Pd(OAc)2/PPh3-catalyzed desulfonylative homocoupling of arylsulfonyl chlorides

Article abstract of DOI:10.1002/cjoc.201400868

The Pd-catalyzed homodimerization with respect to arylsulfonyl chlorides as an efficient method for the synthesis of biaryls has been developed. This desulfonylative reaction which was performed at reflux in 1,4-dioxane for 4 h under air afforded the desired products in good to excellent yields. The Pd(OAc)₂/PPh₃-catalyzed desulfonylative homodimerization of arenesulfonyl chlorides as an efficient method for the synthesis of biaryls was described. The corresponding products were obtained in good to excellent yields.

Full text of DOI:10.1002/cjoc.201400868

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DOI: 10.1002/cjoc.201400868
Pd(OAc) /PPh -Catalyzed Desulfonylative Homocoupling of
2
3
Arylsulfonyl Chlorides
†
,a
†,a
a
,a
,a,b
Qiao Zhao, Liangshun Chen, Hongyue Lang, Shengying Wu,* and Limin Wang*
a
Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology,
Shanghai 200237, China
b
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, China
The Pd-catalyzed homodimerization with respect to arylsulfonyl chlorides as an efficient method for the synthe-
sis of biaryls has been developed. This desulfonylative reaction which was performed at reflux in 1,4-dioxane for 4
h under air afforded the desired products in good to excellent yields.
Keywords biaryls, arylsulfonyl chlorides, desulfonylative, palladium-catalyzed
Introduction
by Tanaka and co-workers with hexamethyldisilane be-
ing used. However, relatively high temperature (140 ℃)
Biaryls have attracted considerable attention recently
owing to their extensive applications in the areas of or-
[15b]
2 3 3
as well as Pd dba •CHCl catalyst was required.
Therefore, a better synthetic approach for coupling of
arylsulfonyl chlorides was desired. Herein, we reported
a Pd(OAc) /PPh -catalyzed homocoupling reaction,
2 3
which was conducted at reflux in 1,4-dioxane for 4 h
under air.
[
1]
[2]
ganometallic catalysis, asymmetric synthesis, func-
[
3]
[4]
tional materials, supramolecular chemistry as well
[
5]
as bioactive natural products, pharmaceuticals and
[
6]
agrochemicals. Coupling reactions were one of the
most studied and applied areas of synthetic methodol-
ogy. Typical procedures for the preparation of dimeric
[7]
Experimental
compounds began with the Ullmann coupling more
than 100 years ago and evolved into one of the most
investigative carbon-carbon bond forming reactions af-
To a 25-mL Schlenk tube equipped with a magnetic
bar was added CuI (0.5 mmol, 94.9 mg), Ag
mmol, 137.9 mg), NaHCO (0.5 mmol, 42.0 mg),
Pd(OAc) (0.025 mmol, 5.6 mg), PPh (0.05 mmol, 13.1
mg), and arylsulfonyl chlorides (0.5 mmol). Then
,4-dioxane (2 mL) was added in the tube and the reac-
2 3
CO (0.5
[8]
terwards. Inspired by the homocoupling reaction of
3
[
8b-8f]
organohalides,
a number of researches were con-
2
3
ducted in the synthesis of biaryls, involving self-cou-
[
9]
pling of arylmetal reagents, dimerization of arylbo-
1
[
10]
ronic acids,
dehydrogenative homocoupled reaction
tion mixture was stirred at reflux for about 4 h. After the
starting material disappeared monitored by TLC, the
reaction mixture was filtered and concentrated to dry-
ness. The crude material was purified by flash chroma-
tography on silica gel using a mixture of ethyl acetate
and hexane as eluent to give the desired homocoupling
products.
[
11]
of arenes, decarboxylative homocoupling of arylcar-
boxylic acid or decarbonylative homodimerization of
[12]
aromatic aldehydes as well as desulfitative dimeriza-
tion of sodium arylsulfinates.
Arenesulfonyl chlorides constitute a large family of
inexpensive and widely available organic compounds
that have been used for more than a century in materials
[
13]
[
14]
science and medicinal chemistry; however, self-cou-
pling reaction regarding to arenesulfonyl chlorides was
less investigated. Miura and co-workers offered the first
attempt in transition metal-catalyzed homocoupling re-
action of arenesulfonyl chlorides involving desulfonyla-
tion, but rigorous reaction condition restricted its appli-
Results and Discussion
From starting point of view, p-toluenesulfonyl chlo-
ride, an inexpensive and readily available starting mate-
rial, was chosen as a model substrate to screen suitable
reaction conditions. Based on previous coupling reac-
[15a]
[15,16]
cation.
Subsequently, the work was explored further
tion reports,
we initiated the preliminary reaction
*
E-mail: wanglimin@ecust.edu.cn, wsy1986wsy@126.com; Tel.: 0086-021-64253881; Fax: 0086-021-64253881
Received December 18, 2014; accepted January 28, 2015; published online March 30, 2015.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201400868 or from the author.
These authors contributed equally to this work.
†
Chin. J. Chem. 2015, 33, 535—538
© 2015 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
535

