SATURATED HETEROCYCLES .227. ELECTRON IONIZATION MASS-SPECTRA OF SOME SUBSTITUTED STEREOISOMERIC 1,6,7,11B-TETRAHYDRO-2H,4H[1,3]OXAZINO[4,3-A]-ISOQUINOLINES AND 1,6,7,11B-TETRAHYDRO-2H[1,3]OXAZINO[4,3-A]-ISOQUINOLIN-4-ONES

The mass spectra of ten substituted oxazino[4,3-a]isoquinolines, two isoquino[2,1-c][1,3]benzoxazines and seven substituted oxazino[4,3-a]isoquinolin-4-ones were recorded under electron impact ionization. Fragmentations were examined by metastable ion analysis, collision induced dissociation and exact mass measurement. The oxazinoisoquinolines and oxazinoisoquinolin-4-ones behaved similarly, although there were a few differences in the fragmentation and especially in the peak intensities. The most important fragmentation began with the opening of the oxazole ring. The substituents affected the fragmentation of the isomeric compounds, whereas the spectra of the stereoisomeric compounds were identical, The two isoquinobenzoxazines differed noticeably from the other compounds in their fragmentation behaviour; the additional phenyl ring prompted entirely new fragmentations unique to this structure.