Synthesis of novel quaternary ammonium salts from 1, 2-benzothiazine derivatives

Article abstract of DOI:10.1080/17415993.2020.1797743

A series of novel 1,2-benzothiazine based quaternary ammonium salts were successfully prepared through different organic transformations. Products of all transformations and final salts were separated out and purified. The product yields were good to exce

Full text of DOI:10.1080/17415993.2020.1797743

Journal of Sulfur Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gsrp20
Synthesis of novel quaternary ammonium salts
from 1, 2-benzothiazine derivatives
Salman Gul , Maria Saleem , Munawar Ali Munawar , Hafiz Adnan Ahmad ,
Ejaz Ahmed , Robina Begum & Zahoor H. Farooqi
To cite this article: Salman Gul , Maria Saleem , Munawar Ali Munawar , Hafiz Adnan Ahmad ,
Ejaz Ahmed , Robina Begum & Zahoor H. Farooqi (2020): Synthesis of novel quaternary
ammonium salts from 1, 2-benzothiazine derivatives, Journal of Sulfur Chemistry, DOI:
10.1080/17415993.2020.1797743
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JOURNAL OF SULFUR CHEMISTRY
https://doi.org/10.1080/17415993.2020.1797743
Synthesis of novel quaternary ammonium salts from 1,
2-benzothiazine derivatives
Salman Gul, Maria Saleem, Munawar Ali Munawar, Hafiz Adnan Ahmad, Ejaz Ahmed,
Robina Begum and Zahoor H. Farooqi
Institute of Chemistry, University of the Punjab, Lahore, Pakistan
ABSTRACT
ARTICLE HISTORY
Received 16 April 2020
Accepted 7 July 2020
A series of novel 1,2-benzothiazine based quaternary ammonium
salts were successfully prepared through different organic transfor-
mations. Products of all transformations and final salts were sepa-
rated out and purified. The product yields were good to excellent
for all transformations. Resultant 1,2-benzothiazine based cationic
amphiphilic systems were stabilized using different counter anions.
All final products were confirmed by 1HNMR and 13CNMR analyses.
1,2-benzothiazine based quaternary ammonium salts have a poten-
tial to be employed as a phase transfer catalyst for various reactions
in future.
KEYWORDS
Sulfur containing
heterocyclic compounds;
benzothiazine derivatives;
quaternary ammonium salts
1. Introduction
Quaternary ammonium salts are ionic compounds that may be represented as NR4+Y−,
where R may be the same or different groups and Y− is a replaceable counter anion.
NR4+Y− system is a result of replacement of all four of the hydrogen atoms directly
bonded to the nitrogen from NH4+Y− by aryl, alkyl or some other groups. The synthesis
and characterization of quaternary ammonium compounds have gained much attention
in the field of organic chemistry due to their potential use as versatile, nontoxic and
cheap phase transfer catalyst in different organic reactions [1]. These compounds are used
CONTACT Munawar Ali Munawar
mamunawar.chem@pu.edu.pk; Zahoor H. Farooqi
zahoor.chem@pu.edu.pk,
zhfarooqi@gmail.com Institute of Chemistry, University of the Punjab, New Campus Lahore 54590, Pakistan
Supplemental data for this article can be accessed here. https://doi.org/10.1080/17415993.2020.1797743
© 2020 Informa UK Limited, trading as Taylor & Francis Group

