Fast and efficient green synthesis of thiosulfonate S-esters by microwave-supported permanganate oxidation of symmetrical disulfides

Article abstract of DOI:10.1080/17415993.2015.1025404

Potassium permanganate absorbed on copper(II) sulfate pentahydrate has been found to be an efficient, inexpensive, and green oxidation agent for the synthesis of "symmetrical" thiosulfonate S-esters by oxidation of the corresponding symmetrical disulfides. The oxidation reactions were carried out under solvent-free reaction conditions within 15 min under the influence of microwave irradiation, as well as (for comparison) supported by conventional heating, to afford yields of the thiosulfonate S-esters in the range of 60-83%. The oxidation reaction appears to proceed (at least partly) via an intermediate symmetrical vic-disulfoxide.

Full text of DOI:10.1080/17415993.2015.1025404

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Fast and efficient green synthesis of
thiosulfonate S-esters by microwave-
supported permanganate oxidation of
symmetrical disulfides
Thi Xuan Thi Luuab, Thao-Tran Thi Nguyenab, Thach Ngoc Leb, Jens
Spanget-Larsena & Fritz Duusa
a Department of Science, Systems and Models, Roskilde University,
PO Box 260, DK-4000 Roskilde, Denmark
b Department of Organic Chemistry, University of Science of Ho
Chi Minh City, 227 Nguyen Van Cu St., Dist. 5, Ho Chi Minh City,
Vietnam
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Published online: 09 Apr 2015.
To cite this article: Thi Xuan Thi Luu, Thao-Tran Thi Nguyen, Thach Ngoc Le, Jens Spanget-Larsen
& Fritz Duus (2015) Fast and efficient green synthesis of thiosulfonate S-esters by microwave-
supported permanganate oxidation of symmetrical disulfides, Journal of Sulfur Chemistry, 36:3,
340-350, DOI: 10.1080/17415993.2015.1025404
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Journal of Sulfur Chemistry, 2015
Vol. 36, No. 3, 340–350, http://dx.doi.org/10.1080/17415993.2015.1025404
Fast and efficient green synthesis of thiosulfonate S-esters
by microwave-supported permanganate oxidation of
symmetrical disulfides
Thi Xuan Thi Luua,b∗, Thao-Tran Thi Nguyena,b, Thach Ngoc Leb, Jens Spanget-Larsena and
Fritz Duusa
aDepartment of Science, Systems and Models, Roskilde University, PO Box 260, DK-4000 Roskilde,
Denmark; bDepartment of Organic Chemistry, University of Science of Ho Chi Minh City, 227 Nguyen
Van Cu St., Dist. 5, Ho Chi Minh City, Vietnam
(Received 20 January 2015; accepted 28 February 2015)
Potassium permanganate absorbed on copper(II) sulfate pentahydrate has been found to be an efficient,
inexpensive, and green oxidation agent for the synthesis of “symmetrical” thiosulfonate S-esters by
oxidation of the corresponding symmetrical disulfides. The oxidation reactions were carried out under
solvent-free reaction conditions within 15 min under the influence of microwave irradiation, as well as (for
comparison) supported by conventional heating, to afford yields of the thiosulfonate S-esters in the range
of 60–83%. The oxidation reaction appears to proceed (at least partly) via an intermediate symmetrical
vic-disulfoxide.
O
S
O
S
R
R
KMnO4/CuSO4 · 5H2O
microwave irradiation
R
S
S
R
O
S
R
S
R
O
Keywords: thiosulfonate S-esters; disulfides; oxidation; potassium permanganate; microwave irradiation
1. Introduction
Thiosulfonate S-esters (general formula: R1-SO2-S-R2), in the following for simplicity referred
to as thiosulfonates, have been known as existing molecular species for more than 80
years, during which they have attracted considerable attention as reactive and synthetically
*Corresponding author. Email: ltxthi@hcmus.edu.vn
© 2015 Taylor & Francis

Journal of Sulfur Chemistry 341
O
S
O
S
O
R
R
5
O
R
R
R
R
S
S
S S
O
2
3
O
O
S
O
S
O
S
O
S
O
O
O
R
R
S
S
R
R
R
R
O
O
O O
4
7
6
Scheme 1. Possible obtainable products by the oxidation of symmetric disulfides.
