Gas-phase fragmentations of N-methylimidazolidin-4-one organocatalysts.

N-methylimidazolidin-4-one organocatalysts were studied in the gas phase. Protonated and sodium-cationized (sodiated) molecules are conveniently accessible by electrospray mass spectrometry. Protonation enables three different closed-shell paths of ring cleavage leading to iminium ions. The fragmentation pattern is largely unaffected by exocyclic substituents and thus is valuable to characterize the substance type as N-methylimidazolidin-4-ones. Sodiated species show a distinctly different fragmentation that is less useful for characterization purposes: apart from signal loss due to dissociation of Na+ , the observation of benzyl radical loss is by far predominant. Only in absence of a benzyl substituent, an analogue of the third ring cleavage (loss of [C2 H5 NO]) is observed. Copyright © 2017 John Wiley & Sons, Ltd.