nanoparticles.[20,21] They are familiar in the rubber industry as sulfur
vulcanization acceptors,[22] and radical chain transfer agents in the reversible addition
fragmentation chain transfer polymerizations.[23–25] They also represent useful synthetic
intermediates.[26,27] As a result, several methods for the synthesis of carbodithioate esters
have been developed.[28]
Commonly, synthesis of S-alkyl/aryl carbodithioate esters is achieved by either nucle-
ophilic substitution reactions under basic medium or transition metal-catalyzed cross-
coupling reactions (Scheme 1). The reaction of sec. amine with carbon disulfide (CS2)
produces an intermediate nucleophile that reacts with various substrates, such as alkyl
halide,[29] allyl acetate,[30] epoxide,[31] tosyl hydrazone [32]and α,β-unsaturated car-
bonyl compounds,[33–35] in one-pot metal-free or under metal-catalyzed reaction con-
ditions to afford the corresponding carbodithioate esters (Scheme 1). Anilines can also be
used for the preparation of carbodithioate esters bearing sec. NH group in the presence of
DMSO and a strong base such as NaOH.[36] Most of the procedures involve harsh reac-
tion conditions, long reaction time, hazardous organic solvents, metal catalysts and bases.
Organyl thiocyanates, often considered as psuedohalides and are easily available, were not

JOURNAL OF SULFUR CHEMISTRY
3
Saidi et al.
Org. Lett., 2006
R3-X
Ref. 29
(X = Cl, Br, I)
RT, 3-12 h, neat
Xia et al.
OMe
O
Tetrahedron, 2009
Ref. 34
Alkaline Al2O3
30 h
R-SCN
+
S
''Our
Ref. 31
RSC Adv., 2012
Azizi et al.
R1R2NH
CS2
O
R
protocol''
H
H
S
S
N
PhO
+
N
N
PEG, RT, 1 h
SDS/H2O
RT
X
n
X
S-Alkyl
carbodithioate
S
n
Ref. 30
Ranu et al.
RSC Adv., 2012
n = 1,2
X = O, CH2
Cinnamyl /
Allyl acetate
Ru(II) Catalyst,
100 oC, water
Sha et al.
Org. Biomol. Chem., 2013
Ref. 32
NNHTs
R
R'
Base, dioxane
110 ºC, 4 h
Scheme 1. Methods for the synthesis of S-alkyl carbodithioate esters.
used as the starting materials, presumably because of the fact that the thiocyanate may
undergo disulfide (–S–S–) bond formation under basic medium.[37,38]
We found that the reaction of a sec. amine with CS2 produces a stable salt, which can
be isolated easily in almost quantitative yield and stored for several weeks in the air. The
salt can efficiently react with alkyl/aroyl methyl/cinnamyl thiocyanates in water medium
at room temperature to afford corresponding carbodithioate esters in the presence of the
anionic phase transfer agent (sodium dodecyl sulfate (SDS)) in excellent yields without for-
mation of other by-products such as organyl disulfide. We report herein an efficient, base-
and metal-free protocol for the synthesis of various S-substituted carbodithioate esters by
using variety of cyclic sec. amine-based dithiocarbamate salts from diverse organyl thio-
cyanates. While organyl thiocyantes have not been used previously as the precursor for
preparation of carbodithioate esters, other notable advantages of this protocol are metal-
and alkali-free conditions, which possibly lead to the avoidance of disulfide bond forma-
tion and clean reactions affording excellent yields, and can be carried out in water medium
at room temperature (Scheme 1).
2. Results and discussion
As a part of preliminary study, as presented in Table 1, we have conducted the reaction
of a neat mixture of benzyl thiocyanate, CS2 and morpholine in a one-pot manner, which
led to the pure desired benzyl morpholine-4-carbodithioate ester 4a in 72% isolated yield
(Table 1, entry 1). The reaction showed partial formation of dibenzyl disulfide on TLC
monitoring of the experiment, although it was not isolated in appreciable quantity after
column chromatography. Considering that the intermediate salt derived from the amine
and CS2 could be the actual nucleophile, the sodium salt of morpholinodithioformate 2a
was used to react with benzyl thiocyanate 3a (Table 1, entry 2). However, we obtained the
desired carbodithioate ester 4a again with the formation of dibenzyl disulfide, presumably
attributable to the basic reaction medium that facilitates disulfide formation from benzyl

4
K. BISWAS ET AL.
Table 1. Optimization of the reaction conditions for the conversion of benzyl thiocyanate to S-alkyl
cabodithioates.