useful reagents within general and industrial organic chemistry,[1] as powerful sulfenylat-
ing reagents,[2] and as blocking agents in protein chemistry.[3] Based upon their synthetic
availability, the thiosulfonates have often been divided into two subgroups, the “symmetrical”
thiosulfonates (R1 = R2), and the “asymmetrical” thiosulfonates (R1 = R2).[1]
“Symmetrical” thiosulfonates have been prepared by oxidation of the corresponding symmet-
rical disulfides by means of hydrogen peroxide,[4–7] m-chloroperbenzoic acid (MCPBA) and
other peroxy acids,[7–12] dimethyldioxirane (DMD),[10] sulfoxides in the presence of a rhenium
catalyst,[13] triphenylphosphite ozonide,[14] tetrabutylammonium peroxymonosulfate,[15] and
dinitrogen tetroxide.[16,17] Symmetrical disulfides can also be converted into the corresponding
thiosulfonates by chlorosolvolysis [18–21] and by means of SelectfluorTM(1-chloromethyl-4-
fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)).[22,23]
Since a symmetrical disulfide is the product formed primarily upon oxidation of a thiol, it has
naturally been attempted with some success to synthesize “symmetrical” thiosulfonates directly
from thiols, for example, by means of chlorosolvolysis [21] and by oxidation with dinitrogen
tetraoxide [24–26] or hydrogen peroxide in the presence of titanium tetrachloride.[27] Very
recently the direct oxidation of thiols into the corresponding thiosulfonates by means of zinc
dichromate trihydrate has also been reported.[28]
The oxidation potentialities of symmetrical disulfides are well investigated and perceived
(Scheme 1).[29] Thus, depending on the nature of the disulfide, the nature of the oxidation
agent, the molar ratio between the disulfide and the oxidation agent, and the reaction condi-
tions in general, the oxidation can result in the formation of the fairly stable thiosulfinate 3, the
most stable and most useful thiosulfonate 4, the sulfinyl sulfone 6, or the vic-disulfone 7. The
vic-disulfoxide 5 has hitherto not been isolated, but there are strong evidences [7,10,11,30,31]
for its transient existence as a reactive intermediate in the controlled oxidation of thiosulfinates
(3) into the corresponding thiosulfonates (4).[7,10–12,30–34] Under appropriate conditions, the
thermally relatively less stable thiosulfinates (3) can undergo disproportionation to form a 1:1
mixture of the corresponding thiosulfonate (4) and the disulfide (2).[35–39] Some non-oxidative
synthetic routes to thiosulfonates depend on the interaction of zinc on sulfinyl chlorides [40–43]
or sulfonyl chlorides.[44,45] The latter type of compounds can also be converted into “sym-
metrical” thiosulfonates upon treatment with potassium iodide in anhydrous acetone containing
catalytic amounts of pyridine [46] or with samarium powder in N,N-dimethylformamide.[47]
In continuation of our investigations of the utility of potassium permanganate [48] absorbed
on copper sulfate pentahydrate as a versatile, efficient, and “green” oxidation agent,[49–52]
we turned our attention toward the stable and useful thiosulfonates as target compounds. The
KMnO4 promoted oxidation process is recognized as “green” (friendly to the environment)
because manganese dioxide (MnO2), the co-product formed by the reduction of KMnO4, can be
isolated easily and subsequently recycled.[53] KMnO4 promoted oxidation reactions of organic

342 T.X.T. Luu et al.
O
S
KMnO4/CuSO4.5H2O
R
R
S
S
R
R
S
MW or D
O
2
4
R: CH3, C2H5, i-C3H7, n-C4H9, t-C4H9, n-C8H17, c-C6H11, C6H5.
