Palladium-catalyzed desulfitative arylation of sulfonamides with sodium arylsulfinates

Article abstract of DOI:10.1080/00397911.2018.1452262

A Pd(II)-catalyzed desulfitative arylation protocol between sulfonamides and sodium arylsulfinates was herein reported. The direct arylation reaction was successfully achieved by a Pd(II)/Ag(I)-mediated system without participation of any external ligands with a release of SO₂. And different N-aryl sulfonamides were obtained readily in up to 86% yields, exhibiting good functional groups tolerance (25 examples).

Full text of DOI:10.1080/00397911.2018.1452262

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
Palladium-catalyzed desulfitative arylation of
sulfonamides with sodium arylsulfinates
Zijian Zhao, Yan Lian, Chang Zhao & Bing Wang
To cite this article: Zijian Zhao, Yan Lian, Chang Zhao & Bing Wang (2018) Palladium-catalyzed
desulfitative arylation of sulfonamides with sodium arylsulfinates, Synthetic Communications, 48:12,
1436-1442, DOI: 10.1080/00397911.2018.1452262
To link to this article: https://doi.org/10.1080/00397911.2018.1452262
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SYNTHETIC COMMUNICATIONS®
018, VOL. 48, NO. 12, 1436–1442
2
https://doi.org/10.1080/00397911.2018.1452262
Palladium-catalyzed desulfitative arylation of sulfonamides
with sodium arylsulfinates
a
a
b
a
Zijian Zhao , Yan Lian , Chang Zhao , and Bing Wang
a
b
School of Chemistry and Materials Science, Huaihua University, Huaihua, Hunan, P.R. China; Huaihua No. 3
High School, Huaihua, Hunan, China
ABSTRACT
ARTICLE HISTORY
Received 29 July 2017
A Pd(II)-catalyzed desulfitative arylation protocol between sulfona-
mides and sodium arylsulfinates was herein reported. The direct
arylation reaction was successfully achieved by a Pd(II)/Ag(I)-mediated
system without participation of any external ligands with a release of
KEYWORDS
Arylation; desulfitative;
palladium catalysis; sodium
arylsulfinates; sulfonamides
SO
to 86% yields, exhibiting good functional groups tolerance
25 examples).
2
. And different N-aryl sulfonamides were obtained readily in up
(
GRAPHICAL ABSTRACT
Introduction
Novel methodologies for direct N-arylation of sulfonamides have been widely studied to
improve the diversification of the significant compounds. Various aryl donators, including
[
1]
[2]
[3]
[4]
aryl halides,
aryl boronic acids,
aryl siloxanes,
aryl nonaflates,
even
[
5]
[6]
cyclohexanones, and so on have been successfully utilized for the straightforward
arylation of sulfonamides with the assistance of various transition metal catalysts, such
as Pd(II), Ni(II), and Cu(II) and etc. As far as we are aware, sodium arylsufinates, which
have been frequently employed as efficient sulfonylation and sulfuration reagents,
came to our consciousness as a direct and good sacrifice of aryl groups in different tran-
sition metallic catalysis in a desulfitative pattern, releasing gaseous SO . Traditionally,
[
7]
[8]
2
involvement of the reagent sodium sulfinates renders the desulfitative arylation means
enjoy the advantages like stability and easy-handling work-up procedure. Up to date, desul-
[
9]
fitative protocols for the constructions of C–C bonds have been well established on the
[
10]
[11]
[12]
substrates of different types, like arylmethyl chlorides,
aldehydes,
aryl triflates,
polyfluoroarenes,[13] olefins,[14] alkynes.[15] While formations of C–N bonds
successfully achieved on the hetero compounds including thiophenol, indoles, azoles,
[16]
have been
CONTACT Zijian Zhao
zjzhao72@163.com
School of Chemistry and Materials Science, Huaihua University,
1
80 Huaidong Rd, Huaihua, Hunan 418000, P. R. China.
1
13
Supplemental data (full experimental details, H and C NMR spectra) can be accessed on the publisher’s website.
2018 Taylor & Francis
©