S
N
O
S
S
Na
2a
or
Solvent
SCN
S
N
+
Temperature,
Additive
O
H
N
S
3a
4a
N
O
O
S
H
2b
Entry
Solvent
T (°C)
Additive
Time (h)
Yielda (%)
1b
2c
3e
4
Neat
Water
Water
Water
EtOH
Water: EtOH
Water
Water
RT
RT
RT
60
60
RT
RT
RT
RT
No
No
No
No
No
1
1
1
1
1
1
1
1
1
72
60d
76
78
82
80
84
96
96
5
6
No
7f
8g
9h
TBAB
SDS
SDS
Water
aYield represents pure isolated product after purification by column chromatography.
bMixture of benzyl thiocyanate (1 mmol), morpholine (2 mmol) and CS2 (1 mmol) in 2 mL solvent was stirred at room
temperature.
cSalt 2a was used.
d20% dibenzyl disulphide was isolated.
eSalt 2b was used.
fTetrabutyl ammonium bromide (TBAB; stoichiometric) was used.
gSodium dodecyl sulfate (SDS; stoichiometric) was used.
hSDS (10 mol%) was used.
thiocyanate 3a.[37,38] In order to avoid the basic reaction medium, we considered that the
dithiocarbamate salt consisting of both organyl cationic and anionic part might be a better
alternative and accordingly, we prepared the salt 2b from a mixture of morpholine and CS2
in diethyl ether following the reported procedure.[39]
The salt 2b contains the morpholino-based cationic and anionic part and stirring a mix-
ture of benzyl thiocyanate 3a and 2b (in equimolar quantity) in water at room temperature
gave rise to a clean reaction without any trace of disulfide formation, producing 4a in 76%
isolated yield (Table 1, entry 3). Heating the reaction mixture of 2b and 3a in water or
ethanol at 60°C resulted in a better yield of 4a (78–82%; Table 1, entries 4 and 5). On the
other hand, use of water–ethanol (1:1) as the solvent and conducting the reaction at room
temperature gave 4a in 80% yield (Table 1, entry 6).
It is likely that organyl thiocyanates are poorly soluble in water, and we employed two
different phase transfer agents, n-tetrabutyl ammonium bromide (TBAB) and SDS. While
the use of TBAB was found to lead to a marginal increase in the yield of 4a (Table 1, entry
7), the presence of SDS (either in stoichiometric or in 10 mol%) afforded 4a in excellent
yield (96%) (Table 1, entries 8 and 9). Thus, excellent conversion of benzyl thiocyanate to
benzyl morpholine-4-carbodithioate ester 4a is indeed possible if we use separately pre-
pared amine-based salt, and perform the reaction under conditions as described in entry
9 of Table 1. In aqueous medium reactions, anionic phase transfer agents as additive are
usually more effective than cationic agents.[40] Here, we used both TBAB (cationic) and

JOURNAL OF SULFUR CHEMISTRY
5
S
NaOH, CS2
N
X
EtOH:H2O (1:1)
Stir at 0-5 ºC
S
Na
n
n = 2, X = O (2a)
NH
n
X
1
H
S
H
N
H
S
S
S
CS2 in diethyl ether
Stir at RT
N
N
or
N
N
X
X
X
H
S
n
S
n
2
n
2b-2d
n = 2, X = NH (2e)
simple preparation
crystalline solid
n = 2, X = O (2b)
easy separation
stored for longer time under air
n = 2, X = CH2 (2c)
n = 1, X = CH2(2d)
H
H
S
N
S
H
S
S
N
N
O
N
O
O
N
S
S
H
Na
2b
2c
2a
(Morpholinium
(Piperidinium
piperidinodithioformate)
(Sodium
morpholinodithioformate)
morpholinodithioformate)
H
S
S
S
H
H
S
H
N
N
N
NH
HN
N
N
N
H
S
S
H
2d
2e
Bis(piperazinium)piperazine-1,4-dicarbodithioate
(Pyrrolidinium
pyrrolidinodithioformate)
Scheme 2. Synthesis of sec. cyclic aliphatic amine-based dithiocarbamate salts (2b–2e).
SDS (anionic) additives and the results are in conformity with previous reports. The bet-
ter functioning of the anionic phase transfer agents such as SDS might be explained in the
light of considering the whole system as a microreactor, where organyl thiocyanate having
resided in the hydrophobic dodecyl core may come in contact with the reactant (here the
dithocarbamate salt) being present in water through the formation of hydrogen bond with
anionic sulfate ion.
Encouraged by this observation, we wanted to develop a general and practical proce-
dure for the conversion of organyl thiocyanates into carbodithioate esters. We prepared
other dithiocarbamate salts (2c–2e) from three different cyclic sec. amines such as piperi-
dine, pyrrolidine and piperazine (Scheme 2), and employed our optimized conditions (as
in Table 1, entry 9) for reaction with various functionalized organyl thiocyanates. The
results are presented in Table 2. It is clearly evident that different chloro-substituted ben-
zyl thiocyanates and naphthyl methyl thiocyanate underwent smooth conversion to the
corresponding carbodithioate esters with all types of dithiocarbamate salts (4a–4m of
Table 2). While 2- and 4-chloro benzyl thiocyanates worked equally efficiently without any
steric encumbrance, the piperazine-based dithiocarbamate salt 2e reacted with benzyl or
2-chlorobenzyl thiocyanates to produce bis-carbodithioate esters in 82–83% yields within
3 h (4l and 4m).