Scheme 2. Conversion of symmetric disulfides into the corresponding thiosulfonate S-esters via solvent-free PP/3CSP
oxidation.
sulfur compounds have been reported quite extensively.[48] However, our literature search on
the formation of thiosulfonates (as the product of a KMnO4 promoted oxidation of symmetric
disulfides) revealed only one single item, describing the conversion of diphenyl disulfide by
means of KMnO4 in boiling propionic acid to form S-phenyl benzenethiosulfonate in the yield
of 8%.[54]
2. Result and discussion
Preliminary attempts to synthesize a “symmetrical” thiosulfonate directly from the pertinent thiol
by means of the oxidation agent xPP/yCSP (x mmol of potassium permanganate absorbed on
y mmol of copper sulfate pentahydrate) turned out to be quite unsuccessful irrespective of the
nature of the thiol as well as the nature of xPP/yCSP (i.e. the ratio x/y). The direct oxidation of
the thiol easily leads to the risk of explosion under strong oxidation condition and is difficult to
be performed with simple alkanethiols in gas phase (e.g. methanethiol, ethanethiol, propanethiol,
etc.); while the oxidation of disulfides happens safely. Moreover, the easy conversion of the thiol
into the corresponding symmetrical disulfide takes place under reaction conditions drastically
different from those required to bring about the subsequent conversion of the disulfide into the
corresponding thiosulfonate with low product selectivity and yield. Therefore, we decided to
focus on the conversion of the symmetrical disulfide (2) into the corresponding thiosulfonate (4)
as the main subject of this investigation (Scheme 2), since the starting materials, the symmetri-
cal disulfides (2), appeared to be available either commercially or obtainable easily by KMnO4
promoted oxidation of the pertinent thiols.[55–57]
In search for the reaction conditions for maximum conversion of the symmetrical disulfides
into the corresponding “symmetrical” thiosulfonates two series of introductory experiments were
carried out, using dibutyl disulfide as the arbitrarily chosen model substance. In the first series of
experiments, the ratio x:y in the oxidation reagents xPP/yCSP was varied and examined under
solvent-free reaction conditions while assisted by microwave irradiation for obtaining the highest
degree of conversion. The results (Figure 1) demonstrated a choice of 1:3 as the best molar ratio,
corresponding to the oxidation agent PP/3CSP.
In the next series of experiments, the molar ratio between dibutyl disulfide and PP/3CSP
was varied and examined under the same reaction conditions as described above. After four
experiments with increasing amounts of PP/3CSP relative to the 1.5 mmol of dibutyl disulfide
(Figure 2), an amount of 6.0 mmol of PP/3CSP finally resulted in complete conversion of the
disulfide into 97% of S-butyl butanethiosulfonate and 3% of a by-product having the same molec-
ular weight as the thiosulfonate, but nevertheless also a completely different mass spectrum, as
disclosed clearly by the GC/MS-analysis of the product mixture. The only plausible structure
attributable to the by-product will be that of the vic-disulfoxide 5 (Scheme 1, R = butyl). How-
ever, the subsequent purification of the product mixture by column chromatography resulted in
the isolation of only one product – that is, the thiosulfonate S-ester. Evidently, the transiently

Journal of Sulfur Chemistry 343
100.00
80.00
60.00
40.00
20.00
0.00
1:1
1:2
1:3
1:4
1:5
KMnO4:CuSO4.5H2O (mol:mol)
Figure 1. Influence of the molar ratio between KMnO4 and CuSO4 5H2O in the oxidation agent KMnO4/CuSO4
5H2O on the efficiency of the oxidation of dibutyl disulfide into S-butyl butanethiosulfonate under solvent-free reaction
conditions and assistance by microwave irradiation (250 W, 9 min., dibutyl disulfide: 1.5 mmol, KMnO4: 6 mmol).
100.00
80.00
60.00
By-prod.
Prod.
40.00
20.00
0.00
1.5:3
1.5:4
1.5:5
1.5:6
Molar ratio
Figure 2. Influence of the molar ratio between dibutyl disulfide and PP/3CSP on the efficiency of the oxidation of
dibutyl disulfide into S-butyl butanethiosulfonate under solvent-free reaction conditions and assistance by microwave
irradiation (250 W, 9–12.5 min).
formed vic-disulfoxide cannot survive under the conditions of the chromatographic separation.
This observation confirms earlier statements as regards the existence and the stability of
vic-disulfoxides.[7,9,10,11,30,31,34,58]
Upon replacement of microwave irradiation by ultrasound irradiation, but otherwise under the
same reaction conditions as described above, the conversion of dibutyl disulfide into the cor-
responding thiosulfonate S-ester amounted to only 6%, even after 5 h of ultrasound irradiation.