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S. GUL ET AL.
as a catalyst to initiate and to speed up various organic reactions like Williamson syn-
thesis [2] and Michael addition [3]. It has also been found that quaternary ammonium
salts are superior over other phase transfer catalytic systems like polyethylene glycol and
crown ethers. They have phase transfer activity comparable to that of cryptands. More-
over, applications of cryptands, polyethylene glycol and crown ethers are limited, and
their high concentration is needed to achieve their phase transfer activity. They are also
known for their excellent antimicrobial abilities [4]. The synthesis of various quaternary
ammonium compounds with different functionalities from various starting materials has
been recently reviewed by various groups [5,6]. To the best of our knowledge, the syn-
thesis and characterization of thiazine-based quaternary ammonium compounds have
been rarely reported in the literature, and it needs to be explored for their versatile
applications.
Thiazines are six-membered ring heterocyclic systems containing sulfur (S) and nitro-
gen (N) atoms in the same ring. When they are fused with the benzene ring, they
produce bicyclic system containing N and S atoms in the same ring, which is known as
benzothiazine. Different derivatives of benzothiazine have excellent microbial activities.
Benzothiazines are known as antipsychotic drugs since last few decades [7]. Potent anticar-
cinogenic, antiinflammatory, fungicidal, herbicidal, antimicrobial and analgesic actions of
benzothiazine derivatives has been widely reported in the literature [8–10]. Benzothiazine
derivatives are also useful in antioxidant [11] and anticancer areas [12]. They are also used
as precursors for the preparation of different organic compounds having anticorrosion [13]
and antidiabetic activities [14].
Due to the aforementioned applications, the synthesis of benzothiazine derivatives has
gained much attention in the last few decades [15]. It is very important to introduce new
protocols for the synthesis of benzothiazine derivatives and quaternary ammonium salts.
In the present study, a series of compounds based on 1,2-benzothiazine nucleus were
prepared using 4-bromoacetophenone as a starting material. Benzothiazene-based novel
quaternary ammonium salts were synthesized by quaternization of 3-(4-bromophenyl)-1-
methyl-1,4-dihydropyrazolo[4,3-c][1,2]benzothiazine 5,5-dioxide. Pyrazolium salts with
−
different anions were obtained by replacement of HSO4 with new anion using suitable
replacement salt.
2. Results and discussions
Schematic illustration involving all steps of transformation along with necessary reac-
tion conditions is shown in Scheme 1. The process was initiated by bromination of
4-bromoacetophenone (a) using N-bromosuccinimide (NBS) as a brominating agent
to obtain product (b) with 95% yield. Purified (b) was dissolved in dried N,N-
Dimethylformamide (DMF) and then heated with dried sodium saccharin (c) to obtain
product (d) as a result of linkage between (b) and (c) through nitrogen of heterocyclic
ring with 89% yield. Twenty-minute refluxing of (d) with sodium metal dissolved in dried
methanol gives product (e) with 74% yield. Replacement of hydrogen atom bonded with
nitrogen of heterocyclic ring with alkyl group (R = Me, Et, Pr, iPr, Bu, Bn) was carried
out using suitable alkyl halide (alkyl bromide or alkyl iodide) in the presence of step-
wise addition of K2CO3 base to obtain product (f) with different R groups having yield
in the range of 94–96%. It is worth mentioning that the yield of the reaction product

JOURNAL OF SULFUR CHEMISTRY
3
(f) was found to be dependent on R and halide (X) groups of alkyl halide used. Base
screening experiments revealed that the yield of (f) also depends on base used in the
reaction. The yield of the product (f) was found to be highest in case of K2CO3 in com-
parison to other bases tested for the same purpose. Treating (f) with hydrazine (N2H4)
in the presence of ethyl alcohol does not only reduce both carbonyl and phenolic groups
but also creates N-N linkage in the form of a new 5-membered heterocyclic ring. The
yield of resulting product (g) was found to be in the range of 81–83%. Replacement of
hydrogen directly bonded to nitrogen by methyl group was carried out by refluxing of
product (g) in the presence of MeOH and K2CO3 to obtain product (h) with the rea-
sonable yield. Quaternization of 3-(4-bromophenyl)-1-methyl-1,4-dihydropyrazolo[4,3-
c][1,2]benzothiazine 5,5-dioxide (h) was carried out by adding dimethyl sulfate (DMS)
into stirred solution of any one of (h) in xylene at 60°C. The temperature was raised,
and the process was further continued at 100°C for 6 h to obtain a series of quaternary
ammonium salts based on benzothiazine compounds (i). The properties and applica-
tions of quaternary ammonium salt do not only depend on the structure of its cation
but also depend on the type of counter anion. The surface and micellar properties of
quaternary ammonium salts like their surface activity, solubility, aqueous stability and
associative behavior depend on nature, size and geometry of counter ions. The effect
of counter ions on properties and applications of quaternary ammonium salts has been
widely reported in the literature [16–19]. Therefore, replacement of HSO4− with different
anions was also carried out by treating (h) with the suitable source salt to obtain a vari-
ety of quaternary compounds to be used for different applications. The resulting products
are shown in Scheme 1 (i). Proton NMR and Carbon-13 NMR data along with spectra
for all prepared quaternary ammonium salts and their structures are given as supporting
information.
3. Conclusion
A series of quaternary ammonium salts was successfully prepared from benzothiazine
derivatives by multi-step routs involving various organic transformations starting from 4-
bromoacetophenone to final cationic amphiphilic salts having different anions. All steps
involved in overall scheme of synthesis were facile with good to excellent yields. Medicinal,
antimicrobial and catalytic applications of the synthesized cationic amphiphilic systems are
in progress in our laboratory and will be reported shortly.
4. Experimental
4.1. Preparation of 2-bromo-1-(4-bromorophenyl)ethanone
4-Bromoacetophenone (10 mmol) and p-toluenesulfonic acid (p-TsOH) (2.58 g, 15 mmol)
were taken in acetonitrile (30 mL). During stirring, NBS (1.78, 10 mmol) was added slowly.
Reaction mixture was refluxed for 2 h, and then solvent was evaporated on rotary. The
residue was dissolved in dichloromethane, washed with 95 mL water, dried with MgSO4
and solvent was removed by evaporation to achieve a product with the 95% yield.