6
K. BISWAS ET AL.
Table 2. Synthesis of diverse S-alkyl carbodithioates from organyl thiocyanates and dithiocarbamate
salts.a,b
S
H
S
N
n
X
N
S
N
X
X
X
R
S
H
n
n
SDS (10 mol%)
Water, RT
SCN
4a-4k
or
or
R
+
H
N
S
S
S
R
N
N
R = H, 2-Cl, 4-Cl
S
S
S
H
S
n
2
N
N
2b, X = O, n = 2
2c, X = CH2, n = 2
2d, X = CH2, n = 1
3
S
R
4l, 4m
2e, X = NH, n = 2
R1 SCN (3)
Salt (2)
Time (h)
1.0
T (°C)
Product (4)
Yield (%)
96
−
Entry
1
2b
RT
S
S
N
SCN
O
4a
2
3
4
2b
2b
2b
1.0
1.0
1.5
RT
RT
S
98
97
87
S
N
SCN
O
4b
Cl
Cl
S
S
N
SCN
O
4c
Cl
Cl
S
RT
S
N
SCN
SCN
O
4d
S
5
2c
1.0
RT
95
S
4e
N
S
6
7
2c
2c
1.0
1.5
RT
RT
98
89
S
N
N
SCN
SCN
Cl
Cl
4f
S
S
4g
(continued)

JOURNAL OF SULFUR CHEMISTRY
7
Table 2. Continued.
−
Entry
8
R1 SCN (3)
Salt (2)
Time (h)
1.0
T (°C)
Product (4)
Yield (%)
2c
RT
97
94
96
S
SCN
S
N
4h
Cl
Cl
S
9
2d
2d
2.0
2.5
RT
RT
S
N
SCN
4i
10
S
SCN
S
N
4j
Cl
Cl
S
11
12
2d
2e
2.5
3.0
RT
RT
86
82
SCN
S
N
4k
S
S
S
N
N
S
SCN
SCN
4l
13
2e
3.0
RT
83
Cl
S
S
S
N
N
S
C
4m
Cl
aA mixture of 2 (1.0 mmol), 3 (1.0 mmol), SDS (10 mol%) in water (2 mL) was stirred at RT in open air. For 4l and 4m,
compound 3 (2 mmol) was used.
bYield represents pure product isolated by column chromatography.
To broaden the scope of the reaction further, alkyl thiocyanates bearing β-carbonyl
function (e.g. aroyl methyl, 5) or β-alkenyl function (e.g. styrenyl methyl, 6) were subjected
to similar reaction conditions. Corresponding functionalized organic carbodithioate esters
bearing carbonyl or styrenyl methyl group could be easily synthesized in aqueous medium
at ambient temperature. Three different sec. amine-based dithiocarbamate salts (2b–2d)
were used and corresponding carbodithioates bearing Cl, Br or NO2 groups attached with
the aromatic ring (7a–7e, 8a and 8b) were obtained in high yields (Table 3). All the com-
pounds were characterized by spectral data and compared with melting points wherever
known and reported.

8
K. BISWAS ET AL.
Table 3. Synthesis of functionalized S-alkyl carbodithioates.a,b
O
O
X
n
SCN
S
N
R/
R/
H
N
H
S
S
N
7a-7e
R/ = 4-Cl, 4-Br, 3-NO2
SDS (10 mol%)
Water, RT
X
X
S
n
+
n
or
5
S
or
2b, X = O, n = 2
2c, X = CH2, n = 2
2d, X = CH2, n = 1
Ph
S
N
Ph
SCN
X
n
8a, 8b
6
−
Entry
1
R2 SCN (5 and 6)
Salt (2)
Time (h)
3.0
T (°C)
Product (7 and 8)
Yield (%)
95
2b
RT
O
O
O
SCN
S
N
S
7a
Br
Br
Cl
Br
2
3
4
2c
2c
2c
3.0
4.0
3.5
RT
94
95
86
O
O
O
SCN
SCN
S
N
S
7b
7c
Br
RT
O
S
N
S
Cl
O
RT
O
SCN
S
N
S
7d
NO2
NO2
5
2d
3.0
RT
96
O
O
SCN
S
N
S
7e
Cl
Cl
S
6
7
2b
2c
1.5
1.5
RT
92
93
S
N
SCN
SCN
O
8a
S
RT
S
N
8b
aA mixture of 2 (1.0 mmol), 5 or 6 (1.0 mmol), SDS (10 mol%) in water (2 mL) was stirred at RT in open air.
bYield represents pure product isolated by column chromatography.

JOURNAL OF SULFUR CHEMISTRY
9
H
S
R
R
S
H
N
R
S
H
N
SDS/H2O
RT
Not formed
through
homolytic fission
of b-bond of
alkyl thiocyanate
H
S
C
N
+
R
S
N
S
N
+
SCN
4
FeCl3 solution
gives blood red
colouration
S
2
3
Scheme 3. Proposed reaction mechanism.
3. Mechanism
The reaction presumably occurs via a simple nucleophilic substitution reaction. Organyl
thiocyanates are considered as psuedohalides that might not produce the corresponding
carbocation easily and hence the reaction is expected to proceed via the SN2 pathway
(Scheme 3). The dithiocarbamate salt consisting of both organyl cationic and anionic sys-
tem seems to render better results than using an in situ mixture of sec. amine and CS2 or the
corresponding sodium salt. Use of additives such as SDS likely help the organic reactants
become more homogeneous affording excellent conversions. The possibility of the forma-
tion of thiyl radical via β-bond cleavage of the alkyl thiocyanate can be excluded since
the reaction conditions do not support radical formation nor is the corresponding disul-
fide formed in the reaction.[41,42] On the other hand, aqueous ferric chloride solution
produces blood-red coloration indicating elimination of the thiocyanate anion.