This observation led us to conclude, that the oxidation of the disulfide into the corresponding
thiosulfonate S-ester fundamentally requires a sufficiently high reaction temperature. In order to
confirm this conclusion, the same oxidation reaction as described above, that is, the oxidation

344 T.X.T. Luu et al.
Table 1. The optimized yield following the molar ratio of disulfides and PP/3CSP under solventless conditions.a
Entry
1
Product
Method A
Method B
Yield (GC, timeb, Pc)
Yield (GC, timeb, Temp.d)
O
O
S
82 (100, 11.2, 250)
83 (100, 9.0, 250)
63 (72, 3.45, 250)
80 (100, 11.2, 103)
78 (97, 9.0, 101)
68 (89, 3.45, 100)
S
O
O
2
3
S
S
O
O
S
S
O
S
O
4
5
80 (97, 12.5, 250)
68 (91, 3.5, 150)
73 (100, 12.5, 103)
63 (83, 3.5, 100)
S
O
S
O
S
O
S
O
6
7
75 (95, 4.4, 250)
70 (86, 4.6, 250)
65 (89, 4.4, 98)
71 (89, 4.6, 96)
S
5
5
O
S
O
S
O
O
S
8
60 (62, 10.4, 500)
68 (87, 10.4, 91)
S
aYields were determined by GC/MS.
btime = reaction time in minutes.
cP = power of microwave oven (Watt).
dtemp. = reaction temperature (°C).
of dibutyl disulfide into S-butyl butanethiosulfonate, was carried out at the same temperature as
measured by the end of the microwave-assisted experiment, but now with the microwave irradia-
tion being replaced by conventional heating. The latter reaction, which was carried out within the
same period of time as found optimal for the microwave-assisted reaction, afforded a somewhat
lower yield of S-butyl butanethiosulfonate, while not even traces of the vic-disulfoxide could be
detected (Table 1).
Subsequently, seven additional symmetrical disulfides (R-S-S-R), representing an appropriate
selection of aliphatic, cyclic, and aromatic species (R = Me, Et, Pri, But, n-C8H17, cyclohexyl,
and C6H5) were subjected to solvent-free oxidation by xPP/yCSP under microwave irradiation
as well as under conventional heating conditions (Scheme 2). The reaction conditions found
optimum for the oxidation of dibutyl disulfide into S-butyl butanethiosulfonate were intended to
be used as starting reaction conditions also for the seven additional symmetrical disulfides.
However, it very soon became evident that the oxidation of a symmetrical disulfide into the
corresponding thiosulfonate S-ester depends decisively on the nature of the disulfide R-group.
Therefore, for each of the symmetrical disulfides chosen, a series of experiments were performed

Journal of Sulfur Chemistry 345
O
O
O
O
O
R1SSR2
O
R1SSR2
+
R1SSR2
O
+
R1SSR1 + R2SSR2 R1SSR1 R2SSR2
+ +
MW
O
O
R1
R2
t-C4H9
t-C4H9
n-C4H9
n-C8H17
C6H5
n-C8H17
Scheme 3. Products obtained by solvent-free PP/3CSP oxidation of asymmetric disulfides.
in order to determine the optimum reaction conditions for total or maximum conversion into
the corresponding thiosulfonate S-ester. The microwave-assisted permanganate oxidation of the
chosen eight symmetrical disulfides was found to give yields of the corresponding thiosulfonate
S-esters in the range of 60–83% within 4–13 min (Method A, Table 1). In all cases, except
a single one (diphenyl disulfide) the crude product mixture contained also a minor amount
(3–14%, determined by GC/MS) of the corresponding vic-disulfoxide 5 (Scheme 1), but these
apparently very unstable species never survived the subsequent purification by means of column
chromatography.
As described above for the oxidation of dibutyl disulfide into S-butyl butanethiosulfonate,
all of the seven additionally selected symmetrical disulfides were also found able to undergo
oxidation into the corresponding thiosulfonate S-esters by means of conventional heating to
the same temperature as measured by the end of the microwave-assisted oxidation reactions.
