Angewandte
Communications
Chemie
Cross-Coupling
Cross-Coupling of Sodium Sulfinates with Aryl, Heteroaryl, and Vinyl
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Abstract: An efficient photoredox/nickel catalyzed sulfonyla-
tion reaction of aryl, heteroaryl, and vinyl halides has been
achieved for the first time. This newly developed sulfonylation
protocol provides a versatile method for the synthesis of
diverse aromatic sulfones at room temperature and shows
excellent functional group tolerance. The electrophilic cou-
pling partners are not limited to aryl, heteroaryl, and vinyl
bromides and iodides, but also includes less reactive aryl
chlorides as suitable substrates for this transformation.
(
aryl amines, indolines, triarylphosphine oxides, and thioethers
[10]
by different C–heteroatom bond formations, thus confirm-
ing the enormous potential of dual photoredox/metal catalysis
not only in the improvement of known reactions but also in
the discovery of novel catalytic protocols.
As part of our continuing studies in the area of photo-
redox and transition-metal catalysis, we herein report the first
photoredox/metal catalyzed cross-coupling of sulfinate salts
with aryl, heteroaryl, and vinyl halides at room temperature
Scheme 1). This protocol provides a versatile approach to
aromatic sulfones with a broad substrate scope and excellent
functional group tolerance. Notably, less-reactive aryl chlor-
ides could also be converted into the corresponding sulfones.
S
ulfones are highly important organic molecules because of
their versatile synthetic utility in organic synthesis as well as
the widespread presence of sulfonyl groups in pharmaceut-
icals, agrochemicals, biologically active compounds, and
[
1,2]
polymer materials.
pounds are synthesized by oxidation of sulfides, sulfonyla-
tion of arenes, or palladium or copper-catalyzed arylation of
Conventionally, these valuable com-
[3]
[
4]
[
5]
sulfinate salts. These methods suffer from significant draw-
backs, including the use of foul-smelling thiols and strong
oxidizing reagents, harsh acidic treatments, and high reaction
temperatures, which can limit the functional group tolerance
and substrate scope. Alternatively, SO surrogates such as
Scheme 1. Photoredox/nickel catalyzed synthesis of aromatic sulfones
2
DABCO·(SO ) and K S O have been applied to the syn-
at room temperature.
2
2
2
2
5
thesis of sulfones by fixation of sulfur dioxide to generate
sulfinate anion intermediates which can then undergo (SO )-
2
[
6]
arylation/alkylation.
Our study commenced with 4-bromobenzonitrile (1a) and
sodium 4-methylbenzenesulfinate (2a) as model substrates.
Initially, the ratio of 1a and 2a was set as 1:1 with PC1 as the
In recent years, increasing attention has been devoted to
the field of dual photoredox and transition-metal catalysis,
and useful transformations have been achieved by this
photocatalyst, NiCl ·glyme as the nickel source, dtbbpy as the
2
[7–10]
strategy.
In particular, photoredox/nickel catalysis
ligand, and DMF as the solvent, which afforded the corre-
sponding sulfone 3a in 43% yield only (Table 1, entry 1). The
use of K CO as a base decreased the yield dramatically
proved attractive because of the unique catalytic properties
[
8–10]
of nickel catalysts.
Pioneering works in this field focused
2
3
3
2
on C(sp )ÀC(sp ) bond formations by coupling aryl halides
(entry 2). The yield of 3a increased to 70% when two
equivalents of 2a were employed (entry 3). After screening
several commonly used photocatalysts, including an organic
dye (entries 4–8), the Ir complex PC4 was found to give the
best result (entry 6). A series of nickel catalysts such as
NiBr ·O(CH CH OCH ) , Ni(OAc) ·4H O, Ni(acac) , NiCl ,
3
with benzylic trifluoroborates and a-carboxy sp -carbon
[
8]
atoms. Since then, progress has been made in the field of
[
9]
CÀC bond formation. Moreover, this elegant strategy has
also been applied to the synthesis of aryl ethers, aryl esters,
2
2
2
3
2
2
2
2
2
[
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[
*] H. Yue, C. Zhu, Prof. Dr. M. Rueping
Institute of Organic Chemistry, RWTH Aachen University
Landoltweg 1, 52074 Aachen (Germany)
and Ni(cod)2 were subsequently examined, however no
further improvement was observed (entries 9–13). The use
of DMF as a solvent was found to be crucial for this
transformation. When other solvents were utilized, the
sulfonylation reaction either did not take place or occurred
in low yield (entries 14–16). Performing the reaction under
undegassed conditions provided the product in 18% yield,
thus indicating the importance of avoiding the presence of
molecular oxygen in the reaction (entry 17). Control experi-
ments confirmed the role of the photocatalyst, light, and
nickel catalyst for the reaction (entries 18 and 19). In
addition, a CFLamp was tested and proved suitable for this
E-mail: magnus.rueping@rwth-aachen.de
Prof. Dr. M. Rueping
King Abdullah University of Science and Technology (KAUST), KAUST
Catalysis Center (KCC)
Thuwal, 23955-6900 (Saudi Arabia)
E-mail: Magnus.Rueping@Kaust.edu.sa
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[
] These authors contributed equally to this work.
Supporting information and the ORCID identification number(s) for
Angew. Chem. Int. Ed. 2018, 57, 1371 –1375
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1371