An efficient access to β-ketosulfones: Via β-sulfonylvinylamines: Metal-organic framework catalysis for the direct C-S coupling of sodium sulfinates with oxime acetates

Article abstract of DOI:10.1039/c8ra02389a

A copper-based framework Cu₂(OBA)₂(BPY) was synthesized and used as a recyclable heterogeneous catalyst for the synthesis of β-sulfonylvinylamines from sodium sulfinates and oxime acetates via direct C-S coupling reaction. The transformation was remarkably affected by the solvent, and chlorobenzene emerged as the best option. This Cu-MOF displayed higher activity than numerous conventional homogeneous and MOF-based catalysts. The catalyst was reutilized many times in the synthesis of β-sulfonylvinylamines without considerably deteriorating in catalytic efficiency. These β-sulfonylvinylamines were readily converted to the corresponding β-ketosulfones via a hydrolysis step with aqueous HCl solution. To the best of our knowledge, this direct C-S coupling reaction to achieve β-sulfonylvinylamines was not previously conducted with a heterogeneous catalyst.

Full text of DOI:10.1039/c8ra02389a

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An efficient access to b-ketosulfones via b-
sulfonylvinylamines: metal–organic framework
catalysis for the direct C–S coupling of sodium
sulfinates with oxime acetates†
Cite this: RSC Adv., 2018, 8, 17477
Tuong A. To,
Anh N. Q. Phan and Nam T. S. Phan
Chau B. Tran, Ngoc T. H. Nguyen, Hai H. T. Nguyen, Anh T. Nguyen,
*
A copper-based framework Cu2(OBA)2(BPY) was synthesized and used as a recyclable heterogeneous
catalyst for the synthesis of b-sulfonylvinylamines from sodium sulfinates and oxime acetates via direct
C–S coupling reaction. The transformation was remarkably affected by the solvent, and chlorobenzene
emerged as the best option. This Cu-MOF displayed higher activity than numerous conventional
homogeneous and MOF-based catalysts. The catalyst was reutilized many times in the synthesis of b-
sulfonylvinylamines without considerably deteriorating in catalytic efficiency. These b-sulfonylvinylamines
were readily converted to the corresponding b-ketosulfones via a hydrolysis step with aqueous HCl
solution. To the best of our knowledge, this direct C–S coupling reaction to achieve b-
sulfonylvinylamines was not previously conducted with a heterogeneous catalyst.
Received 19th March 2018
Accepted 26th April 2018
DOI: 10.1039/c8ra02389a
rsc.li/rsc-advances
ketosulfones, heterogeneous catalysts should be utilized for the
formation of b-sulfonylvinylamines to achieve easy catalyst
1. Introduction
recovery and recycling, as well as facile product isolation and
purication.
Sulfone derivatives have emerged as essential intermediates for
the synthesis of numerous compounds with potentially valuable
biological activities.1–4 Diverse synthetic protocols have been
developed for the construction of these skeletons owing to their
signicance. Tang et al. previously reported the synthesis of b-
Metal–organic frameworks (MOFs) are crystalline and self-
organizing reticular materials, consisting of metal cations
sharing polytopic organic linkers.11–15 Applications of MOFs in
the eld of catalysis are somewhat delaying behind other
domains.16,17 With remarkably high porosity and almost innite
synthetic tunability, MOFs have exhibited several advantages in
catalysis over non-porous and zeolitic materials.18,19 Generally,
catalytically active sites on MOFs could originate from the
metal-based building units or from functional groups on the
organic linkers.20–22 The isolation of metal points in the
networks would provide a greater number of active sites for the
reactants.23,24 Many organic reactions conducted with MOFs-
based catalysts have been declared in the literature.20,25–28
Nevertheless, b-sulfonylvinylamines and b-ketosulfones were
not previously synthesized utilizing heterogeneous catalysts,
and the exploration of recyclable catalysts should be necessary
for the construction of these skeletons. In this manuscript, we
would like to illustrate an efficient access to b-sulfonylvinyl-
amines from sodium sulnates and oxime acetates via direct
C–S coupling reaction utilizing Cu2(OBA)2(BPY) metal–organic
framework catalysis. The Cu-MOF catalyst was reutilized many
times without a noticeably deterioration in catalytic efficiency.
