Mass spectra of spiro-benzoxazin-4-one and spiro-quinazolin-4-one derivatives.

Abstract

Mass spectra of a series of spiro-benzoxazin-4-one and spiro-quinazolin-4-one derivatives were measured by electron impact ionization, and their characteristic fragmentation patterns were discussed.Spiro-benzoxazin-4-ones and spiro-quinazolin-4-ones were found to display different fragmentation pathways and different peak intensities. In particular, the base peak in mass spectra of spiro-benzoxazin-4-ones resulted from the molecular ion by the retro-Diels-Alder reaction with hydrogen migration. On the other hand, the base peak in mass spectra of spiro-quinazolin-4-ones resulted from the molecular ion by the cycloalkane ring decomposition. The difference in the main two processes was based on the difference in the ionization energy of the oxygen atom and the nitrogen atom at the 1-position. The difference in hydrogen migration was based on the defference in electronegativity of the heteroatom at the 1-position.