Mass spectral fragmentation and rearrangement of isatin derivatives

Mass spectral fragmentation pathways were formulated for 1-alkylisatins, 1-alkyl-3-arylimino-2-indolinones and 3-arylimino-2-indolinons bearing no substituent at the 1-position. Deuterium-labelled and ¹³C-labelled compounds were utilized in this study. An interesting rearrangement of the 1-alkyl compounds, in which the 1-alkyl substituent is incorporated into a fulvene ion, was established.