Polymer-supported imidazolium salt

On the other hand, polymeric beads of supported ILs ( polymer-supported imidazolium salt, PSIS) were also prepared via the covalent anchoring of an imidazolium salt to a polystyrene resin.These PSISs, which have the advantage of significantly enhancing the nucleophilicity of metal salts compared with conventional methods, have been used as efficient catalysts for nucleophilic fiuorination and for other nucleophilic substitution reactions. In particular, the authors found that the applied PSIS had many practical merits product recovery and purification was simple and catalyst recovery and reuse were easy (Figure 4.12). 

Figure 4.12 Example of a polymer-supported imidazolium salt (PSIS).

Scheme 5.6-4 Preparation of polymer-supported imidazolium salt catalysts, where DVB = divinylbenzene and MX = NaBp4 or KOTf [80].

Scheme4 Preparation of polymer-supported imidazolium salts PS[HMIM][BF4 and PS[HMIM][OTf with PS = polymer support [27. ...

The recent development of polymers containing imidazolium, thiazolium and related structures as supported equivalents of ionic liquids (i.e. 148 and 149, Scheme 10.23) is an interesting development of this field [356-361], The corresponding salts containing basic counter-anions can act as basic catalysts but can also be transformed, depending on the exact structure, into N-heterocydic car-benes that can act as nucleophilic organocatalysts [362]. As an example, resins 148... 

A novel use ofthe salt [BMIM][PF6] is to enhance microwave absorption and hence accelerate the rate of a reaction. Ley found that [BMIM][PF6] enhanced the rate of the microwave promoted thionation of amides using a polymer supported thionating agent [304]. Hardacre et al. have developed a protocol for the synthesis of deuterated imidazoles and imidazolium salts [305]. The procedure involves the platinum- or palladium- catalyzed deuterium exchange of 1-methyl-d -imidazole with D2O to give 1-methylimidazole-d , followed by reaction with a deuterated alkyl halide. 

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