SYNTHETIC COMMUNICATIONS®
1437
caffeines, coumarins, and even CuCN[17] have also been readily arylated in the same
manner. Very recently, applications of potassium iodide and dialkyl phosphites for the
[
18]
[19]
formations of C–I and C–P bonds
in a similar manner.
mediated by a Pd(II)-catalyst were well-illustrated
Cheng has disclosed a desulfitative synthesis of carboxylic acids in a liganded Cu(I)-
[
20]
mediated system.
Inspired by An’s description, CuI was capable to make the desulfita-
[
21]
tive arylations of sulfonamides took place in the absence of any external organic ligands.
Herein, we would like to unveil a Pd(II)-catalyzed method for arylation of sulfonamides
with sodium arylsulfinates with the assistance a silver oxidant in the absence of any
external ligands (Scheme 1).
Discussion
Firstly, reactions between S-phenyl sulfonamide (1a) and sodium phenylsulfinate (2a) were
conducted to obtain the optimal conditions, which were summarized in Table 1. In the
presence of palladium diacetate (5 mol%) and silver acetate (2.0 equiv.), the arylation
reaction took place readily in 1,4-dioxane, but in low efficiency, for only 32% of 3aa
was isolated after column seperation (entry 1). Other simple Pd(II) catalysts, such as
Pd(TFA) (TFA for trifluoroacetic acid) and PdCl offered superior performance to that
2
2
Pd(OAc) did. For 45 and 42% yields of 3aa were obtained in the system (entries 2
2
and 3). Disappointingly, phosphine-liganded palladium catalysts, such as Pd(PPh ) Cl
3
2
2
and Pd(dppf) Cl (dppf stands for diphenylphosphino ferrocene) were incapable of making
2
2
the desulfitative transformation happen for only trace of the desired product 3aa was
detected after 24 h (entries 4 and 5). By contrast, nitriles-coordinated Pd(II)-catalysts,
which were exemplified by Pd(MeCN) Cl and Pd(PhCN) Cl rendered the coupling of
2
2
2
2
1
a and 2a easily, leading to the formation of 3aa in medium yields, up to 62% (entries 6
and 7). However, Pd(PPh ) failed to make the desufitative arylation happen, for only trace
3
4
of 3aa was found over the consumption of 2a as monitored by TLC (entry 8). Other
Scheme 1. Desulfitative arylation methodologies.