4
S. GUL ET AL.
Scheme 1. Schematic illustration involving all steps of organic transformations starting from 4-
bromoacetophenone (a) to quaternary ammonium salts having different anions (i).
4.2. Preparation of 2-[2-(4ꢀ-bromophenyl)-2-oxoethyl]-1,2-
benzisothiazol-3(2H)-one 1,1-dioxide
2-Bromo-1-(4ꢀ-bromophenyl)ethanone (15 mmol) was dissolved in dry DMF, and dried
sodium saccharin (3.08 g, 15 mmol) was added to the heated mixture at 120°C for 3 h.
When TLC showed that all 2-bromo-1-(4-bromophenyl)ethanone has converted to the
product, then it was added to slightly acidic cold water to obtain white precipitates that
were filtered and washed with excessive water and methanol to remove all impurities. Prod-
uct purity was confirmed with the help of two-dimensional TLC, and the product was
synthesized with the 89% yield.
4.3. Preparation of 3-(4ꢀ-bromobenzoyl)-4-hydroxy-2H-1,2-benzothiazine
1,1-dioxide
Sodium metal (4.83 g, 210 mmol) was dissolved in completely dried methanol (45 mL), and
2-[2-(4ꢀ-bromophenyl)-2-oxoethyl]-1,2-benzisothiazol-3(2H)-one 1,1-dioxide (30 mmol)

