SATURATED HETEROCYCLES .227. ELECTRON IONIZATION MASS-SPECTRA OF SOMESUBSTITUTED STEREOISOMERIC -TETRAHYDRO-2H,4H[1,3]OXAZINO[4,3-A]-ISOQUINOLINES AND ETRAHYDRO-2H[1,3]OXAZINO[4,3-A]-ISOQUINOLIN-4-ONES

The mass spectra of ten substituted oxazino[4,3-a]isoquinolines, two i soquino[2,1-c][1,3]benzoxazines and seven substituted oxazino[4,3-a]is oquinolin-4-ones were recorded under electron impact ionization. Fragm entations 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 intensiti es. The most important fragmentation began with the opening of the oxa zole ring. The substituents affected the fragmentation of the isomeric compounds, whereas the spectra of the stereoisomeric compounds were i dentical, The two isoquinobenzoxazines differed noticeably from the ot her compounds in their fragmentation behaviour; the additional phenyl ring prompted entirely new fragmentations unique to this structure.