The yields of the thiosulfonate S-esters obtained under the conditions of conventional heating
(Method B, Table 1) are comparable to or slightly lower than those obtained under the assistance
of microwave irradiation.
Inspired by the successful syntheses of “symmetrical” thiosulfonate S-esters by microwave-
assisted permanganate oxidation of symmetrical disulfides, we investigated the reactivity of three
asymmetrical disulfides toward PP/3CSP under microwave irradiation and solvent-free condi-
tions as before. However, the results were quite disappointing (Scheme 3): 6 different products
were observed in varying amounts (depending evidently on the nature of R1 and R2), appar-
ently owing to the occurrence of a complicated combination of oxidation and disproportionation
processes. In this respect our results are comparable to those reported earlier for the oxidation
of asymmetrical disulfides by means of hydrogen peroxide,[7] m-chloroperbenzoic acid,[7] and
sodium periodate.[33]
3. Conclusion
Comprehensive experimental work has made it possible for us to introduce a new, efficient, fast,
and green (eco-friendly) synthetic method for the preparation of “symmetrical” thiosulfonate
S-esters in fair to high yields by solvent-free oxidation of symmetrical disulfides by means of
PP/3CSP under the assistance of microwave irradiation, subsidiarily also under the influence of
conventional heating.
4. Experimental
4.1. Instrumentation and chemicals
4.1.1. Instrumentation
Microwave irradiations were performed by means of a CEM MDS 200 batch microwave oven.
Ultrasound irradiation was performed by means of a BRANSON 1210E-MT ultrasonic bath,

346 T.X.T. Luu et al.
operating at frequency 47 kHz. GC/MS analyses were performed on a Hewlett Packard 5890
GC 5971A MS apparatus equipped with a J&W DB-5MS capillary column (30 m, 0.25 mm i.d.,
0.25 µm film thickness) and a Hewlett Packard 7673A autosampler. NMR spectra were recorded
on a Varian Mercury 300 NMR spectrometer.
4.1.2. Chemicals
All commercially available chemicals used were from Aldrich. All synthesized symmetric as
well as asymmetric disulfides used as starting materials were analyzed for authenticity and purity
by NMR and GC/MS before being used.
4.1.2.1. Preparation of commercially unavailable disulfides. Finely ground solid potassium
permanganate (KMnO4, 70 mmol, 11.06 g) was added slowly in small portions during 2 h into a
500 mL round bottom flask containing 210 mmol of the pertinent thiol (1-butanethiol, 2-methyl-
2-propanethiol, cyclohexanethiol, or 1-octanethiol). The exothermal reaction was performed with
magnetic stirring, and the reaction flask should be placed in an ice/water bath to prevent potential
superheating of the more or less inflammable thiols. Subsequently, the reaction mixture was
stirred for 6 h at room temperature. Then, the reaction mixture was extracted with 4 × 50 mL of
diethyl ether. The combined extracts were filtered through a 1.5–2 cm layer of celite 545, and then
dried by anhydrous Na2SO4. After removal of the solvent by rotary evaporation, the disulfide
was obtained in an almost quantitative yield as a colorless oil of purity > 99% (according to
analysis by GC/MS). The 1H and 13C NMR spectra of all of the four disulfides synthesized were
compatible with those reported in the literature.
Dibutyl disulfide: 1H NMR (CDCl3): δH = 2.69 (t, J = 7.2 Hz, 4H), 1.61–1.71 (m, 4H),
1.36–1.48 (m, 4H), 0.93 (t, J = 7.2 Hz, 6H). 13C NMR (CDCl3): δC = 38.90 (2C), 31.33 (2C),
21.67(2C),13.71 (2C). MS: m/z = 178[M]+, 122, 87, 79, 57, 41.
Di t-butyl disulfide: 1H NMR (CDCl3): δH = 1.31 (s, 18H). 13C NMR (CDCl3): δC = 46.1 (2C),
30.6 (6C). MS: m/z = 178[M]+, 122, 107, 57, 41.
