The 70 eV mass spectra of 4β‐phenyl‐substituted cyclopentane‐ and cyclohexane cis‐fused 1,3‐oxazin‐2(3H)‐ones, the two related 2‐thiones, 6,7‐cis‐trimethylene‐5β‐phenyl‐1,4‐oxazepin‐3(4H)‐one and its 2β‐methyl derivative were recorded and their fragmentations examined by means of metastable ion analysis, collision induced dissociation technique and exact mass measurement. The fragmentation patterns of the 1,3‐oxazin‐2(3H)‐ones were relatively simple: the favored formation of cycloalkene ions implied that a considerable proportion of the molecular ions might possess an enol structure. Changes in the size of the fused cycloalkane ring had little or no effect on the fragmentations. Instead, small changes in the heterocyclic part of the molecule caused remarkable effects on the fragmentation behavior. Compared to 1,3‐oxazin‐2(3H)‐ones studied, both 1,3‐oxazine‐2(3H)‐thiones and 1,4‐oxazepin‐3(4H)‐ones showed much more complicated fragmentation patterns.
ASJC Scopus subject areas
- Organic Chemistry