Editorial [Hot Topic:Synthesis in Ionic Liquids (Guest Editor: Kenneth K. Laali)]

Application of ionic liquids (ILs) in synthesis continues to experience astonishing growth. The realization that physical and chemical properties of the ILs can be tailored by judicious selection of the cation and anion structures, has undoubtedly contributed to the enthusiasm by the synthetic chemistry community to exploit these alternative media for a wide variety of organic and organometallic transformations, not only as environmentally more acceptable/green alternatives to conventional volatile organic solvents (VOS), but also as Lewis and protic acid catalysts. The recovery and recycling aspects have also had a tremendous impact on the field, in a worldwide effort to switch from VOS to ILs. Application of ILs in the area of catalysis, in particular in biocatalysis and asymmetric catalysis are two of most recently emerging and promising areas in IL chemistry. Since both of these developing areas have focused strongly on the use of imidazolium-based ILs, this brings out an important issue concerning the acidity of C2 position on the imidazolium ring, which could generate N-heterocyclic carbenes with relative ease. This aspect needs to be taken into consideration when performing base-catalyzed transformations in these media, as it could open up unwanted reaction channels involving the IL itself! In relation to the above, the three review articles selected for this special issue of COS are devoted to biocatalysis (enzyme-mediated), asymmetric catalysis, and to the chemistry of the C2 position of the imidazolium ILs respectively: i) M. M. Salunkhe and associates (Institute of Scienec, Mumbai) discuss and analyze the developments achieved over the course of the last decade in enzyme-mediated reactions in ILs. It has been shown that enzymes are stabilized in certain ILs and could be irreversibly activated by incubation in the ILs. ii) S. J. Malhotra and coworkers (New Jersey Institute of Technology) summarize the progress made during recent years in the area of asymmetric catalysis in ILs, employing organometallics and organocatalysts. iii) E. Ennis and S. T. Handy (Middle Tennessee State University) focus on the issue of C2 acidity in the imidazolium ILs, and draw attention to the deprotonation path as a potential side reaction in certain transformations such as the Baylis-Hillman and Negishi-type coupling reactions. They also discusses methods available so far for the synthesis of C2 substituted imidazolium-ILs, in an effort to avid these potential side reactions. As an advisory board member for COS and the executive editor for this special issue I would like to acknowledge and to thank the contributors for their efforts to provide timely review summaries and to analyze the current state of affair in these areas.