Silica gel-promoted new one-pot procedure for the synthesis of 1,3-oxathiolan-5-one

Article abstract of DOI:10.1080/17415993.2017.1313256

A highly selective two-component silica gel-promoted synthesis of 1,3-oxathiolan-5-one derivatives in N,N-Dimethylformamide (DMF) is presented. The reaction was carried out using aromatic aldehyde and mercaptoacetic acid in the presence of silica gel in DMF with heating. The reactions were worked up by separating the silica gel and recovering the solid product after adding water in excellent yields without any chromatographic purification. Structures of the compounds were satisfactorily confirmed by ¹H NMR and LCMS spectral analysis.

Full text of DOI:10.1080/17415993.2017.1313256

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Silica gel-promoted new one-pot procedure for the
synthesis of 1,3-oxathiolan-5-one
Manoj P. Thakare, Rahimullah Shaikh & Dipak Tayade
To cite this article: Manoj P. Thakare, Rahimullah Shaikh & Dipak Tayade (2017): Silica gel-
promoted new one-pot procedure for the synthesis of 1,3-oxathiolan-5-one, Journal of Sulfur
Chemistry, DOI: 10.1080/17415993.2017.1313256
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Date: 13 April 2017, At: 04:35

JOURNAL OF SULFUR CHEMISTRY, 2017
http://dx.doi.org/10.1080/17415993.2017.1313256
Silica gel-promoted new one-pot procedure for the synthesis
of 1,3-oxathiolan-5-one
Manoj P. Thakare, Rahimullah Shaikh and Dipak Tayade
Department of Chemistry, GovernmentVidarbha Institute of Science and Humanities, SantGadge Baba
Amravati University, Amravati, India
ABSTRACT
ARTICLE HISTORY
Received 28 January 2017
Accepted 27 March 2017
A highly selective two-component silica gel-promoted synthesis of
1,3-oxathiolan-5-one derivatives in N,N-Dimethylformamide (DMF) is
presented. The reaction was carried out using aromatic aldehyde and
mercaptoacetic acid in the presence of silica gel in DMF with heat-
ing. The reactions were worked up by separating the silica gel and
recovering the solid product after adding water in excellent yields
without any chromatographic purification. Structures of the com-
pounds were satisfactorily confirmed by 1H NMR and LCMS spectral
analysis.
KEYWORDS
1,3-oxathiolan-5-one; silica
gel; one-pot synthesis;
aldehyde; mercaptoacetic
acid
1. Introduction
1,3-Oxathiolan-5-one nucleus-containing heterocyclic compounds are well known for
their biological properties and are important heterocyclic compounds occurring in nat-
ural and medicinal molecules. They are also the intermediates in the synthesis of many
bioactive compounds [1]. The derivatives of 2-(hydroxyl-methyl)- 1,3-oxathiolan-5-ones
can be used as building blocks for the preparation of oxathiolanyl-nucleoside containing
molecule Coviracil [2–4]. 1,3-Oxathiolanes is one such class of heterocyclic compounds
which have attracted much attention as they have been reported to possess a wide range of
biological activities, including antiviral [5], anticonvulsant [6], antiulcer [7], and antifungal
activity [8]. In addition, they also showed anti-HIV and anti-HBV activity [9], and oxathi-
olanes act both as agonists [10–12] and antagonists on muscarinic receptors. Cevimeline
(cis-2-methylspiro [1, 3-oxathiolane-5, 3ꢀ-quinuclidine hydrochloride) is a selective M1
receptor agonist. It is also used as fungicides [13], herbicides [14], plant growth regulators
CONTACT Manoj P. Thakare
manojorg@rediffmail.com
Supplemental data for this article can be accessed here. http://dx.doi.org/10.1080/17415993.2017.1313256
© 2017 Informa UK Limited, trading as Taylor & Francis Group

2
M. P. THAKARE ET AL.
[15], or enzymes inhibitors [16–18]. 1,3-Oxathiolane have been used as precursors of mod-
ified nucleosides, such as the N-thioxonucleosides which often present anti-viral activities
(Figure 1) [19].
Many methods have been described for the preparation of 1,3-oxathiolan-5-ones as
shown in Figure 2. These include one-pot reactions of carbonyl compounds and mer-
captoacetic acid with heating in the presence of PTSA [20] or two-step syntheses using
ZnCl2 [21] or 2-Methyl-2-phenyl-1,3-oxathiolan-5-ones in the presence of acetophenone
and mercaptoacetic acid using LiBr as a catalyst [22]. The synthesis of 1,3-oxathiolan-5-one
was also catalyzed by dimethyltin-diiodide-HMPTA complex [23] and molecular iodine in
[bmim][BF4] [24].
In addition, cobalt-doped Zns nanoparticles [25] and Y(OTf)3 [26] have been used
for the synthesis of 1,3-oxathiolan-5-ones. Formation of 1,3-oxathiolan-5-ones has been
observed as a by-product during the synthesis of thiazolidinones using conventional
and/or ultra-sonication methods [27]. Microwave irradiation, for example, was used as an
alternative method for the synthesis of 1,3-oxathiolan-5-one [28]. Finally, 1,3-oxathiolan-
5-one was also prepared using DCC [29]. 1,3-Oxathiolan-5-one was also synthesized using
Mukaiyama reagent in N,N-Dimethylformamide (DMF) at room temperature [30].
Figure 1. Some biologically important oxathiolane compounds.
Figure 2. Different methods for the synthesis of 1,3-oxathiolan-5-one derivatives.

