The electron ionization spectra of seven diexo norbornane- and norbornene-fused six- and seven-membered heterocycles containing O and N in positions 1 and 3 are reported. Molecular ions of norbornane-fused oxazines, especially the 2-anilino derivative, underwent retro-Diels-Alder fragmentation leading to a cleavage of the heterocyclic ring whereas, in norbornene-fused compounds, two concurrent retro-Diels-Alder fragmentations occurred. Fragmentation patterns of norbornane-fused oxazin-2-ones(or -thiones) are closely related to each other and, in some cases, provide evidence for the presence of minor amounts of the ionized open-chain tautomers in the gas phase. The ionized molecular ions of the 2-anilino derivatives appear to exist as mixtures of 2-phenylimino and 2-anilino isomers with exo- and endocyclic C = N bonds, respectively.
|Number of pages||4|
|Journal||Rapid Communications in Mass Spectrometry|
|Publication status||Published - Jan 1 1997|
ASJC Scopus subject areas
- Analytical Chemistry
- Organic Chemistry