title: Electron ionization and electrospray mass spectra of diaryl-substituted enaminoketones and their thio analogs.
abstract: Electron ionization (EI) and positive electrospray ionization (ESI) mass spectra of selected diaryl enaminoketones and enaminothiones have been studied. In the EI mass spectra of both classes of compound, molecular ion peaks are accompanied by the peaks corresponding to the [M-H](+) ions. The formation of these ions can be rationalized by a cyclization reaction resulting in the formation of the respective isoxazolium and isothiazolium cations. Under positive ESI conditions, in the spectra recorded for the enaminoketones peaks corresponding to the [M+H](+), [M+Na](+) and [2M+Na](+) ions appeared, while in the spectra recorded for the enaminothiones, peaks corresponding to the [M-H](+) ions were dominant. These ions are most likely formed by oxidation of the neutral enaminothione molecules on the surface of the positively charged stainless steel capillary in the ESI ion source (anodic oxidation).
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Wileńska
authors.forename: Witold
authors.initials: W
authors.lastname: Danikiewicz
authors.forename: Marta
authors.initials: M
authors.lastname: Bugaj
authors.forename: Krystyna
authors.initials: K
authors.lastname: Kamieńska-Trela
authors.forename: Adam
authors.initials: A
authors.lastname: Krówczyńsk