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1
Investigation into the Synthesis of
Isoxazolo2,3-apyridinium Tosylates from
Pyridine N-Oxides and Alkynyliodonium Tosylates
Dr. Michael W. Justik and Samantha L.
KristufekThe School of Science, Penn State Erie,
The Behrend College, Erie, PA 16563-0203
Abstract In previous investigations soft'
nucleophiles such as arene oxides, arene
thiolates and toluenesulfonanilides have been
observed to attack alkynyl iodinium salts in a
Michael-type reaction to generate alkylidine
carbene intermediates which subsequently undergo
a 1,5-intramolecular C-H insertion reaction to
afford a benzo-fused heterocyclic product. In
the presented research phenyl(phenylethynyl)iodoni
um tosylate was treated with a soft' nucleophile
in the form of substituted pyridine N-oxides in
an attempt to prepare isoxazolo2,3-apyridinium
salts, heterocycles which contain cationic
nitrogen bridging two aromatic rings. It was
discovered that the major products of these
reactions areMIcm rather (Z)-2-phenyl-2-(pyridiny
l)oxy-1-ethen-1-ylphenyliodonium ditosylates
derived from an apparent additon-protonation
sequence. These compounds are the first known
examples of a pyridinyl enol ether. .
Alkynyliodonium Salt Chemistry
Initial Survey

• React with nucleophiles at two different
  positions
• Several reaction pathways have been observed
  following soft nucleophilic addition

Reaction of 4-picoline N-oxide with
phenyl(phenylethynyl)iodonium tosylate
Synthesis of a Frozen Intermediate

Conclusions

• We have demonstrated the first isolable adduct of
  pyridine N-oxides with organoiodinanesthey are
  the first examples of pyridinyl enol ethers it
  may be possible to preserve this structural
  moiety in subsequent reactions
• Unlike other aryl-Nu nucleophiles, pyridine
  N-oxides prefer the addition-protonation pathway
  in their reaction with alkynyliodonium salts as
  opposed to 1,5-insertion or 1,2-rearrangement
  pathways
• Isoxazolo2,3-apyridinium salts may be within
  the reaction mixtures albeit in low yield
  affording the opportunity to optimize the
  reaction conditions toward their formation

J. Org. Chem., 2000, 8659.
J. Org. Chem., 1996, 5440.
Acknowledgements The author would like to thank
Penn State Erie, The Behrend College for new
faculty start-up funds. The Bruker Avance 400
NMR Spectrometer used in this work was made
possible by gifts from the Thomas Lord Charitable
Trust and The Orris C. Hirtzel and Beatrice Dewey
Hirtzel Memorial Foundation.