These b-sulfonylvinylamines were readily converted to b-keto-
sulfones with a hydrolysis step with aqueous HCl solution.
ketosulfones via
oxidative coupling reaction of sulfonylhydrazides with enam-
ides.5
Kumar and Muthyala employed 1-butyl-3-
a tetrabutylammonium iodide-mediated
methylimidazolium p-toluenesulnate as a reagent to afford
the corresponding b-ketosulfones.6 Loghmani-Khouzani and
Hajiheidari prepared b-ketosulfones by the reaction of thiols
with a-bromoacetophenones, subsequently followed by an
oxidation step.7 Yang et al. demonstrated an efficient protocol to
achieve b-ketosulfones via a visible-light initiated direct oxy-
sulfonylation between alkenes and sulnic acids under
transition-metal-free conditions.8 Xie et al. synthesized b-keto-
sulfones based on a photoinduced radical fragmentation and
rearrangement of vinyl tosylates.9 Recently, Tang et al. reported
for the rst time the Cu(OAc)2-catalyzed synthesis of b-sulfo-
nylvinylamines from oxime acetates and sodium sulnates, and
upon hydrolysis, corresponding b-ketosulfones were readily
achieved in high yields.10 To establish greener pathways to b-
Faculty of Chemical Engineering, HCMC University of Technology, VNU-HCM, 268 Ly
Thuong Kiet, District 10, Ho Chi Minh City, Viet Nam. E-mail: ptsnam@hcmut.edu.vn;
Fax: (+84 8) 38637504; Tel: (+84 8) 38647256 ext. 5681
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c8ra02389a
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the expected b-ketosulfone. Product structure was subsequently
2. Experimental
2.1. Synthesis of metal–organic framework Cu2(OBA)2(BPY)
1
conrmed by GC-MS, H NMR, and 13C NMR.
In a typical procedure, 4,40-oxybis(benzoic) acid (H2OBA)
(0.258 g, 1 mmol), copper(II) nitrate trihydrate (Cu(NO3)2$3H2O)
(0.242 g, 1 mmol), and 4,40-bipyridine (BPY) (0.078 g, 0.5 mmol)
were dissolved in the mixture of DMF and distilled water (14
mL, 11 : 3 v/v). The mixture was magnetically stirred for 30 min
to obtain a clear solution. The solution was subsequently
distributed to three 10 mL vials. The vials were carefully capped
and heated at 85 ꢀC in an isothermal oven for 48 h. Green
crystals were formed during the experiment. Aer the vials were
cooled to ambient temperature, the solid product in each vial
was collected by decantation, and washed in DMF (3 ꢁ 10 mL).
Solvent exchange was consequently performed with methanol
(3 ꢁ 10 mL) at room temperature. The framework was then
3. Results and discussion
The Cu2(OBA)2(BPY) was synthesized in 75% yield from 4,40-
oxybis(benzoic) acid, copper(II) nitrate trihydrate, and 4,40-
bipyridine following a literature approach.29,30 The copper–
organic framework was consequently characterized by utilizing
conventional analysis methods (Fig. S1–S7†). The Cu-MOF was
initially used as a heterogeneous catalyst for the direct C–S
coupling reaction between 1-(thiophen-2-yl)ethanone O-acetyl
oxime and sodium benzenesulnate to produce (Z)-2-
(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine (Scheme 1a).
First, the inuence of temperature on the reaction yield was
explored. The reaction was performed in toluene under argon
for 3 h, at 10 mol% catalyst, with reactant molar ratio of 1 : 1
and reactant concentration of 0.25 M, at room temperature,
60 ꢀC, 80 ꢀC, 100 ꢀC, and 120 ꢀC, respectively. The reaction did
not proceed at room temperature and 60 ꢀC with no trace
quantity of product being noted. Increasing the temperature to
ꢀ
dried at 150 C for 6 h under vacuum on a Shlenkline to have
0.29 g of Cu2(OBA)2(BPY) in the form of green crystals (75%
yield regarding H2OBA).