JOURNAL OF SULFUR CHEMISTRY
5
was added to reflux for 20 min. Then, reaction mixture was poured to slightly acidic ice-
cold water, and yellow precipitates were formed that was filtered and recrystallized with
methanol to have a pure product with the 74% yield.
4.4. Preparation of 2-alkyl-3-(4ꢀ-bromobenzoyl)-4-hydroxy-2H-1,2-benzothiazine
1,1-dioxide
3-(4ꢀ-bromobenzoyl)-4-hydroxy-2H-1,2-benzothiazine 1,1-dioxide (15 mmol) was dis-
solved in acetonitrile (50 mL), and alkyl bromide or iodide (15 mmol) was added. Potas-
sium carbonate (2.07 g, 15 mmol) was taken and divided into three parts, where the first
portion was added after 10 min stirring and remaining two installments were added with
the time difference of 15 min during reflux of 2 hr. When the chromatographic analysis
(TLC) showed that all amount of substrate has been converted to product, then the reac-
tion mixture was poured into slightly acidic ice-cold water and pale yellow product was
obtained in the form of precipitates that were filtered and dried at 70°C.
4.5. Preparation of 3-(4ꢀ-bromophenyl)-4-methyl-2,4-dihydropyrazolo[4,3-c][1,2]
benzothiazine 5,5-dioxide
2-Alkyl-3-(4ꢀ-bromobenzoyl)-4-hydroxy-2H-1,2-benzothiazine 1,1-dioxide (7.5 mmol)
and hydrazine monohydrate (2.91 mL, 60 mmol) were dissolved in ethanol, and the mix-
ture was refluxed for 3 h. When reactants showed no spot on the TLC plate, then reaction
contents were added to slightly acidic ice-cold water, and pH of the mixture was adjusted
at 7–8 to precipitate out the required product. Then, white precipitates were subjected to
filtration and drying to obtain pure product with 83% yield.
4.6. Preparation of
3-(4-bromophenyl)-1-methyl-1,4-dihydropyrazolo[4,3-c][1,2]benzothiazine
5,5-dioxide
3-(4ꢀ-Bromophenyl)-4-methyl-2,4-dihydropyrazolo[4,3-c][1,2] benzothiazine 5,5-dioxide
(15 mmol) was taken in acetonitrile (50 mL), and CH3I (15 mmol) was added. Potassium
carbonate (2.07 g, 15 mmol) was taken and divided into three parts, where the first portion
was added after 10 min stirring and remaining two installments were added with the time
difference of 15 min during reflux of 2 h. When the TLC result showed that all amount of
substrate has been converted to product, then the reaction mixture was poured into slightly
acidic ice-cold water. The pure product was obtained by precipitation followed by filtration
and drying at 70°C.
4.7. Quaternization of
3-(4-bromophenyl)-1-methyl-1,4-dihydropyrazolo[4,3-c][1,2]benzothiazine
5,5-dioxide
DMS (0.21 mmol) was added in a stirred solution of title compound in xylene at 60°C.
After dissolving DMS, the reaction mixture was further heated at 100°C for additional 6 h.
After the completion of the reaction, the reaction mixture was cooled and the solvent was

6
S. GUL ET AL.
removed. The crude product was adsorbed on silica gel to carry out its purification using
column chromatography.
4.8. General procedure for the replacement of anions
Separately prepared aqueous solution of anion replacement salt (0.6 mmol) and an aqueous
solution of the earlier synthesized pyrazolium salt (0.5 mmol) immediately produced the
precipitates on mixing at laboratory temperature. The precipitates were filtered and washed
with ice-cold water followed by drying at room temperature. Almost in all reactions,
quantitative yields were obtained during anion replacement.
4.9. Characterization of products
The synthesized quaternary ammonium salts were separated, purified and characterized.
1HNMR and 13CNMR analyses were used for confirmation of the products. The NMR
spectra of each product were recorded using dimethyl sulfoxide (DMSO) as a solvent.
Chemical shift values are reported asδ (ppm).1HNMR and 13CNMR spectra of all products
are given in supporting information, while data are presented as follows:
1H NMR (600 MHz, DMSO) δ 8.38 (d, J = 7.9 Hz, 1H), 8.17 (d, J = 7.7 Hz, 1H), 8.09 (t,
J = 7.8 Hz, 1H), 8.02 (t, J = 7.7 Hz, 1H), 7.97 (d, J = 8.3 Hz, 2H), 7.68 (d, J = 8.2 Hz, 2H),
4.53 (s, 3H), 4.09 (s, 3H), 2.77 (s, 3H).
13C NMR (151 MHz, DMSO) δ 140.54, 134.63, 133.70, 133.44, 133.37, 132.27, 127.82,
126.27, 125.93, 123.59, 123.17, 120.89, 38.85, 37.96, 36.22.

