Isomerization of thioamidomethylpyridine ylides and isoquinoline ylides under electron impact

The electron impact and collision-induced dissociation spectra of 2-(2-carbethoxy-1-imino-1-methylthio)-ethylene isoquinoline ylide(I), 2-(2-cyano-1-phenylamino-1-methylthio)-ethylene pyridine ylide (2), 2-(2-carboethoxy-1-amino-1-thio)-ethylene pyridine ylide (3), 2-(2-carboethoxy-1-amino-1-thio)-ethylene isoquinoline ylide (4) and 2-(1-N-phenylamide-1-cyano)-ethylene pyridine ylide (5) were studied. The molecular ions of compounds 1-4 were shown to undergo cyclization to the corresponding heterocyclic compounds, analogous to the reaction of compound I in solution. Proposed fragmentation schemes are presented based on tandem mass spectrometry and high resolution mass spectrometry data.