ELECTRON-IMPACT INDUCED FRAGMENTATIONS OF SOME QUINAZOLINEDIONES AND BENZOXAZINONES

Mass spectral fragmentations of 3-substituted 2,4(1H,3H)-quinazolinediones, 2-phenylimino-4H-3,1-benzoxazin-4-ones and 2-thioxo-2,3-dihydroquinazolidin-4(1H)-one were examined using metastable-ion analysis and exact mass measurements. The isomeric compounds were easy to distinguish from their mass spectra. For quinazolinediones, the most surprising feature was the loss of CO2 showing that a rearrangement due to anilino migration must occur in these compounds. In comparison, the benzoxazinones showed no elimination of carbon dioxide.