Dioctyl disulfide: 1H NMR (CDCl3): δH = 2.68 (t, J = 7.2 Hz, 4H), 1.62–1.72 (m, 4H),
1.28–1.42 (m, 20H), 0.88 (t, J = 7.2 Hz, 6H). 13C NMR (CDCl3): δC = 39.2 (2C), 31.8 (2C),
29.26 (2C), 29.23 (2C), 29.21 (2C), 28.6 (2C), 22.7 (2C), 14.1 (2C). MS: m/z = 290[M]+, 178,
145, 115, 102, 87, 71, 57.
1
Dicyclohexyl disulfide: H NMR (CDCl3): δH = 2.64–2.74 (m, 2H), 1.98–2.10 (m, 4H), 1.74–
1.86 (m, 4H), 1.56–1.66 (m, 2H), 1.15–1.40 (m, 10H). 13C NMR (CDCl3): δC = 49.9 (2C), 32.9
(4C), 26.1 (4C), 25.7 (2C). MS: m/z = 230[M]+, 148, 113, 83, 55, 41.
4.1.2.2. Preparation of oxidant xPP/yCSP. The copper sulfate pentahydrate was dissolved
completely in de-ionized water. Then, the pertinent amount of KMnO4 was added, followed by a
sufficient volume of de-ionized water to obtain a homogeneous solution. The solution was stirred
for 10 min at 80°C. Subsequently water was removed from the solution by rotational evaporation,
until the weight of the remaining solid mass was equal to the sum of the weights of the original
ingredients. Finally, the obtained solid mass was ground in a mortar into a fine homogeneous
powder.
4.2. Typical procedures
4.2.1. Oxidation of dibutyl disulfide into the corresponding thiosulfonates by PP/3CSP under
solvent-free reaction conditions assisted by microwave irradiation (Method A)
A pertinent quantity of finely ground PP/3CSP (6 mmol, 5.45 g) was added to a test tube
(h = 20.0 cm, d = 3.0 cm) containing also the disulfide (1.5 mmol). The test tube was placed

Journal of Sulfur Chemistry 347
into a beaker available in the microwave oven. For each of the disulfides, an irradiation
programme was applied to determine the most efficient reaction conditions (with respect to max-
imum yield of product, most convenient irradiation power (W), and the shortest reaction time
(minutes)), see Table 1. For every experiment, the temperature of the reaction mixture was mea-
sured immediately after reaction stop. After cooling, the reaction mixture was stirred with 50 mL
of chloroform during 30 min and then filtered through a 2 cm layer of celite. Subsequently, the
solvent was removed from the extract by rotational evaporation, and the remaining crude product
was analyzed by GC/MS and NMR spectroscopy. Finally, the thiosulfonate was purified by flash
column chromatography (7 g silica gel, Davisil, grade 710, 4–20 µm, 60 A, 99%) using as eluent
a mixture of hexane and dichloromethane.
4.2.2. Oxidation of dibutyl disulfide into corresponding thiosulfonates by PP/3CSP under
solvent-free reaction conditions assisted by conventional heating (Method B)
A test tube (h = 20.0 cm, d = 3.0 cm) containing a pertinent quantity of finely ground PP/3CSP
(6 mmol, 5.45 g) and the disulfide (1.5 mmol) was placed in an oil bath heated to the temperature
measured by the reaction stop of the parallel reaction run under microwave irradiation. The test
tube was kept in the oil bath for a period of time corresponding exactly to that found at optimum
by Method A. After cooling, the reaction mixture was worked up as described in Method A.
4.3. Spectroscopic data
The identity and purity of all of the thiosulfonates synthesized were ensured by 1H and 13C NMR
spectroscopy as well as by GC/MS. Furthermore, all of the thiosulfonates were also analyzed by
IR spectroscopy in order to obtain information concerning the occurrence of conformational
1
isomerism.[59] The observed H and 13C NMR spectroscopic data for the eight thiosulfonate
S-esters synthesized are listed below, and all of them were found compatible with those reported
in the literature.[60–62]
1
Methyl methanethiosulfonate: H NMR (CDCl3): δH = 3.32 (s, 3H), 2.71 (s, 3H). 13C NMR
(CDCl3): δC = 48.89, 18.36. MS: m/z = 126[M]+, 111, 95, 81, 64.
