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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
Author(s) -
Maltsev Oleg V.,
Chizhov Alexander O.,
Zlotin Sergei G.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100388
Subject(s) - nitromethane , iminium , chemistry , nucleophile , michael reaction , ionic liquid , electrospray ionization , catalysis , organocatalysis , combinatorial chemistry , ionic bonding , mass spectrometry , ion , enantioselective synthesis , organic chemistry , chromatography
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.