1
438
Z. ZHAO ET AL.
a
Table 1. Optimization of reaction conditions.
b
Entry
[Pd]
Pd(OAc)
Pd(TFA)
PdCl
Pd(PPh
Pd(dppf)
Pd(MeCN)
Pd(PhCN)
Pd(PPh
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
Pd(MeCN)
–
[O]
Sol.
Yield (%)
1
2
3
4
5
6
7
8
9
2
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
THF
32
45
42
Trace
Trace
62
58
Trace
55
2
2
3
)
2
Cl
2
2
2
Cl
2
Cl
2
2
Cl
2
3
)
4
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
Cl
2
2
2
2
2
2
2
2
2
2
2
2
2
Ag
AgNO
Ag
AgOTf
2
CO
3
1
1
1
1
1
1
1
1
1
1
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
Trace
Trace
Trace
2
O
c
K
2
S
2
O
8
n.d.
DCP
DTBP
n.d.
n.d.
n.d.
Trace
58
O
2
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
Toluene
DCE
Trace
38
82 (80)
n.d.
DMSO
d
e
1,4-Dioxane/DMSO
1,4-Dioxane/DMSO
a
Reaction conditions: 1a (0.3 mmol), 2a (0.36 mmol), [Pd] (5 mol%), [O] (2.0 equiv.), under argon atmosphere or noted in sol.
2.0 mL) at 120 °C for 24 h.
(
b
c
Isolated yields.
Stands for not detected.
d
The ratio is 9:1 by volume.
e
The yield in the parentheses was obtained in 0.5 mmol scale.
DCE, dichloroethane; DCP, dicumyl peroxide; DMSO, dimethyl sulfoxide; DTBP, di-tert-butyl peroxide; THF, tetrahydrofuran.
oxidants were also screened in the Pd-mediated protocol. Except Ag CO , other silver salts,
2
3
like AgNO , Ag O, and AgOTf did not offer any positive results for trace or maximum 55%
3
2
of 3aa was checked in the systems (entries 9–12). Furthermore, other organic oxidants such
as K S O (entry 13), dicumyl peroxide (entry 14), di-tert-butyl peroxide (entry 15), and
2
2 8
clean oxidant molecular dioxygen (entry 16) proved to be totally ineffective to the arylation
system for no reaction was detected in the Pd-Ag-mediated system after 24 h. For solvents,
pure solvents including tetrahydrofuran (entry 17), toluene (entry 18), dichloroethane
(
entry 19), and dimethyl sulfoxide (DMSO for entry 20) gave inferior yields to that
1
,4-dioxane did in the existence of the combination of Pd(MeCN) Cl and AgOAc. How-
2
2
ever, beyond our expectations, the addition of DMSO as co-solvent of 1,4-dioxane (ratio
9
:1) raised the yield of 3aa dramatically up to a 82% ratio (entry 21). This probably was
due to the better solubility of 2a in the mixture of the solvents. Meanwhile, Pd(MeCN)
Cl was proved crucial to the transformation for no reaction was detected in the absence
2
2
of only AgOAc (entry 22).
With the optimal conditions in hands, the scope and limitations of the substrates on the
sulfonamides were evaluated in the Pd-Ag-mediated system, which was summarized in
Table 2. First, para-methylphenyl sulfonamide (1b) coupled with 2a successfully, forming

SYNTHETIC COMMUNICATIONS®
1439
a
Table 2. Substrates scope of the sulfonamides.
b
Entry
1
R
3
Yield (%)
1
2
3
4
5
6
7
8
9
0
1
2
3
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
4-CH
2-CH
4-CH
3
3
3
C
C
6
H
H
4
3ba
3ca
3da
3ea
3fa
3ga
3ha
3ia
3ja
3ka
3la
3ma
3na
85
78
82
79
72
78
81
68
76
80
72
48
45
6
OC
4
H
6
4
4-tBuC
4-FC
4-ClC
4-BrC
4-NO
4-CF
2-Naphthyl
2-Thiophenyl
6 4
H
6 4
H
6
H
4
6 4
H
2
C
C
6
6
H
H
4
4
3
1
1
1
1
CH
CH
3
3
CH
2
a
b
Reaction conditions: 1 (0.5 mmol), 2a (0.6 mmol), Pd(MeCN)
3.5 mL in 9:1 ratio) at 120 °C for 24 h.
Isolated yields.
2 2
Cl (5.0 mol%), AgOAc (1.0 mmol), in 1,4-dioxane/DMSO
(
DMSO, dimethyl sulfoxide.
the desired arylated product 3ba in a good 85% yield (entry 1). The variation of the methyl
group on the para- or ortho-positions of the S-phenyl sulfonamide showed a slight
influence on the efficiency of the transformation for 78% of 3ca was isolated successfully
(
entry 2). Other electron-donating groups, such as methoxy- (entry 3) and tert-butyl (entry
4
) which occupied on the para-positions of S-phenyl sulfonamides, provided the desired
products 3da and 3ea in 82 and 79% yields, respectively. S-Halophenyl sulfonamides,
which were exemplified by S-(4-fluorophenyl) sulfonamide (1f for entry 5),
S-(4-chlorophenyl) sulfonamide (1g for entry 6) and S-(4-bromophenyl) sulfonamide
(
(
1h for entry 7), expressed good capabilities in the coupling with sodium phenylsulfinate
2a), for the corresponding products 3fa–3ha were furnished in yields from 72 to 82%.
Decreased yields were generally observed when electron-withdrawing groups were deco-
rated on the phenyl sulfonamides. For instance, S-(4-nitrophenyl) sulfonamide (1i) and
S-(4-trifluorophenyl) sulfonamide (1j) afforded the arylated products 3ia and 3ja in only
6
8 and 76% yields, separately (entries 8 and 9). The compatibilities of S-polyaryl or hetero-
aryl-decorated sulfonamides were also checked in the system and 2-naphthyl sulfonamide
1k for entry 10) and 2-thiophenyl sulfonamide (1l for entry 11) offered an easy access to
(
the arylated products 3ka and 3la in yields of 80 and 72%. Surprisingly, alkyl sulfonamides
like methyl sulfonamide (1m) and ethyl sulfonamide (1n) gave the desired arylated
products 3ma and 3na in yields of 48 and 45% (entries 12 and 13).
Successively, the tolerance of the functional groups of sodium arylsulfinates was also
checked in the system as shown in Table 3. First, sodium p-tolylsulfinate (2b) coupled with
1
a readily, forming the desired molecule 3ab in 85% yield (entry 1). However, change of
the position of the methyl groups on the sodium arylsulfinates affected the yield of the
arylated products slightly for N-(o-methylphenylated)-S-phenyl sulfonamide 3ac was
provided in 78% yield (entry 2). Also, expected N-(p-methoxyphenylated) sulfonamides

