Mass-spectrometric identification of isomeric 1-benzoyl-2-azetidinones and 2-phenyl-4,5-dihydro-1,3-oxazin-6-ones

The mass spectra of isomeric 1-benzoyl-2-azetidinones and 2-phenyl-4,5-dihydro-1,3-oxazin-6-ones were analyzed. A more stable molecular ion and high intensities of the peaks of the ions formed from the molecular ion with the loss of ketene or a substituted ketene are characteristic for the former compounds, while low stability of the molecular ion and a higher probability of the loss of one of the groupings in the 4 position are characteristic for the latter compounds. Fragmentation schemes that are confirmed by the high-resolution mass spectra are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1627–1631, December, 1980.We sincerely thank E. Simova and C. Drey for providing us with samples of a number of the compounds.