An Efficient Base-Free N-Arylation of Imidazoles
and Amines with Arylboronic Acids Using
Copper-Exchanged Fluorapatite
SCHEME 1
,
†
†
M. Lakshmi Kantam,* Gopaldasu T. Venkanna,
†
†
Chidara Sridhar, Bojja Sreedhar, and
Boyapati M. Choudary‡
an efficient approach to N-arylimidazoles via Cu(OAc)2-
Inorganic and Physical Chemistry DiVision, Indian Institute of
Chemical Technology, Hyderabad 500 007, India, and Ogene
Systems PVt. Ltd., 11-6-56, GSR Estates, Moosapet, Hyderabad,
India
mediated coupling of imidazoles with readily available arylbo-
6
ronic acids.
Later, Collman and co-workers reported using Cu(II) com-
plexes with nitrogen-chelating bidentate ligands in the coupling
7
of imidazoles at room temperature. Very recently, Xie and co-
workers have shown the simple copper salt catalyzed coupling
of imidazoles with arylboronic acids in protic solvent without
ReceiVed July 6, 2006
8
any base. The development of mild and cost-effective catalytic
procedures for N-arylation of imidazoles and amines still
9
remains an active research area. Recently, calcium hydroxya-
patite has been used as a heterogeneous support for transition
metals, and the supported hydroxyapatite is used for organic
1
0
transformations. In this direction, we recently performed an
efficient N-arylation of imidazoles and other heterocycles with
chloro- and fluoroarenes using basic copper apatite catalysts.11
Herein, we report the facile N-arylation of imidazoles and
amines catalyzed by heterogeneous basic copper fluorapatite
(CuFAP) (Scheme 1) at room temperature. Various arylboronic
acids were examined for the synthesis of N-arylimidazoles and
N-arylamines.
N-Arylation of imidazoles and amines with arylboronic acids
was accomplished with copper-exchanged fluorapatite (Cu-
FAP) in methanol at room temperature. The products
N-arylimidazoles and N-arylamines were isolated in good
to excellent yields. A variety of arylboronic acids were
converted to the corresponding N-arylimidazoles and N-
arylamines, demonstrating the versatility of the reaction.
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out to ensure useful organic transformations. The synthesis of
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2
structural units in biologically active inhibitors. The most
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59.
straightforward route to N-arylimidazoles involves the direct
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(
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(
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†
Indian Institute of Chemical Technology.
Ogene Systems.
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‡
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(
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10.1021/jo0614036 CCC: $33.50 © 2006 American Chemical Society
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J. Org. Chem. 2006, 71, 9522-9524
Published on Web 11/16/2006