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

The deactivation pathways of Jørgensen–Hayashi‐type organocatalysts modified with an ionic liquid fragment in asymmetric Michael reactions of α,β‐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‐α,α‐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. Poisonous parasites: Deactivation pathways of Jørgensen–Hayashi‐type catalysts modified with an ionic group in asymmetric Michael reactions that involve an iminium‐ion formation step have been studied by ESI‐MS(+). “Parasitic” oxidation and hydrolysis side reactions that poisoned the catalysts were revealed (see image) along with a possible solution.