Ionic Liquid as Reaction Media

In SILP carbonylation we have introduced a new methanol carbonylation SILP Monsanto catalyst, which is different from present catalytic alcohol carbonylation technologies, by using an ionic liquid as reaction medium and by offering an efficient use of the dispersed ionic liquid-based rhodium-iodide complex catalyst phase. In perspective the introduced fixed-bed SILP carbonylation process design requires a smaller reactor size than existing technology in order to obtain the same productivity, which makes the SILP carbonylation concept potentially interesting for technical applications. 

Other progress in the Hantzsch thiazole synthesis includes a,a-dibromoketones as a superior alternative to a-dibromoketones <07SC2501> and ionic liquid as reaction medium <07T11066>. 

Here, we will review the various issues related to biocatalytic reactions in ionic liquids. Biocatalyst tested in ionic liquids will be discussed firstly, and then the effect of ionic liquids on the activity, selectivity as well as on the stability of biocatalyst in ionic liquids will be surveyed. Finally, various applications of ionic liquids as reaction medium for biocatalytic transformations will be reviewed. 

Ionic liquids as reaction medium and promoter without any catalyst have been also used (04AJC1067, 06JHC685, 05MI1085). 

Epoxidation. Procedure modification includes the use of an ionic liquid as reaction medium. 

One of the main objectives of using ionic liquid as reaction medium is the possibility to recycle the catalyst. The catalytic solution could indeed be reused eight times for the oxidation of benzyl alcohol to benzaldehyde, with only a slight loss of activity. In addition, the recovered ionic liquid solvent could be recovered and reused for new oxidations of other substrates. 

Sunitha S, Kanjilal S, Reddy PS (2007) Ionic liquids as reaction medium for Upase-catalyzed methanolysis of sunflower oil. Biotechnol Lett 29 1881-1885 Sunna A, Hunter L, Hutton C et al. (2002) Biochemical characterization of a recombinant ther-moalkalophilic lipase and assessment of its substrate enantioselectivity. Enzyme Microb Technol 31 472 76... 

Heinze X, Schwikal K., Barthel S., Ionic liquids as reaction medium in ceUulose functionedization, Macromol. Biosci., 5, 2005, 520-525. 

Use of Ionic Liquids as Reaction Medium 7. Concluding Remarks 310... 

New developments in the Suzuki cross-coupling reaction include the application of microwave, polymer-bound catalysts, nanoparticles, and ionic liquids as reaction medium. A discussion of these methods exceeds the scope of this chapter. 

The carboxylation of epoxides is strongly dependent on the reaction conditions such as temperature and solvent The use of ionic liquids as reaction medium seems to accelerate the reaction with respect to any other organic solvent, most probably because ionic liquids promote the formation of and/or stabilize polar or ionic intermediates. Heterogeneous catalysts such as oxides [95] or supported ammonium salts [92] or metal complexes [94] work well under these conditions. The solvent can play a key role in such reactions. Amides such as di-methylformamides or dialkylacetamides can themselves promote the carboxylation of epoxides, albeit with a low TON [100]. Most likely this is due to the abil-... 

The aspects of medium engineering summarized so far were a hot topic in biocatalysis research during the 1980s and 1990s [5]. Nowadays, all of them constitute a well-established methodology that is successfully employed by chemists in synthetic applications, both in academia and industry. In turn, the main research interests of medium engineering have moved toward the use of ionic liquids as reaction media and the employment of additives. 

The primary emphasis of most published work on the Wittig reaction, and its counterparts, continues to be applications in synthesis. A potentially useful advance in this area is the use of ionic liquids as a medium for Wittig reactions. Developments in the coordination chemistry of ylide derivatives, particularly iminophosphoranes, continue apace and show that these compounds afford a diverse range of metal complexes. 

The so-called second generation ionic hquids were prepared from organic cations and AlCl anions [170]. Since AICI3 was present in these liquids, they were used as catalysts in Lewis acid catalyzed reactions. Also many of the third generation ionic liquids have been used as solvents for catalytic reactions [171-174], However, it is also known that third generation ionic liquids are capable of catalyzing reactions, either in substoichiometric amounts or as reaction medium. This will be discussed in this section. 

The application of ionic liquids as a reaction medium for the copper-catalyzed aerobic oxidation of primary alcohols was reported recently by various groups, in attempts to recycle the relatively expensive oxidant TEMPO [150,151]. A TEMPO/CuCl-based system was employed using [bmim]PF6 (bmim = l-butyl-3-methylimodazolium) as the ionic liquid. At 65 °C a variety of allylic, benzylic, aliphatic primary and secondary alcohols were converted to the respective aldehydes or ketones, with good selectiv-ities [150]. A three-component catalytic system comprised of Cu(C104)2, dimethylaminopyridine (DMAP) and acetamido-TEMPO in the ionic liquid [bmpy]Pp6 (bmpy = l-butyl-4-methylpyridinium) was also applied for the oxidation of benzylic and allylic alcohols as well as selected primary alcohols. Possible recycling of the catalyst system for up to five runs was demonstrated, albeit with significant loss of activity and yields. No reactivity was observed with 1-phenylethanol and cyclohexanol [151]. 

The double carbonylation of iodobenzene with diethylamine catalyzed by Pd(OAc)2-PPh3 was carried out in l-butyl-3-methylimidazolium tetrafluoroborate 315 as reaction medium at 80 °C and 38 atm of CO to give phenyl-glyoxamide 314 as the predominant product (83%) accompanied by benzamide 313 (17%) (Equation (29)). The use of ionic liquids showed the same reactivity and product selectivity as those using diethylamine as solvent for this reaction, while separation of products and recycling of the catalyst was easier. ... 

The synthesis of a-methylene-7-lactone 317 through carbonylation of but-3-yn-l-ol 316 catalyzed by Pd(ll)-PPh2(2-Py) has been carried out in l-butyl-3-methylimidazolium tetrafluoroborate 315 as reaction medium in high yield with excellent product selectivity (Equation (30))4 Although the ionic liquid containing the catalytic species was recovered, a significant decrease in yield occurred with the recycled catalyst, which appears to be attributed to the decomposition of the catalyst during the isolation procedure ... 

Alvaro, M., Ferrer, B., Garcia, H., Narayana, M., Screening of an ionic liquid as medium for photochemical reactions, Chem. Phys. Let., 362, 435-440, 2002. 

Zhou, L. and Wang, L. (2006) Functionalized Ionic Liquid as an Efficient and Recyclable Reaction Medium for Phosphine-Free Palladium-Catalyzed Heck Reaction. Synthesis, 2653-2658, DOI 10.1055/S-2006-942466. 

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