1
440
Z. ZHAO ET AL.
a
Table 3. Substrates scope of sodium arylsulfinates.
b
Entry
2
Ar
3
Yield (%)
1
2
3
4
5
6
7
8
9
0
1
2
3
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
4-CH
2-CH
4-CH
3
C
C
6
H
H
4
4
3ab
3ac
3ad
3ae
3af
3ag
3ah
3ai
3aj
3ak
3al
3am
3an
85
78
86
79
81
72
80
70
58
62
80
n.d.
n.d.
3
6
3
6 4
OC H
6 4
4-FC H
4-ClC
2-ClC
4-BrC
2-BrC
6
H
H
4
6
4
6
H
H
4
6
C
4
4-CF
3
6
H
4
1
1
1
1
4-CNC
6
H
4
2-Naphthyl
2-Thiophenyl
CH CH
3
2
a
b
Reaction conditions: 1a (0.5 mmol), 2 (0.6 mmol), Pd(MeCN)
3.5 mL in 9:1 ratio) at 120 °C for 24 h.
Isolated yields.
2 2
Cl (5.0 mol%), AgOAc (1.0 mmol), in 1,4-dioxane/DMSO
(
DMSO, dimethyl sulfoxide.
3
ad were isolated successfully in 86% yield (entry 3). Halogenated phenyl groups were also
well-tolerated in the system for sodium 4-fluorophenyl (entry 4), 4-chlorophenyl (entry 5),
-chlorophenyl (entry 6), 4-bromophenyl (entry 7), 2-bromophenyl (entry 8) sulfinates
2
were compatible in the protocol and the desired products 3ae–3ai were separated in yields
of 70–81% range. Electron-withdrawing groups decorated arylsulfinates were also tested in
the system and N-(4-trifluoromethylphenylated) and N-(4-cyanophenylated) products 3aj
and 3ak were isolated in 58 and 62% yields, respectively (entries 9 and 10). Polyaryl group
like sodium 2-naphthylsulfinate offered the desired 2-naphthylated product 3al in 80%
yield (entry 11). However, heteroaryl group like 2-thiophenyl showed a negative effective
to the arylation protocol, as well as the alkylsulfinate did, for 2-thiophenylation and ethyla-
tion reactions were not observed in the Pa/Ag-mediated system (entries 12 and 13).
Based on the extensive literature explorations, the mechanism of the Pd/Ag-mediated pro-
tocol was proposed, which was illustrated by the reaction between 1a and 2a (Scheme 2).
Firstly, Pd(II)-catalyst coordinated with the substrate 1a, forming the liganded-palladium
intermediate A. Successively, sodium phenylsulfinate (2a) attacked the intermediate A
through the anionic interaction, forming another key intermediate B. Next, the key inter-
mediate B was transformed into another key intermediate C, with a release of a molecular
SO . Then reductive elimination made the formation of final product 3aa with Pd(0), which
2
þ
was reoxided into Pd(II) in the presence of Ag for the completion of a catalytic circle.
Conclusion
In summary, we have successfully developed a general and efficient Pd/Ag-mediated
transformation towards N-arylated sulfonamides with sodium arylsulfinates through a
desulfitative pathway. The transformation enjoyed good functional group compatibility
and high efficiency. The practical and facile methodology offered a promising avenue
towards the compounds of great significance.