JOURNAL OF SULFUR CHEMISTRY
7
1H NMR (400 MHz, DMSO) δ 8.39 (d, J = 7.8 Hz, 1H), 8.19 (d, J = 7.7 Hz, 1H), 8.10 (t,
J = 7.8 Hz, 1H), 8.02 (d, J = 7.1 Hz, 1H), 7.99 (d, J = 8.5 Hz, 2H), 7.66 (d, J = 8.5 Hz,
2H), 4.52 (s, 3H), 4.08 (s, 3H), 2.78 (s, 3H).
13C NMR (101 MHz, DMSO) δ 140.66, 134.66, 133.74, 133.57, 133.44, 133.37, 132.16,
127.64, 126.36, 126.02, 123.65, 123.04, 120.76, 38.85, 37.96, 36.22.
1H NMR (400 MHz, DMSO) δ 8.38 (d, J = 7.7 Hz, 1H), 8.19 (d, J = 6.6 Hz, 1H), 8.10 (t,
J = 7.1 Hz, 1H), 8.03 (t, J = 7.6 Hz, 1H), 7.99 (d, J = 8.5 Hz, 2H), 7.65 (d, J = 8.5 Hz, 2H),
4.52 (s, 3H), 4.08 (s, 3H), 2.78 (s, 3H).
13C NMR (101 MHz, DMSO) δ 140.66, 134.65, 133.75, 133.57, 133.44, 133.37, 132.16,
127.65, 126.36, 126.02, 123.65, 123.03, 120.77, 38.85, 37.98, 36.24.
1H NMR (400 MHz, DMSO) δ 8.39 (d, J = 7.7 Hz, 1H), 8.20 (d, J = 7.4 Hz, 1H), 8.10 (t,
J = 7.5 Hz, 1H), 8.06–7.98 (m, 3H), 7.66 (d, J = 8.1 Hz, 2H), 4.52 (s, 3H), 4.09 (s, 3H),
2.79 (s, 3H).
13C NMR (101 MHz, DMSO) δ 140.67, 134.67, 133.73, 133.59, 133.46, 133.36, 132.15,
127.63, 126.38, 126.04, 123.64, 123.01, 120.75, 38.86, 37.98, 36.24.

8
S. GUL ET AL.
1H NMR (400 MHz, DMSO) δ 8.39 (d, J = 7.7 Hz, 1H), 8.19 (d, J = 6.7 Hz, 1H), 8.10 (t,
J = 7.1 Hz, 1H), 8.03 (t, J = 7.3 Hz, 1H), 7.99 (d, J = 8.5 Hz, 2H), 7.66 (d, J = 8.5 Hz, 2H),
4.52 (s, 3H), 4.08 (s, 3H), 2.78 (s, 3H).
13C NMR (101 MHz, DMSO) δ 140.67, 134.63, 133.74, 133.57, 133.44, 133.39, 132.14,
127.62, 126.38, 126.02, 123.65, 123.00, 121.55, 120.74, 38.82, 37.99, 36.25.
1H NMR (600 MHz, DMSO) δ 8.38 (d, J = 7.9 Hz, 1H), 8.16 (d, J = 7.8 Hz, 1H), 8.07 (t,
J = 7.3 Hz, 1H), 8.02 (t, J = 7.6 Hz, 1H), 7.98 (d, J = 8.4 Hz, 2H), 7.65 (d, J = 8.3 Hz, 2H),
4.52 (s, 3H), 4.09 (s, 1H), 3.23 (q, J = 7.1 Hz, 1H), 0.53 (t, J = 7.1 Hz, 1H).
13C NMR (151 MHz, DMSO) δ 140.66, 135.55, 134.66, 134.50, 133.54, 133.45, 132.16,
127.76, 126.30, 125.08, 123.31, 121.66, 120.78, 47.81, 37.95, 36.19, 12.23.