JOURNAL OF SULFUR CHEMISTRY
3
Many of the reported methods have limitations, such as long reaction times, diffi-
cult workup, and formation of by-products. In addition, others employ harsh reaction
conditions, use of expensive and toxic reagents, and explosive reagents like LiBr. In the
case of DCC as a dehydrating agent it was difficult to remove the by-product, i.e. DCU,
without purification. Furthermore, purification of the product required a large amount
of volatile solvents. These methods are cumbersome and/or require specialized equip-
ment; therefore, it is important to develop a new simple method which can eliminate these
difficulties.
2. Results and discussion
In the initial stages of this study a model reaction was examined using benzaldehyde and
mercaptoacetic acid keeping in mind that silica gel may provide assistance in removal of
water in the final step of the condensation to afford 1, 3-oxathiolan-5-one. No conversion
was observed upon treatment of mercaptoacetic acid and benzaldehyde with silica gel in
dichloromethane (DCM) or in DCE at their refluxing temperatures. On the other hand,
low yields of product were obtained in refluxing acetonitrile (ACN) and THF. In addition,
chromatographic purification was required to obtain the required product. This suggests
that DCM, DCE, ACN, or THF are not suitable solvents for the synthesis of 1, 3-oxathiolan-
5-one (Table 1).
However, reaction yields were excellent when DMF was used as the solvent and no
chromatographic purification was required. In the DMF reaction 1.0 mmol of benzalde-
hyde and 1.0 mmol of mecaptoacetic acid in 5 mL of DMF were stirred continuously for
5 min at room temperature followed by addition of 0.5 g of silica gel. It was then stirred for
an additional 1 h at 100°C followed by removal of the silica by filtration. The filtrate was
then diluted with ice-cold water and the precipitate collected by filtration and dried under
reduced pressure to afford the pure product in 96% yield. This result clearly demonstrates
that DMF is far superior to ACN, EtOH, or THF as the solvent for the model reaction.
The ready availability, low cost, and the absence of a purification step are advantages
that dictate DMF as the solvent of choice for further studies. In addition, the insolubil-
ity of the silica gel in the organic solvent facilitates its removal from the reaction mixture
(Scheme 1).
After optimization of the reaction conditions we then used these conditions to study
different aromatic aldehydes and observed the corresponding products in excellent yields
(Table 2). The reactions were very clean at 100°C and completed within 0.5–1.5 h. The
Table 1. Effect of various solvents.a,b
Entry
Solvent
Time (h)
Yield (%)
1
2
3
4
5
6
DCM
DCE
ACN
THF
Ethanol
DMF(100°C)
24
24
20
10
0.8
0.5
No Conversion
No Conversion
30
32
46
96
aYields are after purification of the compounds.
bConfirmed by TLC, 1H NMR and LCMS.