2.2. Catalytic studies
In a typical catalytic experiment, a mixture of 1-(thiophen-2-yl) 80 ꢀC resulted in only 10% yield. The reaction yield was
ethanone O-acetyl oxime (0.25 mmol, 45.8 mg), sodium benze- remarkably improved to 60% for the reaction conducted at
nesulnate (0.3 mmol, 49.2 mg), Cu2(OBA)2(BPY) (10 mol%) in 100 ꢀC. Boosting the temperature to 120 ꢀC did not led to higher
chlorobenzene (1 mL) was added to a 10 mL screw-cap vial with yield of the desired product (Fig. 1). It was noted that the yield of
magnetic stirrer bar. The catalyst amount was calculated the expected product was improved by changing the reactant
regarding the copper/1-(thiophen-2-yl)ethanone O-acetyl oxime molar ratio, having investigated the reaction with 1-(thiophen-
molar ratio. The mixture was stirred at 100 ꢀC for 3 h under an 2-yl)ethanone O-acetyl oxime : sodium benzenesulnate molar
argon atmosphere. Aer the reaction was complete, aliquots ratio of 2 : 1, 1 : 1, 1 : 1.2, and 1 : 1.5, respectively. The reaction
were withdrawn from the reaction mixture, quenched with utilizing two equivalents of 1-(thiophen-2-yl)ethanone O-acetyl
brine (1 mL), extracted with ethyl acetate (3 ꢁ 1 mL), and dried oxime afforded 69% yield. Similar yield was achieved by
over anhydrous Na2SO4. Samples were then analyzed by GC employing 1.2 equivalents of sodium benzenesulnate.
concerning n-dodecane internal standard, giving GC yield of (Z)- Increasing the amount of sodium benzenesulnate to 1.5
2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine. Ethyl acetate equivalents was not necessary as the yield of (Z)-2-
was removed under vacuum, and the crude product was puried (phenylsulfonyl)-1-(thiophen-2-yl)ethenamine
was
not
by recrystallization in chlorobenzene and hexane.
enhanced noticeably (Fig. 2).
As the direct C–S coupling reaction using the copper-based
In order to achieve 2-(phenylsulfonyl)-1-(thiophen-2-yl)
ethanone, aer the rst step, the reaction mixture was cooled framework catalyst proceeded in solution, changing the
to room temperature and ltered to remove the Cu2(OBA)2(BPY) solvent could led to higher yield. Tang et al. previously reported
catalyst. The ltrate was then magnetically stirred with aqueous for the rst time the Cu(OAc)2-catalyzed synthesis of b-sulfo-
HCl solution (1 M, 1 mL) at 80 ꢀC for 3 h. The resulting mixture nylvinylamines from oxime acetates and sodium sulnates, and
was quenched with brine (5 mL), and the organic ingredients pointed out that toluene was the best solvent for this trans-
were extracted into ethyl acetate (3 ꢁ 5 mL). The combined ethyl formation.10 We consequently studied the impact of different
acetate solution was dried over anhydrous Na2SO4. The solvent solvents on the yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)
was subsequently removed under vacuum, and the crude ethenamine. The reaction was conducted at 100 ꢀC in each
product was puried by silica gel column chromatography solvent under argon for 3 h, in the presence of 10 mol% catalyst,
utilizing hexane and ethyl acetate (3 : 1, v/v) as eluent to obtain with 1.2 equivalents of sodium benzenesulnate and at reactant
Scheme 1 The direct C–S coupling reaction utilizing Cu2(OBA)2(BPY) catalyst (a), and the hydrolysis step to form b-ketosulfone (b).
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Fig.
1 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine
vs. temperature.
Fig. 3 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine
vs. solvent.
concentration of 0.25 M. DMSO and DMF were not appropriate
for the reaction, producing the b-sulfonylvinylamine product in
18% and 36% yields, respectively. Changing the solvent to
mesitylen, 64% yield was observed, while 68% and 66% yields
were detected to the case of toluene and cumene, respectively.