JOURNAL OF SULFUR CHEMISTRY
9
1H NMR (600 MHz, DMSO) δ 8.38 (d, J = 7.9 Hz, 1H), 8.17 (d, J = 7.8 Hz, 1H), 8.08 (t,
J = 8.4 Hz, 1H), 8.02 (t, J = 7.7 Hz, 1H), 7.99 (d, J = 8.4 Hz, 2H), 7.63 (d, J = 8.4 Hz, 2H),
4.52 (s, 3H), 4.07 (s, 3H), 3.15–3.12 (m, 2H), 1.00–0.90 (m, 2H), 0.35 (t, J = 7.4 Hz, 3H).
13C NMR (151 MHz, DMSO) δ 140.32, 135.21, 134.46, 134.23, 133.49, 133.46, 132.21,
127.67, 126.31, 125.12, 123.37, 121.89, 120.67, 53.42, 53.26, 37.96, 36.13, 20.23,
10.81.
1H NMR (400 MHz, DMSO) δ 8.38 (d, J = 7.8 Hz, 1H), 8.17 (d, J = 6.8 Hz, 1H), 8.10–7.96
(m, 4H), 7.63 (d, J = 8.4 Hz, 2H), 4.53 (s, 3H), 4.08 (s, 3H), 3.16–3.12 (m, 2H), 1.01–0.92
(m, 2H), 0.36 (t, J = 7.3 Hz, 3H).
13C NMR (101 MHz, DMSO) δ 140.36, 135.22, 134.46, 134.29, 133.47, 132.17, 127.64,
126.31, 125.10, 123.35, 121.92, 120.67, 53.45, 37.94, 36.11, 20.20, 10.80.
1H NMR (400 MHz, DMSO) δ 8.39 (d, J = 7.6 Hz, 1H), 8.18 (d, J = 7.4 Hz, 1H), 8.11–7.99
(m, 4H), 7.63 (d, J = 7.9 Hz, 2H), 4.52 (s, 3H), 4.07 (s, 3H), 3.17 (t, J = 6.9 Hz, 2H),
0.92–0.89 (m, 2H), 0.80–0.75 (m, 2H), 0.50 (t, J = 7.0 Hz, 3H).
13C NMR (101 MHz, DMSO) δ 140.37, 135.13, 134.49, 134.21, 133.52, 133.47, 132.20,
127.62, 126.34, 125.14, 123.36, 122.01, 120.64, 51.67, 37.94, 36.12, 28.88, 19.19,
13.45.

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S. GUL ET AL.
1H NMR (400 MHz, DMSO) δ 8.39 (d, J = 7.8 Hz, 1H), 8.18 (d, J = 7.1 Hz, 1H), 8.11–7.99
(m, 4H), 7.63 (d, J = 8.4 Hz, 2H), 4.52 (s, 3H), 4.07 (s, 3H), 3.17 (t, J = 7.3 Hz, 2H),
0.94–0.87 (m, 2H), 0.83–0.74 (m, 2H), 0.50 (t, J = 7.2 Hz, 3H).
13C NMR (101 MHz, DMSO) δ 140.40, 135.16, 134.46, 134.23, 133.53, 133.47, 132.18,
127.59, 126.36, 125.15, 123.33, 122.03, 121.55, 120.62, 118.35, 51.64, 37.97, 36.14, 28.91,
19.18, 13.43.
1H NMR (600 MHz, DMSO) δ 8.38 (d, J = 8.0 Hz, 1H), 8.17 (d, J = 7.7 Hz, 1H), 8.08 (t,
J = 7.8 Hz, 1H), 8.02 (d, J = 15.2 Hz, 1H), 7.99 (d, J = 8.3 Hz, 2H), 7.63 (d, J = 7.7 Hz,
2H), 4.51 (s, 3H), 4.07 (s, 3H), 3.15 (t, J = 7.3 Hz, 2H), 0.98–0.91 (m, 4H), 0.84–0.79 (m,
2H), 0.74–0.68 (m, 5H).
13C NMR (151 MHz, DMSO) δ 139.94, 134.54, 133.96, 133.71, 132.98, 132.94, 131.77,
127.17, 125.87, 124.75, 122.90, 121.67, 120.19, 51.62, 37.45, 35.65, 30.34, 26.66, 25.19, 21.69,
13.67.