Zhao et al.
COMMUNICATION
condition study (see Table S1). It was found that the
Table 2 Screening of other reaction conditions in homocou-
pling of p-toluenesulfonyl chloride
a
reaction was catalyzed by Pd(OAc)
PPh and promoted by Ag CO and CuI in the presence
of NaHCO , affording the desired product 2a in 90%
2
with the ligand of
3
2
3
Pd(OAc)2 (5 mol%), PPh (10 mol%)
3
3
SO Cl
2
Oxidant, Cu, Base, Solvent, reflux
yield (see Table S1, Entry 6). Encouraged by this result,
a systematic study was conducted to further enhance
yield. Firstly, various common ligands and palladium
catalysts were examined as summarized in Table 1. Af-
ter screening ligands carefully (Table 1, Entries 1－8),
1a
2a
b
Entry Oxidant Copper salt Base
Solvent
NaHCO3 1,4-dioxane 90
NaHCO 1,4-dioxane 76
Yield /%
PPh
and high-yield point of view. Furthermore, palladium
catalysts such as PdCl , PdCl (PPh , Pd(PPh
Pd (dba) and Pd dba •CHCl failed to improve yield of
3
was a very suitable ligand from both the economic
1
2
3
4
5
6
7
8
9
1
Ag CO CuI
2
3
2
2
3
)
2
3 4
) ,
Ag
O
CuI
2
3
2
2
2
3
3
AgOAc CuI
AgNO3 CuI
NaHCO3 1,4-dioxane 45
NaHCO3 1,4-dioxane 43
corresponding product (Table 1, Entries 9－13).
BQ
CuI
CuI
NaHCO
3
3
1,4-dioxane 36
1,4-dioxane 67
Table 1 Screening of palladium catalysts in homocoupling of
a
p-toluenesulfonyl chloride
K S O
2 2 8
NaHCO
Ag CO CuBr
NaHCO3 1,4-dioxane 82
NaHCO3 1,4-dioxane 88
NaHCO3 1,4-dioxane 72
Pd, Ligand, CuI, Ag CO
2
3
2
3
SO Cl
2
Ag CO CuCl
2
3
NaHCO , 1,4-dioxane
3
reflux
Ag CO CuTC
2 3
1a
2a
0
Ag CO CuI
KH PO 1,4-dioxane 75
b
2
3
2
4
Entry Cat./mol%
Ligand/mol%
Yield /%
1
1
Ag
2
CO
3
CuI
K
3
PO
4
1,4-dioxane 67
1,4-dioxane 74
1,4-dioxane 48
1,4-dioxane 65
1,4-dioxane 37
1
2
3
4
5
6
7
8
9
1
Pd(OAc)
Pd(OAc)
2
2
(5)
(5)
PPh
3
(10)
(10)
90
36
43
81
90
92
83
12
13
14
15
16
17
18
19
20
1
Ag CO CuI
Na CO
2
3
2
3
PCy
3
Ag CO CuI
Cs CO
2
3
2
3
t
Pd(OAc) (5)
P( Bu) •HBF (10)
2
3
4
Ag CO CuI
Et N
2
3
3
Pd(OAc) (5)
dppb (10)
2
Ag CO CuI
NaOH
2
3
Pd(OAc)
2
(5)
dppp (10)
dppe (10)
dppm (10)
Ag CO CuI
NaHCO3 DMF
NaHCO Toluene
70
2
3
Pd(OAc) (5)
2
Ag
2
CO
3
CuI
3
36
Pd(OAc) (5)
2
Ag CO CuI
NaHCO3 DCE
34
2
3
Pd(OAc) (5)
1,10-phenanthroline (10) 56
2
Ag CO CuI
NaHCO3 CH CN
67
2
3
3
PdCl (5)
PPh (10)
55
80
74
54
85
2
3
i
Ag CO CuI
NaHCO3 PrOH
58
85
2
3
0
PdCl (PPh ) (5)
—
2
3 2
2
Ag CO CuI
NaHCO3 THF
2
3
11
Pd(PPh
3
)
4
(5)
—
—
a
Reaction conditions: 1a (0.5 mmol), Pd(OAc)
2
(5 mol%), PPh
3
12
Pd (dba) (5)
2 2
(
10 mol%), oxidant (0.5 mmol), copper salt (0.5 mmol), base (0.5
13
Pd dba •CHCl (5) —
2 3 3
mmol), solvent (2 mL), reflux for 4 h under air. BQ＝benzo-
a
b
Reaction conditions: 1a (0.5 mmol), Pd catalyst (5 mol%),
quinone. Yields of isolated products.
ligand (10 mol%), CuI (0.5 mmol), Ag CO (0.5 mmol), NaHCO
3
2
3
b
(
0.5 mmol), 1,4-dioxane (2 mL), reflux for 4 h under air. Yields
sent method, we applied the optimum reaction condi-
tions to a variety of arylsulfonyl chlorides (Table 3). In
general, the reaction proved successful for arenesulfonyl
chlorides with electron-poor or electron-neutral groups
on the phenyl rings, affording the corresponding prod-
ucts in good to excellent yields, whereas symmetrical
biaryls bearing electron-rich groups were obtained in
slightly lower yields. For example, products with meth-
oxyl, acylamino substituents at the aryl moiety were
isolated in 64% and 50% yields, respectively (2b, 2c).
By contrast, 4,4'-dimethylbiphenyl and biphenyl were
observed with distinct increased yields (90% and 93%,
2a and 2d). Substrates with halogen, trifluoromethyl,
trifluoromethoxy-substituents at the para-position of the
of isolated products.
Next, evaluation with other oxidants identified
CO as the most efficient one (Table 2, Entries 1－
2 3
Ag
). Various copper salts were sequentially investigated
Table 2, Entries 7－9) because negligible product was
6
(
detected in the absence of copper salt (see Table S1,
Entry 3). To our delight, all copper salts delivered fair
yields of 72%－88%. In addition, further modification
of the reaction condition revealed that NaHCO
best base compared with KH PO , K PO , Na
Cs CO , Et N and NaOH (Table 2, Entries 10－15);
,4-dioxane was found to be a more suitable solvent
Table 1, Entries 1, 16－21). However, when the reac-
3
was the
2
4
3
4
2 3
CO ,
2
3
3
1
(
3 3
benzene ring (F, Cl, Br, CF , OCF ) furnished desired
tion was conducted at lower temperature, the isolated
yield for symmetric biaryl was obviously decreased.
To demonstrate the efficiency and scope of the pre-
biaryls in good to excellent yields (80%－96%, 2f, 2g,
2h, 2k, 2l), especially for bromo-substituent (96%).
Apparently, the ortho- substituents gave a relatively
536
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© 2015 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2015, 33, 535—538