4. Conclusion
In conclusion, we have shown that easily accessible and air-stable cyclic sec. amine-based
dithiocarbamate salts can serve as efficient reagents for the preparation of a large variety
of S-substituted carbodithioate esters from rarely used organyl thiocyanates as a common
strategy. The use of this type of salt not only shows superior activity to the existing one-pot
three-component procedure but also establishes it as alternative reagent, obtained easily in
quantitative conversion, for the preparation of carbodithioate esters. The simple procedure
can be carried out at room temperature, in water medium and affords excellent yields.
Further applications of these easily accessible salts are currently under active pursuit from
this laboratory. This method also establishes that the sec. amine-based dithiocarbamate
salts can serve as a stable more reactive alternative than in situ use of volatile CS2 and sec.
amine reagent, not only for this reaction, but also for other purposes, which are currently
being pursued in this laboratory.
5. Experimental
5.1. General information
Morpholine, piperidine and pyrrolidine were purchased from Lancaster and used after
distillation. Piperazine was purchased from Loba Chemie. CS2 and SDS were purchased
from SD Fine-Chem Limited and used directly. Benzyl, naphthyl methyl, cinnamyl and
aroyl methyl thiocyanates were prepared from reported procedure and purified by column
chromatography before use. Melting point of the solid compounds was determined in a

10
K. BISWAS ET AL.
concentrated H2SO4 bath. FT-IR spectra were recorded with a FT-IR-8300 SHIMADZU
spectrophotometer using a KBr pellet method for solid compounds and in neat for liq-
uid compounds. NMR spectra were taken in CDCl3 using a Bruker AV-300 spectrometer
operating for 1H at 300 MHz and for 13C at 75 MHz.
5.2. General procedure for the synthesis cyclic ammonium salts of dithiocarbamic
acid (2b–2e) [39]
A solution of CS2 (5 mmol) in diethyl ether (5 mL) was slowly added to a solution of
morpholine (10 mmol) or piperidine (10 mmol) or pyrrolidine (10 mmol) in diethyl ether
(5 mL). The reaction mixtures were stirred for 30 min at room temperature. Solid salts were
precipitated during this time and were filtered off through a Buchner funnel, washed with
diethyl ether and dried under vacuum to obtain the desired salts 2b–2d. In the case of
2e, a solution of CS2 (6 mmol) in diethyl ether (5 mL) was slowly added to a solution of
piperazine (9 mmol) in diethyl ether (6 mL). The reaction mixture was stirred for 45 min
at room temperature. The grey solids were filtered off, washed with diethyl ether and dried
under vacuum to obtain the desired salt 2e.
5.2.1. Morpholinium morpholinodithioformate (salt 2b) [39]
White solid; yield: 1.23 g (98%); Mp: 197–200°C, Lit. Mp 195–197°C.[39] IR (KBr):
ν
= 2854, 2711, 2475, 1583, 1420, 1255, 1215, 1112, 978, 876 cm−1
.
max
5.2.2. Piperidinium piperidinodithioformate (salt 2c) [39]
White solid; yield: 1.20 g (98%); Mp: 164–166°C, Lit. Mp 160°C.[39] IR (KBr):
ν
= 2936, 2843, 2731, 2497, 1583, 1409, 1215, 1122, 958 cm−1
.
max
5.2.3. Pyrrolidinium pyrrolidinodithioformate (salt 2d)
Off-white solid; yield: 1.05 g (96%); Mp: 149–151°C. IR (KBr): ν
= 2946, 2864, 2516,
max
2393, 1390, 1318, 1164, 999, 938 cm−1
.
5.2.4. Bis(piperazinium)piperazine-1,4-dicarbodithioate (salt 2e)
Grey solid; yield: 1.19 g (97%); Mp: 238–242°C. IR (KBr): ν
= 3162, 2915, 2434, 2331,
max
1634, 1390, 1225, 1123, 958, 855 cm−1
.
5.3. General procedure for the synthesis of S-alkyl carbodithioate esters
A mixture of organyl thiocyanate (1 mmol), dithiocarbamate salt (1 mmol) and SDS
(0.1 mmol) in water (2 mL) was stirred vigorously using a magnetic bar at room tempera-
ture. The progress of the reaction was monitored by TLC. After the reaction was continued
for specified time, as mentioned in Tables 2 and 3, the reaction mixture was extracted with
ethyl acetate (3 × 5 mL) and the combined organic extracts were collected over anhydrous
Na2SO4. Evaporation of the volatiles afforded the crude product, which was further puri-
fied by column chromatography over silica gel. Elution with a mixture of ethyl acetate-light
petroleum furnished the desired product. Yields of the products are shown in Tables 2 and
3.

