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Abstract

The chemical industry is under considerable pressure to replace many of the volatile organic compounds (VOCs) that are currently used as solvents in organic synthesis. The toxic and/or hazardous properties of many solvents, notably chlorinated hydrocarbons, combined with serious environmental issues, such as atmospheric emissions and contamination of aqueous effluents is making their use prohibitive. This is an important driving force in the quest for novel reaction media. Curzons and coworkers, for example, recently noted that rigorous management of solvent use is likely to result in the greatest improvement towards greener processes for the manufacture of pharmaceutical intermediates. The current emphasis on novel reaction media is also motivated by the need for efficient methods for recycling homogeneous catalysts. The key to waste minimisation in chemicals manufacture is the widespread substitution of classical 'stoichiometric' syntheses by atom efficient, catalytic alternatives. In the context of homogeneous catalysis, efficient recycling of the catalyst is a conditio sine qua non for economically and environmentally attractive processes. Motivated by one or both of the above issues much attention has been devoted to homogeneous catalysis in aqueous biphasic and fluorous biphasic systems as well as in supercritical carbon dioxide. Similarly, the use of ionic liquids as novel reaction media may offer a convenient solution to both the solvent emission and the catalyst recycling problem.

Selective chemical reactions in supercritical carbon dioxide, water, and ionic liquids

“…Such compounds appear very attractive as novel reaction media toward greener processes in organic synthesis. Their unique properties have been reflected by their use in a wide range of stoichiometric, as well as catalytic, reactions (196,197). Researchers have focused on ILs formed from dialkylimidazolium halides which are readily prepared from 1-methylimidazole and a slight excess of the desired haloalkane (198).…”

Remarkable rate acceleration of SmI3-mediated iodination of acetates of Baylis-Hillman adducts in ionic liquid: facile synthesis of (Z)-allyl iodides

“…On the other hand, the so-called room temperature ionic liquids (RTILs), especially those derived from 1-n-alkyl-3-methylimidazolium cations, have been shown to have versatile applications in organic synthesis as reaction media (Wasserscheid and Keim, 2000;Welton, 1999;Sheldon, 2001). The attractive-ness of RTILs as green solvents lies in their wide liquid range, good solvating ability, tunable polarity, highly thermal stability, negligible vapor pressure, and easy recycleability.…”

Amino acid ionic liquid‐based titanomagnetite nanoparticles: An efficient and green nanocatalyst for the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazoles

“…[3,4] ILs have become attractive as environmentally friendly reaction media and catalysts and have been widely used in organic reactions due to their environmental benignity, high thermal stability, reusability, negligible vapour pressure and easy handling. [5][6][7] Despite promising advantages, ILs have disadvantages including high viscosity resulting in decreased catalytic activity and homogeneous behaviour in reactions making product separation and catalyst recovery more complicated. To solve such problems, immobilization of ILs onto various nanosized solid supports, especially magnetic nanomaterials, has been the most promising solution.…”