ORGANIC
LETTERS
2011
Vol. 13, No. 9
2310–2313
Synthesis of Unsymmetrically Substituted
Bipyridines by Palladium-Catalyzed Direct
CꢀH Arylation of Pyridine N-Oxides
Sasa Duric and C. Christoph Tzschucke*
€
Freie Universitat Berlin, Institut fur Chemie und Biochemie, Takustrasse 3, 14195 Berlin,
€
Germany
Received March 2, 2011
ABSTRACT
Substituted bipyridines were efficiently prepared by direct coupling between pyridine N-oxides and halopyridines using a palladium
catalyst. Pyridine N-oxides with electron-withdrawing substitutents gave the best yields. This method allows the convenient preparation of
2,20-, 2,30-, and 2,40-bipyridines which are useful as functionalized ligands for metal complexes or as building blocks for supramolecular
architectures.
Bipyridines constitute an important class of heterocycles
with numerous applications. Particularly, 2,20-bipyridines
have found widespread use as chelating ligands for a wide
range of different metal ions,1 and their complexes have
been employed as catalysts,2 as photosensitizers,3 in light-
emitting diodes,4 as fluorescent dyes,5 and as building
blocks for supramolecular architectures.6 Bipyridine mo-
tifs are also present in natural products with antibiotic and
cytotoxic activities.7 Due to their importance, numerous
different synthetic approaches to bipyridines have been
described.8 Among these, transition-metal-catalyzed
cross-coupling reactions between halopyridines and pyr-
idyl organometallics are the most general and flexible
ones.9 However, pyridyl organometallics usually need
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r
10.1021/ol200565u
Published on Web 04/01/2011
2011 American Chemical Society