JOURNAL OF SULFUR CHEMISTRY
11
All the products were identified and characterized by spectral data (FT-IR, 1H and 13
NMR), by melting point for solid compounds (compared wherever known).
C
5.3.1. Benzyl morpholine-4-carbodithioate (Table 2, 4a) [32]
Light yellow solid; yield: 0.243 g (96%); Mp: 64–65°C, Lit. Mp 59–60°C.[32] IR (KBr):
ν
= 3038, 2976, 2869, 1920, 1635, 1617, 1559, 1489, 1456, 1304, 1271, 1235, 924, 825,
max
725, 543 cm−1. 1H NMR (CDCl3, 300 MHz): δ 3.73 (s, 4H, 2 × OCH2), 4.01–4.33 (m, 4H,
2 × NCH2), 4.57 (s, 2H, SCH2), 7.22–7.39 (m, 5H). 13C NMR (CDCl3, 75 MHz): δ 42.02
=
(SCH2), 50.81 (NCH2), 66.27 (OCH2), 127.65, 128.67, 129.42, 135.78, 197.11 (C S).
5.3.2. 2-Chlorobenzyl morpholine-4-carbodithioate (Table 2, 4b)
White crystalline solid; yield: 0.281 g (98%); Mp: 94–96°C. IR (KBr): ν
= 3053, 2992,
max
2931, 2855, 1918, 1654, 1635, 1617, 1542, 1444, 1347, 1310, 1271, 1053, 1028, 868,
1
731, 582 cm−1. H NMR (CDCl3, 300 MHz): δ 3.77 (s, 4H, 2 × OCH2), 4.17 (s, br, 4H,
2 × NCH2), 4.76 (s, 2H, SCH2), 7.21–7.64 (m, 4H). 13C NMR (CDCl3, 75 MHz): δ 39.48
(SCH2), 50.91 (NCH2), 66.25 (OCH2), 126.98, 129.10, 129.61, 131.56, 134.12, 134.58,
=
196.91 (C S).
5.3.3. 4-Chlorobenzyl morpholine-4-carbodithioate (Table 2, 4c)
White solid; yield: 0.278 g (97%); Mp: 79–81°C. IR (KBr): ν
= 3007, 2977, 2916, 2870,
max
1
1833, 1656, 1620, 1542, 1423, 1268, 1217, 1034, 998, 837, 643 cm−1. H NMR (CDCl3,
300 MHz): δ 3.66 (s, 4H, 2 × OCH2), 3.90 (s, 2H, NCH2), 4.17 (s, 2H, NCH2), 4.47 (s, 2H,
SCH2), 7.17–7.25 (m, 4H). 13C NMR (CDCl3, 75 MHz): δ 40.83 (SCH2), 50.83 (NCH2),
=
66.10 (OCH2), 128.60, 130.57, 133.26, 134.59, 196.50 (C S).
5.3.4. (Naphthalen-1-yl) methyl morpholine-4-carbodithioate (Table 2, 4d)
Light brown solid; yield: 0.263 g (87%); Mp: 115–117°C. IR (KBr): ν
= 3053, 2976,
max
2900, 2869, 1699, 1578, 1538, 1420, 1356, 1301, 1271, 1189, 998, 786, 630 cm−1. 1H NMR
(CDCl3, 300 MHz): δ 3.66 (s, 4H, 2 × OCH2), 3.91–4.06 (m, 4H, 2 × NCH2), 4.95 (s, 2H,
SCH2), 7.31–7.52 (m, 4H), 7.71–7.98 (m, 2H), 8.00–8.01 (m, 1H). 13C NMR (CDCl3,
75 MHz): δ 40.34 (SCH2), 50.47 (NCH2), 66.23 (OCH2), 123.93, 125.46, 126.01, 126.50,
=
128.34, 128.80, 128.83, 131.06, 131.84, 133.90, 197.25 (C S).
5.3.5. Benzyl piperidine-1-carbodithioate (Table 2, 4e) [43]
Pale yellow viscous liquid; yield: 0.238 g (95%). IR (neat): ν
= 3040, 2974, 2864, 1945,
max
1620, 1590, 1545, 1495, 1358, 1340, 1291, 1279, 1222, 1016, 980, 840, 742 cm−1. H
NMR (CDCl3, 300 MHz): δ 1.62 (s, 6H, NCH2(CH2)3), 3.80 (s, br, 2H, NCH2), 4.21 (s,
br, 2H, NCH2), 4.49 (s, 2H, SCH2), 7.15–7.33 (m, 5H). 13C NMR (CDCl3, 75 MHz):
δ 24.29 (NCH2CH2CH2), 25.79 (NCH2CH2), 42.25 (SCH2), 52.67 (NCH2), 127.45, 128.56,
1
=
129.38, 136.12, 195.31 (C S).
