One-pot three-component Biginelli-type reaction catalyzed by ionic liquids in aqueous media

Hydration of sulfobetaine dizwitterions as a function of alkyl spacer length

The solvation and structure of bolaform dizwitterions containing two sulfobetaine moieties in concentrated aqueous solution were determined using neutron diffraction with isotopic substitution (NDIS) combined with modelling of the measured structure factors using Empirical Potential Structure Refinement (EPSR). Strongly directional local hydration was observed in the polar regimes of the dizwitterions with 48-52 water molecules shared between dizwitterion molecules in a first shell water network around each zwitterion pair. Overall, the double zwitterions were highly hydrated, providing experimental evidence in support of the potential formation of protein-resistant hydration layers at zwitterion-water interfaces.

The Biginelli reaction with an imidazolium-tagged recyclable iron catalyst: kinetics, mechanism, and antitumoral activity

The present work describes the synthesis, characterization, and application of a new ion-tagged iron catalyst. The catalyst was employed in the Biginelli reaction with impressive performance. High yields have been achieved when the reaction was carried out in imidazolium-based ionic liquids (BMI⋅PF6, BMI⋅NTf2, and BMI⋅BF4), thus showing that the ionic-liquid effects play a role in the reaction. Moreover, the ion-tagged catalyst could be recovered and reused up to eight times without any noticeable loss in activity. Mechanistic studies performed by using high-resolution electrospray-ionization quadrupole-time-of-flight mass (HR-EI-QTOF) spectrometry and kinetic experiments indicate only one reaction pathway and rule out the other two possibilities under the development conditions. The theoretical calculations are in accordance with the proposed mechanism of action of the iron catalyst. Finally, the 37 dihydropyrimidinone derivatives, products of the Biginelli reaction, had their cytotoxicity evaluated in assays against MCF-7 cancer cell linages with encouraging results of some derivatives, which were virtually non-toxic against healthy cell linages (fibroblasts).

Facile Biginelli-Type Reactions Catalysed by Super Acidic Ionic Liquid under Solvent-Free Conditions

[MeC(OH)2]+ClO4- as a super acidic ionic liquid is an extremely active catalyst for Biginelli-type reactions. The present method is especially effective for the inactive aliphatic aldehydes. The solvent-free conditions, high catalytic activity, wide substrates tolerance and convenient product isolation make the protocol more advantageous.

Mechanistic studies on Lewis acid catalyzed Biginelli reactions in ionic liquids: evidence for the reactive intermediates and the role of the reagents

This paper describes the use of common Lewis acids supported in imidazolium-based ionic liquids as the catalysts to promote the Biginelli reaction. The ionic liquid effect and the reaction mechanism are discussed on the basis of nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and theoretical calculations. Indeed, the results showed that the ionic medium plays a fundamental role in the synthesis of biologically active dihydropyrimidinones due to the stabilization of the charged intermediates proposed in the mechanism. When conducted in an ionic liquid as solvent, the reaction mechanism is more complex than in other Lewis acid catalyzed Biginelli reactions.

Application of Ionic Liquids in Multicomponent Reactions

This chapter reports the applicability of ionic liquids in the formation of different types of multicomponent reactions. Easy work-up, relatively short reaction times, good to high yields of the desired products, mild reaction conditions, low cost, availability, and reusability of the employed ionic liquids are the striking ­features of the reported methodologies.