4
M. P. THAKARE ET AL.
Scheme 1. Proposed approach for the synthesis of 1, 3-oxathiolan-5-one.
proposed reaction mechanism is shown in Scheme 2 and the results obtained mentioned
in Table 2.
We think that silica gel can activate the acid group of intermediate A with gen-
eration of an electron-deficient carbon. This facilitates the intra-molecular addition of
hydroxyl to form intermediate B. After the loss of water molecule intermediate B affords
1, 3-oxathiolan-5-ones (Scheme 2).
3. Conclusion
In this article, we report silica gel as an environment-friendly promoter for the synthesis
of 1,3-oxathiolan-5-ones via two-component one-pot condensation of aromatic aldehy-
des and mercaptoacetic acid. The reactions are quick and no workup is required which
makes it a clean and green alternative to other reported procedures (Figure 2). This method
avoids the use of toxic, expensive, hazardous chemicals, and provides easy access to phar-
maceutically important 1,3-oxathiolan-5-one derivatives in good to excellent yields. At
the same time, there is no requirement of any chromatographic purification for the iso-
lation of desired products. As there is no formation of by-products and purification is also
not required, this procedure is also useful for the parallel synthesis of a large number of
compounds.
4. Experimental
4.1. General remarks
All melting points were uncorrected and were measured using an electro-thermal appa-
1
ratus. H NMR spectra were recorded on Bruker Advance II 400 NMR spectrometer
using CDCl3 or DMSO-d6 as solvents and tetramethylsilane as internal standard and
chemical shifts being reported in part per million (δ) relative to TMS. LCMS spectra
were obtained using Acquity BEH C-18 column (2.1 × 100 mm, 1.7 μm), and gradient
mobile phase consisting of 5 mM ammonium acetate in water and ACN, and a flow rate
of 0.5 mL/min. Analytical thin layer chromatography (TLC) was performed on Silica gel
60F254 (Merck, Germany). The spots were visualized by exposure to UV light at 254 nm
and DNP stain.
4.2. General procedure
Mercaptoacetic acid (1.0 mmol) was added to a stirred solution of aromatic aldehyde
(1.0 mmol) in DMF (5 mL) at room temperature. After 5 min, silica gel (0.5 g) was added to
the reaction mixture at room temperature and heated to stir at 100°C. The progress of the

JOURNAL OF SULFUR CHEMISTRY
5
Table 2. Synthesis of 2-aryl-1,3-oxathiolan-5-one using aromatic aldehyde and mercaptoacetic acid in
DMF using silica gel.a,b
Entry
A
Aldehyde
Product
Time (h)
1
Yield (%)a
96c
B
C
D
1
93c
0.5
0.5
91
92
E
F
0.5
1.5
89
91
G
H
0.5
0.5
90
95
(continued).

6
M. P. THAKARE ET AL.
Table 2. Continued.
Entry
I
Aldehyde
Product
Time (h)
1.5
Yield (%)a
85
J
1.5
1.5
83
80
K
L
1.5
1.5
82
75
M
aReaction condition: 1.0 mmol of aromatic aldehyde, 1.0 mmol of mercaptoacetic acid and 0.5 g of silica gel in DMF (5 mL)
at 60°C.
bConfirmed by TLC, 1H NMR and LCMS.
cRef. [22].
reaction was monitored by thin layer chromatography using n-hexane/ethyl acetate (8:2).
After completion of the reaction, silica was removed by filtration. The filtrate was diluted
with ice water to obtain solid as a product. The crude product was collected by filtration
and washed with ice water. The solid was again washed with ice cooled 10% diethyl ether
in pentane for the fast removal of traces of water to get crystals and dried under reduced
pressure to afford the pure product (3a–m).
4.3. Analytical data
4.3.1. 2-Phenyl-1,3-oxathiolan-5-one (3a)
1
White solid, M.P.85–87°C; H NMR (400 MHz, CDCl3): 7.40–7.47 (5H, m), 6.47 (1H,
s), 3.87 (1H, d, J = 16.4 Hz), 3.76 (1H, d, J = 16.8 Hz). LCMS calcd for C9H8O2S (M+)
180.91, found 180.91.
4.3.2. 2-(4-Nitrophenyl)-1,3-oxathiolan-5-one (3b)
Yellow solid, M.P. 83–85°C; 1H NMR (400 MHz, CDCl3): 8.27 (2H, d, J = 8.4 Hz), 7.64
(2H, d, J = 8.4 Hz), 6.54 (1H, s), 3.90 (1H, d, J = 16.4 Hz), 3.76 (1H, d, J = 16.4 Hz).
LCMS calcd for C9H7NO4S (M+) 224.01, found 223.99.

JOURNAL OF SULFUR CHEMISTRY
7
Scheme 2. Plausible mechanism for silica gel-promoted synthesis of 1,3-oxathiolan-5-one in DMF.
4.3.3. 2-(4-Bromophenyl)-1, 3-oxathiolan-5-one (3c)
White solid; M.P. 91–93°C;1H NMR (400 MHz; CDCl3): 7.54 (2H, d, J = 8.4 Hz), 7.34 (2H,
d, J = 8.4), 6.41 (1H, s), 3.86 (1H, d, J = 16.8), 3.75 (1H, d, J = 16.8); LCMS: m/z [M+]
calculated for C9H7BrO2S: 258.94, found: 259.03.
4.3.4. 2-(4-Iodophenyl)-1, 3-oxathiolan-5-one (3d)
White solid; M.P. 93–95°C;1H NMR (400 MHz; CDCl3): 7.75 (2H, d, J = 8.0), 7.20 (2H,
d, J = 8.0), 6.40 (1H, s), 3.86 (1H, d, J = 16.4), 3.75 (1H, d, J = 16.4); LCMS: m/z [M+]
calculated for C9H7IO2S: 307.12, found: No ionization.
4.3.5. 2-(3,5-Difluorophenyl)-1,3-oxathiolan-5-one (3e)
White solid; M.P. 99–101°C;1H NMR (400 MHz, DMSO-d6): 7.26–7.34 (3H, m), 6.69 (1H,
s), 4.07 (1H, d, J = 16.4 Hz), 4.00 (1H, d, J = 16.4 Hz). LCMS calcd for C9H6F2O2S (M−-
F) 217.01, found: 197.08.