5.3.6. 2-Chlorobenzyl piperidine-1-carbodithioate (Table 2, 4f)
Yellow viscous liquid; yield: 0.280 g (98%). IR (neat): ν
= 3010, 2970, 2860, 1996, 1580,
max
1
1546, 1493, 1357, 1340, 1280, 1224, 1074, 946, 840, 746, 650 cm−1. H NMR (CDCl3,
300 MHz): δ 1.69 (s, 6H, NCH2(CH2)3), 3.87 (s, br, 2H, NCH2), 4.29 (s, br, 2H, NCH2),
4.72 (s, 2H, SCH2), 7.18–7.23 (m, 2H), 7.34–7.38 (m, 1H), 7.54–7.58 (m, 1H). 13C NMR

12
K. BISWAS ET AL.
(CDCl3, 75 MHz): δ 24.29 (NCH2CH2CH2), 25.62 (NCH2CH2), 39.66 (SCH2), 51.42
=
(NCH2), 53.10 (NCH2), 126.96, 128.95, 129.55, 131.56, 134.45, 134.54, 194.91 (C S).
5.3.7. (Naphthalen-1-yl) methyl piperidine-1-carbodithioate (Table 2, 4g)
White solid; yield: 0.268 g (89%); Mp: 93–95°C. IR (KBr): ν
= 3038, 2947, 2870, 1620,
max
1596, 1563, 1542, 1474, 1435, 1399, 1365, 1281, 1235, 1210, 1113, 980, 870, 776, 670,
1
588 cm−1. H NMR (CDCl3, 300 MHz): δ 1.63 (s, 6H, NCH2(CH2)3), 3.75 (s, br, 2H,
NCH2), 4.27 (s, br, 2H, NCH2), 4.93 (s, 2H, SCH2), 7.31–7.58 (m, 4H), 7.71–7.85 (m,
2H), 8.0–8.01 (m, 1H). 13C NMR (CDCl3, 75 MHz): δ 24.29 (NCH2CH2CH2), 25.90
(NCH2CH2), 40.56 (SCH2), 52.83 (NCH2), 124.11, 125.49, 125.96, 126.43, 128.30, 128.66,
=
128.78, 131.42, 131.90, 133.88, 195.26 (C S).
5.3.8. 4-Chlorobenzyl piperidine-1-carbodithioate (Table 2, 4h)
White solid; yield: 0.277 g (97%); Mp: 83–85°C. IR (KBr): ν
= 3007, 1961, 2855, 1632,
max
1617, 1577, 1542, 1508, 1481, 1429, 1378, 1281, 1225, 1110, 1080, 974, 843, 746, 652 cm−1
.
1H NMR (CDCl3, 300 MHz): δ 1.62 (s, 6H, NCH2(CH2)3), 3.79 (s, br, 2H, NCH2), 4.22
(s, br, 2H, NCH2), 4.44 (s, 2H, SCH2), 7.15–7.27 (m, 4H). 13C NMR (CDCl3, 75 MHz):
δ 24.27 (NCH2CH2CH2), 25.54 (NCH2CH2), 41.20 (SCH2), 53.08 (NCH2), 128.67, 130.70,
=
133.21, 135.04, 194.70 (C S).
5.3.9. Benzyl pyrrolidine-1-carbodithioate (Table 2, 4i) [43]
Yellow liquid; yield: 0.223 g (94%). IR (neat): ν
= 3048, 2970, 2865, 1903, 1590, 1440,
max
1365, 1308, 1216, 1070, 1012, 944, 826, 780, 503 cm−1. H NMR (CDCl3, 300 MHz):
δ 1.92−2.10 (m, 4H, NCH2(CH2)2), 3.62 (t, J = 6.3 Hz, 2H, NCH2), 3.93 (t, J = 6.9 Hz,
2H, NCH2), 4.58 (s, 2H, SCH2), 7.22–7.33 (m, 3H), 7.38–7.41 (m, 2H). 13C NMR (CDCl3,
75 MHz): 24.29 (NCH2CH2), 26.08 (NCH2CH2), 41.30 (SCH2), 50.52 (NCH2), 55.03
1
=
(NCH2), 127.39, 128.56, 129.27, 136.55, 192.46 (C S).
5.3.10. 4-Chlorobenzyl pyrrolidine-1-carbodithioate (Table 2, 4j)
Pale yellow solid; yield: 0.261 g (96%); Mp: 60–62°C. IR (KBr): ν
= 2966, 2864, 1903,
max
1595, 1441, 1328, 1092, 1009, 948, 825, 744, 507 cm−1. H NMR (CDCl3, 300 MHz):
δ 1.92−2.10 (m, 4H, NCH2(CH2)2), 3.62 (t, J = 6.3 Hz, 2H, NCH2), 3.93 (t, J = 6.9 Hz,
2H, NCH2), 7.24–7.27 (m, 2H), 7.32–7.35 (m, 2H). 13C NMR (CDCl3, 75 MHz): 24.25
(NCH2CH2), 26.05(NCH2CH2), 40.21 (SCH2), 50.56 (NCH2), 55.15 (NCH2), 128.61,
1
=
130.56, 133.10, 135.42, 191.81 (C S).