Ethyl ethanethiosulfonate: 1H NMR (CDCl3): δH = 3.33 (q, J = 7.5 Hz, 2H), 3.16 (q, J = 7.2
Hz, 2|H), 1,48 (t, J = 7.2 Hz, 3H), 1.43 (t, J = 7.5 Hz, 3H). 13C NMR (CDCl3): δC = 57.15,
30.68, 15.20, 8.39. MS: m/z = 154[M]+, 139, 125, 95, 62.
1
i-Propyl 1-methylethanesulfonate: H NMR (CDCl3): δH = 3.61–3.73 (m, 1H), 3.27–3.41 (m,
1H), 1.48 (d, J = 2.4 Hz, 6H), 1.46 (d, J = 2.1 Hz, 6H). 13C NMR (CDCl3): δC = 63.59, 43.03,
24.34 (2C), 16.39 (2C). MS: m/z = 182[M]+, 140, 117, 103, 76, 61, 43.
n-Butyl butanethiosulfonate: 1H NMR (CDCl3): δH = 3.30 (t, J = 7.8 Hz, 2H), 3.14 (t, J = 7.5
Hz, 2H), 1.84–1.95 (m, 2H), 1.68–1.78 (m, 2H), 1.38–1.56 (m, 4H), 0.97 (t, J = 7.2 Hz, 3H),
0.95 (t, J = 7.5 Hz, 3H). 13C NMR (CDCl3): δC = 62.46, 35.95, 31.66, 25.51, 21.75, 21.29,
13.56, 13.46. MS: m/z = 210[M]+, 121, 89, 56, 41.
t-Butyl 1,1-dimethylethanethiosulfonate: 1H NMR (CDCl3): δH = 1.62 (s, 9H), 1.47 (s, 9H). 13
C
NMR (CDCl3): δC = 68.13, 56.43, 31.56 (3C), 23.77 (3C). MS: m/z = 210[M]+, 146, 89, 57.
n-Octyl octanethiosulfonate: 1H NMR (CDCl3): δH = 3.29 (t, J = 7.8 Hz, 2H), 3.13 (t, J = 7.8
Hz, 2H), 1.86–1.93 (m, 2H), 1.69–1.79 (m, 2H), 1.38–1.46 (m, 2H), 1.28–1.35 (m, 18H), 0.88
(t, J = 6.9 Hz, 6H). 13C NMR (CDCl3): δC = 62.74, 36.28, 31.74, 31.70, 29.68, 29.08, 29.02,
28.96, 28.93, 28.60, 28.00, 23.54, 22.62, 22.60, 14.08, 14.07. MS: m/z = 323[M]+, 177, 145,
112, 69, 55, 41.

348 T.X.T. Luu et al.
1
Cyclohexyl cyclohexanethiosulfonate: H NMR (CDCl3): δH = 3.42–3.53 (m, 1H), 3.02–3.12
(m, 1H), 2.28–2.38 (m, 2H), 2.06–2.11 (m, 2H), 1.90–2.00 (m, 2H), 1.20–1.80 (m, 14H). 13C
NMR (CDCl3): δC = 71.51, 50.4, 34.30 (2C), 26.27 (2C), 25.94 (2C), 25.25 (2C), 25.17, 25.10.
MS: m/z = 262[M]+, 149, 117, 83, 64, 55, 41.
Phenyl benzenethiosulfonate: 1H NMR (CDCl3): δH = 7.29–7.61 (m, 10H).13C NMR (CDCl3):
δC = 142.92, 136.57, 133.65 (2C), 131.42 (2C), 129.44, 128.81 (2C), 127.81 (2C), 127.54. MS:
m/z = 250[M]+, 184, 141, 125, 109, 77, 65, 51.
Funding
The authors are grateful to the Vietnamese National Foundation for Science and Technology Development (NAFOSTED)
for financial support under grant number [104.01–2011.40]. The authors are also indebted to the Danish Interna-
tional Development Agency (DANIDA) for financial support via the Enhancement of Research Capacity (ENRECA)
programme.
Supplemental data
Supplemental data for this article can be accessed at doi:10.1080/17415993.2015.1025404
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