Ionic liquids preparation protocols

Protocol for the Deposition of Zinc from a Type III Ionic Liquid Preparation of Ionic Liquids... 

Using a similar protocol, Loupy and coworkers have reported the synthesis of chiral ionic liquids based on (ll ,2S)-(-)-ephedrinium salts under microwave irradiation conditions (Scheme 4.21a) [75]. Importantly, the authors were also able to demonstrate that the desired hexafluorophosphate salts could be prepared in a one-pot protocol by in situ anion-exchange metathesis (Scheme 4.21b). The synthesis and transformation of so-called task-specific ionic liquids is discussed in more detail in Section 7.4. 

In addition to the ionic liquid-mediated procedure in solution (see Scheme 6.112), Leadbeater and coworkers also presented a solid-phase protocol for a one-pot Mannich reaction employing the above mentioned chlorotrityl linker [67]. In this approach, p-chlorobenzaldehyde and phenylacetylene were condensed with readily prepared immobilized piperazines (Scheme 7.56). 

Analogous to epoxides, aziridines can be prepared by the methylenation of imines. In this case, ethyl diazoacetate is the most common source of carbenes. For example, the imine derived from p-chlorobenzaldehyde 148 is converted to the c/j-aziridinyl ester 149 upon treatment with ethyl diazoacetate in the presence of lithium perchlorate <03TL5275>. These conditions have also been applied to a reaction medium of the ionic liquid l-n-butyl-3-methylimidazolium hexafluorophosphate (bmimPFe) with excellent results <03TL2409>. An interesting enantioselective twist to this protocol has been reported, in which a diazoacetate derived from (TJ)-pantolactone 150 is used. This system was applied to the aziridination of trifluoromethyl-substituted aldimines, which were prepared in situ from the corresponding aminals under the catalysis of boron trifluoride etherate <03TL4011>. 

The preparation of water-miscible ionic liquids can be a more demanding process, as the separation of the desired and undesired salts may be complex. The use of silver salts described above allows the preparation of many salts in very high purity, but is clearly too expensive for large-scale use. As a result, a number of alternative protocols have been developed that employ cheaper salts for the metathesis reaction. The most common approach remains to carry out the exchange in aqueous solution using either the free acid of the appropriate anion, the ammonium salt, or an alkali metal salt. When using this approach, it is important that the desired ionic liquid can be isolated without excess contamination from unwanted halide-... 

While certain TSIL have been developed to puU metals into the IL phase, others have been developed to keep metals in an IL phase. The use of metal complexes dissolved in IL for catalytic reactions has been one of the most fruitfijl areas of ionic liquid research to date. StiU, these systems have a tendency to leach dissolved catalyst into the co-solvents that are used to extract the product of the reaction from the ionic liquid. Consequently, Wasserscheid et al. have pioneered the use of TSILs based on the dissolution into a conventional IL of metal complexes that incorporate charged phosphine ligands in their structure [16-18]. These metal complex ions become an integral part of the ionic medium, and remain there when the reaction products arising from their use are extracted into a co-solvent. Certain of the charged phosphine ions that are the basis of this chemistry (e.g., P(m-C6H4S03 Na+)3) are commercially available, while others are prepared using established phosphine synthetic protocols. 

Figure 1 Two-step synthetic protocol for the preparation of bistriflamide ionic liquids.

The in situ preparation of aryl and heteroaryl azides from the corresponding aryl halides via L-proline-promoted Cnl-catalyzed coupling reactions in the presence of alkynes allows the one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles (e.g. 226). Liang et al. also reported the one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles (e.g. 227) from aryl bromides or iodides and terminal alkynes in the presence of sodium azide using diamine-promoted Cnl-catalyzed reactions. It has also been shown that this type of synthesis can be carried out in a mixture of the ionic liquid [bmim][BF4] and water (Scheme 3.32). Starting with boronic acids, the catalytic approach to aryl azides and l-aryl-1,2,3-triazoles can be carried out under milder reaction conditions and improved substrate tolerance (Scheme 3.33). In fact, it was demonstrated that both electron-rich and electron-poor aryl boronic acids 228 could be efficiently converted into the corresponding aryl azides (229) in the presence of sodium azide and CUSO4. A one-pot protocol... 

A significant application was reported by Tan et They prepared modified gold nanopartieles deeorated with [PeeewJCl on their surface. In the presence of As(iii), the nanopartiele solution turned from red to blue. This was due to the seleetive interaetion of the ionic liquid with As(iii). With the colorimetric probe, authors developed a protocol for naked eye speciation test of As(iii) and As(v) at levels below the World Health Organization (WHO) guideline of 10 pg L. ... 

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