5.3.11. (Naphthalen-1-yl) methyl pyrrolidine-1-carbodithioate (Table 2, 4k)
White solid; yield: 0.247 g (86%); Mp: 116–118°C. IR (KBr): ν
= 3040, 2950, 2880,
max
1542, 1450, 1400, 1364, 1342, 1280, 1210, 1134, 1072, 980, 808, 770, 672, 540 cm−1. H
NMR (CDCl3, 300 MHz): δ 1.87–1.97 (m, 4H, NCH2(CH2)2), 3.51 (t, J = 6.9 Hz, 2H,
NCH2), 3.94 (t, J = 6.6 Hz, 2H, NCH2), 5.01 (s, 2H, SCH2), 7.34–7.40 (m, 1H), 7.43–7.54
(m, 2H), 7.58 (d, J = 6.9 Hz, 1H), 7.76 (d, J = 8.1 Hz, 1H), 7.81–7.84 (m, 1H), 8.08 (d,
J = 8.1 Hz, 1H). 13C NMR (CDCl3, 75 MHz): δ 24.29 (NCH2CH2), 26.06 (NCH2CH2),
39.64 (SCH2), 50.51 (NCH2), 55.02 (NCH2), 124.08, 125.50, 125.98, 126.44, 128.17, 128.61,
1
=
128.81, 131.77, 131.85, 133.92, 192.33 (C S).

JOURNAL OF SULFUR CHEMISTRY
13
5.3.12. Dibenzyl piperazine-1,4-dicarbodithioate (Table 2, 4l) [44]
White solid; yield: 0.343 g (82%); Mp: 124–126°C, Lit. Mp 122–123°C. IR (KBr):
ν
= 3068, 3038, 2931, 1538, 1505, 1474, 1435, 1413, 1277, 1210, 1159, 1043, 924,
max
849, 694 cm−1. H NMR (CDCl3, 300 MHz): δ 4.18 (s, br, 8H, 4 × NCH2), 4.51 (s, 4H,
1
2 × SCH2), 7.19–7.32 (m, 10H). 13C NMR (CDCl3, 75 MHz): δ 42.16 (SCH2), 48.71
=
(NCH2), 127.74, 128.69, 129.39, 135.51, 197.53 (C S).
5.3.13. Bis-(2-chlorobenzyl) piperazine-1,4-dicarbodithioate (Table 2, 4 m)
Grey solid; yield: 0.404 g (83%); Mp: 148–150°C. IR (KBr): ν
= 2916, 1640, 1420, 1276,
max
1041, 990, 928, 846, 744 cm−1. 1H NMR (CDCl3, 300 MHz): δ 4.28 (s, br, 8H, 4 × NCH2),
4.72 (s, 4H, 2 × SCH2), 7.18–7.26 (m, 4H), 7.35–7.39 (m, 2H), 7.53–7.56 (m, 2H). 13C
NMR (CDCl3, 75 MHz): δ 39.64 (SCH2), 48.99 (NCH2), 126.98, 129.21, 129.63, 131.54,
=
133.81, 134.56, 197.19 (C S).
5.3.14. 4-Bromo phenacyl morpholine-4-carbodithioate (Table 3, 7a)
White solid; yield: 0.342 g (95%); Mp: 164–166°C. IR (KBr): ν
= 2967, 2906, 2855,
max
1
1686, 1583, 1430, 1276, 1125, 1112, 990, 816, 539 cm−1. H NMR (CDCl3, 300 MHz):
δ 3.71 (t, J = 4.8 Hz, 4H, 2 × OCH2), 3.97 (s, br, 2H, NCH2), 4.2 (s, br, 2H, NCH2), 4.77
(s, 2H, SCH2), 7.54–7.59 (m, 2H), 7.84–7.88 (m, 2H).13C NMR (CDCl3, 75 MHz): δ 44.28
=
(SCH2), 51.55 (NCH2), 66.21 (OCH2), 128.85, 130.06, 132.08, 134.88, 192.28 (C O),
=
195.65 (C S).
5.3.15. 4-Bromo phenacyl piperidine-1-carbodithioate (Table 3, 7b)
White solid; yield: 0.336 g (94%); Mp: 116–118°C. IR (KBr): ν
= 3007, 2947, 2869,
max
1687, 1584, 1438, 1362, 1286, 1253, 973, 858, 666 cm−1. H NMR (CDCl3, 300 MHz):
δ 1.65 (s, 6H, NCH2(CH2)3), 3.89 (s, br, 2H, NCH2), 4.18 (s, br, 2H, NCH2), 4.77 (s,
2H, SCH2), 7.54–7.57 (m, 2H), 7.86–7.89 (m, 2H). 13C NMR (CDCl3, 75 MHz): δ 24.16
(NCH2CH2CH2), 25.95 (NCH2CH2), 44.50 (SCH2), 51.76 (NCH2), 53.66 (NCH2), 128.62,
1
=
=
130.09, 131.99, 135.04, 192.71 (C O), 193.70 (C S).
