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Enantioselective synthesis, also called asymmetric synthesis, [1] is a form of chemical synthesis.It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereomeric) products in unequal amounts."
In the petroleum refining and petrochemical industries, the initialism BTX refers to mixtures of benzene, toluene, and the three xylene isomers, all of which are aromatic hydrocarbons. The xylene isomers are distinguished by the designations ortho – (or o –), meta – (or m –), and para – (or p –) as indicated in the adjacent diagram.
Toluene is also found in cigarette smoke and car exhaust. If not in contact with air, toluene can remain unchanged in soil or water for a long time. [39] Toluene is a common solvent, e.g. for paints, paint thinners, silicone sealants, [40] many chemical reactants, rubber, printing ink, adhesives (glues), lacquers, leather tanners, and ...
A wide variety of carbohydrates, as well as nitrogen nucleophiles (ex. amino acids), can be used to furnish highly stereochemically enriched products. The aminopolyol products can then undergo further reactions to prepare aminosugars. Petasis used this reaction to prepare Boc-protected mannosamine from D-arabinose. [19]
Although stoichiometric chiral reducing agents often afford products with high enantioselectivity, the necessity of a stoichiometric amount of chiral material is a disadvantage. [ 2 ] The catalytic, asymmetric reduction of ketones may be accomplished through the use of catalytic amounts of an oxazaborolidine catalyst in conjunction with borane ...
The process of chemical reaction can be considered as involving the diffusion of reactants until they encounter each other in the right stoichiometry and form an activated complex which can form the product species. The observed rate of chemical reactions is, generally speaking, the rate of the slowest or "rate determining" step.
Asymmetric hydrogenation has replaced kinetic resolution based methods has resulted in substantial improvements in the process's efficiency. [ 12 ] can be seen in a number of specific cases where the For example, Roche's Catalysis Group was able to achieve the synthesis of ( S , S )-Ro 67-8867 in 53% overall yield, a dramatic increase above the ...
Several entrainers can be used for this specific process: benzene, pentane, cyclohexane, hexane, heptane, isooctane, acetone, and diethyl ether are all options as the mixture. [2] Of these benzene and cyclohexane have been used the most extensively, but since the identification of benzene as a carcinogen, toluene is used instead. [citation needed]