Catalysis/catalysts organic synthesis

Certain classical coordination complexes (see Coordination Complexes) of iron (e.g. Prussian blue) will be dealt with in other articles (see Iron Inorganic Coordination Chemistry and Cyanide Complexes of the Transition Metals), as will much of the chemistries of iron carbonyls (see Metal Carbonyls) and iron hydrides (see Hydrides) (see Carbonyl Complexes of the Transition Metals Transition Metal Carbonyls Infrared Spectra, and Hydride Complexes of the Transition Metals). The use of organoiron complexes as catalysts (see Catalysis) in organic transformations will be mentioned but will primarily be covered elsewhere (see Asymmetric Synthesis by Homogeneous Catalysis, and Organic Synthesis using Transition Metal Carbonyl Complexes). 

Chapters devoted primarily to catalysis have been published in earlier volumes of the Handbook. Note especially chapter 43 on absorption and catalysis on surfaces, chapter 57 on catalysis in organic synthesis, and chapter 61 on coordination catalysts. In this volume we add several chapters that will continue our coverage of these important applications of the rare earths. 

G.W. Roberts, "The influence of mass and heat transfer on the performance of heterogeneous catalysts in gas/liquid/solid systems in P.N. Rylander and H. Greenfield (eds.). Catalysis in Organic Synthesis, Academic Press, New York (1976) 1. 

Organopalladium compounds prepared as discussed in this section can also serve as catalysts or catalyst precursors. Further investigations along this line will undoubtedly broaden the scope and applicability of the Pd catalysis in organic synthesis. 

In an idealistic sense, a chemical approach which uses a small amount of a chiral catalyst to produce either enantiomer, cleanly and efficiently from a prochiral precursor, is the preferred method. For such asymmetric catalysis the efficiency of chiral multiplication can be infinite. The use of chiral metal complexes as homogeneous catalysts has become one of the most powerful economically and environmentally sound strategies for the preparation of enantiopure compounds. An excellent comprehensive review of asymmetric catalysis in organic synthesis has recently been published by Noyori [30]. 

Alkene metathesis is a catalytic reaction that has brought revolutions during the last 15 years, not only in catalysis and organic synthesis but also in polymer and material science. This is due to the discovery of the catalytic mechanism based on metal-caibene by Chauvin [1] and of well-defined, efficient catalysts from 1990 based on coordinatively unsaturated alkylidene-metal complexes mainly derivatives of molybdenum by Schrock [2] and of ruthenium (Ru) by Gmbbs [3]. The increasing importance of alkene metathesis and its catalysts by the scientific community has led to the award of 2005 chemistry Nobel Prize to the main pioneers in this field, Chauvin, Gmbbs, and Schrock [1-3]. 

Combination of super B rousted acid with simple Bronsted acid or Lewis acid would be a new system for acid catalysis in organic synthesis. The example of super BLA would be an interesting tool for selective organic transformations. We have already shown excellent examples in Scheme 1.3 using the Tf2NH-chiral Lewis acid combined system. Scheme 1.36 exemplifies some additional recent reactions based on pentafluorophenyl bis (triflyl)methane and chiral Lewis acid catalyst [38]. 

Acid—Base Catalysis. Inexpensive mineral acids, eg, H2SO4, and bases, eg, KOH, in aqueous solution are widely appHed as catalysts in industrial organic synthesis. Catalytic reactions include esterifications, hydrations, dehydrations, and condensations. Much of the technology is old and well estabhshed, and the chemistry is well understood. Reactions that are cataly2ed by acids are also typically cataly2ed by bases. In some instances, the kinetics of the reaction has a form such as the following (9) ... 

It is apparent that the use of enzymatic catalysis continues to grow Greater availabiUty of enzymes, development of new methodologies for thek utilization, investigation of enzymatic behavior in nonconventional environments, and the design and synthesis of new biocatalysts with altered selectivity and increased stabiUty are essential for the successhil development of this field. As more is learned about selectivity of enzymes toward unnatural substrates, the choice of an enzyme for a particular transformation will become easier to predict. It should simplify a search for an appropriate catalyst and help to estabhsh biocatalytic procedures as a usehil supplement to classical organic synthesis. 

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