5.3.16. 4-Chloro phenacyl piperidine-1-carbodithioate (Table 3, 7c)
Yellowish white solid; yield: 0.298 g (95%); Mp: 110–112°C. IR (KBr): ν
= 3007, 2961,
max
2855, 1690, 1587, 1438, 1347, 1244, 1113, 971, 858, 682, 548 cm−1. H NMR (CDCl3,
300 MHz): δ 1.65 (s, 6H, NCH2(CH2)3), 3.89 (s, br, 2H, NCH2), 4.19 (s, br, 2H, NCH2), 4.77
(s, 2H, SCH2), 7.54–7.58 (m, 2H), 7.85–7.90 (m, 2H). 13C NMR (CDCl3, 75 MHz): δ 24.18
(NCH2CH2CH2), 25.42 (NCH2CH2), 26.09 (NCH2CH2), 44.49 (SCH2), 51.78 (NCH2),
1
=
=
53.72 (NCH2), 128.67, 130.11, 132.01, 135.00, 192.75 (C O), 193.63 (C S).
5.3.17. 3-Nitro phenacyl piperidine-1-carbodithioate (Table 3, 7d)
Pale yellow solid; yield: 0.279 g (86%); Mp: 109–111°C. IR (KBr): ν
= 2926, 2854, 1697,
1
max
1613, 1532, 1430, 1337, 1204, 1112, 1072, 979, 804, 733, 672 cm−1. H NMR (CDCl3,
300 MHz): δ 1.73 (s, 6H, NCH2(CH2)3), 3.97 (s, br, 2H, NCH2), 4.25 (s, br, 2H, NCH2),
4.86 (s, 2H, SCH2), 7.69–7.74 (m, 1H), 8.40–8.46 (m, 2H), 8.90–8.91 (m, 1H). 13C NMR
(CDCl3, 75 MHz): δ 24.16 (NCH2CH2CH2), 26.02 (NCH2CH2), 44.09 (SCH2), 52.09
=
(NCH2), 53.79 (NCH2), 123.45, 127.49, 129.95, 134.13, 137.87, 148.58, 191.84 (C O),
=
193.39 (C S).

14
K. BISWAS ET AL.
5.3.18. 4-Chloro phenacyl pyrrolidine-1-carbodithioate (Table 3, 7e)
Pale yellow solid; yield: 0.287 g (96%); Mp: 102–104°C. IR (KBr): ν
= 2957, 2876,
max
1676, 1583, 1430, 1286, 1184, 1080, 990, 958, 825, 528 cm−1. 1H NMR (CDCl3, 300 MHz):
δ 1.94–2.03 (m, 2H, NCH2CH2), 2.06–2.14 (m, 2H, NCH2CH2), 3.74 (t, J = 6.9 Hz, 2H,
NCH2), 3.9 (t, J = 6.9 Hz, 2H, NCH2), 4.85 (s, 2H, SCH2), 7.44–7.47 (m, 2H), 8.01–8.04
(m, 2H). 13C NMR (CDCl3, 75 MHz): δ 24.33 (NCH2CH2), 26.12 (NCH2CH2), 44.04
=
(SCH2), 50.80 (NCH2), 55.53 (NCH2), 128.99, 130.01, 134.43, 139.88, 190.68 (C O),
=
192.43 (C S).
5.3.19. (E)-Cinnamyl morpholine-4-carbodithioate, (Table 3, 8a) [30]
White crystalline solid, yield: 0.257 g (92%); Mp: 80–82°C (Lit. reported as yellowish vis-
cous liquid). IR (KBr): ν
= 3038, 2961, 2869, 1720, 1620, 1577, 1469, 1304, 1268,
max
1
1220, 1113, 992, 755 cm−1. H NMR (CDCl3, 300 MHz): δ 3.78 (t, J = 4.5 Hz, 4H,
=
2 × OCH2), 4.17–4.24 (m, 6H, 2 × NCH2, SCH2), 6.28–6.38 (m, 1H, PhCH CHCH2),
6.67 (d, J = 15.6 Hz, 1H, PhCH), 7.23–7.41 (m, 5H). 13C NMR (CDCl3, 75 MHz): δ 39.97
(SCH2), 50.90 (NCH2), 66.26 (OCH2), 123.68, 126.45, 127.76, 128.56, 133.95, 136.60,
=
197.03 (C S).
5.3.20. (E)-Cinnamyl piperidine-1-carbodithioate (Table 3, 8b) [30]
White crystalline solid; yield: 0.258 g (93%); Mp: 73–75°C (Lit. reported as yellowish vis-
cous liquid). IR (KBr): ν
= 3048, 2947, 2869, 1617, 1566, 1472, 1435, 1265, 1235, 1135,
max
1
1116, 1110, 973, 743 cm−1. H NMR (CDCl3, 300 MHz): δ 1.63 (s, 6H, NCH2(CH2)3),
3.82 (s, br, 2H, NCH2), 4.01–4.13 (m, 2H, SCH2), 4.23 (s, br, 2H, NCH2), 6.20–6.31
(m, 1H, PhCH CHCH2), 6.56 (d, J = 15.9 Hz, 1H, PhCH), 7.12–7.31 (m, 5H). 13C
=
NMR (CDCl3, 75 MHz): 24.32 (NCH2CH2CH2), 26.00 (NCH2CH2), 40.23 (SCH2), 51.37
=
(NCH2), 124.17, 126.44, 127.67, 128.54, 133.59, 136.72, 195.04 (C S).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
KB and SG thank the UGC, New Delhi, for award of their fellowships under UGC-FDP program.
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