ORGANIC
LETTERS
2011
Vol. 13, No. 7
1726–1729
The Coupling of Arylboronic Acids with
Nitroarenes Catalyzed by Rhodium
Xingwang Zheng, Jinchang Ding, Jiuxi Chen,* Wenxiao Gao, Miaochang Liu, and
Huayue Wu*
College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325035,
P. R. China
jiuxichen@wzu.edu.cn; huayuewu@wzu.edu.cn
Received January 26, 2011
ABSTRACT
The coupling of arylboronic acids with electron-deficient nitroarenes was realized for the first time by using a rhodium(I) catalyst under an air
atmosphere, achieving unsymmetrical diaryl ethers with yields ranging from poor to good. From a deuterium labeling experiment, the oxygen
atom is derived from ambient water. The efficiency of this reaction was demonstrated by its compatibility with fluoro, bromo, chloro, and
trifluoromethyl groups.
Diaryl ethers constitute an important building block for
the synthesis of natural products, and polymer science and
pharmacologically activecompounds.1 Common synthetic
routes for the preparation of these compounds involve an
Ullmann coupling reaction of aryl halides and phenols
with copper in the form of a metal salt.2 These methods,
which suffer from drawbacks as a result of limited applica-
tion, use copper in stoichiometric amounts. Later, many
improved methods have been reported for the synthesis of
symmetrical or unsymmetrical diaryl ethers in the presence
of copper3 or palladium4 catalytic systems that enable the
Ullmann coupling reaction. To the best of our knowledge,
only three examples have been described in which aryl
halides are not coupled to oxygen via a phenol but via an
inorganic oxygen source (K3PO4/H2O,5a KOH,5b or
CsOH5c) to afford diaryl ethers.5 By far, transition-me-
tal-catalyzed Ullmann coupling reactions, which generally
employ aryl halides and organometallics as coupling part-
ners, have served as the most common methods for con-
structing biaryl ether unions. However, several problems
still remain, such as a high catalyst loading and elevated
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r
10.1021/ol200251x
Published on Web 03/04/2011
2011 American Chemical Society