JOURNAL OF SULFUR CHEMISTRY
11
1H NMR (600 MHz, DMSO) δ 8.15 (d, J = 6.9 Hz, 1H), 8.08 (dd, J = 6.9, 1.8 Hz, 1H),
7.96–7.91 (m, 2H), 7.86 (d, J = 8.1 Hz, 2H), 7.55 (d, J = 8.1 Hz, 2H), 7.05 (t, J = 7.4 Hz,
1H), 6.94 (t, J = 7.6 Hz, 2H), 6.72 (d, J = 7.4 Hz, 2H), 4.45 (s, 3H), 4.32 (s, 2H), 4.06 (s,
3H).
13C NMR (151 MHz, DMSO) δ 137.95, 135.22, 134.87, 134.29, 133.31, 133.27, 132.06,
128.91, 128.39, 127.47, 126.28, 125.45, 122.97, 120.57, 55.74, 37.95, 36.34.
1H NMR (400 MHz, DMSO) δ 8.14 (d, J = 6.6 Hz, 1H), 8.11–8.06 (m, 1H), 7.98–7.91 (m,
1H), 7.87 (d, J = 8.4 Hz, 1H), 7.54 (d, J = 8.4 Hz, 2H), 7.06 (t, J = 7.4 Hz, 1H), 6.94 (t,
J = 7.6 Hz, 2H), 6.71 (d, J = 7.4 Hz, 2H), 4.44 (s, 1H), 4.33 (s, 1H), 4.06 (s, 1H).
13C NMR (101 MHz, DMSO) δ 141.08, 135.26, 134.92, 134.29, 133.34, 132.81, 132.00,
128.91, 128.50, 128.38, 127.41, 126.31, 125.46, 122.93, 121.72, 120.54, 55.72, 37.93, 36.32.

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S. GUL ET AL.
1H NMR (600 MHz, DMSO) δ 8.15 (d, J = 7.1 Hz, 1H), 8.09 (d, J = 7.4 Hz, 1H), 7.97–7.90
(m, 2H), 7.87 (d, J = 8.3 Hz, 2H), 7.55 (d, J = 8.3 Hz, 2H), 7.06 (t, J = 7.3 Hz, 1H), 6.94
(t, J = 7.5 Hz, 2H), 6.72 (d, J = 7.4 Hz, 2H), 4.45 (s, 3H), 4.33 (s, 2H), 4.07 (s, 3H).
13C NMR (151 MHz, DMSO) δ 141.06, 135.25, 134.90, 134.29, 133.32, 132.89, 132.05,
128.91, 128.48, 128.39, 127.47, 126.30, 125.46, 122.99, 121.77, 120.57, 55.74, 37.99, 36.38.
1H NMR (400 MHz, DMSO) δ 8.36 (d, J = 7.8 Hz, 1H), 8.15 (d, J = 7.7 Hz, 1H), 8.06 (t,
J = 7.2 Hz, 1H), 8.01 (d, J = 7.6 Hz, 1H), 7.98 (d, J = 8.3 Hz, 2H), 7.66 (d, J = 8.3 Hz,
2H), 4.51 (s, 3H), 4.13 (s, 3H), 3.90–3.84 (m, 1H), 0.57 (d, J = 6.7 Hz, 6H).
13C NMR (101 MHz, DMSO) δ 142.23, 136.75, 136.03, 134.54, 133.61, 133.33, 132.44
128.00, 126.13, 125.31, 124.15, 121.01, 120.04, 57.46, 37.77, 36.23, 20.16.
1H NMR (600 MHz, DMSO) δ 8.37 (d, J = 7.8 Hz, 1H), 8.17 (d, J = 7.6 Hz, 1H), 8.07 (t,
J = 7.6 Hz, 1H), 8.03–7.99 (m, 3H), 7.64 (d, J = 8.3 Hz, 2H), 4.49 (s, 3H), 4.11 (s, 3H),
3.91–3.86 (m, 1H), 0.58 (d, J = 6.7 Hz, 6H).
13C NMR (151 MHz, DMSO) δ 142.33, 136.75, 136.07, 134.58, 133.69, 133.40, 132.38,
127.88, 126.20, 125.38, 124.05, 120.93, 120.13, 57.45, 37.77, 36.23, 20.14.

JOURNAL OF SULFUR CHEMISTRY
13
Acknowledgements
The authors are highly thankful to Higher Education Commission (HEC), Pakistan for funding
under Indigenous Scholarship Scheme for MPhil and PhD studies awarded to Salman Gul to carry
out his PhD work. Financial support from University of the Punjab under project No:/503/EST.I for
the year of 2019–2020 is also acknowledged.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
Authors received funding from Higher Education Commission (HEC), Pakistan and University of
the Punjab, Lahore, Pakistan to carry out this work.
ORCID
Robina Begum http://orcid.org/0000-0002-0470-3374
Zahoor H. Farooqi http://orcid.org/0000-0003-3200-2935
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