Chiral Ionic Liquid/ESI-MS Methodology as an Efficient Tool for the Study of Transformations of Supported Organocatalysts: Deactivation Pathways of Jorgensen-Hayashi-Type Catalysts in Asymmetric Michael Reactions

The deactivation pathways of Jorgensen-Hayashi-type organocatalysts modified with an ionic liquid fragment in asymmetric Michael reactions of alpha,beta-enals with C- (nitromethane, dimethylmalonate) or N-nucleophiles (N-carbobenzyloxyhydroxylamine) that involved an iminium-ion formation step were studied for the first time by the electrospray ionization mass spectrometry (ESI-MS). Parasitic side reactions and undesirable cation intermediates that poisoned the catalysts were identified in accordance with their m/z values as well as their relation to the reported mechanisms of Michael reactions in the presence of O-TMS-alpha,alpha-diarylprolinol (TMS=trimethylsilyl) derivatives. The proposed approach may be useful for the study of transformations of other types of organocatalysts modified with ionic groups in various organocatalytic reactions and for the development of novel robust catalysts and processes that would be suitable for large-scale industrial applications.