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Communication | Special issue | Vol 40, No. 2, 1995, pp.531-537
Published online, 1st January, 1970
DOI: 10.3987/COM-94-S77
Reactions of Azapyrylium Ions with Nucleophiles: From Crazy products to a Novel Pyridine Synthesis

Kai Homann, Reinhold Zimmer, and Hans-Ulrich Reissig

*Institut of Organic Chemistry, Technical University Dresden, D-01062 Dresden, Germany

Abstract

Reaction of an azapyrylium ion as generated from a 6H-1,2-oxazine provided a β-azidoaldehyde by subsequent substitution, [3,3] sigmatropic rearrangement, and retro-Diels-Alder reaction. With moderately electron-rich alkynes azapyrylium ions react in a Diels-Alder reaction with inverse electron demand, and after fragmentation of a formyl cation pyridine derivatives are formed. Mechanism, scope and limitations of this novel pyridine synthesis are discussed.