8
M. P. THAKARE ET AL.
4.3.6. 2-[3,5-Bis(trifluoromethyl)phenyl]-1,3-oxathiolan-5-one (3f)
Off white solid; M.P. 113–115°C;1H NMR (400 MHz, CDCl3): 7.92 (3H, s), 6.54 (1H, s),
3.93 (1H, d, J = 16.8 Hz), 3.81 (1H, d, J = 16.8 Hz). LCMS calcd for C11H6F6O2S (M+)
315.22, found 314.96.
4.3.7. 2-(2-Chloro-5-nitrophenyl)-1,3-oxathiolan-5-one (3g)
White solid; M.P. 96–97°C;1H NMR (400 MHz, DMSO-d6): 8.28 (2H, s), 7.87 (1H,d,
J = 8.4 Hz), 6.99 (1H, s), 4.10 (1H, d, J = 16.4 Hz), 4.03 (1H, d, J = 16.4 Hz). LCMS calcd
for C9H6ClNO4S (M+) 259.97, found No ionization.
4.3.8. 2-(Benzo[d][1, 3]dioxol-4-yl)-1,3-oxathiolan-5-one (3h)
White solid; M.P. 103–106°C;1H NMR (400 MHz, CDCl3): 6.84–6.90 (3H, m), 6.53 (1H,
s), 6.03 (2H, s), 3.79–3.85 (2H, m). LCMS calcd for C10H8O4S (M+) 225.23, found 225.00.
4.3.9. 2-(3-chloropyridin-4-yl)-1,3-oxathiolan-5-one (3i)
Light brown solid; M.P. 180–182°C;1H NMR (400 MHz, DMSO-d6): 8.71 (1H, s), 8.62
(1H,s), 7.52 (1H, s), 6.90 (1H, s), 4.09 (1H, d, J = 16.4 Hz),3.98 (1H, d, J = 16.4 Hz). LCMS
calcd for C8H6ClO2S (M+) 216.66, found 216.07.
4.3.10. 2-(5,6-dichloropyridin-3-yl)-1,3-oxathiolan-5-one (3j)
White solid; M.P. 181–184°C;1H NMR (400 MHz; DMSO-d6) 8.54 (1H, s), 8.35 (1H, s),
6.74 (1H, s), 4.01–4.10 (2H, m); LCMS: calcd for C8H5Cl2NO2S: 249.94, found: 249.86.
4.3.11. 2-(2-chloro-5-iodopyridin-3-yl)-1,3-oxathiolan-5-one (3k)
Black oil; M.P. 183–185°C;1H NMR (400 MHz, DMSO-d6): 8.07 (1H, s), 8.06 (1H, s), 7.12
(1H, s), 4.17 (1H, d, J = 16.4 Hz), 4.02 (1H, d, J = 16.4 Hz). LCMS calcd for C8H5ClNO2S
(M+) 341.88, found 342.08.
4.3.12. 2-(quinolin-6-yl)-1,3-oxathiolan-5-one (3l)
Off white solid; M.P. 130–132°C;1H NMR (400 MHz, DMSO-d6): 8.95 (1H, s),8.44 (1H,
d, J = 8.0 Hz), 8.12 (1H, s), 8.09 (1H, d, J = 8.8 Hz), 7.86 (1H, d, J = 8.8 Hz), 7.57–7.60
(1H, m), 6.91 (1H, s), 4.14 (1H, d, J = 16.4 Hz), 4.02 (1H, d, J = 14.4 Hz). LCMS calcd for
C12H9NO2S (M+) 232.04, found 232.13.
4.3.13. 2-(thiophen-2-yl)-1,3-oxathiolan-5-one (3m)
1
Brown oil; H NMR (400 MHz, DMSO-d6): 7.43 (1H, d, J = 4.8 Hz), 7.32 (1H, d,
J = 3.2 Hz), 7.01–7.03 (1H, m), 6.67 (1H, s), 3.78–3.88 (2H, m). LCMS calcd for C7H6O2S2
(M+) 187.25, found 187.17.
Acknowledgements
We are thankful to the Head, Department of Chemistry, for his continuous support and guidance
throughout the work.
Disclosure statement
No potential conflict of interest was reported by the authors.

JOURNAL OF SULFUR CHEMISTRY
9
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