Are Ionic Liquids Suitable Media for Organocatalytic Reactions?

Abstract

Recent developments in organocatalysis have shown that these reactions can be advantageously performed in nonclassical media, such as ionic liquids or water. Among many organocatalysts, proline and its derivatives have attracted enormous attention, and these compounds have recently also been efficiently utilized in ionic liquids. Performing organocatalytic reactions in such media offer possibilities for easy catalyst recovery and reuse, on top of simplified product isolation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Enantioselective Aldol Reaction using Recyclable Montmorillonite‐Entrapped N‐(2‐Thiophenesulfonyl)prolinamide

“…[6] Therefore, the recovery and reuse of this expensive organocatalyst is important from a cost and environmental standpoint. Although recovery and reuse of organocatalysts using polymer supports, [7] ionic liquid supports, [8] and fluorous chemistry [9] have been developed, these anchored organocatalysts have some disadvantages, including multi-step syntheses and deactivation of the inherent catalysis. Recently, Kaneda and co-workers have reported a pioneering work for the entrapment of MacMillans organocatalyst on Montmorillonite using a cation exchange method, which allows facile separation from the reaction mixture and reuse of the entrapped catalyst.…”

Organocatalytic, Asymmetric Aldol Reactions with a Sustainable Catalyst in a Green Solvent

“…The chosen solvent should also be sustainable to maximize the environmental and economic benefits. Organocatalyzed reactions have been carried out in water [5] and ionic liquids, [6] although the green credentials of both these solvents have been questioned. [7] In some cases, reactions have been carried out without a solvent, [8] but in many cases DMF, DMSO, acetonitrile, or chlorinated solvents were employed.…”

Characterization of hexacationic imidazolium ionic liquids as effective and highly stable gas chromatography stationary phases

“…Because of their composition, ILs possess outstanding and unique properties such as recyclability, non-flammability, ionic conductivity, thermal and chemical stability, negligible vapour pressure and high polarity [2]. These characteristics make them attractive materials for synthetic applications mainly as 'green' alternatives to volatile organic solvents [3][4][5], organocatalysts [6], electrolyte materials [7], liquid-liquid extractions [8][9][10], mass spectrometric applications [11,12] and IR, Raman and fluorescence spectroscopy [13]. Organic cations such as imidazolium, pyridinium, ammonium and phosphonium can be easily combined with a variety of anions (halides, PF 6 À , BF 4 À , SbF 6 À , etc.…”