On the double benzylic hydrogen migration in the molecular ion of N-(5-phenylvaleryl)-1-azacyclopentane-2-thione

It is shown on the basis of deuterium labeling that in the metastable molecular ions of N-(5-phenylvaleryl)-1-azacyclopentane-2-thione, decomposing by unimolecular fragmentation, both benzylic hydrogens migrate to the thiolactam ring to generate the protonated [gamma]-thiobutyric lactam species with m/z 102. A mechanism is given for the formation of these ions that is proposed to be mediated by intramolecular acid-base reactions and an ion/molecule complex.