SATURATED HETEROCYCLES .232. ELECTRON IONIZATION MASS-SPECTROMETRY OFSOME SUBSTITUTED, STEREOISOMERIC, PARTLY SATURATED 1,3-BENZOXAZINO-1,3-BENZOXAZINES AND 3,1-BENZOXAZINO-1,3-BENZOXAZINES

The electron ionization mass spectra of five substituted, partly satur ated 3,1-benzoxazino-1,3-benzoxazines and four substituted 1,3-benzoxa zino-1,3-benzoxazines were measured and analysed. The fragmentation pa thways were elucidated by metastable ion analysis and exact mass measu rement. Although the principal fragmentations were similar for all the se compounds, there was an important difference between the two groups as concerns the fragmentation routes. Both routes led to the same fra gment ion, but in different ways depending on the ring structure. On t he basis of the different fragmentation mechanisms, the 3,1-benzoxazin o-1,3-benzoxazines and the 1,3-benzoxazino-1,3-benzoxazines can be dis tinguished mass spectrometrically. The saturation, the stereochemistry and the substituents all affected the fragmentations, mainly the peak intensities.