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and 2). By carefully controlling the reaction time, 2g
chemoselectively gave the monoarylated product 1o
only (entry 5). In the presence of one equivalent of
KI, the aryl bromides also gave the desired N-arylat-
ed products in satisfactory yields, but with prolonged
reaction time (entries6, 7 and 8). Under our condi-
tions, substrate 2j constantly yielded a chemoselective
product 1p (entry 8).
In summary, a copper-catalyzed N-arylation of aryl
halidesand azoleswasachieved efficiently in lower
nitrile solvents without any additional ligand, in
which the nitrile actually acted asboth a ligand and a
solvent. We also found that Cu metal exhibited much
higher catalytic ability than cuprousasltsunder our
conditionsand an in situ newly formed “fresh CuI”
was proposed for an explanation. Finally, the first
monodentate nitrile ligand-mediated highly efficient
and practical “ligand-free-like” copper-catalyzed N-
arylation of azoles was established, which featured
with extremely inexpensive and convenient perform-
ances. Further studies to generalize this procedure to
other typesof N-containing substrates are underway.
Experimental Section
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Typical Procedure; Preparation of 1-Phenylpyrazole
(1a)
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A stirred suspension of PhI (2a, 810 mg, 4 mmol), pyrazole
(3a, 41 mg, 6 mmol), Cu(0) powder (51 mg, 0.8 mmol) and
Cs2CO3 (2.60 g, 8 mmol) in MeCN wasrefluxed for 12 h
(monitored by TLC) under the nitrogen. After it wascooled
to room temperature, the solid was filtered off and MeCN
wasevaporated. The reisdue waspurified by chromatogra-
phy (silica gel, 40% CH2Cl2 in PE) to give desired product
1a; yield: 547 mg (95%).
A similar procedure was used for the preparation of ary-
lated products 1a–p (see Table 3 and Table 4).
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Supporting Information
Experiments, characterization, H and 13C NMR spectra for
1
products 1a–p, MS and 13C DEPT spectra for new product
1f, preparation procedure of the Cu1+ sample from the reac-
tion residue of entry 10 in Table 1 and its XPS and AES
spectra are available as Supporting Information.
Acknowledgements
This work was supported by NNSF of China (20672066) and
SRFDP (20050003032).
References
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