Organic mass spectrometry—X. Electron impact fragmentations of alkylthio group in 2‐alkylthio‐5‐aminothiazolo[5,4‐d] pyrimidines

In order to discuss hydrogen transfer in the skeletal fragmentation of thioethers on electron impact, mass spectra of a series of 2‐n‐alkylthio‐5‐aminothiazolo [5,4‐d]pyrimidines have been determined. To aid the interpretation of the hydrogen migration, deuterium‐labeled compounds which are substituted with deuterium in each position of 2‐n‐butylthio‐5‐aminothiazolo‐pyrimidines were studied. By correlation of the spectra obtained from such labeled compounds, the initial hydrogen migration in the fragmentation to produce [M  SH], [MS  CH3] and m/e 184 ions is concluded to be as follows: migration of the α‐hydrogen atom to the sulfur induces formation of the [M  SH] ion; migration of the β‐hydrogen atom to the sulfur or nitrogen atom by a McLafferty rearrangement induces formation of the m/e 184 ion; and migration of γ‐hydrogen atom to the sulfur induces formation of the [M  SCH3] ion.