Grafted ionic liquid phase

Grafted Ionic Liquid-Phase-Supported Synthesis... 

In a related study, the group of Bazureau applied their polyethylene glycol-grafted ionic liquid phases (ILPs) to the preparation of 2-thioxotetrahydropyrimidinones [105], After the initial formation of acrylate-bound ILPs utilizing acryloyl chloride in refluxing dichloromethane, several primary amines were attached in a Michael addi-... 

Knoevenagel Reactions on a Grafted Ionic Liquid Phase... 

Bazureau et al. reported the synthesis of novel ester and carbonyl groups appended functionalized grafted ionic liquid phases. Two synthetic strategies were developed for the preparation of the ionic liquid phases (Scheme 16) [96],... 

J. Fraga-Dubreuil, J.P. Bazureau, Grafted ionic liquid-phase-supported synthesis of small organic molecules. Tetrahedron Lett. 42 (2001) 6097-6100. 

Previous work [111] by our group has demonstrated that RTIL-catalyzed 1,3-dipolar cycloaddition under the action of microwave irradiation leads to dramatically shorter reaction times with better yields of isolated products. We have recently investigated the reactivity of the formyl group covalently grafted on the ionic liquid phase 75 in the Knoevenagel reaction with malonic derivatives 76 [112], as shown in Scheme 8.76. 

Another method used for recycling TSOSs consists in using the so-called supported ionic liquid phase (SILP) [44-49], The general principle is using an OS with a trialkoxysilane moiety that can be grafted covalently to a particle of silica. The particle, now coated with onium salt, has a special affinity for other onium salts, especially ILs. ILs can therefore get immobilized on a solid particle and subsequently be used for immobilizing other reagents (transition metal complexes, proline, etc.). This method has recently been reviewed and employs mostly non-functional ILs, so it won t be explained in more detail [44-49] (Fig. 17). 

For application in 1,3-dipolar cycloaddition reactions, diversity could be introduced by first reacting the benzaldehyde-grafted ionic liquid with different alkyl amines using microwave heating. This was followed by conventional heating with an imidate to give the desired supported product. Treatment of the bound cydoad-duct with NaOMe in methanol resulted in cleavage from the ionic liquid phase (Scheme 7.15). 

The ionic liquid grafted benzaldehydes prepared for the 1,3-dipolar cydoaddition reactions have also been used successfully as substrates for Knoevenagel reactions using microwave irradiation (Scheme 7.16). One equivalent of different malonate derivatives with a variety of electron-withdrawing groups was added to the ionic liquid phase and piperidine was used as catalyst. Reaction times varied from 15-60 min. The product was cleaved from the ionic liquid phase by using the NaOMe... 

A heterogeneous catalytic system was prepared upon grafting a cationic dihydroimidazolium-tagged silane on solid Si02. The resulting supported ionic liquid phase (SILP) has been used to immobilize [y-l,2-H2SiV2Wio04o] and was employed in a mixture of acetonitrile/t-butyl alcohol at 20°C for the oxidation of different substrates terminal olefins (66-82% yield), non-hindered internal olefins (> 70% yield) in 24 h, and sulfides (81-95% yield) in 4—lOh. ... 

The first use of room temperature ionic liquids as potential novel soluble phases for combinatorial synthesis has recently been described. As model reaction the Knoevenagel condensation of salicyl aldehyde grafted on to an imidazolium-derived ionic liquid was studied under the action of microwave irradiation (Scheme 12.19) [66]. Reactions were performed without additional solvent in the presence of a basic catalyst, utilizing microwave irradiation in a designated monomode microwave reac-... 

The last of the direct methods for graft initiation in liquid phase presented in this review involves chemical additives. Either free radical or ionic initiators can be chosen. Benzoyl peroxide is reported for grafting styrene on Nylon fibers in methanol media (71,105-107), as well as vinyl acetate (106). Azoisobutyro-nitrile has been employed in systems where the graft monomer is styrene (71,106) or vinyl acetate (106). Redox systems involving hydrogen peroxide and monomers like styrene (106,108,109). vinyl acetate (106), acrylic acid (108,109), methyl... 

Apart from the traditional solid supports (see above), several publications also report the successful use of microwave enhancement for supported transformations involving soluble polymers49-54, fluorous phase conditions55,56, and ionic liquids grafted onto polymeric supports57,58. 

Other interesting systems have been employed, such as CO/HjO (water gas) or CO/Hj (syngas) as reducing mixtures [49, 50], phase transfer catalysis [37], and more recently, aqueous [46, 47] and non-aqueous ionic liquid [48] biphasic catalysis which offer more promise for practical uses. Some interesting examples of metal complexes grafted onto oxides [55, 56] or supported metals [38, 39] as arene hydrogenation catalysts have been provided. 

Another interesting approach for the elaboration of ionosilica stationary phases consists in the formation of poly(ionic liquid) (PIL)-grafted silica phases. Poly(l-allylimidazole)-grafted silica appeared as a versatile stationary phase for... 

These charged [N-F]+ reagents are appropriate for fluo-rinations conducted in ionic liquids allowing for the recovery and reuse of the cinchona alkaloids. Grafting cinchona alkaloids onto a polystyrene support or using a fluorous-phase soluble cinchona alkaloid constitutes another approach to recycling the source of chirality in the enantioselective electrophilic fluorination. ... 

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