Organocatalysts wrapped around by poly(ethylene glycol)s (PEGs): a unique host–guest system for asymmetric Michael addition reactions

Abstract

Asymmetric Michael addition reactions of unmodified ketones to nitroalkenes were performed in PEGs catalyzed by novel pyrrolidinyl-thioimidazolium salts to give products in up to 97% yield and 99% enantioselectivity; ESI mass spectrometric detection for the first time gave evidence of the presence of the PEG-organocatalyst host-guest complex.

Pyrrolidine-Based Chiral Quaternary Alkylammonium Ionic Liquids as Organocatalysts for Asymmetric Michael Additions

“…Therefore, several groups introduced quaternary ammonium groups into chiral catalysts [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Thereinto, pyrrolidinetype imidazolium ILs, DABCO ILs and pyridinium ILs all produced encouraging results for the Michael additions of ketones or aldehydes to nitroolefins.…”

Recyclable Fe3O4 Nanoparticles Catalysts for Aza-Michael Addition of Acryl Amides by Magnetic Field

“…In contrast, the smooth instances of magnetic nanostructure-based catalysts that display creditable catalytic reactivity are as yet unusual in practice. We design a magnetic nanoparticles-based catalytic The aza-Michael addition reaction of acryl amides is significant for preparing kinds of β-amino carbonyl compounds from readily manufactured raw materials in a sustainable and clean method [41][42][43][44][45][46]. Recently, the researches in aza-Michael addition by the imidazolium-based polymer [47], enzymes [48][49][50][51], and room-temperature ionic liquids (RTILs) have given a novelty way to achieve the important β-amino carbonyl derivatives [28].…”

Supramolecular Host-Guest Asymmetric Induction In Organic Synthesis

“…A host-guest complex of PEG-ionic-pyrrolidine as a reusable, highly efficient system for the direct enantioselective Michael addition of ketones to nitroalkenes was developed using novel pyrrolidinyl-thioimidazolium salts, such as chiral organocatalysts, and several solvents including PEG-200, PEG-400 and PEG-800 [36]. The best results were obtained using cyclohexanone, PEG-800 and various aryl nitroalkenes, which reacted smoothly to afford high yields (75-97%) and high enantioselectivities (88-99%; Table 5).…”

“…Lehn [38] proposed a hierarchical order of the terms 'templating', 'self-assembly' and 'self-organization'. Diagram of a PEG-organocatalyst system used for the enantioselective Michael addition of ketones to nitroalkenes that can be detected by ESI-MS [36]. Self-assembly may or may not involve an actual template, such as a metal cation; thus, the template effect itself is not strictly an example of self-assembly, but it has been classified by Lehn as the unit step in a self-assembly process that comprises several steps occurring spontaneously in a single operation.…”