Subject ionic liquids, syntheses

The synthesis of ionic liquids with BF4 and PF6 as cations has been the subject of much research since they are the most widely used in catalysis. However, it is difficult to make these ionic liquids in a pure form. The original route used to prepare ionic liquids with these anions consists of a metathesis (anion-cation exchange) reaction in which the imidazolium chloride is reacted with the sodium salt of the anion in a suitable solvent [8], The reaction is illustrated in Scheme 4.2 for the tetrafluoroborate salt. 

In the process of developing the Stetter reaction in ionic liquids, Gree and coworkers applied their methodology to the synthesis of haloperidol (Scheme 25) [101], A variety of aromatic aldehydes react with methyl acrylate 160 when butyl-methylimidazolium tetrafluoroborate [bmim][BF ] is used as solvent. In the synthesis of haloperidol, electron-deficient aldehyde 153 was subjected to standard reaction conditions with 160 to provide 161 in good yield. 

We begin with a brief summary of some of the review articles that have been written on the subject of ionic liquids. Wilkeswrote a short history of ionic liquids describing the chronological development of ionic liquids with an emphasis on listing the names and pictures of those involved in the research. Holbrey and Seddon and Earle and Seddon reviewed the literature of ionic liquids composed entirely of ions which were mainly of interest to electrochemists. Recently, however, it has become apparent that, inter alia, their lack of measurable vapor pressure characterizes them as green solvents, and that a wide range of chemical reactions (reviewed here) can be performed in them. Wassercheid and Keim reviewed the literature of ionic liquids, not only the synthesis and physical properties of the ILs, but also their use as... 

Vladimir M. Egorov was born in Odintsovo-10, Moscow Region, Russia, in 1982. He received his MS in chemistry from Moscow State University in 2005. The subject of his diploma thesis was to develop a method of analytical reagents immobilization on cellulose matrix by dissolution or reconstitution using ionic liquids. Currently, he is a postgraduate student at the MSU Chemistry Department. His research interests include (but not limited to) application and synthesis of novel ionic liquids and computational chemistry. He has been a prize-winner of numerous contests in chemistry, mathematics, and biology. 

In the last few years the different suppliers of ionic liquids have developed several purity grades. Merck has introduced synthesis , high purity and ultrapurity (see Chapter 1.2) and other suppliers also follow this purity scheme. In the past much attention was focussed on impurity effects. However, as the different suppliers are about to establish large scale production lines where the costs for the educts have to be quite low one has to be prepared that the problem of impurities may return. As many groups (in part without any experience at all) have entered the field of ionic liquids in recent years we would like to draw attention to the subject of impurities. Impurities can be a concern but do not necessarily have to be a concern. We could also imagine that for some processes impurities are beneficial but, as a minimum, one should know their role in the respective process. 

Several reviews have been published within the year which are of general relevance to the photoreactions of aromatic compounds. The subjects of these reviews include photochemistry in ionic liquids and in isotropic and anisotropic media, organic synthesis utilizing photoinduced electron-transfer reactions," heteroatom-directed photoarylation processes, photochromism, and photochemical molecular devices. Reviews more directly pertinent to the sections in the present chapter include those of the photoisomerization of five-membered heteroaromatic azoles, the photocycloaddition of benzene derivatives to alkenes, Diels-Alder additions of anthracenes, advances in the synthesis of polycyclic aromatic compounds, diarylethene-based photochromic switches, the photo-Fries rearrangement, and the application of Diels-Alder trapping of photogenerated o-xylenols to the synthesis of novel compounds. " A number of chapters in the two recently published handbooks of photochemistry and photobiology and in the revised edition of the text on photochromism are also pertinent to the current subject matter. 

In addition to the subjects covered in the first edition we have added five new chapters describing newly emerging areas of interest for ionic liquids in synthesis. The book now ranges from the most fundamental theoretical understanding of ionic liquids through to their industrial applications. 

The novice reader may think that the subject is an emerging field however, the green chemistry name is an umbrella for many well-established ideas and techniques that already exist in the literature. None of the techniques under the green technology label can therefore be considered new. For example, the first room-temperature ionic liquid, ethylammonium nitrate [EtNH3] [N03] , which melts at 12°C was discovered by Paul Walden in 1914 [40], Ionic liquids were also observed in Friedel-Crafts acylation and alkylation reactions [41,42], The reader is directed to two reviews that chronicle the historical development of ionic liquids [43,44]. Microwave-assisted synthesis was developed by Gedeye and Westaway at Laurentian University in Sudbury, Canada [45-48],... 

The greatest number of publications regarding ionic liquids is on the subject of their use as solvents for synthesis. Most of these simply report the yields of closely related reactions in one or a few ionic liquids and do not attempt to understand how ionic liquids might affect these reactions in any systematic manner. In spite of this, it has been demonstrated that ionic liquids can have dramatic effects upon the products and rates of chemical reactions. This occurs through interactions between the ionic liquid ions and the starting materials and activated complexes of the reaction. This has been extensively reviewed elsewhere [1, 2,4,8,120]. 

The use of ionic liquids in synthesis is the subject of a monograph by Wasserscheid and Welton (2008). A number of reaction types may be advantageously carried out in room-temperature ionic liquids. They include the following ... 

The determination of the sites of the C—C double bonds in unsaturated fatty acid derivatives and other lipids plays an outstanding role in the analytical application of mass spectrometry. Much work has been published on the localization of double bonds in monoolefins, and a number of extensive reviews has appeared on the topic . Two major methodologies have been employed. In the first one, unsaturated C—C bonds are converted to appropriate derivatives by synthesis in the liquid phase, which are then subjected to mass spectrometric analysis mostly by using standard El techniques. These methods will be mentioned only briefly in the next section, including some recent work which has not yet been mentioned in the reviews. The second methodology takes advantage of the bimolecular reactivity of neutral olefins with ionic reagents in the gas phase,... 

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