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.