, Volume 15, Issue 1, pp 66-70

Mass-spectrometric study of physiologically active β-thiosemicarbazones of N-alkylisatins

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The molecular ions of isatin (I) and N-methyl- (II) and N-ethylisatin (III) β-thiosemicarbazones undergo fragmentation via many pathways with the elimination of NH3, H2S, CO, CH2N2, CHN3, CH2N2S, CH2NS, and CHNS particles; this is due to primary localization of the charge on the heteroatoms of the thiosemicarbazone residue. A previously unknown rearrangement, which consists in migration of an HS group to the β-carhon atom of the heteroring with subsequent ejection of a CHN3 fragment. The [M — CO]+ ions undergo fragmentation with the elimination of CH2N2S; in the case of II and III fragmentation is preceded by detachment of a hydrogen atom (II) or a methyl group (III) from the substituent attached to the ring nitrogen atom. The [M — CO, -H, -CH2NS]+ (II) and [M — CO, -CH3, -CH2N2S]+ (III) ions undergo fragmentation with the ejection of HCN in two ways through both the ring nitrogen atom and the thiosemicarbazone residue. Schemes for the principal pathways of fragmentation and rearrangements are presented. The compositions of the ions were confirmed by the high-resolution mass spectra and the mass spectra of the N-deuteroalkyl derivatives.