J. T. Myers, J. M. Hanna Jr. / Tetrahedron Letters 53 (2012) 612–615
615
Summary
In summary, we have shown that a variety of novel benzisoxaz-
olo[2,3-a]pyridinium tetrafluoroborates (1) can be conveniently
prepared from pyridine N-oxide, which may facilitate investiga-
tions into the biological activity of these compounds. In doing so,
we have also expanded the scope of the palladium-catalyzed direct
arylation of pyridine N-oxide to include 2-bromoacetanilides as
coupling partners to give the previously unknown 2-(2-acetamido-
aryl)pyridine N-oxides (4). In addition, we have shown that the di-
References and notes
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20. To our knowledge, this is the first example of the application of microwave
heating to the direct arylation of pyridine N-oxide, although Kappe et al. have
recently reported the microwave-promoted direct arylation of electron-rich
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rect arylation gives
4 in synthetically useful yields using
microwave heating without any special water- or oxygen-exclu-
sion techniques. Further application of this strategy to the synthe-
sis of other novel heterocyclic systems is being investigated in our
laboratory.
Acknowledgments
The project described was supported by NIH Grant Number P20
RR-016461 from the National Center for Research Resources. Addi-
tional support was provided by the Winthrop University Depart-
ment of Chemistry, Physics, and Geology and the Winthrop
University Research Council.
Supplementary data
Supplementary data (experimental procedures, detailed prod-
uct characterization data, compound spectra) associated with this
article can be found, in the online version, at doi:10.1016/
21. Although the reasons for this are unclear, microwave heating has been
reported to give better yields, reduce side reactions and improve
reproducibility in certain cases. For a review see 21 Kappe, C. O. Angew.
Chem., Int. Ed. 2004, 43, 6250.