Pd(OAc)
2
/PPh
3
-Catalyzed Desulfonylative Homocoupling of Arylsulfonyl Chlorides
a
Table 3 The homocoupling scope of arylsulfonyl chlorides
R
R
Pd(OAc) , PPh , Ag CO , CuI, NaHCO
3
2
3
2
3
SO Cl
2
R
1,4-dioxane, reflux, 4 h
1
2
HN
O
NH
O
H CO
OCH3
3
2
a 90%
2
b 64%
2c 50%
2f 80%
F
F
2d 93%
2
e 34%
Br
Cl
Cl
Br
Br
Br
2i 81% b
2g 86%
2h 96%
Br
F3CO
OCF3
F C
CF3
3
Br
j 65%
b
2
2l 86%
2k 93%
S
S
2o 72% b
2m 57%
2n 60%
a
Reaction conditions: 1 (0.5 mmol), Pd(OAc)
,4-dioxane (2 mL), reflux for 4 h under air. Ag O (0.5 mmol) was employed as oxidant.
2
(5 mol%), PPh
3
(10 mol%), CuI (0.5 mmol), Ag
2
3 3
CO (0.5 mmol), NaHCO (0.5 mmol),
b
1
2
lower product yield than the para- or meta- ones due to
steric hindrance (2e, 2h, 2i, 2j). It is noteworthy that the
starting materials with naphthyl and heteroaryl struc-
tures delivered the desired products in moderate to good
yields (2m, 2n, 2o).
by Ag(I) regenerats the catalytically active Pd(II) spe-
cies to finish the catalytic cycle.
[
20]
Conclusions
In conclusion, a new method allowing for the syn-
thesis of various symmetrical biaryl units via homocou-
pling of arylsulfonyl chlorides has been developed. Ad-
ditionally, high-yield biaryls, which are core motifs and
important building blocks in the construction of com-
plex molecules, are achieved. Combined with other
coupling reactions, this approach could be applied in the
synthesis of pharmaceuticals, functional materials, and
coordination compounds.
A plausible mechanism is outlined in Scheme 1. The
first step of the reaction is insertion of the copper iodide
[
17]
into the S－Cl bond, and then CuI/Pd(II)L
n
exchange
Subsequently,
group is lost from Pd(II) intermediate promoted by
[18]
occurs to form the Pd(II) species c.
SO
the thermal conditions, and intermediate d dispropor-
tionation to Pd(II) species e and diarylpalladium f which
undergoes reductive elimination to generate the product
2
[19]
[
15b]
g and Pd(0) species h.
Finally reoxidation of Pd(0)
Scheme 1 Plausible mechanism
Acknowledgement
Ag(0)
Ag(I)
The work was supported by the National Natural
Science Foundation of China (Nos. 21272069,
Pd(II)Ln
CuI
ArSO CuICl
ArSO Cl
2
2
2
0672035), the Fundamental Research Funds for the
e
Pd(0)Ln
b
a
Central Universities, and the Key Laboratory of Organ-
ofluorine Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences.
Ar-Ar
g
h
(
ArSO )PdClL
2 n
Ar PdL
2
n
c
f
References
ArPdClLn
SO2
d
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Chin. J. Chem. 2015, 33, 535—538
© 2015SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
537

Zhao et al.
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