Mass spectra of new heterocycles: XI. Fragmentation of 5-(methylsulfanyl)-1-[2-(vinyloxy)ethyl]-1H-pyrrol-2-amines under electron impact and chemical ionization

Fragmentation patterns of the molecular ions of 5-(methylsulfanyl)-1-[2-(vinyloxy)ethyl]-1H-pyrrol- 2-amines generated by electron impact (70 eV) and chemical ionization (methane as reagent gas) were studied for the first time. The electron impact mass spectra of all the examined compounds showed abundant molecular ions whose subsequent fragmentation followed three main pathways: elimination of EtS radical, elimination of methyl radical from the MeS group, and cleavage of the C-N and/or C-C bonds which is accompanied by rearrangement processes. Further decomposition of the [M - EtS]+ ion is determined by the structure of the amino group. The chemical ionization mass spectra displayed strong molecular and [M + H]+ ion peaks together with representative series of fragment ion peaks. Unlike electron impact, the main decomposition pathway under chemical ionization is elimination of methylsulfanyl radical from the [M + H]+ ion to give abundant [M + H — MeS]+ ion.