346
Y.-H. Liu et al. / Tetrahedron Letters 50 (2009) 343–346
our own observation, a major side-reaction in the reaction might
be debromination of aryl bromides (i.e., the reduction of aryl bro-
mides to the corresponding arene). Additionally, in some cases,
particularly for electron-rich bromoarene substrates, the self-cou-
pling to produce diaryls was a detectable side-reaction.
NMR and MS, and compared to authentic samples or the literature
data.
Acknowledgments
In summary, a simple and efficient CuI/glyoxal bis(phenylhyd-
razone) catalytic system has been developed for the aromatic C–
O coupling reaction. Under mild reaction conditions, diarylether
could be obtained in good to excellent yields from cheaper starting
materials, inexpensive reagents and easily handled reaction sol-
vents. This protocol provides a useful alternative and complement
to the corresponding copper and palladium processes for diaryl-
ether synthesis.
General procedure for the CuI-catalyzed O-arylation of phenols
with aryl bromides: Under N2 atmosphere, a 100-mL three-necked
flask was charged with phenol (1 mmol), potassium phosphate
(2 mmol), hydrazone ligand L1 (10 mol % with respect to phenol),
CuI (10 mol % with respect to phenol), aryl bromide (1.5 mmol),
and the dried CH3CN (1 mL). Care was taken to make sure the con-
tents were well stirred. The reaction mixture was then heated in an
oil bath of 60 or 80 °C during times that are indicated in Table 2.
The reaction mixture was cooled to room temperature, mixed with
15 mL of diethyl ether, and filtered to remove any insoluble resi-
dues. Solvents were removed under reduced pressure, and the res-
idue purified by column chromatography on silica gel (60–90 °C
petroleum ether) to obtain the analytically pure product in the iso-
lated yields indicated in Table 2. All diarylether products in this
Letter are known compounds, and are partly characterized by 1H
The authors thank National Natural Science Foundation of
China (Project Nos. 20672116 and 20872142) for financial support
of this work.
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