Organic synthesis catalysts

Abstract Several bismuth-catalyzed synthetic reactions, which proceed well in aqueous media, are discussed. Due to increasing demand of water as a solvent in organic synthesis, catalysts that can be used in aqueous media are becoming more and more important. Although bismuth Lewis acids are not very stable in water, it has been revealed that they can be stabilized by basic ligands. Chiral amine and related basic ligands combined with bismuth Lewis acids are particularly useful in asymmetric catalysis in aqueous media. On the other hand, bismuth hydroxide is stable and works as an efficient catalyst for carbon-carbon bond-forming reactions in water. 

Use Organic synthesis, catalyst solvent, oil extraction, manufacturing of adipic and maleic acids. 

Use Organic synthesis, catalyst for polymerization of olefins, high-energy aircraft and missile fuel, production of ethyl mercuric chloride. 

Chemicals. Intermediate chemical in several reactions and various organic synthesis, catalyst,... 

In organic synthesis, two kinds of Pd compounds, namely Pd(II) salts and Pd(0) comple.xes, are used. Pd(II) compounds are used either as stoichiometric reagents or as catalysts and Pd(0) complexes as catalysts. Pd(Il) compounds such as PdCh and Pd(OAc)2 are commercially available and widely used as... 

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

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. 

Extremozymes—enzymes that can tolerate relatively harsh conditions, suggested as catalysts for complex organic synthesis of fine chemicals and pharmaceuticals (Govardhan and Margolin, 1995). 

Covalent fluondes of group 3 and group 5 elements (boron, tin, phosphorus, antimony, etc ) are widely used m organic synthesis as strong Lewis acids Boron trifluoride etherate is one of the most common reagents used to catalyze many organic reactions. A representative example is its recent application as a catalyst in the cycloadditions of 2-aza-l,3-dienes with different dienophiles [14] Boron trifluoride etherate and other fluonnated Lewis acids are effective activators of the... 

L. Brandsma, S. E. Vasilevsky, and H. D. Verkiuijsse, in Application of Transition Metal Catalysts in Organic Synthesis. Springer-Verlag, Heidelberg, 1998. 

Because the anioas of nitroalkanes are stable, retro-acyladoc smoothly In the presence of a base catalyst. This type of reacdo organic synthesis." Nucleophilic attack of water or alcohol to ct-the ring cleavage v/ith the formadon of Oj-nitro acids and Oj-niti... 

Chloroaluminate(III) ionic liquid systems are perhaps the best established and have been most extensively studied in the development of low-melting organic ionic liquids with particular emphasis on electrochemical and electrodeposition applications, transition metal coordination chemistry, and in applications as liquid Lewis acid catalysts in organic synthesis. Variable and tunable acidity, from basic through neutral to acidic, allows for some very subtle changes in transition metal coordination chemistry. The melting points of [EMIM]C1/A1C13 mixtures can be as low as -90 °C, and the upper liquid limit almost 300 °C [4, 6]. 

W. P. Weber, G. W. Gokel, Phase Transfer Catalyst in Organic Synthesis, Springer-Verlag, W. Berlin (1977). 

Tantalum and niobium are added, in the form of carbides, to cemented carbide compositions used in the production of cutting tools. Pure oxides are widely used in the optical industiy as additives and deposits, and in organic synthesis processes as catalysts and promoters [12, 13]. Binary and more complex oxide compounds based on tantalum and niobium form a huge family of ferroelectric materials that have high Curie temperatures, high dielectric permittivity, and piezoelectric, pyroelectric and non-linear optical properties [14-17]. Compounds of this class are used in the production of energy transformers, quantum electronics, piezoelectrics, acoustics, and so on. Two of... 

Perhaps the most successful industrial process for the synthesis of menthol is employed by the Takasago Corporation in Japan.4 The elegant Takasago Process uses a most effective catalytic asymmetric reaction - the (S)-BINAP-Rh(i)-catalyzed asymmetric isomerization of an allylic amine to an enamine - and furnishes approximately 30% of the annual world supply of menthol. The asymmetric isomerization of an allylic amine is one of a large and growing number of catalytic asymmetric processes. Collectively, these catalytic asymmetric reactions have dramatically increased the power and scope of organic synthesis. Indeed, the discovery that certain chiral transition metal catalysts can dictate the stereo-... 

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