The yield was upgraded to 86% for the reaction carried out in o-
xylene. Similarly, 85% and 84% yields were obtained for the
reaction in p-xylene and m-xylene, respectively. Moving to 1,4-
dioxane, the yield was decreased to 65% yield. n-Butanol and
ethyl acetate should not be used for this reaction. Compared to
these solvents, chlorobenzene emerged as the solvent of choice,
affording 87% yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)
ethenamine (Fig. 3).
oxime, ranging from 0.05 M to 0.50 M. Very low yield of the b-
sulfonylvinylamine product was detected with reactant
concentration of 0.05 M. Extending the concentration to 0.17 M
afforded 39% yield. Interestingly, increasing the reactant
concentration to 0.25 M signicantly accelerated the trans-
formation, affording 87% yield of (Z)-2-(phenylsulfonyl)-1-
(thiophen-2-yl)ethenamine. However, lower yield of the
desired product was observed for the reaction with higher
reactant concentration (Fig. 4). This could be explained due to
the mass transfer of the reactants when a solid catalyst was
employed. Having these results, the impact of catalyst quantity
on the reaction was consequently explored. The reaction was
performed at 100 ꢀC in chlorobenzene under argon for 3 h, with
1.2 equivalents of sodium benzenesulnate and reactant
One more factor that should be explored is the reactant
concentration. We consequently conducted the reaction with
various concentrations of 1-(thiophen-2-yl)ethanone O-acetyl
Fig. 2 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine Fig. 4 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine
vs. reactant molar ratio.
vs. reactant concentration.
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concentration of 0.25 M, in the presence of 5 mol%, 7.5 mol%,
10 mol%, 12.5 mol%, and 15 mol% catalyst, respectively. It was
noted that no trace evidence of the b-sulfonylvinylamine
product was detected in the absence of the catalyst. Utilizing
5 mol% catalyst resulted in 67% yield, while 73% yield was
obtained for the case of 7.5 mol% catalyst. The yield of (Z)-2-
(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine was improved to
87% for the reaction utilizing 10 mol% catalyst. Extending the
catalyst amount to 15 mol% did not led to higher yield of the
desired product (Fig. 5). Noted that benzenesulnic acid was
inactive in this reaction, with the desired product being detec-
ted in trace amount. Additionally, potassium benzenesulnate
was signicantly less reactive than the sodium salt, affording
only 16% yield.
To highlight the benet of the Cu2(OBA)2(BPY) in the direct
C–S coupling reaction, its catalytic efficiency was compared to
other homogeneous and heterogeneous catalysts. The reaction
was conducted at 100 ꢀC in chlorobenzene under argon for 3 h,
with 1.2 equivalents of sodium benzenesulnate and reactant
concentration of 0.25 M, in the presence of 10 mol% catalyst.
Several homogeneous copper catalysts displayed reasonable
activity for the reaction. The CuCl-catalyzed transformation
progressed to 63% yield, while 65% yield was detected for the
case of CuBr. Utilizing Cu(OAc)2 as catalyst, the yield was
improved to 72% (Fig. 6). Noted that in the rst Cu(OAc)2-
catalyzed synthesis of b-sulfonylvinylamines from oxime
acetates and sodium sulnates, Tang et al. pointed out that
thiophene oxime acetate was less reactive than benzene oxime
acetate.10 Moving to copper-based MOFs as catalysts, it was
noted that MOF-199 and VNU-18 exhibited very low activity
towards the direct C–S coupling reaction, with less than 10%
yield being recorded. Cu(OBA) was more active, affording the b-
sulfonylvinylamine product in 55% yield. This value was
improved to 71% for the reaction utilizing Cu2(BPDC)2(DABCO)
catalyst, while 74% yield was observed for that employing
Cu2(BPDC)2(BPY) catalyst. Compared to these homogeneous
Fig. 6 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine
vs. homogeneous catalyst.
and heterogeneous catalysts, Cu2(OBA)2(BPY) displayed higher
performance, generating the expected product in 87% yield
(Fig. 7).
Since the direct C–S coupling reaction between 1-(thiophen-
2-yl)ethanone O-acetyl oxime and sodium benzenesulnate
proceeded in chlorobenzene, the leaching experiment was then
carried out to conrm that if any copper species in the liquid
phase contributed to the yield of (Z)-2-(phenylsulfonyl)-1-
Fig. 5 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine Fig. 7 Yield of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine
vs. catalyst quantity.
vs. heterogeneous catalyst.
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(thiophen-2-yl)ethenamine. The reaction was performed at
ꢀ
100 C in chlorobenzene under argon for 3 h, with 1.2 equiva-
lents of sodium benzenesulnate and reactant concentration of
0.25 M, in the presence of 10 mol% catalyst. Upon the
completion of the reaction, the copper-based framework cata-
lyst was removed from the reactor by centrifugation. The liquid
phase was subsequently transferred to a new and clean screw-
cap vial. Fresh reagents were consequently added to this vial.
