Ionic liquids Morita-Baylis-Hillman reaction

Using electrospray ionization mass spectrometry in both positive and negative ion modes, the on-line scanning of the Morita-Baylis-Hillman reaction in the presence of imidazolium ionic liquids has been investigated. The interception of several supramolecular species indicated that ionic liquids co-catalyse the reactions by activating the aldehyde toward nucleophilic enolate attack and by stabilizing the zwitterionic species that act as the main intermediates.175... 

At the same time as new applications of ionic liquids are discovered on almost a daily basis, limitations of these reaction media are also uncovered. While studying the Morita-Baylis-Hillman reaction in ionic liquids, Aggarwal observed that [bmim][Cl] was deprotonated by the weak base present in the reaction mixture, leading, after reaction with benzaldehyde, to salt 111 (Scheme 49). Deprotonation of imidazolium salts with strong bases (KCyBu or NaH) is well known, providing, for example, an easy route to Pd-carbene complexes (Section 2.3.5.1). However, this observation limits the use of imidazolium-based ionic liquids even in weakly basic conditions, where they can react with electrophiles. It also explains previous works reporting low yields for reactions performed in these conditions, such as the Horner-Wadsworth-Emmons reaction in [emimlCPFe] or [emim][BF4]. ... 

Morita-Baylis-Hillman Reaction Co-catalyzed by Ionic Liquids... 

Morita-Baylis-Hillman reaction The Morita-Baylis-Hillman (MBH) reaction of aldehydes RCH=0 with the methylene acceptor CH2=CHC02Me, catalysed by DABCO in ionic liquids possessing [EtS04] anion, has been found to exhibit second-order kinetics in aldehyde and first order in acrylate and DABCO. This behaviour is in line with the kinetics reported for DMSO and other aprotic polar solvents but differs from the general observation of the first order in aldehyde, acrylate, and DABCO in other organic solvents. ... 

A review of the Morita-Baylis-Hillman (MBH) reaction has covered mechanism, activated olefins and electrophiles as substrates, multicomponent and intramolecular reactions, and the use of ionic liquid reaction media. ... 

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