Effects of N-substitution on the fragmentations of some cyclohexene-fused 2-N-phenyliminoperhydro-3,1-oxazines and related thiazines

Pirjo Vainiotalo, Tuula Partanen, Ferenc Fülöp, Gábor Bernáth, Kalevi Pihlaja

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Six cyclohexene-fused 2-N-phenyliminoperhydro-3,1-oxazines and four related thiazines were prepared and their mass spectrometric behavior was studied by means of metastable ion analysis and exact mass measurement. In most of the fragmentations, extensive rearrangements took place. The decompositions through the retro-Diels-Alder reaction initiated by the double bond dominated in the case of the unsubstituted compounds. The effect of the double bond, however, was greatly outweighed by the effect of the substituent on the ring nitrogen atom. In comparison with the unsubstituted compounds, both electron-releasing (methyl) and electron-withdrawing (benzyl) substituents increased the contribution of the ring cleavage reactions in the heterocyclic part of the molecule; in the case of the benzyl group the loss of the substituent also became important. For isomeric compounds, the relative peak intensities were so different that such compounds were easy to differentiate.

Original languageEnglish
Pages (from-to)125-129
Number of pages5
JournalJournal of the American Society for Mass Spectrometry
Issue number2
Publication statusPublished - Apr 1991


ASJC Scopus subject areas

  • Structural Biology
  • Spectroscopy

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