The resulting mixture was magnetically stirred at 100 ꢀC under
argon for 3 h. Under these conditions, no additional (Z)-2-
(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine was detected.
This result veried that the direct C–S coupling reaction
utilizing Cu2(OBA)2(BPY) catalyst progressed under truly
heterogeneous catalysis (Fig. 8).
To gain more information about the pathway of the reaction,
(2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO) was utilized as
a radical scavenger. In the rst experiment, TEMPO was added
at the beginning of the reaction, and no trace amount of
product was detected. In the second experiment, aer the rst
1 h reaction time, TEMPO was introduced to the reactor, and the
Fig. 8 Leaching test verified that the reaction proceeded under truly
heterogeneous catalysis.
Scheme 2 Plausible mechanism for the formation of (Z)-2-(phenylsulfonyl)-1-(thiophen-2-yl)ethenamine.
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reaction mixture was magnetically stirred under argon at 100 ꢀC
for further 2 h. Under these conditions, no additional b-sulfo-
nylvinylamine product was observed. Furthermore, the direct
C–S coupling reaction was also allowed to proceed in the pres-
ence of 1,1-diphenylethylene. It was noted that the trans-
formation was considerably affected by this radical scavenger.
These observations veried that radical species should be
involved in the catalytic cycle. With these data, and based on
previous report,10 a plausible pathway was proposed (Scheme 2).
Initially, a copper enamide intermediate was produced from the
oxime acetate, while copper(II) were converted to copper(III)
species. A sulfonyl free radical was then formed via a single-
electron-transfer (SET) process, releasing the copper(II)
species. Next, the sulfonyl free radical attacked to the enamide
intermediate, followed by the regeneration of the copper(II)
species. Finally, tautomerization of the imine intermediate
afforded the corresponding b-sulfonylvinylamine.
Fig. 10 XRD observations of the new (a) and reused (b)
Cu2(OBA)2(BPY).
As mentioned previously, the Cu2(OBA)2(BPY) displayed
higher catalytic performance than numerous homogeneous and
MOF-based catalysts. To emphasize the signicance of this
catalyst, one important issue would be its reusability. The
copper-based framework was accordingly explored for reus-
ability in 10 sequential catalytic runs. The reaction was carried
XRD (Fig. 10) and FT-IR (Fig. 11). Analysis results veried that
the catalyst structure was preserved during the experiments.
With the signicance of b-ketosulfones in pharmaceutical
and agrochemical industries, we expanded the work to achieve
these valuable structures via a hydrolysis step (Scheme 1b and
ꢀ
out at 100 C in chlorobenzene under argon for 3 h, with 1.2
ꢀ
equivalents of sodium benzenesulnate and reactant concen-
tration of 0.25 M, in the presence of 10 mol% catalyst. Aer each
catalytic cycle, the copper-based catalyst was collected by
centrifugation, washed extensively with DMF and methanol,
dried at 150 ꢀC under vacuum on a Shlenkline for 6 h. This
catalyst sample was subsequently utilized for next catalytic run
with the same reaction conditions. It was noted that the Cu2(-
OBA)2(BPY) was reusable many times without a substantial
deterioration in catalytic efficiency. Certainly, 86% yield of the
desired product was still obtained for the 10th catalytic run
(Fig. 9). Additionally, the reutilized catalyst was characterized by
Table 1). The reaction was performed at 100 C in chloroben-
zene under argon for 3 h, with 1.2 equivalents of sodium ben-
zenesulnate and reactant concentration of 0.25 M, in the
presence of 10 mol% catalyst. Aer that, the catalyst was
recovered, the reaction mixture was treated with aqueous HCl
solution, and the expected b-ketosulfone was puried by silica
gel column chromatography. Following this procedure, 2-
(phenylsulfonyl)-1-(thiophen-2-yl)ethanone was obtained in
76% yield (entry 1). Tang et al. previously demonstrated the
Cu(OAc)2-catalyzed synthesis of b-sulfonylvinylamines from
oxime acetates and sodium sulnates, and upon hydrolysis,
corresponding b-ketosulfones were produced in high yields.10 It
was reported that thiophene-based ketoximes were less reactive
than benzene-based ketoximes. In this work, we also found that
Fig. 9 Catalyst reutilizing studies.