SYNTHETIC COMMUNICATIONS®
1441
Scheme 2. Proposed mechanism.
Experimental
Typical synthetic procedure of N-aryl sulfonamides
Under the argon atmosphere, a Schlenk tube (15 mL) equipped with a magnetic bar was
loaded with the sulfonamide 1 (0.5 mmol), sodium arylsulfinates 2 (0.6 mmol, 1.2 equiv.),
Pd(MeCN) Cl (6.5 mg, 5 mol%), and AgOAc (166.9 mg, 1.0 mmol) in one portion. Then,
2
2
the mixture of 1,4-dioxane/DMSO (3.5 mL in a 9:1 ratio) was added to obtain a clear
solution and the reaction mixture was allowed to stir at 120 °C for 24 h. After cooling to
room temperature, the mixture was filtered through a short celite pad and washed with
dichloromethane (15 mL � 3). The filtrate was concentrated and the oily crude product
was purified by column chromatography using silica gel (200–300 mesh) as stationary
phase and a petroleum ether and ethyl acetate (3/1) as eluent to give the N-aryl
sulfonamides 3 in noted yields.
Spectra data of N-aryl sulfonamides 3
N,S-diphenyl sulfonamide (3aa)
1
White solid, mp: 105–107 °C. Yield: 80%. H NMR (400 MHz, CDCl ) δ ¼ 7.81 (d,
3
J ¼ 7.6 Hz, 2H), 7.57 (t, J ¼ 7.3 Hz, 1H), 7.47 (t, J ¼ 7.5 Hz, 2H), 7.29 (d, J ¼ 8.0 Hz,
13
2
H), 7.16 (t, J ¼ 7.4 Hz, 1H), 7.11 (d, J ¼ 7.8 Hz, 2H), 6.81 (br.s, NH) (ppm). C NMR
(
100 MHz, CDCl ) δ ¼ 139.1, 136.4, 133.18, 129.5, 129.2, 127.3, 125.7, 122.0 (ppm). IR
3
(
in KBr): ν ¼ 3257, 2961, 2362, 1727, 1599, 1496, 1463, 1410, 1337, 1264, 1158, 1094,
−
1
1
7
022, 921, 803, 754, 697, 631, 599, 561 cm . MS(EI) m/z (%): 233.0, 168.0, 141.0, 92.0,
þ
7.0, 65.0. HRMS(EI) m/z: [M] Calcd for C H NO S: 233.0510; Found 233.0505.
1
2
11
2
Funding
The authors are grateful for the financial support from the Fundamental Research Funds for the Key
Laboratory of Research and Utilization of Ethnomedicinal Plant Resources of Hunan Province (No.
YYZW2015-7) and the financial support from the Huaihua University Program (No. ZWX2016-11).

1
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Z. ZHAO ET AL.
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