17482 | RSC Adv., 2018, 8, 17477–17485
Fig. 11 FT-IR spectra of new (a) and reutilized (b) Cu2(OBA)2(BPY).
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Table 1 Synthesis of b-ketosulfones via Cu2(OBA)2(BPY)-catalyzed direct C–S coupling reaction, followed by hydrolysis step
Entry
Reactant 1
Reactant 2
Product
Isolated yield
76%
1
2
3
88%
91%
4
89%
5
6
7
83%
76%
80%
8
9
80%
82%
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Table 1 (Contd.)
Entry
Reactant 1
Reactant 2
Product
Isolated yield
90%
10
11
12
78%
65%
13
14
74%
79%
1-p-tolylethanone O-acetyl oxime was more reactive than 1-
(thiophen-2-yl)ethanone O-acetyl oxime, and 2-(phenylsulfonyl)-
1-p-tolylethanone was generated in 88% yield (entry 2).
4. Conclusions
The copper–organic framework Cu2(OBA)2(BPY) was utilized as
a recyclable heterogeneous catalyst for the direct C–S coupling
reaction between sodium sulnates and oxime acetates to
produce b-sulfonylvinylamines. The solvent expressed
a remarkable impact on the transformation, and chlorobenzene
emerged as the best option. This Cu-MOF was more active
towards the coupling reaction than a series of copper-based
homogeneous and MOF-based catalysts. The coupling reac-
tion utilizing Cu2(OBA)2(BPY) catalyst progressed under truly
heterogeneous catalysis. The catalyst was reutilized many times
in the synthesis of b-sulfonylvinylamines without a considerably
deterioration in catalytic efficiency. These b-sulfonylvinyl-
amines were promptly converted to corresponding b-keto-
sulfones via a hydrolysis step with aqueous HCl solution. The
fact that b-sulfonylvinylamines were generated under a hetero-
geneous catalysis approach, and readily converted to b-keto-
sulfones upon hydrolysis, was consequently protable to
pharmaceutical and agrochemical industries.
Several benzene-based ketoximes were utilized in the synthesis
of b-ketosulfones via Cu2(OBA)2(BPY)-catalyzed direct C–S coupling
reaction, followed by hydrolysis step. 1-(4-Methoxyphenyl)-2-
(phenylsulfonyl)ethanone was achieved in 91% (entry 3). Simi-
larly, the reactions of meta- and ortho-substituted ketoximes
afforded the corresponding products in high yields (entries 4 and
5). Ketoximes possessing a halogen substituent were slightly less
reactive, forming 1-(4-bromophenyl)-2-(phenylsulfonyl)ethanone,
and 1-(4-chlorophenyl)-2-(phenylsulfonyl)ethanone in 76%, and
80% yields, respectively (entries 6 and 7). 2-(Phenylsulfonyl)-1-
(pyridin-2-yl)ethanone was also obtained in 80% yield (entry 8).
3,4-Dihydronaphthalen-1(2H)-one O-acetyl oxime was also reactive,
and 82% yield of 2-(phenylsulfonyl)-3,4-dihydronaphthalen-1(2H)-
one was recorded (entry 9). Different sodium benzenesulnates
were also used, and 2-(4-methoxyphenylsulfonyl)-1-(thiophen-2-yl)
ethanone (entry 10), 2-(4-chlorophenylsulfonyl)-1-(thiophen-2-yl)
ethanone (entry 11), 2-(4-bromophenylsulfonyl)-1-(thiophen-2-yl)
ethanone (entry 12), and 2-(naphthalen-2-ylsulfonyl)-1-(thiophen-
2-yl)ethanone (entry 13) were generated in 90%, 78%, 65%, and
74% yields, respectively. Additionally, the transformation of
sodium ethanesulnate afforded 2-(ethylsulfonyl)-1-(thiophen-2-yl)
ethan-1-one in 79% yield (entry 14).
Conflicts of interest
There are no conicts to declare.
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Acknowledgements
The Vietnam National University – Ho Chi Minh City (VNU-
HCM) is acknowledged for nancial support via project No.
NV2018-20-02.
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